Environmental geochemistry: 40 years research at Imperial College, London, UK

Applied Geochemistry 27 (2012) 939–953

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Environmental geochemistry: 40 years research at Imperial College, London, UK Iain Thornton ⇑ Imperial College and Imperial College Consultants, London, UK

a r t i c l e

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Article history: Available online 17 September 2011

a b s t r a c t This paper reviews the development of multi-purpose geochemical mapping and the progress of research in applied environmental geochemistry and health at Imperial College over the past 40 years. With funding from the research councils, UK government, EU, industry and NGOs, research has provided the basis for postgraduate training in areas ranging from the applications of geochemistry to plant, agricultural livestock and wildlife nutrition, to evaluating contamination from metalliferous mining and smelting, understanding the chemical nature of the urban environment and relationships between geochemistry and human health and disease. Examples include (1) the influence of Mo in marine black shales on the Cu nutrition of grazing cattle and sheep, (2) the importance of soil ingestion on trace element intake and metabolism and metal exposure in farm livestock, (3) the impacts of soil contamination from historical metalliferous mining and smelting on agriculture and human exposure to metals, including potential health problems from Cd at Shipham and from As in SW England, (4) the growth of urban geochemistry and the importance of Pb in the urban environment, (5) the health impacts due to Hg losses from the informal sector Au mining in Brazil, and (6) health issues relating to F- excess and Se deficiency in China. Ó 2011 Elsevier Ltd. All rights reserved.

1. Introduction The author joined the Applied Geochemistry Research Group (AGRG), at the Imperial College of Science and Technology, London, in 1964 to further develop studies into the application of geochemical reconnaissance mapping to agriculture, under the direction of Professor John Webb, who developed the concept of multi-purpose geochemical mapping and its relevance to plant and animal health (Webb, 1964). This paper, based on a plenary lecture at the Annual Conference of the Society for Environmental Geochemistry and Health in Galway 2010, presents a review covering the development of multidisciplinary research over the period 1964–2004, into areas ranging from geochemical influence on plant and animal health in the UK, the mineral nutrition of wildlife in Kenya, soil contamination arising from historical metalliferous mining and smelting, contamination of rivers and estuaries and effects on oyster culture, geochemical mapping of the urban environment and the application of geochemistry to human health and epidemiology. Initially funded by the Natural Environment Research Council, other sources of financial support have included the Wolfson Foundation, the Agricultural Research Council, the White Fish Authority, Industry, the European Commission, The Peoples Trust for Endangered Species and other NGOs. The general area of applied environmental geochemistry has been recently reviewed (Thornton, 2010). The aim of the present ⇑ Address: Orchard End, Mill Lane, Pavenham, MK43 7NL, UK. Tel.: +44 (0) 1234 825189. E-mail address: [email protected] 0883-2927/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.apgeochem.2011.07.015

paper is to re-examine and assess some of this multi-faceted and multi-disciplinary research undertaken by AGRG (later renamed the Environmental Geochemistry Research Group (EGRG)) at Imperial College, focussing on some of the areas that the author personally found scientifically challenging and at the same time exciting, and to share some of the broader issues raised and some of the many questions that remain unanswered. 2. Geochemistry and livestock production In the UK, successful livestock farming largely depends on the production of pasture herbage of sufficient quality to meet the nutritional requirements of grazing cattle and sheep. The chemical composition of the herbage is to a great extent dependant on the supply of both major and trace elements from the soil, which in turn is related to the geochemistry of the soil parent material. Research by the AGRG into relationships between geochemical mapping and agricultural problems in UK commenced in 1964 and has been reviewed by Thornton (2002). The prime example successfully showing a clear relationship between geochemistry and animal health concerned the distribution of Mo in soils and pasture and Cu deficiency in cattle in Derbyshire, UK. Excess Mo in the diet of grazing cattle reduces the utilisation of dietary Cu and over a period of months may lead to the reduction of Cu reserves in the liver and deficiency symptoms in the animal (Fig. 1). A geochemical reconnaissance survey of some 2330 km2 (900 miles2) based on the sampling of active sediment from tributary streams at a density of 1 sample per 2.59 sq km2 (1 mile2)

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(part of a project funded by the Institute of Geological Sciences (now BGS)) showed anomalous concentrations of Mo in areas underlain by lower Namurian (Carboniferous) shale (Fig. 2) (Fletcher, 1968; Webb et al., 1968). These marine black shales contained up to 50 mg/kg Mo, and topsoil overlying these rocks ranged 4–35 mg/kg Mo. Copper deficiency in cattle induced by Mo was known to occur in parts of the anomalous stream sediment pattern area (Fig. 3). However the results of blood Cu tests carried out elsewhere within the anomaly indicated that all the raised Mo pattern was suspect, the incidence of hypocuprosis being twice as high as outside the anomaly. Subsequent trials in collaboration with the

Veterinary Investigation Service showed that Cu injections could increase the live weight gain of affected herds by more than 50% over a 6 month period. Most of the animals that were found to be Cu deficient and which responded to Cu supplementation showed no outward symptoms of disorder – a clear example of a sub-clinical deficiency (Thornton et al., 1972). Following this, stream sediments were sampled systematically in nine areas within England and Wales totalling 2850 km2 (1100 miles2) underlain by marine black shales ranging in age from Ordovician to Cretaceous, showing soils and pasture herbage with above normal concentrations of Mo. It was suggested that appreciable areas (over 800,000 ha) of the UK underlain by marine black shales may be enriched in Mo and may be potentially limiting to livestock performance (Thomson, 1971; Thomson et al., 1972). Subsequent mapping of herds with low blood Cu values (hypocupraemia), identified by the Veterinary Investigation Service, showed over 1700 to be located in areas with molybdeniferous soils (Leech, 1984; Leech et al., 1982; Leech and Thornton, 1987). This example of how geochemical mapping could be of benefit to agriculture was recognised as important by the then Ministry of Agriculture, and, with their support finance was obtained from the Wolfson Foundation to produce the prototype Wolfson Geochemical Atlas of England and Wales (Webb et al., 1978). This comprised maps showing the distribution of 24 trace elements and metals including both Mo and Cu. These further defined areas of potential Cu deficiency in grazing livestock (Fig. 4). Subsequently, special regional committees were set up by the Agricultural Development and Advisory Service to ensure that the geochemical data were put to practical use.

Fig. 2. Geology of the Derbyshire area, showing the outcrop of Namurian shale.

Fig. 3. Recognised occurrence of clinical copper deficiency (hypocuprosis) in cattle in the Derbyshire area.

Fig. 1. An example of copper deficiency symptoms in cattle.

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the ground (Thornton, 1974). Collaborative research with the MRI then found that under experimental conditions the addition of 10% soil to the diet of sheep reduced Cu absorption and utilisation by as much as 50%, and that as little as 2% soil ingestion significantly reduced Cu use (Suttle et al., 1975). Further work, based on the use of artificial rumen systems at the MRI, showed that large amounts of Fe were released from soil which acted as a powerful Cu antagonist. It was proposed that accidentally ingested soil provides a source of large amounts of Fe in the rumen of sheep. This Fe interacts with dietary Cu so reducing its utilisation (Suttle et al., 1984; Brebner, 1986). It was later shown that ingested soil was a significant source of dietary Co for sheep and that Co extracted from soil was synthesised into vitamin B12 in the sheep’s rumen (Brebner et al., 1987). Nutritional deficiency of Co in sheep causes severe emaciation, often referred to as ill-thrift or pine, and is found in several areas of the UK underlain by coarse grained sedimentary and acid igneous rocks and responds rapidly to Co supplementation. It was suggested that ingested soil could prove to be an important source of dietary Co. 2.1. Selenium

Fig. 4. Map showing the distribution of Mo in stream sediments in England and Wales. Compiled by the Applied Geochemistry Research Group as part of the Wolfson Geochemical Atlas of England and Wales (Webb et al., 1978).

Currently, with changes in farming practice towards less intensive livestock production, less concentrate feed and more dependence on grass and silage, problems of both clinical and sub-clinical Cu deficiency could be expected to increase, but as free veterinary advice to farmers is no longer available, production problems due to Cu deficiency may still be largely undetected by the farming community. Molybdenum accumulation has also been found in recent marine alluvium (locally known in the UK as ‘‘saltings’’), reclaimed for agricultural use, and is thought to be due to the fixation of Mo by soil sesquioxides and organic matter. Extensive UK coastal areas are affected in Norfolk, Suffolk and Essex, as shown in Fig. 4. Vegetation growing on these alluvial soils, which have a pH ranging from 7 to 8, thus favouring the uptake of Mo into plants, is potentially toxic to ruminants (Smart, 1991). As previously noted (Thornton, 1993), similar marine black shales and marine estuarine alluvium are found in many parts of the world, but with the exception of North America, have as yet received little attention by livestock farmers. Further research by AGRG in collaboration with the Moredun Research Institute (MRI) demonstrated that the Cu nutrition of grazing sheep (and presumably cattle) was also influenced by the involuntary ingestion of soil. Excess wear of sheep’s teeth, previously shown in New Zealand, was found to be caused by accidental ingestion of soil (Healy, 1967, 1968). Under UK conditions and using Ti as a stable indicator of soil ingestion, it was shown that between 2% and 20% of the dry matter intake of grazing cattle was soil, and up to 30% or 40% in sheep as they grazed closer to

Elevated concentrations of Se were found in both stream sediments and soils (also enriched in Mo),derived from marine black shales and slates of Lower Carboniferous and Ordovician age, providing the first evidence of seleniferous soils in Britain (Webb et al., 1966). Later studies, based on the analysis of over 500 British soils, showed total concentrations of Se to range from 0.01 to 4.7 mg/kg Se. Soils formed from calcareous and coarse sedimentary rocks contained less Se than those from fine grained sediments (Smith, 1983). Largest amounts of Se were found in peaty soils and in soils in areas of sulphide mineralisation. It was concluded that it was unlikely that raised Se levels potentially toxic to livestock would be found in Britain (Thornton et al., 1983). It is noted that soils developed from black shales in Eire contain from 30 to over 300 mg/kg Se and result in chronic selenosis in cattle and horses (Fleming and Walsh, 1957). However, as Se is an essential trace element in animal nutrition and deficiency can lead to ‘‘white muscle disease’’, a degenerative muscle disease in sheep, attention was drawn to those soils of low Se content where deficiency in grazing animals might occur. It is generally agreed that soils containing <0.5 mg/kg Se are likely to support pastures with potentially inadequate Se concentrations (Underwood and Suttle, 1999). In this respect acid soils formed on coarse sandy parent materials were considered to be the most suspect. An earlier survey of erythrocyte glutathione peroxidise activity in sheep (a reliable indicator of Se status) had indicated that nearly 50% of the farms covered were unable to provide grazing sheep with sufficient Se to meet their nutritional requirements (Anderson et al., 1979). However, the response to these findings by the animal feed industry was to add Se to all mineral supplements for sheep so that the identification of Se deficient soils and pastures was then only of academic interest. As a result, careless administration of Se supplements has in some cases resulted in Se poisoning or selenosis. 3. Geochemistry and arable cropping The geochemical map for Cu also assisted in the identification of soils on which Cu deficiency was likely to occur in cereal crops. Low total concentrations of Cu in stream sediments were found to reflect low total concentrations in soils and low available (extracted with 0.05 M diammonium EDTA) concentrations (Jordan et al., 1975). The geological beds in the UK with the lowest stream

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sediment concentrations are the Folkestone and Sandgate Beds of the Lower Greensand (Cretaceous) in Sussex, the Upper Greensand (Cretaceous) in Wiltshire and the Breckland sand (a chalk–sand drift overlying Cretaceous chalk) in Suffolk. Copper deficiency has occurred in cereal and other crops on sandy soils in these areas. A controlled field trial treating barley with Cu at three sites on the Lower Greensand showed an average increase in grain yield of 20%, despite the absence of visual deficiency symptoms (Jordan, 1975). This clearly illustrates the potential economic importance of unrecognised marginal (sub-clinical) trace element deficiency and the application of geochemical maps to focus attention on such areas of potential deficiency. 4. Impacts of metalliferous mining and smelting on the geochemical environment A major aspect of postgraduate research within AGRG concerned the environmental and community health impacts relating to metal(loid) contamination of soils and waters and the legacy from historical mining and smelting. As noted earlier, the Wolfson Geochemical Atlas of England and Wales (Webb et al., 1978) provided systematic baseline information both on the natural distribution of metals and the extent and degree of regional contamination arising from human activities. The geochemical maps clearly show anomalies for Pb, Zn, Cd, Cu and As in mineralised areas where mining and smelting operations have resulted in extensive contamination of the surface environment (Thornton, 1996). Research on this topic has been recently reviewed by the author (Thornton, 2010), and those aspects discussed below are limited to areas where there is a continuing problem or a potential health risk to the local community. 4.1. Cadmium at Shipham In 1979 a value of 500 mg/kg Cd was recorded in a surface soil sample in the vicinity of the village of Shipham, Somerset (SW England). Repeat analysis by AGRG and a commercial laboratory in Canada confirmed this unlikely high value. Subsequently, detailed sampling of land around the village and of household gardens in the village confirmed very large values for both Cd and Zn. Zinc was mined in shallow pits as the ore smithsonite (ZnCO3) over the period 1700–1850. Mineral veins run under part of

Shipham (Fig. 5), and there is an early record of mining around the houses and of subsidence in the village. Housing development extended onto land reclaimed from the old workings. The remains of some of these workings (locally known as ‘‘gruffy ground’’) are seen in agricultural land to the north of the village. The ore, with appreciable amounts of Cd as a trace element, was washed in ponds and calcined within the village, before transport to Bristol for the manufacture of brass. These findings were reported to the (then) Department of the Environment (DoE) and the Government minister responsible held a press conference and informed the nation about the high Cd. The media response was immediate with headlines on the front page of several national newspapers (Fig 6). In a subsequent television documentary about Shipham, an eminent Cd scientist from Sweden advised the government to evacuate the village as he considered that there was a potential health risk to the population. The DoE then rapidly organised and funded a multi-institution investigation, involving AGRG, MAFF Food Science Division, St. Mary’s Hospital Medical School, and Local Government, with co-ordination by DoE. Samples of garden soil and housedust were taken from ca. 300 homes in Shipham and from a nearby Somerset village, North Petherton, which had no history of mining and was selected as a control. These were analysed for Cd, Zn and Pb. In Shipham, over 90% of the surface (0–5 cm) soils contained in excess of 20 mg/kg Cd, and 60% exceeded 60 mg/kg, ranging up to 340 mg/kg. Amounts of Zn were also extremely large, mostly over 3000 mg/kg and up to 6.4%. Background levels of Cd in British agricultural soils mostly range from 0.1 to 2.0 mg/kg (Alloway, 1995), and garden soils in North Petherton did not exceed 7 mg/kg. The average concentration of Cd in Shipham housedust was 26 mg/kg (range 1–373 mg/kg) and of Zn 2256 mg/kg (range 270–8200 mg/kg). 90% of the dusts exceeded 10 mg/kg Cd and 1000 mg/kg Zn (Thornton et al., 1980). Analysis of 168 samples of winter vegetables grown in Shipham showed Cd concentrations to range from 0.02 to 1.77 mg/kg (mean 0.23 mg/kg) fresh weight. Summer vegetables ranged from 0.01 to 3.56 mg/kg Cd (mean 0.52 mg/kg). These values are much larger than would be considered normal and home grown vegetables could possibly constitute a potential hazard to the population. From dietary studies, an average human intake of 200 lg Cd per week was calculated, compared with an average UK intake of 140 lg per week. Individual intake rarely exceeded the WHO

Fig. 5. Geology of the area around Shipham, Somerset, showing the location of mineral veins.

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Fig. 6. Shipham: headline news in the British Press.

provisional tolerable weekly intake of 450–500 lg Cd. Drinking water supplies came from outside the mineralised area and did not contain elevated levels of metals. A programme of blood and urine sampling did not indicate significant exposure to Cd, though there was a small increase in the B2 microglobulin level in the urine of some residents. There were no other symptoms of kidney dysfunction identified. Many of the older long term residents refused to participate in the health study. On completion of the study, the DoE issued a guidance leaflet with precautionary advice to villagers to limit their consumption of home grown vegetables and not to smoke cigarettes. Villagers did not take this too seriously. The reason that there was no evidence of adverse health effects is probably due to several factors. The high pH of garden soils limited Cd uptake into vegetable plants and only a small % of the diet was home grown. Water supplies were not contaminated with Cd. The large amounts of Zn in the soil and plants, which is preferentially absorbed to Cd, may have afforded some protection for the population. A later collaborative study, based on epidemiological data held by the Small Area Health Statistics Unit at Imperial College Medical School, showed no evidence of adverse health effects, including risk of mortality, cancers and stroke, in the Shipham area (Elliott et al., 2000). In parallel to the health investigation, a study was made into Cd and Zn in agricultural soils and pasture plants in fields around Shipham grazed by livestock (Matthews, 1982; Matthews and Thornton, 1982). Previously, attempts to reclaim mined land for grazing by reseeding with commercial seed mixture had met with failure. However a self seeded sward was later established through windblown seed from neighbouring land where metal resistant strains were growing successfully. Tolerance to both Cd and Zn was established in the grass Holcus lanatus (Yorkshire fog). For most of the year this sward appeared healthy, though some chlorosis was apparent in both grass and weed species in early spring. Cadmium and Zn concentrations in surface soils ranged up to 440 and 5000 mg/kg, respectively, but little of this metal was translocated to the aerial parts of the plant. Grass growing in soil with 440 mg/kg Cd contained only 2.8 mg/kg Cd in the dry matter. Weed plants of the Compositae family, including daisy, yarrow and

dandelion, accumulated much larger amounts of Cd (10–60 mg/kg) than grass species. On the basis of these results farmers were advised to keep weed species to a minimum in the sward to prevent the risk of Cd induced Cu deficiency in grazing livestock. 4.2. Soil contamination from lead mining and smelting As noted above, the Wolfson Geochemical Atlas showed extensive anomalous patterns of Pb and Zn in areas of historical metalliferous mining and smelting. Research into Pb-contaminated land in Derbyshire (central England), estimated at ca. 250 km2, measured the intake and impact of Pb on cattle and sheep. Herbage and faeces samples were taken every month for 18 months on 11 farms with soil Pb contents ranging from 95 to 5100 mg/kg. A survey of grazing cattle showed blood Pb levels to broadly reflect amounts of Pb in the soil. Between 40% and 70% of the Pb intake was shown to be as a result of directly ingested soil (Thornton and Abrahams, 1983). None of the animals tested showed symptoms of clinical Pb poisoning. This is rarely found in cattle. Lameness in young lambs had been reported earlier in flocks grazing old Pb mining areas, though the animals recovered spontaneously when moved onto uncontaminated pastures (Stewart and Allcroft, 1956). Further studies in Derbyshire applied sequential extraction procedures to measure the forms and associations of metal contaminants in soils. The exchangeable fractions of Pb, Zn and Cd were greater at historical smelter sites than at mining sites, indicating greater mobility and potential availability of these metals. The amount of exchangeable metal in the soil was related to concentrations in the pasture herbage (Li, 1993; Li and Thornton, 2001). At farms in Derbyshire, where high concentrations of Pb in soils had been reported, elevated amounts of F were also found, ranging up to 1500 mg/kg, compared to 200–400 mg/kg F in uncontaminated soils. Some surface soils (0–15 cm) near an old fluorspar mine and a Pb rake (pasture area with residual mine spoil) contained several % of both F and Pb, and washed pasture herbage ranged up to 370 mg/kg F DM. It was suggested that the problems in young lambs noted above could have been due to ingested F as well as Pb (Geeson et al., 1998).

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4.3. Effects of metal contaminants in soil on nitrogen cycling bacteria A series of experiments was carried out to determine the effects of large amounts of Pb, Zn and Cd on N fixation and cycling in agricultural soils in old mining areas (with up to 8000 mg/kg Pb, 34000 mg/kg Zn and 400 mg/kg Cd), compared with control soils with normal metal contents. Nitrogen fixation was estimated using the acetylene reduction assay, mineralisation by the breakdown of added peptone and nitrification by the oxidation of NH3–N and NO2 —N. The activities of the free-living N-fixing organisms showed little difference between the various sites tested at any one time and the amount of N fixed was small (0.3–0.5 g N/ha/d) (Rother et al., 1982). The amount of N fixed by white clover was much greater (80 g N/ha/h) and again there were no consistent differences between the sites (Rother et al., 1983). It was thought probable that, in soils contaminated with metals, tolerant strains of N-cycling bacteria are selected and develop into populations which are active and capable of rapid growth as those in noncontaminated soils. This development of tolerance in N-cycling bacteria was later confirmed under laboratory conditions. 4.4. Exposure to lead in the local population In this same area of historical Pb–Zn mining in Derbyshire, a collaborative study with St. Mary’s Hospital (now part of Imperial College) showed that when households were grouped according to the Pb content of the garden soils the amounts of Pb in the blood and hair of the 2–4 year old children increased with that in the soil and housedust. However, none of the Pb values in children were high enough to be considered hazardous at the time, even though the amounts in the soil and dust were extremely high, peaking at 2.8% and 2.5%. It was suggested that the major pathway of Pb to the children was through inhalation and involuntary ingestion of dust particles (Barltrop et al., 1975). A later study was conducted in the village of Winster, Derbyshire where garden soils and housedusts sampled from 45 homes averaged 7000 and 1500 mg/kg Pb, respectively (Cotter-Howells, 1992; Cotter-Howells and Thornton, 1991). Many of the older houses had soil Pb values of 1% or more as in the 1700’s mine wastes had been used in the foundations. A small blood Pb survey of 13 1–8 year old children conducted by the local general practitioner showed values ranging from 6 to 21 lg/dL and did not give rise to concern at the time, as all were below 25 lg/dL, above which the children would have been regarded as at risk and referred to a paediatrician. An examination of Pb-rich particles by scanning electron microscopy (SEM) led to the identification of the insoluble mineral pyromorphite as a weathering product of galena in the Winster soils and dusts (Cotter-Howells and Thornton, 1991). It was then shown, using computer-controlled SEM that a significant proportion of Pb bearing particles in soils, dusts and on the children’s hands was composed of this Pb-phosphorous mineral pyromorphite (Watt et al., 1993). This may well have contributed to the low bioavailability of Pb and to blood Pb concentrations lower than those predicted by some Pb exposure models. However, in the light of present day knowledge, perhaps, this and other old mining villages should be revisited. 4.5. Soil contamination; arsenic and copper Regional geochemical maps have shown extensive anomalies of As, Cu and other metals in those parts of SW England associated with mineralised areas around granite intrusions. While Cu and Sn have been mined since Roman times, it was only when the use of As as an insecticide was discovered in the late 1880s that it’s production became an important by-product of the Sn/Cu mines. The ore arsenopyrite was crushed and calcined and the

vapour collected as ‘‘arsenic soot’’ or ‘‘crude arsenic’’ (Dines, 1956). From about 1860–1900, Cornwall was the world’s major producer of As. These mining and smelting activities left a legacy of As-rich mine tailings and extensive areas of contaminated land. Early studies by AGRG compared As distribution in stream sediments and soils and showed an area of in excess of 700 km2 affected, with alluvial and upland topsoil within the Tamar area ranging up to 900 mg/kg and 2500 mg/kg As, respectively, and up to 2000 mg/kg Cu (Colbourn et al., 1975). Pasture herbage, sampled in the autumn from the alluvial fields along the river Tamar, ranged up to 35 mg/kg As and 22 mg/kg Cu DM compared with mean values of less than 0.5 mg/kg As and 8 mg/kg Cu in control areas. Grazing cattle were left on the contaminated land for only short periods of time and did not appear to be adversely affected. Studies covering a wider area of Cornwall of 9000 km2 showed 1.3% of surface (0–15 cm) soils to be highly contaminated with As and 6.6% designated as moderately contaminated (Abrahams, 1983; Abrahams and Thornton, 1987). Highest concentrations of As in pasture herbage were found in early spring and late autumn and possibly reflected some degree of soil contamination. Soil ingestion by grazing cattle was then investigated on 11 farms and in general terms accounted for 50–80% of the total As ingested (Thornton and Abrahams, 1983). The rate of soil ingestion ranged from 1.5% to 18% of dry matter intake in early spring and 0.2–4% in summer when herbage was abundant. Up to 97% of the total dry matter intake of As may be via ingested soil (Abrahams and Thornton, 1994). Cattle grazing As-contaminated land ingested ca. 30 times the amount of As as those on uncontaminated pasture. 4.6. Soil contamination: arsenic, antimony and bismuth Soils and pasture herbage sampled on farm land in some historical mining and smelting areas were analysed for As, Sb and Bi (Li and Thornton, 1993). Concentrations of the three elements were elevated in soils associated with Pb–Zn mineralisation in Derbyshire and Somerset and with Sn–Cu mineralisation in Cornwall, the mean values being 31 mg/kg As, 103 mg/kg Sb and 0.45 mg/ kg Bi near an old Pb smelter in Derbyshire, 350, 38 and 0.4, respectively, in the old Zn mining area at Shipham, Somerset, and 390, 2.2 and 16, respectively, in Cornwall. Concentrations of As and Sb in pasture herbage increased with increasing levels in the soil in Cornwall; uptake of Bi increased with increasing pH over the range pH 5–8. Actual concentrations of the three metalloids in herbage remained fairly low in all areas, even on highly contaminated soils, but it was concluded that soil-contaminated herbage could be an important pathway for these elements to livestock grazing contaminated land (Li and Thornton, 1993). 4.7. Arsenic exposure in local populations in Cornwall and Devon Studies in 32 home gardens in the Hayle-Camborne area of Cornwall showed As concentrations to range widely in surface soils from around 150 to 900 mg/kg (Xu and Thornton, 1985). Arsenic was determined in six garden crops and in most cases did not exceed 1 mg/kg DM, with maximum concentrations in lettuce (geometric mean 0.86 mg/kg) and lowest in peas and beans (0.04 mg/kg). Arsenic in vegetables increased with both total As in soils and As extracted with a dilute acid-fluoride solution, though the uptake was influenced by soil Fe and P. In no case did As in the vegetables exceed the then statutory limit of 1 mg/kg As fresh weight in foods offered for sale in spite of the large amounts of As present in the soils, and it was concluded that home grown vegetables only made a small contribution to human exposure. Exposure in young children may well result from direct ingestion of dust and soil through hand-to-mouth activity. A study of

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70 households in the Hayle-Camborne area, with As in surface garden soils ranging from 120 to 1100 mg/kg (median 340 mg/kg), showed As in house dusts to range from 9 to 330 mg/kg (median 56 mg/kg) and it was assumed that a young child could ingest up to 42 lg As per day (Johnson, 1983). A further study in 23 households in villages associated with past As mining, found garden soils ranging up to 770 mg/kg As and housedusts up to 460 mg/kg. Quantities of As on the hands of 1–3 year old children did not exceed 3.5 lg. Assuming a 2-year old child ingests 100 mg dust per day, at the maximum dust level of 460 mg/kg As, the child will ingest 46 lg As per day (Harding, 1993). Later research by Kavanagh (1998) focussed on an area of 25 km2 around the village of Gunnislake and the Devon Great Consuls Mine (SW England), mainly worked from 1844 to 1903, on the banks of the River Tamar, which borders the counties of Devon and Cornwall. Highly elevated concentrations of As, Cu, Sb and Bi were found in soils and waste materials, compared with a nearby unmineralised control village, Cargreen. Concentrations of total urinary As including its organo metabolites (monomethylarsonic acid and dimethylarsinic acid) were found to be slightly raised in the local population in the mining area, indicating low levels of human exposure (Kavanagh et al., 1997, 1998; Farago et al., 1997; Farago and Kavanagh, 1999). It was proposed that the main routes of exposure were ingestion of dust and soil and inhalation of airborne dust particles. Arsenic in samples of unwashed scalp hair increased with increasing soil As concentrations. Washed hair contained less As, but remained higher in the Gunnislake area compared with the Cargreen control group (Farago and Kavanagh, 1999). Hamilton (2000) reviewed the overall subject of environmental contamination with As and other potentially toxic elements in west Devon and concluded that ‘‘particular attention needs to be paid to low level chronic intake of As—especially for children following ingestion of solid matter from the hands’’, and noted the exposure pathway through inhalation of fine-grained dusts. On a broader scale, a pilot ecological study was undertaken into a possible relationship between As contamination in SW England and bladder cancer incidence (Leonardi et al., 1995), in which high exposure to As was defined as living in an area where the concentration of As in stream sediments was greater than 100 mg/kg. This amounted to around 15% of Devon and Cornwall, with some 26% of the population of the two counties. The rate for bladder cancer incidence, calculated as a crude rate ratio of exposed to unexposed was 1.02 and showed no evidence of an increased incidence of bladder cancer in the ‘‘exposed’’ population. It was concluded that a more detailed study was required in which some measure of individual exposure to As could be determined. In summary, there is as yet no evidence showing that any type of cancer or ill-health in Devon and Cornwall is caused by high local levels of As in soils and dusts.

5. Urban environmental geochemistry The term urban geochemistry was coined by the author to describe research activities at the interface of environmental geochemistry and urban pollution (Thornton, 1991). This subject is concerned with the complex interactions and relationships between chemical elements and their compounds in the urban environment, the influence of past and present human and industrial activities on these, and the impacts or effects of geochemical parameters in urban areas on plant, animal and human health. Research in this area has recently been reviewed by Wong et al. (2006). The first records of elevated levels of trace metals in British urban soils were those of Purves (1966, 1968), showing substantial contamination of garden and parkland soils in Edinburgh and

Dundee, Scotland. Studies by AGRG into Cd contamination in Shipham, Somerset, detailed above, included sampling of soils and housedusts in a control village of North Petherton, underlain by unmineralised bedrock. Many of the soils and housedusts contained in excess of 1000 mg/kg Pb (Moorcroft et al., 1982). Similar amounts were found in a village in Hampshire, underlain by chalk. These findings instigated the then Department of the Environment to commission a nationwide survey of metals in urban soils and dusts. In 1981/1982, a survey of Cu, Pb, Zn and Cd was carried out by AGRG in ca. 100 households in each of 53 towns, villages and city boroughs in England, Wales and Scotland. These were chosen to reflect differences in geographical location and geology, the degree of industrial/urban development, and population distribution (Thornton et al., 1985; Culbard et al., 1988). This comprehensive study (5228 homes) showed that concentrations of Pb in garden soils and house dust were sufficiently large to warrant concern that a proportion of urban children were likely to be exposed to significant amounts of Pb, as 10% of houses had in excess of 2000 mg/kg Pb in house dust and 5% of garden soils were above this level. In the seven London Boroughs sampled (n = 580), levels of Pb were high, with 18% dusts and 10% soils exceeding 2000 mg/kg. In the old mining district of Winster, Derbyshire, 93% of garden soils exceeded 2000 mg/kg Pb, with 1% Pb or more in several gardens. An ancillary study in Brighton, on the south coast of England, showed the age of the property to be a controlling factor in the content of Pb in both dust and soil, reflecting the accumulation of Pb over time and the long half-life of the metal (Table 1) (Davies and Thornton, 1987). In parallel, a study based on automated SEM procedures developed methods for apportioning the sources of Pb in household dusts. It was concluded that paint, road dusts and garden soils were the main Pb sources (Hunt et al., 1992). Following the results of the national survey, in the winter of 1984/1985 a comprehensive study of 97 two-year old children was carried out in inner-city Birmingham, in central England. This multi-disciplinary study was designed to provide quantitative information for Pb intakes from all exposure routes (Davies et al., 1990), and included recordings on video of each child’s behaviour to determine the frequency of hand-to-mouth activity. This provided detailed measurements to allow the calculation of Pb uptake based on Pb intake from air, dust and diet. Based on the data shown in Table 2, Pb uptake from the gut was calculated as 35 lg per day, and from inhalation 1.1 lg per day. Blood Pb was principally related to the amount of Pb in the house dust (dust Pb loading) and the child’s rate of hand touching activity. The mean blood Pb concentration was 12 lg/100 mL. It can be assumed that blood Pb will have fallen appreciably by the present time as Pb in petrol was phased out in 1986, though up-to-date information is not available. Eighty-five of the original households were again sampled in 1996, showing that Pb concentrations in housedust had fallen by around 50%, and those in garden soil by only 10% (Wang et al., 1997a). From the results of this later study, it was predicted that mean blood Pb would have fallen to 9.7 lg/ 100 mL, with 42% exceeding 10 lg/100 mL. Table 1 Geometric mean concentrations of Pb (mg/kg) in housedust and garden soil in houses of different ages in Brighton, UK. House age

Vacuum dust

Garden soil (0–5 cm)

Geometric mean lead concentration of dust and soil (lg/g) Pre-1870 982 1146 1870–1919 1874 1014 1920–1939 619 368 1940–1959 433 292 1960–1986 241 131

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Table 2 Lead in blood, environmental samples, hand wipes, dust and water; inner-city Birmingham, UK. Sample type

N

Geo. mean

Percentile 5th

Percentile 95th

Birmingham lead study Blood (lg/100 mL) Air (lg/m3), internal Air (lg/m3), external Housedust (lg/g) Housedust (lg/m2) Soil (lg/g) Handwipe (lg) Diet (lg/g) Water (lg/L)

97 1206 605 94 93 87 704 96 96

11.7 0.26 0.43 424 60 313 5.7 0.025 19

6 0.08 0.12 138 4 92 1.9 <0.02 5

24 0.87 1.53 2093 486 1160 15.1 0.06 100

A study in 1991/1992 of 660 London school children showed a geometric mean blood Pb value of 3.7 lg/100 mL (range 1.0–15.0), and recommended a reduction in the ‘‘action level’’ from 25 lg/ 100 mL to 10 lg/100 mL (O’Donohoe et al., 1998). It has, however, been stated recently by the British Paediatric Surveillance Unit that ‘‘a small proportion of children may continue to be exposed to harmful levels of Pb, usually in the home’’. The latest data are from the University of Bristol Centre for Child and Adolescent Health, reporting on a 582 children subset of the ALSPAC Study in which 27% at an age of 30 months had blood Pbs over 5 lg/dL. Five years later, at the ages of 6 and 7 years, those with an earlier blood Pb of 5–10 lg/dL had significantly lower scores for reading (49%) and for writing (51%). A doubling of the blood Pb from 5 to 10 lg/dL showed a drop of 1/3 of a grade in Standard Assessment Tests (SATS), and above 10 lg/dL the children were likely to display antisocial behaviour and to be hyperactive (Chandramouli et al., 2009).

in the interpretation of urban geochemical maps, where data based on ‘‘total’’ concentrations of metals could be misleading and lead to unnecessary ‘‘housing blight’’ and planning difficulties. Urban geochemical studies have now been undertaken in many countries and continue to be a major focus of several geological surveys. It is not possible to review these in the present paper but the following are some examples (a) Geochemical studies in the urban area of Berlin, Germany, based on 4000 samples of topsoil (0–20 cm) showed elevated values for several metals, especially Pb and Hg in industrial and commercial areas (Birke and Rouch, 2000) and (b) A survey of urban geochemistry in Trondheim, Norway (Ottesen and Langedal, 2001) based on the sampling of 314 surface soils in gardens, parks and industrial areas to provide a database for environmental health risk evaluation. In the latter study, pollution levels were low, though Cd, Hg, Pb and Zn contaminated surface soils occurred in the central and older parts of the city and along main roads. Currently, collaboration between the Geological Survey of Ireland and the Norwegian Geological Survey concerns a Soil Survey of Dublin based on 1000 soil samples to provide information on soil chemistry in the urban environment relevant to human health, land use planning and urban regeneration (the SURGE Project). Further studies at Imperial College include EGRG postgraduate research to compile and interpret geochemical maps in Gibralter (Mesilio, 2000; Mesilio et al., 2003) and a survey of 65 urban households in Shanghai, China (Wang, 1997; Wang et al., 1997b). Collaboration with Hong Kong Polytechnic University, whose workers planned and undertook an urban geochemical survey of the densely populated area of Kowloon, Hong Kong, showed several metal hotspots in old industrial and residential areas (Li et al., 2004). 5.2. Platinum

5.1. Urban geochemical surveys Based on techniques of systematic sampling and analysis previously developed for geochemical reconnaissance surveys by AGRG and BGS, systematic sampling of urban topsoil (0–15 cm) was undertaken in 1996 in the London Borough of Richmondupon-Thames, a non-industrial residential area of 56 km2 and Wolverhampton, an industrial city in the West Midlands of 70 km2. In Richmond Pb concentrations were appreciably higher in the township than in neighbouring parkland with peak levels (>1000 mg/ kg) near busy road junctions and in the gardens of older houses (>500 mg/kg). In Wolverhampton the highest concentrations of Pb and especially Zn were located in areas of historical and contemporary industrial activity (Kelly, 1996; Kelly et al., 1996). The compilation of geochemical maps for some 25 further urban areas has been undertaken by BGS, based on the ‘‘total’’ concentration of metals in soils and focussing attention on hotspots where human exposure is potentially high (Fordyce et al., 2005). To assist local government in the application of these maps for land use planning, it is necessary to consider the solubility and potential bioavailability of the metals in order to assess possible risks to urban population groups. Under the NERC funded Urban Regeneration and Environment Programme, a consortium of four UK institutions (led by EGRG) conducted a multidisciplinary study in two English midland cities, Wolverhampton and Nottingham. This included the application of sequential chemical extraction, mineralogical analysis by SEM, Pb isotope studies, the development of a combined model to predict metal solubility in the soil and uptake into vegetables, and the production of maps showing potential risk to the average and highly exposed adult and infant sectors of the population (Hough et al., 2004; Thornton et al., 2008). It was concluded that this approach was necessary to assist local government

Since 1993, all new gasoline engine automobiles in the UK have been fitted with 3-way catalytic converters containing Pt, Pd and Rh. This has resulted in the accumulation of Pt and Pd in roadside soils and dusts from exhaust emissions. It has been estimated that the input of Pt from UK traffic from 1993 to 1999 varied between 120 and 250 kg (Farago et al., 1996, 1998). A program of sampling dusts from roads of high and low traffic density showed concentrations of Pt in the range of <0.30–4 ng/g and Pd < 2.1–57.9 ng/g, with higher concentrations associated with high traffic density. Metallic Pt is considered to be biologically inert and non-allergenic, and as emitted Pt is probably in the metallic or oxide form, it was concluded that the sensitising potential would be very low, and, at the time of writing, there was no evidence for adverse health effects in the general environment. A later experimental study with simulated lung fluid showed potential health risks due to the likely formation of Pt-chloride complexes in the respiratory tract. These have toxic and allergenic effects (Colombo et al., 2008). 6. Geochemical reconnaissance and water quality assessment; arsenic Collaboration between AGRG and the Cornwall River Authority, commencing in 1973, aimed at studying the possible application of geochemical reconnaissance based on multi-element analysis of sediment from tributary streams to aid in the assessment of water quality and to the mapping of the potential resources of potable waters. Studies were conducted in the catchments of the Fowey, Gannel, Carnon and Red rivers, providing an array of mineralisation and past mining activities and of catchment types. The Fowey was selected to provide an uncontaminated baseline. The sediments and waters of the uncontaminated tributaries of the Gannel,

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Carnon and Red rivers had similar trace element concentrations to those of the Fowey. Both sediments and waters of tributaries with past mining activities had significantly higher levels of Cu, Pb and Zn, though these ranged widely (Aston et al., 1974). It was concluded that surveys based on stream sediment analysis could prove useful as a preliminary indicator of sites where, under certain conditions of rainfall and runoff, the metal load in associated waters may exceed recommended limits (Thornton and Webb, 1977). This aspect of research in AGRG was then taken forward to focus on the metalloid As, which was for many years regarded as a contaminant associated with the Cu/Sn mining industry in SW England. The As, present as the mineral arsenopyrite, was frequently dumped along the river banks, and the eroded wastes are found in the river sediments. The map showing the regional distribution of As in England and Wales, based on the sampling and analysis of active stream sediments, shows an anomalous pattern for SW England, reflecting this contamination of tributary drainage (Webb et al., 1978). Detailed sampling of sediments and waters in the catchments of the rivers Tamer, Lyhner and Tavy illustrated the large degree of variation in As values between individual sampling stations, reflecting the main sources: the weathering and erosion of naturally occurring mineral veins; the dissolution and erosion of mine spoil; surface run-off from soils; and the dispersion of arsenical fumes from smelters (Aston et al., 1975). In general, the data showed that within SW England the distribution of As in river waters on both a regional and more local catchment basis can be related to the As content of stream sediments, thus confirming the potential use of geochemical reconnaissance surveys to water quality assessment. Further studies in the river Carnon and its estuary showed that large amounts of Fe, precipitated when the river water mixes with estuarine water, take out of solution substantial concentrations of Cu and As by sorption or co-precipitation. Eighty percent of the As in solution is removed on entering estuarine waters; this removal mechanism plays an important role for water quality of the estuarine water and shows a sink for As in the estuarine sediment (Johnson and Thornton, 1987).

7. Geochemistry and oyster culture A pilot programme of oyster seed production at the White Fish Authorities hatchery on the bank of the River Conway estuary, North Wales was unsuccessful due to intermittent failure of the oyster larvae to develop and settle satisfactorily. It was suggested that Pb and Zn mineralisation and mining activity in the tributaries of the river had given rise to metal contamination in the estuarine waters causing poor larvae performance. The larvae were reared in unfiltered water pumped on a daily basis from the estuary. After spat fall, they remained in flow tanks for ca. 8 weeks before transfer to trays in the Menai Straits. In April 1969, a detailed stream sediment and water survey confirmed concentrations of both Pb and Zn of 1% or more in sediments in the vicinity of mine tailings and mine adit drainage in the Conway catchment. Mean values of 900 mg/kg Zn and 250 mg/kg Pb were found in the estuarine sediments. The Zn content of the estuarine water showed marked seasonal and tidal fluctuations, ranging from 0.5 to 470 lg/L Zn, nearly 50 times the Zn concentration found in uncontaminated river and marine waters. Comparison between the Zn contents of water and particulate matter showed that by far the greater proportion of the total Zn was in the water (Elderfield et al., 1971). Beaker trials were conducted to study the effect of Zn, over the range recorded, on the young stages of the larvae of Crassostrea gigas. Increasing concentrations of Zn, added to sea water both as ZnSO4 and as natural mine adit water, resulted in decreasing growth, and increasing incidence of

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abnormality and larval mortality (Brereton et al., 1973). It was suggested that the effect of short term exposure to Zn may well have contributed to the intermittent failure of larvae and irregular productivity previously recorded at the hatchery. As a result of this study, the hatchery was moved from the metal contaminated Conway estuary to Anglesey, North Wales on the waters of the uncontaminated Menai Straits, a narrow stretch of shallow tidal water, which separates the island of Anglesey, off the NW coast of Wales from the mainland. Following this study, a further four estuaries were selected for geochemical investigation, each being of potential for shellfish production. Both the tributary drainage and estuarine sediments of the River Helford, a growing area for oysters, and Restronguet Creek, a holding area, both in Cornwall, were contaminated with metals, reflecting the history of base metal mining in their catchments. Those of the River Colne and Poole Harbour, growing areas for oysters with no history of mining, had relatively low metal contents (Aston and Thornton, 1973). A more detailed study of metals in sediments and waters of the tributary drainage in the hinterland of these estuaries and that of the Conway confirmed the sources of contamination from past and present day mining activities. It was concluded that geochemical reconnaissance based on stream sediment sampling would pinpoint potentially contaminated estuaries. Preliminary studies showed metal accumulation by oysters reflected the composition of estuarine mud (Thornton et al., 1975). A clear example is shown by the accumulation of Cu by oysters in the Helford estuary turning the flesh a blue colour.

8. Geochemical surveys and off-shore sewage disposal In collaboration with the Clyde River Purification Board, surveys of bottom sediments and waters were undertaken in 1972 and 1973 in an area off Garoch Head in the Firth of Clyde, to the west of Glasgow, Scotland, part of a commercial fishery, where the disposal of sewage sludge had taken place since 1904. The sludge contained large amounts of organic material and the metals Cd, Cr, Cu, Pb and Zn, reflecting inputs of industrial wastes and effluents to the Glasgow sewage system. Concern had previously been expressed of possible metal accumulation in some of the fauna within the dumping area; these included the commercial species Pandalus spp. (pink shrimp) and Nephrops norvegicus (Norway lobster/Dublin Bay prawn). Metal contamination of sediments was confined to the immediate deposit area and limited to within 2 km of the dumping ground, thus showing no evidence of large scale transport and confirming low bed mobility (Mackay et al., 1972). Sludges dumped contained 6–19 mg/kg Cd, 140–4240 mg/ kg Cr, 350–3270 mg/kg Cu, 300–850 mg/kg Pb and 580–7000 mg/ kg Zn. Sediments in the disposal area ranged from 4 to 8 mg/kg Cd, 87–175 mg/kg Cr, 250–300 mg/kg Cu, 270–400 mg/kg Pb and 440–680 mg/kg Zn. Depth of contamination of the sediments was confined to 40–50 cm. Relatively high values for metals in waters, compared with other Clyde areas and the Irish Sea, were thought to reflect both industrial contamination from the upper estuary and local contamination from sludge dumping (Halcrow et al., 1973). A high percentage of Pb was found to be contained in the particulate phase in the waters over the disposal area, which might constitute a hazard to filter-feeding organisms. Numbers of the in-faunal species (those living in the soft sea bottom) in the disposal area were dominated by polychaete worms, with a total absence of molluscs. Epi-faunal species, shrimp and whelk, taken with an Agassiz trawl, were higher within and around the sludge disposal area than from a nearby control area, probably related to the large amounts of organic debris. The whelk had appreciably raised tissue levels of Zn and the shrimp of Mn. Few Norway lobsters were caught, probably due to over fishing

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by non-British trawlers. Considering the small size of the area affected, it was concluded that the changes in numbers of fauna resulting from sludge disposal was probably not of economic importance (Halcrow et al., 1973). The trace metal content of demersal fish species was not significantly different from those reported elsewhere in the United Kingdom. Sludge dumping at this location in the Firth of Clyde ceased in 1974. A survey in 1985 of surface sediments in this old disposal area showed trace metal concentrations to be much lower, though with marked elevations at depth. It was concluded that about 1=4 to ½ of the input metals were retained in the sediment (Rodger et al., 1991). A parallel survey of the benthic community showed a marked recovery of fauna approaching ‘‘what should be considered as normal for this slightly (metal) enriched area’’ (Moore and Rodger, 1991). The authors concluded that this was ‘‘a reliable reflection of the resilience of the marine environment’’. Further sampling and analysis of sediments and fauna has been focused on organic constituents (Webster et al., 2005). 9. Geochemistry and human health In the opinion of the author, there are very few documented relations between the geochemical nature of rocks and soils and the incidence of human disease. Many attempts have been made by geochemists on the one hand to find diseases to fit geochemical patterns and of epidemiologists on the other to find geochemical patterns to fit diseases. The dangers of finding empirical relationships with no evidence of causality have been emphasised by Shaper (1979). As noted previously (Thornton and Webb, 1979; Thornton, 1987), in the UK the majority of the population live in large cities and towns, far removed from the natural geochemical environment. Little food is home grown and the majority of the diet comes from numerous sources both in Britain and overseas. Morbidity and mortality data are usually based on administrative units, which may be at local authority, district or county level. Conversely, geochemical maps are based on a much more detailed sampling network. The exceptions are mainly in regions where the population live in more remote areas and still largely depend on locally produced or home grown foodstuffs and/or local water supplies (i.e. live close to the land). In this respect, the most significant progress in linking geochemistry and human disease has taken place in China. Collaboration between AGRG and the Institute of Geochemistry at Guiyang, supported by the Royal Society and the Chinese Academy of Sciences, examined some of these relationships. The occurrence of both Keshan disease (an endemic cardiomyopathy) and Kaschin Beck disease (an endemic osteoarthropathy) have been shown to be related to the status of Se in the environment (Xu and Jiang, 1985), and have been decreased by Se supplementation. Endemic fluorosis is prevalent in several areas in China and has been associated with F-rich waters, natural F-enriched foods, and pollution by smoke as a result of burning F-rich coal. In the latter case, both dental and skeletal fluorosis are widespread in Zhijin County, Guizhou Province, where coal is burnt in houses with no ventilation and the staple diet, maize, is heavily contaminated with F (10–100 mg/kg DM) on drying (Zheng and Hong, 1988). This is clearly an example of a geochemically related disease. 10. AGRG/EGRG research in environmental geochemistry overseas 10.1. Brazil Informal sector Au mining in the Brazilian Amazon by the garimpeiros widely uses Hg to form an amalgam with the Au to separate

the metal from river sediment. Gold production in the River Tapajos system was estimated at 10–20 tonnes annually, from 1979 to the 1990s, with a similar loss of Hg into the ecosystem. A preliminary study, with EU DG1 and private funding, by a small team of European and Brazilian scientists led by the author, sampled blood and urine from miners, Au traders and local fisheating communities at four locations in the catchment of the river Tapajos, a tributary of the Amazon, with the support of GEDEBAM – an NGO concerned with the protection of the health of Amazonian communities. Evidence of excessive exposure to Hg was found in both traders, who burn off Hg from the amalgam, and the fish eating community (Cleary and Thornton, 1994; Cleary et al., 1994). In particular, at the Au mining camp of Crepuri (on the river Tapajos), six gold traders exceeded 100 lg/L Hg in urine, the highest being 843 lg/L Hg. Four out of the 22 sampled of the fish-eating community in the riverside village of Jacareacanga exceeded or approached a blood Hg level of 200 lg/L, a level associated with neurological changes. Elevated Hg levels were found in fish ranging up to 2.6 mg/kg fresh weight; 21 out of a total of 51 fish sampled exceeded the European Community Environmental Quality Standard of 0.30 mg/kg (Cleary and Thornton, 1994). Following these results, a feasibility study was undertaken, and a multidisciplinary project funded for a 4-year period by the European Commission, with financial control and management by Imperial College Consultants. This involved (a) setting up and equipping two speciality laboratories for Hg analysis on University campuses; (b) a medical team from the university of Odense in Denmark who were recruited to undertake detailed blood and urine sampling and make health checks on exposed populations including specific tests to identify possible neurological disorders; c) a German team to investigate methods of improving the mining process to cut down losses of Hg into the river system; (d) a Brazilian team to undertake dietary studies on fish eating riverine communities. The outcome was 4-fold: a simple modification to the mining process was developed, tested and demonstrated to the local miners, reducing Hg losses by as much as 70%; gold traders, who burn off Hg from the amalgam to purify the Au, were persuaded to install safety equipment to reduce losses of Hg vapour into the atmosphere and thus reduce human exposure; villagers, living along the river and depending on fish as their main dietary source, were found to greatly exceed WHO recommended guidelines for Hg intake; this was reflected in raised tissue levels. Medical tests did not show any major health effects (i.e. similar to those found in exposed populations in Japan), though measureable minor neurological disorders were found. Advice was given on the consumption of different fish species, as Hg accumulates up the food chain and pisciverous fish contain the highest Hg levels. Laboratories were donated by the EU to the two host universities, who were encouraged to set up consultancy arrangements to finance their future operation. At the conclusion of the project, a regional symposium was organised in Santarem to disseminate the results of the work to institutions in neighbouring Amazonian countries with similar Au mining activities. A preliminary study into the levels of Hg in different fish species in the River Tapajos was then undertaken, showing pisciverous fish with the highest concentrations as a result of biomagnification (Uryu et al., 2001). More detailed research into factors influencing Hg accumulation, including seasonal and spatial variations, showed Hg in fish tissues to be greater at low water than at high water, corresponding to a greater percentage of methylmercury (Howard, 2001). It was recommended that the riverine communities of the Tapajos river basin replace pisciverous fish with those of other feeding habit in their routine diet. Later studies showed that Hg in bottom sediments from the Rio Tapajos and flood plain mostly ranged from 10 to 250 ng/g while Hg in the water column was mostly in the particulate phase ranging up to 14 ng/L (Roulet et al., 1998, 2000).

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10.2. Chile Research carried out within the EU funded INCO-DC WAQUAMINAR project, a study of water quality in mining areas of South America, was focussed on the Rio Loa which flows through the Atacama desert in Northern Chile, and provides the main source of drinking and irrigation water for local communities. Very high concentrations of As, B and Li were found in the river water (mean 1400 lg/L As) and sediment (range 400–11,300 mg/kg As). The main source was identified as the El Tatio geothermal field in the headwaters in the Andes, though groundwater inputs may also contribute to As inputs in the middle and lower stretches of the Loa. Emissions from the Cu smelting plant at Chuquicamata, mine wastes deposited in the bed and banks of the river, and As-rich effluents from the water treatment plant at Calama are other potential sources of As (Romero et al., 2003). Chemical tests based on sequential extraction procedures showed that As in the river sediments was predominantly bound to Fe–Mn oxides as an adsorbed species probably removed from the river water (Dadea et al., 2001). The As is not readily mobile and this adsorption process may reduce the bioavailability of As in the river system. The high incidence of skin, lung and bladder cancers in the local communities has been linked to exposure to As, though reliable epidemiological data are not available. 10.3. Kenya A reconnaissance geochemical survey of the mineral status of soils and plants was undertaken in the Lake Nakuru National Park, Kenya’s first rhinoceros sanctuary (Maskall, 1991; Maskall and Thornton, 1989). Located in the Rift Valley, soils are mainly derived from volcanic ash sediments. Total concentrations of Cu and Co were very low and Se and P low. Grasses, the diet of impala and water buck, contained higher levels of Cu and Co and lower levels of Se than browse plants, the diet of the black rhinoceros. Concentrations of Mo were relatively high in all plants and increased in wetter soils of high pH. Elevated Mo levels in both grasses and browse plants are likely to contribute to Cu deficiencies in impala and water buck; 30% of impala sampled had a blood Cu level below that regarded as normal in domestic livestock. At the conclusion of this study, recommendations were made to the Department of Wildlife, Conservation and Management for mineral supplements to be made available to the wildlife. Further studies were conducted on the dark-brown clays developed from lavas from Mount Kenya at Solio Wildlife Reserve, where low levels of Cu and Co were found; on soils developed from basaltic lavas at Aberdare’s Salient and Amboselie National Park; and on basalts at Lewa Downs Wildlife Reserve, where higher concentrations of trace elements were found, reflecting the basic nature of the parent material (Maskall and Thornton, 1991). A final study, based on systematic soil and vegetation sampling, carried out in the Shimba Hills National Reserve, indicated potential mineral deficiencies of Na, K, P and Zn in the herbage diet of the sable antelope (Sutton et al., 2002).

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vicinity of the mine were relatively high due to seepage of metals from mine dump sites (Jung, 1993; Jung and Thornton, 1997). Elevated concentrations of As, Sb and Bi were found in stream sediments and surface soils in the vicinity of the Dalsung Cu–W mine in Korea, decreasing with distance from the mine. Soils and waste materials from the mine dumps averaged 2500 mg/kg As, 54 mg/kg Sb and 436 mg/kg Bi. Concentrations of the three metalloids were slightly elevated in soybean leaves and spring onions (Jung et al., 2002). Geochemical surveys were undertaken along 23 river valleys in Korea underlain by black shale and oil shale (Kim, 1993; Kim and Thornton, 1993). The average trace element concentration of Okchon uraniferous black shale was 6.4 mg/kg Cd, 136 mg/kg Mo and 8.6 mg/kg Se. Molybdenum concentrations ranged up to 167 mg/kg in alluvial soils and 59 mg/kg in garden soils developed from the black shale and were not associated with any obvious phytotoxicity. Concentrations of Cd in lettuce were raised and posed a potential health problem from long-term exposure. 10.5. Romania A survey of metal(loid) concentrations in soils and vegetables was undertaken in the town of Zlatna, western Romania, population 9000, dominated by a large Cu smelter (Pope et al., 2005). The smelter, situated in the centre of the town, processed 80,000 tons of ore concentrate per annum, producing 14,000 tons Cu. Concentrations of Cu in surface soils in and around the town ranged from 40 to 12,000 mg/kg (arithmetic mean 1683 mg/kg), with some of the highest values in the grounds of the school. Soil contamination with Pb, Zn and As was also large, ranging up to 7860, 6360 and 484 mg/kg, respectively, in the school grounds adjacent to the smelter. Residents of Zlatna are exposed to levels of these elements that far exceed recommended guideline values. 10.6. Slovakia The coal-fired power-plant in the Prievidza district of central Slovakia has emitted in excess of 3000 tonnes As since commencing operations in the 1950s. This has resulted from the combustion of brown coal containing up to 1500 mg/kg As. An environmental and health study involving EGRG and several European partners from Germany, the Czech Republic and Slovakia, with funding from the EU (the EXPASCAN project) was undertaken over the period 1999–2000, including the analysis of soils and dusts from 550 households (Keegan et al., 2002). Arsenic levels in garden soils sampled within 5 km of the power plant ranged from 14 to 134 mg/kg (geom. mean 43 mg/kg, n = 40), and in housedust 7– 57 mg/kg (geo. mean 19 mg/kg, n = 25). A case-control study of non-melanoma skin cancer showed that its incidence was 21% higher in the vicinity of the power plant, decreasing with distance away from the emission source. However, as emissions were highest 20 years ago, current environmental levels might not reflect past exposure (Pesch et al., 2002; Thornton et al., 2003). 10.7. Sweden

10.4. Korea Studies in the vicinity of the Sambo Pb–Zn mine, one of the biggest base metal mines in Korea, found elevated concentrations of metals in surface soils around the mine dump, with mean values of 12, 210, 2700 and 8300 mg/kg for Cd, Cu, Pb and Zn, respectively, and up to 640 mg/kg Pb and 1230 mg/kg Zn in household gardens. Soybean leaves and spring onions accumulated Cd and Zn and potential health problems from long-term exposure were noted (Jung and Thornton, 1996). Concentrations of Cd, Cu, Pb and Zn in paddy soils, rice plants and irrigation waters in the immediate

Soil and road dust samples were taken on a 0.5 km grid within the city of Landskrona, southern Sweden, the site of the only secondary Pb smelter in Scandinavia (Farago et al., 1999). Soil Pb and Zn levels were elevated within a distance of 3.5 km. of the smelter, with mean concentrations of 792 mg/kg Pb and 421 mg/ kg Zn in an industrial section within 0.5 km. Concentrations of Pb in house dusts from homes with young children were only slightly raised, and blood Pb levels in the 37 children tested ranged from 1.5 to 5.1 lg/100 mL. The relatively low levels of Pb in the home and in the children’s blood were thought to be due to the fact that

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shoes are removed at the entrance, the housing is relatively new and floors are wood or plastic.

11. Summary and conclusions This paper presents the results of applied research undertaken by AGRG/EGRG over the period 1964–2004. The most significant contribution to agriculture was the recognition of widespread Mo anomalies in marine black shales, initially shown by geochemical mapping, leading to elevated Mo concentrations in soil and pasture herbage, causing both clinical and sub-clinical Cu deficiency in cattle. This may not be recognised on many farms and will result in a loss in production. Rates of soil ingestion by cattle and sheep have been determined and shown to be a major exposure pathway for toxic metals and As on contaminated land. Ingested soil is also a source of dietary Co. Iron in soil ingested has been shown experimentally to reduce the absorption and utilisation of dietary Cu in the rumen of sheep. Metal contamination of soils is high in UK areas of historical metalliferous mining and smelting. Levels of Cd and Zn in the old Zn mining district of Shipham are very large in both household garden soils and indoor dusts. It was concluded that exposure of the local population to Cd was relatively low due to low consumption of home grown produce. No adverse health effects were found, though many long term residents did not participate in health studies. Agricultural pastures in the Pb–Zn mining area of Derbyshire are contaminated with Pb and the main exposure route to cattle was shown to be ingested soil. Blood Pb values increased by small amounts with increasing soil Pb, but symptoms of Pb poisoning were absent. Household gardens and indoor dusts in some old mining villages are heavily contaminated with Pb. Lead on the hands of young children was measured and blood Pb shown to fall within a range acceptable in the 1980s. Much of the Pb was shown by SEM to be present in soil, dust and on children’s hands as the insoluble mineral pyromorphite, thus resulting in the metal’s low bioavailability. However, in the light of present knowledge, it is now recommended that detailed blood Pb surveys are conducted in old UK mining areas. Arsenic contamination of both agricultural and urban land has been shown to be widespread in the historical Cu–Sn mining areas of Cornwall and Devon. Intake into grazing cattle was mainly through ingested soil and there were no apparent adverse health effects. Arsenic uptake into home grown vegetables was low in heavily contaminated garden soils and the main exposure route to local populations was considered to be ingested and inhaled dust and soil. Analysis of urine showed levels of inorganic As and organic As metabolites to be slightly raised in high As localities. A nation-wide survey of metals in urban dusts and soils showed levels of Pb in the home environment to be of concern to the health of the young child. A detailed study of all sources of Pb intake and uptake in the 2-year old child was undertaken in Birmingham, including behavioural measurements to quantify hand-to-mouth activity. Blood Pb was principally related to dust Pb loading and the rate of mouthing by the child. In 1985 the mean blood Pb was 12 lg/dL; on the basis of repeat environmental sampling, this was predicted to have fallen to 9.7 lg/dL by 1995. Urban geochemical surveys based on the systematic sampling of surface soils in Richmond-on-Thames, Wolverhampton and Nottingham have shown elevated levels of Pb and Zn along main roads and near roundabouts, in the gardens of old houses and in the vicinity of past and present-day industry. Urban geochemical maps, based on ‘‘total’’ metal concentrations in soil may be misleading, as much of the Pb for example may be insoluble and biologically inert. More detailed analysis of the chemistry and

mineralogy of the metals gave a more realistic picture of their availability and of possible human exposure. This will assist in land use planning by local government. Levels of Pt and Pd were raised in roadside dusts and soils from vehicles with catalytic converters. It was predicted that adverse health effects were unlikely due to the insoluble nature of metallic Pt. Positive relationships between geochemistry and human health are mostly confined to remote areas of the world. In China, the Se responsive Keshan and Kaschin-beck diseases have been prevented by Se supplementation and; endemic fluorosis is widespread, mainly caused by F-rich water and food contamination through burning F-rich coal. Several other aspects of research by AGRG/EGRG in the UK and overseas are briefly detailed. Of particular importance is the study of Hg use by informal sector Au miners in the Brazilian Amazon leading to Hg losses into the river system, accumulation in pisciverous fish and exposure in fish-eating riverine communities. Outputs from research have resulted in improved mining methods to reduce Hg losses, better practices by traders to lower Hg losses into the atmosphere and reduce human exposure, and dietary guidance on the safety of different fish species.

12. Directions for future research There are many areas in which research in applied environmental geochemistry will continue to contribute to the health, well being and prosperity of global populations. Multi-element national and regional geochemical surveys based on the systematic sampling of sediments, rocks, and/or soils have yet to be undertaken in many developing and emerging countries where finance and infrastructure are limited. As noted in this paper, such surveys are of direct application to agricultural production, water quality assessment and issues of public health. In more affluent economies, direct relationships between the geochemistry of rocks and soils and the health of crops and livestock have already been shown. It is proposed that this research area should be further advanced as sustainable agriculture will in future depend on less intensive management systems and will for example provide a closer link between the nutrition of livestock and soil chemical composition. Possible effects of climate change will also need to be examined. Urban geochemical surveys continue to proliferate and will assist with risk assessments and decision support systems for local government regarding land use planning and advice to the home gardener. However, as noted in this paper, it will be important to avoid the creation of land/property blight by only producing maps based on ‘‘total’’ concentrations of potentially harmful elements. It will be equally important to take into account interactions with chemical factors influencing the bioavailability of elements, potential uptake by food plants and their bio accessibility in ingested and inhaled soils and dusts. Relationships between geochemistry and epidemiology are beset with problems but may well provide useful results to assist the health professional to understand the distribution and cause of some diseases, particularly in less developed parts of the world. For example, as previously noted by the author (Thornton, 2001), it will be essential to obtain reliable information on the actual impacts of As contamination worldwide, both natural and manmade, on national economies, human health and the overall environment. There are obvious implications to the understanding of human disease, and to current and future agricultural production, potable water supplies, riverine and inshore fisheries, urban development and planning, and overall land use. It is also the responsibility of those in more affluent countries to continue to assist in the surveying of As enrichment in groundwater and soils and to

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undertake research into the chemistry and mineralogy of source materials and into exposure pathways and remediation technologies to provide potable water supplies and wholesome food crops for local populations. Acknowledgments The author acknowledges the state of the art laboratory facilities and technical support at AGRG/EGRG under the direction of M. Thompson and M. Ramsey. He is grateful to the many MSc and PhD students whose enthusiasm and hard work made a major contribution to much of the research reported. References Abrahams, P., 1983. Distribution, Dispersion and Agricultural Significance of Metals in Soils of the Mining Regions of Southwest England. Unpubl. PhD Thesis, Univ. London. Abrahams, P., Thornton, I., 1987. Distribution and extent of landcontaminated by arsenic and associated metals in mining regions of southwest England. Trans. Inst. Min. Metall. Sect. B: Appl. Earth Sci. 96, 131–138. Abrahams, P., Thornton, I., 1994. The contamination of agricultural land in the metalliferous province of southwest England: implications to livestock. Agric. Ecosys. Environ. 48, 125–137. Alloway, B.J., 1995. Cadmium. In: Alloway, B.J. (Ed.), Heavy Metals in Soils. Blackie Academic and Professional, London, pp. 122–151. Anderson, P.H., Berrett, S., Patterson, D.S.P., 1979. The biological selenium status of livestock in Britain as indicated by erythrocyte glutathione peroxidise activity. Vet. Res. 104, 235–238. Aston, S., Thornton, I., 1973. The application of regional geochemical reconnaissance surveys in the assessment of water quality and estuarine pollution. Water Res. 9, 189–195. Aston, S.R., Thornton, I., Webb, J.S., Purves, J.B., Milford, B.L., 1974. Stream sediment composition: an aid to water quality assessment. Water Air Soil Pollut. 3, 321– 325. Aston, S.R., Thornton, I., Webb, J.S., Millford, B.L., Purves, J.B., 1975. Arsenic in stream sediments and waters of South West England. Sci. Total Environ. 4, 347–358. Barltrop, D., Strehlow, C.D., Thornton, I., Webb, J.S., 1975. Absorption of lead from dust and soil. Postgrad. Med. J. 51, 801–804. Birke, N., Rouch, U., 2000. Urban geochemistry: investigations in the Berlin metropolitan area. Environ. Geochem. Health 22, 233–248. Brebner, J., 1986. The Role of Soil Ingestion in the Trace Element Nutrition of Grazing Livestock. Unpubl. PhDThesis, Univ. London. Brebner, J., Suttle, N.F., Thornton, I., 1987. Assessing the availability of ingested soil cobalt for the synthesis of vitamin B12 in the ovine rumen. Proc. Nutr. Soc. 46, 766A. Brereton, A., Lord, H., Thornton, I., Webb, J.S., 1973. Effect of zinc on growth and development of larvae of the Pacific Oyster Crassostrea gigas. Mar. Biol. 19, 96– 101. Chandramouli, K., Steer, C.D., Ellis, M.E., Emond, A.M., 2009. Effects of early childhood lead exposure on academic performance and behaviour of school age children. Arch. Dis. Child. 94, 844–848. Cleary, D., Thornton, I., 1994. The environmental impact of gold mining in the Brazilian Amazon. In: Hester, R.E., Harrison, R.M. (Eds.), Mining and its Environmental Impact. Issues, Environmental Science and Technology. Royal Society of Chemistry, London, pp. 17–29. Cleary, D., Thornton, I., Brown, N., Kazantzis, G., Delves, T., Worthington, S., 1994. Mercury in Brazil. Nature 369, 613–614. Colbourn, P., Alloway, B.J., Thornton, I., 1975. Arsenic and heavy metals in soils associated with regional geochemical anomalies in South-West England. Sci. Total Environ. 4, 359–363. Colombo, C., Monhenius, A.J., Plant, J.A., 2008. Platinum, palladium and rhodium release from vehicle exhaust catalysts and road dust exposed to simulated lung fluids. Ecotoxicol. Environ. Safety 71, 722–730. Cotter-Howells, J., 1992. Lead Minerals in Soils Contaminated by Mine-Waste: Implications to Human Health. Unpubl. PhD Thesis, Univ. London. Cotter-Howells, J., Thornton, I., 1991. Sources and pathways of environmental lead to children in a Derbyshire mining village. Environ. Geochem. Health 13, 127– 135. Culbard, E.B., Thornton, I., Watt, J., Wheatley, M., Moorcroft, S., Thompson, M., 1988. Metal contamination in British urban dusts and soils. J. Environ. Qual. 17, 226– 234. Dadea, C., Fanfani, L., Keegan, T.L., Farago, M., Thornton, I., 2001. Sequential extraction in stream sediments from the Loa basin(Northern Chile). In: Cidu, R. (Ed.), Proc. 10th Internat. Symp. Water–Rock Interaction, vol 2. A.A. Balkema, Lisse, pp. 1055–1058. Davies, D.J.A., Thornton, I., 1987. The influence of house age on lead levels in dusts and soils in Brighton, England. Environ. Geochem. Health 9, 65–67. Davies, D.J.A., Thornton, I., Watt, J.M., Culbard, E.B., Harvey, P.G., Delves, H.T., Sherlock, J.C., Smart, G.A., Thomas, J.F.A., Quinn, M.J., 1990. Lead intake and blood lead in two-year-old U.K. urban children. Sci. Total Environ. 90, 13–29.

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Dines, H.G., 1956. The Metalliferous Mining Region of South-West England, vol. 1. Memoirs of the Geological Survey of Great Britain. HMSO, London. Elderfield, H., Thornton, I., Webb, J.S., 1971. Heavy metals and oyster culture in Wales. Mar. Pollut. Bull. 2, 44–47. Elliott, P., Arnold, R., Cockings, S., Eaton, N., Jarup, L., Jones, J., Quinn, M., Rosato, M., Thornton, I., Tristan, E., Wakefields, J., 2000. Risk of mortality, cancer incidence and stroke in a population potentially exposed to cadmium. Occupat. Environ. Med. 57, 94–97. Farago, M.E., Kavanagh, P.J., 1999. High arsenic containing soils in south west England and human exposure assessment. In: Armannson, A. (Ed.), Proc. 5th Internat. Symp. Geochemistry of the Earth’s Surface, Reykjavik, Iceland. Balkema, Rotterdam, pp. 181–184. Farago, M.E., Kavanagh, P., Blanks, R., Kelly, J., Kazantzis, G., Thornton, I., Simpson, P.R., Cook, J.M., Parry, S., Hall, G.M., 1996. Platinum metal concentrations in urban road dust and soil in the United Kingdom. Fres. J. Anal. Chem. 354, 660–663. Farago, M.E., Thornton, I., Kavanagh, P., Elliott, P., Leonardi, G.S., 1997. Health aspects of human exposure to high arsenic concentrations in soil in south-west England. In: Abernathy, C.O., Calderon, R.L., Chappell, W.R. (Eds.), Arsenic Exposure and Health Effects. Chapman and Hall, London, pp. 191–209. Farago, M.E., Kavanagh, P., Blanks, R., Kelly, J., Kazantzis, G., Thornton, I., Simpson, P.R., Cook, J.M., Delves, H.T., Hall, G.M., 1998. Platinum concentrations in road dust and soil, and in blood and urine in the United Kingdom. Analyst 123, 451– 454. Farago, M.E., Thornton, I., White, N.D., Tell, I., Martensson, M.-B., 1999. Environmental impacts of a secondary lead smelter in Landskrona, southern Sweden. Environ. Geochem. Health 21, 67–82. Fleming, G.A., Walsh, T., 1957. Selenium occurrence in certain Irish soils and its toxic effect on animals. Roy. Irish Acad. Proc. 58, 151–166. Fletcher, W.K., 1968. Geochemical Reconnaissance in Relation to Copper Deficiency in Livestock in the Southern Pennines and Devon. Unpubl. PhD Thesis, Univ. London. Fordyce, F.M., Brown, S.E., Ander, E.L., Rawlins, B.G., O’Donnell, K.E., Lister, T.R., Breward, N., Johnson, C.C., 2005. GSUE: urban geochemical mapping in Great Britain. Geochem. Explor. Environ. Anal. 5, 325–336. Geeson, N.A., Abrahams, P.W., Murphy, M.P., Thornton, I., 1998. Fluorine and metal enrichment of soils and pasture herbage in the old mining areas of Derbyshire, UK. Agric. Ecosys. Environ. 68, 217–231. Halcrow, W., Mackay, D.W., Thornton, I., 1973. The distribution of trace metals and fauna in the Firth of Clyde in relation to the disposal of sewage sludge. J. Mar. Biol. Assoc. UK 53, 721–739. Hamilton, E.I., 2000. Environmental variables in a holistic evaluation of land contaminated by historic mine wastes: a study of multi-element mine wastes in West Devon, England using arsenic as an element of potential concern to human health. Sci. Total Environ. 249, 171–221. Harding, E.R., 1993. Arsenic Contamination of Garden Soils and Housedusts in West Cornwall. Unpubl. MSc Thesis, Univ. London. Healy, W.B., 1967. Ingestion of soil by sheep. Proc. N. Z. Soc. Anim. Prod. 27, 109– 120. Healy, W.B., 1968. Ingestion of soil by dairy cows. N. Z. J. Agric. Res. 11, 487–499. Hough, R.L., Breward, N., Young, S.B., Crout, N.M.J., Tye, A.M., Moir, A.M., Thornton, I., 2004. Assessing potential risk of heavy metal exposure from consumption of home-grown vegetables by urban populations. Environ. Health Perspect. 112, 215–221. Howard, B.M., 2001. Mercury Accumulation in Fishes of the Rio Tapajos, Brazilian Amazonia. Unpubl. PhD Thesis, Univ. London. Hunt, A., Johnson, D.L., Watt, J.M., Thornton, I., 1992. Characterising the sources of particulate lead in housedust by automated scanning electron microscopy. Environ. Sci. Technol. 26, 1513–1532. Johnson, L.R., 1983. A Study of Arsenic in Housedusts and Garden Soils with Relation to Geochemistry and Health. Unpubl. MSc Thesis, Univ. London. Johnson, C., Thornton, I., 1987. Hydrological and chemical factors controlling the concentrations of Fe, Cu, Zn and As in a river system contaminated by acid mine drainage. Water Res. 21, 359–365. Jordan, W.J., 1975. The Application of Regional Geochemical Reconnaissance to Arable Cropping in England and Wales. Unpubl. PhD Thesis, Univ. London. Jordan, W.J., Alloway, B.J., Thornton, I., 1975. The application of regional geochemical reconnaissance data in areas of arable cropping. J. Sci. Food Agric. 26, 1413–1423. Jung, M.C., 1993.Dispertion and Environmental Impacts of Heavy Metals in Metalliferous Mines in Britain and Korea. Unpubl. PhD Thesis, Univ. London. Jung, M.C., Thornton, I., 1996. Heavy metal contamination of soils and plants in the vicinity of a lead–zinc mine, Korea. Appl. Geochem. 11, 53–59. Jung, M.C., Thornton, I., 1997. Environmental contamination and seasonal variation of metals in soils, plants and waters in the paddy fields around a Pb–Zn mine in Korea. Sci. Total Environ. 198, 105–121. Jung, M.C., Thornton, I., Chon, H.-T., 2002. Arsenic, Sb and Bi contamination of soils, plants, waters and sediments in the vicinity of the Dalsung Cu–W mine in Korea. Sci. Total Environ. 295, 81–89. Kavanagh, P.J., 1998. Impacts of High Arsenic Concentrations in South West England on Human Health and Agriculture. Unpubl. PhD Thesis, Univ. London. Kavanagh, P.J., Farago, M.E., Thornton, I., Elliott, P., Goessler, W., Irgolic, K.J., 1997. Urinary arsenic concentrations in a high arsenic area of south west England. Analyst 123, 27–29. Kavanagh, P., Farago, M.E., Thornton, I., Goessler, W., Kuehnelt, D., Schlagenhaufen, C., Irgolic, K.J., 1998. Urinary arsenic species in Devon and Cornwall residents, UK. A pilot study. Analyst 123, 27–29.

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Keegan, T., Hong, Bing., Thornton, I., Fragao, M.E., Jakubis, M., Pesch, B., Ranft, U., Niewenhuijsen, M.J., The EXPASCAN Study Group, 2002. Assessment of arsenic levels in Prievidza district. J. Exp. Anal. Environ. Epidemiol. 12, 179–185. Kelly, J.P., 1996. Influence of Geology and Anthropogenic Activity on the Geochemistry of Urban Soils. Upubl. PhD Thesis, Univ. London. Kelly, J.P., Thornton, I., Simpson, P.R., 1996. Urban geochemistry: a study of the influence of anthropogenic activity on the heavy metal content of soils in traditionally industrial and non-industrial areas of Britain. Appl. Geochem. 11, 363–370. Kim, K.W., 1993. Influence of Uraniferous Black Shales on Trace Elements in Soils and Crops in Korea. Unpubl. PhD Thesis, Univ. London. Kim, K.W., Thornton, I., 1993. Influence of Ordovician black shales on the trace element composition of soils and food crops, Korea. Appl. Geochem. Suppl. 2, 249–255. Leech, A., 1984. The Application of Regional Geochemistry to the Causes and Predicted Incidence of Bovine Hypocupraemia. Unpubl. PhD Thesis, Univ. London. Leech, A.F., Thornton, I., 1987. Trace elements in soils and pasture herbage on farms with bovine hypocupraemia. J. Agric. Sci. 1987, 591–597. Leech, A., Howarth, R.J., Thornton, I., Lewis, G., 1982. Incidence of bovine copper deficiency in England and the Welsh borders. Vet. Rec. 111, 203–204. Leonardi, G.S., Elliott, P., Thornton, I., 1995. Arsenic contamination and bladder cancer: an ecological study. In: Ann. Conf. Internat. Soc. Environmental Epidemiology and International Society for Exposure Analysis. Abstract PO71. Epidemiology 6, Supplement to No. 4. Li, X.D., 1993. The Study of Multi-Element Associations in Rock–Soil–Plant Systems in Some Old Metalliferous Mining Areas and Natural Geological Formations, England. Upubl. PhD Thesis, Univ. London. Li, X.D., Thornton, I., 1993. Arsenic, antimony and bismuth in soil and pasture herbage in some old metalliferous mining areas in England. Environ. Geochem. Health 15, 135–144. Li, X.D., Thornton, I., 2001. Chemical partitioning of trace and major elements in soils contaminated by mining and smelting activities. Appl. Geochem. 16, 1693–1706. Li, X.D., Lee, S.I., Wong, S.C., Shi, W., Thornton, I., 2004. The study of metal contamination in urban soils of Hong Kong using a GIS-based approach. Environ. Pollut. 129, 113–124. Mackay, D.W., Halcrow, W., Thornton, I., 1972. Sludge dumping in the Firth of Clyde. Mar. Pollut. Bull. 3, 7–10. Maskall, J.E., 1991. The Influence of Geochemistry of Trace Elements on Soils and Plants in Wildlife Conservation Areas of Kenya. Unpubl. PhD Thesis, Univ. London. Maskall, J.E., Thornton, I., 1989. The mineral status of Lake Nakuru National Park, Kenya: a reconnaissance survey. Afr. J. Ecol. 27, 191–200. Maskall, J.E., Thornton, I., 1991. The influence of geochemistry on trace element concentrations in soil and plants of wildlife conservation areas of Kenya. Environ. Geochem. Health 13, 93–107. Matthews, H., 1982. The Distribution of Cadmium and Associated Elements in the Soil–Plant System at Sites in Britain Contaminated by Mining, Smelting and Metal-Rich Bedrock. Unpubl. PhD Thesis, Univ. London. Matthews, H., Thornton, I., 1982. Seasonal and species variation in the content of cadmium and associated metals in pasture plants at Shipham. Plant Soil 66, 181–193. Mesilio, L., 2000. A Geochemical Reconnaissance Survey of Soils in Gibraltar. Unpubl. MSc Thesis, Imperial College of Science, Technology and Medicine, London, UK. Mesilio, L., Farago, M.E., Thornton, I., 2003. Reconnaissance soil geochemical survey of Gibraltar. Environ. Geochem. Health 25, 1–8. Moorcroft, S., Watt, J., Thornton, I., Wells, J., Strehlow, C.D., Barltrop, D., 1982. Composition of dusts and soils in an apparently uncontaminated rural village in Southwest England – implications to human health. In: Hemphill, D.D. (Ed.), Trace Substances in Environmental Health, vol. XIV. University of Missouri, Columbia, Missouri, USA, pp. 155–163. Moore, D.C., Rodger, G.K., 1991. Recovery of a sewage sludge dumping area. 11. Macrobenthic community. Mar. Ecol. Prog. Ser. 75, 301–308. O’Donohoe, J., Chalkley, S., Richmond, J., Barltrop, D., 1998. Blood lead in UK children: a time for a lower action level. Clinical Sci. 98, 219–223. Ottesen, R.T., Langedal, M., 2001. Urban geochemistry in Tondheim, Norway. Norges Geologiske Undersøkelse Bull. 438, 63–69. Pesch, B., Ranft, V., Jacubis, P., Niewenhuijsen, M.J., Hergemoller, A., Unfried, K., Jacubis, M., Miskovic, P., Keegan, T., The EXPASCAN Study Group, 2002. Environmental arsenic exposure from a coal-burning power plant as a potential risk factor for non-melanoma skin cancer: results from a case-control study in the district of Prievidza, Slovakia. Am. J. Epidemiol. 155, 798–809. Pope, J.M., Farago, M.E., Thornton, I., Cordos, E., 2005. Metal enrichment in Zlatma, a Romanian copper smelting town. Water Air Soil Pollut. 162, 1–18. Purves, D., 1966. Contamination of urban garden soils with copper and boron. Nature 210, 1077. Purves, D., 1968. Trace-element contamination of urban soils. Trans. 9th Int. Congr. Soil Sci. 2, 351–355. Rodger, G.K., Davies, I.M., Moore, D.C., 1991. Recovery of a sewage sludge dumping ground. 1. Trace metal concentration in the sediment. Mar. Ecol. Prog. Ser. 75, 293–299. Romero, L., Alonso, H., Campano, P., Fanfani, L., Cidu, R., Dadea, C., Keegan, T., Thornton, I., Farago, M., 2003. Arsenic contamination in waters and sediments of the Rio Loa (Second Region, Chile). Appl. Geochem. 18, 1399–1416.

Rother, J.A., Millbank, J.W., Thornton, I., 1982. Seasonal fluctuations in nitrogen fixation (acetylene reduction) by free-living bacteria in soils contaminated with cadmium, lead and zinc. J. Soil Sci. 33, 101–113. Rother, J.A., Millbank, J.W., Thornton, I., 1983. Nitrogen fixation by white clover (Trifolium repens) in grassland on soils contaminated with Cd, Pb and Zn. J. Soil Sci. 34, 127–136. Roulet, M., Lucotte, M., Canuel, R., Rheault, I., Tran, S., De Freitos Gog, Y.G., Farella, N., Souza do Vale, R., Sousa Passos, C., Jesus, De., da Silva, E., Mergler, D., Amorim, M., 1998. Distribution and partition of mercury in waters of the Tapajós River Basin, Brazilian Amazon. Sci. Total Environ. 213, 203–211. Roulet, M., Lucotte, M., Canuel, R., Farella, N., Courcelles, M., Guimarães, J.-R.D., Mergler, D., Amorim, M., 2000. Increase in mercury contamination in lacustrine sediments following deforestation in the central Amazon. Chem. Geol. 165, 243–266. Shaper, A.G., 1979. Epidemiology for geochemists. Philos. Trans. Roy. Soc. Lond. B 288, 127–136. Smart, L., 1991. The Agricultural Implications of Anomalous Molybdenum Concentrations in Reclaimed Saltmarsh Soils along the Suffolk Coast. Unpubl. MSc Thesis, Imperial College of Science, Technology and Medicine, London. Smith, C.A., 1983. The Distribution of Selenium in Some Soils Developed on Silurian, Carboniferous and Cretaceous Systems in England and Wales. Unpubl. PhD Thesis, Univ. London. Stewart, W.L., Allcroft, R., 1956. Lameness and poor thriving in lambs on farms in old lead mining areas in the Pennines. 1. Field investigations. Vet. Rec. 68, 723– 728. Suttle, N.F., Alloway, B.J., Thornton, I., 1975. An effect of soil ingestion on the utilization of dietary copper by sheep. J. Agric. Sci. Cambridge 84, 249–354. Suttle, N.F., Abrahams, P., Thornton, I., 1984. The role of soil times dietary sulphur interaction in the impairment of copper absorption by ingested soil in sheep. J. Agric. Sci. Cambridge 103, 81–86. Sutton, P., Maskall, J., Thornton, I., 2002. Concentrations of major and trace elements in soil and grass at Shimba Hills National Reserve, Kenya. Appl. Geochem. 17, 1003–1016. Thomson, I., 1971. Regional Geochemical Studies of Black Shale Facies with Particular Reference to Trace Element Disorders in Animals. Unpubl. PhD Thesis, Univ. London. Thomson, I., Thornton, I., Webb, J.S., 1972. Molybdenum in black shales and the incidence of bovine hypocuprosis. J. Sci. Food Agric. 23, 879–891. Thornton, I., 1974. Biochemical and soil ingestion studies in relation to trace element nutrition of livestock. In: Proc. 2nd Internat. Symp. Trace Element Metabolism in Animals, Wisconsin, pp. 451–454. Thornton, I., 1987. Mapping of trace elements in relation to human disease. Clin. Nutr. 6, 97–104. Thornton, I., 1991. Metal contamination of soils in urban areas. In: Bullock, P., Gregory, P.J. (Eds.), Soils in the Urban Environment. British Society of Soil Science. Blackwell Scientific Publications, Oxford. Thornton, I., 1993. Environmental geochemistry and health in the 1990’s: a global perspective. Appl. Geochem. Suppl. 2, 203–210. Thornton, I., 1996. Impacts of mining on the environment; some local, regional and global issues. Appl. Geochem. 11, 355–361. Thornton, I., 2001. Arsenic: the ‘King of Poisons’ in antiquity – a possible threat to future sustainability. In: Chappell, W.R., Abernathy, C.O., Calderon, R.I. (Eds.), Arsenic Exposure and Health Effects, vol. IV. Elsevier Science Ltd., Amsterdam, pp. 1–7. Thornton, I., 2002. Geochemistry and the mineral nutrition of agricultural livestock and wildlife. Appl. Geochem. 17, 1017–1028. Thornton, I., 2010. Research in applied environmental geochemistry, with particular reference to geochemistry and health. Geochem. Explor. Environ. Anal. 10, 317– 329. Thornton, I., Abrahams, P., 1983. Soil ingestion – a major pathway of metals into livestock grazing contaminated land. Sci. Total Environ. 28, 287–294. Thornton, I., Webb, J.S., 1977. Potential application in the water industry of regional geochemical maps of England and Wales. J. Inst. Water Eng. Sci. 31, 11–25. Thornton, I., Webb, J.S., 1979. Geochemistry and health in the United Kingdom. Philos. Trans. Roy. Soc. Lond. B288, 151–168. Thornton, I., Kershaw, G.F., Davies, M.K., 1972. An investigation into copper deficiency in cattle in the Southern Pennines. 1: identification of suspect areas using geochemical reconnaissance followed by blood copper surveys. 11: response to copper supplementation. J. Agric. Sci. 78, 157–171. Thornton, I., Watling, H., Darracott, A., 1975. Geochemical studies in several rivers and estuaries used for oyster rearing. Sci. Total Environ. 4, 325–345. Thornton, I., John, S., Moorcroft, S., Watt, J., 1980. Cadmium at Shipham: a unique example of environmental geochemistry and health. Trace Substances Environ. Health XIV, 27–37. Thornton, I., Kinniburgh, D.G., Pullen, G., Smith, C.A., 1983. Geochemical aspects of selenium in British soils and implications to animal health. Trace Elem. Environ. Health XV11, 391–398. Thornton, I., Culbard, E.B., Moorcroft, S., Watt, J., Wheatley, M., Thompson, M., Thomas, J.F.A., 1985. Metals in urban dusts and soils. Environ. Technol. Lett. 6, 137–144. Thornton, I., Farago, M.E., Keegan, T., Nieuwenhuijsen, M.J., Colvile, R.N., Pesch, B., Ranft, U., Miskovic, P., Jakubis, P., the EXPASCAN Study Group, 2003. Environmental impacts, exposure assessment and health effects related to arsenic emissions from a coal-fired power plant in Central Slovakia; the EXPASCAN Study. In: Chappell, W.R., Abernathy, C.O., Calderon, R.L., Thomas, D.J. (Eds.), Arsenic Exposure and Health Effects, vol. V. Elsevier, pp. 39–49.

I. Thornton / Applied Geochemistry 27 (2012) 939–953 Thornton, I., Farago, M.E., Thums, C.R., Parrish, R.R., McGill, R.A.R., Breward, N., Fortey, N.J., Simpson, P., Young, S.D., Tye, A.M., Crout, N.M.J., Hough, R.L., Watt, J., 2008. Urban geochemistry: research strategies to assist risk assessment and remediation of Brownfield sites in urban areas. Environ. Geochem. Health 30, 565–576. Underwood, E.J., Suttle, N. S., 1999. Selenium. In: The Mineral Nutrition of Livestock, third ed. pp. 421–475. Uryu, Y., Malm, O., Thornton, I., Payne, I., Cleary, D., 2001. Mercury accumulation of fish and its implications to other wildlife of the Tapajos Basin, Brazilian Amazon. J. Soc. Conserv. Biol. 15, 438–446. Wang, Y., 1997. Risk Assessment of Exposure to Lead: Comparison between Shanghai, China and Birmingham, UK. Unpubl. PhD Thesis, Univ. London. Wang, Y., Thornton, I., Farago, M., 1997a. Changes in lead concentrations in the home environment in Birmingham, England over the period 1984–1996. Sci. Total Environ. 207, 149–156. Wang, Y., Thornton, I., Farago, M.E., 1997b. Comparative risk assessment of lead exposure in Birmingham and Shanghai. In: Proc. 30th Internat. Geological Congress, Beijing 1997, vol. 19, pp. 53–63. Watt, J., Thornton, I., Cotter-Howells, J., 1993. Physical evidence suggesting the transfer of soil Pb into young children via hand-to-mouth activity. Appl. Geochem. Suppl. 2, 269–272.

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