- Email: [email protected]
River water quality in the Humber catchment: an introduction using GIS-based mapping and analysis
The Science of the Total Environment 251r252 Ž2000. 9᎐26
River water quality in the Humber catchment: an introduction using GIS-based mapping and analysis Takashi Oguchi a , Helen P. Jarvie b, Colin Neal b,U a
Center for Spatial Information Science, Faculty of Science 5th Building, Uni¨ ersity of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan b Institute of Hydrology, Maclean Building, Crowmarsh Gifford, Wallingford, Oxfordshire OX10 8BB, UK Accepted 5 January 2000
Abstract The regional water quality of the Humber catchment was mapped for key inorganic chemical determinands using a GIS system and an extensive Environment Agency and LOIS monitoring database. The resultant maps revealed the major factors affecting the general characteristics of regional water quality. Sewage inputs from industrial and domestic sources account for the high concentration of many determinands in urban areas. The concentrations of particulate components increase in tidal zones because of sediment trapping and tidal re-suspension effects. Some determinands also exhibit localized high concentrations related to coal mine drainage, soil pollution caused by past ore mining, bedrock geology, the agricultural use of fertilizers and the ingression of seawater into the estuary. 䊚 2000 Elsevier Science B.V. All rights reserved. Keywords: Water quality; Humber catchment; Sewage inputs
1. Introduction A major objective of the Land-Ocean Interaction Study ŽLOIS. has been the collection, compilation and analysis of river water quality data for the eastern UK ŽNeal et al., 1997a, 1998a.. Under the Rivers Research programme ŽRACSŽR.., de-
U
Corresponding author.
tailed water quality data have been collected by establishing a new water quality monitoring network along the major rivers in the eastern UK. Particular emphasis has been placed on the Humber catchment, which covers an area of approximately 24 000 km2 and provides the largest contribution of freshwater to the North Sea of all the British rivers ŽJarvie et al., 1997a.. Eleven water quality sampling sites were established with weekly sampling over a period of 6 years for a
0048-9697r00r$ - see front matter 䊚 2000 Elsevier Science B.V. All rights reserved. PII: S 0 0 4 8 - 9 6 9 7 Ž 0 0 . 0 0 4 1 1 - 3
10
T. Oguchi et al. r The Science of the Total En¨ ironment 251 r 252 (2000) 9᎐26
wide range of chemical determinands, and additional sampling during periods of high river flow to provide greater temporal resolution and for more accurate flux determinations. This has facilitated detailed investigation of the hydrochemical behaviour of the major river systems draining into the Humber Estuary Že.g. Jarvie et al., 1997b; Neal et al., 1996, 1997b; Robson and Neal, 1997a., but, given the limited number of the LOIS sampling sites, only limited information about regional variations and extremes in water quality within such a large catchment area can be derived. To examine the spatial variability in river water quality across the Humber catchment, LOIS scientists were granted access to the Environment
Agency’s ŽEA. water quality databases. Water quality data for major rivers draining into the North Sea were compiled within an electronic database at the Institute of Hydrology ŽWater Information System, WIS. as a part of the LOIS project ŽMoore, 1997; Tindall and Moore, 1997.. The WIS database brings together data collected by the EA, including water quality data for rivers, sewage and trade effluents. For the Humber catchment, this involved data collected by two EA regions: YorkshirerNorthumbria Region Žnorthern and central regions of the Humber catchment draining into the Yorkshire Ouse. and Midlands Region Žsouthern Humber catchment draining into the Trent. and their predecessors Žthe Natio-
Fig. 1. Map of the Humber catchment.
T. Oguchi et al. r The Science of the Total En¨ ironment 251 r 252 (2000) 9᎐26
nal Rivers Authority and Water Authorities. for the period 1986᎐1996. Although the EA data are characterized by less frequent sampling and fewer measured determinands than the LOIS data, the number of the monitoring sites is much larger and covers a wider and more dense spatial network. In this study, EA data are used along with the LOIS data to describe the spatial patterns in river water quality in the Humber rivers in relation to catchment characteristics and processes. The value of regional water quality analysis was demonstrated in a case study on the River Tweed ŽRobson et al., 1996; Robson and Neal, 1997b.. However, until now, no large-scale analysis of water quality data has been undertaken on the Humber catchment which has a much larger drainage area than the Tweed and contributes greater chemical loads into the North Sea. This study brings together for the first time all the EA and LOIS river water quality data for the major UK rivers network draining into the Humber Estuary, using GIS-aided mapping and analysis. The data are presented in the form of an atlas of water quality maps for the Humber catchment. The work thus extends markedly earlier studies using a more restricted set of information from the Harmonised Monitoring Scheme ŽRobson and Neal, 1997a,b. and preliminary trace element studies ŽNeal et al., 1999. and it provides an important introduction to water quality issues that are relevant to many of the contributions within this special issue of Science of the Total En¨ ironment.
2. Construction of water quality maps Data for the Humber catchment ŽFig. 1. were selected from the database using SQL commands and ArcView ŽESRI, Redlands, CA, USA.. The total number of river water quality monitoring sites within the catchment is 4780 ŽFig. 2.. Of the water quality determinands monitored by the Environment Agency, the chemical determinands chosen for analysis were: major ions Žcalcium,
11
Fig. 2. EA and LOIS monitoring sites of river water quality in the Humber catchment.
chloride, magnesium, sodium, potassium, sulphate., nutrients Žammonia, total oxidized nitrogen, nitrate, nitrite, phosphate., trace elements Žaluminium, barium, boron, cadmium, cobalt, copper, iron, lead, manganese, mercury, nickel, strontium, zinc., and other major determinands Žsuspended solids, dissolved organic carbon.. These determinands were selected because they represent a wide range of sources and chemical behaviour in river water. Some of the trace elements have data for both dissolved concentrations and total acid-available concentrations Ždissolved q acid-available particulate fractions. ŽNeal et al., 1997b, 1999.; whereas only one or the other may be available for some determinands. The average concentration of each determinand was calculated for monitoring sites with more than 50 measurement records. Although water quality at each site varies through time due mainly to seasonal changes in flow conditions,
12
T. Oguchi et al. r The Science of the Total En¨ ironment 251 r 252 (2000) 9᎐26
this paper deals with average concentrations computed from all the available data in order to examine the general characteristics of regional water quality. The effect of the measurement season is assumed negligible if a site has more than 50 measurement records covering several years’ duration. The distributions of average determinand concentration values were mapped along with the drainage divide and major stream networks using ArcView. The stream network was constructed from a digital elevation model with a grid interval of 50 m. The projection system used for the maps is the British National Grid. The concentration values of each determinand were grouped into six categories using the ArcView’s natural break criterion, and the values in different groups were presented using circle symbols with different diameters Že.g. Fig. 3.. The maps generated by these methods revealed that the data distribution for some determinands was too sparse to examine regional differences in concentrations. These determinands were therefore excluded from the following analysis. The average concentrations of both dissolved and total acid-available fractions of trace elements revealed very similar distributions in most cases and therefore, only the maps of total concentrations are presented here. Water quality maps are presented for the average concentrations of the following determinands: suspended solids, nutrients Žammonia, total oxidized nitrogen., major ions Žcalcium, chloride, magnesium, sodium, sulphate., and total acid-available trace elements Žaluminium, boron, cadmium, copper, iron, lead, nickel, zinc..
3. Characteristics of water quality maps The water quality maps for the Humber catchment are shown in Figs. 3᎐18 at the end of this paper. The towns, cities and rivers referred to are shown in Fig. 1. Investigation of the average chemical concentrations have revealed the following characteristics in terms of regional water quality.
3.1. Suspended solids (Fig. 3) The highest concentrations of suspended solids occur in: Ž1. the southern industrialrurban areas including Birmingham, Derby and Stoke on Trent; Ž2. the northern industrialrurban areas including Sheffield, York and Leeds; and Ž3. the tidal reaches along the Humber Estuary including Goole and its vicinity. Suspended solids concentrations are lower in the rural upstream areas Že.g. the upper reaches of the Rivers Rye, Swale, Ure, Wharfe, Derwent and Dove.. 3.2. Ammonia (Fig. 4) The highest concentrations of ammonia occur in the northern and southern industrialrurban areas. Low concentrations occur in the Humber Estuary and the rural upstream areas. 3.3. Total oxidized nitrogen (TON) (Fig. 5) High concentrations of TON occur in the northern and southern industrialrurban areas as well as lowlands along the Rivers Trent, Soar, Tame, Idle, Hull and Foulness. Low concentrations occur in the upper reaches of the Rivers Swale, Ure, Rye, Wharfe, Aire and Dove. 3.4. Calcium (Fig. 6) High concentrations occur in north-eastern areas along the Hull, Derwent, Ouse, Lower Swale, Lower Ouse and Lower Don. Although the calcium concentration data within the southern Humber catchment are sparse, this area also seems to have relatively high calcium concentrations. Low calcium concentrations occur in the north-west area of the catchment, including the Upper Swale, Upper Ure, Upper Nidd, Upper Wharfe and Upper Calder. 3.5. Chloride (Fig. 7) High concentrations of chloride occur within the Humber Estuary and the central part of the
T. Oguchi et al. r The Science of the Total En¨ ironment 251 r 252 (2000) 9᎐26
Fig. 3. Map of suspended-solid concentrations for the Humber catchment Žmgrl..
Fig. 4. Map of ammonia concentrations for the Humber catchment Žmgrl..
13
14
T. Oguchi et al. r The Science of the Total En¨ ironment 251 r 252 (2000) 9᎐26
Fig. 5. Map of total oxidized nitrogen concentrations for the Humber catchment Žmgrl..
Fig. 6. Map of calcium concentrations for the Humber catchment Žmgrl..
T. Oguchi et al. r The Science of the Total En¨ ironment 251 r 252 (2000) 9᎐26
Fig. 7. Map of chloride concentrations for the Humber catchment Žmgrl..
Fig. 8. Map of magnesium concentrations for the Humber catchment Žmgrl..
15
16
T. Oguchi et al. r The Science of the Total En¨ ironment 251 r 252 (2000) 9᎐26
Fig. 9. Map of sulphate concentrations for the Humber catchment Žmgrl..
Fig. 10. Map of aluminium concentrations for the Humber catchment Žgrl..
T. Oguchi et al. r The Science of the Total En¨ ironment 251 r 252 (2000) 9᎐26
Fig. 11. Map of boron concentrations for the Humber catchment Žgrl..
Fig. 12. Map of cadmium concentrations for the Humber catchment Žgrl..
17
18
T. Oguchi et al. r The Science of the Total En¨ ironment 251 r 252 (2000) 9᎐26
Fig. 13. Map of chromium concentrations for the Humber catchment Žgrl..
Fig. 14. Map of copper concentrations for the Humber catchment Žgrl..
T. Oguchi et al. r The Science of the Total En¨ ironment 251 r 252 (2000) 9᎐26
Fig. 15. Map of iron concentrations for the Humber catchment Žgrl..
Fig. 16. Map of lead concentrations for the Humber catchment Žgrl..
19
20
T. Oguchi et al. r The Science of the Total En¨ ironment 251 r 252 (2000) 9᎐26
Fig. 17. Map of nickel concentrations for the Humber catchment Žgrl..
Fig. 18. Map of zinc concentrations for the Humber catchment Žgrl..
T. Oguchi et al. r The Science of the Total En¨ ironment 251 r 252 (2000) 9᎐26
catchment around Doncaster and Nottingham. Most of the other areas are characterized by low chloride concentrations. 3.6. Magnesium (Fig. 8) High concentrations of magnesium occur in the Humber Estuary and the northern industrialr urban areas. There is only very sparse magnesium data for the southern area of the Humber catchment. 3.7. Sulphate (Fig. 9) High to medium concentrations of sulphate occur in the central to southern areas of the Humber catchment. Low concentrations of sulphate occur in northern areas such as the Ouse catchment.
21
3.12. Copper (Fig. 14) Copper concentrations show a similar distribution to suspended solids, except for low concentrations along the River Rother. 3.13. Iron (Fig. 15) Iron concentrations show a similar distribution to suspended solids; however, within South Yorkshire a discrepancy arises on the Rivers Aire and Don: the Aire exhibits high suspended sediment concentrations but relatively low Fe concentrations, whereas the Don has very high Fe and high suspended sediment concentrations. 3.14. Lead (Fig. 16)
3.8. Aluminium (Fig. 10)
Lead concentrations show a similar distribution to suspended solids, except for high concentrations along the Swale and the Ure.
High concentrations of aluminium occur in the northern and southern industrialrurban areas. Low concentrations occur in northern rural areas.
3.15. Nickel (Fig. 17)
3.9. Boron (Fig. 11)
Nickel concentrations show a similar distribution to copper except for low concentrations in the tidal zone.
High concentrations of boron occur within the Humber Estuary. Low concentrations occur in northern rural areas. 3.10. Cadmium (Fig. 12) The characteristics of the cadmium concentration map are similar to those of suspended solids: high concentrations of cadmium occur in the northern and southern industrialrresidential areas as well as the tidal zone. Low concentrations of cadmium tend to occur in the rural upper river reaches. However, the Derwent and Dove catchments are exceptional: despite their rural location, these rivers exhibit high concentrations of cadmium. 3.11. Chromium (Fig. 13) Chromium concentrations show a similar distribution to suspended solids.
3.16. Zinc (Fig. 18) Zinc concentrations show a similar distribution to nickel, apart from a high concentration around Chesterfield.
4. Discussion The chemical concentration maps demonstrate a high variability in water quality for many determinands across the Humber catchment. All the determinands shown in Figs. 3᎐18 except for calcium, chloride and magnesium, show higher concentrations in the large industrialrurban areas to the north of the Humber catchment Žparticularly the LeedsrBradford and SheffieldrDoncaster urban agglomerations in South Yorkshire. and to the south Žparticularly around Birmingham in the
22
T. Oguchi et al. r The Science of the Total En¨ ironment 251 r 252 (2000) 9᎐26
English Midlands.. The high concentrations within these areas can be attributed to sewage discharges and industrial effluents, which have been found to have a major impact on river water quality across the Humber catchment Že.g. Neal et al., 1996, 1997b, 1998b.. More detailed results are discussed in the following sections related to: Ž1. trace metals and suspended solids; Ž2. nutrients; and Ž3. major ions and boron. 4.1. Trace metals and suspended solids Most of the trace metals displayed in this study show very high concentrations clustered in the River Tame to the far south of the Humber catchment, which drains Birmingham and the ‘Black Country’. Chromium, nickel and zinc exhibit particularly high concentrations in the Tame relative to the rest of the Humber catchment, and have a primarily industrial source. Industry in this area has been dominated by metallurgical activity, particularly iron and steel production in the Black Country to the west of Birmingham, and non-ferrous metal working within Birmingham, including manufacture, smelting, forging, casting, electroplating, drawing and wire manufacture, anodizing and precious metal working ŽFord and Tellum, 1994.. Chromium, copper and nickel also show secondary concentration clusters around the industrial agglomerations of South Yorkshire. High suspended solids concentrations also occur within the urban areas of the central and southern Humber catchment, suggesting that domestic and industrial effluents provide a major source of suspended solids to the Humber rivers. Cadmium, chromium, copper, iron and lead have high concentrations in the tidal zone Žthe Humber Estuary and the tidal reaches of the Rivers Ouse, Aire, Don and Trent., and show a similar distribution to suspended solids. Comparisons of total acid-available concentrations and dissolved concentrations of these trace elements demonstrate a high acid-available particulate component within the total trace element concentration. These trace elements are therefore predominantly carried in particulate form and are thus subject to sediment transport effects. The Humber estuary has provided a sink for sedi-
ments contaminated by trace elements from industrial activity over many years ŽMillward et al., 1995., and water and sediment transport mechanisms within the tidal zone actively prevent the escape of sediments ŽSalomons and Forstner, 1984.. These highly contaminated sediments trapped within the tidal zone are subject to further accumulation and cyclical deposition and resuspension, producing the high suspended solids concentrations and high concentrations of cadmium, chromium, copper, ion and lead across the Humber estuary and tidal river reaches. Although no data are available for aluminium concentrations in the tidal zone ŽFig. 10., the concentrations there would be expected to be high, as aluminium also has a high particulaterdissolved ratio, and will thus be subject to the same tidal sediment trapping and mobilization effects. High iron concentrations are found within the central part of the Humber catchment, particularly in the Don catchment in South Yorkshire, and may be related to the discharge of mine drainage into the local river systems ŽYounger, 1997.. Ferruginous mine drainage results from the oxidation of pyrite within the coal measures and associated strata and the removal of the oxidation products by inflowing groundwater ŽFrost, 1979.. In recent years, there has been increasing concern about mine drainage, with the decline of the British coal mining industry, the widespread closure of mines and the cessation of mine dewatering. Flooding of mined voids and discharge of ferruginous waters from the abandoned mines has become a major source of water pollution in South Yorkshire ŽNRA, 1996.. Anomalously high concentrations of cadmium, lead and zinc occur in certain rural locations: cadmium and lead are found in abundance in Derbyshire ŽRivers Derwent and Dove., lead in North Yorkshire Žin the upper Swale and Ure., and zinc in Derbyshire around Chesterfield. These areas correspond to the locations of ore mining, which culminated during the Industrial Revolution. The ore mining activity was localized, where veins rich in galena Žlead sulfide. and blende Žzinc sulfide. were abundant within the Lower Carboniferous rock ŽJarvie et al., 1997a.. The mining fields of Derbyshire and North Yorkshire are
T. Oguchi et al. r The Science of the Total En¨ ironment 251 r 252 (2000) 9᎐26
characterized by large cadmium storage in floodplain sediments ŽBradley and Cox, 1986; Macklin et al., 1997; Neal et al., 1998b.. Although zinc was one of the major products from the both the Derbyshire and Yorkshire Mining Fields, the map of zinc concentration shows elevated concentrations in only one area of Derbyshire. This observation may reflect that the zinc contents in the polluted soils of British mining fields are much lower than their lead contents ŽLewin and Macklin, 1987.. 4.2. Nutrients: total oxidized nitrogen and ammonia The high density of sites where total oxidized nitrogen ŽTON. is monitored makes it difficult to distinguish detailed patterns in concentration ŽFig. 5.. However, it is possible to identify two areas of elevated TON concentrations in the urban and industrial regions and lowland agricultural areas with relatively low population density, particularly the Vales of Trent and Ouse, the Isle of Axholme and the low-lying coastal plain of Humberside. In the urban areas, high TON concentrations reflect input of nitrogenous sewage effluents. The lowlands in the Humber catchment are extensively used for agriculture such as the production of wheat, corn, potato and sugar beat, requiring the use of nitrogenous fertilizers ŽJarvie et al., 1997a.. The highest concentrations of ammonia are clustered in the urban areas of South Yorkshire and the Midlands. However, unlike TON, there are only low concentrations of ammonia in the lower Vale of Ouse and Trent and other major agricultural areas, indicating the agricultural runoff is not a major source of ammonia. A major source of ammonia in river systems is sewage effluent ŽMcNeely et al., 1979; Jarvie et al., 1998.. Although ammonia is measured in the dissolved phase, ammonia concentration distributions are very similar to those of suspended solids, with the exception of low ammonia concentrations in the tidal reaches, where suspended solids concentrations are high. 4.3. Major ions and boron Boron, chloride, and magnesium are abundant
23
in seawater and therefore show very high concentrations in the Humber Estuary, owing to mixing of seawater with the river water from the Humber catchment. There are high concentrations of calcium within the Humber Estuary also originating from a seawater source; however, riverine concentrations of calcium exceed the estuarine concentrations in several places. No data are available for estuarine concentrations of sulphate. However, given known composition of seawater ŽBurton, 1976., elevated concentrations of sulphate would be expected in the estuary. Boron, chloride, calcium and magnesium are all predominantly found within the dissolved phase Že.g. Neal et al., 1998b. and therefore are not related to sediment-associated tidal re-suspension effects. Chloride also occurs in abundance around Doncaster and Nottingham in the central region of the Humber catchment. High chloride concentrations can be attributed to coal mine drainage ŽYounger, 1997.. The Carboniferous rocks within the region, which include the Coal Measures, have saline groundwaters, originating from the diagenesis of marine and brackish waters ŽAllen Dowing and Howitt, 1969., and so the high chloride concentrations in mine drainage may represent relict seawater. The distribution of sites in the non-tidal rivers where boron is measured are very sparse. However, there appears to be a distinction between the high concentrations to the south of the Humber catchment, and the low concentrations to the rural north of the catchment. The major source of boron in river water is sewage effluent, particularly the soluble boron-containing materials used in washing powders and detergents ŽNeal et al., 1998b.. However, the relatively high concentrations of boron in the Rivers Rother and Don may reflect relict seawater from mine drainage. The distribution of calcium concentrations is strongly dependent on geology and weathering of parent materials. The lowest concentrations of calcium occur in the upper river reaches to the north-west of the Humber catchment. These rivers drain the predominantly base-poor carboniferous catchments composed of Millstone Grit and Coal Measure Shales. High calcium concentrations occur in areas underlain by calcareous Permian,
T. Oguchi et al. r The Science of the Total En¨ ironment 251 r 252 (2000) 9᎐26
24
Triassic, Jurassic and Cretaceous sedimentary rocks. For example, some of the highest concentrations of calcium are found on the River Hull which drains the Cretaceous chalk of the North Yorkshire Wolds ŽJarvie et al., 1997a.. Magnesium in the non-tidal rivers shows a similar distribution to calcium, with the exception of the Rivers Derwent and Hull, which have low magnesium concentrations, reflecting the mineral composition of the Cretaceous Chalk. The relatively high concentrations of calcium and magnesium in the central Humber catchment may reflect a relict seawater component from mine drainage. The sparse distribution of mean values for sulphate makes it difficult to interpret the data in detail. The main distinction appears to be the low concentrations to the north of the Humber catchment and high concentrations in the central and southern regions. The high concentrations of sulphate in the central and southern catchment may reflect a large number of potential sources, including effluents from the major urban areas, agricultural fertilizers, geological sources and atmospheric deposition. The geology of the Trent
basin is dominated by Triassic Sandstones and Marls which have abundant gypsum Žcalcium sulphate. deposits ŽEdmunds et al., 1982; Jackson and Lloyd, 1983., providing an important source of sulphate from weathering. Smith et al. Ž1997. estimate that atmospheric deposition contributes approximately 20% of riverine sulphate loads within the Humber catchment.
5. Summary This study has demonstrated the importance of anthropogenic influences on the large-scale regional water quality of the Humber catchment. These anthropogenic influences are dominated by effluent inputs from the major urban centres, which appear to be strongly linked to elevated concentrations of suspended solids, trace metals, boron and ammonia. Agriculture is a major source of TON in the lowland agricultural areas. Coal mining, and subsequent abandonment and discharge of mine waters into the rivers draining the coalfields, provides an important source of iron to the
Table 1 Major factors responsible for high concentrations of determinands
Suspended solids Ammonia Total oxidized nitrogen Calcium Chloride Magnesium Sulphate Aluminium Boron Cadmium Chromium Copper Iron Lead Nickel Zinc U
Sewage
Tidal re-suspension
U
U
Agriculture
Bedrock
Modern seawater
Relict seawater
Mining
Acid rain
A
U U
B E
U
U
U
U U
? ŽU .
ŽU .
U
U
U
U
U
U
U
ŽU .
ŽU .
U
?
?
U
U
U
U
U
U
U
U
U
U
U
U
U
U U
Type
?
Denotes major contributary factor; ŽU . denotes probable contributary factor; ? denotes possible contributary factor.
D F D G A H C A A C C B B
T. Oguchi et al. r The Science of the Total En¨ ironment 251 r 252 (2000) 9᎐26
central Humber catchment. Historical ore mining activity during the Industrial Revolution was responsible for contaminating sediments and soils in the upper reaches of certain rivers in Derbyshire and North Yorkshire. These sediments continue to provide a major localized source of cadmium and lead in the upper reaches of these rural upland rivers. Determinands whose distribution is not directly related to anthropogenic activity include calcium and magnesium, which are subject to geological controls, particularly the distribution of carbonate minerals within the bedrock. High concentrations of chloride, boron, magnesium and calcium in the Humber estuary result from the ingression of modern seawater into the estuary and are thus controlled by tidal effects. High concentrations of these determinands in South Yorkshire, particularly in the Don catchment, may also originate from relict seawater from the Carboniferous strata, discharged via mine drainage. Tidal circulation is responsible for elevated concentrations of suspended solids and trace metals with a high particulate component Žcadmium, chromium, copper, iron and lead. within the estuary and tidal river reaches. With regard to the sources of the chemical determinands, eight broad types characterize the patterns observed ŽTable 1.. These types are as follows: 䢇
䢇
䢇
䢇
䢇
䢇
䢇
Type A Žsuspended solids, aluminium, chromium and copper. ᎏ effluent inputs from urban centres and tidal re-suspension; Type B Žammonia, nickel and zinc. ᎏ effluent inputs from urban centres; Type C Žcadmium, iron and lead. ᎏ effluent inputs from urban centres, tidal re-suspension and mining; Type D Žcalcium and magnesium. ᎏ bedrock, modern seawater and relict seawater sources; Type E Žtotal oxidized nitrogen. ᎏ effluent inputs from urban centres and agricultural runoff; Type F Žchloride. ᎏ modern and relict seawater sources; Type G Žsulphate. ᎏ effluent inputs from
䢇
25
urban centres, bedrock, modern seawater and relict seawater; Type H Žboron. ᎏ effluent inputs from urban centres and modern seawater.
6. Concluding remarks A vast database of water quality data have been brought together under LOIS, using the extensive datasets collected by the Environment Agency and the LOIS community. The application of GIS mapping techniques has facilitated the simplification and presentation of a complex and highly heterogeneous dataset. The maps of the average concentrations of determinands produced by these methods are vital for an understanding of the broad-scale characteristics and controls on water quality in a major drainage system. The maps have permitted visual inspection of relationships between elements from a spatial perspective. The next step in interpreting this regional water quality is to examine a broader suite of inter-element relationships in a graphical environment to investigate key chemical signatures across the catchment and identify discrete source-type localities, for more detailed examination of hydrochemical controls. This work has been taken forward in a companion paper ŽJarvie et al., 2000.. The database compiled under LOIS provides a host of other research possibilities in relation to regional water quality, particularly when combined with other large-scale spatial datasets such as land-use and geology, and with more detailed and specialized monitoring and process-focused research which make up the LOIS Core and Special Topic programmes.
Acknowledgements We would like to thank Andrew Eatherall, David Hill, Dave Morris, Alice Robson, Isabella Tindall and Paul Wass at Institute of Hydrology for providing useful information. The visit of Takashi Oguchi to the Institute of Hydrology for
26
T. Oguchi et al. r The Science of the Total En¨ ironment 251 r 252 (2000) 9᎐26
this research was supported by a grant from Ministry of Education, Science, Sports and Culture, Government of Japan. References Allen Dowing, R., Howitt, F., 1969. Saline groundwaters in the carboniferous rocks of the English East Midlands in relation to the geology. Q. J. Eng. Geol., 1: 241᎐269. Bradley, S.B., Cox, J.J., 1986. Heavy metals in the Hamps and Manifold valleys, North Staffordshire, UK: distribution in floodplain soils. Sci. Total Environ., 50: 103᎐128. Burton, J.D., 1976. Basic properties and processes in estuarine chemistry. In: J.D. Burton, P.S. Liss ŽEds.., Esturine chemistry. Academic Press, London, pp. 1᎐36. Edmunds, W.M., Bath, A.H., Miles, D.L., 1982. Hydrochemical evolution of the East Midlands Triassic sandstone aquifer, England. Geochim. Cosmochim. Acta, 46: 2069᎐2081. Ford, M., Tellum, J.H., 1994. Source, type and extent of inorganic contamination within the Birmingham aquifer system, UK. J. Hydrol., 156 Ž1-4.: 101᎐135. Frost, R.C., 1979. Evaluation of the rate of decrease in the iron content of water pumped from a flooded shaft mine in County Durham, England. J. Hydrol., 40 Ž1r2.: 101᎐111. Jackson, D., Lloyd, J.W., 1983. Groundwater chemistry of the Birmingham Triassic Sandstone aquifer and its relation to structure. Q. J. Eng. Geol. Lond., 16: 135᎐142. Jarvie, H.P., Neal, C., Robson, A.J., 1997a. The geography of the Humber catchment. Sci. Total Environ., 194r195: 87᎐99. Jarvie, H.P., Neal, C., Leach, D.V., Ryland, G.P., House, W.A., Robson, A.J., 1997b. Major ion concentrations and the inorganic carbon chemistry of the Humber rivers. Sci. Total Environ., 194r195: 285᎐302. Jarvie, H.P., Whitton, B., Neal, C., 1998. Nitrogen and phosphorus in east coast UK rivers: speciation, sources and biological significance. Sci. Total Environ., 210r211: 79᎐109. Jarvie, H.P., Oguchi, T., Neal, C., 2000. Pollution regimes and variability in river water quality across the Humber catchment: Interrogation and mapping of an extensive and highly heterogeneous spatial dataset. Sci. Total Environ., 251r252: 27᎐43. Lewin, J., Macklin, M.G., 1987. Metal mining and floodplain sedimentation in Britain. In: F. Gardiner ŽEd.., International geomorphology 1986 Part 1. Wiley, Chichester, pp. 1009᎐1027. Macklin, M.G., Hudson-Edwards, K.A., Dawson, E.J., 1997. The significance of pollution from historic metal mining in the Pennine orefields on river sediments contaminant fluxes to the North Sea. Sci. Total Environ., 194r195: 391᎐397. McNeely, R.N., Neimanis, V.P., Dwyer, L., 1979. Water quality sourcebook: a guide to water quality parameters. Inland Waters Directorate, Water Quality Branch, Ottawa, Canada Ž88 pp..
Millward, G.E., Glegg, G.A., Costello, M.J., Wilson, J.G., Emblow, C.S., Kelly, K.S., 1995. Fluxes and retention of trace metals in the Humber Estuary. Estuarine Coastal Shelf Sci., 44: 97᎐105. Moore, R.V., 1997. The logical and physical design of the Land Ocean Interaction Study database. Sci. Total Environ., 194r195: 137᎐146. National Rivers Authority, 1996. Environmental assessment of selected abandoned minewaters. Report of the National Rivers Authority, Northumbria and Yorkshire Region. Leeds Ž54 pp.. Neal, C., Smith, C.J., Jeffery, H.A., Jarvie, H.P., Robson, A.J., 1996. Trace metal concentrations in the major rivers entering the Humber estuary, NE England. J. Hydrol., 182: 37᎐64. Neal, C., House, W.A., Leeks, G.J.L., Marker, A.H., 1997a. UK fluxes to the North Sea, Land Ocean Interaction Study ŽLOIS.: river basins research, the first 2 years 1993᎐1995. Sci. Total Environ., 194r195: 1᎐4. Neal, C., Robson, A.J., Jeffery, H.A. et al., 1997b. Trace element inter-relationships for the Humber rivers: inferences for hydrological and chemical controls. Sci. Total Environ., 194r195: 321᎐343. Neal, C., House, W.A., Whitton, B.A., Leeks, G.J.L., 1998a. Foreword to special issue: water quality and biology of UK rivers entering the North Sea: the Land Ocean Interaction Study ŽLOIS. and associated work. Sci. Total Environ., 210r211: 1᎐4. Neal, C., Fox, K.K., Harrow, M., Neal, M., 1998b. Boron in the major UK rivers entering the North Sea. Sci. Total Environ., 210r211: 41᎐51. Neal, C., Jarvie, H.P., Oguchi, T., 1999. Acid available particulate trace metals associated with suspended sediments in the Humber rivers: a regional assessment. Hydrol. Process., 13: 1117᎐1136. Robson, A.J., Neal, C., Currie, J.C., Virtue, W.A., Ringrose, A., 1996. The water quality of the Tweed and its tributaries. Inst. Hydrol. Report Ser., 128: 1᎐98. Robson, A.J., Neal, C., 1997a. A summary of regional water quality for eastern UK rivers. Sci. Total Environ., 194r195: 15᎐37. Robson, A.J., Neal, C., 1997b. Regional water quality of the river Tweed. Sci. Total Environ., 194r195: 173᎐192. Salomons, W., Forstner, U., 1984. Metals in the hydrocycle. Springer, Berlin Ž349 pp.. Smith, R.I., Cape, J.N., Binnie, J., Murray, T.D., Young, M., Fowler, D., 1997. Deposition of atmospheric pollutants to the LOIS area. Sci. Total Environ., 194r195: 71᎐85. Tindall, C.I., Moore, R.V., 1997. The Rivers Database and the overall data management for the Land Ocean Interaction Study Programme. Sci. Total Environ., 194r195: 129᎐135. Younger, P.L., 1997. The longevity of minewater pollution: a basis for decision-making. Sci. Total Environ., 194r195: 457᎐466.
River water quality in the Humber catchment: an introduction using GIS-based mapping and analysis Takashi Oguchi a , Helen P. Jarvie b, Colin Neal b,U a
Center for Spatial Information Science, Faculty of Science 5th Building, Uni¨ ersity of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan b Institute of Hydrology, Maclean Building, Crowmarsh Gifford, Wallingford, Oxfordshire OX10 8BB, UK Accepted 5 January 2000
Abstract The regional water quality of the Humber catchment was mapped for key inorganic chemical determinands using a GIS system and an extensive Environment Agency and LOIS monitoring database. The resultant maps revealed the major factors affecting the general characteristics of regional water quality. Sewage inputs from industrial and domestic sources account for the high concentration of many determinands in urban areas. The concentrations of particulate components increase in tidal zones because of sediment trapping and tidal re-suspension effects. Some determinands also exhibit localized high concentrations related to coal mine drainage, soil pollution caused by past ore mining, bedrock geology, the agricultural use of fertilizers and the ingression of seawater into the estuary. 䊚 2000 Elsevier Science B.V. All rights reserved. Keywords: Water quality; Humber catchment; Sewage inputs
1. Introduction A major objective of the Land-Ocean Interaction Study ŽLOIS. has been the collection, compilation and analysis of river water quality data for the eastern UK ŽNeal et al., 1997a, 1998a.. Under the Rivers Research programme ŽRACSŽR.., de-
U
Corresponding author.
tailed water quality data have been collected by establishing a new water quality monitoring network along the major rivers in the eastern UK. Particular emphasis has been placed on the Humber catchment, which covers an area of approximately 24 000 km2 and provides the largest contribution of freshwater to the North Sea of all the British rivers ŽJarvie et al., 1997a.. Eleven water quality sampling sites were established with weekly sampling over a period of 6 years for a
0048-9697r00r$ - see front matter 䊚 2000 Elsevier Science B.V. All rights reserved. PII: S 0 0 4 8 - 9 6 9 7 Ž 0 0 . 0 0 4 1 1 - 3
10
T. Oguchi et al. r The Science of the Total En¨ ironment 251 r 252 (2000) 9᎐26
wide range of chemical determinands, and additional sampling during periods of high river flow to provide greater temporal resolution and for more accurate flux determinations. This has facilitated detailed investigation of the hydrochemical behaviour of the major river systems draining into the Humber Estuary Že.g. Jarvie et al., 1997b; Neal et al., 1996, 1997b; Robson and Neal, 1997a., but, given the limited number of the LOIS sampling sites, only limited information about regional variations and extremes in water quality within such a large catchment area can be derived. To examine the spatial variability in river water quality across the Humber catchment, LOIS scientists were granted access to the Environment
Agency’s ŽEA. water quality databases. Water quality data for major rivers draining into the North Sea were compiled within an electronic database at the Institute of Hydrology ŽWater Information System, WIS. as a part of the LOIS project ŽMoore, 1997; Tindall and Moore, 1997.. The WIS database brings together data collected by the EA, including water quality data for rivers, sewage and trade effluents. For the Humber catchment, this involved data collected by two EA regions: YorkshirerNorthumbria Region Žnorthern and central regions of the Humber catchment draining into the Yorkshire Ouse. and Midlands Region Žsouthern Humber catchment draining into the Trent. and their predecessors Žthe Natio-
Fig. 1. Map of the Humber catchment.
T. Oguchi et al. r The Science of the Total En¨ ironment 251 r 252 (2000) 9᎐26
nal Rivers Authority and Water Authorities. for the period 1986᎐1996. Although the EA data are characterized by less frequent sampling and fewer measured determinands than the LOIS data, the number of the monitoring sites is much larger and covers a wider and more dense spatial network. In this study, EA data are used along with the LOIS data to describe the spatial patterns in river water quality in the Humber rivers in relation to catchment characteristics and processes. The value of regional water quality analysis was demonstrated in a case study on the River Tweed ŽRobson et al., 1996; Robson and Neal, 1997b.. However, until now, no large-scale analysis of water quality data has been undertaken on the Humber catchment which has a much larger drainage area than the Tweed and contributes greater chemical loads into the North Sea. This study brings together for the first time all the EA and LOIS river water quality data for the major UK rivers network draining into the Humber Estuary, using GIS-aided mapping and analysis. The data are presented in the form of an atlas of water quality maps for the Humber catchment. The work thus extends markedly earlier studies using a more restricted set of information from the Harmonised Monitoring Scheme ŽRobson and Neal, 1997a,b. and preliminary trace element studies ŽNeal et al., 1999. and it provides an important introduction to water quality issues that are relevant to many of the contributions within this special issue of Science of the Total En¨ ironment.
2. Construction of water quality maps Data for the Humber catchment ŽFig. 1. were selected from the database using SQL commands and ArcView ŽESRI, Redlands, CA, USA.. The total number of river water quality monitoring sites within the catchment is 4780 ŽFig. 2.. Of the water quality determinands monitored by the Environment Agency, the chemical determinands chosen for analysis were: major ions Žcalcium,
11
Fig. 2. EA and LOIS monitoring sites of river water quality in the Humber catchment.
chloride, magnesium, sodium, potassium, sulphate., nutrients Žammonia, total oxidized nitrogen, nitrate, nitrite, phosphate., trace elements Žaluminium, barium, boron, cadmium, cobalt, copper, iron, lead, manganese, mercury, nickel, strontium, zinc., and other major determinands Žsuspended solids, dissolved organic carbon.. These determinands were selected because they represent a wide range of sources and chemical behaviour in river water. Some of the trace elements have data for both dissolved concentrations and total acid-available concentrations Ždissolved q acid-available particulate fractions. ŽNeal et al., 1997b, 1999.; whereas only one or the other may be available for some determinands. The average concentration of each determinand was calculated for monitoring sites with more than 50 measurement records. Although water quality at each site varies through time due mainly to seasonal changes in flow conditions,
12
T. Oguchi et al. r The Science of the Total En¨ ironment 251 r 252 (2000) 9᎐26
this paper deals with average concentrations computed from all the available data in order to examine the general characteristics of regional water quality. The effect of the measurement season is assumed negligible if a site has more than 50 measurement records covering several years’ duration. The distributions of average determinand concentration values were mapped along with the drainage divide and major stream networks using ArcView. The stream network was constructed from a digital elevation model with a grid interval of 50 m. The projection system used for the maps is the British National Grid. The concentration values of each determinand were grouped into six categories using the ArcView’s natural break criterion, and the values in different groups were presented using circle symbols with different diameters Že.g. Fig. 3.. The maps generated by these methods revealed that the data distribution for some determinands was too sparse to examine regional differences in concentrations. These determinands were therefore excluded from the following analysis. The average concentrations of both dissolved and total acid-available fractions of trace elements revealed very similar distributions in most cases and therefore, only the maps of total concentrations are presented here. Water quality maps are presented for the average concentrations of the following determinands: suspended solids, nutrients Žammonia, total oxidized nitrogen., major ions Žcalcium, chloride, magnesium, sodium, sulphate., and total acid-available trace elements Žaluminium, boron, cadmium, copper, iron, lead, nickel, zinc..
3. Characteristics of water quality maps The water quality maps for the Humber catchment are shown in Figs. 3᎐18 at the end of this paper. The towns, cities and rivers referred to are shown in Fig. 1. Investigation of the average chemical concentrations have revealed the following characteristics in terms of regional water quality.
3.1. Suspended solids (Fig. 3) The highest concentrations of suspended solids occur in: Ž1. the southern industrialrurban areas including Birmingham, Derby and Stoke on Trent; Ž2. the northern industrialrurban areas including Sheffield, York and Leeds; and Ž3. the tidal reaches along the Humber Estuary including Goole and its vicinity. Suspended solids concentrations are lower in the rural upstream areas Že.g. the upper reaches of the Rivers Rye, Swale, Ure, Wharfe, Derwent and Dove.. 3.2. Ammonia (Fig. 4) The highest concentrations of ammonia occur in the northern and southern industrialrurban areas. Low concentrations occur in the Humber Estuary and the rural upstream areas. 3.3. Total oxidized nitrogen (TON) (Fig. 5) High concentrations of TON occur in the northern and southern industrialrurban areas as well as lowlands along the Rivers Trent, Soar, Tame, Idle, Hull and Foulness. Low concentrations occur in the upper reaches of the Rivers Swale, Ure, Rye, Wharfe, Aire and Dove. 3.4. Calcium (Fig. 6) High concentrations occur in north-eastern areas along the Hull, Derwent, Ouse, Lower Swale, Lower Ouse and Lower Don. Although the calcium concentration data within the southern Humber catchment are sparse, this area also seems to have relatively high calcium concentrations. Low calcium concentrations occur in the north-west area of the catchment, including the Upper Swale, Upper Ure, Upper Nidd, Upper Wharfe and Upper Calder. 3.5. Chloride (Fig. 7) High concentrations of chloride occur within the Humber Estuary and the central part of the
T. Oguchi et al. r The Science of the Total En¨ ironment 251 r 252 (2000) 9᎐26
Fig. 3. Map of suspended-solid concentrations for the Humber catchment Žmgrl..
Fig. 4. Map of ammonia concentrations for the Humber catchment Žmgrl..
13
14
T. Oguchi et al. r The Science of the Total En¨ ironment 251 r 252 (2000) 9᎐26
Fig. 5. Map of total oxidized nitrogen concentrations for the Humber catchment Žmgrl..
Fig. 6. Map of calcium concentrations for the Humber catchment Žmgrl..
T. Oguchi et al. r The Science of the Total En¨ ironment 251 r 252 (2000) 9᎐26
Fig. 7. Map of chloride concentrations for the Humber catchment Žmgrl..
Fig. 8. Map of magnesium concentrations for the Humber catchment Žmgrl..
15
16
T. Oguchi et al. r The Science of the Total En¨ ironment 251 r 252 (2000) 9᎐26
Fig. 9. Map of sulphate concentrations for the Humber catchment Žmgrl..
Fig. 10. Map of aluminium concentrations for the Humber catchment Žgrl..
T. Oguchi et al. r The Science of the Total En¨ ironment 251 r 252 (2000) 9᎐26
Fig. 11. Map of boron concentrations for the Humber catchment Žgrl..
Fig. 12. Map of cadmium concentrations for the Humber catchment Žgrl..
17
18
T. Oguchi et al. r The Science of the Total En¨ ironment 251 r 252 (2000) 9᎐26
Fig. 13. Map of chromium concentrations for the Humber catchment Žgrl..
Fig. 14. Map of copper concentrations for the Humber catchment Žgrl..
T. Oguchi et al. r The Science of the Total En¨ ironment 251 r 252 (2000) 9᎐26
Fig. 15. Map of iron concentrations for the Humber catchment Žgrl..
Fig. 16. Map of lead concentrations for the Humber catchment Žgrl..
19
20
T. Oguchi et al. r The Science of the Total En¨ ironment 251 r 252 (2000) 9᎐26
Fig. 17. Map of nickel concentrations for the Humber catchment Žgrl..
Fig. 18. Map of zinc concentrations for the Humber catchment Žgrl..
T. Oguchi et al. r The Science of the Total En¨ ironment 251 r 252 (2000) 9᎐26
catchment around Doncaster and Nottingham. Most of the other areas are characterized by low chloride concentrations. 3.6. Magnesium (Fig. 8) High concentrations of magnesium occur in the Humber Estuary and the northern industrialr urban areas. There is only very sparse magnesium data for the southern area of the Humber catchment. 3.7. Sulphate (Fig. 9) High to medium concentrations of sulphate occur in the central to southern areas of the Humber catchment. Low concentrations of sulphate occur in northern areas such as the Ouse catchment.
21
3.12. Copper (Fig. 14) Copper concentrations show a similar distribution to suspended solids, except for low concentrations along the River Rother. 3.13. Iron (Fig. 15) Iron concentrations show a similar distribution to suspended solids; however, within South Yorkshire a discrepancy arises on the Rivers Aire and Don: the Aire exhibits high suspended sediment concentrations but relatively low Fe concentrations, whereas the Don has very high Fe and high suspended sediment concentrations. 3.14. Lead (Fig. 16)
3.8. Aluminium (Fig. 10)
Lead concentrations show a similar distribution to suspended solids, except for high concentrations along the Swale and the Ure.
High concentrations of aluminium occur in the northern and southern industrialrurban areas. Low concentrations occur in northern rural areas.
3.15. Nickel (Fig. 17)
3.9. Boron (Fig. 11)
Nickel concentrations show a similar distribution to copper except for low concentrations in the tidal zone.
High concentrations of boron occur within the Humber Estuary. Low concentrations occur in northern rural areas. 3.10. Cadmium (Fig. 12) The characteristics of the cadmium concentration map are similar to those of suspended solids: high concentrations of cadmium occur in the northern and southern industrialrresidential areas as well as the tidal zone. Low concentrations of cadmium tend to occur in the rural upper river reaches. However, the Derwent and Dove catchments are exceptional: despite their rural location, these rivers exhibit high concentrations of cadmium. 3.11. Chromium (Fig. 13) Chromium concentrations show a similar distribution to suspended solids.
3.16. Zinc (Fig. 18) Zinc concentrations show a similar distribution to nickel, apart from a high concentration around Chesterfield.
4. Discussion The chemical concentration maps demonstrate a high variability in water quality for many determinands across the Humber catchment. All the determinands shown in Figs. 3᎐18 except for calcium, chloride and magnesium, show higher concentrations in the large industrialrurban areas to the north of the Humber catchment Žparticularly the LeedsrBradford and SheffieldrDoncaster urban agglomerations in South Yorkshire. and to the south Žparticularly around Birmingham in the
22
T. Oguchi et al. r The Science of the Total En¨ ironment 251 r 252 (2000) 9᎐26
English Midlands.. The high concentrations within these areas can be attributed to sewage discharges and industrial effluents, which have been found to have a major impact on river water quality across the Humber catchment Že.g. Neal et al., 1996, 1997b, 1998b.. More detailed results are discussed in the following sections related to: Ž1. trace metals and suspended solids; Ž2. nutrients; and Ž3. major ions and boron. 4.1. Trace metals and suspended solids Most of the trace metals displayed in this study show very high concentrations clustered in the River Tame to the far south of the Humber catchment, which drains Birmingham and the ‘Black Country’. Chromium, nickel and zinc exhibit particularly high concentrations in the Tame relative to the rest of the Humber catchment, and have a primarily industrial source. Industry in this area has been dominated by metallurgical activity, particularly iron and steel production in the Black Country to the west of Birmingham, and non-ferrous metal working within Birmingham, including manufacture, smelting, forging, casting, electroplating, drawing and wire manufacture, anodizing and precious metal working ŽFord and Tellum, 1994.. Chromium, copper and nickel also show secondary concentration clusters around the industrial agglomerations of South Yorkshire. High suspended solids concentrations also occur within the urban areas of the central and southern Humber catchment, suggesting that domestic and industrial effluents provide a major source of suspended solids to the Humber rivers. Cadmium, chromium, copper, iron and lead have high concentrations in the tidal zone Žthe Humber Estuary and the tidal reaches of the Rivers Ouse, Aire, Don and Trent., and show a similar distribution to suspended solids. Comparisons of total acid-available concentrations and dissolved concentrations of these trace elements demonstrate a high acid-available particulate component within the total trace element concentration. These trace elements are therefore predominantly carried in particulate form and are thus subject to sediment transport effects. The Humber estuary has provided a sink for sedi-
ments contaminated by trace elements from industrial activity over many years ŽMillward et al., 1995., and water and sediment transport mechanisms within the tidal zone actively prevent the escape of sediments ŽSalomons and Forstner, 1984.. These highly contaminated sediments trapped within the tidal zone are subject to further accumulation and cyclical deposition and resuspension, producing the high suspended solids concentrations and high concentrations of cadmium, chromium, copper, ion and lead across the Humber estuary and tidal river reaches. Although no data are available for aluminium concentrations in the tidal zone ŽFig. 10., the concentrations there would be expected to be high, as aluminium also has a high particulaterdissolved ratio, and will thus be subject to the same tidal sediment trapping and mobilization effects. High iron concentrations are found within the central part of the Humber catchment, particularly in the Don catchment in South Yorkshire, and may be related to the discharge of mine drainage into the local river systems ŽYounger, 1997.. Ferruginous mine drainage results from the oxidation of pyrite within the coal measures and associated strata and the removal of the oxidation products by inflowing groundwater ŽFrost, 1979.. In recent years, there has been increasing concern about mine drainage, with the decline of the British coal mining industry, the widespread closure of mines and the cessation of mine dewatering. Flooding of mined voids and discharge of ferruginous waters from the abandoned mines has become a major source of water pollution in South Yorkshire ŽNRA, 1996.. Anomalously high concentrations of cadmium, lead and zinc occur in certain rural locations: cadmium and lead are found in abundance in Derbyshire ŽRivers Derwent and Dove., lead in North Yorkshire Žin the upper Swale and Ure., and zinc in Derbyshire around Chesterfield. These areas correspond to the locations of ore mining, which culminated during the Industrial Revolution. The ore mining activity was localized, where veins rich in galena Žlead sulfide. and blende Žzinc sulfide. were abundant within the Lower Carboniferous rock ŽJarvie et al., 1997a.. The mining fields of Derbyshire and North Yorkshire are
T. Oguchi et al. r The Science of the Total En¨ ironment 251 r 252 (2000) 9᎐26
characterized by large cadmium storage in floodplain sediments ŽBradley and Cox, 1986; Macklin et al., 1997; Neal et al., 1998b.. Although zinc was one of the major products from the both the Derbyshire and Yorkshire Mining Fields, the map of zinc concentration shows elevated concentrations in only one area of Derbyshire. This observation may reflect that the zinc contents in the polluted soils of British mining fields are much lower than their lead contents ŽLewin and Macklin, 1987.. 4.2. Nutrients: total oxidized nitrogen and ammonia The high density of sites where total oxidized nitrogen ŽTON. is monitored makes it difficult to distinguish detailed patterns in concentration ŽFig. 5.. However, it is possible to identify two areas of elevated TON concentrations in the urban and industrial regions and lowland agricultural areas with relatively low population density, particularly the Vales of Trent and Ouse, the Isle of Axholme and the low-lying coastal plain of Humberside. In the urban areas, high TON concentrations reflect input of nitrogenous sewage effluents. The lowlands in the Humber catchment are extensively used for agriculture such as the production of wheat, corn, potato and sugar beat, requiring the use of nitrogenous fertilizers ŽJarvie et al., 1997a.. The highest concentrations of ammonia are clustered in the urban areas of South Yorkshire and the Midlands. However, unlike TON, there are only low concentrations of ammonia in the lower Vale of Ouse and Trent and other major agricultural areas, indicating the agricultural runoff is not a major source of ammonia. A major source of ammonia in river systems is sewage effluent ŽMcNeely et al., 1979; Jarvie et al., 1998.. Although ammonia is measured in the dissolved phase, ammonia concentration distributions are very similar to those of suspended solids, with the exception of low ammonia concentrations in the tidal reaches, where suspended solids concentrations are high. 4.3. Major ions and boron Boron, chloride, and magnesium are abundant
23
in seawater and therefore show very high concentrations in the Humber Estuary, owing to mixing of seawater with the river water from the Humber catchment. There are high concentrations of calcium within the Humber Estuary also originating from a seawater source; however, riverine concentrations of calcium exceed the estuarine concentrations in several places. No data are available for estuarine concentrations of sulphate. However, given known composition of seawater ŽBurton, 1976., elevated concentrations of sulphate would be expected in the estuary. Boron, chloride, calcium and magnesium are all predominantly found within the dissolved phase Že.g. Neal et al., 1998b. and therefore are not related to sediment-associated tidal re-suspension effects. Chloride also occurs in abundance around Doncaster and Nottingham in the central region of the Humber catchment. High chloride concentrations can be attributed to coal mine drainage ŽYounger, 1997.. The Carboniferous rocks within the region, which include the Coal Measures, have saline groundwaters, originating from the diagenesis of marine and brackish waters ŽAllen Dowing and Howitt, 1969., and so the high chloride concentrations in mine drainage may represent relict seawater. The distribution of sites in the non-tidal rivers where boron is measured are very sparse. However, there appears to be a distinction between the high concentrations to the south of the Humber catchment, and the low concentrations to the rural north of the catchment. The major source of boron in river water is sewage effluent, particularly the soluble boron-containing materials used in washing powders and detergents ŽNeal et al., 1998b.. However, the relatively high concentrations of boron in the Rivers Rother and Don may reflect relict seawater from mine drainage. The distribution of calcium concentrations is strongly dependent on geology and weathering of parent materials. The lowest concentrations of calcium occur in the upper river reaches to the north-west of the Humber catchment. These rivers drain the predominantly base-poor carboniferous catchments composed of Millstone Grit and Coal Measure Shales. High calcium concentrations occur in areas underlain by calcareous Permian,
T. Oguchi et al. r The Science of the Total En¨ ironment 251 r 252 (2000) 9᎐26
24
Triassic, Jurassic and Cretaceous sedimentary rocks. For example, some of the highest concentrations of calcium are found on the River Hull which drains the Cretaceous chalk of the North Yorkshire Wolds ŽJarvie et al., 1997a.. Magnesium in the non-tidal rivers shows a similar distribution to calcium, with the exception of the Rivers Derwent and Hull, which have low magnesium concentrations, reflecting the mineral composition of the Cretaceous Chalk. The relatively high concentrations of calcium and magnesium in the central Humber catchment may reflect a relict seawater component from mine drainage. The sparse distribution of mean values for sulphate makes it difficult to interpret the data in detail. The main distinction appears to be the low concentrations to the north of the Humber catchment and high concentrations in the central and southern regions. The high concentrations of sulphate in the central and southern catchment may reflect a large number of potential sources, including effluents from the major urban areas, agricultural fertilizers, geological sources and atmospheric deposition. The geology of the Trent
basin is dominated by Triassic Sandstones and Marls which have abundant gypsum Žcalcium sulphate. deposits ŽEdmunds et al., 1982; Jackson and Lloyd, 1983., providing an important source of sulphate from weathering. Smith et al. Ž1997. estimate that atmospheric deposition contributes approximately 20% of riverine sulphate loads within the Humber catchment.
5. Summary This study has demonstrated the importance of anthropogenic influences on the large-scale regional water quality of the Humber catchment. These anthropogenic influences are dominated by effluent inputs from the major urban centres, which appear to be strongly linked to elevated concentrations of suspended solids, trace metals, boron and ammonia. Agriculture is a major source of TON in the lowland agricultural areas. Coal mining, and subsequent abandonment and discharge of mine waters into the rivers draining the coalfields, provides an important source of iron to the
Table 1 Major factors responsible for high concentrations of determinands
Suspended solids Ammonia Total oxidized nitrogen Calcium Chloride Magnesium Sulphate Aluminium Boron Cadmium Chromium Copper Iron Lead Nickel Zinc U
Sewage
Tidal re-suspension
U
U
Agriculture
Bedrock
Modern seawater
Relict seawater
Mining
Acid rain
A
U U
B E
U
U
U
U U
? ŽU .
ŽU .
U
U
U
U
U
U
U
ŽU .
ŽU .
U
?
?
U
U
U
U
U
U
U
U
U
U
U
U
U
U U
Type
?
Denotes major contributary factor; ŽU . denotes probable contributary factor; ? denotes possible contributary factor.
D F D G A H C A A C C B B
T. Oguchi et al. r The Science of the Total En¨ ironment 251 r 252 (2000) 9᎐26
central Humber catchment. Historical ore mining activity during the Industrial Revolution was responsible for contaminating sediments and soils in the upper reaches of certain rivers in Derbyshire and North Yorkshire. These sediments continue to provide a major localized source of cadmium and lead in the upper reaches of these rural upland rivers. Determinands whose distribution is not directly related to anthropogenic activity include calcium and magnesium, which are subject to geological controls, particularly the distribution of carbonate minerals within the bedrock. High concentrations of chloride, boron, magnesium and calcium in the Humber estuary result from the ingression of modern seawater into the estuary and are thus controlled by tidal effects. High concentrations of these determinands in South Yorkshire, particularly in the Don catchment, may also originate from relict seawater from the Carboniferous strata, discharged via mine drainage. Tidal circulation is responsible for elevated concentrations of suspended solids and trace metals with a high particulate component Žcadmium, chromium, copper, iron and lead. within the estuary and tidal river reaches. With regard to the sources of the chemical determinands, eight broad types characterize the patterns observed ŽTable 1.. These types are as follows: 䢇
䢇
䢇
䢇
䢇
䢇
䢇
Type A Žsuspended solids, aluminium, chromium and copper. ᎏ effluent inputs from urban centres and tidal re-suspension; Type B Žammonia, nickel and zinc. ᎏ effluent inputs from urban centres; Type C Žcadmium, iron and lead. ᎏ effluent inputs from urban centres, tidal re-suspension and mining; Type D Žcalcium and magnesium. ᎏ bedrock, modern seawater and relict seawater sources; Type E Žtotal oxidized nitrogen. ᎏ effluent inputs from urban centres and agricultural runoff; Type F Žchloride. ᎏ modern and relict seawater sources; Type G Žsulphate. ᎏ effluent inputs from
䢇
25
urban centres, bedrock, modern seawater and relict seawater; Type H Žboron. ᎏ effluent inputs from urban centres and modern seawater.
6. Concluding remarks A vast database of water quality data have been brought together under LOIS, using the extensive datasets collected by the Environment Agency and the LOIS community. The application of GIS mapping techniques has facilitated the simplification and presentation of a complex and highly heterogeneous dataset. The maps of the average concentrations of determinands produced by these methods are vital for an understanding of the broad-scale characteristics and controls on water quality in a major drainage system. The maps have permitted visual inspection of relationships between elements from a spatial perspective. The next step in interpreting this regional water quality is to examine a broader suite of inter-element relationships in a graphical environment to investigate key chemical signatures across the catchment and identify discrete source-type localities, for more detailed examination of hydrochemical controls. This work has been taken forward in a companion paper ŽJarvie et al., 2000.. The database compiled under LOIS provides a host of other research possibilities in relation to regional water quality, particularly when combined with other large-scale spatial datasets such as land-use and geology, and with more detailed and specialized monitoring and process-focused research which make up the LOIS Core and Special Topic programmes.
Acknowledgements We would like to thank Andrew Eatherall, David Hill, Dave Morris, Alice Robson, Isabella Tindall and Paul Wass at Institute of Hydrology for providing useful information. The visit of Takashi Oguchi to the Institute of Hydrology for
26
T. Oguchi et al. r The Science of the Total En¨ ironment 251 r 252 (2000) 9᎐26
this research was supported by a grant from Ministry of Education, Science, Sports and Culture, Government of Japan. References Allen Dowing, R., Howitt, F., 1969. Saline groundwaters in the carboniferous rocks of the English East Midlands in relation to the geology. Q. J. Eng. Geol., 1: 241᎐269. Bradley, S.B., Cox, J.J., 1986. Heavy metals in the Hamps and Manifold valleys, North Staffordshire, UK: distribution in floodplain soils. Sci. Total Environ., 50: 103᎐128. Burton, J.D., 1976. Basic properties and processes in estuarine chemistry. In: J.D. Burton, P.S. Liss ŽEds.., Esturine chemistry. Academic Press, London, pp. 1᎐36. Edmunds, W.M., Bath, A.H., Miles, D.L., 1982. Hydrochemical evolution of the East Midlands Triassic sandstone aquifer, England. Geochim. Cosmochim. Acta, 46: 2069᎐2081. Ford, M., Tellum, J.H., 1994. Source, type and extent of inorganic contamination within the Birmingham aquifer system, UK. J. Hydrol., 156 Ž1-4.: 101᎐135. Frost, R.C., 1979. Evaluation of the rate of decrease in the iron content of water pumped from a flooded shaft mine in County Durham, England. J. Hydrol., 40 Ž1r2.: 101᎐111. Jackson, D., Lloyd, J.W., 1983. Groundwater chemistry of the Birmingham Triassic Sandstone aquifer and its relation to structure. Q. J. Eng. Geol. Lond., 16: 135᎐142. Jarvie, H.P., Neal, C., Robson, A.J., 1997a. The geography of the Humber catchment. Sci. Total Environ., 194r195: 87᎐99. Jarvie, H.P., Neal, C., Leach, D.V., Ryland, G.P., House, W.A., Robson, A.J., 1997b. Major ion concentrations and the inorganic carbon chemistry of the Humber rivers. Sci. Total Environ., 194r195: 285᎐302. Jarvie, H.P., Whitton, B., Neal, C., 1998. Nitrogen and phosphorus in east coast UK rivers: speciation, sources and biological significance. Sci. Total Environ., 210r211: 79᎐109. Jarvie, H.P., Oguchi, T., Neal, C., 2000. Pollution regimes and variability in river water quality across the Humber catchment: Interrogation and mapping of an extensive and highly heterogeneous spatial dataset. Sci. Total Environ., 251r252: 27᎐43. Lewin, J., Macklin, M.G., 1987. Metal mining and floodplain sedimentation in Britain. In: F. Gardiner ŽEd.., International geomorphology 1986 Part 1. Wiley, Chichester, pp. 1009᎐1027. Macklin, M.G., Hudson-Edwards, K.A., Dawson, E.J., 1997. The significance of pollution from historic metal mining in the Pennine orefields on river sediments contaminant fluxes to the North Sea. Sci. Total Environ., 194r195: 391᎐397. McNeely, R.N., Neimanis, V.P., Dwyer, L., 1979. Water quality sourcebook: a guide to water quality parameters. Inland Waters Directorate, Water Quality Branch, Ottawa, Canada Ž88 pp..
Millward, G.E., Glegg, G.A., Costello, M.J., Wilson, J.G., Emblow, C.S., Kelly, K.S., 1995. Fluxes and retention of trace metals in the Humber Estuary. Estuarine Coastal Shelf Sci., 44: 97᎐105. Moore, R.V., 1997. The logical and physical design of the Land Ocean Interaction Study database. Sci. Total Environ., 194r195: 137᎐146. National Rivers Authority, 1996. Environmental assessment of selected abandoned minewaters. Report of the National Rivers Authority, Northumbria and Yorkshire Region. Leeds Ž54 pp.. Neal, C., Smith, C.J., Jeffery, H.A., Jarvie, H.P., Robson, A.J., 1996. Trace metal concentrations in the major rivers entering the Humber estuary, NE England. J. Hydrol., 182: 37᎐64. Neal, C., House, W.A., Leeks, G.J.L., Marker, A.H., 1997a. UK fluxes to the North Sea, Land Ocean Interaction Study ŽLOIS.: river basins research, the first 2 years 1993᎐1995. Sci. Total Environ., 194r195: 1᎐4. Neal, C., Robson, A.J., Jeffery, H.A. et al., 1997b. Trace element inter-relationships for the Humber rivers: inferences for hydrological and chemical controls. Sci. Total Environ., 194r195: 321᎐343. Neal, C., House, W.A., Whitton, B.A., Leeks, G.J.L., 1998a. Foreword to special issue: water quality and biology of UK rivers entering the North Sea: the Land Ocean Interaction Study ŽLOIS. and associated work. Sci. Total Environ., 210r211: 1᎐4. Neal, C., Fox, K.K., Harrow, M., Neal, M., 1998b. Boron in the major UK rivers entering the North Sea. Sci. Total Environ., 210r211: 41᎐51. Neal, C., Jarvie, H.P., Oguchi, T., 1999. Acid available particulate trace metals associated with suspended sediments in the Humber rivers: a regional assessment. Hydrol. Process., 13: 1117᎐1136. Robson, A.J., Neal, C., Currie, J.C., Virtue, W.A., Ringrose, A., 1996. The water quality of the Tweed and its tributaries. Inst. Hydrol. Report Ser., 128: 1᎐98. Robson, A.J., Neal, C., 1997a. A summary of regional water quality for eastern UK rivers. Sci. Total Environ., 194r195: 15᎐37. Robson, A.J., Neal, C., 1997b. Regional water quality of the river Tweed. Sci. Total Environ., 194r195: 173᎐192. Salomons, W., Forstner, U., 1984. Metals in the hydrocycle. Springer, Berlin Ž349 pp.. Smith, R.I., Cape, J.N., Binnie, J., Murray, T.D., Young, M., Fowler, D., 1997. Deposition of atmospheric pollutants to the LOIS area. Sci. Total Environ., 194r195: 71᎐85. Tindall, C.I., Moore, R.V., 1997. The Rivers Database and the overall data management for the Land Ocean Interaction Study Programme. Sci. Total Environ., 194r195: 129᎐135. Younger, P.L., 1997. The longevity of minewater pollution: a basis for decision-making. Sci. Total Environ., 194r195: 457᎐466.