Polycyclic aromatic hydrocarbons in nearshore marine sediments of Australia

The Science o f the Total Environment, 112 (1992) 143-164 Elsevier Science Publishers B.V., Amsterdam

143

Polycyclic aromatic hydrocarbons in nearshore marine sediments of Australia* W.A. Maher and J. Aislabiel Water Research Centre, University o f Canberra, PO Box 1, Belconnen, A C T 2616, Australia (Received August 1st, 1990; accepted November 8th, 1990)

ABSTRACT The occurrence and fate of polycyclic aromatic hydrocarbons (PAH) in nearshore marine sediments of Australia is discussed. Available information indicates that PAH are accumulating in the sediments and organisms of estuaries and harbours with both highly urbanized/industrialized and non-urban catchments. PAH levels in polluted sediments are similar to those of grossly polluted areas of Japan, North America and Europe, however PAH sources cannot be identified from the information available. PAH appear to persist in reducing environments, while in relatively pristine environments that have been previously exposed to PAH, conditions are probably favourable for the aerobic degradation of PAH by microorganisms.

INTRODUCTION

The occurrence and fate of polycyclic aromatic hydrocarbons (PAH) and their derivatives in the environment is of concern as they are known to be highly mutagenic and carcinogenic (Hoffman and Wynder, 1971). PAH are suspected of causing chronic disturbances of aquatic ecosystems by bringing about metabolic and behavioural changes in organisms (Connell and Miller, 1980) and this may be a long-term threat to their survival. PAH may also enter food chains and ultimately be ingested by humans through fish and crustacea (Varanasi, 1989). PAH are known to enter the marine environment through industrial discharges, petroleum spills and non-point sources such as urban runoff and atmospheric fallout (Neff, 1979; Hoffman et al., 1984). Because of increasing

*This paper is based on work presented at the International Chemical Congress of Pacific Basin Societies held in December 1989 in Honolulu. The conference was sponsored by the Chemical Society of Japan, the Chemical Institute of Canada and the American Chemical Society. tPresent address: Department of Plant and Microbial Sciences, University of Canterbury, Christchurch 1, New Zealand.

0048-9697/92/$05.00

© 1992 Elsevier Science Publishers B.V. All rights reserved

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urban and agricultural activities in the catchments of many Australian estuaries the load of PAH to estuaries and the coastal zone of Australia may be increasing. Approximately 75 % of Australia's population reside in Sydney, Melbourne, Brisbane, Adelaide, Perth and Hobart (Fig. 1) situated on major estuarine systems. Nearly all major industrial complexes and refineries are situated in these cities. Along the eastern coast of Australia, extensive recreational use of estuaries, for example by boating, occurs and many marina's have been constructed. Oil and gas production also occurs in Bass Strait near Melbourne and on the North West shelf. Australia is unique in that, as well as anthropogenic sources, bushfires can occur extensively in catchments and may provide a significant source of PAH. Australian rivers are usually highly turbid and hydrophobic PAH will be transported with particulate material and either remain suspended in the water column or be deposited in the bottom sediments. In the sediment the PAH may undergo microbial degradation and be mineralized or transformed into oxidized derivatives (Cerniglia, 1984a,b). These derivatives may also be highly mutagenic or carcinogenic, and soluble and will probably not remain absorbed to the sediment. It is of critical importance to understand the movements and fate of PAH in marine environments to formulate water quality criteria and to develop catchment management strategies to protect coastal ecosystems. In this paper

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we will attempt to show that: (a) significant quantities of PAH are present in estuaries and other marine areas of Australia (b) the PAH present are not primarily from natural sources (c) PAH are accumulating in marine food chains, are persistent and the physico-chemical conditions prevailing in estuaries may be suitable for PAH to be chemically/microbiologically degraded to soluble oxygenated forms. OCCURRENCE

The results of previous published studies of PAH in nearshore surface marine sediments of Australia are tabulated in Table 1. The locations of some of these studies are shown in Fig. 1. Not all the 16US Environmental Protection Agency priority pollutant PAH have been determined and alkylated PAH have only been determined in one study (Kayal and Connell, 1989). Historically this can be attributed to the lack of suitable PAH standards and analytical equipment. The results of the published studies show that locations can be divided into three categories. (A) very polluted locations which are highly urbanized/industrialized

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catchments. These sediments contain P A H levels similar to those of grossly polluted areas of Japan, North America and Europe (Obana et al., 1981; Macleod et al., 1982; Marcus et al., 1988) (B) slightly polluted locations, which are in non-urban areas subject to power boat activity and have bushfires occurring in the catchment. (C) pristine locations where measurable PAH pollution is only found when there is evidence of power boat activity. The PAH concentrations measured in pristine locations are among the lowest values measured anywhere in the world. These areas have very high biological activity, indicating biosynthesis of PAH is low. Other unpublished PAH data (Fig. 2; Table 2) can also be divided into these categories. The sediments of many urbanized estuaries (e.g. Hobart, Tasmania) have not been analyzed for PAH, but it seems likely that high concentrations of PAH will also be present. SOURCES

Three methods can be used to determine the probable sources of PAH.

(i) Alkylated PAH/parent PAH ratio Calculation of the ratio of specific alkylated PAH/parent PAH has been used to identify the source o f P A H (Youngblood and Blumer, 1975; Lee et al., 1977; Sporstol et al., 1983; Venkatesan and Dahl, 1989). For example, if the methylpyrene/pyrene ratio is < 1, PAH are probably derived from combustion sources, while if the methylpyrene/pyrene ratio is > 2 the source of PAH is probably petroleum. In Australia, two studies [Kayal and Connell, 1989; Maher and Aislabie (unpublished)] have used these ratios to examine

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Fig. 3. Total ion chromatograph of a sediment extract from Hobson's Bay, Melbourne. (1) Acenaphythylene; (2) phenanthrene; (3) anthracene; (4) C1 phenanthrene/anthracene; (5) 2-phenylnapthalene; (6) fluoranthene; (7) pyrene; (8) CI pyrene/fluoranthene; (9) benzo[ghi]fluoranthene; (I0) benz[a]anthracene; (11) chrysene; (12) ?; (13) benzo[b]fluoranthene/benzo[k]fluoranthene; (14) ?; (15) benzo[e]pyrene; (16) benzo[a]pyrene; (17) ?; (18) indeno[1,2,3-cd]pyrene.

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PAH IN N E A R S H O R E M A R I N E S E D I M E N T S O F A U S T R A L I A

sources respectively in the Brisbane River and Hobson's Bay, Melbourne. At the two locations the methylpyrene/pyrene ratios obtained at different sites indicated both combustion and petroleum sources. For non-urban locations, no information on alkylated PAH is available so sources cannot be assigned using these ratios. Bushfires as a source of PAH should also be obvious from gas chromatography-mass spectrometric chromatograms (e.g. Fig. 3). During burning, 1-methyl-7-isopropylphenanthrene (retene) is reported as being formed from resin acids. Retene should appear as a peak after the alkylated phenanthrenes/ anthracenes (Peak 4). In the chromatogram illustrated, retene is not present as this chromatogram is of a sediment extract from a former oil distribution site at Hobson's Bay.

(ii) PAH ratios Another way of identifying sources is by looking at parent PAH ratios. The ratios commonly used in the literature are phenanthrene]fluoranthene; fluoranthene/pyrene; benzo[a]pyrene/benzo[ghi]perylene and benzo[a]pyrene/ perylene. Examination of the calculated ratios for the available published PAH data for Australian marine sediments (Table 3) indicates there are no obvious differences in the ratios of PAH in sediments from highly polluted, slightly polluted and pristine areas. On examination of the published PAH ratios in TABLE 3 PAH ratios in Australian marine sediments Location

Phen/anth

A. Urbanized/industrialized catchments Brisbane 2.5-7.5 Townsville Harbour Gladstone Harbour Yarra River Corio Bay Greenwich Bay B. Non-urban locations Corner Inlet Mallacoota Inlet Burdekin River Hinchinbrook Island Ross River C. Pristine locations Heron Island Green Island

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B[a]P/B[ghi]P

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1-2. l 1-2 1.92

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3.6

150

W.A. M A H E R A N D J. AISLABIE

TABLE 4 PAH ratios in non-atmospheric sources Location Kuwait crude" Fuel oiP Bunker C oil" St. Louisiana crudea Sewageb Street dus( Recreational marinasa Highway runoW

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2.8

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50

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0.47 0.25-0.92

0.15-1.5 2.88

0.3-3.1

7.8 0.84

2 0.02

aPancirov and Brown, 1975. bBorneff and Kunte, 1965. CGiger and Schaffner, 1978. dMarcus et al., 1988. ~Hoffman et al., 1984. sources [mostly non-Australian (Tables 4 and 5)] this is not surprising as the variability in the P A H ratios attributed to specific sources is large. Variability in published P A H ratios is to be expected as, for example, the P A H produced during wood burning will depend on the type of wood, the temperature of burning and the fuel/air ratio. It can be assumed that for other sources m a n y factors such as source material, formation temperature, weathering, etc. will also influence the P A H composition. The P A H ratios will also be dependent on how recently the P A H were deposited, as microbial degradation, particularly of the three-ringed PAH, may have occurred.

(iii) Tri linear plots Tri linear diagrams in which the proportion of three P A H are plotted on the one diagram were used in an attempt to distinguish the different sources of P A H in polluted, slightly polluted and pristine environments. Some differentiation of locations based on P A H composition is evident (Fig. 4); however, when the available P A H data for sources was also plotted (Fig. 5) there was a correlation between most sources and the urban location (Brisbane), but no correlation between sources and the non-urban locations. More information on P A H in probable sources in specific catchments is needed, especially for non-urban areas, before any of the three techniques cited can be used to draw conclusions as to the sources of P A H measured in sediments.

PAH IN NEARSHORE MARINE SEDIMENTS OF AUSTRALIA

151

TABLE 5 P A H ratios in atmospheric sources Location

Phen/anth

Flu/pyrene

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B[a]P/peryl

2.14-11.17

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1.2-5

1.2-1.62

0.63-0.99

0.56

1.15-2.8

0.76-1.31

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3.25-5.55

0.37

0.24

0.11

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1.27-3.57

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0.35-1.62

3.24-18.24

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0.49

0.62

0.89-2.64

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7-10.8

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1.37

0.67

0.05-8.1

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0.55-0.96

0.1-0.2

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0.85

0.42, 0.50

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6.7

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0.88, 1.15

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0.94-1.42

0.48-2.57

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1.32-2.52

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0.48-0.81

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0.55

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1.17-1.55

Sediment affected by coal burning r

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~De Angelis et al., 1980; Hubble et al., 1982; Ramdahl et al., 1982; Ramdahl and Miller, 1983. bMcMahon and Tsoukalas, 1978. CLao et al., 1975. dDavies et al., 1976. eSawicki et al., 1965a,b. fHoffman and Wynder, 1963. gPradhan, 1989. hKatz and Chan, 1980. ~Lao et al., 1975. JGordon, 1976. kPradhan, 1989. ILeeming and Maher (unpublished). mBjorseth et al., 1977; Lunde and Bjorseth, 1977. nBjorseth et al., 1977. °Prahl et al., 1984. PYamauchi and Handa, 1987. qDeRaat, et al., 1987. rHeit, 1985.

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FATE

Accumulation in marine food chains Published studies of the PAH accumulation by bivalves (Table 6) show that, in highly polluted locations, i.e. urban/industrialized catchments, high levels of PAH are also found in bivalves. In slightly polluted and pristine non-urban areas, in the absence of boating activity, PAH concentrations in bivalves are not measurable. Bivalves are unique in that they do not metabolize or eliminate PAH, thus it is not possible to infer that PAH are accumulating in other marine organisms such as fish. The accumulation of PAH in bivalves in estuaries of South East Australia is of concern as these estuaries are used for the commercial production of the Sydney rock oyster Saccostrea commercialis. Persistence To gain some information as to the persistence of PAHs in sediments we can look at depth profiles of PAH in sediment cores. In Fig. 6 the depth profiles of three PAH in three cores representing a very polluted (A), a slightly polluted (B) and a pristine environment (C) are shown. The Greenwich Bay (very polluted) and Corner Inlet (slight pollution) cores are both relatively undisturbed cores with reducing enviroments. The John Brewer Reef (pristine) core is aerated and shows some evidence of mixing. The existence of discrete PAH corresponding maximums at depth (corresponding to events in the catchment, e.g. in the Corner Inlet core, a major bush fire resulting in an input of PAH) and the non-exponential decay of PAH with depth (time), indicates that PAH, at least in reducing environments, may not be degraded. Degradation Microbial degradation of PAH proceeds via the formation of oxidized intermediates (Fig. 7). It has been postulated that the rate of degradation of PAH is limited by the initial oxidation step. A recent study has shown this to be the case for benzo[a]pyrene (Miller et al., 1988). PAH can be photooxidized (NAS, 1972). Most of the larger, deeper Australian estuaries are turbid, hence degradation of PAH by photooxidation will be of little importance as light penetration is limited. However, many of the smaller, shallower estuaries have algal mats on the surface of the bottom of the sediments indicating light penetration to the sediment surface, therefore some photooxidation may occur. Algal mats on the sediment surfaces also produce oxygen and may themselves oxidise PAH (Lindquist and Warshawsky, 1985).

159

PAH IN NEARSHORE MARINE SEDIMENTS OF AUSTRALIA

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The factors that influence the microbial degradation of PAH in sediments have been reviewed by Cerniglia and Heitkamp (1989). We extend this information and consider whether P A H degradation is likely to occur in Australian marine sediments. Considering the microbial degradation of PAH the important factors are: (i) Prior exposure. Rates of PAH degradation are primarily related to the pre-exposure of microbial communities to PAH (Shiaris, 1989b; Kerr and Capone, 1988). Prolonged exposure to PAH will result in the adaption of microbial populations to the presence of PAH and enhanced PAH utilization and degradation (Cernaglia and Heitkamp, 1989; Shiaris, 1989b). Therefore, we would expect to get higher rates of PAH degradation in contaminated sediments compared with pristine sediments under aerobic conditions. Over the last 1000 years there has been a history of delibrate burning and bushfires in Australia which would have contributed PAHs to marine environments. Microbes in some of the so called "pristine" environments may have adapted to degrading PAH. (ii) Chemical structure. The lower molecular weight PAH such as naphthalene are degraded rapidly whereas the higher molecular weight compounds, e.g. benzo[a]pyrene, can be quite resistant to microbial attack and may therefore persist longer. Alkylation of the parent PAH will inhibit degradation, e.g. 2-methylnaphthalene is degraded at a slower rate than naphthalene (Cerniglia and Heitkamp, 1989). PAH derived from combustion processes and adsorbed to soot may be protected from degradation relative to PAH derived from petroleum oil inputs. Recently, it has been shown that pre-exposure of microbial populations to a single PAH, e.g. naphthalene, may result in enhanced degradation of other PAH (e.g. phenanthrene) (Bauer and Capone, 1988).

160

W.A. M A H E R A N D J. AISLABIE

(iii) Available oxygen. Molecular oxygen is thought to be necessary for PAH degradation (Cerniglia and Heitkamp, 1989). Consequently, the highest rates of degradation have been measured in oxygenated surface sediments. Degradation of PAH under anaerobic conditions, should it occur, happens at a very slow rate. Estuaries with urbanized and industrialized catchments normally have reduced sediments with an oxygenated microlayer at best. In contrast, small, shallow, non-urban estuaries are often sandy and bioturbated with deeper aerobic layers, so oxygen will not be limiting. Exposed tidal flats also become oxygenated on exposure to air and may provide aerobic environments for the degradation of PAH. The stimulation of PAH degradation in sediments containing the polychaete worm Capitell capitata has been reported by Kerr and Capone (1988). These worms not only aerate the sediment but also provide nutrients, such as nitrogen and phosphorus, that are essential for microbial growth. Although anaerobic degradation of PAH has not yet been reported in marine sediments, anaerobic degradation of naphthalene under dentrification conditions has recently been reported (Mihelcic and Luthy, 1988a). In contrast to PAH, the anaerobic degradation of oxidized PAH has been reported for example, by iron-reducing bacteria (Lovley et al., 1989) and possibly manganese-reducing bacteria (Mihelic and Luthy, 1989b). The importance of these activities in sediments polluted with PAH requires further investigation. (iv) Available nutrients. While it is well recognized that biodegradation of oil "in situ" is limited by available nutrients (N,P,K) (Atlas, 1984), this may not be the case for the degradation of PAH (Fedorak and Westlake, 1981). Nutrients are not limited in a pristine environment, however an environment receiving high organic wastes may soon become limited in nitrogen and phosphorus. As many estuaries in Australia receive nutrients from agricultural runoff, nutrients will probably not be a limiting factor. In the presence of other carbon sources, PAH degradation proceeds once the readily degraded carbon has been consumed (Shiaris, 1989a). (v) Temperature, pH and salinity. In the Northern Hemisphere the lowest degradation rates occur in winter (0.6°C) and the highest rates in summer (Shiaris, 1989a). Degradation rates of PAH in Australian marine sediments should be high as water temperatures are typically in the range 8-28°C. Laboratory studies (Hambrick et al., 1980) have indicated that the highest PAH degradation rates occur at pH 8, while lower degradation rates occur at pH 5. Marine sediments tend to be buffered at pH 6-7, thus the influence of pH on the degradation of PAH in Australian sediments will probably not be different to that in sediments from locations elsewhere in the world. Reports of the effect of salinity on PAH degradation are conflicting, however there is evidence for the existence of obligate marine PAH degraders (Kerr and Capone, 1988; Shiaris, 1989b).

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In summary, sediments from highly polluted locations subject to high organic loads will be anaerobic with a micro oxidized layer at best and the role of anaerobic microbes, for example iron/maganese or nitrate bacteria, in degrading PAH or PAH derivatives needs to be investigated. In relatively pristine locations (i.e. non-urban areas affected by power boating) oxygenated surficial sediments, relatively high temperatures and nutrient inputs will favour the degradation of PAH. Inputs of PAH with three or less rings from power boat activities will enhance the degradation of higher ringed PAH. The breakdown of PAH by microbes may also be enhanced by the initial oxidation of PAH by photooxidation or oxygen produced by algal mats. CONCLUSIONS

(i) PAH are accumulating in the sediments and shellfish of estuaries with highly urbanized/industrialized catchments (at levels similar to grossly polluted marine environments in the Northern Hemisphere). (ii) There is evidence of the accumulation of PAH in sediments/organisms of estuaries/harbors of non-urban areas subject to boating activity. (iii) PAH sources cannot be identified from the information available. In future studies the 16 US EPA priority pollutant PAH and alkylated derivatives need to be analyzed in sediments and probable sources. (iv) In highly polluted estuaries the role of anaerobic microorganisms in the degradation of PAH or their derivatives needs to be determined. (v) In relatively pristine environments (non-urban/industrialized) conditions are probably favourable for the aerobic degradation of PAH by microorganisms. (vi) Both the aerobic and the anaerobic degradation pathways of PAH need to be investigated. If degradation is occurring "in situ" are PAH being mineralized or are the oxidized forms accumulating? Are the PAH biodegradation products more bioavailable or more toxic than the parent compounds? ACKNOWLEDGEMENT

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