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Heavy metal pollution of coastal river sediments, north-eastern New South Wales, Australia: lead isotope and chemical evidence B. G. Lottermoser

Abstract Heavy metal and metalloid concentrations within stream-estuary sediments (~180-mm size fraction) in north-eastern New South Wales largely represent natural background values. However, element concentrations (Ag, As, Cd, Cr, Cu, Hg, Ni, Pb, Sb, Zn) of Hunter River sediments within the heavily industrialized and urbanized Newcastle region exceed upstream background values by up to one order of magnitude. High element concentrations have been found within sediments of the Newcastle Harbour and Throsby Creek which drains into urbanized and light industry areas. Observed Pb enrichments and low 208Pb/ 204Pb, 207Pb/ 204 Pb and 206Pb/ 204Pb ratios are likely caused by atmospheric deposition of Pb additives from petrol and subsequent Pb transport by road run-off waters into the local drainage system. Sediments of the Richmond River and lower Manning, Macleay, Clarence, Brunswick and Tweed River generally display no evidence for anthropogenic heavy metal and metalloid contamination (Ag, As, Cd, Cr, Cu, Hg, Ni, Pb, Sb, Zn). However, the rivers and their tributaries possess localized sedimentary traps with elevated heavy metal concentrations (Cu, Pb, Zn). Lead isotope data indicate that anthropogenic Pb provides a detectable contribution to investigated sediments. Such contributions are evident at sample sites close to sewage outlets and in the vicinity of the Pacific Highway. In addition, As concentrations of Richmond River sediments gradually increase downstream. This geochemical trend may be the result of As mobilization from numerous cattledip sites within the region into the drainage system and subsequent accumulation of As in downstream river and estuary sediments.

Key words River sediments 7 Heavy metals 7 Lead isotopes 7 Geochemistry

Introduction

Continuous release of organic pollutants, heavy metals and potentially toxic trace elements from point and diffuse pollution sources to hydrological systems results in their accumulation in sediments, particularly in slowly moving eutrophic streams. While sediments are important sinks for pollutants, these sediments can also release them back into the ecosystem. In addition, pollutants may have potential impacts on sediment biota. It is therefore important to understand the content of metals and metalloids in sediments in relation to their chemistry, biogeochemistry, bioavailability and geology (for example, Mackey and others 1992; Arakel and Hongjun 1992). Stream sediment surveys not only provide baseline geochemical data essential for the evaluation of pollution problems, but also help to develop proper sediment pollution standards (Arakel 1995). Sewage effluent and urban stormwater are the major point sources of pollution to enter waterways in New South Wales (EPA 1993). Thus excessive levels of nitrogen, phosphorous, heavy metals and organic pollutants occur in several rivers situated in the densely populated belts of north-eastern New South Wales, sometimes exceeding environmental guidelines (EPA 1993). Much of the environmental work has focused on the water chemistry and little information is available on the siting of pollutants within the sediment solids. An understanding of the siting of heavy metals is important in order to evaluate the potential remobilization of heavy metals and metalloids under changing environmental conditions and to estimate the biological availability of pollutants (Pickering 1986). The aims of this study are to document the concentraReceived: 5 September 1997 7 Accepted: 4 November 1997 tions, speciation and sources of heavy metals and potenB. G. Lottermoser tially toxic metalloids in river-estuary sediments of northSchool of Earth Sciences, James Cook University, PO Box 6811, eastern New South Wales (Fig. 1). It gives the total heavy Cairns, Qld 4870, Australia metal and metalloid concentration of lower Hunter and Tel.: c61-70-421137 Richmond River sediments (Figs. 2, 3). In addition, exFax: c61-70-421284 ploratory studies were conducted on river-estuary sedie-mail: bernd.lottermoser6jcu.edu.au

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Environmental Geology 36 (1–2) November 1998 7 Q Springer-Verlag

Cases and solutions

Materials and methods of analysis Description of study areas North-eastern New South Wales has a warm temperate humid climate. River catchments and flood plains are clustered with urban centres and represent important recreational and aquacultural resources in the region. The lower Hunter River supports one of Australia’s most extensive industrial bases (iron ore smelting, petrochemical and pharmaceutical industries) and represents a well-developed urban and commercial centre. As a result, the lower Hunter River and its estuary are subjected to pronounced anthropogenic stress and associated contaminant input from point and non-point source discharges (Ruello 1976; Hodda and Nicholas 1986). Land use in the Manning, Macleay, Clarence, Richmond, Brunswick and Tweed River catchments is mainly dominated by forestry operations and agriculture. Heavy industry is absent and most of the population is concentrated in rural and coastal townships. Potential pollution sources to the streams include saw mills, wood treatment works, cattle-dip sites, pastures, sewerage works, waste disposal sites, and runoff from highways and buildings.

Fig. 1 Map of north-eastern New South Wales showing the investigated rivers. (1) Hunter-Williams River, (2) Manning River, (3) Macleay River, (4) Clarence River, (5) Richmond River, (6) Brunswick River, (7) Tweed River

ment sites of the lower Manning, Macleay, Clarence, Brunswick and Tweed River (Fig. 1). Also, the siting of heavy metals in fractions of Hunter and Richmond River sediments were operationally defined by sequential extractions and Pb isotope compositions of sediments were evaluated to determine the specific sources of Pb to these coastal river systems.

Sampling and sample preparation Surface estuary and channel stream sediments were sampled with a plastic dredge in 1995–1996 (depth 0–2 cm; approx. 2 kg). A total of 79 sample sites were chosen. Samples were recovered from five locations at a given site and composited to improve site representativity. Samples were dried in original paperbags at room temperature and aggregates formed during drying were broken up with porcelain mortar and pestle. All sediment samples were sieved with a nylon sieve to ~180 mm. In view of common geochemical stream sediment surveys (Van Loon and Barefoot 1989), the ~180-mm size fraction of the sediments was selected as the fraction most likely to reflect hydromorphically dispersed metals and anthropogenic pollution. These processed samples were used for total and sequential element, isotope and X-ray powder diffraction analyses. Analytical techniques Sediments were analysed for their major mineralogical composition by X-ray powder diffraction at the Department of Geology and Geophysics, University of New England. Sample powders (approx. 0.2 g) were dissolved in a hot HF-HCl-HNO3-HClO4 acid mixture (approx. 15 ml), and refluxed with the acid mixture if the sample was only partly dissolved. The extracts were analysed by atomic absorption spectrophotometry (AAS) for their total Ag, Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn contents and by AAS after hydride generation for their total As, Hg and Sb concentrations (Hunter and Richmond River sediments). Richmond River sediments were also analysed for selected metalloids (Bi, Se, Te), whereas lower Manning, Macleay, Clarence, Brunswick and Tweed River sediments were investigated only for their Cr, Cu, Fe, Mn, Ni, Pb


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Fig. 2 Locality map showing stream sediment sample sites in the Hunter-Williams River, Newcastle region. Major industrialized and urbanized areas are also shown

and Zn contents. Analyses were conducted at the Department of Geology and Geophysics, University of New England, and at AnalabsT, Brisbane. Site variability was investigated for a number of sample locations and quality control/assurance of the data was applied using sub-sample triplicates and geochemical reference materials (NBS2704, NBS1646a, GXR-2). Data on geochemical reference materials were within 10% of the accepted values. Sample powders (approx. 5 g) were also dissolved in a hot HF-HCl-HNO3-HClO4 acid mixture and analysed by commercial inductively coupled plasma mass spectrometry (ICP-MS) (AnalabsW, Perth) for their lead isotope ratios. Analytical uncertainty is given at B0.1%. A sequential extraction analysis was performed on sediments of the Hunter and Richmond River in order to determine the solid speciation of selected heavy metals. The analytical procedure followed that of Tessier and others (1979) and Salomons and Förstner (1980) and used a sequence of chemical reagents and MilliporeT water. The wet chemical extraction procedure allowed the differentiation between exchangeable, Fe-Mn oxyhydroxide, carbonate and oxidizable (sulphides, organic matter), and residual element fractions (insoluble oxides, silicates). Approximately 10 g sample powder as starting material; 50 ml of 1 M MgCl2 (pH 7) agitated for 1 h (exchangeable fraction); 20 ml of 0.2 M NH4Ox/HOx (ammonium oxal120


ate/oxalic acid) (pH 3) agitated for 24 h (Fe-Mn oxyhydroxide fraction); 14 ml of 0.02 M HNO3, 8 ml of 30% H2O2 and 20 ml of H2O for 4 h at 857C (carbonate and oxidizable fraction). The extractants were analysed for Ag, Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn at the Department of Geology and Geophysics, University of New England. Richmond River sediments were subjected to an additional extraction step after the MgCl extraction (30 ml of 1 M NaAc/HOAc [sodium acetate/acetic acid] (pH 5) agitated for 5 h) in order to determine the metal content of the carbonate fraction.

Results Hunter River Sediment samples consist of variable major amounts of quartz, albite, orthoclase, microcline, muscovite and montmorillonite, and minor amounts of kaolinite, illite, nontronite, hematite, rutile, goethite and pyrite. The lowest total metal and metalloid concentrations have been found in sediments upstream of the Newcastle region (upper Hunter River, Williams River) (Table 1; Fig. 2) which likely represent natural background concentrations. These sediments possess metal contents up to one

Cases and solutions

Fig. 3 Locality map showing stream sediment sample sites in the Richmond River catchment

Table 1 Summary of element concentrations of sediments sampled. Mean element concentrations of the ~180-mm sediment fraction given in ppm, Fe in wt% (napnot analysed) samples

Hunter river catchment Upper Hunter River (10, 17, 18) Williams River (11–13) North and South Channel (1, 3–8, 19, 20) Throsby Ck – Newcastle Harbour (9, 14–16) Richmond river catchment Wilsons River (W1–4) Richmond River (R1–13, 16–20) Bungawalbin Creek (R14) Sandy Creek (R15) estuary (BA1, 3, 4, 8, 10–13) North Creek (BA5–7, 9) Manning River (MR1–5) Macleay River (MAC1–5) Clarence River (C1–7) Brunswick River (B2–4) Tweed River (TR1–4)

number Cu of samples

Zn

Pb

3 3 9 4

22 16 38 50

92 17 55 30 296 65 784 317

4 18 1 1 8 4

22 24 6 22 14 26

130 117 16 124 60 59

17 25 18 25 34 36

5 5 7 3 4

37 23 19 23 10

112 115 45 66 39

43 35 23 28 23

Ag

Cd

Cr

Ni

37 18 57 135

24 11 33 49

3 3 4.9 12

0.5 0.7 1.2 3.5

~1 102 36 1.4 113 39 0.6 17 5 1.4 67 35 ~1 60 16 na 49 12

~0.5 1.6 0.8 1.4 4.9 4.1

~0.5 ~0.5 ~0.5 ~0.5 ~0.5 ~0.5

na na na na na

na na na na na

3 ~1 3 ~1 3.6 ~1 3 2 ~3 ~3 ~3 ~3 ~3 ~3 na na na na na

na na na na na

66 27 41 16 33 11 30 9 26 9

As

Sb

Hg

0.02 0.02 0.06 0.39

Mn

815 246 760 291

Fe

4.93 1.41 5.17 3.20

~0.08 787 6.17 ~0.08 1140 5.17 ~0.08 119 1.09 ~0.08 374 4.95 ~0.08 187 2.58 ~0.08 209 2.42 na na na na na

362 494 221 196 99

2.83 2.89 1.57 1.91 1.38


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Fig. 4a–c Calculated proportions of Cu, Zn, Pb, Ag, Cr, Ni, Mn and Fe in a samples from the Williams and upper Hunter River [number of samples processed (n) p3], b samples from the South Channel and Newcastle Harbour (np7), c Throsby Creek sediment (np1). Metal concentrations are based on the weight of the starting material (10 g) before extraction

order of magnitude lower than those accumulating in the Newcastle area (North and South Channel, Throsby Creek, Newcastle Harbour). Heavy metals and metalloids are elevated in sediments of the South Channel, sections of the Newcastle Harbour, and particularly in sediments of Throsby Creek (Table 1; Fig. 2). This creek drains the central city light industry and large urbanized areas. The element data of the sequential extraction are presented as the mass of the extracted species divided by the mass of the entire starting material before sequential extraction (10 g for all samples) (Fig. 4). Such a presentation illustrates the behaviour of one element in the same fraction of all samples. Relative proportions of separated elements in the residual phases remain largely constant for samples of the Williams and upper Hunter River (Fig. 4a) and South Channel and Newcastle Harbour (Fig. 4b). In contrast, the Throsby Creek sediment possesses more Zn and Ag incorporated in the exchangeable fraction, more Cu, Cr, Ni, Mn and Fe in the organic matter/sulphide fraction, and lower percentages of heavy metals within the residual fraction (Fig. 4c). Only the adsorptive fraction contains detectable amounts of Cd. Thus Throsby Creek sediments not only contain the highest heavy metal contents, but high percentages of labile Zn, Cd and Ag incorporated into the adsorptive fraction of fine particles. These metals exhibit the greatest tendency to experience potential remobilization under changing environmental conditions and are more biologically available than the other metals. 122


Fig. 5 Pb versus Pb concentration, 207Pb/ 204Pb versus 206 Pb/ 204Pb, and 208Pb/ 204Pb versus 206Pb/ 204Pb in Hunter-Williams River and Newcastle Harbour - Throsby Creek sediments. Isotopic composition of leaded petrol after Gulson and others (1994) 206/204

The sedimentary concentration of total Pb increases from a background of 17 ppm (upper Hunter River) to 317 ppm within Throsby Creek sediments (Table 1). Further, the isotopic composition of the sediments is very heterogenous and the samples exhibit a range of 208Pb/ 204 Pb, 207Pb/ 204Pb and 206Pb/ 204Pb ratios (Fig. 5). However, the sediments conform to a fairly standard pattern: (1) the Pb isotope ratios become less radiogenic downstream, approaching the ratio of Throsby Creek and Newcastle Harbour sediments (that is lower in 208Pb/ 204 Pb, 207Pb/ 204Pb and 206Pb/ 204Pb ratios); and (2) samples from the upper Hunter River and Williams River have the lowest Pb concentrations and the highest 208Pb/ 204 Pb, 207Pb/ 204Pb and 206Pb/ 204Pb ratios. Richmond River Richmond River sediments consist of variable major amounts of quartz, plagioclase, microcline, sanidine, anorthoclase, kaolinite and montmorillonite, and minor amounts of nontronite, halloysite, diopside, muscovite, ilmenite, hematite and goethite. Concentrations of Cr, Cu, Ni and Zn within sediments of the Richmond River

Cases and solutions

catchment tend to decrease downstream and estuary sediments possess distinctly lower metal values than upstream sediments (Fig. 3; Table 1). In contrast, As concentrations increase downstream and maximum contents have been detected within estuary sediments. Slightly elevated Pb concentrations have been found in sediments at Ballina (sample BA7 : 81 ppm; sample BA8 : 99 ppm), Woodburn (sample R17 : 40 ppm) and Wardell (sample R19 : 45 ppm). All sediment samples possess non-detectable Bi (~1 ppm), Se (~0.3 ppm) and Te (~0.3 ppm) concentrations. Sequential extraction on stream and estuary sediments of the Richmond River indicates similar Cr, Cu, Fe and Pb distributions (Fig. 6). However, compared to stream sediment samples (Fig. 6a), estuary samples of the Richmond River (Fig. 6b) tend to possess more Mn and less Ni and Zn in the residual fraction, more Ni and Zn in the adsorptive fraction, and more Zn in the Fe-Mn oxyhydroxide form. Richmond River sediments possess a diverse Pb isotope geochemistry and the samples possess a range of 208Pb/ 204 Pb, 207Pb/ 204Pb and 206Pb/ 204Pb ratios (Fig. 7). Several trends have been recognized within the data: (1) sample BA7 (Ballina) has a high Pb content (81 ppm) and the lowest 208Pb/ 204Pb, 207Pb/ 204Pb and 206Pb/ 204Pb ratios; (2) samples with elevated Pb contents (BA8, Ballina: 99 ppm; R17, Woodburn: 40 ppm; R19, Wardell: 45 ppm) have significantly higher 208Pb/ 204Pb, 207Pb/ 204Pb and 206Pb/ 204Pb ratios than sample BA7; and (3) the majority of stream and estuary sediments possess low Pb concentrations (~35 ppm) with relatively high 208Pb/ 204Pb, 207Pb/ 204Pb and 206Pb/ 204Pb ratios. Other rivers Exploratory studies of the Macleay, Manning, Clarence, Brunswick and Tweed River show metal distributions which appear to be unique for each river system (Table 1). In addition, there are sample sites within the Macleay, Manning, Clarence and Tweed River with relatively high heavy metal concentrations. Distinctly elevated heavy metal values have been found in Browns Creek (sample MR1 : 81 ppm Cu, 140 ppm Pb, 275 ppm Zn), which represents a small tributary to the Manning River. This creek drains Taree’s light industry and sewerage treatment works. Distinctly elevated heavy metal values have

Fig. 6a, b Calculated proportions of Cu, Zn, Pb, Cr, Ni, Mn and Fe in a stream sediment samples from the Richmond River [number of samples processed (n) p4], b estuary sediment samples from the Richmond River (np4). Metal concentrations are based on the weight of the starting material (10 g) before extraction

also been detected within the Macleay River at Kempsey (sample MAC1 : 46 ppm Cu, 79 ppm Pb, 184 ppm Zn). Sediment at this site contains higher Cu, Pb and Zn concentrations than samples taken upstream. Similarly there are sample sites within the Clarence and Tweed River which possess elevated Cu, Pb and Zn values compared to samples taken upstream (max. 25 ppm Cu, 42 ppm Pb, 72 ppm Zn). Elevated metal concentrations of sediments are restricted to individual sample sites within or close to urbanized areas and dispersion trails of heavy metals have not been detected downstream. Lead isotope ratios of the investigated stream sediments vary widely (Fig. 8). However, sediments from the Manning and Macleay River show geochemical trends similar to those of Hunter and Richmond River sediments: (1) samples with low 206Pb/ 204Pb ratios tend to have high Pb Fig. 7 Pb versus Pb concentration, 207Pb/ 204Pb versus 206 Pb/ 204Pb, and 208Pb/ 204Pb versus 206Pb/ 204Pb in Richmond River sediments. Isotopic composition of leaded petrol after Gulson and others (1994) 206/204


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Fig. 8 Pb versus Pb concentration, 207Pb/ 204Pb versus 206 Pb/ 204Pb, and 208Pb/ 204Pb versus 206Pb/ 204Pb in Manning and Macleay River sediments. Isotopic composition of leaded petrol after Gulson and others (1994) 206/204

concentrations (MAC1, Macleay River, Kempsey; 79 ppm; MR1, Browns Creek, Taree: 140 ppm); (2) samples with low 206Pb/ 204Pb ratios and high Pb contents occur downstream of a sewage treatment plant (sample MR1, Taree) and close to the Pacific Highway (sample MAC1, Kempsey); and (3) the majority of stream sediments possess low Pb concentrations (~42 ppm) with relatively high 208 Pb/ 204Pb, 207Pb/ 204Pb and 206Pb/ 204Pb ratios.

Discussion The chemistry of a river sediment is a function of the flux and chemical characteristics of detritus from the watershed to the depositional site and the proportions of inorganic and organic material incorporated into the sediment (Norton and others 1992). In addition, natural geochemical cycles can be influenced by the addition of hydrologic elements or compounds originating from anthropogenic activities. The extent to which a particular sediment reflects pollution on a local or a more regional basis depends primarily on the proximity and degree of mining, industrial and agricultural activity and population density in its environs. Sources of metals in recent sediments include detrital components, natural background concentrations in waters and organic matter and anthropogenic additions including road run-off water, sewage effluent, urban stormwater or industrial discharges.

dustry, port loading facilities and urbanized areas. These findings are in agreement with those of a sediment survey conducted by Ingleton and Birch (1995). Thus industrial discharges and urban stormwater appear to be likely sources of heavy metals within lower Hunter River sediments. The spread of urban pollutants including Pb has been investigated by a number of studies. Studies of Pb isotopic composition have thereby indicated that Pb pollutants are derived mainly from the combustion of Pb additives in petrol (for example, Chow and others 1973; Gulson and others 1981; Shirahata and others 1980; Sanudo-Wilhelmy and Flegal 1994; Graney and others 1995; Gobeil and others 1995). Anthropogenic Pb has thereby been detected in surface soils, sediments and waters on a local, regional and even global basis (for example, Erel and Patterson 1994). In Australia accumulation of heavy metals, particularly Pb, has already been reported from surface soils adjacent to a number of major highways (Wylie and Bell 1973; David and Williams 1975; Bottomley and Boujos 1975; Clift and others 1983). These studies have also shown that the long-range transport of Pb occurs as aerosols, whereas the very short-range transport (~100 m) occurs as particles. Over 60% of cars in New South Wales still used leaded petrol as of 1991 (EPA 1993). Thus the observed Pb enrichment and the low 208Pb/ 204Pb, 207Pb/ 204Pb and 206Pb/ 204 Pb ratios within Throsby Creek and Newcastle Harbour sediments (Fig. 5) are likely caused by atmospheric deposition of Pb additives from petrol in the Newcastle area. Lead particles are subsequently transported by road run-off waters into the local drainage system and accumulate in local creek and harbour sediments.

Richmond River Elevated Fe, Mn, Cr, Cu, Ni and Zn concentrations have been detected in sediments of the upper Richmond and Hunter River Heavy metal concentrations of sediments within Throsby Wilsons River which have a catchment dominated by basalts rich in these elements (Kyogle, Casino and LisCreek and the lower Hunter River (North and South more areas). Regions further downstream dominated by Channel) exceed upstream background values (upper Hunter River) by up to one order of magnitude (Table 1). Quaternary sediments and flood plains have sediments with distinctly lower heavy metal concentrations (Ballina, Exceptionally high concentrations of metals have been found in sediments deposited close to the heavy metal in- Woodburn and Wardell areas). Such markedly different 124


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element distributions are likely the result of downstream dilution of heavy-metal-bearing sediment particles. Thus the geochemistry of Richmond River sediments is largely controlled by the rock types in the catchment area (Cohen and others 1995). Origin of As In contrast to all other heavy metals, As concentrations of sediments increase downstream and reach their maxima in estuary sediments. Elevated As values with corresponding Fe and Mn enrichments are known to occur naturally in near-surface sediments (for example Farmer and Lovell 1986). These elements commonly display significant positive correlations. The enrichments have been interpreted in terms of post-depositional diagenetic remobilization processes: the elements occur in sedimentreducing zones, migrate upward through interstitial waters and are subject to oxidation, adsorption and/or precipitation reactions in near-surface oxidizing layers (Farmer and Lovell 1986). For the Richmond River sediments, a correlation matrix of log-transformed data shows that there is minor correlation between Fe and Mn (Fe-Mn: c0.53). However, there are no correlations of Fe or Mn with As (N: 30; Fe-As: –0.26; Mn-As: –0.26). Therefore a post-depositional diagenetic origin of the detected As values appears to be unlikely. The concentration of As in sediments can be expected to reflect the naturally occurring As content of the corresponding catchment areas except where there has been input from industrial or agricultural activities. Arsenic mineralizations or As-rich rocks such as black shales do not occur in the lower Richmond valley and thus the observed geochemical trend is likely the result of anthropogenic pollution. North-eastern New South Wales, particularly the Richmond River catchment, has several hundred cattle dip sites which are severely contamined by As and it is estimated that about 22 kg of As are buried at each site (EPA 1993). Increasing As concentrations in Richmond River sediments may therefore indicate mobilization of As from contaminated sites into the regional drainage system and accumulation of As in downstream sediments. However, detailed local and regional studies on the hydrology and hydrochemistry of the Richmond valley are needed to evaluate such a suggestion.

ment is the result of natural accumulation of Pb (BA8, Ballina; 99 ppm Pb; Fig. 7). However, in addition to natural Pb in Richmond River sediments which originates from geological bedrock, there is Pb from an isotopically distinct source. A sediment sample was taken close (200 m) to the effluent outlet of the Ballina sewerage works (sample BA7; 81 ppm Pb; Fig. 7). This sample exhibits a relatively high Pb concentration combined with a Pb isotope composition similar to industrial Pb. Thus the observed changes in elemental and isotopic Pb compositions in a local sedimentary trap near the Ballina sewerage works are interpreted to reflect the addition of sewage derived Pb. Other rivers Elevated Cu, Pb and Zn concentrations have been detected in some river-estuary sediments of the Macleay, Manning, Clarence, Brunswick and Tweed River. These variable heavy metal concentrations could reflect natural variations in heavy metal distributions or anthropogenic disturbances of the natural sediment geochemistry. However, changed Pb isotope compositions with higher Pb contents in sediments of the lower Macleay and Manning River point to the input of anthropogenic Pb (Fig. 8). Samples with elevated Pb concentrations and relatively low 206Pb/ 204Pb ratios were taken in urbanized areas (MR1, Taree; MAC1, Kempsey). Responsible pollution sources such as sewage treatment works and the Pacific Highway are in the immediate vicinity (~200 m) of the sample sites. Changes in sediment isotope geochemistry appear to be localized and have not been detected in samples downstream. Therefore the Pb contamination of sediments is most likely the result of short-range (~200 m) Pb inputs from sewage effluent and road runoff waters.

Conclusions

Sediments of coastal rivers in north-eastern New South Wales have heavy metal concentrations which largely represent natural background values. However, heavy metal concentrations (Ag, As, Cd, Cr, Cu, Hg, Ni, Pb, Sb, Zn) of Hunter-Williams River sediments generally increase downstream and reach their maxima in the heavily inOrigin of Pb dustrialized and urbanized Newcastle region (lower HuntThe results of a regional sediment survey conducted by er River, Throsby Creek, Newcastle Harbour). The inCohen and others (1995) did not indicate a change in crease in Pb concentration combined with a distinct heavy metal levels adjacent to possible anthropogenic sources. These authors concluded that Pb concentrations change in the Pb isotope composition reflects the addition of anthropogenic Pb. The elevated Pb values are were generally low, even in the vicinity of major towns and highways, and that anthropogenic sources are a rela- likely caused by the atmospheric deposition of Pb additively insignificant contributor to the regional geochemis- tives from petrol and subsequent transport by road runtry of river sediments. Richmond River sediments exhibit off waters into the local drainage system. a range of Pb isotope ratios, which suggests that the div- Sediments of the Richmond River and lower Manning, Macleay, Clarence, Brunswick and Tweed River generally erse bedrocks in the catchment area determine the Pb display no evidence of anthropogenic metal contaminaisotope composition of the investigated sediments. The sample with the highest Pb concentration has an isotope tion. However, As concentrations within Richmond River composition unlike leaded petrol and thus its Pb enrich- sediments increase downstream. This geochemical trend


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Gobeil C, Johnson WK, MacDonald RW, Wong CS (1995) Sources and burden of lead in St. Lawrence estuary sediments: isotopic evidence. Environ Sci Technol 29 : 193–201 Graney JR, Halliday AN, Keeler GJ, Nriagu JO, Robbins JA, Norton SA (1995) Isotopic record of lead pollution in lake sediments from the northeastern United States. Geochim Cosmochim Acta 59 : 1715–1728 Gulson BL, Tiller KG, Mizon KJ, Merry RH (1981) Use of lead isotopes in soils to identify the source of lead contamination near Adelaide, South Australia. Environ Sci Technol 15 : 691–696 Gulson BL, Mizon KJ, Law AJ, Korsch MJ, Davis JJ, Howarth D (1994) Source and pathways of lead in humans from the Broken Hill mining community – an alternative use of exploration methods. Econ Geol 89 : 889–908 Acknowledgements This study was financed by the Australian Hodda M, Nicholas WL (1986) Nematode diversity and inResearch Council Small Grant Scheme. Mrs J. Cook (University dustrial pollution in the Hunter River estuary, NSW, Austraof New England) devoted much of her time and patience to the lia. Mar Pollut Bull 17 : 251–255 analysis of several river sediments. Ingleton TC, Birch GF (1995) The impact of urban and industrial development on the Hunter River. In: Boyd RL, MacKenzie GA (eds) Advances in the study of the Sydney Basin. Proc 29th Newcastle Symp, Department of Geology, University of Newcastle, pp 52–58 Mackey AP, Hodgkinson M, Nardella R (1992) Nutrient levels and heavy metals in mangrove sediments from the Arakel AV (1995) Towards developing sediment quality asBrisbane River, Australia. Mar Pollut Bull 24 : 418–420 sessment guidelines for aquatic systems: an Australian perNorton SA, Bienert RW, Binford MW, Kahl JS (1992) Straspective. Aust J Earth Sci 42 : 335–369 tigraphy of total metals in PIRLA sediment cores. J Paleolimn Arakel AV, Hongjun T (1992) Heavy metal geochemistry and 7 : 191–214 dispersion pattern in coastal sediments, soil, and water of He- Pickering WF (1986) Metal ion speciation – soils and sedidron Brook floodplain area, Brisbane, Australia. Environ Geol ments (a review). Ore Geol Rev 1 : 83–146 Water Sci 20 : 219–231 Ruello NV (1976) Environmental and biological studies of the Bottomley GA, Boujos LP (1975) Lead in soil of Heirisson IsHunter River. Operculum 6 : 76–84 land, Western Australia. Search 6 : 389–390 Salomons W, Förstner U (1980) Trace element analyses on Chow TJ, Bruland KW, Bertine KK, Soutar A, Koide M, polluted sediments Part II: evaluation of environmental imGoldberg ED (1973) Records in southern California coastal pact. Environ Technol Lett 1 : 506–511 sediments. Science 181 : 551–552 Sanudo-Wilhelmy SA, Flegal AR (1994) Temporal variations Clift D, Dickson IE, Roos T, Collins P, Jolly M, Klindin lead concentrations and isotopic composition in the Southworth A (1983) Accumulation of lead beside the Mulgrave ern California Bight. Geochim Cosmochim Acta 58 : 3315–3320 Freeway, Victoria. Search 14 : 155–157 Shirahata H, Elias RW, Patterson CC (1980) Chronological Cohen D, Rutherford N, Garnett D, Waldron H (1995) A variations in concentrations and isotopic compositions of angeochemical survey of the upper north east region, New thropogenic atmospheric lead in sediments of a remote subalSouth Wales. Vol 1. New South Wales Department of Mineral pine pond. Geochim Cosmochim Acta 44 : 149–162 Resources, Sydney Tessier A, Campbell PGC, Bisson M (1979) Sequential extracDavid DJ, Williams CH (1975) Heavy metal contents of soils tion procedure for the speciation of particulate trace metals. and plants adjacent to the Hume Highway near Marulan, Anal Chem 51 : 844–851 New South Wales. Aust J Exp Agri Anim Husb 15 : 414–418 Van Loon JC, Barefoot RR (1989) Analytical methods for EPA (1993) New South Wales State of the Environment 1993. geochemical exploration. Academic Press, San Diego Environment Protection Authority, Sydney Wylie PB, Bell LC (1973) The effect of automobile emissions Erel Y, Patterson CC (1994) Leakage of industrial lead into on the lead content of soils and plants in the Brisbane area. the hydrocycle. Geochim Cosmochim Acta 58 : 3289–3296 Search 4 : 161–162 Farmer JG, Lovell MA (1986) Natural enrichment of arsenic in Loch Lomond sediments. Geochim Cosmochim Acta 50 : 2059–2067

is possibly due to the mobilization of As from numerous contaminated cattle-dip sites present within the region into the drainage system and subsequent accumulation of As in downstream river and estuary sediments. In addition, there are several localized sedimentary traps close to rural and coastal townships with elevated heavy metal values, particularly Pb concentrations. Lead isotope studies indicate that these sites experience a detectable contribution of Pb as a result of short-range inputs (~200 m) from leaded petrol (Kempsey; Maclay River) and sewage effluent (Taree, Manning River; Ballina, Richmond River).

References

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