Em~ironmentalPollution (Series A) 28 (1982) 135 147

This Project Report is publication No. 348 in the Ministry for Conservation of , Environmental Studies Series

MERCURY CONTAMINATION OF THE , VICTORIA, , FROM AN ABANDONED GOLD FIELD

B. M. BYCROFT,*~ B. A. W. COLLER,* G. B. DEACON,* D, J. COLEMAN~ & P. S. LAKEs

* Department of Chemistry. ~ Department of Zoology. Monash University, Clayton, Victoria 3168, Australia

ABSTRACT In the catchment of the Lerderderg River, Victoria, Australia, gold-mining operations using the mercury amalgamation process were carried out until 50 years ago. The distribution of mercury in water, sediments and fish from the Lerderderg River has been investigated. Mercury in water values were low (0"01 to 0.31 I~g litre-1) and showed no clear correlation with sites of sampling. However, mereury concentrations up to 130 #g g-1 in sediments revealed a pattern of mercury contamination which could be related to past gold-mining activities. Elevated mercury levels were not found in brown trout Salmo trutta, but in river blackfish Gadopsis marmoratus, concentrations elevated to as much as 0"64 #g g- ~ were found in fish living at sites with elevated mercury sediment levels.

INTRODUCTION

Numerous studies in recent years have examined the contamination of biota by mercury from effluents. Attention has been largely devoted to discharges from chlor-alkali plants and papers-mills, quantitatively the most important on a world- wide basis (Newberne, 1974). Another potential source of significant local mercury contamination is that arising from the use of mercury in amalgamation processes for the extraction of gold and silver from ores. Although this extraction technique has been largely superseded by the cyanidation process, amalgamation was widely used in the early days on Victorian gold fields (Smyth, 1869). Significant levels of mercury are known to be contained in the tailings from amalgamation operations. For

i" Present address: Marine Chemistry Laboratory, University of , Parkville, Victoria 3052. Australia. 135 Environ. Pollut. Ser. A. 0143-1471/82/0028-0135/$02.75 © Applied Science Publishers Ltd, England, 1982 Printed in Great Britain 136 B.M. BYCROFTet al. example, tailings from an abandoned gold mine on the , Victoria, Australia, contained 40--90#gg -1 of mercury (Melbourne and Metropolitan Board of Works, 1975). Similarly, tailings from a recently active mine near Woods Point, Victoria, Australia, have been found to contain 88 #g g- ~ of mercury (A. McCredie, pers. comm.). It has been estimated that the weight of mercury consumed in the amalgamation process is of the same order as the weight of gold recovered (Wise, 1966). On this basis, the potential mercury contamination from old gold- mining areas can reach major proportions. For instance, the amount of mercury potentially released to the environment from the Bendigo field, one of the richest early fields in Victoria, would amount to about 900 tonnes. Although it is many years since most Australian gold mines ceased operations, tailings dumps are still prominent features of the local landscape. Material from other dumps has been removed and possibly used for road surfacing or as filling materials in creeks and gullies. Thus, there is potential for a continuing release of mercury from these tailings into adjacent aquatic environments. There are some reports in the literature of studies of mercury contamination from amalgamation processes (e.g. Van Meter, 1972; Walter et al., 1973; Moore & Sutherland, 1980). In Victorian studies, mercury accumulation has been reported in the Woods Point area, near mines recently in operation (Environment Protection Authority, Victoria, 1982), and in the Lakes, downstream from areas which, until the 1930s, were mined for gold (Glover et al., 1980). A preliminary study by the Victorian State Rivers and Water Supply Commission (Bennison & Guest, 1980) indicated that parts of the upper Lerderderg River have elevated levels of mercury. It appeared that this could possibly arise lrom adjacent abandoned gold fields at Blackwood. This paper reports on the distribution of mercury in water, sediments and fish from the Lerderderg River and the relationship between mercury levels and gold- mining activities around Blackwood. It forms part of a larger study, funded by the Environmental Studies Section, Victorian Ministry for Conservation, to investigate the sources and distribution of selected heavy metals in the Lerderderg-Upper Werribee Rivers catchment. Alluvial gold was first discovered near Blackwood in 1851 (Buckingham & Hitchcock, 1980). By 1855 much of the alluvial gold had been recovered, and reef- mining operations began. From 1869, when detailed recording began, over 5000 kg were won from the Blackwood field (Buckingham & Hitchcock, 1980). The largest mine, the Sultan, ceased operations in 1883. However, one mine, the Trojan, from which about 140 kg of gold was recovered (Foster, 1937), operated until about 1937 (L. Armstrong, pers. comm.). Although amalgamation was originally used to recover the gold, later operations in the 1930s involved reworking, by cyanidation, of tailings from amalgamation processes in order to recover residual gold. It is probably more than 50 years since direct amalgamation was used routinely on the Blackwood field. MERCURY IN AN AUSTRALIAN RIVER 137

DESCRIPTION OF THE STUDY AREA (FIG. 1)

The Lerderderg River rises on the southern edge of the , about 110 km northwest of Melbourne. State forest covers most of the catchment. The river, 60km long, flows approximately in a southeasterly direction, passing through the settlements of Blackwood and Darley before joining the . The mean discharge is relatively low, 27.3 megalitres a year (Australian Water Resources Council, 1979). The flow regime is quite variable with generally a spring peak and a summer low (often zero) matching the seasonal pattern of rainfall in the catchment. When the river is flowing, the conductivity in the upper reaches is generally about 100-120/~S cm- 1. The conductivity rises to about 300/~S cm - 1 as the river passes through the agricultural land around Darley. The pH of the water is generally slightly alkaline. Under normal conditions the transparency of the water and the dissolved oxygen are both high--an indication of little organic pollution. Recently, a weir and diversion tunnel were constructed on the river (see Fig. 1). The purpose of these constructions is to divert water from the upper Lerderderg River to Merrimu Reservoir which supplies drinking and irrigation water to surrounding districts.

MATERIALS AND METHODS Sample collection Water, sediment and fish samples were collected from sites along the Lerderderg River and its tributaries, with sampling points focused around Blackwood (see Fig. 1 for location of sampling sites). Samples were also collected from a control site on the adjacent Werribee River, upstream of its confluence with the Lerderderg River. Relatively little gold mining took place in the upper Werribee River catchment. The (surface) water samples were collected weekly over a period of six weeks in October November 1979 when the river level was dropping. A 250 ml aliquot was filtered under pressure through pre-washed membrane filters (0.45/~m, Millipore 47 mm, HAWP) in a plastic (Sartorius) filtration apparatus. The filtered sample was transferred to a BOD bottle (Wheaton) containing 2.5 ml of concentrated nitric acid (BDH, Aristar Grade) and 5 ml of 4 % potassium dichromate (Ajax, Analar Grade) as preservative. The membrane filters were transferred to labelled plastic petri dishes. Field blanks were prepared by the filtration of 250 ml aliquots of distilled water. On each sampling trip the blank was prepared at a different site. All filtered water samples were stored at 4°C and analysed the day following collection. The sediment samples were collected in a summer period, January 1980, and a winter period, August 1980. They were wet-sieved in the field using river water. The complete fraction which passed through a 180/~m (80 mesh) nylon sieve was retained to avoid loss of fines which settled very slowly and may have contained a ! ! • I o q ~ ~ H ! ~z

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70 2a ±~oaaxtt '~ 'a g~ I MERCURY IN AN AUSTRALIAN RIVER 139 substantial proportion of the mercury. Up to three separate samples were collected at each site. An aliquot of the resulting sediment slurry was transferred to a glass- stoppered glass jar, and was used for mercury analysis. A separate aliquot of the well mixed slurry was transferred to a screw-cap jar. This sample was used for percentage moisture determination to allow calculation of the mercury levels on a dry weight basis. Fish were sampled by electroshocking using a custom-built electrofishing unit (240 V pulsed DC) powered by a Honda 1000 W generator. The fish were placed in plastic bags. All sediments and fish were placed on ice for transport to the laboratory where they were stored at -10°C until analysis.

Analytical procedures The filtered water sample was analysed for mercury by the method of the Victorian Environment Protection Authority (H. Blutstein, pers. comm.). Briefly, a 100 ml aliquot of the preserved water sample was digested on a boiling water bath with 0.5g potassium permanganate (Merck No. 5084, low mercury) and 0.3g potassium persulphate (Ajax, Univar). The precipitated manganese dioxide and excess permanganate were reduced by ascorbic acid. The membrane filter contain- ing the non-filtrable residue was analysed for mercury by the aqua-regia/- permanganate method of the US Environmental Protection Agency (1974) for mercury in sediments. The aqua-regia (one part nitric acid to three parts hydrochloric acid) was prepared from Aristar (BDH) grade reagents. An aliquot of the sediment slurry was digested prior to mercury analysis using the procedure of the US Environmental Protection Agency (1974). Each sample was analysed in triplicate. The percentage moisture in the sediment slurry samples was determined by drying a separate aliquot of the slurry at 105°C for 17h. For the fish samples, separate portions of shoulder and tail muscle were removed and separately digested using the method described by Armstrong & Uthe (1971). All mercury analyses were carried out by cold vapour atomic absorption spectrophotometry using an LDC 1235 mercury monitor. The method of standard additions was used for quantification and the accuracy of the analytical methods was verified by the use of appropriate standard reference materials--river sediment (National Bureau of Standards), fly ash (NBS), bovine liver (NBS), pine needles (NBS) and shark tissue (Victorian Department of Fisheries and Wildlife, No. 8040102).

RESULTS Mercury in water The range and logarithmic means of total mercury levels in water at different sites are given in Table 1. Although values for filtered waters and non-filtrable residues 140 B.M. BYCROFT et al.

TABLE 1 MERCURY LEVELS IN WATER (~g litre- 1)

Site No. Range Log mean

1 0.04-0.28 0.14 2 0.01-0.21 0.07 7 0.02-0.09 0.05 13 0-05-0.14 0"08 15 0.04-0.07 0"06 19 0.07-0.31 0.13 were separately determined, they offered no separate distinctive features, except that, where higher levels were recorded, most of the mercury was usually in the residues. The levels are generally low with the highest values recorded at the control sites 1 and 19.

Mercury in sediments The sediment mercury levels in January (the period of summer flow) at different sites are given in Table 2. The mean levels are displayed on a schematic diagram of

TABLE 2 MERCURY LEVELS IN SEDIMENTS COLLECTED IN JANUARY 1980 (#gg- 1 dry weight)

Site No. Mercury concentration 1 2 3

I 0.05 0.24 0.07 2 0.04 0-26 -- 3 0.14 0'38 0'69 4 < 0'02 -- -- 6 0"29 0.99 -- 7 0.57 0.41 0.73 8 0.33 0'30 0"05 9 1.67 1'67 4.03 l0 1.12 0.72 0.74 ll 3-22 68'50 8.31 12 o 120.00 -- -- 13 2.45 1.20 1.60 14 0.32 0.54 0.47 15 0'81 0'47 0'30 17 0"06 0'03 0-03 18 0"13 0.64 0.18 19 0'03 0'07 0"04 20 0"13 -- -- 21 0.04 -- -- 22 0"06 -- --

Up to three separate samples (1,2, 3) were collected at each site. The mean of triplicate determinations of each sample is recorded " From tailings dump (cyanided battery sand) on bank of Yankee Creek (site 11). MERCURY IN AN AUSTRALIAN RIVER 141 the study area (Fig. 2). The levels are low at sites above the major mining activity. On passing through the mining area, however, levels up to as much as 3, 8 and 68/agg -1 were found. Downstream the mercury levels gradually return to background values. The sediment mercury levels collected in winter (August 1980) from four sites indicate that while the mercury concentrations are generally lower than those found

• 57 ee~ .23 120 m • 2 46 26-7 e<.02 • ' •12 -15 • ,40 ee.64 .86

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Fig. 2. Mercury levels in sediment, pg g ~ dry weight. 0, sites of stamping batteries. in the summer flow period (Table 3), river sediments in the area of the past battery operations are clearly contaminated.

Mercury in fish Two species offish were analysed for mercury: brown trout Salmo trutta (Table 4) and blackfish Gadopsis marmoratus (Table 5). These species were the most common in the study area and might be expected to display differences in mercury concentration between sampling sites. Since there were no significant differences between levels of mercury in shoulder and tail muscle, these values were pooled. From Table 4 it can be seen that in the brown trout there is no systematic variation with sampling site although the highest level recorded, 0.35 #g g- i, was from a 'contaminated' site (i.e. a site with high mercury levels in sediments). For blackfish (Table 5), however, there is a clear distinction in the levels found between fish from control sites and fish from contaminated sites. 142 B.M. BYCROFT et al.

TABLE 3 MERCURY IN SEDIMENTS COLLECTED IN AUGUST 1980 (#g g- 1 dry weight)

Site No. Mercury concentration 1 2 3

2 <0.01 0.05 0.01 4 0.19 0.19 0.15 13 0.97 0.67 0.49 15 0.28 0.07 0.13

TABLE 4 MERCURY LEVELS IN BROWN TROUT Salmo trutta Site Mercury level Total Mean Hg No. in sediment fish length (#g g- a) (#gg-1) (cm)

2 0.15 16.4 0.04 21.9 0.18 5 0.40 22.0 0.12 29. I 0.23 11 26.7 13.8 0.15 17.5 0.15 13 1.75 15.2 0.35 15.6 0.23 14 0.43 9.2 0.08 20.8 0.18 15 0.53 8.3 0.15 9.2 0-12 16 -- 23.1 0.17 34.3 0.18 18 0.32 10.8 0.05 41.7 0.28 19 0.05 9.3 0.03 31.2 0.03

TABLE 5 MERCURY LEVELS IN RIVER BLACKFISH Gadopsis marmoratus Site Mercury level Total Mean Hg No. in sediment fish length (l~gg- 1) (lzg g- ~) (cm)

2 0.15 16.0 0.09 17.6 0.08 13 1.75 9.2 0.23 21 '2 0.64 14 0.43 Mean: 12.4 0-17 (7.7 - 20.9) (0.12-0.30) 15 0-53 19.7 0.26 24.3 0.28 16 -- Mean: 16.4 0.23 (8.2-29.0) (0.12-0-31) 19 0.05 Mean: 11.0 0-03 (7.4-23.0) (0.2~.06) MERCURY IN AN AUSTRALIAN RIVER 143

DISCUSSION

A number of workers (Hawkes & Webb, 1962; Aston et al., 1974) have stressed the disadvantages of using concentrations of trace elements in water as a reliable indication of pollution. The major problem is the high degree of fluctuation in water elemental levels, which was clearly evident in this study. The levels certainly are elevated with respect to the normal background of 0.01 #glitre -1 (F6rstner & Wittmann, 1979), but the lack of any decisive trend may indicate the very limited value of analysing fresh waters for mercury. The mercury in sediment levels clearly indicates the presence of contamination in the upper Lerderderg River. Thus, sediment levels 30 to 700 times the normal background value of about 0.1/tg g- 1 (Fitchko & Hutchinson, 1975) were found in Yankee Creek near the Trojan mine. The sources of mercury contamination are clearly related to past gold-mining activities in the catchment. The sediment levels are near the normal background value at sites 1 and 2, in the Lerderderg River upstream of the major Blackwood field of mining activity, and increase significantly in the river (site 3) adjacent to the location of a stamping battery. Site 4 is in the drainage to the Lerderderg River from an abandoned adit of the Joseph Hill's gold mine. It is reported that deposits in gold mines are sometimes associated with mercury mineralisation (Hawkes & Webb, 1962), but the relatively low levels of mercury in the sediments from this site indicate that natural mineralisation is not a significant source of contamination in this area. Conversely, the very high level (120/~g g- 1) found in a tailings heap at the site of the Trojan mine (site 12) implicates mercury-laden mine wastes as the source of contamination. Sediment samples collected from site 11 in Yankee Creek adjacent to the tailings heap contained the highest levels of mercury in sediments found in the study area. This clearly indicates that such tailings heaps can be a continuing source of mercury- rich sediments to the river system. The elevated sediment mercury level at site 9 in Kyneton Gully, below Barry's Reef, is probably related to the activities of the abandoned Tyrconnel mine, near this site. Elevated levels of mercury in sediments at sites 3, 6 and 7 indicate that the sources of contamination are widespread, reflecting the dispersed nature of mining in the Blackwood-Barry's Reef area. This is reflected by the pattern of distribution of the known stamping battery sites (Fig. 2). The batteries were used in the operations to extract the gold from the ore and their distribution no doubt reflects the spatial pattern of mercury usage. In the Lerderderg River downstream from site 13 the sediment mercury levels drop substantially, an indication of no further significant sources, consistent with the distribution of the batteries (Fig. 2) and notwithstanding the limited mining of gold near site 14 (see Fig. 1). However, there is little change in the level between site 14 and the diversion weir (site 15). Since the construction of the weir in 1978, siltation has reportedly taken place (Mayer & Farmar-Bowers, 1979). Thus, mercury-laden sediments transported from the upper catchment could be accumulating at this site. 144 a.M. BYCROFT et al.

Further downstream in the Lerderderg, the sediment mercury concentration returns to background levels at site 17. There is a small rise at site 18, below the town of ; however, effluents from residential and industrial activities at Bacchus Marsh are controlled by EPA licences. The low levels of mercury found in Melton Reservoir (constructed in 1916) indicate that the sediments there are not dominated by long-term build-up of mercury-rich sediments flushed from the Lerderderg River catchment. These sediments would have been greatly diluted by the large volume of low mercury sediments coming in from the rest of the Werribee River catchment, particularly the badly eroding Parwan Creek catchment. The levels of mercury found in the brown trout show no consistent differences between the control sites (2 and 19) and contaminated sites. The comparison is made difficult by the possibility of variation in mercury concentration with fish size (Scott & Armstrong, 1972). Most values, however, appear to be near the 'normal' background level for trout of 0.2 #g g-~ (F6rstner & Wittmann, 1979). Many more data were collected on mercury levels in blackfish. These results show clear differences between control and contaminated sites as designated by sediment mercury levels. For instance, at the control sites mercury levels in the blackfish are < 0.09/~g g- 1, with most values < 0.05 #g g- 1. Conversely, at the contaminated sites, values up to 0.64 #gg-~ were recorded. Both brown trout and blackfish are benthic feeders, with similar ranges of food organisms (Jackson, 1978). However, with increasing size and age, brown trout tend to migrate downstream whereas river blackfish are more sedentary. Such sedentary species can be expected to be better biological indicators of mercury-contaminated sediments. The results of Nisimura et al. (1974) in F6rstner & Wittmann (1979) demonstrate that sedentary fish are better indicators of mercury levels in sediments than non-sedentary fish. In addition, in a study of marine fish, Dix et al. (1975) found that the sand flathead Platycephalus bassensis, a non-migratory benthic feeder, is a good indicator species for mercury pollution. There were sufficient data for blackfish at three sites to investigate a mercury concentration/size relationship. Such relationships have been found many times previously (e.g. Scott & Armstrong, 1972). A power relationship of the form [Hg] = a (size)b, is expected to be a realistic model of any relationship (Working Group on Mercury in Fish, 1980). With length as the size factor, regression analyses were car~'ied out, testing for such a model for black fish collected from sites 14, 16 and 19. There is a significant power-function relationship (r =0.819, n = 14, Fig. 3) between mercury concentration and fish length at site 14, a contaminated site. Here very large blackfish exceeding 25cm could be expected to exceed the Victorian Health Department statutory limit for mercury in sea food of 0.5/~gg-~. The lengths of river blackfish can be up to 35 cm (Lake, 1971); thus, fish at this site could exceed the limit. At site 19, a control site, there was also a significant correlation for the power MERCURY IN AN AUSTRALIAN RIVER 145

-5 site 14 ,.~ • ee ~ r = 819

•05 .÷/. + site, 19 = i • .563

.ol g 15 15 length of fish -cra Fig. 3. Mercury concentration-length relationship for blackflsh Gadopsis marmoratus. model between mercury concentration in blackfish muscle and total fish length (r = 0.563, n = 17, Fig. 3). Thus, only at biologically impossible lengths greater than 105 cm might blackfish from this site be expected to exceed 0.5/~g g- 1, and there is no likelihood of fish from this site accumulating excessive levels of mercury. For blackfish caught at site 16 there was no significant correlation between mercury concentration and length. This site lies between a contaminated area (site 15) and a clean area (site 17).

CONCLUSIONS

Although it is about 50 years since mercury was routinely used in the study area, the old tailings can provide a continuing source of elevated mercury levels in the river sediments. These elevated levels are not reflected in the mercury levels in brown trout. However, elevated mercury levels in river blackfish were associated with contaminated sediments. Blackfish thus show considerable potential as biomonitors of mercury-contaminated sediments in upland rivers of southeastern Australia. The Blackwood goldfield was only a minor field in Australia. Similar studies carried out near some of the larger gold fields in Victoria might be expected to reveal contamination of a much greater scope~ at least in sediments.

ACKNOWLEDGEMENTS

This work was carried out with the support of the Environmental Studies Section, Ministry for Conservation, Victoria, Australia. The contents of the paper do not 146 B.M. BYCROFT et al. necessarily represent the official view of the Ministry. The paper is publication number 348 in the Ministry for Conservation Environmental Studies Series. We wish to thank the staff of the State Rivers and Water Supply Commission for data on the Lerderderg River system; Dr J. Beumer, Mr D. Harrington, Fisheries and Wildlife Division, Ministry for Conservation, and Mr R. Waters for assistance in the collection of the field samples; and Mr L. Armstrong of Blackwood for historical information.

REFERENCES

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VAN METER, W. P. (1972). Mercury concentrations in the aquatic life forms and in the waters of the Upper Clark Fork River. U.S. Nat. Tech. Inform. Serv. P.B. Rep., No. 209638. WALTER, C. M., JUNE, F. C. ~¢; BROWN, H. G. (1973). Mercury in fish sediments, and water in Lake Oake, South Dakota. Y. Water Pollut. Control Fed., 45, 2203-10. WISE, E. M. (1966). Gold and gold compounds. In Kirk-Othmer encyclopedia of chemical technology, 2nd edn, 681-94. New York, John Wiley & Sons, lnterscience. WORglNG Group on MERCURY IN FISH (1980). Report on mercury in fish andfish products. Canberra, Australian Government Publishing Service.