Marine Pollution Bulletin 77 (2013) 428–433

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Marine Pollution Bulletin

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Baseline

Recent mercury contamination from artisanal gold mining on BuruIsland, Indonesia – Potential future risks to environmental healthand food safety

0025-326X/$ - see front matter Crown Copyright � 2013 Published by Elsevier Ltd. All rights reserved.http://dx.doi.org/10.1016/j.marpolbul.2013.09.011

⇑ Corresponding author. Tel.: +61 2 66203250; fax: +61 2 66212669.E-mail address: amanda.reichelt-brushett@scu.edu.au (A.J. Reichelt-Brushett).

Yusthinus Thobias Male a, Amanda Jean Reichelt-Brushett b,⇑, Matt Pocock c, Albert Nanlohy d

a Department of Chemistry, Faculty of Mathematics and Natural Sciences, Pattimura University, Ambon, Indonesiab Marine Ecology Research Centre, School of Environment, Science and Engineering, Southern Cross University, Lismore, NSW, Australiac Environmental Analysis Laboratory, Southern Cross University, Lismore, NSW, Australiad Department of Fisheries and Marine Science, Pattimura University, Ambon, Indonesia

a r t i c l e i n f o

Keywords:MercurySedimentSequential extractionBuru IslandGold mining

a b s t r a c t

In November 2011 gold was found at Mount Botak, Buru Island, Mollucas Province, Indonesia. Since 2012mercury has been used to extract the gold requiring large volumes of water and resulting in deposition ofmercury into Wamsait River and Kayeli Bay. Total mercury in waste ponds was over 680 mg/kg. In sed-iments at the mouth of the local river and a small feeder creek >3.00 mg/kg and >7.66 mg/kg respectively.River and bay sediments were proportionately higher in available mercury than elemental mercury andmore strongly bound mercuric sulfide compared to that in trommel waste. This preliminary investigationraises concerns about the long term distribution and speciation of mercury. The floodplain is an impor-tant agricultural resource, and Mollucas Province is recognised nationally as the centre for Indonesianfish stocks. Challenges for management include communicating the potential future risks to the commu-nity and leaders and identifying mechanisms to reduce mercury waste.

Crown Copyright � 2013 Published by Elsevier Ltd. All rights reserved.

Artisanal or small-scale gold mining is practiced in Africa, SouthAmerica, Philippines, and Indonesia (e.g. van Straaten, 2000; Leviaand Morales, 2013; Castilhos et al., 2006). Such mining operationsare often deemed illegal but potentially provide pathways frompoverty for rural communities. Gold was discovered in 2011 atMount Botak on Buru Island, an island of 12.7 km2 in the MollucasProvince, Indonesia. During 2012, artisanal gold mining in theWamsait village area of the Wae Apu district had become rampantand uncontrolled with large population influxes to the Island. Such‘gold rush’ fever has often been associated with the small-scaledevelopment of newly discovered ore bodies in other countries,bringing economic benefits along with environmental degradationand social challenges (Jønsson et al., 2009). Fortunately, the recentintroduction of a licencing system set up by the local landownersof the Mount Botak area has had positive influences on communityrelations and population pressure. However, environmental pres-sures and impacts associated with the ore processing are ofincreasing concern and not being addressed.

On Buru Island the initial method used to extract the gold wassimple panning operations but since late in 2011 mercury has beenused in the trommel (steel mill grinder) method to extract goldfrom the ore. This extraction process requires large volumes of

water for flushing and results in the deposition of fine sedimentsand mercury into the Wamsait River. This river feeds into KayeliBay, a large bay in the north east of Buru Island. With an estimatedseveral thousand trommel systems operating in the area the cur-rent extent of mercury contamination is of concern to environmen-tal health and food safety. Additional to this, a second minelocation (Gogrea) has been set up on Buru Island and is also withinthe catchment area of Kayeli Bay.

The Kayeli Bay catchment area supports a population of approx-imately 50,000 people and the low lands contain hundreds of hect-ares of rice fields which contribute to the national granary. Thecoastal villagers depend on fisheries resources for daily food andwithin the bay there are permanent house fishing platforms. Resi-dents of villages along the river system depend on the river waterfor domestic use which at some locations includes drinking water.Field studies were completed in July 2012 to investigate the trom-mel extraction methods and extent of mercury use as well as toprovide baseline information on the current extent of mercury con-tamination of soils and sediment from areas surrounding the goldextraction operations. This paper reports on the mercury analysesof field samples collected during July 2012 and is an important firststep in the process of addressing long term mercury pollution anddistribution in the area.

Site investigations were conducted and field samples collectedon the 26th and 27th July 2012. Government officials of Buru

Y.T. Male et al. / Marine Pollution Bulletin 77 (2013) 428–433 429

Island approved the research activity and access to the mine sitewas gained through the exisiting security network. The samplingfocus was in the Mount Botak area and associated trommel activi-ties near Wamsait River (Fig. 1). Ore and trommel waste sampleswere collected on site, sediment samples were collected by handin river areas at road crossing and by snorkel at the marine sites.All samples were stored in polyethylene zip lock bags and wherepossible the sediment samples were stored on ice prior to freezingat Pattimura University laboratories in Ambon. Approximately5.0 g of homogenised sample from each site was dried at roomtemperature and sent to Southern Cross University for analyses.For quarantine purposes and prior to use, all samples were steril-ised by Gamma irradiation at 50 kGy. Gamma rays are short wave-length electromagnetic radiation and this sterilisation method isknown as a ‘cold process’ due to the low level of temperaturechange. This sterilization method is a more suitable for maintain-ing mercury concentrations, speciation and sample integrity com-pared with the alternative of autoclaving or chemical treatment(Yu and Yan, 2003).

Two acid extraction techniques were used in microwave as-sisted digestion for comparative assessment. Sediment were driedfor 48 h at 40 �C, homogenised, and ground with acid cleaned anddistilled water rinsed mortar and pestles. From each homogenateduplicate 0.2 ± 0.01 g samples were weighed into separate Teflontubes. Digestions were completed using 69% Aristar HNO3 and asecond set of digestions were completed using an aqua regia 1:3concentrated HNO3:HCl. Samples were microwaved for 20 minusing a microwave accelerated rection system (MARSXpress�)with 1600 W IEC and frequency of 2450 MHz and allowed to coolfor 15 min before decanting. The elemental analysis was conductedusing a Perkin Elmer NexION 300D Inductively Coupled Plasma

Fig. 1. Location map of Buru Island, Gunung Botak (Mount Botak) mine site, and samplingnot part of this study, is also shown.

Mass Spectrometer (ICPMS). Optimisation was performed as out-lined in the NexION 300D user’s manual, in particular, the nebulis-er gas flow rate and torch alignment were adjusted to yield thegreatest sensitivity possible while maintaining low levels of oxides(<2%) and doubly-charged ions (<3%). Once optimisation was com-pleted, appropriate calibration standards were measured. A three-point calibration curve of 1, 5 and 20 lg/L Hg and 0.1, 1.0 and10.0 lg/L Au were prepared to generate a calibration coefficientof 0.9999 or greater. The sample solutions were then analysedagainst this calibration curve to determine the concentrations. Acalibration standard and independent soil digests were analysedat regular intervals during analytical runs to ensure the instrumentmaintained acceptable linearity and sensitivity criteria.

Duplicate blanks, Montana 2711a certified reference material,and the Australian National Measurement Institute reference sed-iment, AGAL-12, were digested and analysed with each batch ofsamples. The recovery rates for mercury are shown in Table 1.The mercury recovery rates from the certified reference materialsshowed reasonable recovery rates between the two extractiontechniques with aqua regia slightly over-estimating mercury con-centrations. The % recovery of mercury from both reference mate-rials were within 10% of the actual certified value after nitric aciddigestion.

The procedure for the sequential extraction of mercury de-scribed in Bloom et al. (2003) and Yu et al. (2012) was used in thisstudy. Table 2 explains the process used for all samples from thestudy area along with blanks and the two certified standards. Forthe purposes of method verification the sum of the sequentialextraction steps F1 to F5 were compared with the results fromthe extractions of total recoverable mercury. The sum of thesequential extraction showed good mercury recoveries from the

areas. The second and more recently developed (late 2012) Gogrea mine site, while

Table 1Results of analyses of two standard reference materials and the relative % recovery.

Sample Certified value (mg/kg) Total recoverable Hg nitric acid (mg/kg) Total recoverable Hg aqua regia (mg/kg) Sum of sequential extraction (mg/kg)

Montana2711a

7.420 8.110 ± 0.750 8.401 ± 0.475 6.700 ± 0.151

% Recovery 106 113 90AGAL-12 0.530 0.53 ± 0.057 0.617 ± 0.175 0.399 ± 0.070% Recovery 100 116 75

Table 2Extraction process used for the 5 step sequential extraction and the operational description (Bloom et al. (2003) and Yu et al. (2012)).

Sequentialstep

Extractant and method Operationaldiscription

Preparation Sample dried at 40 �C and ground with motar and pestle and 0.2 ± 0.01 g weighed –F1 Weighed sample mixed with 20 mL Milli-Q water, shaken at room temperature for 18 h, centrifuged at 3000 rpm for 20 min, extract

decanted into acid clean glass vials with Teflon caps, repeated 3 � and all washes combined with extract and preserved with 0.2 N BrClfor analyses

Water soluble

F2 Sample from F1 mixed with 20 mL 0.1 M CH3COOH and 0.01 M HCl, shaking, washing, and sample preservation as above Stomach acidsoluble

F3 Sample from F2 mixed with 20 mL 1 M KOH, shaking, washing, and sample preservation as above Organo-chelated

F4 Sample from F3 mixed with 20 mL 12 M HNO3 shaking, washing, and sample preservation as above Elemental HgF5 Sample from F4 microwave digested for 30 min in aqua regia 1:3 concentrated HCl:HNO3 Mercuric

sulfide

430 Y.T. Male et al. / Marine Pollution Bulletin 77 (2013) 428–433

Montana 2711a reference material and reasonable recovery fromthe AGAL-12 reference material (Table 1).

While the gold content of the Earth’s crust is predominantlyvery low (usually < 5 lg/kg and rarely > 10 lg/kg), concentratedores suitable for mining have higher gold concentrations and5 mg/kg is generally considered a low grade ore (e.g. Crocket,1991; Tilling et al., 1973). The ore collected from Mount Botakwas classified into high grade and low grade according to localminers. The gold concentration of the low grade ore was low at

Table 3Mean mercury concentrations (mg/kg) and standard deviations from sequential extractionsIndonesia. Mean gold concentrations (mg/kg) are also provided for the total extractable a

Sample type Sequential extraction steps

F1 F2 F3 F4

SedimentsOre and waste materialUnprocessed ore (low

grade)– – – –

Unprocessed ore (highgrade)

– – – –

Ponded trommel waste afterfirst gold extraction

14.25 (6.46) 80.72 (2.00) 0.695 (0.29) 19.63 (

Semi processed ore 9.278 (1.97) 27.2 (32.3) 6.783 (1.83) 22.41 (Waste pond storage 1

current site (mid 2012)0.247 (0.07) 0.741 (0.35) 0.693 (0.01) 1.830 (

Final processing waste pondstorage 2 past site (early2012)

10.45 (2.60) 72.66 (1.16) 3.64 (3.05) 31.55 (

Final processing waste pondstorage 3 early site(2011)

7.61 (1.49) 12.74 (5.09) 4.426 (0.36) 13.08 (

Sediment from feeder creekto main creek

0.890 (0.15) 0.148 (0.07) 0.198 (0.00) 0.741 (

Tributary to Wamsait River(near bridge)

0.099 (0.00) 0.05 (0.07) 0.199 (0.00) 0.149 (

Wamsait Estuary 0.099 (0.00) 0.099 (0.14) 0.148 (0.07) 0.148 (�20 m offshore Wamsait

River0.148 (0.07) 0.443 (0.35) 0.398 (0.40) 0.642 (

�10 m offshore from KayeliBeach Village

0.05 (0.07) N/D 0.099 (0.20) 0.099 (

�20 m offshore from KayeliBeach Village

0.05 (0.07) 0 (0.00) 0.198 (0.00) 0.099 (

2.23 mg/kg (Table 3). In contrast average gold concentrations ofthe high grade ore were 1383 mg/kg, indicating an exceptionallyrich deposit (Table 3). The extent of this gold deposit and the onenow mined at Gogrea (Fig. 1) are currently unknown.

Metcalf and Veiga (2012) suggest two thirds of the total 25 ton-nes of mercury used per annum in artisanal mining in Zimbabwe islost to tailings. Telmer and Stapper (2007) explained mercury usein a different context and noted that in a whole ore amalgamationprocess in Indonesia for every 20 g of mercury consumed (i.e. not

and total digests of duplicate ore, trommel waste, and sediment samples, Buru Island,qua regia digest for some samples. Refer to Table 2 for F1–F5 extraction proceedures.

Total extractableHg/HNO3

Total extractableaqua regia

F5 Total Hg Au

– – 7.38 (0.79) 7.78 (3.23) 2.23 (0.63)

– – 10.1 (0.66) 10.4 (0.82) 1383 (78)

0.94) 691 (12) 807 825 (57) 918 (24) 166 (23)

21.8) 303 (247) 369 630 (2.1) 632 (62) 131 (2.0)0.06) 7.224 (0.12) 10.7 10.3 (0.8) 11.89 (0.28) 47.9 (3.2)

6.11) 604 (7.3) 723 838 (115) 870 (22) 159 (12)

3.05) 614 (9.3) 652 789 (65.1) 682 (6.3) 187.0 (4.1)

0.06) 5.336 (0.30) 7.31 7.66 (0.42) 9.28 (0.58) 9.03 (6.25)

0.07) 0.199 (0.07) 0.696 0.63 (0.13) 1.827 (0.83) 0.095 (0.02)

0.07) 0.074 (0.11) 0.568 0.64 (0.37) 0.548 (0.08) 1.18 (0.07)0.07) 1.061 (0.17) 2.992 2.35 (0.28) 3.564 (0.43) 0.99 (0.45)

0.00) 0.418 (0.38) 0.666 0.4 (0.01) 0.783 (0.10) N/D

0.00) 0.05 (0.07) 0.397 0.35 (0.00) 1.17 5(0.10) 0.37 (0.17)

Y.T. Male et al. / Marine Pollution Bulletin 77 (2013) 428–433 431

recovered), to produce 1 g of gold, 19 g of mercury is lost to tailingsand 1 g to the atmosphere. Such differences between studies areprobably reflective of the ore type, gold content, and efficiency oftreatment processes in each study although both studies highlightthat mercury loss to tailings is of great concern. Given the high goldconcentrations in the ore from Mount Botak the ratio of gold pro-duction to mercury loss may vary depending on the ore quality,and how many extraction steps are repeated on a given ore.

Mercury concentrations in trommel waste (Table 3) in this studyhighlight that a significant proportion of mercury is lost to the tail-ings produced on Buru Island. The lowest concentration of totalrecoverable mercury found in sediments from trommel wasteponds was 682 mg/kg (Table 3). The pond in use at the time ofsampling was only recently set up and there was very little trom-mel waste in the pond, which would explain the lower mercuryconcentration of �10–11 mg/kg. Concentrations found in trommelwaste ponds on Buru Island were appreciably higher than thosepreviously found in urban tailing piles from small scale gold min-ing in Chile with up to 16.7 mg/kg in surface tailing and 22.4 mg/kgat depths of 2 m (Levia and Morales, 2013). For a more generalcomparison, mercury concentrations in muds of Minimata Bay,the site of a well known mercury pollution incident, peaked inthe 1960s with levels ranging from 19 to 908 mg/kg (Fujiki andTajima, 1992).

Interestingly, ore processing on Buru Island often involves sev-eral steps of extraction and mercury concentrations in ore after thefirst extraction were high at �630 mg/kg (S5) (Table 3). This ore isusually then reworked in the trommels and additional mercury isadded to extract remaining gold. The trommel waste ponds areset up down slope from the trommels so the waste is easily washedinto the ponds. These ponds are drained by trenches dug into thesoil which transport the waste laden water off site. Depending onthe location these trenches lead to lower lying swampy areasand/or to the river. The trenches act as transportation pathwaysof un-retrieved mercury into the river.

While mercury concentrations in marine sediments rarely ex-ceed 0.1 mg/kg concentrations can be as high as 2.0 mg/kg wherenatural geologic enrichment occurs (Lasorsa et al., 2012). The Indo-nesian standard (known as the SNI) and Australian high trigger va-lue (ANZECC/AMRCANZ, 2000) for mercury in aquatic sediments is1.0 mg/kg and if sediments exceed this concentration then furtherinvestigation to understand metal bioavailability and toxicity isrecommended in the decision tree approach used in the ANZECC/AMRCANZ (2000) guidelines. Total mercury in sediment samplesfrom Kayeli Bay near Kayeli Beach Village were generally lowerthan 1.0 mg/kg (Table 3 and Fig. 2). Sediments taken just offshoreof the Wamsait River mouth were some 5–6 times higher in

Fig. 2. Mercury concentrations (mg/kg) in river an

mercury than Kayeli Bay sediments, indicating that mercury entersthe bay from the Wamsait River catchment, but at the time of sam-pling, was not distributed evenly throughout the bay. Sedimentsfrom the two sites sampled within the Wamsait River estuary wereslightly elevated in mercury and a small feeder creek within the lo-cal community and where trommels were operating at the time ofsampling was approximately an order of magnitude higher in mer-cury (Table 3 and Fig. 2).

Mercury contamination from artisanal gold mining hascommonly been recognised (Spiegal and Veiga, 2010; Levia andMorales, 2013) and this study highlights again the magnitude ofenvironmental mercury contamination associated with this pro-cess. The concentrations found in sediments of the Wamsait Riverare comparable to those found in river sediments associated withartisanal mining in north Sulawesi, Indonesia where Limbonget al. (2003) recorded concentrations at one location of over20 mg/kg and commonly 5–10 mg/kg mercury. Mercury was usedin artisanal mining on north Sulawesi for about 2 years prior tosampling by Limbong et al. (2003) and in comparison mercuryuse on Buru Island had come into practice less than 12 monthsprior to sampling in the current investigation. The high concentra-tions of mercury in sediments and trommel waste from Buru Islandsuggest a rapid uptake of mercury use in ore processing since 2011.

The results of the sequential extraction highlight that sedimentsfrom river and bay sites have a higher proportion of available mer-cury (fractions F1–F3) than elemental mercury and more stronglybound mercuric sulfide compared to that of trommel waste(Fig. 3). However, it should be noted that due to the very high con-centrations of mercury in the trommel waste, the actual concentra-tion of available mercury is several orders of magnitude higherthan in sediments from the river and bay (Table 3). The high rela-tive proportion of available mercury in the river and bay sites sug-gests that the behaviour of mercury changes once it enters theriver environment and is exposed to a wide range of complexingagents. Interestingly the organically bound mercury (F3) contrib-utes up to 50% of mecury in Kayeli Bay samples and around 25–30% of Wamsait River samples suggesting both environments havethe capacity for mercury methylation. Further investigation is re-quired to determine the extent of methylation in Kayeli Bay andWamsait River sediments.

Bacterial action, prominent in the organic rich sediments suchas those found in the Wamsait River, convert inorganic mercuryspecies to methylmercury (Gochfeld, 2003). Methylmercurycompounds are easily bioaccumulated and more toxic than inor-ganic forms of mercury, highlighting potential for food chaincontamination (Gochfeld, 2003). Because of the dependence of vil-lagers on local food resources the mercury contamination poses a

d marine sediments during the current study.

Fig. 3. The relative contribution of each sequential extraction phase to the total mercury in ore and sediment samples. Extraction phases F1–F5 are explained in Table 2.

432 Y.T. Male et al. / Marine Pollution Bulletin 77 (2013) 428–433

risk to food safety and is a human health concern. Concerns relatedto mercury poisoning are not only related to uptake directly fromcontaminated food but also through occupational exposure, inter-generational transfer in breast milk (Bose-O’Reilly et al., 2008), andpassing through the placental barrier into the developing foetus(Clarkson, 1992).

Mercury pollution from artisanal gold mining has been recogni-sed as an issue for over 20 years and numerous programs devel-oped to reduce mercury use and pollution have, for variousreasons, had very limited success in countries including Africaand Chile (Hilson and Hilson, 2007). The challenge for reductionof mercury contamination on Buru Island is to develop approachesthat gain community support as well as financial support fromgovernment and industry. This is not an easy task given the activ-ities are currently recognised as illegal. Experience in other arti-sanal mining areas suggest that community engagement andownership of solutions is essential for successfully implementingmercury reduction initiatives (Jennings, 2000; Hilson and Hilson,2007). Understanding the community dynamics will provide aplatform to establish linkages that enables discussions betweenthe artisanal mining industry and expert advise to minimise mer-cury pollution. Solutions specific to the Buru Island circumstancesmay then be identifiable from a tool kit of potential strategies.

People of Buru Island have seen recent changes in communitydynamics, population, economic circumstances, and food supply.The landholders and other key participants are managing them-selves through a ‘gold rush’. To date a factor that has had minimalconsideration is the longer term impact of mercury pollution. Thisstudy provides the first measured mercury concentrations insediments and trommel waste from artisanal mining on Buru Islandand will assist in highlighting the issue to the local and regional

community. The sites of trommel activity are likely to be unsuitablefor future use after the mining is abandoned and the long termtransport of mercury throughout the ecosystem and risk to foodsafety is of concern. Urgent steps are required to develop commu-nity education of the harmful consequences of mercury and pro-vide support to community based management to reducemercury waste.

Acknowledgements

This research was supported by the federally funded IndonesianSAME Program and the Marine Ecology Research Centre, School ofEnvironment, Science and Engineering, and Environmental Analy-sis Laboratory at Southern Cross University. Special thanks to Bar-bara Harrison and Jenny Nolan for laboratory support and GregLuker for GIS support. Quarantine Permit No: IP12022133.

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