Marine Pollution Bulletin 56 (2008) 1553–1569

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Marine Pollution Bulletin

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Heavy metal contamination from gold mining recorded in Porites lobata skeletons,Buyat-Ratototok district, North Sulawesi, Indonesia

Evan N. Edinger a,b,c,*, Karem Azmy c, Wilfredo Diegor c, P. Raja Siregar d

a Department of Geography, Memorial University, St. John’s, NL, Canada A1B 3X9b Department of Biology, Memorial University, St. John’s, NL, Canada A1B 3X9c Department of Earth Sciences, Memorial University, St. John’s, NL, Canada A1B 3X9d Indonesian Forum for the Environment (WALHI), Jl. Tegal Parang Utara No. 14, Jakarta 12790, Indonesia

a r t i c l e i n f o

Keywords:

Submarine mine tailingsArsenicLaser ablation ICP-MSCoral skeletonPorites lobataIndonesia

0025-326X/$ - see front matter � 2008 Elsevier Ltd. Adoi:10.1016/j.marpolbul.2008.05.028

* Corresponding author. Address: Department of Gsity, St. John’s, Canada NL A1B 3X9. Tel.: +1 709 737

E-mail address: eedinger@mun.ca (E.N. Edinger).

a b s t r a c t

Shallow marine sediments and fringing coral reefs of the Buyat-Ratototok district of North Sulawesi,Indonesia, are affected by submarine disposal of tailings from industrial gold mining and by small-scalegold mining using mercury amalgamation. Between-site variation in heavy metal concentrations in shal-low marine sediments was partially reflected by trace element concentrations in reef coral skeletons fromadjacent reefs. Corals skeletons recorded silicon, manganese, iron, copper, chromium, cobalt, antimony,thallium, and lead in different concentrations according to proximity to sources, but arsenic concentra-tions in corals were not significantly different among sites. Temporal analysis found that peak concentra-tions of arsenic and chromium generally coincided with peak concentrations of silica and/or copper,suggesting that most trace elements in the coral skeleton were incorporated into detrital siliciclastic sed-iments, rather than impurities within skeletal aragonite.

� 2008 Elsevier Ltd. All rights reserved.

1. Introduction

Retroactive determination of heavy metal concentrations priorto anthropogenic activities is often crucial to understanding theenvironmental impacts of those activities, particularly in locationswhere these activities have had a long history. Such retroactivedetermination is particularly difficult in coastal marine environ-ments, where bioturbation can obscure the temporal record of met-als in sediments. Coral skeletons have been used extensively torecord the history of metal pollution from dredging, mining, terres-trial runoff, and other sources on coral reefs (Brown and Holley,1982; Howard and Brown, 1984, 1987; Anderegg et al., 1997; Scottand Davies, 1997; Esslemont, 1999, 2000; Fallon et al., 2002; David,2003; Runnalls and Coleman, 2003). The ability of corals to recordmetal pollution varies among metals, due to differences in solubil-ity and differences in the degree to which trace elements can beincorporated into aragonite crystal lattice (Howard and Brown,1984). Arsenic and mercury, two of the principal contaminantsfrom gold mining, present analytical challenges in this context.The atomic radius of arsenic is incompatible with the dimensionsof the aragonite crystal lattice, therefore arsenic incorporated intocoral skeletons is thought to be primarily detrital, having enteredthe coral skeleton as incorporated siliciclastic sediment, rather than

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eography, Memorial Univer-3233; fax: +1 709 737 3119.

as dissolved metal. Mercury presents analytical challenges due toits volatility, which requires distinct analytical techniques formercury in sediments from techniques used for most other metals.

Traditionally, studies of trace elements in coral skeletons haverelied upon mechanical sampling followed by chemical analysisusing atomic absorbtion spectroscopy (AAS, e.g. Khaled et al.,2003), inductively coupled plasma atomic emission spectroscopy(ICP-AES or ICP-OES, optical emission spectroscopy e.g. Bastidasand Garcia, 1997; David, 2003), or solution inductively-coupledplasma-mass spectrometry (ICP-MS, e.g. Scott and Davies, 1997).Of these methods, ICP-MS is the most sensitive, and has the greatadvantage of analyzing a wide suite of elements simultaneously(Scott and Davies, 1997).

Several recent research efforts relating to coral skeletal recordsof pollution have used laser ablation mass-spectrometry (LAM-ICPMS) to reconstruct the history of trace element pollution fromcoral skeletons (Fallon et al., 2002; Runnalls and Coleman, 2003).Laser ablation has several advantages over traditional analyticalmethods, including ability to extract precisely located samplesfrom within the coral skeleton, ability to measure concentrationsof a wide range of elements simultaneously, and direct introduc-tion of sample to the analytical instrument, thus skipping exten-sive cleaning, dissolution and possibilities of contamination oroperator error associated with wet chemistry (Veinott, 2001).

Laser ablation may also introduce some challenges, however.Laser ablation ICP-MS may induce fractionation of some isotopesas the ablation pit becomes deep (Eggins et al., 1998; Gunther

1554 E.N. Edinger et al. / Marine Pollution Bulletin 56 (2008) 1553–1569

and Hattendorf, 2001), and laser ablation necessarily mixes lattice-bound trace elements incorporated from solution with those in-cluded within the skeleton as detrital sediment (e.g. Runnalls andColeman, 2003). Finally, for metals that are heterogeneously dis-tributed within the skeleton, the high spatial precision of off-the-shelf laser ablation IPC-MS systems may contribute to high inter-sample variation that obscures broader patterns.

The objectives of this paper are (1) to compare spatial patternsof trace element concentration in marine sediments with those incoral skeletons, and (2) to examine temporal patterns in trace ele-ment concentrations in coral skeletons as a historical record ofcontamination from gold mining activities. We present trace ele-ment concentrations and chronologies from Porites lobata coralscollected on reefs adjacent to two distinct types of gold miningactivities: submarine tailings disposal of industrial gold mine tail-ings, and small-scale gold mining using mercury amalgamation incoastal watersheds. Our results show that coral skeletons can re-cord trace element contamination from distinct types of gold min-ing activities, including trace elements that are normally notincorporated into aragonite coral skeletons. In addition, we addresstwo methodological points, (1) comparing whole-sediment and<63 lm sediment trace element concentrations, and (2) assessingthe utility of laser-ablation ICP-MS for studying a broad suite oftrace element contaminants in coral skeletons.

1.1. Regional geology and mining history

North Sulawesi contains significant gold mineralization in sev-eral mining districts. The Buyat-Ratototok mining district (Fig. 1)has experienced mining activity back to the 1920s, with extensiverenewed activity beginning in the early to mid-1980s (Turner et al.,1994), and peaking in the late 1980s. Coral reefs fringe much of thecoastline, except within protected shallow bays dominated bymangroves, or along sandy beaches.. Geology of the area is re-viewed in Turner et al. (1994) and Edinger et al. (2007).

Fig. 1. Location and depth of sample sites. Black line through inset map indicates locationdots indicate depth of sediment samples, coral samples indicated in italics.

1.1.1. Industrial mine geology and ore processingThe Newmont Minahasa Raya (PTNMR) gold mine exploited a

refractory sediment hosted deposit with As–Sb–Hg–Tl anomalies(Turner et al., 1994). Gold within the silicified limestone-hosteddeposit is found mostly within fine-grained (<10 lm) arsenian pyr-ite, typically in the form of pyrite crystals with arsenic-rich rims,co-occurring with antimony sulfides and oxides, and mercury sul-fide. The principal ore body exploited by the industrial mine is>80% refractory gold; gold from this deposit was recovered byroasting and cyanidation (Turner et al., 1994). By contrast, goldin the adjacent Kotabunan and Totok watersheds is present as na-tive gold, and is mined by artisanal miners using mercury amal-gamation (Turner et al., 1994; Aspinall, 2001).

Whole ore was roasted at 550–580 �C in the presence of lime-stone and dolomite from the deposit, with the intent of capturingsome arsenic from the host-rock as magnesium arsenate (Weekset al., 1997). Further milling and processing included cyanidationat pH 9–9.2, followed by treatment with ferrous sulfate to producetwo other arsenic-bearing iron phases, ferric arsenate and arsenicalferrihydrite, and to produce mercuric sulfide (Weeks and Wan,2000). These arsenic and mercury-bearing compounds in the trea-ted tailings were thought to be highly insoluble, but may in factundergo dissolution at or slightly below the sediment–water inter-face (PTNMR, 2002b; Blackwood and Edinger, 2007).

Tailings were pumped approximately 5 km from the mine andprocessing site to Buyat Bay, mixed with seawater, and depositedvia pipe 900 m from shore at 82 m depth. While the mill operated,tailings were deposited at approximately 2000 T/day. The miningcompany commenced a monitoring program upon the opening ofthe mine in 1996, and modelled the tailings mound as coveringan area of approximately 0.32 km2, (PTNMR, 2002a). Mining com-pany monitoring data consistently showed high concentrations ofarsenic, antimony, and mercury in mine tailings, but low dissolvedconcentrations of these metals in seawater above the tailingsmound. Tailings disposal was interpreted to pose little environ-

of tailings pipe. Artisanal mining occurs in Totok and Kotabunan watersheds. Size of

E.N. Edinger et al. / Marine Pollution Bulletin 56 (2008) 1553–1569 1555

mental danger on the basis of the low dissolved metal concentra-tions (PTNMR, 2002b), but elevated arsenic and antimony concen-trations in shallow marine sediments suggest tailings dispersal atleast 1 km northeast, and at least 3 km southeast, of the tailingsoutfall, in waters as shallow as 20 m (Edinger et al., 2007). Arsenicin tailings includes both geochemically stable and reactive forms,but antimony in tailings is mostly stable (Blackwood and Edinger,2007).

1.1.2. Small-scale miningSmall-scale mining in Indonesia releases large fluxes of mercury

to air and water, contributing mercury to fish consumed by hu-mans (Kambey et al., 2001; Limbong et al., 2003). In the regionof this study, artisanal gold miners operated extensively in the To-tok and Kotabunan watersheds (Fig. 1) until approximately 1989,although artisanal gold mining continues to a much lesser extentin both areas. No small-scale mining has occurred in the Buyat Riv-er watershed. Concentration of arsenic, cobalt, copper, and othermetals in sediments affected by artisanal mining was slightly high-er than in regional pre-mining background analyses, possibly dueto enhanced erosion associated with mining activities (Edingeret al., 2007).

2. Materials and methods

2.1. Sampling areas

Field sampling took place on fringing reefs of Buyat and TotokBays (Fig. 1). Buyat Bay (approximately 0�50.40N/124�42.30E) is asmall bay exposed to wave action from the Molucca Sea. The BuyatRiver debouches at the NW corner of the bay, and a coarse sandtombolo separates Buyat Bay from Totok Bay. The east side of Buy-at Bay hosts fringing coral reefs; the reefs closest to the beach arenow completely dead, while those monitored by the mining com-pany, in the outer portion of the bay and along the outer margin ofthe Ratototok Peninsula are in better condition (PTNMR, 2002b).Maximum depth in the bay is approximately 90 m. The shelf re-mains relatively flat until reaching the shelf break at about120 m depth, roughly 8 km from shore, from which point the bot-tom descends to bathyal depths (PTNMR, 1994). The shape of theBuyat River mouth, visible plumes of sediment from the Buyat Riv-er, and PTNMR current meter data suggest that surface currentsgenerally flow counter-clockwise around the bay. Bottom currentsappear to follow a similar pattern (PTNMR, 1994, 2002a, b).

Totok Bay (approximately 0�520N/124�42.70E) is a larger bayprotected from wave action by the Ratototok Peninsula. Coastlinesare mangroves along the protected side of the tombolo separatingTotok Bay from Buyat Bay and along the northern margins of thebay, fringing coral reefs along the inner side of the Ratototok Pen-insula and the islands in the bay, and cleared mangrove in front ofRatototok village, and adjacent to the mouth of the Totok River.Maximum depth is about 100 m. The shape of sand spits suggeststhat currents in Totok Bay generally flow in a counter-clockwisedirection around the bay.

The climate is monsoonal, with a rainy season November toApril, and dry season May to October. Sea surface temperatures

Table 1Sediment solution ICPMS error analysis

Measure %CaCO3 %FeO Ti V Cr

% Deviation from MESS-2 standard 33.6 �2.63 1.34 �12.68 �3.2% Deviation from PACS-1 standard 16.25 �2.90 �12.68 �9.28 �7.5Average% deviation among

duplicates (n = 4 pairs)5.41 8.41 3.28 3.61 8.0

range from 27 to 30 C (PTNMR, 1994). Tides in the region are mixedsemi-diurnal and microtidal, with a spring tide range of approxi-mately 1.2 m.

2.2. Sediment sample collection and analysis

Reef sediments and coral skeletons were collected in June 2002(17 sediment samples, BY01-18), with further sediment samplingin August 2004 (25 sediment samples, BY21-52). Sediment analysischaracterized end-members of sediment in the system, includingthree primary sources: artisanal gold mining (the Totok Riverand Kotabunan River) industrial gold mine tailings disposed inBuyat Bay, and the Buyat river, which drains the mine site andhas similar bedrock geology to the Totok River watershed (Edingeret al., 2007). Background sediment composition was determinedfrom two sources: the sites furthest to sea in Totok Bay (BY15,BY45 and BY51), and the description of marine sediments collectedin 1993 for the industrial gold mine’s Environmental ImpactAssessment (PTNMR, 1994).

Sediment samples were collected using a hand-operated Petit-Ponar grab sampler deployed from a motorized outrigger canoeor fishing boat. Position of sampling station positions were re-corded using a hand-held GPS. Depth was determined by thelength of grab sampler rope; depth measurements associated withgrab samples are therefore maximum depth estimates. Visualdescriptions of sediment colour, grain size, and bulk composition(carbonate vs. siliciclastic) were recorded in the field, with subse-quent measurement of grain size distribution and carbonate con-tent in the lab. All samples were frozen immediately upon returnto shore and kept frozen until analysis.

2.3. Sediment trace element analysis

Three gram sediment subsamples were dry-sieved through a0.063 mm polyurethane mesh to account for grain-size relatedbiases in sediment chemistry. Sediment subsamples were homog-enized by stirring, dried, ground to <10 um, and homogenizedagain for analysis.

2.4. Sediment heavy metal concentrations

Concentrations of major and minor elements in the <63 lmfraction of all samples was determined following total dissolutionin HF–HNO3, measured by inductively-coupled plasma mass spec-trometry (ICP-MS). National Research Council of Canada (NRCC)reference materials PACS-1 and MESS-2 were analyzed as un-knowns, together with the samples, to monitor data quality (Ta-ble 1). Approximately 0.2 g dry subsamples were dissolved in2–3 ml of concentrated hydrofluoric acid and 8 N nitric acid in1:1 proportions. Solutions were heated on hot-plates for up toone week, then evaporated to incipient dryness, and diluted to60 ml with nano-pure distilled water. CaCO3 content of sievedsediments was estimated directly from ICP-MS results, accordingto the relationship:

%CaCO3 ¼ ppmCa� 10�4 � ð1=0:40Þ ð1Þ

Mn Co Ni Cu Zn As Sb Pb

3 38.04 5.75 43.69 �5.82 �7.01 �1.61 �3.94 �2.704 33.54 �6.51 29.66 �4.31 0.83 �13.74 8.29 �9.011 8.89 4.35 8.90 3.83 15.84 2.49 4.12 7.42

Fig. 2. X-ray negative of coral skeleton BY04L, showing density bands. Approximatetrack of carbonate sampling and laser ablation analysis indicated by dashed blackline. White scale bar 1 cm.

Fig. 3. Scanning electron microprobe images of reef sediments. A. Bioclasticcarbonates, tailings-contaminated site BY05. Dark matrix within carbonate clastsis highly similar to tailings-derived sediment observed at tailings outfall and reefBY04. B: Mixed siliciclastics and detrital carbonates, reef near Buyat river mouth,BY07. C. Mixed siliciclastics and detrital carbonates, reef near Totok River mouth,BY14. Bright spots in all images indicate presence of trace elements, esp., arsenic,antimony, barium, copper, chromium, and iron.

1556 E.N. Edinger et al. / Marine Pollution Bulletin 56 (2008) 1553–1569

where 0.40 is the weight percent Ca in CaCO3. Although this methodcould overestimate the carbonate content of sediments by includingCa from volcanic rocks, the weight percent of Ca in calcium carbon-ate is more than three times that of the weight percent Ca of calcicplagioclase, such that nearly all Ca was probably present as CaCO3.Pre-mining sediment chemistry is reported as the average of 31marine sediment samples from Buyat Bay and environs, as reportedin the mining company’s original environmental impact assessment(PTNMR, 1994).

Table 2Sediment (<63 lm fraction) trace element concentrations on reefs sampled

Sample characteristics Percent ppm

Sample area Site Sample#

%CaCO3 %FeO Ti V Cr Mn Co Ni Cu Zn As Sb Pb

Buyat Bay affected, protectedfrom wave action

Reef closest totailings outfall

BY04 9.78 4.58 2744.6 124.5 47.0 1268.1 14.5 17.5 58.4 108.9 253.3 164.6 12.0BY43 11.32 4.25 1959.0 91.8 43.5 1233.6 9.2 14.4 37.3 80.4 275.4 273.5 6.7

Tj. Buyat BY05 18.72 4.15 2394.1 108.5 41.6 1081.2 12.0 15.2 44.2 151.3 147.0 115.4 6.0Buyat Bay, affected wave

exposed reefsTj. Sikod (West ofbay)

BY08 21.39 3.76 1770.1 88.1 40.7 1183.9 9.4 39.72 36.41 932.2 194.5 164.5 8.3BY29 22.81 3.48 1427.5 68.7 27.7 866.2 6.4 8.9 18.6 86.5 120.6 142.0 6.3

Tj. Buyat (East ofbay)

BY10 25.82 4.26 1822.3 85.7 26.6 768.6 8.9 11.4 21.7 73.3 79.8 90.7 6.7

Buyat Bay, river influenced Bobokan Point BY07 7.52 5.06 4093.5 182.4 51.9 1330.1 20.8 21.0 62.9 167.8 61.0 18.5 5.9Totok Bay, river influenced Reef near Totok

River mouthBY14 3.68 5.37 3070.2 134.1 29.7 732.9 14.1 16.2 44.7 112.0 49.3 5.7 8.9BY48 4.38 5.74 3323.4 143.9 34.3 820.5 12.7 10.9 38.0 87.8 47.8 4.0 8.9

Totok Bay reference Reef at Pulau Babi BY15 44.48 2.42 535.6 25.8 8.3 205.4 2.6 4.3 10.0 34.0 5.0 1.9 2.5Backgroundsediment

BY45 25.15 4.59 2034.4 89.5 21.5 597.7 9.1 9.1 26.4 59.1 17.8 19.2 6.7

E.N. Edinger et al. / Marine Pollution Bulletin 56 (2008) 1553–1569 1557

2.5. Coral skeleton sample collection and analysis

Domal P. lobata corals were collected whole from approxi-mately 1 m below low tide on seven fringing reefs surroundingBuyat Bay and Totok Bay. Sites BY04, BY05, BY07, BY08, andBY10 were all from fringing reefs surrounding Buyat Bay. SiteBY14 is a small fringing reef near the mouth of the Totok River. SiteBY15 is a fringing reef on the southwest corner of Pulau Babi, in To-tok Bay, approximately 3 km from the Totok River, and serves as areference site for the Totok River. Coral skeletons were cut in halfvertically and air dried in the field prior to shipment to Canada,where all further analysis took place.

Coral skeletons were cut into 8–10 mm thick slabs parallel togrowth lines using a diamond blade rock saw cooled with tapwater. Coral skeleton slabs were rinsed with distilled water aftercutting, and etched in 0.2 N HNO3 prior to analysis. Each coral skel-eton slab was X-rayed to reveal density bands (Fig. 2). For each cor-al, the slab showing the clearest banding, and for which the cutwas most clearly parallel to corallites, was selected for furtheranalysis. Analyses did not follow the axial growth direction ofthe coral, hence distance between growth bands does not directlyreflect coral skeletal extension rates (Edinger et al., 2000).

2.6. Coral skeleton stable isotope sampling and analysis

To verify that density bands in coral skeletons were annualgrowth bands, and to assure time control within coral skeletons,d13C and d18O of coral skeleton aragonite were analyzed in coralBY04, and Sr/Ca ratios of coral skeletal aragonite were analyzedin all samples (see below). Small subsamples of skeleton, approx-imately 320 lg, were drilled from the skeletons along lines per-pendicular to growth banding at 2 mm increments. Samples

Fig. 4. Trace element concentrations

were reacted in inert atmosphere with ultrapure concentratedorthophosphoric acid at 72 C in a Thermo-Finnigan GasbenchII; the produced CO2 was automatically delivered to a Thermo-Finnigan Delta-plus XP isotope ratio mass spectrometer in astream of helium and measured for isotope ratios. Laboratorystandards NBS-18 and NBS-19 were repeatedly measured duringeach analysis run and yielded a routine precision better than 0.1per mille.

2.7. Coral skeleton trace element concentrations

Coral skeleton trace element concentrations were analyzedusing laser ablation-ICPMS. Coral skeleton slabs were cut to46 � 23 � 6 mm (standard thin-section size) blocks for insertioninto the laser ablation sample cell. Distance down the coral skele-ton was recorded to the nearest 10 lm using the position of thesampling carriage. A NuWave UP 213 nm NdYAG laser systemwas interfaced to an HP 4500 quadrupole ICPMS with argon asthe plasma gas, and helium as the carrier gas. The laser was setto 80 um spot size at 10 Hz, yielding an average beam intensityof 0.5 mJ, equivalent to 11 J/cm2. In all analyses, 44Ca was used asthe internal standard. Analyses were conducted on three days:November 14, 2005, November 17, 2005, and August 31, 2006.

Each run of 20 analyses included four analyses of NBS 610 glassstandard, three analyses of MACS-1 coral aragonite referencematerial, and at least one duplicate analysis of coral skeleton fromthe same vertical position within the coral skeleton. In coral BY04,laser ablation spots were matched to the position of the drill holesfor carbonate d13C and d18O analyses. Because of the open skeletalnature of P. lobata, analyses did not strictly follow corallite walls.Duplicate analyses were run to check for consistency, and in caseswhere the initial run displayed significant yield attenuation.

in sediments (<63 lm fraction).

1558 E.N. Edinger et al. / Marine Pollution Bulletin 56 (2008) 1553–1569

Trace element concentrations in coral skeletons were calibratedto the NBS 610 fused glass standard, rather than the MACS-1 car-bonate reference material, because there are, as yet, no publishedcertified values for MACS-1. Instead, the MACS standard was usedfor quality control. The relative standard deviation (RSD) and stan-dard error (sd/n1/2) of each element measured was calculated forthe MACS standard, as a measure of the consistency with whichthe laser-ablated carbonates released each element to the massspectrometer. The results from the LA-ICPMS analyses of the MACSstandard were compared to data obtained by solution ICPMS donein the same lab, using the procedure described for sediment traceelement analysis.

2.8. Data analysis

Prior to statistical analysis, repeat coral skeleton trace elementconcentration data were screened to assess variability and to con-solidate repeat analyses. Repeat analyses for which the initial abla-tion signal displayed significant attenuation were removed.Second, the average of repeat analyses was calculated for pairs thatboth had consistent yield. Because concentrations of trace ele-ments in coral skeletons appeared non-normal, concentrationswere compared among sites using exploratory data analysis(EDA) and the Kruskall–Wallis test. Correlation coefficients amongthe elements analyzed in all coral skeleton ablations were calcu-

Table 4Comparison between whole sediment trace element concentrations and <63 lm sedimen

Element All samples (n = 40)

r2 Coefficient (%

(A) Regression coefficients and r2 values for comparisons between whole sediment and mudCa 0.91 78Fe 0.88 114Cr 0.89 96Co 0.91 104Cu 0.86 117Zn 0.14 36As 0.94 96Sb 0.94 93Pb 0.96 113

(B) Factor by which mud fraction sample was elevated above whole sediment sample for reBay Site Fe Mn Cr Co

Buyat Bay BY04 1.13 1.84 1.32 1.41BY05 1.26 1.76 1.90 1.38BY07 1.07 2.05 1.40 1.36BY08 3.19 5.48 2.81 3.96BY10 1.47 1.52 1.43 1.24

Totok Bay BY14 1.04 1.03 0.82 0.87BY15 2.28 1.11 0.8 0.97

Table 3Correlation matrix among elements in sediment

Element Ca Ti V Cr Mn Fe

Ca –Ti �0.67** –V �0.68** 0.99** –Cr �0.47** 0.49** 0.53** –Mn �0.37** 0.36* 0.38* 0.91** –Fe �0.66** 0.97** 0.97* 0.41** 0.21 –Co �0.67** 0.98** 0.97** 0.47** 0.35* 0.93**

Ni �0.47** 0.50** 0.53** 0.78** 0.74** 0.40*

Cu �0.78** 0.77** 0.79** 0.72** 0.65** 0.68**

Zn �0.21 0.43** 0.46** 0.40* 0.43** 0.35*

As 0.19 �0.48** �0.48** 0.37* 0.54** �0.60**

Sb 0.47** �0.56** �0.57** 0.24 0.40* �0.66**

Pb �0.12 0.26 0.26 0.10 0.19 0.21

All values ln-transformed prior to calculating correlation coefficients. Arsenic and antimomost other trace elements.**p < 0.01, *p < 0.05. N = 40 in all cases.

lated using bivariate linear correlation of log-transformed concen-trations. Correspondence between metal concentrations in the<63 lm fraction of sediment samples and metal concentrationsin coral skeleton bulk analyses was assessed using linear regres-sion between the sediment metal concentrations and the mediancoral skeleton metal concentrations at each location, as deter-mined from the EDA.

Coral Sr/Ca ratios, in mmol/mol were used as a proxy record ofsea surface temperature, and to verify the annual nature of skeletaldensity banding. Because no single isotope of strontium was moreor less variable than the others, Sr/Ca ratios were calculated as theaverage of 84Sr, 86Sr, and 87Sr divided by the average of 42Ca and43Ca,

Sr=Ca mmol=mol ¼ ½averageð84Sr;86Sr;87SrÞ� 1000�=½averageð42Ca and 43CaÞ�: ð2Þ

3. Results

3.1. Sediment constituent analysis

3.1.1. Sediment carbonate content and mineralogyCarbonate content was approximately 10–15% in fluvial and riv-

er-mouth sandy sediments, 14–26% in other marine sediments,

t trace element concentrations

Reef-associated samples (n = 14)

) r2 Coefficient (%)

fraction, all samples0.87 710.87 1060.82 1020.83 1020.64 1060.001 180.76 1150.81 1120.85 96

efs from which corals were sampledNi Cu Zn As Sb Pb

1.51 1.99 0.86 1.94 1.01 1.551.61 3.40 2.92 2.46 2.43 1.171.08 2.14 2.10 1.98 1.14 1.029.22 6.69 31.90 6.39 4.0 2.661.01 2.11 1.58 1.81 2.79 1.66

1.27 0.93 1.22 0.75 1.06 0.770.71 1.30 0.79 1.02 2.04 1.30

Co Ni Cu Zn As Sb Pb

–0.55** –0.81** 0.73** –0.44** 0.66** 0.51** –�0.50** 0.21 �0.06 0.03 –�0.59** 0.08 �0.27 �0.03 0.93** –

0.19 0.07 0.25 0.52** 0.10 0.11 –

ny were highly correlated with each other, and weakly or inversely correlated with

Tabl

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Lase

rab

lati

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Mea

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%M

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337

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0.08

560.

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357

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812

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5712

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711

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96.6

0.37

50.

264

119.

911

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0.00

701

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031

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669

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753

0.17

05.

950.

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14.

5911

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5.09

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90.

277

0.29

47.

3342

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36.8

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5152

2828

5252

5252

5252

4847

5252

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SD(%

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200.

7136

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26.2

921

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132.

994.

633.

893.

768.

794.

2711

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73.8

211

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37.9

826

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27.8

35.

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6339

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620.

540.

641.

660.

591.

6510

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16.2

80.

855.

2737

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Solu

tion

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60.

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460.

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90.

919

1.02

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82.9

599

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99.9

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E.N. Edinger et al. / Marine Pollution Bulletin 56 (2008) 1553–1569 1559

including the tailings, and 15–70% in reef sediments (Table 2). Car-bonates in reef sediments were easily recognizable as poorly-sorted, angular, very coarse-grained bioclasts from corals, calcare-ous algae and molluscs, while carbonates in fluvial and non-reefalsediments were mostly subangular crystalline detrital carbonates(Fig. 3).

Most sediment samples were >70% siliciclastic, except BY05,BY07, BY08, BY10, BY15, BY29, and BY51 (Fig. 3; see Appendix 1).Of the siliciclastic samples, most were dominantly siliciclasticmud, except for shallow nearshore samples BY07, BY09, BY11,BY39, BY41, and BY52, collected near the mouths of the Buyat, To-tok, and Kotabunan rivers, and samples BY16, 17, and 18, collectedin the Buyat and Totok rivers (Table 2, Appendix 1). The samplescollected near the end of the tailings pipe were fine silts.

3.2. Sediment trace element concentrations

3.2.1. Sediment sample analytical accuracy and precisionDuplicate analyses of identical samples for sediment metal con-

centrations (n = 4 pairs) yielded results differing by <3–15% of sig-nal, depending on the element in question, with variation amongpairs mostly below 10% (Table 1). Analysis of PACS-1 and MESS-2standards generally yielded values within 10% of the published val-ued for one of both standards for all elements except Mn, Zn, andAg (Table 1).

3.2.2. Spatial patterns in mud fraction sedimentsTrace element concentrations in the <63 lm fraction of the sed-

iment indicated high concentrations of arsenic and antimony inshallow reef sediments adjacent to the submarine tailings outfall(BY04/BY43, BY05, BY10) and at Tj. Sikod (BY08/BY29), consider-ably elevated above Totok Bay background concentrations (BY45)or Buyat Bay pre-mining sediment concentrations of those ele-ments (Fig. 4, Table 2). Arsenic and antimony were slightly ele-vated above background or pre-mining concentrations in fluvialand nearshore marine sediments of the Buyat River and rivermouth (BY16-BY17, BY09-BY09A) and the Totok River and rivermouth (BY18, BY11-14, BY48). Manganese, chromium, and copperconcentrations were slightly higher in reef sediments of Buyat Baythan in Totok Bay river-influenced reef sediments, but iron, nickel,cobalt, zinc, and lead concentrations were approximately equal inthe two bays. Titanium and vanadium concentrations were higherin Totok Bay river-influenced reef sediments and Bobokan reef sed-iments than in Buyat Bay affected reef sediments (Table 2). Arsenicand antimony were strongly correlated to each other (r = 0.930),and are referred to as tailings metals, while iron, titanium, vana-dium, cobalt, and copper were all strongly correlated with one an-other (r > 0.8), and are referred to as fluvial metals. Manganese andchromium were highly correlated with each other, and wereweakly correlated with both the tailings metals and the fluvialmetals (Table 3).

3.2.3. Comparison of whole sediment and mud fractionTrace element concentrations in the mud fraction were strongly

correlated with whole sediment concentrations for all elementsexcept Zinc (Table 4A). This pattern held true for all samples ana-lyzed, and for the subset of samples from reef environments, andcontaining a high biogenic calcium carbonate content. In reef sed-iments, Ca was 30% lower in the mud fraction than in whole sedi-ments, while all trace elements except Pb were 2–15% higher in themud fraction than in whole sediments. At the tailings-influencedsites dominated by bioclastic reef sediment, particularly BY05,BY07, BY08, and BY10, concentrations of As and Sb in the <63 lmfraction were 1.8–6.4, and 1–4, times higher than whole sedimentconcentrations of these elements, respectively (Table 4B). Concen-trations of arsenic were identical in the whole sediment and mud

1560 E.N. Edinger et al. / Marine Pollution Bulletin 56 (2008) 1553–1569

fractions of sediments from the two Totok Bay reefs, while anti-mony concentrations in Totok Bay reef sediments were 1–2 timeselevated in the mud fraction over whole sediment values.

3.3. Coral skeletal metal analyses

3.3.1. Laser ablation and solution ICP-MS analysis of MACS-1 referencematerial

Among the oxides and elements considered here, MgO, Al2O3,Ti, V, As, Sb, and Tl had RSD values greater than 50%, while SiO2,FeO, Cr, Mn, Co, Ni, Cu, Zn, Ba, and Pb had RSD values less than

0.05

0.04

0.03

0.02

0.01

0.00

BY05-11

BY05-20BY04L-31

BY10-17

BY15-22

BY08-40r

BY14-1

BY14-5

BY07-16BY05-19r BY14-21

0.35

0.30

0.25

0.20

0.15

0.10

0.05

0.00

BY10-01

BY05-13

BY10-03

BY15-13

BY08-8r

BY04 BY 07 BY 08 BY 10 BY 14 BY 15BY 05

BY04 BY 07 BY 08 BY 10 BY 14 BY 15BY 05

AlO

wt%

23

MgO

wt %

A B

DC

Fig. 5. Boxplots showing major oxide concentrations in coral skeleton analyses. (A) Alucoral skeletons.

Table 6Kruskall–Wallis tests comparing trace element concentrations in coral skeletons

Element or oxide Sediment group Ran

Al2O3 Oxides, fluvial BY0SiO2 Oxides, fluvial BY1FeO Oxides, Fluvial BY0Cr Fluvial or tailings BY0Co Fluvial BY0Cu Fluvial BY0Pb Fluvial–artisanal BY0As Tailings BY0Sb Tailings BY0Tl Tailings BY0

Sites: Reef closest to tailings: BY04, Tj. Buyat reef: BY05, Tj. Sikod: BY08, Ratototok PeReference: BY15. Significance indicated by Kruskall–Wallis test.

40% (Table 5). RSD for Sr ranged from 12% to 20%, with the highestvalue observed in 84Sr, and the lowest in 86Sr.

Laser ablation analyses of MACS-1 for SiO2, Ti, V, Mn, As, and Tldiffered from solution analyses by 100% or more, while analyses forFeO, Cr, Co, Ni, Cu, Zn, Sb, Ba, and Pb differed from the solutionanalysis by less than 50%.

3.3.2. Variation in coral skeleton trace element concentrations amongreefs

Median aluminum oxide concentrations were lowest in coralsfrom exposed, siliciclastic poor sites BY08 and BY10 (Fig. 5A,

0.50

0.40

0.30

0.20

0.10

0.00

BY10-17BY08-13

BY14-1

BY14-3BY07-7

By05-1

BY04L-4

BY10-10BY08-12

BY08-15

BY07-5

0.12

0.10

0.08

0.06

0.04

0.02

0.00

BY04L-42

BY04L-38

BY14-1

BY07-5

By05-1

BY04L-33BY10-01

BY15-19r

BY08-7

BY07-3

BY04 BY 07 BY 08 BY 10 BY 14 BY 15BY 05

BY04 BY 07 BY 08 BY 10 BY 14 BY 15BY 05

SiO

wt%

2Fe

O w

t %

minum oxide, (B) silica, (C) magnesium oxide and (D) iron oxide concentrations in

k order among corals Significance

5 > BY04 = BY05 = BY14 = BY15 > BY08 > BY10 P < 0.0014 > BY05 = BY04 > BY08 = BY10 > BY15 > BY07 P < 0.0015 > BY15 > BY08 = BY10 > BY14 > BY04 > BY07 P < 0.0014 > BY07 = BY14 > BY05 = BY08 = BY10 > BY15 P < 0.0014 = BY08 > BY15 > BY05 > By07 = BY10 > BY14 P < 0.0014 > BY15 > BY07 = BY10 > BY05 = BY08 = BY14 P < 0.0015 > BY04 = BY08 > BY07 = BY10 > BY14 = BY15 P < 0.0014 = BY14 > BY05 = BY07 = BY08 = BY10 = BY15 P = 0.1784 > BY14 = BY05 = BY08 > BY07 > BY10 = BY15 P < 0.0014 > BY05 > BY08 = BY14 > BY10 = BY15 > BY07 P < 0.001

ninsula: BY10, Bobokan Reef (Buyat river mouth): BY07, Totok river mouth: BY14,

E.N. Edinger et al. / Marine Pollution Bulletin 56 (2008) 1553–1569 1561

Kruskall–Wallis test, p < 0.001; see Table 6); peak concentrationswere highest in coral BY14, near the mouth of the Totok River. Sim-ilarly, peak Si02 concentrations were observed in site BY14, fol-lowed closely by BY04, closest to the tailings outfall, whilemedian SiO2 concentrations were lowest in corals from exposedsites BY07, BY08, and BY10, and reference site BY15 (Fig. 5B,p < 0.001). Iron oxide concentrations were lowest in corals fromreefs BY04 and BY07, highest in coral BY05, and equally abundantin all other corals (Fig. 5C, p < 0.001).

Median coral skeleton concentrations of Cr and Cu were highestin coral BY04, closest to the tailings outfall (Fig. 6A, B, p < 0.001),while Zn was highest in corals BY04 and BY14 (Fig. 6C,p < 0.001). Highest peak concentration of Cr was observed in coralBY07, in the plume of the Buyat River, although median concentra-tions of Cr were higher in coral BY04 than in BY07. Highest Pb con-centrations were observed in coral BY05, followed by BY04, BY08,and BY10 (Fig. 6D, p < 0.001).

Median arsenic concentrations were statistically indistinguish-able in all corals analyzed (Fig. 7A, p > 0.17), but highest peak con-centrations were observed in corals BY04 and BY14. Medianantimony concentrations were highest in tailings-affected coralBY04, followed by BY05, BY08, and BY14 (Fig. 7B, p < 0.001), andwere lowest in fluvially-affected coral BY07, exposed site BY10,and reference site BY15. Highest median concentrations of thal-lium occurred in coral BY04, close to the tailings outfall, followedby exposed tailings-affected sites BY05 and BY08; lowest Tl con-

10.0

9.0

8.0

7.0

6.0

5.0

4.0

3.0

2.0

1.0

0.0

BY04 BY 07 BY 08 BY 10 BY 14 BY 15BY 05

BY04 BY 07 BY 08 BY 10 BY 14 BY 15BY 05

Cr p

pmZn

ppm

BY15-6

BY14-3

BY07-7

BY04L-26

BY08-33rBY07-14

30

25

20

15

10

5

0

By05-1r

BY05-17r

BY05-7

BY04L-4

BY04L-44

BY04L-29 BY10-17

BY15-16

BY14-1

BY10-14BY08-17BY14-13

A B

DC

Fig. 6. Coral skeleton concentrations of trace elements identified as fluvially associat

centrations were observed in fluvially-affected corals BY07 andBY14, and in reference coral BY15 (Fig. 7C, p < 0.001).

3.3.3. Trace element correlations in coral skeletonsTrace elements in coral skeletons were generally correlated

with silica content, with the exceptions of MgO, Cu, Co, and Pb (Ta-ble 7). Iron and aluminum were very tightly correlated, consistentwith aluminosilicate rocks as a dominant source of iron. Arsenicand antimony, which had extremely high correlations with eachother in sediment samples, particularly those affected by industrialmine tailings, were correlated with each other to the same extentas they were each correlated with silica content. Arsenic was sig-nificantly correlated with iron, but antimony was not.

3.3.4. Trace element chronologies in coral skeletonsPeak concentrations of arsenic in the Buyat Bay reef coral

(BY04) occurred in 1996, the year the mine opened, with secondarypeaks in 1997 and 2001 (Fig. 8A). Barium, generally used as anindicator of fluvial runoff, showed virtually no temporal variation,and no correlation with As, Sb, Cu, or Cr. Peak concentrations of Asand Sb in Tj. Buyat coral BY05 occurred in 1998 and 2000, with aminor peak in 1999 (Fig. 8B). These peaks corresponded with high-er concentrations of SiO2 and Cu, but not with Ba, again indicatinga correlation with sedimentation, but not necessarily with fluvialinput. Peak concentrations of Cr in coral BY05 sometimes coincidedwith SiO2, and sometimes coincided with Ba.

200

180

160

140

120

100

80

60

40

20

0

12.0

10.0

8.0

6.0

4.0

2.0

0.0

BY04 BY 07 BY 08 BY 10 BY 14 BY 15BY 05

BY04 BY 07 BY 08 BY 10 BY 14 BY 15BY 05

Cu

ppm

Pb p

pm

BY05-6r

BY05-15

BY04L-29

BY04L-4

BY04L-44 BY15-17rBY08-15

BY08-8r BY1405BY05-20 BY07-22

BY05-7

BY04L-30

BY15-19r

BY08-35BY14-1

BY07-20

BY05-6r

BY04L-6 BY10-20BY08-14

ed metals in sediment study (Edinger et al., 2007). (A) Cr; (B) Cu; (C) Zn; (D) Pb.

0.50

0.40

0.30

0.20

0.10

0.00

BY04L-14

BY04L-45

BY04L-13

BY10-05BY08-33rBY08-36

BY14-1

BY14-11BY07-20

BY05-19rBY04L-24

BY10-21

BY15-2BY08-21

BY04 BY 07 BY 08 BY 10 BY 14 BY 15BY 05

Tlpp

m

1.00

0.90

0.80

0.70

0.60

0.50

0.40

0.30

0.20

0.10

0.00

BY10-07

BY08-35

BY07-5BY05-19r

BY05-20

BY04L-4

BY04L-3

BY10-22

BY15-5

BY08-31

BY07-4

BY04 BY 07 BY 08 BY 10 BY 14 BY 15BY 05

Sbpp

m5.0

4.0

3.0

2.0

1.0

0.0

BY05-8r

BY04L-47

BY04L-5

BY08-34

BY08-16

BY08-41

BY14-21BY14-1

BY05-19rBY04L-42

BY10-01

BY15-14

BY14-22

BY07-15r

BY04 BY 07 BY 08 BY 10 BY 14 BY 15BY 05

Aspp

mA

B

C

Fig. 7. Coral skeleton concentrations of trace elements identified with industrialmining effluent in sediment study (Edinger et al., 2007). A: As; B: Sb; C: Tl.

1562 E.N. Edinger et al. / Marine Pollution Bulletin 56 (2008) 1553–1569

Peak concentrations of arsenic and antimony in Tj. Buyat coralBY10 were recorded in 2000, and coincided with a minor peak inCr, and with mildly elevated concentrations of SiO2, Cu, and Ba(Fig. 8C). Smaller peaks in Sb and Cr co-occurred, and coincidedwith Cu or SiO2 peaks, but not with peaks in Ba concentration. Peakconcentrations of As in Tj. Sikod coral BY08 occurred in 1996, 1997,and 1999, with a minor peak in late 1998 (Fig. 8D). Peak concentra-tions of As and Cr frequently co-occurred, but peaks in As and Sbdid not. Peak concentrations of As generally coincided with peaksin silica content.

Concentrations of As and Sb in Bobokan coral BY07 (near theBuyat river mouth) were generally low, often close to the detectionlimit for these elements (Fig. 9A). Peak concentrations of Cr in coralBY07 occurred in 1998, 1999, and 2001, and generally coincidedwith peaks in Ba, SiO2, and Cu. Peak concentrations of As and Sbin coral BY14 (Totok River mouth) occurred in 1998, 1999, and2001, with additional high concentrations recorded in the twoablations closest to the upper surface of the coral (Fig. 9B). Thesehigh concentrations probably resulted from remnant tissue con-tamination of the material ablated. Peak concentrations of Sb andCu generally coincided with peak concentrations of SiO2, or to alesser extent, Cu, but had little apparent relationship with Ba con-centrations, except for the elevated As and Sb concentrations in2001. Concentrations of antimony in reference coral BY15 weregenerally below detection limits (Fig. 9C). Arsenic concentrationshad low peaks in 1998, 2000, and near the top of the coral, butthese peaks did not have a clear correspondence with Ba, Cu, orSiO2. Chromium peaks in BY15 were generally associated withminor peaks in silica content. Two major peaks in Cu in 1999–2000 also coincided with increases in silica content.

3.4. Correlations between trace elements in sediments and in coralskeletons

Trace element concentrations in sediments (<63 lm fraction)and coral skeletons were generally not significantly correlated withone another (Table 8). The exceptions to this pattern were antimony,which was weakly positively correlated in sediments and coral skel-etons (r = 0.72, p = 0.071), and manganese and cobalt, which wereboth significantly inversely correlated in sediments and coral skele-tons (Mn: r = �0.84, p = 0.018; Co: r = �0.75, p = 0.05).

4. Discussion

4.1. Nature of trace element incorporation into coral skeleton

Most of the trace elements of greatest concern from gold miningactivities in this region are incompatible with the aragonite crystallattice (Howard and Brown, 1984). Therefore, concentrations ofthese metals in coral skeletons tend to be lower than metals suchas Fe, Cu and Pb, all of which are readily integrated into aragoniteskeletons from solution. Concentrations of Cu and Pb in coral BY04were one to two orders of magnitude higher than concentrations ofAs and Sb, although in the sediments, As and Sb were an order ofmagnitude higher than Cu, and two orders of magnitude higherthan Pb. Peak concentrations of Fe and Cu frequently coincidedin the coral skeleton chronologies.

Concentrations of most metals in coral skeleton analyses werecorrelated with silica, and to a lesser extent, with aluminum oxide,suggesting that most of the trace elements measured were at-tached to detrital sediment particles incorporated into the coralskeletons, with some component of Cu and Pb from solution. Thefact that site BY04 had the highest concentrations of most metalsprobably results from it having exposure to very fine grained me-tal-bearing particles, of which most, but not all, were probably de-rived from the industrial mine tailings. Fine-grained particles aremore easily resuspended onto coral reefs, and are more easilytrapped within the trabeculae of the coral skeleton (Cortes andRisk, 1985; Budd et al., 1993). The other source of fine-grained par-ticulate related to mining is enhanced erosion and transport ofmetalliferous rocks associated with mining and road construction(Appleton et al., 2001; Edinger et al., 2007).

Surprisingly, peak concentrations of arsenic and antimony gener-ally did not coincide in the coral skeleton chronologies, suggestingthat many of the sediment particles incorporated into tailings-af-fected corals were fine-grained arsenates and antimony oxides, trav-

Table 7Correlation matrix among elements recorded in coral skeletons, ln-transformed

MgO Al2O3 SiO2 CaO42 CaO43 FeO Co Cu Zn As Sb Ba Tl

Al2O3 0.060SiO2 �0.063 0.507**

CaO_42 0.040 0.002 0.038CaO_43 0.016 �0.002 0.165* 0.534**

FeO 0.077 0.646** 0.329** 0.006 �0.168*

Co �0.117 0.069 �0.022 0.002 �0.037 0.09Cu 0.068 0.005 0.061 0.041 0.073 0.066 0.19**

Zn 0.008 0.11 0.258** 0.026 0.065 0.079 0.099 0.305**

As 0.034 0.294** 0.247** �0.143* �0.151* 0.215** �0.029 0.000 0.142*

Sb �0.016 0.006 0.252** �0.047 0.013 �0.132 0.027 0.046 0.159* 0.226**

Ba 0.383** 0.128 0.141* 0.144* 0.087 0.308** 0.052 0.127 0.088 �0.012 �0.024Tl �0.32 0.155* 0.261** �0.007 �0.059 0.07 0.024 0.109 0.211** 0.204** 0.280** �0.052Pb 0.133 0.047 0.141* 0.022 0.014 0.171* 0.034 0.234** 0.115 0.112 0.075 0.251** 0.067

** p < 0.01, * p < 0.05. N = 207 in all cases.

0

8

4

12

16

20

[Ba,

Cu]

,ppm

, [Si

/100

] ppm

Ba

Cu

SiO /100

100 20 30 40 50 60 70 80 90 100vertical distance (mm)

2002

2001

2000

1999

1998

1997

1996

BY 04 (closest reef to tailings outfall)

18O

δ

Oδ

7.0

7.5

8.0

8.5

9.0

Sr/C

am

mol

/mol

9.5

AsSb

Cr

0.0

0.4

1.6

0.8

1.2

2.0

[As,

Sb,C

r]

Sr/Ca

-4.5

-5.0

-5.5

-6.0

-6.5

Fig. 8. Coral skeleton trace element chronologies: reef affected by industrial mine tailings. (A) Reef inside Buyat Bay (BY04). (B) Tj. Buyat (BY05). (C) Ratototok Peninsula(BY10); (D) Tj. Sikod (BY08). Annual bands (vertical grey bars) were identified using the skeletal density bands, and verified as annual using Sr/Ca ratios.

E.N. Edinger et al. / Marine Pollution Bulletin 56 (2008) 1553–1569 1563

2002

2001

2000

1999

1998

7.0

7.5

8.0

8.5

9.0

Sr/C

am

mol

/mol

9.5

5 10 15 20 25 30 35 40 45 50

0

8

4

12

16

20

[Ba,

Cu]

, ppm

, [Si

/100

]ppm

SiO /10

Ba Cu

vertical distance (mm)

BY 05 (500 m east of tailings outfall)

0.0

0.4

1.6

0.8

1.2

2.0

[As,

Sb,C

r,] As

Cr

Sb

7.0

7.5

8.0

8.5

9.0

Sr/C

am

mol

/mol

9.5

50 10 15 20 25 30 35 40 45

2002

2001

2000

1999

1998

vertical distance (mm)

BY 10 (1 km east of tailings outfall)

Sb

Cr

As

0.6

0.0

0.40.2

0.81.0

[As,

Sb,C

r,]

Cu

Si/100

Ba

0

8

4

12

16

20

[Ba,

Cu]

,ppm

,[Si

/100

]ppm

Fig. 8 (continued)

1564 E.N. Edinger et al. / Marine Pollution Bulletin 56 (2008) 1553–1569

elling with fine-grained silica from mine tailings, rather than pyritecrystals with arsenic or antimony-rich rims (Blackwood and Edinger,

2007). Amorphous colloidal iron–arsenic phases were observed intailings sediment and in sediments from Buyat Bay reef BY04 and

4.6 ppm

100 20 30 40 50 60 70 80 90 100vertical distance (mm)

0

8

4

12

16

20

[Ba,

Cu]

,ppm

,[Si

/100

] ppm

Ba

Cu

SiO /100

2002

2001

2000

1999

1998

1997

1996

BY 08 (900 m west of tailings outfall)

0.0

0.4

1.6

0.8

1.2

2.0

[As,

Sb,C

r,]

7.5

8.0

8.5

9.0

Sr/C

am

mol

/mol

9.5

Fig. 8 (continued)

E.N. Edinger et al. / Marine Pollution Bulletin 56 (2008) 1553–1569 1565

Tj. Buyat Reef BY05 (Blackwood and Edinger, 2007). However, ironand arsenic peaks did not always coincide in skeletal chronologies,and iron and arsenic were not correlated in coral skeletal analysesfrom site BY04, suggesting that much of the arsenic in coral skeletonsmay have been present as Mg–arsenate, another tailings processingby-product. Arsenic in Totok Bay reefs was likely present as fine-grained arsenopyrite (Blackwood and Edinger, 2007); silt-sizedgrains of arsenopyrite were observed in sediment from both the To-tok and Buyat rivers (Blackwood and Edinger, 2007).

4.2. Influence of grain size on sediment trace element analyses

Sediment trace element analysis results for the mud fractionwere highly consistent with whole sediment concentrations previ-ously reported for the same sites (Edinger et al., 2007; Table 4). Themajor differences encountered were at tailings-influenced sitesdominated by bioclastic reef sediment, particularly BY05, BY08,and BY10 (Edinger et al., 2007). The fine fraction sediment data fur-ther document dispersal of mine-tailings derived sediment ontoreefs 1–2 km away from the mine tailings outfall (Edinger et al.,2007). The high degree of agreement between whole-sedimentand <63 lm fraction analyses reflects the immature nature of mar-ine sediments in this region, i.e. derived from recent mechanicalerosion and chemical weathering of volcanic rocks. This level ofagreement would be unlikely in cases where the dominant sourcesof metals were dissolved, and metals were adsorbed to mineralog-ically differentiated clay minerals.

Although trace element analysis of the <63 lm fraction of sed-iments is routine in environmental analyses (e.g. Salomons andForstner, 1984; and many others), sediment quality guidelines of-

ten apply to whole sediment (e.g. CCME, 2001). Our results empha-size the importance of analyzing the fine fraction of sediments,particularly in mixed carbonate-siliciclastic settings, where coarsebiogenic carbonates dilute the trace element signal incorporatedinto, or adsorbed onto, fine-grained siliciclastic sediments. Revi-sion of sediment quality guidelines to specify analysis of the<63 lm fraction should be considered.

4.3. Evaluation of trace element measurement techniques

Coral skeleton analysis with laser-ablation-ICP-MS successfullyrevealed relative spatial and temporal variation in heavy metalcontamination of reefs from industrial gold mine tailings disposaland enhanced erosion associated with artisanal gold mining. Laserablation ICPMS was effective in quickly and efficiently measuringthe concentrations of most trace elements in these coral skeletons,and successfully avoided selective dissolution of some siliciclasticphases along with carbonates (cf. Runnalls and Coleman, 2003).Concentrations of most, but not all, trace elements in coral skele-tons were well above detection limits for LA-ICP-MS, but mighthave fallen below detection limits for more traditional approacheslike solution AAS or ICP-AES.

Nonetheless, comparison of laser ablation analysis of the MACSreference material with solution analyses of MACS suggested thatlaser ablation gave an incomplete yield for some elements, partic-ularly Ti, V, and As. The high RSD of laser ablation analyses forMgO, Al2O3, Ti, V, As, Sb, and Tl in the MACS reference materialsuggest an inhomogeneous distribution of these elements withinMACS (Table 5). Because MACS is a pressed-powder material com-posed of aragonite coral skeleton spiked with known quantities of

50 10 15 20 25 30 35 40 45

0

8

4

12

16

20

[Ba,

Cu]

,ppm

,[Si

/100

]ppm

Ba

Cu

SiO /100

vertical distance (mm)

2002

2001

2000

1999

BY 07 (closest to Buyat river mouth)

1998

As

Cr

Sb0.0

0.4

1.6

0.8

1.2

2.0

[As,

Sb,C

r,]

7.5

8.0

8.5

9.0

Sr/C

am

mol

/mol

9.5

50 10 15 20 25 30 35 40 45

vertical distance (mm)

2002

2001

2000

1999

BY 14 (closest to Totok river mouth)

1998

0

8

4

12

16

20

[Ba,

Cu]

,ppm

,[Si

/100

]ppm

Ba

Cu

SiO /100

As

Cr

Sb

0.0

0.4

1.6

0.8

1.2

2.0

[As,

Sb,C

r,]

8.0

8.5

9.0

9.5

10.0

Sr/C

am

mol

/mol

Fig. 9. Coral skeleton trace element chronologies: reef affected by fluvial runoff, artisanal mining, and reference site. (A) Bobokan, near Buyat river mouth (BY07); (B) TotokRiver mouth (BY14), affected by artisanal mining; (C) Reference site, Pulau Babi, Totok Bay (BY15). Annual bands (vertical grey bars) were identified using the skeletal densitybands, and verified as annual using Sr/Ca ratios.

1566 E.N. Edinger et al. / Marine Pollution Bulletin 56 (2008) 1553–1569

various trace elements rather than a fused homogenized glass,inhomogeneities can be expected, particularly for elements incom-

patible with the aragonite crystal lattice. Similarly, differences inablation yield between the fused glass standard, the MACS

50 10 15 20 25 30 35 40 45

vertical distance (mm)

BY 15 (reference)

2002

2001

2000

1999

1998

7.0

7.5

8.0

8.5

9.0

Sr/C

am

mol

/mol

9.50

8

4

12

16

20

[Ba,

Cu]

,ppm

,[Si

/100

] ppm

Si/100

Cu

Ba

AsCrSb0.0

0.4

1.6

0.8

1.2

2.0

[As,

Sb,C

r,]

Fig. 9 (continued)

Table 8Relationship between sediment (<63 micron) sediment trace element concentrationsand average coral skeleton trace element concentrations

Metal Linear r2 Linear p Log r2 Log p Sense

Cr 0.317 0.188 0.212 0.298 No trendMn 0.706 0.018 0.788 0.008 NegFe 0.167 0.363 0.148 0.394 No trendCo 0.561 0.053 0.571 0.043 NegCu 0.012 0.812 0.005 0.886 No trendZn 0.030 0.710 0.000 0.99 No trendAs 0.193 0.325 0.201 0.313 No trendSb 0.511 0.071 0.417 0.117 PosPb 0.008 0.846 0.030 0.708 No trendTh 0.033 0.695 0.006 0.578 No trend

N = 7 sites in all cases. Most elements showed no significant relationship betweensediment trace element concentration and mean coral skeleton trace elementconcentration. The three exceptions to this pattern were Mn, Co, and Sb. Mn and Coboth showed significant negative correlations between sediment trace elementconcentration and coral skeleton trace element concentrations. Arsenic concen-trations in sediment and coral skeleton were positively correlated, but the trendwas not significant.

E.N. Edinger et al. / Marine Pollution Bulletin 56 (2008) 1553–1569 1567

pressed-pellet carbonate reference material and the porous arago-nitic coral skeletons may also contribute to analytical uncertainty.

Lateral variation in detrital material incorporation at a scale of100–1000 lm likely accounted for the high variability in most me-tal chronologies, and the relatively low repeatability of laser abla-tion analyses in the coral skeleton samples. Some laser ablationICP-MS systems have been modified to sample from a larger area(50 � 500 lm), rather than a discrete circular ablation pit (e.g. Sin-

clair et al., 1998; Fallon et al., 2002, 2003; Sinclair, 2005). Such amodified laser ablation system could probably avoid some of theproblems with small-scale spatial heterogeneity observed in thisstudy, as it would average the element concentrations within awider area. Similarly, drilling out subsamples of coral skeletonfor solution analysis (cf. Shen and Boyle, 1989; Bastidas and Garcia,1997; David, 2003) would likely yield a greater amount of totalmaterial, possibly avoiding issues with <100 lm scale variationin detrital sediment incorporation into coral skeletons. A drilledsample approach would also allow partitioning of samples for mer-cury analysis by cold-vapour AAS (cf. Bastidas and Garcia, 1997).Although the mass spectrometer detected Hg, and gave a yield incounts per second, it was not possible to directly calibrate thisyield, because neither the NBS 610 standard nor the MACS refer-ence material have published values for mercury concentration.

Acknowledgements

We thank the people of Buyat Pantai for hospitality and assis-tance in the field, particularly Mansur Lombonaung and family.Bayu Suwarno (Kelola) assisted with 2002 field work, and Dr. Han-ny Tioho (Sam Ratulangi University) assisted with 2004 field work.Tracey Novak assisted with sediment analysis, Mike Tubrett as-sisted with LA-ICP-MS analysis, and Pam King and Lakhmali Hewaassisted with solution ICP-MS analysis. Charlie Conway drafted themap. The manuscript benefited from comments by J. Rendell andO. Sherwood. Funded by Memorial University of Newfoundlandinternal grants and an NSERC Discovery grant to EE. Dedicated tothe memory of Father Joseph Stiassny.

Appendix 1

Sample CaCO3%whole

CaCO3%<63 lm

FeO% Ti V Cr 52 Mn Co Ni Cu Zn As Mo Ag Cd Sn Sb Pb Bi Th

BY03 6.45 9.91 4.63 2964.21 134.40 43.48 1259.35 16.87 24.57 63.53 95.54 132.39 4.40 0.854 4.81 3.72 59.96 6.86 0.455 1.783BY04 15.45 14.68 4.58 2744.58 124.51 47.02 1268.12 14.50 17.48 58.41 108.88 253.29 4.28 0.997 4.33 3.10 164.57 11.98 0.355 1.306BY05 46.68 28.08 4.15 2394.12 108.50 41.55 1081.20 12.00 15.18 44.15 151.29 146.97 3.71 0.895 4.05 3.12 115.40 5.99 0.352 0.945BY07 8.04 11.28 5.06 4093.54 182.40 51.88 1330.08 20.76 20.97 62.88 167.78 61.00 3.96 0.691 4.32 3.44 18.52 5.85 0.375 1.428BY08 68.82 32.09 3.76 1770.07 88.06 40.65 1183.90 9.35 39.72 36.41 932.20 194.41 3.96 1.000 3.76 2.81 164.47 8.25 0.306 0.655BY09 8.13 10.85 6.04 5107.29 239.89 59.88 1707.36 23.22 20.02 67.04 114.49 47.24 3.54 0.620 3.87 3.19 12.92 5.40 0.285 1.174BY09A 6.04 8.68 4.85 2960.62 132.41 36.74 1218.73 17.82 19.62 63.41 97.52 46.20 2.94 0.530 3.13 2.81 6.79 5.02 0.241 1.094BY10 56.60 38.74 4.26 1822.26 85.73 26.55 768.63 8.88 11.44 21.70 73.31 79.77 1.61 0.411 0.90 0.96 90.65 6.71 0.129 0.599BY11 6.49 7.45 9.54 7185.72 364.61 65.14 1462.10 25.34 19.60 56.39 129.82 39.95 3.77 0.423 0.84 1.56 5.83 7.35 0.229 0.931BY12avg 4.53 5.33 5.49 2984.93 143.65 27.98 712.78 15.15 14.46 56.14 99.50 34.79 3.33 0.369 0.71 1.27 4.49 9.35 0.235 1.117BY13 3.64 5.90 5.45 2859.79 126.04 26.13 694.26 14.67 13.39 51.74 129.16 37.80 3.04 0.282 0.39 0.94 5.00 10.77 0.233 1.287BY14 5.27 5.52 5.37 3070.19 134.09 29.68 732.94 14.13 16.18 44.72 111.99 49.33 3.96 0.329 0.60 1.13 5.69 8.93 0.172 1.145BY15 84.02 66.71 2.42 535.60 25.79 8.34 205.35 2.64 4.33 9.97 34.03 4.95 1.48 0.058 0.46 0.43 1.90 2.46 0.064 0.257BY16 10.87 9.05 6.88 4854.77 226.69 52.41 1092.98 19.45 18.93 48.29 102.85 21.11 1.32 0.079 0.09 0.88 3.78 5.10 0.071 1.180BY17 8.69 8.53 6.41 3845.22 157.76 35.07 812.75 14.53 14.24 40.11 75.81 30.31 0.87 0.033 0.18 0.71 7.03 5.79 0.081 1.333BY18 6.40 6.41 7.24 4310.52 202.15 38.29 971.48 16.09 14.42 51.43 89.64 44.79 4.08 0.433 0.38 0.97 5.90 9.10 0.223 1.245BY21 21.79 20.56 2.58 754.76 38.87 32.33 1115.40 3.93 11.82 26.98 83.23 523.73 2.38 0.480 0.54 0.89 401.94 6.96 0.112 0.318BY22 26.07 22.55 3.96 1640.44 74.65 30.84 822.56 7.04 12.16 24.82 57.12 172.55 1.86 0.447 0.50 0.59 240.00 7.52 0.104 0.541BY23 20.14 21.23 2.82 815.63 42.87 48.00 978.16 3.72 14.75 37.97 94.05 548.53 4.30 0.179 0.41 0.49 518.34 8.72 0.066 0.349BY24avg 21.04 20.87 2.32 538.88 28.73 35.22 1200.07 2.84 9.82 26.66 57.34 407.07 2.94 0.272 0.34 0.45 336.18 6.15 0.073 0.228BY27 18.78 18.05 3.36 1436.02 71.38 37.91 1040.60 6.16 13.07 29.62 79.24 213.92 1.86 0.559 0.00 0.01 331.44 11.59 0.075 0.612BY28 37.91 26.29 4.59 2236.25 105.91 31.12 902.23 9.48 13.62 28.24 127.82 89.11 1.44 0.340 0.18 0.40 117.00 24.63 0.062 0.662BY29 37.34 34.22 3.48 1427.48 68.74 27.71 866.21 6.44 8.95 18.61 86.48 120.57 1.13 0.332 0.04 0.27 141.99 6.26 0.068 0.436BY30 20.94 20.39 3.43 1377.35 70.24 40.52 1007.02 6.34 12.87 27.33 72.47 291.95 2.20 0.610 0.47 0.67 324.78 7.01 0.089 0.507BY33 21.19 20.16 2.98 1094.99 59.78 39.47 1014.17 5.34 16.64 29.20 76.58 353.31 2.31 0.654 0.05 0.52 360.77 7.13 0.105 0.493BY34 20.87 20.70 4.94 2600.43 120.53 38.41 1002.91 10.15 14.61 38.32 188.22 107.55 1.92 0.778 0.82 0.70 158.68 39.63 0.073 0.765BY35 23.93 20.17 2.83 1036.72 54.88 39.18 1220.96 5.20 17.35 27.20 63.74 456.57 2.12 0.580 0.00 0.17 363.87 7.11 0.058 0.457BY36avg 25.56 20.62 2.94 1049.41 56.44 44.63 1228.62 4.98 13.40 31.63 71.71 579.56 2.74 0.448 0.09 0.31 483.85 8.09 0.084 0.431BY37 19.33 22.78 3.92 1706.68 83.64 50.53 1218.80 7.67 15.66 43.92 102.61 481.96 2.95 0.625 0.87 0.74 396.42 7.13 0.118 0.759BY38 13.89 15.53 4.44 2339.87 106.48 46.12 1160.22 10.22 18.56 41.65 82.04 246.85 1.89 0.530 0.34 0.56 234.43 6.61 0.084 1.000BY39avg 6.94 8.87 8.13 6145.51 279.14 66.71 1221.85 21.43 20.63 58.32 136.41 23.97 2.22 0.131 0.30 1.29 7.64 5.99 0.079 1.392BY40 11.03 13.65 5.60 3468.66 155.08 52.17 1088.97 13.70 15.78 47.04 89.80 134.50 2.09 0.333 0.49 0.61 160.63 6.81 0.082 1.063BY41 5.65 8.35 8.09 5513.26 254.88 61.82 1175.85 20.26 26.86 54.61 139.68 19.10 1.27 0.112 0.19 2.22 6.37 7.21 0.049 1.300BY42 14.72 14.64 4.36 2349.57 102.71 42.51 1092.71 10.15 14.87 41.21 77.66 203.52 1.65 0.604 0.11 0.47 213.69 6.18 0.079 0.855BY43 16.27 16.98 4.25 1958.93 91.83 43.48 1233.58 9.16 14.38 37.31 80.41 275.40 1.83 0.524 0.04 0.37 273.46 6.70 0.093 0.874BY45 40.22 37.73 4.59 2034.42 89.52 21.47 597.67 9.07 9.05 26.40 59.08 17.75 0.79 0.022 0.13 0.79 19.17 6.65 0.071 0.760BY47 26.04 30.79 5.94 2610.38 119.62 27.23 591.85 13.07 10.67 30.40 64.40 14.91 1.32 0.013 0.00 0.23 6.04 7.94 0.071 0.986BY48 6.60 6.57 5.74 3323.37 143.91 34.27 820.49 12.72 10.85 38.01 87.79 47.76 2.96 0.236 0.06 0.72 4.03 8.94 0.158 1.206BY51 30.35 28.44 4.48 2350.94 105.48 27.25 662.79 11.38 10.55 32.21 63.29 21.26 1.40 0.019 0.05 0.60 7.75 8.01 0.075 0.963BY52 12.08 12.12 6.72 5667.31 271.16 36.79 1197.23 19.79 12.90 62.36 398.93 48.21 2.40 1.670 1.83 0.94 17.92 112.52 0.033 0.914

1568E.N

.Edingeret

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PollutionBulletin

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E.N. Edinger et al. / Marine Pollution Bulletin 56 (2008) 1553–1569 1569

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