Mercury and Methylmercury in Freshwater Fish and Sediments in South Korea Using Newly Adopted Purge and Trap GC-MS Detection Method

Mercury and Methylmercury in Freshwater Fishand Sediments in South Korea Using Newly Adopted Purgeand Trap GC-MS Detection Method

Jae-Sung Park & Jung-Sub Lee & Gun-Bae Kim &

Jun-Seok Cha & Sun Kyoung Shin &

Hak-Gu Kang & Eun-Jin Hong & Gi-Taeg Chung &

Young-Hee Kim

Received: 22 September 2008 /Accepted: 7 July 2009 /Published online: 26 July 2009# Springer Science + Business Media B.V. 2009

Abstract The use of purge and trap gas chromatography–mass spectrometry (GC-MS) technique for the determi-nation of methylmercury in biological and sedimentsamples was described. The GC-MS detection systemwas combined with the dithizone extraction method forbiological samples and the distillation method forsediment samples to alleviate matrix interference prob-lems. The method was validated by analysis of CRMssuch as SRM 966 (human blood), BCR 463 (tuna fish),IAEA 407 (fish), ERM CC580 (estuarine sediment),and IAEA 405 (sediment). The performance of thepurge and trap GC-MS method was also tested on fieldsamples of freshwater fish and sediment. The resultswere compared with those of the GC-ECD and the GC-CVAFS, which were used widely for methylmercuryanalysis. Additionally, total mercury and methylmer-cury levels in freshwater fish and sediments fromvarious reservoirs and streams in Korea were measuredto understand mercury contamination status in Koreanpeninsula. Methylmercury concentrations in freshwaterfish were found to correlate with bodyweight, diet habit,

and food availability. In sediment, total mercury con-centrations correlated with methylmercury concentra-tions and organic matter such as %C and %S. However,no significant relationships between methylmercury andsediment organic matter have been found.

Keywords Methylmercury .Mercury . Dithizoneextraction . Distillation technique .

Purge and Trap GC-MS . Sediment . Freshwater fish

1 Introduction

Among many pollutants, methylmercury has beenconcerned as the most harmful mercury species dueto its high toxicity, high solubility in lipids, whichincreases the potential for biological uptake and bio-concentration, and common occurrences in theenvironment (Horvat 1996). Some inorganic mercuryreleased into the aquatic system is known to beconverted to methylmercury via biotic production bysulfate-reducing bacteria in sediment (Mason et al.1999; Mason and Lawrence 1999). These methylmer-cury are uptaken by benthic organisms and accumu-lated in fish through the food chain, which is themajor pathway for human exposure to methylmercury(Boening 2000; Henny et al. 2002; and Mergler et al.2007). Generally, the concentration of total mercury isused as a biomarker for evaluation of the exposurelevel of methylmercury in blood because more than

Water Air Soil Pollut (2010) 207:391–401DOI 10.1007/s11270-009-0144-3

J.-S. Park : J.-S. Lee :G.-B. Kim : J.-S. Cha : S. K. Shin :H.-G. Kang : E.-J. Hong :G.-T. Chung :Y.-H. Kim (*)Chemicals Behavior Research Division,National Institute of Environmental Research,Environmental Research Complex,Kyungseo-dong, Seo-gu,Incheon, Republic of Korea 404-708e-mail: [email protected]

80% of mercury in human blood exists as methylmer-cury forms and determination of total mercury is simplecompared to that of methylmercury (Akagi and Naga-numa 2000; Rice 2004). However, recent studiesshowed that the mercury speciation in human bloodis needed to evaluate the sources of exposure,especially at low exposure levels. Lindberg et al.(2004) revealed that the proportions of methylmercuryto total mercury in blood of non-fish-eating people arerelatively lower than those of fish-eating people andinorganic mercury in blood has a significant associa-tion with the number of dental amalgam fillings.

Thus, there is a growing need for a more simplifiedand popularized analytical method for the determinationof methylmercury in environmental species (Vidler et al.2007). For methylmercury analysis, a succession ofanalytical stages is required. The main steps to speciatemercury are digestion, clean-up, separation, andmercury-specific detection. Coupled techniques includ-ing separation by gas chromatography (GC) or liquidchromatography (LC) and detection by electron capturedissociation (ECD), atomic absorption spectroscopy(AAS), atomic fluorescence spectroscopy (AFS), andinductively coupled plasma–mass spectroscopy (ICP-MS) have been widely used (Westöö 1966; Bloom1989; Blanco et al. 2000; Ullrich et al. 2001; Ignacio etal. 2000). For methylmercury clean-up process, asolvent extraction technique and a distillation techniqueare commonly used (Westöö 1966; Horvat et al. 1993).However, the extraction of methylmercury from bio-logical samples, especially in blood has been a difficulttask because of severe matrix interferences. The solventextraction method using toluene or dichloromethanegenerally gave low extraction efficiencies in certainmatrix (Akagi and Nishimura 1991). Additionally, thedistillation technique has a drawback such as co-distillation of large amounts of volatile compounds inblood and these volatile compounds transferred to thedistillate can interfere with the ethylation reaction and/ordeposit on the GC column leading to inaccuratedeterminations (Liang et al. 2000; Baxter et al 2007).

Thus, in this study, it was considered appropriate todevelop the accurate and simplified methylmercuryanalytical method using popularized analytical instru-ment such as purge and trap GC-MS. The GC-MSdetection system was combined with the dithizoneextraction method and clean-up process by Na2S forbiological samples since the dithizone extractionprocess showed improved extraction efficiencies by

the complexation between dithizone and methylmer-cury (Akagi and Nishimura 1991; Logar et al. 2002).However, for the analysis of sediment, the distillationtechnique with H2SO4/KCl was preferred due to easypreparation and no use of harmful organic solvents. Inthis study, the distillation conditions were controlledwith great cautions to prevent the production ofmethylmercury artifacts by over-distillation (Horvat etal 1993; Quevauviller et al. 1997; Hammerschmidt andFitzgerald 2001). The performance of the purge andtrap GC-MS method was validated by analyzingCRMs. Additionally, total mercury and methylmercurylevels in freshwater fish and sediments from variousreservoirs and streams in Korea were measured tounderstand mercury contamination status in Koreanpeninsula and the analytical results were compared withthose of the GC-ECD and the GC-cold vapor atomicfluorescence spectrometry (CVAFS), respectively.

2 Experimental Section

2.1 Sample Collection and Preparation

From June to September 2006, 57 freshwater fishsamples were collected from reservoirs, lakes, andstreams in Korea (Fig. 1). The water characteristics ofthe sites are various with chlorophyll a concentrationsand chemical oxygen demand ranging 1.1∼15.6 mg/m3

and 1.8∼7.2 mg/L, respectively. The filet of fishsamples were cut into small pieces with dissectionscissors and homogenized to a pastry state. The sampleswere kept frozen until further analysis. Eighty-onesediment samples were also sampled from June toSeptember 2007 by using a Ponar grab sampler (Fig. 1).The sediment were categorized into groups by samplingsites as lake, reservoirs, river 1 (with biochemicaloxygen demand (BOD) lower than 3), river 2 (withBOD higher than 3), urban stream, and plant effluents.All the samples were kept frozen until further analysis.

2.2 Experimental Materials and Apparatus

All reagents used were of ACS grade and all waterwas used as doubly distilled and de-ionized waterobtained from Barnsted UC/A56220-8 (IA, USA).Methylmercury standard stock solution (1 mg∙mL−1)was prepared by dissolving the appropriate amount ofCH3HgCl (Aldrich, MO, USA) in toluene. Purified

392 Water Air Soil Pollut (2010) 207:391–401

0.02% dithizone solution was prepared by dissolving0.011 g of diphenylthiocarbazone in 100 mL toluene.Alkaline sodium sulfide stock solution was preparedby dissolving 0.15 g of Na2S9H2O in 10 mL ofdistilled water. At each use, 0.1 mL of stock solutionwas diluted with 50 mL of 0.1 N NaOH and 50 mL ofethanol. Walpole’s buffer was prepared by mixing200 mL of 1 M CH3COONa and about 200 mL of1 N HCl to adjust to pH 3.0. Sodium acetate buffer(0.2 M) was prepared by dissolving 1.64 g ofCH3COONa in distilled water and added with aceticacid to adjust pH at 4.9. Ethylating reagent, 2%sodium tetraethylborate, was prepared by dissolvingwith 0.2 g of sodium tetraethylborate [NaB(C2H5)4]powder in 10 mL of 1% w/v KOH solution and waskept in ice and darkness after preparation andthroughout the analysis.

For purge and trap GC-MS method, the volatilederivatized ethylmethylmercury were concentratedand injected using Tekmar–Dohrmann purge-and-trap (Mason, OH, USA) with a Tenax A trap(Suppleco, MO, USA) as adsorbent trap. The samplewas purged with helium at 40 mL∙min−1 for 15 min at40°C and followed by desorption at 200°C for 3 min.

Chromatographic analysis was performed with Agilent6890N GC (CA, USA) equipped with Agilent 5973NMS operating in selected ion monitoring (SIM) mode.The DB-5MS capillary column (5% phenyl–95%dimethylpolysiloxane; 30 m×0.5 mm I.D., 0.25 μm)was used with helium as carrier gas at a flow rate of1 mL∙min−1. The column temperature was programmedas follows: 40°C for 4 min, increasing to 280°C at15°C∙min−1 then holding for 5 min. The injection portand detector were operated at 220°C and 230°C,respectively.

2.3 Determination of Methylmercury in BiologicalSamples Using Dithizone Extraction Followedby the Purge and Trap GC-MS Method

Details of dithizone extraction procedures for meth-ylmercury analysis are given elsewhere (Akagi andIkingura 1999). Approximately 0.5∼1 g of biologicalsample and 10 mL of 1 N KOH–ethanol solutionwere placed in a 40-mL screw-capped conicalcentrifuge tube and heated at 100°C for 1 h. Aftercooling to room temperature, 10 mL of 1 N HCl wasadded followed by washing with 5 mL of n-hexane,

S

S-River S-Lake & ReservoirS-Urban streamS-Plant effluentFreshwater Fish

Fig. 1 Sampling sites ofsediments and freshwaterfish in Korean peninsula

Water Air Soil Pollut (2010) 207:391–401 393

and then, 2 mL of 20% EDTA–4Na solution wasadded into the extracted aqueous phase to mask othermetal ions contained in the samples. Five milliliters ofpurified 0.01% dithizone-toluene was added and theaqueous phase was discarded. The remaining excessdithizone in toluene phase was removed by washingwith 5 mL of 1 N NaOH. A fixed volume of thetoluene phase (7 mL) was transferred into 10-mLcentrifuged tube with glass stopper and 2 mL of Na2Ssolution was added to back-extract the methylmercuryinto aqueous phase. The solution was acidified with3∼5 drop of 1 N HCl and aerated with N2 at50 mL∙min−1 for 3 min to expel the excess sulfideions. Lastly, 0.1 mL (0.05∼1 mL) of the aeratedsolution was added into 10 mL of distilled water and5 mL of sodium acetate buffer in a 20-mL syringe,followed by adding 0.2 mL of sodium tetraethylboratesolution. Blanks and standard solutions for a calibra-tion curve were treated in a similar manner. Thecombined solution in the syringe was injected into thesparser connected on the purge and trap sampler.During MS detection, the following ions weremonitored using SIM mode: m/z 202, 217, and 246for CH3HgC2H5; m/z 202, 231, and 260 for Hg(C2H5)2. Between two consecutive analyses, thedistilled water was analyzed in order to clean the

system and eliminate carryover effects. The calibra-tion curve was evaluated in the range from 0.1 to 5 ng(as Hg) and obtained with a determination coefficient,r2>0.995 and less than 7% of RSD of calibrationfactors. The method detection limit was defined as theconcentration equivalent to three times standarddeviation of concentrations of spiked methylmercurysolutions and was found to be 0.1 ng∙g−1 forbiological samples. For quality control purpose,CRMs of IAEA 407 (IAEA, Vienna, Austria) andBCR 463 (ERM, Brussels, Belgium) for fish andstandard reference material (SRM) 966 (NIST, MD,USA) for blood were analyzed. The commerciallyavailable blood samples were obtained from Centrede Toxicologie du Québec (Québec, Canada).

2.4 Determination of Methylmercury in SedimentUsing Distillation Technique Followed by the Purgeand Trap GC-MS Method

Details of distillation protocols for methylmercuryanalysis are given elsewhere (Mason et al. 1999).Briefly, 0.5∼1 g of solid samples was distilled with a1.5 mL of 50% sulfuric acid and 0.6 mL of 20% KClsolution in 22.9 mL of distilled water to isolatemethylmercury from constituents. One milliliter of

Fig. 2 GC chromatogramobtained from CRM IAEA407 sample by the purgeand trap GC-MS method

Table 1 Determination of methylmercury in blood CRM and commercially available blood materials

Materials Certified value (ng∙g−1) Determined value (ng∙g−1) RSD (%) Recovery (%)

SRM 966 (n=5) 16.4±1.4 16.6±1.6 4.9 93∼105M 0605 (n=3) 7.1a (4.6∼9.5) 5.8±0.8 3.3 86∼93M 0618 (n=3) 26.3a (20.0∼32.3) 23.2±1.6 6.4 79∼91

a Data from the total mercury analysis and the materials were spiked with methylmercury


distillate was added into 10 mL of distilled waterand 5 mL of sodium acetate buffer in a 20-mLsyringe, followed by adding 0.2 mL of sodiumtetraethylborate solution. The combined solution inthe syringe was injected into the sparser connectedon the purge and trap sampler. The conditions ofseparation and detection system were identical withthose for biological samples. The method detectionlimit was found to be 0.05 ng∙g−1 for sedimentsamples. For quality control purpose, CRMs of IAEA405 (IAEA, Vienna, Austria), and BCR CC580(ERM, Brussels, Belgium) were analyzed. The com-monly used distillation/GC-CVAFS method (USEPA2001) was used as a control method to compare theresults obtained by the GC-MS method.

2.5 Ancillary Chemical Measurements for SedimentAnalysis

Weighed sediment samples were heated at 105°C for4 h and reweighed in order to calculate the watercontent. After determining the water content of thesediment, the samples were heated at 550°C over-night. The samples were then reweighed and thepercent organic matter in the sediment was deter-mined by the difference as loss on ignition. The totalsulfur contents were determined using PE 2400 seriesII analyzer (Perkin Elmer, USA). Total mercury forsediment samples were analyzed by EPA method7473 (DMA-80, Milestone Srl) and CRM of MESS-3(NRC, Canada) were analyzed for quality control. For

other metal analysis in sediment, the samples weredigested using EPA method 3051 with HNO3/HCland analyzed by ICP-OES (Optimer 5000DV, PerkinElmer). ERA Soil CRM (ERA, USA) was used forquality control materials.

2.6 Statistical Analyses

SPSS version 10.0 for Windows (SPSS Inc., Chicago,IL, USA) was used for all statistical analysis. Thet test and ANOVA were used to compare bloodmercury and methylmercury concentrations betweengroups. The significant level was set to p≤0.05.Pearson’s correlation analysis to determine statisticalsignificance between total mercury and methylmer-cury concentrations was also undertaken. A multipleregression statistical analysis of the sediment datasetwas used to access the primary correlations betweentotal mercury, methylmercury, %C, %S, and othermetals (Fe, Mn, Cu, Cr, Ni, Zn, and Pb).

3 Results and Discussion

3.1 Optimization and Validation of Purge and TrapGC-MS Method

Due to polarity of methylmercury compound, adsorp-tion processes of methylmercury occur on thestationary phase during the chromatographic analysis,causing peak broadening and ghost peaks (Caricchia

Table 2 Determination of methylmercury in fish CRMs

CRMs Certified values (ng∙g−1) Determined values (ng∙g−1) RSD (%) Recovery (%)

IAEA 407 (n=7) 0.20±0.012 GC-MS 0.19±0.016 3.9 85∼95GC-ECD 0.20±0.022 5.7 92∼101

BCR 463 (n=7) 2.83±0.16 GC-MS 2.89±0.26 4.3 98∼108GC-ECD 2.76±0.32 5.9 91∼107

Table 3 Determination of methylmercury in sediment CRMs

CRMs Certified values (ng∙g−1) Determined values (ng∙g−1) RSD (%) Recovery (%)

ERM CC 580 (n=7) 75.0±4.5 GC-MS 74.5±1.0 14.2 85∼108GC-CVAFS 73.1±1.1 13.8 83∼111

IAEA 405 (n=7) 5.49±0.53 GC-MS 5.27±0.28 5.5 89∼102GC-CVAFS 5.41±0.31 5.76 90∼109


et al. 1997). Polar methylmercury compounds areneeded to convert into nonpolar methylmercurycompounds before chromatographic separation(Young and Josep 1995). In this study, sodiumtetraethylborate, NaBEt4, was used for the derivatiza-tion of polar methylmercury compounds to nonpolarethylated methylmercury compounds. After the de-rivatization reaction, the analytes are purged withhelium at 40 mL∙min−1 to adsorb methylmercury onthe trap. The most consistent sensitivity was obtainedfrom 15 min of purging by monitoring the changes ofanalytical signals. The concentrated methylmercury inTenax trap was introduced to GC-MS and wasanalyzed by using selected ion monitoring mode. Inthe SIM mode the ions of m/z 202, 217, and 246 weremonitored for CH3HgC2H5 and m/z 202, 231, and 260for Hg(C2H5)2. The spectrum in Fig. 2 is the GCchromatogram of CRM IAEA 407 sample, showing

CH3HgC2H5 and Hg(C2H5)2 peaks which are con-tributed from CH3Hg

+ and Hg2+ in the sample.The accuracy of the purge and trap GC-MS method

was evaluated by analysis of CRMs such as SRM 966(human blood), BCR 463 (tuna fish), IAEA 407(fish), ERM CC580 (estuarine sediment), and IAEA405 (sediment). As shown in Table 1, obtained resultsof SRM 966 were 16.6±1.6 ng∙g−1 (95% confidenceinterval with n=5), which were within the certifiedrange and the average RSD was 4.9%. High and lowconcentrations of commercially available blood sam-ples were also analyzed. Although not certified fortheir methylmercury concentrations, these materialwas expected to be available for methylmercuryanalysis because they were spiked with methylmer-cury. The analytical results of fish CRM and sedimentCRM were shown in Tables 2 and 3, which were ingood agreement with the certified values.

Species No of samples T-Hg MeHg %MeHg

Mandarin fish 2 413.1±57.8 219.0±45.7 53

Korean piscivorous chub 5 357.9±75.7 254.2±68.2 86

Skin carp 4 220.4±90.3 206.1±159.9 88

Catfish 7 216.1±106.2 140.8±82.3 68

Skygager 6 191.8±117.6 175.7±118.7 90

Sharpbelly 1 153.4 77.0 50

Northern snake head 6 136.5±62.4 102.3±71.7 69

Largemouth bass 9 116.6±58.8 89.8±53.3 84

Carssius cuvieri 1 151.8 125.1 82

Crusian carp 2 59.9±3.0 42.9±0.7 74

Common carp 11 49.2±34.4 50.3±41.1 69

Leather carp 2 35.1±16.7 24.2±10.2 72

Japanese dace 1 183.16 141.4 77

Table 4 Comparison of totalmercury and methylmercuryconcentrations (ng∙g−1) infreshwater fish

0

100

200

300

400

500

0 500 1000 1500 2000weight (g)

[MeH

g] (

ng

/g)

Snake headSkygagerKorean piscivorius chubCommon carp

Fig. 3 Correlations betweenmethylmercury concentra-tions and fish weight ofspecific species


Additionally, methylmercury concentrations of fresh-water fish and sediment were investigated by the purgeand trap GC-MS method and the analytical results werecompared with those of the GC-ECD for freshwater fishand the GC-CVAFS for sediment. For freshwater fishanalysis, methylmercury concentrations between twomethods were significantly related with Person’s coef-ficient of 0.88 (p<0.05) and no statistically significantdifferences were found by the paired t test (p=0.37>0.05). Subsequently, for the sediment analysis, theaverage ratio of methylmercury concentrations betweenthe methods ([MeHg]CVAFS/[MeHg]GC-MS) was 0.9 andits correlation coefficient was 0.79 (p<0.05). Pairedt test results showed no statistically significant differ-ences (p=0.22>0.05). Thus, the GC-MS method wasused as an alternative for a commonly used the GC-ECD and GC-CVAFS method.

3.2 Analysis of Total Mercury and Methylmercuryin Freshwater Fish

For 57 freshwater fish analysis, total mercury concen-trations were in the range of 20.4∼454 ng∙g−1 (mean175.1 ng∙g−1) and methylmercury concentrations werein the range of 12.9∼424 ng∙g−1 (mean 143.2 ng∙g−1)(Table 4). The relatively high methylmercury concen-

trations (216 to 424 ng∙g−1) were found in predatoryspecies such as Korean piscivorous chub, while lowerconcentrations (12.9 to 59.9 ng∙g−1) were found inpolyphagia species such as common carp.

Generally, methylmercury concentrations in fishare expected to be proportional to trophic level andits size while methylmercury bioaccumulation is afunction of several factors such as uptake (diet) andelimination pathways (excretion, growth dilution)(Bloom 1992; Wagemann et al. 1997; Sveinsdottirand Mason 2005). It is interesting to note thatKorean piscivorous chub showed statistically highmethylmercury concentrations, while their bodyweight was much less than that of other species.Korean piscivorous chub are actually the toppredator and long-lived fish with small body size.Thus, it is likely that Korean piscivorous chub canaccumulate methylmercury over their life span withminimal growth dilution, resulting in high methyl-mercury body burden. Overall, while methylmercuryconcentrations increased as fish weight increased,different species showed different patterns andmethylmercury concentration was significantly cor-related with fish body weight (R=0.58∼0.88, p<0.05) except Largemouth bass (Fig. 3). Largemouthbass are carnivores and their food preference iscrayfish, minnows, and frogs. Despite the smallnumber of samples, the relationship between meth-ylmercury concentration and body weight weredivided into two groups. As seen in Fig. 4, the resultclearly showed a distinct pattern that methylmercurybody burden was much higher in Bass 2, comparedto Bass 1, even though their body weights werecomparable. Additionally, two groups were collectedfrom different locations, i.e. Bass 1 from Ju-Namreservoir and Bass 2 from Dam-Yang artificialreservoir. The average concentrations of waterquality-related parameters from 2002 to 2006 wereobtained from the data of water quality monitoringnetworks in Korea. As shown in Table 5, Ju-Namreservoir showed more eutrophic characters with high

0

50

100

150

200

250

100 300 500 700weight (g)

[MeH

g]

(ng

/g)

Bass 1Bass 2

Fig. 4 Correlations between methylmercury concentrationsand fish weight of Largemouth bass: Bass 1 from Ju-Namreservoir and Bass 2 from Dam-Yang reservoir

Table 5 Water quality of Ju-Nam and Dam-Yang reservoirs during 2002~2006

Reservoirs Temp (°C) pH DO (mg/L) Conditions(μmho/cm)

COD (mg/L) SS (mg/L) TN (mg/L) TP (mg/L) Chlorophyll A(mg/m3)

Ju-Nam 17±1 7.6±0.2 8.5±0.6 210±25 7.6±0.5 11.5±4.0 1.28±0.24 0.07±0.02 21.7±8.0

Dam-Yang 13±2 7.5±0.3 9.2±0.8 64±15 2.5±0.4 2.0±0.6 1.65±0.71 0.04±0.01 6.0±4.0


concentrations of total phosphorous, chlorophyll a, andchemical oxygen demand than Dam-Yang reservoirand these indicators are generally related with fishgrowth rates. Lower mercury level in fish from Ju-Namreservoir might be related to dilution effects with fasterfish growth and longer food chain due to easy foodavailability than Dam-Yang reservoir, even though it isdifficult to conclude without comparison of mercurylevels in water and sediment (Sveinsdottir and Mason2005; Hutchson et al. 2008).

3.3 Analysis of Total Mercury and Methylmercuryin Sediment

Eighty-one sediment samples were collected fromvarious sites in Korea to understand the impact of

contaminated sediments on regional scale. Totalmercury concentrations in sediment were in the rangeof 2.43∼1,564.17 ng∙g−1 and methylmercury concen-trations were in the range of N.D.∼5.95 ng∙g−1.Methylmercury were found below the detection limitof 0.05 ng∙g−1 in 13 sediment samples. The propor-tion of methylmercury to total mercury in sedimentsamples (n=68) were 2.52±2.39%.

Methylmercury concentrations and %MeHg insediment are useful indicators reflecting the changesof mercury loading, bioaccessibility of inorganicmercury, and changes in bacterial activities. %MeHgis generally known to be less than 5% and the rangein %MeHg observed in this study (0.86∼3.27%) issimilar to values reported by Stephenson et al. (2008)and Krabbenhoft et al. (2006).

[T-H

g]

(ng

/g)

0

100

200

300

400

500

[MeH

g]

(ng

/g)

0

1

2

3

4

5

%M

eHg

0

2

4

6

8

10

[T-Hg][MeHg]%MeHg

Plant effluent

(n=8)

UrbanStream(n=5)

River 1(BOD<3)(n=23)

River 2(BOD>3)(n=23)

Lake &Reservoir

(n=13)

[T-H

g]

(ng

/g)

0

100

200

300

400

500

[MeH

g]

(ng

/g)

0

1

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%M

eHg

0

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[T-Hg][MeHg]%MeHg

Plant effluent

(n=8)

UrbanStream(n=5)

River 1(BOD<3)(n=23)

River 2(BOD>3)(n=23)

Lake &Reservoir

(n=13)

Fig. 5 Comparison of totalmercury, methylmercury,and %MeHg in sediments

[T-Hg] (ng/g)1 10 100 1000 10000

[MeH

g]

(ng

/g)

0.01

0.1

1

10

100

Plant effulentUrban streamRiver 1(BOD<3)River 2(BOD>3)Lake & Reservoir

Fig. 6 Plots of the correla-tion between total mercuryand methylmercuryconcentrations in sediments


However, there was also clear differences in %MeHgobserved in different sampling sites. As shown in Fig. 5,the lake and reservoir sites had comparatively highmethylmercury concentration (0.94 ng∙g−1) and lowtotal mercury concentrations (27.73 ng∙g−1), whereassediments from the effluent sites were relatively high intotal mercury (433.4 ng∙g−1) but only moderate inmethylmercury (1.78 ng∙g−1). These results areexpressed as the high %MeHg of lake and reservoirsites (3.27%) compared to plant effluent sites (0.86%).

Recent studies showed that atmospheric totalgaseous mercury levels were around 2.63∼4.37 ng/m3

in Korean Peninsula and were enhanced by long-range transport from East Asia (Hong et al. 2007;Choi et al. 2009). Sulfate ions, one of the limitingfactors for methylation, were found to be the majorcontributors of the wet deposition in Korea, whichwas mainly contributed by acidic precipitation (Han et

al. 2008). Thus, methylation in sediment was possiblyenhanced by newly uploaded mercury and highsulfate concentrations from atmospheric deposition.

The concentrations of total mercury and methyl-mercury showed statistically significant correlation(RT-Hg-MeHg=0.41, p<0.05), which was a similarvalue (RT-Hg-MeHg=0.40) of previous study (Benoit etal. 2003). However, the relationship between ecosys-tem (categorized as plant effluent, urban stream, riverand lake, and reservoir) was not included in this study(Fig. 6).

To access the interrelationships between methyl-mercury and other chemical parameters in sediment,organic contents, sulfur contents, and other metals(Cu, Ni, Pb, Zn, Fe, and Mn) were examined and thecorrelations matrix was summarized in Table 6. Whilethere was an indication of a correlation between totalmercury and sediment organic content, it appeared to

Parameter T-Hg MeHg Organic content, % %S

T-Hg 1 0.410 0.408 0.481

MeHg 0.410 1 0.283 NC

Organic content, % 0.408 0.283 1 0.667

%S 0.481 NC 0.667 1

Cr 0.388 NC 0.504 0.773

Ni 0.455 NC 0.622 0.893

Zn 0.667 NC 0.587 0.720

Pb 0.509 NC 0.648 0.911

Fe NC 0.285 NC NC

Mn NC NC NC NC

Table 6 Correlation tablefor the sediment dataset;values listed are correlationcoefficients obtained from amultivariate analysis

NC no correlation

Cr Ni Cu Zn Pb Fe(x100) Mn

[Met

al]

(mg

/kg

)

0

200

400

600

800

1000

1200

1400

1600

1800Plant effluent Urban stream River 1 River 2 Lake & Reservoir

Fig. 7 Heavy metalconcentrations incatergorized sediment(mean±1SD)


be nonlinear. The correlation coefficients, r of thisstudy (RT-Hg-%C=0.48; RMeHg-%C=0.28) showed simi-lar values with those (RT-Hg-%C=0.49; RMeHg-%C=N.C.)found by Mason et al. (Mason and Lawrence 1999).Generally, recent researches suggested that the organiccarbon contents control mercury concentrations andorganic matter complexation/adsorption is the mostimportant phase controlling mercury distribution insurface sediments, except at elevated mercury concen-tration. At high mercury concentration sites, the effectby input sources is likely more important thansediment characteristics (Benoit et al. 1998; Masonand Lawrence 1999).

Other metals concentrations of sediment samplesare given in Fig. 7, showing that total metalconcentrations of plant effluent were also relativelyhigh compared to those of other sites except for theconcentrations of Fe and Mn. Cr, Ni, Zn, Pb, and Hgare all co-correlated and all correlate with %S and %organic contents while methylmercury does notcorrelate significantly with either. These resultsimplied that multielement anthropogenic sources arecontrolling the metal concentrations as well as totalmercury to a large degree whereas methylmercury hasdifferent source inventories than other metals.

4 Conclusion

This study showed that the newly adapted purge andtrap GC-MS method provided a reliable measurementof methylmercury in biological and sediment samplesand can be successfully used as an alternative methodfor commonly used GC-CVAFS or ECD detectionmethod. The present work also described the currentstatus of total mercury and methylmercury levels infreshwater fish and sediment from Korean peninsula.Even though, the current study is preliminary andcannot represent the mercury contamination status inKorea, it is worthy to evaluate the degree ofmethylmercury contaminations in sediment andfreshwater fish since recent study showed the totalmercury level of blood in Korean was much higherthan those in other countries (investigated by KoreaMinistry of Environment in 2005). Thus, much morein-depth and intensive mercury monitoring studiesare required to examine important factors controllingmethylmercury production in sediments and accu-mulation in fish and human.

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Mercury and Methylmercury in Freshwater Fish and Sediments in South Korea Using Newly Adopted Purge and Trap GC-MS Detection Method