한국해양환경. 에너지학회지 Journal of the Korean Society for Marine Environment and Energy Vol. 19, No. 1. pp. 25-36, February 2016 http://dx.doi.org/10.7846/jkosmee.2016.19.1.25 ISSN 2288-0089(Print) / ISSN 2288-081X(Online) Original Article 시화호유역하천퇴적물에서의중금속오염도평가에관한연구 정혜령 1 김경태 1,2 김은수 3 나공태 1,2, 이승용 1 1 한국해양과학기술원환경기반연구센터 2 과학기술연합대학원대학교해양융합과학과 3 한국해양과학기술원해양관측 자료실 Sediment Quality Assessment for Heavy Metals in Streams Around the Shihwa Lake Hyeryeong Jeong 1, Kyung-Tae Kim 1,2, Eun-Soo Kim 3, Kongtae Ra 1,2, and Seung-Yong Lee 1 1 Marine Chemistry & Geochemistry Research Center, Korea Institute of Ocean Science and Technology (KIOST), Ansan 15627, Korea 2 Department of Integrated Ocean Sciences, Korea University of Science and Technology (UST), Ansan 15627, Korea 3 Ocean Observation & Information Section, Korea Institute of Ocean Science and Technology (KIOST), Ansan 15627, Korea 요 약 본연구에서는시화호유역하천퇴적물내중금속의시 공간적인분포특성을조사하였으며다양한오염지수를활용하여오염도및위해영향을평가하였다. 조사지역별로살펴보면 1간선수로 (S1) 에서는 Co, Zn 및 Cd이최대농도를보였으며, 2간선수로 (S2) 와 3간선수로 (S3) 는각각 Ni과 As, 4간선수로 (S4) 는 Cr, Cu, Pb 및 Hg이최대농도를나타내고있어조사지역에따라오염되는중금속원소가다른특성을보였다. 산업지역내하천에서의중금속농도가농업 / 도심지역에비해 3.3(Co)~83(Cu) 배높은결과를보였다. 농집지수 (Igeo) 를통한각각의중금속원소의오염도평가는 Cd과 Cu는 highly polluted, Zn, Pb은 moderately to highly polluted의오염상태를나타냈다. 본연구에서분석된중금속을종합적으로고려한오염부하지수 (PLI) 는산업지역이 10.5로심각한오염상태였으며, 농업 / 도심지역은오염되지않은것으로나타났고, 하계조사시기가다른조사시기에비해상대적으로오염된결과를보였다. 퇴적물기준과의비교를통하여산업지역내하천은 Cr, Ni, Cu, Zn 및 Pb의 85% 가 PEL을초과하는것을알수있었다. mpelq와 SQI를통하여퇴적물내중금속의종합적인오염도및위해영향을고찰한결과, 산업지역내하천퇴적물은독성영향이크며매우나쁨 (very poor) 에해당되는오염상태를보였으며, 하계조사시기에오염도가심해지는경향을나타내었다. Abstract Heavy metals in the stream sediments around Shihwa Lake were studied not only to investigate the characteristics of spacio-temporal distribution but also to assess the pollution degree and ecological risk using various pollution indices. Among metals, Zn had the highest values (1,311 mg/kg) and Hg showed the lowest value (0.261 mg/kg). The order of mean concentrations (mg/kg) of metals was Zn>Cu>Pb>Cr>Ni>Co>As>Cd>Hg in stream sediments around Shihwa Lake. Metal concentrations showed different pollution pattern with industrial region, indicating that these metals originated from different sources and industrial region had higher metal concentration than rural/urban regions. The results of geoaccumulation index (Igeo) showed that the stream sediments were significantly polluted with Cd, Cu, Zn and Pb, indicating moderately to highly polluted by these metals. According to PLI consideration, industrial region was more seriously polluted by metals whereas an rural/urban region was not polluted. About 85% of sampling site for Cr, Ni, Cu, Zn and Pb from industrial regions were exceeded the PEL values. The mpelq and SQI values derived from PEL of industrial region were classified as highly toxic and very poor and metal pollution level tend to be worse in wet season. This indicates that the industrial activities and stromwater runoff represents an important sources of heavy metals around Shihwa Lake. Keywords: Heavy metal( 중금속 ), Pollution( 오염 ), Stream sediment( 하천퇴적물 ), geo-accumulation index( 농집지수 ), Pollution load index( 오염부하지수 ) Corresponding author: ktra@kiost.ac.kr 25
26 정혜령 김경태 김은수 나공태 이승용 1. 서론 중금속은풍화작용, 대기침적혹은도심및산업지역에서의폐기물유출등다양한자연적기원및인위적인기원에의하여환경으로유출된다 (Dawson and Macklin[1998]; Demirak et al.[2006]). 또한중금속은환경내에서독성, 지속성및분해되지않는특성으로인해심각한오염물질로구분되고있다 (Fang and Hong[1999]; Klavins et al.[2000]; Tam and Wong[2000]; Yuan et al.[2004]; Pekey[2006]). 미국환경청 (US EPA) 은비소와크롬은발암등급 A, 카드뮴과납은발암등급 B로우선관리대상오염물질로구분하여관리하고있다 (US EPA[1999]). 중금속은환경내에서용존상태및입자상태로존재하며, 용존상태의중금속은입자의표면에흡착하여저층으로퇴적되어제거된다. 퇴적물내중금속은수환경에비해농도가높으며시 공간에대한변화가작기때문에연구지역의오염상태를평가하는데중요한역할을한다 (Hillier et al.[2001]; Ettler et al. [2006]; Pekey[2006]). 중금속에오염된퇴적물은물리화학적인환경변화에의해수층으로재용출되기때문에중금속에대한잠재적인오염원으로인식되고있다 (Adams et al.[1992]; Soares et al.[1999]; Mucha et al.[2003]). 도심및산업지역의중금속은차량배기가스, 산업분진, 화석연료사용및산업시설의부식에의하여발생하며지붕, 도로및지표면에축적되어있는오염물질은강우시제거되어담수환경및연안환경으로유출된다 (Brown and Peake[2006]; Wang et al.[2015]). 강우유출수는중금속등다양한오염물질에오염되어있으며, 강이나하천을통하여주변수환경에오염물질의주요한공급원으로생태계에심각한악영향을미치고있다 (USEPA[1983]; Sansalone and Buchberger[1997]; Smullen et al.[1999]; Buffleben et al.[2002]). Schiff et al.[2000] 는미국캘리포니아도심지역의경우, 강우유출수의형태로배출되는비점오염유출량은하수처리장과산업폐수의점오염원보다높다고보고하였다. 시화호는 5개의특별관리해역중하나이며안산및시화산업단지생성및운영이후중금속오염이점차적으로심각해졌으며, 다른해역에비해높은중금속오염을나타내고있다 (Ra et al.[2011]; [2013a]; [2013b]). 현재시화호는조력발전소가동및연안오염총량관리제도의시행으로인하여수질은개선되고있으나여전히산업단지인근퇴적물내중금속오염이보고되고있다 (MOF[2014]). 시화호유역에는 10개의하천이존재하며, 이중 5개하천은안산및시화산업단지를, 2개하천은안산시도심지역을, 3개하천은농업지역을대표하고있으며중금속오염이심각한것으로보고한바있다 (Kim et al.[2003]). 특히안산및시화산업단지는현재 18,840 개의기계, 전기 전자, 석유화학등의업체가가동중에있으며이들지역을관통하여흐르는 5개하천 (1~4간선수로및신길천 ) 의길이는약 18.2 km로하천퇴적물에는상당량의중금속이축적되어있으며, 강우시에비점오염형태로시화호로직접유출될것이나시 공간에따른하천퇴적물내중금속오염에대한자료는부족한실정이다. 강우유출수에의한중금속은용존상태혹은입자상태로유출되며 (Harrison and Wilson[1985]; Pitt et al.[1995]), 이전연구에의하면시화산업단지에존재하는 7개우수토구중하나로소유역면적이 2.94 km 2 에불과한 3토구의경우 1회강우시유출되는용존형태의중금속은 0.07(Cd)~58.92(Zn) kg이었으며, 입자상태는 0.24(Cd)~ 187.33(Cu) kg이유출되는것으로나타났다 (Ra et al.[2014]). 안산및시화산업단지의유역면적은 31.9 km 2 이며, 비강우시뿐만아니라강우시비점오염형태로유출되는중금속오염은매우심각할것으로판단된다. 따라서본연구에서는시화호내측유역하천퇴적물내중금속농도의시 공간적인분포특성에대하여조사하였다. 또한농집지수 (geo-accumulation index) 및오염부하지수 (pollution load index) 를활용하여중금속오염도를평가하였으며, mpelq(mean PEL quotient) 와 SQI(sediment quality index) 를통하여퇴적물내중금속의종합적인오염도및독성영향을평가하였다. 2. 재료및방법 2.1 시료채취및분석방법 시화호로유입되는제1간선수로 (S1), 제2간선수로 (S2), 제3간선수로 (S3), 제4간선수로 (S4), 신길천 (S5), 화정천 (S6), 안산천 (S7), 장전보 (S8), 반월천 (S9), 동화천 (S10), 삼화천 (S11) 등 10개하천과반월-동화-삼화천이합류하여흐르는 1개지역 ( 장전보 ) 에대하여 2014년 3월 ~10월총 10회에걸쳐하천의말단에서표층퇴적물을채취하였다 (Fig. 1). 채취된하천퇴적물은동결건조 (Labconco Freezone 6) 및자동분쇄기 (Fritsch Corp. Pulverisette 6) 로분쇄하여분석시까지산세척된폴리에틸렌시료병에넣어보관하였다. 하천퇴적물내중금속분석은분쇄및균질화된시료약 0.1g을테프론산분해용기 (digestion bomb) 에넣고고순도의불산, 질산및과염소산을넣은뒤가열판에서 180 o C로 24시간가열하여완전분해를실시하였다 (Windom et al.[1989]). 용기내의시료가완전히분해되면 1% 질산으로재용해시킨뒤원소에따라적절하게희석하여 ICP MS(Thermo Elemental X 7) 로분석하였다. 퇴적물내수은은미국환경청에기초를둔열분해와금아말감법 (US EPA Method 7473) 을이용한자동수은분석기 (Hydra C) 를이용하여측정하였다. 분석된퇴적물중금속자료의정확도를검증하기위하여퇴적물표준물질인 MESS-3(National Research Council, Canada) 를시료와함께처리하여측정하였으며, Co(93.9)%~As(104.4)% 로매우양호한결과를얻었다 (Table 1). 2.2 퇴적물내중금속오염도및위해성평가시화호하천퇴적물내중금속원소각각의오염도를평가하기위하여농집지수 (geo-accumulation index) 를활용하였다. 농집지수는퇴적물내금속오염도를평가하는하나의방법으로 Muller[1969] 가제안하였으며, 각금속에대하여총 7개등급으로오염여부를세분화하였고다음과같은식에의하여계산된다.
시화호유역하천퇴적물에서의중금속오염도평가에관한연구 27 Fig. 1. Location of sampling sites in the stream sediments around Shihwa Lake. The circle and square symbols represent industrial and rural/ urban regions, respectively. Table 1. Analytical results for Certified Reference Material MESS-3 (n=9) from National Research Council of Canada Metals MESS-3 (mg/kg) Certified value Measured value Recoveries Al (%) 8.59 ± 0.23 8.70 ± 0.41 101.2 Cr (mg/kg) 105 ± 4 104 ± 2 99.2 Co (mg/kg) 14.4 ± 2.0 13.5 ± 0.5 93.9 Ni (mg/kg) 46.9 ± 2.2 45.3 ± 1.6 96.7 Cu (mg/kg) 33.9 ± 1.6 34.4 ± 2.5 101.4 Zn (mg/kg) 159 ± 8 154 ± 3 97.0 As (mg/kg) 21.2 ± 1.1 22.1 ± 0.9 104.4 Cd (mg/kg) 0.24 ± 0.01 0.24 ± 0.01 101.7 Pb (mg/kg) 21.1 ± 0.7 21.7 ± 0.5 102.3 Hg (mg/kg) 0.091 ± 0.009 0.090 ± 0.001 99.3 C Igeo = Log n 2 ---------------- 1.5 B n 여기서, C n 과 B n 은각각중금속의측정및배경농도이며 1.5는지각기원에의한영향을보정하기위하여사용되었다. 본연구에서배경농도는지각의평균농도를이용하였다 (Rudnick and Gao[2003]). Igeo 값이 0보다작으면 background concentration, 0-1이면 unpolluted, 1-2면 moderately to unpolluted, 2-3이면 moderately polluted, 3-4면 moderately to highly polluted, 4-5면 highly polluted, 5 이상이면 very highly polluted의오염도를의미한다. 농집지수는중금속의개별오염도를평가하기때문에퇴적물내존재하고있는중금속의종합적인오염도및위해성을평가하기위하여, pollution load index(pli), mean PEL quotient(mpelq), sediment quality index(sqi) 를이용하였다. 오염부하지수 (Pollution load index; PLI) 는중금속의종합적인오염부하를평가하는데사용되며본연구에서는 9개중금속원소를 이용하여계산하였다 (Tomlinson et al.[1980]). n PLI = ( C 1 /B 1 ) ( C 2 /B 2 ) ( C n /B n ) C 1 ~C n 은각원소의농도, B 1 ~B n 은해당원소의배경농도로나타낸다. PLI 값이 1 이상의경우에는인위적인오염이존재하지만 PLI 값이 1보다작으면오염이존재하지않는것을의미한다. 배경농도는농집지수와같이지각의평균농도를이용하였다 (Rudnick and Gao[2003]). 앞서언급한농집지수 (Igeo) 및오염부하지수 (PLI) 는개별혹은전체중금속의오염정도를평가하는것으로퇴적물내중금속이해양생물에위해영향을미치는여부는판단하지못하는단점이있다. 따라서퇴적물내종합적인중금속의독성영향및위해성평가를위한 mpelq(mean PEL quotient) 를이용하였고이는다음과같은식에의하여계산된다 (Fairy et al.[2001]; Hwang et al.[2008]). 하천퇴적물내중금속의 PEL 값은 Smith et al.[1996] 의값을이용하였다. Mean PEL Quotient = ( C /PEL i i)/n 여기서, C i 와 PEL i 는각중금속의농도와 PEL 값을사용하여 n은사용된미량금속원소의개수이며, 본연구에서는 PEL 기준이존재하는 8개원소 (Cr, Ni, Cu, Zn, As, Cd, Pb, Hg) 를이용하였다. mpelq값이 0.1이하는독성영향이없으며, 0.1~1.0은독성영향이작지만존재하고 1 이상의경우에는독성영향이매우큰것으로구분된다 (Fairy et al.[2001]). 퇴적물내오염도평가를위해서는다양한지수를활용하고있으나, 퇴적물내존재하는다양한오염물질을모두고려한평가방법은앞서언급한오염부하지수 (PLI) 또는 mpelq 를활용하고있다. 그러나이들방법은오염유무판단과독성영향이있는지여부를평
28 정혜령 김경태 김은수 나공태 이승용 가하는것이기때문에분석된오염물질의농도및퇴적물관리기준과의비교등을포함하는캐나다 CCME(Canada Council of Ministers of the Environment) 에서제안한수질지수를활용하여퇴적물의질적평가를실시하였으며, mpelq와동일하게 Co를제외한 PEL 기준이존재하는 8개금속원소를이용하였다 (CCME[2001]; Grapentine et al.[2002]). F 1 F 2 Numnber of failedvariables = ------------------------------------------------------------------ Total Number of variables 100 = Scope mdnc = --------------------------------------- 0.01mdnc + 0.01 = Amplitude p non compliance i 1 mdnc = i = ------------------------------------------------------ Number of tests non compliance i failed test value = --------------------------------------- i guideline i 1 mdnc = Mean degree of non compliance i = Individual guideline P = Total number of guideline used 2 2 F SQI 100 1 +F ------------------ 2 = 2 계산된 CCME_SQI 값이 0-44면매우나쁨 (very poor), 45-59면나쁨 (poor), 60-79면보통 (fair), 80-94면좋음 (good), 95-100이면매 우좋음 (excellent) 의 5개등급으로나뉜다 (Grapentine et al.[2002]; Marvin et al.[2004]). 3. 결과및고찰 3.1 조사지역에따른중금속의농도분포특성 시화호유역에서산업지역, 도심지역및농업지역에산재되어시화호로유입되는 11개하천에대한중금속농도분포는 Table 2와 Fig. 2에나타냈다. 하천퇴적물내 Al은반월천에서 9.5% 의가장높은평균농도를보이고있었으며장전보에서 4.6% 의평균농도를보여지역에따라약 2배의농도차이가존재하고있었다. 입도와상관이높은 Al 분석을통하여반월천에서는세립한퇴적물이존재하며장전보에서는상대적으로조립한퇴적물이존재하는것을알수있었다. Cr은 4간선수로에서 1,144 mg/kg의가장높은농도를보였으며, 입도가가장조립한것으로나타난장전보에서 22 mg/kg의농도를보여조사지역에따라약 53배의농도차이를보이고있었다. 4간선수로에서 Cr의농도는조사시기에따라 131~3,313 mg/kg의큰농도변화를나타냈으며, 하계조사시기인 7월과 8월조사에서 3,000 mg/kg 을초과하는높은농도를보였다. Co의평균농도는 102.7 mg/kg으로 1간선수로에서가장높았으며, Cr과마찬가지로장전보에서 3.9 mg/kg 으로최소농도를나타냈다. Ni은 2간선수로에서 201 mg/kg의최 Table 2. Mean and range of heavy metal concentrations (mg/kg) in the stream sediments around Shihwa Lake TOC Al Cr Co Ni Cu Zn As Cd Pb Hg % % mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg S1 S2 S3 S4 S5 S6 S7 S8 S9 S10 S11 Industrial Mean Rural/Urban Mean 4.86 8.1 (0.24-11.54) (5.4-10.9) 4.30 (0.46-9.55) 1.79 (0.56-6.19) 1.70 (0.39-4.82) 1.13 (0.33-3.13) 0.53 (0.22-0.98) 0.27 (0.06-0.74) 0.14 (0.06-0.36) 0.68 (0.50-0.85) 0.54 (0.34-0.61) 0.73 (0.46-0.87) 7.3 (4.7-9.0) 7.4 (4.9-8.7) 7.2 (5.4-14.0) 6.8 (5.6-7.8) 6.2 (5.4-7.7) 6.3 (5.9-6.8) 4.6 (3.9-6.1) 9.5 (8.3-14.3) 8.3 (7.4-9.6) 8.8 (6.9-10.1) 2.76 7.4 (0.24-11.54) (4.7-14.0) 0.48 (0.06-0.98) 7.3 (3.9-14.3) 243 (46-398) 838 (146-1,882) 290 (180-545) 1144 (131-3,313) 274 (95-692) 39 (32-47) 48 (33-105) 22 (15-35) 81 (68-101) 73 (49-83) 84 (48-106) 558 (46-3,313) 58 (15-106) 102.7 (13.0-167.2) 17.1 (9.0-25.6) 16.0 (7.2-24.8) 19.4 (10.2-35.8) 25.2 (20.4-34.3) 11.3 (8.7-14.7) 7.5 (6.5-8.8) 3.9 (2.8-6.8) 14.6 (12.2-15.9) 13.2 (9.3-14.6) 14.6 (8.5-17.2) 36.1 (7.2-167.2) 10.9 (2.8-17.2) 88 (18-123) 201 (56-464) 1,468 (98-7,697) 2,823 (319-7,651) 5,580 (477-12,348) 1,341 (555-2,669) 20.8 (4.9-35.9) 17.1 (10.1-23.1) 12.12 (1.84-17.94) 1.41 (0.60-4.14) 956 (66-2,834) 274 (63-509) 93 1,115 1,816 41.4 2.07 952 (62-229) (100-6,652) (500-8,689) (10.0-265.7) (0.57-8.00) (88-6,324) 174 2,831 4,635 16.6 9.11 2,522 (38-401) (201-9,891) (469-15,674) (6.5-43.6) (2.37-24.87)(107-9,246) 188 721 446 6.9 1.85 118 (131-280) (211-1,848) (217-867) (2.7-10.1) (0.63-4.15) (45-277) 20 (16-24) 20 (13-45) 9 (7-15) 34 (28-37) 29 (20-33) 35 (23-42) 149 (18-464) 25 (7-45) 24 (18-35) 16 (13-23) 9 (5-15) 26 (21-59) 19 (16-23) 36 (21-67) 1,791 (98-9,891) 22 (5-67) 133 (99-202) 79 (56-104) 59 (33-110) 101 (85-126) 116 (84-207) 121 (92-156) 2,764 (217-15,674) 102 (33-207) 5.6 (3.2-8.1) 3.3 (0.6-7.0) 1.7 (0.1-4.2) 9.1 (6.4-13.2) 7.4 (5.3-11.8) 9.9 (7.7-11.9) 0.24 (0.18-0.35) 0.14 (0.08-0.24) 0.05 (0.01-0.08) 0.10 (0.08-0.13) 0.15 (0.08-0.38) 0.18 (0.10-0.31) 20.5 5.31 (2.7-265.7) (0.57-24.87) 6.2 (0.1-13.2) 0.14 (0.01-0.38) 36 (29-48) 35 (28-50) 24 (16-30) 31 (28-38) 30 (25-44) 39 (31-54) 964 (45-9,246) 32 (16-54) 0.787 (0.032-3.126) 0.157 (0.019-0.278) 0.084 (0.041-0.203) 1.670 (0.132-5.300) 0.090 (0.021-0.190) 0.014 (0.008-0.025) 0.007 (0.003-0.011) 0.005 (0.003-0.007) 0.018 (0.012-0.033) 0.011 (0.009-0.017) 0.024 (0.013-0.040) 0.558 (0.019-5.300) 0.013 (0.003-0.040)
시화호유역하천퇴적물에서의중금속오염도평가에관한연구 29 Fig. 2. Comparison of mean concentrations for total organic carbon and heavy metals in the creek sediments around Shihwa Lake. Dashed and solid lines indicate the TEL (threshold effect level) and PEL (probable effect level) of sediment quality guideline by Smith et al. (1996), respectively. 대농도를나타내고있었으며, Cu는 2간선수로와 4간선수로에서각각 2,823 mg/kg와 2,831 mg/kg의최대농도를보여조사지역에따라최대농도를보이는중금속원소가다른특성을보였다. Ni과 Cu 모두다른중금속과마찬가지로장전보에서최소농도를나타내고있었으며, Cu는조사지역에따라 329배의큰농도차이가있음을알수있었다. Zn은조사시기에따라 477~12,348 mg/kg의매우큰농도범위를보였으며, Cr과마찬가지로하계조사시기인 7월에최대값을나타내고있었다. Zn은 Co와마찬가지로 1간선수로에서 5,580 mg/kg의최대농도를보였고장전보에서 59 mg/kg의최소농도를보여지역에 따라 95배의큰농도차이가존재하고있었다. 4간선수로에서도 Zn의평균농도는 4,635 mg/kg 으로상대적으로높은특징을보이고있었다. As는 3간선수로에서 41.4 mg/kg의최대농도를보여앞서언급한금속원소와는최대농도를보인조사지역이다른것을알수있었다. Cd은 Co 및 Zn과마찬가지로 1간선수로에서 12.1 mg/kg의가장높은농도를보였으며, 최소농도를보인장전보 (0.05 mg/kg) 와는 238배의농도차이가존재하고있었다. Pb은 4간선수로에서 2,522 mg/kg 의최대농도를보였으며조사시기에따라 107~9,246 mg/kg의큰농도범위를나타냈으며, 10회의조사시기중 7월조사가가장높은특징을나타내고있었다. Hg은 Cr, Cu 및 Pb과마찬가지로 4간선수
30 정혜령 김경태 김은수 나공태 이승용 로에서 1.67 mg/kg의최대농도를보였으며, 장전보의 0.005 mg/kg과는 300배이상의농도차이가있는것으로나타났다. 산업단지인 1간선수로에서는 Co, Zn, Cd이최대농도를보였으며, 2간선수로는 Ni, 3간선수로는 As, 4간선수로는 Cr, Cu, Pb, Hg 이최대농도를나타내고있어, 하천주변에존재하는산업형태에따라오염되는중금속원소가상이함을알수있었다. 원소에따라약간의차이는있으나몬순기후의영향으로강우량및강우빈도가높은하계조사시기에상대적으로높은중금속농도를나타내고있었다. 4간선수로 (S4) 퇴적물내 Cu의농도는 3월 ~7월조사시기에는 201~435 mg/kg의농도를보였으나, 7월 21일, 8월 5일, 8월 27일조사에서는각각 9,891 mg/kg, 7,742 mg/kg, 8,125 mg/kg으로농도가급격히증가하였으며, 10월조사에서는 366 mg/kg으로농도가감소한결과를보였다. 이는산업시설주변및도로등의노면에축적되어있는중금속물질이하계조사시기강우유출수에의해하천으로유입된것으로생각된다. 본연구에서조사한시화호유역하천을주변지역의토지이용특성에따라산업지역 (S1~S5) 과농업 / 도심지역 (S6~S11) 으로구분하여중금속농도비교를실시하였다 (Table 2). Al의농도는산업지역과농업 / 도심지역이각각 7.4% 와 7.3% 의평균농도로지역에따른농도차이는보이지않고있었다. 퇴적물내총유기탄소의평균농도는산업지역이 2.76% 로농업 / 도심지역의 0.48% 에비해 5.8배높아산업활동에의하여발생한유기물이하천으로유입된것을알수 있었다. 퇴적물내중금속농도는 Al을제외한모든금속원소에서산업지역이농업 / 도심지역에비해높은결과를보였다. Co, As, Ni 및 Cr은산업지역에서의평균농도가농업 / 도심지역에비해 3.3~9.7배높은결과를보였으며 Cu는산업지역에서의평균농도가농업 / 도심에비해 83배높은결과를보여, 중금속원소중가장심한오염을나타내고있었다. 나머지중금속원소 (Zn, Cd, Pb 및 Hg) 역시산업지역이 27.2~42.1배높은결과를보였다 (Table 2). 결과적으로산업지역을관통하여흐르는하천퇴적물내에는심각한중금속오염이진행되고있음을알수있었다. 시화호유역하천퇴적물내중금속농도를국내 외오염이진행되고있는강이나하천퇴적물과비교를실시한결과, 산업지역뿐만아니라농업및도심지역을포함하여평균농도를계산했음에도 Ni을제외한모든중금속이시화호유역이가장높은농도를나타내고있었다 (Table 3). 산업지역만을고려하면 Ni 역시다른강이나하천에비해중금속에매우오염되어있는것으로나타났다. 또한시화호표층퇴적물에비해 1.3(As)~9.1(Cu) 배높은중금속농도를나타내고있어, 시화호중금속오염의주요한공급원이하천임을알수있었다. 본연구에서는분석한 TOC 및중금속간의상관관계분석결과를 Table 4에나타냈다. TOC는 As를제외한모든항목에서, Al은 Co와 As를제외한모든항목에서양호한양 (+) 의상관성을보였다. Co는 TOC, Zn, Cd을제외한다른중금속원소와는상관성이없는것으로 Table 3. Comparison of metal concentrations (mg/kg) in stream sediments around Shihwa Lake and other regions in the literature Cr Co Ni Cu Zn As Cd Pb Hg Reference Shihwa stream 285.1 22.3 81.0 826.1 1,311.6 12.7 2.5 456.0 0.261 This study Busan stream - - 10.7 56.6 199.6-1.2 35.7 - Lee et al.[2010] Kumho River 76.3 18.9 112.8 183.3 365.8-4.0 243.0 - Kim et al.[2006] Geum River 46.4-13.6 16.2 81.4 3.8 0.2 14.8 0.058 Lee et al.[2014] Alabama stream 15.8-8.0 10.5 25.3 5.6 0.1 20.6 0.151 Lafabrie et al.[2013] Day River 102.3 - - 108.6 100.1-1.3 109.0 - Barakat et al.[2012] Huaihe River - - 32.8 31.3 183.6 - - 53.4 - Wang et al.[2015] Ogunpa River 42.9 16.0 14.5 72.14 274.0-1.7 133.0 - Ladigbolu et al.[2011] Tigris River 84.8-145.6 344.6 203.1 4.6 1.8 265.3 - Memet Varol [2011] Shihwa Lake 86.8 13.2 38.4 91.2 233.0 9.5 0.4 54.3 0.064 Ra et al.[2013] Table 4. Pearson s correlation (r) between TOC and metals in the stream sediments around Shihwa Lake. Bold indicates that correlation is significant at the 0.01 level (2-tailed) TOC Al Cr Co Ni Cu Zn As Cd Pb Hg TOC - Al 0.270 - Cr 0.555 0.308 - Co 0.669 0.217 0.120 - Ni 0.646 0.249 0.792 0.219 - Cu 0.642 0.336 0.870 0.152 0.766 - Zn 0.692 0.324 0.700 0.635 0.585 0.715 - As 0.241 0.139 0.216 0.139 0.208 0.233 0.254 - Cd 0.655 0.280 0.624 0.726 0.538 0.619 0.936 0.217 - Pb 0.426 0.338 0.792 0.199 0.604 0.810 0.853 0.243 0.739 - Hg 0.363 0.371 0.802 0.238 0.561 0.779 0.813 0.193 0.794 0.881 -
시화호유역하천퇴적물에서의중금속오염도평가에관한연구 31 Table 5. Mean values of geo-accumulation index (Igeo), pollution load index (PLI), mpelq (mean-pel-quotient) and Sediment quality index (SQI) for metals in the stream sediments around Shihwa Lake Sites Igeo value Cr Co Ni Cu Zn As Cd Pb Hg PLI mpelq SQI S1 1.6 1.7 0.2 4.3 5.4 1.4 6.3 4.7 2.7 14.6 5.9 20.1 S2 2.1-0.7 1.3 5.3 3.5 1.2 3.0 3.1 0.6 7.9 4.8 31.4 S3 1.0-0.8 0.3 3.8 3.6 1.5 3.5 4.1 0.0 6.7 3.9 36.5 S4 1.9-0.6 0.8 4.5 4.2 0.8 5.6 4.6 3.3 19.0 10.2 27.4 S5 0.7-0.1 1.4 3.8 2.0-0.1 3.6 2.0 0.0 4.6 2.0 46.7 S6-1.8-1.2-1.8-0.9 0.4-0.4 0.8 0.5-2.5 0.9 0.3 100.0 S7-1.6-1.8-2.0-1.4-0.4-1.4 0.0 0.4-3.5 0.6 0.3 98.2 S8-2.7-2.8-3.0-2.4-0.9-2.9-1.6-0.1-4.0 0.3 0.1 100.0 S9-0.8-0.8-1.1-0.7 0.0 0.3-0.5 0.3-2.1 1.0 0.6 92.2 S10-0.9-1.0-1.3-1.2 0.2 0.0 0.0 0.2-2.8 0.9 0.4 100.0 S11-0.8-0.9-1.0-0.4 0.2 0.4 0.3 0.6-1.7 1.2 0.4 91.0 Industrial Mean 1.3-0.1 0.8 4.3 3.8 0.9 4.4 3.7 1.3 10.5 5.3 32.4 Rural/Urban Mean -1.4-1.4-1.7-1.1-0.1-0.7-0.2 0.3-2.8 0.8 0.3 96.9 Fig. 3. Comparison of geo-accumulation index (Igeo) for heavy metals in this study. 나타났으며, As 역시 Zn과의상관성 0.254를제외하고는다른중금속들과상관성이없는것을알수있었다. 그러나 Co와 As를제외한중금속원소간에높은상관성을보이고있는것으로나타났다. 3.2 하천퇴적물내중금속오염도평가시화호하천퇴적물내중금속각각의오염도를평가하기위하여 오염등급을 7개로세분화한농집지수를사용하였고계산결과는 Table 5에나타냈다. 산업지역내농집지수의평균값은 Cd이 4.4로가장높았으며 Cu, Zn, Pb은농집지수가 3을초과하고있어 moderately to highly polluted의오염상태인것으로나타났으나, Cr, Co, Ni, As 및 Hg은오염도는크지않은것을알수있었다 (Fig. 3). 농업 / 도심지역에서의농집지수의평균은음 (-) 의값을가져오염되지않은
32 정혜령 김경태 김은수 나공태 이승용 Fig. 4. Spatial distribution of pollution load index (PLI), mean PEL quotient (mpelq) and sediment quality index (SQI) by CCME (2000) in the stream sediments around Shihwa Lake. 상태로구분되었다. 본연구에서분석된 9개중금속원소에대한지역에따른종합적인오염부하를 PLI 결과는 Table 5 및 Fig. 4에나타냈다. 4간선수로에서 PLI가 19.0으로가장높은결과를보였으며 1간선수로 (14.6)>2간선수로 (7.9)>3간선수로(6.7)> 신길천 (4.6) 의순으로나타났으며 PLI가 1을큰폭으로초과하고있어인위적인오염이심각한것을알수있었다 (Table 5). 농업 / 도심지역에서 PLI값은 0.3( 장전보 ; S8)~1.2( 삼화천 ; S11) 의범위였으며삼화천이다른농업 / 도심지역에비해약간높은오염도를보였다. 산업지역과농업 / 도심지역에서의 PLI의평균값은각각 10.5와 0.8로산업지역이약 13배높은결과를보였고, 이중에서 4간선수로의종합적인중금속오염 도가가장심한상태임을알수있었다. 하천퇴적물내중금속농도는조사지역및조사시기에따른변동이매우크며중금속원소에따라다른특성을나타내기때문에조사시기에따른오염도를비교하기위하여토지이용형태에따른조사시기별 PLI의변화특성은 Fig. 5에나타냈다. 산업지역에서는 3월 PLI값이 7.2를보였으며하계조사시기로갈수록점차적으로증가하여 7월 21일조사에서 20.1의 PLI값으로오염부하가가장큰것을알수있었다. 7월과 8월조사시기에서상대적으로높은 PLI 값을나타내고있어하계조사시기에강우유출수를통해산업지역표면에축적되어있는중금속오염물질이하천으로유입된것으로판단된다. 농업 / 도심지역은모든조사시기에서 PLI 값이 1 이
시화호유역하천퇴적물에서의중금속오염도평가에관한연구 33 Fig. 5. Temporal distribution of pollution load index (PLI), mean PEL quotient (mpelq) and sediment quality index (SQI) by CCME (2000) in the stream sediments from industrial region (left side) and rural/urban region (right side). 하의평균농도를나타내고있어오염이되지않은것을알수있었으며산업지역과는다르게하계조사시기가다른조사시기에비해 PLI값이높지않은것으로나타났다. 3.3 퇴적물기준과의비교를통한퇴적물위해성평가퇴적물내중금속은환경내지속적으로존재하며, 저서생태계및수생태계에직 간접적으로영향을미치기때문에각국은퇴적물기준을마련하여관리를실시하고있다. 본연구에서는주의기준인 TEL(threshold effect level) 과관리기준인 PEL(probable effect level) 의퇴적물기준 (sediment quality index) 과의비교를실시하였으며, 우리나라에는담수에대한퇴적물기준이설정되어있지않아 Smith et al.[1996] 의 TEL과 PEL을이용하였다. 총 110개하천퇴적물시료중 TEL을초과하는시료는 Cr이 83.6%(92개 ) 로가장많았으며 Hg은 23.6%(26개 ) 만이초과하는것으로나타났다. PEL을초과하는농도는 Ni이 59개 (53.6%) 로분석 된중금속원소중가장많았으며, Cr은절반에해당되는 55개시료가 PEL을초과하는것으로나타났고, Cu(48개 )>Zn(47개 )>Pb(44 개 )>As(21개 )>Cd(19개 )>Hg(11개 ) 의순이었다 (Table 6). 산업지역 (n=50) 과농업 / 도심지역 (n=60) 으로구분하여퇴적물기준과비교를실시한결과, 산업지역은 Cr, Ni, Cu 및 Zn은 90% 를초과하는시료에서 PEL을초과하는것으로나타났으며, Pb 역시 86% 에해당되는시료 (43개) 가 PEL을초과하고있었다. As는 21 개가 PEL을초과하고있었으며 1간선수로와 3간선수로가 PEL을초과하는빈도가가장높았다. Cd과 Hg의경우, PEL을초과하는시료는각각 19개와 11개였으며, 1간선수로와 4간선수로가 PEL을초과하는빈도가높은것으로나타났다. 따라서산업지역하천퇴적물내중금속농도는모든조사시기에걸쳐 PEL을초과하는농도를보이고있어하천퇴적물에서식하는저서생물등에심각한위해영향을줄것으로판단되며, 강우유출수를통하여시화호로유입되면해양생태계에도심각한영향을미칠것으로생각된다. 농업
34 정혜령 김경태 김은수 나공태 이승용 Table 6. Assessment of sediment quality toxicity with ranges of metals concentrations in the stream sediments defined by the sediment quality guidelines (SQGs), especially TEL and PEL by Smith et al.[1996] Site Cr Ni Cu Zn As Pb Cd Hg All sites (n=110) Industrial region (n=50) Rural/urban region (n=60) <TEL 18 20 56 50 32 41 62 84 TEL-PEL 37 31 6 13 57 25 29 15 >PEL 55 59 48 47 21 44 19 11 <TEL 0 0 0 0 4 0 2 24 TEL-PEL 1 1 2 3 25 7 29 15 >PEL 49 49 48 47 21 43 19 11 <TEL 18 20 56 60 28 41 60 60 TEL-PEL 36 30 4 0 32 18 0 0 >PEL 6 10 0 0 0 1 0 0 / 도심지역의경우, Ni(10개 ) 과 Cr(6개 ) 이 PEL을초과하는것으로나타났으며, 도심지역보다는반월천과삼화천등으로이를제외한다른중금속원소의오염이되지않은지역이었다. 이는국내에는담수환경의퇴적물기준이존재하지않아, 외국의 PEL 기준을사용하였기때문으로지역에따른배경농도차이에기인한결과이며시화호유역의농업 / 도심지역에서는 Ni과 Cr의오염은없는것으로판단된다. 퇴적물기준을가지고있는 8개원소에대한종합적인위해성을평가하기위하여사용된 mpelq의평균은 4간선수로 (S4) 가 10.2로독성영향이매우큰것 (highly toxic) 으로나타났다 (Table 5, Fig. 4). 4간선수로의경우, 6월을제외한모든조사시기에서 mpelq가 1을초과하는값을보이고있어지속적인독성영향이존재하는것을알수있었다. 산업지역의하천에서 mpelq의평균값은 2.0( 신길천 ; S5)~5.9(1간선수로 ; S1) 로독성영향이큰것 (highly toxic) 으로나타났다. 농업 / 도심지역모든하천의 mpelq값은 0.1( 장전보 ; S8)~0.6( 반월천 ; S9) 으로작지만독성영향이존재하는것 (marginally toxic) 을알수있었다. 조사시기별 mpelq값의평균은산업지역의경우, 7월 21일과 8월 27일조사에서각각 13.41과 9.22의값을보여하계조사시기가상대적으로독성영향이클것으로예상되었으며, 나머지조사시기역시 mpelq 값이 1을초과하여독성영향이큰것 (highly toxic) 을알수있었다 (Fig. 5). 농업 / 도심지역의경우 0.28(8월 27일 )~0.35(10월 7일 ) 의범위를나타내고있어, 다소독성영향이존재하는것으로나타났으며조사시기에따른차이는보이지않았다 (Fig. 5). 앞서설명한 mpelq는환경시료내중금속농도가퇴적물기준을얼마나초과하여저서생태계에독성영향을줄것인지를판단하는것으로, 독성영향을미칠것인지에대한평가에주로사용한다. 그러나실제환경시료에서중금속등오염물질은몇가지대상물질이얼마나높은농도로기준을초과하는지에대한종합적인고려가필요하므로본연구에서는퇴적물내존재하는오염도및위해영향을종합적으로판단하기위하여 SQI(CCME-PEL) 를활용하였다 (Grapentine et al.[2002]; Shim and Hong[2007]; Hong et al. [2014])). 조사지역에따른 SQI 지수는산업지역인 1간선수로에서 20.1로 매우나쁨 (very poor) 에해당되는퇴적물상태인것으로나타났으며, 나머지산업지역인 2~4간선수로역시매우나쁨 (very poor) 에해당되는것을알수있었다. 신길천에서의 SQI의평균은 46.7로평균적으로나쁨 (poor) 에해당되는것으로나타나, 간선수로에비해오염도및독성영향이작은것으로나타났다. 농업 / 도심지역에서의 SQI는 91.0~100으로좋음 (good) 에서매우좋음 (excellent) 에해당되는상태를보이고있었다 (Fig. 4). 산업지역과농업 / 도심지역으로조사지역을구분하여조사시기에따른 SQI 값은 Fig. 5에나타냈다. 산업지역은 10월조사가 47의 SQI값을나타내나쁨 (poor) 에해당되는상태이며, 나머지모든조사시기에서 44이하의 SQI 값을보여매우나쁨 (very poor) 에해당되는오염및독성영향상태로나타났고, 하계조사인 7월 21일조사가가장심각한오염을보임을알수있었다 (Fig. 5). 농업 / 도심지역의경우 7월 21일과 10월조사에서각각 90과 94의값을나타내좋음 (good) 의등급이었으며, 나머지조사시기는 95이상의 SQI 값을나타내매우좋음 (excellent) 의해당되는등급인것으로나타났다 (Fig. 5). 4. 결론 본연구에서는시화호중금속오염의유입원을파악하기위하여유역에존재하는하천퇴적물내중금속시 공간적인오염특성파악, 오염도및위해성을평가하였다. Co, As, Ni은산업지역에서의평균농도가농업 / 도심지역에비해각각 3.3~6.0배정도높은결과를나타냈다. Cr, Cu, Zn, Cd, Pb 및 Hg는산업지역이농업 / 도심지역에비해각각 9.7배, 82.8배, 27.2배, 36.9배, 29.8배및 42.1배높은평균농도를보이고있어, 산업지역의하천퇴적물은이들중금속원소에심각하게오염된상태임을알수있었다. 퇴적물관리기준과의비교를통하여, 농업 / 도심지역에서는 Cu(10개 ), Zn(6개 ), Pb(1 개 ) 가 PEL을초과하고있었으나, 산업지역은 Cr, Ni, Cu, Zn의금속원소가 90% 가 PEL을초과하고있는것으로나타났다. 독성영향의유무를평가하는 mpelq와퇴적물의종합적인오염도를나타내는 SQI 분석결과, 산업지역은독성영향이크며퇴적물오염상태가매우나쁨 (very poor) 인것으로나타났다. 특히하계조사시기에중금속농도및오염상태가악화되는결과를보여, 강우유출수를통해산
시화호유역하천퇴적물에서의중금속오염도평가에관한연구 35 업지역표면에축적되어있는중금속오염물질이하천으로유입된것으로판단된다. 하천퇴적물및주변유역의표면에축적되어있는높은농도의중금속은별다른처리과정없이강우유출수와함께시화호로직접이동되어수질, 저질및생태계에해로운영향을미칠것이기때문에각각의중금속의정확한오염원을밝히기위한추가적인조사가필요할것으로생각된다. 후 본연구는한국해양과학기술원연구사업 금속안정동위원소를활용한오염원추적연구 (PE99402) 의연구비지원에의해수행되었습니다. 기 References [1] Adams, W.J., Kimerle, R.R. and Barnett, J.W., 1992, Sediment quality and aquatic life assessment, Environ. Sci. Technol., Vol. 26, No. 10, 1864-1875. [2] Barakat, A., Baghdadi, M. El, Rais, J. and Nadem, S., 2012, Assessment of heavy metal in surface sediments of Day River at Beni-Mellal region, Morocco, Res. J. of Environ. Earth Sci., Vol. 4, No. 8, 797-806. [3] Buffleben, M.S., Zayeed, K., Kimbrough, D., Stenstrom, M.K. and Suffer, I.H., 2002, Evaluation of urban non-point source runoff of hazardous metals entering Santa Monica Bay, California, Water Sci. Technol., Vol. 45, No. 9, 263-268. 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