Geochemical Characteristics and Nitrates Contamination of Shallow Groundwater in the Ogcheon Area

옥천지역 천부지하수의 지구화학적 특성 및 질산염 오염 특성

  • Lee, In-Gyeong (Department of Earth and Environmental Sciences, Chungbuk National University) ;
  • Choi, Sang-Hoon (Department of Earth and Environmental Sciences, Chungbuk National University)
  • 이인경 (충북대학교 지구환경과학과) ;
  • 최상훈 (충북대학교 지구환경과학과)
  • Published : 2010.02.28

Abstract

The geochemical and nitrogen isotopic analyses for shallow groundwater of Ogcheon area were carried out to characterize the geochemical characteristics of the groundwater and to identify the source of nitrate. Groundwater shows a neutral pH to weakly alkalic condition with pH values ranging from 6.9 to 8.4. The average of EC, Eh and DO is $344.2\;{\mu}s/cm$, 195 mV, 4 mg/L, respectively. According to piper diagram, chemical composition of groundwater is dominantly characterized by Ca-$HCO_3$ type. On the other hand, groundwater type in the study area include Ca-Cl+$NO_3$ type that were highly influenced by agricultural activities. $NO_3$-N concentration of the collected samples(n=45) range from 12.4 to 34.2 mg/l. These data show that the $NO_3$-N concentration exceeds Korea Drinking Water Standard (10 mg/l). The $\delta^{15}N-NO_3$ values range from $2.7^{\circ}/_{\circ\circ}$ to $18.8^{\circ}/_{\circ\circ}$. The enrichments of heavy isotope in the groundwater indicate that major origin of nitrate pollution were associated with animal and human waste. Also the denitrification may have partly contributed as one of the sources of nitrogen.

충북 옥천 지역 천부지하수의 지화학적 특성과 질산염의 기원을 규명하기 위하여 지화학 및 질소동위원소 연구가 수행되었다. 지하수의 pH는 6.9~8.4로 중성 내지 약알칼리성으로 나타났다. 지하수의 전기전도도, 산화환원전위 및 용존산소량은 각각 $344.2\;{\mu}s/cm$, 195 mV, 4 mg/L이다. 채취된 45개의 시료에서 검출되어진 질산성 질소의 농도는 12.4 mg/l~34.2 mg/l 범위를 보이며, 모두 먹는물 수질기준의 10 mg/l를 초과하는 것으로 나타났다. 질산성 질소의 동위원소 분석 결과, $\delta^{15}N-NO_3$$2.7^{\circ}/_{\circ\circ}{\sim}18.8^{\circ}/_{\circ\circ}$이다. 이와 같이 지하수내 15N의 부화는 질산성질소의 오염기원이 동물분뇨임을 지시한다. 또한 일부는 탈질화작용이 기여한 것으로 보여진다.

Keywords

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