HR: 1340h
AN: H23A-1406    [Abstracts]
TI: Hydrochemical and Isotopic Evidence of Natural Attenuation at the Gas Station Contaminated with Fuel Hydrocarbon
AU: * Ko, K
EM: kyungsok@kigam.re.kr
AF: Korea Institute of Geosciences & Mineral Resources, 30 Gajeongdong Yuseonggu, Daejeon, 305-350 Korea, Republic of
AU: Oh, I
EM: insuk1260@hotmail.com
AF: Kongju University, Division of Earth Environmental Sciences, 182 Shinkwandong, Kongju, 314-701 Korea, Republic of
AU: Suk, H
EM: sxh60@kowaco.or.kr
AF: Korea Institute of Water and Environment, 462-1 Cheonmindong Yuseonggu, Daejeon, 305-730 Korea, Republic of
AU: Lee, K
EM: kslee@kbsi.re.kr
AF: Korea Basic Science Institute, 52 Yeoeundong Yuseonggu, Daejeon, 305-333 Korea, Republic of
AB: Groundwater flow, hydrochemistry and the carbon isotope composition (d13C) of dissolved inorganic carbon (DIC) were measured to know the effect of natural attenuation which is induced by biodegradation of petroleum hydrocarbon at the abandoned gas station contaminated fuel hydrocarbons. The aquifer sediment consists of 4 to 5 m of unconsolidated and weathered soils overlying granite. The monitoring results of water level showed the immediate response of that to rainfall. This implies that the site is an unconfined aquifer or is located at the near of groundwater recharge area. The contaminant transport modeling using GMS showed that the contaminants, BTEX, transported to two main directions, south and southwest from UST and pipeline. These results were proved by the filed observation of the BTEX from the groundwater seepage at the streams of south and southwest area. The geochemical indicator of natural attenuation, red iron precipitate, was also observed at the groundwater seepage. The hydrochemical indicators, Fe(II), Mn(II), sufides, and methane, of terminal electron accepting processes represented the sulfate reducing and methanogenesis environment of the site. d13C values of DIC ranged from -20.2 to -9.3 permil and increased in the source zone by the microbial degradation of hydrocarbon under methanogenic condition. The enrichment of isotopically heavy C is caused by the production of light 12CH4 from microbial respiration. The molar ratio of Ca to HCO3 is about 2.5 and this indicates the contribution of microbial oxidation of fuel hydrocarbon to DIC in groundwater. The geochemical modeling using PHREEQC showed the oversaturation of siderite, rhodocrosite and goethite and the saturation index of calcite increased as the increase of bicarbonate, indicating the enhanced microbial degradation. From the research results, the mineralogical, hydrological and microbiological factors can exert influence on groundwater chemistry and d13C of DIC.
DE: 1041 Stable isotope geochemistry (0454, 4870)
DE: 1831 Groundwater quality
SC: Hydrology [H]
MN: Fall Meeting 2005