• Environmental Engineering Research
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• v.13 no.2
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• pp.73-78
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• 2008

For a given soil-contaminated site, a level of soil contamination is characterized and decisions on risk may be made from the risk assessment. The study evaluated critical design factors for the determination of sample size in the sampling design plan and the assessment of soil contaminant- leaching to groundwater. Two variables, the minimum relative detectable difference (T) and coefficient of variation (CV) were evaluated for the sample size determination. The minimum number of samples can be appropriately determined by CV under a T value greater than or equal to 0.2. Soil-contaminant leaching to groundwater was evaluated by using the Soil Screening Level equation of U.S. Environmental Protection Agency and the Risk Based Screening Level equation of American Society for Testing and Materials, with the same input parameters. The groundwater concentrations estimated from soil contaminant concentrations were significantly affected by the Darcy velocity of groundwater and the organic content of soil.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2000.11a
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• pp.266-269
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• 2000

To understand the gaseous behaviour of volatile organic compounds in the unsaturated zone, their volatilization coefficient k$_{Lg}$ is evaluated. An experiment is conducted to examine the dependence of k$_{Lg}$ on the concentration of the dissolution, presence of unsaturated zone and depth of the unsaturated zone. The results show that the volatilization coefficient is not dependent on the concentration under the constant temperature and pressure. It is also find that k$_{Lg}$ depends on the presence of the unsaturated zone rather than its depth.depth.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2003.09a
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• pp.467-470
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• 2003

Leaking underground storage tanks are a major source of groundwater contamination by petroleum hydrocarbons. Aerobic bioremediation has been highly effective in the remediation of many fuel releases. However, Bioremediation of aromatic hydrocarbons in groundwater and sediments is ofen limited by the inability to provide sufficient oxygen to the contaminated zones due to the low water solubility of oxygen. Nitrate can also serve as an electron acceptor and results in anaerobic biodegradation of organic compounds via the processes of nitrate reduction and denitrification. Because nitrate is less expensive and more soluble than oxygen. it may be more economical to restore fuel-contaminated aquifers using nitrate rather than oxygen. And denitrifying bacteria are commonly found in the subsurface and in association with contaminated aquifer materials. These studies have shown that BTEX and MTBE can be degraded by the nitrate-amended microcosms under aerobic and anaerobic conditons. Biodegradation of the toluene and ethylbenzne compounds occurred very quickly under denitrifying conditions. MTBE, benzene and p-xylene were recalcitrant under denitrifying conditions in this study, But finally Biodegradaton was observed for all of the test compounds.

• Journal of Animal Science and Technology
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• v.47 no.3
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• pp.481-490
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• 2005

Nitrate contamination in water system is a critical environmental problem caused by excessive application of chemical fertilizer and concentration of livestock. In order to prevent further contamination, therefore, it is necessary to understand the origin of nitrate in nitrogen loading sources and manage the very source of contamination. The objective of this study was to examine the nitrate contamination sources in different agricultural system by using nitrogen isotope ratios. Groundwater and runoff water samples were collected on a monthly basis from February 2003 to November 2003 and analyzed for nitrogen isotopes. The nitrate concentrations of groundwater in livestock fanning area were higher than those in conventional and organic fanning area and exceeded the national drinking water standard of 10mg N/ l. The ${\delta}^{15}N$ranges of chemical fertilizer and animal manure were - 3.7${\sim}$+2.3$\textperthousand$ and +12.5${\sim}$26.7$\textperthousand$, respectively. The higher ${\delta}^{15}N$ of animal manure than those of chemical fertilizer reflected isotope fractionation and volatilization of '''N. The different agricultural systems and corresponding average nitrate concentrations and ${\delta}^{15}N$ values were: conventional farming, 5.47mg/e, 8.3$\textperthousand$; organic fanning, 5.88mg/e, 10.1$\textperthousand$; crop-livestock farming, 12.5mg/e, 17.7%0. These data indicated that whether conventional or organic agriculture effected groundwater and runoff water quality. In conclusions, relationship between nitrate concentrations and ${\delta}^{15}N$ value could be used to make a distinction between nitrate derived from chemical fertilizer and from animal manure. Additional investigation is required to monitor long-term impact on water quality in accordance with agricultural systems.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2003.04a
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• pp.368-371
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• 2003

Leaking underground storage tanks are a major source of groundwater contamination by petroleum hydrocarbons. Bioremediation of aromatic hydrocarbons in groundwater and sediments is often limited by dissolved oxygen. Aerobic bioremediation has been highly effective in the remediation of many fuel releases, but Many aromatic hydrocarbons degrade very slowly under anaerobic conditions. Nitrate is a good alternative electron acceptor to oxygen and denitrifying bacteria are commonly found in the subsurface and in association with contaminated aquifer materials. Because nitrate is less expensive and more soluble than oxygen. it may be more economical to restore fuel-contaminated aquifers using nitrate rather than oxygen. This study show that biodegradation of BTEX and MTBE is enhanced by the nitrate-amended microcosms under aerobic/anaerobic conditons. Although aromatic hydrocarbons degrade very slowly under anaerobic conditions. Biodegradaton was observed for all of the test compounds.

• Journal of Soil and Groundwater Environment
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• v.20 no.2
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• pp.1-9
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• 2015

Groundwater has been a very precious resource for human life and economic development in the world. With increasing population and food demand, the groundwater use especially for agriculture is largely elevated worldwide. The very much large groundwater use results in depletion of major aquifers, land subsidences in many large cities, anthropogenic groundwater contamination, seawater intrusion in coastal areas and accompanying severe conflicts for water security. Furthermore, with the advent of changing climate, securing freshwater supply including groundwater becomes a pressing and critical issue for sustainable societal development in every country because prediction of precipitation is more difficult, its uneven distribution is aggravating, weather extremes are more frequent, and rising sea level is also threatening the freshwater resource. Under these difficulties, can groundwater be sustaining its role as essential element for human and society in the near future? We have to focus our efforts and wisdom on answering the question. Korean government should increase its investment in securing groundwater resources for changing climate.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2003.10a
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• pp.70-86
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• 2003

Despite its usability, TCE has been managed as a hazardous material due to the toxicity and many contamination cases were surveyed in some developed countries. U.S.EPA(Kram et al., 2001) suggested DNAPL characterization methods and approaches based on survey experiences at several sites. However, Korea has not the least assessment of contamination and trial of remediation, although there are a lot of doubtable areas where ground water would be contaminated with TCE. In this study, we try to assess the volume and extent of ground water contamination with TCE and delineate the contamination source zones in an industrial area. Ground water in this area flows through fractures and the contaminant TCE has the properties of high volatility, high density and low partitioning to soil material. Thus, we applied a variety of technical approaches to identify the contamination status; documentary, hydrogeochemical, hydrogeological and geological surveys. In addition, additional survey was performed based on the interim findings, which showed that ground water contamination was limited to the relatively small area with high concentrations to the deep place. The contamination source zone is estimated to be the asphalt test institute where a great deal of TCE has been used to analyze the amount of asphalt soluble in TCE since 1984. Based on the contamination characterization and a myriad of documents about ground water remediation, appropriate site remediation management options will be recommended later. This study is now under way and this paper was focused on describing the technical approaches used to achieve the goals of this study.

• Journal of Soil and Groundwater Environment
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• v.24 no.4
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• pp.1-10
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• 2019

Recently, groundwater contamination by mixed occurrence of arsenic (As) and nitrate ($NO_3{^-}$) has been a serious environmental issue all around world. In this study, we investigated the microbial As(III) oxidation characteristic under denitrification process to examine the feasibility of the microbial consortia in wetland sediment to simultaneously treat these two contaminants. The detail objectives of this study were to investigate the effects of $NO_3{^-}$ on the oxidation of As(III) in anaerobic environments and observe the microbial community change during the As oxidation under denitrification process. Results showed that the As(III) was completely and simultaneously oxidized to As(V) under denitrification process, however, it occurred to a much less extent in the absence of sediment or $NO_3{^-}$. In addition, the significant increase of As(III) oxidation rate in the presence of $NO_3{^-}$ suggested the potential of As oxidation under denitrification by indigenous microorganisms in wetland sediment. Genera Pseudogulbenkiania, and Flavisolibacter were identified as predominant microbial species driving the redox process. Conclusively, this study can provide useful information on As(III) oxidation under denitrifying environment and contribute to develop an effective technology for simultaneous removal of As(III) and $NO_3{^-}$ in groundwater.

• Economic and Environmental Geology
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• v.34 no.5
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• pp.485-498
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• 2001

This study was objected to identify the temporal and spatial variations oi groundwater quality and contamination using monthly groundwater monitoring data collected from 30 wells in Daejung watershed, Jeju Island. Water samples were analyzed for major cations. anions, and environmental isotopes including $^{18}0-H_2$O,$^{2}H-H_2$O and$^{15}$ N-NO$_3$The groundwater represented mostly Na(Mg)-HCO$_3$ type, with local change toward Ca-HCO$_3$ type and Na-Cl type. Groundwater quality depends upon various factors such as the local groundwater flowpaths, input of surface contaminants with recharge events, and sea-water intrusion along the coastal area. Nitrate contamination changed temporally according to recharge events and spatially. $\delta$$^{18}$ O-$\delta$$_2$H data for monthly sampled groundwaters showed distinctive clusters, implying that groundwater was originated from independent precipitation, and subsequently recharged very fash. Using$\delta$$^{15}$ N-NO$_3$ data, major sources of nitrate and its areas of influence could be identified. The areas under influence of livestock farms showed relatively high NO$_3$-N concentrations and$\delta$$^{15}$ N values higher than 5$\textperthousand$. The agricultural areas in southeastern part showed very high concentrations of NO$_3$-N with the $\delta$$^{15}$ N values of lower than 5$\textperthousand$.

• Korean Journal of Ecology and Environment
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• v.37 no.4 s.109
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• pp.431-435
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• 2004

A nitrate-contaminated groundwater was hydrogeochemically investigated to estimate the factors controlling groundwater quality in an alluvial fan area. Even though monthly groundwater levels increased with monthly rainfalls, the monthly $NO_3^--N$ concentrations in groundwater showed a small variation, mostly exceeding a maximum contaminant level of 10 mg $L^{-1}$ in environmental quality standards for groundwater during 2003. The 2003 annual groundwater recharge was 1,730 mm =20,056 mm-18,326 mm. Where 20,056 mm and 18,326 mm are annual sum of daily increase and decrease in ground water level. However, the annual sum of increase in ground water level (20,056 mm) was approximately 10 times higher than annual rainfall. Moreover, the annual sum of daily ground water level decrease (-18,326mm) showed that a large amount of groundwater was discharged with $NO_3^-$-contamination. Hydrogeochemically, a large amount of groundwater input and output through the alluvial fan area were observed after rainfall with a considerably high concentration of $NO_3^-$. Consequently, this alluvial fan area including forest area reflects on the evidence under the condition of 'nitrogen excess' or 'nitrogen saturation'. In addition, such a large amount of groundwater outflow can cause environmental damage in surface water, associated with $NO_3^-$- contamination. This study also expects that this hydrogeochemical data will be useful for water management.