Kyoungphile Nam

Relationship between biodegradation rate and percentage of a compound that becomes sequestered in soil

A study was conducted to determine whether the rate of biodegradation of phenanthrene determines the extent of its sequestration. Samples of a single soil type with different biodegradative activities were used. Various rates of biodegradation were obtained by use of different incubation temperatures, adding a bacterial culture or both. Much of the compound became biologically unavailable (sequestered) when the initial rates of biodegradation were slow, and little remained if the soil had high degradative activity. A portion of the compound remaining in soils with previously low activity was degraded if the soil samples were reinoculated and incubated under favorable conditions, but a significant amount of the compound was still microbiologically unavailable. The data show that the percentage of a compound that will be sequestered in a microbiologically unavailable form is determined by the initial rate of its biodegradation in soil.

Study on Heavy Metal Contamination Characteristics and Plant Bioavailability for Soils in the Janghang Smelter Area

Potential risk of heavy metals to various receptors including humans depends on the bioavailability of the heavy metals in soil. In this study, the heavy metal extraction methods using 0.1N HCl and aqua regia were compared with the Tessier`s sequential extraction method to assess whether these two methods can be used to determine the plant-available heavy metal concentrations. The contamination characteristics of copper (Cu), cadmium (Cd), lead (Pb), and arsenic (As) found in soils collected from 75 sites around the closed Janghang smelter were analyzed by extracting heavy metals using 0.1 N HCl, aqua regia, and the Tessier`s sequential extraction method. The portion of metals bioavailable to plants is considered as the sum of the fraction 1 (exchangeable) and the fraction 2 (carbonates binding) of the Tessier`s 5-step sequential extraction method, which were determined to be 3.1 3.82, 0.6 0.15, 20.6 18.78, and 7.0 6.48 mg/kg for Cu, Cd, Pb, and As, respectively, in this study. When the extraction using aqua regia and the Tessier`s extraction method were compared, the extracted Cu and Pb concentrations did not show significant differences, whereas the extracted Cd and As concentrations showed significant differences. These results indicate that the portion of Cd and As in the fraction 5 of the Tessier`s sequential extraction can not be extracted using aqua regia. Using aqua regia, which is the official test method, higher concentrations of Cu, Cd, Pb and As were extracted than the sum of the fraction 1 and 2. The results show that only 9, 40, 39 and 10% of Cu, Cd, Pb and As using aqua regia can be uptaken by plants (i.e., plant-available). Using 0.1N HCl, the portion of Cd equivalent to about 66% the fraction 1 could be extracted, while, with Pb, the portion of the fraction 1 and about 90% of the fraction 2 could be extracted. With As, the portion equivalent to the fraction 1, 2 and 79% of the fraction 3 was extracted, while with Cu, the portion equivalent to the fraction 1, 2, 3 and 20% of the fraction 4 was extracted using 0.1N HCl.

Applicability of Soil Washing with Neutral Phosphate for Remediation of Arsenic-contaminated Soil at the Former Janghang Smelter Site

In accordance with the view on remediated soil as a resource, this study assessed the applicability of soil washing with the neutral phosphate for remediation of arsenic (As)-contaminated soil. Three soil samples of different land uses (i.e., rice paddy, upland field and forest land) were collected from the study site, and the aqua regia-extractable As concentrations were 59.2, 30.8 and 53.1 mg/kg, respectively. Among the neutral phosphate reagents, ammonium phosphate showed the highest As washing efficiency. The optimized washing condition was 2-hr washing with 0.5 M ammonium phosphate solution (pH 6) and soil to liquid ratio of 1 : 5. The extraction efficiencies of As did not guarantee the residual soil As concentrations to satisfy the Korea soil regulatory level (i.e., Worrisome level) in the three soil samples. To enhance washing efficiency, the As-contaminated soil was submerged in washing solution (1 : 1, w/v) for 24 hr and 1-hr washing with 0.5 M ammonium phosphate solution was tested. As extraction efficiencies of 36.1 (rice paddy), 21.4 (upland field) and 26.4% (forest land) were attained, which satisfied the Worrisome level for Region 1 (25 mg/kg of As) in rice paddy, but not in upland field and forest land.

Determination of Human Health Risk Incorporated with Arsenic Bioaccessibility and Remediation Goals at the Former Janghang Smelter Site

ABSTRACT Metal concentrations in the former Janghang smelter area were determined and human health risk of arsenic (As) withbioaccessibility was investigated. Site investigation of the area within 1.5 km from the Janghang smelter showed the Asconcentrations of 4.8~169.8 mg/kg (avg. 37.8 mg/kg). For 85 samples out of 126 samples, As concentrations were higherthan the Worrisome Level of the Korean Soil and Environment Conservation Act, and seven samples exceeded theCountermeasure Standard. Risk assessment for As incorporated with the bioaccessibility revealed that potential humanhealth risk of the carcinogenic (1.8~5.0 × 10 −5 ) was above the acceptable risk range (10~10 −6 ) while the risk of the non-carcinogenic was not found. Remediation goals based on risk incorporated with bioaccessibility of As ranged from 10.8 to20.0 mg/kg. Such difference in the remediation goals resulted from various bioaccessibility of As (i.e., between8.7~66.3%) at the study site.Key words : Former Janghang smelter, Arsenic, Bioaccessibility, Risk assessment

The Toxicity Assessment of Explosives Contaminated Soil using Soil Microbial Activity Tests

This study was conducted to determine the toxic effect of TNT and RDX on indigenous soil microbes by measuring enzymatic activity. Denitrification activity, dehydrogenase activity, phosphatase activity, and fluorescein diacetate hydrolytic activity were determined for military firing range, field, and paddy soils exposed to TNT, and RDX from 0 to 1,000 mg/kg and 0 to 4,000 mg/kg, respectively, for 2, 4, and 8 weeks. Soil microbial enzymatic activities decreased with higher TNT and RDX concentration and longer exposure time. Microbial enzymatic activities of firing range soil were higher than field and paddy soils, indicating that indigenous microbes in firing range might have been adapted to TNT and RDX due to pre-exposure of the explosives. In addition, the toxicity of TNT and RDX decreased with higher organic matter because TNT and RDX tend to absorb to soil organic matter. No Observable Effect Concentration (NOEC) values of each microbial enzymatic activity were derived by the geometric mean of NOECs from exposure times (2, 4, and 8 weeks) and soil types (firing range, field, paddy soil). The derived NOECs ranged from 45.3 to 55.2 mg/kg for TNT and 286 to 309 mg/kg for RDX.

Field Applicability Study of Landfarming for Petroleum Hydrocarbons Contaminated Soils

ABSTRACT The landfarming treatment for the remediation of the petroleum contaminated soil at the returned U.S. Military bases wasinvestigated in this study. Specifically, the bioaugmentation performance using various commercially available petroleum-degrading bacteria was evaluated and the directions for enhancing the performance of the landfarming treatment weresuggested. The environmental factors of the soils at the returned U.S. Military bases chosen for remediation indicate thatthe landfarming treatment can be used as the remediation technique; however, the addition of nitrogen or phosphorus isrequired. The lab-scale landfarming treatment tests using the model soil and the site soil showed that the degradationefficiency was greater with the model soil than the site soil and that the treatment performance was not affected by thenumber of bacteria present in the soil in the range of 10 6 -10 12 CFU/g. These results suggest that the successful landfarmingtreatment depends on the petroleum degradability of bacteria used and the environmental conditions during the treatmentrather than the number of petroleum-degrading bacteria used. Key words: Landfarming, Petroleum-contaminated soil, Soil remediation, Petroleum-degrading bacteria, Contaminantaging

Development of Korean Risk-Based Corrective Action (K-RBCA) Software

위해성에 근거한 복원 전략(Risk-Based Remediation Strategy, RBRS)은 위해성평가(Risk Assessment)를 통하 여 오염지역의 위해성 또는 오염원을 효율적으로 관리하 기 위한 의사결정과정이다. 이는 토양에 잔류하는 오염물 질의 농도에 의존하여 오염지역 복구 및 수준을 결정하던 기존의 방법과는 다르게, 오염물질의 수용체에 대한 노출 가능성과 위해성에 근거하여 오염지역의 복구 여무 결정 및 정화 수준을 결정하는 방법으로, 미국, 네덜란드, 영국 등 선진국에서 이미 널리 시행되고 있다. 선진국에서는 위 해성평가를 보다 수월하게 수행할 수 있도록 전문적인 소 프트웨어를 개발하여 사용하고 있다. 미국의 RBCA Tool Kit for Chemical Releases(ASTM, 2007), APIs DSS (American Petroleum Institute, 1999)와 CalTOX (California EPA, 2002), 영국의 CLEA(DEFRA and EA, 2002), 네덜란드의 CSOIL(RIVM Netherlands, 2001)등과 같은 소프트웨어가 대표적이며, 이러한 소프트 웨어들은 위해성평가를 하기 위해 필요한 기본적인 데이 터베이스와 노출 시나리오, 위해도 및 목표정화수준 산정 기능 등을 제공하여 평가자가 쉽게 이해하고 수행할 수 있도록 한다. 위해성평가 소프트웨어의 기본이 되는 위해 성평가 매뉴얼은 대부분 미국의 Soil Screening Guidance (US EPA, 1996)와 Risk-Based Corrective Action(ASTM, 1995)을 따르고 있으며, 영국(DEFRA and EA, 2002)과 네덜란드(RIVM, 2001)는 이를 바탕으로 자국의 현황에 맞게 수정하여 사용하고 있다. 우리나라도 2005년 ‘토양환경보전법’을 개정하여 위해 성평가에 대한 근거 조항을 도입함으로써 제도적 기반을 마련하였으나 그 이후 본격적으로 시행되지 못하고 있다. 여러 가지 사회적, 제도적 이유가 있으나 위해성평가의 수 행 주체가 불분명하고 본격적인 평가를 위한 기술적 기반 이 충분히 조성되지 못한 데 기인하는 측면이 크다. 위해 성평가를 위한 기술적 지원을 위하여 본 연구진에서는 한 국형 위해성평가 소프트웨어를 개발하였고, 이를 Korean Risk-Based Corrective Action(K-RBCA)라고 명명하였다. 본 기술자료에서는 미국에서 개발되어 사용 중인 RBCA Tool Kit for Chemical Releases, APIs DSS, CaLTOX 를 중심으로 위해성평가 소프트웨어를 분석하여 위해성평 가 소프트웨어의 주요 기능과 기본적인 설정이 어떠한지 살펴보고, 기존 상용 소프트웨어를 기반으로 한국의 위해 성평가 시행 수준에 적합한 기능과 설정을 가진 소프트웨 어 개발에 대한 연구 결과를 기술하였다.

Effect of Basic Oxygen Furnace Slag used as Structural Filling Materials on the Subsurface Environment

The effect of blast oxygen furnace (BOF) slag used as filling materials on the soil environment was studied using column tests that simulated the flow of the BOF slag leachate through the soil layer. The Cu, Mn, Zn, Ni, and F contents of the leachate affected soil were similar to that of the controls (i.e., soils that were not affected by the leachate). The As, Cd, and Pb contents were lower in the leachate affected soils than the controls. The changes in these contaminants contents can be attributed to the interactions between anions such as alkalinity generating anions (e.g., CO3 , HCO3 −, OH−) or calcium ions with heavy metals or F, which consequently affected the fate of heavy metals and F in the leachate affected soils. The germination and growth of Spinapis alba in the soils affected by the leachate and the controls were also similar. However, the proportion of alkalophilic bacteria in the soils affected by the leachate significantly increased, and this can be explained by the increased soil pH due to the alkaline leachate. Overall, this study shows that the alkalinity of the BOF slag leachate, rather than the presence of heavy metals and F in the leachate, needs to be considered when the BOF slag is to be reused as structural filling materials.

Screening-Level Ecological Risk Assessment for Beneficial Reuse as Soil of Dredged Sediment Contaminated with Heavy Metals

This study conducted a screening-level ecological risk assessment for heavy metals in dredged sediment for recycling in terrestrial environment. Toxicological information of six heavy metals (i.e., Cu, Zn, Cd, Pb, Cr, and Ni) was collected from ECOTOX of US Environmental Protection Agency, and screened and qualified for the use in the screening-level ecological risk assessment. According to the number of terrestrial ecological receptors for which toxicological information is available, PNEC (Predicted No Effect Concentration) of each heavy metal was derived using either stochastic approach (for Cu, Zn, and Cd), or deterministic approach (for Pb, Cr, and Ni). Hazard quotients of the six heavy metals were derived for a field-collected dredged sediment using the PNEC derived and the PEC (Predicted Environmental Concentration) determined for the dredged sediment. The HQs of Cu, Zn, Cr, Pb and Ni were higher than unity indicating a possibility of ecological risk of the five heavy metals when the dredged sediment is applied in terrestrial environment. Accordingly, remediation processes or a higher-level ecological risk assessment would be needed for the recycling of the material.

Risk Evaluation of Monopotassium Phosphate (MKP) and Bentonite Application via the Mobility Reduction of Soil TNT and Heavy Metals

Simultaneous mobility reduction of explosives and heavy metals in an operational range by monopotassium phosphate (MKP) and bentonite spreading technology was investigated. Potassium ion and phosphate ion in MKP act as explosives sorption enhancer and insoluble heavy metal phosphate formation, respectively, while bentonite acts as the explosives adsorbent. Then, the decrease in surface water concentration of the pollutants and resulting risk reduction for local residents of the operational range, by MKP/bentonite application was estimated. Under untreated scenario, the noncancer hazard index (HI) exceeded unity on February, July and August, mainly due to 2,4,6-trinitrotoluene (TNT); however, MKP/bentonite treatment was expected to lower the noncancer hazard index by decreasing the surface water concentration of explosives and heavy metals (especially TNT). For example, on July, estimated surface water concentration and HI of TNT were 0.01 mg/L and 1.1, respectively, meanwhile the sorption coefficient of TNT was 3.9 mg 1�n kg �1 L n . However, by MKP/bentonite treatment, the TNT sorption coefficient increased to 113.8 mg 1�n kg �1 L n and the surface water concentration and HI decreased to about 0.002 mg/L and 0.2, respectively. Based on the result, it can be concluded that MKP/bentonite spreading is a benign technology that can mitigate the risk posed by the pollutants migration from operational ranges.