Geonha Kim

Dechlorination of atrazine using zero-valent iron (Fe0) under neutral pH conditions.

Zero-valent iron (Fe0) is frequently used for the dechlorination of pesticides, because it is economical, easily acquired and stable. The kinetics of dechlorination by Fe0 are improved at low pH, but this requires additional acid addition, while dechlorination hardly occurs under basic conditions. Due to the buffer capacity of geological materials such as clay and sediment, however, the addition of acid to obtain a low pH may not be effective. In this research, the dechlorination constants of atrazine by Fe0 were measured with the addition of buffer solution to simulate the buffer capacity of sediment. In the presence of the buffer solution, the pH values remained neutral, while dechlorination occurred more slowly than that observed under acid additions but faster than that without any buffer. When the initial concentrations of atrazine were 10mg/L, 30 mg/L, and 50mg/L, its dechlorination was explained using pseudo-first order reaction kinetics. The pseudo-first order constants were 3.01 x 10(-2)d(-1) at 10 mg/L, 3.23 x 10(-2)d(-1) at 30 mg/L and 3.38 x 10(-2)d(-1) at 50mg/L. In addition, the half-lives of atrazine were 8.91 d at 10mg/L, 9.32 d at 30 mg/L, and 10.00 d at 50mg/L. Acid addition may not be omitted to obtain acidic pH conditions when dechlorination is necessary in geologic materials.

Correlation assessment and monitoring of the potential pollutants in the surface sediments of Pyeongchang River, Korea

Abstract The study provides a baseline for the assessment of the organic and inorganic pollution specially, heavy metal contamination in the surface sediments of Pyeongchang River, South Korea. The assessment of the study areas was done with respect to metal pollution load, ecological risk and geoaccumulated risk. Based upon the used indices, a priority index ( P index ) was used to rank the utmost contaminated sites. Though the concentrations of mercury in all sediments were below the guideline, the significant enriched contamination was observed by all applied indices. As expected, the values of pollution load index ( PLI ), ecological risk index ( RI ) and geoaccumulation risk index ( I geo ) demonstrated lower heavy metal contamination in upstream areas compared to the downstream. Admittedly, sediments were unpolluted to slightly-polluted according to PLI while high to extremely high ecological risks were observed in several sediment samples. Furthermore, all the samples were uncontaminated as per I geo . After simplification of I geo , the P index showed the utmost contaminated sediments with a value of 2.537. Notably, protective measures should be taken to the highly contaminated areas which are prioritized by P index . Admittedly, the maximum concentrations of total organic carbon, total nitrogen, inorganic nitrogen, total phosphorous, inorganic phosphorous, calcium, magnesium, sodium and potassium were significantly observed as 7.8×10 4 , 3,185, 36, 1,032, 3.7, 1,5163, 2,881, 669 and 4,076mg/kg accordingly.

Potential value of phosphate compounds in enhancing immobilization and reducing bioavailability of mixed heavy metal contaminants in shooting range soil

Shooting range soils contain mixed heavy metal contaminants including lead (Pb), cadmium (Cd), and zinc (Zn). Phosphate (P) compounds have been used to immobilize these metals, particularly Pb, thereby reducing their bioavailability. However, research on immobilization of Pbs co-contaminants showed the relative importance of soluble and insoluble P compounds, which is critical in evaluating the overall success of in situ stabilization practice in the sustainable remediation of mixed heavy metal contaminated soils. Soluble synthetic P fertilizer (diammonium phosphate; DAP) and reactive (Sechura; SPR) and unreactive (Christmas Island; CPR) natural phosphate rocks (PR) were tested for Cd, Pb and Zn immobilization and later their mobility and bioavailability in a shooting range soil. The addition of P compounds resulted in the immobilization of Cd, Pb and Zn by 1.56-76.2%, 3.21-83.56%, and 2.31-74.6%, respectively. The reactive SPR significantly reduced Cd, Pb and Zn leaching while soluble DAP increased their leachate concentrations. The SPR reduced the bioaccumulation of Cd, Pb and Zn in earthworms by 7.13-23.4% and 14.3-54.6% in comparison with earthworms in the DAP and control treatment, respectively. Bioaccessible Cd, Pb and Zn concentrations as determined using a simplified bioaccessibility extraction test showed higher long-term stability of P-immobilized Pb and Zn than Cd. The differential effect of P-induced immobilization between P compounds and metals is due to the variation in the solubility characteristics of P compounds and nature of metal phosphate compounds formed. Therefore, Pb and Zn immobilization by P compounds is an effective long-term remediation strategy for mixed heavy metal contaminated soils.

Influence of physicochemical properties of soil on pH of pore water

AbstractpH of soil pore water is the important factor in heavy metal retention and migration in soil. Buffer capacity of clays such as kaolinite, hectorite, attapulgite, and Na-bentonite were determined. The magnitude of buffer capacity is in the order of hectorite>Na-bentonite>attapulgite>kaolinite. Carbonate content and CEC of soil affect most on the magnitude of buffer capacity while effects of organic content and surface area were negligible. Attempts were made to simulate buffer capacity experimental results in this research. In order to model the buffer capacity of soil, chemical interactions between proton and surface functional group were modeled using the diffuse double layer theory. An empirical model as functions of carbonate content and CEC were proposed as well. Predictions made by the diffuse double layer model agreed with experimental results well.

Mortality rates of pathogen indicator microorganisms discharged from point and non-point sources in an urban area

This research measured the mortality rates of pathogen indicator microorganisms discharged from various point and non-point sources in an urban area. Water samples were collected from a domestic sewer, a combined sewer overflow, the effluent of a wastewater treatment plant, and an urban river. Mortality rates of indicator microorganisms in sediment of an urban river were also measured. Mortality rates of indicator microorganisms in domestic sewage, estimated by assuming first order kinetics at 20 degrees C were 0.197 day(-1), 0.234 day(-1), 0.258 day(-1) and 0.276 day(-1) for total coliform, fecal coliform, Escherichia coli, and fecal streptococci, respectively. Effects of temperature, sunlight irradiation and settlement on the mortality rate were measured. Results of this research can be used as input data for water quality modeling or can be used as design factors for treatment facilities.

Determination of Electron Donors by Comparing Reaction Rates for In Situ Bioremediation of Nitrate-Contaminated Groundwater

Groundwater contaminated by nitrates occurs frequently. In this research, fumarate, acetate, formate, lactate, propionate, ethanol, and methane were evaluated as a potential electron donor and carbon source by comparing the denitrification rate for the in situ bioremediation of nitrate contaminated groundwater. The denitrification rate for each substance was the quickest in the order of: fumarate > hydrogen > formate/Lactate > ethanol > propionate > methanol > acetate. Microcosm studies were performed with fumarates and acetates. When fumarates were used as a substrate, nitrates were removed completely at a rate of 0.66mmol/day, while the conversion rate from nitrate to nitrogen gas and other by-products was 87%. For the microcosm test, 42 mg of fumarates were needed to remove 30 mg of NO3 −-N/L. When using acetate as a sole carbon source, 31% of nitrates were removed during the initial adjustment period. Among the removed fractions, however, 83% of the nitrates were removed by the cell growth. Overall, the nitrate removal rate was 0.37 mmol/day when acetate was used as a sole carbon source. The acetate showed longer lag time before denitrification occurred, which implied that fumarate would have been a better carbon source compared to acetate as more amounts were utilized for nitrate removal than cell growth.

Biosecurity procedures for the environmental management of carcasses burial sites in Korea

Avian influenza and foot-and-mouth disease are two main contagious pathogenic viral disease which are responsible for the massive burials of livestock in Korea since burial is the primary measure to control these outbreaks. Biosecurity is a set of preventive measures designed to prevent the risk of spreading of these infectious diseases. The main objective of this paper is to discuss about the requirements of biosecurity and develop protocol outlines for environmental management of burial sites in Korea. Current practice prescribes to minimize the potential for on-farm pollution and the spread of the infectious diseases. Specific biosecurity procedures such as proper assessment of leachate quality, safe handling and disposal of leachate, adequate leachate pollution monitoring, necessary seasonal management of burial site, and appropriate sterilization process must be carried out to prevent the indirect transmission of pathogens from the burial sites. Policy makers should acquire robust knowledge of biosecurity for establishing more effective future legislation for carcasses disposal in Korea.

Impact of pH buffer capacity of sediment on dechlorination of atrazine using zero valent iron

This research investigated the role of the pH buffer capacity of sediment on the dechlorination of atrazine using zero valent iron (ZVI). The buffer capacity of the sediment was quantified by batch experiments and estimated to be 5.0 cmol OH− · pH−1. The sediments were spiked with atrazine at 7.25-36.23 mg kg−1 (6.21 × 10−7–3.09 × 10−6 mol atrazine · g−1 sediment) for the batch experiments. The buffer capacity of the sediment maintained the sediment suspension at neutral pH, thereby enabling continuous dechlorination until the buffer capacity of the sediment was depleted. The pseudo-first order dechlorination constants were estimated to be in the range of 1.19 × 10−2−7.04 × 10−2 d−1 for the atrazine-spiked sediments.

Ultrasonic Enhancement of Drainage Material Filterability

Various research studies have been undertaken in an effort to enhance the filterability of drainage material for soil improvement in land reclamation work. The principal concern with existing drainage strategies is that their effectiveness decreases significantly with time, due to clogging of the soil. In this study, we investigated the enhancement of drain filterability with the application of ultrasound. Specially designed and fabricated equipment was used to apply ultrasonic energy to the soil samples during experimentation. The results showed that the application of ultrasonic energy significantly increased the filterability of the soil samples. Thus, these results advocate the use of ultrasound for enhanced drainage filterability.

Monitoring and assessing heavy metals in topsoils as potential diffuse pollutants in the Pyeongchang River Basin, Korea.

Topsoils, mainly from crop fields, orchards, forests, and barns around the Pyeongchang River, were collected to investigate their heavy metal concentrations. Pollution load index, ecological risk index, and enrichment factor were applied to assess levels of heavy metal contamination for topsoils. The concentrations of cadmium (Cd) (1.7 mg/kg) and chromium (Cr) (4.1 mg/kg) exceeded the troublesome level in one site, whereas zinc (Zn) (396.7 to 711.1 mg/kg) and nickel (Ni) (40.1 to 95.3 mg/kg) in several topsoils exceeded the troublesome to countermeasure levels, according to soil contamination standards for the study areas. A significant risk of contamination was observed for mercury (Hg) by all indices, although the concentration in most of the topsoils was below the guideline. As expected, a positive linear correlation was observed for the values of pollution load index and ecological risk index, demonstrating lower heavy metal contamination in upstream areas compared to those downstream. High to extremely high ecological risk was observed in several samples for Zn and Ni, while all of the soils were unpolluted to slightly polluted, according to the pollution load index. A baseline study was not performed earlier for these sites, so these assessed values of heavy metals should be used as reference values for further assessment.