Ilwon Ko

Arsenic contamination of soils and sediments from tailings in the vicinity of Myungbong Au mine, Korea

Abstract Geochemical characteristics of As contamination in the Myungbong gold mine area in Korea were investigated, and the mine tailings were found to contain high concentrations of As (2,500–6,420 mg/kg). The mine tailings are an obvious candidate for the source of contamination in the study area. From the sequential, and oxalate, extraction analyses the majority of the As in the tailings was found to be associated with Fe oxides produced when sulfide minerals are oxidised. Mineralogical examinations showed the formation of poorly crystalline Fe oxides on a rim of pyrite, onto which the As was retained. The sediments of two ponds affected by the tailings also contained significant levels of As. High concentrations of dissolved As were also found in pond and stream waters. It has been suggested that the mobility of the As was increased by the reductive dissolution of Fe oxides under reducing conditions in the pond. Agricultural fields, located beneath the tailing dumps, have been contaminated by the continuous use of contaminated stream water and groundwater for irrigation.

Adsorption properties of soil humic and fulvic acids by hematite

Abstract The adsorption isotherms and their size fractionations of soil humic and fulvic acids (HA and FA, respectively) were determined at pH 7, 9.2 and 11, where the surfaces of the hematite are positively, neutrally and negatively charged, respectively. The Mw, Mn and polydispersity in the solution after adsorption were measured in order to investigate the preferential adsorption trend of the HA and FA. The measured adsorption was consistent with the adsorption from Langmuir isotherm fitting. The adsorption of HA onto the hematite was more favorable than that of FA due to the preferential adsorption of high molecular weight fractions and the greater hydrophobicity. As the solution pH increased, the preferential adsorption for the high molecular weight fractions partially deviated with higher polydispersity. This indicates that the adsorption of the HA and FA onto hematite was affected by the molecular conformation, and the electrostatic repulsion between the HA and FA and the hematite lead to the kinetically sluggish adsorption. Further, it implies that the adsorption properties of soil organic matter may affect the adsorption of metal and metalloid onto the adsorbent like iron-oxide in the geochemical environments.

Geochemical and Geophysical Monitoring of Salinewater Intrusion in Korean Paddy Fields

The saline water intruded zone in paddy fields near the seashore can be diagnosed accurately by joint exploration with geophysical and geochemical methods. Using the electromagnetic (EM) sounding technique, the weakly consolidated zone which introduces saline water into such an area of near seashore paddy fields in Korea was detected from the variation of electrical conductivity distribution following field irrigation. Vertical electrical sounding (VES) with Schlumberger array and chemical analysis of top soils, and groundwater in the study area verified the intruded zone near the surface. The VES results showed that the intrusion of seawater occurred in the form of a channel down to 30 m below sea level. Geochemical analysis of the top soil samples for the six major elements found in seawater indicated that the region showing high concentrations is concordant with the weakly consolidated zone near the surface. The degree of contamination in the study area was investigated by comparing the soil data with those from a nearby old reclamation field. If remediation work is not done for this intrusion zone, the sodicity degree in the paddy soil is expected to increase compared with the reference site data.

Effect of Scale-up and Seasonal Variation on Biokinetics in the Enhanced Bioremediation of Petroleum Hydrocarbon-contaminated Soil

The biodegradation rate of petroleum hydrocarbon-contaminated soil was evaluated by the effect of temperature variation through bioaugmentation and biostimulation. In this study, biokinetics of batch-, pilot-, and field-scale biodegradation were performed by the optimization of enhanced biodegradation, minimizing the inhibitory effects of seasonal variations such as the rainy and cold winter seasons. From the relationship between remedial timescale and initial concentration, the biokinetic isolines of the biodegradation were smaller in the winter than those in the other seasons. The scale-up of biodegradation process led to enhance its activation energy, and then the field-scale remedial action should be performed in the way to lower the activation energy from the chemical diffusion and microbial activation. Therefore, a remedial or field worker can obtain the remedial timescale from the given apparent data of biokinetics with respect to initial TPH concentration only after the simple remedial investigation.

Application of arsenic field test kit to stream sediment: effect of fine particles and chemical extraction.

Abstract The field test kit for the on-site analysis of arsenic has been previously evaluated for aqueous solutions such as surface water and groundwater. In this study, the field test kit was optimized for arsenic determination in a sandy sediment The field test kit was found to be applicable to on site screening of arsenic contamination at levels around 6 mgkg−1, the soil regulatory standard for arsenic concentration in Korean soils. However, the method requires a simple chemical pre-extraction. This arsenic extraction has been optimized and the effects of soil–solution ratio, extraction time and fine particles are discussed in detail. The fine particles in the sediment sample strongly bind to arsenic resulting in variability of its extraction, both in extractability and extraction time. Under the optimized conditions, the arsenic content using the field test kit had a high regression coefficient with respect to that found by chemical analysis of the sediment sample.