Mercury wet deposition in rural Korea: concentrations and fluxes

The characteristics of Hg wet deposition were investigated in a rural area of Korea from August 2006 to July 2008. The volume weighted mean (VWM) Hg(T) concentration and cumulative Hg(T) flux were 8.8 ng L(-1) and 9.4 μg m(-2) per year, respectively. The VWM Hg(T) concentration varied seasonally, similar to the seasonal pattern in atmospheric Hg(p) concentration. The enhancement of both VWM Hg(T) and atmospheric Hg(p) concentrations in spring and winter was likely caused by the long-range transport of Hg from China. Monthly VWM Hg(T) and atmospheric Hg(p) concentrations were well correlated (R(2) = 0.36); however, there was no correlation between VWM Hg(T) and RGM (reactive gaseous mercury) concentrations, suggesting that Hg(p) was responsible for the majority of the Hg in wet deposition at this site. The VWM Hg(T) concentration in snow was statistically higher than in rain. In addition, the atmospheric Hg(p) concentration appeared to be elevated for snow events as well. This suggests that both elevated Hg(p) concentrations and the enhanced scavenging efficiency of snow for Hg(p) were responsible for the elevated VWM Hg(T) concentrations measured during snow events.     

Degradation of different pesticides in water by microplasma: the roles of individual radicals and degradation pathways

Environmental Science and Pollution Research - Pesticides are emergent toxins often identified in aquatic environments. In the present study, microplasma was employed to reduce the pesticide...     

Distribution of inorganic arsenic species in mine tailings of abandoned mines from Korea

The main objective of the present study is to determine arsenic species in mine tailings by applying an ion exchange method. Three abandoned mines, Jingok, Cheonbo and Sino mines in Korea, which had produced mainly gold, were selected for the collection and analysis of the tailings. It was found that the arsenic speciation using an ion exchange method was effective to separate As(III) and As(V) in leachate of mine tailings. The concentration of As(V) was found to be 63-99% in the leachate, indicating that As(V) would be the major arsenic species in the mine tailings and the tailings were under oxic conditions. The total concentrations of arsenic and metal elements in the mine tailings were up to 62,350 mg/kg As, 40 wt.% Fe, 21,400 mg/kg Mn, and 7,850 mg/kg Al. Sulfate was the dominant anion throughout the leachate, reaching a maximum dissolved concentration of 734 mg/l. The results of XRD and SEM in the mine tailings showed that main arsenic-containing minerals were pyrite (FeS2) and arsenopyrite (FeAsS) which would be the source of arsenic contamination in the study area.     

Dissolved organic matter effects on the performance of a barrier to polycyclic aromatic hydrocarbon transport by groundwater

In order to contain the movement of organic contaminants in groundwater, a subsurface sorption barrier consisting of sand or clay minerals coated with a cationic surfactant has been proposed. The effectiveness of such a sorption barrier might be affected by the presence of dissolved organic matter (DOM) in the groundwater. To study the impact of DOM on barrier performance, a series of batch experiments were performed by measuring naphthalene and phenanthrene sorption onto sand coated with cetylpyridinium chloride (CPC) and bentonite coated with hexadecyltrimethylammonium bromide (HDTMA) in the presence of various concentrations of DOM. The overall soil-water distribution coefficient (K*) of naphthalene and phenanthrene onto CPC-coated sand decreased with increasing DOM concentration, whereas the K* of the compounds onto HDTMA-coated bentonite slightly increased with increasing DOM concentration. To describe the overall distribution of polycyclic aromatic hydrocarbons (PAHs) in the systems, a competitive multiphase sorption (CMS) model was developed and compared with an overall mechanistic sorption (OMS) model. The modeling studies showed that while the OMS model did not explain the CPC-coated sand experimental results, a model that included competitive sorption between DOM and PAH did. The experimental results and the modeling study indicated that there was no apparent competition between DOM and PAH in the HDTMA-coated bentonite system, and indicated that in groundwater systems with high DOM, a barrier using HDTMA-coated bentonite might be more effective.     

Long-term fate of the herbicide cinosulfuron in lysimeters planted with rice over four consecutive years

In order to elucidate the long-term fate of the sulfonylurea herbicide cinosulfuron, the 14C-labelled chemical was applied to a clay loam soil, encased in two lysimeters, 22 days after rice (Oryza sativa L.) transplanting, and rice plants were grown for four consecutive years. Throughout the experimental period, leaching through soil profiles, absorption and translocation by rice plants, and distribution of 14C by downward movement in the soil layers were clarified. The total volume of leachates collected through the lysimeter soil over the four years amounted to 168 and 146 L in lysimeters I and II, respectively. The leachates contained 2.43% and 2.99% of the originally applied 14C-radioactivity, corresponding to an average concentration of 0.29 and 0.41 microg/L as the cinosulfuron equivalent in lysimeters I and II, respectively. The total 14C-radioactivity translocated to rice plants in the third and fourth year was 0.69% and 0.60% (lysimeter I), and 1.02% and 0.84% (lysimeter II) of the 14C applied, respectively. Larger amounts of cinosulfuron equivalents (0.54-0.75%) remained in the straw in the fourth year than in any other parts. The 14C-radioactivities distributed down to a depth of 70 cm after four years were 56.71-57.52% of the 14C applied, indicating the continuous downward movement and degradation of cinosulfuron in soil. The non-extractable residues were more than 88% of the soil radioactivity and some 45-48% of them was incorporated into the humin fraction. The 14C-radioactivity partitioned into the aqueous phase was nearly 30% of the extractable 14C, suggesting strongly that cinosulfuron was degraded into some polar products during the experimental period. It was found out in a supplemental investigation that flooding and constant higher temperature enhanced mineralization of [14C]cinosulfuron to 14CO2 in soil, indicating the possibility of chemical hydrolysis and microbial degradation of the compound in the flooded lysimeter soil.     

Monitoring the impact of dissolved oxygen and nitrite on anoxic biofilm in continuous denitrification process

An anoxic biofilm involved in continuous denitrificationprocess was monitored to investigate the effect of differentconcentrations of influent dissolved oxygen (DO) or nitrite onthe biofilm. Microelectrode measurements evidenced nitrateremoval activity of biofilm. When different concentrations ofDO were applied to the reactor, generally decreasedconcentrations of DO were observed as bed depth increased fromthe bottom of the reactor. Greatest decrease of the DO wasobserved in the lower 20% of the bed depth. Nitrate removalefficiency was inversely proportional to influent DOconcentrations (8.3-11.9 DO mg L^-1) or nitrite loadingrates (0-5.5 N-NO₂ ^- kg m^-3 day^-1) employed in this study. Nitrite loading rates to achieve morethan 90% of nitrate removal efficiency were 1.46 N-NO₂ ^-kg m^-3 day^-1 or less at pH 7.5 and 0.34 N-NO₂ ^- kg m^-3 day^-1 or less at pH 6.8. Nitrate removal efficiency was 63% or more within the lower 20% of the bed depth at the nitrite loading rates that allowed more than 90% of nitrate removal efficiency of the reactor. The results of this study provide first quantitative data that nitrate removalperformance of an anoxic biofilm is inhibited by DO or nitrite,reported to be a limiting factor in the suspended biologicaldenitrification process.     

Biodegradation and detoxification of organophosphate insecticide, malathion by Fusarium oxysporum f. sp. pisi cutinase

Efficiencies of two lypolytic enzymes (fungal cutinase and yeast esterase) in malathion degradation were investigated. Surprisingly, degradation rate of malathion by fungal cutinase was very high, i.e. almost 60% of initial malathion (500 mg l(-1)) was decomposed within 0.5 h, and nearly 50% of the degraded malathion disappeared within initial 15 min. With the yeast esterase, despite the same concentration, more than 65% of malathion remained even after 2-day treatment. During enzymatic degradation of malathion, two malathion-derived compounds were detected, and time-course changes in composition were also monitored. In the degradation by both fungal cutinase and yeast esterase, two additional organic chemicals were produced from malathion: malathion monoacid (MMA) and malathion diacid (MDA) by ester hydrolysis. Final chemical composition after 2 d was significantly dependent on the enzyme used. Fungal cutinase produced MDA as a major degradation compound. However in the malathion degradation by yeast esterase, an isomer of MMA was produced in abundance in addition to MDA. Toxic effects of malathion and its final degradation products were investigated using various recombinant bioluminescent bacteria. As a result, the degradation products (including MMA) by esterase severely caused membrane damage and inhibition of protein synthesis in bacterial cells, while in the fungal cutinase processes, malathion was significantly degraded to non-toxic MDA after the extended period (2 days).     

Investigation of 3H, 99Tc,and 90Sr transport in fractured rock and the effects of fracture-filling/coating material at LILW disposal facility

Environmental Geochemistry and Health - Batch adsorption, batch diffusion, and flow-through column experiments were conducted using groundwater and fractured rock collected in unsaturated zone to...     

Geochemical occurrences of arsenic and fluoride in bedrock groundwater: a case study in Geumsan County,Korea

Rio Grande, the southernmost Brazilian port and industrial center, is marked by mercury-polluted ground cover. This pollution varies spatially, with levels exceeding 1,000 μg kg⁻¹ in 30% of the urban territory. The risk of Hg impact as a result of deliberate and involuntary geophagy is increased by restrained urban conditions in combination with the large proportion of the population living at low-income levels. Laboratory tests have demonstrated that ingestion of Hg-polluted soil by rats results in significant alterations in animal health such as stagnation in body weight increase, and significant mercury accumulation in the liver and kidney. The consumption of Hg-contaminated urban soil also provoked changes in hematological profiles of experimental animals by increasing the number of platelets. The present study indicates the potential for the local population of Rio Grande living in mercury-polluted districts, specifically young children, to experience health disturbances.