Application of micrometeorological approaches to measure methane exchange in a dry paddy field in the western coast of Korea

The exchange processes of CH₄ were investigated in a paddy field in the Hari area of Kang Hwa Island over an 8 day period in late April 2002. The quantification of CH₄ fluxes was made under dry field condition of early spring by concurrently measuring its concentrations (at the two heights of 1 and 5 m) and the relevant micrometeorological parameters. To help elucidate the factors determining the mobilization characteristics of CH₄, the results of our measurement data were examined using a number of approaches. The results of the trajectory analysis indicated that its concentration changed very sensitively with the influence of different source types, as seen from the air mass movement patterns. The concentrations and fluxes of methane, when examined over this short-term scale, showed moderately strong patterns across 24 h period in which higher values tend to occur during morning or evening. The overall results of our field measurements suggest that CH₄ exchange processes in the paddy area proceeded in a fairly complicated manner. The study area behaved as a net source of CH₄ to the atmosphere with a net daily emission rate of 3.6 mg m⁻² despite the fact that downward deposition was observed more frequently than upward emission.     

The exceedance patterns of air quality criteria: a case study of ozone and nitrogen dioxide in Seoul, Korea between 1990 and 2000

In this study, the environmental behavior of two major airborne pollutants, ozone and nitrogen dioxide, was investigated with respect to their exceedance patterns of air quality criteria. For this purpose, we used data sets collected from a total of 31 air quality monitoring stations dispersed across the Seoul metropolitan city between 1990 and 2000. In the case of NO(2), the frequency of hourly exceedance data sets exhibited little changes in the early 90s. However, it increased dramatically after 1995, probably in compliance with a rapid increase in the total number of automobiles. Likewise, the daily exceedance of O(3) in the early 90s was not significant, approaching 100 cases (except in 1994). However, its total quantity began to surpass 300 cases since around 1996. Comparison of those exceedance data was also made among spatially divided data groups. In the case of NO(2), the occurrence of exceedance data was dominated by the western part of the city in both magnitude and frequency. On the other hand, that for O(3) was characterized by notably strong occurrences in the eastern counterpart. The overall results of our analysis of the NO(2) and O(3) exceedance data sets indicate an inextricable linkage between the two pollutants in association with geographical and meteorological factors.     

Contents of chlordane-, PCB- and DDT-compounds and the biotransformation capacity of fishes in the lake area of eastern Finland

Fish samples (perch, roach, vendace and rainbow trout) from the lake area in castern Finland were found to be contaminated not only with PCB- and DDT-compounds but also with chlordane-compounds. The contents of pollutants were strongly species specific and were studied against the biotransformation capacity of the fishes. No chlordane compounds were found in rainbow trout, which is superior to the other species in its biotransformation capacity.     

In-situ electrochemical measurements of total concentration and speciation of heavy metals in acid mine drainage (AMD): assessment of the use of anodic stripping voltammetry

We assessed the use of anodic stripping voltammetry (ASV) for in-situ determinations of both total concentration and speciation of dissolved heavy metals (Cd, Cu, Pb and Zn) in acid mine drainage (AMD). In the Kwangyang Au–Ag mine area of South Korea, different sites with varying water chemistry within an AMD were studied with a field portable anodic stripping voltammeter. Anodic stripping voltammetry after wet oxidation (acidification) was very sensitive enough to determine total concentration of dissolved Cd because Cd was dominantly present as ‘labile’ species, whilst the technique was not so effective for determining total Cu especially in the downstream sites from the retention pond, due to its complexation with organic matter. For dissolved Pb, the concentrations determined by ASV after wet oxidation generally agreed with those by ICP-AES. In the downstream samples (pH>5), however, ASV data after wet oxidation were lower than ICP-AES data because a significant fraction of dissolved Pb was present in those samples as ‘inert’ species associated with colloidal iron oxide particles. The determination of total dissolved Zn by ASV after wet oxidation appeared to be unsatisfactory for the samples with high Cu content, possibly due to the interference by the formation of Zn–Cu intermetallic compounds on the mercury coated electrode. In AMD samples with high dissolved iron, use of ultraviolet irradiation was not effective for determining total concentrations because humate destruction by UV irradiation possibly resulted in the removal of a part of dissolved heavy metals from waters through the precipitation of iron hydroxides.     

Emission of PCDD/Fs and dioxin-like PCBs from metallurgy industries in S. Korea

The metallurgy industry and municipal waste incinerators are considered the main sources of polychlorinated dibenzo-p-dioxin and dibenzofurans (PCDD/Fs) in many countries. This study investigated the emission factors and total emissions of PCDD/Fs and dioxin-like polychlorinated biphenyls (PCBs) emitted from metallurgy industries (including ferrous and nonferrous foundries) in Korea. The toxic equivalency (TEQ) emission factor of PCDD/Fs was the highest for secondary copper production, at 24451 ng I-TEQ/ton. The total estimated emissions of PCDD/Fs from these sources were 35.259 g I-TEQ/yr, comprising 0.088 g I-TEQ/yr from ferrous foundries, 31.713 g I-TEQ/yr from copper production, 1.716 g I-TEQ/yr from lead production, 0.111 g I-TEQ/yr from zinc production, and 1.631 g I-TEQ/yr from aluminum production. The total estimated annual amounts of dioxin-like PCBs emitted from these sources were 13.260 g WHO-TEQ/yr, comprising 0.014 g WHO-TEQ/yr from ferrous foundries, 12.675 g WHO-TEQ/yr from copper production, 0.170 g WHO-TEQ/yr from lead production, 0.017 g WHO-TEQ/yr from zinc production, and 0.384 g WHO-TEQ/yr from aluminum production. The highest emission factor was found for secondary copper smelting, at 9770 ng WHO-TEQ/ton.     

Distribution characteristics of polychlorinated biphenyls in crucian carp (Carassius auratus) from major rivers in Korea

Polychlorinated biphenyls (PCBs) levels in crucian carp were determined at 20 locations along four major river systems, several small-scale rivers and a wetland in Korea. Twenty-eight congeners, ranging from tri- to hepta-CBs were detected. A gas chromatograph with a mass selective detector was used to quantify the individual PCB congeners. The objectives of this study were to investigate the levels of contamination of PCBs in freshwater fish and to observe the pattern of their distribution. The sampling locations were chosen among 31 sampling sites that are currently used as environmental residue checkpoints by the Korean Ministry of Environment. Concentrations of individual congeners ranged from not detectable (n.d.) to 0.75 ng g(-1) on a wet weight basis. The total concentrations of PCBs at each site ranged from n.d. to 5.41 ng g(-1) of wet weight. The most heavily contaminated site was the Nakdong estuary located near the Shinpyung-Janglim factory district. The PCB 153 and 138 were the principal congeners and penta- and hexa-chlorinated biphenyls comprised the main congener groups.     

Photochemical oxidation of reduced sulfur compounds in an urban location based on short time monitoring data

This study examines the oxidation of reduced sulfur compounds (RSCs) in urban ambient air. The photochemical conversions of RSC (such as DMS, CS₂, H₂S, DMDS, and CH₃SH) to a further oxidized form (e.g., SO₂, MSA, and H₂SO₄) were assessed using a photochemical box model. For our model simulation of RSC oxidation, measurements were taken at an urban monitoring station in Seoul, Korea (37.6° N, 127° E) during three separate time periods (e.g., Sept. 17–18, Oct. 23, and Oct. 27–28, 2003). The results indicate that DMS and H₂S were the dominant RSCs with concentrations of 370 ± 140 and 110 ± 60 pptv, respectively. The photochemical conversion of DMDS to SO₂ was found to occur more efficiently than other RSCs. The overall results of our study suggest that photochemical conversion of RSCs accounted for less than 15% of the observed SO₂ during the measurement period. The SO₂ production from DMS oxidation (mainly by the reaction with OH) was found to be affected primarily by the abstraction channel due to high NO_x levels during the experimental conditions.     

Recovery of phosphates from wastewater using converter slag: Kinetics analysis of a completely mixed phosphorus crystallization process

A phosphorus crystallization process for recovering phosphates was developed using a completely mixed reactor and powdered converter slag as a seed crystal. This completely mixed phosphorus crystallization process achieved a stable and high phosphorus recovery: the average PO4-P removal efficiency during 200 d of operation was 87%, with a range of 70-98%. The apparent volume of the slag doubled due to crystal growth during the long-term phosphorus-removal experiments. The Ca2+ concentration, slag dosage, and temperature were found to govern the phosphorus recovery system for a given condition of pH and hydraulic retention time. The equations for the rate constant and reaction order were obtained by evaluating the model parameters. The model developed in this study was observed to successfully simulate the behavior of effluent PO4-P in a completely mixed phosphorus crystallization reactor over a wide variety of operating conditions of temperature, Ca2+ concentration, and influent PO4-P. Model investigations of design factors suggest that the completely mixed phosphorus crystallization process with influent PO4-P concentrations of less than 10 mg l(-1) could ensure effluent PO4-P concentrations of less than 0.5 and 1.0 mg l(-1) during summer and winter in Korea, respectively.     

Analysis of regional and temporal characteristics of PM10 during an Asian dust episode in Korea

This study analyzes the regional and temporal distributions of PM10 concentrations observed in major metropolitan cities in Korea before, during and after a recent Asian dust episode in 2002. There were spatial and temporal variations in PM10 concentrations among the mid-western, the southwestern, the southeastern, and the southern parts of Korea during this Asian dust period due to the different air mass movement time and the different wind directions and speeds of prevailing winds in each city or region. The origins of the three-day Asian dust episode were identified by an analysis of two-day backward isentropic air trajectories. The different origins for each day also significantly contributed to the spatial and temporal variations in PM10 concentrations. A significant relationship was found between PM10 concentrations on the day preceding the first peak day and the first peak day of the Asian dust period but only in the mid-western areas. The concentrations of PM10 just after the Asian dust episode were much higher than those just before. There was a significant increase in a coarse fraction, having soil origins, of particles during the Asian dust episode. Concentrations of Mn, Fe, Ni and Cr extracted from the total suspended particulate (TSP) samples collected in 7 cities during the Asian dust episode were much higher when compared with other days in 2001. However, the Asian dust did not consistently increase the concentrations of lead, cadmium and copper as they are influenced by local sources such as local traffic or industrial emissions.     

Determination of gas phase adsorption isotherms--a simple constant volume method

Single and ternary solute gas phase adsorption isotherms were conducted in this study to evaluate the effectiveness of a simple constant volume method, which was utilized by using Tedlar gas sampling bags as a constant volume batch reactor. For this purpose, gas phase adsorption of toluene, methyl ethyl ketone (MEK), and methyl isobutyl ketone (MIBK) on two types of activated carbons, BPL-bituminous base and OVC--coconut base, were investigated. For the single solute adsorption, the experimental adsorption data were found to be well correlated with Freundlich and Myers adsorption equations. The pore size distribution of adsorbents was found to affect their adsorption capacities; its effect was dependant on the solute concentration. The ternary adsorption experimental isotherms were accurately predicted by using the well-known model, i.e., ideal adsorbed solution theory (IAST).