Airborne manganese concentrations on the Korean peninsula from 1991 to 2006

In this study, the distribution of airborne manganese (Mn) bound with particulate matters (PM) was investigated using data sets collected from 15 major cities in Korea over a 16-year time span (1991–2006). The mean Mn concentration measured from all the major cities in Korea throughout the entire study period was 71 ng m^?3, while the annual mean values of different cities ranged from 10.5 ng m^?3 in Yeosu (2003) to 615 ng m^?3 in Wonju (2006). The Mn levels were considerably larger in industrialized areas than in other land-use types. The Mn concentrations in the major industrial cities of Pohang, Incheon, and Ansan averaged 255, 98.2, and 84.6 ng m^?3, respectively; these values were far higher than those measured typically at most cities, e.g., 20–60 ng m^?3. Seasonal patterns characterized by the peak occurrence in spring and the noticeable drop in summer reflected the effects of the massive PM inflow from China (spring) and effective washout by summer monsoon in East Asia, respectively. Examination of Mn data over a long-term period indicated that the temporal trends of Mn seen in most cities were fairly constant through time since the 1990s, although some abnormalities were observed in cities of strong man-made activities (e.g., Pohang and Wonju). In light of the severity of airborne Mn pollution in many urban areas, it is desirable to establish an abatement strategy that can help effectively reduce Mn levels.     

The trends of composite environmental indices in Korea

In this paper we construct for the first time an annual Composite Environmental Index from 1986 to 1995 in Korea, which is useful for evaluating the efficiency of environmental policies. Nine types of environmental problems are examined. On average, the composite index has increased annually by 5.3% over the 1986-1995 period, which implies that overall environmental quality has deteriorated gradually during this period. Problems such as the greenhouse effect, loss of biodiversity, natural resource depletion, and ecotoxication led to deterioration of environmental quality in the 1990s.     

Evaluation of non-enteric sources of non-methane volatile organic compound (NMVOC) emissions from dairies

Dairies are believed to be a major source of volatile organic compounds (VOC) in Central California, but few studies have characterized VOC emissions from these facilities. In this work, samples were collected from six sources of VOCs (Silage, Total Mixed Rations, Lagoons, Flushing Lanes, Open Lots and Bedding) at six dairies in Central California during 2006–2007 using emission isolation flux chambers and polished stainless steel canisters. Samples were analyzed by gas chromatography/mass spectrometry and gas chromatography/flame ionization detection. Forty-eight VOCs were identified and quantified in the samples, including alcohols, carbonyls, alkanes and aromatics. Silage and Total Mixed Rations are the dominant sources of VOCs tested, with ethanol as the major VOC present. Emissions from the remaining sources are two to three orders of magnitude smaller, with carbonyls and aromatics as the main components. The data suggest that animal feed rather than animal waste are the main source of non-enteric VOC emissions from dairies.     

Applicability of a continuous-flow system inner-coated with S-doped titania for the photocatalysis of dimethyl sulfide at low concentrations

The present study investigated the photocatalytic activity of an S-doped TiO₂ photocatalyst with regards to dimethyl sulfide degradation under visible-light irradiation, along with its deactivation and reactivation. The dimethyl sulfide conversion was between 85% and 93% for the lowest relative humidity range (10–20%) and close to 100% for the two higher relative humidity ranges (45–55% and 80–90%). The conversion was also close to 100% for the two lowest input concentrations (0.039 and 0.195 ppm), while it was between 91% and 96% at 3.9 ppm and between 85% and 90% at 7.9 ppm. In contrast to the input concentration dependences on conversion, the calculated degradation rates increased as input concentrations increased. The dimethyl sulfide conversion at low concentrations (≤0.39 ppm), which are associated with non-occupational inn occurring. However, catalyst deactivations were observed during the photocatalytic process whdoor air quality issues, was up to nearly 100% for long time periods (at least 603 h), without any significant catalyst deactivatioen higher concentrations (3.9 and 7.8 ppm) were used. The photocatalyst, reactivated by using two types of air (dried and humidified) under visible-light irradiation, did not regain all of its initial activities. Sulfate groups were qualitatively identified as the reaction products on the photocatalyst surface. In addition, gaseous byproducts, quantitatively determined, included dimethyl disulfide, methanol, and SO₂. It is noteworthy that the peak concentration of dimethyl disulfide (0.79 ppm = 790 ppb), generated over the photocatalytic process with the highest dimethyl sulfide input concentration, exceeded the odor threshold value of 0.1–3.6 ppb for dimethyl disulfide.     

Characterization of polychlorinated dibenzo-p-dioxins and dibenzofurans in different particle size fractions of marine sediments

The distribution of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) was examined according to particle size in marine sediments, with a particular focus on fine particulates. Samples from different coastal sites were fractionated into five size groups (<2, 2-5, 5-10, 10-20, and 20-63 microm diameter) by gravitational split-flow thin fractionation. Despite the different size profiles and PCDD/F contents of the sediments at each site, PCDD/F levels in fractionations tended to increase as the particle size decreased; the PCDD/F levels in the finest particles were up to 16 times higher than in the coarsest particles, which was associated with their organic carbon contents. Log normalization showed high levels of PCDD/Fs in the fine silt particles (2-10 microm), which are consumable by aquatic biota. Because of the different toxicity and bioavailability of PCDD/Fs in different sediment particle sizes, it is important to study particle actions to understand their effects on the aquatic ecosystem.