Sunyoung Bae

Patterns of VOC and BTEX concentration in ambient air around industrial sources in Daegu, Korea

Patterns of VOC and BTEX (Benzene, Toluene, Ethylvenzene, and Xylene) distribution at industrial emission sources, proximal residential areas of industrial estates, and ambient air were studied in Daegu, Korea. Daytime and night-time sampling was done at 12 sites and 9 emission sources to provide samples for analyses, using the TO-14 method. Measured BTEX component ratios B/T, T/EB, T/X and EB/X in ambient air were found to be 2.6 g, 11.3 g, 1.0 g and 1.2 g in the residential area; 2.2 g, 11.0 g, 1.0 g and 1.6 g in the commercial area; and 1.0 g, 14.9 g, 1.0 g and 1.3 g in the industrial area. The significant difference observed between the ratios for the residential and commercial areas implies that the two areas have different emission sources. This is also indicated by the significant differences observed between daytime and nighttime BTEX concentrations. Toluene and xylene were detected at very high concentrations, at the sampling sites. This pattern reflects the type of industrial processes and materials that are managed at the emission sources, as well as topographic/climatic factors that impact upon pollutant transport processes in the atmosphere. The BTEX distribution pattern in Daegu is observed to be similar to that of several Asian cities, particularly Hong Kong. These results are useful in the design of emission source control measures for VOCs and BTEX in Daegu.

Coastal Pollution Mitigation with Lime and Zero Valent Iron

The Taiwan Strait region has many miles of coastline, and the Taiwan Straits Tunnel (TST) project faces many potential pollution problems as construction proceeds through sensitive areas. Conventional approaches for pollution mitigation require further examination. The recent development of nanoscale particle technology has shown distinct advantages for contaminant attenuation and ground improvement. This paper is focused on trace metals and is part of the overall effort to develop the nanoscale particle technology. Trace metals in ground and surface waters represent a continued threat to human and ecological health. One of the difficulties in removing toxic concentrations of trace metals from solution is the variable oxidation state and amphoteric nature of multiple constituents. In particular, while cationic metals (e.g., Pb2+, Cd2+, Ni2+) may be rendered less mobile under high pH conditions, anionic metals (e.g., AsO4 3−, CrO4 2−, SeO4 2−)may become more mobile. The objective of this research was to evaluate the sorption of both cationic and anionic trace elements, including arsenic (As), cadmium (Cd), chromium (Cr) and selenium (Se) under batch conditions. Mixtures of a local residual soil were tested alone and in combination with lime and zero valent iron. It was hypothesized that lime would raise the pH and precipitate positively charged metals while zero valent iron would create reducing conditions favorable to the immobilization of negatively charged metals. Results indicate that the use of lime and/or zero valent iron can increase the sorption capacity of soil. Compared to the baseline soil, sorption capacity increased with addition of lime for arsenic and cadmium while it decreased for chromium and selenium. In the case of zero valent iron addition, sorption capacity increased for cadmium, chromium and selenium, while showing no change for arsenic. When both lime and zero valent iron were used, the sorption capacity increased for all metals tested. These results suggest that the combined use of lime and zero valent iron may serve as an alternative treatment technology for removing trace metals from contaminated water systems.