Masao Kishida

Characteristics of the abundance of polychlorinated dibenzo-p-dioxin and dibenzofurans, and dioxin-like polychlorinated biphenyls in sediment samples from selected Asian regions in Can Gio, Southern Vietnam and Osaka, Japan.

The levels of polychlorinated dibenzo-p-dioxin and dibenzofuran (PCDD/PCDFs), and dioxin-like polychlorinated biphenyls (DL-PCBs) were determined in sediment samples from Can Gio, South Vietnam, and Osaka, Japan. Can Gio is known for the defoliation of its mangrove forests by aerial spraying with Agent Orange during the Vietnam War, whereas Osaka is renowned for a PCDD/PCDF pollution accident at a municipal solid-waste incinerator. For comparison, we also analyzed PCDD/PCDFs and DL-PCBs in sediment samples from Hue and Hanoi, Vietnam. The toxic equivalent quantity (TEQ) values in Can Gio were as high as those in Hue, Hanoi, and suburban areas of Osaka, but much lower than those in urban areas of Osaka. The proportion of the World Health Organization (WHO)-TEQ value contributed by 2,3,7,8-tetrachlorinated dibenzo-p-dioxin (TCDD) in Can Gio was approximately 30%, higher than the values in the other sample areas. These data suggest that residual sedimentary TCDD that originated from aerial spraying of Agent Orange occur in only low concentrations in Can Gio. The main contributors to WHO-TEQ values in Can Gio are natural sources, as in Hue. In contrast, commercial PCBs are the dominant contributors to WHO-TEQ values in Hanoi. In Osaka, agrochemicals used in rice cultivation, the incineration of solid waste, and commercial PCBs equally contributed to WHO-TEQ values at suburban locations. The dumping of incinerator-related materials and/or the inadequate management of commercial PCBs have resulted in significantly elevated WHO-TEQ values of 240-370 ng kg(-1)dw at urban locations in Osaka.

Temporal variation of atmospheric polycyclic aromatic hydrocarbon concentrations in PM10 from the Kathmandu Valley and their gas-particle concentrations in winter

The concentrations of polycyclic aromatic hydrocarbons (PAHs) in particulate matter (PM) with a diameter <10 µm (PM10, 50% cut off) were investigated in the Kathmandu Valley, Nepal, during 2003. In order to understand the dynamics of atmospheric PAHs in winter, the PAH concentrations in total PM and in the gaseous phase were investigated in the valley in December 2005. Total of 45 PAH compounds (∑45PAHs) were analysed by high-resolution gas chromatography/high-resolution mass spectrometry (HRGC/HRMS). In 2003, the ∑45PAH concentrations in PM10 ranged between 4.3 and 89 ng m−3 (annual average; 27 ± 24 ng m−3). The average concentrations of ∑45PAHs in December 2005 were 210 ± 33 ng m−3 in total PM and 430 ± 90 ng m−3 in the gaseous phase. The ∑45PAH concentration in PM accounted for more than 30% of the sum of their particulate and gaseous forms. Phenanthrene (Ph) was the most predominant compound in the gaseous phase, whereas four- to seven-ring PAHs were predominant in total PM. The highest values of ∑45PAHs occurred in the winter and spring. Estimates of emission sources based on diagnostic molecular ratios showed that atmospheric PAHs in the Kathmandu Valley mainly originated from the exhaust gas of diesel engine. In the winter and spring, PAH pollution would be accelerated by the operations of brick kilns and the frequent formation of an atmospherically stable layer in the valley.

Gas–particle concentrations of atmospheric polycyclic aromatic hydrocarbons at an urban and a residential site in Osaka, Japan: Effect of the formation of atmospherically stable layer on their temporal change

A comparative study on atmospheric polycyclic aromatic hydrocarbons (PAHs) in particulate matter and the gaseous phase was performed at an urban and a residential site in Osaka, Japan, during 2005-2006. PAH concentrations at the urban site were found to be approximately twice higher than those at the residential site. At both sites, particulate PAH concentrations increased mainly in winter while the trends of temporal change in gaseous PAH concentrations were not clearly observed. The main sources of PAHs were estimated to be local traffic, e.g., diesel engines with catalytic converter. PAH concentrations did not significantly negatively correlate with ozone concentrations and meteorological parameters. Gas-particle partitioning coefficients of representative PAHs with low molecular weight (LMW) significantly negatively correlated with ambient temperature, showing that temporal change in the LMW PAH concentrations in PM could be attributable to the shift of their gas-particle distribution caused by the change in ambient temperature. For the first time, we studied the effect of the formation of atmospherically stable layer following an increase in PAH concentrations in Japan. At the urban site, PAHs showed a significant positive correlation with potential temperature gradients, indicating that temporal variability in PAH concentrations would be dominantly controlled by the formation of atmospherically stable layer in Osaka area.

Effect of extraction temperature on pressurized liquid extraction of polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans, and dioxin-like polychlorinated biphenyls from a sediment sample using polar and non-polar solvents

This study is the first to investigate the effect of extraction temperature (150, 175, and 200 degrees C) on the simultaneous pressurized liquid extraction (PLE) of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and dioxin-like polychlorinated biphenyls (DL-PCBs) from a sediment sample (certified reference material: JSAC 0431). To provide basic data that will help to determine the optimum conditions for PLE, six single solvents (toluene, dichloromethane [DCM], benzene, acetonitrile, acetone, and methanol) were used as an extraction solvent. The results obtained by PLE with each solvent were compared with those obtained by Soxhlet extraction using toluene. The efficiency of PLE for 2,3,7,8-substituted PCDDs, 2,3,7,8-substituted PCDFs, and DL-PCBs, as obtained by PLE using the solvents toluene, DCM, benzene, and acetonitrile, showed an increase with increasing extraction temperature. The recoveries of PCDDs, PCDFs, and DL-PCBs obtained by PLE using toluene were similar to or inferior to those obtained using the Soxhlet method. In contrast, their recoveries obtained by PLE using DCM, benzene, and acetonitrile were similar to or higher than those obtained using the Soxhlet method. Notably, the recoveries of PCDDs, PCDFs, and DL-PCBs using benzene at 200 degrees C were 117+/-15, 123+/-13, and 115+/-12%, respectively. When using acetone and toluene, the recoveries of tetra-hexaCDDs and tetra-hexaCDFs also increased with extraction temperature. In particular, the recoveries of 2,3,7,8-tetraCDD and 2,3,7,8-tetraCDF obtained with acetone at 200 degrees C were 181+/-21 and 167+/-14%, respectively. However, the efficiency of PLE for heptaCDDs and/or heptaCDFs was insufficient at all the tested temperatures. Furthermore, the efficiency of PLE for octaCDD and/or octaCDF showed a pronounced decrease with increasing extraction temperature, yielding recoveries of approximately 40% at 200 degrees C. We found that heptaCDF isomers were produced from authentic octaCDF during the PLE procedure with acetone at 200 degrees C, indicating that the lower recoveries of highly chlorinated DDs and/or DFs are attributable to their degradation.