Motor vehicle (MV) emissions and ambient particle concentrations under a variety of situations were studied in Toronto and Vancouver, Canada. Petroleum biomarkers (i.e., hopanes and steranes) were used to determine the fraction of fine particle organic carbon (OC) attributed to primary particles in MV exhaust. Source profiles obtained from a tunnel and from direct tailpipe emissions were applied to ambient measurements at locations ranging from rush hour traffic to a regional background site. The greatest amount of MV OC, 4.0 mu gC m(-3) out of 9.1 mu gC m(-3) or 43%, was observed 75 m south of a commuter highway during a period that included morning rush hour. Monthly estimates of MV-OC were determined for a downtown Toronto monitoring site for 2 years. Total OC concentrations were greater in the summer, due to secondary OC, but the amount of MV-OC did not exhibit a strong seasonal pattern. However, on a per cent basis, MV contributions from primary OC emissions were greatest in the winter (15-20%) and smallest in the summer (10-15%) with a two-year average of 14% of the OC or about 5% of the PM2.5. (c) 2006 Elsevier Ltd. All rights reserved.
Hong Kong's persistent unhealthy level of fine particulate matter is a current public health challenge, complicated by the city being located in the rapidly industrializing Pearl River Delta Region of China. While the sources of the region's fine particulate matter (PM2.5) are still not well understood, this study provides new source information through ground measurements and statistical analysis of 24 elements associated with particulate matter collected on filters. Field measurements took place over 4 months (October 2002, December 2002, March 2003, and June 2003) at seven sites throughout the Pearl River Delta, with three sites located in Hong Kong and four sites in the neighboring province, Guangdong. The 4-month average element concentrations show significant variation throughout the region, with higher levels of nearly every species seen among the northern Guangdong sites in comparison to Hong Kong. The high correlation (Pearson r>0.8) and similar magnitudes of 11 species (Al, Si, S, K, Ca, Mn, Fe, Zn, Br, Rb, and Pb) at three contrasting sites in Hong Kong indicate that sources external to Hong Kong dominate the regional levels of these elements. Further correlative analysis compared Hong Kong against potential source areas in Guangdong Province (Shenzhen, Zhongshan, and Guangzhou). Moderate correlation of sulfur for all pairings of Hong Kong sites with three Guangdong sites in developed areas (average Pearson r of 0.52–0.94) supports the importance of long-distance transport impacting the region as a whole, although local sources also clearly impact observed concentrations. Varying correlative characteristics for zinc when Hong Kong sites are paired with Shenzhen (average r=0.86), Guangzhou (average r=−0.65) and Zhongshan (average r=0.45) points to a source area located south of Guangzhou and locally impacting Zhongshan. The concentration distribution and correlative characteristics of bromide point to sources located within the Pearl River Delta, but the specific location is yet inconclusive. Uniquely poor correlation of eight species (Al, Si, K, Ca, Mn, Fe, Rb, and Pb) for the pairing of Hong Kong sites with Guangzhou, in addition to the relatively higher concentrations measured at Guangzhou, indicates a significant regional impact due to land development and industrial activities in the Guangzhou vicinity.
Size distributions and particle number concentrations of atmospheric aerosols in the size (diameter) range from 15 mn to 10 mu m were measured on board of a research ship during three cruises in China adjacent seas. The total particle number concentrations were in average around 4000 cm(-3) in Yellow Sea, 2000 cm(-3) in East China Sea and 1000 cm(-3) in South China Sea. The observed size distributions were fitted with two or three log-normal modes and the data were classified according to time, regions and calculated air mass back-trajectories. The size distribution spectra of air masses of polluted continental origin as their back-trajectories showed were characterized by single mode with total number concentrations between 1000 and 10000 cm(-3). The size distributions in marine air masses showed dual mode characteristics, one maximum at 40-60 nm and the other at 160-190 nm with total number concentrations below 1000 cm(-3). This type of dual mode was more pronounced at longer residence time of the air masses over the ocean. The burst of ultra-fine (UF) particles and the consequent growth processes were observed twice in Yellow Sea and possible reasons leading to these events are discussed. The particle growth rate (GR) was 3.4 +/- 0.9 and 3.5 +/- 1.6 nm h(-1), respectively (95% confidence interval), indicating that the UF particles can grow to cloud condensation nuclei (CCN) within the next 1-2 days.) (C) 2007 Elsevier Ltd. All rights reserved.
BACKGROUND: Previous studies have shown that polybrominated diphenyl ethers (PBDEs) behave as weak estrogens in animal and cell culture bioassays. In vivo metabolites of PBDEs are suspected to cause these effects. OBJECTIVES: To identify candidate metabolites, mouse plasma samples were collected after continuous oral and subcutaneous exposure to DE-71, a widely used commercial pentabromodiphenyl ether product, for 34 days. METHODS: Samples were extracted, separated into neutral and phenolic fractions, and analyzed by gas chromatographic mass spectrometry. RESULTS: In the plasma samples of orally treated animals, 2,2',4,4',5,5'-hexabromodiphenyl ether (BDE-153) represented 52% of total measurable PBDEs, whereas it represented only 4.3% in the DE-71 mixture. This suggested that BDE-153 was more persistent than other congeners in mice. Several metabolites were detected and quantitated: 2,4-dibromophenol, 2,4,5-tribromophenol, and six hydroxylated PBDEs. The presence of the two phenols suggested cleavage of the ether bond of 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) and 2,2',4,4',5-pentabromodipheny ether (BDE-99), respectively. The hydroxylated (HO)-PBDEs might come from hydroxylation or debromination/hydroxylation. Among the quantitated hydroxylated metabolites, the most abundant was 4-HO-2,2',3,4'-tetra-BDE, which suggested that there was a bromine shift during the hydroxylation process. para-HO-PBDEs have been proposed to behave as endocrine disruptors. CONCLUSIONS: There seem to be three metabolic pathways: cleavage of the diphenyl ether bond, hydroxylation, and debromination/hydroxylation. The cleavage of the diphenyl ether bond formed bromophenols, and the other two pathways formed hydroxylated PBDEs, of which,para-HO-PBDEs are most likely formed from BDE-47. These metabolites may be the most thyroxine-like and/or estrogen-like congeners among the HO-PBDEs.