Intra-community spatial variation of size-fractionated PM mass, OC, EC, and trace elements in the Long Beach, CA area
ABSTRACT Local traffic patterns and proximity to pollution sources are important in assessing particulate matter (PM) exposure in urban communities. This study investigated the intra-community spatial variation of PM in an urban area impacted by numerous local and regional sources. Weekly size-segregated (<0.25, 0.25–2.5, and >2.5 μm) PM samples were collected in the winter of 2005. During each 1-week sampling cycle, data were collected concurrently at four sites within four miles of one another in the Long Beach, CA area. Coefficients of divergence analyses for size-fractionated PM mass, organic and elemental carbon, sulfur, and 18 other metals and trace elements suggest a wide range of spatial divergence. High spatial variability was observed in the <0.25 μm and 0.25–2.5 μm PM fractions for many elements associated with motor vehicle emissions. Relatively lower spatial divergence was observed in the coarse fraction, although road dust components were spatially diverse but highly correlated with each other. Mass and OC concentrations were homogeneously distributed over the sampling sites. Possible oil combustion sources were identified using previously documented markers such as vanadium and nickel and by distinguishing between primary sulfur and secondary sulfate contributions. This study shows that, although PM mass in different size fractions is spatially homogeneous within a community, the spatial distribution of some elemental components can be heterogeneous. This is evidence for the argument that epidemiological studies using only PM mass concentrations from central sites may not accurately assess exposure to toxicologically relevant PM components.
- SourceAvailable from: Yoshito Kumagai
Article: Southern California Particle Center
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ABSTRACT: To investigate the characteristics of aerosols in north China, the samples of water-soluble ions, including anions (F−, Cl−, NO2−, NO3−, SO42−) and cations (NH4+, K+, Na+, Ca2+, Mg2+) in 8 size-segregated particle fractions, are collected using a sampler from Sep. 2009 to Aug. 2010 at four sites in urban areas (Beijing, Tianjin and Tangshan) and a background region (Xinglong) in the Jing-Jin-Ji urban agglomeration. High spatial variability is observed between the urban areas and the background region. The results of chemical composition analysis showed that secondary water soluble ions (SO42− + NO3− + NH4+) (SWSI) composed more than half the total ions, and are mainly found in fine particles (aerodynamic diameters less than 2.1 μm), while Mg2+ and Ca2+ contributed to a large fraction of the total water-soluble ions in coarse particles (aerodynamic diameters greater than 2.1 μm and less than 9.0 μm). The concentrations of SO42−, NO3− and NH4+ are higher in summer and winter and lower in spring and autumn. Mg2+ and Ca2+ are obviously abundant in winter in Beijing, Tianjin and Tangshan. In contrast, Mg2+ and Ca2+ are abundant in autumn in Xinglong. The SWSI showed a bimodal size distribution with the fine mode at 0.43–1.1 μm and the coarse mode at 4.7–5.8 μm, and had different seasonal variations and bimodal shapes. NH4+ played an important role in the size distributions and the formations of SO42− and NO3−. Heterogeneous reaction is the main formation mechanism of SO42− and NO3−, which tended to be enriched in the coarse mode of aerosol. The sulfur oxidation ratio (SOR) and nitrogen oxidation ratio (NOR) indicated high photochemical oxidation property over the whole Jing-Jin-Ji urban agglomeration.Atmospheric Environment 10/2013; 77:250–259. · 3.11 Impact Factor
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ABSTRACT: Continuous coarse particulate matter (CPM, PM10−2.5) concentrations were measured hourly at three different sites in the Los Angeles area from April 2008 through May 2009 as part of a larger study of the characteristics and toxicology of CPM. Mean hourly concentrations calculated seasonally ranged from less than 5 μg m to near 70 μg m at the three sites depending upon the CPM source variability and prevailing meteorology. Different diurnal concentration profiles were observed at each site. Correlation analysis indicates that CPM concentrations can generally be explained by wind-induced road dust re-suspension, particularly in drier seasons. CPM concentrations between the sites were not appreciably correlated and metrics used to assess variability between the sites—the coefficients of divergence—indicated that CPM concentrations were heterogeneous. The relative CPM contribution to observed PM10 concentrations varied by season and between sites. Additional concurrent CPM data available within a few km of the three sites indicate that intra-community variability can be on the same order as that observed for inter-community variability, although a similar analysis using PM10 data yielded reduced heterogeneity. The results indicate that accurate exposure assessment to CPM in the Los Angeles area requires measurements of CPM concentrations at different sites with higher temporal resolution than a single daily mean value.Aerosol Science and Technology - AEROSOL SCI TECH. 01/2010; 44(7):526-540.