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.
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ABSTRACT: To assess the impact of past, current and proposed air quality regulations on coarse particulate matter (CPM), the concentrations of CPM mass and its chemical constituents were examined in the Los Angeles Basin from 1986 to 2009 using PM data acquired from peer-reviewed journals and regulatory agency database. PM10 mass levels decreased by approximately half from 1988 to 2009 at the three sampling sites examined- located in downtown Los Angeles, Long Beach and Riverside. Annual CPM mass concentrations were calculated from the difference between daily PM10 and PM2.5 from 1999 to 2009. High CPM episodes driven by high wind speed/stagnant condition caused year-to-year fluctuations in the 99th/98th percentile CPM levels. The reductions of average CPM levels were lower than those of PM10 in the same period, therefore the decrease of PM10 level was mainly driven by reductions in the emission levels of PM2.5 (or fine) particles, as demonstrated by the higher annual reduction of average PM2.5 (0.92 microg/m3) compared with CPM (0.39 microg/m3) from 1999 to 2009 in downtown Los Angeles despite their comparable concentrations. This is further confirmed by the significant decrease of Ni, Cr, V and EC in the coarse fraction after 1995. On the other hand, the levels of several inorganic ions (sulfate, chloride and to a lesser extent nitrate) remained comparable. From 1995 to 2008, levels of Cu, a tracer of brake wear, either remained similar or decreased at a smaller rate compared with elements of combustion origins. This differential reduction of CPM components suggests that past and current regulations may have been more effective in reducing fugitive dust (Al, Fe and Si) and combustion emissions (Ni, Cr, V, and EC) rather than CPM from vehicular abrasion (Cu) and inorganic ions (NO3(-), SO4(2-) and Cl(-)) in urban areas. Implications: Limited information is currently available to provide the scientific basis for understanding the sources and physical and chemical variations of CPM, and their relations to air quality regulations and adverse health effects. This study investigates the historical trends of CPM mass and its chemical components in the Los Angeles Basin to advance our understanding on the impact of past and current air quality regulations on the coarse fraction of PM. The results of this study will aid policy makers to design more targeted regulations to control CPM sources to ensure substantial protection of public health from CPM exposure. Supplemental Materials: Supplemental materials are available for this article. Go to the publisher's online edition of the Journal of the Air & Waste Management Association for (1) details of the sampling sites and (2) the daily concentrations of high CPM/PM10 episodes.Journal of the Air & Waste Management Association (1995) 05/2012; 62(5):541-56. · 1.20 Impact Factor
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ABSTRACT: Recent studies have linked acute respiratory and cardiovascular outcomes to measurements or estimates of traffic-related air pollutants at homes or schools. However, few studies have evaluated these outdoor measurements and estimates against personal exposure measurements. We compared measured and modeled home outdoor concentrations with personal measurements of traffic-related air pollutants in the Los Angeles air basin (Whittier and Riverside). Personal exposure of 63 children with asthma and 15 homes were assessed for particulate matter with an aerodynamic diameter less than 2.5 μm (PM(2.5)), elemental carbon (EC), and organic carbon (OC) during sixteen 10-day monitoring runs. Regression models to predict daily home outdoor PM(2.5), EC, and OC were constructed using home outdoor measurements, geographical and meteorological parameters, as well as CALINE4 estimates at outdoor home sites, which represent the concentrations from local traffic sources. These home outdoor models showed the variance explained (R(2)) was 0.97 and 0.94 for PM(2.5), 0.91 and 0.83 for OC, and 0.76 and 0.87 for EC in Riverside and Whittier, respectively. The PM(2.5) outdoor estimates correlated well with the personal measurements (Riverside R(2) = 0.65 and Whittier R(2) = 0.69). However, excluding potentially inaccurate samples from Riverside, the correlation between personal exposure to carbonaceous species and home outdoor estimates in Whittier was moderate for EC (R(2) = 0.37) and poor for OC (R(2) = 0.08). The CALINE4 estimates alone were not correlated with personal measurements of EC or other pollutants. While home outdoor estimates provide good approximations for daily personal PM(2.5) exposure, they may not be adequate for estimating daily personal exposure to EC and OC. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s11869-010-0099-y) contains supplementary material, which is available to authorized users.Air Quality Atmosphere & Health 09/2012; 5(3):335-351. · 1.98 Impact Factor
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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