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: Motor vehicle emissions usually constitute the most significant source of ultrafine particles (diameter <0.1 microm) in an urban environment, yet little is known about the concentration and size distribution of ultrafine particles in the vicinity of major highways. In the present study, particle number concentration and size distribution in the size range from 6 to 220 nm were measured by a condensation particle counter (CPC) and a scanning mobility particle sizer (SMPS), respectively. Measurements were taken 30, 60, 90, 150, and 300 m downwind, and 300 m upwind, from Interstate 405 at the Los Angeles National Cemetery. At each sampling location, concentrations of CO, black carbon (BC), and particle mass were also measured by a Dasibi CO monitor, an aethalometer, and a DataRam, respectively. The range of average concentration of CO, BC, total particle number, and mass concentration at 30 m was 1.7-2.2 ppm, 3.4-10.0 microg/m3, 1.3-2.0 x 10(5)/cm3, and 30.2-64.6 microg/m3, respectively. For the conditions of these measurements, relative concentrations of CO, BC, and particle number tracked each other well as distance from the freeway increased. Particle number concentration (6-220 nm) decreased exponentially with downwind distance from the freeway. Data showed that both atmospheric dispersion and coagulation contributed to the rapid decrease in particle number concentration and change in particle size distribution with increasing distance from the freeway. Average traffic flow during the sampling periods was 13,900 vehicles/hr. Ninety-three percent of vehicles were gasoline-powered cars or light trucks. The measured number concentration tracked traffic flow well. Thirty meters downwind from the freeway, three distinct ultrafine modes were observed with geometric mean diameters of 13, 27, and 65 nm. The smallest mode, with a peak concentration of 1.6 x 10(5)/cm3, disappeared at distances greater than 90 m from the freeway. Ultrafine particle number concentration measured 300 m downwind from the freeway was indistinguishable from upwind background concentration. These data may be used to estimate exposure to ultrafine particles in the vicinity of major highways.Journal of the Air & Waste Management Association (1995) 09/2002; 52(9):1032-42. · 1.20 Impact Factor
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ABSTRACT: Atmospheric ultrafine particles (diameter < 0.1 μm) are under study by inhalation toxicologists to determine whether they pose a threat to public health, yet, little is known about the chemical composition of ultrafine particles in the atmosphere of cities. In the present work, the number concentration, size distribution, and chemical composition of atmospheric ultrafine particles is determined under wintertime conditions in Pasadena, CA, near Los Angeles. These experiments are conducted using a scanning dif ferential mobility analyzer, laser optical counter, and two micro-orifice impactors. Samples are analyzed to create a material balance on the chemical composition of the ultrafine particles. The number concentration of ultrafine particles in the size range 0.017 < dp < 0.1 μm, analyzed over 24-h periods, is found to be consistently in the range 1.3 × 104 ± 8.9 × 103 particles cm-3 air. Ultrafine particle mass concentrations are in the range 0.80−1.58 μg m-3. Organic compounds are the largest contributors to the ultrafine particle mass concentration. A small amount of sulfate is present in these particles, at concentrations too low to tell whether it exists as unneutralized sulfuric acid. Iron is the most prominent transition metal found in the ultrafine particles. These data may assist the health effects research community in constructing realistic animal or human exposure studies involving ultrafine particles.Environmental Science & Technology - ENVIRON SCI TECHNOL. 03/1998; 32(9).
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ABSTRACT: Motor vehicle emissions usually constitute the most significant source of ultrafine particles (diameter <0.1 μm) in an urban environment. Zhu et al. (J. Air Waste Manage. Assoc., 2002, accepted for publication) conducted systematic measurements of the concentration and size distribution of ultrafine particles in the vicinity of a highway dominated by gasoline vehicle. The present study compares these previous measurements with those made on Interstate 710 freeway in Los Angeles. The 710 freeway was selected because more than 25% of the vehicles are heavy-duty diesel trucks. Particle number concentration and size distribution in the size range from 6 to 220 nm were measured by a condensation particle counter and a scanning mobility particle sizer, respectively. Measurements were taken at 17, 20, 30, 90, 150, and 300 m downwind and 200 m upwind from the center of the freeway. At each sampling location, concentrations of carbon monoxide (CO) and black carbon (BC) were also measured by a Dasibi CO monitor and an Aethalometer, respectively. The range of average concentration of CO, BC and total particle number concentration at 17 m was 1.9–2.6 ppm, 20.3–24.8 μg/m3, 1.8×105–3.5×105/cm3, respectively. Relative concentration of CO, BC and particle number decreased exponentially and tracked each other well as one moves away from the freeway. Both atmospheric dispersion and coagulation appears to contribute to the rapid decrease in particle number concentration and change in particle size distribution with increasing distance from the freeway. Average traffic flow during the sampling periods was 12,180 vehicles/h with more than 25% of vehicles being heavy-duty diesel trucks. Ultrafine particle number concentration measured at 300 m downwind from the freeway was indistinguishable from upwind background concentration. These data may be used to estimate exposure to ultrafine particles in the vicinity of major highways.Atmospheric Environment. 01/2002;