Urban-Scale Seasonal and Spatial Variability of Ultrafine Particle Number Concentrations
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In epidemiological studies, ultrafine particle (UFP) data from a single monitoring site are generally used as a measure of population exposure potentially resulting in exposure misclassification. From August 2009 to October 2010, 1-week campaigns were conducted during each season. The temporal and spatial variations of UFP number size distributions were investigated at 12 monitoring sites distributed across a 9 × 9 km urban area in Rochester, New York using a Fast Mobility Particle SizerTM spectrometer. The overall average number concentrations of 5.6- to 560-nm particles in summer, winter, spring, and fall were 9,025, 10,939, 4,955, and 14,485 cm−3, respectively. Coefficients of divergence and correlation coefficients were calculated between site pairs to assess the spatial heterogeneity in the particle number size distributions. Moderate spatial divergence and uniform temporal variation were found for the chosen sites. Elevated UFP number concentrations were observed near highways, off-road diesel engines, and residential wood combustion sources, indicating significant contributions to the UFP exposure of people living adjacent to these sources. Our results suggest that one stationary monitoring site may not represent the actual human UFP exposure over a whole urban area.
KeywordsUltrafine particles (UFP) Number size distributions Exposure Spatial–temporal variability Coefficients of divergence (COD)
This work was supported by the New York State Energy Research and Development Authority (NYSERDA) through Contracts 8650 and 10604 and the United States Environmental Protection Agency (EPA) through Science to Achieve Results (STAR) Grant RD83107801, a Syracuse Center of Excellence CARTI project award, which is supported by a grant from the U.S. Environmental Protection Agency [award no. X-83232501-0]. Although the research described in this article has been funded in part by the EPA, it has not been subjected to the Agency’s required peer and policy review and, therefore, does not necessarily reflect the views of the Agency and no official endorsement should be inferred.
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