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Spatial Variation of Particle Number Concentration in School Microscale Environments and Its Impact on Exposure Assessment

Citation

Salimi, F and Mazaheri, M and Clifford, S and Crilley, LR and Laiman, R and Morawska, L, Spatial Variation of Particle Number Concentration in School Microscale Environments and Its Impact on Exposure Assessment, Environmental Science & Technology, 47, (10) pp. 5251-5258. ISSN 0013-936X (2013) [Refereed Article]

Copyright Statement

2013 American Chemical Society

DOI: doi:10.1021/es400041r

Abstract

It has not yet been established whether the spatial variation of particle number concentration (PNC) within a microscale environment can have an effect on exposure estimation results. In general, the degree of spatial variation within microscale environments remains unclear, since previous studies have only focused on spatial variation within macroscale environments. The aims of this study were to determine the spatial variation of PNC within microscale school environments, in order to assess the importance of the number of monitoring sites on exposure estimation. Furthermore, this paper aims to identify which parameters have the largest influence on spatial variation as well as the relationship between those parameters and spatial variation. Air quality measurements were conducted for two consecutive weeks at each of the 25 schools across Brisbane, Australia. PNC was measured at three sites within the grounds of each school, along with the measurement of meteorological and several other air quality parameters. Traffic density was recorded for the busiest road adjacent to the school. Spatial variation at each school was quantified using coefficient of variation (CV). The portion of CV associated with instrument uncertainty was found to be 0.3, and, therefore, CV was corrected so that only noninstrument uncertainty was analyzed in the data. The median corrected CV (CVc) ranged from 0 to 0.35 across the schools, with 12 schools found to exhibit spatial variation. The study determined the number of required monitoring sites at schools with spatial variability and tested the deviation in exposure estimation arising from using only a single site. Nine schools required two measurement sites and three schools required three sites. Overall, the deviation in exposure estimation from using only one monitoring site was as much as 1 order of magnitude. The study also tested the association of spatial variation with wind speed/direction and traffic density, using partial correlation coefficients to identify sources of variation and nonparametric function estimation to quantify the level of variability. Traffic density and road to school wind direction were found to have a positive effect on CVc and, therefore, also on spatial variation. Wind speed was found to have a decreasing effect on spatial variation when it exceeded a threshold of 1.5 (m/s), while it had no effect below this threshold. Traffic density had a positive effect on spatial variation and its effect increased until it reached a density of 70 vehicles per five minutes, at which point its effect plateaued and did not increase further as a result of increasing traffic density.

Item Details

Item Type:Refereed Article
Keywords:particle number concentration, spatial variation, microscale
Research Division:Earth Sciences
Research Group:Atmospheric Sciences
Research Field:Atmospheric Aerosols
Objective Division:Environment
Objective Group:Air Quality
Objective Field:Antarctic and Sub-Antarctic Air Quality
Author:Salimi, F (Dr Farhad Salimi)
ID Code:104342
Year Published:2013
Web of Science® Times Cited:19
Deposited By:Menzies Institute for Medical Research
Deposited On:2015-11-10
Last Modified:2015-12-18
Downloads:0

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