Abstract
Determination of intra-urban spatial variations in air pollutant concentrations for exposure assessment requires substantial time and monitoring equipment. The objective of this study was to establish if short-duration measurements of air pollutants can be used to estimate longer-term pollutant concentrations. We compared 5-min measurements of black carbon (BC) and particle number (PN) concentrations made once per week on 5 occasions, with 4 consecutive 1-week average nitrogen dioxide (NO2) concentrations at 18 locations at a range of distances from busy roads in Glasgow, UK. 5-min BC and PN measurements (averaged over the two 5-min periods at the start and end of a week) explained 40–80%, and 7–64% respectively, of spatial variation in the intervening 1-week NO2 concentrations for individual weeks. Adjustment for variations in background concentrations increased the percentage of explained variation in the bivariate relationship between the full set of NO2 and BC measurements over the 4-week period from 28% to 50% prior to averaging of repeat measurements. The averages of five 5-min BC and PN measurements made over 5 weeks explained 75% and 33% respectively of the variation in average 1-week NO2 concentrations over the same period. The relatively high explained variation observed between BC and NO2 measured on different time scales suggests that, with appropriate steps to correct or average out temporal variations, repeated short-term measurements can be used to provide useful information on longer-term spatial patterns for these traffic-related pollutants.
Highlights
Two approaches are possible: continuously mobile monitoring, where the monitoring equipment is moved throughout the duration of the study; and peripatetic monitoring, where mobile equipment is deployed at specific sites for short time periods before moving to another site
In a fourth approach we examined the bivariate relationships between estimates of the overall averages of NO2, black carbon (BC) and particle number (PN) concentrations for the 4-week period across the 18 sites
The spot measurements showed a less consistent spatial pattern between successive weekly measurements than was observed for NO2 (R2 ranges of 29e81% and 0e29% for BC and PN respectively)
Summary
Peripatetic measurements allow collection of observations through a monitoring network over a period of time and over relatively large areas with limited equipment. This approach has been used to monitor air pollution at sequential locations in studies in Canada (Abernethy et al, 2013; Deville Cavellin et al, 2016; Larson et al, 2009), Germany (Merbitz et al, 2012), India (Saraswat et al, 2013), the Netherlands (Klompmaker et al, 2015), Spain (Rivera et al, 2012), Switzerland (Ragettli et al, 2014) and the USA (Riley et al, 2016). 18 at the end of each weekly monitoring period were, on average across all weeks, Pollutant n Rb (p) Slope (95% CI)
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