Trends of road dust emissions contributions on ambient air particulate levels at rural, urban and industrial sites in southern Spain

摘要

The impact of road dust emissions on PM₁₀ and PM_2.5 (atmospheric particulate matter with diameteer < 10 μm and 2.5 μm mass concentrationsrecorded from 2003 to 2010 at 11 locations (rural, urban and industrial) insouthern Spain was estimated based on the chemical characterization of PMand the use of a constrained Positive Matrix Factorization, where thechemical profile of local road dust samples is used as a priori knowledge.Results indicate that road dust increased PM₁₀ levels on average by21–35% at traffic sites, 29–34% at urban background sites heavilyaffected by road traffic emissions, 17–22% at urban-industrial sites and9–22% at rural sites. Road dust contributions to ambient PM levels show amarked seasonality with maxima in summer and minima in winter, likely due tothe rainfall frequency. Decreasing concentration trends over the samplingyears were found at some traffic and urban sites but in most cases the decreases were lesssignificant than for vehicle exhaust emissions, while concentrationsincreased at industrial sites, probably due to local peculiarities.Concerning PM_2.5, road dust contributions were lower than in PM₁₀, asexpected but still important (21–31%, 11–31%, 6–16% and 7% fortraffic, urban background, urban-industrial and rural sites, respectively).In addition the three main sources of road dust (carbonaceous particles,brake wear and road wear/mineral) were identified and their contributions toroad dust mass loadings estimated, supporting the idea that air quality managers should drivemeasures aimed at preventing the build-up of road dust particles on roads.