Organic Compounds in Dust from Rural and Urban Paved and Unpaved Roads Taken During the San Joaquin Valley Fugitive Dust Characterization Study

摘要

Road dust is a major source for airborne particulate matter (PM). It is an agglomerate of deposited particles fromnvehicle exhaust, tire wear, break-lining wear, road surface and litter abrasions, local soil dust, vegetative detritus,nand atmospheric fallout from many sources. Consequently, road dust is a mixture of coarse PM (road surfacenabrasions, soil dust, tire wear, and brake-lining wear) and fine PM (vehicular exhaust and portions of mostnsources of coarse PM). Although most studies concerned with road dust report the inorganic composition, only anfew focus on organic constituents. Here, as part of the San Joaquin Valley Fugitive Dust Characterization Study,nroad dust samples from paved and unpaved urban and rural roads have been analyzed for close to 200nindividual organic compounds, including n-alkanes, n-alkanoic and alkenoic acids, n-alkanols, n-alkanals, nalkan-n2-ones, alkylcyclohexanes, steroids, steranes, hopanes, triterpenoids, isoprenoids, benzothiazoles, polycyclicnaromatic hydrocarbons, saccharides, pesticides, plasticizers, and diphenylamines. Organic compoundsnindicative of both higher plant detritus and traffic-related emissions (exhaust plus tire wear) are highest in pavednroad dust, suggesting that the grinding of plant detritus by vehicle tires on the hard paved surface liberatennatural lipids and other natural occurring compounds that then admix with the road dust and can becomenairborne. Fossil fuel combustion markers such as hopanes and polycyclic aromatic hydrocarbons are highest fornmost paved roads and farming staging areas and lowest for unpaved roads. The highest level of vehicularnexhaust organics associated with road dust was found in rural paved road dust. Rural roads compared withnurban roads are typically not swept and have lower traffic density and as a result lower traffic induced resuspension.nConsequently, vehicular exhaust deposited onto paved roads is more likely to accumulate on ruralnroads than on urban roads.