Atmospherically Derived Organic Surface Films along an Urban-Rural Gradient

Abstract

Atmospherically derived organic films have been found on an impervious surface along an urban-rural gradient in the Toronto, Ontario, Canada area. Film thickness and concentrations, expressed on an aerial basis, of sigman-alkanes, sigmaPCB, sigmaPAH, and sigmaOC (organochlorine) pesticides decrease along this gradient, coincident with lower atmospheric emissions (PCB and PAH) and less accumulation in thinner rural films (OC pesticides). For PCBs and some OC pesticides, patterns of chemical abundance also shift, indicating a "fresh" pattern near emission sources (downtown) versus aged patterns at rural locations that are indicative of atmospheric transport. Plant-derived n-alkane concentrations were greater at urban than rural sites, and we hypothesize greater urban plant wax production and erosion due to air pollution. As expected, along the urban-rural gradient the concentration of particle-phase PAH decreased more rapidly than that of gas-phase compounds, but unexpectedly the contribution of alkylated PAH increased from urban to rural locations. Distances over which concentrations decline by 63% vary from 50 km for persistent gas-phase compounds (e.g., P1,2CB) to 10-20 km for reactive gas-phase compounds (e.g., naphthalene, fluoranthene) to <5-10 km for particle-phase compounds (e.g., P6-10CB, benzo[b]fluoranthene, benzo[e]pyrene).

Polycyclic aromatic hydrocarbons on indoor/outdoor glass window surfaces in Guangzhou and Hong Kong, south China

“…In Hong Kong, the streets are generally narrow, and the buildings are close to the roadside; the higher contributions of BghiP suggest that the major source of PAHs on the window surfaces might be local vehicle emissions. Generally, the patterns of individual PAH concentrations in this study were consistent with those of previously reported film samples (Gingrich et al, 2001;Unger and Gustafsson, 2008). The concentration pattern at all sampling sites showed an increase in the predominantly light-weight PAHs (Flu, Phe, Flur, and Pyr) in comparison with urban air particulate samples as well as a greater abundance of heavy-weight PAHs, such as BbF, BkF, BaP, Ind, DahA, and BghiP, than in the total urban air (gas plus particle phases) .…”

“…Comparing the PAH concentrations measured in this study with the limited observations of PAH levels in glass films, the areanormalized PAH concentrations in Hong Kong and Guangzhou were much lower than those reported in downtown Toronto, Canada (Gingrich et al, 2001). PAH concentrations in Guangzhou were found to be similar to those in the suburban areas of Toronto, and the concentrations in Hong Kong were similar to those in the rural areas of Toronto (Gingrich et al, 2001).…”

“…PAH concentrations in Guangzhou were found to be similar to those in the suburban areas of Toronto, and the concentrations in Hong Kong were similar to those in the rural areas of Toronto (Gingrich et al, 2001). Both the area-normalized and mass-normalized PAH concentrations in Hong Kong were comparable to those in the city center and suburban areas of Stockholm (Unger and Gustafsson, 2008).…”

“…The few existing studies on this topic show that organic films can range from 11 to 1000 nm in thickness and that the proportion of organic matter ranges from approximately 5e20% (Diamond et al, 2000;Liu et al, 2003b;Wu et al, 2008). Due to the high proportion of organic content of the film, the concentrations of semi-volatile organic compounds (SVOCs) are high on the artificial surfaces of urban areas (Butt et al, 2004;Gingrich et al, 2001;Liu et al, 2003a). SVOCs can accumulate in organic films through the exchange and partitioning of gasphase chemicals with air and/or the direct deposition of particlephase compounds (Diamond et al, 2000;Law and Diamond, 1998;Liu et al, 2003b).…”

Reaction of gas phase OH with unsaturated self-assembled monolayers and relevance to atmospheric organic oxidations

“…[1][2][3][4][5][6][7] Airborne particles also have a complex composition, with organic compounds as major components. [8][9][10][11] The chemistry associated with particles is of major interest because they are known to have adverse impacts on climate, human health and the chemistry of the atmosphere.…”