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(463) Metals and semivolatile organic compounds detected on an urban impervious surface. Liu, Qintao1, Diamond, Miriam1, Gingrich, Sarah1, Ondov, John2, Maciejczyk, Polina2, Stern, Gary3, 1 2 3 ABSTRACT- Organic films have been found to develop on impervious surfaces. The organic phase of the film develops within several days after which particles start to accumulate rapidly as the dry deposition velocity increases due to the 'sticky' nature of the film. Consequently, the film contains organic compounds that are in dynamic equilibrium with the gas-phase in air, and organic and inorganic compounds and elements associated with deposited air particles. In this study, impervious surfaces, namely the exterior surface of windows, were sampled in downtown Baltimore, Maryland. Metals were analysed by neutron activation analysis with a Ge counter. PAHs and PCBs were extracted with solvent, fractionated on silica gel column and analysed by GC-MS and GC-ECD. PCBs in the film were dominated by the penta homologue group, PAH signatures closely resembled that of vehicle emissions, and n-alkanes were derived from biogenic and petrogenic sources. The film contains high concentrations of Fe and Zn followed by Ba, Sr, Zr, Cr, Sb, Se, Co, Sc, Cs, Ag and Cd. Low concentrations of rare earth metals were also found on the window, such as Ce, Nd, Hg, Th, Hf, Gd, Yb, Ta, Eu, Tb, Lu and Ir. Dry deposition of the metals at two sites was studied on clean and dirty windows that were sampled at the same time interval. The deposition of metals on the dirty windows was about 6 times higher than on the clean windows, confirming that the film increases the dry deposition velocity of particles and hence particle accumulation. This implies that rapid film development that is promoted by elevated VOC emissions to air, will increase film development that, in turn, will increase the accumulation of other atmospherically deposited constituents like metals. Key words: deposition of metals, neutron activation analysis, PAHs, PCBs, GC-MS |
