Volume 8, No. 4, December 2008, Pages 437-446 PDF(270 KB)
Dry Deposition of Polycyclic Aromatic Hydrocarbons Associated with Atmospheric Particulate Matters in an Urban Site, Mumbai, India
S. K. Sahu, G.G. Pandit, V.D. Puranik
Environmental Assessment Division, Bhabha Atomic Research Centre, Trombay, Mumbai
The rate of dry deposition of polycyclic aromatic hydrocarbons (PAHs) depends on the size of the particulate matter on which they are adsorbed. The distribution of PAHs on size-fractionated aerosol samples has been studied during winter and in the absence of precipitation to estimate the dry deposition flux of individual PAHs. Size-fractionated ambient particulate matter samples were collected during a 72-hour period, using an eight-stage cascade impactor. Filter paper samples were then extracted ultrasonically, and PAH characterization and quantification performed with a high-performance liquid chromatograph (HPLC) system with UV-visible detector. Total PAH concentrations associated with the size-segregated ambient particulate matters collected on different impactor stages were in the range of 18.3 to 66.6 ng/m3. The size distribution of atmospheric total PAHs was found to be bimodal. The modeled deposition velocity (Vd,i) at the sampling site for the particle size range of < 0.4 µm, 0.4-1.1 µm, 1.1-3.3 µm and 3.3-9.0 µm were found to be 0.004 cm/sec, 0.037 cm/sec, 0.283 cm/sec and 2.72 cm/sec, respectively. The dry deposition flux for individual PAHs at the sampling site was found to be in the range of 0.17 μg/m2/day-2.69 μg/m2/day. The results indicate that the dry deposition of PAHs is mainly due to gravitational settling of coarse particulates.
PAHs; Size distribution; HPLC; Cascade impactor; Deposition velocity; Dry deposition flux.