Measurement of size-fractionated atmospheric particulate matter and associated polycyclic aromatic hydrocarbons in Mumbai, India, and their dry deposition fluxes

Size-fractionated particulate matter (PM), associated polycyclic aromatic hydrocarbons (PAHs), and their dry deposition fluxes were measured in a coastal urban environment of Mumbai, India. PM samples were collected using a variable configuration cascade impactor (VCCI) with 11 size fractionation stages. Dry deposition samples were collected using a round-bottomed PVC tray. High-performance liquid chromatography (HPLC) was used for the identification and quantification of PAHs in samples. PM were observed to range between 58 and 130 μg m−3, with a mean dry deposition flux of 1298 mg m−2 day−1. Observed PM concentrations during the sampling period were found to be well above the WHO Air Quality Guidelines. A strong linear correlation was observed between the gravitational settling velocities and estimated dry deposition velocities for PM. Concentrations of PAHs associated with PM were observed to be in the range 101–145 ng m−3 while their dry deposition fluxes varied from 1008 to 1160 ng m−2 month−1. The molecular diagnostic ratios (MDRs) indicated that sources of PAHs in the study area were petrogenic as well as non-traffic. The dry deposition velocities calculated for PAHs were in the order of 10−4 cm s−1 to 10−3 cm s−1 in the entire size range.