Air quality at a semi-arid, suburban site at Agra with respect to SO2,NOx and metallic constituents

Abstract: Concentrations of SO2, NOx and metals Al, Fe, Pb, Cu, Mn, Zn, V, Ni and Si were determined during 1999-2001, at a sub-urban site, Dayalbagh, Agra. SO2 and NOx were measured by the impinger absorption technique using West and Gaeke and Sodium Arsenite methods respectively. Size distribution of metals was determined using a Kimoto Cascade Sampler and analysis by ICP-AES. Both SO2 and NOx concentration showed a seasonal dependence with a maximum in winter followed by summer and monsoon. In winter months, SO2 concentrations ranged between 6.0 -15.6 ìgm-3 while 4.8 – 12 ìgm-3 in summer and 4.0 – 8.4 ìgm-3 in monsoon. The daily mean values of NOx during winter ranged between 15 – 18 ìgm-3, while between 11.6 – 14.2 ìgm-3 during summer and between 11 -2.5 ìgm-3 in monsoon. The concentrations of both SO2 and NOx at this site are comparable to those reported from the temperate regions. Measured size distribution of Al and Si were consistent with suspended dust being the major source. Size distributions of Pb, Ni, V, Cu, Zn were bimodel suggesting contributions from suspended dust and anthropogenic sources. The importance of suspended dust was investigated using Al as traces and suspended dust ratios of Al to each of these metals. Suspended dust was found to be an important source of Pb, Mn, and Fe but not of Ni, V, Zn and Cu.