Chemistry of dew at urban and agricultural site

Dew samples were collected on the two sites of northern India during 2000 and 2001. Total 42 samples were collected on urban and agricultural sites.Ca, Mg, Na, K, NH4, NO3, SO4, Cl, F, CH3COO and HCOO were ananlysed in the dew samples. Total volume of dew collected was 2% of the rainwater at that year. pH varies between the 5.9 to 6.4 at urban air and 6.0 to 6.9 at agricultural site.The process for the dew formation may be dry deposition on the surfaces, dew formation and incorporation of gaseous species in the dew. Calcium was the dominant species in the sample from both the sites. At urban air, concentrtaion of NO3,SO4,CH3COO were higher than the agricultural site. This is probably due to the incorpaoration of gaseous pollutant like NO2, SO2 and CH3COOH in urban areas. Concentrtaion of NO3, SO4, HCOOH and CH3COOH showed no variation in the two consecutive dew episode in urban site however, at agricultural site concentration of these species along with the crustal component (Ca, Mg) and NH4 lower down. CaSO4, MgSO4, CaNO3, MgNO3,Ammonium nitrate and ammonium sulphate were tha major component of the dew