Chemical characteristics of individual rain events from a semi-arid region in India: Three-year study

摘要: Abstract A systematic study of individual precipitation (wet-only) events ( n = 91 ), collected for three years (2000–2002) during the period SW-monsoon (June–September) from a semi-arid region (Ahmedabad, 23°03′N, 72°38′E) in India, reveals that rainwater is characteristically alkaline nature (pH range: 5.2–8.2, Av.=6.7). The ionic ratio Cl− and Na+ each event closely follows sea-salt composition. measured abundances Ca2+ (5.5–1057 μeq l−1), Mg2+ (1.5–251 μeq l−1) HCO3− (8–836 μeq l−1); non-sea-salt (nss) components varying as 94–99% 0–84%; linear regression parameters among (nss-Ca2++nss-Mg2+) (slope=0.71, r 2 0.96 ) all tend to suggest crustal sources dominate chemical composition precipitation. concentrations acidic constituents SO2−4 NO3− vary over wide range, 4.8 431 1.0 115 μeq l−1, respectively; NH4+ varied 1.7 220 μeq l−1 K+ 0.6–53 μeq l−1. significant impact anthropogenic on evident based nss-fraction (67–99%, VWM=86%) equivalent nss-SO42−/NO3− (0.8–6.7, VWM=2.5). With exception NH4+, concentration an species rain largely controlled by amount. inter-annual variations volume-weighted-mean are not significantly pronounced; making this representative data set region.