Chemical characteristics of rainwater at an urban site of south-central India

The pH variation and the chemical characteristics of rainwater have been studied during monsoons from 1999 to 2001 at Hyderabad, a city in south-central India. The pH varied from 5.5 to 7.2 with an average of 6.4 which is in alkaline range considering 5.6 as the neutral pH of cloud water with atmospheric CO2 equilibrium. Out of 28 rain events, only two events were observed in acidic range (<5.6) which occurred after continuous rains. The equivalent concentration of components followed the order: Ca2+>Cl−>SO42+>NH4+>Na+>HCO3−>NO3−>K+>Mg2+. The ratios of different components with respect to seawater ratios were observed to be higher, indicating the significant influence of non-marine sources at this site.