Rain water and throughfall chemistry in the silent valley forest in south India

Rain water and throughfall samples were collected at the Silent Valley forest during the two consecutive southwest summer monsoon seasons (June–September) of 1989 and 1990. All the samples were analysed for Cl−, SO42−, NO3−, NH4+, Na+, K+, Ca2+, Mg2+ and pH. The average pH of rain water was 5.31 and that of throughfall was 6.38 indicating that the throughfall is 10 times more alkaline than the rain water. The buffering of H+ in throughfall was due to interaction with canopy. It was found that the ionic concentrations in throughfall were higher than those in rain water, except for NH4+. Enrichment of ionic components in throughfall is attributed to the interaction of precipitation with the forest canopy.