Chemical composition of precipitation in a forest area of Chongqing, southwest China

Ten-day composite samples of precipitation, throughfall and stemflow from a Masson pine (Pinus massoniana) forest, were collected between June 1991 and May 1992 from the remote Jinyun and Simian mountains and from the industrial area of Chongqing. Samples were analysed for ammonium, calcium chloride, magnesium, nitrate, potassium, sodium sulphate and pH. Seasonal average ion concentrations are presented for ammonium, calcium and sulphate. The annual mean pH of throughfall, stemflow and precipitation were 4.47, 3.82 and 2.92, respectively. The annual ion deposition was 50.6, 69.7 and 0.215 g per m2, respectively. The pH varied seasonally and was minimal in winter. Ammonium and calcium contributed 80 per cent of the total cations and sulphate 90 per cent of total anions. High sulphate concentrations in rainwater in Chongqing were attributed to the burning of locally produced coal containing 3 to 5 per cent sulphur.