<正>对下蜀次生栎林不同降水组份中硫含量和ｐＨ 值进行连续的观测与分析；揭示了ＳＯ２ －４ 和ｐＨ 值在不同降水组份中的变化规律以及ＳＯ２ －４ 与其它化学成分的相互关系，结果为进一步阐明本区酸性沉降物对森林生态系统的影响提供了理论依据。

The characteristics of sulphate and pH value of precipitation, throughfall, stemflow and runoff water were studied in Xiashu Ecological Station in Jiangsu, China. The results showed as follows:(1) The sulfate (SO 2- 4) concentration of precipitation ranged from 1.07 mg/L to 22.61 mg/L. Average concentration of sulfate in throughfall and stemflow increased to 2.5 and 15 times as compared to precipitation respectively, and to 3 and 7.5 times in surface runoff and underground runoff respetively. (2) The percentage of anions in precipitation and thronghfall was about 73%～80% for SO 2- 4,8%～16% for NO - 3, 9% for Cl - and 1%～2% for F -.Ca 2+ was about 61%～72% of total cations (Ca 2+ ,Mg 2+ ,K +,Na +),17%～26% for K +,7%～8% for Na + and 3%～5% for Mg 2+ respectively. By a multiple regression analysis, SO 2- 4 concentration was very significantly correlated with Ca 2+ in precipitation and throughfall.(3) The pH value of throughfall and runoff in the oak stand was higher than that of precipitation,with cations leaching. The pH value of stemflow was lower than that of precipitation. In the loblloly pine stand, the pH value of throughfall was lower than that of precipitation.