重庆缙云山降水pH值和化学组成特征分析

Analysis on pH and Chemical Composition of Rainfall in Jinyun Mountain, Chongqing, China

对重庆缙云山自然保护区1998—1999年126个降雨水样的pH值和主要化学组成成分等特征进行了分析研究。结果表明,缙云山降水pH值平均值为5.23,电导率为33.90μS·cm-1,降水的酸化与污染程度低于重庆市市区和我国南方其它酸雨区域。缙云山降水中SO42-占阴离子总量的84.61%,N H4+和C a2+为主要的阳离子。N H4+和C a2+的大量存在极大地中和了酸根离子对雨水的酸化作用,降低了酸雨发生频率,但酸化雨对森林生态系统仍具有潜在的威胁。缙云山降水pH值和各离子含量存在明显的季节变化特点,总体表现为冬春季污染程度高于夏秋季,这可能与降水量的季节变化有关。酸雨对森林生态系统的影响存在延迟性,故需要对保护区酸沉降特征进行更仔细和综合的动态研究。

The pH and chemical composition of 126 precipitation samples collected from April 1998 to November 1999 in Jinyun Mountain, Chongqing, China, were analyzed. Theresults showed that the average pH was 5.23 and the average conductivity was 33.90 μs·cm-1, which implied that the pollution in Jinyun Mountain was better than that in the other acid rain region of southern China and Chongqing urban areas. The concentration of accounted for 84.61%of total anions, and the concentration of and Ca2+accounted for 77.36%of total cations of rainfall inJinyun Mountain. The high concentration of and Ca2+neutralized greatly the acidity of acid ions, resulted in relatively high pH and lower frequency of acidrain, but the acidifying rain might injure the forest ecosystem potentially. The seasonal variations in the rainfall pH and chemical composition were evident, which may be related to the seasonal variations in precipitation amount in Jinyun Mountain. The effects of acid rain on forest ecosystem had time lag, so it wasnecessary to study the dynamic characteristics of acid deposition more carefully and comprehensively.