酸沉降影响下水相硫和氮在森林冠层的动态过程

Dynamic process of liquid phase sulfur and nitrogen in forest canopy under acid deposition.

为了阐明大气酸沉降对森林冠层水相硫和氮迁移的影响,在2001～2002两年期间对韶山森林的大气降水、穿冠水和地表穿透水进行了监测.结果表明,韶山大气降水、穿冠水和地表穿透水的离子是极不平衡的.森林冠层的降水从大气降水到穿冠水再到地表穿透水,其pH值呈增加趋势,认为韶山森林植被对酸雨的缓冲作用及对酸性物质的中和作用是非常明显的.大气降水中SO42^-和NO3^-的平均最大浓度出现在春季,尤其是春季大气降水NO3^-浓度达到夏季的3.27倍,这主要是由降水量的季节变化所引起,春季少雨期时浓度升高,夏季多雨期时浓度降低,即稀释效应.韶山地区降水的SO42^-/NO3^-在2.66～15.53,因此韶山大气降水中硫酸是主要成分.韶山是旅游景点,每年有超过100万人次的游客至此,汽车尾气的排放导致了大气降水中NO3^-浓度的加重.森林冠层空间3个层次中pH值与SO4^2-、NO^3-以及Ca^2＋的回归分析和数学模拟结果表明,SO4^2-与pH值的相互关系最显著,表明H＋与SO4^2-的来源一致,主要来源于工业污染.

To illustrate the effects of acid deposition in Shaoshan area on the migration of liquid phase sulfur and nitrogen in forest canopy, we monitored the rainfall, canopy throughfall and ground-fall in 2001 - 2002. The results showed that the ions in test objects were extremely unbalanced, and the pH values was increased in order of rainfall, canopy throughfall, and ground-fall, illustrating that vegetation, especially forest canopy, had evident effects in buffering acid rain and neutralizing acid substances. The maximum mean concentrations of SO4^2- and NO^3 - in rainfall both appeared in spring, and the NO3^- concentration in spring was 3.27 times of that in summer, due to the scarce rainfall in spring and the plentiful rainfall in summer. The SO4^2-/NO3^ - ratio in the rainfall in Shaoshan ranged from 2.66 to 15.53, indicating that SO4^2- was the predominant ion. As a place for tourism, Shaoshan has more than 1 million tourists each year, and the NOx from the tail gas of automobiles also gives contribution to the acid rain. Regression analyses of the pH, SO4^2- , NO3^- and Ca^2＋ in test objects showed that the correlation of SO4^2 - with pH was more significant than that with other ions, suggesting that the origins of H^＋ and SO4^2- were identical, and both came from industrial sources.