酸沉降背景下太湖流域碱基离子流失特征模拟研究

Simulation study on the characteristics of base ion loss in Taihu Lake Watershed under the background of acid deposition

太湖流域是我国酸沉降较严重的区域之一,酸沉降对流域碱基离子流失产生了显著影响。通过室内模拟试验,研究了流域内代表性碳酸盐岩及其风化产物和流域分布广泛的沙壤土在不同pH模拟酸溶液作用下碱基离子的释放特征。结果表明:1)碳酸盐岩中碱基离子释放量与酸溶液pH和粒径均呈显著负相关(P<0.01)。在10 d试验期内,Ca^(2+)释放量最小值为0.26 g/kg,最大值达14.30 g/kg,且比K^(+)、Na^(+)和Mg^(2+)释放量高1个数量级。2)碳酸盐岩风化产物与沙壤土中碱基离子对模拟酸溶液的敏感性为Ca^(2+)>Mg^(2+)>K^(+)。其释放量不仅与模拟酸溶液pH有关,还取决于介质本身特征(本身离子总量、成土母质环境及交换态离子量)。3)太湖流域不同介质对模拟酸溶液的缓冲能力存在显著差异,表现为碳酸盐岩>白云岩风化产物>石灰岩风化产物>沙壤土。分析认为,大量的碳酸盐与质子迅速发生的中和作用是碳酸盐岩及其风化产物具有较强缓冲能力的关键因素。

Taihu Lake Watershed is one of the areas with acid deposition in China,and acid deposition has a significant effect on the loss of base ions in the basin.The release characteristics of base ions from the representative carbonate rocks and their weathered products as well as the widely distributed sandy loam soil in the watershed under the action of simulated acid solutions with different pH were studied by laboratory simulation tests.The results indicated that:1)The release of base ions in carbonate rocks was significantly negatively associated with pH and the particle size of acid solution(P<0.01).During the 10 days test period,the minimum release of Ca^(2+)was 0.26 g/kg,and the maximum release was 14.30 g/kg,which was one order of magnitude higher than K^(+),Na^(+)and Mg^(2+).2)The sensitivity of base ions in the weathered products of carbonate rocks and sandy loam soil to simulated acid solution was in the order of Ca^(2+)>Mg^(2+)>K^(+).The amount of base ions released was not only related to the pH of simulated acid solution,but also depended on the characteristics of the medium,including its total amount of ions,parent material environment and amount of exchangeable cations.3)The buffering capacity of different media for simulated acid solution in Taihu Lake Watershed was significant distinction,that was,carbonate rocks>the weathered products of dolomite>the weathered products of limestone>sandy loam soil.It was considered that a large number of carbonates would neutralize protons rapidly,which was the key factor for carbonate rocks and their weathered products to have strong buffering capacity.