模拟酸雨对土壤重金属镉形态转化的影响

在模拟酸雨作用下,研究了酸雨对不同Cd污染程度下土壤重金属Cd释放和形态分布、转化规律的影响.结果表明,模拟酸雨浸泡土壤后,土壤pH值高于酸雨浸泡前的土壤pH值和模拟酸雨的pH值,表明土壤表面存在质子的消耗,这可能与硫酸根的专性吸附释放羟基和矿物表面的质子化有关.酸雨浸泡土壤能增加土壤活性态Cd的含量,酸雨酸度越大,土壤Cd含量越高,Cd的活化能力越大.当昆山土壤pH值平均由7.20下降到6.42时,Cd的活化率增加了0.34% ～ 3.29%,因此,在昆山土壤酸化严重的背景下,其土壤重金属Cd的活化趋势明显,由重金属Cd释放而对人类和生物造成的风险较大.

Effect of simulated acid rains on Cd form transformation in contaminated soil

The release and form distribution, transformation of Cd in different Cd polluted soils affected by simulated acid rain (SCR) were studied. Results showed that soil pH after soaked in SCR was higher than that without SCR and SCR pH, which indicated H+ consumption in the processes of Cd2+ desorption. The quantity of active fraction of Cd in soils soaked in SCR increased and the active ability enhanced with the increase of rain acidy. The active ability of Cd also promoted with the increase of contamination degree, and the ability of residual fraction of Cd transferring to active fraction became stronger with the increase of rain acidy. On the condition of soil pH decreased from 7.2 to 6.42 in Kunshan City, the activation grade of Cd increased by 0.34% ~ 3.29%, which indicated the high risk of Cd to human and environment in Kunshan City.