北京地区3种污灌土壤镉最大吸附容量的推求

Maximum Cadmium Adsorption Capacities of Three Sewage-Irrigating Soil Types in Beijing

土壤对重金属的吸附容量是土壤重金属污染风险评价的一项重要指标,研究土壤对重金属的最大吸附容量对加强土壤环境的科学管理具有重要意义.采用阳离子交换量、平衡吸附方程和实验实测法推求了北京地区3种污灌土壤对重金属镉的最大吸附容量.由阳离子交换量(CEC)推求的北野厂、衙门口和永乐店3种污灌土壤对镉的最大吸附容量分别为:4822、4148和4721mg·kg-1;由单表面Langmuir方程推求的3种污灌土壤对镉的最大吸附容量均为5000mg·kg-1,由传统双表面Langmuir方程推求的3种土壤对镉的最大吸附容量分别为7040、6950和6994mg·kg-1,由双表面Langmuir方程的Sposito方法推求的3种污灌土壤对镉的最大吸附容量均为6200mg·kg-1;恒温25℃条件下,上述3种污灌土壤对镉的单分子层最大吸附容量实测值分别为5700、5600和5600mg·kg-1,多分子层最大吸附容量实测值分别为9000、8000和8120mg·kg-1.比较而言,双表面Langmuir方程是目前推求污灌土壤对镉最大吸附容量的较好方法.

The heavy metal adsorption capacity of soil played an important role in the risk assessment of heavy metal pollution, so it was necessary to study the maximum heavy metal adsorption capacity of soil ,that could make the soil environment management more scientific. Adopting the CEC method, adsorption equilibrium equation and experiments to study the maximum cadmium adsorption capacities of three sewage-irrigating soils at 25℃, that were Beiyechang soil,Yamenkou soil and Yongledian soil, the results were as follows：the maximum cadmium adsorption capacities of the three soils calculated by the CEC were 4822mg·kg^-1,4148mg·kg^-1 and 4721mg·kg^-1 ,respectively; The theoretic values calculated by the single surface Langmuir equation were all 5000mg·kg^-1 ,calculated by the conventional two-surface Langmuir equation were 7040mg· kg^-1, 6950mg·kg^-1 and 6994mg·kg^-1, calculated by the Sposito method of the two-surface Langmuir equation were all 6200mg·kg^-1 ;The experimental maximum adsorption capacities of single layer by the three soils were 5700mg·kg^-1 5600mg·kg^-1 and 5600mg·kg6-1,respectively,and the experimental maximum adsorption capacity of multilayer were 9000mg·kg^-1, 8000mg·kg^-1 and 8120mg·kg^-1. Comparing to the other methods,the two-surface Langmuir equation was a highly effective method to calculate the maximum cadmium adsorption capacity.