我国林地土壤有效态镉的影响因素及拟合模型

选取全国13个具有代表性的不同气候带和植被类型的森林土壤，通过外源添加重金属镉（Cd），比较分析土壤Cd的固-液分配系数（K_d）和有效态Cd的分布特征，探讨了土壤/土壤溶液性质对K_d及土壤有效态Cd的影响，并建立了土壤K_d及有效态Cd的拟合模型.结果表明，在不同浓度Cd处理的土壤中，其K_d值的变化范围为0.91~623.66L/kg，平均值为53.11L/kg，最大值和最小值的差异达到684.37倍；土壤孔隙水中Cd浓度（PW-Cd）的变化范围为0.309~104.450mg/L，其最大值与最小值的差异为338；DTPA提取态Cd含量（DTPA-Cd）从未添加Cd处理的本底土壤C0至最大添加量128mg/kg，其最大值与最小值的差异分别为9和1.4倍.土壤溶液pH值与lgK_d呈显著正相关（R²=0.49，P<0.001），其与PW-Cd含量呈显著负相关（R²=0.41，P<0.05）；单一的土壤溶液Mg²⁺可解释46%的DTPA-Cd的变异.在对土壤性质的回归分析中，并未发现有单一的主控土壤性质影响Cd的固液分配，当回归方程中加入其它土壤或溶液性质时，可在一定程度上提高拟合模型的预测能力.总之，土壤溶液pH值和Mg²⁺对K_d和有效态Cd含量的影响比较显著.

The influencing factors andsimulationmodels of available cadmium in forest soils in China

The 13 representative forest soils were selected in different climatic zones with various forest stands across the mainland of China. The soils were spiked with cadmium and then the distribution characteristics of soil solid-solution partition coefficient (K_d) and soil available cadmium (Cd) concentrations were analyze. The influences of soil/solution properties on K_d and soil available cadmium, and the corresponding empirical prediction models were further explored. K_d values varied from 0.91 to 623.66 L/kg with the average value of 53.11L/kgand variation of 684.37 folds between the maximum and minimum values in different spiked Cd treatments. The Cd concentration in soil pore water (PW-Cd) ranged from 0.309 (S13) to 104.450mg/L (S4) with the variation of 338 folds. The differences of DTPA extractable Cd (DTPA-Cd) contents were 9 and 1.4 folds, for the treatment of no Cd spiked soils and largest spiked dosage 128mg/kg, respectively. The results also showed that the pH positively correlated with K_d (R²=0.49, P<0.001) and inversely correlated with PW-Cd contents (R²=0.41, P<0.05). Single soil solution Mg²⁺ concentrations could explain 46% variance of the DTPA-Cd concentrations. No single controlling significant soil properties were found to affect the soil soil-liquid partition coefficient (K_d) according to the multiple regression equations. The simulation models were slightly improved by incorporation of other soil/solution properties. In conclusion, the soil solution pH and Mg²⁺ was two controlling factors.