铁改性生物炭对黄绵土Pb^(2+)运移过程影响及模型分析

Effect of Iron-Modified Biochar on Pb^(2+)Transport in Loessial Soil and Model Analysis

[目的]明确不同铁改性生物炭施加量下土壤重金属的运移过程,以期为黄土区土壤重金属污染防治提供理论依据。[方法]以铁改性生物炭与黄绵土质量比分别为0%(CK),1%(A_(1)),2%(A_(2)),3%(A_(3)),4%(A_(4))和5%(A_(5))6组处理为研究对象,以Pb^(2+)为示踪离子,利用室内土柱进行溶质运移模拟试验,研究了不同铁改性生物炭施加量对黄绵土中Pb^(2+)运移过程的影响并进行模型模拟。[结果](1)A_(1),A_(2),A_(3),A_(4)和A_(5)处理的饱和导水率(K_(s))比CK分别减少了6.90%,20.70%,27.60%,31.03%和37.93%,即K s随铁改性生物炭施加量增大而逐渐减小。(2)不同处理的Pb^(2+)浓度达到平衡时的总历时比CK分别延长了1.79,13.00,34.98,35.34,40.81 h,随铁改性生物炭施加量增加,重金属初始和完全穿透时间明显推迟。(3)两区模型(TRM)和对流-弥散方程(CDE)的拟合曲线均能与实测曲线较好吻合,但TRM的决定系数(R^(2))大于CDE,均方根误差(RMSE)小于CDE,因此TRM的模拟精度更高。[结论]土壤中施加铁改性生物炭能较好地减缓重金属的运移过程,对调控土壤中重金属运移及防止地下水污染具有重要作用。

[Objective]The aims of this study are to explicit the transport processes of heavy metals in soil under different addition amounts of iron-modified biochar,and to provide theoretical basis for soil heavy metals pollution control in loess area.[Methods]The mass ratios of iron-modified biochar to loessial soil were 0%(CK),1%(A_(1)),2%(A_(2)),3%(A_(3)),4%(A_(4))and 5%(A_(5)),respectively,and Pb^(2+)was used as the tracer ion to simulate solute transport tests in indoor soil column.The effects of different amounts of iron-modified biochar on Pb^(2+)transport in loessial soil were studied and simulated.[Results](1)The saturated water conductivity(K s)of A_(1),A_(2),A_(3),A_(4) and A_(5) treatments decreased by 6.90%,20.70%,27.60%,31.03%and 37.93%compared with CK,respectively,which indicated that K_(s) gradually decreased with the increasing amount of iron-modified biochar application.(2)Compared with CK,the total duration of Pb^(2+)concentration under different treatments was extended by 1.79,13.00,34.98,35.34 and 40.81 hours,respectively.With the increasing of iron-modified biochar application,the initial and complete penetration time of heavy metals were significantly delayed.(3)The fitting curves of the two-zone model(TRM)and the convection-dispersion equation(CDE)agreed well with the measured curves,but the coefficient of determination(R 2)of TRM was greater than that of CDE,and the root mean square error(RMSE)was less than that of CDE,so the simulation accuracy of TRM was better.[Conclusion]The application of iron-modified biochar in soil can effectively slow down the transport process of heavy metals,and provide theoretical reference for prevention of heavy metal pollution in loess area.