生物炭影响地带性土壤等温吸附丁草胺的特征及关键机制

Effects of biochar on butachlor adsorption isotherm and mechanisms in different soils

为解析土壤理化性质与生物炭添加效果之间的相关性,明确生物炭影响地带性土壤等温吸附丁草胺的特征及关键机制,本研究采用9种不同理化性质地带性土壤,加入系列用量稻壳生物炭,考察了丁草胺在生物炭-土壤混合体中的等温吸附特征。结果表明:在不同生物炭添加剂量条件下,丁草胺在土壤中的吸附等温线均遵循Freundlich吸附模型,生物炭添加显著增加了9种地带性土壤对丁草胺的吸附能力[模型平衡常数(Kf)增加],降低了线性吸附的程度[模型指数(1/n)降低]。生物炭添加剂量越高,丁草胺吸附容量越大。热力学计算结果显示,在0.5%~2%生物炭添加条件下,丁草胺在地带性土壤中的吉布斯自由能为-16.30~-21.67 kJ·mol^(-1),表明吸附过程是自发且有利的。皮尔森相关性分析结果表明,土壤有机碳与Kf增长率呈显著负相关,说明土壤可溶性有机质抑制生物炭对丁草胺的吸附。多元线性回归方程分析结果显示,当土壤未添加生物炭时,土壤有机碳、pH、黏粒、粉粒4种土壤理化性质对Kf值的解释能力高达99%,而当生物炭添加为0.5%、1%、2%时,土壤有机碳、pH、黏粒、粉粒4种土壤理化性质对Kf值的解释能力分别下降至83%、70%、90%。通径系数研究表明,生物炭添加剂量从0上升至1%时,土壤黏粒和土壤粉粒对丁草胺吸附的直接作用系数增大,而有机碳和pH对丁草胺吸附的直接作用系数减小。研究表明,生物炭输入改变了丁草胺的吸附特征,土壤黏粒和土壤粉粒等土壤质地因素对丁草胺吸附产生重要影响。

This study utilized nine different types of soils with varying physicochemical properties,to which a range of rice husk biochar dosages were added.We investigated the isothermal adsorption characteristics of butachlor in the biochar-soil mixtures,analyzing correlation between soil physicochemical properties and the effects of biochar addition.The results indicated that the adsorption isotherms of butachlor in the biochar-soil composites conformed to the Freundlich adsorption model.The addition of biochar significantly enhanced the adsorption capacity of the nine zonal soils for butachlor(increased adsorption coefficient Kf values)and reduced the degree of linear adsorption(decreased 1/n values).After biochar supplementation,the adsorption capacity for butachlor was significantly increased.Thermodynamic calculations showed that the Gibbs free energy of butachlor in the nine soils ranged from-16.30 kJ·mol^(-1) to-21.67 kJ·mol^(-1) after biochar addition,suggesting that the adsorption process was spontaneous and favorable.Pearson correlation analysis revealed a significant negative correlation between soil organic carbon content and amorphous iron oxides with the rate of increase in,indicating that soil organic carbon and amorphous iron oxides inhibited the adsorption of butachlor by biochar.Multivariate linear regression analysis revealed that,without biochar,soil organic carbon content,pH,and clay,and silt levels accounted explained 99%of the the Kf value.However,when biochar addition was increased to 0.5%,1%,and 2%,the explanatory power of these four soil physicochemical properties for the Kf value decreased to 83%,70%,and 90%,respectively.This suggests that the introduction of biochar alters the adsorption mechanism of butachlor.Pathway analysis revealed that at 0 biochar addition,the direct effect coefficients of the four soil physicochemical properties were in the order of:soil organic carbon>sand>pH>clay,and at 1%biochar addition,the order was:clay>sand>soil organic matter>pH.The aforementioned results indicate that after the addition of biochar to soil,soil texture significantly influences the effectiveness of butachlor adsorption in soil.