有机质对广西酸性富硒土中Se(Ⅳ)吸附解吸特性的影响

Effect of Organic Matter on Se(Ⅳ)Sorption in Acidic Selenium-rich Latosolic Red Soil in Guangxi

为探究有机质在酸性富硒土吸附Se(Ⅳ)过程中的作用,以广西典型富硒区的赤红壤为材料,研究了酸性富硒土去除有机质后,土壤硒的赋存形态、土壤对Se(Ⅳ)的吸附解吸特征及吸附前后土壤基团的变化。结果表明:①去除有机质后,土壤中有机结合态硒大幅度减少,铁锰结合态硒成为土壤硒的主要赋存形态。②吸附试验表明,土壤对Se(Ⅳ)吸附过程以多分子层的不均质表面吸附为主,吸附过程受控于化学反应与化学吸附;去除有机质后,土壤对Se(Ⅳ)吸附量和吸附强度均显著下降。③解吸试验表明,吸附以难解吸的专性吸附为主;去除有机质后,解吸量与解吸率下降,固液分配系数Kd值下降。④傅里叶变换红外光谱表明,土壤吸附Se(Ⅳ)与静电引力、络合反应和配位体交换有关;去除有机质减少了有机官能团的数量,导致吸附量减少。综上,有机质的存在,提升了酸性富硒土对Se(Ⅳ)的吸附容量和吸附强度,是造成酸性富硒土硒有效性较低的重要因素。

To explore the role of organic matter in Se(Ⅳ)adsorption by acid Se(Ⅳ)-rich soil,the occurrence forms of soil Se,the adsorption and desorption characteristics of soil Se(Ⅳ),and the changes of soil groups before and after adsorption were studied in latosolic red soil from typical Se-rich areas in Guangxi.The results show that:1)After the removal of organic matter,organic bound Se in soil is decreased significantly,and Fe and Mn bound Se is the main occurrence form of soil Se.2)The adsorption experiment shows that the adsorption process of soil to Se(Ⅳ)is mainly the heterogeneous surface adsorption of the multi molecular layer,and the adsorption process is controlled by chemical reaction and chemical adsorption.After the removal of organic matter,the adsorption capacity and intensity of soil to Se(Ⅳ) are decreased significantly.3)The desorption experiment shows that the adsorption is mainly specific adsorption which is difficult to desorb.After removing organic matter,the desorption amount and rate are decreased,and Kd value is decreased.4)Fourier spectrum shows that the adsorption of Se(Ⅳ)on soil is related to ligand exchange and electrostatic attraction.The removal of organic matter reduces the number of organic functional groups,resulting in the reduction of adsorption.In conclusion,the existence of organic matter improves the adsorption capacity and intensity of Se(Ⅳ)on acid Se-rich soil,which is an important factor for the low Se availability of acid selenium-rich soil.