冻融作用对土壤吸附重金属的影响

Effect of Freeze-Thaw on the Adsorption of Heavy Metals by Soil

以Pb2+和Cd2+为目标污染物研究冻融作用对土壤吸附重金属的影响,推断了影响机制,并分析了温度对冻融土壤吸附重金属的影响.结果表明,冻融作用降低了土壤对重金属的吸附量,影响了吸附曲线的斜率,但未改变吸附曲线形状,这与冻融作用改变土壤理化性质有关:冻融作用影响了土壤对Pb2+和Cd2+的吸附机制,引起专性吸附向非专性吸附转变,利于Pb2+和Cd2+向环境的解吸和释放.冻融作用未影响土壤对Pb2+和Cd2+的吸附热力学性质,随着温度的升高,冻融土壤和未冻融土壤对Pb2+的吸附量逐渐升高,属于吸热反应;对Cd2+的吸附量降低,属于放热反应.

We used Pb2＋ and Cd2＋ as target pollutants to study the effect of freeze-thawing cycles on the adsorption of heavy metals by soil,decuced the effect mechanisms,and analyzed the effect of temperature on heavy metal adsorption on freeze-thaw soils.The results show that the freeze-thawing cycles reduced the Pb2＋ and Cd2＋ adsorption on soil,and changed the slope of Pb2＋ and Cd2＋ adsorption isotherms.Freeze-thawing cycles changed the adsorption mechanism of soil from specific adsorption to nonspecific adsorption,and it promotes soil to desorbe and release Pb2＋ and Cd2＋ to the environment.Freeze-thaw did not change the therm odynamic property of Pb2＋,Cd2＋ adsorption on soil,with the rise of temperature,Pb2＋ adsorptions on freeze-thaw soil and untreated soil were increased,which belong to endothermic reaction;but the adsorption of Cd2＋ reduced with temperature rise,which belongs to the exothermic reaction.Under the same pH conditions,the adsorption quantities of Pb2＋ and Cd2＋ on freeze-thaw soil were lower than those on untreated soil.