干旱区绿洲灌漠土Cu、Zn和Pb的吸附解吸特征

土壤重金属吸附解吸是影响土壤系统中重金属移动性和归宿的主要过程,影响重金属的生物有效性以及重金属在食物链中的传递等.配制一系列不同浓度的重金属,灌漠土对重金属溶液进行吸附实验24 h以达到平衡,再用硝酸铵和乙酸铵进行解吸实验24 h以达到平衡.利用热力学吸附平衡法,对西北干旱区绿洲灌漠土重金属Cu、Ni和Pb的吸附解吸行为进行序批实验研究.实验结果表明:(1)灰漠土在常温下对铜、锌和铅重金属离子的吸附等温线符合Freundlich型吸附模式,灰漠土对重金属铜、锌和铅的吸附能力由强到弱的顺序为:铅,铜,锌.(2)硝酸铵和乙酸铵解吸重金属的量与灰漠土吸附重金属量呈现出线性正相关,乙酸铵解吸重金属的量比硝酸铵解吸重金属的量大,两种解吸剂对铜、锌和铅重金属离子的解吸能力由大到小的顺序都为:铜,锌,铅,说明了一般外源的铜、锌和铅进入土壤以后,铜和锌可能比铅容易向四周转移.(3)硝酸铵和乙酸铵的解吸率呈谷形曲线,开始时硝酸铵和乙酸铵解吸重金属量的百分比随灰漠土吸附重金属量的增加而减小,在吸附量达到某一特定值时,解吸率随吸附量的增加而增加.灰漠土对铜、锌和铅的吸附作用以专性吸附为主,被灰漠土吸附的铜、锌和铅重金属离子较难解吸.

Sorption and desorption of copper, zinc and lead in the irrigated desert soil from the oasis in the arid regions, northwest China

Sorption - desorption of heavy metals in soils, one of the primary processes controlling the fate and mobility of heavy metals in soils, play a dominant role in the migration and pollution effects of heavy metals in the soil-plant system. The sorption experimentation of copper, zinc and lead by grey desert soil absorbed at equal rates for 24 hours, The desorption experimentation of copper, zinc and lead by ammonium acetic and ammonium nitrate desorbed at equal rates for 24 hours, Laboratory batch experiments were carried to study the sorption and desorption of Cu, Ni and Pb in the irrigated desert soil from the oasis in the arid regions, northwest China.Experimental results show:(1) the adsorption isotherm model of copper, zinc and lead by grey desert soil at 25℃ fits the Freundlich adsorption equation; the sorption capability on copper, zinc and lead in grey desert soil was in the following order: lead > copper > zinc.(2) extremely significant positive linear relationship was observed between heavy metal adsorption capability of the grey desert soil and heavy metal desorption capability. The desorption capability of copper, zinc and lead desorbed by ammonium acetic was more than the desorption capability of copper, zinc and lead desorbed by ammonium nitrate, their desorption capability on copper, zinc and lead in gery desert soil was in the follwing order: copper > zinc > lead, it explain that copper and zinc were easier transferred than lead around the soil.(3) the desorption rate of copper, zinc and lead desorbed by ammonium acetic and ammonium nitrate characterized generally as valley-like curves, with the increasing of the copper, zinc and lead adsorption, the desorption rate decreased first, then increased, the adsorption of copper, zinc and lead by the grey desert soil is mainly specific adsorption. Heavy metal adsorbed by the grey desert soil will be difficult to be released.