胡敏酸和柠檬酸对铜在土壤中吸附-解吸行为的影响

Effect of Humic Acid and Citric Acid on Adsorption and Desorption of Copper in Different Soils

铜在土壤中的吸附-解吸行为及其影响因素是评价铜在环境中去向的主要因素之一。本研究采用一次平衡法,目的是为了阐明两种可溶性有机碳(DOC)——胡敏酸(HA)和柠檬酸(CA)对铜在不同土壤中的吸附-解吸行为的影响。结果表明,HA有显著促进土壤对铜的吸附的趋势,但在碱性土壤中比在酸性土壤中的促进效果更为明显;而CA显著抑制碱性土壤对铜离子的吸附,对铜离子在酸性土壤中的吸附行为的影响随加入铜离子浓度的不同而异,低浓度时(<63.54mg·L-1)CA对铜离子的吸附有抑制作用,而随着铜离子浓度的升高,CA又反过来促进土壤对铜离子的吸附。被碱性土壤吸附的铜离子很难用中性盐解吸出来。产生上述现象的原因可能与铜离子随pH变化的水解程度不同和不同类型DOC本身性质不同有关。土壤对铜吸附行为的变化有可能用来预测重金属对水体的污染潜力。

Behaviors of copper adsorption and desorption in various soils and their influencing factors are important parameters for evaluating the fate of copper in the environment. Batch experiments were conducted to investigate the effect of different dissolved organic carbon （DOC）, i.e., humic acid （HA） and citric acid （CA）, on the adsorption and desorption of copper in different soils. The addition of HA increased the adsorption of copper, with more considerable increase being observed in the alkaline soil than in the acid soil. On the other hand, CA decreased the copper adsorption in the alkaline soils, while in the acid soil, the effect of CA on the adsorption of copper varied with the concentration of added copper, with the effect changing from negative to positive when the concentration of added copper changed from less than 63.54 mg·L^-1 to higher than 63.54 mg·L^-1. The copper adsorbed on the alkaline soil was difficult to be desorbed by neutral salt. The changes of copper hydrolysis with pH and the native properties of DOC might all contribute to the copper behaviors mentioned above. The copper adsorption-desorption in different soils might be useful for evaluating its potential contamination in the groundwater.