Adsorption Characteristics and the Effect of Dissolved Organic Matter on Mercury(II) Adsorption of Various Soils in China

To evaluate the adsorption characteristics and effects of dissolved organic matter (DOM) from wheat straw (DOMW) and swine manure (DOMS) on mercury [Hg(II)] adsorption by soils, a series of experiments was conducted on 26 soils with different soil properties.Results showed that the values of K-d (a solid-liquid partition coefficient) of soils varied within a range of 0.768-14.386L g(-1). K-d values were mainly controlled by soil organic matter (SOM), cation exchange capacity (CEC), soil nitrogen (N), and soil sulfur (S). When DOMW and DOMS were added to the soil samples, the amount of Hg(II) adsorbed by the soils decreased significantly. Furthermore, based on the decreased percentage of adsorption of Hg(II) by soil upon adding DOMW (P-DOMW) or DOMS (P-DOMS), about 73.08% soils, the values of P-DOMS were smaller than those of P-DOMW. The P-DOMW values were related to SOM, pH, free Fe oxide content, and CEC, whereas P-DOMS values were related to soil free Fe/Al oxide contents. Therefore, we should pay more attention about mercury risk caused by the addition of exogenous organic matter in soils, especially for the soils with low or high pH, less SOM, low CEC, and less free Fe/Al oxide.