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| Effects of colloidal and dissolved organic matters on Cd adsorption in soil |
| Received:December 01, 2022 Revised:February 07, 2023 |
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| KeyWord:adsorption;Cd;livestock manure;colloid;dissolved organic matter |
| Author Name | Affiliation | E-mail | | LIANG Yun | School of Environment and Resources, Chongqing Technology and Business University, Chongqing 400067, China | | | HOU Mengbin | School of Environment and Resources, Chongqing Technology and Business University, Chongqing 400067, China | | | ZHANG Wei | School of Public Administration, Chongqing Technology and Business University, Chongqing 400067, China | weizhang@ctbu.edu.cn | | WANG Xingmin | School of Environment and Resources, Chongqing Technology and Business University, Chongqing 400067, China | |
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| Abstract: |
| Organic fertilizer-derived organic matter is an important exogenous factor affecting the fate of heavy metals in soil. In addition to the dissolved organic matter, the effect of colloidal organic matter on the sorption of heavy metals in soil has been rarely investigated. In this study, the sorption kinetics and sorption isotherms of cadmium（Cd）in three soil varieties obtained from sloping farmland, paddy field, and irrigation and non-irrigation rotation field, in the presence and absence of pig manure-derived colloidal organic matter（COM, 10-0.45 μm）and dissolved organic matter（DOM, <0.45 μm）, were investigated. The results showed that the quasi-secondary kinetic equation and Langmuir model were superior in the fitting of sorption dynamics（R2>0.90）and sorption isotherms（R2>0.95）of Cd, respectively. Each soil sample exhibited a strong nonlinear sorption of Cd as indicated by the low Freundlich nonlinearity index（n<0.42）. The sorption intensity of Cd by the three soil samples followed the trend of irrigation and non-irrigation rotation field>paddy field>sloping farmland, which was positively correlated to soil pH, soil organic matter, and silt content. Both COM and DOM exhibited mobilizing effects towards Cd sorption by the three soil samples, with DOM showing a greater impact. Particularly, Cd sorption in the soil from the irrigation and non-irrigation rotation field was affected by COM and DOM more extensively than that in the other two soil samples. Furthermore, a rapid decrease of Cd sorption was observed when COM or DOM were less than 30 mg·L-1（calculated by C）, followed by an insignificant increase thereafter. Therefore, the potential mobilization of heavy metals including but not limited to Cd, especially in the runoff, should be considered upon the application of animal manure to heavy metal contaminated fields. |
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