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| Effects of corn-straw biochar on cadmium adsorption, nutrient contents, and chemical forms in red soil |
| Received:July 08, 2017 |
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| KeyWord:red soil;corn-straw biochar;cadmium;nutrient elements;isothermal adsorption |
| Author Name | Affiliation | E-mail | | WANG Yi-min | College of Environment, Hohai University, Nanjing 210098, China | | | TANG Dou-dou | College of Environment, Hohai University, Nanjing 210098, China | | | ZHANG Xiao-hui | College of Environment, Hohai University, Nanjing 210098, China | | | YUAN Xu-yin | College of Environment, Hohai University, Nanjing 210098, China | yxy_hjy@hhu.edu.cn | | XU Lan | College of Environment, Hohai University, Nanjing 210098, China | |
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| Abstract: |
| To better understand the effects of corn-straw biochar on soil cadmium (Cd) adsorption, and chemical forms of nitrogen (N) and phosphorus (P) and their transformation in soil, we performed an incubation experiment with the addition of different biochar levels. Red soil samples were mixed with corn-straw biochar, at a ratio of 0%, 2%, 4%, and 8% soil weight. These mixtures were cultivated in an incubator for 35 days. We explored the effects and mechanisms of biochar addition on soil Cd2+ adsorption, and the bioavailability and chemical forms of nutrient elements[N, P, and potassium (K)] in red soil using isothermal adsorption and chemical extraction methods. Results showed that biochar addition increased the soil pH and organic matter content, and enhanced the Cd2+ adsorption capacities in soil. These adsorption behaviors were well fitted with both Freundlich and Langmuir equations (R2>0.90). The results of SEM-EDAX indicated that the biochar had adsorbed some Cd2+ in the studied soil. Owing to soil pH changes by biochar addition, we explored the role of different pH values on red soil Cd2+ adsorption behavior. At pH 4~8, Cd2+ adsorption by red soil was enhanced with increasing pH. Zeta potential results of soil suspension showed that biochar application could increase the amount of negative charge in soil, thus proving that more Cd2+ would be adsorbed in red soil through the electrostatic effect. In addition, the chemical forms of the nutrient elements varied in response to biochar application in red soil. Specifically, the bioavailable forms of P (KCl-P), N (IEF-N), and K in red soil significantly increased with biochar addition. The P forms (Ca-P, Fe-P) were also enhanced by biochar addition, but no significant changes in total transferable N (TTN) content was observed. Based on the above results, we concluded that corn-straw biochar application could decrease the environmental risk of heavy metal contaminated soil, and significantly improve the quality of soil fertility. |
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