State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, P. O. Box, 821, Nanjing, China; University of Chinese Academy of Sciences, Beijing, 100049, China.
State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, P. O. Box, 821, Nanjing, China.
Sci Total Environ. 2020 Nov 20;744:140868. doi: 10.1016/j.scitotenv.2020.140868. Epub 2020 Jul 17.
How paddy cultivation influences the adsorption isotherms, envelopes, and the kinetics of hexavalent chromate (Cr(VI)) on Fe (hydro)oxide-rich paddy soil, as well as the mechanisms involved, remain largely unaddressed. To this end, the Cr(VI) adsorption characteristics on a paddy soil, in comparison with its parent upland Oxisol, were studied. The results showed that Cr(VI) adsorption capacities (Q) were higher in the surface Oxisol than in the same layer of paddy soil. The Q increased by 18.0% and 41.3% after removal of soil organic matter (SOM) from the surface Oxisol and paddy soil layers, respectively, indicating that Cr(VI) adsorption was considerably inhibited by SOM. The adsorption and desorption isotherms demonstrated that non-electrostatic adsorption was mainly responsible for Cr(VI) adsorption, accounting for 59.37%-83.42% of Cr(VI) adsorption capacities. The negative shift of the zeta potential-pH curves with Cr(VI) loading further corroborated the finding that non-electrostatic adsorption is largely responsible for Cr(VI) retention. Cr(VI) adsorption at equilibrium, obtained by the stirred flow chamber technique, and the free Fe (hydro)oxides (Fe) contents were in the same order, suggesting that Fe are the main adsorbents for Cr(VI). Therefore, paddy cultivation has had a profound impact on the electrochemical properties of the Oxisol and on subsequent Cr(VI) adsorption characteristics.
稻田耕作如何影响富含铁（氢）氧化物的水稻土对六价铬（Cr(VI)）的吸附等温线、包络线和动力学，以及涉及的机制，在很大程度上仍未得到解决。为此，研究了 Cr(VI)在水稻土上的吸附特性，并与母质旱地土壤进行了比较。结果表明，表层旱地土壤的 Cr(VI)吸附容量（Q）高于同一层水稻土。去除表层旱地土壤和水稻土中土壤有机质（SOM）后，Q 分别增加了 18.0%和 41.3%，表明 SOM 对 Cr(VI)吸附有明显的抑制作用。吸附和解吸等温线表明，非静电吸附是 Cr(VI)吸附的主要机制，占 Cr(VI)吸附容量的 59.37%-83.42%。Cr(VI)负载下的动电电位-pH 曲线的负移进一步证实了非静电吸附是 Cr(VI)保留的主要原因。通过搅拌流动室技术获得的平衡 Cr(VI)吸附量和游离铁（氢）氧化物（Fe）含量呈相同顺序，表明 Fe 是 Cr(VI)的主要吸附剂。因此，稻田耕作对旱地土壤的电化学性质及其随后的 Cr(VI)吸附特性产生了深远的影响。
