稻-鳝种养结合模式对稻田土壤性质及镉吸附与解吸的影响

Effects of rice-eel coculture system on soil properties and Cd adsorption and desorption in paddy field

在稻-鳝种养结合和非种养结合(水稻单一种植)模式下,设置不同氮肥减量梯度试验,研究稻田土壤对典型重金属镉吸附和解吸能力的差异.结果表明:稻-鳝种养具有降低稻田土壤pH、增加土壤全氮、有机质含量以及阳离子交换量(CEC)的作用;减氮处理组中,稻-鳝种养结合模式下的稻田土壤Cu、Zn、Pb、Cd及Cr含量有高于非种养结合模式的趋势,两种模式下的As和Hg差异不显著;稻田土壤对Cd^2+的吸附热力学曲线均可用Langmiur和Freundlich模型拟合,但Freundlich模型拟合效果更好,表明稻田土壤对Cd^2+的吸附更可能是一个不均一的多相界面,吸附的Cd^2+之间存在相互作用力;Langmuir模型得到的稻田土壤Cd2最大吸附量为986-1081 mg/kg,种养结合模式下稻田土壤Cd2+的最大吸附量高于非种养结合模式;稻田土壤对Cd2+的解吸量与吸附量成显著正相关.稻-鳝种养结合模式可通过改变稻田土壤的有机质、CEC等理化性质,影响稻田土壤对Cd^2+的吸附过程,增大土壤Cd^2+的最大吸附量.

Under the mode of rice-eel coculture and rice monoculture,different nitrogen reduction gradients were set up to study the difference of cadmium adsorption and desorption in paddy soil.The results showed that rice-eel coculture could reduce pH,increase total N,organic matter and cation exchange capacity(CEC)of paddy soil.In the nitrogen reduction groups,the content of Cu,Zn,Pb,Cd and Cr in rice-eel coculture system was higher than that in rice monoculture system,but the difference of As and Hg was not significant.Langmuir and Freundlich models could be used to fit the thermodynamic curves of Cd^2+adsorption in paddy soil,but Freundlich model had better fitting effect,which indicated that the adsorption of Cd^2+in paddy soil was more likely to be an heterogeneous interface,and there was an interaction between the adsorbed Cd^2+.The maximum adsorption capacity of Cd^2+in paddy soil obtained by Langmuir model was 986-1081 mgkg.The maximum adsorption capacity of Cd2+in paddy soil in rice-eel coculture system was higher than that in rice monoculture system.There was a significant positive correlation between Cd^2+desorption and adsorption in paddy soil.In conclusion,the rice-eel coculture system could change the physical and chemical properties of organic matter and CEC of paddy soil,so as to affect the adsorption process of Cd^2+and increase the maximum adsorption amount of Cd^2+.