磺胺嘧啶在作物根际土壤中的吸附/解吸特性研究

采用根际袋盆栽实验,研究了在小麦和玉米根际效应作用下,土壤对磺胺嘧啶(Sulfadiazine,SD)吸附/解吸热力学与动力学特性.结果表明,小麦和玉米根际与非根际对SD的吸附/解吸均较快,描述2种作物根际与非根际对SD吸附过程最优动力学方程皆为Elovich方程,其次是双常数方程和抛物线方程.在实验所采用的SD浓度范围内,不同处理小麦和玉米根际与非根际对SD的吸附量均随着SD浓度的增加而增加,但根际对SD的吸附能明显高于非根际.用Freundlich方程描述小麦和玉米根际与非根际对SD等温吸附行为最为适宜.SD在小麦和玉米根际与非根际的解吸过程都是非线性的,且在根际的解吸能力明显低于非根际.此外,将小麦和玉米根际与非根际的平均吸附常数(Kf-ads)及平均解吸常数(Kf-des)与土壤有机质、pH、黏粒3种理化性质关系进行逐步回归分析发现,有机质是影响根际SD吸附/解吸行为的关键因素.

Adsorption/desorption characteristics of sulfadiazine on the rhizospheric soils

Rhizospheric soils incubated by rhizospheric bags were used to investigate the adsorption and desorption of sulfadiazine by soils under different rhizosphere effects. The studies showed that the adsorption and desorption of sulfadiazine by the test soils was very rapid. Elovich equation was the optimal model to describe the adsorption of sulfadiazine, followed by two-constant equation and parabolic equation, whereas parabolic diffusion equations were not suitable. The adsorption of sulfadiazine by these test soils increased with the increasing concentration of sulfadiazine within the range of sulfadiazine concentrations used in the experiment, but the amount of sulfadiazine adsorbed and fixed on rhizospheric soils was much higher than that on non-rhizospheric soils. The adsorption of sulfadiazine by the soils could fit well with the Freundlich equation, while Langmuir equation was not applicable to describe the isothermal adsorption processes of sulfadiazine by the test soils. The desorption processes of sulfadiazine on the test soils was non-linear. The desorption ability of rhizospheric soils was lower than that in non-rhizospheric soils. In addition, the relationship between average adsorption constants (K_f-ads) and average desorption constant (K_f-des) and the content of soil organic matter, pH, and sticky grain content showed that soil organic matter is the key factors affecting adsorption/desorption behaviors of sulfadiazine in root-soil interface.