川西平原水稻土对磺胺甲噁唑的吸附动力学研究

Analysis of the adsorption effects of sulfamethoxazole on the paddy field soil based on the collected samples from the West Sichuan Plain

磺胺甲噁唑（SMX）在水稻土上的吸附动力学研究鲜有报道。采用批量吸附试验,系统分析了川西平原6种代表性水稻土对SMX的吸附动力学特征,并考察了水稻土粒径对吸附过程的影响。结果表明：1）6种水稻土对SMX的吸附量均随吸附时间延长而增大,并在120 h内达到吸附平衡;2）SMX在黏性水稻土上的吸附量（≥66.15μg/g）高于沙质水稻土（≤59.62μg/g）;3）双室一级动力学模型（R2adj为0.97～1.00,均值为0.99）对SMX在水稻土上吸附过程的拟合度优于拟二阶动力学模型（R2adj为0.80～0.98,均值为0.91）和拟一阶动力学模型（R2adj为0.72～0.97,均值为0.84）;4）双室一级动力学模型包括快室和慢室吸附两个过程,而水稻土上SMX的快室吸附过程在吸附前12 h内完成,且吸附贡献较慢室吸附大（f1〉f2）;5）粒径小于830μm的水稻土对SMX的吸附作用随颗粒粒径减小而增大;6）大多数情况下,同种水稻土的快室吸附速率随土壤粒径增大而减小。研究表明,川西平原水稻土的粒径分布在SMX迁移过程中起到了重要作用。

The article is aimed to bring about a report for the analysis of the adsorption kinetics of sulfamethoxazole（ SMX） on the natural paddy soils by taking the samples we have collected from those of the West Sichuan Plain,in hoping to provide more comprehensive fundamental data for the risk assessment and contamination control of SMX in the said ecosystem context. In the article,we have collected and adopted six representative types of paddy soils from the above mentioned area and have done a batch of experimental tests so as to identify and determine the adsorption kinetics of SMX on the soil. What is more,we have also tested the effects of the soil particle-size on the adsorption behaviors. The results of our experimental tests prove that：（ 1） The adsorption effect of SMX on the six types of paddy soil tends to increase with the extension of the adsorption period with the adsorptive balance found by the 120thhour;（ 2）The adsorption amount of SMX on the clayey paddy soils（ ≥66. 15μg/ g） tends to be greater than that on the sandy soil（ ≤59. 62 μg/g）;（ 3） The first order two-compartment model（ R2adj： 0. 97-1. 00,mean： 0. 99） proves to be the best way for simulating the adsorption kinetics of SMX on such soil,whereas the second-order kinetics model（ i. e. R2adj： 0. 80-0. 98,mean： 0. 91） and the first-order kinetics model（ i. e. R2adj： 0. 72-0. 97,mean： 0. 84） turn to be less suitable and available;（ 4） The first order two-compartment model is supposed to include both the fast and the slow adsorption compartment,in which the fast one can normally be accomplished during the first 12 hours and contribute the major part to the total adsorption（ f1 f2）;（ 5） For adsorption of the soil particles on the SMX of the paddy soil indicates a rising tendency with the decrease of the particle size on the condition that its sizes are less than 830 μm;（ 6） In most situations,for the same type of soil,the fast adsorption rate tends also to decrease with the increase of the particle size. Thus,it can be concluded that the particle size of the paddy soil proves to entail an important function on the transformation and transfer behaviors of the SMX.