生物质炭对磺胺类抗生素在坡耕地紫色土中吸附-解吸及淋溶过程的影响

Effects of Biochar Application on Sorption-Desorption Process and Leaching Behaviour of Sulfonamide Antibiotics

吸附–解吸是影响抗生素类污染物在土壤中迁移转化及生物有效性的重要过程,本文以川中丘陵区坡耕地紫色土为研究对象,通过批量平衡实验和柱实验研究生物质炭施用(投加量0(B0)、39.75 t/hm^2(B1)和198.75 t/hm^2(B2))及田间老化作用(夏季干湿交替)对3种典型磺胺类抗生素(磺胺嘧啶(SD)、磺胺二甲基嘧啶(SM2)及磺胺甲恶唑(SMZ))在紫色土中的吸附–解吸和淋溶行为的影响。结果表明:在几种处理中,3种磺胺类抗生素吸附强弱的顺序都表现为SD>SMZ>SM2;与B0处理相比,添加生物质炭能增加土壤对3种抗生素的吸附能力,其中SM2的吸附显著增加(P<0.05),但这种促进作用在经过老化过程后有所减弱。在解吸过程中,3种抗生素的Freundlich常数Kf大小顺序为SD>SMZ>SM2,表明SD在土壤中吸附容量最大且不易解吸,其次是SMZ和SM2;相应的迟滞系数H大小顺序为SD<SMZ<SM2,与Freundlich常数n值趋势一致,表明紫色土对SD亲和力最强,解吸最难,而SM2则解吸最易,可逆性最强。与B0处理土柱相比,3种磺胺抗生素在B1处理土柱中迁移更慢。

Sorption and desorption are an important process that will influence the behavior of transport, transform and bioavailability of antibiotics in soils. In this study, batch and column experiments were carried out to study the effects of biochar application on the sorption-desorption process and leaching behaviour of three typical sulfonamide antibiotics （Sulfadiazine, SD; Sulfamethazine, SM2; and Sulfamethoxazole, SMZ） in a sloping cropland purple soil which is distributed widely and abundantly in Sichuan hilly area. Biochar was applied to the tested soil with the amounts of 0 （B0）, 39.75 t/hm^2 （B1） and 198.75 t/hm^2 （B2） respectively and went through a half-year dry-wet alternate aging process （from May to November）. The results showed that the adsorption capacity of three sulfonamides followed the order of SD〉SMZ〉SM2; Compared with B0, addition of fresh biochar enhanced the adsorption of SD, SM2 and SMZ, among which the improvement for SM2 was significant （P〈0.05）, but such effect became less obvious after the ageing process. As for the desorption process, the value of Freundlich coefficient Kf of three sulfonamides followed the order of SD〉SMZ〉SM2, indicating that SD had the highest adsorption capacity and lowest desorption capacity with SM2 inversely. The hysteresis coefficient （H） of three sulfonamides followed the order of SDn. It suggested that SM2 desorbed the fastest from purple soil due to the lowest appetency, while SM2 behaved oppositely. Three sulfonamide antibiotics transported more slowly in B1 compared with B0.