磺胺类抗生素和氟苯尼考(FFC)是浙江省常用的抗生素。它们在土壤上吸附弱,容易迁移,环境风险高。近年来,大多数关于粪便抗生素对农田土壤的潜在风险的研究是在实验室条件下通过添加粪便进行的;因此,不可能评估自然施肥下抗生素污染的风险。因此,进行批量平衡试验,探讨不同土壤类型和粪肥类型对土壤中抗生素吸附的影响,其中五种类型的旱地农田土壤[林安(LA),嘉善(JS),龙游(LY),开化(KH),和金华(JH)]在浙江省已经使用了不同的肥料(鸡粪,猪粪,和化肥)选择了很长时间,和四种常用抗生素[磺胺嘧啶(SD),磺胺二甲嘧啶(SMT),磺胺甲恶唑(SMZ)和FFC]被选中。结果表明,4种抗生素在实验土壤中的吸附能力较弱,吸附容量按以下顺序降低:SMT(1.44-13.23mg1-(1/n)·L1/n·kg-1)>SMZ(0.73-6.05mg1-(1/n)·L1/n·kg-1)>SD(0.16-5.57mg1-(1/n)·L1/n·kg-1)>FFC(0.27-3.81mg1-n)。Freundlich模型在拟合SD的等温线吸附方面优于线性模型,SMT,FFC,其中SD和FFC属于“S”型吸附,SMT属于“L”型吸附。对于SMZ,线性模型的拟合效果优于Freundlich模型。总有机碳(TOC)和溶解有机碳(DOC)含量能较好地预测4种抗生素的吸附量(r=0.548~0.808),阳离子交换容量(CEC)和电导率(EC)值可以更好地预测SMT和FFC的吸附容量(r=0.758-0.841)。与施用化肥相比,施用肥料增加了TOC值,DOC,CEC,和酸性和中性土壤中的EC,有利于抗生素在土壤上的吸附。同时,施用肥料还增加了酸性和中性土壤的pH值,不利于抗生素在土壤上的吸附。此外,施用肥料降低了TOC值,DOC,CEC,EC,和碱性土壤中的pH值。较低的pH有利于抗生素在土壤上的吸附,而其他四种的含量较低不利于抗生素在土壤上的吸附。对于肥力低的酸性土壤,肥料的施用增加了土壤肥力,从而增加了抗生素在土壤上的吸附,比如洛杉矶的土壤和鸡粪,LY(1)土壤与猪粪,和JH土壤中的鸡粪和猪粪。然而,对于高肥力的酸性和中性土壤,施用粪肥显著提高了土壤pH值,从而降低了抗生素在土壤中的吸附,如含鸡粪和猪粪的JS土壤和含鸡粪的LY(2)土壤。对于肥力和pH值较高的钙质土壤(如KH土壤),4种抗生素在施用粪肥后土壤上的吸附曲线表现出多样性:施用鸡粪和猪粪后SD的吸附能力显著增加,而SMT和SMZ的吸附能力显著下降,施用鸡粪后,FFC的吸附能力明显下降。因此,根据土壤肥力施用粪肥可以有效控制粪便抗生素的环境风险。
Sulfonamide antibiotics and florfenicol(FFC) are commonly used antibiotics in Zhejiang Province. They have weak adsorption on soil and are easy to migrate, with high environmental risks. In recent years, most of the studies on the potential risk of fecal-derived antibiotics to farmland soil were conducted by adding manure under laboratory conditions; therefore, it is impossible to assess the risk of antibiotic pollution under natural fertilization. Therefore, batch balance experiments were conducted to explore the effects of different soil types and manure types on the adsorption of antibiotics in the soil, in which five types of dryland farmland soils[Lin\'an(LA), Jiashan(JS), Longyou(LY), Kaihua(KH), and Jinhua(JH)]in Zhejiang Province that have been used with different fertilizers(chicken manure, pig manure, and chemical fertilizer) for a long time were chosen, and four types of commonly used antibiotics[sulfadiazine(SD), sulfamethazine(SMT), sulfamethoxazole(SMZ), and FFC]were selected. The results showed that the adsorption of the four antibiotics in the experimental soil was weak, and the adsorption capacity decreased in the order of:SMT(1.44-13.23 mg1-(1/n)·L1/n·kg-1)>SMZ(0.73-6.05 mg1-(1/n)·L1/n·kg-1)>SD(0.16-5.57 mg1-(1/n)·L1/n·kg-1)>FFC(0.27-3.81 mg1-(1/n)·L1/n·kg-1). The Freundlich model was superior to the linear model in fitting the isotherm adsorption of SD, SMT, and FFC, in which SD and FFC belonged to \"S\" type adsorption, and SMT belonged to \"L\" type adsorption. For SMZ, the fitting effect of the linear model was better than that of the Freundlich model. The contents of total organic carbon(TOC) and dissolved organic carbon(DOC) could better predict the adsorption capacity of the four antibiotics(r=0.548-0.808), and the values of cation exchange capacity(CEC) and electrical conductivity(EC) could better predict the adsorption capacity of SMT and FFC(r=0.758-0.841). Compared with the application of chemical fertilizer, manure application increased the values of TOC, DOC, CEC, and EC in acidic and neutral soils, which was conducive to the adsorption of antibiotics on the soil. Meanwhile, manure application also increased pH in acidic and neutral soils, which was not conducive to the adsorption of antibiotics on the soil. In addition, manure application reduced the values of TOC, DOC, CEC, EC, and pH in alkaline soils. The lower pH was conducive to antibiotic adsorption on the soil, whereas the lower content of the other four was not conducive to antibiotic adsorption on the soil. For the acidic soil with low fertility, the application of manure increased soil fertility and thus increased the adsorption of antibiotics on the soil, such as the LA soil with chicken manure, the LY(1) soil with pig manure, and the JH soil with chicken manure and pig manure. However, for the acidic and neutral soils with high fertility, the application of manure had significantly increased soil pH and thus reduced the adsorption of antibiotics on the soil, such as the JS soil with chicken manure and pig manure and the LY(2) soil with chicken manure. For calcareous soil with high fertility and pH(such as KH soil), the adsorption profiles of the four types of antibiotics on the soil showed diversity after the application of manure:the adsorption capacity of SD increased significantly after the application of chicken manure and pig manure, whereas the adsorption capacity of SMT and SMZ decreased significantly, and the adsorption capacity of FFC declined significantly after the application of chicken manure. Therefore, manure application according to soil fertility could effectively control the environmental risk of fecal antibiotics.