生物质炭对坡耕地紫色土中抗生素吸附-解吸及迁移的影响

Effects of Biochar on Adsorption-Desorption and Migration of Antibiotics in Slope Farmland of Purple Soil

以磺胺嘧啶、磺胺二甲基嘧啶和氟苯尼考为目标抗生素,通过室内批量平衡试验研究施用生物质炭(投加量0、2.145和28.65 kg/m^2,经3 a田间老化)对石灰性紫色土中抗生素等温吸附-解吸特征的影响;并利用长20 m、宽5 m的坡耕地(6°)野外小区,开展面施2.145 kg/m^2生物质炭和在坡底构建一定宽度(40 cm)和深度(40 cm)含28.65 kg/m^2生物质炭可渗透反应土墙试验,研究两种不同生物质炭施用方式对暴雨条件下抗生素迁移行为的影响。结果表明:生物质炭的添加显著增强紫色土对抗生素的吸附与固持作用,其等温吸附和解吸行为均能被Freundlich方程较好地拟合;不论施炭与否,磺胺嘧啶和磺胺二甲基嘧啶都表现为非线性吸附,而对于Kow值最低的氟苯尼考,生物质炭的施用则为其引入了新的非线性吸附机制。耕作层面施生物质炭能更有效地阻控抗生素向深层土壤的垂向淋失迁移;在坡底修建生物质炭可渗透反应土墙(顶端构筑为地埂-边沟)则能更大幅度地削减抗生素随地表径流的输出负荷,其中以对正辛醇-水分配系数最低的氟苯尼考的削减率最小。

Sulfadiazine,sulfadimethazine and fluorophenicol were taken as tested antibiotics,indoor batch experiments were conducted to study the effects of different biochar addition(0,2.145 and 28.65 kg/m^2)followed by 3 a field ageing on the adsorption and desorption of antibiotics in slope farmland of calcareous purple soil,meanwhile field plot(20 m long and 5 m wide)experiment was conducted to study antibiotic transport in slope(6°)farmland with 2.145 kg/m^2 biochar surface application and the biochar permeable reactive wall(40 cm in width and 40 cm in depth,with biochar content of 28.65 kg/m^2)at plot bottom.The results showed that biochar addition significantly enhanced the adsorption and immobilization of antibiotics in purple soil,the isothermal adsorption and desorption fitted well with Freundlich equation.Sulfadiazine and sulfadimethazine exhibited nonlinear adsorption with or without biochar addition,but biochar addition introduced a new nonlinear sorption mechanism for florfenicol with the lowest Kow.Biochar surface application prevented more effectively the vertical leaching of antibiotics into the deep soil,while biochar permeable reactive wall with a ditch-ridge top reduced more effectively antibiotic output loads in the surface runoff,among of which,the lowest reduction was found for florfenicol with the smallest n-octanol/water partition coefficient.