果园生态养鸡鸡粪DOM的淋溶特征及其对抗生素迁移的影响

为研究粪源溶解性有机物与抗生素的共迁移行为及机制,以川中丘陵区典型石灰性紫色土为对象,通过吸附平衡试验与填装土柱试验,结合光谱学表征手段,研究鸡粪溶解性有机物(Dissolved Organic Matter,DOM)的淋溶特征及其对磺胺嘧啶(Sulfadizine,SD)、氟苯尼考(Florfenicol,FFC)及泰乐菌素(Tylosin,TYL)吸附和淋溶的影响。结果表明:鸡粪DOM以色氨酸为主要成分,吸附性强于腐殖酸成分,可增加土壤表面对抗生素的吸附位点。3种抗生素的等温吸附过程均符合线性和Freundlich方程,并以物理吸附为主。SD和FFC在紫色土中吸附性较弱,当与鸡粪DOM(200 mg/L)同时进入土壤时,其吸附未发生显著变化;而当鸡粪DOM先与土壤作用后,SD和FFC与土壤表面已吸附的鸡粪DOM成分通过非共价作用结合,吸附显著增加,相应吸附容量参数(K_f值)分别增加77.28%和114.36%。TYL在紫色土中的吸附很强,对鸡粪DOM的影响不敏感。在模拟降雨条件(20 mm/h)下,SD和FFC极易淋溶,与平衡吸附试验结果一致,SD和FFC在鸡粪DOM预先与土壤作用的土柱中穿透分别延迟了0.49和0.25个孔隙体积,淋溶总量减少了12.04%和15.35%,而鸡粪DOM与抗生素同时进入土壤的处理也表现出减少抗生素迁移的趋势。TYL未发生穿透而主要分布在表层土壤中,鸡粪DOM对它的淋溶无显著影响。综上,鸡粪DOM与抗生素发生共迁移的过程中,大量鸡粪DOM中色氨酸物质在土壤中的吸附,对弱吸附性抗生素的淋溶迁移具有显著的阻滞作用。

Leaching characteristics of dissolved organic matter in chicken manure and its effect on antibiotic migration in orchard

Abstract: Raising chickens in orchard has been widely developed in China, serving as a popular ecological breeding mode, due to the direct usage of chicken manure as a fertilizer to achieve comprehensive utilization of land resources and agricultural wastes, and thereby to reduce the addition of herbicides and insecticides. However, the organic matter and antibiotics leaching from the chicken manure have posed a potential pollution risk on the orchard soil and the surrounding water environment. Research on the co-transport behavior of manure-derived dissolved organic matter and antibiotics is lacking, particularly on the relevant mechanism. This study aims to investigate the migration characteristics of dissolved organic matter (DOM) in chicken manure, and theirs effects on the adsorption and leaching features of sulfadiazine (SD), florfenicol (FFC) and tylosin (TYL) in an orchard in the typical calcareous purple soil area of central Sichuan, China. Batch equilibrium and packed soil column experiments were carried out using the combined techniques of spectroscopic characterization. The results indicated that tryptophan was the main component of the tested chicken manure DOM, to increase the adsorption sites for antibiotics on the soil surface, indicating a stronger adsorption in soil, compared with that of humic acid. The isotherm adsorption of three antibiotics fitted well by both the linear and Freundlich equations, indicating a physical adsorption process dominated. There were weak adsorption capacities of SD and FFC in the studied orchard soil. Their adsorption almost remain constant, when spiked simultaneously with chicken manure DOM (200 mg C/L). In the case, the adsorption of SD and FFC increased significantly (p<0.05), when the chicken manure DOM was introduced to the soil in advance. The corresponding Kf values for SD and FFC increased by 77.28% and 114.36%, respectively, due to the binding of antibiotics to the previously adsorbed chicken manure DOM on the soil surface via a mechanism of noncovalent interactions. There was a strong absorption capacity of TYL in the tested soil. TYL was not sensitive to the presence of chicken manure DOM in its migration process for most soil adsorption sites. Under a simulated rainfall of 20 mm/h, SD and FFC were highly mobile, leaching out almost simultaneously with the water flow tracer Br- from the soil column. Being consistent with the results from the batch experiment, the chicken manure DOM in the treatment of injection prior to antibiotics delayed the breakthrough of SD and FFC by 0.49 and 0.25 PV, and their total leaching amount decreased by 12.04% and 15.35%, respectively. The decrease leaching of SD and FFC also occurred in the treatment of simultaneous injection of chicken manure DOM and antibiotics. Most residues of TYL retained in the topsoil without penetrating, indicating that the chicken manure DOM had no impact on the leaching of TYL. Therefore, for the highly mobile antibiotics, the chicken manure DOM can be expected to increase the retention of antibiotics in the soil through a co-adsorption mechanism. The finding demonstrated that the adsorption of tryptophan from chicken manure DOM can pose a significant blocking effect on the leaching of weakly adsorbed antibiotics in the co-transport process of manure DOM and antibiotics in soil due to chicken raising