抗生素在紫色土地表径流和地下渗流中的迁移

以川中丘陵区典型石灰性紫色土为对象,在生态养鸡果园管理模式下,探究不同种类粪源抗生素在连续自然降雨事件下随土壤水文过程的迁移浓度、通量及其对降雨的动态响应规律。结果表明,在蓄满产流机制下,连续强降雨导致地表径流和地下渗流中的抗生素浓度急剧增加。降雨过程中,抗生素浓度对降雨强度有明显响应,浓度峰与雨强峰一一对应,地下渗流的响应峰存在15~30min滞后。磺胺类抗生素在地表径流和地下渗流中的平均浓度分别高达1.22,4.07μg/L。在优先流作用下,吸附性较强的喹诺酮类和四环素类抗生素即使在降雨初期也能在地下渗流中被检出。地下渗流也是研究区紫色土中抗生素迁移的重要路径,其迁移总通量比地表径流高2个数量级。此外,鸡粪处理下抗生素迁移浓度和通量显著高于对照,表明粪源基质对污染物具有辅助运移作用。pH值和胶体浓度是主要影响因素,在降雨过程中的变化可引起抗生素形态及其与胶体结合作用改变。相关分析表明,胶体浓度与抗生素都呈正相关,pH值与磺胺类、四环素类抗生素和泰乐菌素呈显著正相关,而与氟苯尼考和喹诺酮类抗生素负相关。

Antibiotics migration in surface runoff and leachate from purple soil

This study aimed to investigate the concentration, flux and dynamics of several antibiotics via soil hydrological processes responding to continuous natural rainfalls. Field trials were carried out in a chicken-raising orchard of typical calcareous purple soil located in the hilly area of central Sichuan province. The results showed that a drastic increase of the antibiotic concentrations in the surface runoff and leachate could be led by continuous heavy rainfalls under a saturation excess mechanism. During the rainfalls, the antibiotic concentrations fluctuated consistently corresponding to the rainfall intensity, while the leachate responded with a time lag between 15~30minutes. The mean concentrations of sulfonamides reached up to 1.22 and 4.07μg/L in the surface runoff and leachate, respectively. Along with the soil preferential flow, the strongly adsorptive quinolones and tetracyclines were detected in the leachate even in the beginning of the rainfall. Leaching was an important path for antibiotic migration in the studied purple soil, as the total flux of leachate was two orders of magnitude higher than that of surface runoff. Furthermore, the concentration and flux of antibiotics for the chicken manure plots were significantly higher than that in the control plot, suggesting that the manure-derived substrate had accelerated the antibiotics transport. The variation of pH value and colloid concentration during rainfalls caused changes in ionic forms of the antibiotics and their binding with colloids, thus being the main factors affecting the migration. According to statistics, positive correlations were observed between the concentration of antibiotics and colloids. pH value showed significantly positive correlations with sulfonamides, tetracyclines and tylosin, while negative correlations were observed for florfenicol and quinolones.