Transport of Antibiotic Florfenicol in Agricultural Soils Associated with Dairy Waste.

Abstract: The widespread occurrence of pharmaceuticals and personal care products (PPCPs) in the environment has been recognized as an emerging issue. Land application of concentrated animal feeding operation (CAFO) waste has been identified to be a major source discharging these emerging contaminants to soils. In this study, laboratory-scale experiments were conducted to evaluate the effect of manure-borne colloids derived from dairy waste on the transport of antibiotic florfenicol in agricultural soils. Experiments showed that the sorption capacities for florfenicol in soils amended with solid manure were increased. By contrast, the sorption capacities of this antibiotic in soils irrigated with dairy wastewater were less than those in non-amended soils. It suggests that the manure-borne colloids derived from wastewater may compete with florfenicol or block soil sorption sites, resulting in decreased florfenicol sorption in agricultural soils. A soil column experiment was further conducted to evaluate the effect of these wastewater-associated colloids on the transport of florfenicol. We found that the colloids from dairy wastewater may facilitate the transport of florfenicol in soil and potentially accelerate its leaching to groundwater. In addition, a two-site nonequilibrium contaminant transport model was developed to fit the observed facilitated-transport process. The information from this study is very useful for assessing the potential environmental risk of veterinary pharmaceutical contaminants associated with land application of CAFO waste.