Modeling Manure wlloid-Facilitated Transport of the Weakly Hydrophobic Antibiotic Florfenicol in Saturated Soil Columns

摘要

Field application of livestock manure introduces animalrnhormones and veterinary antibiotics into the environment. Colloidsrnpresent in manure may potentially intensify the environmental risk ofrngroundwater pollution by colloid-facilitated contaminant transport. Therntransport behavior of the veterinary antibiotic florfeniwl in saturatedrnhomogeneously packed soil columns has been investigated in both thernpresence and absence of manure colloids. Results show that facilitatedrntransport of florfeniwl is significant in the presence of manure colloids.rnMultiple chemical and physical processes caused by the presence ofrnmanure colloids were considered to contribute to facilitated transport.rnFlorfenicol breakthrough curves (BTCs) were fit well by two models.rnThe two-site nonequilibrium adsorption contaminant transport modelrnsuggested the mechanisms for facilitated florfenicol transport are asrnfollows: manure colloids decrease the sorption capacity of florfeniwl to soil, enhance the instantaneous equilibrium adsorption,rnand suppress the time-dependent kinetic adsorption processes. The colloid-facilitated model further evaluated the partitionrncoefficient of florfenicol to colloids and indicated that cotransport has little contribution. A stepwise inverse model fittingrnapproach resulted in robust parameter estimation. The adoption of the nonlinear Freundlich adsorption equation in the two-siternnonequilibrium model significantly increased the fit of the model to the breakthrough curves.