Effects of Cu and Ca On Ciprofloxacin Transport in Saturated Porous Media.

Ciprofloxacin (CIP), an emerging contaminant, has been frequently detected in soils and water; however, their transport behaviors in soils remain largely unknown. This study examined CIP transport in saturated porous media under the influence of divalent cations Cu and Ca. Laboratory columns packed with quartz sand before and after removing metal oxides on sand surface (native and clean sand) were used to test the effects of Cu and Ca on CIP retention and transport. In general, in cation-free solution CIP manifested a much higher mobility in saturated column with clean sand than the native sand. Divalent cations Ca and Cu had different influence on CIP transport under both sand media. In clean sand, when co-transported with CIP, the present of Cu significantly increased the mobility of CIP for both reversible and irreversible kinetic interaction between CIP and sand media whereas Ca mainly influenced the reversible CIP sand interaction. In addition, both Ca and Cu could replace CIP presorbed in clean sand. But, in native sand, only Cu co-transported with CIP could increase CIP mobility. Both Ca and Cu could effectively replace CIP presorbed on native sand.  Our study demonstrated the importance of cations in CIP transport in the soil environment.