SORPTION AND DEGRADATION OF CIPROFLOXACIN IN NATURAL SOILS

Ciprofloxacin is an antibiotic commonly used for treating bacterial infections in humans and livestock. First synthesized in the 1980s, this first-generation fluoroquinolone has become an emerging contaminant in recent years due to its accumulation in environmental settings. In its most abundant zwitterionic form, ciprofloxacin has a high binding affinity for target enzymes but a low aqueous degradation rate. Due to this chemical stability, the antibiotic seldom breaks down in natural settings and is widely considered among the most prevalent and potentially harmful pharmaceutical pollutants. Additionally, when ciprofloxacin is present in environmental settings, microorganisms readily transfer genes responsible for antibiotic resistance, leading to diminished effectiveness in combating subsequent infections. Since the implications of this antibiotic are well understood, it is essential to understand its geochemical behavior in aqueous and nearshore environments. Specifically, the antibiotic’s affinity to soil organic matter, which has been linked to accelerated microbial growth, was investigated. Pristine soil samples collected from various locations in the Francis Marion National Forest were separated by their A, E, and B horizons. These soils contained varying levels of organic matter and/or clay mineral content. The soils were exposed to aqueous ciprofloxacin solutions of various concentrations and thoroughly mixed in a batch reactor for seven days. Ciprofloxacin solution concentration changes and chemical transformations were measured using UV-Vis and HPLC techniques. Areas of similar soil character were then mapped to regionally extrapolate these findings. Moreover, such areas which are proximal to agricultural lands and feed lots were flagged for their increased risk of environmental contamination.