Sorption and transport of polar organic compounds in groundwater

Abstract

Currently, pharmaceutical compounds have been widely detected in surface waters and groundwaters, leading to increased interest in the transport of these compounds in the subsurface environment. In this study, the sorption of four pharmaceuticals with various characteristics (non-hydrophobic, hydrophobic, ionizable monoprotic, ionizable amphoteric); acetaminophen (analgesic), 17[alpha]-ethynyl estradiol (synthetic hormone), nalidixic acid (antibiotic) and norfloxacin (antibiotic), were evaluated with silica, alumina, and Porapak P (hydrophobic medium). The pH dependent sorption of nalidixic acid and norfloxacin to silica and alumina were studied at pH4 to pH9. The fundamental sorption characteristics were revealed from this study and were extended to sorption and column transport of these pharmaceuticals to natural aquifer media from shallow aquifer, in Central Thailand. The column breakthrough curves of 17[alpha]-ethynyl estradiol and nalidixic acid showed sorption-related nonequilibrium characteristics. The UFBTC, one dimensional finite different transport model was used to model the column experiment data. The comparisons of Retardation Factor from column transport studies and predicted from batch studies were presented. Finally, the subsurface sediments (clayey silts and sands) with varying surface property (i.e., AEC, CEC) and organic carbon contents from three boreholes in groundwater recharge area, Central Thailand were studied for sorption affinity and compared to the more common pollutant (i.e., pesticide mobility scale)