Natural River Attenuation of Pharmaceuticals: Sorption and Biological Transformation
Date Issued
2009
Date
2009
Author(s)
Lin, Chih-Ann
Abstract
This research used designed batch experiments to verify the fate (sorption and biotransformation, in particular) for four frequently used and detected pharmaceuticals (acetaminophen, caffeine, propranolol, and acebutolol) in aqueous environments. cetaminophen, caffeine, propranolol, and acebutolol have all demonstrated significant potential to degrade in the natural aqueous system. For acetaminophen, biodegradation play a major role (the half-lives (t1/2) of biodegradation and sorption together was 2.1 days while sorption alone was 4.4 days); for caffeine, biodegradation and sorption are both important (t1/2 of biodegradation and sorption together was 0.6 days; the t1/2 of sorption was 2.2 days). However, in the case of propranolol and acebutolol, sorption seems to be the most significant removal mechanism (the t1/2 of sorption was approximately 2.2 days and biodegradation didn’t enhance this degradation rate). In desorption experiments, the results showed that sorption are mostly irreversible (small than 3% reversibility). Because of low organic sediment content (1.7%) and the properties of target compounds (acetaminophen, propranolol, and acebutolol) are alkaline, it was implied that the sorption mechanism in this condition likely belong to chemical sorption (ionic interaction). In Kd determination experiment, caffeine, propranolol, and acebutolol had high Kd values, ranging from 245.0 to 1901.0 L/kg. It means that there is high tendency of target compounds to be sorbed to the sediment even though in low organic carbon content system. The results of logKoc values were dissimilar between experimentally derived and calculated values based on correlation equations. It is probably owing to the fact that those approaches are well applied for hydrophobic interaction, but fail to predict sorption of polar and ionic compounds. Laboratory results were further combined with other studies and extrapolated to the field conditions, the information demonstrated that the degradation possibility of pharmaceuticals just by natural attenuation. However, the rivers in Taiwan have high flow rate and with steep slopes. It is implied that the residual pharmaceuticals may enter the ocean before significant attenuation during river transport. Filed occurrence data further supported this conclusion, and it is suggested that these pharmaceuticals are in need to be treated by advanced process before releasing to the aqueous environments.
Subjects
pharmaceuticals
emerging contaminants
sorption
biodegradation
distribution coefficient (Kd)
Type
thesis
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