Persistence And Partitioning Of Eight Selected Pharmaceuticals In The Aquatic Environment: Laboratory Photolysis, Biodegradation, And Sorption Experiments

摘要

We selected eight pharmaceuticals with relatively high potential ecological risk and high consumption-namely, acetaminophen, atenolol, carbamazepine, ibuprofen, ifenprodil, indomethacin, mefenamic acid, and propranolol-and conducted laboratory experiments to examine the persistence and partitioning of these compounds in the aquatic environment. In the results of batch sunlight photolysis experiments, three out of eight Pharmaceuticals-propranolol, indomethacin, and ifenprodil-were relatively easily pho-todegraded (i.e., half-life < 24 h), whereas the other five pharmaceuticals were relatively stable against sunlight. The results of batch biodegradation experiments using river water suggested relatively slow biodegradation (i.e., half-life > 24 h) for all eight pharmaceuticals, but the rate constant was dependent on sampling site and time. Batch sorption experiments were also conducted to determine the sorption coefficients to river sediments and a model soil sample. The determined coefficients (K_d values) were much higher for three amines (atenolol, ifenprodil, and propranolol) than for neutral compounds or carboxylic acids; the K_d values of the amines were comparable to those of a four-ring polycyclic aromatic hydrocarbon (PAH) pyrene. The coefficients were also higher for sediment/soil with higher organic content, and the organic carbon-based sorption coefficient (logK_(oc)) showed a poor linear correlation with the octanol-water distribution coefficient (log D_(ow)) at neutral pH. These results suggest other sorption mechanisms-such as electrochemical affinity, in addition to hydrophobic interaction-play an important role in sorption to sediment/soil at neutral pH.