Monitoring and effects of nicosulfuron in aquatic mesocosms: development of a simple analytical procedure and evidence for low toxicity to phytoplankton communities

A new analytical procedure is proposed for monitoring nicosulfuron (sulfonylurea herbicide) in aquatic mesocosms derived from complex ecosystems. The approach is based on alternate use of the anionic and molecular forms of the pesticide during the procedure. It also takes into account the sensitivity of the molecule to hydrolysis. The procedure involves solid-phase extraction on a polystyrene-divinylbenzene support followed by a conventional high-performance liquid chromatographic analysis with UV-diode array detection. Recovery tests on samples from natural waters demonstrated that the performances obtained were convenient for monitoring aquatic mesocosms (recoveries of 91+/-12% at 0.5 microg L(-1)). The method was used to monitor nicosulfuron in mesocosms initially spiked at 2 or 30 microg L(-1) . The evolution curves were compared to those obtained from mesocosms contaminated with atrazine at the same initial doses. The sensitivity of phytoplankton communities to nicosulfuron in aquatic mesocosms was found to be very limited.