Monitoring of sulfonylurea herbicides in stream water draining intensively cultivated areas in southern Sweden during a 9-year period (1998-2006)

In 1998 a co-operation was initiated between DuPont and the Swedish University of Agricultural Sciences (SLU) with the aim of generating knowledge on environmental behaviour of sulfonylurea (SU) herbicides under Swedish agricultural conditions. Results from a 9-year monitoring programme of SU herbicides in surface waters are presented. The report includes the analytical results from 536 samples collected during 1998 to 2006 from up to 4 intensively cultivated agricultural catchments in the southern portion of Sweden. The following seven SU herbicides were included: chlorsulfuron, flupyrsulfuronmethyl- sodium, metsulfuron-methyl, rimsulfuron, thifensulfuron-methyl, tribenuron-methyl and triflusulfuron-methyl. Results on detection frequency and concentration levels are presented and related to amounts applied in the investigated areas as well as to the Swedish Guideline Values (GV) for surface waters. The application of SU herbicides to a variety of crops was quite comprehensive during the 9- year investigation period, with tribenuron-methyl being the most extensively used herbicide on 16-33% of the arable catchment area each year. Thifensulfuron-methyl was the secondly most widespread SU herbicide. Analytical results showed that SU herbicides were occasionally detected in stream water draining intensively cultivated areas in Sweden (on average in 13% of the samples collected each year). These findings were essentially restricted to samples collected during or shortly after the main application season. The level of detected concentration was typically in the 0.01-0.1