The commonly used non-selective herbicide glyphosate (N-[Phosphonomethyl]gl
ycin) occurred in surface water of two small tributaries of the river Ruhr
in North-Rhine-Westphalia (FRG) with a maximum concentration of 590 ng/l. I
n the examined catchment areas weed control application in rail tracks is o
ne of the main sources of an input to surface water. The occurrence of the
metabolite aminomethyl phosphonic acid (AMPA) was linked to glyphosate load
rather than to a detergent inflow via municipal sewage. The observed disap
pearance of glyphosate was faster than the disappearance of diuron indicati
ng a lower persistence. A final assessment of the importance of highly pola
r pesticides in organic contaminant of surface water needs extended water m
onitoring analyses and further field investigation.