Concentrations of the triazine herbicides atrazine, simazine, cyanazine, metribuzin and propazine were
determined in streams draining forestry and agricultural catchments in Tasmania, Australia, between
1989 and 1992. Atrazine and simazine were used extensively by the forestry industry in a winter spraying
programme, and applications of the other herbicides occurred in cropped agricultural catchments during
spring and summer. Of 29 streams sampled intensively for triazines, 20 contained detectable residues.
Median contaminations over all samples were 2.85, 1.05, <0.05, <0.05 and <0.05 �g L-1 for
atrazine, simazine, cyanazine, metribuzin and propazine, respectively. All herbicide concentrations
ranged over several orders of magnitude up to 53 mg L-1, with atrazine and simazine having significantly
higher concentrations than the others. Atrazine concentrations were examined in streams
draining forestry plantations for periods of up to two years. A decline in concentration was observed
with time, but this was strongly influenced by rainfall events. Atrazine contamination from single
spraying events persisted at a low level for up to 16 months. Contamination of Big Creek with atrazine
to 22�g L-1 after aerial spraying led to an increase in stream invertebrate drift only on the day of
spraying and to a short-term increase in movement of brown trout. On examination of biological effects
of triazines in surface waters reported in the literature, it was concluded that the observed frequent
contamination of Tasmanian streams with triazines may cause occasional minor short-term disturbance
to stream communities.
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