Fate and effects of triclopyr ester in a first‐order forest stream

Abstract

AbstractThe fate and the effects of triclopyr butoxyethyl ester (TBEE) were investigated in a first‐order forest stream. Quantification of TBEE in stream‐water samples showed maximal concentration of 0.848 and 0.949 μg ml−1 at sampling stations nearest two discrete injection points. Average TBEE concentrations ranged from 0.32 μg ml−1 at stations nearest injection points to 0.02 μg ml−1 approximately 225 m downstream. Periods of exposure to aqueous TBEE concentrations in excess of 0.001 μg ml−1 ranged from 55 min in fast‐flowing upstream locations to 120 min at slower, downstream sampling locations. Simultaneous quantitation of triclopyr acid (TRI) residues in stream‐water samples indicated that natural degradative mechanisms rapidly converted TBEE to TRI, and that sorption to natural allochthonous materials occurred as chemical pulses moved downstream. Chemical behaviour resulted in short‐term, pulse‐type exposures to TBEE, with decreasing magnitude and slightly increasing duration in relation to downstream distance. Short‐term, low‐level exposures generated in this stream treatment resulted in slightly elevated drift (∼3‐ to 4‐fold increase) for up to 36 h, but no measurable reductions in abundance of benthic invertebrates. Increases in chlorophyll a concentrations in epilithic periphyton from treated sections indicated short‐term eutrophication or growthregulation effects of the herbicide applications.