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Environmental Engineering Graduate Seminar

Dr. Megan McConville, Northern Michigan University

Abstract: 

The sea lamprey (Petromyzon marinus) is a parasitic fish which preys on commercially relevant species in the Great Lakes including walleye and lake trout. Large quantities of 3-trifluromethyl-4-nitrophenol (TFM) and 2’,5-dichloro-4’-nitrosalicylanilide (niclosamide) have been used in tributaries of the Great Lakes since the late 1950s to kill the invasive fish. While TFM (relatively selective to the sea lamprey) and niclosamide (not species-specific) are added in small concentrations, the environmental fate of these lampricides, particularly their photochemical fate, is not well understood. This work examines the direct and indirect photodegradation pathways and finds that both compounds generally photodegrade to less toxic, less persistent compounds. In the presence of organic matter, the rate of niclosamide photolysis is tripled while the rate of TFM is unchanged. Despite these findings, the estimated half-life of niclosamide is still five times slower than the TFM half-life (19.6 ± 0.9 hours and 3,040 ± 70 hours for TFM and niclosamide, respectively). Laboratory studies were then applied to three full-scale lampricide treatments to assess photodegradation in situ.  These results demonstrate that while some TFM may undergo photolysis in tributaries, most of the lampricide mass added will reach the Great Lakes before being photochemically degraded.