Triphenyltin hydroxide (TPTH) is an organotin fungicide used to protect crops, such as potatoes, beets, rice, and pecans, from fungal diseases. At nanomolar concentrations, TPTH causes adverse effects on non-target organisms, including algae, zooplankton, mollusks, and fish. In this study, the photochemical reaction kinetics of TPTH were measured in the UV-254 and UV-H2O2 systems using a merry-go-round Rayonet reactor. In 5 mM phosphate-buffered water at pH 7, TPTH exhibited a molar extinction coefficient of 1.16×104 M-1 cm-1 and an effective quantum yield of 3.0(± 0.1)×10-2 mol Ein-1 for the UV-254 system. The degradation of TPTH was faster in the UV-H2O2 process due to reaction with hydroxyl radicals. The apparent second-order rate constant for TPTH reaction with hydroxyl radicals was determined to be 5.5×108 M-1 s-1. Irradiation experiments indicated that TPTH is effectively transformed into other products, which were tentatively identified here. The biological activity of TPTH and its phototransformation products was measured using bacterial growth inhibition assays. TPTH inhibited the growth of gram-positive Staphylococcus sp. (ATCC 14389) with an observed IC50 of approximately 400 µg L-1, but no growth inhibition was recorded for gram-negative Escherichia coli (ATCC 25922) at TPTH concentrations up to 10,000 µg L-1. The antibacterial activity of phototransformation products was assessed using the potency equivalents approach with Staphylococcus sp., and the results indicated that select products exhibit antibacterial activity. These findings suggest that TPTH transformation products must be considered when assessing the toxicity of TPTH-contaminated water systems.

Residual toxicity of triphenyltin hydroxide and its transformation products in UV-254 and UV-H2O2 processes

2019 Spring National Meeting

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.