Transformation product bottleneck: Photo-recalcitrance of rotenolone limits the aquatic degradation of rotenone in a temperature-dependent manner
Year: 2026
Type: preprint
Abstract: The environmental fate and toxicity of transformation products (TPs) are frequently overlooked. However, in many cases, TPs are functional analogs that exhibit similar, and often greater, toxicity as the parent compound. In cases where the TP is persistent in the environment, the rate of TP degradation can influence the overall environmental fate. Rotenolone (12𝛼-hydroxy-rotenone, ROH) is the primary TP of rotenone (ROT), a pesticide utilized ubiquitously and highly popular in cold regions. Both ROT and ROH are mitochondrial NADH inhibitors, however ROH is more persistent than ROT and remains unregulated. 2 This work investigated the aquatic photochemical pathways and transformation products of ROH, including simulated Subarctic (low-temperature) conditions. Given that ROT degradation is driven by photolysis, we hypothesized that inhibited photochemical activity of ROH accounts for its persistence. Our results suggest ROH persistence is largely attributed to significantly reduced triplet state lifetimes, absorbance, and apparent quantum yields. Temperature was identified as a significant driver of ROH photolysis, accelerating the direct photochemical transformation rate, with half-lives ranging from approximately 115 h (6 °C) to 66 h (19 °C). This suggests that the cool temperatures of Subarctic surface waters further contribute to ROH persistence. Degradation was accelerated in the presence of chromophoric dissolved organic matter (CDOM); Fenton experiments confirmed ROH reacts with hydroxyl radical at near diffusion-limited rates (2.9×1010 ± 1.1×109 M-1 s-1 at 20 °C). Nontarget analysis of ROH photoproducts revealed novel transformation intermediates not previously identified. These were observed to further transform to smaller products, suggesting that ROH photochemical transformation represents the final step in detoxification. Thus, the photochemical recalcitrance of ROH is involved in limiting the detoxification of ROT following aquatic pesticidal use. These results strongly suggest including ROH monitoring during ROT pesticide applications.
Source: ChemRxiv
Language: English
Subfield: Pollution
Field: Environmental Science
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7221474841