Abstract

The influences of dissolved organic matter (DOM) on neonicotinoid photochemical degradation and product formation in natural waters remain unclear, potentially impacting the sustainability of river systems. Therefore, our overall objective was to investigate the photodegradation mechanisms and phototransformation byproducts of two neonicotinoid pesticides, imidacloprid and thiamethoxam, under simulated sunlight at the microcosm scale, to assess the implications of DOM for insecticide degradation in rivers. Direct and indirect photolysis were investigated using twelve water matrices to identify possible reaction pathways with two DOM sources and three quenching agents. Imidacloprid, thiamethoxam, and potential degradants were measured, and reaction pathways identified. The photodegradation rates for imidacloprid (0.156 to 0.531 h−1) and thiamethoxam (0.027 to 0.379 h−1) were measured. The Mississippi River DOM with 4-hydroxy- 2,2,6,6-tetramethylpiperidinyloxy resulted in rapid formation of imidacloprid desnitro and imida- cloprid urea as compared to other treatments. These observations indicate that the production of reactive oxygen species has the potential to influence the photodegradation of imidacloprid, via indirect photolysis, resulting in the formation of degradation products (e.g., imidacloprid desnitro) potentially harmful to non-target species. The findings offer insight into the potential role DOM in river systems has on sustainable water quality related to these two neonicotinoid degradation pathways and byproduct formations.

Document Type

Article

Publication Date

1-2024

Notes/Citation Information

© 2024 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

Digital Object Identifier (DOI)

https://doi.org/10.3390/su16031181

Funding Information

This article is based upon work that was supported by the National Institute of Food and Agriculture, U.S. Department of Agriculture, under award number 2018-67019-27794, and a Hatch multistate capacity funding grant (W-4045). This project was also supported with funding from the Robert B. Daugherty Water for Food Global Institute at the University of Nebraska–Lincoln. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the authors and do not necessarily reflect the view of the U.S. Department of Agriculture or the Robert B. Daugherty Water for Food Global Institute at the University of Nebraska–Lincoln.

Share

COinS