Fate of chlorpyrifos bound residues in paddy soils: Release, transformation, and phytoavailability

Jiayin Zhong; Dahang Shen; Hao Li; Yan He; Qian Bao; Wei Wang; Qingfu Ye; Jay Gan

doi:10.1016/j.envint.2022.107338

Fate of chlorpyrifos bound residues in paddy soils: Release, transformation, and phytoavailability

Environ Int. 2022 Aug:166:107338. doi: 10.1016/j.envint.2022.107338. Epub 2022 Jun 9.

Authors

Jiayin Zhong¹, Dahang Shen¹, Hao Li¹, Yan He², Qian Bao¹, Wei Wang³, Qingfu Ye¹, Jay Gan⁴

Affiliations

¹ Institute of Nuclear Agricultural Sciences, Key Laboratory of Nuclear Agricultural Sciences of Ministry of Agriculture of PRC and Zhejiang Province, Zhejiang University, Hangzhou 310058, China.
² College of Environmental and Natural Resource Sciences, Zhejiang University, Hangzhou 310058, China.
³ Institute of Nuclear Agricultural Sciences, Key Laboratory of Nuclear Agricultural Sciences of Ministry of Agriculture of PRC and Zhejiang Province, Zhejiang University, Hangzhou 310058, China. Electronic address: wei_wang@zju.edu.cn.
⁴ Department of Environmental Sciences, University of California, Riverside, CA 92521, USA.

PMID: 35716507
DOI: 10.1016/j.envint.2022.107338

Abstract

Chlorpyrifos (CPF) is a widely used organophosphorus insecticide that tends to form bound residues (BRs) in soils. However, the stability and biological activity of CPF-BRs remain to be explored. Facilitated by carbon-14 tracing, this study obtained CPF-BRs initially formed in two typical paddy soils (¹⁴C-CPF-BR_in), and further investigated their release, transformation and phytoavailability using duckweed (Lemna minor) as a model aquatic organism. Most ¹⁴C-CPF-BR_in in soils were composed of the parent CPF and its metabolite 3,5,6-trichloro-2-pyridinol (2-OH-TCP), which was mainly formed through reversible entrapment by soil fulvic acids and humin (>80%). At 36 d, 66.67-80.90% of the ¹⁴C-CPF-BR_in was released, of which only 2-OH-TCP could be released into the water and absorbed by the duckweed, with bioconcentration factors ranging from 247.99 to 324.68 L kg^-1. The subsequent metabolism of released ¹⁴C-CPF-BR_in in duckweed included phase I metabolism from 2-OH-TCP to 4-OH-TCP and phase II metabolism of conjugation of TCP with plant endogenous amino acids. The study suggested that CPF bound residues have high bioavailability in paddy field environments. Given that many pesticides and non-pesticide chemicals share structures analogous to CPF, the findings have important implications for better understanding the environmental and human health risks of man-made chemicals.

Keywords: Bound residues; Chlorpyrifos; Environmental risk; Paddy soils; Release and transformation.