Occurrence of Neonicotinoid Insecticides in Finished Drinking Water and Fate during Drinking Water Treatment

Abstract

Neonicotinoid insecticides are widespread in surface waters across the agriculturally intensive Midwestern United States. We report for the first time the presence of three neonicotinoids in finished drinking water and demonstrate their general persistence during conventional water treatment. Periodic tap water grab samples were collected at the University of Iowa over 7 weeks in 2016 (May–July) after maize/soy planting. Clothianidin, imidacloprid, and thiamethoxam were ubiquitously detected in finished water samples at concentrations ranging from 0.24 to 57.3 ng/L. Samples collected along the University of Iowa treatment train indicate no apparent removal of clothianidin or imidacloprid, with modest thiamethoxam removal (∼50%). In contrast, the concentrations of all neonicotinoids were substantially lower in the Iowa City treatment facility finished water using granular activated carbon (GAC) filtration. Batch experiments investigated potential losses. Thiamethoxam losses are due to base-catalyzed hydrolysis under high-pH conditions during lime softening. GAC rapidly and nearly completely removed all three neonicotinoids. Clothianidin is susceptible to reaction with free chlorine and may undergo at least partial transformation during chlorination. Our work provides new insights into the persistence of neonicotinoids and their potential for transformation during water treatment and distribution, while also identifying GAC as a potentially effective management tool for decreasing neonicotinoid concentrations in finished drinking water.

Neonicotinoid insecticide hydrolysis and photolysis: Rates and residual toxicity

“…Karmakar et al () observed significantly larger k obs for thiamethoxam in phosphate‐buffered solutions at pH 4.0 (100 times larger) and pH 7.0 (10 times larger) than was observed in the present study. Klarich et al (), however, saw no hydrolysis at pH 7, consistent with the present results.…”

“…Baseline imidacloprid results are similar to previously reported hydrolysis studies, in which imidacloprid was only observed to react at pH values >9 (Zheng and Liu ; Liu et al ). Thiamethoxam hydrolysis kinetics at high pH were similar to previously reported work (Liqing et al ; Karmakar et al ; Klarich et al ). Karmakar et al () observed significantly larger k obs for thiamethoxam in phosphate‐buffered solutions at pH 4.0 (100 times larger) and pH 7.0 (10 times larger) than was observed in the present study.…”

Pesticides from the EU First and Second Watch Lists in the Water Environment

“…The presence of neonicotinoids has been detected in various types of water reservoirs, including ditches, pools, ponds, mountain streams, rivers, periodic marshes, meltwater, and groundwater, effluents from WWTPs, and drinking water . The monitoring data were mainly available for four or less EU countries although neonicotinoids are widely used in Europe as Plant Protection Products (PPPs) and biocides.…”

A Uniform Practice for Conceptualizing and Communicating Food‐Energy‐Water Nexus Studies

“…(Kearns et al, 2016). Common insecticides used in urban and agricultural areas have been detected in drinking water and in 40% of sampled streams in the Midwest, the latter at levels that caused harm to artificial aquatic ecosystems (Klarich et al, 2017;Rogers et al, 2016).…”