Validation and application of a modified QuEChERS method for extracting neonicotinoid residues from New Zealand maize field soil reveals their persistence at nominally hazardous concentrations
2019
Pook, Chris | Gritcan, Iana
The widespread use of neonicotinoid insecticides is controversial due to their persistence in the environment and concerns the long-term consequences of their use. We present a simple, low-cost method for the sensitive and efficient extraction of three important neonicotinoids from soil with a detection limit <1 ng g−1 wet soil. We have validated this method by applying it to uncontaminated soil samples spiked with thiamethoxam, clothianidin and imidacloprid at environmentally concentrations. Absolute recoveries were >80% for thiamethoxam, clothianidin and imidacloprid. We also applied the method to soil samples collected from maize fields in New Zealand's North Island and found imidacloprid in 43 out of 45 samples and clothianidin in every one. Mean imidacloprid concentrations varied from 0.5 to 9.4 ng g−1 (wet weight) and clothianidin from 2.1 to 26.7 ng g−1 (wet weight). Imidacloprid concentrations exceed the New Zealand Environmental Protection Agency's Environmental Exposure Limit of 1 ng g−1 (dry weight) at eight of the nine sites sampled. These results are also remarkable because we have detected multiple neonicotinoid residues at every site. Imidacloprid residues appear to persist at significant concentrations at five of our sites from an application at least two years previous. This is only the third study to report the presence of neonicotinoid residues in NZ's environment and the first to show that those residues are persistent in the environment at nominally hazardous concentrations.
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