Researchers track insecticides in water

The most widely used class of insecticides worldwide is neonicotinoids. Unfortunately, neonicotinoids act non-selectively against most insects and may adversely affect non-targeted organisms that consume plants or contact surfaces treated with these compounds. Researchers Matthew Berens  (MS 2020, now a Postdoctoral Associate at UMD's Natural Resources Research Institute), Paul Capel, and Bill Arnold from the Department of Civil, Environmental, and Geo- Engineering are seeking more information about neonicotinoid insecticides in surface and groundwater.

Berens, Capel, and Arnold study what drives wide-scale environmental contamination by neonicotinoids, and their work has been recognized by the journal Environmental Toxicology and Chemistry (ET&C). Each year the editors select from all papers submitted to the journal in the previous year those that are innovative or creative with potential impact on the field. The work of Berens, Capel, and Arnold was highlighted as an Exceptional Paper of 2021.

Berens, Capel, and Arnold measured neonicotinoid concentrations at 65 locations in Minnesota. The sites represented rivers, streams, lakes, groundwater, and treated wastewater. They used their collected data to assess the influence of land use and hydrology on the occurrence of neonicotinoids and to assess potential effects on aquatic life.

Findings showed that neonicotinoid concentrations were highest near agricultural lands, followed by urban land, and then by undeveloped, predominantly forested lands. Two neonicotinoids were found in almost every water sample: clothianidin was most frequently detected in agricultural areas (detection frequency = 100%), and imidacloprid was most often found in urban environments (detection frequency = 97%). The researchers also found that high neonicotinoid concentrations were especially common following the spring planting season and during times of elevated streamflow, such as after a rain event. Consistently low levels of neonicotinoids were found in groundwater. In contrast, the highest concentrations in the study were found in treated wastewater, which suggests that home use may play a previously overlooked role in causing neonicotinoid contamination. None of the samples exceeded the individual neonicotinoid toxicity thresholds for aquatic organisms, but 10% of the samples exceeded a chronic benchmark for neonicotinoid mixtures. Over half of the samples contained two or more neonicotinoids, but observed concentrations show the level of risk to aquatic life was low.

This study, the first of its size in Minnesota, is critical to building a better understanding of what drives wide-scale environmental contamination by neonicotinoids.

M. J. Berens, P. D. Capel, and W. A. Arnold. (2021). “Neonicotinoid insecticides in surface water, groundwater, and wastewater across land-use gradients and potential effects,” Environmental Toxicology and Chemistry, 40(4), 1017–1033. doi: 10.1002/etc.4959 (Open Access)