Assessing surface and subsurface transport of neonicotinoid insecticides from crop fields

Authors: FRAME, SARAH - Pennsylvania State University; PEARSONS, KRISTEN - Pennsylvania State University; Elkin, Kyle; Saporito, Louis - Lou; PREISENDANZ, HEATHER - Pennsylvania State University; KARSTEN, HEATHER - Pennsylvania State University; TOOKER, JOHN - Pennsylvania State University

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/14/2020
Publication Date: 12/23/2020
Citation: Frame, S., Pearsons, K., Elkin, K.R., Saporito, L.S., Preisendanz, H., Karsten, H., Tooker, J. 2020. Assessing surface and subsurface transport of neonicotinoid insecticides from crop fields. Journal of Environmental Quality. 50(2):476-484. https://doi.org/10.1002/jeq2.20185.
DOI: https://doi.org/10.1002/jeq2.20185

Interpretive Summary: The advent of new pest control insecticides has been a positive on many fronts including greater harvest yields. Known as a systemic pesticide, plants can absorb these insecticides which can be used as a less farming intensive biological control method against insects that damage these crops. Since their commercialization however, there has been negative press overshadowing their utility. One of these negative issues is their ability to be transported surprising distances through soil by infiltrating rainwater. Analysis of soil samples receiving neonicotinoid treatments support this idea and suggest that the transport pathways and persistence of these pesticides is a crucial component to assess the potential adverse effects on downstream aquatic environments.

Technical Abstract: Increased use of neonicotinoid-coated crop seeds has led to a greater introduction of neonicotinoid insecticides into the environment, where they are vulnerable to transport by rainfall and snowmelt. To understand the timing and relative importance of surface and subsurface flow for transport of these insecticides from agricultural fields, we planted maize seeds coated with thiamethoxam in lysimeter plots in central Pennsylvania, U.S.A. For the next year, we sampled water generated by rainfall and snowmelt, and used mass spectrometry to analyze these samples for the neonicotinoids thiamethoxam and clothianidin (metabolite), which originated from the coated seeds. For the surface and subsurface transport pathways, we found that thiamethoxam exhibited strong “first flush” dynamics, with concentrations highest (max: 5.98 µg/L) during the first two events following planting and generally decreased for the remainder of the study to concentrations below the method limit of detection (<0.01 µg/L). The metabolite clothianidin, however, persisted at detectable concentrations throughout the study and did not exhibit “first flush” dynamics. The mass of thiamethoxam and clothianidin exported during the study period accounted for approximately 1.09% of the mass applied, with more than 90% of the total mass transported in subsurface flow and less than 10% transported in surface runoff. These results suggest that surface runoff, at least for our site, is a relatively small contributor to the overall fate and transport of these neonicotinoid insecticides, and that the delivery ratio observed for these compounds is similar to those of other trace-level emerging contaminants known to negatively influence aquatic ecosystems.