An Eddy Covariance System to Quantify Fluxes of Pesticides in an Agricultural Environment

Synthetic pesticides applied in agricultural fields to control pests can volatilize into the atmosphere in either gas or particle phase (Rajmohan et al., 2020). Understanding the biosphere–atmosphere exchange of these compounds is crucial, as this exchange influences various atmospheric chemical processes that ultimately determine the environmental fate of pesticides. However, data quantifying these processes remain limited (Hörtnagl et al., 2010).

This work aims to test the eddy covariance flux system developed by combining a High-Resolution Time of Flight Iodide Chemical Ionization Mass Spectrometer (HR-TOF-I-CIMS) which measures a wide range of compounds including pesticides in the atmosphere at 10 Hz, with a Sonic Anemometer which gives high frequency vertical wind speed. These two observations can be combined to obtain the biosphere to atmosphere exchange of pesticides.

Here we are going to present the results from the campaign which was conducted from 20^th march to 14^th April 2025, at an arable farm located in Rothamsted Research, Okehampton, Devon (50°46'26.4"N 3°54'11.2"W). The site had minimal local obstructions, essential to capture well developed turbulent eddies.

The measurements were done at a height of 3.6 m above ground and the I-CIMS was kept in a temperature-controlled trailer with a heated inlet mounted at the top of the trailer connecting the two instruments.

Initial results indicate successful capture of atmospheric turbulence, with a footprint extent of approximately 350 m in both directions at the given measurement height. Flux footprint analysis (Figure), performed using a simple two-dimensional parameterization model (Kljun et al., 2015), revealed major contributions from the SE and NW directions.

Additionally, preliminary results with targeted analysis via CIMS for fluxes of specific compounds will be presented, validating system performance, followed by spectra and cospectra analysis that reveals the contributions across different frequency scales.