Online field measurements of Chlorothalonil show that volatilization is key to pesticide exposure

Abstract

Pesticide usage has been expanding since the 1950s. However, their use has been known to harm human and environmental health for decades. Recent studies have shown that these two factors are impacted by pesticide diffusion in the atmosphere. The gaseous diffusion of pesticides in the atmosphere is known as volatilization. Although it is a known process, pesticide volatilization has been scarcely measured, especially for periods beyond a few days after pesticide application. Pesticide concentration is usually measured mainly by offline gas-chromatography mass spectrometry, which makes it difficult to deploy in the field for long-term studies. In this study, we report the first online concentration measurements of Chlorothalonil, a fungicide, over a wheat field using a highly sensitive proton transfer reaction, quadrupole injection, time of flight, mass spectrometer (PTR-QI-TOF-MS) for several weeks after its application. The volatilization computed by inverse dispersion modeling was sustained over more than three weeks, leading to up to 50% of the applied quantity being lost by volatilization. High-temporal volatilization dynamics indicate that the understorey contributes significantly to the emissions. Our findings suggest that Chlorothalonil volatilization may contribute significantly to atmospheric exposure, and transfer by deposition to nearby fields and over larger areas. Online PTR-QI-TOF-MS measurements should be developed further to quantify human exposure and the spread of pesticides through the atmosphere.