Atmospheric degradation of two pesticides mixed with volatile organic compounds emitted by citrus trees. Ozone and secondary organic aerosol production

Abstract

Once pesticides are released into the environment, their active ingredient and other formulation compounds, such as coadjuvants or solvents, may undergo biological and chemical degradation, and form a range of products that could be even more hazardous than their precursors. These degradation products may also interact with the natural biogenic compounds emitted by treated crops, which leads to secondary air pollutants, such as ozone (O3) or fine particulate matter, which directly affect human health and climate warming. This research provides evidence for the atmospheric process influencing the atmospheric and environmental fate of pesticides, active substance chloropicrin and commercially formulated chlorpyriphos, which interact with biogenic volatile organic compounds (α-pinene and a mixture of monoterpenes) simulating mixtures of terpenes emitted by orange trees at the large outdoor European PHOto-REactor (EUPHORE). Significant SOA formations were observed during the photolysis and/or ozonolysis of both pesticides in the presence of biogenic volatile organic compounds. For the photolysis of chloropicrin in the presence of α-pinene, the aerosol and O3 formation yields ranged from 6 to 16% and 167–338%, respectively, depending on the initial conditions. For the photolysis of commercial chlorpyrifos in the presence of a mixture of terpenes, the formed aerosol yield was 24%, higher than those obtained by the photolysis of the terpenes in the absence of pesticides. Both pesticides in combination with terpenes increased O3 formation. O3 reacted with those terpenes, which increased particulate matter formation and may pose atmospheric issues on local and global scales.