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Crops, permanent grasslands and even forests: a pilot study conducted by the Inrae research institute and the University of Bordeaux revealed the “unexpected persistence” of pesticide residues in almost all of 47 sites studied across France from 2019 to 2021.
The scientists searched for 111 substances at these 47 sites. Result : “98% of the sites studied present at least one substance. In total, 67 different molecules were found, mostly fungicides and herbicides“, according to this study published recently in the journal Environmental Science & Technology.
These jobs “demonstrate unexpected persistence of pesticide molecules in the environment, well beyond their theoretical degradation time and at higher than expected concentrations“, according to the researchers, who underline in a press release “an increased need for soil monitoring”.
Field crop plots (cereals, oilseeds, etc.)are the most contaminated, with up to 33 different substances found in a single site, and an average of 15 molecules in the soil“.
“More unexpectedly, in soils under forests, permanent grasslands, fallow land or in organic farming for several years, more than 32 different pesticides have been detected, at concentrations mostly lower than for field crop sites.“, they continue.
The most frequently detected molecules are glyphosate, the most used herbicide in the world, and AMPA, its main metabolite (degraded residue), respectively”present in 70% and 83% of the soils sampled“.
Fungicides, used against fungi and molds in cereal fields, are also found in “more than 40% of sites“, as well as insecticides of the pyrethroid family, some of which “can be used in organic farming“.
The theoretical degradation time of 90% of the initial concentrations of the substances is estimated at 170 days for glyphosate, 1,000 days for its metabolite AMPA and more than eight years for certain fungicides.
THE “major risk estimated for earthworms“, key players in soil health, “is due to insecticides and fungicides“, according to the study.
Environmental contamination from pesticide residues has long been monitored for aquatic environments and the atmosphere, but “this is not yet the case for floors“, underline the researchers, who believe that increased monitoring could be based on the Inrae Soil Quality Measurement Network, which includes 2,200 sites in metropolitan France.