Pesticides in soil: study finds 'unexpected persistence'

A disturbing phenomenon

Pesticides in soil: study finds 'unexpected persistence'

A disturbing phenomenon. Scientists from the Inrae research institute in collaboration with the University of Bordeaux conducted a study aimed at assessing the contamination by pesticides of nearly fifty soils, sampled throughout mainland France. The result of this study brought to light a result that was alarming to say the least. Indeed, the research revealed the "unexpected persistence" of pesticide residues at nearly all of the 47 sites surveyed, from 2019 to 2021.

Scientists searched for 111 substances at these 47 sites. Result: “98% of the sites studied present at least one substance. A total of 67 different molecules were found, mostly fungicides and herbicides,” according to this study recently published in the journal Environmental Science.

This work "demonstrates an unexpected persistence of pesticide molecules in the environment, well beyond their theoretical degradation time and at concentrations higher than those expected", 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 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 widely 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 are insecticides from 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, 1000 days for its metabolite AMPA and more than eight years for certain fungicides.