Degradation of 14C-glyphosate and aminomethylphosphonic acid (AMPA) in
three agricultural soils |
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Authors: | Abdul Jabbar Al-Rajab and Michel Schiavon |
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Institution: | 1. Laboratory of Soil and Environmental Sciences,UMR 1120 INPL/ENSAIA-INRA;54505 Vandoeuvre-lès-Nancy Cedex,France;Agriculture and Agri-Food Canada,London,Ontario,N5V 4T3,Canada 2. Laboratory of Soil and Environmental Sciences,UMR 1120 INPL/ENSAIA-INRA;54505 Vandoeuvre-lès-Nancy Cedex,France |
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Abstract: | Glyphosate (N-phosphonomethyl glycine) is the most used herbicide worldwide. The degradation of 14C-labeled glyphosate was
studied under controlled laboratory conditions in three di erent agricultural soils: a silt clay loam, a clay loam and a sandy loam soil.
The kinetic and intensity of glyphosate degradation varied considerably over time within the same soil and among di erent types of
soil. Our results demonstrated that the mineralization rate of glyphosate was high at the beginning of incubation and then decreased
with time until the end of the experiment. The same kinetic was observed for the water extractable residues. The degradation of
glyphosate was rapid in the soil with low adsorption capacity (clay loam soil) with a short half-life of 4 days. However, the persistence
of glyphosate in high adsorption capacity soils increased, with half-live of 19 days for silt clay loam soil and 14.5 days for sandy
loam soil. HPLC analyses showed that the main metabolite of glyphosate, aminomethylphosphonic acid (AMPA) was detected after
three days of incubation in the extracts of all three soils. Our results suggested that the possibility of contamination of groundwater by
glyphosate was high on a long-term period in soils with high adsorption capacity and low degrading activities and/or acid similar to
sandy loam soil. This risk might be faster but less sustainable in soil with low adsorption capacity and high degrading activity like the
clay loam soil. However, the release of non-extractable residues may increase the risk of contamination of groundwater regardless of
the type of soil. |
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Keywords: | glyphosate aminomethylphosphonic acid (AMPA) mineralization degradation soil |
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