Glyphosate and AMPA mobility from soybean soils after amendment with poultry litter.

MARINO, D.J.; ALONSO L.L.; NAVARRO, M.

Valdivia

Congreso; SETAC Latin America 14th Biennal Meeting; 2021

Society of Environmental Toxicology and Chemistry

The use of poultry litter (PL) as an organic amendment in agricultural soils is a common practice due to the fertilization purposes and the material recycling, in terms of circular economy. Besides providing nutrients into the soil cultivable layers, the material can alter properties (as pH, electric conductivity, organic matter content) that can affect the sorption of soil pollutants that persist in those layers, as the commonly applied glyphosate (GLP) and its degradation metabolite, AMPA. The aim of this work was to evaluate the effect of PL amendment on the mobility of GLP and AMPA after a rainfall, by studying the surface runoff and the soil column. For this purpose, 18 plots of 1 m2 were randomly selected, and PL was applied on soils (PL-soils) at 5 ton/ha. according to reported conventional practice application rate. Another 3 random plots were kept unamended (UA-soils) to contrast the influence of the practice on 1: runoff water quality measured through soluble phosphorus, GLP and AMPA, 2: GLP and AMPA in soils profile. After 72h stabilization, a rainfall simulation was carried out and runoff water and soils were collected from each plot. For GLP and AMPA analysis in soils, PL and runoff waters, pre-column derivatization was applied with FMOC-Cl. Samples were spiked with isotopically labeled GLP and analyzed by LC-MS/MS. Glyphosate and AMPA were not detected in PL (< 0.1 µg/kg). Initial mean levels of GLP and AMPA in soils were 40±25 µg/kg and 61±26 µg/kg, respectively. After the rainfall simulation assays, quantifiable concentrations of GLP and AMPA were detected in both analyzed fractions of soils (0-2 cm and 2-20 cm) and in runoff water. GLP concentrations were significantly lower than those detected prior to the rainfall, which denotes the pesticide dissipation during the assay. Concentrations of these compounds, in surface runoff, were higher in soils amended with poultry litter than unamended ones, and both were also detected at the 2-20 cm soil layer. The increased concentration of soluble phosphorus species after the amendment was a relevant factor in the mobility of GLP from soil into surface runoff and favored the vertical mobility (leaching) of both GLP and AMPA, with greater incidence on the metabolite. Considering the extensively reported presence of pesticides in soils from Argentina, the risk of compounds mobilization after PL application, and the simultaneous release of veterinary antibiotics, the practice should be further investigated to prevent environmental consequences.