Glyphosate sorption to soils and sediments predicted by pedotransfer functions

Abstract

Glyphosate is the most applied herbicide for weed control in agriculture worldwide. Excessive application of glyphosate induces water pollution. The transfer of glyphosate to freshwater and groundwater is largely controlled by glyphosate sorption to soils and sediments. Sorption coefficients are therefore the most sensitive parameters in models used for risk assessment. However, the variations in glyphosate sorption among soils and sediments are poorly understood. Here we review glyphosate sorption parameters and their variation with selected soils and sediment. We use this knowledge to build pedotransfer functions that allow predicting sorption parameters, Kd, Kf and n, for a wide range of soils and sediments. We gathered glyphosate sorption parameters, 101 Kf, n and equivalent Kd, and associated soil properties. These data were then used to perform stepwise multiple regression analyses to build the pedotransfer functions. The linear (Kd) and Freundlich (Kf, n) pedotransfer functions were benchmarked against experimental data. We found the following major points: (1) Under current environmental conditions, sorption is best predicted by the Kd pedotransfer function. (2) The pedotransfer function is Kd = 7.20*CEC -1.31*Clay ? 24.82 (Kd in L kg -1 , CEC in cmol kg -1 and clay in %). (3) Cation exchange capacity (CEC) and clay content are the main drivers of Kd variability across soils and sediments. Freundlich parameters are additionally influenced by pH and organic carbon. This suggests that the formation of complexes between glyphosate phosphonate groups and soil-exchanged polyvalent cations dominates sorption across the range of analyzed soils.

Sorption and desorption behaviours of 2,4‐D and glyphosate in calcareous soil from Antalya, Turkey

“…; Gimsing & Borggaard ; Dollinger et al . ) and organic carbon content (Morillo et al . ; Wang et al .…”

“…; Dollinger et al . ) seems to play a major role for soil sorption of glyphosate in soils. The order of this parameter's responsibility on sorption was not clear in the literature.…”

Time‐Dependent Sorption and Desorption of Glyphosate in Soils: Multi‐reaction Modeling

“…The high affinity of the Commerce soil may be attributed to the relatively high content of amorphous Fe and Al oxides, which are materials with a demonstrated high affinity for GPS (Sprankle et al, 1975; Sheals et al, 2002; Gimsing et al, 2007). The high cation exchange capacity of the Sharkey soil probably allows GPS complex formation with surface exchangeable polyvalent cations (probably Ca 2+ in this case) (de Jonge and de Jonge, 1999; Dollinger et al, 2015), although ligand exchange at edge sites of layer silicates may also be of significance (Borggaard and Gimsing, 2008).…”

Abiotic Factors Influence Surface Water Herbicide Concentrations Following Silvicultural Aerial Application in Oregon's North Coast Range

“…For example, Louch et al () observed glyphosate at approximately 0.060 μg/L immediately following aerial application and 0.115 μg/L during the first significant storm event in Oregon's north coast range using similar application prescriptions under modern BMPs. Because glyphosate and AMPA have low water solubility and high K OC , moderate mobilization into surface water is expected during storm events via overland flow (Tatum ; Candela et al ; Dollinger et al ). If glyphosate were mobilized, however, this likely occurred during the first or second storm event when TSS concentrations ranged approximately 350 to 500 mg/mL, indicating substantial surface soil runoff.…”