Abstract:Nonequilibrium sorption plays an active role in the transport of organic contaminants in soil. We applied a two-stage, one-rate model (2S1R) and a new, nonlinear variant (2S1RN) of this model to examine the effects of wastewater irrigation on the sorption kinetics of atrazine (2-chloro-4-ethylamino-6-isopropylamino-1,3,5-triazine) in soil. The models were applied to previously published sorption-desorption data sets, which showed pronounced deviations between sorption curves and desorption curves (sorption-des… Show more
“…Revealing the nature of DOM‐fractionation processes is of special consequence for the fate of contaminants, which may differentially interact with DOM fractions in the sorbed and mobile phases, particularly in agricultural systems that are exposed to high input of DOM (Drori et al, 2005; Anagu et al, 2011).…”
Interactions of dissolved organic matter (DOM) with soil minerals, such as metal oxides and clays, involve various sorption mechanisms and may lead to sorptive fractionation of certain organic moieties. While sorption of DOM to soil minerals typically involves a degree of irreversibility, it is unclear which structural components of DOM correspond to the irreversibly bound fraction and which factors may be considered determinants. To assist in elucidating that, the current study aimed at investigating fractionation of DOM during sorption and desorption processes in soil. Batch DOM sorption and desorption experiments were conducted with organic matter poor, alkaline soils. Fourier‐transform infrared (FTIR) and UV‐Vis spectroscopy were used to analyze bulk DOM, sorbed DOM, and desorbed DOM fractions. Sorptive fractionation resulted mainly from the preferential uptake of aromatic, carboxylic, and phenolic moieties of DOM. Soil metal‐oxide content positively affected DOM sorption and binding of some specific carboxylate and phenolate functional groups. Desorptive fractionation of DOM was expressed by the irreversible‐binding nature of some carboxylic moieties, whereas other bound carboxylic moieties were readily desorbed. Inner‐sphere, as opposed to outer‐sphere, ligand‐exchange complexation mechanisms may be responsible for these irreversible, as opposed to reversible, interactions, respectively. The interaction of aliphatic DOM constituents with soil, presumably through weak van der Waals forces, was minor and increased with increasing proportion of clay minerals in the soil. Revealing the nature of DOM‐fractionation processes is of great importance to understanding carbon stabilization mechanisms in soils, as well as the overall fate of contaminants that might be associated with DOM.
“…Revealing the nature of DOM‐fractionation processes is of special consequence for the fate of contaminants, which may differentially interact with DOM fractions in the sorbed and mobile phases, particularly in agricultural systems that are exposed to high input of DOM (Drori et al, 2005; Anagu et al, 2011).…”
Interactions of dissolved organic matter (DOM) with soil minerals, such as metal oxides and clays, involve various sorption mechanisms and may lead to sorptive fractionation of certain organic moieties. While sorption of DOM to soil minerals typically involves a degree of irreversibility, it is unclear which structural components of DOM correspond to the irreversibly bound fraction and which factors may be considered determinants. To assist in elucidating that, the current study aimed at investigating fractionation of DOM during sorption and desorption processes in soil. Batch DOM sorption and desorption experiments were conducted with organic matter poor, alkaline soils. Fourier‐transform infrared (FTIR) and UV‐Vis spectroscopy were used to analyze bulk DOM, sorbed DOM, and desorbed DOM fractions. Sorptive fractionation resulted mainly from the preferential uptake of aromatic, carboxylic, and phenolic moieties of DOM. Soil metal‐oxide content positively affected DOM sorption and binding of some specific carboxylate and phenolate functional groups. Desorptive fractionation of DOM was expressed by the irreversible‐binding nature of some carboxylic moieties, whereas other bound carboxylic moieties were readily desorbed. Inner‐sphere, as opposed to outer‐sphere, ligand‐exchange complexation mechanisms may be responsible for these irreversible, as opposed to reversible, interactions, respectively. The interaction of aliphatic DOM constituents with soil, presumably through weak van der Waals forces, was minor and increased with increasing proportion of clay minerals in the soil. Revealing the nature of DOM‐fractionation processes is of great importance to understanding carbon stabilization mechanisms in soils, as well as the overall fate of contaminants that might be associated with DOM.
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