Pesticide desorption from soils facilitated by dissolved organic matter coming from composts: experimental data and modelling approach

Abstract

Dissolved organic matter (DOM) interaction with pesticides was examined studying the ability of DOM to desorb 8 pesticides previously sorbed to soil. DOM was originating from municipal waste composts at two maturity degrees, recovered at 20°C and by hot-pressurised subcritical water. Pesticide desorption depended on their previous sorption on soil. When sorption was low (K OC B 50, sulcotrione, metalaxyl), water was more efficient than DOM for desorption. On the contrary, when sorption was high (K OC C 2000, trifluraline), little effect of DOM was observed. For the moderately sorbed pesticides, DOM favoured pesticide desorption compared to water. For the lowest sorbed pesticides (K OC B 100), hysteresis was increased with larger proportions of DOM extracted with subcritical-water. Dissolved organic matter extracted from fresh-immature compost had larger capacity to mobilize the sorbed pesticides than the DOM from the mature compost. The pesticide desorption resulted from the positive and competitive interactions between pesticide, DOM and soil surfaces. These interactions were modelled considering separate partitioning coefficients. A general equation allowed the deduction of specific coefficients describing interactions in solution between pesticides and the non-sorbed fraction of DOM remaining in solution. This fraction was supposed to contain the most hydrophilic fraction of DOM and was able to interact with the most polar pesticide (amitrol). When pesticide hydrophobicity increased, the partitioning between pesticide and DOM decreased. Modelling the three-phase system (liquid, DOM and solid phases) pointed out that the solid phase played the most important role on pesticide behaviour through the sorption process of DOM and pesticides.

Optimization of QuEChERS method for the analysis of organochlorine pesticides in soils with diverse organic matter

“…For the HS study, the OS6 (carrots cultivation field) sample was chosen and for the LS study a sample from a previously studied sandy soil with low SOC was used. SOM drives pesticide behaviour in soils mainly through retention process [] and therefore the present extraction method was validated according to the HS or LS soils samples. The results of validation where investigated for each individual compound and are described in the following paragraphs.…”

Low-Molecular-Weight Organic Acids Influence the Sorption of Phenanthrene by Different Soil Particle Size Fractions

“…The presence of DOM in solution inhibits PAH sorption by soils (Gao et al, 2007). The association of DOM with PAHs in solution has been proposed as an important process that results in enhanced solubility (Cells et al, 1998; Ling et al, 2005, 2006; Barriuso et al, 2011). The affinity of DOM to PAHs is controlled by the molecular properties of the PAHs (Raber and Kogel‐Knabner, 1997).…”

Effect of Organic Matter on the Behavior and Control Effectiveness of Herbicides in Soil

“…The DOM has its origin from the percolation of the litter and the activity of the soil microbial biomass, molecular organic acids, and macromolecular structures (enzymes, humic acids, polyphenols and amino sugars) (Traversa and D'Orazio, 2008). This fraction is composed of organic colloids dispersed in solution is due to their high surface charge (Barriuso et al, 2011). Cox et al (2004) and Williams et al (2002) have stated that limitations on the role of SOM in the reduction of herbicide leaching should be taken into account, since the presence of DOM may favor leaching through herbicide interactions (facilitated transport), as well as interactions on soil surfaces (sorption competition).…”