Contribution of Soil Components on the Sorption of Chlorpyrifos

Abstract

It is generally assumed that the sorption of a nonionic pesticide on soil depends mainly on the content of soil organic matter (SOM); however, there are other factors that can contribute to this process. The possible causes of variation in the carbon-normalized partition coefficient (K OC ) for chlorpyrifos (CPF) for a diverse set of ten soils have been investigated. On the one hand, the analysis of the chemical composition of the SOM was analyzed, and on the other hand, the likely interactions between the organic matter and the mineral phase were assessed. Sorption experiments of CPF were performed on whole soil, on soils treated with 2% hydrofluoric acid (HF), and onto calcined soil at 550 °C. Organic matter chemistry of soil was determined by 13 C CP/MAS NMR spectroscopy; K OC values were positively correlated with aryl C relative proportion and negatively correlated with alkyl C and O-aryl C proportions and prediction equation of K OC was found (R 2 = 0.82, p < 0.001). To evaluate possible organomineral interactions, a mathematical model was proposed which calculates the concentration of CPF at equilibrium (C cal ) considering adsorption coefficients for the organic (K DHF ) and inorganic (K D550 °C) soil constituents, separately. The comparison between C cal and the equilibrium concentration obtained from experimental data (C exp ) onto whole soil allowed us to confirm that interactions between the OM and clay affect the adsorption of CPF in whole soil. Such findings should be taken into account in the development of predictive models for the evaluation of the fate and transport of this pesticide in soil.

Sorption of Polycyclic Musks on Soil Components of Different Aggregate Sizes: The Effect of Organic-mineral Interactions

“…The K oc value was used to estimate the potential mobility of OPs in soils. However, the report of wide variations in K oc values is common in the scienti c literature both between soils (Smernik and Kookana 2015, Ahangar et al 2008, Savini et al 2016) and between different isolated aggregate fractions (Bon eur et al 2016, Bonin andSimpson 2007). Many studies are devoted to elucidate the relative role of soil mineral and organic components to K oc variation with different model contaminants.…”

“…As a multi-component and structurally organized combination, soil matrix contained different aggregates size organic-mineral complexes (Zhou, Liu and Tang 2004). Some studies have shown that the organicmineral interaction may block adsorbable functional groups on SOM surfaces, which changed con guration of SOM when associated with minerals and resulted in a negative contribution of minerals to OPs sorption by soils (Savini et al 2016 ). However, minerals may also positively contribute to OPs sorption in speci c soils as organic-mineral interaction highly exposed (He et al 2011).…”