Separating the effects of organic matter–mineral interactions and organic matter chemistry on the sorption of diuron and phenanthrene

• Published in: Chemosphere (Oxford) 2008-06, Vol.72 (6), p.886-890
• Main Authors: Ahangar, Ahmad Gholamalizadeh, Smernik, Ronald J., Kookana, Rai S., Chittleborough, David J.
• Format: Article
• Language: English
• Subjects: Adsorption; Aluminum Silicates - chemistry; Applied sciences; Biological and physicochemical properties of pollutants. Interaction in the soil; Clay minerals; Diuron; Diuron - chemistry; Earth sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; Exact sciences and technology; herbicide residues; Humic Substances; Magnetic Resonance Spectroscopy; Models, Chemical; NMR spectroscopy; organic matter-mineral interactions; Phenanthrene; Phenanthrenes - chemistry; Pollution; Pollution, environment geology; Soil - analysis; Soil and sediments pollution; soil organic matter; soil pollution; Sorption
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2008.03.059

Even though it is well established that soil C content is the primary determinant of the sorption affinity of soils for non-ionic compounds, it is also clear that organic carbon-normalized sorption coefficients ( K OC) vary considerably between soils. Two factors that may contribute to K OC variability are variations in organic matter chemistry between soils and interactions between organic matter and soil minerals. Here, we quantify these effects for two non-ionic sorbates—diuron and phenanthrene. The effect of organic matter–mineral interactions were evaluated by comparing K OC for demineralized (HF-treated) soils, with K OC for the corresponding whole soils. For diuron and phenanthrene, average ratios of K OC of the HF-treated soils to K OC of the whole soils were 2.5 and 2.3, respectively, indicating a substantial depression of K OC due to the presence of minerals in the whole soils. The effect of organic matter chemistry was determined by correlating K OC against distributions of C types determined using solid-state 13C NMR spectroscopy. For diuron, K OC was positively correlated with aryl C and negatively correlated with O-alkyl C, for both whole and HF-treated soils, whereas for phenanthrene, these correlations were only present for the HF-treated soils. We suggest that the lack of a clear effect of organic matter chemistry on whole soil K OC for phenanthrene is due to an over-riding influence of organic matter–mineral interactions in this case. This hypothesis is supported by a correlation between the increase in K OC on HF-treatment and the soil clay content for phenanthrene, but not for diuron.