Effect of Organic and Mineral Soil Fractions on Sorption Behaviour of Chlorophenol and Triazine Micropollutants

Abstract

This article compares the sorption behaviour of 2,4,6-trichlorophenol, 2,3,4,6-tetrachlorophenol, pentachlorophenol, chlorotriazine atrazine, methylthiotriazine ametryn, methoxytriazine atratone, hydroxyatrazine, and didelakylated atrazine in a topsoil and an aquifer sediment before and after removal of sorbent organic matter and in humic acid. Freundlich isotherm coeffi cients K f and 1/n and free energy change (∆G°) were calculated for all compounds in all sorbents. According to sorbent pH values, chlorophenolate anions and uncharged triazine species dominated in all sorption experiments with topsoil and aquifer sediment. In experiments with humic acid, chlorophenols, atrazine, and didealkylated atrazine existed almost completely as neutral species, whereas protonated species dominated for hydroxyatrazine, atratone, and ametryn. In addition to a hydrophobic partition, sorption of all compounds in native soil and sediment sorbents includes specifi c, more polar interactions, which greatly depend on sorbate acidity/ basicity, specifi c properties of the sorbent organic matter and of mineral surface, as well as on the system pH. A signifi cantly greater sorption intensity of all compounds in "organic-free" than in the native aquifer sediment confi rmed the importance and possible dominance of mineral surface in the sorption process. Sorption intensity of chlorophenol and triazine compounds in humic acid was closely related to compound hydrophobicity. Greater sorption of almost completely protonated hydroxyatrazine than of the more hydropohobic but uncharged atrazine indicated different humic acid reaction sites for two compounds and consequently different sorption mechanisms.

Herbicide micropollutants in surface, ground and drinking waters within and near the area of Zagreb, Croatia

“…Groundwater is used for irrigation or as the main source of public drinking water supply in many parts of the world. The interaction of herbicides with organic substances in water and soil organic matter and soil minerals may significantly influence the mobility and persistence of herbicides in soil (Stipičević et al 2009). The binding of organic micropollutants to the organic matter dissolved in water increases their mobility through the soil column.…”

“…They are often applied directly to the soil. Their persistence and behaviour in a soil environment depend on an herbicide's physical and chemical properties as well as on the soil type, climate conditions and environmental characteristics Stipičević et al 2009;Mudhoo and Garg 2011;Stipičević et al 2015). The environmental distribution of herbicides and the potential risks they may cause to the environment are determined by the herbicide's water solubility, lipophilicity, vapour pressure, as well as by the rate and mode (photochemical, microbiological) of degradation (Stamper and Touvinen 1998;Konstantinou et al 2001;Navarro et al 2004;Udiković Kolić et al 2007;Shankar et al 2008;Krutz et al 2010).…”

Fate and Determination of Triazine Herbicides in Soil

“…The latter is a less polar compared to atrazine and has been shown to exhibit greater extent of sorption on HS (Erny et al, 2011;Prosen & Zupančič-Kralj, 2000). In comparison of methylthio-, methoxy-and chlorotriazine sorption on sediments and mineral soil components, sorption intensity was related to the basicity (pK a ) and water solubility of compounds, but not their logK ow (Prosen et al, 2007;Stipičević et al, 2009) - Fig. 2.…”

“…2. Dealkylated triazine transformation products are weakly sorbed on humic substances compared to parent compounds (Erny et al, 2011), while hydroxyatrazine, a dechlorinated atrazine TP, is extensively sorbed on mineral components of the soil/sediment (Stipičević et al, 2009). Knowledge of sorption/desorption behaviour of triazines is frequently applied in bioremediation either to enhance their leaching or to stabilise the residues in the contaminated sites (Delgado-Moreno et al, 2010; Jones at al., 2011; J.F.…”

“…(Aboul-Kasim & Simoneit, 2001;Kleineidam et al, 2002). The most frequently used method to obtain the experimental data for isotherm construction remains the batch equilibrium method (Celano et al, 2008;Kleineidam et al, 2002;Konda et al, 2002;Kovaios et al, 2006;Lima et al, 2009;Ling et al, 2006;Stipičević et al, 2009). Other approaches are by chromatographic estimation (Bermudez-Saldana et al, 2006) or indirectly by structural descriptors (Schüürmann et al, 2006).…”