Comparison of Pesticide Sorption by Physicochemically Modified Soils with Natural Soils as a Function of Soil Properties and Pesticide Hydrophobicity

Abstract

The objectives of this paper were to determine the efficiency of physicochemically modified soils with a surfactant in the sorption of pesticides, the stability against washing of the pesticides sorbed, and the effective sorption capacity of surfactant adsorbed by soils as a function of pesticide hydrophobicity and soil characteristics. Five soils of different characteristics and five pesticides (penconazole, linuron, alachlor, atrazine and metalaxyl) with different Kow values were selected and octadecyltrimethylammonium bromide (ODTMA) was chosen as model of cationic surfactants. Sorption-desorption isotherms were obtained and constants Kf and Kfd for natural soils (from Freundlich equation) and K and Kd for ODTMA-soils (from linear equation) were determined. Sorption on ODTMA-soils was higher than on natural soils. K increased 27-165 times for penconazole, 22-77 times for linuron, 7-14 times for alachlor, 9-23 times for atrazine, and 21-333 times for metalaxyl in relation to Kf. Sorption coefficients normalized to 100% of total organic matter (TOM) from organo soils K OM (K 100/%TOM), were always higher than those from natural soils Kf OM (Kf 100/%OM), indicating that the organic matter (OM) derived from the ODTMA (OM ODTMA ) had a greater sorption capacity than the OM of the natural soil. K OM values were also higher than the Kow (octanol/water distribution coefficient) value for each pesticide. The similarity of the high K OM values for the sorption of each pesticide by the five soils and the linearity of isotherms point to a partitioning of the pesticides between surfactant and water. The use in this work of different soils and various pesticides, unusual in this type of investigation, allowed us to obtain equations to know the sorbed amount of a given pesticide by the surfactant-modified soils as a function of the OM content derived from the cation and the Kow of the pesticide. The results obtained are of interest when it becomes necessary to increase the sorption capacity of soils with low OM contents with a view to delaying pesticide mobility in soils from pollution point sources (high concentration in small area), and preventing the pollution of waters.

Modification of clay barriers with a cationic surfactant to improve the retention of pesticides in soils

“…Specific surface area was determined by the N 2 adsorption-desorption method at −196 • C on a Micromeritics Gemini analyser (Norcross, USA). Clay minerals and Soil B were saturated with ODTMA by treating natural samples with a solution of ODTMA bromide in deionised water at temperature of 30 • C. Surfactant concentration was always lower than its critical micellar concentration (0.12 g/L) and we used a relation clay or soil/solution suitable to contain an amount of organic cation equivalent to 1.25 times the CEC of each sample [17,27]. The suspensions were shaken for 2 h and were subsequently centrifuged, washed with deionised water repeatedly until free of bromide ions as indicated by AgNO 3 , freeze-dried and kept in an atmosphere at controlled humidity for later use.…”

Desorption and mobilization of three strobilurin fungicides in three types of soil

“…The efficiency of the process is dependent on many factors such as properties of the pesticide used, dissolved organic matter, soil properties, and environmental conditions (Kah and Brown 2006;Margoum et al 2006;Pateiro-Moure et al 2009a, b;Chen et al 2010;Ding et al 2011). Among the parameters, soil properties such as soil organic matter, clay content, pH, and CEC are predominant (Rodríguez-Cruz et al 2006;Jiang et al 2011). In this study, we investigated three Chinese soils with their different capabilities of adsorption, desorption, and mobility of JS399-19, azoxystrobin, and kresoxim-methyl.…”

“…The environmental risk of pesticides mainly depends on its mobility in the soil (Rodríguez-Cruz et al 2006;Jiang et al 2011). The process of adsorption, desorption, and leaching plays a critical role in the environmental behavior of chemical pesticides in natural environments (Pateiro-Moure et al 2010;González-Rodríguez et al 2011).…”

Stakeholder engagement in social learning to resolve controversies over land-use change to plantation forestry

“…Reports in literature suggest pesticides with log Kow values between 4 and 8 have the potential to bioaccumulate in organisms; however, bioaccumulation is also affected by the molecular weight of compounds. Compounds greater than 600 units weight or 100 g/mol have been found less able to enter animal cells (FIMBAP 2007;Kah and Brown 2008;Rodriguez-Cruz et al 2006;Stenersen 2004;Tomlin 2006). A rating for potential eco-toxicity of the commonly used pesticides was applied using a scale of X low risk to XXX high risk, -otherwise not considered a significant risk under routine applications c Ecosystem load refers to a quantitative measure of the amount of active ingredient applied to the environment per unit area at a particular point in time Attitudes towards pesticide use A broad spectrum of attitudes towards pesticide use was present within the PAC, with some members favouring restricted use and others fully supporting pesticide use to maintain productivity and boost returns.…”