Adsorption and Movement of Carbofuran in Four Different Soils Varying in Physical and Chemical Properties

Abstract

Laboratory studies were conducted to determine the adsorption and movement of carbofuran on four divergent textured Indian soils at a fixed volume fraction (f s = 0.1) of methanol/water mixtures using batch equilibrium and soil thin layer chromatography (soil TLC) techniques. The measured equilibrium adsorption isotherms for silt loam (FSL and ASL) and loam (KL) soils were L-shaped and for sandy loam (BSL) soil S-shaped, all being well fitted by the Freundlich isotherm. A higher adsorption of carbofuran was observed on FSL followed by ASL, KL and BSL soils as anticipated by the values obtained for the Freundlich constant, K F and partition coefficient, K D . The Frontal Retardation factor (FR f ) values obtained from soil TLC studies were inversely proportional to the K F and K D values.The affinity of carbofuran towards organic carbon, organic matter and clay content of the soils was evaluated by calculating the K OC , K OM and K C values. The negative magnitude of the Gibbs' free energy (∆G 0 ) indicated the spontaneity of the adsorption of carbofuran onto the soils studied. The leaching index (LI) of carbofuran calculated for the soils studied indicated its high potential to leach into shallow aquifers and ground water. Pearson's correlations calculated for K F and K D against the soil properties showed a highly significant correlation with the clay + silt content of the soils. Multiple regression of K F and K D against the soil properties indicated that the mineral content of the soils (clay and clay + silt) is the best predictor of carbofuran adsorption, followed by soil pH. Predicted log K OM values were also evaluated by using the aqueous solubility, the 1-octanol/ water partition coefficient (K OW ), the adsorbability index (AI) and the first-order molecular connectivity index ( 1 χ) of carbofuran. Use of the aqueous solubility, and the 1-octanol/water partition coefficient (K OW ) to predict the extent of adsorption gave values which displayed a considerable error in comparison to those measured experimentally, whereas the use of the adsorbability index (AI) and the first-order molecular connectivity index ( 1 χ) of carbofuran improved the predictions considerably.

Effectiveness of Carbaryl, Carbofuran and Metolachlor Retention in Soils under the Influence of Different Colloid

“…Minerals 2021, 11, x 9 of 18 material evoked a higher affinity of carbofuran to the soil than the addition of humic acids. It was in accordance with studies of Singh and Srivastava, (2009) [73] who found that carbofuran is better correlated with the mineral content of the soils than with their organic matter. Nevertheless, kaolinite's presence in the L soil material had no effect on the carbofuran sorption (22.4%), indicating that other (2:1) clay minerals (illite and montmorillonite) were better pesticide sorbents [62,74] in the studied case.…”

Integrated ecological risk assessment of pesticides in tropical ecosystems: A case study with carbofuran in Brazil

“…The higher toxicity observed in cladocerans exposed to leachate dilutions is consistent with the high leaching potential of carbofuran [45,46]. This behavior is due to its high water solubility (322 mg/L), low sorption (K OC $ 23.3 ml/g), and moderate persistence (soil median degradation time (DT50) $ 29 d; aqueous hydrolysis DT50 at 208C and pH 7 $ 37 d; http:// sitem.herts.ac.uk/aeru/iupac/118.htm).…”

“…The lower toxicity of leachate dilutions, compared with runoff, may be related to the adsorption of some carbofuran to the soil organic matter during its percolation trough the soil profile. Despite this contribution of soil organic matter to pesticide sequestration, the sandy texture seems to have mitigated this effect and increased carbofuran mobility [46].…”

Adsorption and desorption kinetics of carbofuran in acid soils

“…These results were consistent with those of the batch tests, where Freundlich's K F was significantly correlated with soil organic matter and clay (Table 4). Other authors previously found the contents in clay and organic matter to play a key role in carbofuran retention by soils [10,30,37,38]. However, K F was more markedly influenced by organic matter than by clay (Table 4).…”