Comparative Study of Sorption-Desorption Behavior of Benzimidazole Based Pesticides on Selected Soils

A commercially available fungicide, Carbendazim and two newly synthesized Benzimidazole fungicides 2-(4-fluorophenyl)-1H-benzimidazole (FBNZ) and N-(1H-benzimidazol-2-ylmethyl) acetamide (ABNZ were investigated for their sorption-desorption behavior on four different agricultural soils of Pakistan, involving batch equilibrium method. The data obtained in all tests showed linear adsorption isotherms. All three fungicides showed a greater degree of adsorption on soil samples. Average adsorption percentage for soil1 was 15.7%, 8.0% and 17.6%; for Soil 2 it was found to be 13.8%, 18.1% and 23.9%, for Soil 3 it was 34.3%, 29.7%, and 23.8% and for Soil 4 it was 33.4% and 35.5% for Carbendazim, FBNZ and ABNZ respectively. The Kd parameters are low indicating that the interaction between the soil particles and fungicides were low. The sorption parameter was low in soil1 and soil 2 as compared to soil 3 and soil 4 for all the fungicides. This is because of low clay content in soil 1 and soil 2 as compare to soil 3 and soil 4. Desorption studies reveal that the adsorbed fungicides were firmly retained by soil particles and their adsorption was almost irreversible. The results indicate that soil organic matter (SOM) and appropriate pH also play promising role in sorption capacity. Newly Synthesized FBNZ and ABNZ show great antifungal activity. FBNZ causes 35% inhibition of Aspergillusflavus while ABNZ causes 40% inhibition of Microsporumcanis and Fusariumsolani.