Evaluation of Sorption and Leaching Potential of Malathion and Atrazine in Agricultural Soils of India

Movement of pesticides through soils to groundwater and surface water has long been considered a potentially serious environmental problem in different parts of the world. Remediation of such problems requires monitoring of site specific data. Considering these facts a laboratory based investigation was carried out to determine the sorption and leaching parameters of two contrasting and widely used pesticides (malathion and atrazine) in three different agricultural soils: loamy sand (Typic Xerosament), sandy loam (Acid Lateritic Haplustalf) and clay loam (Hyperthermic Typic Haplusterts). Standard batch sorption technique was used to determine the sorption coefficient (K-d) and organic carbon distribution coefficient (K-oc). Miscible displacement experiments were conducted to determine the transport parameters such as pore water velocity (nu), dispersion coefficient (D), retardation factor (R) and degradation rate constant (lambda). The results of batch sorption experiments revealed that malathion had higher K-d values as compared to atrazine for all soils. The grouping of soils according to sorption capacity followed the order: clay loam > sandy loam > loamy sand, for both malathion and atrazine. The results of miscible displacement experiments revealed that malathion could leach up to 30 cm depth whereas atrazine could leach up to 65 cm depth in the test soils. The values of transport parameters determined by method of moments ranged from 0.79 to 1.63 cm/h for nu and 3.15 to 12.26, cm(2)/h for D in the test soils. The R values of malathion obtained using K-d were em 3.1 to 3.4 times higher than atrazine for the test soils. The half life of malathion and atrazine obtained from lambda ranged from 0.3 to 1.7 days and 50 to 64 days, respectively in the above mentioned soils.