title: Adsorption study of 14C-paraquat in two Malaysian agricultural soils.
abstract: The adsorption equilibrium time and effects of pH and concentration of (14)C-labeled paraquat (1,1(')-dimethyl-4,4(')-bipyridylium dichloride) in two types of Malaysian soil were investigated. The soils used in the study were clay loam and clay soils from rice fields. Equilibrium studies of paraquat in a soil and pesticide solution were conducted. Adsorption equilibrium time was achieved within 2 h for both soil types. The amount of (14)C-labeled paraquat adsorbed onto glass surfaces increased with increasing shaking time and remained constant after 10 h. It was found that paraquat adsorbed by the two soils was very similar: 51.73 (clay loam) and 51.59 μ g g(-1) (clay) at 1 μ g/ml. The adsorption of paraquat onto both types of soil was higher at high pH, and adsorption decreased with decreasing pH. At pH 11, the amounts of (14)C-labeled paraquat adsorbed onto the clay loam and clay soil samples were 4.08 and 4.05 μ g g(-1), respectively, whereas at pH 2, the amounts adsorbed were 3.72 and 3.57 μ g g(-1), respectively. Results also suggested that paraquat sorption by soil is concentration dependent.
authors.affiliation: Product Development and Advisory Services Division, Malaysian Palm Oil Board, 50720, Kuala Lumpur, Malaysia.
authors.forename: Halimah
authors.initials: H
authors.lastname: Muhamad
authors.forename: B Sahid
authors.initials: BS
authors.lastname: Ismail
authors.forename: Mehdi
authors.initials: M
authors.lastname: Sameni
authors.forename: Nashriyah
authors.initials: N
authors.lastname: Mat
mesh_terms: D000327:Adsorption; D000383:Agriculture; D006863:Hydrogen-Ion Concentration; D010269:Paraquat / Q000032:analysis* / Q000737:chemistry*; D012989:Soil Pollutants / Q000032:analysis* / Q000737:chemistry*
chemical_list: D012989:Soil Pollutants; D010269:Paraquat