title: Distribution of organophosphate insecticides in a Thai biomass-water system.
abstract: Sorption and leaching of the organophosphate (OP) pesticides chlorpyrifos, profenofos, methyl parathion and malathion were investigated with four different types of biomass: coconut husk, rice husk, peat moss and peanut shell. Organic carbon contents of the biomass were in the range of 35.4-45.4%. Sorption studies were carried out by the batch (equilibrium) method at 4 different OP spike concentrations and at pH 3-7. Sorption isotherms conformed to a linear Freundlich equation and the Freundlich constant or sorption coefficient (KD) confirmed that biomass organic carbon content was the principal sorbent factor affecting OP sorption. For a given sorbent, correlation of the extent of sorption with sorbate chemical properties was examined. Column leaching experiments involving different masses of coconut husk and peanut shell pre-spiked with OPs at the level equivalent to actual spraying concentrations in some Thai tangerine orchards were conducted. These experiments included repeated spikings and leaching. A water flow rate of 20 mL min(-1) was employed corresponding to the current average watering regime. Retardation and biodegradation with these sorbents were also examined.
authors.affiliation: International Postgraduate Program in Environmental Management, Chulalongkorn University, Thailand.
authors.forename: Siraprapa
authors.initials: S
authors.lastname: Romyen
authors.forename: Darryl
authors.initials: D
authors.lastname: Hawker
authors.forename: Benjalak
authors.initials: B
authors.lastname: Karnchanasest
mesh_terms: D018533:Biomass; D006801:Humans; D010755:Organophosphates / Q000737:chemistry*; D010575:Pesticides / Q000737:chemistry*; D013785:Thailand; D014874:Water Pollutants, Chemical / Q000737:chemistry*; D018508:Water Purification; D014881:Water Supply
chemical_list: D010755:Organophosphates; D010575:Pesticides; D014874:Water Pollutants, Chemical