title: Subcritical water extraction to evaluate desorption behavior of organic pesticides in soil.
abstract: We evaluated the feasibility of extracting organic pesticides in soil using a hot-water percolation apparatus at 105 degrees C and 120 kPa pressure. Efficiency of the method was assessed by extracting six selected pesticides (acetochlor, atrazine, diazinon, carbendazim, imidacloprid, and isoproturon) from previously equilibrated soil at 13.6-65.8 mg/kg concentration range. Studies were performed on brown forest soil with clay alluviation (Luvisol). The method developed was compared to the traditional batch equilibrium method in terms of desorbed amount of pesticides from soil and extraction time. Pesticides in the liquid phase from the batch sorption experiment and in the effluent from the hot-water percolation were quantified by high-performance liquid chromatography with UV detection. The results of the percolation experiment are in close correlation with those of the conventional soil testing method. Desorbed quantities by hot-water percolation were 85% acetochlor, 62% atrazine, 65% carbendazim, 44% diazinon, 95% imidacloprid, and 84% isoproturon, whereas using batch equilibrium method 101, 66, 64, 37, 81, and 90% were desorbed, expressed as the percentage of the adsorbed amount of pesticide on soil following equilibration. The average time for hot-water extraction was 3.45 min, in contrast to the 16 h time consumption of the traditional batch method. The effect of temperature on stability of selected compounds was also evaluated using pesticide-spiked sand without soil. Recoveries of analytes ranged between 84.6 and 91.1% with reproducibility of 7.9-10.2%, except for diazinon, for which recovery was 59.4% with 14.4% relative standard deviation since decomposition occurred at elevated temperature. The percolation process has been described by a first-order kinetic equation. The parameters calculated from the equation provide an opportunity to estimate the amount of compound available for desorption, the rate of desorption processes in the studied soil-pesticide-water system, and modeling the leaching process to obtain additional information on the environmental behavior of the examined pesticide.
authors.affiliation: Institute for Veterinary Medicinal Products, 8 Szállás Street, H-1107 Budapest, Hungary. livia@oai.hu
authors.forename: Lívia N
authors.initials: LN
authors.lastname: Konda
authors.forename: György
authors.initials: G
authors.lastname: Füleky
authors.forename: György
authors.initials: G
authors.lastname: Morovján
mesh_terms: D001280:Atrazine / Q000302:isolation & purification; D001562:Benzimidazoles / Q000302:isolation & purification; D002219:Carbamates; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D003976:Diazinon / Q000302:isolation & purification; D006358:Hot Temperature; D007093:Imidazoles / Q000302:isolation & purification; D008433:Mathematics; D008782:Methylurea Compounds / Q000302:isolation & purification; D008956:Models, Chemical; D000073943:Neonicotinoids; D009574:Nitro Compounds; D010575:Pesticides / Q000737:chemistry / Q000302:isolation & purification*; D010671:Phenylurea Compounds; D012987:Soil / Q000032:analysis*; D012989:Soil Pollutants / Q000302:isolation & purification*; D014052:Toluidines / Q000302:isolation & purification; D014867:Water
chemical_list: D001562:Benzimidazoles; D002219:Carbamates; D007093:Imidazoles; D008782:Methylurea Compounds; D000073943:Neonicotinoids; D009574:Nitro Compounds; D010575:Pesticides; D010671:Phenylurea Compounds; D012987:Soil; D012989:Soil Pollutants; D014052:Toluidines; D014867:Water; C082359:imidacloprid; C028904:isoproturon; C043377:acetochlor; C006698:carbendazim; D001280:Atrazine; D003976:Diazinon