Dissipation of insecticides in a Mediterranean soil in the presence of wastewater and surfactant solutions. A kinetic model approach.
The simultaneous disappearance of four organophosphorous insecticides in a Mediterranean calcareous soil was evaluated in the presence of surfactant solutions and municipal wastewater. A cationic, an anionic and a non-ionic surfactant were used at a low (0.75 mg L(-1)) and at a high (twice the critical micelle concentration) concentration level. The cationic surfactant was also studied at a higher concentration. Dissipation in control soil was rapid for malathion (half-life 4 days), intermediate for dimethoate and methidathion (ca. 6 days) and slow for diazinon (29 days). Wastewater did either not modify (diazinon, dimethoate and methidathion) or slightly enhance (malathion) insecticide decay. The increase in concentration of the non-ionic surfactant Tween 80 resulted in enhanced dissipation rates for all the pesticides except diazinon. The addition of the anionic surfactant did not show a clear trend. At the highest cationic surfactant concentration a reduction of pesticide disappearance occurred linked with a reduced availability, since the insecticides were retained on the surfactant-modified soil (final residual concentration of 85% for diazinon and approximately 55% for methidathion and dimethoate). Soil microbial activity, estimated by measuring dehydrogenase activity, was low in wastewater- and surfactant-treated soil at the high levels. Fitting of the experimental data to commonly used mathematical models was poor and alternatives were looked for.
Department of Environmental Geochemistry, Estación Experimental del Zaidín (CSIC), Granada, Spain.
Ma Carmen
MC
Hernández-Soriano
Ma Dolores
MD
Mingorance
Aranzazu
A
Peña
D003976:Diazinon / Q000737:chemistry*; D004117:Dimethoate / Q000737:chemistry*; D004785:Environmental Pollutants; D007306:Insecticides / Q000737:chemistry*; D007700:Kinetics; D008294:Malathion / Q000737:chemistry*; D008954:Models, Biological; D009946:Organothiophosphorus Compounds / Q000737:chemistry*; D010088:Oxidoreductases / Q000378:metabolism; D012987:Soil; D012988:Soil Microbiology; D012989:Soil Pollutants / Q000737:chemistry*; D013501:Surface-Active Agents; D014865:Waste Disposal, Fluid; D014874:Water Pollutants, Chemical
D004785:Environmental Pollutants; D007306:Insecticides; D009946:Organothiophosphorus Compounds; D012987:Soil; D012989:Soil Pollutants; D013501:Surface-Active Agents; D014874:Water Pollutants, Chemical; D010088:Oxidoreductases; D008294:Malathion; D004117:Dimethoate; C005828:methidathion; D003976:Diazinon