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.
Hernández-Soriano
Ma Carmen
MC
Department of Environmental Geochemistry, Estación Experimental del Zaidín (CSIC), Granada, Spain.
Mingorance
Ma Dolores
MD
Peña
Aranzazu
A
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