title: Behavior of two phenyl urea herbicides in clayey soils and effect of alternating dry-wet conditions on their availability.
abstract: Adsorption and mobility of linuron (3-(3,4-dichlorophenyl)-1-methoxy-1-methylurea) and diuron (3-(3,4-dichlorophenyl)-1, 1-dimethylurea) were studied in clayey soils from the Gharb area (Morocco). Soils A and B were planted with sun flower (Helianthus annuus) while soil C was planted with sugar cane (Saccharum offcinarum). Adsorption was studied for linuron in soils A and B, while mobility was studied only in soil B. Adsorption data were found to fit the Freundlich equation with correlation coefficients r2 > 0.9. Freundlich coefficients (Kf, nf) were in agreement with L and S isotherm types for soils A and B, respectively. Values of Koc (195 and 102) indicate moderate adsorption. Desorption isotherms for linuron showed hysteresis for both soils. The pesticide would be more bound to soil A (H = 8.44) than to soil B (H = 4.01). The effect of alternating wet and dry conditions was tested for soils A and B. Results showed that retention would increase in soil subject to an additional wet and dry cycle. In the case of diuron isotherm was of type L in soil C. Desorption was noticeable at high concentrations and tended to decrease when concentrations diminished. Mobility of linuron was tested in polyvinyle chloride (PVC) columns, which received different treatments before their percolation. The pesticide was more mobile in a previously saturated column. In columns subject to a drying step after saturation with water, linuron mobility was greatly reduced.
authors.affiliation: Laboratoire de Chimie-Physique, Faculté des Sciences de Rabat, Rabat, Morocco.
authors.forename: Jamila
authors.initials: J
authors.lastname: Haouari
authors.forename: Abdelmalek
authors.initials: A
authors.lastname: Dahchour
authors.forename: Arancha
authors.initials: A
authors.lastname: Peña-Heras
authors.forename: Xzavier
authors.initials: X
authors.lastname: Louchard
authors.forename: Berndt
authors.initials: B
authors.lastname: Lennartz
authors.forename: Mohamed Elbelghiti
authors.initials: ME
authors.lastname: Alaoui
authors.forename: Ahmad
authors.initials: A
authors.lastname: Satrallah
mesh_terms: D000327:Adsorption; D001682:Biological Availability; D004237:Diuron / Q000737:chemistry / Q000378:metabolism; D006368:Helianthus / Q000378:metabolism*; D006540:Herbicides / Q000737:chemistry* / Q000378:metabolism; D007700:Kinetics; D008044:Linuron / Q000737:chemistry / Q000378:metabolism; D011891:Rain; D031786:Saccharum / Q000378:metabolism*; D012987:Soil; D012989:Soil Pollutants / Q000737:chemistry* / Q000378:metabolism; D012995:Solubility
chemical_list: D006540:Herbicides; D012987:Soil; D012989:Soil Pollutants; D008044:Linuron; D004237:Diuron