Sorption behaviour of diuron under a mediterranean climate

Abstract

The assessment of field-like sorption behaviour is critical to predict the fate and transport of organic compounds, especially when long time periods are considered. We compared field-derived sorption isotherms for diuron from a 4-year database collected in a Mediterranean catchment with adsorption and desorption isotherms from classical batch studies. In addition, a new technique of drying the slurry samples inbetween various desorption steps was applied in order to reflect the recurrent drying of the topsoil under Mediterranean climate conditions. Our results show first that the field-derived isotherms indicated a larger sorption capacity of the soil at small diuron concentrations (larger Kf and smaller exponent for the Freundlich parameters) than those derived from standard batch experiments. Second, when the soil was dried before desorption, chemical release was reduced by up to 29% as compared with normal desorption, resulting in isotherms that were in line with results from the field experiment. These results suggest that the drying-wetting cycles are a key factor in the long-term adsorption and desorption processes under field conditions. Third, the new approach of batch desorption experiments that allow the fast and careful complete drying of soil suspensions appears to be an appropriate method to assess sorption behaviour of herbicides over a long time period.

Organic amendments affecting sorption, leaching and dissipation of fungicides in soils

“…Physical retention in smaller size pores should be affected by residence time of the fungicide in the soil and can be partially responsible for the low recoveries of tricyclazole. Also, long‐term experiments have shown an increase in pesticide adsorption with residence time in soil, mainly owing to limited desorption from the soil 33. The formation of bound residues could also contribute to these results, since Cox et al 34 showed that tricyclazole has a higher tendency than metalaxyl to form bound residues with increasing residence time in the soil, on account of stronger interaction with soil colloidal components.…”

Environmental Behaviour of Metolachlor and Diuron in a Tropical Soil in the Central Region of Brazil

“…The much lower adsorption coefficients of diuron in the deeper soil horizon indicate that molecules not retained in the surface are prone to leaching to groundwater due to much lower retention. Louchart et al (2005) studying the sorption behaviour of diuron under a Mediterranean climate showed that soil drought plays a major role in modifying the sorption behaviour of herbicides in soil and therefore their availability to transfer by overland flow or infiltration. The drying-wetting cycles that are likely to occur in natural field conditions, particularly in the study region where temperatures get high during the day (up to 35-40°C) drying the soil very quickly, may affect the fate of herbicides in tropical environments.…”

Selection of low cost materials for the sorption of copper and herbicides as single or mixed compounds in increasing complexity matrices

“…These are high values compared to those reported for soils [48][49][50]. It shows a fairly high affinity of sediment for diuron and 3,4-DCA, which needs however to be validated in more complex matrices like SEM.…”