Influence of adsorption-desorption phenomena on pesticide run-off from soil using simulated rainfall
✍ Scribed by Gouy, Véronique; Dur, Jeanne-Chantal; Calvet, Raoul; Belamie, René; Chaplain, Véronique
- Publisher
- John Wiley and Sons
- Year
- 1999
- Tongue
- English
- Weight
- 242 KB
- Volume
- 55
- Category
- Article
- ISSN
- 1526-498X
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✦ Synopsis
The surface run-oþ of a number of pesticides (diuron, isoproturon, atrazine, alachlor, aclonifen, triýuralin, lindane and simazine), chosen for their range of adsorption behaviours, was studied using simulated rainfall applied to small plots over a short time (one hour). Pesticides were applied together onto bare soil using two diþ erent sandy loam soils from Jailliere and Coet Dan sites. The surface run-oþ samples were collected throughout the running of the event and concentrations of pesticides were measured in both liquid and solid phases. Sorption isotherms for isoproturon and diuron on Jailliere soil as well as eroded particles were measured under equilibrium conditions and compared to their partitioning during surface run-oþ .
At the rainfall intensity used, both soils generated a large load of eroded particles. The average run-oþ ýow rate increased with time for the Jallie re soil, while it remained relatively constant at a higher level for the Coet Dan soil. The concentrations of each pesticide in the run-oþ samples decreased as the experiments proceeded. The pesticides were classiüed into two types by their partitioning between the solid and liquid phases. Atrazine, simazine, diuron, isoproturon and alachlor were mainly transported in surface run-oþ water. By contrast, 90% of triýuralin and aclonifen was adsorbed onto eroded particles. Lindane was intermediate, with a 37% adsorption level. When the contribution of eroded particles was minor, the agrochemical concentrations were inversely proportional to the water ýow rate. We have proposed a model that describes the mass of chemicals extracted from soil into surface water during a surface run-oþ event of a given average duration and ýow rate. This model takes into account the dilution of the soil solution and the desorption of chemicals through two parameters called, respectively, the dilution factor and the extraction retardation factor. The desorption kinetic was the limiting step in the surface run-oþ of weakly sorbed chemicals, such as isoproturon.