Estimating transformation rates of pesticides, to be used in the TOXSWA model, from water-sediment studies
2002
Adriaanse, P.I. | Vink, J.P.M. | Brouwer, W.W.M. | Leistra, M. | Tas, J.W. | Linders, J.B.H.J. | Pol, J.W.
In the Dutch registration procedure the TOXSWA model is used to calculate the exposure of aquatic organisms to the pesticides applied in agriculture. The transformation rates in water and sediment, needed as input for the computations, are not asked directly in the registration procedure. Various test guidelines for water-sediment studies are discussed; they only yield pesticide dissipation rates in water and sediment. Water-sediment studies for three compounds were simulated with TOXSWA to estimate the transformation rates from the measured data. It was found that a detailed interpretation of the experiments and reported data is crucial before the water-sediment studies can be simulated correctly. Using the model, pesticide transformation could be assigned to mainly one of the layers or to both layers. These transformation rates do not depend on system properties, such as volumes of water and sediment, nor on the surface area of their interface. The procedure has to be tested for more pesticides and studies. The factors determining microbial transformation of pesticides in aquatic systems were studied; this allows improved characterization of the systems by measurements.
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