|Title||Comparison of pesticide concentrations at drinking water abstraction points in The Netherlands simulated by DROPLET version 1.2 and 1.3.2 model suites|
|Author(s)||Adriaanse, P.I.; Beltman, W.H.J.|
|Source||Wageningen : Wageningen University & Research, Statutory Research Tasks Unit for Nature & the Environment (WOt-technical report 100) - 52|
|Department(s)||Alterra - Environmental risk assessment|
|Publication type||Research report|
|Abstract||The user-friendly software tool DROPLET (acronym for DRinkwater uit OPpervlaktewater-Landbouwkundig gebruik Evaluatie Tool) assists the Dutch Board for the Authorization of Plant Protection Products and Biocides (Ctgb) in evaluating whether pesticides may exceed the 0.1 μg/L standard in one of the Dutch surface water abstraction points for drinking water production. Based upon Good Agricultural Practice DROPLET uses the peak concentration in the FOCUS D3 ditch (with spray drift deposition according to Dutch numbers) as starting point for the final, expected concentration at the abstraction points
situated in the larger waterbodies downstream. This report compares concentrations in the abstraction points calculated by the old model suite (FOCUS-SWASH 3.1, FOCUS-MACRO 4.4.2, FOCUS-TOXSWA 3.3.1 and DROPLET 1.2) with those calculated by the more recently released model suite (FOCUS-SWASH 5.3, including the substance database SPIN 3.3, FOCUS-MACRO 5.5.4, FOCUS-TOXSWA 4.4.3 and DROPLET 1.3.2). The concentrations in the drinking water abstraction points calculated by the new model suite may be up to a factor of approximately 2.5 higher than the ones calculated by the old model suite. This is practically entirely due to the increased pesticide mass in the drainage fluxes calculated by the new version of the MACRO model. The calculations by the TOXSWA and DROPLET models have not been changed. Because no
measured water and mass fluxes for drainage are available for the D3 scenario, it is not possible to indicate whether the fluxes calculated by MACRO 4.4.2 or those by MACRO 5.5.4 reflect better reality. Thus no recommendation can be made on the model suite to be used in the Dutch exposure assessment for drinking water production from surface waters.