Sensitivity analysis of the Substance Emission Model v2.1.2 component of the Greenhouse Emission Model

The substance emission model (SEM) simulates fate of plant protection products applied to crops grown in soilless cultures in greenhouses. It is part of the Greenhouse Emission Model used for regulatory risk assessment. This report presents a sensitivity analysis of SEM version 2.1.2 and is split into two parts. The first part of the report focuses on sensitivity of SEM predictions to the following (groups of) parameters: 1) the time step length of the numerical solution; 2) parameters defining partitioning processes in the cultivation part of the model; 3) saturated vapour pressure and solubility of the modelled substance; 4) deposition distribution of the applied substance; 5) degradation rate in the condensation water; 6) dissipation rate on the crop surface; 7) area fraction of the pots on tables. The second part of the report deals with sensitivity to the date of substance application. Results show that mass emitted from the greenhouse predicted by SEM (and hence the concentration in the receiving water course) is potentially highly sensitive to the application date. Based on these results we propose a procedure in which 12 GEM simulations for different application dates in each month of the year are performed. From the 12 concentration (PEC90) values resulting from these simulations the 90th percentile is determined, which is subsequently multiplied with a safety factor to avoid underestimation.