Modelling the fate of veterinary compounds in groundwater and surface water using the FOCUS models

Modelling the fate of veterinary compounds in groundwater and surface water using the FOCUS models In this project harmonised input parameters for the FOCUS groundwater model PEARL and the FOCUS Surface waters models (SWASH, PRZM, MACRO, TOXSWA) were suggested and it was assessed whether the currently used options and parameters are still valid. Furthermore, recommendations were developed about how the models could be used and how their results could be interpreted in the risk assessment for veterinary medicines. The results of this project can aid in future the discussions on guidance documents for the ERA of veterinary medicines. The report also includes a manual for performing FOCUS simulations. It was also investigated in how far FOCUS tools could be used to evaluate mitigation options for veterinary compounds. Following results were obtained:
► In addition to Okehampton Hamburg, Jokioinen and Piacenza scenarios may be as well of relevance for the assessment of PEC groundwater.
► The crop maize should be additionally considered in the risk assessment for manure applications.
► The crop grass/alfalfa scenario should be used for a scenario when animals are kept under outdoor conditions. It is recommended to divide the application over the period of treatment and to use an incorporation depth of 0 m.
► Technically, risk mitigation could be performed for run-off scenarios using the FOCUS SWAN routine. The software uses vegetated buffer strips as mitigation option. However, results would only be valid for locations with vegetated buffer strips and are thus not applicable in the general risk assessment.
► In case sorption are pH dependent and not correlated to the organic carbon content, it is recommended to use worst-case selections (e.g. minimum sorption constants).