Parameterization and regionalization of redox based denitrification for GIS-embedded nitrate transport modeling in Pleistocene aquifer systems

At the regional scale, more and more questions are arising regarding the evaluation of management strategies to minimize the nutrient input into ground- and surface water. Therefore, the quantification of the chemical transformation processes and the spatio-temporal differentiation of the nitrate transport behavior at regional scales are essential. The EU Water Framework Directive (WFD) stipulated new sustainable management concepts in the face of climate change and the change of land use systems. Considering the prospective changes, a valid prediction of the substance flux using scale-dependent adapted model tools is a necessity. The objective of this paper is the parameterization of redox based denitrification dynamics in groundwater via the entire flow path from recharge to discharge by the geochemical proxies redox potential and Fe-concentration. The used model approach Model of Diffuse Emissions via Subsurface Trails (MODEST) combines GIS embedded grid-based conceptual groundwater flow and substance transport modeling at larger scales with substance degradation rates, the latter based on denitrification half-lives between 6 months and 120 years determined for the individual compartments of the modeled region, the State Brandenburg. The resulting regional nitrate retention potential represents the basic information for the evaluation of renovated, sustainable land and water management approaches, mitigating diffuse nitrate pollution in the younger Pleistocene glacial landscapes.