NItrate REcovery CApacity Status

Nitrate pollution remains a significant concern for water quality. Since the 90s, Europe has been actively working to reduce nitrate levels and improve water quality. Yet, restoring water quality is a slow process as nitrates may remain for decades within aquifers as a legacy. While imperative, assessing Nitrate Recovery Capacity (NRC) faces challenges due to strong variabilities in nitrate transfer times and percentages removed by bacterial consumption within anoxic zones, often requiring intricate models. Here, we propose to leverage an innovative regional-scale assessment method to investigate the correlation between NRC and a readily accessible catchment attribute: lithology. Comparing nitrate concentrations with proxies of conservatively transferred element, NIRECAS determines the nitrate reactivity and legacy of a region. Within consistent geological contexts, the method analyzes the correlation between these factors and lithology while providing uncertainties of the correlation estimates. Our objectives are to (i) investigate the control of lithology on nitrate reactivity and legacy using 200 pilot sites in the Armorican Massif (France) taken as a first experimental region and (ii) extend and generalize the methodology to other European regions. Our deliverables include (1) a methodology for regional scale NRC mapping using available lithology databases, (2) maps of NRC for one to several European regions where lithology is found to be the primary controlling factor, (3) a user-friendly interface to a priori assess the percentage and transfer time of nitrate removed.This should provide key information on the ability of vulnerable regions to restore water quality while catching the legacy of past agricultural practices at the relevant resolution. Besides, NIRECAS should serve as a valuable predictive tool to assess the impact of current agricultural strategies on future generations and support the transition of practices over the medium and long term.