Abstract In the Nitrate Vulnerable Zones farmers are required to implement measures to reduce the nitrogen (N) surplus. Nevertheless, in some cases the status of the water bodies show that the effect of these measures remains insufficient despite the global decrease in N surpluses. The present work aims to contribute with a method that produces an appropriate indicator for the N mitigation measures effectiveness for reducing groundwater nitrate pollution. The Global Risk Index (GRI) results from overlaying the agricultural N surplus hazard and aquifer vulnerability. It includes both irrigation activity and precipitation contribution to water recharge calculated at the municipality level. It integrates a range of regional datasets combined with monitored nitrate (NO3−) concentrations in groundwater under a GIS framework. Results show that the pollution status of the Tagus Vulnerable Zone (TVZ) aquifers has been aggravating in spite of the overall reduction in the N surpluses that resulted from the implementation of the Nitrates Directive measures. Twelve years after the TVZ designation, the GRI indicates high and moderate NO3- pollution risk, respectively in 33 % and 66 % of the territory. Scenario analysis indicates the potential of targeted measures for ending high risk areas and reducing moderate risk areas to 13 %. This supports that N mitigation measures must be reformulated and spatially targeted according to site specific hazards and vulnerabilities.

中文翻译：

---

将农业氮过剩危害转化为地下水污染风险：对硝酸盐脆弱区缓解措施有效性的影响

摘要 在硝酸盐脆弱区，农民需要采取措施减少氮（N）过剩。然而，在某些情况下，水体的状况表明，尽管全球氮盈余减少，但这些措施的效果仍然不足。目前的工作旨在提供一种方法，为减少地下水硝酸盐污染的 N 缓解措施的有效性产生适当的指标。全球风险指数 (GRI) 由农业氮过剩危害和含水层脆弱性叠加而成。它包括在市政一级计算的灌溉活动和降水对水补给的贡献。它整合了一系列区域数据集，并在 GIS 框架下监测地下水中的硝酸盐 (NO3−) 浓度。结果表明，尽管实施硝酸盐指令措施导致氮过剩总体减少，但塔霍脆弱区 (TVZ) 含水层的污染状况一直在恶化。在 TVZ 指定 12 年后，GRI 表明该地区分别有 33% 和 66% 的高和中度 NO3 污染风险。情景分析表明，有针对性的措施可以结束高风险地区并将中等风险地区减少到 13%。这支持必须根据场地特定的危害和脆弱性重新制定 N 缓解措施并在空间上有针对性。在 TVZ 指定 12 年后，GRI 表明该地区分别有 33% 和 66% 的高和中度 NO3 污染风险。情景分析表明，有针对性的措施可以结束高风险地区并将中等风险地区减少到 13%。这支持必须根据场地特定的危害和脆弱性重新制定 N 缓解措施并在空间上有针对性。在 TVZ 指定 12 年后，GRI 表明该地区分别有 33% 和 66% 的高和中度 NO3 污染风险。情景分析表明，有针对性的措施可以结束高风险地区并将中等风险地区减少到 13%。这支持必须根据场地特定的危害和脆弱性重新制定 N 缓解措施并在空间上有针对性。