Contamination Assessment and Temporal Evolution of Nitrates in the Shallow Aquifer of the Metauro River Plain (Adriatic Sea, Italy) after Remediation Actions

Over the last decades, groundwater resources at global level have suffered a significant deterioration due to nitrate pollution, mainly related to the input of agricultural fertilizers, manure, sewage, and untreated urban and industrial effluents. The most impacted waters are those forming surface and shallow reservoirs, which usually play a key role in supplying waters to civil, agricultural, and industrial activities. The terminal portion of the Metauro River plain, located in central Italy along the Adriatic Sea coastline, hosts a strategic phreatic aquifer that, along with the surface water of the Metauro River, supplies water to the local population (i.e., about 60,000 people). This shallow coastal aquifer experiences a long-lasting story of nitrate contamination since the 1970s when the increase in the use of agricultural fertilizers contributed to very high levels of pollution (NO3- > 100 mg/L). This fact prompted the local authorities to carry out remediation actions that involve a pumping system to inject the NO3--poor waters from the Metauro River course directly into the shallow aquifer. The present work was aimed at defining the contamination of nitrates in this important water resource. The main geochemical characteristics and the temporal evolution of NO3- concentrations (between 2009 and 2020), in the shallow coastal aquifer of the Metauro River plain, were analyzed by means of classical geochemical analyses and multivariate methods accounting for the compositional nature of the data, to assess the efficiency of the in-situ remediation over time.

Automated summary

In recent decades, global groundwater resources have faced significant deterioration due to nitrate pollution caused by agricultural fertilizers, manure, sewage, and untreated urban and industrial effluents. Surface and shallow reservoirs, which are crucial for supplying water to civil, agricultural, and industrial activities, are the most affected. The Metauro River plain in central Italy, along the Adriatic Sea coastline, is home to a strategic phreatic aquifer that, along with the river's surface water, provides water to the local population. This coastal aquifer has been contaminated by nitrates since the 1970s, with high pollution levels resulting from increased use of agricultural fertilizers. Local authorities have implemented remediation measures, including pumping NO3--poor waters from the river directly into the shallow aquifer. This study aims to analyze the nitrate contamination of this important water resource by examining its geochemical characteristics and temporal evolution between 2009 and 2020, using classical geochemical analyses and multivariate methods to assess the effectiveness of in-situ remediation.