Large volumes of water resources at global level are seriously affected by nitrate contamination, mainly due to an exaggerated use in agricultural practices. The most impacted waters are those forming surface bodies and shallow reservoirs, the latter mostly hosted in alluvial plains, where highly permeable deposits are usually dominating. These aquifers play a key role in supplying waters to civil, agricultural, and industrial activities. Nitrate pollution by diffuse sources was first targeted in Europe by the Nitrate Directive (91/676/CEE) and subsequently by the Water Framework Directive (2000/60/EC), which also defined the “Nitrate Vulnerable Zones”, which are intended to be territories that drain nitrate polluted (or at risk of pollution) waters. Concerning the shallow aquifers, NO3- vulnerable zones were identified as those containing, or that could be containing, >50 mg/L of NO3, as specified by the Italian Law Decree 152/2006 (modified and integrated by the L.D. 30/2009). Accordingly, the administration of the Marche Region (central-eastern Italy) has declared the Metauro river plain (located in the northern part of the region) that hosts a phreatic aquifer, as highly vulnerable by nitrates. In this work, the terminal portion of the fluvial plain was investigated during three hydrogeochemical surveys (June 2019, September and November 2020), in the framework of the bilateral Interreg Italy-Croatia project ASTERIS: Adaptation to Saltwater intrusion in sEa level RIse Scenarios. Although the main target of the project was dedicated to the interaction between fresh and saline waters, strikingly high nitrate contents (up to 104 mg/L) in the phreatic aquifer were determined, and in more than a half of the studied waters the NO3- concentrations resulted to be >50 mg/L. Historical data available from 2009 confirm that most of the monitored wells maintained high NO3- concentration levels up to today. The high NO3- concentrations strongly limit the water exploitation potential by the local water supply company for drinking purpose and the waters from the Metauro river, whose NO3- content is <8 mg/L, are injected into the shallow aquifer in the inner part of the valley. Despite the large amount of river water driven underground, the dilution effect is only detectable in limited portions of the territory where the NO3- contents are below the normative level. It is to note that NO3- shows a dramatic decrease downstream the reinjection site and near the Metauro river, suggesting riveraquifer exchanges. The NO3- pollution is a long-lasting story since nitrate started to increase in the seventies but interventions to reduce the nitrogen loads on the ground and the adopted measures aimed at the protection of aquifers did not produce satisfactory results. This implies that mapping spatial and temporal variations of NO3- concentrations is of paramount importance to detect the most critical areas where to intervene.

Dissolved nitrates in the lower Metauro River aquifer (Marche Region, central Italy): a long-lasting story

Marco Taussi
;
2021-01-01

Abstract

Large volumes of water resources at global level are seriously affected by nitrate contamination, mainly due to an exaggerated use in agricultural practices. The most impacted waters are those forming surface bodies and shallow reservoirs, the latter mostly hosted in alluvial plains, where highly permeable deposits are usually dominating. These aquifers play a key role in supplying waters to civil, agricultural, and industrial activities. Nitrate pollution by diffuse sources was first targeted in Europe by the Nitrate Directive (91/676/CEE) and subsequently by the Water Framework Directive (2000/60/EC), which also defined the “Nitrate Vulnerable Zones”, which are intended to be territories that drain nitrate polluted (or at risk of pollution) waters. Concerning the shallow aquifers, NO3- vulnerable zones were identified as those containing, or that could be containing, >50 mg/L of NO3, as specified by the Italian Law Decree 152/2006 (modified and integrated by the L.D. 30/2009). Accordingly, the administration of the Marche Region (central-eastern Italy) has declared the Metauro river plain (located in the northern part of the region) that hosts a phreatic aquifer, as highly vulnerable by nitrates. In this work, the terminal portion of the fluvial plain was investigated during three hydrogeochemical surveys (June 2019, September and November 2020), in the framework of the bilateral Interreg Italy-Croatia project ASTERIS: Adaptation to Saltwater intrusion in sEa level RIse Scenarios. Although the main target of the project was dedicated to the interaction between fresh and saline waters, strikingly high nitrate contents (up to 104 mg/L) in the phreatic aquifer were determined, and in more than a half of the studied waters the NO3- concentrations resulted to be >50 mg/L. Historical data available from 2009 confirm that most of the monitored wells maintained high NO3- concentration levels up to today. The high NO3- concentrations strongly limit the water exploitation potential by the local water supply company for drinking purpose and the waters from the Metauro river, whose NO3- content is <8 mg/L, are injected into the shallow aquifer in the inner part of the valley. Despite the large amount of river water driven underground, the dilution effect is only detectable in limited portions of the territory where the NO3- contents are below the normative level. It is to note that NO3- shows a dramatic decrease downstream the reinjection site and near the Metauro river, suggesting riveraquifer exchanges. The NO3- pollution is a long-lasting story since nitrate started to increase in the seventies but interventions to reduce the nitrogen loads on the ground and the adopted measures aimed at the protection of aquifers did not produce satisfactory results. This implies that mapping spatial and temporal variations of NO3- concentrations is of paramount importance to detect the most critical areas where to intervene.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11576/2694350
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