Abstract
Hydrogeochemical characterization and statistical methods were used to investigate the groundwater quality and the origin of constituents (anthropic or natural) in groundwater of the Coreca area (Calabria, South Italy). Coreca is characterized by an articulated geological setting where the three main geological complexes that distinguish the Northern Calabria Peloritan Orogen (CPO) outcrop. This complex asset affects the quality of groundwater mainly exploited for irrigation use. In particular, the presence of ultramafic rocks (e.g., serpentinite and metabasite) promotes the release of harmful elements such as Cr and Ni. In the studied area, two groups of waters were identified: Ca-HCO3 waters strongly controlled by the interaction with Ca-rich phases (e.g., limestone), and Mg-HCO3 waters related to the interaction of meteoric water with the metamorphic units. Statistical elaboration allowed to detect, in the Mg-HCO3 group, a good correlation between Cr and Ni (not observed in Ca waters) and a negative correlation between Cr, Ca and Al, in agreement with direct interaction with ultramafic rocks characterized by low concentrations of CaO and Al2O3. The concentration of major and trace elements has been compared with the Italian law limit values and the drinking water guidelines provided by the World Health Organization (WHO). Only three samples showed Mn and Ni concentration higher than the Italian law threshold. Furthermore, the assessment of groundwater quality was carried out using salinity and metal indexes. The groundwater quality assessment for irrigation allowed to classify the resource as “excellent to good” and “good to permissible”; nevertheless, a salinity problem and a magnesium hazard were found. Lastly, a metal index (MI) calculation revealed values <1 for almost all samples, pointing to good overall quality. Only a few samples showed a value extremely higher than 1, attributable to prolonged interaction with ultramafic rocks and/or localized anthropogenic pollution. From a general point of view, groundwater showed a generally good quality except for limited areas (and limited to the set of constituents analyzed) and a mild exceedance of the maximum salinity thresholds that must be monitored over time. Through a multidisciplinary approach, it was possible to ascertain the main anomalies attributable to the interaction with the hosting rocks and not (with few exceptions) to anthropic processes.
Highlights
Groundwater composition is closely linked to the geological and structural setting of the hosting aquifer due to physical and chemical characteristics that depend on several factors, such as water–rock interaction processes, residence time, hydrodynamic conditions, and mixing processes [1,2]
The Mg group exhibited a good correlation between Cr and Ni, in agreement with previous studies carried out in areas with ultramaphic rocks in [11,69,70,71,72,73,74] and a negative correlation between Cr, Ca, and Al, consistent with a direct interaction with ultramaphic rocks characterized by low concentrations of CaO and Al2O3 [75]
Rock and water compositions were elaborated following statistical methods combined with hydrogeochemical modeling and conventional plots to investigate groundwater and related geochemical processes
Summary
Groundwater composition is closely linked to the geological and structural setting of the hosting aquifer due to physical and chemical characteristics that depend on several factors, such as water–rock interaction processes, residence time, hydrodynamic conditions, and mixing processes [1,2]. Groundwater represents an essential part of water resources for human survival and economic development. The contamination in groundwater can persist for a long time due to the low flow rate of groundwater in an aquifer and may involve major ions and trace constituents. High levels of contaminants can make water unsuitable for drinking, irrigation, fishing, and recreation [9], causing serious adverse effects on human and biota health [10]. The correct management and characterization of groundwater resources is one of the most challenging current and future issues of global interest
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