The fate of iron in waters from a coastal environment impacted by metallurgical industry in Northern Italy: hydrochemistry and Fe-isotopes

• Published in: Applied geochemistry Vol. 34; pp. 222 - 230
• Main Authors: Castorina, F., Petrini, R., Galic, A., Slejko, F.F., Aviani, U., Pezzetta, E., Cavazzini, G.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.07.2013; Elsevier
• Subjects: altitude; aquifers; Brackish; coasts; dissolved oxygen; Earth sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; Exact sciences and technology; Geochemistry; groundwater; hydrochemistry; industry; iron; isotope fractionation; landfills; leaching; Pollution, environment geology; saltwater intrusion; seawater; solubility; stable isotopes; Italy; Adriatic Sea; Southern Europe; East Mediterranean; Mediterranean Sea; Europe; MED, Adriatic Sea; MED, Italy; diagenesis; sea water; altitude; fractionation; stable isotopes; salinity; salt-water intrusion; ground water; industry; leaching; coastal environment; precipitation; trace elements; aquifers; hydrochemistry; landfills; brackish water; zoning; pH; iron; solubility
• ISSN: 0883-2927; 1872-9134
• DOI: 10.1016/j.apgeochem.2013.04.003

•Coastal aquifers inland the northern Adriatic Sea (Italy) are characterized by high iron concentrations.•Interactions between marine water and freshwater occur at different extent.•Salinity gradients and redox zoning contribute in driving iron cycling.•Iron isotopes traces Fe-oxide precipitation–dissolution reactions and possible sources.•The iron cycle has implications for the fate of potentially harmful elements. The source and cycling of Fe in groundwaters from the phreatic aquifer which characterizes a site impacted by metallurgical activity in a coastal area of northern Italy (Adriatic Sea) have been investigated by Fe-isotope analyses, H–O–Sr stable-isotope systematics and major and trace element chemistry. Waters are characterized by circum-neutral to alkaline pH and dissolved O2 zoning, and range from a low-salinity Ca–Mg–HCO3 type to a brackish Na–Cl type resulting from seawater intrusion. The O–H isotopic data indicate that the Ca–Mg–HCO3 waters originate from meteoric precipitation that infiltrated at elevated altitudes, and that a variable seawater fraction, in some cases exceeding 90%, characterizes the Na–Cl type waters. The Fe content ranges from 0.48 to 9.99mg/L and from 2.50 to 43.8mg/L in low-salinity and brackish waters, respectively. The δ56Fe value varies over the wide range from +0.87‰ to −5.29‰ in low-salinity waters and between +2.15‰ and −2.34‰ in brackish waters. The isotopically lighter compositions are interpreted as reflecting isotopic fractionation during repeated cycling of Fe precipitation. Positive δ56Fe values might indicate either a higher solubility of oxyhydroxides, which during diagenesis preferentially incorporated the isotopically heavier fraction of Fe, or the leaching of the foundry landfill disposal which characterizes the site.