Zinc (Zn) isotope analysis is an increasingly valuable tool for tracing anthropogenic heavy-metal contamination in marine environments. Zinc is sensitive to mass-dependent isotope fractionation during biological and geochemical processes, and anthropogenic Zn often shows a bi-modal δ⁶⁶/⁶⁴Zn distribution, with lighter signatures associated with high-temperature emissions and heavier signatures linked to solid residues from industrial activities such as smelting, refining, coal combustion, waste incineration, and galvanization. Polluted effluents discharge Zn into coastal waters, where it is efficiently scavenged and ultimately accumulates in marine sediments.
A method for Zn isotope analysis in complex marine sediment matrices was developed and validated, using anion-exchange chromatography as the central step for Zn isolation. Zinc was separated using small columns (1 ml) packed with Bio-Rad AG-MP-1M anion-exchange resin (100–200 mesh, Cl⁻ form), enabling effective removal of major matrix elements and potential isobaric interferences. Purified Zn fractions were analysed for isotope ratios by multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS; Nu Plasma II) using a standard–sample bracketing approach, with results normalized to SRM-683 and reported relative to the JMC-Lyon reference standard.
The method was applied to Haifa Bay sediments, including: (1) sediment-trap samples collected at 15 m and 30 m water depth and recovered approximately quarterly between October 2020 and September 2022, and (2) short sediment cores from 60 m water depth along the western boundary of the bay, and from a 1400 m site approximately 50 km northwest of the bay. Certified reference materials (CRMs) with published δ⁶⁶/⁶⁴Zn values and the anthropogenic CRM BCR-723 (Austrian tunnel road dust; no published δ⁶⁶/⁶⁴Zn data) were processed alongside the samples. Measured δ⁶⁶/⁶⁴Zn values span from natural to clearly heavier δ⁶⁶/⁶⁴Zn signatures, indicating significant anthropogenic Zn contributions and demonstrating that this approach provides a robust framework for tracing Zn contamination in coastal sediments.