Zinc isotopes as tracers of anthropogenic sources and biogeochemical processes in contaminated mangroves

Abstract

Recent work has shown that variations in zinc (Zn) isotope ratios enable us to identify contamination sources in the terrestrial environment and uptake processes in higher plants. Here in this study, we demonstrate that this also holds true for mangrove forests, which play an important role in the biogeochemical cycling of metals in tropical coastal ecosystems and that are seriously threatened by anthropogenic pollution. To this end, we determined zinc concentration and isotope composition (expressed using the δ66Zn notation relative to the JMC 3-0749-L standard) in sediments and tree leaves collected from a mangrove close to Rio de Janeiro in Brazil. The δ66ZnJMC values of sediments vary between +0.36 and + 0.84‰ and fall on a mixing line between detrital terrestrial sources (characterized with δ66ZnJMC = +0.28 ± 0.12‰, 2σ) and metallurgical ore sources (δ66ZnJMC = +0.86‰ ±0.15‰, 2σ). Leaves of Laguncularia racemose, in contrast, showed δ66ZnJMC values ranging between +0.08 and + 0.23‰, suggesting that processes including uptake, translocation and bioavailability in the rhizosphere control the isotope composition of zinc in the mangrove plant. Please note that this is an author-produced PDF of an article accepted for publication following peer review. The definitive publisher-authenticated version is available on the publisher Web site.

Assessment of the metal contamination evolution in the Loire estuary using Cu and Zn stable isotopes and geochemical data in sediments

“…This trend can be interpreted as a binary mixing process between Zn derived from terrigenous material and multiple anthropogenic Zn sources. Since sediment particle transport from rivers to oceans does not alter significantly Zn isotope compositions of the particulate phase (Araújo et al, 2018;Guinoiseau et al, 2018), isotope ratios in the suspended sediments behave conservatively, reflecting the relative Zn contributions of natural and anthropogenic sources.…”

Copper, Zinc and Lead Isotopic Delta Values and Isotope Ratios of Various Geological and Biological Reference Materials

“…2017), Zn (Araújo et al . 2017a, 2018, Desaulty and Petelet‐Giraud 2020) and Pb (Jeong et al . 2018, Nazarpour et al .…”

Zinc isotope composition as a tool for tracing sources and fate of metal contaminants in rivers

“…3). Most of the sediments and SPM taken from lakes and rivers with little human impact ([Zn]particulate ≤ 200 mg/kg) have Zn isotope compositions varying from δ 66/64 Zn=+0.14 to +0.32‰ (n= 129, IQR, Araújo et al, 2017aAraújo et al, , 2017bAraújo et al, , 2019Araújo et al, , 2018Chen et al, 2009b;Guinoiseau et al, 2018Guinoiseau et al, , 2017Petit et al, 2015Petit et al, , 2008Sivry et al, 2008;Thapalia et al, 2010Thapalia et al, , 2015 this study) (Fig. S2).…”

“…In their studies in the Sepetiba Bay (Brazil), Araújo et al (2018Araújo et al ( , 2017aAraújo et al ( , 2017b used Zn isotope compositions for core samples of stream sediments and SPM to reconstitute a timeline for changes in zinc contamination related to industrial metallurgy. From studying core samples of stream sediment, Sivry et al (2008) and Petit et al (2015) have also shown how zinc ore-smelter activity affects the river Lot's watershed (France).…”