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

• Published in: The Science of the total environment 2020-08, Vol.728, p.138599-138599, Article 138599
• Main Authors: Desaulty, Anne-Marie, Petelet-Giraud, Emmanuelle
• Format: Article
• Language: English
• Subjects: Anthropogenic source; Catchment; Earth Sciences; MC-ICP-MS; Sciences of the Universe; Tracer; Zn isotopes
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2020.138599

Zinc is a ubiquitous metal, acting both as an essential and a toxic element to organisms depending on its concentration and speciation in solution. Human activities mobilize and spread large quantities of zinc broadly in the environment. Discriminating the natural and various anthropogenic zinc sources in the environment and understanding zinc's fate at a catchment scale are key challenges in preserving the environment. This review presents the state of the art in zinc isotope studies applied to environmental purposes at a river-basin scale. Even though the study of zinc isotopes remains less developed than more “traditional” lead isotopes, we can assess their potential for being a relevant tracer of zinc in the environment. We present the principles of zinc isotope measurements from collecting samples to mass spectrometry analysis. To understand the fate of zinc released in the environment by anthropogenic activities, we summarize the main processes governing zinc distribution between the dissolved and solid phases, with a focus on the isotope fractionation effects that can modify the initial signature of the various zinc sources. The signatures of zinc isotopes are defined for the main natural sources of zinc in the environment: bulk silicate earth (BSE), zinc sulfide ore deposits, and coal signatures. Rivers draining natural environments define the “geological background for surface water”, which is close to the BSE value. We present the main anthropogenic sources (metallurgical waste, effluents, fertilizers, etc.) with their respective isotope signatures and the main processes leading to these specific isotope characteristics. We discuss the impact of the various anthropogenic zinc emissions based on the available studies based on zinc isotopes. This literature review points out current knowledge gaps and proposes future directions to make zinc isotopes a relevant tracer of zinc (and associated trace metals) sources and fate at a catchment scale. [Display omitted] •Though zinc is essential for life, in excess it may be toxic to organisms.•Many human activities mobilize & spread large quantities of Zn in the environment.•Determining the origin of Zn in rivers is a key factor to improve the water quality.•Main zinc anthropogenic inputs have δ66/64Zn values distinct from natural inputs.•δ66/64Zn values are a useful tool to trace metal sources at a catchment scale.