Stable isotopic signature of cadmium in tracing the source, fate, and translocation of cadmium in soil: A review

Cadmium (Cd), one of the most severe environmental pollutants in soil, poses a great threat to food safety and human health. Understanding the potential sources, fate, and translocation of Cd in soil-plant systems can provide valuable information on Cd contamination and its environmental impacts. Stable Cd isotopic ratios (δ114/110Cd) can provide "fingerprint" information on the sources and fate of Cd in the soil environment. Here, we review the application of Cd isotopes in soil, including (i) the Cd isotopic signature of soil and anthropogenic sources, (ii) the interactions of Cd with soil constituents and associated Cd isotopic fractionation, and (iii) the translocation of Cd at soil-plant interfaces and inside plant bodies, which aims to provide an in-depth understanding of Cd transport and migration in soil and soil-plant systems. This review would help to improve the understanding and application of Cd isotopic techniques for tracing the potential sources and (bio-)geochemical cycling of Cd in soil environment. Cadmium is one of the most severe environmental pollutants in soil, but Cd fate in soil is affected by multiple sources, soil constituents, and (bio)geochemical processes. The stable Cd isotopic technique is a powerful tool to improve the understanding of Cd fate in soil-plant systems. This review introduces the potential Cd sources and tracing models, Cd interactions with typical soil constituents, and Cd translocation in soil-plant systems, and also highlighted the current limitations of stable isotopic technique, which provides a novel insight to understand Cd biogeochemical cycling in soil-plant system and environmental effects on human health.