Non-traditional stable metal and metalloid isotopes and their potential applications in earth, ocean, and environmental sciences

Recent technological advancement has revolutionized the field of non-traditional stable metal and metalloid isotopes for their wide range of applications, from the study of earth surface and interior processes, reconstructing past oceanic environments, tracing contaminants to biomedical investigations. Beyond the conventional stable isotopes (e.g., H, C, O, N, S), this field now explores a diverse array of stable isotopes (e.g., Li, B, Mg, Si, Ca, K, V, Cr, Ni, Fe, Cu, Zn, Sr, Mo, Cd, Ba, Hg, U) and their potential applications. This review delves into the applications of stable metal and metalloid isotopes as an important tool for tracing sources and elucidating various processes within the realm of earth, ocean, and environmental studies. The fundamental concept of mass-dependent and -independent isotope fractionations are introduced first in this article, followed by a discussion on the selected "emerging" stable isotopes like Li isotopes (δ⁷Li), B isotopes (δ¹¹B), and Mo isotopes (δ⁹⁸Mo) and highlighted their applications as a proxy for earth surface processes, paleo-pH, and paleo-redox conditions in oceans respectively ; various measurement techniques and their advantages/disadvantages including chemical extractions of elements of interest and their isotope measurements using a Multi-Collector Inductively Coupled Plasma Mass Spectrometer (MC-ICPMS). Finally, this article highlights the caveats and limitations, challenges, and scopes for future research in the field of non-traditional stable isotopes.