Mercury isotopes in the atmosphere: Synthesis, perspectives and analytical considerations

Abstract

Mercury (Hg) transport in the atmosphere plays a critical role in its global distribution, although it is not yet fully understood. The use of Hg stable isotopes in atmospheric studies has gained significant attention due to advances in technology, enabling precise isotope measurements even at low concentrations. Isotopic analysis is key to identifying Hg sources and understanding processes crucial for implementing the Minamata Convention. Our review synthesizes published data on atmospheric Hg isotopes, showing that mass-dependent fractionation (δ²⁰²Hg) is effective at differentiating between sampling sites, while mass-independent fractionation (Δ¹⁹⁹Hg) reflects photochemical transformations. Natural and anthropogenic emissions can be distinguished by isotope composition (natural: δ²⁰²Hg = −0.1 ‰, Δ¹⁹⁹Hg = −0.1 ‰; anthropogenic: δ²⁰²Hg = −1.6 ‰, Δ¹⁹⁹Hg = −0.3 ‰). Some preconcentration methods, however, may introduce biases and complicate the interpretation of Hg isotopic fingerprints. We offer recommendations to address these challenges and improve future studies of atmospheric Hg isotopes for more reliable analysis.