Felsic volcanism in South China with Cu, Hg, and S released exacerbated environmental changes that drove the end-Permian extinction.

The Hg isotopic signature may provide insight into tracking the sources and pathways of both airborne particulate matter (PM) and particle-bound Hg (PHg) in the atmosphere. However, separating and concentrating trace levels of PHg and accurately analyzing its isotope ratios remain a technical challenge. Here, we optimized a combustion-trapping dual-stage protocol specifically for the pre-concentration of Hg from a PM sample collected on a quartz fiber membrane (QFM) for high-precision Hg isotopic analysis. The protocol was validated by testing synthetic samples of varying concentrations and trapping solutions of different volumes, and by comparison with two conventional methods (acid digestion and column purification). Using the dual-stage protocol, an individual sample containing up to 570 ng of Hg can be combusted at programmed temperatures in an Hg-free O₂ stream, and the volatilized gaseous Hg was trapped in a 5 mL acid (4 M HNO₃ and 1.3 M HCl) mixture. The method results in a relatively lower procedural blank and quantitative recovery (99 ± 6%, 2SD, n = 90). Long-term measurements of three certified reference materials (CRM021, CRM024, and GBW07405) with complex matrices using the optimized protocol gave identical Hg isotopic ratios of both mass-dependent fractionation (MDF) and mass-independent fractionation (MIF), in agreement with the results obtained from the standard addition method. The protocol was applied to two PM_2.5 samples collected on a 20.3 × 12.5 cm QFM. The result showed evident variations of both MDF and MIF, highlighting the importance of studying Hg isotopic compositions in PM of variable environments in order to fully understand the behaviors of Hg and its isotopes in the atmosphere.

The element mercury (Hg) can develop large mass‐independent fractionation (MIF) (Δ¹⁹⁹Hg) due to photo‐chemical reactions at Earth's surface. This results in globally negative Δ¹⁹⁹Hg for terrestrial sub‐aerially‐derived materials and positive Δ¹⁹⁹Hg for sub‐aqueously‐derived marine sediments. The mantle composition least affected by crustal recycling is estimated from high‐³He/⁴He lavas from Samoa and Iceland, providing an average of Δ¹⁹⁹Hg = 0.00 ± 0.10, Δ²⁰¹Hg = −0.02 ± 0.0.09, δ²⁰²Hg = −1.7 ± 1.2; 2SD, N = 11. By comparison, a HIMU‐type lava from Tubuai exhibits positive Δ¹⁹⁹Hg, consistent with altered oceanic crust in its mantle source. A Samoan (EM2) lava has negative Δ¹⁹⁹Hg reflecting incorporation of continental crust materials into its source. Three Pitcairn lavas exhibit positive Δ¹⁹⁹Hg which correlate with ⁸⁷Sr/⁸⁶Sr, consistent with variable proportions of continental (low Δ¹⁹⁹Hg and high ⁸⁷Sr/⁸⁶Sr) and oceanic (high Δ¹⁹⁹Hg and low ⁸⁷Sr/⁸⁶Sr) crustal material in their mantle sources. These observations indicate that MIF signatures offer a powerful tool for examining atmosphere‐deep Earth interactions.