Ruoyu Sun

The rise of mercury since the Industrial Revolution is regarded as a global signature of industrialisation. We use lake sediment records from sub-Antarctic Macquarie and Campbell Islands spanning the period before and after 1850 Common Era (CE) to investigate how local colonial disturbance influences mercury sources and cycling. Although mercury accumulation increased 1.1- to 74-fold across all lakes following European arrival (1810 CE), isotope responses were lake specific. Our findings identify colonisation as an unrecognised driver of mercury cycling that can override the global industrialisation signature in the Southern Hemisphere. Colonisation-driven ecological changes, including the introduction of invasive rabbits altered mercury cycling through two connected processes. Firstly, vegetation disturbance and erosion increased catchment-derived mercury. Secondly, marine biological mercury cycling shifted to terrestrial biological cycling through food web reorganisation. These responses reveal that colonisation, primarily through the introduction of invasive species, was a significant driver of Anthropocene mercury cycling, alongside industrialisation.

Mercury (Hg) concentrations and isotope compositions preserved in sedimentary successions provide important information for investigating long-term Hg cycling, volcanism, environmental perturbations, and Earth-system evolution. During the past decade, the rapid expansion of sedimentary Hg research has generated a large volume of concentration and isotope data. However, these data remain dispersed across individual studies and are reported using heterogeneous stratigraphic frameworks, metadata conventions, and analytical formats, limiting their accessibility and large-scale reuse. Here we present DeepSedHg (Deep-time Sedimentary Mercury Concentrations and Isotope Compositions) database, a comprehensive global compilation of published sedimentary Hg concentrations and isotope records spanning approximately 2.7 billion years of Earth history. DeepSedHg version 1.0 integrates data from 199 peer-reviewed publications published between 2010 and February 2026 and contains 28264 sample-level records. The database includes 27,990 Hg measurements, of which 3,736 contain both concentration and isotope data. Each record is accompanied by standardized metadata describing stratigraphy, numerical age, lithology, depositional environment, geographic location, paleogeographic position, and associated geochemical parameters. All records were subjected to systematic data harmonization and quality-control procedures, including duplicate screening, metadata verification, chronostratigraphic standardization, coordinate validation, and consistency checks of geochemical variables. The resulting database provides broad temporal, spatial, and environmental coverage of sedimentary Hg records and is distributed in a machine-readable format together with comprehensive metadata documentation. DeepSedHg is publicly available through Zenodo (https://doi.org/10.5281/zenodo.20713398) and an online tool (https://deepsedhg.pages.dev, which is intended to support future synthesis studies, meta-analyses, data-driven investigations, and interdisciplinary research on Hg cycling and environmental change throughout Earth history.

During the Toarcian Oceanic Anoxic Event (T-OAE, ~ 183 Ma), marine primary productivity (MPP) exhibited pronounced spatial heterogeneity, with limited organic carbon burial in many regions and unclear mechanisms for its subsequent recovery. Here, we present high resolution mercury isotopes, nitrogen and sulfur isotopes, iron speciation, and redox data from a marine sedimentary succession in the Neuquén Basin, Argentina, to investigate post T-OAE MPP recovery in a back-arc setting. Our results demonstrate that subaerial arc volcanism significantly intensified terrestrial chemical weathering (CIA from ~ 46 to ~ 70), enhancing terrestrial phosphorus input to the ocean. The resulting phosphorus supply exceeded nitrogen availability, triggering nitrogen fixation (δ¹⁵N _bulk from + 13.81‰ to + 2.81‰), which effectively alleviated nitrogen limitation and sustained elevated MPP (TOC from < 1 wt% to 3.75 wt%). The increased organic carbon burial further promoted the upward migration of the sulfate reduction zone toward the sediment–water interface, enhancing sulfate supply and sulfur isotopic fractionation (as recorded by strongly negative δ³⁴S _py values). This study demonstrates that regional arc volcanism acted as a key driver of post T-OAE marine productivity recovery by modulating weathering and nutrient cycling, providing new insights into the recovery of marine ecosystems after a major oceanic anoxic event.

The Paleocene–Eocene Thermal Maximum (PETM) coincided with North Atlantic Igneous Province emplacement, but volcanic versus surface carbon sources remain debated. Here, we present high resolution Hg concentration and isotope data from the United States Mid-Atlantic Shelf, revealing a pronounced Hg increase (2–3 times background) coincident with the PETM onset, together with a significant negative shift in Δ¹⁹⁹Hg (down to − 0.24‰). A Hg isotope mixing model indicates that more than half of the Hg was derived from terrestrial soil or sedimentary rocks. Mercury is often stored in vegetation, soils and sedimentary rocks in close association with organic matter, and the Hg-isotope evidence for enhanced Hg release from these reservoirs provides further evidence for enhanced organic carbon oxidation. We explore whether these Hg data can be used as an independent approach to quantitatively assess total organic carbon (including both fossil and soil carbon) oxidation due to terrestrial erosion. Our estimates arrive at ~ 1400 Pg C release under an average scenario and up to ~ 4520 Pg C (upper limit), supporting the hypothesis that terrestrial carbon mobilization constituted an important contributor to a positive feedback on PETM hyperwarming.

Understanding how inorganic mercury (IHg, primarily Hg(II)) and methylmercury (MeHg, primarily monomethylmercury) transform and cycle in coastal food webs is essential for evaluating Hg exposure risks, yet relevant species-specific mercury (Hg) isotope studies remain scarce. Here, we optimized a purge-trap method that enabled efficient separation and isotopic analysis of IHg and MeHg in marine organisms. Applying this method to surface and benthic organisms collected from the Bohai Sea in winter and summer, we reveal distinct seasonal and habitat-specific Hg dynamics. Surface organisms primarily accumulated MeHg that had undergone photodemethylation in the water column, while benthic organisms assimilated a mixture of photodegraded water-column MeHg (64–80%) and nonphotodegraded MeHg produced in sediments (20–36%). In vivo MeHg demethylation was substantially enhanced in surface organisms during summer, contributing ∼36% of the organismal IHg pool. Species-specific isotope signatures further suggest that methylation of IHg in sediments is a major source of MeHg to the water column, with ∼14–19% of it being photodegraded before biological uptake. Together, these findings provide new mechanistic insight into coastal Hg cycling and advance the isotopic framework for assessing ecological risks associated with marine Hg exposure.

Evaluating the effectiveness of the Minamata Convention requires a clear understanding of how emission controls reshape atmospheric mercury (Hg) budgets. Here, we present a multi-year investigation of gaseous elemental Hg (GEM) concentrations and isotope compositions in urban Tianjin, China, spanning three distinct periods: a pre-control phase (2018), the COVID-19 lockdown (2021–2022), and a post-pandemic phase under strengthened controls (2024–2025). By integrating long-term monitoring with isotope-based source apportionment, we capture changes in Hg sources and processes that are not evident from concentration data alone. Mean GEM concentrations declined sharply from pre-control levels (∼4.6 ng m⁻³) to regional background values (∼1.5 ng m⁻³) during the COVID-19 lockdown, with no rebound following the resumption of socioeconomic activities. This sustained decline was accompanied by a pronounced isotopic transition, from negative δ²⁰²Hg and near-zero Δ¹⁹⁹Hg and Δ²⁰⁰Hg values characteristic of primary anthropogenic emissions to near-zero to positive δ²⁰²Hg and negative Δ¹⁹⁹Hg and Δ²⁰⁰Hg values indicative of the regionally well-mixed background Hg pool. Comparisons with other cities in China and South Asia further demonstrate that effective emission controls drive convergence toward background-like GEM concentrations and isotopic signatures. Isotopic mixing models indicate that the collapse of primary anthropogenic emissions accounted for nearly all of the observed concentration decline since the 2020s. Together, our results reveal a fundamental regime shift in urban atmospheric Hg cycling from local primary emission-dominated to background-dominated conditions modulated by secondary surface processes.

Photochemical and microbial-mediated reduction of mercury (Hg) are recognized as key processes and pathways for Hg geochemical cycling and atmospheric emissions. However, these processes cannot fully account for the total budget of global elemental Hg(0) production. Here we show that net Hg(0) production is significantly enhanced in a goethite-Hg(II)-DOM ternary system under dark conditions, representing a ubiquitous mineral-organic interface in surface ecosystems. This enhancement arises from the combined effects of preferential adsorption of monodentate [Hg-DOM] ⁺ complexes, retention of electron-donating DOM in the aqueous phase, and lower interfacial energy barriers for Hg(II) reduction by goethite. We estimate that ternary interactions, as an underappreciated source of terrestrial Hg(0) emissions, release about 6.3% of topsoil Hg to the atmosphere. These findings underscore the need to integrate mineral-Hg(II)-DOM ternary systems into predictive models of the global Hg cycle and associated ecological risks.

Evaluating the effectiveness of the Minamata Convention requires a clear understanding of how emission controls reshape atmospheric mercury (Hg) budgets. Here, we present a multi-year investigation of gaseous elemental Hg (GEM) concentrations and isotope compositions in urban Tianjin, China, spanning three distinct periods: a pre-control phase (2018), the COVID-19 lockdown (2021–2022), and a post-pandemic phase under strengthened controls (2024–2025). By integrating long-term monitoring with isotope-based source apportionment, we capture changes in Hg sources and processes that are not evident from concentration data alone. GEM concentrations declined sharply from pre-control levels (~4.6 ng m⁻³) to regional background values (~1.5 ng m⁻³) during the COVID-19 lockdown, with no rebound following the resumption of socioeconomic activities. This sustained decline was accompanied by a pronounced isotopic transition, from negative δ²⁰²Hg and near-zero Δ¹⁹⁹Hg and Δ²⁰⁰Hg values characteristic of primary anthropogenic emissions to near-zero to positive δ²⁰²Hg and negative Δ¹⁹⁹Hg and Δ²⁰⁰Hg values indicative of the regionally well-mixed background Hg pool. Comparisons with other cities in China and South Asia further demonstrate that effective emission controls drive convergence toward background-like GEM concentrations and isotopic signatures. Isotopic mixing models indicate that the collapse of primary anthropogenic emissions accounted for nearly all of the observed concentration decline since the 2020s. Together, our results reveal a fundamental regime shift in urban atmospheric Hg cycling from local primary emission-dominated to background-dominated conditions modulated by secondary surface processes.