It is widely accepted that global cooling since the Late Miocene, particularly the Northern Hemisphere glaciation, has led to a progressive weakening of the East Asian summer monsoon and intensified aridification of Asian inland. Here we present a detailed record of monsoon precipitation over the past 7 Ma, retrieved from two carbonate carbon isotope profiles from the Chinese Loess Plateau (CLP). Our results show that the CLP at the northern edge of the East Asian summer monsoon has been getting wetter rather than drier since similar to 2.7 Ma. This climatic reversal coincided with the increased aridification in Central Asia. Combined with climate model simulations and existing Asia-Pacific hydroclimate records, we suggest that the Westerlies-monsoon interaction forced by the Northern Hemisphere glaciation, induced both a differential evolution of the East Asian summer monsoon at mid- and low-latitudes and an east-west antiphased precipitation change over the mid-latitude Asia since similar to 2.7 Ma. Specifically, the Northern Hemisphere glaciation, and the associated 'Arctic Amplification' intensified and shifted westerlies southward after similar to 2.7 Ma that blocked the northwestward invasion of monsoon moisture, thereby simultaneously drying Central Asia and placing more precipitation to North China. Our findings challenge the prevailing view of the evolution of Asian inland deserts and monsoon, and provide new insights into Asian climate change in the context of interactions between the Westerlies and the East Asian summer monsoon.

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 (similar to 4.6 ng m-3) to regional background values (similar to 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 delta 202Hg and near-zero Delta 199Hg and Delta 200Hg values characteristic of primary anthropogenic emissions to near-zero to positive delta 202Hg and negative Delta 199Hg and Delta 200Hg 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.

This study has conducted an analysis of the helium abundance, enrichment mechanisms, and sources in coalbed methane (CBM) from the Luling coal mine in the Huaibei Coalfield, China. Geochemical testing results indicate that the helium concentration in the coalbed methane is significantly higher than atmospheric levels but below the threshold for industrial exploitation, indicating that the reservoir is helium-lean and remains below commonly cited commercial extraction thresholds order of 0.1

The Skagerrak-Centered large igneous province (SCLIP) was active 299 million years ago when Earth's climate transitioned into an interval of intensified glaciation. A link between the SCLIP and global climate change has been hypothesized but there is little direct evidence of concurrent volcanism and climate change in coeval sedimentary layers from the late Carboniferous to the early Permian. We combined carbon isotopes, mercury contents and isotopes, and elemental geochemistry of the Taiyuan Formation in the Hedong Coalfield, North China to identify two episodes of volcanism during the early and late Gzhelian (latest Carboniferous). Both episodes are marked by Hg enrichments, positive Delta 199Hg excursions and negative delta 13Corg excursions; only late Gzhelian volcanism was associated with reduced rates of continental weathering and was followed by global cooling. We hypothesize that the late Gzhelian volcanic episode had a greater environmental impact than that in the early Gzhelian because late Gzhelian volcanism was likely more intense and of longer duration. The SCLIP may have contributed to global cooling via the release of sulfate aerosols that results in atmospheric cooling and/ or from ocean fertilization and increased removal of organic carbon via the biological pump.

Continental weathering regulates global carbon sequestration by delivering essential nutrient elements, such as zinc (Zn), to the oceans via river discharge. This influx of Zn influences marine phytoplankton growth and, in turn, helps regulate Earth's climate. While silicate weathering has traditionally been recognized as the primary mechanism for land-to-ocean nutrient transport, growing evidence suggest that carbonate dissolution may also play a substantial role in contributing to the marine nutrient pool. In this study, using Zn isotopes as tracers, we systematically evaluate the contribution of continental weathering, with a focus on carbonate dissolution, to marine Zn influx, employing data from the Pearl River as a representative case and expanding the analysis to a global scale. Our results show that carbonate dissolution is the dominant source of dissolved Zn in the Pearl River, leading to the delta Zn-66 value up to similar to 1 parts per thousand, significantly higher than that derived from weathered silicates. In the estuary, however, anthropogenic inputs significantly increase the Zn loads, resulting in a substantial decrease in the delta Zn-66 of river water flowing into the ocean. Extrapolating our result to a global dataset of 49 major rivers provides a preliminary estimation that carbonate weathering could account for a large contribution to total marine Zn influx, which requires to be well investigated in future studies.

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.

Mercury (Hg) stable isotopes have emerged as a powerful tracer to resolve the sources, transformations, and deposition pathways of atmospheric Hg. Beyond conventional mass-dependent fractionation (MDF), atmospheric reactions can induce unique Hg mass-independent fractionation (MIF). This review synthesizes current sampling strategies and pretreatment protocols for gaseous Hg(0) and reactive Hg(II) in particulates and precipitation, and compiles their isotope compositions (S202Hg for MDF, p199Hg for odd-MIF and p200Hg for even-MIF) across terrestrial background, urban-industrial, marine boundary layer, and polar regions. Terrestrial background Hg(0) typically exhibits positive S202Hg with negative p199Hg and p200Hg, whereas reactive Hg(II) shows negative S202Hg with positive p199Hg and p200Hg. These complementary patterns reflect predominant roles of photoreduction of Hg(II) and vegetation uptake of Hg(0). Urban-industrial Hg(0) tends to have low S202Hg and elevated p199Hg and p200Hg, consistent with anthropogenic influence. However, post-emission transformations frequently obscure primary isotope signatures of Hg(II), complicating source-receptor relationships. In polar regions, reactive Hg (II) bears strong imprints of photoredox reactions at the snow-atmosphere interface, typically exhibiting very negative p199Hg values. Integrating isotope observations with deposition pathways indicates that dry deposition of Hg(0) often dominates fluxes to both terrestrial and marine surfaces. Scenario analysis under Shared Socioeconomic Pathways project notable increases in S202Hg and p199Hg under low-emission futures. To better implement the Minamata Convention in a changing climate, future research should prioritize species-specific Hg sampling, better mechanistic understanding of isotope fractionation, and expanded isotope monitoring in underrepresented regions.

Mercury (Hg) stable isotopes are increasingly used to reconstruct volcanic activity and ocean redox conditions in geological deep time, but the primary sedimentary signals may be modified by water-column and early diagenetic processes, potentially complicating their paleoenvironmental implications. Here we investigate Hg concentrations and isotopic compositions in organic-rich sediments collected along a shelf-to-slope transect across the Namibian continental margin in the Benguela Upwelling System, which spans contrasting depositional settings and redox conditions associated with a persistent oxygen minimum zone. We found that while all sites share the same primary Hg source (atmospheric deposition), they differ markedly in Hg distribution and isotope signatures. The suboxic shelf break site (GC4) has the lowest Hg content, highest Hg/TOC, and lightest δ202Hg, whereas the oxic slope site (GC5) has higher Hg content, lower Hg/TOC, and substantially heavier δ202Hg (by 0.43‰) but similar Δ199Hg (∼0.15–0.16‰). These contrasts are consistent with lateral sediment transport and redeposition, during which oxidative loss of organic matter and Hg repartitioning preferentially retain lighter Hg isotopes at the remobilization site while exporting heavier Hg to the slope, producing substantial mass-dependent fractionation but little mass-independent fractionation. In contrast, the highly productive anoxic shelf site (25020) shows higher Δ199Hg (0.22 ± 0.06‰, 2SD) and δ202Hg (0.14 ± 0.13‰) than the other sites, a pattern that is likely caused by upwelling-driven Hg recycling, whereby Hg(II) and methylmercury in anoxic bottom waters and sediments are returned to the surface ocean and photochemically reprocessed, resulting in positive shifts in both Δ199Hg and δ202Hg in the residual Hg pool.Our results demonstrate that sediment reworking and upwelling-driven Hg recycling may substantially alter the sedimentary Hg distribution and isotopic signatures. Thus, the application of Hg and its stable isotopes as paleoenvironmental tracers requires careful consideration of the impact of depositional environment and local redox conditions. More broadly, our findings also highlight the potential of Hg isotopes as a tracer of ancient upwelling systems and the associated ocean anoxia.

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.

Inert gases in CBM, such as helium (He) and argon (Ar), serve as important geochemical tracers that aid in studying the origin of CBM. In this study, 12 CBM samples were collected from the Luling coal mine in the Huaibei Coalfield. Gas composition analysis was conducted on these samples to measure the concentrations of methane, N2, CO2, He, and Ar. Additionally, the isotopic compositions of helium and argon in the gas samples were analyzed.Methane is the most prominent component in CBM, with concentrations ranging from 91.80

The Late Triassic Carnian Pluvial Event has been widely attributed to massive CO 2 and CH 4 emissions and global warming associated with activity of the Wrangellia Large Igneous Province (LIP). Global warming led to increased denitrification and disruption of the nitrogen cycle. However, the mechanistic links between volcanism and climatic shifts remain incompletely resolved, particularly due to the lack of mercury (Hg) and nitrogen (N) isotope constraints in terrestrial sections. Here, we present a lacustrine succession in the Tarim Craton of northwestern China. Hg concentration and isotope anomalies record the signal of Wrangellia LIP activity, the probable source of released carbon that drove global warming and changes in the nitrogen cycle. The study section preserves four horizons showing increases of Hg contents and Hg isotopic anomalies (i.e., increases of Delta 199 Hg to 0 to +0.2%o relative to background Delta 199 Hg of -0.05%o) that we interpret to represent discrete episodes of volcanic emissions from the Wrangellia LIP (100-600 kyr). The first three episodes became progressively increasing volcanic Hg contributions, whereas the fourth (final) episode was distinctly weaker in intensity. The delta 15 N isotope data show a positive correlation with Delta 199 Hg, reflecting a convergent trend of change. These data support a global greenhouse effect triggered by excess carbon dioxide released into the atmosphere from volcanic eruptions, which we infer stimulated denitrification in water bodies, thereby generating more nitrous oxide (which has -300 & times; the warming potential of carbon dioxide per molecule) and exacerbating Late Triassic warming. The four Hg anomalies were followed by negative Delta 199 Hg excursion, which was related to enhanced terrigenous Hg deposition that may reflect volcanism-induced climate change in the terrestrial environment and subsequent feedbacks through weathering and denitrification. Our results are significant in (1) providing evidence linking the Late Triassic CPE to volcanic activity (possibly of the Wrangellia LIP), (2) documenting for the first time four volcanic eruptions corresponding to four known global negative carbon isotope excursions (NCIEs), and (3) highlighting the potential for nitrogen-cycle climate feedbacks leading to extreme greenhouse warming at short timescales as well as climate feedbacks at longer timescales. These findings have implications for the operation of N-cycle feedbacks in the modern climate system and the future trajectory of present-day climate change.

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.

It is not uncommon for coalfields to be affected by igneous intrusions, but the formation mechanism of mineral and chemical composition in thermally altered coals (TACs) during the rock-coal contact metamorphism is not yet fully understood, although there have been a number of studies. The present study reports effects of a mafic/intermediate sill (porphyrite) on the mineralogy and geochemistry of low-sulfur (total sulfur content 0.24%-0.56%, dry basis) coals in the Zhangzhuang Mine of the Huaibei Coalfield, eastern China. The porphyritic sill intruded along the coal seam roof. Towards the intrusion, the coal random vitrinite reflectance values increase from 1.38% (for the unaltered coal) to 5.19% (for the TAC). Similarly, the moisture content and ash yield of coals increase closer to the intrusion, whereas the volatile matter yield, nitrogen, hydrogen, and sulfur contents tend to decrease. The intrusion-related hydrothermal affected zone in coal is estimated as thick as 100-cm, especially in the zone of 0-10-cm concentrated below the sill. Minerals present in the TACs consist mainly of clay minerals (kaolinite, illite, and chamosite), carbonate minerals (Fe-containing dolomite, ankerite, and calcite), and quartz. Most of these minerals are suggested to be epigenetic, forming under intrusion-related hydrothermal influence. The enrichment of Mn, Zn, and Sr in the TACs is closely related to carbonate minerals directly precipitated from hydrothermal fluids, whereas the enrichment of Ba, Cr, Ni, Rb, Tl, Cu, and Pb associated with clay minerals that might form indirectly due to the clay alteration and adsorption. The abnormal enrichment of Hg in the coal closest to the intrusion may be caused by its adsorption onto carbonate minerals. The depletion of Be and Co in the TACs is principally associated with organic matter affected by igneous intrusion. The concentrations of V and U are unaffected, which is mainly related to clay minerals with minor portion associated with organic matter.

Climatic warming and the resulting increase in soil respiration affect the sequestration and transformation of soil components, as well as their transport to the surrounding ecosystems. However, the integrated mechanistic details of these processes remain elusive. Here we apply an extraction protocol that utilizes two sequential extraction techniques to isolate and analyze both dissolved and solid-state soil components and to assess their dark and photoinduced fates under varying temperature conditions, intended to simulate global warming. We observe a net increase in total sulfur (1.2-41.0%), which is ascribed to S sequestration-redox reactions involving both sulfide oxidation to So ⇌ SO42- and the reverse (S2-/S22- ⇌ SO42-) via SO42- plus soil organic sulfur plus sulfides/pyrites (SOS + Sn2-) decrease and/or increase under sunlight, dark, and control conditions. Higher transformation and mineralization of various components occurs in dark/microbial conditions by the wide day-night experimental temperature variation (10-42 °C) in comparison with the control at constant temperature (25 °C). Remarkably, the photosynthetically-derived soil organic carbon (SOC)/humic substances (HS)-bound mineral neoformation through uptake and sequestration of various components, including As and Hg, is specifically detected under sunlight and control conditions. A major role is played by seven redox-active metals (Fe, Mn, Cu, Hg, Ni, As, and U), which are involved in both organo-mineral complexation and redox processes. Importantly, the dark/microbial dissolution of iron minerals is primarily responsible for the increased export of water-extractable or labile As (33.8-89.7%) over a period of 0-150 days, with no evidence of sequestration. In contrast, As sequestration and relatively low water-extractable As export occur under sunlight (9.0-25.5%) and control (17.4-38.4%) samples. A net decrease in Hg levels is observed over a period of 0 to 150 days, along with relatively low sequestration across three treatments, appearing the highest losses under sunlight conditions (9.8-17.4%) when compared to dark (5.2-11.4%) and control (3.6-11.6%) samples. This effect may be attributed to the reduction of Hg(I, II)‒DOM into gaseous Hg⁰. These findings could assist in managing soil components and predicting where and when the side effects of global warming-such as erosion-associated mobilization of soil components, including As and Hg into surrounding surface water, groundwater, and the atmosphere-are likely to manifest.

Legacy gold mining in Australia, closely tied to 19th-century colonisation and predating environmental protection laws, has left substantial mercury (Hg) contamination. Historical records in Walhalla, Victoria, indicate that Hg loss via the amalgamation process between 1867 and 1889 ranged between 2.65 tonnes and 34.4 tonnes, with further emissions in the following two decades. Dendrochemical analysis of exotic gymnosperms planted in Walhalla provides the first chronological record of colonial-era Hg emissions in Victoria. Local Bhutan cypress (Cupressus torulosa) and Douglas fir (Pseudotsuga menziesii) show elevated Hg during the peak of mining (1885-1914), reaching 44 ± 17 ng g-1 and 29 ± 9 ng g-1 respectively. Additionally, soils near gold-processing sites contain Hg at concentrations 2.5 orders of magnitude greater than background concentrations (41 ± 34 mg kg-1). Stringers Creek sediments exceed the Australian high risk sediment guideline by 22 times (3.3 ± 3.4 mg kg-1). Methylmercury (MeHg; 9.4 ± 10.8, max 32 ng g-1) content of some waterfall sediments is in the global top 10 %. The nonlinear MeHg - total Hg relationship (Spearman ρ = 0.93, p = 0.005) suggests reduced methylation efficiency under high Hg loading. In soils, the relationship between total Hg vs. organic matter relation (R2 = 0.47) indicates organic content is a driver of Hg retention. This study establishes an "emission-dendrochemistry-environment" evidence chain, confirming 19th-century mining as a major Australian Hg source with enduring ecological impacts and provides critical information that must be incorporated into national Hg management strategies.

High-precision analysis of mercury (Hg) isotope compositions is fundamental for tracing the Hg cycle in the environment. However, accurate and precise Hg isotope analysis for samples with low Hg concentrations (sub-ppb level) remains one of the most prominent challenges in the analysis and application of Hg isotopes. In this study, we developed a new method for high-precision Hg isotope analysis using a dry cold vapor generation (dry-CVG) system coupled to MC-ICP-MS. The dry-CVG system removed water content from the Hg(0) cold vapor and thus significantly inhibited the formation of oxides and hydrides, providing better signal intensity, stability and precision for Hg isotope analysis. Under optimized conditions, the analytical uncertainties were +/- 0.07 parts per thousand and +/- 0.06 parts per thousand (2SD) for delta 202Hg and Delta 199Hg, respectively at a concentration of 0.1 ng mL-1 (0.75 ng Hg consumption), which is comparable to the typical precision reported in the literature but obtained at 10-fold higher Hg concentrations. Moreover, our method substantially improved the precision for Hg isotope analysis at higher concentrations (>= 2.0 ng mL-1), reaching +/- 0.02 parts per thousand and +/- 0.01 parts per thousand (2SD) for delta 202Hg and Delta 199Hg, respectively. The accuracy and precision of this method were further verified using a variety of certified reference materials with different types of natural matrices (including plant, soil and sediment). Thus, our method provides a promising approach for accurate Hg isotope analysis at low concentrations with high precision, and may expand the future application of Hg isotopes in geochemical and environmental studies.

Abstract Although mercury (Hg) is a neurotoxic metal of global relevance, its Antarctic biogeochemical cycles are not well characterized. Here, we present the total Hg (THg) distribution and stable isotopic fractionation between the Zhongshan Station and Dome A (1,248 km), in eastern Antarctica, to characterize THg sources and controlling factors. Surface snow samples and snow blocks similarly exhibited higher THg concentrations in the coastal and interior sections than the intermediate section. From the THg distribution and stable isotopic fractionation (notably for 200Hg and 202Hg), we inferred an adjacent oceanic Hg source for the coastal section and primary oceanic sources at 63°S–55°S and 50°S–45°S for the intermediate and interior sections, respectively. Snow drifting and postdepositional effects also influenced THg concentrations and stable isotopic fractionation, particularly in areas with marked terrain slope variations. Finally, the stratospheric contribution of THg near Dome A was negligible, with a possible transport pathway through the lower troposphere.