Hg Emissions Research Articles

Mercury Stable Isotope Composition of Lichens and Mosses from Northern Eurasia Reveals Hg Deposition Pathways and Sources

Mercury (Hg) concentrations in lichens and mosses can be used as surrogates for atmospheric Hg deposition to continental surfaces. In this study, we collected and analyzed Hg concentrations (n = 334) and isotopic composition (n = 67) of epiphytic tree lichens and terricolous lichens and mosses from remote locations across the Eurasian Arctic and sub-Arctic (50 to 72° N, 30 to 180° E). The total Hg (THg) concentrations ranged from 13 to 7700 ng g–1. Epiphytic tree lichens had significantly higher median THg levels (243 ng g–1) than terricolous lichens (35 ng g–1) and mosses (74 ng g–1). THg is substantially higher in both tree lichens and terricolous lichens near the Arctic Ocean shore and up to 300 km inland. The combined δ202Hg, Δ199Hg, and Δ200Hg signatures suggest that the elevated coastal Hg levels are delivered by marine air masses rich in gaseous and particulate-oxidized HgII forms, such as HgBr2. Similar to other vegetation Hg isotope studies, inland terricolous lichen and moss Δ200Hg are near zero, indicating a dominant (63%) atmospheric Hg0 origin followed by HgII wet and dry deposition. Inland tree lichens carry a more positive Δ200Hg of 0.15‰, similar to the atmospheric HgII end-member, suggesting that they preferentially accumulate HgII wet and dry deposition compared to colocated terricolous lichens. Mosses from the European sub-Arctic show a low δ202Hg of −3.1‰, which we speculate to result from regional soil Hg0 emissions that are recaptured by mosses. Overall, the Hg isotope variability of mosses and lichens reveals latitudinal gradients in Hg deposition pathways and identifies preferential Hg0 or HgII uptake.

New utilizations of natural CuFeS2 as the raw material of Cu smelting for recovering Hg0 from Cu smelting flue gas

Limits on Hg0 emissions from Cu smelting flue gas (Cu-SFG) are stipulated severely by the Minamata Convention. In this work, acid-treated CuFeS2, derived from the simple acid treatment of natural CuFeS2 as the raw material of Cu smelting, was developed as a reusable sorbent to recover Hg0 in the Cu-SFG. Hg0 capture by natural CuFeS2 was closely related to the amounts of adsorption sites and active S22−. After acid treatment, not only the surface of natural CuFeS2 became porous and roughened, but also some impurities in it were removed; hence, more adsorption sites for Hg0 adsorption and more active S22− for oxidizing Hg0 adsorbed were formed on acid-treated CuFeS2, causing its superior performance in capturing Hg0. Moreover, after acid treatment and Hg0 capture, the property of natural CuFeS2 for Cu smelting barely varied, implying that the spent acid-treated CuFeS2 may be reused. Furthermore, most Hg0 in the Cu-SFG can be recovered as liquid Hg using the condensers in Cu smelters. Therefore, Hg0 recovery using acid-treated CuFeS2 was an economically viable and eco-friendly method to control Hg0 emissions from the Cu-SFG, double as a viable way to develop the new utilization of natural CuFeS2 as the raw material of Cu smelting.

Ecosystem Mercury Recovery and Health Benefit Under the Minamata Convention in a Changing Climate

Mercury (Hg) is a toxic metal that can be released from natural and anthropogenic processes. Gaseous elemental Hg is the main form of Hg in the atmosphere with a long residence time, allowing its long-range transport and deposition at a global scale. The deposited Hg can be transformed into methylmercuy (MeHg), which bioaccumulates and biomagnifies in aquatic ecosystems and is a known developmental neurotoxin to humans. Chronic exposure in pregnant women via fish consumption, even at the modest levels, can impact intellectual development in infants, which is considered as a global environmental health issue. To protect human health and the environment, the Minamata Convention on Mercury, a legally binding international treaty, entered into force in 2017 to reduce anthropogenic emissions and releases of Hg and Hg compounds. With the enforcement of the Convention, anthropogenic Hg emissions and releases are projected to decrease in the foreseeable future, but the recovery of the ecosystem and mitigation of health impact from Hg pollution are expected to lag behind. In this paper, we provide a critical review on the processes affecting when and to which extent Hg-affected ecosystems will recover under the Minamata Convention in the context of climate change and associated human health benefit. Our review is organized around seven major scientific questions. These seven questions covered historical Hg change in the ecosystem, major factors and processes, and future assessment. The impact of implementation of Minamata Convention and climate change on Hg emission, atmospheric transportation and deposition, biota accumulation, and human exposure should be comprehensively evaluated. The Hg stable isotope tool and process-based integrated global model should be integrated together, which also should consider future global social-economic pathways and mitigation options. We hope that the knowledge gaps and potential tools identified will assist the understanding of global biogeochemical cycling of Hg, inform policy-making on mitigation and community adaptation, and support the effectiveness evaluation and future improvement of the Minamata Convention on Mercury.Graphical Abstract

Migration and control of mercury in hazardous chemical waste incineration

This study evaluated the emission and control characteristics of mercury during hazardous chemical waste incineration. Meanwhile, for the complex flue gas conditions generated by hazardous chemical waste incineration, the commercial activated carbon used in the incineration system was modified with CuBr2, and its Hg0 removal performance was tested. The results showed that the major proportion of Hg was in the fly ash, and the content accounted for 74.53 % of the total Hg. The Hg content in the fly ash increased with decreasing fly ash particle size. In the exhaust flue gas, the Hg content was 11.05 % of the total Hg, in which the mass percentages of Hg2+ and Hg0 were 59.08 % and 40.92 %, respectively. The flue gas purification equipment of the incineration system had a removal efficiency of 92.40 % for HgT. The saturated Hg0 removal capacity of the modified activated carbon was improved by 33.51 times. Under simulated incineration flue gas conditions, the modified activated carbon was able to achieve an Hg0 removal efficiency of 92.85 %. The results can contribute to the understanding of Hg emissions from hazardous chemical incineration systems and provide guidance for efficient Hg removal from activated carbon.

Factors influencing mercury levels in Leach's storm-petrels at northwest Atlantic colonies

Mercury (Hg) is a globally distributed heavy metal, with negative effects on wildlife. Its most toxic form, methylmercury (MeHg), predominates in aquatic systems. Levels of MeHg in marine predators can vary widely among individuals and populations. Leach's storm-petrels (Hydrobates leucorhous) have elevated levels of Hg but the role of Hg in storm-petrel population declines is unknown. In this study, we used egg and blood samples to study variation in Hg exposure among several northwest Atlantic colonies during breeding seasons, thereby evaluating relative toxicity risk within and among colonies. Total mercury (THg) concentrations were higher with increasing colony latitude, and were more pronounced in blood than in eggs. THg concentrations in blood were mostly associated with low toxicity risk in birds from the southern colonies and moderate risks in birds from the northern colonies; however, those values did not affect hatching or fledging success. THg concentrations in both eggs and blood were positively correlated with δ34S, emphasizing the role of sulfate-reducing bacteria in methylation of THg acquired through marine food webs, which is consistent with enriched δ34S profiles. By associating tracking data from foraging trips with THg from blood, we determined that blood THg levels were higher when storm-petrel's intensive search locations were over deeper waters. We conclude that spatial variation in THg concentrations in Leach's storm-petrels is attributable to differences in ocean depth at foraging locations, both at individual and colony levels. Differences in diet among colonies observed previously are the most likely cause for observed blood THg differences. As one of the few pelagic seabird species breeding in Atlantic Canada, with limited overlap in core foraging areas among colonies, Leach's storm-petrels can be used as biomonitors for less sampled offshore pelagic regions. The global trend in Hg emissions combined with legacy levels warrant continued monitoring for toxicity effects in seabirds.

Fungal necromass presents a high potential for Mercury immobilization in soil

Past industrial activities have generated many contaminated lands from which Mercury (Hg) escapes, primarily by volatilization. Current phytomanagement techniques aim to limit Hg dispersion by increasing its stabilization in soil. Although soil fungi represent a source of Hg emission associated with biovolatilization mechanisms, there is limited knowledge about how dead fungal residues (i.e., fungal necromass) interact with soil Hg. This study determined the Hg biosorption potential of fungal necromass and the chemical drivers of passive Hg binding with dead mycelia. Fungal necromass was incubated under field conditions with contrasting chemical properties at a well-characterized Hg phytomanagement experimental site in France. After four months of incubation in soil, fungal residues passively accumulated substantial quantities of Hg in their recalcitrant fractions ranging from 400 to 4500 μg Hg/kg. In addition, infrared spectroscopy revealed that lipid compounds explained the amount of Hg biosorption to fungal necromass. Based on these findings, we propose that fungal necromass is likely an important factor in Hg immobilization in soil.

Total mercury concentrations in sharks, skates and rays along the South African coast.

Global declines in elasmobranch populations resulting from several stressors raises conservation concern. Additionally, apex predators bioaccumulate high concentrations of total mercury (THg), due to biomagnification. Although South Africa is considered one of the top ten contributors of Hg emissions globally, information on Hg concentrations in elasmobranchs is limited. The aim of this study was to evaluate the THg concentrations in 22 species of elasmobranchs along the South African coastline. Concentrations ranged between 0.22 and 5.8mg/kg in Haploblepharus pictus (dark shysharks) and Rostroraja alba (white skates) on the south coast, respectively. Along the east coast it ranged between 0.21 and 17.8mg/kg in Mobula kuhlii (shortfin devil rays) and Sphyrna lewini (scalloped hammerheads), respectively. Mercury concentrations on the east coast were in the same range or higher compared to the same species sampled between 2005-10 from the same region, with generally higher concentrations compared to the same species sampled globally.

The Release and Reduction of Mercury from Solid Fuels through Thermal Treatment Prior to Combustion

The main source of mercury (Hg) anthropogenic emissions is the combustion of hard and lignite coal in power plants. Reduction of Hg emissions from coal-based power production systems involves Hg removal from the fuel before combustion/gasification by thermal treatment (i.e., low-temperature pyrolysis). Herein, we present the results of laboratory and bench-scale studies on Hg removal from coal via thermal fuel treatment. The influence of the process temperature and coal residence time in the reaction zone on Hg removal efficiency and fuel parameters is studied. The properties of the process products are analyzed as follows: proximate and ultimate analysis for solids as well as H2, N2, CO, CO2, CH4, organic compounds C2–C5, density, and HHV for gaseous. The results show a substantial reduction of Hg in the fuel using a low-temperature pyrolysis process. At moderate pyrolysis temperature provided Hg removal efficiencies of up to 50% for hard coal and over 90% for lignite, with a moderate decrease in the chemical enthalpy of the fuel.

Assessment of tree-ring mercury radial translocation and age effect in Masson pine: Implications for historical atmospheric mercury reconstruction

The tree ring has been regarded as an emerging archive to reconstruct historical atmospheric mercury (Hg) trends, but with the large knowledge gaps in the reliability. In this study, we comprehensively evaluated the Hg source, radial translocation and age effect of Masson pine (Pinus massoniana) tree ring at Mt. Jinyun in Chongqing, to assess the suitability of such tree ring as the archive of atmospheric Hg. Results showed that distinct variabilities among Masson pine tree-ring Hg concentration profiles. The Hg concentration significantly increased along with stem height (P < 0.05), indicating the Hg in tree rings mainly derived from foliage uptake atmospheric Hg. We found a distinct age effect that the tree ring of young trees had the higher Hg concentration. Besides, we used the advection-diffusion model to demonstrate how Hg concentration shifted by the advection or/and diffusion in tree rings. The modeling results showed that the advection induced radial translocation during the young growth period of tree was a plausible mechanism to result in the tree-ring Hg record largely different from the trend of anthropogenic Hg emissions in Chongqing. We finally suggest that in further Hg dendrochemistry, better discarding the tree-ring Hg profile of the young growth period to reduce impacts of the radial translocation and age effect.

Understanding adsorption mechanisms of mercury over unburned carbon

Mercury (Hg) emissions from coal-fired power plants are extremely toxic and have caused widespread concern. Unburned carbon is considered as a promising adsorbent for the removal of elemental mercury (Hg0). However, the relationship between adsorption energy and adsorbent structure is still ambiguous. Here, we innovatively constructed a novel three-dimensional (3D) unburned carbon model to enrich the theoretical model in density functional theory calculation. Through comparing the adsorption energy, we found that the adsorption energy of Hg0 in 3D unburned carbon model is closer to experimental value than that of two-dimensional (2D) model, so we believe this novel 3D model with double defects should be a practical theoretical model of unburned carbon for exploring the relative reaction mechanism of unburned carbon. Based on 28 structures from the 3D model and 2D model, we performed various electronic structure analyses to obtain an intuitive understanding of adsorption mechanism of Hg0 at the atomic scale. Surprisingly, we found an obvious linear relationship between adsorption energy and minimum electrostatic potential (ESP) with a square correlation coefficient of 0.99, which delivers unprecedented details about the adsorption mechanism of Hg0 over unburned carbon. The expression of linear fitting is y = 1.19 x. We hope this linear relationship can facilitate the design of effective adsorbents for Hg0 and deepen fundamental understanding of removal mechanism of other flue gases by carbon-based adsorbents.

A high efficiency and high capacity mercury adsorbent based on elemental selenium loaded SiO2 and its application in coal-fired flue gas

Massive Hg emissions from coal-fired units cause serious environmental pollution and result in a substantial waste of Hg resources. In this study, the prepared millimeter-grade Se/SiO2 adsorbent was applied as a filler to adsorb mercury in a fixed-bed reactor to obtain the high value-added product HgSe, which solved the problem of short contact time and secondary pollution caused by the traditional injection mercury removal adsorbents. Experimental Hg removal showed that the 25 % Se-loaded adsorbent exhibited excellent Hg removal performance at 150 °C, with a saturation adsorption capacity of mercury was as high as 101.04 mg/g, nearly 300 times that of commercial activated carbons. Additionally, the influence of the flue gas composition on the Hg removal performance of Se/SiO2 was studied. The results showed that O2, NO, and HCl increased the efficiency of Hg removal and SO2 and SO3 had trivial impact on the Hg removal performance. The Hg temperature-programmed desorption test results showed that the adsorbed Hg appeared predominantly as HgSe on the sample surface. DFT calculations verified that Se loading improved Hg removal performance and defined the adsorption mechanism. Moreover, the prepared Se/SiO2 adsorbent carrier was soluble SiO2, which provided a good condition for the subsequent high-purity collection of HgSe. Finally, the technological process of Hg removal via Se-loaded adsorbents and the recovery of HgSe were proposed, which could offer a new way to achieve the resource utilization of Hg.

A high spatial resolution dataset for anthropogenic atmospheric mercury emissions in China during 1998–2014

China is the largest atmospheric mercury (Hg) emitter globally, which has been substantially investigated. However, the estimation of national or regional Hg emissions in China is insufficient in supporting emission control, as the location of the sources may have significant impacts on the effects of Hg emissions. In this concern, high-spatial-resolution datasets of China’s Hg emissions are necessary for in-depth and accurate Hg-related studies and policymaking. Existing gridded datasets are constructed using population distribution as the proxy, which is limited as Hg emissions are closely related to energy consumption and economic processes. This study constructs a dataset of anthropogenic atmospheric Hg emissions in China gridded to a 1 km resolution during 1998–2014. This dataset is produced based on data of land uses, individual enterprises, roadmaps, and population, uncovering Hg emissions in agriculture, industries, services, and residents. This dataset can promote the reliability of Hg-related studies at a high spatial resolution. Moreover, this dataset can support spatially explicit Hg reduction of economic sectors.

Air Pollutant Emission Inventory of Waste-to-Energy Plants in China and Prediction by the Artificial Neural Network Approach.

The waste-to-energy (WTE) plant has been deployed in 205 cities in China. However, it always faces public resistance to be built because of the great concerns on flue gas pollutants (FGPs). There are limited studies on the socioeconomic heterogeneity analysis and prediction models of WTE capacity/ FGP emission inventories (EIs) based on big data. In this study, the incinerator level emission factors (EFs) in 2020 of PM, SO2, NOx, CO, HCl, dioxins, Hg, Cd + Tl, and Sb + As+ Pb + Cr + Co + Cu + Mn + Ni were calculated based on 322,926 monitoring values of all the 481 WTE plants (1140 processing lines) operating in China, with uncertainties in the range of ±34.70%. The EFs were significantly 45-96% lower than the national standard (GB18485-2014) and had negative relationships with local socioeconomic elements, while WTE capacity and FGP EIs had significantly positive correlations. Gross domestic product, area of built district, and municipal solid waste generation were the main driving forces of WTE capacity. The WTE capacity increased by 150% from 2015 to 2020, while the total emission of PM, SO2, CO, dioxins, Hg, and Sb + As + Pb + Cr + Co + Cu + Mn + Ni decreased by 42.46-88.24%. The artificial neural network models were established to predict WTE capacity and FGP EIs in the city level, with the mean square errors ranging from 0.003 to 0.19 within the model validation limits. This study provides data and model support for the formulation of appropriate WTE plans and a pollutant emission control scheme in different economic regions.

Novel Determination of Elemental Mercury in Silicate Rock by Thermal Desorption

Much importance has been given in the recent literature to the determination and speciation of mercury in contaminated mine waste and soil. Among mercury species, the concentration of elemental mercury is a key parameter for risk assessment. However, at present, a validated analytical method for the quantitation of Hg(0) in solid matrices does not exist. In the present study, the reliability of a thermal desorption technique in quantifying elemental mercury in Hg(0) amended silica glass, a reference shelf standard, and in a Hg(0)-bearing mineralized silicate rock, considered representative of mine tailings, has been addressed. Mercury release has been measured at variable temperature using a thermo-desorption method combined with a mercury vapor analyzer. The results allowed the peak temperature for the emission of free and matrix-bound Hg(0) components to be identified, suggesting that 100 °C represents a suitable temperature for Hg(0) isothermal release. Experiments with the shelf standard exposed to a specific sorbent keeping the temperature constant at 100 °C provided 90% and 98% Hg(0) recovery after 2 and 24 h, respectively. Experiments with the mineralized rock demonstrated that free elemental mercury was recovered after 6 h, while 60 h were required for the free and matrix bound Hg(0) release. The limits of detection and quantification of the method were 1.3 ng and 3.0 ng, respectively. This approach allows elemental mercury in solid matrices to be determined, allowing the quantification of Hg(0) in contaminated mine tailings and soil.

Measurement report: Atmospheric mercury in a coastal city of Southeast China – inter-annual variations and influencing factors

Abstract. The long-term monitoring of atmospheric mercury is an important part of the effective evaluation of the Minamata Convention on Mercury. Gaseous elemental mercury (GEM), along with conventional air pollutants and meteorological parameters, was simultaneously observed in Xiamen, Southeast China, in January and July over the period 2012–2020. GEM concentrations in January were highest in 2015 (4.47 ng m−3) and decreased by 2020 (3.93 ng m−3), while GEM concentrations in July were highest in 2017 (2.65 ng m−3) and lowest in 2020 (1.56 ng m−3). The temporal variation of GEM was typically characterized by higher concentrations in winter than in summer and in nighttime than in daytime. Bivariate polar plots and the concentration-weighted trajectory (CWT) model were used to identify the source regions of GEM on a local and regional scale. The results indicate that the high GEM concentrations in January 2015 were likely due to a combination of high-level Hg emissions and adverse meteorological conditions. Generalized additive models (GAMs), which use a regression analysis method, were established and applied to investigate the influencing factors on the inter-annual variation of GEM. The factors anthropogenic emissions, meteorological conditions, and transportation explained 37.8 %±11.9 %, 31.4 %±9.0 %, and 30.8 %±9.9 % on average of the variation of GEM concentrations, respectively. There was a positive relationship of daily GEM concentrations with T and RH, mostly linking to natural surface emissions and Hg chemical transformations. The interpretation rate of anthropogenic emissions has significantly decreased since 2012, indicating the effectiveness of emission mitigation measures in reducing GEM concentrations in the study region.

Dispersion of airborne mercury species emitted from the cement plant

The cement industry is the second largest source of anthropogenic mercury (Hg) emissions in Europe, accounting for 11% of global anthropogenic Hg emissions. The main objective of this study was to examine the influence of Hg emissions from the Salonit Anhovo cement plant on Hg levels measured in the ambient air at Vodarna, 1 km downwind from the flue gas chimney. The findings reveal that the plant raw mill operational status plays an important role in Hg concentrations in the flue gas emitted from the plant. Emitted total gaseous mercury was, on average, higher (49.4 μg/m3) when raw mills were in the direct mode (both raw mills-off) and lower (23.4 μg/m3) in the combined mode (both raw mills-on). The average Hg concentrations in Vodarna were 3.14 ng/m3 for gaseous elemental mercury, 53.7 pg/m3 for gaseous oxidised mercury, and 41.9 pg/m3 for particulate bound mercury for the whole measurement period. Atmospheric Hg speciation in Vodarna, coupled with plant emissions and wind data, has revealed that the total gaseous mercury emitted from the cement plant is clearly related to all Hg species measured in Vodarna. Wind blowing from the northeastern quadrant (mostly NE, ENE) is responsible for the elevated Hg levels in Vodarna, where gaseous oxidised mercury levels are highly linked to the cement plant emissions. However, elevated levels of Hg species in the absence of northeastern winds indicate potential inputs from other unknown local sources as well as inputs from regional and global transport mechanisms.

Changes of production and consumption structures in coastal regions lead to mercury emission control in China

AbstractChina is important in the global mercury (Hg) cycle and is experiencing substantial economic structure transitions. There are pronounced differences in economic development, industrial structure, and consumption patterns across regions in China. However, the impacts of regional economic structure transitions (i.e., production and final demand structures) on Hg emissions in China remain unknown. Here, we reveal the transboundary impacts of changes in regional economic structures on provincial Hg emissions in China. We found that the transitions of production and final demand structures in coastal regions led to Hg emission reductions in China during 2007–2017. In particular, production structure changes in East Coast contributed to 36 metric tons of national Hg emission reduction, where 28 metric tons occurred in other regions (especially Hebei). Its final demand structure transition contributed to 19 metric tons of national emission reduction, where 15 metric tons occurred in other regions (especially Henan). Unfortunately, production structure changes in Northwest and final demand structure changes in Southwest contributed to Hg emission increments in China during 2007–2017. For instance, changes in the final demand structure of Southwest caused 34 metric tons of emission increments, mainly from provinces within the region. Thus, spatially explicit measures for China's Hg emission control can focus on the optimizations of production structure in Northwest and final demand structure in Southwest, as well as the promotion of interregional joint actions between East Coast and North China (especially Hebei and Henan). The findings of this study can inform region‐specific policy decisions and interregional joint efforts to control Hg emissions around the world.

Mercury isotope evidence for Arctic summertime re-emission of mercury from the cryosphere

During Arctic springtime, halogen radicals oxidize atmospheric elemental mercury (Hg0), which deposits to the cryosphere. This is followed by a summertime atmospheric Hg0 peak that is thought to result mostly from terrestrial Hg inputs to the Arctic Ocean, followed by photoreduction and emission to air. The large terrestrial Hg contribution to the Arctic Ocean and global atmosphere has raised concern over the potential release of permafrost Hg, via rivers and coastal erosion, with Arctic warming. Here we investigate Hg isotope variability of Arctic atmospheric, marine, and terrestrial Hg. We observe highly characteristic Hg isotope signatures during the summertime peak that reflect re-emission of Hg deposited to the cryosphere during spring. Air mass back trajectories support a cryospheric Hg emission source but no major terrestrial source. This implies that terrestrial Hg inputs to the Arctic Ocean remain in the marine ecosystem, without substantial loss to the global atmosphere, but with possible effects on food webs.

Environmental impacts of 222Rn, Hg and CO2 emissions from the fault zones in the western margin of the Ordos block, China.

Investigating the emissions of soil gas including radon, mercury and carbon dioxide (222Rn, Hg and CO2) from the solid earth to the atmosphere through active fault zones is of great significance for accession of atmospheric environment. In this study, the concentrations and fluxes of 222Rn, Hg and CO2 were measured at the main active fault zones at the western margin of the Ordos block, China. The concentrations of 222Rn, Hg and CO2 were in the range of 0-60.1kBq m-3, 3-81ng m-3 and 0.04-9.23%, respectively, while the fluxes of 222Rn, Hg and CO2 are in the range of 1.99-306.99mBq m-2s-1, 0-15.12ng m-2h-1 and 0-37.91g m-2d-1, respectively. Most of the major fault zones at the study area are CO2 risk-free regions (CO2 concentration in soil gas < 5%). However, the extend of 222Rn pollution at the fault zones of F1, F4, F5 and F9 (the fault number) and that of Hg pollution at the fault zones of F2, F4, F5 and F7 were higher than the pollution level of 1. The annual emission of Hg and CO2 from the western margin of the Ordos block was estimated to be 2.03kg and 0.70 Mt, respectively. Comprehensive analyses indicated that the higher emission rates of soil gases from the active fault zones were related to the seismic activities. The results suggest that the earthquake activity is a dominant factor enhancing the emission of 222Rn, Hg and CO2 from the solid earth through active fault zones and, furthermore, resulting great impact on the atmospheric environment.

Sediment records of global and regional Hg emissions to the atmosphere in North China over the last three centuries

Reconstructing the long-term Hg history in major emission countries is important for understanding the global Hg cycle and controlling Hg pollution. In this study, the atmospheric Hg history was reconstructed over the last three centuries based on three lacustrine sediment records from southeastern Inner Mongolia in North China, and its relationship with global and regional Hg emissions was revealed. These records show little Hg pollution in the 18th and 19th centuries. This implies a limited influence of Hg emitted from Europe and North America in this region, which is confirmed by their different Hg trends during the two World Wars and the post-1970s. Atmospheric Hg in the region had increased gradually since the 1900s, primarily contributed by emissions from the former Soviet Union in Lake Dalihu (DLH) and Lake Zhagesitai (ZGST) and from the Beijing-Tianjin-Hebei region in Lake Kulunnao (KLN). In the last century, two decreases in Hg fluxes occurred in the KLN core due to the economic recession in the 1960s–1970s and reduced energy consumption and industrial production in the 1990s. In the DLH and ZGST cores, only one decrease occurred, corresponded with the dissolution of the Soviet Union in the 1990s. Although atmospheric Hg emissions in China had stabilized or even decreased in the last decade, atmospheric Hg continued to increase, particularly in KLN, because of emissions from small cities in the region. This study can help understand Hg sources and control Hg pollution in North China and supplement the understanding of the global Hg cycling.