Trend analysis from 1970 to 2008 and model evaluation of EDGARv4 global gridded anthropogenic mercury emissions

Key factors influencing Hg levels and trends in unperturbed oligotrophic temperate and boreal lakes

Mercury (Hg) is a toxic metal that presents a major risk to ecosystems, biota, human health, and remains a priority concern. In temperate and boreal lakes Hg and methylmercury (MMHg) are expected to vary as a function of atmospheric Hg deposition, lake water chemistry, catchment characteristics and climate variables. The aim of this study was to quantify Hg and MMHg in unperturbed oligotrophic lakes and to identify the factors controlling their distribution. We first hypothesized that lake Hg (and MMHg to lesser extent) spatial variations are linked to atmospheric deposition, catchment characteristics, and terrestrial exportation of dissolved organic carbon (DOC). We secondly examined if lake Hg concentrations have followed the decrease in atmospheric Hg emission observed between the mid-1990s to the end-2010s. We found that overall, atmospheric Hg has little impact on lake Hg and MMHg concentrations, which are both primarily influenced by DOC input originating from the forest catchment. The relationship between DOC and Hg differed between the spring and the fall, with a Hg-to-DOC ratio twice as high in spring. This seems related to snowmelt input of Hg (with a relatively reduced input of DOC) or the internal lake build-up of Hg during the ice-covered period. Of the 10 lakes intensively visited over a 20-year period, only 3 showed significant lake Hg decreases despite significant negative trends in atmospheric Hg concentrations, suggesting a lag between atmospheric and surface water temporal trends. Overall, terrestrial catchments retain around 80% of atmospheric Hg implying that large Hg pools have been built up in soils in the last decades. As such, the reduction of atmospheric Hg alone will not necessarily result in Hg decreases in lakes, since the Hg concentrations may be modulated by DOC export trends and catchment characteristics. This stresses the need to improve our understanding of the processes governing Hg transfers from catchments into lakes.

Explore the spatial pattern of carbon emissions in urban functional zones: a case study of Pudong, Shanghai, China

It is crucial for the development of carbon reduction strategies to accurately examine the spatial distribution of carbon emissions. Limited by data availability and lack of industry segmentation, previous studies attempting to model spatial carbon emissions still suffer from significant uncertainty. Taking Pudong New Area as an example, with the help of multi-source data, this paper proposed a research framework for the amount calculation and spatial distribution simulation of its CO2 emissions at the scale of urban functional zones (UFZs). The methods used in this study were based on mapping relations among the locations of geographic entities and data of multiple sources, using the coefficient method recommended by the Intergovernmental Panel on Climate Change (IPCC) to calculate emissions. The results showed that the emission intensity of industrial zones and transport zones was much higher than that of other UFZs. In addition, Moran's I test indicated that there was a positive spatial autocorrelation in high emission zones, especially located in industrial zones. The spatial analysis of CO2 emissions at the UFZ scale deepened the consideration of spatial heterogeneity, which could contribute to the management of low carbon city and the optimal implementation of energy allocation.

International trade shapes global mercury-related health impacts

Mercury (Hg) is a strong neurotoxin with substantial dangers to human health. Hg undergoes active global cycles, and the emission sources there of can also be geographically relocated through economic trade. Through investigation of a longer chain of the global biogeochemical Hg cycle from economic production to human health, international cooperation on Hg control strategies in Minamata Convention can be facilitated. In the present study, four global models are combined to investigate the effect of international trade on the relocation of Hg emissions, pollution, exposure, and related human health impacts across the world. The results show that 47% of global Hg emissions are related to commodities consumed outside of the countries where the emissions are produced, which has largely influenced the environmental Hg levels and human exposure thereto across the world. Consequently, international trade is found to enable the whole world to avoid 5.7 × 10⁵ points for intelligence quotient (IQ) decline and 1,197 deaths from fatal heart attacks, saving a total of $12.5 billion (2020 USD) in economic loss. Regionally, international trade exacerbates Hg challenges in less developed countries, while resulting in an alleviation in developed countries. The change in economic loss therefore varies from the United States (-$4.0 billion) and Japan (-$2.4 billion) to China (+$2.7 billion). The present results reveal that international trade is a critical factor but might be largely overlooked in global Hg pollution mitigation.

Present Knowledge and Future Perspectives of Atmospheric Emission Inventories of Toxic Trace Elements: A Critical Review

Toxic trace elements (TEs) can pose serious risks to ecosystems and human health. However, a comprehensive understanding of atmospheric emission inventories for several concerning TEs has not yet been developed. In this study, we systematically reviewed the status and progress of existing research in developing atmospheric emission inventories of TEs focusing on global, regional, and sectoral scales. Multiple studies have strengthened our understanding of the global emission of TEs, despite attention being mainly focused on Hg and source classification in different studies showing large discrepancies. In contrast to those of developed countries and regions, the officially published emission inventory is still lacking in developing countries, despite the fact that studies on evaluating the emissions of TEs on a national scale or one specific source category have been numerous in recent years. Additionally, emissions of TEs emitted from waste incineration and traffic-related sources have produced growing concern with worldwide rapid urbanization. Although several studies attempt to estimate the emissions of TEs based on PM emissions and its source-specific chemical profiles, the emission factor approach is still the universal method. We call for more extensive and in-depth studies to establish a precise localization national emission inventory of TEs based on adequate field measurements and comprehensive investigation to reduce uncertainty.

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.

Measurement(s)	anthropogenic mercury emissions in China
Technology Type(s)	MATLAB, ArcGIS

Global Health Impact of Atmospheric Mercury Emissions from Artisanal and Small-Scale Gold Mining

Artisanal and small-scale gold mining (ASGM) is the leading source of mercury (Hg), a global neurotoxin. Past research has focused on the health impacts on miners and nearby residents; here, we estimate the risk for global general populations by employing a comprehensive atmosphere-land-ocean-ecosystem and exposure-risk-valuation model framework. Our results suggest that ASGM sources contribute 12%, 10%, and 0.63% to the atmospheric Hg deposition, plankton methylmercury concentrations, and soil total Hg concentrations at present day, respectively, and cause 5.8×10⁵ points of intelligence quotient decrements and 1,430 deaths for global general populations per year. The monetized global health impact of ASGM ($154 billion) is 1.5 times its local impact and accounts for half of the total revenue of ASGM ($319 billion). A major spatial decoupling between the health impact and economic gains is also revealed, suggesting that intervention measures such as awareness-raising, capacity-building, and technology transfer funded by the Global North are cost-effective.

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Contributions of ASGM to MeHg concentrations in different organisms are calculated

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The global health impact of atmospheric Hg from ASGM is first revealed

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The health impacts and economic gains of ASGM are compared

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Intervention measures for ASGM are proved to be cost-effective

Looping Mercury Cycle in Global Environmental-Economic System Modeling

The Minamata Convention on Mercury calls for Hg control actions to protect the environment and human beings from the adverse impacts of Hg pollution. It aims at the entire life cycle of Hg. Existing studies on the Hg cycle in the global environmental-economic system have characterized the emission-to-impact pathway of Hg pollution. That is, Hg emissions/releases from the economic system can have adverse impacts on human health and ecosystems. However, current modeling of the Hg cycle is not fully looped. It ignores the feedback of Hg-related environmental impacts (including human health impacts and ecosystem impacts) to the economic system. This would impede the development of more comprehensive Hg control actions. By synthesizing recent information on Hg cycle modeling, this critical review found that Hg-related environmental impacts would have feedbacks to the economic system via the labor force and biodiversity loss. However, the interactions between Hg-related activities in the environmental and economic systems are not completely clear. The cascading effects of Hg-related environmental impacts to the economic system throughout global supply chains have not been revealed. Here, we emphasize the knowledge gaps and propose possible approaches for looping the Hg cycle in global environmental-economic system modeling. This progress is crucial for formulating more dynamic and flexible Hg control measures. It provides new perspectives for the implementation of the Minamata Convention on Mercury.

Assessment of Mercury Concentrations and Fluxes Deposited from the Atmosphere on the Territory of the Yamal-Nenets Autonomous Area

The problem of mercury input and its further distribution in the Arctic environment is actively debated, especially in recent times, due to the observed processes of permafrost thawing causing the enhanced release of mercury into the Arctic atmosphere and further distribution in the terrestrial and aquatic ecosystem. The atmospheric mercury deposition occurs via dry deposition and wet scavenging by precipitation events. Here we present a study of Hg in wet precipitation on the remote territory of the Russian Arctic; the data were obtained at the monitoring stations Nadym and Salekhard in 2016–2018. Mercury pollution of the Salekhard atmosphere in cold time is mainly determined by regional and local sources, while in Nadym, long-range transport of mercury and local fuel combustion are the main sources of pollutants in the cold season, while internal regional sources have a greater impact on the warm season. Total mercury concentrations in wet precipitation in Nadym varied from <0.5 to 63.3 ng/L. The highest Hg concentrations in the springtime were most likely attributed to atmospheric mercury depletion events (AMDE). The contributions of wet atmospheric precipitation during the AMDE period to the annual Hg deposition were 16.7% and 9.8% in 2016/2017 and 2017/2018, respectively. The average annual volume-weighted Hg concentration (VWC) in the atmospheric precipitation in Nadym is notably higher than the values reported for the remote regions in the Arctic and comparable with the values obtained for the other urbanized regions of the world. Annual Hg fluxes in Nadym are nevertheless close to the average annual fluxes for remote territories of the Arctic zone and significantly lower than the annual fluxes reported for unpolluted sites of continental-scale monitoring networks of the different parts of the world (USA, Europe, and China). The increase of Hg deposition flux with wet precipitation in Nadym in 2018 might be caused by regional emissions of gas and oil combustion, wildfires, and Hg re-emission from soils due to the rising air temperature. The 37 cm increase of the seasonally thawed layer (STL) in 2018 compared to the 10-year average reflects that the climatic changes in the Nadym region might increase Hg(0) evasion, considering a great pool of Hg is contained in permafrost.

A new approach to evaluate regional inequity determined by PM2.5 emissions and concentrations

PM_2.5 is one of the most severe types of air pollution that threatens human health. Its emissions have a notable spillover effect once released into the atmosphere and transported. In domestic trade, PM_2.5 emissions can be indirectly imported from external regions. Thus, regional inequity caused by PM_2.5 needs to be integrated and comprehensively estimated. Based on PM_2.5 emissions/concentrations grid maps and an input-output model, this study first examined the temporal-spatial changes in PM_2.5 emissions/concentrations across China. Additionally, a detailed relationship between PM_2.5 emissions and concentrations was examined at multiple scales, both temporal and spatial. Finally, this study developed a new approach with which to evaluate regional inequity. The results show that PM_2.5 emissions and concentrations increased between 1990 and 2012 and 1998 and 2016, respectively; the increase was more obvious for PM_2.5 emissions. Spatially, a rapid increase in PM_2.5 emissions was observed in the North China Plain and the Sichuan Basin. Between 1998 and 2012, the distribution of PM_2.5 concentrations was similar to that of emissions; however, between 2013 and 2016, 46.6% of the total area showed a decrease, mainly in the central and southern parts of China. Relationship analysis revealed that PM_2.5 emissions and concentrations are closely correlated in both time and space. There was obvious regional inequity among provinces; developed regions always imported considerably more PM_2.5 emissions from undeveloped regions than they exported. Overall, the regional inequity estimation framework shows that provinces along the coastline, especially developed provinces, have advantages under the regional inequity estimation framework, while most of the inland regions have disadvantages, especially in the west and north.

A Vector Map of Carbon Emission Based on Point-Line-Area Carbon Emission Classified Allocation Method

An explicit spatial carbon emission map is of great significance for reducing carbon emissions through urban planning. Previous studies have proved that, at the city scale, the vector carbon emission maps can provide more accurate spatial carbon emission estimates than gridded maps. To draw a vector carbon emission map, the spatial allocation of greenhouse gas (GHG) inventory is crucial. However, the previous methods did not consider different carbon sources and their influencing factors. This study proposes a point-line-area (P-L-A) classified allocation method for drawing a vector carbon emission map. The method has been applied in Changxing, a representative small city in China. The results show that the carbon emission map can help identify the key carbon reduction regions. The emission map of Changxing shows that high-intensity areas are concentrated in four industrial towns (accounting for about 80%) and the central city. The results also reflect the different carbon emission intensity of detailed land-use types. By comparison with other research methods, the accuracy of this method was proved. The method establishes the relationship between the GHG inventory and the basic spatial objects to conduct a vector carbon emission map, which can better serve the government to formulate carbon reduction strategies and provide support for low-carbon planning.

Mercury in Marine Mussels from the St. Lawrence Estuary and Gulf (Canada): A Mussel Watch Survey Revisited after 40 Years

Various species of marine mussels have been used, in the last 50 years, as sentinel organisms for monitoring metal contamination along marine coasts. There are two main reasons for this: these mollusks concentrate metals in their soft tissue and they are geographically widespread. In practice, trace metal concentrations in mussel soft tissue reveal (after some correction for biotic effects) the contamination level of their surrounding environment. We present the results of a mercury (Hg) survey in Mytilus spp. collected in the summers of 2016, 2018, and 2019 at 51 stations distributed along the coasts of the Estuary and Gulf of St. Lawrence. Mercury concentrations ranged from 0.063 to 0.507 µg g−1 (dry weight, dw), with a grand mean of 0.173 ± 0.076 µg g−1 dw (±1 standard deviation), and a median of 0.156 µg g−1 dw for the 504 individuals analyzed. Mercury contents per individual mussel were significantly (p < 0.01) related to shell length and dry tissue weight, with the smaller individuals having the highest Hg concentrations. To take into account these biotic effects, we normalized Hg concentrations of the mussel soft tissue for constant shell length (L) and soft tissue weight (TW) based on the log-log relationships between Hg content and L or TW. The normalized Hg contents of mussels varied from 10.9 to 66.6 ng per virtual individual of 35 mm length and 0.17 g dry weight. A similar normalization procedure applied to 1977–1979 data, yielded a very similar range: 12 to 64 ng. This observation suggests that the Hg bioavailable to marine mussels in the study area did not change over a span of 40 years. Regional Hg distribution patterns indicate a gradual decrease of Hg content in mussels downstream from freshwater discharges to the St. Lawrence Estuary and the Baie des Chaleurs, suggesting that rivers constitute a significant Hg source in these estuarine systems. Atmospheric Hg deposition and concentration in marine waters of the Atlantic Ocean are known to have decreased in the last decades. However, in coastal environments, the response to these changes does not seem to be rapid, probably because of the long residence time of Hg in soils before being exported to coastal areas.

Patterns of blood mercury variation in two long-distance migratory thrushes on Mount Mansfield, Vermont

We investigated mercury (Hg) blood concentrations in Bicknell's thrush (Catharus bicknelli) and Swainson's thrush (C. ustulatus), congeneric long-distance migratory songbirds, from 2000-2017 at a montane forest site in north-central Vermont. We analyzed variation in blood Hg of both species using mixed-effects models, incorporating atmospheric wet Hg deposition data from a nearby sampling location. Although Hg deposition varied among years and seasonally, we detected no temporal trend in either atmospheric deposition or blood Hg, nor evidence of a relationship between the two. Sampling date had the strongest effect on blood Hg concentration, which declined seasonally, followed by age and sex of the individual. The data did not support an effect of species. We believe that the absence of a clear relationship between local atmospheric deposition and thrush blood Hg concentrations suggests that Hg cycling dynamics, mechanisms of transfer, and timing of uptake by montane forest biota are complex and poorly understood. The blood Hg concentrations of ~0.07-0.1 μg/g we documented in Bicknell's and Swainson's thrush are below those found to negatively impact physiological or reproductive endpoints in other invertivorous terrestrial passerines. To better evaluate the validity of Bicknell's thrush as a bioindicator of MeHg availability in montane forest ecosystems, we recommend (1) effects-based investigations, (2) a more robust understanding of Hg and MeHg cycling, (3) more clear geospatial and temporal links between Hg deposition and biotic uptake, and (4) more thorough documentation of Hg burdens across the species' annual cycle.

Seasonal Evolution of Size-Segregated Particulate Mercury in the Atmospheric Aerosol Over Terra Nova Bay, Antarctica

Size-fractionated particulate mercury (PHg) measurements were performed from November 2017 to January 2018 at Terra Nova Bay (Antarctica) for the first time. Samples were collected every 10 days by a six-stage high-volume cascade impactor with size classes between 10 μm and 0.49 μm. Total PHg concentrations were maxima (87 ± 8 pg m⁻³) in November, then decreased to values ~40% lower and remained almost constant until the end of the sampling period (~30 pg m⁻³). The trimodal aerosol mass distribution reveals that from 30% to 90% of the total PHg came in the size > 1.0 μm. Hg in the two coarse fractions was probably produced by the adsorption of oxidized Hg species transported by air masses from the Antarctic plateau or produced locally by sea ice edges. PHg in accumulation mode seemed to be related to gas–particle partitioning with sea salt aerosol. Finally, average dry deposition fluxes of PHg were calculated to be 0.36 ± 0.21 ng m⁻² d⁻¹ in the accumulation mode, 47 ± 44 ng m⁻² d⁻¹ in the first coarse mode, and 37 ± 31 ng m⁻² d⁻¹ in the second coarse mode. The present work contributed to the comprehension of the Hg biogeochemical cycle, but further research studies are needed.

A Chemical Transport Model Emulator for the Interactive Evaluation of Mercury Emission Reduction Scenarios

Implementation of the Minamata Convention on Mercury requires all parties to “control, and where feasible, reduce” mercury (Hg) emissions from a convention-specified set of sources. However, the convention does not specify the extent of the measures to be adopted, which may only be analysed by decision-makers using modelled scenarios. Currently, the numerical models available to study the Hg atmospheric cycle require significant expertise and high-end hardware, with results which are generally available on a time frame of days to weeks. In this work we present HERMES, a statistical emulator built on the output of a global Chemical Transport Model (CTM) for Hg (ECHMERIT), to simulate changes in anthropogenic Hg (Hganthr) deposition fluxes in a source-receptor framework, due to perturbations to Hganthr emissions and the associated statistical significance of the changes. The HERMES emulator enables stakeholders to evaluate the implementation of different Hganthr emission scenarios in an interactive and real-time manner, simulating the application of the different Best Available Technologies. HERMES provides the scientific soundness of a full CTM numerical framework in an interactive and user-friendly spreadsheet, without the necessity for specific training or formation and is a first step towards a more comprehensive, and integrated, decision support system to aid decision-makers in the implementation of the Minamata Convention.

Gaseous mercury capture by coir fibre coated with a metal-halide

Toxic gaseous elemental mercury (GEM) is emitted to the atmosphere through a variety of routes at rates estimated at over 5000 tonnes per annum, a large fraction of which is Anthropogenic. It is then widely disbursed atmospherically and eventually deposited, where it is subject to further biogeochemical cycling, including re-emission. Research into capture of point source mercury emissions revolves almost exclusively around the use of activated carbons, various catalytic oxidation substrates, or as a by-product of acidic treatments of flue gas during SOx and NOx reduction methods. GEM is very non-reactive in its native state, but capture rates are greatly enhanced if GEM is first oxidized, or at least where oxidation states play a role at the substrate GEM interface. Little research has been devoted to capture of GEM directly. However, presented here is a novel adaption of coir fibers for use as a substrate in capturing GEM emissions directly. Various coir modifications were investigated, with the most effective being fibers coated with CuI crystals dispersed in a non-crosslinked poly-siloxane matrix. Scanning electron microscopy was used to view surface morphologies, and sorption characteristics were measured using atomic absorption spectroscopy (AAS). These results indicate that coir fibers modified by CuI-[SiO₂] _n show great promise in their ability to efficiently sorb GEM, and could potentially be utilized in a variety of configurations and settings where GEM emissions need to be captured.

IMPLICATIONS

Highly toxic gaseous elemental mercury (GEM) has proved very difficult to capture, requiring complex catalytic oxidation or expensive gas scrubbing technologies. The modified coir fiber described in this work can effectively capture GEM without prior catalytic oxidation or any other physicochemical treatment of the gas. The solution provided here is made from renewable resources, is low cost, and the raw materials are readily available in bulk. Further, the mercury is bound in a stable and insoluble form that can be readily isolated from the substrate. This filtration device can be adapted to suit a variety of settings for GEM capture.

An updated review of atmospheric mercury

The atmosphere is a key component of the biogeochemical cycle of mercury, acting as a reservoir, transport mechanism, and facilitator of chemical reactions. The chemical and physical behavior of atmospheric mercury determines how, when, and where emitted mercury pollution impacts ecosystems. In this review, we provide current information about what is known and what remains uncertain regarding mercury in the atmosphere. We discuss new ambient, laboratory, and theoretical information about the chemistry of mercury in various atmospheric media. We review what is known about mercury in and on solid- and liquid-phase aerosols. We present recent findings related to wet and dry deposition and spatial and temporal trends in atmospheric mercury concentrations. We also review atmospheric measurement methods that are in wide use and those that are currently under development.

Mercury Benefits of Climate Policy in China: Addressing the Paris Agreement and the Minamata Convention Simultaneously

National commitments under the Paris Agreement on climate change interact with other global environmental objectives, such as those of the Minamata Convention on Mercury. We assess how mercury emissions and deposition reductions from national climate policy in China under the Paris Agreement could contribute to the country's commitments under the Minamata Convention. We examine emissions under climate policy scenarios developed using a computable general equilibrium model of China's economy, end-of-pipe control scenarios that meet China's commitments under the Minamata Convention, and these policies in combination, and evaluate deposition using a global atmospheric transport model. We find climate policy in China can provide mercury benefits when implemented with Minamata policy, achieving in the year 2030 approximately 5% additional reduction in mercury emissions and deposition in China when climate policy achieves a 5% reduction per year in carbon intensity (CO₂ emissions 9.7 Gt in 2030). This corresponds to 63 Mg additional mercury emissions reductions in 2030 when implemented with Minamata Convention policy, compared to Minamata policy implemented alone. Climate policy provides emissions reductions in sectors not considered under the Minamata Convention, such as residential combustion. This changes the combination of sectors that contribute to emissions reductions.

Metal contamination of river otters in North Carolina

Aquatic apex predators are vulnerable to environmental contaminants due to biomagnification. North American river otter (Lontra canadensis) populations should be closely monitored across their range due to point and nonpoint pollution sources. Nonetheless, no information exists on environmental contaminants in the North Carolina otter population. Metals and metalloids occur naturally across the landscape, are essential for cellular function, and become toxic when concentrated unnaturally. We conducted our study across the three Furbearer Management Units (FMU) and 14 river basins of North Carolina. We determined the concentrations of arsenic, cadmium, calcium, cobalt, copper, iron, lead, magnesium, manganese, mercury, molybdenum, selenium, thallium, and zinc in liver and kidney samples from 317 otters harvested from 2009 to 2016. Arsenic, lead, and thallium samples were tested at levels below the limit of detection. With the exception of cadmium, we detected all other elements at higher levels in the liver compared with the kidney. Specifically, cadmium, cobalt, copper, iron, magnesium, manganese, mercury, molybdenum, and zinc levels differed by tissue type analyzed. Most element concentrations remained stable or increased with otter age. We detected higher levels of mercury and selenium in the Lower Pee Dee and Cape Fear river basins. River basins within the Mountain FMU were higher in cadmium, copper, iron, lead, and zinc, whereas the Coastal Plain FMU was lower in cobalt and manganese. None of the elements occurred at toxic levels. Our research establishes baseline concentration levels for North Carolina, which will benefit future monitoring efforts and provide insight into future changes in the otter population.

Climate influence on mercury in Arctic seabirds

The historic influence of interannual weather and climate variability on total mercury concentrations (THg) in the eggs of two species of Arctic seabird in the Canadian High Arctic was investigated. Time series of THg in the eggs of northern fulmars (Fulmarus glacialis) and thick-billed murres (Uria lomvia) from Prince Leopold Island span 40 years (1975-2014), making these among the longest time series available for contaminants in Arctic wildlife and uniquely suitable for evaluation of long-term climate and weather influence. We compiled a suite of weather and climate time series reflecting atmospheric (air temperature, wind speed, sea level pressure) and oceanic (sea surface temperature, sea ice cover) conditions, atmosphere-ocean transfer (snow and rain), as well as broad-scale teleconnection indices such as the Arctic Oscillation (AO) and North Atlantic Oscillation (NAO). We staggered these to the optimal time lag, then in a tiered approach of successive General Linear Models (GLMs), strategically added them to GLMs to identify possible key predictors and assess any main effects on THg concentrations. We investigated time lags of 0 to 10 years between weather/climate shifts and egg collections. For both fulmars and murres, after time lags of two to seven years, the most parsimonious models included NAO and temperature, and for murres, snowfall, while the fulmar model also included sea ice. Truncated versions of the datasets (2005-2014), reflective of typical time series length for THg in Arctic wildlife, were separately assessed and generally identified similar weather predictors and effects as the full time series, but not for NAO, indicating that longer time series are more effective at elucidating relationships with broad scale climate indices. Overall, the results suggest a significant and larger than expected effect of weather and climate on THg concentrations in Arctic seabirds.

High resolution carbon emissions simulation and spatial heterogeneity analysis based on big data in Nanjing City, China

The accurate examination of the spatial distribution of carbon emissions is critical for carbon reduction strategies. Large uncertainties still exist for previous studies which tried to simulate carbon emissions in spatial, and the resolution needs to be improved to a large extent. At a city level, this study collected various sources of big data and designed a new methodology to examine carbon emissions in Nanjing city at a high resolution of 300 m. In addition, regional differences were compared, and influence factors were analyzed. This study found, the core urban area in Nanjing presented an obvious intensity variation, but the emission intensities were much lower than in those from the peripheral region where industrial land was mainly distributed. Broad areas away from urban areas, where cropland and rural residential land were distributed, presented low carbon emission intensities. Regionally, the districts in the core urban area always presented high emission intensities. The characteristics of land usage and social-economic development were key factors in determining carbon emissions. An increase in ecological land and a decrease in developed land will help carbon reduction strategies greatly. For social and economic development, adjustments in the structure of industry and energy use efficiency improvements will play key roles in the reduction of carbon emissions.

Measure-Specific Effectiveness of Air Pollution Control on China's Atmospheric Mercury Concentration and Deposition during 2013-2017

China took aggressive air pollution control measures from 2013 to 2017, leading to the mitigation of atmospheric mercury pollution as a cobenefit. This study is the first to systematically evaluate the effect of five major air pollution control measures in reducing mercury emissions, the total gaseous mercury (TGM) concentration and mercury deposition flux (FLX) for unit emissions reduction. From 2013 to 2017, China's mercury emissions decreased from 571 to 444 tons, resulting in a 0.29 ng m^-3 decrease in the TGM concentration, on average, and in a 17 μg m^-2 yr^-1 decrease in FLX. Ultralow emission renovations of coal-fired power plants are identified as the most effective emission abatement measure. As a result of this successful measure, coal-fired power plants are no longer the main mercury emitters. In 2017, the cement clinker sector became the largest emitter due to the use of less effective mercury removal measures. However, in terms of the mitigated TGM concentration and FLX levels per unit emission abatement, newly built wet flue gas desulfurization (WFGD) systems in coal-fired industrial boilers have become particularly effective in decreasing FLX levels. Therefore, to effectively reduce atmospheric mercury pollution in China, prioritizing mercury emissions control of cement clinkers and coal-fired industrial boilers is recommended.

Anthropogenic atmospheric toxic metals emission inventory and its spatial characteristics in Guangdong province, China

Atmospheric toxic metals (TMs) may cause adverse effects on the environment and human health due to their bioavailability and toxicity. High-resolution TMs emission inventory is important input data for assessing human exposure risks, especially synergistic toxicity of multiple toxic metals. By using the latest city- and enterprise-level environment statistical data, an emission inventory of five TMs (Hg, As, Pb, Cd, Cr) in Guangdong province for the year of 2014 was developed using a bottom-up approach. The total emissions of Hg, As, Pb, Cd and Cr in Guangdong were estimated as 17.70, 32.59, 411.34, 13.13, and 84.16 t, respectively. Major emission sources for each TM were different. Hg emissions were dominated by coal combustion (33%), fluorescent lamp (18%) and cement (17%). 78% of Hg emissions were in the form of Hg⁰, 19% of Hg²⁺, and only 3% of Hg^p due to strict particulate matter control policies. Coal combustion (48%), nonferrous metal smelting (25%) and iron and steel industry (24%) were the major sources of As. Pb emissions primarily came from battery production (42%), iron and steel industry (21%) and gasoline combustion (17%). Cd and Cr emissions were dominated by nonferrous metal smelting (71%) and iron and steel industry (82%), respectively. Most of these TMs were emitted in the non-Pearl River Delta region, where the newly-built iron and steel industry, nonferrous metal smelting and cement production factories were intense. The uncertainties in the five TM emissions were high, due much to high uncertainties in TM emission factors and limited activity data. Thus, to improve the accuracy of these estimates, we recommend more field tests of TM emissions, especially for the industrial process sector. This study provides scientific support for formulating robust TMs control policies to alleviate the high risk of TMs exposure in Guangdong.

Global and Local Impacts of Delayed Mercury Mitigation Efforts

Mercury (Hg) is emitted to air by natural and anthropogenic sources, transports and deposits globally, and bioaccumulates to toxic levels in food webs. It is addressed under the global 2017 Minamata Convention, for which periodic effectiveness evaluation is required. Previous analyses have estimated the impact of different regulatory strategies for future mercury deposition. However, analyses using atmospheric models traditionally hold legacy emissions (recycling of previously deposited Hg) constant, and do not account for their possible future growth. Here, using an integrated modeling approach, we investigate how delays in implementing emissions reductions and the associated growing legacy reservoir affect deposition fluxes to ecosystems in different global regions. Assuming nearly constant yearly emissions relative to 2010, each 5-year delay in peak emissions defers by additional extra ca. 4 years the return to year 2010 global deposition. On a global average, each 5-year delay leads to a 14% decrease in policy impacts on local-scale Hg deposition. We also investigate the response of fish contamination in remote lakes to delayed action. We quantify the consequences of delay for limiting the Hg burden of future generations and show that traditional analyses of policy impacts provide best-case estimates.

Understanding factors influencing the detection of mercury policies in modelled Laurentian Great Lakes wet deposition

We used chemical transport modelling to better understand the extent to which policy-related anthropogenic mercury emissions changes (a policy signal) can be statistically detected in wet deposition measurements in the Great Lakes region on the subdecadal scale, given sources of noise. In our modelling experiment, we consider hypothetical regional (North American) and global (rest of the world) policy changes, consistent with existing policy efforts (Δglobal = -18%; Δregional = -30%) that divide an eight-year period. The magnitude of statistically significant (p < 0.1) pre- and post-policy period wet deposition differences, holding all else constant except for the policy change, ranges from -0.3 to -2.0% for the regional policy and -0.8 to -2.7% for the global policy. We then introduce sources of noise-trends and variability in factors that are exogenous to the policy action-and evaluate the extent to which the policy signals can still be detected. For instance, technology-related variability in emissions magnitude and speciation can shift the magnitude of differences between periods, in some cases dampening the policy effect. We have found that the interannual variability in meteorology has the largest effect of the sources of noise considered, driving deposition differences between periods to ±20%, exceeding the magnitude of the policy signal. However, our simulations suggest that gaseous elemental mercury concentration may be more robust to this meteorological variability in this region, and a stronger indicator of local/regional emissions changes. These results highlight the potential challenges of detecting statistically significant policy-related changes in Great Lakes wet deposition within the subdecadal scale.

Screening differences between a local inventory and the Emissions Database for Global Atmospheric Research (EDGAR)

In the vast majority of Latin American and South American countries, global emission inventories (EIs) are often used for modelling air quality. In particular the Emission Database for Global Atmospheric Research EDGAR is widely deployed but several studies have pointed to some gaps in comparison with national/regional inventories which incur errors in interpreting results. In Cuba, due to scarcity of a spatially distributed national inventory, EDGAR has been used as entry for air quality modelling without verifying their reliability over the region. Our goal in this article is to compare and contrast EDGAR with a local inventory and to evaluate similarities or discrepancies. We use advanced comparison techniques developed by the Forum for Air Quality Modelling in Europe-FAIRMODE. This approach differs from others in the detailed way in which it points out the differences and gets insights in possible explanations. Overall, EDGAR provided spatially smoother results and relatively lower values in hotspot areas. Coarse differences in terms of activities were low for all analyzed sectors. However, EDGAR overestimates emission factors (EFs) of stationary sources for CO by a factor of 3 and SO₂ by a factor of 1.5 while underestimates those of PPM₁₀ by a factor of 25. Most of the road transport EFs are overestimated in EDGAR; PM₁₀, CO and NOx are 2 times higher, while CH₄ and SO₂ are 5 to 20 times higher. Large differences were found on the spatial distribution of energy and industrial sources. EDGAR can be regionally accepted as a reference but it is not recommended for air quality simulation over Cuba. A more complete reporting must be expected when more official national data are due. A review and evaluation of local emission inventories over Cuba can be useful for identifying potential areas for future improvement.

What's hot about mercury? Examining the influence of climate on mercury levels in Ontario top predator fishes

Mercury (Hg) levels in Ontario top predator fishes have been increasing in recent decades. These increases may be a result of many additive factors, including global climate change. Only recently has research been conducted on how climate change may impact Hg levels in freshwater fishes at large-scales. We examined the relationship between Hg trends and (1) local weather, (2) large-scale climate drivers, and (3) anthropogenic Hg emissions, in native cool water (walleye and northern pike) and warm water (smallmouth bass and largemouth bass) predatory fishes in Ontario, Canada, for historical (1970-1992) and recent (1993-2014) time periods. For each fish species studied, > 25% of Ontario's secondary watersheds shifted from historically declining to recently increasing fish Hg trends, and ≥ 50% of watersheds experienced increasing trends between 1993 and 2014. Recent fish Hg increased at up to 0.20µg/g/decade; which were significant (p < 0.05) for walleye, northern pike and smallmouth bass. Multiple linear regressions revealed a complex interplay of local weather, large-scale climate drivers, and anthropogenic Hg emissions influencing fish Hg levels. Recent Hg levels for walleye and largemouth bass increased with changes in global climate drivers, while higher precipitation influenced smallmouth bass Hg levels the most. Walleye Hg levels increased during the positive phases of global climate drivers, reflecting the local influence of local temperatures and precipitation indirectly. Differentiating the effects of climate-related parameters and emissions is increasingly crucial to assess how changing multiple environmental stressors may impact health of wildlife and humans consuming fish.

A review of global environmental mercury processes in response to human and natural perturbations: Changes of emissions, climate, and land use

We review recent progress in our understanding of the global cycling of mercury (Hg), including best estimates of Hg concentrations and pool sizes in major environmental compartments and exchange processes within and between these reservoirs. Recent advances include the availability of new global datasets covering areas of the world where environmental Hg data were previously lacking; integration of these data into global and regional models is continually improving estimates of global Hg cycling. New analytical techniques, such as Hg stable isotope characterization, provide novel constraints of sources and transformation processes. The major global Hg reservoirs that are, and continue to be, affected by anthropogenic activities include the atmosphere (4.4-5.3 Gt), terrestrial environments (particularly soils: 250-1000 Gg), and aquatic ecosystems (e.g., oceans: 270-450 Gg). Declines in anthropogenic Hg emissions between 1990 and 2010 have led to declines in atmospheric Hg0 concentrations and HgII wet deposition in Europe and the US (- 1.5 to - 2.2% per year). Smaller atmospheric Hg0 declines (- 0.2% per year) have been reported in high northern latitudes, but not in the southern hemisphere, while increasing atmospheric Hg loads are still reported in East Asia. New observations and updated models now suggest high concentrations of oxidized HgII in the tropical and subtropical free troposphere where deep convection can scavenge these HgII reservoirs. As a result, up to 50% of total global wet HgII deposition has been predicted to occur to tropical oceans. Ocean Hg0 evasion is a large source of present-day atmospheric Hg (approximately 2900 Mg/year; range 1900-4200 Mg/year). Enhanced seawater Hg0 levels suggest enhanced Hg0 ocean evasion in the intertropical convergence zone, which may be linked to high HgII deposition. Estimates of gaseous Hg0 emissions to the atmosphere over land, long considered a critical Hg source, have been revised downward, and most terrestrial environments now are considered net sinks of atmospheric Hg due to substantial Hg uptake by plants. Litterfall deposition by plants is now estimated at 1020-1230 Mg/year globally. Stable isotope analysis and direct flux measurements provide evidence that in many ecosystems Hg0 deposition via plant inputs dominates, accounting for 57-94% of Hg in soils. Of global aquatic Hg releases, around 50% are estimated to occur in China and India, where Hg drains into the West Pacific and North Indian Oceans. A first inventory of global freshwater Hg suggests that inland freshwater Hg releases may be dominated by artisanal and small-scale gold mining (ASGM; approximately 880 Mg/year), industrial and wastewater releases (220 Mg/year), and terrestrial mobilization (170-300 Mg/year). For pelagic ocean regions, the dominant source of Hg is atmospheric deposition; an exception is the Arctic Ocean, where riverine and coastal erosion is likely the dominant source. Ocean water Hg concentrations in the North Atlantic appear to have declined during the last several decades but have increased since the mid-1980s in the Pacific due to enhanced atmospheric deposition from the Asian continent. Finally, we provide examples of ongoing and anticipated changes in Hg cycling due to emission, climate, and land use changes. It is anticipated that future emissions changes will be strongly dependent on ASGM, as well as energy use scenarios and technology requirements implemented under the Minamata Convention. We predict that land use and climate change impacts on Hg cycling will be large and inherently linked to changes in ecosystem function and global atmospheric and ocean circulations. Our ability to predict multiple and simultaneous changes in future Hg global cycling and human exposure is rapidly developing but requires further enhancement.

A Highly Resolved Mercury Emission Inventory of Chinese Coal-Fired Power Plants

As the largest coal consumer in China, the coal-fired power plants have come under increasing public concern in regard to atmospheric mercury pollution. This study developed an up-to-date and high-resolution mercury emission inventory of Chinese coal-fired power plants using a unit-based method that combined data from individual power plants, provincial coal characteristics, and industry removal efficiencies. National mercury emissions in 2015 were estimated at 73 tons, including 54 tons of elemental mercury, 18 tons of gaseous oxidized mercury and 1 ton of particle-bound mercury. Pulverized coal boilers emitted 65 tons, mainly in the coastal provinces and coal-electricity bases. Circulating fluidized bed boilers emitted 8 tons, mainly in Inner Mongolia and Shanxi Province. The average mercury emission intensity over the Chinese mainland was 18.3 g/GWh, which was similar to the limit for low-rank coal-fired units in the United States. The overall uncertainty of national mercury emission was estimated to be -19% to 20%, with the mercury content in coal being the major contributor. In most provinces, monthly mercury emissions generally peaked in December and August. However, monthly partition coefficients of southwest China were obviously lower than other regions from June to October due to the high proportion of hydropower generation.

Total Mercury Released to the Environment by Human Activities

We estimate that a cumulative total of 1540 (1060-2800) Gg (gigagrams, 10⁹ grams or thousand tonnes) of mercury (Hg) have been released by human activities up to 2010, 73% of which was released after 1850. Of this liberated Hg, 470 Gg were emitted directly into the atmosphere, and 74% of the air emissions were elemental Hg. Cumulatively, about 1070 Gg were released to land and water bodies. Though annual releases of Hg have been relatively stable since 1880 at 8 ± 2 Gg, except for wartime, the distributions of those releases among source types, world regions, and environmental media have changed dramatically. Production of Hg accounts for 27% of cumulative Hg releases to the environment, followed by silver production (24%) and chemicals manufacturing (12%). North America (30%), Europe (27%), and Asia (16%) have experienced the largest releases. Biogeochemical modeling shows a 3.2-fold increase in the atmospheric burden relative to 1850 and a contemporary atmospheric reservoir of 4.57 Gg, both of which agree well with observational constraints. We find that approximately 40% (390 Gg) of the Hg discarded to land and water must be sequestered at contaminated sites to maintain consistency with recent declines in atmospheric Hg concentrations.

Inversion Approach to Validate Mercury Emissions Based on Background Air Monitoring at the High Altitude Research Station Jungfraujoch (3580 m)

The reduction of emissions of mercury is a declared aim of the Minamata Convention, a UN treaty designed to protect human health and the environment from adverse effects of mercury. To assess the effectiveness of the convention in the future, better constraints about the current mercury emissions is a premise. In our study, we applied a top-down approach to quantify mercury emissions on the basis of atmospheric mercury measurements conducted at the remote high altitude monitoring station Jungfraujoch, Switzerland. We established the source-receptor relationships and by the means of atmospheric inversion we were able to quantify spatially resolved European emissions of 89 ± 14 t/a for elemental mercury. Our European emission estimate is 17% higher than the bottom-up emission inventory, which is within stated uncertainties. However, some regions with unexpectedly high emissions were identified. Stationary combustion, in particular in coal-fired power plants, is found to be the main responsible sector for increased emission estimates. Our top-down approach, based on measurements, provides an independent constraint on mercury emissions, helps to improve and refine reported emission inventories, and can serve for continued assessment of future changes in emissions independent from bottom-up inventories.

Methylmercury Mass Budgets and Distribution Characteristics in the Western Pacific Ocean

Methylmercury (MeHg) accumulation in marine organisms poses serious ecosystem and human health risk, yet the sources of MeHg in the surface and subsurface ocean remain uncertain. Here, we report the first MeHg mass budgets for the Western Pacific Ocean estimated based on cruise observations. We found the major net source of MeHg in surface water to be vertical diffusion from the subsurface layer (1.8-12 nmol m^-2 yr^-1). A higher upward diffusion in the North Pacific (12 nmol m^-2 yr^-1) than in the Equatorial Pacific (1.8-5.7 nmol m^-2 yr^-1) caused elevated surface MeHg concentrations observed in the North Pacific. We furthermore found that the slope of the linear regression line for MeHg versus apparent oxygen utilization in the Equatorial Pacific was about 2-fold higher than that in the North Pacific. We suggest this could be explained by redistribution of surface water in the tropical convergence-divergence zone, supporting active organic carbon decomposition in the Equatorial Pacific Ocean. On the basis of this study, we predict oceanic regions with high organic carbon remineralization to have enhanced MeHg concentrations in both surface and subsurface waters.

Particulate-phase mercury emissions from biomass burning and impact on resulting deposition: a modelling assessment

Mercury (Hg) emissions from biomass burning (BB) are an important source of atmospheric Hg and a major factor driving the interannual variation of Hg concentrations in the troposphere. The greatest fraction of Hg from BB is released in the form of elemental Hg ( Hg ( g ) 0 ) . However, little is known about the fraction of Hg bound to particulate matter (HgP) released from BB, and the factors controlling this fraction are also uncertain. In light of the aims of the Minamata Convention to reduce intentional Hg use and emissions from anthropogenic activities, the relative importance of Hg emissions from BB will have an increasing impact on Hg deposition fluxes. Hg speciation is one of the most important factors determining the redistribution of Hg in the atmosphere and the geographical distribution of Hg deposition. Using the latest version of the Global Fire Emissions Database (GFEDv4.1s) and the global Hg chemistry transport model, ECHMERIT, the impact of Hg speciation in BB emissions, and the factors which influence speciation, on Hg deposition have been investigated for the year 2013. The role of other uncertainties related to physical and chemical atmospheric processes involving Hg and the influence of model parametrisations were also investigated, since their interactions with Hg speciation are complex. The comparison with atmospheric HgP concentrations observed at two remote sites, Amsterdam Island (AMD) and Manaus (MAN), in the Amazon showed a significant improvement when considering a fraction of HgP from BB. The set of sensitivity runs also showed how the quantity and geographical distribution of HgP emitted from BB has a limited impact on a global scale, although the inclusion of increasing fractions HgP does limit Hg ( g ) 0 availability to the global atmospheric pool. This reduces the fraction of Hg from BB which deposits to the world's oceans from 71 to 62 %. The impact locally is, however, significant on northern boreal and tropical forests, where fires are frequent, uncontrolled and lead to notable Hg inputs to local ecosystems. In the light of ongoing climatic changes this effect could be potentially be exacerbated in the future.

Chemical Speciation of Selenium and Mercury as Determinant of Their Neurotoxicity

The antagonism of mercury toxicity by selenium has been well documented. Mercury is a toxic metal, widespread in the environment. The main target organs (kidneys, lungs, or brain) of mercury vary depending on its chemical forms (inorganic or organic). Selenium is a semimetal essential to mammalian life as part of the amino acid selenocysteine, which is required to the synthesis of the selenoproteins. This chapter has the aim of disclosing the role of selenide or hydrogen selenide (Se^-2 or HSe^-) as central metabolite of selenium and as an important antidote of the electrophilic mercury forms (particularly, Hg²⁺ and MeHg). Emphasis will be centered on the neurotoxicity of electrophile forms of mercury and selenium. The controversial participation of electrophile mercury and selenium forms in the development of some neurodegenerative disease will be briefly presented. The potential pharmacological use of organoseleno compounds (Ebselen and diphenyl diselenide) in the treatment of mercury poisoning will be considered. The central role of thiol (-SH) and selenol (-SeH) groups as the generic targets of electrophile mercury forms and the need of new in silico tools to guide the future biological researches will be commented.

Recent Decline of Atmospheric Mercury Recorded by Androsace tapete on the Tibetan Plateau

We combined the mercury passive sampling method and plant biomonitoring together to understand the long-term changes of atmospheric mercury concentrations on the Tibetan Plateau. Through the analysis of leaves of Androsace tapete that represent growing periods spanning the past decade, we explored the historical records of atmospheric mercury from 2006 to 2015. Mercury concentration was stable in the leaves of Androsace tapete during the period between 2006 and 2009, while a significant decrease occurred after the year of 2010. The decreasing trend is consistent with the monitoring data of the ground-based stations in other regions globally. Despite the potential uncertainties using a passive sampling method and biomonitoring technique, we suggest that Androsace tapete is a potential biomarker that could provide reliable and effective historical records of atmospheric mercury concentrations and offer new perspectives in monitoring mercury and perhaps other atmospheric pollutants in regions where long-term active monitoring was missing.

Monsoon-driven transport of atmospheric mercury to the South China Sea from the Chinese mainland and Southeast Asia-Observation of gaseous elemental mercury at a background station in South China

Concentrations of gaseous elemental mercury (GEM) were continuously monitored from May 2011 to May 2012 at the Wuzhishan State Atmosphere Background Monitoring Station (109°29'30.2″ E, 18°50'11.0″ N) located in Hainan Island. This station is an ideal site for monitoring long-range transport of atmospheric pollutants from mainland China and Southeast Asia to South China Sea. Annual average GEM concentration was 1.58 ± 0.71 ng m^-3 during the monitoring period, which was close to background values in the Northern Hemisphere. GEM concentrations showed a clear seasonal variation with relatively higher levels in autumn (1.86 ± 0.55 ng m^-3) and winter (1.80 ± 0.62 ng m^-3) and lower levels in spring (1.16 ± 0.45 ng m^-3) and summer (1.43 ± 0.46 ng m^-3). Long-range atmospheric transport dominated by monsoons was a dominant factor influencing the seasonal variations of GEM. The GEM diel trends were related to the wind speed and long-range atmospheric mercury transport. We observed 30 pollution episodes throughout the monitoring period. The analysis of wind direction and backward trajectory suggested that elevated GEM concentrations at the monitoring site were primarily related to the outflows of atmospheric Hg from mainland China and the Indochina peninsula. The △GEM/△CO values also suggested that GEM was significantly affected by the long-range transport from the anthropogenic sources and biomass burning in Asia and Indochina peninsula.

Atmospheric chemistry of mercury in Antarctica and the role of cryptogams to assess deposition patterns in coastal ice-free areas

Mercury in the Antarctic troposphere has a distinct chemistry and challenging long-term measurements are needed for a better understanding of the atmospheric Hg reactions with oxidants and the exchanges of the various mercury forms among air-snow-sea and biota. Antarctic mosses and lichens are reliable biomonitors of airborne metals and in short time they can give useful information about Hg deposition patterns. Data summarized in this review show that although atmospheric Hg concentrations in the Southern Hemisphere are lower than those in the Northern Hemisphere, Antarctic cryptogams accumulate Hg at levels in the same range or higher than those observed for related cryptogam species in the Arctic, suggesting an enhanced deposition of bioavailable Hg in Antarctic coastal ice-free areas. In agreement with the newest findings in the literature, the Hg bioaccumulation in mosses and lichens from a nunatak particularly exposed to strong katabatic winds can be taken as evidence for a Hg contribution to coastal ecosystems by air masses from the Antarctic plateau. Human activities on the continent are mostly concentrated in coastal ice-free areas, and the deposition in these areas of Hg from the marine environment, the plateau and anthropogenic sources raises concern. The use of Antarctic cryptogams as biomonitors will be very useful to map Hg deposition patterns in costal ice-free areas and will contribute to a better understanding of Hg cycling in Antarctica and its environmental fate in terrestrial ecosystems.

Trends in mercury wet deposition and mercury air concentrations across the U.S. and Canada

This study examined the spatial and temporal trends of mercury (Hg) in wet deposition and air concentrations in the United States (U.S.) and Canada between 1997 and 2013. Data were obtained from the National Atmospheric Deposition Program (NADP) and Environment Canada monitoring networks, and other sources. Of the 19 sites with data records from 1997-2013, 53% had significant negative trends in Hg concentration in wet deposition, while no sites had significant positive trends, which is in general agreement with earlier studies that considered NADP data up until about 2010. However, for the time period 2007-2013 (71 sites), 17% and 13% of the sites had significant positive and negative trends, respectively, and for the time period 2008-2013 (81 sites) 30% and 6% of the sites had significant positive and negative trends, respectively. Non-significant positive tendencies were also widespread. Regional trend analyses revealed significant positive trends in Hg concentration in the Rocky Mountains, Plains, and Upper Midwest regions for the recent time periods in addition to significant positive trends in Hg deposition for the continent as a whole. Sulfate concentration trends in wet deposition were negative in all regions, suggesting a lower importance of local Hg sources. The trend in gaseous elemental Hg from short-term datasets merged as one continuous record was broadly consistent with trends in Hg concentration in wet deposition, with the early time period (1998-2007) producing a significantly negative trend (-1.5±0.2%year(-1)) and the recent time period (2008-2013) displaying a flat slope (-0.3±0.1%year(-1), not significant). The observed shift to more positive or less negative trends in Hg wet deposition primarily seen in the Central-Western regions is consistent with the effects of rising Hg emissions from regions outside the U.S. and Canada and the influence of long-range transport in the free troposphere.

A Modeling Comparison of Mercury Deposition from Current Anthropogenic Mercury Emission Inventories

Human activities have altered the biogeochemical cycle of mercury (Hg) since precolonial times, and anthropogenic activities will continue to perturb the natural cycle of Hg. Current estimates suggest the atmospheric burden is three to five times greater than precolonial times. Hg in the upper ocean is estimated to have doubled over the same period. The Minamata convention seeks to reduce the impact human activities have on Hg releases to the environment. A number of the Articles in the Convention concern the development of detailed inventories for Hg emissions and releases. Using the global Hg chemical transport model, ECHMERIT, the influence of the anthropogenic emission inventory (AMAP/UNEP, EDGAR, STREETS) on global Hg deposition patterns has been investigated. The results suggest that anthropogenic Hg emissions contribute 20-25% to present-day Hg deposition, and roughly two-thirds of primary anthropogenic Hg is deposited to the world's oceans. Anthropogenic Hg deposition is significant in the North Pacific, Mediterranean and Arctic. The results indicate immediate reductions in Hg emissions would produce benefits in the short term, as well as in the long term. The most impacted regions would be suitable to assess changes in Hg deposition resulting from implementation of the Minamata convention.

Flow Analysis of the Mercury Associated with Nonferrous Ore Concentrates: Implications on Mercury Emissions and Recovery in China

This study investigated the flow of mercury (Hg) associated with zinc (Zn), lead (Pb), and copper (Cu) concentrates and provided new insights on the Hg emissions and recovery in both metals-production and wastes-disposal processes in China. Total Hg input from concentrates consumed in China reached 1005.4 t, of which 31.7% was dumped as discarded slags and 2.3% was stabilized (permanent storage). Approximately 202.1 t of Hg was directly emitted to air, water, and soil. More specifically, metals production processes emitted 100.4 t Hg to air. Wastes disposal processes contributed to an additional 47.8 t of atmospheric Hg emissions (which were ignored in most emission inventories) and 32.7 and 21.3 t of Hg to water and soil, respectively. At the same time, out of the 62.6 t of recovered Hg, 95.2% was reclaimed from acid slags. Interim storage of 398.9 t of Hg also highlights the significance of acid slags as potential Hg recovery sources due to the global ban on primary Hg production. The uncertainty ranges (confidence interval: 10%-90%) for Hg emissions to air, water, and soil and for Hg recovery were (-75%, 89%), (-96%, + 111%), (-120%, + 149%), and (-78%, 92%), respectively.

Observed decrease in atmospheric mercury explained by global decline in anthropogenic emissions

Observations of elemental mercury (Hg(0)) at sites in North America and Europe show large decreases (∼ 1-2% y(-1)) from 1990 to present. Observations in background northern hemisphere air, including Mauna Loa Observatory (Hawaii) and CARIBIC (Civil Aircraft for the Regular Investigation of the atmosphere Based on an Instrument Container) aircraft flights, show weaker decreases (<1% y(-1)). These decreases are inconsistent with current global emission inventories indicating flat or increasing emissions over that period. However, the inventories have three major flaws: (i) they do not account for the decline in atmospheric release of Hg from commercial products; (ii) they are biased in their estimate of artisanal and small-scale gold mining emissions; and (iii) they do not properly account for the change in Hg(0)/Hg(II) speciation of emissions from coal-fired utilities after implementation of emission controls targeted at SO2 and NOx. We construct an improved global emission inventory for the period 1990 to 2010 accounting for the above factors and find a 20% decrease in total Hg emissions and a 30% decrease in anthropogenic Hg(0) emissions, with much larger decreases in North America and Europe offsetting the effect of increasing emissions in Asia. Implementation of our inventory in a global 3D atmospheric Hg simulation [GEOS-Chem (Goddard Earth Observing System-Chemistry)] coupled to land and ocean reservoirs reproduces the observed large-scale trends in atmospheric Hg(0) concentrations and in Hg(II) wet deposition. The large trends observed in North America and Europe reflect the phase-out of Hg from commercial products as well as the cobenefit from SO2 and NOx emission controls on coal-fired utilities.

Impacts of the Minamata convention on mercury emissions and global deposition from coal-fired power generation in Asia

We explore implications of the United Nations Minamata Convention on Mercury for emissions from Asian coal-fired power generation, and resulting changes to deposition worldwide by 2050. We use engineering analysis, document analysis, and interviews to construct plausible technology scenarios consistent with the Convention. We translate these scenarios into emissions projections for 2050, and use the GEOS-Chem model to calculate global mercury deposition. Where technology requirements in the Convention are flexibly defined, under a global energy and development scenario that relies heavily on coal, we project ∼90 and 150 Mg·y(-1) of avoided power sector emissions for China and India, respectively, in 2050, compared to a scenario in which only current technologies are used. Benefits of this avoided emissions growth are primarily captured regionally, with projected changes in annual average gross deposition over China and India ∼2 and 13 μg·m(-2) lower, respectively, than the current technology case. Stricter, but technologically feasible, mercury control requirements in both countries could lead to a combined additional 170 Mg·y(-1) avoided emissions. Assuming only current technologies but a global transition away from coal avoids 6% and 36% more emissions than this strict technology scenario under heavy coal use for China and India, respectively.

Observational and modeling constraints on global anthropogenic enrichment of mercury

Centuries of anthropogenic releases have resulted in a global legacy of mercury (Hg) contamination. Here we use a global model to quantify the impact of uncertainty in Hg atmospheric emissions and cycling on anthropogenic enrichment and discuss implications for future Hg levels. The plausibility of sensitivity simulations is evaluated against multiple independent lines of observation, including natural archives and direct measurements of present-day environmental Hg concentrations. It has been previously reported that pre-industrial enrichment recorded in sediment and peat disagree by more than a factor of 10. We find this difference is largely erroneous and caused by comparing peat and sediment against different reference time periods. After correcting this inconsistency, median enrichment in Hg accumulation since pre-industrial 1760 to 1880 is a factor of 4.3 for peat and 3.0 for sediment. Pre-industrial accumulation in peat and sediment is a factor of ∼ 5 greater than the precolonial era (3000 BC to 1550 AD). Model scenarios that omit atmospheric emissions of Hg from early mining are inconsistent with observational constraints on the present-day atmospheric, oceanic, and soil Hg reservoirs, as well as the magnitude of enrichment in archives. Future reductions in anthropogenic emissions will initiate a decline in atmospheric concentrations within 1 year, but stabilization of subsurface and deep ocean Hg levels requires aggressive controls. These findings are robust to the ranges of uncertainty in past emissions and Hg cycling.

Distant drivers or local signals: where do mercury trends in western Arctic belugas originate?

Temporal trends of contaminants are monitored in Arctic higher trophic level species to inform us on the fate, transport and risk of contaminants as well as advise on global emissions. However, monitoring mercury (Hg) trends in species such as belugas challenge us, as their tissue concentrations reflect complex interactions among Hg deposition and methylation, whale physiology, dietary exposure and foraging patterns. The Beaufort Sea beluga population showed significant increases in Hg during the 1990 s; since that time an additional 10 years of data have been collected. During this time of data collection, changes in the Arctic have affected many processes that underlie the Hg cycle. Here, we examine Hg in beluga tissues and investigate factors that could contribute to the observed trends after removing the effect of age and size on Hg concentrations and dietary factors. Finally, we examine available indicators of climate variability (Arctic Oscillation (AO), the Pacific Decadal Oscillation (PDO) and sea-ice minimum (SIM) concentration) to evaluate their potential to explain beluga Hg trends. Results reveal a decline in Hg concentrations from 2002 to 2012 in the liver of older whales and the muscle of large whales. The temporal increases in Hg in the 1990 s followed by recent declines do not follow trends in Hg emission, and are not easily explained by diet markers highlighting the complexity of feeding, food web dynamics and Hg uptake. Among the regional-scale climate variables the PDO exhibited the most significant relationship with beluga Hg at an eight year lag time. This distant signal points us to consider beluga winter feeding areas. Given that changes in climate will impact ecosystems; it is plausible that these climate variables are important in explaining beluga Hg trends. Such relationships require further investigation of the multiple connections between climate variables and beluga Hg.