Anthropogenic Mercury Emissions Research Articles

Mercury Deposition, Climate Change and Anthropogenic Activities: A Review

As a toxic and harmful global pollutant, mercury enters the environment through natural sources and human activities. Based on large numbers of previous studies, this paper summarizes the characteristics of mercury deposition, the impact of climate change and human activities on mercury deposition from a global perspective. The results indicate that the mercury accumulation level was relatively low before the Industrial Revolution of 1840, while after the industrialization, intensive industrial activities produced large amounts of anthropogenic mercury emissions and the accumulation increased rapidly. The cold climate is conducive to the accumulation of mercury, whereas the warm climate works to the disadvantage of mercury accumulation. Before the industrialization, the kustelite and mercury mining and the widespread use of cinnabar were the main sources of anthropogenic mercury; After the industrialization, the coal combustion, the non-ferrous metal smelting, the waste incineration and the chlor-alkali industry development have led to a significant increase in anthropogenic emissions of mercury, which in turn has caused a sharp increase in mercury deposition. Through analysis, the author finds that most of the research areas are distributed in the Northern Hemisphere, including Europe, North America and China of Asia, but only in parts of the Southern Hemisphere, including South America, Africa and Antarctica; The study mainly focuses on the time scales since the Holocene, and there are not many studies focusing on the time scales before the Holocene; The natural record bodies widely used in the previous studies are fen peat and lacustrine deposits. The ice core records with higher resolution are very few, and there are almost no stalagmite records. Since few studies have been conducted on the relationship between precipitation change and mercury accumulation, the impact of climate change, especially the impact of humidity change on the mercury accumulation mechanism has not yet been deeply studied. Therefore, due to the fact that the research spots are unevenly distributed, the mercury deposition records with the longer time scales and higher resolution are not available and the study on relationship between precipitation and mercury accumulation is not deep enough, the relevant research needs to be further carried out.

Mercury Exposure through Fish Consumption in Traditional Communities in the Brazilian Northern Amazon.

Artisanal small-scale gold mining (ASGM) is the main source of anthropogenic mercury emissions and contamination in Latin America. In the Brazilian northern Amazon, ASGM has contaminated the environment and people over the past century. The main contamination route is through fish consumption, which endangers the food security and livelihoods of traditional communities. Our study aims to assess the potential toxicological health risks caused by the consumption of Hg-contaminated fish across five regions in Amapá State. We sampled 428 fish from 18 sites across inland and coastal aquatic systems. We measured the total mercury content in fish samples, and the results were applied to a mercury exposure risk assessment targeting three distinct groups (adults, women of childbearing age, and children). Mercury contamination was found to exceed the World Health Organization’s safe limit in 28.7% of all fish samples, with higher prevalence in inland zones. Moreover, the local preference for carnivorous fish species presents a serious health risk, particularly for communities near inland rivers in the region. This is the first study to provide clear recommendations for reducing the mercury exposure through fish consumption in Amapá State. It builds scientific evidence that helps decision-makers to implement effective policies for protecting the health of riverine communities.

A revised pan-Arctic permafrost soil Hg pool based on Western Siberian peat Hg and carbon observations

Abstract. Natural and anthropogenic mercury (Hg) emissions are sequestered in terrestrial soils over short, annual to long, millennial timescales before Hg mobilization and run-off impact wetland and coastal ocean ecosystems. Recent studies have used Hg-to-carbon (C) ratios (RHgC's) measured in Alaskan permafrost mineral and peat soils together with a northern circumpolar permafrost soil carbon inventory to estimate that these soils contain large amounts of Hg (between 184 and 755 Gg) in the upper 1 m. However, measurements of RHgC on Siberian permafrost peatlands are largely missing, leaving the size of the estimated northern soil Hg budget and its fate under Arctic warming scenarios uncertain. Here we present Hg and carbon data for six peat cores down to mineral horizons at 1.5–4 m depth, across a 1700 km latitudinal (56 to 67∘ N) permafrost gradient in the Western Siberian Lowland (WSL). Mercury concentrations increase from south to north in all soil horizons, reflecting a higher stability of sequestered Hg with respect to re-emission. The RHgC in the WSL peat horizons decreases with depth, from 0.38 Gg Pg−1 in the active layer to 0.23 Gg Pg−1 in continuously frozen peat of the WSL. We estimate the Hg pool (0–1 m) in the permafrost-affected part of the WSL peatlands to be 9.3±2.7 Gg. We review and estimate pan-Arctic organic and mineral soil RHgC to be 0.19 and 0.63 Gg Pg−1, respectively, and use a soil carbon budget to revise the pan-Arctic permafrost soil Hg pool to be 72 Gg (39–91 Gg; interquartile range, IQR) in the upper 30 cm, 240 Gg (110–336 Gg) in the upper 1 m, and 597 Gg (384–750 Gg) in the upper 3 m. Using the same RHgC approach, we revise the upper 30 cm of the global soil Hg pool to contain 1086 Gg of Hg (852–1265 Gg, IQR), of which 7 % (72 Gg) resides in northern permafrost soils. Additional soil and river studies in eastern and northern Siberia are needed to lower the uncertainty on these estimates and assess the timing of Hg release to the atmosphere and rivers.

Computational Chemistry-Based Evaluation of Metal Salts and Metal Oxides for Application in Mercury-Capture Technologies

Anthropogenic mercury emission to the atmosphere adversely affects the environment, wildlife, and human health. Accordingly, the design and implementation of improved mercury-capture technologies h...

The effect of mechanical-chemical-brominated modification on physicochemical properties and mercury removal performance of coal-fired by-product

Coal combustion is one of the largest anthropogenic mercury emission source in China, while the coal-fired by-product such as fly ash (FA) and bottom ash (BA) are raw material for making mercury removal adsorbent with low-cost and high efficient and recycling. The mechanical-chemical brominated FA (FA-MC-Br) and BA (BA-MC-Br) were prepared through the omni-directional planetary ball mill. The physicochemical properties of FA, FA-MC-Br, BA, and BA-MC-Br were compared and discussed based on analyses of the X-ray photoelectron spectroscopy, Brunauer-Emmet-Teller, Scanning Electron Microscopy, and mercury temperature programmed desorption, etc. The mercury-removal ability of the four samples was estimated by fixed-bed react system which showed that the mechanical-chemical-brominated modification has no significant effect on the pore structures of FA and BA but obviously reducing their particle sizes and increase the amorphous phase on surface of FA and BA. Besides, the Fe content on the surface of BA was enhanced as well. The Br loading rate of FA-MC-Br and BA-MC-Br is 61.35% and 48.67%, respectively. The mercury removal ability of FA/BA can be significantly improved by the mechanical-chemical-brominated modification. The reaction mechanism and pathways of Hg0 removal by FA-MC-Br and BA-MC-Br can be deduced as the following two parts: (a) HgO is adsorbed and oxidized by the active chemisorbed oxygen and Fe3+ on the surface of samples. (b) HgBr2 is generated by the reaction between the C-Br and Hg0, which follows the Eley-Rideal mechanism.

Atmospheric mercury accumulation rate in northeastern China during the past 800 years as recorded by the sediments of Tianchi Crater Lake.

An evaluation of the history of anthropogenic mercury (Hg) emissions is needed to quantify total atmospheric Hg emissions since the Industrial Revolution. Thus more long-term records of Hg accumulation rate from natural archives are needed. In the present study, a sediment core from Tianchi Lake, a crater lake in northeastern China, was used to reconstruct atmospheric Hg accumulation rates during the past 800 years. The results show that both Hg concentration and Hg accumulation rate began to increase from 29.5 to 40.2 ng g-1 and from 1.44 to 2.26 μgm-2yr-1, respectively, at ~ 1750 AD, synchronous with the initiation of the Industrial Revolution. The Hg accumulation rate and Hg concentration increased significantly at ~ 1850 AD, and subsequently, there were two prominent peaks, at ~ 1940 AD and ~ 1980 AD, which are temporally consistent with the Second World War and the peak in commercial usage of Hg, respectively. The Hg accumulation rate and Hg concentration decreased after ~ 1980 AD, possibly because of the decrease in the global Hg background at that time. Differences in regional Hg emissions and atmospheric circulation may be responsible for the different trends in Hg accumulation rate after ~ 1980 AD in the Tibetan Plateau and northeastern China. Our results provide new data for evaluating natural and anthropogenic Hg emissions to the atmosphere in China.

Natural Kaolin: Sustainable Technology for the Instantaneous and Energy-Neutral Recycling of Anthropogenic Mercury Emissions.

Kaolin, a natural and inexpensive clay mineral, is ubiquitous in soil, dirt, and airborne particles. Amongst four commonly available clay minerals, kaolin, as a result of its layered structure, is the most efficient natural gaseous Hg adsorbent to date (Langmuir maximum adsorption capacity Qm =574.08 μg g-1 and Freundlich Qm =756.49 μg g-1 ). The Hg uptake proceeds by homogeneous monolayer and heterogeneous processes. Hg physisorption on kaolin occurs in the dark, yet the adsorption rate is enhanced upon irradiation. The effects of several metal complexes, salts, halides and solvents on the Hg uptake were examined. The addition of CuCl2 particles leads to a significant enhancement of the Hg uptake capacity (>30 times) within second timescales and without irradiation. The physisorption with kaolin is switched to chemisorption upon the addition of CuCl2 to kaolin. This process is entirely reversible upon the addition of Zn/Sn granules at room temperature without any added energy. However, the investment of a small amount of renewable energy can speed up the process. This technology demonstrates the facile and efficient capture and recycling of elemental Hg0 from air. A wide range of metal particles and diverse physicochemical processes, which include the microphysics of nucleation, are herein examined to explore the potential reaction mechanism by using a suite of complementary analytical techniques. These new mechanistic insights open a new era of energy-neutral environmental remediation based on natural soil/airborne particles.

An assessment of temporal trends in mercury concentrations in fish

The importance of fish consumption as the primary pathway of human exposure to mercury and the establishment of fish consumption advisories to protect human health have led to large fish tissue monitoring programs worldwide. Data on fish tissue mercury concentrations collected by state, tribal, and provincial governments via contaminant monitoring programs have been compiled into large data bases by the U.S. Environmental Protection Agency's Great Lakes National Monitoring Program Office (GLNPO), the Ontario Ministry of the Environment's Fish Contaminants Monitoring and Surveillance Program (FMSP), and many others. These data have been used by a wide range of governmental and academic investigators worldwide to examine long-term and recent trends in fish tissue mercury concentrations. The largest component of the trend literature is for North American freshwater species important in recreational fisheries. This review of temporal trends in fish tissue mercury concentrations focused on published results from freshwater fisheries of North America as well as marine fisheries worldwide. Trends in fish tissue mercury concentrations in North American lakes with marked overall decreases were reported over the period 1972-2016. These trends are consistent with reported mercury emission declines as well as trends in wet deposition across the U.S. and Canada. More recently, a leveling-off in the rate of decreases or increases in fish tissue mercury concentrations has been reported. Increased emissions of mercury from global sources beginning between 1990 and 1995, despite a decrease in North American emissions, have been advanced as an explanation for the observed changes in fish tissue trends. In addition to increased atmospheric deposition, the other factors identified to explain the observed mercury increases in the affected fish species include a systematic shift in the food-web structure with the introduction of non-native species, creating a new or expanding role for sediments as a net source for mercury. The influences of climate change have also been identified as contributing factors, including considerations such as increases in temperature (resulting in metabolic changes and higher uptake rates of methylmercury), increased rainfall intensity and runoff (hydrologic export of organic matter carrying HgII from watersheds to surface water), and water level fluctuations that alter either the methylation of mercury or the mobilization of monomethylmercury. The primary source of mercury exposure in the human diet in North America is from the commercial fish and seafood market which is dominated (>90%) by marine species. However, very little information is available on mercury trends in marine fisheries. Most of the data used in the published marine trend studies are assembled from earlier reports. The data collection efforts are generally intermittent, and the spatial and fish-size distribution of the target species vary widely. As a result, convincing evidence for the existence of fish tissue mercury trends in marine fish is generally lacking. However, there is some evidence from sampling of large, long-lived commercially-important fish showing both lower mercury concentrations in the North Atlantic in response to reduced anthropogenic mercury emission rates in North America and increases in fish tissue mercury concentrations over time in the North Pacific in response to increased mercury loading.

Primary Suppliers Driving Atmospheric Mercury Emissions through Global Supply Chains

Summary The Minamata Convention on Mercury, which came into force in 2017, aims to control mercury-related risks to human beings and ecosystems by reducing anthropogenic mercury (Hg) emissions. Existing studies have identified direct atmospheric Hg emitters and final consumers causing atmospheric Hg emissions but overlooked primary suppliers driving atmospheric Hg emissions through global supply chains. Here, we identify critical primary suppliers and supply-chain paths for global atmospheric Hg emissions in 2015. Results show that China, Indonesia, and India are major primary suppliers causing global atmospheric Hg emissions. Major sectors and critical supply-chain paths from the supply viewpoint are related to resource extraction and power generation. Findings of this study can support supply-side measures to implement the Minamata Convention on Mercury, such as the optimization of labor and capital input structures and the optimization of product-allocation behaviors to downstream producers.

Comparison of Mercury Contamination in Four Indonesian Watersheds Affected by Artisanal and Small-Scale Gold Mining of Varying Scale

Artisanal and small-scale gold mining (ASGM) accounts for almost half of anthropogenic mercury (Hg) emissions worldwide and causes widespread water pollution. In Indonesia, several studies have identified harmful levels of Hg in areas affected by ASGM. While most of these studies focus on mining areas with thousands of miners, water contamination in smaller ASGM areas is less understood. We evaluated Hg contamination in four ASGM areas in Central Java of varying scale (from 30 to 3000 amalgamator barrels at each area), including Jatiroto, Kebonsari, Gumelar, and Kulon Progo. At each location, we collected water samples along river transects upstream and downstream of ASGM areas during the dry season (June–July 2017). Total Hg (THg) concentrations in stream water increased by orders of magnitude from upstream to downstream of ASGM activities at Jatiroto (1.35–4730 ng/L), with smaller observed increases at the other locations. Dissolved THg concentrations exceeded USEPA criteria for aquatic life (12 ng/L) at two of the four ASGM areas. THg concentrations in tailings exceeded 150,000 ng/L. Notably, THg concentrations in stream water were not directly related to the scale of mining, with Jatiroto having the highest concentrations as second smallest mining areas of the four in this study. Downstream of the mining areas, the fraction of dissolved methyl Hg to dissolved THg reached 20%, indicating that active Hg methylation occurs in the watersheds. Further study is needed to investigate Hg transport in the wet season when rainfall and high stream discharge may mobilize contaminated sediment near mining areas.

Development and application of an updated geospatial distribution model for gridding 2015 global mercury emissions

Mercury is a global pollutant that poses threats to ecosystems and to human health. Due to its global transport, mercury contamination is found in regions of the Earth that are remote from major emissions areas, including the Polar regions. Global anthropogenic emission inventories identify important sectors and industries responsible for emissions at a national level; however, to be useful for air transport modelling, more precise information on the locations of emission is required. This paper describes the methodology applied, and the results of work that was conducted to geospatially distribute anthropogenic mercury emissions as part of the global anthropogenic mercury emissions inventory for 2015 prepared by AMAP/UNEP for the Global Mercury Assessment (GMA) 2018 (UN Environment, 2019). This work includes the identification and use of emission point sources as well as distributing diffuse emissions for 21 emission (industry) sectors. The basic approach involves assigning emission estimates to geo-located point sources, using reported emissions information where available, and otherwise assigning a modelled emission to the point. Emissions which cannot be assigned to point sources are distributed using sector-specific proxies. Mercury speciation highly depends on industry processes and air pollution control technology. Different Hg speciation ratios are therefore applied per sector and country technology level. The resulting global emission datasets include total mercury (HgT), gaseous elemental mercury (Hg0), divalent mercury (Hg2+) and particulate mercury (HgP) in kg per year per raster cell (kg/a). The spatial resolution is flexible and the vertical resolution of the data is based on a set of predefined height classes. The resolution of the GMA2018 emission data is 0.25° × 0.25° with three (physical emission) height classes (0–50, 50–150 and > 150m). A comparison with the EMEP European mercury emission was made based on spatial correlation between the two datasets. Suggested improvements for future work include the further development of proxy data and the implementation of a more structured reporting of emissions by countries.

Effect of air pollution control devices on mercury isotopic fractionation in coal-fired power plants

Coal combustion is an important source of anthropogenic mercury (Hg) emissions. Air pollution control devices (APCDs) are widely used in coal-fired power plants (CFPPs) to reduce pollutant emissions including Hg. To gain insight into the Hg isotopic fractionation produced by APCDs, the Hg isotopic compositions of feed coal (FC) samples and combustion byproducts from 7 CFPP utility boilers in Hebei Province of China were studied. Significant mass-dependent fractionation (MDF) was observed in combustion byproducts when comparing with FC samples, while mass-independent fractionation (MIF) was not identified. Compared to FC samples, no significant difference in bottom ash (BA, δ202HgBA-FC = 0.08 ± 0.16‰, 1SD, n = 3) samples while light isotopes were enriched in fly ash (FA, δ202HgFA-FC = −0.38 ± 0.75‰, 1SD, n = 7) samples. Boilers lacking of a selective catalytic reducer (SCR) unit produced gypsum (GY) samples with negative MDF signatures compared to FC samples (δ202HgGY-FC, no SCR = −0.22 ± 0.10‰, 1SD, n = 3). In contrast, boilers equipped with a SCR unit produced GY samples with higher MDF signatures (δ202HgGY-FC, SCR = 0.54 ± 0.40‰, 1SD, n = 3), probably as a result of the oxidation of Hg0 in the SCR unit. Calculated isotopic signatures of gaseous Hg in the stack emission (SE, δ202HgSE-FC = 0.03 ± 0.20‰, 1SD, n = 7) had no significant difference from that of FC samples. The results suggested distinct isotopic compositions should be fully considered during tracing Hg pollution via Hg isotopic signatures, especially when solid produced by CFPPs were involved.

Urban source term estimation for mercury using a boundary-layer budget method

Abstract. Mercury is a heavy metal of particular concern due to its adverse effects on human health and the environment. Recognizing this problem, the UN Minamata Convention on Mercury was recently adopted, where signatory countries agreed to reduce anthropogenic mercury emissions. To evaluate the effectiveness of the convention, quantitative knowledge on mercury emissions is crucial. So far, bottom-up approaches have successfully been applied to quantify mercury emission – especially for point sources. Distributed sources make up a large share of the emission; however, they are still poorly characterized. Here, we present a top-down approach to estimate mercury emissions based on atmospheric measurements in the city of Zurich, Switzerland. While monitoring the atmospheric mercury concentrations during inversion periods in Zurich, we were able to relate the concentration increase to the mercury emission strength of the city using a box model. By means of this boundary-layer budget approach, we succeeded in narrowing down the emissions of Zurich to range between 41±8 kg a−1 (upper bound) and 24±8 kg a−1 (lower bound). Thereby, we could quantify emissions from mixed, diffuse and point-like sources and derive an annual mercury per capita emission of 0.06 to 0.10 g a−1. The approach presented here has the potential to support authorities in setting up inventories and to validate emission estimations derived from the commonly applied bottom-up approaches. Furthermore, our method is applicable to other compounds and to a wide range of cities or other areas, where sources or sinks for mercury and other atmospheric pollutants are presumed.

Mercury levels in blood, urine and hair in a nation-wide sample of Spanish adults

Mercury (Hg) is among the top 10 environmental chemicals of major public health concern (WHO). The Minamata Convention on Mercury (United Nations Environment Program, 2017), commits signing countries to control anthropogenic mercury emissions and reduce human exposure. Human biomonitoring (HBM) programs, are the most straight-forward approaches to get information on the actual exposure levels in the population and assess over time. We report here the results of a HBM study in a nationwide cross-section of Spanish adults (18–65y) as baseline values obtained before the Minamata Convention entered into force. Subsequent follow-ups will show if the Convention has been successful. The study includes 1880 blood samples, 1704 urine samples and 577 hair samples from all Spanish regions collected and analysed under a strictly quality controlled and quality assured protocol. The EU-DEMOCOPHES project demonstrated that fish and seafood are the major sources of mercury exposure and that the Spanish as well as the Portuguese populations have higher levels than other European countries. The data from the present study confirms this pattern at national level and that inhabitants in coastal regions have higher values than from inland regions. The geometric mean (GM) for blood is 6.35 μg Hg/l, in urine is 1.11 μg Hg/l and for hair is 1.91 μg Hg/g. In an international comparison these values are not exceptional. Spanish concentrations fall into the group of Easter Mediterranean populations. Although information on gender, age, occupational sector, geographical area, sampling period and frequency of fish consumption is reported in the tables, the purpose of this paper has not been to analyse the determinants of exposure in detail but to provide baseline data for future assessments and for regional authorities.

Major sources of mercury emissions to the atmosphere: The U.S. case

In 1989, the two major sources of mercury emissions to the atmosphere in the U.S. were coal-fired power plants (80 tons Hg) and waste to energy power plants (82 tons Hg). This paper examines what has happened to these two major sources of mercury emissions since 1989. A comparison within the waste management industry is, also, provided. The 2014 total anthropogenic emissions of mercury in the U.S. were 51.8 t. The results of the analysis of emissions by industrial sector showed that the largest source of anthropogenic mercury were coal-fired power plants. Among industrial processes, the ferrous metals recycling and the cement industries were the largest emitters of mercury. With regard to waste-to-energy power plants, all of which, since the nineties, have installed advanced emission control systems, the results have been very satisfactory: The authors obtained mercury emission data from operators of most of the waste-to-energy (WTE) power plants in the US. The results showed that in 2014 the 77 U.S. WTE plants in total emitted 0.4 tons of mercury, corresponding to 0.77% of the U.S. total. This number was one half of that reported by the National Emissions Inventory (NEI) for “municipal waste combustion’’ (0.64 t) due to the fact that the NEI survey included incinerators without energy recovery. A 2002 Earth Engineering Center study had shown that the mercury emissions of the U.S. WTE industry decreased from 81.8 t in 1989 to 2.2 t in 2001. The present study showed that between 2001 and 2014 the U.S. WTE industry mercury emissions were reduced further, by a factor of seven.

Source Attribution for Mercury Deposition with an Updated Atmospheric Mercury Emission Inventory in the Pearl River Delta Region, China.

We used CMAQ-Hg to simulate mercury pollution and identify main sources in the Pearl River Delta (PRD) with updated local emission inventory and latest regional and global emissions. The total anthropogenic mercury emissions in the PRD for 2014 were 11,939.6 kg. Power plants and industrial boilers were dominant sectors, responsible for 29.4 and 22.7%. We first compared model predictions and observations and the results showed a good performance. Then five scenarios with power plants (PP), municipal solid waste incineration (MSWI), industrial point sources (IP), natural sources (NAT), and boundary conditions (BCs) zeroed out separately were simulated and compared with the base case. BCs was responsible for over 30% of annual average mercury concentration and total deposition while NAT contributed around 15%. Among the anthropogenic sources, IP (22.9%) was dominant with a contribution over 20.0% and PP (18.9%) and MSWI (11.2%) ranked second and third. Results also showed that power plants were the most important emission sources in the central PRD, where the ultra-low emission for thermal power units need to be strengthened. In the northern and western PRD, cement and metal productions were priorities for mercury control. The fast growth of municipal solid waste incineration were also a key factor in the core areas. In addition, a coordinated regional mercury emission control was important for effectively controlling pollution. In the future, mercury emissions will decrease as control measures are strengthened, more attention should be paid to mercury deposition around the large point sources as high levels of pollution are observed.

Eurasian river spring flood observations support net Arctic Ocean mercury export to the atmosphere and Atlantic Ocean

Midlatitude anthropogenic mercury (Hg) emissions and discharge reach the Arctic Ocean (AO) by atmospheric and oceanic transport. Recent studies suggest that Arctic river Hg inputs have been a potentially overlooked source of Hg to the AO. Observations on Hg in Eurasian rivers, which represent 80% of freshwater inputs to the AO, are quasi-inexistent, however, putting firm understanding of the Arctic Hg cycle on hold. Here, we present comprehensive seasonal observations on dissolved Hg (DHg) and particulate Hg (PHg) concentrations and fluxes for two large Eurasian rivers, the Yenisei and the Severnaya Dvina. We find large DHg and PHg fluxes during the spring flood, followed by a second pulse during the fall flood. We observe well-defined water vs. Hg runoff relationships for Eurasian and North American Hg fluxes to the AO and for Canadian Hg fluxes into the larger Hudson Bay area. Extrapolation to pan-Arctic rivers and watersheds gives a total Hg river flux to the AO of 44 ± 4 Mg per year (1σ), in agreement with the recent model-based estimates of 16 to 46 Mg per year and Hg/dissolved organic carbon (DOC) observation-based estimate of 50 Mg per year. The river Hg budget, together with recent observations on tundra Hg uptake and AO Hg dynamics, provide a consistent view of the Arctic Hg cycle in which continental ecosystems traffic anthropogenic Hg emissions to the AO via rivers, and the AO exports Hg to the atmosphere, to the Atlantic Ocean, and to AO marine sediments.

Characteristics of particulate-bound mercury at typical sites situated on dust transport paths in China

The concentrations and seasonal variations of PBM (particulate-bound mercury) were observed at four dust source sites (Duolun, Yulin, Hetian, and Tazhong), two megacities (Shanghai and Beijing), and an island site (Huaniao Island) to obtain the spatiotemporal characteristics of PBM in dust transport path from desert area in China to the East China Sea. The highest annual mean concentrations of PBM in TSP (PBMTSP) were observed at megacity sites, reaching 146.7 pg/m3 and 274.7 pg/m3 in Shanghai and Beijing attributed primarily to anthropogenic emissions, while 39.7 pg/m3, 67.3 pg/m3, 61.0 pg/m3, 23.5 pg/m3 and 43.6 pg/m3 over Duolun, Yulin, Hetian, Tazhong, and Huaniao Island, respectively. PBM concentrations were higher in winter and autumn, while lower in spring and summer due to the variation of meteorological conditions (especially temperature and wind speed) together with the emission sources. Enrichment factors (EFs) of PBMTSP and PBM2.5 reached 158 and 1452 in Beijing, showing the serious anthropogenic emissions impacted on PBM pollution in megacities, and the profound high level of EFs of mercury in sand dust source sites (17–64 for TSP and 38–252 for PM2.5), suggesting the obvious mixing effect of dust and anthropogenic aerosols in dust source areas. Human activities played a major role in the increase of PBM concentrations and the enrichment factors during the long-range transport of air mass in China. The significant anthropogenic mercury emissions in the dust source areas and their long-range transport driven by the East Asian Monsoon might impact on the ecological cycle of mercury and should be taken into the mercury inventories. Coal combustion and smelting contributed 52–94% to PBM over all three types of sampling sites, and mining operations were additional sources of PBM in Yulin. In the coastal area, sea salt is an important source of PBM, and shipping could also contribute a certain proportion to PBM pollution which shouldn't be ignored.

A vegetation control on seasonal variations in global atmospheric mercury concentrations

Anthropogenic mercury emissions are transported through the atmosphere as gaseous elemental mercury (Hg(0)) before they are deposited to Earth’s surface. Strong seasonality in atmospheric Hg(0) concentrations in the Northern Hemisphere has been explained by two factors: anthropogenic Hg(0) emissions are thought to peak in winter due to higher energy consumption, and atmospheric oxidation rates of Hg(0) are faster in summer. Oxidation-driven Hg(0) seasonality should be equally pronounced in the Southern Hemisphere, which is inconsistent with observations of constant year-round Hg(0) levels. Here, we assess the role of Hg(0) uptake by vegetation as an alternative mechanism for driving Hg(0) seasonality. We find that at terrestrial sites in the Northern Hemisphere, Hg(0) co-varies with CO2, which is known to exhibit a minimum in summer when CO2 is assimilated by vegetation. The amplitude of seasonal oscillations in the atmospheric Hg(0) concentration increases with latitude and is larger at inland terrestrial sites than coastal sites. Using satellite data, we find that the photosynthetic activity of vegetation correlates with Hg(0) levels at individual sites and across continents. We suggest that terrestrial vegetation acts as a global Hg(0) pump, which can contribute to seasonal variations of atmospheric Hg(0), and that decreasing Hg(0) levels in the Northern Hemisphere over the past 20 years can be partly attributed to increased terrestrial net primary production.

Food preference and ecotoxicological tests with millipedes in litter contaminated with mercury

Worldwide, various guidelines and directives for human health and the environment aim to reduce anthropogenic mercury (Hg) emission. Forest ecosystems are natural sinks of this element, transferring it from the atmosphere to litter and soil. Millipedes play an important role in litter/soil and may be negatively affected by contamination. As a pioneering contribution to ecotoxicological test guidelines with millipedes in litter, the present study evaluated food preference of millipedes and mercury toxicity, to prevent interference of food types in toxicity responses. Four food preference tests were performed with Trigoniulus corallinus and Rhinocricus padbergi in relation to leaf morphology, leaf fragmentation level and palatability/nutritional quality. Ecotoxicological effects on these animals were evaluated with increasing concentrations of HgCl2 spiked in litter. In both species, Hg concentrations were measured in repugnatorial glands, casts, exoskeleton and gut. In 28day trials, high bioaccumulation factors (BAF) of Hg were found in gut (= 56), exoskeleton (= 49) and casts (= 39) of R. padbergi. BAFs in the gut, exoskeleton and casts of T. corallinus were lower: 52, 45 and 32, respectively. Mortality tests indicated higher sensitivity of T. corallinus to Hg, compared with R. padbergi. Regarding leaf morphology, lanceolate, linear, obovate and ovate leaf shapes and entire margin were preferred by both species. Although higher biomass gain for both species was observed by ingestion of smaller fragmentation stages, T. corallinus preferred more fragmented leaves while R. padbergi consumed more leaves with lower fragmentation level. Both species preferred and grew better in cellulose-rich litter with lower lignin content corresponding to the mixed litter, over single species leaves of Myrceugenia scutellata and Inga edulis. Therefore, future ecological tests with millipedes should consider the use of entire leaves with less irregular shapes, and higher cellulose and lower lignin contents, to provide ideal conditions for millipede growth and activity.