Anthropogenic Mercury Emissions Research Articles

Past and present mercury accumulation in the Lake Baikal seal: Temporal trends, effects of life history, and toxicological implications.

Despite global efforts to reduce anthropogenic mercury (Hg) emissions, the timescale and degree to which Hg concentrations in the environment and biota respond to decreased emissions remain challenging to assess or predict. In the present study we characterize long-term trends and life-history patterns in Hg accumulation and toxicological implications of Hg contamination for a freshwater seal from one of the world's largest lakes (Lake Baikal, Siberia, Russia) using contemporary tissues and archival teeth. Stable isotope analysis and Hg analyses of soft tissues (muscle, liver, kidney, blood, brain, heart) and teeth from 22 contemporary seals revealed rapid changes in diet and Hg accumulation in the first year of life with a stable diet and increase in tissue Hg throughout the rest of life. Although maternal transfer of Hg was an important source of Hg to seal pups, reproduction and lactation by female seals did not appear to result in sex-related differences in Hg concentrations or age-related accumulation in adult seals. Based on Hg analysis of archival teeth (n = 114) and reconstructed values for soft tissues, we also assessed temporal trends in seal Hg between the years 1960 and 2013. Seal Hg concentrations in hard (teeth) and soft (e.g., muscle, liver) tissues were highest in the 1960s and 1970s, followed by a decrease. The decline in seal Hg concentrations in recent decades was most likely driven by a reduction in Hg inputs to the lake, suggesting that global and regional efforts to reduce Hg emissions have been successful at reducing ecosystem and human health risks posed by Hg in Lake Baikal. Environ Toxicol Chem 2018;37:1476-1486. © 2018 SETAC.

Present and Future Mercury Concentrations in Chinese Rice: Insights From Modeling

AbstractWe construct a rice paddy biogeochemical cycle model to investigate processes governing rice mercury sources and to understand factors influencing spatiotemporal variability in Chinese rice mercury concentrations. The rice paddy model takes atmospheric mercury deposition, simulated from a global atmospheric chemistry transport model (GEOS‐Chem), and soil and irrigable surface water mercury concentrations obtained from literature and calculates rice inorganic (IHg) and methylmercury (MeHg) concentrations. We use ranges of GEOS‐Chem‐simulated future atmospheric mercury deposition—no policy and strict policy to regulate mercury emissions from Chinese coal‐fired power plants under the Minamata Convention on Mercury—to simulate future rice IHg and MeHg concentrations. Sensitivity analyses suggest that rice IHg and MeHg concentrations are more sensitive to the process of soil desorption than infiltration of recently introduced mercury (atmospheric and irrigation source). The rate of internal methylation via microbial activity has the largest modeled influence on rice MeHg concentration. We find that soil mercury, rather than atmospheric deposition, explains observed spatial variability in rice IHg and MeHg concentrations and captures locations of rice mercury hot spots (>20 ng/g; China National Standard Limit). Under our future scenarios, the Chinese median rice IHg and MeHg concentration increases by 13% and decrease by 18% under no policy and strict policy, respectively. Regions with the largest percentage decline in rice IHg and MeHg concentrations under strict policy are in central China, which have high rice mercury concentrations, rice production, and consumption. Our study suggests that addressing Chinese rice mercury contamination requires attention to contaminated soil and regulation of anthropogenic mercury emissions.

Semi-automatic system for methylmercury determination in biological samples

For living creatures the presence of methylmercury is the most dangerous result of anthropogenic mercury emission. In order to improve and facilitate the determination of methylmercury (MeHg) with the manual Headspace Tenax Gas Chromatography - Atomic Fluorescence (HS-Tenax-GC-AFS) method, a low cost, semi-automatic measurement system (SA-GC-AFS) was designed and constructed. The developed MeHg determination method was optimized and validated according to the Eurachem recommendations. The validation parameters of the developed method were as follows: linearity: 0.9997, method detection limit: 1.4 ng/g; repeatability: 5.6%; recovery: 99–102%. The estimated combined uncertainty of the method was U = 11.2%. Comparing with the manual method the repeatability was improved and the reduction of analyst effort was obtained. The SA-GC-AFS method was successfully applied to MeHg determination in 76 racoon (Procyon lotor) samples (muscle, liver, kidney, brain). The SA-GC-AFS system is the good, low cost alternative to the expensive commercial automated MeHg determination systems.

Preliminary assessment of the possibility of mercury removal from hard coal with the use of air concentrating tables

Abstract Mercury is characterized by highly toxic properties. The natural biogeochemical cycle of mercury occurs in the environment, which results in the fact that even a small amount of mercury emitted to the environment is a potential threat to human health. The process of coal combustion is one of the main sources of anthropogenic mercury emissions. For this reason, on 31 July 2017 the European Commission has adopted the mercury emission standards for large combustion plants. The issue of mercury emissions is particularly important for Poland. Forecasts concerning energy consumption in Poland show that coal will be the main source for energy production in the coming decades. Therefore, actions enabling the reduction of mercury emissions from coal-fired power plants will have to be implemented. The mercury emissions from coal-fired power plants may be reduced through the application of a number of methods. These methods can be divided into two main groups: the post-combustion methods which allow for mercury removal from flue gases, and the pre-combustion methods which allow for mercury removal from coal before its combustion. The effectiveness of mercury removal from coal is determined by the mode of its occurrence in coal. In the case of mercury occurrence in the adventitious inorganic constituents of coal, high effectiveness will be obtained in the coal cleaning processes. In the case of mercury occurrence in the organic matter as well as in the inherent inorganic constituents of coal, the effectiveness of this method will be low. Mercury could be removed from such coals through the process of thermal pretreatment at the temperature of 200-400°C (mild pyrolysis). In the paper, the possibility of mercury removal from hard coal through the process of dry deshaling on an air concentrating table was examined. Six raw coals (coal feed), clean coals and the rejects derived from their dry deshaling were analyzed. The mercury content was measured in the examined samples. The content of mercury in raw coals and clean coals were compared. Additionally, the effectiveness of mercury removal from coal with rejects was determined. For the analyzed coals, the effectiveness of mercury removal from coal in the process of dry deshaling on an air concentrating table ranged from 9 to 96%. This effectiveness is similar to the effectiveness of mercury removal from coal in the processes of coal washing. It should be mentioned that, when compared to the coal washing processes, the dry deshaling process is characterized by lower investment and operating costs. Therefore, the dry deshaling process on an air concentrating table should be considered as a competitive method for the coal washing processes. There is also a possibility of an increase in the mercury removal efficiency from coal in the process of dry deshaling as a result of the thermal pretreatment of clean coal derived from dry deshaling. This solution is only recommended for coals in which mercury occurs in the organic matter as well as in the inorganic constituents characterized by a relatively low temperature of mercury release.It should be emphasized that the dry deshaling process allowed for a decrease of mercury content is not suitable for every coal. Although for five of the analyzed coals the mercury content in clean coal was lower in the range from 11 to 53%, for one coal the mercury content was higher by 19%. The effect of decreasing the mercury content in coal is more evident when it is related to the amount of energy contained in coal (i.e. for example to the lower heating value). For five of the analyzed coals mercury content expressed in such a way decreased in the range from 11 to 53 %, and for one coal the mercury content was, however, higher. Nevertheless, the difference was not very significant (ca. 5%).

A 320 Year Ice-Core Record of Atmospheric Hg Pollution in the Altai, Central Asia.

Anthropogenic emissions of the toxic heavy metal mercury (Hg) have substantially increased atmospheric Hg levels during the 20th century compared to preindustrial times. However, on a regional scale, atmospheric Hg concentration or deposition trends vary to such an extent during the industrial period that the consequences of recent Asian emissions on atmospheric Hg levels are still unclear. Here we present a 320 year Hg deposition history for Central Asia, based on a continuous high-resolution ice-core Hg record from the Belukha glacier in the Siberian Altai, covering the time period 1680-2001. Hg concentrations and deposition fluxes start rising above background levels at the beginning of the 19th century due to emissions from gold/silver mining and Hg production. A steep increase occurs after the 1940s culminating during the 1970s, at the same time as the maximum Hg use in consumer products in Europe and North America. After a distinct decrease in the 1980s, Hg levels in the 1990s and beginning of the 2000s return to their maximum values, which we attribute to increased Hg emissions from Asia. Thus, rising Hg emissions from coal combustion and artisanal and small-scale gold mining (ASGM) in Asian countries determine recent atmospheric Hg levels in Central Asia, counteracting emission reductions due to control measures in Europe and North America.

Impacts of large-scale circulation on urban ambient concentrations of gaseous elemental mercury in New York, USA

Abstract. The impact of large-scale circulation on urban gaseous elemental mercury (GEM) was investigated through analysis of 2008–2015 measurement data from an urban site in New York City (NYC), New York, USA. Distinct annual cycles were observed in 2009–2010 with mixing ratios in warm seasons (i.e., spring–summer) 10–20 ppqv ( ∼ 10–25 %) higher than in cool seasons (i.e., fall–winter). This annual cycle was disrupted in 2011 by an anomalously strong influence of the US East Coast trough in that warm season and was reproduced in 2014 associated with a particularly strong Bermuda High. The US East Coast trough axis index (TAI) and intensity index (TII) were used to characterize the effect of the US East Coast trough on NYC GEM, especially in winter and summer. The intensity and position of the Bermuda High appeared to have a significant impact on GEM in warm seasons. Regional influence on NYC GEM was supported by the GEM–carbon monoxide (CO) correlation with r of 0.17–0.69 (p ∼ 0) in most seasons. Simulated regional and local anthropogenic contributions to wintertime NYC anthropogenically induced GEM concentrations were averaged at ∼ 75 % and 25 %, with interannual variation ranging over 67 %–83 % and 17 %–33 %, respectively. Results from this study suggest the possibility that the increasingly strong Bermuda High over the past decades could dominate over anthropogenic mercury emission control in affecting ambient concentrations of mercury via regional buildup and possibly enhancing natural and legacy emissions.

Evaluation of costs associated with atmospheric mercury emission reductions from coal combustion in China in 2010 and projections for 2020

Coal combustion is the most significant anthropogenic mercury emission source in China. In 2013, China signed the Minamata Convention affirming that mercury emissions should be controlled more strictly. Therefore, an evaluation of the costs associated with atmospheric mercury emission reductions from China's coal combustion is essential. In this study, we estimated mercury abatement costs for coal combustion in China for 2010, based on a provincial technology-based mercury emission inventory. In addition, four scenarios were used to project abatement costs for 2020. Our results indicate that actual mercury emission related to coal combustion in 2010 was 300.8Mg, indicating a reduction amount of 174.7Mg. Under a policy-controlled scenario for 2020, approximately 49% of this mercury could be removed using air pollution control devices, making mercury emissions in 2020 equal to or lower than in 2010. The total abatement cost associated with mercury emissions in 2010 was 50.2×109 RMB. In contrast, the total abatement costs for 2020 under baseline versus policy-controlled scenarios, having high-energy and low-energy consumption, would be 32.0×109 versus 51.2×109, and 27.4×109 versus 43.9×109 RMB, respectively. The main expense is associated with flue gas desulfurization. The unit abatement cost of mercury emissions in 2010 was 288×103 RMB/(kgHg). The unit abatement costs projected for 2020 under a baseline, a policy-controlled, and an United Nations Environmental Programme scenario would be 143×103, 172×103 and 1066×103 RMB/(kgHg), respectively. These results are much lower than other international ones. However, the relative costs to China in terms of GPD are higher than in most developed countries. We calculated that abatement costs related to mercury emissions accounted for about 0.14% of the GDP of China in 2010, but would be between 0.03% and 0.06% in 2020. This decrease in abatement costs in terms of GDP suggests that various policy-controlled scenarios would be viable.

Valuing environmental impacts of mercury emissions from gold mining: Dollar per troy ounce estimates for twelve open-pit, small-scale, and artisanal mining sites

Mercury is a toxic pollutant that distributes globally once emitted into the air. Mercury emission is the primary environmental impact of small-scale and artisanal gold mining, which are responsible for nearly half of anthropogenic mercury emissions each year. Considering that small-scale, artisanal, and formal gold mining are linked by the global gold price, this analysis evaluates the question - In dollar terms, what is the difference in mercury emission impact, per ounce of gold production, from these three forms of mining? To answer this question, a calibrated benefit transfer approach is employed to apply environmental valuation literature estimates (of mercury's impact on global earnings) to twelve gold mining sites around the world. The results indicate a mean impact range of <$1–$5 for two formally operated open-pit mines in Nevada, $200–$600 for small-scale and artisanal sites that concentrate gold ore prior to mercury amalgamation, and $500–$3200 for small-scale and artisanal sites that amalgamate all of the ore. Given the vast disparity between impact per ounce estimates, even small leakages in gold production from formal to informal operations could increase the net environmental impact of global gold production. Future research ought to estimate this leakage rate by modeling small-scale and artisanal miners’ price elasticity of supply.

Anthropogenic mercury emissions from 1980 to 2012 in China

China was considered the biggest contributor for airborne mercury in the world but the amount of mercury emission in effluents and solid wastes has not been documented. In this study, total national and regional mercury emission to the environment via exhaust gases, effluents and solid wastes were accounted with updated emission factors and the amount of goods produced and/or consumed. The national mercury emission in China increased from 448 to 2151 tons during the 1980–2012 period. Nearly all of the emissions were ended up as exhaust gases and solid wastes. The proportion of exhaust gases decreased with increasing share of solid wastes and effluents. Of all the anthropogenic sources, coal was the most important contributor in quantity, followed by mercury mining, gold smelting, nonferrous smelting, iron steel production, domestic wastes, and cement production, with accounting for more than 90% of the total emission. There was a big variation of regional cumulative mercury emission during 1980–2012 in China, with higher emissions occurred in eastern areas and lower values in the western and far northern regions. The biggest cumulative emission occurred in GZ (Guizhou), reaching 3974 t, while the smallest cumulative emission was lower than 10 t in XZ (Tibet). Correspondingly, mercury accumulation in soil were higher in regions with larger emissions in unit area. Therefore, it is urgent to reduce anthropogenic mercury emission and subsequent impact on ecological functions and human health.

Mercury in tunas and blue marlin in the North Pacific Ocean.

Models and data from the North Pacific Ocean indicate that mercury concentrations in water and biota are increasing in response to (global or hemispheric) anthropogenic mercury releases. In the present study, we provide an updated record of mercury in yellowfin tuna (Thunnus albacares) caught near Hawaii that confirms an earlier conclusion that mercury concentrations in these fish are increasing at a rate similar to that observed in waters shallower than 1000 m. We also compiled and reanalyzed data from bigeye tuna (Thunnus obesus) and blue marlin (Makaira nigricans) caught near Hawaii in the 1970s and 2000s. Increases in mercury concentrations in bigeye tuna are consistent with the trend found in yellowfin tuna, in both timing and magnitude. The data available for blue marlin do not allow for a fair comparison among years, because mercury concentrations differ between sexes for this species, and sex was identified (or reported) in only 3 of 7 studies. Also, mercury concentrations in blue marlin may be insensitive to modest changes in mercury exposure, because this species appears to have the ability to detoxify mercury. The North Pacific Ocean is a region of both relatively high rates of atmospheric mercury deposition and capture fisheries production. Other data sets that allow temporal comparisons in mercury concentrations, such as pacific cod (Gadus macrocephalus) in Alaskan waters and albacore tuna (Thunnus alalunga) off the US Pacific coast, should be explored further, to aid in understanding human health and ecological risks and to develop additional baseline knowledge for assessing changes in a region expected to respond strongly to reductions in anthropogenic mercury emissions. Environ Toxicol Chem 2017;36:1365-1374. © 2017 SETAC.

Characteristics of total gaseous mercury concentrations at a coastal area of the Yangtze Delta, China

ABSTRACTIn this study, we report on total gaseous mercury (TGM) field observations made in the rural area of Shanghai, Chongming Island, China, from September 2009 to April 2012. The average TGM was 2.65 ± 1.73 ng m−3 in Chongming Island, which is higher than the TGM background value of the Northern Hemisphere (1.5–1.7 ng m−3); this indicates that to some extent, the Chongming area has been affected by anthropogenic mercury emissions. The observed TGM follows a seasonal pattern; concentrations are highest in winter, followed by autumn, summer, and spring. There is also a clear diurnal variation in TGM. All peak values appear between 7:00 and 9:00 in all four seasons; this appears to be the result of the height change in the atmospheric boundary layer that occurs between day and night. TGM concentrations in Chongming remain high in the westerly wind direction, especially in the southwest direction because of its low frequency, so the greatest source contribution to TGM in Chongming lies to the northwest. Wind speed is also a significant factor affecting TGM, and was negatively correlated with TGM concentrations. TGM is also closely related to carbon monoxide (CO) concentrations, indicating that TGM is impacted by human activities. The slope of the linear fitting of TGM and CO demonstrates that the contribution of noncoal source emissions to TGM in summer is greater than in autumn, mainly because the high temperature and intensive sunlight in summer increase mercury emissions from natural sources.Implications: Except for some studies in the coastal areas (e.g., Kang Hwa Island by Kim et al., 2006, An–Myun Island by Kim et al., 2002, and Okinawa by Chan et al., 2008), data specifically for coastal areas are lacking. Monitoring of total gaseous mercury (TGM) in the rural area of Shanghai, Chongming Island, can help us understand mercury distribution.

Shipboard and ground measurements of atmospheric particulate mercury and total mercury in precipitation over the Yellow Sea region

The first ever shipboard measurements for atmospheric particulate mercury (Hg(p)) over the Yellow Sea and ground measurements for atmospheric Hg(p) and total mercury (THg) in precipitation at the remote sites (Deokjeok and Chengshantou) and the urban sites (Seoul and Ningbo) surrounding the Yellow Sea were carried out during 2007–2008. The Hg(p) regional background concentration of 56.3 ± 55.6 pg m−3 over the Yellow Sea region is much higher than the typical background concentrations of Hg(p) in terrestrial environments (<25 pg m−3) which implies significant impact of anthropogenic mercury emission sources from East Asia. The episodes of highly elevated Hg(p) concentrations at the Korean remote site were influenced through long-range transport from source regions in the Liaoning Province - one of China's most mercury-polluted regions and in the western region of North Korea. Interestingly, wet scavenging of atmospheric Hg(p) is the predominant mechanism regulating concentration of THg in precipitation at the Chinese sites; whereas, wet scavenging of gaseous oxidized mercury (GOM) might play the more important role than that of Hg(p) at the Korean sites. The highest annual wet and dry deposition fluxes of Hg were found at the Ningbo site. The comparison between wet and dry deposition fluxes suggested that dry deposition might play the more important role than wet deposition in Chinese urban areas (source regions); whereas, wet deposition is more important in Korean areas (downwind regions).

Tracking mercury emission flows in the global supply chains: A multi-regional input-output analysis

Mercury emissions from nonferrous metal production have overtaken that from energy consumption as the leading contributor of global anthropogenic mercury emissions. Though Minamata Convention has put restrictions on import or export of mercury-added products, the inter-connected global economy that features an intensive correlated supply chain still has large impacts on mercury emissions. Therefore, this study aims to track global nonferrous metal related mercury emission flows among 186 individual economies for the year of 2010, by applying an empirically validated multi-regional input-output (MRIO) model. The total amount of direct mercury emissions is 974 tonnes, to which gold production contributed a dominant proportion. However, a spectacular 2/3 of mercury emissions from nonferrous metal production were traded internationally, primarily as exports from emerging economies such as mainland China and Colombia to wealthy economies including the USA and Germany through global supply chains. Understanding the redistribution of mercury emissions along the global supply chains can facilitate international efforts to reduce mercury emissions from nonferrous metal production.

Mercury in Bituminous Coal Used in Polish Power Plants

Abstract Poland is a country with the highest anthropogenic mercury emission in the European Union. According to the National Centre for Emissions Management (NCEM) estimation yearly emission exceeds 10 Mg. Within that approximately 56% is a result of energetic coal combustion. In 121 studied coal samples from 30 coal mines an average mercury content was 112.9 ppb with variation between 30 and 321 ppb. These coals have relatively large contents of chlorine and bromine. Such chemical composition is benefitial to formation of oxidized mercury Hg2+, which is easier to remove in Air Pollution Control Devices. The Hgr/Qir (mercury content to net calorific value in working state) ratio varied between 1.187 and 13.758 g Hg · TJ−1, and arithmetic mean was 4.713 g Hg · TJ−1. Obtained results are close to the most recent NCEM mercury emission factor of 1.498 g Hg · TJ−1. Value obtained by us is more reliable that emission factor from 2011 (6.4 g Hg · TJ−1), which caused overestimation of mercury emission from energetic coal combustion.

Mercury emission and speciation from industrial gold production using roasting process

Gold production has been identified as an important source of anthropogenic mercury emissions. Few measurements have been conducted on the mercury emission in the industrial gold production. In this study, field measurements on mercury concentration and speciation profile in the roasting flue gas were conducted in a two-stage roasting gold smelter, and the corresponding mercury emission factors were obtained using mass balance analysis. The average mercury concentration in the feed gold concentrates was 730.0μg/kg, and the daily input mercury was 94.9g in this research. In the roasting procedure, 38.4%, 27.3% and 9.0% of input mercury was removed into the sulfuric acid, contaminated water and arsenic, respectively, while 22.8% of input mercury flowed into the cyanidation-refining procedure within the roasting residue and the dust collected from the gas cooling tower and the electrostatic precipitator. Finally, 2.3% and 5.9% of input mercury was emitted into the atmosphere with the roasting flue gas and the refining flue gas. Mercury concentration in the roasting flue gas was 4.02μg/m3, where the proportion of Hgp:Hg2+:Hg0 was 11:57:33. The balance calculation results indicated that the atmospheric mercury emission factor was 2.27×10−3gmercury/g gold produced for the tested smelter. Both the emission factor and mercury removal efficiencies of air pollution control devices are useful for development of a more accurate emission inventory.

Lignites and subbituminous coals combustion in Polish power plants as a source of anthropogenic mercury emission

Coal combustion is one of the main anthropogenic sources of mercury emission to the atmosphere. A total of 121 subbituminous coal samples and 29 lignite samples representative for coals burned in Polish power and heat and power plants were acquired and examined. The average mercury content in subbituminous coal samples was 104μgkg−1 (4.591gHgTJ−1), varying from 18 to 518μgkg−1. The average chlorine and bromine content were 2200ppm and 12ppm, respectively. For lignite samples the average mercury content was 197μgkg−1 (21.380gHgTJ−1), varying from 60 to 665μgkg−1. Lignite samples contained significantly less chlorine (40ppm on average) and bromine (4ppm) than coal samples. The Cl·Hg−1 ratio for subbituminous coal samples varied between 103 and 105. For lignite samples this ratio was around 10. Mercury mass balances were performed for two subbituminous coal-fired plants and one lignite-fired plant. The chemical composition of each type of coal had a significant influence on mercury concentration and speciation in the flue gas. The proportion of oxidized mercury (Hg2+) correlated with chlorine content. The relatively large proportion of particulate-bound mercury (Hgp) and Hg2+ measured favored mercury removal by the electrostatic precipitator (65% on average), and by the wet flue gas desulfurization units (32%). Results of mercury emissions from the stack to the atmosphere were 2.0–5.0 and 15.1μgm−3, for plants burning subbituminous coal and lignite, respectively. The mercury leaving the stack from three plants was over 90% elemental mercury (Hg0). Calculated mercury emission factors for plants burning subbituminous coal and lignite were: 0.71–1.80gHgTJ−1 (subbituminous coal) and 6.09gHgTJ−1 (lignite).

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.

Mercury dynamics and mass balance in a subtropical forest, southwestern China

Abstract. The mid-subtropical forest area in southwest China was affected by anthropogenic mercury (Hg) emissions over the past 3 decades. We quantified mercury dynamics on the forest field and measured fluxes and pools of Hg in litterfall, throughfall, stream water and forest soil in an evergreen broadleaved forest field in southwestern China. Total Hg (THg) input by the throughfall and litterfall was assessed at 32.2 and 42.9 µg m−2 yr−1, respectively, which was remarkably higher than those observed from other forest fields in the background of North America and Europe. Hg fluxes across the soil–air interface (18.6 mg m−2 yr−1) and runoff and/or stream flow (7.2 µg m−2 yr−1) were regarded as the dominant ways for THg export from the forest field. The forest field hosts an enormous amount of atmospheric Hg, and its reserves is estimated to be 25 341 µg m2. The ratio of output to input Hg fluxes (0.34) is higher compared with other study sites. The higher output / input ratio may represent an important ecological risk for the downstream aquatic ecosystems, even if the forest field could be an effective sink of Hg.

A dual-inlet, single detector relaxed eddy accumulation system for long-term measurement of mercury flux

Abstract. The fate of anthropogenic emissions of mercury (Hg) to the atmosphere is influenced by the exchange of elemental Hg with the earth surface. This exchange holds the key to a better understanding of Hg cycling from local to global scales, which has been difficult to quantify. To advance research about land–atmosphere Hg interactions, we developed a dual-inlet, single detector relaxed eddy accumulation (REA) system. REA is an established technique for measuring turbulent fluxes of trace gases and aerosol particles in the atmospheric surface layer. Accurate determination of gaseous elemental mercury (GEM) fluxes has proven difficult due to technical challenges presented by extremely small concentration differences (typically &lt; 0.5 ng m−3) between updrafts and downdrafts. We present an advanced REA design that uses two inlets and two pairs of gold cartridges for continuous monitoring of GEM fluxes. This setup reduces the major uncertainty created by the sequential sampling in many previous designs. Additionally, the instrument is equipped with a GEM reference gas generator that monitors drift and recovery rates. These innovations facilitate continuous, autonomous measurement of GEM flux. To demonstrate the system performance, we present results from field campaigns in two contrasting environments: an urban setting with a heterogeneous fetch and a boreal peatland during snowmelt. The observed average emission rates were 15 and 3 ng m−2 h−1, respectively. We believe that this dual-inlet, single detector approach is a significant improvement of the REA system for ultra-trace gases and can help to advance our understanding of long-term land–atmosphere GEM exchange.

Impact of Measurement Uncertainties on Receptor Modeling of Speciated Atmospheric Mercury.

Gaseous oxidized mercury (GOM) and particle-bound mercury (PBM) measurement uncertainties could potentially affect the analysis and modeling of atmospheric mercury. This study investigated the impact of GOM measurement uncertainties on Principal Components Analysis (PCA), Absolute Principal Component Scores (APCS), and Concentration-Weighted Trajectory (CWT) receptor modeling results. The atmospheric mercury data input into these receptor models were modified by combining GOM and PBM into a single reactive mercury (RM) parameter and excluding low GOM measurements to improve the data quality. PCA and APCS results derived from RM or excluding low GOM measurements were similar to those in previous studies, except for a non-unique component and an additional component extracted from the RM dataset. The percent variance explained by the major components from a previous study differed slightly compared to RM and excluding low GOM measurements. CWT results were more sensitive to the input of RM than GOM excluding low measurements. Larger discrepancies were found between RM and GOM source regions than those between RM and PBM. Depending on the season, CWT source regions of RM differed by 40–61% compared to GOM from a previous study. No improvement in correlations between CWT results and anthropogenic mercury emissions were found.