Historical releases of mercury to air, land, and water from coal combustion

Historical shifts in mercury deposition in northeastern China: From vegetation to human activity

Mercury (Hg) pollution is a pervasive environmental issue that greatly threatens ecosystem and human health. However, the primary natural factors and human-induced phase shifts affecting Hg deposition in typical areas remain unclear. With its long history of industrialization, northeastern China is an important area for Hg pollution research. Here, we constructed an accurate chronological framework using varve counting combined with Hg concentration measurements to reconstruct the high-resolution Hg depositional history of Sihailongwan Maar Lake (SHML) in northeastern China over the past 1400 years. High (low) Hg flux in the SHML sediments was closely linked to an increase (decrease) in broadleaved tree coverage. During the Medieval Climate Anomaly, warming promoted the expansion of broadleaved trees, increasing Hg flux. Conversely, colder climates hindered broadleaved tree growth during the Little Ice Age, reducing Hg flux. However, Hg flux has significantly increased since the Current Warm Period (∼1850 CE) and was strongly correlated with regional population growth, causing a gradual increase in Hg deposition with increasing human activities and decreased natural input. Four-phase regime shifts in Hg flux influenced by anthropogenic activities were identified using the Sequential T-test Analysis of Regime-Shifts algorithm, highlighting the influence of government policies, economic development, and social changes on Hg deposition. This study elucidated the role of vegetation in northeastern China before large-scale human activities and the complex effects of human activities on Hg deposition.

The impact of mercury exposure on male reproduction: Mechanistic insights

Mercury is a pervasive environmental toxin with significant negative effects on human health. In occupational settings, incidents such as the Minamata and Niigata disease in Japan and the large-scale methylmercury poisoning in Iraq have highlighted the severe health impacts of mercury exposure. It is widely accepted that all forms of mercury including methylmercury and mercuric chloride have the potential to induce toxic effects in mammals, and there is increasing concern about the impact of environmentally relevant levels of mercury on reproductive functions. This review summarizes current knowledge on the mechanisms of mercury toxicity, focusing specifically on its impact on male reproductive health across species. We searched the literature and found that mercury exposure is associated with testicular degeneration, altered spermatogenesis, and Leydig cell deformation. In addition, mercury can disrupt sperm motility, steroidogenesis and interfere with the hypothalamic-pituitary-gonadal axis by generation of reactive oxygen species, inducing mitochondrial dysfunction, epigenetic changes, and DNA damage. At the molecular level, mercury has been found to dysregulate the expression of key steroidogenic and spermatogenic genes, significantly reducing overall fertility potential. However, specific mechanisms of action remain to be fully elucidated. Similarly, comprehensive data on the potential transgenerational effects of paternal mercury exposure are lacking. In this review, we discuss both animal and human studies, and highlight the need for further research due to lack of standardization and control for variables such as lifestyle, immune system function, and exposure concentrations.

Mercury records from natural archives reveal ecosystem responses to changing atmospheric deposition

Global ecosystems face mercury contamination, yet long-term data are scarce, hindering understanding of ecosystem responses to atmospheric Hg input changes. To bridge the data gap and assess ecosystem responses, we compiled and compared a mercury accumulation database from peat, lake, ice and marine deposits worldwide with atmospheric mercury deposition modelled by GEOS-Chem, focusing on trends, magnitudes, spatial-temporal distributions and impact factors. The mercury fluxes in all four deposits showed a 5- to 9-fold increase over 1700-2012, with lake and peat mercury fluxes that generally mirrored atmospheric deposition trends. Significant decreases in lake and peat mercury fluxes post-1950 in Europe evidenced effective environmental policies, whereas rises in East Asia, Africa and Oceania highlighted coal-use impacts, inter alia. Conversely, mercury fluxes in marine and high-altitude ecosystems did not align well with atmospheric deposition, emphasizing natural influences over anthropogenic impacts. Our study underscores the importance of these key regions and ecosystems for future mercury management.

Quantified retrospective biomonitoring of fetal and infant elemental exposure using LA-ICP-MS analysis of deciduous dentin in three contrasting human cohorts

BACKGROUND

Spatial elemental analysis of deciduous tooth dentin combined with odontochronological estimates can provide an early life (in utero to ~2 years of age) history of inorganic element exposure and status.

OBJECTIVE

To demonstrate the importance of data normalization to a certified reference material to enable between-study comparisons, using populations with assumed contrasting elemental exposures.

METHODS

We used laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) of dentin to derive a history of elemental composition from three distinct cohort studies: a present day rural cohort, (the New Hampshire Birth Cohort Study (NHBCS; N = 154)), an historical cohort from an urban area (1958-1970), (the St. Louis Baby Tooth Study (SLBT; N = 78)), and a present-day Nigerian cohort established to study maternal HIV transmission (Dental caries and its association with Oral Microbiomes and HIV in young children-Nigeria (DOMHaIN; N = 31)).

RESULTS

We report Li, Al, Mn, Cu, Zn, Sr, Ba and Pb concentrations (µg/g) and qualitatively examine As, Cd and Hg across all three cohorts. Rates of detection were highest, both overall and for each cohort individually, for Zn, Sr, Ba and Li. Zinc was detected in 100% of samples and was stably present in teeth at a concentration range of 64 - 86 µg/g. Mercury, As and Cd detection rates were the lowest, and had high variability within individual ablated spots. We found the highest concentrations of Pb in the pre- and postnatal dentin of the SLBT cohort, consistent with the prevalent use of Pb as an additive to gasoline prior to 1975. The characteristic decline in Mn after the second trimester was observed in all cohorts.

IMPACT

Spatially resolved elemental analysis of deciduous teeth combined with methods for estimating crown formation times can be used to reconstruct an early-life history of elemental exposure inaccessible via other biomarkers. Quantification of data into absolute values using an external standard reference material has not been conducted since 2012, preventing comparison between studies, a common and highly informative component of epidemiology. We demonstrate, with three contrasting populations, that absolute quantification produces data with the lowest variability, compares well with available data and recommends that future tooth biomarker studies report data in this way.

Elemental biomapping of human tissues suggests toxic metals such as mercury play a role in the pathogenesis of cancer

Toxic metals such as mercury, lead, and cadmium have multiple carcinogenic capacities, including the ability to damage DNA and incite inflammation. Environmental toxic metals have long been suspected to play a role in the pathogenesis of cancer, but convincing evidence from epidemiological studies that toxic metals are risk factors for common neoplasms has been difficult to gain. Another approach is to map the location of potentially toxic elements in normal human cells where common cancers originate, as well as in the cancers themselves. In this Perspective, studies are summarized that have used elemental biomapping to detect toxic metals such as mercury in human cells. Two elemental biomapping techniques, autometallography and laser ablation-inductively coupled-mass spectrometry imaging, have shown that multiple toxic metals exist in normal human cells that are particularly prone to developing cancer, and are also seen in neoplastic cells of breast and pancreatic tumors. Biomapping studies of animals exposed to toxic metals show that these animals take up toxic metals in the same cells as humans. The finding of toxic metals such as mercury in human cells prone to cancer could explain the increasing global incidence of many cancers since toxic metals continue to accumulate in the environment. The role of toxic metals in cancer remains to be confirmed experimentally, but to decrease cancer risk a precautionary approach would be to reduce emissions of mercury and other toxic metals into the environment from industrial and mining activities and from the burning of fossil fuels.

Quantification and assessment of hazardous mercury emission from industrial process and other unattended sectors in India: A step towards mitigation

Hazardous pollutants like Mercury (Hg) have emerged as a pressing challenge in recent times where the expanding industrial sector is regarded as the major source in developing country India. In this study, we are trying to identify all possible industrial sectors at district level to quantify Hg emission load across India for the year 2019 using IPCC methodology where the country-specific technological emission factors are used. We have included 5 major sectors out of which emission from coal combustion in thermal power plants accounts for 186.5 t/yr of Hg emission followed by non-ferrous metal production (88.3 t/yr), captive power plants (65.5 t/yr) and fly ash generation from various manufacturing industries (45.9 t/yr). A total of 459.4 t/yr of Hg is released into the ecosystem in 2019 with an uncertainty of ± 48%. This study also estimated that about 233 million people living in and around 10 km periphery of major industrial zones with as many as 17 million people residing near the 10 major hotspots are susceptible to hazardous Hg emissions directly or indirectly. This information would be quite useful in formulating future Hg emission control strategies in India. ENVIRONMENTAL IMPLICATIONS: Present study is the first-of-its-kind quantification of Hg emission load from the Industrial process and many unattended sectors over India, which will not only give an insight into potential hotspots regions across the country but also assess the population exposed to it. It will provide aid in tracking the mercury burden to match the international conventions. The findings suggest that about 233 million people are likely to be exposed to hazardous Hg emissions. It will also enlighten the government, policymakers, stakeholders and people about their mercury footprint and envision protecting the biomes and formulating future control strategies in India.

Disentangling fine particles (PM2.5) composition in Hanoi, Vietnam: Emission sources and oxidative potential

A comprehensive chemical characterization of fine particulate matter (PM2.5) was conducted at an urban site in one of the most densely populated cities of Vietnam, Hanoi. Chemical analysis of a series of 57 daily PM2.5 samples obtained in 2019-2020 included the quantification of a detailed set of chemical tracers as well as the oxidative potential (OP), which estimates the ability of PM to catalyze reactive oxygen species (ROS) generation in vivo as an initial step of health effects due to oxidative stress. The PM2.5 concentrations ranged from 8.3 to 148 μg m-3, with an annual average of 40.2 ± 26.3 μg m-3 (from September 2019 to December 2020). Our results obtained by applying the Positive Matrix Factorization (PMF) source-receptor apportionment model showed the contribution of nine PM2.5 sources. The main anthropogenic sources contributing to the PM mass concentrations were heavy fuel oil (HFO) combustion (25.3 %), biomass burning (20 %), primary traffic (7.6 %) and long-range transport aerosols (10.6 %). The OP activities were evaluated for the first time in an urban site in Vietnam. The average OPv levels obtained in our study were 3.9 ± 2.4 and 4.5 ± 3.2 nmol min-1 m-3 for OPDTT and OPAA, respectively. We assessed the contribution to OPDTT and OPAA of each PM2.5 source by applying multilinear regression models. It shows that the sources associated with human activities (HFO combustion, biomass burning and primary traffic) are the sources driving OP exposure, suggesting that they should be the first sources to be controlled in future mitigation strategies. This study gives for the first time an extensive and long-term chemical characterization of PM2.5, providing also a link between emission sources, ambient concentrations and exposure to air pollution at an urban site in Hanoi, Vietnam.

Nanocellulose-stabilized nanocomposites for effective Hg(II) removal and detection: a comprehensive review

Mercury pollution, with India ranked as the world's second-largest emitter, poses a critical environmental and public health challenge and underscores the need for rigorous research and effective mitigation strategies. Nanocellulose is derived from cellulose, the most abundant natural polymer on earth, and stands out as an excellent choice for mercury ion remediation due to its remarkable adsorption capacity, which is attributed to its high specific surface area and abundant functional groups, enabling efficient Hg(II) ion removal from contaminated water sources. This review paper investigates the compelling potential of nanocellulose as a scavenging tool for Hg(II) ion contamination. The comprehensive examination encompasses the fundamental attributes of nanocellulose, its diverse fabrication techniques, and the innovative development methods of nanocellulose-based nanocomposites. The paper further delves into the mechanisms that underlie Hg removal using nanocellulose, as well as the integration of nanocellulose in Hg detection methodologies, and also acknowledges the substantial challenges that lie ahead. This review aims to pave the way for sustainable solutions in mitigating Hg contamination using nanocellulose-based nanocomposites to address the global context of this environmental concern.

Pollution and health risk assessment of mine tailings contaminated soils in India from toxic elements with statistical approaches

The rapid mining activities of mica mines in Giridih district, India, have led to toxic metal pollution of agricultural soil. This is a key concern for environmental risk and human health. 63 top soil samples were collected at a distance of 10 m (Zone 1), 50 m (Zone 2), and 100 m (Zone 3) from near 21 mica mines with agriculture fields. The mean concentration of total and bio-available toxic elements (TEs - Cr, Ni, Pb, Cu, Zn, and Cd) was higher in zone 1 across three zones. The Positive matrix factorization model (PMF) and Pearson Correlation analysis were used to identify waste mica soils with TEs. Based on PMF results, Ni, Cr, Cd, and Pb were the most promising pollutants and carried higher environmental risks than the other TEs. Using the self-organizing map (SOM), zone 1 was identified as a high-potential source of TEs. Soil quality indexes for TEs risk zone 1 were found to be higher across three zones. Based on the health risk index (HI), children are more adversely affected than adults. Monte Carlo simulations (MCS) model and sensitivity analysis of total carcinogenic risk (TCR), children were more affected by Cr and Ni than adults through ingestion exposure pathways. Finally, a geostatistical tool was developed to predict the spatial distribution patterns of TEs contributed by mica mines. In a probabilistic assessment of all populations, non-carcinogenic risks appeared to be negligible. The fact that there is a TCR can't be ignored, and children are more likely to develop it than adults. Mica mines with TEs contamination were found to be the most significant anthropogenic contributor to health risks based on source-oriented risk assessment.

Mercury Pollution History in Tropical and Subtropical American Lakes: Multiple Impacts and the Possible Relationship with Climate Change

Sediment cores obtained from 11 tropical and subtropical American lakes revealed that local human activities significantly increased mercury (Hg) inputs and pollution levels. Remote lakes also have been contaminated by anthropogenic Hg through atmospheric depositions. Long-term sediment-core profiles revealed an approximately 3-fold increase in Hg fluxes to sediments from c. 1850 to 2000. Generalized additive models indicate that c. 3-fold increases in Hg fluxes also occurred since 2000 in the remote sites, while Hg emissions from anthropogenic sources have remained relatively stable. The tropical and subtropical Americas are vulnerable to extreme weather events. Air temperatures in this region have shown a marked increase since the 1990s, and extreme weather events arising from climate change have increased. When comparing Hg fluxes to recent (1950-2016) climatic changes, results show marked increases in Hg fluxes to sediments during dry periods. The Standardized Precipitation-Evapotranspiration Index (SPEI) time series indicate a tendency toward more extreme drier conditions across the study region since the mid-1990s, suggesting that instabilities in catchment surfaces caused by climate change are responsible for the elevated Hg flux rates. Drier conditions since c. 2000 appear to be promoting Hg fluxes from catchments to lakes, a process that will likely be exacerbated under future climate-change scenarios.

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.

Biomonitoring of mercury in water, sediments, and fish (brown and rainbow trout) from remote alpine lakes located in the Himalayas, Pakistan

Mercury (Hg) contamination of aquatic ecological units and subsequent bioaccumulation are major environmental problems of international scope. Moreover, the biogeochemistry of Hg in the remote alpine lakes aquatic ecosystem in the Himalayas remains largely unexplored. The current study investigated Hg concentrations in different environmental compartments such as water, fish, and sediments in the remote alpine lakes (RALs) including Glacial-fed Lake, Ice melting-fed Lake, and Rain-fed Lake in northern areas of Pakistan. The mean concentration of Hg in Rain-fed Lake water was (1.07 µg L-1), Ice melting-fed Lake (1.16 µg L-1), and Glacial-fed Lake (1.95 µg L-1). For fish muscle tissues, mean concentration of Hg was 1.02 mg kg-1 in the Rain-fed Lake, and 1.2 mg kg-1 for the Ice melting-fed Lake, and 1.51 mg kg-1 in the Glacial-fed Lake. Meanwhile, 0.27 mg kg-1 was observed for sediments in the Rain-fed Lake, 0.33 mg kg-1 for the Ice melting-fed Lake, and 0.38 mg kg-1 for the Glacial-fed Lake, respectively. Chronic daily intake (CDI) and potential health quotient (PHQ) for water showed high health risk in Glacial-fed Lake and low in Rain-fed Lake (PHQ < 1). The target hazard quotient (THQ) values for both the Brown and Rainbow trout in all the studied lakes water were less than 1, indicating no health risk. Furthermore, the Hg level showed high level of contamination in the sediments of all the studied lakes (190 ≤ RI < 380). Overall, Glacial-fed Lake water was more polluted with Hg, as compared to Rain-fed Lake and Ice melting-fed Lake. In the light of the abovementioned results, further research work is urgently needed to shed light on the biological and geochemical monitoring of Hg in arid high-altitude ecosystems along with source identification, mercury speciation, and other potential pollutants.

Improved atmospheric mercury simulation using updated gas-particle partition and organic aerosol concentrations

The gaseous or particulate forms of divalent mercury (Hg^II) significantly impact the spatial distribution of atmospheric mercury concentration and deposition flux (FLX). In the new nested-grid GEOS-Chem model, we try to modify the Hg^II gas-particle partitioning relationship with synchronous and hourly observations at four sites in China. Observations of gaseous oxidized Hg (GOM), particulate-bound Hg (PBM), and PM_2.5 were used to derive an empirical gas-particle partitioning coefficient as a function of temperature (T) and organic aerosol (OA) concentrations under different relative humidity (RH). Results showed that with increasing RH, the dominant process of Hg^II gas-particle partitioning changed from physical adsorption to chemical desorption. And the dominant factor of Hg^II gas-particle partitioning changed from T to OA concentrations. We thus improved the simulated OA concentration field by introducing intermediate-volatility and semi-volatile organic compounds (I/SVOCs) emission inventory into the model framework and refining the volatile distributions of I/SVOCs according to new filed tests in the recent literatures. Finally, normalized mean biases (NMBs) of monthly gaseous element mercury (GEM), GOM, PBM, WFLX were reduced from -33%-29%, 95%-300%, 64%-261%, 117%-122% to -13%-0%, -20%-80%, -31%-50%, -17%-23%. The improved model explains 69%-98% of the observed atmospheric Hg decrease during 2013-2020 and can serve as a useful tool to evaluate the effectiveness of the Minamata Convention on Mercury.

Reconstructing atmospheric Hg levels near the oldest chemical factory in central Europe using a tree ring archive

The Chemical Factory in Marktredwitz (CFM) is known as the oldest chemical factory in Germany (1778-1985), and from the beginning of the 20^th century focused primarily on the production of mercury (Hg) compounds. Due to extensive pollution, together with employee health issues, the CFM was shut in 1985 by a government order and remediation works proceeded from 1986 to 1993. In this study, tree ring archives of European Larch (Larix decidua Mill.) were used to reconstruct changes of air Hg levels near the CFM. Mercury concentrations in larch boles decreased from 80.6 μg kg^-1 at a distance of 0.34 km-3.4 μg kg^-1 at a distance of 16 km. The temporal trend of atmospheric Hg emissions from the CFM reconstructed from the tree ring archives showed two main peaks. The first was in the 1920s, with a maximum tree ring Hg concentration 249.1 ± 43.9 μg kg^-1 coinciding with when the factory had a worldwide monopoly on the production of Hg-based seed dressing fungicide. The second peak in the 1970s, with a maximum tree ring Hg concentration of 116.4 ± 6.3 μg kg^-1, was associated with a peak in the general usage and production of Hg chemicals and goods. We used the tree ring record to reconstruct past atmospheric Hg levels using a simple model of Hg distribution between the larch tree rings and atmosphere. The precision of the tree ring model was checked against the results of air Hg measurements during the CFM remediation 30 years ago. According to the tree ring archives, the highest air Hg concentrations in the 1920s in Marktredwitz were over 70 ng m^-3. Current air Hg levels of 1.18 ng m^-3, assessed in the city of Marktredwitz, indicate the lowest air Hg in the past 150 years, underscoring the effective remediation of the CFM premises 30 years ago.

In vitro and in silico Studies Reveal Bacillus cereus AA-18 as a Potential Candidate for Bioremediation of Mercury-Contaminated Wastewater

Mercury (Hg) pollution is a worldwide problem and increasing day by day due to natural and anthropogenic sources. In this study, mercury-resistant (HgR) bacterial isolates were isolated from industrial wastewater of Ittehad Chemicals Ltd., Kala Shah Kaku, Lahore, Pakistan. Out of 65 bacterial isolates, five isolates were screened out based on showing resistance at 30–40 μg/ml against HgCl2. Selected Hg-resistant bacterial isolates were characterized as Bacillus subtilis AA-16 (OK562835), Bacillus cereus AA-18 (OK562834), Bacillus sp. AA-20 (OK562833), Bacillus paramycoides AA-30 (OK562836), and Bacillus thuringiensis AA-35 (OK562837). B. cereus AA-18 showed promising results in the resistance of HgCl2 (40 μg/ml) due to the presence of merA gene. Scanning electron microscopy (SEM) analysis of immobilized B. cereus AA-18 showed the accumulation Hg on the cell surface. The inoculation of immobilized B. cereus AA-18 remediated 86% Hg of industrial wastewater up to 72 h at large scale (p &lt; 0.05). In silico analysis showed structural determination of MerA protein encoded by merA gene of B. cereus AA-18 (OK562598) using ProtParam, Pfam, ConSurf Server, InterPro, STRING, Jpred4, PSIPRED, I-TASSER, COACH server, TrRosetta, ERRAT, VERIFY3D, Ramachandran plot, and AutoDock Vina (PyRx 8.0). These bioinformatics tools predicted the structural-based functional homology of MerA protein (mercuric reductase) associated with mer operon harboring bacteria involved in Hg-bioremediation system.

High concentrations of HgS, MeHg and toxic gas emissions in thermally affected waste dumps from hard coal mining in Poland

This study aims to provide numerous environmental research approaches to understand the formation of mineral and organic mercury compounds in self-heating coal waste dumps of the Upper Silesian Coal Basin (USCB). The results are combined with environmental and health risk assessments. The mineralogy comprised accessory minerals in the fine fraction of thermally affected waste, i.e., Hg sulfides, most likely cinnabar or metacinnabar. Moreover, other metals, e.g., Pb, Zn and Cu, were found as sulfide forms. Apart from Hg, the ICP-ES/MS data confirmed the high content of Mn, Zn, Pb, Hg, Cr and Ba in these wastes. The high concentration of available Hg resulted in elevated MeHg concentrations in the dumps. There were no correlations or trends between MeHg concentrations and elemental Hg, TS, TOC, and pH. Furthermore, we did not detect microbial genes responsible for Hg methylation. The organic compounds identified in waste and emitted gases, such as organic acids, or free methyl radicals, common in such burn environments, could be responsible for the formation of MeHg. The concentration levels of gases, e.g., benzene, formaldehyde, NH₃, emitted by the vents, reached or surpassed acceptable levels numerous times. The potential ecological and human health risks of these dumps were moderate to very high due to the significant influence of the high Hg concentrations.

Release characteristics of elemental mercury during low calorific value coal combustion

The dynamic release characteristics of Hg⁰ during low calorific value coal combustion were investigated in a combining laboratory-scale furnace coupled with atomic fluorescence spectroscopy. The results show that the sulfur has an inhibitory effect on the homogeneous oxidation of Hg⁰ in flue gas. The instant intensity of Hg⁰ release increases with increasing temperature while the amount of Hg⁰ release gradually decreases with increasing temperature. Compared with that under air, the instant intensity of Hg⁰ release under O₂/CO₂ atmosphere increases to some extent with a lower decreasing rate of Hg⁰ release peak. The release ratio of elemental mercury (Hg) from Yuwu (YW) and Qinxin (QX) coal increases while that from Yonghao (YH) coal decreases under O₂/CO₂ atmosphere. In the range of 800-1100°C, the release rate of Hg reaches more than 96% under the residence time of 50 s.

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.

Phytoremediation technology and food security impacts of heavy metal contaminated soils: A review of literature

Heavy metal accumulation in soil and water is one of major problems caused by inorganic contaminants. Their presence in agricultural soils in high quantities have impacted the food security significantly and, by extension, the human health. Amongst various physico-chemical methods available for remediation of heavy-metals-polluted-sites, phytoremediation approaches have been found to be safe and environment friendly. This review gathered scattered information on heavy metal phytoremediation studies published in both review and research articles. It described the impact of heavy metals on food security and comprehensively discussed the application of different phytoremediation approaches for treatment of heavy metal-polluted soils, the basic principles underlining them, their strengths and weaknesses. Our findings indicated that, while hundreds of hyper-accumulator plants are being reported yearly, only few describe limitations inherent in them, such as low growth rate, low biomass production, and low metal tolerance. Hence, this review also gave a detailed overview of research gaps in phytotechnology and advocates consideration of the 'omics' studies; genomics, proteomics, metabolomics and likes in selecting and enhancing potential plants for phytoremediation. For a sustainable large-scale phytoremediation application, we established a multi-technology repair strategy via the combination of different methods like application of biological composts, plant-growth promoting microorganisms, and phytohormones for stimulation of the plant-growth during phytoremediation. We also gave comprehensive insights to proper disposal of plants used for phytoremediation, this subject is often not well considered/planned while deciding the application of plants for removal of heavy metals from polluted environments.

The silver linings of mercury: Reconsideration of its impacts on living organisms from a multi-timescale perspective

Research on mercury (Hg), a naturally occurring element in Earth's lithosphere, has been extremely hot in the past few decades due to the outbreak of a series of disastrous poisoning incidents. However, such studies might provide us a biased view towards Hg if no thorough review about its long-term effects on living organisms from a multi-timescale perspective was performed. Hg might have played a mysterious role in critical intervals (e.g., mass extinction and oceanic anoxia events) in several geologic periods due to the elevated Hg levels induced by volcanism whereas it has long been used for various purposes in human history. Therefore, it is necessary to go through previous studies and historical records of different timescales (10⁰ to 10⁶ yr). In this work, we conducted a thorough review of Hg knowledge at three different timescales, i.e., geologic periods (10⁶ yr), human history (10³ yr), and contemporary history (10⁰ yr), summarizing recent advances and indicated potential research gaps. By doing so, we demonstrated that it is possible to achieve safe and sustainable Hg applications despite the current Hg crisis. However, such silver linings depend on a better understanding of ecosystem dynamics. Besides, considering the possible dire consequences of erupted Hg levels as suggested in geological periods, swift actions to mitigate the impacts of anthropogenic activities on the Hg cycle will be another key point. Overall, this review presented a unique perspective of Hg combining different timescales, shedding light on the importance of a better understanding of the global ecosystem as a whole and maintaining the sustainability of planet Earth in the future.

Effects of Elemental Mercury Vapor Inhalation on Arterial Blood Gases, Lung Histology, and Interleukin-1 Expression in Pulmonary Tissues of Rats

We investigated the effects of elemental mercury vapor inhalation on arterial blood gases (ABGs), lung histology, and interleukin-1 (IL-1) expression in pulmonary tissues in rats. A total of 42 Sprague Dawley rats were divided randomly into three groups. Rats in the first group were used as the control (CG). A short-term group (STG) and a long-term group (LTG) were exposed to 500 μg/m3 of mercury vapor 2 hrs/day for 21 days and 65 days, respectively. After exposure periods were completed, arterial blood samples were obtained, and ABGs were measured. Lung tissue sections were prepared for histology evaluation and immune-stained to detect IL-1 expression. There was a significant decrease in body weight in both STG (15%) and LTG (22%) compared with the CG. In the LTG, six out of 14 (43%) rats died, including two males and four females, while none of the rats in the STG died during the experiment. In both STG and LTG, a significant acid-base imbalance was characterized by a significant decrease in blood pH values and a significant increase in PCO2 values. Both PO2 and SpO2 blood values were significantly decreased in the STG and LTG, while no changes were observed in HCO3 values in all groups. Histological evaluation of lung tissues revealed severe lesions characterized by pulmonary emphysema and inflammatory cellular infiltrate. IL-1 expression in lung tissues was not significantly different between exposed rats and control subjects. These results indicate significant alterations in blood acid-base status characterized by severe respiratory acidosis with hypoxemia and no evidence of compensatory alkalosis in rats after exposure to short- and long-term elementary mercury vapor.

Mechanism study of mechanochemical bromination on fly ash mercury removal adsorbent

Current approaches for Mechanochemical bromination (MCB) modified fly ash have been focusing on the efficiency and mechanism of mercury removal, but the MCB activation mechanism is still not clear. Selecting activated carbon (AC), hematite (He), anatase (An), and mullite (Mu) to simulate four main fly ash components, and the above samples were MCB modified by omni-directional planetary ball mill with NaBr crystal as modifier. Based on the physicochemical properties and mercury removal ability of each pure component before and after modification, the activation mechanism of MCB was obtained. The results indicate that single mechanochemical modification has almost no effect on the mercury removal ability of each component. The mercury removal ability of fly ash improved by MCB is mainly due to the C-Br generated by reaction between NaBr and AC, and the covalently bonded Br (M-Br) on He also provides a certain contribution. However, the contribution of An and Mu is a little. The MCB activation mechanism is verified that original AC and He are firstly converted into unsaturated carbon and He with surface lattice defects by MCB process, then react with Br free radicals to form C-Br and M-Br, while An and Mu do not mechanochemically react with NaBr during the MCB process.

Ambient air particulates and Hg(p) concentrations and dry depositions estimations, distributions for various particles sizes ranges

Ambient air TSP concentrations, dry deposition fluxes and particulate-bound mercury (Hg(p)) concentrations were measured and analyzed at a complex (traffic, residential and commercial) site. Zhang and He's model^[1] was used to predict the dry deposition fluxes of ambient air particulates and Hg(p) at this complex site. The results revealed that October had the highest mean particulate concentration and lowest Hp(p) concentration and dry deposition flux. The mean calculated dry deposition fluxes of PM_2.5 and PM_2.5-10 accounted for 1%-2% and 0.06%-5% of the average total calculated dry deposition particle flux, respectively. The average calculated particle dry depositions flux of PM₁₀₊, accounted for 93%-99% of the average total calculated dry depositions particle flux. Finally, the model of Zhang and He underestimated the ambient air dry depositions fluxes of both particulates and Hg(p) for all particles sizes (PM_2.5, PM_2.5-10, PM₁₀⁺) at the mixed site in this study. Better results concerning the dry deposition fluxes of pollutants were obtained as the particles size increased.

Hg(II) Binding to Thymine Bases in DNA

The compounds of mercury can be highly toxic and can interfere with a range of biological processes, although many aspects of the mechanism of toxicity are still obscure or unknown. One especially intriguing property of Hg(II) is its ability to bind DNA directly, making interstrand cross-links between thymine nucleobases in AT-rich sequences. We have used a combination of small molecule X-ray diffraction, X-ray spectroscopies, and computational chemistry to study the interactions of Hg(II) with thymine. We find that the energetically preferred mode of thymine binding in DNA is to the N3 and predict only minor distortions of the DNA structure on binding one Hg(II) to two cross-adjacent thymine nucleotides. The preferred geometry is predicted to be twisted away from coplanar through a torsion angle of between 32 and 43°. Using 1-methylthymine as a model, the bis-thymine coordination of Hg(II) is found to give a highly characteristic X-ray spectroscopic signature that is quite distinct from other previously described biological modes of binding of Hg(II). This work enlarges and deepens our view of significant biological targets of Hg(II) and demonstrates tools that can provide a characteristic signature for the binding of Hg(II) to DNA in more complex matrices including intact cells and tissues, laying the foundation for future studies of mechanisms of mercury toxicity.

A complete atmospheric emission inventory of F, As, Se, Cd, Sb, Hg, Pb, and U from coal-fired power plants in Anhui Province, eastern China

Anhui Province is the most important energy production base for eastern China. Many large pithead coal-fired power plants are being operated in the coal-rich Huainan and Huaibei coalfields in northern Anhui. To assess the environmental risks of local coal-fired power plants, a complete atmospheric emission inventory of F, As, Se, Cd, Sb, Hg, Pb, and U from coal-fired power plants in Anhui was compiled by a simple mass-balance-based method. The results indicated that the atmospheric emissions of F, As, Se, Cd, Sb, Hg, Pb, and U in 2017 from the Anhui coal-fired power plants were 578 t, 2.01 t, 15.3 t, 0.57 t, 0.18 t, 2.80 t, 23.7 t, and 0.099 t, respectively. The emission factor is the major contributor to the uncertainties in this inventory. With increasing energy demand by the more developed eastern China region, the atmospheric emissions of volatile hazardous elements will continue to increase in the near future.

Contamination Assessment of Heavy Metals in Agricultural Soil, in the Liwa Area (UAE)

The Liwa area is a primary food production area in the United Arab Emirates (UAE) and has intensively been used for agriculture. This study investigates the pollution levels with heavy metals in agricultural soils from the Liwa area. Thirty-two soil samples were analyzed for Mn, Zn, Cr, Ni, Cu, Pb, Cd, Co, and As. Results revealed that heavy metal levels varied in the ranges 220.02-311.21, 42.39-66.92, 43.43-71.55, 32.86-52.12, 10.29-21.70, 2.83-8.84, 0.46-0.69, 0.03-0.37 mg/kg for Mn, Zn, Cr, Ni, Cu, Pb, Cd, Co, and As, respectively. All samples presented low As concentrations with an average of 0.01 mg/kg. The variations in bulk metal contents in the soil samples were related to multiple sources, including agrochemicals, atmospheric dust containing heavy metals, and traffic-related metals. Enrichment factor analysis indicates that Cd, Ni, Zn, and Cr were highly enriched in soils, and they could originate from non-crustal sources. Based on the geo-accumulation index (I_geo), the soil samples appeared uncontaminated with Mn, Cr, Zn, Pb, Co, As, Cu, uncontaminated to moderately contaminated with Ni and moderately contaminated with Cd. The contamination factors suggest low contamination, except for Ni, which showed moderate contamination. The average pollution load index (PLI) revealed unpolluted to low pollution of all soil samples. The ecological risk assessment (PERI) showed that all heavy metals posed a low risk, except for Cd which exhibited a high ecological risk.

Soil and ambient air mercury as an indicator of coal-fired power plant emissions: a case study in North China

Coal-fired power plants (CFPPs) are an important anthropogenic mercury (Hg) source in China, and it is crucial to understand the environmental impacts of this detrimental element emitted from this source. In the present study, field experiments were conducted for measuring Hg in ambient atmosphere and upland agricultural soils within a radius of 10 km surrounding a large scale coal-fired power plant (1550 MW) in Tangshan, Hebei province. Short-term (20 min) average of gaseous elemental mercury (GEM or Hg0) in ambient air varying from 1.5 to 9.0 ng/m3 and total Hg (THg) in surface agricultural soil (0-20 cm) varying from 9.2 to 43.5 μg/kg at different sites were observed. THg in two soil cores decreased with depth, with concentrations being 2-2.5 times higher in the surface layer than that in the deep layer (50-60 cm), indicating the possibility of the atmospheric input of Hg. Based on the information of the total atmospheric Hg emission since this CFPP's operation in 1970s and the increased THg in nearby soils, it was estimated that about 3.9% discharged Hg has accumulated in the nearby agricultural soils. The low retention rate of the total emitted Hg by soils is a result of high proportion of Hg0 (79.5%) in stack gas emission and potential loss of Hg from soil surface reemission. The positive shifting (~ 0.5‰) of Hg isotopic signature (δ202Hg) from deep soil to surface soil reflected Hg deposition from nearby CFPP emissions that are featured with much heavier Hg isotopic signatures inherited from feed coal (δ202Hg: -0.50‰) and different combustion products (δ202Hg: -0.95 to 3.71‰) compared with that in deep soil layer (δ202Hg: ca -1.50‰). Overall, this study demonstrated that this CFPP has a slight but distinguishable effect on the elevation of ambient GEM and agricultural soil THg in the local environment.

Mercury in the human thyroid gland: Potential implications for thyroid cancer, autoimmune thyroiditis, and hypothyroidism

Objective

Mercury and other toxic metals have been suggested to be involved in thyroid disorders, but the distribution and prevalence of mercury in the human thyroid gland is not known. We therefore used two elemental bio-imaging techniques to look at the distribution of mercury and other toxic metals in the thyroid glands of people over a wide range of ages.

Materials and methods

Formalin-fixed paraffin-embedded thyroid tissue blocks were obtained from 115 people aged 1–104 years old, with varied clinicopathological conditions, who had thyroid samples removed during forensic/coronial autopsies. Seven-micron sections from these tissue blocks were used to detect intracellular inorganic mercury using autometallography. The presence of mercury was confirmed using laser ablation-inductively coupled plasma-mass spectrometry which can detect multiple elements.

Results

Mercury was found on autometallography in the thyroid follicular cells of 4% of people aged 1–29 years, 9% aged 30–59 years, and 38% aged 60–104 years. Laser ablation-inductively coupled plasma-mass spectrometry confirmed the presence of mercury in samples staining with autometallography, and detected cadmium, lead, iron, nickel and silver in selected samples.

Conclusions

The proportion of people with mercury in their thyroid follicular cells increases with age, until it is present in over one-third of people aged 60 years and over. Other toxic metals in thyroid cells could enhance mercury toxicity. Mercury can trigger genotoxicity, autoimmune reactions, and oxidative damage, which raises the possibility that mercury could play a role in the pathogenesis of thyroid cancers, autoimmune thyroiditis, and hypothyroidism.

Denitrification devices in urban boilers change mercury isotope fractionation signatures of coal combustion products

The installation rate of denitrification devices is accelerating in Chinese urban boilers. Previous studies on pulverized coal-fired boilers without denitrification devices showed that combustion products containing mainly oxidized mercury (Hg) preferably enriched lighter Hg isotopes than feed coals. However, the magnitude of this enrichment becomes less pronounced if denitrification devices are installed. The underlying Hg isotope fractionation mechanisms are still unclear. In this study, three types of urban boilers (two pulverized coal-fired boilers, one circulating fluidized bed boiler and one municipal waste incinerator boiler) all installed with denitrification devices were measured for Hg isotope compositions of their feed fuels and corresponding combustion products. We observed little mass independent fractionation but very significant mass dependent fractionation (MDF) between feed fuels and combustion products. The fly ash and desulfurization products both enriched heavier Hg isotopes than feed coals in three coal-fired boilers, and the enrichment of heavy Hg isotopes increased with sequential removal of combustion products in all boilers. Different from previously suggested kinetic MDF for gaseous Hg⁰(g)→Hg^II(g) and gaseous Hg^II(g)→particulate Hg^II(p) in coal combustion flue gases, we propose an equilibrium MDF for Hg⁰(g)↔Hg^II(g) followed by a kinetic MDF for Hg^II(g)→Hg^II(p). This equilibrium MDF most likely occurs during Hg⁰(g) oxidation in denitrification devices, which enriches heavy Hg isotopes in oxidized products (Hg^II(g) and Hg^II(p)) that are then sequestrated in fly ash and desulfurization products. The paradigm shift of MDF in boilers with denitrification devices was further verified by parallel Hg isotope measurement in urban atmosphere particulates. Our study clearly demonstrates that modern coal-fired boilers with denitrification devices have a quite different MDF compared to traditional boilers without denitrification devices. This has important implications for estimating isotope signatures of urban boiler Hg emissions, and for isotope tracing of anthropogenic Hg emissions.

Using a geographic information system to assess local scale methylmercury exposure from fish in nine communities of the Eeyou Istchee territory (James Bay, Quebec, Canada)

Exposure to methylmercury is a concern for those who rely on fish as a traditional food in the Eeyou Istchee territory of James Bay, Quebec, Canada, because industrial land uses overlap with community water bodies where fish are harvested. Consequently, this study assessed if traditional practices, particularly fishing, increased the risk of exposure to methylmercury from the consumption of locally harvested fish. We designed a geographic information system (GIS) that included land use and fish methylmercury tissue concentrations to assess clustering of potential hot spots. We also used generalized linear models to assess the association of fish consumption to blood organic-mercury concentrations, and logistic regression models to assess the probability of fish exceeding the safety threshold for methylmercury tissue concentrations in areas of high intensity land use. The GIS demonstrated significant clustered hot spots around regions of hydroelectric and mining land use. Our results also revealed that adult consumption of pike, lake trout and/or walleye, and child consumption of pike or walleye were significantly associated with blood organic-mercury concentrations. Further, large fish harvested in a community with high intensity land use yielded a 77% probability that the fish exceeded the safety threshold. From a human exposure perspective, our study highlights the need for further research on children who consume fish from this region.

Determination of mercury thermospecies in South African coals in the enhancement of mercury removal by pre-combustion technologies

Samples of South African bituminous coals were analysed for total mercury (Hg) and Hg thermospecies concentrations using an RA-915 + Zeeman Mercury Analyser. Total mercury concentrations in samples of coals (n = 57) ranged between 10 ng g⁻¹ and 493 ng g⁻¹ with a mean value of 150 ± 53 ng g⁻¹. Thermospecies of Hg were determined by monitoring Hg response as a function of sample temperature, increasing at 0.8 °C/s from ambient to 720 °C. This approach provides important information on thermal release of Hg species, as indicated by their appearance over specific temperature intervals. This permits identification of the presence of Hg thermospecies in coal and their quantification in each time (temperature) interval. It was found that 76% of tested bituminous coal samples release Hg species within low temperature intervals (20–180 °C and180–360 °C). The information generated in this study will aid in the selection of suitable coals for pre-combustion treatment that can lead to significant reduction of atmospheric Hg emission during coal combustion at power stations. This analytical approach can also be used for the creation of a system of coal classification based on the temperature of release of various Hg thermospecies.

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.

Mercury, cadmium, copper, arsenic, and selenium measurements in the feathers of adult eastern brown pelicans (Pelecanus occidentalis carolinensis) and chicks in multiple breeding grounds in the northern Gulf of Mexico

Several trace metals and metalloids have been introduced into aquatic ecosystems due to anthropogenic activities. Some of these elements like mercury (in the form of methylmercury) are easily transferred from one trophic level to another and can accumulate to toxic quantities in organisms at the top of aquatic food webs. For this reason, seabirds like the eastern brown pelican (Pelecanus occidentalis carolinensis) are susceptible to heavy metal and metalloid toxicity and may warrant periodic monitoring. Mercury, cadmium, copper, arsenic, and selenium were measured in the feathers of adult brown pelicans and chicks in several breeding colonies (Shamrock Island, Chester Island, Marker 52 Island, North Deer Island, Raccoon Island, Felicity Island, Gaillard Island, Audubon Island, and Ten Palms Island) in the northern Gulf of Mexico. Overall, most chicks and adults examined had mercury levels in feathers that were below the concentration range in which birds show symptoms of mercury toxicity. However, chicks in the Audubon Island and Ten Palms Island colonies displayed mercury levels that were 3 times higher than values observed in 5 other colonies. In addition, several adults and chicks displayed selenium concentrations that are above what is considered safe for birds. Cadmium quantities in feathers were below levels that trigger toxicity in birds. Similarly, arsenic measurements were at quantities below the average of what has been reported for birds living in contaminated sites. Finally, we identify pelican breeding colonies that may warrant monitoring due to elevated levels of contaminants.

A quantitative assessment of atmospheric emissions and spatial distribution of trace elements from natural sources in China

Natural sources, such as soil and wind-erosion dust (SWD), biomass open burning (BOB), sea salt spray (SSAS) and biogenic source (BIO), are major contributors to atmospheric emissions of trace elements (TEs) globally. In this study, we used a comprehensive approach to account for area-, production- and biofuel consumption-based emission factor calculation methods, and thus developed an integrated high-resolution emission inventory for 15 types of TEs (As, B, Cd, Co, Cr, Cu, Hg, Mn, Mo, Ni, Pb, Sb, Se, V and Zn) originated from natural sources in China for the year 2015. The results show that national emissions of TEs in 2015 range from 7.45 tons (Hg) to 1, 400 tons (Zn) except for the extremely high emissions of Mn (10, 677 tons). SWD and BIO are identified as the top two source contributors, accounting for approximately 67.7% and 26.1% of the total emissions, respectively. Absolute emissions of TEs from natural sources are high in the Xinjiang, Inner Mongolia and Tibet autonomous regions with large areas of bare soil and desert. However, emission intensity of TEs per unit area in the Southern provinces of China is higher than those in Northern China and Southwestern China, with the Yunnan and Sichuan provinces displaying the highest emission intensity. Our results suggest that controlling SWD can play a significant role in reducing fugitive particulate matter and the associated emissions of TEs from natural sources in China; and desertification control is particularly critical in the Northwest provinces where the majority of deserts are located.

A critical review of mercury speciation, bioavailability, toxicity and detoxification in soil-plant environment: Ecotoxicology and health risk assessment

Environmental contamination by a non-essential and non-beneficial, although potentially toxic mercury (Hg), is becoming a great threat to the living organisms at a global scale. Owing to its various uses in numerous industrial processes, high amount of Hg is released into different environmental compartments. Environmental Hg contamination can result in food chain contamination, especially due to its accumulation in edible plant parts. Consumption of Hg-rich food is a key source of Hg exposure to humans. Since Hg does not possess any identified biological role and has genotoxic and carcinogenic potential, it is critical to monitor its biogeochemical behavior in the soil-plant system and its influence in terms of possible food chain contamination and human exposure. This review traces a plausible link among Hg levels, its chemical speciation and phytoavailability in soil, accumulation in plants, phytotoxicity and detoxification of Hg inside the plant. The role of different enzymatic (peroxidase, catalase, ascorbate peroxidase, superoxide dismutase, glutathione peroxidase) and non-enzymatic (glutathione, phytochelatins, proline and ascorbic acid) antioxidants has also been elucidated with respect to enhanced generation of reactive radicles and resulting oxidative stress. The review also outlines Hg build-up in edible plant tissues and associated health risks. The biogeochemical role of Hg in the soil-plant system and associated health risks have been described with well summarized and up-to-date data in 12 tables and 4 figures. We believe that this comprehensive review article and meta-analysis of Hg data can be greatly valuable for scientists, researchers, policymakers and graduate-level students.

Particulates and particulates-bound mercury (Hg(p)) sizes (PM18, PM10, PM2.5, PM1, PM<1) distributions study by using MOUDI sampler at a complex sampling site

The objectives of this study were to measure ambient air particles concentrations of different particulates sizes ranges (PM₁₈, PM₁₀, PM_2.5, PM₁, PM_<1) at a complex (traffic, residential and commercial) site. Besides, particulates-bound mercury (Hg(p)) concentrations for various particulates sizes (PM₁₈, PM₁₀, PM_2.5, PM₁, PM_<1) at mixed site were also studied. Finally, ambient air particulates and Hg(p) size distributions were also described at this complex sampling site. The results showed that the average PM₁₈, PM₁₀, PM_2.5, PM₁, PM_<1 concentrations were 48.83, 41.78, 35.41, 19.89, and 11.86 μg/m³, respectively. And the average ambient air particulates-bound mercury (Hg(p)) which attached on PM₁₈, PM₁₀, PM_2.5, PM₁, PM_<1 particles concentrations were 0.0838, 0.0867, 0.0790, 0.0546, and 0.0373 ng/m³, respectively, in the summer season. In addition, the average ambient air Hg(p) which attached on PM₁₈, PM₁₀, PM_2.5, PM₁, PM_<1 particles concentrations were 0.0175, 0.0144, 0.0120, 0.0092, and 0.0057 ng/m³, respectively, in the autumn season. Finally, the average ambient air Hg(p) which attached on PM₁₈, PM₁₀, PM_2.5, PM₁, PM_<1 particles concentrations were 0.0070, 0.0053, 0.0038, 0.0026, and 0.0014 ng/m³, respectively, in the winter season. And July has the average highest PM₁₈ and PM₁₀ concentrations. As for PM_2.5, PM₁ and PM_<1 particulates, the average highest particulates concentrations all occurred in November. In addition, the highest average Hg(p) in PM₁₈, PM₁₀, PM_2.5, PM_1, and PM_<1 concentrations all occurred in July. Moreover, the average particles and particulates-bound mercury m.m.d. values were ranged from 1.0 to 1.8 and 0.7 to 2.0 μm from July to December of 2018, respectively, at this mixed sampling site. As for monthly ambient air particles sizes distributions, the results further showed that the main peaks for July, September, and December all occurred in the sizes of 10-18 μm. The main peaks for October and November all occurred in the sizes of 2.5-10 μm. As for monthly Hg(p) sizes distributions, the results further showed that the main peaks for July occurred in the size of 0.3-1 μm. The main peak for September occurred in the size of 1-2.5 μm. The main peaks for October to December all occurred in the size of 10-18 μm. The above finding further concluded that the particulates-bound mercury (Hg(p)) was tended to be associated with the large particles sizes mode during the winter season. Finally, this study further shows that the Taichung Thermal Power Plant was responsible for the main emission source of Hg(p) especially in summer season of Central Taiwan.

Elemental bioimaging shows mercury and other toxic metals in normal breast tissue and in breast cancers

OBJECTIVE

Exposure to toxic metals such as mercury has been proposed to be a risk factor for the development of breast cancer since some metals can promote genetic mutations and epigenetic changes. We sought to find what toxic metals are present in normal breast tissue and in the tumours of women who had mastectomies for invasive ductal breast carcinoma.

MATERIALS AND METHODS

Formalin-fixed paraffin-embedded blocks from mastectomies for breast carcinoma were examined from 50 women aged 34-69 years. Paraffin blocks selected for elemental analysis were from breast tissue not involved by carcinoma and from the carcinoma itself. Seven micrometer-thick sections were stained with autometallography to demonstrate the presence of mercury, and subjected to laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) to confirm the presence of mercury and to detect other toxic metals.

RESULTS

Autometallography-detected mercury was seen in intraductal secretions and some luminal epithelial cells of normal breast lobules in 26 (55%) of the 47 samples where lobules were present, and in 10 (23%) of carcinomas from the 44 samples where carcinoma was present. In eight samples ductal carcinoma in situ was present and one of these contained mercury. LA-ICP-MS confirmed the presence of mercury in samples that stained with autometallography, and detected lead, iron, nickel, aluminium, chromium and cadmium in some samples.

CONCLUSIONS

Mercury was present in normal breast lobules in more than half of mastectomy samples that contained an invasive carcinoma, and in a smaller proportion of carcinomas and ductal carcinomas in situ. Other toxic metals that may interact synergistically with mercury could be detected in some samples. These findings do not provide direct evidence that toxic metals such as mercury play a role in the pathogenesis of breast cancer, but suggest that future molecular biological investigations on the role of toxic metals in breast cancer are warranted.

Sources, bioaccumulation, health risks and remediation of potentially toxic metal(loid)s (As, Cd, Cr, Pb and Hg): an epitomised review

The release of potentially toxic metal(loid)s (PTMs) such as As, Cd, Cr, Pb and Hg has become a serious threat to the environment. The anthropogenic contribution of these PTMs, especially Hg, is increasing continuously, and coal combustion in thermal power plants (TPPs) is considered to be the highest contributor of PTMs. Once entered into the environment, PTMs get deposited on the soil, which is the most important sink of these PTMs. This review centred on the sources of PTMs from coal and flyash and their enrichment in soil, chemical behaviour in soil and plant, bioaccumulation in trees and vegetables, health risk and remediation. Several remediation techniques (physical and chemical) have been used to minimise the PTMs level in soil and water, but the phytoremediation technique is the most commonly used technique for the effective removal of PTMs from contaminated soil and water. Several plant species like Brassica juncea, Pteris vittata and Helianthus annuus are proved to be the most potential candidate for the PTMs removal. Among all the PTMs, the occurrence of Hg in coal is a global concern due to the significant release of Hg into the atmosphere from coal-fired thermal power plants. Therefore, the Hg removal from pre-combustion (coal washing and demercuration techniques) coal is very essential to reduce the possibility of Hg release to the atmosphere.

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.

Potential Ecological Risk and Human Health Risk Assessment of Heavy Metal Pollution in Industrial Affected Soils by Coal Mining and Metallurgy in Ostrava, Czech Republic

The heavy metal pollution of soils has become serious environmental problem, mainly in localities with high industrialization and rapid growth. The purpose of this detailed research was to determine the actual status of heavy metal pollution of soils and an assessment of heavy metal pollution in a highly industrialized city, Ostrava, with a history of long-term impacts from the metallurgy industry and mining. The ecological risks to the area was subsequently also assessed. The heavy metals Cd, Hg, Cu, Mn, Pb, V, Zn, Cr and Fe were determined in top-soils (0–20 cm) using atomic absorption spectrometry (F AAS, GF AAS) from three areas with different anthropogenic loads. The obtained data expressed as mean metal concentrations were very varied among the sampled soils and values of all analyzed metal concentrations were higher than its background levels. To identify the ecological risk and assessment of soil pollution, various pollution indices were calculated, such as single pollution indices (I_geo, CF, EF, PI) and total complex indices (IPI, PLI, PI_Nemerow, C_deg, mC_deg, E_r and PERI). The identification of pollution sources was assessed using Pearson’s correlation analysis and multivariate methods (HCA, PCA/FA). The obtained results confirmed three major groups of metals (Fe–Cr, Pb–Cu and Mn–V). A human health risk was identified in the case of Pb, Cd and Cr, and the HI value of V for children also exceeded 1.

Salient to Whom? The Positioning of German Political Parties on Agricultural Pollutants in Water Bodies

Scholars have increasingly argued for an integration of policies on agriculture and water due to their strong interlinkage. The entry of agricultural pollutants into water represents one of the main pressures on Europe’s ground and surface waters. This not only poses a risk to the environment and human health but also jeopardizes meeting the targets set by the EU Water Framework Directive. Research on the political agenda setting has shown that issue salience is key for triggering policy change. Nevertheless, Germany has repeatedly failed to adopt adequate policy measures despite the salience of the issue among the German public and increasing pressure by the EU. In this study, I shed light on the positioning of political parties in Germany on agricultural pollutants to explain the absence of policy change. More specifically, I ask whether there is an ideological division between political parties that hampers the adoption of effective, integrated policy measures. A qualitative content analysis of election manifestos published between 1998 and 2018 finds that political parties’ policy positions are predominantly influenced by their placement on an environmental and an economic ideological dimension. As a result, political parties in Germany advocate conflictive policy approaches, which is detrimental to the adoption of effective policy measures.

Mercury emission from underground coal fires in the mining goaf of the Wuda Coalfield, China

The Wuda Coalfield, Inner Mongolia suffers from serious coal fires for more than half a century. Fire-extinguishing projects have been carried out to suppress the coal fires since the last decade, but sporadic surface fires still occur and underground fires are more prevailing. Here, we used a real-time RA-915M Mercury Analyzer with modified inlet to monitor gaseous Hg concentrations in fumes emitted from boreholes that were designed to detect and control the underground coal fires. Meanwhile, offline methods were used to collect the fumes and analyze the contents of the gases including CO, CO₂, CH₄, C₂H₆, C₂H₄ and C₂H₂. The results showed that gaseous Hg concentrations in fumes from boreholes ranged from 6.42 ± 0.73 to 123.53 ± 34.66 ng m^-3, with an average value of 49 ± 44 ng m^-3. We suggest that the amounts of coal left for burning or smoldering mainly accounted for the large variation in fume Hg concentrations of underground coal fires. The gaseous Hg concentrations in near-surface air surrounding boreholes varied from 2.38 ± 0.28 to 13.10 ± 0.97 ng m^-3, with a mean value of 6.68 ± 3.09 ng m^-3. They were higher than the ambient air Hg concentrations measured at a background site near the Yellow River (<2 ng m^-3), suggesting underground coal fires were one significant Hg pollution source. Importantly, we found that gaseous Hg concentrations in the boreholes had significantly positive correlations with temperatures and CO (a traditional coal-fire index gas) contents, implying that Hg has the potential to serve as an index gas to monitor the occurrences of underground coal fires in mining goafs.

Assessment of air pollution by mercury in South African provinces using lichens Parmelia caperata as bioindicators

Large-scale assessment of atmospheric air pollution by mercury (Hg) using lichen Parmelia caperata as biological indicator was undertaken using samples from five provinces of South Africa collected between 2013 and 2017. Analysis of lichens provides time-integrated data, which correspond to the mean Hg concentration in air at a specific location over a long time period. Determination of Hg in lichens was carried out by direct thermal decomposition of samples using a Zeeman-effect atomic absorption spectrometer, thereby requiring no chemical pretreatment. The lowest mercury concentration of 60 ± 8.0 ng g^-1 (n = 45) was measured in lichens from Limpopo province. This value was accepted as a background Hg concentration in SA lichens. The Hg in lichens from northern parts of Mpumalanga province varied from 72 ± 9.0 to 100 ± 17 ng g^-1 (n = 45), while in southern parts of the province, where 11 coal-fired electrical power stations are located, values ranged from 139 ± 7.0 to 183 ± 10 ng g^-1 (n = 28). The highest Hg concentration, 218 ± 21 ng g^-1 (n = 10), was found in lichens from Secunda, Mpumalanga province. It could be traced to the possible Hg emission during thermal treatment of coal at the largest SA industrial plant that transforms coal into liquid fuels. In Pretoria and Johannesburg, cities in Gauteng province, Hg in lichens was between 110 and 162 ng g^-1 (n = 48). Based on the results of measurements, the equation connecting Hg concentration in lichens with Hg concentration in air has been derived. It was used for the calculation of atmospheric Hg concentration in South African provinces. Calculated values (0.8-1.45 ng m^-3) were found to be within statistical summary of mean atmospheric Hg in remote places (1.70 ± 0.17 ng m^-3), and in other locations (1.5-3.0 ng m^-3) lower than in impacted areas of the world (5.20 ± 3.47 ng m^-3).

Sources, toxicity, and remediation of mercury: an essence review

Mercury (Hg) is a pollutant that poses a global threat, and it was listed as one of the ten leading 'chemicals of concern' by the World Health Organization in 2017. The review aims to summarize the sources of Hg, its combined effects on the ecosystem, and its remediation in the environment. The flow of Hg from coal to fly ash (FA), soil, and plants has become a serious concern. Hg chemically binds to sulphur-containing components in coal during coal formation. Coal combustion in thermal power plants is the major anthropogenic source of Hg in the environment. Hg is taken up by plant roots from contaminated soil and transferred to the stem and aerial parts. Through bioaccumulation in the plant system, Hg moves into the food chain, resulting in potential health and ecological risks. The world average Hg concentrations reported in coal and FA are 0.01-1 and 0.62 mg/kg, respectively. The mass of Hg accumulated globally in the soil is estimated to be 250-1000 Gg. Several techniques have been applied to remove or minimize elevated levels of Hg from FA, soil, and water (soil washing, selective catalytic reduction, wet flue gas desulphurization, stabilization, adsorption, thermal treatment, electro-remediation, and phytoremediation). Adsorbents such as activated carbon and carbon nanotubes have been used for Hg removal. The application of phytoremediation techniques has been proven as a promising approach in the removal of Hg from contaminated soil. Plant species such as Brassica juncea are potential candidates for Hg removal from soil.

Modified 3D-printed device for mercury determination in waters

3D printing technology is increasingly used in flow analysis, to develop low cost and tailor-made devices. The possibility of grafting specific molecules onto 3D printed parts offers new perspectives for the development of flow systems. In this study, a MPFS system including a dicarboxylate 1,5-diphenyl-3-thiocarbazone grafted 3D-printed device has been developed for mercury determination. For this purpose, the surface of 3D-printed cuboids was first modified with amine functional groups and then grafted with dicarboxylate 1,5-diphenyl-3-thiocarbazone. This new grafted device resulted in selective mercury preconcentration with extraction and elution yields higher than 90% even at high sampling flow rates. The detection can then be carried out in two ways: a direct detection of mercury extracted onto 3D-printed grafted cuboids by atomic absorption spectrophotometry after amalgam on gold or a detection of mercury in solution after elution with l-cysteine by spectrophotometry or cold vapour atomic absorption spectrometry.

Evaluation of Mercury Transformation and Benthic Organisms Uptake in a Creek Sediment of Pearl River Estuary, China

A large fraction of mercury contaminant in the environment is from industrial production, and it potentially impairs human health once entering the food chain. Millions of people reside in the Pearl River Delta region, and water quality in the estuary directly affects their drinking water safety. Considering the highly intense anthropogenic activities and industrial productions, we attempted to measure the sediment mercury concentration in the Pearl River estuary. In this work, samples of a creek sediment within this region were collected and mercury concentrations were quantified. Total mercury, simultaneously extracted mercury, methylmercury, and bio-accumulated mercury were individually assayed. Results indicated that total mercury concentrations of investigated sites ranged from 1.073 to 4.450 µg/g dry sediment. The mercury in the sediment also transformed into more toxic methylmercury, which then adversely affected benthos biodiversity. Correlation analysis revealed that, mercury was accumulated into benthic microorganisms, mainly through the uptake of methylmercury. High concentrations of acid-volatile sulfide in the sediment indicated the presence of active sulfate-reducing bacteria, which could also catalytically transform inorganic mercury into methylmercury. Correlation analysis further showed that sulfate-reducing bacteria activity accounted for methylmercury formation.

Outlook of carbon capture technology and challenges

The greenhouse gases emissions produced by industry and power plants are the cause of climate change. An effective approach for limiting the impact of such emissions is adopting modern Carbon Capture and Storage (CCS) technology that can capture more than 90% of carbon dioxide (CO₂) generated from power plants. This paper presents an evaluation of state-of-the-art technologies used in the capturing CO₂. The main capturing strategies including post-combustion, pre-combustion, and oxy - combustion are reviewed and compared. Various challenges associated with storing and transporting the CO₂ from one location to the other are also presented. Furthermore, recent advancements of CCS technology are discussed to highlight the latest progress made by the research community in developing affordable carbon capture and storage systems. Finally, the future prospects and sustainability aspects of CCS technology as well as policies developed by different countries concerning such technology are presented.

Insights into the Potential Role of Mercury in Alzheimer's Disease

Mercury (Hg), which is a non-essential element, is considered a highly toxic pollutant for biological systems even when present at trace levels. Elevated Hg exposure with the growing release of atmospheric pollutant Hg and rising accumulations of mono-methylmercury (highly neurotoxic) in seafood products have increased its toxic potential for humans. This review aims to highlight the potential relationship between Hg exposure and Alzheimer's disease (AD), based on the existing literature in the field. Recent reports have hypothesized that Hg exposure could increase the potential risk of developing AD. Also, AD is known as a complex neurological disorder with increased amounts of both extracellular neuritic plaques and intracellular neurofibrillary tangles, which may also be related to lifestyle and genetic variables. Research reports on AD and relationships between Hg and AD indicate that neurotransmitters such as serotonin, acetylcholine, dopamine, norepinephrine, and glutamate are dysregulated in patients with AD. Many researchers have suggested that AD patients should be evaluated for Hg exposure and toxicity. Some authors suggest further exploration of the Hg concentrations in AD patients. Dysfunctional signaling pathways in AD and Hg exposure appear to be interlinked with some driving factors such as arachidonic acid, homocysteine, dehydroepiandrosterone (DHEA) sulfate, hydrogen peroxide, glucosamine glycans, glutathione, acetyl-L carnitine, melatonin, and HDL. This evidence suggests the need for a better understanding of the relationship between AD and Hg exposure, and potential mechanisms underlying the effects of Hg exposure on regional brain functions. Also, further studies evaluating brain functions are needed to explore the long-term effects of subclinical and untreated Hg toxicity on the brain function of AD patients.