Hg Emissions Research Articles

Impacts of Removal Compensation Effect on the Mercury Emission Inventories for Nonferrous Metal (Zinc, Lead, and Copper) Smelting in China.

Nonferrous metal smelting (NFMS) is one of the key sources of mercury (Hg) emissions to the air and cross-media Hg transfer in China. In this study, a "Hg removal compensation effect" between upstream and downstream air pollution control devices (APCDs) in NFMS was uncovered based on the investigation of field test data. The relationships between the Hg concentration in flue gas and the Hg removal efficiencies of typical APCDs were established, and an advanced probabilistic mass flow model regarding this effect was developed. Model comparison shows that the probabilistic essence of the advanced model prevents the underestimation of the deterministic model caused by using the geometric means of the Hg contents of metal concentrates, and the consideration of the removal compensation effect leads to more accurate estimation of the overall Hg removal efficiency of cascaded APCDs. The Hg emission abatement in the NFMS sector from 2010 to 2017 was evaluated to be 55.6 t, which was 13.5% higher than the estimate without considering the Hg removal compensation effect. The overall uncertainty of the improved model was reduced. This study provides a new methodology for more accurate evaluation of the effectiveness of the national implementation plan for the Minamata Convention on Mercury.

Determination of Total Mercury and Carbon in a National Baseline Study of Urban House Dust

Mercury (Hg) is one of the top ten chemicals of concern for public health, according to the World Health Organization. This study investigates Hg concentrations in house dust collected from urban single family homes, to better understand typical indoor residential exposures. Using direct solid sample analysis, total Hg and carbon (TC) were determined in the <80 µm fraction of settled dust samples collected under the Canadian House Dust Study. Hg concentrations displayed a log-normal distribution with median/geomean of 0.68/0.70 mg/kg (n = 995). A small subset (<1%) of homes exhibited anomalously high dust Hg concentrations (>9.0 mg/kg). A comparison of Hg concentrations in fresh dust and household vacuum dust collected from the same homes indicated no significant difference in the two sampling methods. Total carbon concentrations displayed a median/geomean of 29.3/28.5% (n = 1011). A significant correlation between total Hg and TC in house dust (p < 0.00001) reflects the association between Hg and organic carbon previously observed in soil and sediments. The results of this study indicate a 10-fold enrichment in house dust compared with the average background concentrations reported for soil and sediments (0.07 mg/kg). The observed enrichment is attributable to Hg emissions from indoor sources and/or Hg carried home from occupational sources.

Experimental study and reaction mechanism on the process of Br addition for mercury emission control

Application of halogen additive (CaCl2, CaBr2) has recently been shown to decrease Hg0 concentration significantly in the hazardous waste incineration flue gas. However, the reaction mechanism of Hg0 oxide active substance has currently not yet been studied. In this paper, the effect of CaBr2 on Hg0 oxidation under different combustion conditions and the reaction mechanism of effective reaction components (bromine free radicals) detected by the EPR (Electron Paramagnetic Resonance) method are studied. For the first time, the correlation between bromine radical and Hg0 oxidation is shown, which eventually affects the transformation path of Hg0 in the flue gas. Under different working conditions, the oxidation effect of CaBr2 solution additives on Hg0 in flue gas has been verified in the experiment platform. CaBr2 can still effectively oxidize Hg0 in complex flue gas conditions of the hazardous waste incineration plant. These results provide a new fundamental understanding of the oxidation path of Hg0 under the influence of bromine free radicals and show that spraying calcium bromide solution is an effective means to avoid atmospheric Hg0 emissions, contributing to its global distribution in a significant way.

Removal of Mercury from Acidic Solutions of Mercury Chloride by Means of Sorbents Prepared by Catalyzed Vulcanization of Vegetable Oils

Mercury is a metallic element, dangerous and toxic for the environment. Presently, the incineration of municipal solid waste (MSW) belongs to important sources of Hg emissions. Methods of conversion of metallic mercury and mercury compounds from soluble and toxic forms into water insoluble/non-toxic form (HgS) are sought after. Gaseous HCl and a significant part of HgCl2 vapors present in flue gas from incineration of MSW can be removed there by absorption in hot water. Efficiencies of Hg2+ removal from acidic water solutions by means of sorbents prepared by catalyzed reaction of sulfur with vegetable oils (inverse vulcanization) were studied. These kinds of sorbents were tested and found to be exploitable for selective removal of mercury ions from aqueous solutions, particularly from acidic solutions containing HCl at higher temperatures (50–75 °C). Presence of relatively high concentrations of salts of some other metallic elements (Fe, Zn, Ca) had only very small effects on Hg-sorption. Mercury adsorbed on such sorbents converts relatively quickly into a non-toxic form (HgS). Reactive sulfides and SH‑groups present on the surface of the sorbent particles contribute to a faster sorption of mercury and its conversion to HgS. Leaching of zinc from the catalyst (Zn‑diethyldithiocarbamate) present in the vulcanized sorbents is negligible at neutral conditions and small (about 10 %) at acidic conditions (pH = 1.5).

Mercury pollution in China: implications on the implementation of the Minamata Convention.

Mercury (Hg) is a toxic metal released into the environment through human activities and natural processes. Human activities have profoundly increased the amount of Hg in the atmosphere and altered its global cycling since the Industrial Revolution. Gaseous elemental Hg is the predominant form of Hg in the atmosphere, which can undergo long-range transport and atmospheric deposition into the aquatic systems. Hg deposition elevates the methylmercury (MeHg) level in fish through bioaccumulation and biomagnification, which poses a serious human health risk. Acute poisoning of MeHg can result in Minamata disease, while low-level long-term exposure in pregnant women can reduce the intelligence quotient of infants. After five sessions of intergovernmental negotiation, the Minamata Convention on mercury entered into force in August 2017 to protect human health and the environment from Hg pollution. Currently China contributes the largest quantity of Hg production, consumption, and emission globally. However, the status of Hg pollution in the environment in China and its associated health risk remains relatively unknown, which hinders the development of implementation plans of the Minamata Convention. In this paper, we provide a comprehensive review on the atmospheric release of Hg, distribution of air Hg concentration, human exposure to MeHg and health impacts caused by Hg pollution in China. Ongoing improvement of air pollution control measures is expected to further decrease anthropogenic Hg emissions in China. Air Hg concentrations in China are higher than the background values in the Northern Hemisphere, with spatial distribution largely influenced by anthropogenic emissions. Long-term observations of GEM in China show a decline in recent years. The net Hg transport outflow from China in 2013 is estimated to be 511 t year-1, and ∼60% of such outflow is caused by natural surface Hg emissions. Hg concentrations in fish and rice in China are relatively low and therefore the associated risks of human Hg exposure are low. Future research needs and recommendations for the implementation of the Minamata Convention are also discussed in this paper.

Tracing the sources and depositional history of mercury to coastal northeastern U.S. lakes.

Mercury (Hg) deposition was reconstructed in sediment cores from lakes in two coastal U.S. National Parks: Acadia National Park (ANP) and Cape Cod National Seashore (CCNS), to fill an important spatial gap in Hg deposition records and to explore changing sources of Hg and processes affecting Hg accumulation in these coastal sites. Recent Hg deposition chronology was assessed using (1) a newly developed lead-210 (210Pb) based sediment age model which employs 7Be to constrain deposition and sediment mixing of 210Pb-excess, (2) coinciding Pb flux and isotope ratios (206Pb/207Pb), and (3) Hg isotope ratios and their response to changes in Hg flux. At both sites, Hg flux increased substantially from pre-1850 levels, with accumulation in ANP peaking in the 1970s, whereas in CCNS, Hg levels were highest in recent sediments. Negative values of δ202Hg and Δ199Hg indicated terrestrially-derived Hg was a major constituent of Hg flux to Sargent Mountain Pond, ANP, although recent decreases in Hg flux were in agreement with precipitation Hg records, indicating a rapid watershed response. By contrast, δ202Hg and Δ199Hg profiles in Long Pond, CNNS reflect direct Hg deposition, but disturbances in the sedimentary record were indicated by bomb fallout radionuclide inventories and by peaks in both Pb and Hg isotope depth profiles. These cores provided poor reconstructions of atmospheric deposition and reveal responses that are decoupled from emissions reduction due to complex post-depositional redistribution of atmospheric metals including Hg. The application of multiple tracers of Hg deposition provide insight into the sources and pathways governing Hg accumulation in these lakes.

Mercury Isotope Fractionation during the Exchange of Hg(0) between the Atmosphere and Land Surfaces: Implications for Hg(0) Exchange Processes and Controls.

Atmosphere-surface exchange of elemental mercury (Hg(0)) is a vital component in global Hg cycling; however, Hg isotope fractionation remains largely unknown. Here, we report Hg isotope fractionation during air-surface exchange from terrestrial surfaces at sites of background (two) and urban (two) character and at five sites contaminated by Hg mining. Atmospheric Hg(0) deposition to soils followed kinetic isotope fractionation with a mass-dependent (MDF) enrichment factor of -4.32‰, and negligible mass-independent fractionation (MIF). Net Hg(0) emission generated average MDF enrichment factors (ε202Hg) of -0.91, -0.59, 1.64, and -0.42‰ and average MIF enrichment factors (E199Hg) of 0.07, -0.20, -0.14, and 0.21‰ for urban, background, and Hg mining soils and cinnabar tailing, respectively. Positive correlations between ε202Hg and ambient Hg(0) concentration indicate that the co-occurring Hg(0) deposition (accounting for 10-39%) in a regime of net soil emission grows with ambient Hg(0). The MIF of Hg(0) emission from soils (E199Hg range -0.27 to 0.14‰, n = 8) appears to be overall controlled by the photochemical reduction of kinetically constrained Hg(II) bonded to O ligands in background soils, while S ligands may have been more important in Hg mining area soils. In contrast, the small positive MIF of Hg(0) emission from cinnabar ore tailing (mean E199Hg = 0.21‰) was likely controlled by abiotic nonphotochemical reduction and liquid Hg(0) evaporation. This research provides critical observational constraints on understanding the Hg(0) isotope signatures released from and deposited to terrestrial surfaces and highlight stable Hg isotopes as a powerful tool for resolving atmosphere-surface exchange processes.

Significance of soil moisture on temperature dependence of Hg emission

Soil moisture is a key factor for mercury (Hg) emission from soil. Despite its significance for Hg emissions, the effect of soil moisture on Hg flux and fractions has not been thoroughly investigated. The objective of this study was to elucidate the influences of soil moisture and temperature on Hg fluxes from soils and Hg fractions. A kinetic study was performed to measure Hg emission fluxes of six soil samples under different temperature (T) (15 °C, 20 °C, 25 °C, 30 °C, and 35 °C) and moisture conditions (0%, 10%, and 20% added water). The results showed that the Hg fluxes increased with increases in T and soil moisture. A linear correlation was found between ln (Hg emission flux) and 1/T for the six soil samples at different moisture contents (R2 = 0.73–0.99). The range of activation energy (Ea) values was 25.31–57.86 kJ/mol. The Hg fractions in soils of different moisture content were determined by a sequential extraction method. The results demonstrated that soil moisture affected the Hg fractions in soils. The Ea values had different relationships with soil moisture in different soils. There were correlations between Ea and the elemental and mercuric sulfide fractions for air-dried soils. However, for moist soils, Ea was negatively correlated with the water-soluble and acid-soluble fractions. Collectively, the combination of the Hg emission kinetics and Hg fraction measurement of different moist soils indicated that Hg emission was affected by both total Hg concentration and Hg fractions.

Elucidating sources of mercury in the west coast of Korea and the Chinese marginal seas using mercury stable isotopes

Nearshore systems play an important role as mercury (Hg) sources to the open ocean and to human health via fish consumption. The nearshore system along East Asia is of particular concern given the rapid industrialization, which contributes to significant anthropogenic Hg emissions and releases. We used Hg stable isotopes to characterize Hg sources in the sediment and fish along the west coast of Korea, located at the northeast of the East China Sea. The Hg isotope ratios of the west coast sediments (δ202Hg; −0.89 to −0.27‰, Δ199Hg; −0.04 to 0.14‰) were statistically similar with other nearshore sediments (δ202Hg; −0.99 to −0.30‰, Δ199Hg; −0.04 to 0.19‰) and overlapped with the industrial Hg source end-member (δ202Hg; −0.5‰, Δ199Hg; 0.01‰) estimated from the Chinese marginal seas. Using a ternary mixing model, we estimated that industrial Hg sources contribute 83–97% in the west coast of Korea, and riverine and atmospheric Hg sources play minor roles in the Korean west coast and the Chinese marginal seas. The comparison between Hg isotope ratios of the sediment and nearshore fish revealed that the fish in the most west coast sites are exposed to MeHg produced in the sediment. At a few southwest coast sites, external MeHg produced in rivers and the open ocean water column appears to be more important as a source in fish. This is supported by much higher δ202Hg (0.74‰; similar to oceanic fish) and lower δ202Hg (−0.71‰; similar to riverine sources) compared to fish collected from other west coast sites influenced by sedimentary MeHg. The substantial Hg contributions from industrial activities suggest the national policies regulating anthropogenic Hg releases can directly mitigate human Hg exposure originating via local fish consumption. This study contributes to the growing regional and global inventories of Hg fluxes and sources exported into coastal oceans.

Role of Trade in India's Rising Atmospheric Mercury Emissions.

India is among the largest emitters of atmospheric mercury (Hg) in the world. India's production activities have associated Hg emissions which can be attributed to final demands (e.g., purchases by households, governments, and private investments) of nations driving upstream production from the demand perspective, or primary inputs (e.g., labor and capital supply) of nations enabling downstream production from the supply perspective. This study identifies key nations and sectors that directly and indirectly drove India's Hg emissions from both the demand and supply perspectives during 2004-2014. While domestic final demand was the dominant driver from the demand perspective (driving about 80-85% of the total), USA, China, and UAE are important foreign drivers. Similarly, from the supply perspective, domestic primary inputs were the dominant drivers. However, the share of foreign inputs enabling Hg emissions increased from 16 to 23% during the decade. Saudi Arabia, Indonesia, Australia, and China are the top foreign supply-side drivers. The Construction sector is an important demand-side driver, whereas fossil fuel sectors are important supply-side drivers. These findings can guide global and national policies for demand- and supply-side management of Hg emissions in India and assist in the successful implementation of the Minamata Convention on Mercury.

A stepwise emission clustering analysis method for analyzing the effects of heavy metal emissions from multiple income groups

Emissions of various heavy metals (i.e. Hg, As, Cd, Cr and Pb) have emerged as one of the most tremendous pressures on the socio-economic and environmental systems. The pressures caused by such heavy metals would be getting intensified if no adequate and timely solution is implemented, especially because their emissions are associated with economic activities (i.e. regional trade and household consumption). In this study, emissions of various heavy metals derived from regional trade as well as rural and urban household consumption are quantified to identify the critical regions and significant household consumption. In order to detail the impacts of household consumption on such emissions, rural and urban household are divided respectively into five and seven groups with hierarchic income from poorest to richest. The Hg, As, Cd, Cr and Pb emissions caused by intermediate commodity consumption are 1172.86, 2607.57, 23.28, 57.49 and 85.16 tons, respectively. Among them, such emissions induced by self-consumption are 662.95, 1539.34, 12.28, 33.10 and 43.49 tons. Shandong, Guangdong and Jiangsu are identified for high self-emissions due to their advanced economy and rare resources. On the contrast, Hebei and Shanxi with abundant resources are the critical regions for the high transfer-out emissions. Moreover, emissions of multiple heavy metals are inequal due to the variations of rural and urban income groups. Emissions caused by R5 are identified through stepwise cluster analysis for its significant difference in compare with other income groups. It is verified that the main difference of emissions in economically developed regions are caused by rural income groups, while urban income groups are the critical reason for the disaggregation of emissions in less developed regions. Policies should be further implemented based on the regional similarity and income-group inequality.

Utilization of desulfurization gypsum potentially impairs the efforts for reducing Hg emissions from coal-fired power plants in China

The thermal instability of most mercury (Hg) species in flue gas desulfurization (FGD) gypsum may lead to the release of large amounts of Hg into the atmosphere. In this study, gypsum samples were collected from 13 major coal-fired power plants (CFPPs) for evaluating the Hg thermal stability within a temperature range of 100–200 °C. Results indicated that the release ratio of Hg from FGD gypsum varied considerably among the CFPPs. Such significant differences were caused by different proportions of the major Hg compounds, especially of HgClx (HgCl2 and Hg2Cl2), in the FGD gypsum samples. The release ratio appeared extremely sensitive to changes in the treatment temperature and duration. Wallboard manufacturing and its use as cement retarder are the leading causes of Hg emission (corresponding to greater than 95% of the total) during FGD gypsum resource utilization. The total average Hg emitted due to FGD gypsum resource utilization in China in 2017 was estimated to be 11.42 tons (ranging between 2.15 and 38.35 tons), which accounted for about 23.8 % (ranging between 4.6 and 79.8%) of the stack Hg emissions from CFPPs in that year. The results of this study indicate that the resource utilization processes of FGD gypsum are important Hg emission sources and that they should be considered with care in future emission control policies.

(Noble Gas)n -NC+ Molecular Ions in Noble Gas Matrices: Matrix Infrared Spectra and Electronic Structure Calculations.

An investigation of pulsed‐laser‐ablated Zn, Cd and Hg metal atom reactions with HCN under excess argon during co‐deposition with laser‐ablated Hg atoms from a dental amalgam target also provided Hg emissions capable of photoionization of the CN photo‐dissociation product. A new band at 1933.4 cm−1 in the region of the CN and CN+ gas‐phase fundamental absorptions that appeared upon annealing the matrix to 20 K after sample deposition, and disappeared upon UV photolysis is assigned to (Ar) n CN+, our key finding. It is not possible to determine the n coefficient exactly, but structure calculations suggest that one, two, three or four argon atoms can solvate the CN+ cation in an argon matrix with C−N absorptions calculated (B3LYP) to be between 2317.2 and 2319.8 cm−1. Similar bands were observed in solid krypton at 1920.5, in solid xenon at 1935.4 and in solid neon at 1947.8 cm−1. H13CN reagent gave an 1892.3 absorption with shift instead, and a 12/13 isotopic frequency ratio–nearly the same as found for 13CN+ itself in the gas phase and in the argon matrix. The CN+ molecular ion serves as a useful infrared probe to examine Ng clusters. The following ion reactions are believed to occur here: the first step upon sample deposition is assisted by a focused pulsed YAG laser, and the second step occurs on sample annealing: (Ar)2 ++CN→Ar+CN+→(Ar) n CN+.

Mercury spatiality and mobilization in roadside soils adjacent to a savannah ecological reserve

Mercury (Hg) is a persistent environmental pollutant of global concern. Recognized anthropic contributions to environmental Hg pollution include fuel fossil emissions, soil erosion, and industrial and mining activities. Environmental Hg that enters water bodies can be methylated before entering the food chain and contaminating man and wildlife. We used a kriging approach for sampling and X-ray crystallography to study the pressure of road-traffic Hg emissions on soil Hg concentrations in an ecological reserve (ESECAE) in Central Brazil’ savannah. We took samples of organic (n = 144) and mineral (n = 144) layers from the road-side and from the undisturbed soils at 0.1, 1, and 2 km from traffic, inside the ESECAE. Overall, total mercury (THg) concentrations determined by atomic absorption spectrophotometry were significantly higher in the organic layer than in the mineral layer. The mean soil THg in the organic and mineral layers was highest at the roadside (respectively 19.77 ± 12.01 and 16.18 ± 11.54 μg g−1), gradually decreasing with the distance from the road. At 2 km, the mean soil THg was 0.09 ± 0.30 and 0.029 ± 0.03 μg g−1, respectively, for the organic and mineral layers. X-ray crystallography showed mineralogical similarity of the sampled soils, indicating Hg externality, i.e, it did not originate from existing soil minerals. Co-kriging analysis (n = 288) confirmed Hg hotspots on the roadsides and a faster mobilization occurring up to a distance of 1 km for both layers. The soil reception and retention of traffic Hg emissions are mainly in the organic layer and can impact subsoil and adjacent areas. Thus, traffic soil-Hg pollution is limited to the road proximities; THg concentrations are high up to 100 m with an inflection point at 1 km.

Quantification of Spatial and Temporal Trends in Atmospheric Mercury Deposition across Canada over the Past 30 Years.

Mercury (Hg) is a pollutant of concern across Canada and transboundary anthropogenic Hg sources presently account for over 95% of national anthropogenic Hg deposition. This study applies novel statistical analyses of 82 high-resolution dated lake sediment cores collected from 19 regions across Canada, including nearby point sources and in remote regions and spanning a full west-east geographical range of ∼4900 km (south of 60°N and between 132 and 64°W) to quantify the recent (1990-2018) spatial and temporal trends in anthropogenic atmospheric Hg deposition. Temporal trend analysis shows significant synchronous decreasing trends in post-1990 anthropogenic Hg fluxes in western Canada in contrast to increasing trends in the east, with spatial patterns largely driven by longitude and proximity to known point source(s). Recent sediment-derived Hg fluxes agreed well with the available wet deposition monitoring. Sediment-derived atmospheric Hg deposition rates also compared well to the modeled values derived from the Hg model, when lake sites located nearby (<100 km) point sources were omitted due to difficulties in comparison between the sediment-derived and modeled values at deposition "hot spots". This highlights the applicability of multi-core approaches to quantify spatio-temporal changes in Hg deposition over broad geographic ranges and assess the effectiveness of regional and global Hg emission reductions to address global Hg pollution concerns.

Mercury emissions and distribution in a waste incineration plant based on the 30B and Ontario Hydro methods

Flue gas mercury emissions from waste rotary kiln incineration plants in Northern China was sampled using the US Environmental Protection Agency's 30B method and Ontario Hydro (OH) method. The average mercury emissions concentration was 13.38 ± 4.08 μg/Nm3 (based on the 30B method) and 18.66 ± 8.19 μg/Nm3 (based on the OH method). Coincidentally, it was also found that the uncertainty in Hg measurements of the raw feedstock was responsible for the fluctuation in the flue gas Hg data. The Hg emission consisted of Hg0, followed by Hg2+ and Hgp species, accounting for 59–82%, 3–26% and 14.84–16.03% of total Hg, respectively. Mercury was released from the ash to the flue gas after the fabric filter due to the high temperature. Based on the 30B and OH methods, the re-release rates of total Hg were 45.09% and 40.38%, respectively. The scrubbing tower in this type of system can remove most of the Hg2+ from the flue gas, and the total Hg removal efficiencies across the desulfurization units were 59.70% and 92.19%, respectively.

Bottom-Heavy Trophic Pyramids Impair Methylmercury Biomagnification in the Marine Plankton Ecosystems.

Methylmercury (CH3Hg+, MMHg) in the phytoplankton and zooplankton, which form the bottom of marine food webs, is a good predictor of MMHg in top predators, including humans. Therefore, evaluating the potential exposure of MMHg to higher trophic levels (TLs) requires a better understanding of relationships between MMHg biomagnification and plankton dynamics. In this study, a coupled ecological/physical model with 366 plankton types of different sizes, biogeochemical functions, and temperature tolerance is used to simulate the relationships between MMHg biomagnification and the ecosystem structure. The study shows that the MMHg biomagnification becomes more significant with increasing TLs. Trophic magnification factors (TMFs) in the lowest two TLs show the opposite spatial pattern to TMFs in higher TLs. The low TMFs are usually associated with a short food-chain length. The less bottom-heavy trophic pyramids in the oligotrophic oceans enhance the MMHg trophic transfer. The global average TMF is increased from 2.3 to 2.8 in the warmer future with a medium climate sensitivity of 2.5 °C. Our study suggests that if there are no mitigation measures for Hg emission, MMHg in the high-trophic-level plankton is increased more dramatically in the warming future, indicating greater MMHg exposure for top predators such as humans.

Assessment of the Impact of a Motorway on Content andSpatial Distribution of Mercury in Adjacent Agricultural Soils

The distribution of Hg in the vicinity of roads is probably not exclusively dependent on car emissions, but also on the presence of other point or diffuse sources of Hg emissions located from metres to several km away. The source of mercury in urbanised areas is pollution derived from the burning of fuels and industrial and transport waste, while in agricultural areas, it is constituent in mineral fertilisers and crop protection products. The research objective was to evaluate the content and spatial distribution of mercury in arable soils adjacent to the A1 motorway in Poland. The research material consisted of 40 soil samples taken from 20 test points on four transects at distances of 5, 10, 25 and 50 m from a noise barrier and in the direction of an arable field, and 10 m from the noise barrier in the direction of the motorway. Total mercury content was determined by atomic absorption spectrometry using an AMA 254 analyser. The spatial relationship between adjacent observations of variables was assessed using Moran’s I overall autocorrelation coefficient. Probability maps of mercury distribution in the field and pollution indicators were elaborated in ArcGIS 10.4.1. using Inverse Distance Weighted interpolation. Analysis of the spatial correlation of Moran’s I showed a lack of spatial dependence between tested points, which may evidence that the motorway does not affect mercury contents in the soil. The elevated mercury content at a single test point may indicate a random event unrelated to the motorway’s operation.

Strategic-level performance enhancement of a 660 MWe supercritical power plant and emissions reduction by AI approach

Power plant heat rate is a plant level performance parameter that indicates the economy of power production, equipment’s safety, and availability. In this paper, seven operating parameters, including the performance indices of integrated energy devices and the environmental conditions are incorporated for modeling the power plant heat rate by Artificial Neural Network (ANN), Support Vector Machine (SVM), and automated machine learning (AutoML) approach. The parametric significance order is determined by ANN and SVM-based Monte Carlo analytics and other machine learning-driven algorithms. Subsequently, the best-performing model is selected based on the external validation test and deployed for knowledge mining purposes. The improvement in the power plant heat rate by the parametric adjustment is achieved and subsequently, up to 3.12 percentage point (pp) increase in the thermal efficiency of the power plant is confirmed.Moreover, the fuel savings corresponding to the improved power plant heat rate are also calculated at three power generation modes. Their equivalence to an annual reduction in emissions is quantified. It is estimated that the accumulated reduction in CO2, SO2, CH4, N2O, and Hg emissions, i.e., 288.2 kilo tons / year (kt/y), can be achieved under 3.15% improvement in the power plant heat rate, corresponding to 75% power generation mode.

Long-range transport of La Soufrière volcanic plume to the western North Pacific: Influence on atmospheric mercury and aerosol properties

Volcanic eruptions are important natural sources of gases and aerosols to the environment. However, their impact on the global cycle of trace elements, including mercury (Hg), remains poorly understood. On 9 April 2021, La Soufrière volcano (13.33°N, 61.18°W) erupted in the Caribbean Sea. Ozone Monitoring Instrument (OMI) measurements of sulfur dioxide (SO2) tracked the transport of volcanic SO2 in the troposphere over long distances from the source, including to the western North Pacific ∼10 day after eruption. A spike in gaseous and particle-bound mercury concentrations along with a peak in aerosol back-scattering coefficient at Lulin Atmospheric Background Station (LABS, 23.47°N, 120.87°E; 2862 m AMSL) coincided with the volcanic plume transport on 19 April. The slope of gaseous elemental mercury vs. carbon monoxide concentrations during the event was 0.027, which is distinctly higher than for Southeast Asia biomass burning (slope = 0.005) and East Asia outflow (0.011) pollution sources. Arrival of the plume high above Taiwan was confirmed by significant changes in signature aerosol properties. Thus, with critical observational evidence, our study reported for the first time enhanced mercury levels ∼18000 km downwind from a volcano source, providing an important check on volcanic Hg emission strength.