Corrigendum: Contaminants from a former Croatian coal sludge dictate the structure of microbiota in the estuarine (Rasa Bay) sediment and soil.

[This corrects the article DOI: 10.3389/fmicb.2023.1126612.].

Contaminants from a former Croatian coal sludge dictate the structure of microbiota in the estuarine (Rasa Bay) sediment and soil.

Introduction: Croatian superhigh-organic-sulfur Rasa coal had been mined for nearly 400 years. The release of hazardous trace elements (HTEs) and toxic organic pollutants (TOPs) into the local environment by coal mining, preparation, and combustion activities has resulted in pollution. Methods: In this study, the diversity and composition of microbial communities in estuarine sediment and soil samples as well as community function responses to the pollutants were investigated. Results: The results showed that PAH degradation does occur following 60 years of natural attenuation, the location is still heavily polluted by polycyclic aromatic hydrocarbons (PAHs) and HTEs. Microbial analyses have shown that high concentrations of PAHs have reduced the diversity and abundance of microbial communities. The pollution exerted an adverse, long-term impact on the microbial community structure and function in the brackish aquatic ecosystem. Microorganisms associated with the degradation of PAHs and sulfur-containing compounds have been enriched although the diversity and abundance of the microbial community have reduced. Fungi which are believed to be the main PAH degrader may play an important role initially, but the activity remains lower thereafter. It is the high concentrations of coal-derived PAHs, rather than HTEs, that have reduced the diversity and abundance of microbial communities and shaped the structure of the local microbiota. Discussion: This study could provide a basis for the monitoring and restoration of ecosystems impacted by coal mining activities considering the expected decommission of a large number of coal plants on a global scale in the coming years due to growing global climate change concerns.

Distribution, chemical fractionation, and potential environmental risks of Hg, Cr, Cd, Pb, and As in wastes from ultra-low emission coal-fired industrial boilers in China.

This study conducted a comprehensive investigation of the distribution, chemical fractionation, and potential environmental risks of Hg, Cd, Cr, Pb, and As in waste based on new data from five ultra-low emission (ULE) coal-fired industrial boilers (CFIBs). The results showed that fly ash was enriched with Cd, Pb, As, and Hg, while its Cr contents were not invariably higher than those of slag. Fly ash was the predominant output flow for Hg, Cd, Cr, Pb, and As in the tested ULE boilers, with higher proportions of HTEs in the fly ash and lower proportions of HTEs in the flue gas than in the non-ULE boilers. The average proportions of residual Hg, Cd, Cr, Pb, and As in wastes revealed the following order: slag > fly ash > flue gas desulfurization (FGD) by-products. The potential environmental risks of Hg, Cd, Cr, Pb, and As in the fly ash, slag, and FGD by-products of CFIBs at the county level in the Beijing-Tianjin-Hebei Air Pollution Transmission Channel Cities ("2 +26 cities") region showed spatial heterogeneity. It is predicted that the potential release of Pb, Cr, and Cd in the fly ash would increase and that of the FGD by-products would decrease after the implementation of the ULE retrofitting of all CFIBs.

Bioaccessibility of arsenic, lead, and cadmium in contaminated mining/smelting soils: Assessment, modeling, and application for soil environment criteria derivation.

Soil environment criteria (SEC) are commonly derived from the total concentration of pollutants in soils, resulting in overly stringent values. Herein, we examined the feasibility of deriving the SEC by using the bioaccessibility of pollutants. In this regard, soil samples from 33 locations at 12 mining/smelting sites in China were collected and examined in terms of soil properties, chemical fraction distributions, and bioaccessibilities of cadmium (Cd), lead (Pb), and arsenic (As). The gastric (GP) and intestinal phases (IP) of the potentially hazardous trace elements (PHEs) were measured by in vitro assays, showing that these values varied from 11 % to 72 %, 1-79 %, and 2-27 % for Cd, Pb and As, respectively. Pearson analysis showed that the GP and IP bioaccessibilities of these PHEs were mainly influenced by soil pH, CEC, and clay fraction and positively correlated with the sequential extraction form. The random forest regression (RF) model showed excellent performance in predicting the gastric phase (GP) bioaccessibilities of Cd, Pb, and As, with a mean R2 and RMSE of 0.86 and 0.31, respectively. Both the measured and predicted bioaccessibilities were feasible to be used to derive SEC. This work will contribute to the development of regional soil environmental standards based on bioaccessibility for Cd-, Pb-, and As-contaminated mining/smelting soils.

Retention of trace elements in coal-fired flue gas by a novel heterogeneous agglomeration technology.

Heterogeneous agglomeration (HA) is a very potential technology for coal-fired flue gas treatment. In this paper, the distribution and migration mechanisms of trace elements (TEs) such as Se, As and Pb in CFPPs were studied on a 30,000 m3/hr pilot-scale experimental platform. The influences of HA on the removal efficiency of gaseous and particulate TEs were well analyzed. The results showed that Se, As and Pb were enriched in fly ash, and their sensitivity to particle size is quite different. The content of Se was the highest in PM1, reaching 193.04 mg/kg at the electrostatic precipitator (ESP) outlet. The average particle size of the total dust before ESP increased significantly from 21.686 to 62.612 µm after injecting the heterogeneous agglomeration adsorbent, conducive to its further removal by ESP. In addition, the concentrations of gaseous Se, As and Pb in the flue gas decreased after adsorbent spray, and accordingly, their contents in the hierarchical particles increased, indicating that the adsorbent could effectively promote the adsorption of gaseous trace elements in fly ash and reduce the possibility of their escape to the atmosphere. Total concentrations of Se, As and Pb emitted by wet flue gas desulfurization (WFGD) are 0.223, 0.668 and 0.076 µg/m3, which decreased by 59.98%, 47.69% and 90.71%, respectively. Finally, a possible HA mechanism model was proposed, where chemical adsorption, physical condensation and collision agglomeration of gaseous TEs and fine particles with adsorbent droplets occurred to form larger agglomerates.

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.

Measurements of the leachability of potentially hazardous trace elements from solid coal gasification wastes in China.

Solid wastes from commercial coal gasification plants are a significant environmental issue in China because of the large quantities produced. In recent years, with the rapid development of coal gasification technologies in China, more and more coal gasification residues are being disposed of in landfills because of the low utilization of the residues. In the present study, the column leaching procedure M1314 developed by the U.S. Environmental Protection Agency was used to evaluate the potential for environmental pollution by potentially hazardous trace elements (Be, V, Mn, Cr, Co, Ni, Cu, Zn, As, Se, Sr, Mo, Cd, Sb, Cs, Ba, Tl, Pb, Hg, Th, and U) in the coarse and fine gasification residues from two plants using General Electric (GE) and Gaskombinat Schwarze Pumpe (GSP) coal gasification technologies in northwest China. The potentially hazardous trace elements in the residues show different release patterns with the liquid-solid ratio increasing. The cumulative leached concentrations of the potentially hazardous trace elements from the coal gasification residues were generally low, and only Mo in the leachate of GSP fine residue was moderately soluble. V in the GSP coal gasification residues showed an increasing leachability in the leaching procedure. As, Se, Mo, Sb, and Tl in some leachates exceeded their thresholds in Level III of the Chinese Quality Standard for Groundwater and/or the Maximum Contaminant Levels of the U.S. National Primary Drinking Water Regulations. According to the risk assessment code, Se in the GE fine residue and Mo in the GE and GSP fine residues had medium risk to the ecosystem. Those data indicated that the potential for environmental pollution by those elements from coal gasification plants should be given consideration.

Impact of a tire fire accident on soil pollution and the use of clay minerals as natural geo-indicators.

Following the occurrence of a fire at a tire landfill in the surrounding area of Madrid City (Spain), polycyclic aromatic hydrocarbons (PAHs) and trace elements present in soils were analyzed to assess the impact of the fire. The capacity of the soils' clay mineral fraction to reflect this air pollution incident was studied. Fourteen soil samples were collected at different distances under the smoke plume, and they were subjected to high-performance liquid chromatography-photodiode array detection, inductively coupled plasma mass spectrometry and X-ray diffraction analyses. Clay minerals content showed a strong correlation with the pollutants potentially released in the tire fire, acenaphthene, pyrene, benzo(a)pyrene and benzo(a)fluoranthene. Trace metals Zn and Se were related to the proximity of the tire fire without any relationship with clay minerals content. This work suggests the use of natural clay minerals as potential PAHs geo-indicators in response to air pollution, complementary to current air and biological analyses.

Long-term leaching of As, Cd, Mo, Pb, and Zn from coal fly ash in column test.

Globally, millions of tons of coal fly ash (CFA) are generated per year, and the majority of this material is usually stored in stock piles or landfills, and in a long-term, it can be an environmental hazard if rainwater infiltrates the ashes. Long-term leaching studies of Brazilian ashes are scarce. The purpose of this study was to evaluate arsenic, cadmium, molybdenum, lead, and zinc leaching behavior from a Brazilian CFA by a column experiment designed to simulate field conditions: slightly acid rain considering seasonality of precipitation and temperature for a long-term leaching period (336 days). All elements were leached from CFA, except lead. Elements leaching behavior was influenced by leaching time, leaching volume, and temperature. Higher leachability of As and Cd from CFA during warm and wet season was observed. Results indicate a potential risk to soil and groundwater, since ashes are usually stored in uncovered fields on power plants vicinity.

Power production waste.

In this paper, the research literatures published in 2018 about power production waste generated from the coal-fired power plants and nuclear power plants are reviewed. The wastes from coal-fired plants include fly ash, flue gas desulfurization gypsum, spent selective catalytic reduction catalyst, hazardous trace elements, and the management, reuse, and disposal of these wastes are discussed. The treatment and disposal of wastes generated from nuclear power plants is also considered. PRACTITIONER POINTS: Reuse and disposal of coal-fired and nuclear power plant waste is discussed in this annual literature review. Emission of hazardous trace elements from coal-fired power plant is summarized. Radiological contaminant removal and radionuclides waste disposal is essential for nuclear power plant.

Fate of potentially hazardous trace elements during the entrained-flow coal gasification processes in China.

With the rapid and wide application of the coal gasification technology in China, the corresponding environmental issues require increasing attention. In this study, the feed coal, coal gasification wastewater samples at key technical links, and the coal gasification residues were collected from three entrained-flow coal gasification plants in Northwest China and were characterized to understand the migration and partition of 21 potentially hazardous trace elements (PHTEs) in coal gasification process and their potential environmental impacts. Compared with Chinese coal, the concentrations of the PHTEs in the feed coals are mainly at the level of "depleted" and "normal". Undergoing the heating process in the gasifier, purification procedure for the syngas, and the residue-wastewater separation, the PHTEs in the feed coals are transferred into gaseous phase, wastewater, and gasification residues. The PHTEs are easier to be released into the gaseous phase during the GSP gasification process compared with the OMB and GE gasification processes. The chalcophile elements Zn, As, Se, Cd, Sb, Tl, Pb, and Hg tend to be enriched in the fine residues, and the retention capability of Hg by the residues is the lowest. With the grey water circulation and the use of additives, the black water samples have higher PHTEs concentrations than other water samples. Except for Sr, Mo, Sb, and Cs, most of the elements in the original water samples can be reduced effectively by removing the particulate matters. In some cases, Cr6+, Zn, As, Se, Cd, and Pb in the original wastewater samples exceed the limit for industrial use as indicated in the Chinese Environmental Quality Standards for Surface Water and the Emission Standard for Pollutants from Coal Industry. The potential environmental impacts of As and Se in the water cannot be reduced by filtration. The environmental impacts of the coal gasification residues should be further evaluated.

Emission and transformation behavior of minerals and hazardous trace elements (HTEs) during coal combustion in a circulating fluidized bed boiler.

Emission of hazardous trace elements (HTEs) from energy production is receiving much attention due to concerns about the toxicity to the ecosystem and human health. This study presented new field measurement data on the HTEs partitioning behavior and size-segregated elemental compositions of gaseous particular matter (PM) generated from a commercial circulating fluidized bed (CFB) power plant. Mineralogical and morphological characteristics of combustion ash and PM2.5 (particle diameter less than 2.5 µm) were determined by X-ray diffractometer (XRD) and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDS). Functional groups alteration during CFB combustion was characterized by Fourier transform infrared spectroscopy (FTIR). The presence of aliphatic hydrogen at 2910 cm-1 and 2847 cm-1 in the PM2.5 suggested that the aliphatic carbon-rich volatiles were absorbed on the fine particles with large surface area. Fine fly ash (PM2.5) occurred as irregular glass particles or/and as unburned carbon. The typical irregular particles were mainly composed of Al-Si-Ca or Al-Si-Fe phases. The enrichment behavior of HTEs was determined for the airborne size-segregated particular matter. Elemental occurrences, combustion temperature, unburnt carbon, and limestone additives during CFB combustion were critical in the transformation behavior of HTEs. The total potentially mobile pollutants that exit the CFB power plant every year were estimated as follows: 0.22 tons of Cr, 0.12 tons of Co, 0.73 tons of Ni, 0.04 tons of As, 0.07 tons of Se, 3.95 kg of Cd, and 3.34 kg of Sb.

Study on emission of hazardous trace elements in a 350 MW coal-fired power plant. Part 2. arsenic, chromium, barium, manganese, lead.

Hazardous Trace elements (HTEs) emitted from coal combustion has raised widespread concern. Studies on the emission characteristics of five HTEs, namely arsenic (As), chromium (Cr), barium (Ba), manganese (Mn), lead (Pb) at three different loads (100%, 83%, 71% output) and different coal types were performed on a 350 MW coal-fired power plant equipped with SCR, ESP + FF, and WFGD. HTEs in the flue gas at the inlet/outlet of each air pollution control device (APCD) were sampled simultaneously based on US EPA Method 29. During flue gas HTEs sampling, coal, bottom ash, fly ash captured by ESP + FF, fresh desulfurization slurry, desulfurization wastewater were also collected. Results show that mass balance rate for the system and each APCD is in an acceptable range. The five studied HTEs mainly distribute in bottom and ESP + FF ash. ESP + FF have high removal efficiency of 99.75-99.95%. WFGD can remove part of HTEs further. Total removal rate across the APCDs ranges from 99.84 to 99.99%. Concentration of HTEs emitted to atmosphere is within the extremely low scope of 0.11-4.93 µg/m3. Emission factor of the five studied HTEs is 0.04-1.54 g/1012J. Content of As, Pb, Ba, Cr in solid samples follows the order of ESP + FF ash > bottom ash > gypsum. More focus should be placed on Mn in desulfuration wastewater, content of which is more than the standard value. This work is meaningful for the prediction and removal of HTEs emitted from coal-fired power plants.