Mechanism for leaching of fluoride ions from carbon dross generated in high-temperature and low-lithium aluminum electrolytic systems.

Carbon dross, a hazardous solid waste generated during aluminum electrolysis, contains large amounts of soluble fluoride ions for the main components of the electrolyte (such as Na3AlF6 and NaF). Response surface methodology (RSM) was used to investigate the mechanism for fluoride ion leaching from carbon dross via water leaching, acid leaching and alkali leaching, and the kinetic and thermodynamic principles of the leaching process were revealed. The RSM predicted the optimum conditions of water leaching, alkali leaching and acid leaching, and the conditions are as follows: temperature, 50 °C; shaking speed, 213 r·min-1; particle size, 0.075 mm; shaking speed, 194 r·min-1; liquid-solid ratio, 12.6 mg·L-1; sodium hydroxide concentration, 1.53 mol·L-1; liquid-solid ratio, 25.0 mg·L-1; sulfuric acid concentration, 2.00 mol·L-1; and temperature, 60 °C，and actual results which were almost consistent with the predicted results were gained. The fluoride ions in the alkaline and acid leaching solutions were mainly the dissociation products of fluorides such as Na3AlF6, Na5Al3F14 and CaF2, as indicated by thermodynamics calculations. In particular, the fluoride compounds dissolved in alkali solution were Na3AlF6, Na5Al3F14, AlF3, ZrF4, K3AlF6, while the acid solution could dissolve only Na3AlF6 and CaF2. The leaching kinetics experiments showed that the leaching rate fit the unreacted shrinking core model [1-2/3α-(1-α)2/3 =kt] and that the leaching process was controlled by internal diffusion. This study provides theoretical guidance for the removal of soluble fluoride ions from carbon dross and will also assist in the separation of electrolytes from carbon dross. ENVIRONMENTAL IMPLICATION: Carbon dross, a hazardous waste generated during the aluminum electrolysis production process, contains a large amount of soluble fluoride. Improper storage will lead the fluoride ions pollution in soil, surface water or groundwater under the direct contact between carbon dross and rainfall, snow or surface runoff. The influence of wind will cause carbon dross dust to pollute further areas. With the human body long-term contact with fluoride ion contaminated soil or water, human health will be seriously harmed.

Study on potential microbial community to the waste water treatment from bauxite desilication process.

Discharging waste water from the bauxite desilication process will bring potential environmental risk from the residual ions and organic compounds, especially hydrolyzed polyacrylamide. Characterization of the microbial community diversity in waste water plays an important role in the biological treatment of waste water. In this study, eight waste water samples from five flotation plants in China were investigated. The microbial community and functional profiles within the waste water were analyzed by a metagenomic sequencing method and associated with geochemical properties. The results revealed that Proteobacteria and Firmicutes were the dominant bacterial phyla. Both phylogenetical and clusters of orthologous groups' analyses indicated that Tepidicella, Paracoccus, Pseudomonas, and Exiguobacterium could be the dominant bacterial genera in the waste water from bauxite desilication process for their abilities to biodegrade complex organic compounds. The results of the microbial community diversity and functional gene compositions analyses provided a beneficial orientation for the biotreatment of waste water, as well as regenerative using of water resources. Besides, this study revealed that waste water from bauxite desilication process was an ideal ecosystem to find novel microorganisms, such as efficient strains for bio-desilication and bio-desulfurization of bauxite.

Comparison of bacterial community structure in PM2.5 during hazy and non-hazy periods in Guilin, South China.

In recent years, significant efforts have been made to study changes in the levels of air pollutants at regional and urban scales, and changes in bioaerosols during air pollution events have attracted increasing attention. In this study, the bacterial structure of PM2.5 was analysed under different environmental conditions during hazy and non-hazy periods in Guilin. A total of 32 PM2.5 samples were collected in December 2020 and July 2021, and the microbial community structures were analysed using high-throughput sequencing methods. The results show that air pollution and climate change alter the species distribution and community diversity of bacteria in PM2.5, particularly Sphingomonas and Pseudomonas. The structure of the bacterial community composition is related to diurnal variation, vertical height, and urban area and their interactions with various environmental factors. This is a comprehensive study that characterises the variability of bacteria associated with PM2.5 in a variety of environments, highlighting the impacts of environmental effects on the atmospheric microbial community. The results will contribute to our understanding of haze trends in China, particularly the relationship between bioaerosol communities and the urban environment. Supplementary Information: The online version contains supplementary material available at 10.1007/s10453-022-09777-0.

Prediction Model Risk-of-Bias Assessment Tool for coronary artery lesions in Kawasaki disease.

Objective: To review and critically appraise articles on prediction models for coronary artery lesions (CALs) in Kawasaki disease included in PubMed, Embase, and Web of Science databases from January 1, 1980, to December 23, 2021. Materials and methods: Study screening, data extraction, and quality assessment were performed by two independent reviewers, with a statistics expert resolving discrepancies. Articles that developed or validated a prediction model for CALs in Kawasaki disease were included. The Critical Appraisal and Data Extraction for Systematic Reviews of Prediction Modeling Studies checklist was used to extract data from different articles, and Prediction Model Risk-of-Bias Assessment Tool (PROBAST) was used to assess the bias risk in different prediction models. We screened 19 studies from a pool of 881 articles. Results: The studies included 73-5,151 patients. In most studies, univariable logistic regression was used to develop prediction models. In two studies, external data were used to validate the developing model. The most commonly included predictors were C-reactive protein (CRP) level, male sex, and fever duration. All studies had a high bias risk, mostly because of small sample size, improper handling of missing data, and inappropriate descriptions of model performance and the evaluation model. Conclusion: The prediction models were suitable for the subjects included in the studies, but were poorly effective in other populations. The phenomenon may partly be due to the bias risk in prediction models. Future models should address these problems and PROBAST should be used to guide study design.

Atmospheric outflow of anthropogenic iron and its deposition to China adjacent seas.

Atmospheric deposition of iron (Fe) can increase marine primary productivity, consequently affect ocean biogeochemical cycles and climate change. In this study, we develop an adaptor to generate anthropogenic Fe emission inventories for China in 2012 and 2016 via anthropogenic PM2.5 emissions from Multi-resolution Emission Inventory for China (MEIC) using local source-specific mass fractions of Fe in PM2.5. Using the generated emission inventories, we simulated Fe concentrations as well as dry deposition fluxes to China marginal seas using a WRF-CMAQ model during four campaign periods. The simulated Fe concentrations are in good agreement with observations except for those in presence of severe dust-intrusion events (NMB -13% ~ -27%), indicating a reasonably good performance of the generated Fe emissions and leaving the large underestimation of Fe concentrations mainly due to nature dust emissions. Simulated Fe concentrations over China marginal seas are in the range of 62-6.5 × 102 ng m-3, providing 2.0-12.5 µg m-2 d-1 to the seas during the study periods. We also found that inputs of total Fe in PM2.5 to the seas in presence of dust-intrusion events are 3 and 13 times larger than those in presence of haze events or on less polluted days. Due to lower Fe solubility in nature mineral aerosols than in anthropogenic aerosols, dry deposition fluxes of bioavailable Fe on haze days almost double that in dust days. The total anthropogenic emissions of Fe over China in 2012 and 2016 are estimated as 5.5 × 102 Gg and 3.3 × 102 Gg, respectively. Iron and steel industry are the dominant sources of Fe, accounting for 59-63% of the total anthropogenic Fe emissions. Geotropically, stronger emissions per area were distributed in eastern China, e.g., 2.3 to 15.4 ng m-2 s-1 in eastern China versus <0.4 ng m-2 s-1 in western China.

Fullerene carbon dot catalytic amplification-aptamer assay platform for ultratrace As+3 utilizing SERS/RRS/Abs trifunctional Au nanoprobes.

Under microwave conditions, Au-doped carbon dots (CDAu) were prepared using fullerene as a precursor, and characterized in details. It is found that CDAu can strongly catalyze the reaction of HAuCl4-fructose to generate gold nanoparticles (AuNPs). The new nanocatalytic reaction was studied by surface-enhanced Raman scattering (SERS), resonance Rayleigh scattering (RRS) and absorption (Abs) spectrometry. Based on the specific aptamer (AptAs)-As+3 reaction mediated the CDAu-HAuCl4-fructose nanoreaction, and the products of AuNPs as SERS/RRS/Abs trifunctional indicator nanoprobes, a new trimode Apt assay strategy was developed for detection of ultratrace As+3. A 0.07-0.70, 0.10-0.60 and 0.20-0.70 µg L-1 were determined by SERS, RRS and Abs, with detection limits (DL) of 0.04, 0.06, 0.10 µg L-1 respectively. The aptamer-regulation CDAu catalytic amplification platform can be also used to assay 1.7-13.3 nmol L-1 Pb2+ and 2.0-12 µmol L-1 Hg2+, with DL of 0.80 nmol L-1 and 0.90 µmol L-1 respectively.

[Analysis of Pollution Characteristics and Primary, Secondary Contributions of Firework Burnings in Qingdao During the Spring Festival].

Atmospheric pollution frequently occurs in northern China during winter heating period, wherein nitrate became the dominant driver for PM2.5 accumulations. However, sulfate accumulation was found to be significantly higher than that of nitrate during firework burning events and exhibited different pollution characteristics. Online data available from February 2, 2019 to February 10, 2019, including observation data measured from AIM-IC in suburban Qingdao and meteorological data from national automatic monitoring station, were analyzed. The results showed that particulate accumulation, dust and firework burning events were observed. The primary contribution rates of the most intensive firework burning to PM2.5 and PM10 were 69.8% and 63.8%, respectively. In contrast to a severe accumulation of nitrate during the particulate accumulation event, the sulfate formed prior and exhibited more severe accumulation than nitrate during the firework burning events. The primary contribution factors n(SO42-)/n(K+) and n(NO3-)/n(K+) of firework burnings was 1.2 and 1.3 (molar ratios), respectively. The secondary contribution factors were 2.1 and 1.6 times, under relatively stable meteorological conditions. However, during the transit of dry and cold air, the value of secondary contribution factors decreased substantially and exhibited nearly the same values as the primary ones.

Spatial Distribution and Source of Inorganic Elements in PM2.5 During a Typical Winter Haze Episode in Guilin, China.

Guilin, a famous tourist city, is located in northeast Guangxi Province of Southwest China. However, recently, abnormal haze events occurred frequently in the winter. To characterize inorganic elements in PM2.5 and associated sources during a winter haze episode, 30 samples were collected from 6 sites in Guilin from December 16 to 20, 2016, and 24 inorganic elements were measured using an inductively coupled plasma mass spectrometer. The results showed that the sum of 24 inorganic elements varied from 5.47 ± 0.45 to 9.26 ± 0.73 µg m-3, and accounting for 6.81% ± 13.35% to 8.63% ± 15.05% of PM2.5 at all sites. Among them, crustal elements, including K, Ca, Na, Mg, Al, Fe, and Ti contributed approximately 82% ± 6%-90% ± 3%. Cluster results combined the coefficient of divergence and hierarchical cluster for inorganic elements and the sites showed that YS designated as the background site had obvious spatial heterogeneity, specially, mass concentration, and Igeo (index of geoaccumulation) values of Ni, Cr, Mo, and Ba were higher than those at the other five sites, which indicating that PM2.5 in Guilin was significantly affected by interregional transport. The results of source apportionment showed that Al, Ti, B, Fe, Ca, Mg, and Cr were derived from road and building dust, whereas Sb, As, and Hg originated from coal combustion, Co and V from vehicle emission (such as diesel and gasoline combustion), and other metals (Zn, Pb, Mn, Ba, Cu, Ni, Se, Cd, Mo, Tl, K, and Na) from coal combustion and industrial processes.

A nanogold resonance Rayleigh scattering method for determination of trace As based on the hydride nanoreaction.

In H2 SO4 solution, As(III) was reduced to arsine (AsH3 ) by NaBH4 , and was absorbed in HAuCl4 solution to form nanogold particles (NGs) that exhibited a resonance Rayleigh scattering (RRS) effect at 370 nm. Under the selected conditions, when the As(III) concentration increased the RRS peak also increased due to the formation of more NGs. There was a linear correlation between RRS intensity and As(III) concentration in the range 6-1000 ng/mL, with a detection limit of 3 ng/mL. This new hydride generation-nanogold reaction RRS (HG-NG RRS) method was applied to determine trace amounts of As in milk samples, with satisfactory results.

Catalysis of aptamer-modified AuPd nanoalloy probe and its application to resonance scattering detection of trace UO(2)2+.

AuPd nanoalloy and nanopalladium with a diameter of 5 nm were prepared, using sodium citrate as the stabilizing agent and NaBH(4) as the reductant. The nanocatalyst containing palladium on the surface exhibited a strong catalytic effect on the slow NiP particle reaction between NiCl(2) and NaH(2)PO(2), and the NiP particle system showed a resonance scattering (RS) peak at 508 nm. The RS results showed that the Pd atom on AuPd nanoalloy surface is the catalytic center. Combining the aptamer cracking reaction of double-stranded DNA (dsDNA)-UO(2)(2+), AuPd nanoalloy aggregation, and AuPd nanoalloy catalysis, both AuPd nanoalloy RS probe and AuPd nanoalloy catalytic RS assays were developed for the determination of 40-250 pmol L(-1) UO(2)(2+) and 5.0-50 pmol L(-1) UO(2)(2+), respectively.

[Heavy metal concentrations and pollution assessment of edible crops grown on restored manganese mine lands in Guangxi, South China].

A survey on the crops grown on the restored manganese mine lands in Pingle and Lipu of Guangxi was conducted, and the heavy metal concentrations in the edible parts of the crops were analyzed. The results showed that the heavy metal concentrations in the crops were 1.18-20.46 mg x kg(-1) for Zn, 0.52-16.16 mg x kg(-1) for Pb, 0.33-6.62 mg x kg(-1) for Cr, 0.01-6.24 mg x kg(-1) for Cu, and 0.01-2.76 mg x kg(-1) for Cd. Among the crops, beans had the highest concentrations of almost all test metals, followed by potatoes. The assessment of single factor pollution indices indicated that in the main, the crops were not polluted by Zn and Cu, but heavily polluted by Pb, Cr and Cd, with the pollution rate being 100%, 96.9% and 75.0%, respectively. Comprehensive pollution index indicated that all the crops were polluted by heavy metals, with the heavy, medium and light pollution grade being 87.5%, 9.4% and 3.1%, respectively. Planting edible crops directly on manganese mine wastelands might have great risk for human health, and the existing restoration patterns should be reconsidered.