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The oxidation of sulfide ores is a common phenomenon. To better understand the current development and status of oxidation studies of sulfide ores (OSSO), a bibliometric analysis of OSSO was conducted by mapping the spatiotemporal distribution of the knowledge domain and the research focus using VOSviewer and Citespace tools. The data were derived from the Web of Science (WOS) core collection database from 2000 to 2018. Study emphases covered publication outputs, countries/regions, organizations, top journals, research focus and keyword co-occurrence network, and theme development. The results include the following findings: (1) The line of the 3-year moving average of publications (3-year MAP), h-index (3-year MAH), and authors (3-year MAA) increased from 2001 to 2018. Conversely, the h-index continuously declined. (2) Asia had the most publications, with 1052, followed by Europe, with 923, and America, with 767. China, the USA, and Australia are the most active countries. (3) The top 10 organizations with the most publications are five Chinese organizations and one organization from each of the following countries: Russia, Australia, France, and India. (4) Hydrometallurgy, Minerals Engineering, Ore Geology Reviews, Geochimica Et Cosmochimica Acta, and Economic Geology are among the top 10 journals that researchers are most concerned about. (5) Cooperation among different organization or different countries is the most effective way to produce the most influential papers. (6) The OSSO is still focused on the process of oxidation by using different methods and techniques. In future work, it is necessary to progress new methods to understand the process of self-heating and prevent spontaneous combustion disaster of sulfide ore which result from OSSO.

Hyporheic zone (HZ) sediments in river systems are often contaminated with heavy metals as a legacy of natural processes and anthropogenic activities. The geochemical behaviors of heavy metals in the HZ sediments at the laboratory scale have been extensively studied. However, the watershed-scale distributions of heavy metals in the HZ sediments and the processes controlling their distributions have not been well studied. Here, we report a watershed-scale study of heavy metals (i.e., Cr, Ni, Cu, Zn, Cd, and Pb) distributions in the HZ of the Maozhou River watershed, a heavily polluted area within the Pearl River Delta, southern China. Statistical analysis revealed that the spatial distribution of studied heavy metal concentrations was highly correlated with that of the sediment-associated sulfide at the watershed-scale. Metal extraction analysis and double-spherical aberration-corrected scanning transmission electron microscope imaging (Cs-STEM) further confirmed the strong association of heavy metals with sulfur. These observations demonstrated that the formation of metals-sulfide precipitates was the key process controlling the watershed-scale distributions of heavy metals (especially for Cr, Ni and Zn) in the HZ sediments. Additionally, high permeability of the HZ sediments may prevent Ni, Zn, Cd and Pb accumulation in sediments. Specially, Cu distribution was mainly affected by organic-Cu complexation. In the estuary area, salinity input likely affected the distributions of Ni, Zn and Cd through cation exchange processes. The findings improved our understanding of the distributions of heavy metals and the processes controlling their distributions at the watershed-scale, and have implications for remediating and managing contaminated HZ sediments., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Phosphorus (P) pollution can trigger severe marine eutrophication, which further leads to harmful algal blooms, and a deterioration of sea water quality. The P burial and regeneration in offshore sediments can directly affect the eutrophication levels of estuarine and coastal ecosystems. Although many researches on redox-dependent P burial and regeneration were studied, such process in the presence of silicate is still poorly understood, and the effects of pyrite formation on organic P (OP) burial and regeneration also remain unclear. In this study, a sulfidic sediment core was collected in the offshore of an estuary in the north Yellow Sea, China. Results indicated that indigenous biological input was found to be the primary source of organic matter in upper sediments. The regenerated P under reducing conditions was dominated by labile FeP and OP. The PO 4 3- released from FeP and OP that could be captured by Al/Fe/Mn (oxyhydr) oxides in surface sediments and Ca minerals in deep sediments. CaP, AlP, unreactive Al/Fe-Si-P and some stable metal chelated OP were the main burial P fractions. Sulfate reduction and formation of insoluble metal sulfides including the pyrite promoted OP decomposition by anaerobic decomposition, removing metal ions from the "metal-OP" chelates and restoring the phosphatase activity., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Karst water, which provides 25% of the world's drinking water, is especially vulnerable to anthropogenic contamination. Such is the case in southwestern China with trace element pollution in important karst aquifers. Approximately 20% of the total study area consisted of abandoned mine tailings with elevated concentrations of Fe, S, Mn, As, Cu, and Cr. Acid mine drainage (AMD) water originating from pyrite oxidation of the tailings was characterized by low pH and high concentrations of Fe, SO 4 2- , and As. Concentrations of Fe, Mn, Al, SO 4 2- , As, Cd, and Pb in spring water in wet and dry seasons were greater than WHO and USEPA drinking water guidelines. Based on the results of mineral characterizations, hydrogeochemistry, and isotopic compositions (δ 34 S SO4 , δ 18 O SO4 , and δ 18 O H2O ), the chemistry of AMD water was primarily controlled by pyrite oxidation, river water by atmospheric precipitation, and spring water by carbonate rock dissolution and mixing with river and AMD waters. A three-end-member mixing model identified the contributions of these different end members to spring water quality. Although AMD water was characterized by the lowest mixing percentages during the wet (14.1%) and dry (26.9%) seasons, it played a very important role in degrading spring water quality. Based on these findings, an investigation strategy was developed for illuminating seasonal water quality and potential remediation methods corresponding to the contaminants in the spring water are also proposed to manage this seriously polluted karst system. Results could benefit remediation planning for these distinctively complex and vulnerable systems in other regions of the world., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Solid-phase speciation and porewater chemistry measured by the diffusive gradients in thin films (DGT) technique were used to understand the diagenesis of sulfur (S), iron (Fe), and phosphorus (P) in sediments of Jiaozhou Bay (China), which has been impacted by multiple anthropogenic perturbations. Despite water eutrophication, sediments of the bay are low in organic carbon and sulfide, but high in unsulfidized Fe(II). Dissimilatory iron reduction (DIR) prevails in sediments of the bay, and there is no evidence for responses of S and Fe diagenesis to the water eutrophication, which is largely attributable to unique depositional and diagenetic regimes in association with multiple anthropogenic perturbations. Good coupling of porewater Fe 2+ and P in the porewaters suggests that P mobilization is driven mainly by DIR. Low Fe 2+ /P ratios in porewaters imply that oxidative regeneration of Fe oxides within the upper sediments is incapable of efficiently scavenging upward diffusing P., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Several abundant but yet uncultivated bacterial groups exist in extreme iron- and sulfur-rich environments, and the physiology, biodiversity, and ecological roles of these bacteria remain a mystery. Here we retrieved four metagenome-assembled genomes (MAGs) from an artificial acid mine drainage (AMD) system, and propose they belong to a new deltaproteobacterial order, Candidatus Acidulodesulfobacterales. The distribution pattern of Ca. Acidulodesulfobacterales in AMDs across Southeast China correlated strongly with ferrous iron. Reconstructed metabolic pathways and gene expression profiles showed that they were likely facultatively anaerobic autotrophs capable of nitrogen fixation. In addition to dissimilatory sulfate reduction, encoded by dsrAB, dsrD, dsrL, and dsrEFH genes, these microorganisms might also oxidize sulfide, depending on oxygen concentration and/or oxidation reduction potential. Several genes with homology to those involved in iron metabolism were also identified, suggesting their potential role in iron cycling. In addition, the expression of abundant resistance genes revealed the mechanisms of adaptation and response to the extreme environmental stresses endured by these organisms in the AMD environment. These findings shed light on the distribution, diversity, and potential ecological role of the new order Ca. Acidulodesulfobacterales in nature.

Trace metal element contamination in mining areas is always a huge environmental challenge for the global mining industry. In this study, an abandoned sphalerite mine near the Yanshan Mountains was selected as subject to evaluate the soil and water contamination caused by small-scale mining. The results show that (1) Pearson correlation matrix and principal component analysis (PCA) results reveal that Zn, Cu, Cd, and Pb were greatly affected by the operation of mines, especially mineral tailings. The contents of trace metal elements decrease with the increase of the distance from the mining area. Zinc, Pb, and Cd were discovered in almost all soil samples, and Zn accounted for about 80% of pollution of the topsoil. (2) The trace element pollution levels in the topsoil of the three villages were ranked as follows: Cd > Cu > Pb~Zn. The potential ecological risk of farmland around the mine ranges from lower to higher, with Cd being the most harmful. (3) Human health risk assessment results show that trace elements in the mining area pose obvious non-carcinogenic health risks to children while the risks to adults are not equally obvious. The carcinogenic risk of Cd and Cr is within a safe range and does not pose an obvious cancer risk to the population.

The stainless steel pickling residue (SSPR) produced from the stainless steel industries in China contains large amounts of heavy metals such as chromium (Cr) and nickel (Ni). The study found that the hexavalent chromium Cr (VI) was the primary contributor to the leaching of Cr in the toxicity character leaching test. A chemical fixation with sodium sulfide was used to treat the SSPR, and the response surface methodology (RSM) was employed to optimize the process. The results revealed that the sodium sulfide dose and curing time had significant effects on the fixation of Cr. The higher was the sodium sulfide dose, and the longer the curing time, the lower the leaching concentration of Cr would be. The water addition amount had insignificant effect when it was higher than 70%. A dose of 1.2% sodium sulfide on dry mass basis, a water addition of 90-100%, and a curing time of longer than 10 days in the open air could reduce the leaching of Cr to below the beneficial use threshold. The low chemical dose and simple procedures established in this study make this treatment method cost-effective for rendering the SSPR into a nonhazardous and useful material.

Antimony (Sb) usually occurs associated with arsenic, lead, and other metal elements in sulfide deposits, and most is currently being extracted from the Karst areas, southwest China. In these areas, the acid generated from the oxidative dissolution of sulfide minerals is neutralized by the abundant carbonates but little is known about the effect of this process on the geochemical behavior of Sb and other contaminants. In this study, physicochemical properties (pH, EC) and the trace elements (Sb, As, Cu, Pb, Zn, Sr, etc.) concentrations in waters from mining-impacted Karstic environments were determined in order to determine their distribution and migration potential. It was found that pH values ranged from 6.51 to 9.82, and EC values varied from 369 to 1705 μs·cm -1 in river water samples. Waters of various types such as adit waters, flotation drainage, leaching waters, and river waters all contained high concentrations of dissolved trace elements, reaching up to 5475 μg·L -1 Sb, 1877 μg·L -1 As, 10,371 μg·L -1 Zn, 1309 μg·L -1 Pb, 46 μg·L -1 Cu, and 1757 μg·L -1 Sr. The elevated concentrations of dissolved Sr indicated that Sr could be considered as an indicator of oxidative dissolution of sulfide minerals in the Karst rivers. A proportion of the trace elements were removed in the streams in the vicinity of the mine due to adsorption onto particulate matter, whereas migration of trace elements in the downstream of mine area was attributed to dispersion in dissolved forms. Strontium and Sb have a strong hydrophilicity compared to the other elements analyzed; in contrast, Pb had a high affinity for suspended particulate matter (SPM). It was also found that downstream sediments had elevated concentrations of mining-derived trace elements, but there was a significant decrease in concentration of contaminants in aqueous phase, suggesting that contaminant behavior was conservative in the water-sediment systems under the oxic conditions prevailing in these waters. There was a good correlation between Sb and As in water-SPM-sediment system, indicating that Sb and As are homologous in water environment of the study area.

Arsenic sulfide residue (ASR), a by-product from the treatment of arsenic-bearing acidic wastewater, is abundantly generated but not properly disposed of in China. The utilization of such high-content arsenic waste residue is limited by the market. The traditional methods of stabilization/solidification (S/S) by lime cement or iron salt have a large mass/volume addition, high dumping cost and secondary pollution risk. In this paper, hydrothermal technology was used to treat three kinds of ASRs obtained from different smelters to minimize waste. The leaching toxicity and chemical speciation of the generated products was also evaluated by TCLP and BCR analyses. It was found that the hydrothermal treatment could greatly reduce the volume and moisture content of the ASRs. TCLP tests showed that the leachability of arsenic and heavy metals significantly decreased after the treatment. According to the BCR analysis, most of the unstable As, Cd and Cr transformed into a residual fraction. Finally, XRD, SEM, Raman and XPS techniques were carried out to reveal the mechanism. As a result, hydrothermal treatment can efficiently achieve the dehydration, volume reduction and stabilization/solidification of ASRs.

The seasonal variations of taste and odor (T&O) compounds in western Lake Chaohu were evaluated from July to December 2013. High values were detected in particulate fractions, with peak values 28.25 ng/L for geosmin (GEO), 45.18 ng/L for dimethyltrisulfide (DMTS), 714.77 ng/L for β-cyclocitral, 11.23 ng/L for β-ionone in surface water, and 14.21 ng/L for GEO, 103.68 ng/L for DMTS, 11.97 ng/L for β-ionone in overlying water, all exceeding their odor thresholds. The maximum off-flavor concentrations in sediment ranged from 2010.76 ng/kg for GEO to 1.7 ng/kg for β-ionone. Positive correlations could be found not only between Anabaena and particulate GEO (r = 0.813, p < 0.01), but also between Microcystis and total β-cyclocitral (r = 0.652, p < 0.01) or β-ionone (r = 0.560, p < 0.01) in surface water. TP, TN, PO4-P, Chl-a and organic matter contributed significantly to the variations of T&O compounds in water or sediment. The cause of the variations of T&O compounds was the accumulation and degradation of cyanobacteria in water rather than nutrient-rich sediment.

Arsenic biogeochemistry has been studied extensively in acid sulfate-chloride hot springs, but not in acid sulfate hot springs with low chloride. In this study, Zhenzhuquan in Tengchong geothermal area, a representative acid sulfate hot spring with low chloride, was chosen to study arsenic geochemistry and microbial community structure using Illumina MiSeq sequencing. Over 0.3 million 16S rRNA sequence reads were obtained from 6-paired parallel water and sediment samples along its outflow channel. Arsenic oxidation occurred in the Zhenxhuquan pool, with distinctly high ratios of arsenate to total dissolved arsenic (0.73-0.86). Coupled with iron and sulfur oxidation along the outflow channel, arsenic accumulated in downstream sediments with concentrations up to 16.44 g/kg and appeared to significantly constrain their microbial community diversity. These oxidations might be correlated with the appearance of some putative functional microbial populations, such as Aquificae and Pseudomonas (arsenic oxidation), Sulfolobus (sulfur and iron oxidation), Metallosphaera and Acidicaldus (iron oxidation). Temperature, total organic carbon and dissolved oxygen significantly shaped the microbial community structure of upstream and downstream samples. In the upstream outflow channel region, most microbial populations were microaerophilic/anaerobic thermophiles and hyperthermophiles, such as Sulfolobus, Nocardia, Fervidicoccus, Delftia, and Ralstonia. In the downstream region, aerobic heterotrophic mesophiles and thermophiles were identified, including Ktedonobacteria, Acidicaldus, Chthonomonas and Sphingobacteria. A total of 72.41-95.91% unassigned-genus sequences were derived from the downstream high arsenic sediments 16S rRNA clone libraries. This study could enable us to achieve an integrated understanding on arsenic biogeochemistry in acid hot springs.

Our current natural product program researches the second metabolites of a fungus Penicilliumcrustosum YN-HT-15 isolated from the red soil (Yunnan Province, China), to discover potential antitumor chemical entities. Two new compounds were isolated from the ethyl acetate extract of the fermentation broth of the fungus, and their structures were characterized as 1-(2',4'-dihydroxy-5'-methyl-3'-methylsulfanylmethyl-phenyl)-ethanone and R-3-(3'-acetyl-2',6'-dihydroxy-5'-methylphenyl)-2-methyl-propionic acid methyl ester on the basis of spectroscopic data.

A cross-comparison of six strains isolated from two different regions, Chambishi copper mine (Zambia, Africa) and Dexing copper mine (China, Asia), was conducted to study the leaching efficiency of low grade copper ores. The strains belong to the three major species often encountered in bioleaching of copper sulfide ores under mesophilic conditions: Acidithiobacillus ferrooxidans, Acidithiobacillus thiooxidans, and Leptospirillum ferriphilum. Prior to their study in bioleaching, the different strains were characterized and compared at physiological level. The results revealed that, except for copper tolerance, strains within species presented almost similar physiological traits with slight advantages of Chambishi strains. However, in terms of leaching efficiency, native strains always achieved higher cell density and greater iron and copper extraction rates than the foreign microorganisms. In addition, microbial community analysis revealed that the different mixed cultures shared almost the same profile, and At. ferrooxidans strains always outcompeted the other strains.

Antimony (Sb(V)) in Sb mine drainage has adverse effects on the receiving water environments. This study for the first time demonstrated the feasibility of using sulfate-reducing bacteria (SRB) to convert sulfate ions in SMD into sulfides that reduce Sb(V) to Sb(III) and to form complex with Sb(III) as precipitate. The principal compound in the precipitate was stibnite (Sb2S3) at pH 7 and pH 9. The Sb(V) removal mechanism is sulfate-reduction and sulfide oxidization-precipitation, different from the conventional SRB-precipitation processes for heavy metals. The Sb(V)/sulfate ratio is noted an essential parameter affecting the Sb removal efficiency from SMD., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

This study investigated metals of tailings from Tonglvshan mine in Daye and assessed the effect of metal contamination in water and sediment near the tailing reservoir. The concentration of copper, lead, zinc, cadmium, chromium and nickel was measured in deposit samples taken from a profile in an abandoned flotation tailing reservoir, as well as in water and sediment samples near the reservoir. The results of this study indicate that copper concentration ranges from 780 to 4390 mg/kg, 2-10 times higher than the limit values in soil, while the contents of other metals are below the limit values. Metal levels in water and sediments are high and varied widely in different sampling sites. The mean concentrations of copper, lead, zinc, cadmium, chromium and nickel in waters are 27.76, 2.28, 8.20, 0.12, 5.30 and 3.04 mg/L, while those in sediments are 557.65, 96.95, 285.20, 0.92, 94.30 and 4.75 mg/kg, respectively. All of the results indicate that the environment near the tailing reservoir is polluted to some extent by some kinds of metals, especially by copper, lead, zinc and cadmium, which may be caused not only by some discharge sources of metals, but also by life garbage and sewage.

The crystal structure of medicated realgar in China was validated as alpha-As4 S4 by X-ray diffraction and Raman spectroscopy in the present paper. Ten batches of medicinal realgar were analyzed including realgar ore, medicinal realgar powder, and prepared Chinese medicine. Identification of two As4 S4 polymorphs confirmed that the crystal structure of medicated realgar in China is alpha-As4 S4. Studies on 18 batches of preparative realgar powder showed that processing of realgar can not change the crystal structure of realgar.

The research is designed to explore the SEM-AVS concept as a tool to assess bioavailability and toxicity of heavy metals in heavily polluted river sediments. The value of AVS and SEM is in a high level and only a few benthic invertebrate are found. Abundance of benthic invertebrate has significant correlation with SEM/AVS (r= -0.913, p<0.01) and SEM-AVS (r= -0.725, p<0.05). The analytical results of MDS (Non-matric Multi-dimensional Scaling) analysis indicate the benthic community structures of seven among nine stations where the SigmaSEM(5)-AVS<0 are similar. The two facts indicate the SEM-AVS concept also is useful to heavily polluted river sediments.

The surface layer of sediment and overlying water samples of Foshan Waterway, a typical municipal polluted river in Pearl River Delta, have been sampled and analyzed. The analytical items of sediment and overlying water include AVS, Eh, SEM(Pb), SEM(Cd), SEM(Cu), SEM(Zn), SEM(Ni), SEM(Cr), and Eh, DO, respectively. The benthic macroinvertebrate investigation has been done at the same time in the same place. Combing the results above, the relationship between AVS and heavy metals biotoxicity in Foshan waterway has been discussed. The main object is to examine if the SEM-AVS criterion is valid in judging the biotoxicity of heavy metals in the heavily polluted river. The range of AVS is from 0.339 micromol/g to 69.579 micromol/g, with the average of 20.283 micromol/g. The maximum sigmaSEM5 (Sum of SEM(PB), SEM(Cd), SEM(Cu), SEM(Zn), SEM(Ni)) is 23.067 micromol/g, while the minimum is 1.062 micromol/g. Both the species and quantity of benthic macroinvertebrate are little, and most of them belong to pollution bearable species, with Limnodrilus sp. as dominative species. There are 9 sampling stations where the sigmaSEM5-AVS are below zero, and the analytical results of Non-matric multi-dimentional scaling (MDS) indicate the benthic community structure of 7 sampling stations among them are similar. It means that the heavy metals biotoxicity in the heavily polluted river has close relationship with the value of SEM-AVS. It also proves that heavy metals biotoxicity in sediment is complicated, which can't be explained by SEM-AVS completely.