Oxidation Of Elemental Sulfur Research Articles

Bacterial Communities Associated with the Oxidation of Elemental Sulfur in Calcareous Soils of Oman

Bacterial Communities Associated with the Oxidation of Elemental Sulfur in Calcareous Soils of Oman

Biochar pH reduction using elemental sulfur and biological activation using compost or vermicompost

This study aimed to improve biochar’s quality for arid land applications by using elemental sulfur as a pH reducer agent co-applied with compost or vermicompost as biological activators. Biochar pH was decreased by the addition of elemental sulfur, with the highest reduction from 8.1 to 7.2 occurring when co-amended with vermicompost. Elemental sulfur increased the water-soluble concentrations of calcium, magnesium, and many other elements, and stimulated substrate-induced respiration, especially when co-amended with vermicompost. The bacterial diversity community structure were significantly affected by all treatments. The Shannon index significantly increased in response to compost and sulfur treatments, while the vermicompost treatments showed higher microbial evenness and equitability diversity indices. Multivariate analyses indicated that elemental sulfur oxidation was associated with specific sulfur-oxidizing bacterial clusters. Integrating biochar with sulfur and (vermi)compost was found to be a promising sustainable technology for managing excessive biochar alkalinity, increasing its fertility and potential for application in aridlands.

From Genes to Bioleaching: Unraveling Sulfur Metabolism in Acidithiobacillus Genus.

Sulfur oxidation stands as a pivotal process within the Earth's sulfur cycle, in which Acidithiobacillus species emerge as skillful sulfur-oxidizing bacteria. They are able to efficiently oxidize several reduced inorganic sulfur compounds (RISCs) under extreme conditions for their autotrophic growth. This unique characteristic has made these bacteria a useful tool in bioleaching and biological desulfurization applications. Extensive research has unraveled diverse sulfur metabolism pathways and their corresponding regulatory systems. The metabolic arsenal of the Acidithiobacillus genus includes oxidative enzymes such as: (i) elemental sulfur oxidation enzymes, like sulfur dioxygenase (SDO), sulfur oxygenase reductase (SOR), and heterodisulfide reductase (HDR-like system); (ii) enzymes involved in thiosulfate oxidation pathways, including the sulfur oxidation (Sox) system, tetrathionate hydrolase (TetH), and thiosulfate quinone oxidoreductase (TQO); (iii) sulfide oxidation enzymes, like sulfide:quinone oxidoreductase (SQR); and (iv) sulfite oxidation pathways, such as sulfite oxidase (SOX). This review summarizes the current state of the art of sulfur metabolic processes in Acidithiobacillus species, which are key players of industrial biomining processes. Furthermore, this manuscript highlights the existing challenges and barriers to further exploring the sulfur metabolism of this peculiar extremophilic genus.

Rates of iron(III) reduction coupled to elemental sulfur or tetrathionate oxidation by acidophilic microorganisms and detection of sulfur intermediates

Bioleaching processes and acid mine drainage (AMD) generation are mainly driven by aerobic microbial iron(II) and inorganic sulfur/compound oxidation. Dissimilatory iron(III) reduction coupled to sulfur/compound oxidation (DIRSO) by acidophilic microorganisms has been described for anaerobic cultures, but iron reduction was observed under aerobic conditions as well. Aim of this study was to explore reaction rates and mechanisms of this process. Cell-specific iron(III) reduction rates for different Acidithiobacillus (At.) strains during batch culture growth or stationary phase with iron(III) (∼40 mM) as electron acceptor and elemental sulfur or tetrathionate as electron donor (1% or 5 mM, respectively) were determined. The rates were highest under anaerobic conditions for the At. ferrooxidans type strain with 6.8 × 106 and 1.1 × 107 reduced iron(III) ions per second per cell for growth on elemental sulfur and tetrathionate, respectively. The iron(III) reduction rates were somehow lower for the anaerobically sulfur grown archaeon Ferroplasma acidiphilum, and lowest for the sulfur grown At. caldus type strain under aerobic conditions (1.7 × 106 and 7.3 × 104 reduced iron(III) ions per second per cell, respectively). The rates for five strains of At. thiooxidans (aerobe) were in between those for At. ferrooxidans (anaerobe) and At. caldus (aerobe). There was no pronounced pH dependence of iron(III) reduction rates in the range of pH 1.0–1.9 for the type strains of all species but rates increased with increasing pH for four other At. thiooxidans strains. Thiosulfate as sulfur intermediate was found for At. ferrooxidans during anaerobic growths on tetrathionate and iron(III) but not during anaerobic growths on elemental sulfur and iron(III), and a small concentration was measured during aerobic growths on tetrathionate without iron(III). For the At. thiooxidans type strain thiosulfate was found with tetrathionate grown cells under aerobic conditions in presence and absence of iron(III), but not with sulfur grown cells. Evidence for hydrogen sulfide production at low pH was found for the At. ferrooxidans as well as the At. thiooxidans type strains during microaerophilic growth on elemental sulfur and for At. ferrooxidans during anaerobic growths on tetrathionate and iron(III). The occurrence of sulfur compound intermediates supports the hypothesis that chemical reduction of iron(III) ions takes place by sulfur compounds released by the microbial cells.

Elemental sulfur redox bioconversion for selective recovery of phosphorus from Fe/Al-bound phosphate-rich anaerobically digested sludge: Sulfur oxidation or sulfur reduction?

The biological oxidation of elemental sulfur (S0) to sulfate and the reduction of S0 to sulfide provide a potential route for extracting and reclaiming phosphorus (P) from anaerobically digested sludge (ADS). However, the treatment performance, stability, and cost-effectiveness of the two opposing bioprocesses based on S° for selective P recovery from ADS remain unclear. This study aimed to compare the roles of S0-oxidizing bacteria (S0OB) and S0-reducing bacteria (S0RB) in liberating insoluble P from ADS through single-batch and consecutive multibatch experiments. Changes in P speciation in the sludge during the biological extraction processes were analyzed by using complementary sequential extraction and P X-ray absorption near-edge spectroscopy. Results showed that S0OB treatment extracted more phosphate from the sludge compared with S0RB treatment, but it also released a considerable amount of metal cations (e.g., heavy metals, Mg2+, Al3+, Ca2+) and negatively affected sludge dewaterability due to intense sludge acidification and cell lysis. At pH 1.2, the S0OB treatment released 92.9% of P from the sludge, with the dissolution of HAP, Fe-PO4, Mg3(PO4)2, and P-fehrrihy contributing 26.8%, 22.1%, 12.8%, and 10.5%, respectively. The S0RB treatment released 63.6% of P from the sludge at pH 7.0, with negligible dissolution of metal cations, thereby avoiding costly purification of the extract and alkali neutralization for pH adjustment. This treatment involved the replacement of phosphates bounded with Fe-PO4 (FePO4 and P-fehrrihy) and Al–PO4 (P-Alumina and AlPO4) with biogenic sulfides, with contributions of 72.7%, and 20.9%, respectively. Consecutive bioprocesses for P extraction were achieved by recirculating the treated sludge. Both S0OB and S0RB treatments did not affect the extent of sludge dewatering but considerably weakened the dewatering rate. The S0OB-treated sludge exhibited prolonged filtration time (from 3010 s to 9150 s) and expressing time (from 795 s to 4690 s) during compression dewatering. After removing metal cations using cation exchange resin (CER) and neutralizing using NaOH, a vivianite product Fe3(PO4)2·8H2O (purity: 84%) was harvested from the S0OB-treated extract through precipitation with FeSO4·7H2O. By contrast, a vivianite product Fe3(PO4)2·8H2O (purity: 81%) was directly obtained from the S0RB-treated extract through precipitation with FeSO4·7H2O. Ultimately, 79.8 and 57.9wt% of P were recovered from ADS through S0OB extraction–CER purification–alkali neutralization–vivianite crystallization, and S0RB extraction–vivianite crystallization, respectively. Collectively, biological S0 reduction is more applicable than biological S0 oxidation for selectively reclaiming P from Fe/Al-associated phosphate-rich ADS due to better cost-effectiveness and process simplicity. These findings are of significance for developing sludge management strategies to improve P reclamation with minimal process inputs.

Microbial electrolysis cell simultaneously enhancing methanization and reducing hydrogen sulfide production in anaerobic digestion of sewage sludge

The effects of microbial electrolysis cells (MECs) at three applied voltages (0.8, 1.3, and 1.6 V) on simultaneously enhancing methanization and reducing hydrogen sulfide (H2S) production in the anaerobic digestion (AD) of sewage sludge were studied. The results showed that the MECs at 1.3 V and 1.6 V simultaneously enhanced the methane production by 57.02 and 12.70% and organic matter removal by 38.77 and 11.13%, and reduced H2S production by 94.8 and 98.2%, respectively. MECs at 1.3 V and 1.6 V created a micro-aerobic conditions for the digesters with oxidation-reduction potential as −178∼-232 mv, which enhanced methanization and reduced H2S production. Sulfur reduction, H2S and elemental sulfur oxidation occurred simultaneously in the ADs at 1.3 V and 1.6 V. The relative abundances of sulfur-oxidizing bacteria increased from 0.11% to 0.42% and those of sulfur-reducing bacteria decreased from 1.24% to 0.33% when the applied voltage of MEC increased from 0 V to 1.6 V. Hydrogen produced by electrolysis enhanced the abundance of Methanobacterium and changed the methanogenesis pathway.

Quantitative evolved gas analysis: Winchcombe in comparison with other CM2 meteorites

AbstractTwo bulk Winchcombe along with six other CM2 meteorite samples were subjected to quantitative evolved gas analysis. The observed release patterns for almost all volatile species demonstrate close similarity for all the samples and especially between those for Winchcombe. This can be considered as a fingerprint for this petrological type of meteorites. We identified several gases including H2, H2O, O2, CO, CO2, and SO2 released in different temperature ranges. The sources and mechanisms of their release were also established. Some of the gases, H2, CO, and CO2, are released as a result of oxidation of macromolecular organic material from oxygen derived from oxygen‐bearing minerals (a part of CO2 is also released as a result of decomposition of carbonates). The others, O2 and H2O, are associated with the phase transformation/decomposition of phyllosilicates and (oxy)hydrates, while a high‐temperature release of SO2 is associated mostly with the decomposition of sulfides and in few cases also with sulfates. A low‐temperature release of SO2 is due to evaporation and oxidation of elemental sulfur from the meteoritic matrix and organic material. The total concentrations of H (mostly represented by H2O), C, and S, calculated according to calibration of the quadrupole mass spectrometer with reference gases and decomposition of solid samples (CaSO4·2H2O and NaHCO3) are in reasonable agreement with those determined by independent methods. Variations in the ratio of the carbon amounts released as CO2 and CO (/CCO) between the samples could be an indicator of their terrestrial weathering.

Deciphering the biodesulfurization pathway employing marine mangrove Bacillus aryabhattai strain NM1-A2 according to whole genome sequencing and transcriptome analyses

In the biogeochemical cycle, sulfur oxidation plays a vital role and is typically referred to as the elemental sulfur or reductive sulfide oxidation process. This study aimed to characterize a subtropical mangrove-isolated bacterial strain using biochemical, whole-genome, and transcriptome sequencing analyses to enhance our understanding of sulfur metabolism and biodegradation from a molecular genetic perspective. Strain NM1-A2 was characterized as Gram-positive and found to have a close molecular phylogenetic relationship with Bacillus aryabhattai. NM1-A2 efficiently converted dibenzothiophene (DBT) into 2-hydroxybiphenyl (2-HBP) via a 4S pathway with 95% efficiency, using enzymes encoded by the dsz operon (dszA, dszB, and dszC), which determine monooxygenases (DszA & DszC) and desulfinase (DszB). The whole-genome sequence of NM1-A2 had a length of approximately 5,257,678 bp and included 16 sulfur metabolism-related genes, featuring the ABC transport system, small subunit (ssu) and cysteine (cys) gene families, and adenosine 5′-phosphosulfate (APS) and 3′-phosphoadenosine-5′-phosphosulfate (PAPS) biosynthesis-related genes. Transcriptomic analysis of NM1-A2 using three sulfur groups—magnesium sulfate (MS), sulfur powder (SP), and sodium thiosulfate (ST) resulted in a significant number of differentially expressed genes (1200, 2304, and 2001, respectively). This analysis revealed that intracellular cysteine concentration directly regulated the expression of cys and ssu genes. Sulfate did not directly affect cys gene expression but repressed ssu gene expression. The cys gene expression levels decreased during the conversion of sulfate to sulfide and cysteine. The transcriptomic data was validated by analyzing the expression patterns of NM1-A2 using real-time quantitative PCR validation analysis. The expression levels of cysl, mccB, and nrnA were significantly upregulated, while cysH, metB, and sat were downregulated in the SP, ST, and MS groups, respectively. This research contributes to our understanding of marine mangrove microorganisms' bacterial efficiency through characterization, whole-genome, and transcriptome sequencing-based molecular degradation of organic compounds in the mangrove ecosystem, which may enhance nutrient availability.

Rare earth elements (bio)leaching from zircon and eudialyte concentrates

Sands containing placers enriched with heavy minerals such as zircon, garnet, ilmenite, rutile, magnetite and monazite are recovered as construction material from the German Baltic Sea coast. The heavy minerals could be concentrated by gravity and magnetic separation. Rare earth elements (REE) were enriched in zircon concentrates as well as in concentrates of the zirconium-containing mineral eudialyte from a deposit in Greenland. In order to test bioleaching for REE extraction from these concentrates, experiments with cultures of mesophilic as well as moderately thermophilic, acidophilic, lithoautotrophic bacteria and gluconic acid-producing organoheterotrophic bacteria were run in shake flasks or pH-controlled 2 L bioreactors at 30 °C or 42 °C. Elemental sulfur and glucose served as substrate for the autotrophs and heterotrophs, respectively. Chemical leaching experiments as controls for bioleaching by the autotrophs were run without bacteria and adjusted over time to the same pH by sulfuric acid addition as previously measured in the inoculated bioreactors, in order to estimate bioleaching versus chemical leaching at the same pH. Chemical leaching experiments as controls for bioleaching by the heterotrophs were run with added gluconic acid as well as other organic acids. The results showed no significant differences in REE extraction between chemical and biological runs under same conditions (pH, temperature or gluconic acid concentration), indicating that bioleaching was in fact acid leaching based on the enzymatic oxidation of elemental sulfur to sulfuric acid in case of the autotrophs and gluconic acid production from glucose in case of the heterotrophs. The amount of extracted REEs increased with decreasing pH. Mesophiles versus moderate thermophiles did not show remarkable differences. The extraction efficiency for the single REEs was maximum 35% for zircon concentrates but up to about 70% for the eudialyte concentrate. This study allows for a comparison of chemical leaching vs. bioleaching and shows the limitation of bioleaching for processing heavy minerals for REE extraction.

CRISPR/Cas12a-Mediated Genome Editing in Thioalkalivibrio versutus

Haloalkaliphilic Thioalkalivibrio versutus, a dominant species for sulfide removal, has attracted increasing attention. However, research on T. versutus is limited by the lack of genetic manipulation tools. In this work, we developed a CRISPR/AsCas12a-mediated system in T. versutus for an efficient and implementable genome editing workflow. Compared to the CRISPR/Cas9-mediated system, the CRISPR/AsCas12a system exhibited enhanced editing efficiency. Additionally, as Cas12a is capable of processing the crRNA maturation independently, the CRISPR/AsCas12a system allowed multiplex gene editing and large-fragment DNA knockout by expressing more than one crRNA under the control of one promoter. Using the CRISPR/AsCas12a system, five key genes of the elemental sulfur oxidation pathway were knocked out. Simultaneous deletion of the rhd and tusA genes disrupted the ability of T. versutus to metabolize elemental sulfur, resulting in a 24.7% increase in elemental sulfur generation and a 15.2% reduction in sulfate production. This genome engineering strategy significantly improved our understanding of sulfur metabolism in Thioalkalivibrio spp.

Acid pressure oxidation leaching of arsenopyrite in the presence of pyrite: Oxygen consumption kinetics

In the process of extraction of gold from refractory sulphide ores, arsenopyrite and pyrite represent two of the major hosts for gold in solid solution. In this study, the pressure oxidation of arsenopyrite and arsenopyrite-pyrite mixtures in a H2SO4–O2 system have been investigated, with the aim of using the oxygen consumption kinetics to probe the oxidation mechanisms. The effects of temperature (180–220 °C), acidity (pH 0.5–2.5), dissolved iron concentration (10 and 30 g/L) and molar ratios (0:1–3:1) of pyrite-to-arsenopyrite (Py/Aspy) were evaluated. Kinetic analysis of arsenopyrite dissolution at 180–220 °C via a shrinking core model indicated an activation energy (Ea) of 48.46 kJ/mol, suggesting a mixed interface reaction and diffusion control. The order of the reaction to acidity was 0.16 at 200 °C, suggesting that [H+] is likely not the rate-limiting factor under typical reaction conditions. The addition of Fe(II) ions to the feed enhanced arsenopyrite oxidation, due to the formation of Fe(III) as a surrogate oxidant to drive the reaction.The Ea for Py/Aspy of 1:1 exhibited two behaviours, calculated to be 77.32 kJ/mol below 200 °C and decreasing to 34.59 kJ/mol above 200 °C. The former was attributed to surface control due to the oxidation of elemental sulphur, followed by a switch to mixed control at elevated temperatures. As Py/Aspy was increased to 2:1 and 3:1, a single behaviour was observed, with Ea values of 56.01 kJ/mol and 43.35 kJ/mol respectively. These values imply a mixed control and begin to approximate literature values for pyrite oxidation. A time-to-a-given-fraction method was also used to examine changes in Ea with reaction extent. Arsenopyrite was found to be under mixed control for most of the reaction extent. At increasing pyrite fractions, oxidation was observed to be reaction-limited at the initial stage of reaction, potentially reflecting the kinetics of sulphur oxidation.

Dynamic Modeling and Simulation of the Sulfur Combustion Furnace in Industrial Smelter

In industrial smelters, sulfuric acid is manufactured using the elemental sulfur in a series of three-unit operations: elemental sulfur oxidation, sulfur dioxide catalytic conversion, and sulfur trioxide absorption. The sulfur oxidation, which is the basic step in this process, is generally performed under a sulfur combustion furnace that ensures the production of the process gas stream, which will be the main supply stream to the other unit operations. In this paper, a dynamic model is developed based on the fundamental mass and energy balance, including the sulfur oxidation and the dynamic flow behavior aspects within the furnace. The obtained model is simulated in the Matlab/Simulink environment and data from an industrial plant were used to validate the model. The simulation results and the plant measurement comparison showed an accuracy of 96%, with a mean absolute error of 16.12 °C and a root mean square error of 23.27 °C. Afterwards, the effect of different operating conditions and disturbance parameters on the sulfur combustion furnace performance were studied. Finally, the relationship and a correlation between the temperature and sulfur dioxide molar fraction at the outlet of the furnace were investigated for industrial use.

Mineral weathering of iron ore tailings primed by Acidithiobacillus ferrooxidans and elemental sulfur under contrasting pH conditions

The acidophilic sulfur oxidizing bacterium (SOB), Acidithiobacillus ferrooxidans, has been found to stimulate elemental sulfur (S0) oxidation and mineral weathering in alkaline Fe ore tailings. However, A. ferrooxidans growth and activities depend on the pH conditions surrounding their interfaces with minerals. The present study aimed to investigate how pH influences bacterial growth and functions in Fe ore tailings. A simulated aquatic ‘homogeneous’ incubation system was initially adjusted into acidic (pH 4), neutral (pH 7) and alkaline (pH 9) conditions, which mimicked the microenvironmental conditions of the water-cell-mineral interfaces in the tailings. It was found that A. ferrooxidans grew well and oxidised S0 under the prevailing and initially acidic conditions (pH < 6). These stimulated the weathering of biotite and amphibole-like minerals and the formation of nanosized jarosite and ferrihydrite-like minerals mediated by extracellular polymer substrate (EPS). In contrast, the initially neutral/alkaline pH conditions (i.e., pH > 7) with the presence of the alkaline tailings restricted SOB growth and functions in S0-oxidation and mineral weathering. These findings suggest that it is essential to prime acidic conditions in microenvironments to support SOB growth, activities, and functions toward mineral weathering in tailings, providing critical basis for involving SOB in eco-engineered pedogenesis in tailings.

Oxidative self-heating modeling of iron sulfides during the processing of high sulfur oil

Scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) were used to analyze the surface micromorphology and components of the iron oxide sulfide powders respectively. Differential scanning calorimetry (DSC) and thermogravimetry (TG) were used to investigate the self-heating properties. It was observed that temperature had a significant effect on the microscopic morphology and composition of the sulfide products. The product powders were homogeneously distributed in small particles and the composition of the products were converted from non-stationary FeS to FeS2 with the sulfidation temperature increased. The apparent activation energy at a sulfidation temperature of 300 °C was 66.5 % of that at a sulfidation temperature of 150 °C. The apparent activation energies were 114.65 kJ/mol, 95.41 kJ/mol, 89.5 kJ/mol and 76.27 kJ/mol respectively at 150 °C, 200 °C, 250 °C and 300 °C during the self-heating reaction phase. There was only one main weight loss phase for the 100 °C, 150 °C and 200 °C products, while the 250 °C and 300 °C products had an additional weight loss phase before the main weight loss phase. The apparent activation energies of the main weight loss phase of the five temperature products were 318.1–333.7 kJ/mol, 266.2–293.2 kJ/mol, 212.7–234.0 kJ/mol, 174.7–193.1 kJ/mol and 168.7–188.7 kJ/mol, respectively. The apparent activation energies of the first weight loss phase of the 250 °C and 300 °C products were 217.4–243.2 kJ/mol and 198.2–214.6 kJ/mol respectively. The mechanism function for the thermal oxidation of elemental sulfur in the first weight loss phase was determined to follow the spherical contraction phase boundary reaction model, i.e. g(α)= [1-(1-α)1/3]m. In the main weight loss phase, the mechanism function for the thermal oxidation of iron sulfate followed the random nucleation followed by subsequent growth model, i.e. g(α)= [ln(1-α)]m.

Water content and communities of sulfur-oxidizing bacteria affect elemental sulfur oxidation in silty and sandy loam soils

Sulfur (S)-oxidizing microorganisms regulate S biogeochemistry in soil ecosystems, affecting ecosystem productivity and food quality. Elemental sulfur (S0) supplies SO42− to plants after oxidation by S-oxidizing microorganisms, and soil pH, organic carbon, water content, and temperature affect the oxidative process. However, how soil water content and texture interact to affect S-oxidizing microbial communities and S0 oxidation is unclear. In this study, S0 oxidation rate and abundance and composition of microbial communities were examined in silty loam and sandy loam soils with different levels of water holding capacity (WHC) (20%, 40%, 60%). Total bacteria were analyzed using the 16S rRNA gene, S-oxidizing bacteria with soxB, and fungi with the ITS gene. The oxidation rate increased significantly with increases in WHC in the sandy loam soil but not in the silty loam soil. The difference might be because the interaction between water content and texture affected the area of contact between S0 and S-oxidizers. At 40% and 60% WHC, the oxidation rate was significantly higher in sandy loam soil than in silty loam soil. The higher oxidation rate was attributed to high ratios of soxB to 16S rRNA gene abundances and key oxidizers in the sandy loam soil. The ratio of soxB to 16S rRNA was significantly higher in the sandy loam soil than in the silty loam soil, irrespective of WHC. The sandy loam soil also contained abundant and diverse typical S-oxidizing bacteria and unknown soxB-containing bacteria. Differences in abundance and composition of S-oxidizing bacterial communities between the two soils might be caused by different cropping histories.

Enhanced biological antimony removal from water by combining elemental sulfur autotrophic reduction and disproportionation

Antimony (Sb), a toxic metalloid, has serious negative effects on human health and its pollution has become a global environmental problem. Bio-reduction of Sb(V) is an effective Sb-removal approach. This work, for the first time, demonstrates the feasibility of autotrophic Sb(V) bio-reduction and removal coupled to anaerobic oxidation of elemental sulfur (S0). In the S0-based biological system, Sb(V) was reduced to Sb(III) via autotrophic bacteria by using S0 as electron donor. Meanwhile, S0 disproportionation reaction occurred under anaerobic condition, generating sulfide and SO42- in the bio-systems. Subsequently, Sb(III) reacted with sulfide and formed Sb(III)-S precipitate, achieving an effective total Sb removal. The precipitate was identified as Sb2S3 by SEM-EDS, XPS, XRD and Raman spectrum analyses. In addition, it was found that co-existing nitrate inhibited the Sb removal, as nitrate is the favored electron acceptor over Sb(V). In contrast, the bio-reduction of co-existing SO42- enhanced sulfide generation, followed by promoting Sb(V) reduction and precipitation. Illumina high-throughput sequencing analysis revealed that Metallibacterium, Citrobacter and Thiobacillus might be responsible for Sb(V) reduction and S0 disproportionation. This study provides a promising approach for the remediation of Sb(V)-contaminated water.

Both Water Content and Sulfur-Oxidizing Bacterial Community Affect Elemental Sulfur Oxidation in Soils with Different Textures

Both Water Content and Sulfur-Oxidizing Bacterial Community Affect Elemental Sulfur Oxidation in Soils with Different Textures

Mineralogy of the RBT 04262 Martian meteorite as determined by micro‐Raman and micro‐X‐ray fluorescence spectroscopies

AbstractMartian meteorites and terrestrial analogs represent the only samples available on Earth for studying mineralogy features of our neighbor planet Mars. This work characterizes the Roberts Massif (RBT) 04262 Martian meteorite by using mainly Raman spectroscopy. By means of this technique, it was confirmed that the meteorite matrix is composed by pyroxene and plagioclase (converted to maskelynite due to the shock pressure). Olivine‐coarse grains embedded in the matrix were also observed. These grains were coated by hydrated magnesium and calcium sulfates, which would belong to the Mars sulfate deposits or to the terrestrial weathering. Although the sulfates could be formed on Mars due to the oxidation of sulfides or elemental sulfur along the sulfur Mars cycle, their distribution along cracks and fractures confirm that are weathering products. However, other S‐bearing compounds that belong to Mars were found, such as elemental sulfur and a thermally transformed iron sulfide. Finally, the calcium phosphate merrillite and titanomagnetite were also detected. Taking this into account, the minerals found were classified into primary minerals that belong to Mars (pyroxene, olivine, elemental sulfur, and titanomagnetite), secondary ones that are alteration products of the primary minerals (maskelynite, iron sulfide, and merrillite), and terrestrial weathering products (sulfates gypsum and epsomite).

Organic Amendments and Elemental Sulfur Stimulate Microbial Biomass and Sulfur Oxidation in Alkaline Subtropical Soils

Sulfur deficiency arising due to intensive cultivation, use of sulfur free fertilizers and reduction in atmospheric sulfur depositions has become a major issue limiting crop production in many parts of the world. Elemental sulfur could be a good source of available S, but its slow oxidation is a problem for its efficient use as a sulfur fertilizer. Main objective of the study was to assess the effect of organic amendments (OA) and elemental sulfur (ES) on microbial activities, sulfur oxidation and availability in soil. A laboratory incubation experiment was carried out for a 56 days period using two sulfur deficient alkaline soils. Organic amendments (OA), i.e., farmyard manure (FYM), poultry litter (PL) and sugarcane filter cake (SF), were applied (1% w/w) with or without elemental sulfur (ES) at 50 mg kg−1. Application of ES alone or in combination with OA significantly increasedCO2-C evolution, microbial biomass, and enzyme activities in the soils, except dehydrogenase activity (DHA) which was not affected by ES application. Combined application of OA and ES had a more pronounced effect on microbial parameters compared to ES or OA applied alone. Ratios of dehydrogenase activity-to-microbial biomass C and arylsulfatase activity-to-microbial biomass C were high in ES+FYM and ES+SF treatments, respectively. Elemental sulfur got sufficiently oxidized resulting in significant improvement in plant available S. Relatively more ES was distributed into C-bonded-S than ester bonded-S. Increase in sulfur availability in ES+OA amended soils was the combined function of sulfur oxidation and mineralization processes through improved microbial activity.

Combination application of elemental sulfur and earthworm increased the lead (Pb) uptake by ryegrass (Lolium perenne L.) in contaminated agricultural soil.

The phytoremediation efficiency is largely depends on the bioavailability of heavy metal in soil. The activity of earthworms and oxidation of elemental sulfur (S0) in soil has influence on heavy metal speciation transformation in soil. By conducting pot experiment, we examined the possibility of enhancing phytoextraction efficiency of lead (Pb) in soil by ryegrass (Lolium perenne L.) with application of both S0 and earthworms. Results showed that the addition of S0 decreased soil pH and increased soil CEC, while a slight trend of decrease for soil pH and increase for CEC was found with earthworm application. In soil treated with earthworms, the addition of S0 increased the concentration of DTPA-extractable Pb by 9.9~20.8%. The concentration of diffusive gradients in thin film (DGT)-extractable Pb was increased by 26.31~32.9% with S0 and earthworm addition. In soil treated with earthworms, the addition of S0 increased the concentration of Pb in shoots of ryegrass by 55.7~110.4% and the translocation factor of Pb in ryegrass was also increased by S0 addition. Our results suggested that the combination application of earthworms and S0 could be an effective way to enhance the remediation efficiency of ryegrass for Pb-contaminated soil.