Sulfur Recycling Research Articles

Biodegradation of carbon disulfide and hydrogen sulfide using a moving bed biofilm reactor coupled with sulfur recycling: Performance, mechanism, and potential application

In this work, a moving bed biofilm reactor (MBBR) was equipped for simultaneous biodegradation of CS2 and H2S. MBBR was started up and operated with different inlet concentrations and retention time; results indicated that approximately 81.9% CS2 and 93.9% H2S could be degraded, and the maximum elimination capacities of 209.3 g/(m3·h) and 138.5 g/(m3·h) were achieved for CS2 and H2S, respectively. The biodegradation mechanisms, including mass transfer, kinetics, and electron transfer, were then investigated. The mass transfer fraction and the maximum degradation rate per unit filter volume were calculated for evaluating the characteristics of mass transfer in MBBR. The variations of extracellular polymeric substances secretion, electron transport system activity and ATP enzyme activity showed that MBBR had an excellent performance for waste gas purification. Subsequently, the recovery of sulfur was explored via morphology, crystal structure, and generation kinetics, indicating that a modified Gompertz model could precisely describe the kinetics of sulfur recovery, and the product selectivity of 51.7% was achieved for sulfur. The microbial community analysis suggested that the dominant genera for biodegradation and sulfur recovery were Acidithiobacillus and Mycobacterium. Finally, MBBR system was validated for treatment of actual waste gas; results indicated that maximum elimination capacities of 134.1 g/(m3·h) and 117.1 g/(m3·h) were obtained for CS2 and H2S, respectively, suggesting that MBBR had the potential for application.

Archean atmospheric sulfur stocked in the Cretaceous gold deposits

The giant Cretaceous Jiaodong gold province is the world's third largest gold mining district, while the source of the ore-forming fluids and AuS remains controversial. The elemental sulfur is a key carrier for gold and the isotopic composition is an ideal tracer of the sulfur source, which makes it crucial for understanding gold deposit genesis and guiding ore exploration. Here, we show the Au-bearing pyrite in the gold deposits from Jiaodong bears a non-zero Δ33S signature from −0.07 ‰ to 0.31 ‰ showing the mass-independent fractionation (S-MIF). This clearly indicates involvement of Archean atmospheric sulfur during the Cretaceous gold mineralization. The MIF-bearing sulfur was likely remobilized from the Archean supracrustal rocks in the basement of the Jiaodong region via fluid-rock interaction while the hydrothermal ore-forming fluids passed through the crustal-scale fault zones. The Phanerozoic gold deposits from Jiaodong have relatively minor S-MIF signals compared with the Archean orogenic gold deposits due to more material (S) cycling and dilution. This new discovery of S-MIF signal in the Phanerozoic ore deposits implies that the recycling of crustal sulfur may be a more common process and play an important role in forming hydrothermal gold deposits.

The recycling of sulphur in waste and conversion to manganese sulphate: Process optimization, kinetic study, mechanistic insights

The recycling of sulphur in waste and conversion to manganese sulphate: Process optimization, kinetic study, mechanistic insights

A sulfide self-driven fuel cell for H2O2 electrosynthesis and sulfur recycling

An energy-free method is developed to produce H2O2 directly from air and sulfur from sulfide-contained wastewater simultaneously. The sulfide self-driven fuel cell can recycle chemical energy into electric energy and sulfide contaminants to sulfur. The H2O2 electrosynthesis strategy is no need for external energy or fuels, which is driven by the electrical energy from sulfide pollutants oxidation. The fuel cell exhibits excellent battery performances, e.g. the highest open cell voltage of 1.29 V and a running current of >100 mA cm−2 at 0 V. The initial current efficiency for H2O2 is 97.94 ± 1.85 %. For wastewater and air tests, the fuel cell can produce 24.75 ± 0.35 mmol L−1 H2O2 solution within 10 h, with an average productivity of 0.37 ± 0.03 mmol cm−2 h−1. It not only can recover the resource and energy from pollutants but also reduce the production energy consumption. The excellent two-electron route oxidation performances of sulfide are proven using in-situ electrochemical technology. This attempt can shed light on H2O2 electrosynthesis and the recycling of sulfide-contained wastewater.

Oxygenolytic sulfoquinovose degradation by an iron-dependent alkanesulfonate dioxygenase

Sulfoquinovose (6-deoxy-6-sulfo-D-glucose, SQ), the polar head group of sulfolipids in plants, is abundant in nature. Many bacteria degrade SQ through pathways termed sulfoglycolysis producing C3 or C2 sulfonates, while certain bacteria degrade SQ through direct oxygenolytic cleavage of the SQ C-S bond, catalyzed by a flavin-dependent alkanesulfonate monooxygenase (sulfo-ASMO pathway). Here we report bioinformatics and biochemical studies revealing an alternative mechanism for oxygenolytic cleavage of the SQ C-S bond, catalyzed by an iron and α-ketoglutarate-dependent alkanesulfonate dioxygenase (SqoD, sulfo-ASDO pathway). In both the ASMO and ASDO pathways, the product 6-dehydroglucose is reduced to glucose by NAD(P)H-dependent SquF. Marinomonas ushuaiensis, a marine bacterium, which harbors the sulfo-ASDO gene cluster is shown utilizing SQ as a carbon source for growth, accompanied by increased transcription of SqoD. The sulfo-ASDO pathway highlights the range of microbial strategies for degradation of this ubiquitous sulfo-sugar, with potential implications for sulfur recycling in different biological environments.

Sulfide/Air Fuel Cell for Sulfur Recycling from Sulfide-Containing Wastewater

Sulfide/Air Fuel Cell for Sulfur Recycling from Sulfide-Containing Wastewater

Isethionate is an intermediate in the degradation of sulfoacetate by the human gut pathobiont Bilophila wadsworthia

The obligately anaerobic sulfite-reducing bacterium Bilophila wadsworthia is a common human pathobiont inhabiting the distal intestinal tract. It has a unique ability to utilize a diverse range of food- and host-derived sulfonates to generate sulfite as a terminal electron acceptor (TEA) for anaerobic respiration, converting the sulfonate sulfur to H2S, implicated in inflammatory conditions and colon cancer. The biochemical pathways involved in the metabolism of the C2 sulfonates isethionate and taurine by B.wadsworthia were recently reported. However, its mechanism for metabolizing sulfoacetate, another prevalent C2 sulfonate, remained unknown. Here, we report bioinformatics investigations and invitro biochemical assays that uncover the molecular basis for the utilization of sulfoacetate as a source of TEA (STEA) for B.wadsworthia, involving conversion to sulfoacetyl-CoA by an ADP-forming sulfoacetate-CoA ligase (SauCD), and stepwise reduction to isethionate by NAD(P)H-dependent enzymes sulfoacetaldehyde dehydrogenase (SauS) and sulfoacetaldehyde reductase (TauF). Isethionate is then cleaved by the O2-sensitive isethionate sulfolyase (IseG), releasing sulfite for dissimilatory reduction to H2S. Sulfoacetate in different environments originates from anthropogenic sources such as detergents, and natural sources such as bacterial metabolism of the highly abundant organosulfonates sulfoquinovose and taurine. Identification of enzymes for anaerobic degradation of this relatively inert and electron-deficient C2 sulfonate provides further insights into sulfur recycling in the anaerobic biosphere, including the human gut microbiome.

Bifunctional Cobalt–Nickel Sulfide Nanoflowers as Electrocatalysts for Concurrent Energy-Efficient Hydrogen Production and Sulfur Recycling

Electrocatalytic water splitting is an important approach for sustainable and green production of hydrogen but is greatly hampered by the sluggish oxygen evolution reaction (OER). Therefore, developing a favorable alternative reaction to replace OER for both energy-efficient coproduction of hydrogen and value-added chemicals is highly desirable. Herein, a thermodynamically favorable sulfion oxidation reaction (SOR) electrocatalyzed by CoNi2S4 nanoflowers (CoNi2S4 NFs) is reported to couple with the hydrogen evolution reaction (HER) for energy-efficient hydrogen production and sulfur recovery. In this coupled system, only a low cell voltage of 0.3 V is required to produce hydrogen at 10 mA cm–2, much lower than that of water splitting (1.76 V). Meanwhile, S2– ions are selectively electrooxidized to sulfur with a high yield of 220.5 g h–1 m–2, realizing electrochemical upcycling of sulfur-containing pollutants. This strategy provides an attractive route for both energy-effective hydrogen generation and sulfur recycling.

Removal and Resource Utilization of High Concentration Flue Gas Sulfur Dioxide Using Manganese Carbonate Ore

The removal of high concentration flue gas sulfur dioxide (SO2) using manganese carbonate ore desulfurization (MCO-FGD) is a promising route that combines economic benefits and pollution control. However, the problems of intermediate oxidation and by-product control have plagued the industrial application of the MCO-FGD technique for a long time. Based on the fact that there is symbiosis of manganese and iron in natural manganese ore, in this study, small amounts of Fe(III) and MnO2 were introduced into the MCO-FGD reaction system to enhance the oxidation of SO2 to SO4− and suppress the manganous dithionate (MnS2O6) by-product generation. The results suggested that the addition of Fe(III) led to the generation of potent oxidant Mn(III) in the reaction system, which accelerated the generation of SO3−• radicals and, thus, enhanced the oxidation of SO2. Under the optimum reaction conditions, the 2.0% of inlet SO2 could be removed to 62 ppm, obtaining 90.1% manganese leaching efficiency, and the concentration of MnS2O6 in the desulfurized liquid was kept below 2.5 g/L after a six-stage desulfurization. The results are of great importance for the sustainable development of the manganese metallurgical industry, which provides theoretical and technical support for the recycling of sulfur and manganese. The influences of different operational conditions on SO2 removal, the catalytic mechanism, and manganese leaching were studied to provide theoretical and technical support for resourceful MCO-FGD technology.

Influence of the Interface Wettability of Membranes on Electrolysis Reduction of SO2 to H2S

Converting SO2 to H2S is an important process for sulfur recycling. In our previous study, electroreduction of SO2 to H2S was achieved by using a gas-permeable catalyst membrane. In this paper, the influence of the interface wettability of the membrane was investigated since it has a great effect on the conversion of SO2 to H2S. A 94% increase in the current density and a 189% increase in H2S flux were obtained after treating the membrane using NH3 plasma when the contact angle is 93°. A formula for H2S membrane flux was established, in which the contact angle θ and surface pH have a negative effect on H2S flux. The elevated wettability (smaller θ) increased the current density of H2S production but hindered H2S diffusion due to the increased immersion depth. The surface pH increase resulting from the current density increase had tiny effects on H2S separation.

Reprogramming the sulfur recycling network to improve l-cysteine production in Corynebacterium glutamicum

A bifunctional H2S2-responsive genetic circuit was established to realize sulfur recycling in Corynebacterium glutamicum, and the production of l-cysteine and the SCR were significantly increased by using this system.

Pollution-free recycling of lead and sulfur from spent lead-acid batteries via a facile vacuum roasting route

Traditional pyrometallurgical recovery of spent lead-acid batteries (LABs) requires a temperature higher than 1000 °C, with accompanying hard-to-collect wastes such as lead dust and sulfur oxides. Against this background, sodium carbonate (Na2CO3) was proposed as a low-cost, safe, and non-toxic reagent for recycling the high-risk environmental elements lead (Pb) and sulfur (S), in spent LAB lead paste, enabling the one-step conservation of multi-component Pb species, including lead sulfate (PbSO4), metallic lead (Pb), and lead dioxide (PbO2), to lead oxide (PbO) and sodium sulfate (Na2SO4). The possible reaction pathways of Pb and S species in vacuum roasting was confirmed by Gibbs free energy reaction with an estimated average activation energy of 272.5 kJ/mol. The insoluble PbO in the reaction product (PbO/Na2SO4/Na2CO3) can be recycled by vacuum filtration, while Na2CO3 and Na2SO4 were separated using a carbonation method. Life cycle assessment revealed that for recycling 1.0 t of spent LABs, the vacuum roasting can reduce the carbon footprint −2.1 × 103 kg CO2 eq, promoting global decarbonization. The designed route is highlighted with waste-free production and is outlined by the twelve principles of green chemistry, showing its great engineering application potential for spent LAB recycling.

Mercury, organic matter, iron, and sulfur co-cycling in a ferruginous meromictic lake

Mercury (Hg) speciation in natural waters is controlled by redox conditions and microbiological activity. Water columns of meromictic lakes have large and stable redox chemical and biological gradients that allow the investigation of many Hg chemical transformations. In this study, Hg speciation (elemental Hg = Hg0, methylated Hg = MeHg) and partitioning between truly dissolved (<3 kDa), colloidal (<0.45 μm and >3 kDa), and particulate (>0.45 μm) fractions, were determined throughout a high-resolution water column profile in the ferruginous meromictic Lake Pavin (Massif Central, France) in July 2018. Total Hg concentrations (THg) in water ranged between 0.4 and 8.8 pmol L−1. The particulate phase represented 10–70% of the THg, with a peak found in the mesolimnion associated with the particulate organic carbon maximum. In the mesolimnion, the colloidal fraction represented 12–68% of THg, and the highest value was found at the top of the sulfidic zone, whereas the truly dissolved Hg species (70 ± 9%) dominated in all the rest of the sulfidic zone. MeHg ranged from less than 10% of THg in the oxic mixolimnion to more than 90% in the anoxic monimolimnion. The Hg methylation was most active within the suboxic zone where iron and sulfate reduction are occurring. These results, associated with those of the partition of organic matter (OM), sulfur, and iron, in conjunction with thermodynamic calculations, allow us to present a conceptual scheme for the Hg cycle in the lake. Atmospheric Hg deposited onto surface waters of the lake is partially photo-reduced and returned to the air, another part is scavenged by biogenic particulate matter and conveyed at depth by settling organic material. Water stratification and redox changes create a sequence of reactions from oxic to ferruginous waters where Hg is successively (i) desorbed from particulate OM where mineralization occurs, (ii) adsorbed onto iron-oxy(hydr)oxides, (iii) desorbed where they dissolved, (iv) precipitate as HgS, (v) methylated, and (vi) reduced as Hg0 in the deepest part of the lake. In brief, the (micro)biological uptake, OM, iron and sulfur recycling, through associated microbial consortia, control the Hg cycling in the Pavin waters.

An approach towards utilization of water-quenched blast furnace slag for recovery of titanium, magnesium, and aluminum

Resource utilization of water-quenched blast furnace slag (BFS) for recovery of valuable metals such as titanium, magnesium, and aluminum are strategic issues for the iron and steel industry's long-term development. This study proposed a sustainable strategy for simultaneous Ti, Mg, and Al extraction from water-quenched BFS using the ammonium sulfate roasting-dilute acid leaching method. The results showed that the roasting reaction was carried out at a roasting temperature of 380 °C, a mass ratio of (NH4)2SO4 to water-quenched BFS of 2.5:1, and a roasting time of 90 min, and the valuable metals were converted into the corresponding sulfates. The roasted slag was then leached by the 1 mol/L sulfuric acid solution, with Ti, Mg, and Al leaching efficiency reaching 95.45%, 98.92%, and 92.32%, respectively. We proposed the mechanism for extracting valuable metals from water-quenched BFS using an ammonium sulfate roasting-dilute acid leaching process based on XRD and SEM-EDS analysis. Furthermore, an efficient separation process for converting Ti, Mg, and Al in the pregnant solution to TiO2, MgC2O4.2H2O, and Al2O3 was developed. The final filtrate was directly evaporated and crystallized to obtain (NH4)2SO4, which can be used in the roasting process, resulting in ammonia and sulfur recycling. The method proposed in this paper can be effectively applied to the extraction, separation, and recovery of Ti, Mg, and Al in water-quenched BFS, which is completely consistent with the concept of clean production and efficient utilization of industrial solid wastes. It is extremely important for the iron and steel industry's long-term production.

A thermodynamic model for sulfur content at sulfide saturation (SCSS) in hydrous silicate melts: With implications for arc magma genesis and sulfur recycling

Modeling the effect of H2O on the “sulfur content at sulfide saturation” (SCSS) in silicate melt is essential for the estimation of SCSS in both arc magmas and slab melts. Here we present a thermodynamic approach, in which, SCSS in hydrous silicate melt has been modeled as a combination of S dissolving as S2− and HS−/H2S, based on the sulfide capacity (CS2−) and the hydro-sulfide capacity (CHS), respectively. By adopting the thermodynamic framework of O’Neill and Mavrogenes (2002), S dissolution as HS−/H2S can be modeled in an analogous fashion to that for modeling S2− in anhydrous melt with the relation: lnHSSCSS=-ΔG°Fes-FeO/RT+lnCHS-lnaFeOmelt+lnaFeSsulfide. To obtain an expression for CHS, we compiled published experimental data on SCSS in hydrous silicate melts covering a PT range of 0.15–3 GPa and 785–1600 °C, and melt H2O contents of ∼1–13 wt%. While the contribution of S dissolving as S2− in basaltic and andesitic melts can be calculated based on the updated SCSS model for anhydrous basic melt from O’Neill (2021), S2− is considered negligible in rhyolitic and dacitic melts, i.e., when melt FeO content <∼5 wt%. We propose an expression for CHS as a function of temperature, mole fractions of cations for the normalized anhydrous melt composition, ln(XOH + XH2O), and a Na + K-Al term for alkaline-enriched rhyolitic melts. The coefficients for cation mole fractions are adopted from the expression for CS2− from O’Neill (2021); the coefficients for the 1/T and Na + K-Al terms are obtained from regression. The reproducibility of compiled SCSS values is ±50% for hydrous rhyolitic and dacitic melts, and ±10–30% for hydrous basaltic and andesitic melts, representing a significant improvement in comparison to previous models.Our model produces SCSS values for the primitive arc magmas compiled by Ruscitto et al. (2012), that are in most cases higher than the measured S contents, implying sulfide under-saturated conditions during mantle wedge melting. The contribution of H2S dissolution to the calculated SCSS values varies in a range of 70–1234 ppm, which increases with the increase of H2O content (0.3–6.2 wt%). H2S dissolution therefore contributes to the higher S content in arc basalt compared to MORB, an observation which is further corroborated by the positive correlation between H2O and S contents in primitive arc magmas. Applying our current model to experimentally produced sediment melts spanning a PT range of 690–1050 °C and 2.5–4.5 GPa, demonstrates that sediment melts, especially those of intermediate supercritical character with >25 wt% H2O and peralkaline in composition, can have high SCSS values as a result of H2S dissolution, and act as the transfer medium for S recycling between the slab and mantle wedge under reduced conditions.

Geochemical behavior and recycling of sulfur in subduction zones

俯冲带是全球最大的物质循环系统，控制着硫(S)在地球内部圈层及表层的循环，影响着大气圈、水圈、生物圈、岩石圈的稳定性以及地球的宜居性。厘清S在俯冲带中的地球化学行为和循环特征对理解地球各储库的氧化还原状态、岩浆作用与演化、成矿物质聚集、以及地球大气成分等具有重要意义。本文首先总结了进入俯冲带之前的大洋岩石圈的S结构模型，对S在大洋板片中的分布状态和地球化学特征进行了系统归纳。随后，系统阐述了俯冲带高压-超高压变质岩记录的板片变质及脱水过程中硫的地球化学行为。岩石学研究表明俯冲板片中的S多以硫化物相存在，硫酸盐矿物在弧前深度就已被释放或分解。相较于熔体，俯冲带流体中S的溶解度更高，是运移硫的更有效方式。DEW模型计算结果显示，流体中S含量总体较低，但在俯冲板片~90km处其含量有一个峰值(浓度0.5%~1.0%)。岩相学证据、地球化学测试结果、磷灰石S近边吸收结构(S-XANES)特征以及模拟结果都显示俯冲深部流体中S多以HS^-及H₂S形式存在，不含大量的SO₄^2-及硫酸盐；中<i>f</i>_S₂流体有利于S迁移出俯冲板片，从而促进俯冲带大规模S循环，而高<i>f</i>_S₂流体在流-岩交换过程沿流体通道发生S的锁固作用而不利于俯冲带S循环。质量平衡计算显示全球俯冲带S输入通量为4.65×10¹³g/yr，弧下深度板片S输出通量为2.91×10¹²g/yr，板片-岛弧S循环效率仅6.3%。俯冲板片在弧下深度可能存在一个短暂高效的S释放窗口，释放流体的<i>δ</i>³⁴S值为-2.1±3.0‰。基于高压-超高压变质岩中硫化物的研究，初步厘清了俯冲板片中S的地球化学行为，首次从板片角度全面、定量地限定了俯冲带的脱硫通量、效率、种型和同位素特征，提出俯冲带循环的S不是岛弧岩浆的氧化剂，与岛弧环境的正<i>δ</i>³⁴S值也无直接因果联系，对解析俯冲带S循环和理解地球长期的S循环具有重要意义。最后，本文还展望了俯冲带S循环的未来发展方向，应在俯冲带流体氧化还原性质(硫酸盐的命运)、俯冲沉积物对S循环的制约、俯冲带环境下多硫同位素的分馏效应、S循环与其它挥发分(如C等)循环之间的耦合关系、地球历史上深部S循环等方向做出探索，更深入地理解俯冲带及全球S循环过程。

Sulphur isotopes (δ34S and Δ33S) in sulphides from cratonic mantle eclogites: A glimpse of volatile cycling in ancient subduction zones

Multiple sulphur isotopic compositions of sulphides from Kaapvaal craton mantle eclogites allow to elucidate the recycling of sulphur into the deep Earth and to differentiate between recycled crust and mantle origins of eclogite-hosted sulphides, including the precious metals that they capture. We present multiple sulphur isotope ratio measurements by secondary ion mass spectrometry for sulphides from a collection of mantle-derived eclogite xenoliths from Proterozoic and Mesozoic kimberlite occurrences in South Africa (Premier, Roberts Victor, Jagersfontein). Previous work established that the host eclogites have elemental and oxygen isotopic compositions in support of seawater-altered oceanic lithosphere protoliths, and for many of these xenolith suites Archean ages have been suggested.The eclogite-hosted sulphides have δ34S values from −5.7 to +29‰, with the upper end of this wide range representing the highest-ever recorded δ34S composition of material derived from the Earth's mantle. The Δ33S values range from −0.29 to +0.18‰ and do not record significant mass-independent sulphur isotope fractionation, i.e., there is no compelling S-MIF signature. Most of the sulphide grains have δ34S values that fall within a range between −6 and +4‰, and they probably retain an isotopic record of sulphides that formed originally within altered oceanic crust. In contrast, the highly positive δ34S values from +13 to +29‰ detected in sulphide grains from a single eclogite xenolith are similar to those of marine sulphates, which were probably a minor sulphur component of the oceanic crustal protolith. The lack of a significant S-MIF signature in the eclogitic sulphides that show δ34S evidence for a recycled crust origin implies that this sulphur component stems from a <2.4Ga post-Archean surficial reservoir. This finding suggests that the cratonic mantle eclogites may have formed from post-Archean oceanic crust (e.g., Paleoproterozoic eclogite protoliths), or – as is preferred here – the ‘surficial’ sulphur was introduced into the cratonic root during relatively young metasomatic events and is thus unrelated to eclogite petrogenesis and Archean continent formation.

Nitrogen and Sulfur Recycling and Diagnostic in Cover Crop-Maize Systems

It remains uncertain how oat (Avena sativa L.) and hairy vetch (Vicia villosa Roth.) impact both nitrogen (N) and sulfur (S) recycling in cover crop-maize (Zea mays L.) systems as well as N and S diagnostic methods in maize. Field trials were conducted at three sites in the southeastern Argentinean Pampas to evaluate the effect of oat, hairy vetch, and bare fallow combined with four N and S fertilization treatments (unfertilized, N-, S-, and NS-fertilized) on maize. Soil N and S content at maize sowing, chlorophyll meter reading (CMR) at silking, and grain yield were determined. Overall, soil NO3−-N content (0–60 cm) at maize sowing was hairy vetch > bare fallow > oat, while SO4−2-S content was hairy vetch > bare fallow = oat. Maize yield response to N was predicted from soil NO3−-N content (R2 = 0.80). The CMR was negatively correlated with cover crop residue quality (carbon (C)/N and C/S ratios). Also, CMR accurately predicted variations in maize grain yield. In the unfertilized treatment, maize yield was hairy vetch > bare fallow > oat, in two of the three sites. There was no yield response to N or S with hairy vetch. Oat and hairy vetch differentially affected N and S recycling in cover crop-maize cropping systems. Soil NO3−-N and SO4−2-S content at maize sowing combined with CMR are reliable diagnostic tools to assess maize N and S, allowing for sustainable fertilization management.

Sulfur isotope behavior during metamorphism and anatexis of Archean sedimentary rocks: A case study from the Ghost Lake batholith, Ontario, Canada

Recycling of surface-derived sulfur into the deep earth can impart distinct sulfur isotope signatures to magmas. The details of sulfur transfer from sedimentary rocks to magmas (and ultimately igneous rocks) through metamorphism and devolatilization and/or partial melting, however, is difficult to trace. To understand this process in detail we studied multiple-sulfur isotope compositions of sulfides in the Archean (c. 2685 Ma) Ghost Lake batholith (GLB) and its surrounding host metasedimentary rocks of the Superior Craton (Ontario, Canada) by high spatial resolution secondary ion mass spectrometry, complemented by high-precision gas source isotope ratio mass spectrometry measurements. The GLB comprises strongly peraluminous biotite+cordierite, biotite+muscovite, and muscovite+garnet+tourmaline granites to leucogranites, which are thought to represent the partial melts of surrounding metagreywackes and metapelites. The metasedimentary rocks display a range of metamorphic grades increasing from biotite-chlorite (280-380°C) at ∼5 km away from the GLB to sillimanite-K-feldspar grade (∼660°C) immediately adjacent to the batholith, thus providing a natural experiment to understand sulfur isotope variations from low- to high-grade Archean sedimentary rocks, as well as granites representative of their partial melts.We find that metasedimentary sulfide δ34S values increase with progressive metamorphism at most 2-3‰ (from −1‰ up to +1 to +2‰). An increase in δ34S values in pyrrhotite during prograde metamorphism can be explained through Rayleigh fractionation during pyrite desulfidation reactions. Pyrite from all but one of the granite samples preserve δ34S values similar to that of the high-grade metasedimentary rocks, indicating that partial melting did not result in significant fractionation of δ34S. The exception to this is one granite sample from a part of the batholith characterized by abundant metasedimentary inclusions. This sample contains pyrite with heterogeneous and low δ34S values (down to −16‰) which likely resulted from incomplete homogenization of sulfur between the granitic melt and metasedimentary inclusions. Small (several tenths of a permil), mostly positive Δ33S are observed in both the metasedimentary rocks and granites.Our results suggest that Archean strongly peraluminous granites could be a high-fidelity archive to quantify the bulk sulfur isotope composition of the Archean siliciclastic sediments. Further, our findings indicate that subduction of reduced sulfur-bearing sediments in the Archean with δ34S at or near 0‰ should result in release of sulfur-bearing fluids in the mantle wedge with similar values (within a few permil). S-MIF (if initially present in Archean surface material) may be preserved during this process. However, the absence of S-MIF in igneous rocks does not preclude assimilation of Archean sedimentary material as either S-MIF may not be originally present in the Archean sedimentary sulfur and/or homogenization or dilution could obscure any S-MIF originally present in assimilated Archean sediments.

Two radical-dependent mechanisms for anaerobic degradation of the globally abundant organosulfur compound dihydroxypropanesulfonate

2(S)-dihydroxypropanesulfonate (DHPS) is a microbial degradation product of 6-deoxy-6-sulfo-d-glucopyranose (sulfoquinovose), a component of plant sulfolipid with an estimated annual production of 1010 tons. DHPS is also at millimolar levels in highly abundant marine phytoplankton. Its degradation and sulfur recycling by microbes, thus, play important roles in the biogeochemical sulfur cycle. However, DHPS degradative pathways in the anaerobic biosphere are not well understood. Here, we report the discovery and characterization of two O2-sensitive glycyl radical enzymes that use distinct mechanisms for DHPS degradation. DHPS-sulfolyase (HpsG) in sulfate- and sulfite-reducing bacteria catalyzes C-S cleavage to release sulfite for use as a terminal electron acceptor in respiration, producing H2S. DHPS-dehydratase (HpfG), in fermenting bacteria, catalyzes C-O cleavage to generate 3-sulfopropionaldehyde, subsequently reduced by the NADH-dependent sulfopropionaldehyde reductase (HpfD). Both enzymes are present in bacteria from diverse environments including human gut, suggesting the contribution of enzymatic radical chemistry to sulfur flux in various anaerobic niches.