Formation Of Hydrogen Sulfide Research Articles

A review on prospects and challenges of biological H2S removal from biogas with focus on biotrickling filtration and microaerobic desulfurization

The production of biogas from sulfate-rich materials under anaerobic digestion results in the formation of hydrogen sulfide (H2S). The recommended level of H2S in the produced biogas for direct combustion purposes is in the range of 0.02 to 0.05% w/w (200 to 500 ppm), therefore, desulfurization is required to avoid damages to combustion equipment and prevent the formation of sulfur dioxide (SO2) which is an acid rain precursor. It has been well documented that physical, thermal, and chemical desulfurization approaches suffer from high operation costs as well as waste production needing to be disposed of. Accordingly, a great deal of efforts has been put into biological methods because of being more environmentally friendly and more economically advantageous in comparison with the other techniques. Biotrickling filtration (BTF) and microaerobic desulfurization have shown a high potential for H2S removal at pilot- and large-scale plants. Despite all the progress made and the promising aspects keeping these methods at the core of interest, there are still challenges to be addressed. The present article attempts to briefly review and discuss the challenges and future prospects of BTF and microaerobic desulfurization.

Dealing with hydrogen sulfide induced problems downstream of sewer rising mains

Abstract The problems that arise from hydrogen sulfide formation in sewer rising mains are often dealt with by adding chemicals. The most commonly used chemicals are sodium hydroxide and magnesium hydroxide, ferric (or ferrous) chloride, calcium nitrate and oxygen. As there is a lack of tools to evaluate and compare dosing strategies, it is hard to identify the most appropriate dosing chemical in terms of investment and operating costs. As a consequence, chemical selection is often done ad-hoc. In this study, the average dosing costs (operating and capital) of these chemicals is assessed by simulations with a dynamic mathematical model, describing the transformations of sulfide, carbon and nitrogen in a sewer rising main. Based on the results of the simulations, and other parameters, a systematic approach to selecting dosing products for sewer rising mains is outlined.

Release of hydrogen sulfide under intermittent flow conditions - the potential of simulation models.

For engineering purposes it is especially useful to be able to predict and control sewer corrosion rates and odor impacts as well as to design effective measures aiming to reduce effects related to hydrogen sulfide formation and release. Doing so, it is important to use modeling tools that are capable of assessing variations of dissolved oxygen, dissolved sulfide and hydrogen sulfide gas concentrations for a wide range of environmental scenarios. Two such models were assessed: AEROSEPT, an empirical formulation, and WATS, a conceptual and more complex approach. The models were applied to evaluate the effects of transitions between pressure mains and gravity sewers in the air-liquid mass transfer of hydrogen sulfide at the Ericeira sewer system in Portugal. This network is known to have odor and corrosion problems, especially during summer. Despite the unavoidable uncertainties due to the unsteady flow rate and the quantification of air velocity and turbulence, the simulation results obtained with both models have been shown to adequately predict the overall behavior of the system.

In-situ prevention of hydrogen sulfide formation during anaerobic digestion using zinc oxide nanowires

The utilization of Anaerobic Digestion (AD) technology for biogas and energy generation is often hindered by high concentration of sulfur-containing compounds in wastewater and consequential hydrogen sulfide (H2S) in biogas. In this work, we demonstrated a process, where independent mechanisms of anaerobic microorganisms and an inorganic reactive adsorbent (zinc oxide nanowires) worked synergistically to remove soluble sulfide (HS−) and prevent H2S formation during AD. Using a model aqueous sodium sulfide (Na2S) system, the nanowires (dosage 1g/L) effectively removed sulfides from the Na2S solution to a maximum of 625mg S2−/L per gram of ZnO. During 24h and 3-day long (involving three consecutive sulfate feeding cycles) AD studies using anaerobic microbial medium (2g/L SO42− and 1g/L ZnO), no decrease in methanogenic activity and biogas production were observed using the ZnO nanowires, indicating that the nanowires can reduce the sulfide toxicity during AD. The post-process analysis of the recovered nanomaterial using energy-dispersive X-ray spectroscopy and X-ray diffraction showed the presence of sulfur and zinc sulfide (ZnS), respectively, validating HS− removal by the nanowires. This process intensification approach of combining AD and H2S removal into a single process step will help extend AD technology to high sulfate containing wastewaters.

Chalcopyrite Leaching in Acidic Chloride Solution without Sulphates

Chalcopyrite leaching in acidic chloride solution without sulphates. The effect of dissolved oxygen and ferrous/ferric/cupric ions in solution on the leaching behavior of chalcopyrite and the phenomenology of the passivating layer formation on the chalcopyrite surface in an aqueous acidic chlorinated medium with dissolved oxygen and without sulphate are studied. The research was performed using pure chalcopyrite samples with particle sizes of +45 to -75 microns (-200+325 mesh). It was found that the formation of hydrogen sulfide (H2S) at room temperature and atmospheric pressure is a possible precursor of passivating species that prevent chalcopyrite dissolution.

The response of a shallow hypertrophic lake to innovative restoration measures – Uzarzewskie Lake case study

The aim of nitrate treatment as a restoration method is to bring about a reduction of the high potential reactivity of sediments by the oxidation of biodegradable organic matter. As a consequence, oxygen uptake by sediments is reduced, sulphate reduction is lowered, hydrogen sulphide formation diminished and iron present in sediments binds phosphorus (P) effectively. This approach was applied in Uzarzewskie Lake, where innovative nitrate treatment of sediments was proposed through the diversion of subsurface waters to the lake hypolimnion. Nitrate-rich and oxygenated water from two tributaries was directly delivered to the hypolimnion through pipelines in order to increase redox potential and eliminate sediments as a P source. Research on selected physico-chemical and biological water characteristics was conducted in the years 2005–2015 to determine the results of restoration measures.P concentrations in lake waters were reduced both in surface water layers and the hypolimnion, hence epilimnetic chlorophyll-a content was diminished as well. Statistically significant changes in phytoplankton community structure were noted as the biomass of cyanobacteria had decreased in 2010 and 2013–2014 in comparison to 2006, while cryptophytes biomass increased in 2011–2013 in relation to 2007. Unfortunately, planktivorous fish domination in fish fauna exert a distinct pressure on zooplankton, thus Rotifera dominated and Cladocera were rarely noted. Additionally, the morphometric lake features (steep slopes, small surface surrounded by forest) create unfavorable conditions for submerged macrophyte development, and hinder the effectiveness of the restoration. Long-term studies revealed that the reconstruction of the phytoplankton community was not permanent, hence further restoration activity is required, with the inclusion of new techniques.

Analysis of MTHFR, CBS, Glutathione, Taurine, and Hydrogen Sulfide Levels in Retinas of Hyperhomocysteinemic Mice.

PurposeHyperhomocysteinemia (Hhcy) is implicated in certain retinal neurovascular diseases, although whether it is causative remains uncertain. In isolated ganglion cells (GCs), mild Hhcy induces profound death, whereas retinal phenotypes in Hhcy mice caused by mutations in remethylation (methylene tetrahydrofolatereductase [Mthfr+/−]) or transsulfuration pathways (cystathionine β-synthase [Cbs+/−]) demonstrate mild GC loss and mild vasculopathy. The current work investigated compensation in vivo of one pathway for the other, and, because the transsulfuration pathway yields cysteine necessary for formation of glutathione (GSH), taurine, and hydrogen sulfide (H2S), they were analyzed also.MethodsRetinas isolated from wild-type (WT), Mthfr+/−, and Cbs+/− mice (12 and 22 weeks) were analyzed for methylene tetrahydrofolate reductase (MTHFR), cystathionine-β-synthase (CBS), and cystathionase (CTH) RNA/protein levels. Retinas were evaluated for levels of reduced:oxidized GSH (GSH:GSSG), Slc7a11 (xCT), taurine, taurine transporter (TAUT), and H2S.ResultsAside from decreased CBS RNA/protein levels in Cbs+/− retinas, there were minimal alterations in remethylation/transsulfuration pathways in the two mutant mice strains. Glutathione and taurine levels in Mthfr+/− and Cbs+/− retinas were similar to WT, which may be due to robust levels of xCT and TAUT in mutant retinas. Interestingly, levels of H2S were markedly increased in retinas of Mthfr+/− and Cbs+/− mice compared with WT.ConclusionsGanglion cell loss and vasculopathy observed in Mthfr+/− and Cbs+/− mouse retinas may be milder than expected, not because of compensatory increases of enzymes in remethylation/transsulfuration pathways, but because downstream transsulfuration pathway products GSH, taurine, and H2S are maintained at robust levels. Elevation of H2S is particularly intriguing owing to neuroprotective properties reported for this gasotransmitter.

Environmental boundary and formation mechanism of different types of H2S corrosion products on pipeline steel

To establish an adequate thermodynamic model for the mechanism of formation of hydrogen sulfide (H2S) corrosion products, theoretical and experimental studies were combined in this work. The corrosion products of API X60 pipeline steel formed under different H2S corrosion conditions were analyzed by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction. A thermodynamic model was developed to clarify the environmental boundaries for the formation and transformation of different products. Presumably, a dividing line with a negative slope existed between mackinawite and pyrrhotite. Using experimental data presented in this study combined with previously published results, we validated the model to predict the formation of mackinawite and pyrrhotite on the basis of the laws of thermodynamics. The established relationship is expected to support the investigation of the H2S corrosion mechanism in the oil and gas industry.

Sulphurous Mineral Waters: New Applications for Health.

Sulphurous mineral waters have been traditionally used in medical hydrology as treatment for skin, respiratory, and musculoskeletal disorders. However, driven by recent intense research efforts, topical treatments are starting to show benefits for pulmonary hypertension, arterial hypertension, atherosclerosis, ischemia-reperfusion injury, heart failure, peptic ulcer, and acute and chronic inflammatory diseases. The beneficial effects of sulphurous mineral waters, sulphurous mud, or peloids made from sulphurous mineral water have been attributed to the presence of sulphur mainly in the form of hydrogen sulphide. This form is largely available in conditions of low pH when oxygen concentrations are also low. In the organism, small amounts of hydrogen sulphide are produced by some cells where they have numerous biological signalling functions. While high levels of hydrogen sulphide are extremely toxic, enzymes in the body are capable of detoxifying it by oxidation to harmless sulphate. Hence, low levels of hydrogen sulphide may be tolerated indefinitely. In this paper, we review the chemistry and actions of hydrogen sulphide in sulphurous mineral waters and its natural role in body physiology. This is followed by an update of available data on the impacts of exogenous hydrogen sulphide on the skin and internal cells and organs including new therapeutic possibilities of sulphurous mineral waters and their peloids.

Indications of the prominent role of elemental sulfur in the formation of the varietal thiol 3-mercaptohexanol in Sauvignon blanc wine

Elemental sulfur is a fungicide traditionally used to control Powdery Mildew in the production of grapes. The presence of sulfur residues in grape juice has been associated with increased production of hydrogen sulfide during fermentation, which could take part in the formation of the varietal thiol 3-mercaptohexanol. This work examines whether elemental sulfur additions to Sauvignon blanc juice can increase the levels of sought-after varietal thiols. Initial trials were performed in South Africa and indicated a positive impact of sulfur on the levels of thiols. Further experiments were then carried out with New Zealand Sauvignon blanc and confirmed a positive relationship between elemental sulfur additions and wine varietal thiols. The formation of hydrogen sulfide was observed when the addition of elemental sulfur was made to clarified juice, along with an increase in further reductive sulfur compounds. When the addition of sulfur was made to pressed juice, prior to clarification, the production of reductive sulfur compounds was drastically decreased. Some mechanistic considerations are also presented, involving the reduction of sulfur to hydrogen sulfide prior to fermentation.

The role of carbon dioxide in the transport and fractionation of metals by geological fluids

Although carbon dioxide is one of the major components of crustal fluids responsible for ore deposit formation, its effect on transport and precipitation of metals remains unknown, due to a lack of direct experimental data and physical–chemical models for CO2-rich fluids. To fill this gap, we combined laboratory experiments and thermodynamic modeling to systematically quantify the role played by CO2 for the solubility of economically important metals such as Fe, Cu, Zn, Au, Mo, Pt, Sn under hydrothermal conditions. Solubility measurements of common ore minerals of these metals (FeS2, CuFeS2, ZnS, Au, MoS2, PtS, SnO2) were performed, using a flexible-cell reactor equipped with a rapid sampling device, in a single-phase fluid (CO2–H2O–KCl) at 350–450°C and 600–750bar, buffered with iron sulfide and oxide and alkali-aluminosilicate mineral assemblages. In addition, another type of experiments was conducted to measure gold solubility in more sulfur-rich supercritical CO2–H2O–S–NaOH fluids at 450°C and 700bar using a batch reactor that allows fluid quenching. Our results show that the solubilities of Si, Au, Mo, Pt and Cu either decrease (within <1log unit) or remain constant upon CO2 increase, whereas those of Fe, Zn and Sn increase significantly (>1log unit) with CO2 contents in the fluid increasing from 0 to 50wt%. These data were interpreted using a simple model that does not require any new adjustable parameters, and is based on the dielectric constant of the H2O–CO2 solvent and on the Born solvation parameter for the dominant metal-bearing species in an aqueous fluid. Our predictions using this model suggest that in a supercritical CO2–H2O–S-salt fluid typical of metamorphic Au deposits, in equilibrium with pyrite and chalcopyrite, the Cu/Fe ratio decreases by up to 2 orders of magnitude with an increase of CO2 content from 0 to 70wt%. This effect is due to the decrease of the fluid dielectric constant in the presence of CO2, which favors the stability of neutral species (FeCl20) compared to charged ones (CuCl2−). Our results explain the Fe enrichment and Cu depletion in metamorphic gold deposits formed by CO2-rich fluids. The transport of gold is unfavorable in the presence of CO2 only in S-rich (>0.5wt%S) fluids in which Au forms the negatively charged Au(HS)2− and Au(HS)S3− complexes. By contrast, it is only weakly affected in S-poor (<0.1wt%S) acidic-to-neutral fluids in which the uncharged Au(HS)0 complex predominates. Thus, even at very high CO2 contents (>50wt% CO2), the capacity of such fluids to transport gold (up to 100s ppb Au) remains comparable to that of aqueous fluids. These findings are in agreement with analyses of natural fluid inclusions in metamorphic deposits. In more saline oxidizing and S-rich fluids such as those in magmatic porphyry Cu–Au deposits, the Fe, Cu, and Au solubilities in the presence of CO2 decrease by ∼1 order of magnitude with CO2 increasing to 20–30wt%, following the decrease in the stability of their dominant charged species (FeCl42−, CuCl2−, Au(HS)2− and Au(HS)S3−), but stay almost constant at higher CO2 contents (30–70wt%) as controlled by the neutral species (FeCl20, Cu(HS)0 and Au(HS)0). Such solubility trends suggest a new potential trigger of ore precipitation in porphyry systems by CO2 pulses from the magmatic chamber, which may operate along with commonly admitted depositional mechanisms such as cooling, vapor-brine immiscibility, and water–rock interaction. The direct effect of CO2 on the mobility of Pt and Mo, metals that likely form hydrogen sulfide and oxy-hydroxide complexes, respectively, is expected to be weak in most settings. Among the studied elements, Sn is the only one whose solubility may be favored at high CO2 content (>20wt%) due to carbonate complexing. This study demonstrates, for the first time, that, contrary to common belief, the presence of CO2 in a supercritical fluid may lead to enhanced mobility or, on contrary, to massive precipitation of some metals, depending on salinity and sulfur content, and, more generally, to significant fractionations between different metals.

Formation of Hydrogen Sulfide in Wine: Interactions between Copper and Sulfur Dioxide.

The combined synergistic effects of copper (Cu2+) and sulfur dioxide (SO2) on the formation of hydrogen sulfide (H2S) in Verdelho and Shiraz wine samples post-bottling was studied over a 12-month period. The combined treatment of Cu2+ and SO2 significantly increased H2S formation in Verdelho wines samples that were not previously treated with either Cu2+ or SO2. The formation of H2S produced through Cu2+ mediated reactions was likely either: (a) directly through the interaction of SO2 with either Cu2+ or H2S; or (b) indirectly through the interaction of SO2 with other wine matrix compounds. To gain better understanding of the mechanisms responsible for the significant increases in H2S concentration in the Verdelho samples, the interaction between Cu2+ and SO2 was studied in a model wine matrix with and without the presence of a representative thiol quenching compound (4-methylbenzoquinone, 4MBQ). In these model studies, the importance of naturally occurring wine compounds and wine additives, such as quinones, SO2, and metal ions, in modulating the formation of H2S post-bottling was demonstrated. When present in equimolar concentrations a 1:1 ratio of H2S- and SO2-catechol adducts were produced. At wine relevant concentrations, however, only SO2-adducts were produced, reinforcing that the competition reactions of sulfur nucleophiles, such as H2S and SO2, with wine matrix compounds play a critical role in modulating final H2S concentrations in wines.

Ecological aspects of water impoundment in the tropics.

Recognition of the potentially harmful effects of water development in the tropics had led to increasing efforts to assess the environmental impact of such projects prior to construction. Decisions regarding the development or non-development of water resources must be based on sound investigation of both the long-and short-term effects of reservoir construction and operation. The environmental effects of water impoundment vary greatly with the characteristics of the region as well as the type of reservoir to be constructed (area and depth of reservoir, ratio of water inflow to storage). Of major concern are the reduction of reservoir capacity as sediments accumulate behind the dam and the loss of these sediments to downstream agriculture and fisheries. The potential impact of altered flow regimes, siltation, reduction in beach formation and nutrient enrichment at the mouths of rivers, and the possibility of saltwater encroachment should receive careful stdy. A thorough description of the plants and animals to be affected by inundation should be made to determine the possible loss of rare or key organisms as well as the potential development of "nuisance species". Included in this survey should be a detailed study of existing fish and the potential for commercial fishery development in the proposed reservoir. Consideration should be given to vegetation removal in the reservoir basin prior to inundation, since decaying vegetation can result in deoxygenation, formation of hydrogen sulfide, possible development of suitable habitats for undesirable species and snagging of fish nets. Sanitation and land use practices as well as erosion in the watershed surrounding the reservoir must be controlled to prevent accelerated eutrophication caused by increased nutrient loading. Inundation in tropical areas can have serious sociological and human health implications including the increase of diseases, e.g., malaria, schistosomiasis, onchocerciasis, and dysentery, and the probable resettlement and alteration of land use practices. Census information and surveys concerning land use, housing and health standards and the social and economic structure of the community to be affected must be evaluated in order to anticipate and avoid potential problems. The archaeologic, historic, scenic and recreational value of the site to be inundated must also be considered. Studies of the EL Cajón site on the Sula River in Honduras and the Purari River Project in Papua, New Guinea, are utilized as examples in this report.

Formation and Transport Mechanism of Hydrogen Sulfide in Coal Seam

H2S gas would pose a threat to coal mine safety. This article from the biodegradation, microbial sulfate reduction, thermal decomposition chemistry, chemical sulfate reduction and magmatic 5 aspects to analyze the formation mechanism of hydrogen sulfide gas in coal mine, a coal mine combined with field data, analysis of hydrogen sulfide gas in the coal mining the transport mechanisms. Research for the comprehensive management of coal mine hydrogen sulfide gas has certain significance.

Ratiometric QD-FRET Sensing of Aqueous H2S in Vitro.

We report a platform for the ratiometric fluorescent sensing of endogenously generated gaseous transmitter H2S in its aqueous form (bisulfide or hydrogen sulfide anion) based on the alteration of Förster resonance energy transfer from an emissive semiconductor quantum dot (QD) donor to a dithiol-linked organic dye acceptor. The disulfide bridge between the two chromophores is cleaved upon exposure to bisulfide, resulting in termination of FRET as the dye diffuses away from the QD. This results in enhanced QD emission and dye quenching. The resulting ratiometric response can be correlated quantitatively to the concentration of bisulfide and was found to have a detection limit as low as 1.36 ± 0.03 μM. The potential for use in biological applications was demonstrated by measuring the response of the QD-based FRET sensor microinjected into live HeLa cells upon extracellular exposure to bisulfide. The methodology used here is built upon a highly multifunctional platform that offers numerous advantages, such as low detection limit, enhanced photochemical stability, and sensing ability within a biological milieu.

Hydrogen sulfide formation, fate, and behavior in anhydrite-sealed carbonate gas reservoirs: A three-dimensional reactive mass transport modeling approach

A novel hydrogeochemical modeling approach is developed to unravel thermochemical sulfate reduction (TSR) in hydrocarbon reservoirs. Our numerical model couples a web of interconnected hydrogeochemical reactions to three-dimensional (3-D) and reservoir-wide diffusive mass transport. Our modeling approach simulates a semigeneric gas reservoir sealed by anhydrite. The calculated diagenetic processes fit the observations in reservoirs affected by TSR: formation of water, precipitation of calcite, metal (di-)sulfides, and elemental sulfur as replacements of dissolved anhydrite at the expense of CH4(g), as well as formation of hydrogen sulfide (H2S). By varying input parameters, the crucial factors controlling TSR have been identified. Our results highlight that reservoir-wide diffusive mass transport is one prerequisite for TSR. An increase in the rate constant of abiotic sulfate reduction (ASR) and in diffusive mass fluxes, as well as lack of precursor minerals for metal (di-)sulfide precipitation, can increase the souring intensity and accelerate H2S outgassing. In contrast, precipitation of elemental sulfur, which is stable according to the chemical thermodynamics, weakens H2S formation. Our modeling shows that TSR is complex and cannot be represented by the single reaction ASR and by simple correlations between the rate constant of ASR and the H2S gas content. The application of 3-D reactive transport modeling presented here, despite its semigeneric nature, provides a good example of how such an approach can be used ahead of drilling. Our modeling helps to investigate TSR in time and space to quantify the mass conversion of all reactants involved within this web and to predict the souring level.

Hydrogen sulfide formation in oil and gas

Hydrogen sulfide (H2S) can be a significant component of oil and gas upstream production, where H2S can be naturally generated in situ from reservoir biomass and from sulfate-containing minerals through microbial sulfate reduction and (or) thermochemical sulfate reduction. On the other hand, the technologies employed in oil and gas production, especially from unconventional resources, also can contribute to generation or delay of appearance of H2S. Steam-assisted gravity drainage and hydraulic fracturing used in production of oil sands and shale oil/gas, respectively, can potentially convert the sulfur content of the petroleum into H2S or contribute excess amounts of H2S during production. A brief overview of the different classes of chemical reactions involved in the in situ generation and release of H2S is provided in this work. Speciation calculations and reaction mechanisms are presented to explain why thermochemical sulfate reduction progresses at faster rates under low pH. New studies regarding the degradation of a hydraulic fracture fluid additive (sodium dodecly sulfate) are reported for T = 200 °C, p = 17 MPa, and high ionic strengths. The absence of an ionic strength effect on the reaction rate suggests that the rate-limiting step involves the reaction of neutral species, such as elemental sulfur. This is not the case with other thermochemical sulfate reduction studies at T &gt; 300 °C. These two different kinetic regimes complicate the goal of extrapolating laboratory results for field-specific models for H2S production.

Are there multiple mechanisms of anaerobic sulfur oxidation with ferric iron in Acidithiobacillus ferrooxidans?

To clarify the pathway of anaerobic sulfur oxidation coupled with dissimilatory ferric iron reduction in Acidithiobacillus ferrooxidans strain CCM 4253 cells, we monitored their energy metabolism gene transcript profiles. Several genes encoding electron transporters involved in aerobic iron and sulfur respiration were induced during anaerobic growth of ferrous iron-grown cells. Most sulfur metabolism genes were either expressed at the basal level or their expression declined. However, transcript levels of genes assumed to be responsible for processing of elemental sulfur and other sulfur intermediates were elevated at the beginning of the growth period. In contrast, genes with predicted functions in formation of hydrogen sulfide and sulfate were significantly repressed. The main proposed mechanism involves: outer membrane protein Cyc2 (assumed to function as a terminal ferric iron reductase); periplasmic electron shuttle rusticyanin; c4-type cytochrome CycA1; the inner membrane cytochrome bc1 complex I; and the quinone pool providing connection to the sulfur metabolism machinery, consisting of heterodisulfide reductase, thiosulfate:quinone oxidoreductase and tetrathionate hydrolase. However, an alternative mechanism seems to involve a high potential iron-sulfur protein Hip, c4-type cytochrome CycA2 and inner membrane cytochrome bc1 complex II. Our results conflict with findings regarding the type strain, indicating strain- or phenotype-dependent pathway variation.

Use of glutathione during white wine production – impact on S-off-flavors and sensory production

Recently two OIV resolutions (OENO 445-2015 and OENO 446-2015) were adopted, defining the use of glutathione (GSH) up to a maximum level of 20 mg/L in must and wine. Various studies have shown the benefits of GSH addition, especially in Sauvignon blanc wines. On the other hand, the formation of hydrogen sulfide (H2 S) and other S-off-flavors favored by GSH addition are reported. To investigate the effect of glutathione on the color development, the sensory expression and the formation of sulfide off-flavors, Riesling, Sauvignon Blanc and Chardonnay grapes were processed under different conditions and musts were obtained with different phenolic contents. By the addition of GSH as a pure substance or the use of GSH-rich inactivated yeast preparations, the GSH concentration in the musts was varied. Bottled wines showed generally lower GSH levels than the corresponding musts. However, higher GSH concentrations after yeast aging could be determined, which may explain increased protection against oxidation during further storage. The sensory analysis after bottling showed that the fruity character of Riesling and Sauvignon blancs was enhanced at moderate GSH addition. Overuse of GSH in musts with low phenolic content, however, can lead to sensory perceptible S-off-flavors in the later wines.

Sulfur Cycle by In Situ Analysis in the Sediment Biofilm of a Sewer System

AbstractThe corrosion and odor caused by hydrogen sulfide formation are serious problems in sewer operations, and the cost to prevent these problems is high. Understanding the sulfur cycle mechanism and controlling the sulfur cycle in sediment biofilm are essential to solve these problems. In this review, the reaction mechanisms of the sulfur cycle in sediment biofilm in sewer systems revealed by using in situ microelectrode measurements and molecular biological technologies are summarized. The results indicated that the profile of the reaction process of the sulfur cycle in sediment biofilm was primarily affected by the substrate concentration change in the liquid phase and the various substrate penetrations in sediment biofilm. The biological community’s distribution and shifting of sulfate reduction bacteria and sulfide oxidation bacteria across the sediment biofilm were in response to the substrate change of the microenvironment in sediment biofilm. The influence of flow fluctuation on the profile of ...