Low Concentrations Of Hydrogen Sulfide Research Articles

Contrasting Intermediate-Temperature La0.7Sr0.3VO3.86-⸹ (LSV) Porous Catalyst Elevated Sulfur Tolerance Using Gaseous and Liquid Fuel Explored through Experimental and Modeling Characterization Over Time

The U.S. Army is investigating Solid Oxide Fuel Cells (SOFCs), which can produce clean, secure, and sustainable energy to replace existing power sources. Today SOFCs are known to provide high density, high efficiency power with long term stability at low cost and environmental impact, utilizing a variety of naturally sourced fuels such as hydrogen, hydrocarbons, and alcohols. This fuel flexibility makes SOFCs attractive for use with multiple applications and helps bridge the gap between current hydrogen-fueled SOFC technologies and future hydrocarbon-fueled based use. Despite this potential, many technical hurdles remain, such as thermal stress cracking and coarsening, delamination, and catalyst contamination. Catalyst contamination is of particular concern for the U.S. Army, which operates on JP-8 kerosene-based fuel via AR-70 single fuel policy, as sulfur impurities commonly found in naturally sourced hydrocarbon-based fuels, can poison the catalyst, permanently degrading SOFC system performance, even at low concentrations. As the U.S. Army begins to investigate SOFCs to enable additional capabilities like silent watch, advanced radios, and exportable power in their fleet, catalyst poisoning from sulfur presents a concerning technology gap that must be addressed, especially since it is also possible that sulfur contaminated fuel, scavenged in theater, may be used, and could contain elevated levels (>300ppm) of sulfur.While lower temperature SOFC operation is also actively being pursued to help alleviate physical material degradation issues, with the introduction of hydrocarbon-based fuels, catalyst development to reduce sulfur poisoning degradation also needs further exploration. This study continues to experimentally and theoretically investigate the response of sulfur tolerant anode catalyst La0.7Sr0.3VO3.86-⸹ (LSV) at currently targeted SOFC intermediate operating temperatures (400-600°C). We have previously investigated low and moderate hydrogen sulfide (H2S) concentrations (30ppm, 300ppm) in balance hydrogen and methane gas environments for up to 100 hours. In this work, LSV showed significant sulfur tolerance in hydrogen and methane balance gases when compared to the industry standard Ni-YSZ anode, where sulfur adsorption rates were 278-287x lower in some cases. The lowest rates occurred between 600-700°C, which is attributed to the cubic structure the material presents in this temperature range. Higher adsorption rates were observed in the monoclinic/tetragonal structure the material presents at temperatures between 400-500°C. Average adsorption rates were overall higher in methane. When compared against Ni-YSZ, which is known to accumulate sulfur from hydrogen sulfide via two-step dissociative adsorption, LSV was observed to accumulate sulfur through weak chemisorption (H2S*, 0.43 eV max) of molecular hydrogen sulfide on oxygen deficient surfaces and one-step dissociative adsorption (H2S*, 0.34 eV, max, HS*+H*, 8.34 eV, max) on oxygen sufficient surfaces. The weak chemisorption behavior on oxygen deficient surfaces is attributed to the reduced oxygen stoichiometry of the material, in which only vanadium V2+/3+ couples exist. Overall, molecular adsorption/dissociation was observed to occur near strontium defects on LaO/SrO terminations. The propensity of H2S adsorption on LSV surfaces was observed to be significantly less for oxygen deficient LSV, and significantly higher for oxygen sufficient LSV, when compared to H2S adsorption calculations on Ni (100) surfaces, which follow a two-step dissociative adsorption reaction (H2S* → HS*+H* → H*+S*), resulting in a strongly adsorbed S* species (5.96 eV, max).Under the Army’s single fuel policy, it is more likely SOFCs would be fueled using hydrogen and/or methane, which are both gases, however SOFCs in the future could also be directly fueled using liquid alcohol fuels, or as scavenged from theater. Typical small alcohol molecules (methanol or ethanol) do not contain high concentrations of sulfur; however, alcohols can be contaminated with sulfur-containing hydrocarbons. This work will investigate sulfur adsorption using methanol contaminated with 300ppm thiophene using the same operating temperature and heating duration conditions with hydrogen and methane. These results will be contrasted against the 300ppm H2S hydrogen and methane results previously reported. Figure 1

Gold-nanoparticle-decorated Tin Oxide of a Gas Sensor Material for Detecting Low Concentrations of Hydrogen Sulfide

Gold-nanoparticle-decorated Tin Oxide of a Gas Sensor Material for Detecting Low Concentrations of Hydrogen Sulfide

Hybrid material based on single walled carbon nanotubes and cobalt phthalocyanine bearing sixteen pyrene moieties as a sensing layer for hydrogen sulfide detection

We report on a sensor platform for the determination of hydrogen sulfide based on a new hybrid material obtained by the non-covalent functionalization of single-walled carbon nanotubes (SWCNT) with a novel cobalt phthalocyanine bearing 16 pyrene substituents (CoPc-Pyr). The structural features of the hybrid were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–Vis spectroscopy, and thermogravimetric analysis (TGA). The sensor characteristics of SWCNT/CoPc-Pyr hybrid layers prepared by spin coating of its suspension in dichloromethane were studied against low concentrations of hydrogen sulfide (0.5–50 ppm) with the limit of detection (LOD) of 38 ppb and response and recovery time of 60 s and 80 s, respectively. This LOD value lies in the appropriate range and the prepared hybrid material is promising for the creation of the sensors for the detection of H2S, which can be used as an important biomarker of halitosis and asthma. It was shown that the SWCNT/CoPc-Pyr hybrid could be successfully used for the selective detection of H2S in the presence of carbon dioxide, hydrogen, ethanol, acetone, and dichloromethane.

Comparison of Operating Atmosphere Impact on La0.7Sr0.3V3.86-⸹ (LSV) Intermediate-Temperature Solid Oxide Fuel Cell Sulfur Tolerance Explored Through Experimental and Modeling Characterization Over Time

Experts have long projected that in the future solid oxide fuel cells (SOFCs) could provide a viable path for the replacement of existing power sources and the production of clean, secure, and sustainable energy. Today, not only have SOFCs matured as a technology with a proven ability to provide high density, high efficiency power with long term stability at low cost and environmental impact, but with the theoretical capacity to utilize a variety of naturally sourced fuels. This theoretical capacity makes their potential use attractive in many additional applications and positions SOFCs to be the technology which can bridge the gap between current hydrocarbon fueled technologies and future hydrocarbon fueled electric technologies. That said, there remains many technical hurdles associated with the incorporation of naturally sourced fuels, to include thermal stress cracking and catalyst coarsening, delamination, and poisoning. Catalyst poisoning, specifically arising from sulfur impurities in naturally sourced fuels, remains one of the largest SOFC technical challenges, since their presence, even at low concentrations, have now shown permanent performance degradation. As the U.S. Army begins to investigate SOFCs to enable additional capabilities like silent watch, advanced radios, and exportable power in their fleet, catalyst poisoning from sulfur impurities presents a concerning technology gap which must be addressed, as the entire fleet operates on JP-8 kerosene-based fuel, which by specification can contain up to 3000 ppm of sulfur, via AR-70 single fuel policy.As SOFC technologies migrate to lower temperature operation to resolve physical degradation issues, the development catalysts materials with greater sulfur tolerance are being explored to resolve issues of chemical degradation related to sulfur poisoning. In this study, a previously reported, high temperature, sulfur tolerant SOFC catalyst, La0.7Sr0.3VO3.86-⸹ (LSV), was further experimentally investigated via Optical Microscopy, X-ray Diffraction, Scanning Electron Microscopy and Energy Dispersive Spectroscopy for its sulfur tolerance at currently targeted SOFC intermediate operating temperatures (400-600°C) in wide range of hydrogen sulfide (30ppm, 300ppm and 10vol%) balance hydrogen gas environments for up to 100 hours. When compared against the industry standard Ni-YSZ anode, LSV was observed to have significantly lower (287x) sulfur adsorption rates, with the lowest rates observed between 600-700°C. This behavior is attributed the cubic structure the material presents in this temperature range. Higher adsorption rates were observed in the monoclinic/tetragonal structure the material presents at temperatures between 400-500°C. This study was further supplemented by a theoretical investigation of hydrogen sulfide adsorption on low index LSV surfaces via periodic Density Functional Theory. When compared against Ni-YSZ, which is known to accumulate sulfur from hydrogen sulfide via two-step dissociative adsorption, LSV was observed to accumulate sulfur through weak chemisorption (0.43 eV max) of undissociated molecular hydrogen sulfide only. The weak chemisorption behavior is attributed to structural surface changes due to oxygen vacancies near strontium defects, wherein the strongest adsorption energies were observed, and in direct contrast to similar calculations of hydrogen sulfide adsorption with low index surfaces of LVO3, wherein no adsorption was observed.Since it is likely SOFCs will operate on hydrocarbon fuels, as well as compressed hydrogen gas in the future, this study is also currently experimentally investigating sulfur accumulation under the same operating conditions above with hydrogen sulfide mixtures in methane gas. Methane is a small hydrocarbon chain, which will help minimize the accumulation of carbon deposition. Initial comparisons of sulfur adsorption between hydrogen and methane gas mixtures, using low hydrogen sulfide concentrations, show they are statistically similar, although methane gas exposure was observed to result in the formation of two activation energies, which was not observed with hydrogen mixture previously. The methane gas was also observed to promote LSV to take the monoclinic/tetragonal structure at lower operating temperatures than hydrogen mixtures. This observation may lead to elevated sulfur adsorption rates at higher hydrogen sulfide concentrations. Finally, it was originally observed during experimental exposure experiments with hydrogen sulfide/hydrogen gas balance mixtures that higher concentrations of lattice oxygen, present at lower temperatures, had a positive correlation with sulfur accumulation in the LSV material. This study is therefore currently theoretically investigating the effect of lattice oxygen content on the LSVs structure via Density Functional Theory, which could lead to further derivation from optimal cubic configuration, which may lead to configurations which increase sulfur adsorption. Figure 1

DEVELOPMENT OF BIOFILM ON POLYURETHANE FOAM AND ITS APPLICATION IN A BIO-TRICKLING FILTER FOR TREATMENT OF ODOR FROM DOMESTIC SOLID WASTE

This study investigates the ability of a self-fabricated bio-trickling filter using commercial polyurethane foam as bio-media for treatment of odor-causing gases (e.g., ammonia, hydrogen sulfide, and mercaptans) under different nitrogen loadings in gas and liquid phases. The experimental results showed that the biological filter operating with a gas flow rate of 11.44 m3/h and an empty bed residential time of 19.67 s could treat the multi-components emitted from domestic solid waste. Ammonia treatment efficiency was achieved in the range of 87.3 to 99.7% with the highest ammonia input concentration of l47.3 mg/m3. The efficiency of mercaptans treatment was from 60.2 to 72.8% with an input concentration of about 8 mg/m3 while the low input and output concentrations of hydrogen sulfide were found (≤ 0.002 mg/m3). Besides, there was a significant difference between elimination capacity of NH3-N (gas phase) and accumulated capacity of NH4+-N and NO3--N (liquid phase) although the ammonia treatment efficiency was very high, which could be attributed to the denitrification process. The results from this study hence suggest using bio-trickling filter for effective treatment of NH3 and other odor in gas generated from domestic solid waste.

In situ detection of the fine scale heterogeneity of active cold seep environment of the Formosa Ridge, the South China Sea

The active cold seep at Formosa Ridge (Site F) sustains the most flourishing ecosystem on the continental slope of the northern South China Sea. However, the physicochemical environment around the cold seep has scarcely been investigated. The knowledge about the variability of the seafloor habitat around the cold seep was poor and the key processes within the associated chemosynthetic ecosystem remain unclear. Here, we used an in situ integrated sensors detection approach combined with geochemical measurements to investigate the environmental condition around the chemosynthetic ecosystems fueled by the hydrocarbon seepage. Methane, hydrogen sulfide, dissolved oxygen and other biogenic elements in the bottom water were detected on a fine scale. The mixed gas composition and carbon isotope value of methane from the vent fluids suggested its origin was predominantly biogenic with slight thermogenic incorporation. Both horizontal and vertical variations in methane and oxygen concentrations were observed, which showed contrasting trends in fields from the center of flourishing communities to the margin of sediments. The concentration of methane decreased from 31,200 ppm at the flourishing center to 381 ppm at the margin on a horizontal gradient. The low concentration of hydrogen sulfide indicated that sulfide could be an energy-limiting factor for chemoautotrophic symbionts. The in situ oxygen levels were variable near the flourishing community but homogeneous at the margins. The results suggested that the availability of oxygen and methane played a substantial role in structuring the seep communities. Overall, from the flourishing center to the periphery, the chemical gradients drive the spatial distribution of chemosynthetic community at site F. The observations of the fine scale survey highlight the heterogeneity of microenvironments and provide novel information on the environmental dynamics within site F for the first time. • In situ detection of the fine scale environment in the cold seep were conducted. • Variations of methane and oxygen were observed from the center to the periphery. • The low sulfide level could be a limiting factor for the chemosynthetic community.

Chemoresistive gas-sensing properties of highly dispersed Nb2O5 obtained by programmable precipitation

Abstract Nb2O5 powder obtained by programmable precipitation was used to form a thick gas-sensing film as part of a chemoresistive gas sensor, by screen-printing. The coating of orthorhombic Nb2O5 consisted of nanoparticles with a size of 41.0 ± 2.5 nm. XPS revealed Nb5+, Nb4+ and Nb2+ as well as oxygen vacancies in the crystal structure of niobium oxide. As a result of studying the chemoresistive gas-sensing properties of Nb2O5, it has been shown that among the analysed gases (H2, CO, NH3, H2S and О2), the greatest sensitivity was observed for oxygen and hydrogen sulphide. Nanocrystalline niobium oxide showed a high and reproducible response to 0.02–20% О2 (S1 = 1.1–19.0) at a very low detection temperature of 200 °C for oxygen sensors. At an operating detection temperature of 250 °C, a high and reproducible response to low concentrations of hydrogen sulphide of 4–100 ppm (S2 = 1.2–6.6) was detected for Nb2O5. The influence of humidity on the received signals when detecting oxygen and hydrogen sulphide was studied in detail: there was a decrease in the resistance and the response value at 95% humidity in the medium of both gases. However, unlike the process of detecting H2S (when the response of S2 was almost lost), when determining oxygen, the response of S1 was reduced by a factor of two only, which suggests the possibility of determining the content of O2 in high humidity conditions.

Biogeochemical cycling of sulfur, manganese and iron in ferruginous limnic analog of Archean ocean

The early evolution of life on Earth was intimately coupled with the evolution of ocean chemical composition and redox conditions in Archean ocean. However, the measurements of chemical and isotopic compositions of Archean sedimentary rocks does not provide sufficient information for understanding the biogeochemical processes that characterized oceans during this period. In this research, the cycling of the redox-sensitive elements in the water column and sediments of the seasonally stratified Lake Sihailongwan, China, was studied. It was found that during the stratification, the concentrations of sulfate ions in the epilimnion were <100 μmol L−1. The hypolimnion of the lake becomes anoxic and contains iron, manganese and low concentrations of hydrogen sulfide. These conditions are similar to those suggested to exist in the Archean ocean, and therefore the biogeochemical cycles in Lake Sihailongwan may be analogous to those in the Archean ocean. In Lake Sihailongwan, the chemocline is always deeper than the thermocline. The hypolimnion is supersaturated with respect to iron sulfide in August, while in May and October, this supersaturation is present only in the lower hypolimnion. The concentration profiles of the redox species in the water column and in the sediments show that dissolved iron(II) and manganese(II) diffuse from the sediments into the water column, while hydrogen sulfide and sulfate diffuse into the sediment. At the hypolimnion, the sulfur isotope fractionation values are consistent with microbial sulfate reduction, possibly combined, to a minor extent, with disproportionation of zero-valent sulfur. The absolute sulfur isotope fractionation factor increases between spring and autumn and decreases with water depth, possibly due to precipitation of iron sulfide in the lower hypolimnion. The fraction of highly reactive iron in the sediments is mainly composed of iron(II) carbonates and the most reactive iron(III) (hydr)oxide phases. Iron-based redox proxies are consistent with sediment deposition under ferruginous water column conditions. In the sediment, concentrations of sulfate and hydrogen sulfide are low, and sulfur isotope composition of sedimentary pyrite is equal to that of the epilimnetic sulfate. The obtained results demonstrated that despite a low sulfate concentration in the water column, sulfur isotope fractionation is high. However, due to the complete consumption of the sulfate reservoir, the large isotope fractionation is not preserved in the sedimentary record.

Interactions and microbial variations in a biotrickling filter treating low concentrations of hydrogen sulfide and ammonia

A lab-scale biotrickling filter (BTF) packed with porcelain Rasching ring and ceramsite was applied for co-treating of low concentrations of hydrogen sulfide (H2S) and ammonia (NH3), as major pollutants typically found in e.g., intensive livestock production facilities. In this study, the outlet gas concentrations of H2S and NH3 were used for indicators if the treated gas reached odor-free condition. Overall, excellent removal efficiencies were obtained for both H2S and NH3 in the BTF during Stage I (H2S alone) and Stage II (H2S and NH3). Specifically, the H2S outlet concentration was below the detection limit (∼3.6 ppbv) and the NH3 outlet concentration was less than 0.4 ppmv when the inlet concentrations of H2S and NH3 were around 1.8 ppmv and 35.3 ppmv, respectively. In this case, the running empty bed residence time was 10.2 s. During Stage II, the outlet H2S concentration was decreased significantly when the inlet NH3 concentration was increased, likely due to the influence by pH. Meanwhile, the outlet nitrous oxide (N2O) concentration was kept low (<2% NH3) during the experiment, suggesting a proper operation of the BTF. After the inlet gas shifted from H2S alone at Stage I to H2S and NH3 at Stage II, the main sulfur-oxidizing bacteria (SOB) species in the BTF switched from Acidithiobacillus to Thiobacillus.

Hydrogen sulfide alleviates cigarette smoke-induced COPD through inhibition of the TGF-β1/smad pathway.

Smoking has become a major cause of chronic obstructive pulmonary disease through weakening of the respiratory mucus-ciliary transport system, impairing cough reflex sensitivity, and inducing inflammation. Recent researches have indicated that hydrogen sulfide is essential in the development of various lung diseases. However, the effect and mechanism of hydrogen sulfide on cigarette smoke-induced chronic obstructive pulmonary disease have not been reported. In this study, rats were treated with cigarette smoke to create a chronic obstructive pulmonary disease model followed by treatment with a low concentration of hydrogen sulfide. Pulmonary function, histopathological appearance, lung edema, permeability, airway remodeling indicators, oxidative products/antioxidases levels, inflammatory factors in lung, cell classification in bronchoalveolar lavage fluid were measured to examine the effect of hydrogen sulfide on chronic obstructive pulmonary disease model. The results showed that hydrogen sulfide effectively improved pulmonary function and reduced histopathological changes, lung edema, and permeability. Airway remodeling, oxidative stress, and inflammation were also reduced by hydrogen sulfide treatment. To understand the mechanisms, we measured the expression of TGF-β1, TGF-βIand TGF-βII receptors and Smad7 and phosphorylation of Smad2/Smad3. The results indicated that the TGF-β1 and Smad were activated in cigarette smoke-induced chronic obstructive pulmonary disease model, but inhibited by hydrogen sulfide. In conclusion, this study showed that hydrogen sulfide treatment alleviated cigarette smoke-induced chronic obstructive pulmonary disease through inhibition of the TGF-β1/Smad pathway. Impact statement COPD has become a severe public health issue in the world and smoking has become a major cause of COPD. As a result, it is a demandingly needed to explore new potential therapy for cigarette smoke-associated COPD. The present study suggested that H2S treatment improved pulmonary function and reduced histopathological changes, lung edema, permeability, inflammation, airway remodeling and oxidative injury in a COPD model induced by cigarette smoke. Although additional studies are required to elucidate the pharmacodynamics, pharmacokinetics, and pharmacology of H2S in the cigarette smoke-associated COPD, our findings provide an experimental basis for the potential clinical application of H2S in COPD treatment.

Evaluation of Short-Term Exposure Levels on Ammonia and Hydrogen Sulfide During Manure-Handling Processes at Livestock Farms

BackgroundAmmonia and hydrogen sulfide are harmful gases generated during aerobic/anaerobic bacterial decomposition of livestock manure. We evaluated ammonia and hydrogen sulfide concentrations generated from workplaces at livestock farms and determined environmental factors influencing the gas concentrations.MethodsFive commercial swine farms and five poultry farms were selected for monitoring. Real-time monitors were used to measure the ammonia and hydrogen sulfide concentrations and environmental conditions during the manure-handling processes. Monitoring was conducted in the manure storage facility and composting facility. Information on the farm conditions was also collected through interview and walk-through survey.ResultsThe ammonia concentrations were significantly higher at the swine composting facilities (9.5–43.2 ppm) than at other manure-handling facilities at the swine and poultry farms, and high concentrations of hydrogen sulfide were identified during the manure agitation and mixing process at the swine manure storage facilities (6.9–19.5 ppm). At the poultry manure-handling facilities, the ammonia concentration was higher during the manure-handling processes (2.6–57.9 ppm), and very low hydrogen sulfide concentrations (0–3.4 ppm) were detected. The air temperature and relative humidity, volume of the facility, duration of manure storage, and the number of animals influenced the gas concentrations.ConclusionA high level of hazardous gases was generated during manure handling, and some levels increased up to risk levels that can threaten workers' health and safety. Some of the farm operational factors were also found to influence the gas levels. By controlling and improving these factors, it would be possible to protect workers' safety and health from occupational risks.

Transdermal Detection of Low Concentrations of Hydrogen Sulfide

Transdermal Detection of Low Concentrations of Hydrogen Sulfide

English

Anaerobic co-digestion improves the pig faeces digestion process. This work presents anaerobic digestion of pig faeces (C) as compared to 2 co-substrates: Sludge (L) from waste waters and bovine ruminal gastric content (R). Pig faeces used were generated in a local farm at the Juarez Autonomous University of Tabasco (UJAT), with a total population of 148 animals. Analytical determinations were made on the substrate and co-substrates. Each treatment was performed in triplicate (9 experimental units), for 18 weeks. C+R co-digestion had the highest removal of chemical oxygen demand (COD) with 90%. Biogas production (0.012 L day-1) was quantified for C and C+R, with concentrations of 70.87±8.65 and 71.89 ± 7.60% of methane (CH4), respectively. For C+L, it was 0.009 L day-1, with 77.89±6.74% of CH4. Results obtained showed that co-digestion of C+L was better with regards to the quality of biogas from low hydrogen sulfide (H2S) concentrations (70.33±6.36 ppm). The use of anaerobic co-digestion systems represents an alternative treatment for faeces generated in pig farms and other kinds of wastes to reduce the potential source of infection produced by these types of waste. Key words: Biogas, digester, manure, pig faeces, rumen.

Pre- and posttreatment with hydrogen sulfide prevents ventilator-induced lung injury by limiting inflammation and oxidation.

Although essential in critical care medicine, mechanical ventilation often results in ventilator-induced lung injury. Low concentrations of hydrogen sulfide have been proven to have anti-inflammatory and anti-oxidative effects in the lung. The aim of this study was to analyze the kinetic effects of pre- and posttreatment with hydrogen sulfide in order to prevent lung injury as well as inflammatory and oxidative stress upon mechanical ventilation. Mice were either non-ventilated or mechanically ventilated with a tidal volume of 12 ml/kg for 6 h. Pretreated mice inhaled hydrogen sulfide in low dose for 1, 3, or 5 h prior to mechanical ventilation. Posttreated mice were ventilated with air followed by ventilation with hydrogen sulfide in various combinations. In addition, mice were ventilated with air for 10 h, or with air for 5 h and subsequently with hydrogen sulfide for 5 h. Histology, interleukin-1β, neutrophil counts, and reactive oxygen species formation were examined in the lungs. Both pre-and posttreatment with hydrogen sulfide time-dependently reduced or even prevented edema formation, gross histological damage, neutrophil influx and reactive oxygen species production in the lung. These results were also observed in posttreatment, when the experimental time was extended and hydrogen sulfide administration started as late as after 5 h air ventilation. In conclusion, hydrogen sulfide exerts lung protection even when its application is limited to a short or delayed period. The observed lung protection is mediated by inhibition of inflammatory and oxidative signaling.

Foliar application of sodium hydrosulfide (NaHS), a hydrogen sulfide (H2S) donor, can protect seedlings against heat stress in wheat (Triticum aestivum L.)

Temperature extremes represent an important limiting factor to plant growth and productivity. Low concentration of hydrogen sulfide (H2S) has been proven to function in physiological responses to various stresses. The present study evaluated the effect of foliar application of wheat seedlings with a H2S donor, sodium hydrosulfide (NaHS), on the response to acute heat stress. The results showed that pretreatment with NaHS could promote heat tolerance of wheat seedlings in a dose-dependent manner. Again, it was verified that H2S, rather than other sulfur-containing components or sodion derived from NaHS solution, should contribute to the positive role in promoting wheat seedlings against heat stress. To further study antioxidant mechanisms of NaHS-induced heat tolerance, superoxide dismutase (SOD, EC 1.15.1.1), catalase (CAT, EC 1.11.1.6) and ascorbate peroxidase (APX, EC 1.11.1.11) activities, and H2S, hydrogen peroxide (H2O2), malonaldehyde (MDA), and soluble sugar contents in wheat seedlings were determined. The results showed that, under heat stress, the activities of SOD, CAT, and APX, H2S, H2O2, MDA, and soluble sugar contents in NaHS-pretreated seedlings and its control all increased. Meanwhile, NaHS-pretreated seedlings showed higher antioxidant enzymes activities and gene expression levels as well as the H2S and soluble sugar levels, and lower H2O2, MDA contents induced by heat stress. While little effect was detected in antioxidant enzymes activities and soluble substances contents in pretreated wheat seedlings compared with its control under normal culture conditions (data not shown). All of our results suggested that exogenous NaHS could alleviate oxidative damage and improve heat tolerance by regulating the antioxidant system in wheat seedlings under heat stress.

Measurement of Low Hydrogen Sulfide Concentrations in the Coastal Area Near the Ulsan Industrial Complex

Measurement of Low Hydrogen Sulfide Concentrations in the Coastal Area Near the Ulsan Industrial Complex

Ultrastructural changes in epithelial cells of rats exposed to low concentration of hydrogen sulfide for 50 days

ABSTRACTHydrogen sulfide (H2S) and other volatile sulfur compounds (VSCs) appear mainly in the oral air of patients with halitosis. It seems that VSCs are directly involved in the pathogenesis of gingival diseases. In previous studies, short-term (7 hours–4 days), high concentrations (5–400 ppm) of H2S applications on periodontal tissues have been evaluated in a culture medium. The aim of the present study was to investigate the potential effects of lower (equivalent to halitosis) concentrations of H2S on rat gingival tissue for longer-term inhalation. The threshold level of pathologic halitosis perceived by humans at 250 ppb of H2S was converted to rat equivalent concentration (4.15 ppm). Rats in the experimental (H2S) group (n=8) were exposed to H2S continuously but not the control rats (n=8). After 50 days, the gingival sulcular tissue samples of each rat were taken and examined using transmission electron microscope. Ultrastructural changes in the sulcular epithelia of the rat gingiva showed deformation of celullar shape, vacuolization, and disintegrity of intercelullar connection by loss of desmosomes and collagen fibrils. No basal membrane damage was observed. Inhalation of low levels of H2S (equivalent of halitosis) in the oral environment causes ultrastructural celullar damages in rat sulcular mucosa. These results suggest that halitosis may be the potential reason for periodontal destruction in humans.

Structural changes in periodontium of rats exposed to a low concentration of hydrogen sulfide for 50 days

The aim of the present study was to investigate the effect of H2S inhalation at a low concentration (at human equivalent dose of pathologic halitosis) on rat periodontium over a long term (50 days). The threshold level of pathologic halitosis perceived by humans at 250 ppb of H2S was converted to rat equivalent concentration (4.15 ppm). Rats in the experimental (H2S) group (n = 8) were exposed to H2S continuously but not the control rats (n = 8). After 50 days, periodontal tissue samples were taken from the mandibular first molar region and examined histopathologically to determine inflammatory cell infiltration (ICI), osteoblastic activities, number of osteoclasts, and resorption lacunae. Sulcular epithelium layer destruction was observed in the H2S group. Frequency of ICI was significantly higher in the H2S group compared to the control group ( P &lt;0.05). The number of osteoclasts were found significantly higher in the H2S group (34.28 ± 3.28) compared to the control group (8.85 ± 1.85) ( P &lt;0.05) and the number of resorption lacunae were also higher in the cementum tissue (6.1 ± 2.4) and alveolar bone (3.8 ± 1.5) versus their corresponding control groups (1.6 ± 0.5 and 1.4 ± 0.5, respectively) ( P &lt;0.05). There were no statistically significant differences between the two groups with regard to osteoblastic activity. H2S inhalation induces inflammatory changes in the periodontium as well as resorption of the alveolar bone and cementum tissue in rats. These histopathologic changes in periodontal tissues support the idea that long-term H2S inhalation may have a destructive effect on periodontal tissues.

Transdermal Detection of Low Concentrations of Hydrogen Sulfide

We report here a novel approach to measure circulating hydrogen sulfide (H2S) non‐invasively as a potential way to diagnose and monitor endothelial dysfunction and peripheral artery disease (PAD). PAD is a life‐threatening condition caused by arterial constriction and obstruction of blood flow leading to limb ischemia. Current methods to diagnose and monitor PAD lack sensitivity, result in frequent false‐negatives, and require specialized technicians. Recent studies indicate that decreased H2S production is an underlying cause of PAD. In addition, reduced plasma H2S correlates with endothelial dysfunction in untreated hypertension, diabetes, sleep apnea and other cardiovascular diseases. Conversely, excess H2S is cytotoxic causing irreversible damage to mitochondrial function. Therefore, careful monitoring of plasma H2S levels is essential to diagnose and treat vascular disease and to prevent H2S toxicity. This device was designed to measure H2S at the surface of the skin to test the hypothesis that the diffusion rate (and therefore gas phase concentration) of H2S is directly proportional to the concentration of H2S in the blood. Our results demonstrate that the device is sensitive enough to detect H2S at 10 part per billion (ppb) or lower in gas standards and in the headspace of a 3 nM solution of Na2S (H2S donor). In vitro studies used excised rat skin superfused on the subcutaneous surface with a H2S solution. H2S was detected in a stream of N2 gas flowing through a sealed chamber on the epidermal side both by GC/MS measurement and with the sensor only when the superfusing solution contained an H2S donor demonstrating that H2S diffuses through the skin. The diffusion rate of H2S through excised abdominal skin from a male Sprague‐Dawley rat is approximately 1.42×10−9 μmol/s/cm2/μM. The device also detected increases in H2S on the skin surface in anesthetized rats within seconds of intra‐venous injection of Na2S at doses that caused a fall in arterial pressure, with an estimated average diffusion rate of 4×10−8 μmol/s/cm2/μM. Therefore, this noninvasive, highly‐sensitive and portable device has the potential to transform diagnosis and monitoring of early stage PAD and to monitor H2S biosynthesis or exposure in vivo.

계사 및 우사 내 암모니아 및 황화수소 노출농도 평가

Objectives: There are many hazardous agents at livestock farms. In particular, gases can be detrimental to both workers and animals. This study evaluated ammonia and hydrogen sulfide concentrations in broiler hen barns and beef cattle barns according to sampling location and height. Methods: Three broiler hen barns and three beef cattle barns were selected for gas monitoring in this study. Ammonia and hydrogen sulfide concentrations were measured using a direct-reading instrument which could measure the target gases simultaneously. Gas monitoring was conducted at human breathing height and animal breathing height at three points in each livestock farm. Results: Ammonia concentrations at the broiler hen barns ranged from 3.3 to 12.5 ppm by sampling location and height, but hydrogen sulfide was not detected. In the beef cattle barns, ammonia ranged from 3.1 to 16.3 ppm and low concentrations of hydrogen sulfide were detected at some animal breathing heights. The gas concentrations detected at each livestock farm were significantly higher in the animal breathing zones than in human breathing zones (p<0.0001). Conclusions: We found a difference in gas concentrations between human breathing zones and animal breathing zones. Gas monitoring should be conducted to improve the related environment considering both workers' and animals' health and safety.