Hydrogen Sulfide Concentrations Research Articles

The Optimization of Sulphide Oxidizing Bacteria (SOB) for Oil Corrosivity Reduction at Indramayu Coast, The Northern Coastal Area of West Java

Highlight Research First NR-SOB from Indramayu coast was successfully isolated and identified. Bactrerial characterization morphologically and biochemically, foster with in situ hybridization confirm the isolate was Thiobacillus denitrificans, and Arcobacter sp. Both isolate, Thiobacillus denitrificans and Arcobacter sp., were able to grow in sulphide rich environment in the presence of essential nutrient Thiobacillus denitrificans and Arcobacter sp. exhibit an outstanding sulphide oxidation ability up to 100% in the presence of nitrate. Abstract Crude oil production triggers the formation of hydrogen sulphide, also known as souring, which is extremely toxic and corrosive to the environment. It additionally give an adverse consequence to aquatic, terrestrial, and human existence. Studies of hydrogen sulphide reduction in sediments polluted by crude oil have been carried out recently to investigate the capability of indigenous Nitrate-Reducing Sulphide Oxidising Bacteria, hereinafter referred to as NR-SOB, as bioremediation agents. The experiments utilised hydrogen sulphide with 200 µM concentration combined with NO3 with different concentrations of 100 µM, 200 µM, and 300 µM. Measurements of the hydrogen sulfide concentrations were observed up to 48 hours within the experimental period. The SOB used in this study were taken from Balongan Bay at Indramayu coast using Nansen bottle to carry out water sample. The sulphide-oxidising ability of SOB was then evaluated at room temperature in control environment. Methylene blue method was applied to monitor the sulphide concentration. The results showed a complete removal of hydrogen sulphide concentrations in 48 hours accompanied with gradual drops of nitrate in all experiment series. Sulphide oxidation rate was detected to appear between 6.8 and 10.2 fmol/cell/hour. Measurements of cell abundance after 48 hours showed 6.2 x 105, 7.5 X 105, and 8.2 X 105 cell/ml from Experiments I, II, and III respectively. Using MSS selective medium, the bacteria were identified as Thiobacillus denitrificans and Arcobacter sp. Overall, the isolated NR-SOB from the coast of Balongan Bay, Indramayu proves to be a promising candidate for sulphide controls and mitigation.

Effect of feeding gas type and nitrogen: Sulfur ratio on a novel sulfide-driven denitrification methane oxidation (SDMO) system

To save treatment costs of nitrogen-polluted water, a novel sulfide-driven denitrification methane oxidation (SDMO) system, which integrated autotrophic denitrification (AD) and denitrification anaerobic methane oxidation (DAMO) to simultaneously realize wastewater denitrification and biogas utilization in situ, has been operated. In this work, nine groups V0—V8 were derived from a mature SDMO reactor which already enriched AD and DAMO microorganisms. Batch tests about them were proceeded to investigate the effect of feeding gas type and N/S ratio on kinetic performance, microorganism community structure, and functional genes. Results showed as N/S rising up from 2.3 to 23.3, the nitrate removal efficiency decreased from 100 % to 15.4 % but its contribution by DAMO/AD ratio increased from 0.5 to 2.2. Biogas serving as feeding gas enhanced nitrate removal efficiency to 100 % at most in group V3 (N/S = 2.3, H2S = 1.5 %) whereas DAMO and AD contribution for nitrate removal was 33.1 % and 65.6 % respectively. Low H2S content gave little effect on microorganism community structure but high hydrogen sulfide content decreased the abundance of DAMO bacteria Candidatus Methylomirabilis to ∼ 4 % and increase abundance of AD bacteria Thiobacillus to > 20 %. Comparing with V1 feeding with methane, nitrate reduction genes napA, narG, nirK, nirS, cnorB and sulfide oxidation gene soxB up-regulated to > 3.0 × 109 copies/g in HS groups (biogas with high H2S content > 1 %) while gene pmoA up-regulated to ∼ 1.0 × 109 copies/g in LS groups (biogas with low H2S content < 1 %). This study provided more comprehensive understanding for the effect of feeding gas type and N/S ratio on SDMO system.

Stability and structure of platinum sulfide complexes in hydrothermal fluids

Knowledge of the chemical speciation of platinum and the solubility of Pt-bearing minerals in hydrothermal fluids is required to assess Pt transport, remobilization and concentration in the Earth’s crust. In this study, we combined PtS(s) solubility measurements in a hydrothermal reactor allowing fluid sampling, in situ X-ray absorption spectroscopy, and first-principles molecular dynamics simulations to systematically investigate the structure, composition and stability of Pt sulfide complexes in model aqueous H2S-bearing solutions up to 300 °C and 600 bar. The results demonstrate that tetrahydrosulfide, PtII(HS)42–, is the major Pt-bearing complex in aqueous solutions saturated with PtS(s) over a wide range of dissolved hydrogen sulfide concentrations, from < 0.2 to ∼ 2 molal. The equilibrium constants of the dissolution reaction of PtS(s) generated in this study, PtS(s) + 3 H2S(aq) = Pt(HS)42– + 2 H+ (β4), are described by the equation log10β4 = 0.9 × 1000/T(K) – 19.7 (± 0.5) over the temperature range 25–300 °C and pressure range Psat–600 bar. Furthermore, the stepwise formation constants of four PtII-HS complexes, Pt(HS)+, Pt(HS)20, Pt(HS)3–, and Pt(HS)42–, were estimated, for the first time, from molecular dynamics simulations. The generated constants indicate that the maximum solubility of platinum in the form of Pt(HS)42– in reduced H2S-dominated hydrothermal fluids at moderate temperatures (≤ 350 °C) is close to 1 ppb Pt at near-neutral pH of 6–8 and hydrogen sulfide concentrations of 0.1 molal. Although this solubility is much greater than that of Pt-Cl, Pt-OH and Pt-SO4 complexes at such conditions, it is yet too low to account for significant Pt transport in most shallow-crust hydrothermal settings, characterized by the presence of both sulfide and sulfate. Complexes with S-bearing ligands, very likely other than H2S/HS–, such as S3–, would be required to account for Pt hydrothermal mobility. Our results provide a basis for more systematic future studies, using combined approaches, of the role of hydrothermal fluids in the behavior of platinum group elements in nature.

Air Quality Monitoring: Co, Co2, H2s Gases

Objetive: to evaluate the concentration levels of CO, CO2 and H2S in the air in different areas of the district of Alto Selva Alegre and to elaborate a diffusion map of the concentration levels of these gases in the air, with the purpose of proposing air quality mitigation plans for the concentration of gases. Theoretical framework: air quality is affected by the emission of different gases into the atmosphere by both anthropogenic and natural activity. Method/design/approach: used in the gas monitoring involved the use of Aeroqual S500 digital portable equipment at 09 points distributed in the areas with the highest vehicular traffic. At each monitoring point, the concentration levels of the three gases were recorded and then compared between the morning and afternoon hours. Results and conclusion: The results showed that: Chilina-Cayma Bridge crossing, presents a higher concentration of carbon monoxide and hydrogen sulfide, registering an average 4453.50 μg/m3 in 8 hours and average 37.75 μg/m3, respectively. In Brazil-Commissariat Avenue, there is a higher CO2 concentration, registering an average 262.86 mg/m3. The maps of CO, CO2 and H2S concentration diffusion show variations between zones and sampling hours (morning and afternoon). It is concluded that the presence of gases generates consequences on people's health. Research implications: Analysis of gas concentrations influencing air quality and their effect on human health Originality/value: Maps of the behavior of gases that affect air quality as a result of the activity of the vehicle fleet.

Increasing Drilling Speed by Absorption and Hydraulic Supercharging of Drill String in Formation Containing Hydrogen Sulfide: A Case Study

Increasing drilling speed and shortening the well construction period are the goals of the drilling field. The use of downhole speed-up tools has been noted for its advantages such as no additional cost, no change in drilling equipment and no impact on normal drilling operations. However, conventional downhole speed-up tools cannot meet the needs when the drilled formation contains hydrogen sulfide. Then, the technology test on increasing drilling speed by absorption and hydraulic supercharging of drill string in hydrogen sulfide formation was carried out in well Wanweiye1 (WWY1), Anhui Province, China. The results show that: firstly, the speed-up device by absorption and hydraulic supercharging of drill string can be used in the formation containing hydrogen sulfide, and can still perform normal drilling operations with a hydrogen sulfide concentration of 567 ppm; secondly, the speed-up technology by absorption and hydraulic supercharging of drill string has a significant speed-raising effect in the region containing hydrogen sulfide and can raise the speed by 62.5% to 92.05%; thirdly, the speed-up device by absorption and hydraulic supercharging of drill string can meet the needs of high density killing fluid. Once the well WWY1 suffered an overflow, the device did not affect the killing operation when the killing fluid density reached 2.2 g/cm3 and killing time reached 104.8 h.

Protective mechanisms of sulfur against arsenic phytotoxicity in Brassica napus by regulating thiol biosynthesis, sulfur-assimilation, photosynthesis, and antioxidant response

The contamination of agricultural soils with Arsenic (As) is a significant environmental stress that restricts plant growth, metabolism, and productivity worldwide. The present study examined the role of elemental sulfur (S0) in protecting Brassica napus plants from Arsenic (As) toxicity. Arsenic (100, and 200 mg As kg−1 soil) in soil caused detrimental effects on five Brassica napus cultivars (Neelam, Teri-Uttam Jawahar, Him Sarson, GSC-101, and NUDB 26–11). The As toxicity inhibited the growth and photosynthesis indices in all cultivars with more deterioration effects in NUDB 26–11. Plant absorption and uptake of As caused the generation of oxidative injury by accumulating the reactive oxygen species (ROS), which simultaneously decreased the plant defence capability and ultimately the photosynthesis. Application of sulfur (S0, 100 or 200 mg S kg−1 soil) alleviated the negative impacts and toxicity of As on the photosynthesis and growth matrices of plants, especially under high S level. S0 also boosted the antioxidant potential of plants and toned-down lipid peroxidation and ROS aggravation such as superoxide anion (O2•−) and H2O2, hydrogen peroxide, in As affected plants. In general, S0 at 200 mg kg−1 soil more perceptibly increased the functionality of antioxidant enzymes, and non-enzymatic antioxidants, metal chelators and non-protein thiols. Further amendment of soil with S0 at fifteen days before seed sowing affected by As-induced toxic effects (added to soil at the time of sowing) considerably intensified the endogenous hydrogen sulfide (H2S) content and its regenerating enzymes D-cysteine desulfhydrase (DCD) and L-cysteine desulfhydrase (LCD) that further strengthened the defense capability of plants to withstand As-stress. Our results suggest the role of H2S in the S-induced defense operation of the B. napus plants in restraining As toxicity. The current study shows that S0 as a source of S might be used to promote the growth of B. napus plants in polluted agricultural soils.

Depth Profiles of Dissolved Oxygen (DO) and Hydrogen Sulfide (H2S) Concentration in a Tropical Freshwater Reservoir

This study aims to determine the profile of dissolved oxygen and H2S based on depth in the Jatiluhur Reservoir related to fish culture in floating net cages. The scope of this research is focused on the location of floating net cage cultivation. Dissolved oxygen distribution is classified as a positive heterograde type where dissolved oxygen levels higher in the metalimnion layer due to the photosynthesis process that occurs effectively by aquatic plants and phytoplankton. Jatiluhur Reservoir shows signs of organic pollution, with BOD5 and COD levels exceeding the quality standard. This organic substance comes from the waste of floating net cages. BOD5 and COD values that exceed the quality standard result in increased oxygen consumption during the decomposition process; therefore, a hypoxic layer occurs. This occurrence can cause water conditions to become anoxic, producing H2S gas. The H2S value in the Jatiluhur Reservoir was observed to exceed 0.002 mg/L and showed an increase in the metalimnion layer.

Identification of sulfur–oxidizing Thiothrix bacteria on microcrustaceans from the sulfidic groundwaters of Mangalia (southeastern Romania)

Movile Cave, located in southeastern Romania close to the Black Sea, is one of the most remarkable diversity hotspots worldwid with 52 species of invertebrates of which 37 are endemic (Brad et al. 2021). Due to the high concentration of hydrogen sulfide in its water, the primary production of organic matter in Movile Cave relies almost entirely on the chemoautotrophic activity of microorganisms, notably sulfur-oxidizing gammaproteobacteria belonging to the genus Thiothrix. In the presence of oxygen, these filamentous bacteria can oxidize hydrogen sulfide and reduce it into various sulfidic compounds, generating energy in the process. In sulfidic ecosystems, Thiothrix bacteria are frequently found free-living but also as epibionts or ectosymbionts growing on other organisms, such as amphipods (Flot et al. 2014). However, it is unclear whether Thiothrix bacteria also grow on microcrustaceans such as copepods or ostracods, of which several species are known from the sulfidic mesothermal aquifer of Mangalia, where Movile Cave is located. To find it out, we combined DNA sequencing using the reference bacterial 16S ribosomal RNA gene with morphological observations (including fluorescence microscopy). Our results reveal that Thiothrix bacteria are indeed present on microcrustaceans from Movile Cave and surrounding wells in the Mangalia region, highlighting the versatility of Thiothrix-crustacean associations in sulfidic ecosystems. This is the first report of an association between Thiothrix and groundwater microcrustaceans, and the second report of an association between Thiothrix and a nonmarine ostracod (Khalzov et al. 2021).

Enhancement of methanogenic activity by micronutrient control: Micronutrient availability in relation to sulfur transport

The main purpose of this research was to clarify the influence of the addition of iron (Fe) alone (0–100 mg/L) or 50 mg/L of Fe with 2 mg/L each of cobalt (Co), copper (Cu) and nickel (Ni) on the methanogenic activity of a mesophilic two-stage UASB system treating ethanol wastewater at a fixed chemical oxygen demand (COD) loading rate of 16 kg/m3/day under a continuous mode of operation and steady state condition. The addition of Fe provided the dual benefits of a reduction in both the dissolved sulfide and the hydrogen sulfide (H2S) content in produced gas, resulting in marginally improved hydrogen (H2) and methane (CH4) productivities. When the Fe dosage was increased beyond the optimum value of 50 mg/L, the process performance drastically declined, as a consequence of the high total volatile fatty acid (VFA) concentrations that inhibited both the acidogens and methanogens predominantly present in the 1st and 2nd reactors, respectively. The chemical precipitation of iron sulfide was responsible for the reduction of produced H2S in both the aqueous and gaseous phases as well as the minimization of added amounts of all other micronutrients to fulfil the sufficiency of all micronutrients for anaerobic digestion (AD). The addition of 2 mg/L each of Co, Cu and Ni together with 50 mg/L Fe resulted in the greatest enhancement in process performance, as indicated by the improved CH4 yield (mL/g COD applied) to about 42.3%, compared to that without micronutrient supplement.

Synthesis of refinery desulfurization solvent network with multi-stage solvent regeneration

Increasing process of sour crude oil and demand of low-sulfur oil products expand the desulfurization units in refineries, which raises the desulfurization solvent circulation as well as the energy cost for solvent regeneration. In this work, synthesis of desulfurization solvent network with multi-stage solvent regeneration is investigated to reduce the energy cost. Firstly, this work presents superstructures for desulfurization solvent network with regeneration considering one-stage structure, two-stage cascaded structure, and two-stage parallel structure, respectively. Next, mathematical models for the three cases are formulated as nonlinear programming problems where the objective function aims to minimize the total energy consumption. Finally, a case study is conducted to illustrate the proposed method. The results show that the two-stage structures reduce more energy costs than the one-stage structure by 7.65% and 8.46%, respectively, which means that two-stage regeneration is more attractive. Besides, the parallel structure is better than the cascaded structure, because the energy requirement for solvent regeneration is more sensitive to the outlet concentration of hydrogen sulfide than the inlet concentration.

Feasibility of hydrogen storage in depleted hydrocarbon chalk reservoirs: Assessment of biochemical and chemical effects

Hydrogen storage is one of the energy storage methods that can help realization of an emission free future by saving surplus renewable energy for energy deficit periods. Utilization of depleted hydrocarbon reservoirs for large-scale hydrogen storage may be associated with the risk of chemical/biochemical reactions. In the specific case of chalk reservoirs, the principal reactions are abiotic calcite dissolution, acetogenesis, methanogenesis and biological souring. Here, we use PHREEQC to evaluate the dynamics and the extent of hydrogen loss by each of these reactions in hydrogen storage scenarios for various Danish North Sea chalk hydrocarbon reservoirs. We find that: (i) Abiotic calcite dissolution does not occur in the temperature range of 40-180° C. (ii) If methanogens and acetogens grow as slow as the slowest growing methanogens and acetogens reported in the literature, methanogenesis and acetogenesis cannot cause a hydrogen loss more than 0.6% per year. However, (iii) if they proceed as fast as the fastest growing methanogens and acetogens reported in the literature, a complete loss of all injected hydrogen in less than five years is possible. (iv) Co-injection of CO2 can be employed to inhibit calcite dissolution and keep the produced methane due to methanogenesis carbon neutral. (v) Biological sulfate reduction does not cause significant hydrogen loss during 10 years, but it can lead to high hydrogen sulfide concentrations (1015 ppm). Biological sulfate reduction is expected to impact hydrogen storage only in early stages if the only source of sulfur substrates are the dissolved species in the brine and not rock minerals. Considering these findings, we suggest that depleted chalk reservoirs may not possess chemical/biochemical risks and be good candidates for large-scale underground hydrogen storage.

Вплив компонентів газових викидів на ріст мікроводоростей Chlorella vulgaris

The annual growth of environment anthropogenic impact, in particular, the increase of gaseous emissions amount leads to the need of their disposal. A promising solution for this problem may be the use of microalgae to absorb carbon dioxide and oxides of nitrogen and sulfur. It is important to determine the cultivation conditions for further establishment of rational parameters for the gaseous emissions disposal, which will increase the profitability of the process, reduce environmental pollution and obtain biomass for further use. The aim of the work is to analyze studies of the gaseous components impact on the growth and development of microalgae Chlorella vulgaris. The task is to determine the effect of oxides of carbon, nitrogen, sulfur and gaseous emissions on the growth and development of microalgae Chlorella vulgaris. The typical composition of gaseous emissions from a coal-fired thermal power plant based on water vapor, oxides of carbon, nitrogen, and sulfur, which can be assimilated by microalgae cells, is considered. Carbon dioxide in this mixture is 12±2 %, which is a rational concentration for growing biomass of adapted strains. However, when applying a high concentration of CO2 to the culture medium, it is necessary to stabilize the pH, because increasing the carbon dioxide content in the culture medium leads to acidification, while the consumption of CO2 by microalgae in photosynthesis increases the pH value. It is determined that nitrogen oxides, the main part of which is NO, in concentrations up to 100 ppm contribute to the accumulation of biomass and synthesis of nutrients in cells. It is necessary to reduce the concentration of sulfur oxides to 60–100 ppm and avoid their gradual accumulation, as this leads to acidification of the environment and cell death. When using Chlorella vulgaris to purify biogas from CO2 and H2S, the concentration of hydrogen sulfide should not exceed 100 ppm to eliminate its inhibitory effect on cell growth.

Hydrogen Sulfide Mitigates Chilling Injury of Postharvest Banana Fruits by Regulating γ-Aminobutyric Acid Shunt Pathway and Ascorbate-Glutathione Cycle.

This study aimed to determine the effect of hydrogen sulfide on chilling injury (CI) of banana (Musa spp.) during cold storage (7°C). It was observed that hydrogen sulfide application (2 mmol L–1) markedly reduced the CI index and showed significantly higher chlorophyll contents, along with suppressed chlorophyll peroxidase and chlorophyllase enzyme activity. The treated banana fruits exhibited substantially higher peel lightness (L*), along with significantly a lower browning degree and soluble quinone content. The treated bananas had substantially a higher endogenous hydrogen sulfide content and higher activity of its biosynthesis-associated enzymes such as D-cysteine desulfhydrase (DCD) and L-cysteine desulfhydrase (LCD), along with significantly lower ion leakage, lipid peroxidation, hydrogen peroxide, and superoxide anion concentrations. Hydrogen sulfide-treated banana fruits showed an increased proline content and proline metabolism-associated enzymes including ornithine aminotransferase (OAT), Δ1-pyrroline-5-carboxylate synthetase (P5CS), and proline dehydrogenase (PDH). In the same way, hydrogen sulfide-fumigated banana fruits accumulated higher endogenous γ-aminobutyric acid (GABA) due to enhanced activity of glutamate decarboxylase (GAD) and GABA transaminase (GABA-T) enzymes. The hydrogen sulfide-treated fruits exhibited higher total phenolics owing to lower polyphenol oxidase (PPO) and peroxidase (POD) activity and stimulated phenylalanine ammonia lyase (PAL). The treated banana exhibited higher ascorbate peroxidase (APX), catalase (CAT), glutathione reductase (GR), dehydroascorbate reductase (DHAR), monodehydroascorbate reductase (MDHAR), and superoxide dismutase (SOD) activity, along with higher glutathione (GSH) and ascorbic acid (AsA) concentrations and a significantly lower dehydroascorbic acid (DHA) content. In conclusion, hydrogen sulfide treatment could be utilized for CI alleviation of banana fruits during cold storage.

Bacterial Proliferation Reduces Sulphur Toxicity in Stabilization Ponds: Safer Water Resources by Photosynthesis

Background: Studies suggest that sulfur may react with plants or monocellular organisms, such as fungi, to produce toxic agents. It has been theorized that sulfur enters cells and affects their respiration. This study reports on a phototroph development that leads to the diminution and/or production of sulfur and release of hydrogen sulfide from public ponds. Methods: This study was conducted in anoxic stabilization ponds at a dimension of 1×0.25×1 (m), with a hydraulic retention time of 6 days. The ponds’ water was tested during the dark and light cycles. The experiments were carried out by factorial design and measured three variables: volumetric organic loading, sulphate concentrations and temperature. Results: Cyanobacteria and Rhodobacter species were the most abundant phototroph cellular organisms. The mean value of total sulfur and un-ionized hydrogen sulfide concentration were 74 mg/L and 21 mg/L, respectively, at the volumetric organic loading of 100 g BOD5/m3 per day. The efficiencies of biochemical and chemical oxygen removal were 71.9% and 59.1%, respectively. The mean proliferation rate of photosynthetic sulfur bacteria was 3.4×106 cells/ml. Conclusion: photosynthetic sulfur bacteria significantly reduced the sulfur concentration generated in the ponds. The illumination of bright light enhanced the sulfur reduction by the photosynthetic sulfur bacteria in the wastewater of the anoxic stabilization ponds.

ACTIVITY OF NITRO-OXIDATIVE PROCESSES IN PREGNANT WOMEN WITH IDIOPATHIC ARTERIAL HYPOTENSION

Primary violation of vascular tone and reactivity is considered the main hemodynamic link in the pathogenesis of idiopathic arterial hypotension (IAH). Two gaseous messengers - nitric oxide (NO) and hydrogen sulfide (H2S) play an important role in the regulation of vascular tone.&#x0D; The research aims at determining the state of the NO system and the level of H2S in women with IAH and their effect on the uteroplacental blood flow.&#x0D; Material and Methods. A number of 20 pregnant women with IAH at 40-41 weeks of gestation were examined (group I); the second group included 20 pregnant women with normotony at 39-40 weeks of gestation. The concentration of the complex of nitrates and nitrites was determined by the reaction of formation of a colored complex by Griss reagent. The content and production of peroxynitrite in alkali and alkaline earth metals were determined according to the procedure described by Vanuffelen et al. Detection of hydrogen sulfide content in blood plasma was performed by the method of Dombkowski et al. Studies of uteroplacental blood flow were performed on ultrasonic diagnostic device "SA-8000 EX" using color Doppler mapping and pulse mapping dopplerometry of the blood flow in the uterine arteries (UA). The assessment of blood flow velocity curves was carried out by determining the pulsation index (PI) in both arteries taking into account the average value.&#x0D; Results. The results of the study showed that an average level of nitrites and nitrates in pregnant women with IAH was 37.0% higher than in women with normotension, and peroxynitrite values were 2.4 times higher, respectively. In contrast, the concentration of H2S in pregnant women with IAH was almost 1.4 times lower, than in pregnant women with normal blood pressure. Doppler study of blood flow indices in UA showed a moderate increase in PI in 28.0% of pregnant women with IAH. Thus, indices of vascular resistance in UA of pregnant women with IAH were higher, on average, by 19.0% than in pregnant women with normotension.&#x0D; Conclusions. High levels of nitrites and nitrates in pregnant women with IAH form the basis for the development of nitrosatous stress, which is accompanied by increasing concentration of highly toxic peroxynitrite. Significant increase in peroxynitrite is one of the causes of endothelial dysfunction. In pregnant women with IAH due to the low content of H2S - its vasoconstrictive effects are prevalent, which may indicate an indirect interaction between both of these systems of vasoregulation.

Effect of Fungal, Bacterial and Alkaline Augmentations on the Biogas Composition of Selected Plant-based Substrates

Lignocellulosic residues are interesting sources of renewable energy, if only their biomass recalcitrance could be reduced through appropriate pretreatment technologies and augmentations, to enhance anaerobic digestion. This study aimed at assessing the effects of bacterial, fungal and alkaline augmentations, on the biogas composition of selected plant-based substrates, namely: maize cob , rice straw and water hyacinth. Standard methods were adopted; the substrates were mechanically pretreated, loaded in single, dual and composite combinations, into five 54 L capacity metallic batch anaerobic digesters. Codigestion was encouraged with the addition of cow rumen waste. The set ups were allowed to run for 42 days under mesophilic conditions, while stirring daily. The biogas composition namely: methane, carbon IV oxide and hydrogen sulfide concentrations were measured on the 42nd day. The results showed that the composite with the combined treatments showed the highest concentration of methane (87%), followed by the composites with fungal augmentation (80%), bacterial (77%) and then alkaline (75%) augmentations. The least percentage of methane (9%) was recorded in the composite without treatment and no cow rumen waste added, which also had the highest percentages of hydrogen sulphide and carbon IV oxide. To improve the yield and quality of biogas generated from a lignocellulosic biomass, appropriate pretreatment strategies and augmentations are required.

Stimulation of the endogenous hydrogen sulfide synthesis restores constitutive nitric oxide synthesis and endothelium-dependent vasodilation in old rats

Abstract Funding Acknowledgements Type of funding sources: None. Introduction Hydrogen sulfide (H2S) is a gas transmitter of endogenous origin, which has an important regulatory function in the human body. Endogenous H2S is synthesized by three enzymes, cistationine-β-synthase (CBS), cistationine-γ-liase (CSE), and 3-mercaptopyruvate sulfurtransferase (3-MTS), which is coupled to the activity of cysteine aminotransferase (CAT). CAT, CBS, and CSE are pyridoxal-5- phosphate (PLP)-dependent enzymes. It is known that with age the exchange of hydrogen sulfide is disturbed against the background of increasing oxidative and nitrosative stress. At the same time there is a decrease of constitutive synthesis of nitric oxide (NO). Recent studies show that hydrogen sulfide closely interacts with the NO system. Activation of H2S biosynthesis and restoration of its pools in tissues of old animals may be a promising direction of cardiovascular disease prevention. The aim of the current work was to study the effect of H2S-synthesizing enzymes cofactor pyridoxal-5-phosphate (PLP) on the endothelium-dependent relaxation of smooth muscle vessels in old rats, as well as the H2S content and cNOS activity in aortic tissues. Methods Old rats (22-24 months old) were PLP administered per os in dose of 0,7 mg per kg daily for 2 weeks.The content of hydrogen sulfide, activity of cNOS and iNOS was measured in aortic tissues.Vascular reactions were determined in experiments on isolated aortic strips. To clarify the role of either NO or H2S in the endothelium-dependent vasorelaxation, N-nitro-L-arginine methyl ester hydrochloride (L-NAME) (Sigma, USA, 27 mg/kg) or O-carboxymethylhydroxylamine (O-CMH) (50 mg/kg) (Sigma, USA) was injected intraperitoneally 30 min before sacrificing. Results We showed that the H2S content was 1.6 times lower in old rat aorta compared to adult ones. PLP administration for 2 weeks induced a significant increase of H2S content in aortic tissue of old rats (P&amp;lt;0.05). It was found that with aging, the activity of cNOS decreases by 3 times, and the stimulation of endogenous Н2S leads to an increase in the activity of this enzyme in the aortic tissues by 2.1 times as compared with those in old animals. At the same time, the activity of the iNOS enzyme with aging increases by 3.8 times, and after the introduction of PLP, it decreases almost halved. Also shown, that PLP significantly improved endothelium-dependent aortic smooth muscle relaxation in old rats. The amplitude of acetylcholine-induced relaxation which was significantly reduced in old rats was increased more than 2.5-fold. This effect was reversed by inhibitors of NO-synthase and 3-mercaptopyruvate sulfurtransferase indicating the involvement of NO and H2S in the improved endothelium-dependent vascular relaxation. Conclusions Thus, H2S acts as a regulator of the NO system that increases cNOS activity and NO synthesis in aortic tissue, which improves endothelium-dependent relaxation of aortic smooth muscle in aged rats.

Links of Hydrogen Sulfide Content With Fluid Components and Physical Properties of Carbonate Gas Reservoirs: A Case Study of the Right Bank of Amu Darya, Turkmenistan

Hydrogen sulfide (H2S) in carbonate gas reservoirs shows strong relevance with the natural gas components and has an obvious impact on reservoir types and their petrophysical properties. In this work, core and fluid samples were collected from the Right Bank of Amu Darya reservoirs, Turkmenistan. Then, fluid composition analysis and flash evaporation experiments were performed to investigate the components of reservoir fluid. Petrophysical properties, that is, porosity and permeability, and micropore structures of cores were determined by permeameter–porosimeter and scanning electron microscope (SEM) analysis, respectively. Results in this work indicate that the H2S content shows obvious relevance to fluid components in carbonate gas reservoirs. With the increase of H2S content, the total heavy hydrocarbons and potential condensate content decrease, while the condensate density increases. In addition, at higher H2S content, larger pore and vug porosity was observed. However, in reservoirs with lower H2S content, the matrix pores are relatively tight and prone to develop fractures. Furthermore, sulfate thermochemical reduction (TSR) is found to be the dominant contributor to high H2S content in carbonate reservoirs through material and thermodynamic condition analysis. The Gibbs free energy and normalized hydrocarbon content show that the consumption of heavy hydrocarbons generally increases with carbon numbers during TSR, but reaches a minimum at the components of C7 to C9. Finally, the relationship between TSR and rock petrophysical properties was discussed, indicating that pore volume enlargement and the dissolution effect of acidic gases are the main mechanisms for TSR to improve carbonate reservoir property. Results in this study present comprehensive analyses of the links between H2S content and fluid components and petrophysical properties in carbonate gas reservoirs.

Integrating transcriptome and physiological analysis to reveal the essential responses of Daphnia magna to antimony trioxide nanoparticle

Antimony (Sb) pollution has already posed a severe threat to the aquatic ecosystem. However, the toxicity mechanisms of Sb on aquatic organisms are far from being elucidated. One of the crucial questions remaining unresolved is the characterization of molecular toxicity of Sb(III). Transcriptomics profiling combined with physiological characterizations was applied to investigate the response of Daphnia magna to nano-size antimony trioxide (nATO) and its soluble Sb(III) counterpart antimony potassium tartrate (APT) in the present study. Both nATO and APT induced the formation of oxidative stress, enhanced the activities of anti-oxidative enzymes, altered the metabolism of xenobiotics, increased the concentration of hydrogen sulfide (H2S) and nitric oxide (NO), and triggered the self-protection mechanisms such as ubiquitin-mediated proteolysis. In addition, nATO and APT caused damage to the nervous system of D. magna, inhibited its locomotion and nutrient uptake in a concentration-dependent manner. Moreover, nATO exposure enhanced the autophagy activity, reflected by the up-regulated expression of hypoxia-inducible factor-1α, calmodulin-dependent protein kinase-β, and inositol-requiring enzyme 1. The present study, for the first time, depicted a global map of cellular response to nATO, provided essential information on Sb(III) toxicity to aquatic organisms, and is of great significance to the development of Sb management strategies.

Real-time methods of hydrogen sulfide detection

A comparative analytical review of existing methods and means of measuring hydrogen sulfide content in gasses was performed. The method of infrared laser absorption spectroscopy, which uses semiconductor diode lasers tunable in the mid-infrared range as emission sources, is proving to be one of the most promising methods for solving these problems.