High Levels Of Hydrogen Sulfide Research Articles

Increasing the efficiency of the bactericide use at PS-4 of "Ozenmunaigas" JSC

Background: The study is devoted to increasing the efficiency of bactericidal treatment of sediments at the oil fields of Ozenmunaigas JSC. Calculations were carried out to assess the capability of heating the formation and the pipeline, hydraulic heat loss when injecting a bactericide, and the efficiency of mixing the reagent with water. The analysis revealed the ineffectiveness of mixing the bactericide with water at low temperatures and rates of inhibitor introduction.
 Aim: The purpose of the study was to identify solutions to overcome the problems caused by the increased content of hydrogen sulfide in the fields of Ozenmunaigas JSC. This included addressing the temperature issues during bactericide delivery and increasing the rate of inhibitor injection.
 Materials and methods: Heat loss calculations were carried out using the UniSim program for both tank heating and input lines, as well as an analysis of bactericide mixing inside the pipeline using the ANSYS program.
 Results: The results of the study led to specific recommendations and measures that could mitigate the problems associated with temperature and rate of injection. These included measures such as heating and insulation, temperature control, regular inspection of thermal insulation, and selection of a new reagent with improved mixing properties at lower temperatures. It is also recommended to install reagent flow and temperature sensors along with power supply control.
 Conclusion: The implementation of the proposed measures will effectively solve the problems associated with high levels of hydrogen sulfide. This approach will ensure a smooth and safe flow of bactericide and help maintain the operating efficiency of the affected facilities.

Genesis of hydrogen sulfide in natural gas reservoirs in the Western Qaidam Basin

In recent years, gas reservoirs containing high levels of hydrogen sulfide have been found in salinized lacustrine carbonate rocks in the upper member of the Lower Ganchaigou Formation (E32) in the Yingxiongling area of the western Qaidam Basin. This poses great safety risks to drilling and development. To clarify the genetic mechanisms of hydrogen sulfide, we have analyzed the geochemical characteristics and sulfur isotopes of natural gas and predicted the distribution of hydrogen sulfide. The results show that (1) natural gas in the Yingxiongling area is dominated by wet gas, with relatively high nonhydrocarbon content. The gas is E32oil-type gas in a mature stage. (2) Hydrogen sulfide in natural gas reservoirs is less likely to originate from biological and volcanic geneses, and it is primarily a product of thermochemical sulfate reduction. The high-quality Oligocene source rocks distributed across a large area, the saline-deposit formations widely distributed in the western Qaidam Basin, and the high geothermal gradients and large numbers of developed pore-type reservoirs, all combine to provide favorable conditions for the formation of hydrogen sulfide reservoirs. (3) During the E32 deposition period, rock salt developed in the center of the lake basin, the sealing conditions for oil and gas were favorable, and the formation temperature was high during the reservoir formation period. Development of subsalt porous reservoirs is conducive to enrichment of hydrogen sulfide, and comprehensive prediction indicates that the subsalt formation in the Central Yingxiongling-Ganchaigou area is an enrichment zone for hydrogen sulfide. The research results are of considerable significance for the exploration and deployment, and the production safety, of hydrogen sulfide-containing reservoirs.

Artificial intelligence applied to model the sulphur absorption process - a possible application in cure with sulphurous mineral water

The presence of Sulphur in human body is estimated to be around .25 percent from total body weight. The modern therapy includes among others the usage of Sulphur us spring waters as crenotherapy or external use like - therapeutic and preventive treatment for a large category of diseases. High levels of hydrogen sulphide are extremely toxic and as result the model of absorption of Sulphur could be useful as predictor in a daily treatment during a cure with sulphurous mineral water. This quantity of chemical elements from a specific diet rich in these elements absorbed in human organism is one of the most important characteristics of a benefic cure in medical diseases. The most studied mechanisms of absorption were studied for Zinc, Magnesium, Iron and Calcium. The most common way to develop a mathematical model is to use the pharmacokinetic equations based on Michaelis-Menten approach (first order model) and to develop it thereafter for quantitative relations. In some cases, only experimental data can exists and the pharmacokinetic model is not completely elucidated or a simplified model doesn’t exist yet. A model based on genetic programming is proposed in order to discover a mathematical relationship between dietary sulphate (mmol/day) and total sulphate in ileostomy fluid (mmol/day) using experimental data published in literature. The set of terminals that are used in genetic programing – GP (using Polish notation) is reduced to basic operation (sum, difference, multiplication and division) along with the most plausible operations that could have physical meaning: rooted square, exponential and power. The formulas discovered by GP using experimental proved a good fit of data with discovered mathematical formula, e.g. the rooted mean square error below 1.5% and R2  94.36%. Mathematical formulas discovered by genetic programming can be used as an alternative to pharmacokinetic model in order to predict sulphate and sulphite absorption and excretion. The usage of this method is especially efficient when the mechanism of absorption in not elucidated enough to provide a compartmental model given by a set of equations. A correlation with pharmacokinetic equations in the case that these exist will help the improvement of terminals and alphabet used by genetic programming in order to have a model closer to one that have a physical meaning

Evaluation of endobronchial volatile sulfur compounds for rapid diagnosis of lung abscesses caused by obligate anaerobes using Oral Chroma™: A pilot study.

Endobronchial volatile sulfur compounds in patients with lung abscess or lung cancer were measured using the Oral Chroma™ gas chromatograph. High levels of hydrogen sulfide and methyl mercaptan were observed in some patients with lung abscess but not in patients with lung cancer. Measuring endobronchial volatile sulfur compounds could be useful for the rapid diagnosis of lung abscess caused by obligate anaerobes.

Optimization of the Cultivation Conditions of Indigenous Wild Yeasts and Evaluation of their Leavening Capacity

Ethiopia has a high demand for baker's yeast in the bread and beverage industries. Unfortunately, Ethiopia has no producing plant for baker's yeast and instead relies on costly imports. The objective of this work was to identify the most productive and useful indigenous baker's yeasts isolated from local fermented foods and drinks, honey and Molasses using leavening ability as the major metric. Six of the test isolates produced a maximum cell mass at 30oC, pH of 5.5 and 48 hours of incubation. Isolate AAUTf1 did not produce hydrogen sulfide, while isolates AAUTf5, AAUTj15 and AAUSh17 produced low levels of this chemical, and isolates AAUMl20 and AAUWt21 produced high levels of hydrogen sulfide, neglecting their utility in baking. The leavening performance of isolates AAUTf1 (Candida humilis) and AAUTf5 (Kazachstania bulderi) had the highest dough volume of 131 cm3 and 128 cm3 respectively in 120 min. Isolates AAUSh17 (Saccharomyces cerevisiae) and AAUTj15 (Saccharomyces cerevisiae) raised the dough volume of 127 cm3 and 125 cm3 respectively, at 60 min compared to commercial yeast (117 cm3 in 90 min). The study also revealed that mixed cultures of indigenous yeasts had better leavening capacity than single cultures. The co- inoculated cultures of AAUTf1 + AAUTf5 + AAUTj15, AAUTf5 + AAUTj15, and AAUTf1 + AAUTj15 + AAUSh17 reached 143 cm3 at 90 min, 141 cm3 and 140 cm3 both at 60 min, respectively. Thus, the indigenous isolates are candidates for optimizing utilization of yeast for fast promotion and utilization in the bakery industries.

Dexamethasone ameliorates H2S-induced acute lung injury by increasing claudin-5 expression via the PI3K pathway.

Acute lung injury (ALI) is a major outcome of exposure to high levels of hydrogen sulfide (H2S). Dexamethasone (DXM) has been used to treat ALI. However, the mechanisms involved in H2S-induced ALI and the protective mechanisms of DXM in treating ALI are still nebulous. To explore the mechanisms involved, we evaluated the role of claudin-5 in the protective effect of DXM against H2S-induced ALI. Sprague-Dawley rats were exposed to H2S to establish the ALI model. In parallel with the animal model, a cell model was also established by incubating human umbilical vein endothelial cells (HUVECs) with NaHS. Lung hematoxylin-eosin staining, electron microscope assay, and wet/dry ratio were used to identify whether the ALI was successfully induced by H2S, and changes in claudin-5 expression were detected in both rats and HUVECs. Our results revealed that claudin-5 was markedly decreased after H2S exposure and that DXM significantly attenuated the H2S-induced downregulation of claudin-5 in both rats and HUVECs. In the animal experiment, p-Akt and p-FoxO1 presented a similar tendency as claudin-5, but their levels decreased 6 h prior to the levels of claudin-5. In a further investigation, the DXM-induced protective effect on ALI and rescue effect on downregulation of claudin-5 were both blocked by LY294002. The current study demonstrated that claudin-5 was involved in the development of H2S-induced ALI and that DXM exerted protective effects through increasing claudin-5 expression by activating the phosphatidylinositol 3-kinase pathway. Therefore, claudin-5 might represent a novel pharmacological target for treating ALI induced by H2S and other hazardous gases.

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.

Inhibition of hydrogen sulfide biosynthesis sensitizes lung adenocarcinoma to chemotherapeutic drugs by inhibiting mitochondrial DNA repair and suppressing cellular bioenergetics.

Therapeutic manipulation of the gasotransmitter hydrogen sulfide (H2S) has recently been proposed as a novel targeted anticancer approach. Here we show that human lung adenocarcinoma tissue expresses high levels of hydrogen sulfide (H2S) producing enzymes, namely, cystathionine beta-synthase (CBS), cystathionine gamma lyase (CSE) and 3-mercaptopyruvate sulfurtransferase (3-MST), in comparison to adjacent lung tissue. In cultured lung adenocarcinoma but not in normal lung epithelial cells elevated H2S stimulates mitochondrial DNA repair through sulfhydration of EXOG, which, in turn, promotes mitochondrial DNA repair complex assembly, thereby enhancing mitochondrial DNA repair capacity. In addition, inhibition of H2S-producing enzymes suppresses critical bioenergetics parameters in lung adenocarcinoma cells. Together, inhibition of H2S-producing enzymes sensitize lung adenocarcinoma cells to chemotherapeutic agents via induction of mitochondrial dysfunction as shown in in vitro and in vivo models, suggesting a novel mechanism to overcome tumor chemoresistance.

Epithelial sodium channel is involved in H2S-induced acute pulmonary edema

Acute pulmonary edema is one of the major outcomes of exposure to high levels of hydrogen sulfide (H2S). However, the mechanisms involved in H2S-induced acute pulmonary edema are still poorly understood. Therefore, the present study is designed to evaluate the role of epithelial sodium channel (ENaC) in H2S-induced acute pulmonary edema. The Sprague–Dawley rats were exposed to sublethal concentrations of inhaled H2S, then the pulmonary histological and lung epithelial cell injury were evaluated by hematoxylin–eosin staining and electron microscopy, respectively. In addition to morphological investigation, our results also revealed that H2S exposure significantly decreased the alveolar fluid clearance and increased the lung tissue wet–dry ratio. These changes were demonstrated to be associated with decreased ENaC expression. Furthermore, the extracellular-regulated protein kinases 1/2 pathway was demonstrated to be implicated in H2S-mediated ENaC expression, because PD98059, an ERK1/2 antagonist, significantly mitigated H2S-mediated ENaC down-regulation. Therefore, our results show that ENaC might represent a novel pharmacological target for the treatment of acute pulmonary edema induced by H2S and other hazardous gases.

Hydrogen Sulfide and Neuroinflammation.

The innate and adaptive immune system plays an important role in diverse forms of central nervous system (CNS) pathologies including neurodegenerative diseases and peripheral nerve injury. Evidence for an innate inflammatory response in Alzheimer's disease (AD) was described 20 years ago, and subsequent studies have documented roles of inflammation in Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), multiple sclerosis (MS), and a growing number of other CNS pathologies. Although inflammation may not be the initiating factor for neurodegenerative pathologies, experimental data suggests that persistent inflammatory responses involving microglia and astrocytes, as well as blood monocyte-derived macrophages, clearly contribute to disease progression. High levels of hydrogen sulfide exert toxic effects to CNS. On the other hand, low and physiological levels of H2S may have beneficial effects on number of tissues including CNS. For example, a number of studies have reported that H2S exerts anti-inflammatory and anti-apoptotic effects in CNS. In this chapter, studies related to the role of H2S in neuroinflammation and neurodegeneration will be reviewed and discussed. In particular, we will focus on the role of H2S in neuroinflammation associated with PD.

α-ENaC, a therapeutic target of dexamethasone on hydrogen sulfide induced acute pulmonary edema

Acute pulmonary edema (APE) is one of the fatal outcomes after exposure to high levels of hydrogen sulfide (H2S), available evidence suggest that dexamethasone (DXM), a potent anti-inflammatory agent, has been widely used or proposed as a therapeutic approach for H2S-induced APE in clinical practice, however, the underlying mechanism remains poorly understood. Ample evidence suggest that epithelial Na+ channel, especially for the subunit α-epithelial Na+ channel (α-ENaC) plays a critical role in alveolar fluid clearance. Therefore, the present study is undertaken to investigate the effects of DXM on α-ENaC following H2S exposure. The Sprague Dawley rats were exposed to H2S to establish APE model, in parallel, A549 cells were treated with NaHS to establish cell model. In vivo study, we found that DXM significantly attenuated H2S-induced lung histopathological changes and alveolar fluid clearance decrement, however, these preventive effects of DXM can be obviously counteracted by the mifepristone (MIF), the glucocorticoid receptor (GR) blocker. Moreover, DXM markedly attenuated H2S-mediated α-ENaC down-regulation, and similarly, the process can be partially retarded by MIF. Furthermore, DXM obviously prevented H2S-mediated ERK1/2 activation both in vitro and in vivo study. These results, taken together, suggested that DXM exerted protective effects on H2S-induced APE, and α-ENaC might be a potential therapeutic target for APE induced by H2S.

Carbon dioxide and hydrogen sulfide associations with regional bacterial diversity patterns in microbially induced concrete corrosion.

The microbial communities associated with deteriorating concrete corrosion fronts were characterized in 35 samples taken from wastewater collection and treatment systems in ten utilities. Bacterial communities were described using Illumina MiSeq sequencing of the V1V2 region of the small subunit ribosomal ribonucleic acid (SSU-rRNA) gene recovered from fresh corrosion products. Headspace gas concentrations (hydrogen sulfide, carbon dioxide, and methane), pore water pH, moisture content, and select mineralogy were tested for correlation to community outcomes and corrosion extent using pairwise linear regressions and canonical correspondence analysis. Corroding concrete was most commonly characterized by moisture contents greater than 10%, pore water pH below one, and limited richness (<10 taxa). Bacterial community composition was not correlated to geographic location when considered independently from other environmental factors. Corrosion was most severe in sites with high levels of hydrogen sulfide (>100 ppm) and carbon dioxide (>1%) gases, conditions which also were associated with low diversity biofilms dominated by members of the acidophilic sulfur-oxidizer genus Acidithiobacillus.

Dexamethasone ameliorates H₂S-induced acute lung injury by alleviating matrix metalloproteinase-2 and -9 expression.

Acute lung injury (ALI) is one of the fatal outcomes after exposure to high levels of hydrogen sulfide (H2S), and the matrix metalloproteinases (MMPs) especially MMP-2 and MMP-9 are believed to be involved in the development of ALI by degrading the extracellular matrix (ECM) of blood-air barrier. However, the roles of MMP-2 and MMP-9 in H2S-induced ALI and the mechanisms of dexamethasone (DXM) in treating ALI in clinical practice are still largely unknown. The present work was aimed to investigate the roles of MMP-2 and MMP-9 in H2S-induced ALI and the protective effects of DXM. In our study, SD rats were exposed to H2S to establish the ALI model and in parallel, A549 cells were incubated with NaHS (a H2S donor) to establish cell model. The lung HE staining, immunohistochemisty, electron microscope assay and wet/dry ratio were used to identify the ALI induced by H2S, then the MMP-2 and MMP-9 expression in both rats and A549 cells were detected. Our results revealed that MMP-2 and MMP-9 were obviously increased in both mRNA and protein level after H2S exposure, and they could be inhibited by MMP inhibitor doxycycline (DOX) in rat model. Moreover, DXM significantly ameliorated the symptoms of H2S-induced ALI including alveolar edema, infiltration of inflammatory cells and the protein leakage in BAFL via up-regulating glucocorticoid receptor(GR) to mediate the suppression of MMP-2 and MMP-9. Furthermore, the protective effects of DXM in vivo and vitro study could be partially blocked by co-treated with GR antagonist mifepristone (MIF). Our results, taken together, demonstrated that MMP-2 and MMP-9 were involved in the development of H2S-induced ALI and DXM exerted protective effects by alleviating the expression of MMP-2 and MMP-9. Therefore, MMP-2 and MMP-9 might represent novel pharmacological targets for the treatment of H2S and other hazard gases induced ALI.

Biogas Production from Thin Stillage on an Industrial Scale—Experience and Optimisation

With the increasing demand for renewable energy and sustainable waste treatment, biogas production is expanding. Approximately four billion litres of bio-ethanol are produced annually for vehicle fuel in Europe, resulting in the production of large amounts of stillage residues. This stillage is energy-rich and can be used for biogas production, but is a challenging substrate due to its high levels of nitrogen and sulphate. At the full-scale biogas production plant in Norrköping, Sweden (Svensk Biogas i Linköping AB), thin grain stillage is used as a biogas substrate. This paper describes the plant operation and strategies that have been implemented to digest thin stillage successfully. High ammonia concentrations in the digester have resulted in syntrophic acetate oxidation (SAO) becoming the major pathway for acetate degradation. Therefore, a long hydraulic retention time (HRT) (40–60 days) is used to allow the syntrophic acetate-oxidising bacteria time to grow. The high sulphate levels in thin stillage result in high levels of hydrogen sulphide following degradation of protein and the activity of sulphate-reducing bacteria (SRB), the presence of which has been confirmed by quantitative polymerase chain reaction (qPCR) analysis. To optimise biogas production and maintain a stable process, the substrate is diluted with tap water and co-digested with grain residues and glycerine to keep the ammonium nitrogen (NH4-N) concentration below 6 g L−1. Combined addition of iron, hydrochloric acid and cobalt successfully precipitates sulphides, reduces ammonia toxicity and supplies microorganisms with trace element. Mesophilic temperature (38 °C) is employed to further avoid ammonia toxicity. Together, these measures and doubling the digester volume have made it possible to increase annual biogas production from 27.7 TJ to 69.1 TJ.

Removal of hydrogen sulfide using carbonated steel slag

High levels of hydrogen sulfide are sometimes observed in the pore water of eutrophic sediments. It is important to reduce the hydrogen sulfide concentration to maintain health ecosystems as well as aquaculture activities in enclosed water bodies. The purpose of this study is to reveal the removal mechanism of hydrogen sulfide using carbonated steel slag produced through carbonation processes to alleviate alkaline impacts. Batch adsorption experiments revealed that hydrogen sulfide was adsorbed onto carbonated steel slag based on a pseudo-first-order kinetic model; its adsorption maximum was 7.5mgg−1. The removal mechanisms of the hydrogen sulfide included (1) the formation of pyrite, and (2) oxidation to sulfur coupled with the reduction of manganese oxide on the carbonated steel slag.

The sulfur chain in biogas production from sulfate‐rich liquid substrates: a review on dynamic modeling with vinasse as model substrate

AbstractVinasse is a sulfate‐rich liquid substrate, from which high levels of hydrogen sulfide in biogas can be obtained due to the sulfate reduction process under anaerobic conditions. Hydrogen sulfide is corrosive and toxic and must be removed for any utilization of the biogas. Mathematical models have been developed to study separately sulfate reduction in anaerobic digestion and sulfide removal from biogas streams. However, the levels of hydrogen sulfide produced in the anaerobic digestion stage have an effect on the sulfide removal processes in the next stage. As a method to study both processes and their interaction, a new approach is introduced and reviewed in the present article: the sulfur chain in biogas production. The necessity of studying the sulfate reduction processes in vinasse as a typical sulfate‐rich substrate to predict hydrogen sulfide concentrations in the gas phase, as well as the best model approach to that aim are established here. In addition, the approaches to model sulfide removal based on direct conversion processes, the models' capability to predict the removal of hydrogen sulfide from the biogas (at levels between 20 000 and 30 000 ppmv) as well as the concentration profile of the reactants in this removal processes are discussed. © 2013 Society of Chemical Industry

Evaluation of Coating Performance on Silver Exposed to Hydrogen Sulfide

Twelve coatings applied to sterling silver coupons were subjected to high levels of hydrogen sulfide to test their effectiveness in preventing tarnish in indoor environments. Silver coupons were assessed over the course of the experiment using visual observation, image analysis of digital photographs, gloss measurement, and colorimetry. Acrysol WS-24, Agateen Air Dry Lacquer No. 27, HMG Heat and Waterproof Adhesive, and PVAc AYAT generally performed best. Mowiol 28-99 performed very well on some areas but was mediocre otherwise. Butvar B-98 and Acryloid B-48N were generally less effective in retarding tarnish. Acryloid B-72 and Butvar B-76 performed less well. Aquazol 500, Aquazol 500 topped with Renaissance Wax, and Renaissance Wax were least effective. Coating thickness proved to be a significant factor in coating performance.

Ecological release and niche partitioning under stress: Lessons from dorvilleid polychaetes in sulfidic sediments at methane seeps

Organisms inhabiting methane seep sediments are exposed to stress in the form of high levels of hydrogen sulfide, which result mainly from sulfate reduction coupled to anaerobic methane oxidation. Dorvilleidae (Polychaeta) have successfully invaded this ecosystem, and multiple species in divergent genetic clades co-occur at high densities. At methane seeps in the NE Pacific off California and Oregon, the genera Ophryotrocha, Parougia and Exallopus are especially well represented. To test the hypothesis that dorvilleid coexistence is facilitated by niche partitioning through sulfide tolerance and trophic patterns, we examined dorvilleid species-specific patterns of occurrence and nutrition at methane seeps off Eel R. [ER] on the Californian continental slope and at Hydrate Ridge [HR] on the Oregon continental slope, and in two habitats (clam bed and microbial mat) characterized by lower and higher hydrogen sulfide levels, respectively. Microelectrode measurements of hydrogen sulfide enabled characterization of environmental sulfide levels for species sampled in background sediment cores and in colonization trays. Dorvilleids tolerated H2S levels from 10μM to over 2.6mM, with the majority of species inhabiting sediments with similar environmental H2S concentrations (median 85–100μM). Dorvilleid species richness was greater at HR than ER, but did not differ between clam bed and microbial mat habitats. Species distribution patterns reflected preferences for ER clam bed (lower sulfide levels), ER mat and HR clam bed (moderate sulfide levels), or HR mat (very high sulfide levels). Nutritional patterns, including trophic diversity and functional similarity, were examined using community stable isotope metrics based on δ15N and δ13C. Within each region, dorvilleid species exhibited multiple trophic strategies. Co-existing congeners typically exhibited distinct isotope signatures, suggesting trophic partitioning. Trophic diversity and δ15N range for whole assemblages (measured by Total Hull Area and Standard Elliptical Area using species averages) and functional redundancy or species packing (measured as distance to nearest neighbor) among species and individuals were generally higher at ER, where sulfide levels were lower than at HR. In contrast, average trophic diversity among individuals within a species was greater at HR than ER. In colonization experiments involving agar-based manipulations of sulfide in tray sediments that mimicked clam bed and mat conditions, dorvilleids comprised 68% and 48% of colonists at ER and HR, respectively. Dorvilleid species richness was higher in trays that were initially more sulfidic. However, habitat exerted stronger influence on the composition of colonizing dorvilleids than did sulfide additions. In the NE Pacific, regional, habitat and vertical (down-core) variation in hydrogen sulfide creates complex environmental heterogeneity at methane seeps, promoting high diversity of stress-tolerant taxa such as dorvilleid polychaetes.

Effect of persistent trace compounds in landfill gas on engine performance during energy recovery: A case study

Performances of gas engines operated with landfill gas (LFG) are affected by the impurities in the LFG, reducing the economic viability of energy recovery. The purpose of this study was to characterize the trace compounds in the LFG at the Odayeri Landfill, Istanbul, Turkey which is used for energy recovery. Composite gas samples were collected and analyzed for trace compounds (hydrocarbons, siloxanes, and volatile halogenated hydrocarbons) over a 3-year period. Trace compounds entering the gas engines, their impact on the engine performance were evaluated. The operational problems included deposit formation in the combustion chamber, turbocharger, and intercooler of engine before the scheduled maintenance times. High levels of hydrogen sulfide, as well as chlorinated and fluorinated compounds cause corrosion of the engine parts and decrease life of the engine oils. Persistence of siloxanes results in deposit formation, increasing engine maintenance costs. Pretreatment of LFG is necessary to protect the engines at the waste-to-energy facilities with persistence levels of siloxanes and volatile halogenated hydrocarbons.

Twenty-four years in the mud: what have we learned about the natural history and ecology of the mangrove rivulus, Kryptolebias marmoratus?

Although first described in 1880, Kryptolebias marmoratus avoided scientific scrutiny until 1961, when it was identified as the only known selfing hermaphroditic vertebrate. The subsequent intense interest in this fish as a laboratory animal, continuing to this day, might explain the paucity of wild collections, but our collective knowledge now suggests that the inherent difficulty of wild collection is more a matter of "looking in all the wrong places." Long thought to be rare in the mangroves, and it is rare in certain human-impacted habitats, K. marmoratus can be quite abundant, but in microhabitats not typically targeted by ichthyologists: ephemeral pools at higher elevations in the swamp, crab burrows, and other fossorial or even terrestrial haunts. Field studies of this enigmatic fish have revealed almost amphibious behaviors. During emersion these fish tolerate extended dry periods. In water, they are exposed to temperature extremes, high levels of hydrogen sulfide, and depleted dissolved oxygen. Finally, their catholic diet and a geographically variable sex life completes a portrait of an unusual animal. A clearer picture is emerging of adult life, with initial population density estimates now known and some indication of high population turnover in burrows, but juvenile habitat and adult oviposition sites remain unknown.