Hydrogen Sulfide Concentrations Research Articles

Hazard Identification and Risk Assessment of Biogas Plant with Proton Exchange Membrane Fuel Cell Technology

Biogas-fed proton exchange membrane fuel cell (PEMFC) plants offer a sustainable energy solution, but their operation can pose significant hazards and risks. Ensuring the safety of these plants is paramount, especially given the potential for fires, explosions, and chemical exposures. This study evaluated hazards and risks in biogasfed proton exchange membrane fuel cell (PEMFC) plants using six analytical methods: Dow's fire and explosion index (FEI), Dow's chemical expo-sure index (CEI), Hazard and Operability Study (HAZOP), Risk Matrix Analysis (RMA), Bayesian Network (BN) and ALOHA® software hazard modelling. The FEI analysis revealed that the anaerobic digester and bio-gas storage tank exhibited severe hazards (FEI =170), thereby signifying the highest risks within the plant. CEI analysis revealed the spread of the highest hydrogen sulfide (H2S) concentration up to 129 meters from the anaerobic digester and storage tank location. Further assessment was conducted, calculating risk values using the RMA and performing additional HAZOP analysis specifically for these units. The results confirmed similar risk levels (4-20) between the units, except for a higher explosion risk in the storage tank. The novelty of this research lies in the application of Bayesian Network (BN) analysis. In addition to assessing the hazards associated with PEMFC, our BN analysis reveals that the risk of fire attributed to PEMFC ranges between 10% and 18%, while the risk of explosion falls within the range of 3% to 17%. Based on the hierarchy control concept, several effective mitigation controls were proposed to enhance the safety of biogas-fed PEMFC plants. In future research, a deeper exploration of human error and equipment malfunctions within hazard modelling is crucial for a more precise hazard assessment.

A Predictive Model for Wellbore Temperature in High-Sulfur Gas Wells Incorporating Sulfur Deposition

HSG (high-sulfur gas) reservoirs are prevalent globally, yet their exploitation is hindered by elevated levels of hydrogen sulfide. A decrease in temperature and pressure may result in the formation of sulfur deposits, thereby exerting a notable influence on gas production. Test instruments are susceptible to significant corrosion due to the presence of hydrogen sulfide, resulting in challenges in obtaining bottom hole temperature and pressure test data. Consequently, a WTD (wellbore temperature distribution) model incorporating sulfur precipitation was developed based on PPP (physical property parameter), heat transfer, and GSTP (gas–solid two-phase) flow models. The comparison of a 2.53% temperature error and a 4.80% pressure error with actual field test data indicates that the established model exhibits high accuracy. An analysis is conducted on the impact of various factors, such as production, sulfur layer thickness, reservoir temperature, and reservoir pressure, on the distribution of the wellbore temperature field and pressure field. Increased gas production leads to higher wellhead temperatures. The presence of sulfur deposits reduces the flow area and wellhead pressure. A 40% concentration of hydrogen sulfide results in a 2 MPa pressure drop compared to a 20% concentration. Decreased reservoir pressure and temperature facilitate the formation of sulfur deposits at the wellhead.

Integrated microcontroller mq sensors for monitoring biogas: Advancements in methane and hydrogen sulfide detection

Recent technological advances in microcontroller systems enable novel biogas monitoring capabilities. This study investigates microcontroller-based quantification of methane and hydrogen sulfide concentrations in biogas derived from anaerobic digestion. Anaerobic digesters were fed either 100% cow dung substrates or a 50:50 mixture of cow dung with municipal solid waste (MSW). Methane levels were monitored using an MQ-4 sensor, hydrogen sulfide via an MQ-136 sensor, and temperature with a K-type thermocouple, all integrated with an ATmega 2560 microcontroller system. The 100% cow dung digester produced biogas with maximum methane concentrations of 3488 ppm at 21 days, indicating improved methane production compared to the 50:50 mixture of cow dung with MSW. Hydrogen sulfide reached 195 ppm and 192 ppm for the 100% cow dung and mixed digesters. Mesophilic temperature conditions were maintained throughout the digestion process. Real-time quantification of biogas composition demonstrates the capabilities of microcontroller-based anaerobic digester monitoring to provide precise methane and hydrogen sulfide measurements.

In situ synthesis of porous metal-organic frameworks NH2-UiO-66 on tea stem biochar and application in odours adsorption

Multiple odour nuisance in livestock farming is a notorious problem that has a significant impact on the living environment of surrounding communities. Adsorbents based on metal-organic framework (MOF) materials show great promise for controlling odour pollution, as they offer a high specific surface area, a controllable structure and an abundance of active sites. However, the MOF formation process is prone to problems such as pore clogging or collapse and reduced porosity, which limits its further application. In this study, a series of odour adsorbents were prepared by in situ growth of NH2-UiO-66 on tea stem biochar (TSBC) using a hydrothermal method and named UiO (Zr)-TSBCx. The physical and chemical properties and composition of UiO (Zr)-TSBCx have been systematically characterized using SEM, TEM, XRD, FT-IR, N2 adsorption-desorption and XPS. The release of odours from the pig farm effluent was monitored using in-situ continuous Proton-Transfer-Reaction Mass Spectrometry (PTR-MS), and the obtained primary compositions were tested for further adsorption. In dynamic adsorption experiments focused on butyric acid, UiO (Zr)-TSBC2 showed a high adsorption capacity of 3.99 × 105 μg/g and exceptional structural stability. UiO (Zr)-TSBC2 showed variable adsorption efficiencies for different odorous gases, with the best performance for the removal of ammonia, toluene and butyric acid. It also demonstrated the ability to rapidly mitigate instantaneous high concentrations of hydrogen sulfide (H2S), methanethiol and toluene resulting from agitation. Additionally, based on the relationship between the adsorption amount and the structural characteristics of the adsorbent as well as the nature of the odours, a possible adsorption mechanism of UiO (Zr)-TSBC2 for a variety of odours released from pig farm effluent was proposed. This work demonstrates a novel approach to promote deodorization applications in livestock and poultry farming environments by the in-situ growth of NH2-UiO-66 on biochar prepared from tea stem.

Effect of Antimicrobial Photodynamic Therapy on the Tongue Dorsum on Reducing Halitosis and the Duration of the Effect: A Randomized Clinical Trial.

Antimicrobial photodynamic therapy (PDT) is a treatment that is gaining popularity in modern clinical medicine. However, little is known about the effect of PDT alone on reducing oral halitosis and the duration of the effect. This trial examined the effect of PDT on the tongue dorsum on reducing oral halitosis and the duration of the effect. This study was approved by the Ethics Committee of Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, and Okayama University Hospital (CRB20-015), and it was registered in the Japan Registry of Clinical Trials (jRCTs061200060). Twenty-two participants were randomly assigned to two groups: an intervention group and control group. PDT was performed in the intervention group using red laser emission and methylene blue gel on the middle and posterior area of the tongue dorsum. The concentration of volatile sulfur compounds, bacterial count on the tongue dorsum, probing pocket depth, bleeding on probing, and simplified oral debris index score were determined before and 1 week after PDT. The Mann-Whitney U test was used to assess the significance of the differences in each parameter between the two groups. We found that the hydrogen sulfide concentration and bacterial count on the tongue dorsum were decreased in the intervention group, but there was no statistically significant difference between the two groups. These results indicated that performing only PDT on the tongue dorsum may not contribute to reducing halitosis.

Process simulation, optimization, and cost analysis of a proposed sulfur recovery unit by applying modified Claus technology

Removing sour gas from any suitable gas sweetening technology in a cost-effective and environmentally responsible manner is a major challenge. This paper discusses how to safely and economically dispose of small amounts of acid gases resulting from the amine sweetening process. A two-stage Claus desulfurization unit was studied and simulated to treat acid gases resulting from natural gas sweetening operations in Ras Gharib oil fields (Egypt). These acid gases are used as feedstock for the proposed plant to produce a valuable product, such as elemental sulfur, which is used as a raw material in many industries. Although many sulfur recovery techniques are available for various conditions and applications, the Claus process is a critical and widely used method for recovering elemental sulfur from gaseous hydrogen sulfide. This work represents the potential benefits of treating acid gases with high hydrogen sulfide content. In addition, operational variables that could affect sulfur production and sulfur recovery efficiency of the studied Claus unit were studied and optimized. Aspen HYSYS simulation software (version 9) was used to evaluate the economic aspects and optimize the operational parameters of the unit for producing sulfur from acid background gases. The results showed that the maximum sulfur production was achieved at a catalytic converter reactor temperature of 270 °C and 210 °C for the first and second catalytic reactor, respectively, with an air flow rate of 933.3 kg mol/h. The economic study of the proposed desulfurization unit showed that the Claus unit would be economically acceptable with an expected return on investment of approximately 10% and an average payback period of 10 years. Moreover, the introduced plant has a positive impact on the environment by reducing the concentration of hydrogen sulfide in the gas from 69.58 to 0.16%.

Hydrogen Sulfide Delivery to Enhance Bone Tissue Engineering Cell Survival.

Though crucial for natural bone healing, local calcium ion (Ca2+) and phosphate ion (Pi) concentrations can exceed the cytotoxic limit leading to mitochondrial overload, oxidative stress, and cell death. For bone tissue engineering applications, H2S can be employed as a cytoprotective molecule to enhance mesenchymal stem cell (MSC) tolerance to cytotoxic Ca2+/Pi concentrations. Varied concentrations of sodium hydrogen sulfide (NaSH), a fast-releasing H2S donor, were applied to assess the influence of H2S on MSC proliferation. The results suggested a toxicity limit of 4 mM for NaSH and that 1 mM of NaSH could improve cell proliferation and differentiation in the presence of cytotoxic levels of Ca2+ (32 mM) and/or Pi (16 mM). To controllably deliver H2S over time, a novel donor molecule (thioglutamic acid-GluSH) was synthesized and evaluated for its H2S release profile. Excitingly, GluSH successfully maintained cytoprotective level of H2S over 7 days. Furthermore, MSCs exposed to cytotoxic Ca2+/Pi concentrations in the presence of GluSH were able to thrive and differentiate into osteoblasts. These findings suggest that the incorporation of a sustained H2S donor such as GluSH into CaP-based bone graft substitutes can facilitate considerable cytoprotection, making it an attractive option for complex bone regenerative engineering applications.

Determination of emission factors from a landfill through an inverse methodology: Experimental determination of ambient air concentrations and use of numerical modelling

The application of numeric modelling for determining the impact of landfills needs for reliable emission source data. In this study, a methodology for the characterization of the emission profiles of the different sources present in landfills for emission factors determination, applying an indirect methodology, is presented. Ambient air concentrations of volatile organic compounds (VOCs), hydrogen sulphide (H2S) and ammonia (NH3) were determined in three potentially emission sources in Can Mata landfill (Hostalets de Pierola, Catalonia, Spain): dumping areas, pre-closed zone and leachate reservoir as well as in biogas, for the determination of emission factors. Multi-sorbent bed and Tenax TA tubes were used for a wide range of VOCs sampling, and analysis was conducted through TD-GC/MS. H2S and NH3 were sampled and analysed using Radiello passive samplers. The highest total VOC (TVOC) concentrations were found in dumping areas (0.7–3.5 mg m−3), followed by leachate reservoir (0.3–0.6 mg m−3) and pre-closed area (77–165 μg m−3). On the other hand, the highest H2S and NH3 concentrations were found in leachate reservoir, presenting values of 0.8–1.1 mg m−3 and 1.7–1.8 mg m−3, respectively. With the application of odour thresholds to the concentrations obtained, the most critical compounds regarding odour annoyances were determined. The highest odour units (O.U.) were found in leachate reservoir due to H2S concentrations, whereas VOCs contributed mainly to O.U. in the dumping areas. The obtained ambient air concentrations were used for the indirect determination of the emission factors through numerical modelling using a Eulerian dispersion model. The emission factors obtained for the landfill for TVOC, H2S and NH3 were in the range of 0.44–10.9 g s-1, 0.16–1.02 g s−1 and 0.23–1.82 g s−1, respectively, depending on the emission source. Reliable emission factors are crucial to obtain landfill impact maps, which are essential for the correct management of these facilities.

Modeling the effects of sidestreams recycling on wastewater treatment plant performance operated by anaerobic-anoxic-oxic (A2/O) processes using GPS-X8 simulation

The water separated by sludge treatment processes is known as the sidestreams, such as the centrate, underflow belt thickener, and supernatant gravity thickener. The sidestreams have significant amounts of contaminants, particularly nutrients, and are returned to the wastewater treatment plant head. Returning the sidestreams to the head of the plant causes both technical and financial problems. This paper models the effect of sidestreams on the treatment of mainstream in full-scale conventional activated sludge systems operated with anaerobic/anoxic/oxic (A2/O). The effects of sidestreams nutrients and inert materials, the pollutants fate in the A2/O system, oxygen consumed, and energy required by sidestreams are modeled using GPS-X8 simulation. The results showed that the discharge ratio of the sidestreams to the mainstream is 4 %. The proportion of the pollutants present in the sidestream to the mainstream were 4.3 %, 4.7 %, 8.8 %, 21 %, 40 %, and 11 % for BOD, COD, TSS, NH4, PO4, and H2S, respectively. The GPS-X model showed that high orthophosphate and hydrogen sulfide concentrations were seen in the anaerobic zone. While all other pollutants begin to decay, phosphates and hydrogen sulfide gas also begin to decrease gradually in anoxic and oxic zones, noting the high concentrations of nitrates and sulfates in the oxic zone. An added 10 % of oxygen is needed for the sidestreams ammonia oxidation, which is more than the amount needed for the oxidation of BOD. The percentage of alkali used to improve the nitrification process due to the ammonia in the sidestreams was 30 % of the specified amount of ammonia in the mainstream. This study proved that the plant's sidestreams adversely increased oxygen, energy, and alkali consumption.

Assessment of some air pollutants in the Sanctuary of the Beata Vergine dei Miracoli (Saronno, Italy) and first evaluation of a new axial passive sampler for nitrogen dioxide

In the present study the concentration of some air pollutants (nitrogen dioxide, sulphur dioxide, hydrogen sulphide, ammonia and BTEX, i.e. benzene, toluene, ethylbenzene and xylene) was monitored inside and outside the Sanctuary of the Beata Vergine dei Miracoli (Saronno, Italy) by passive air sampling (using radial samplers), during two sampling periods in 2022 (April 27-May 11 and May 11-May 25). Concurrently, particulate matter (PM10 and PM2.5) concentration was determined by using sensors based on laser scattering technology. Moreover, we took advantage of the location of this sanctuary (proximity to an air monitoring central unit) to evaluate the performance of a new axial-type sampler for nitrogen dioxide. Sulphur dioxide concentration was in the range 0.8–3.1 µg/m3, with outdoor values higher than indoor ones, whereas no detectable concentrations of hydrogen sulphide were found (<0.1 µg/m3). A different trend was observed for ammonia, where indoor concentrations were higher than outdoor ones (3.6–5.5 vs 2.7–3.1 µg/m3). Among BTEX, only for benzene statistical differences (p-value < 0.05) between the indoor and outdoor concentrations were found, suggesting additional indoor sources for this hydrocarbon. Toluene results as the most abundant among these hydrocarbons (1.7–2.3 µg/m3) in outdoor environments, whereas, in indoor environments, benzene has the higher concentration (6–9 µg/m3). The indoor concentrations of NO2 (15.4–22.2 µg/m3 for radial samplers and 48–60 µg/m3 for axial samplers) are not only much higher than the recommended limit values to guarantee proper conservation of artefacts (5 µg/m3), but also close to the values for human health preservation (40 µg/m3), suggesting the need of proper strategy to improve indoor air quality inside the Sanctuary. The preliminary results obtained for the new axial-type sampler for nitrogen dioxide are very encouraging, given the closeness of the obtained concentration data to those measured by monitoring central unit, even though further experiments will have to be carried out to validate this sampler.

The CBS/H2S signalling pathway regulated by the carbon repressor CreA promotes cellulose utilization in Ganoderma lucidum

Cellulose is an important abundant renewable resource on Earth, and the microbial cellulose utilization mechanism has attracted extensive attention. Recently, some signalling molecules have been found to regulate cellulose utilization and the discovery of underlying signals has recently attracted extensive attention. In this paper, we found that the hydrogen sulfide (H2S) concentration under cellulose culture condition increased to approximately 2.3-fold compared with that under glucose culture condition in Ganoderma lucidum. Further evidence shown that cellulase activities of G. lucidum were improved by 18.2-27.6% through increasing H2S concentration. Then, we observed that the carbon repressor CreA inhibited H2S biosynthesis in G. lucidum by binding to the promoter of cbs, a key gene for H2S biosynthesis, at “CTGGGG”. In our study, we reported for the first time that H2S increased the cellulose utilization in G. lucidum, and analyzed the mechanism of H2S biosynthesis induced by cellulose. This study not only enriches the understanding of the microbial cellulose utilization mechanism but also provides a reference for the analysis of the physiological function of H2S signals.

Photosynthetic process for removing H2S and CO2 from biogas using the microalgae Chlorella sorokiniana

Biogas is an alternative source of energy that contributes on reducing the emissions of polluting gas in comparison to fossil fuels as well as promoting the treatment of organic waste. However depending on the substrate used in its production, it may have a high concentration of carbon dioxide (CO2) and hydrogen sulfide (H2S); in these cases a treatment is necessary to make its use viable, for comply with current legislation and avoid damage to materials and health. Currently, the most widely used methods are physical-chemical, such as absorption, adsorption, membrane separation, and Pressure Swing Adsorption (PSA), among others. However, these methods are expensive and generate waste that needs to be treated. In this sense, biological methods have proved to be promising alternatives, especially photosynthetic processes using microalgae. This study aimed to evaluate the efficiency in removing CO2 and H2S from biogas through a bench-scale purifier prototype consisting of a photobioreactor and an absorption column, in a continuous biogas flow system. The experiment lasted 240 hours, during which 9 m³ of biogas were treated. In the first 24 hours, the flow rate was 1 L/min, resulting in an average removal of 60.8% of H2S and 20.2% of CO2. Between 24 hours and 240 hours of the study, the average biogas flow rate was 0.54 L/min, and an improvement in removal was observed, reaching 83.4% of H2S and 29.7% of CO2. The system showed efficiency in biogas treatment. However, possibilities for improvement were identified in terms of biogas flow and process, which could further enhance the results presented here.

Influence of hydrogen sulphide on the corrosion and hydrogenation of 07Cr16Ni6 steel

The effect of hydrogen sulphide concentration on the corrosion behaviour of 07Cr16Ni6 austenitic-martensitic stainless steel in a 5% NaCl + 0.5% CH3COOH solution was studied to determine the role of H2S in the corrosion product formation and corrosion mechanism. Unstable passivation of steel is detected in a solution containing &lt;100 mg/dm3 H2S. Steel corrodes in an electrochemically active state at &gt;100 mg/dm3 H2S. When the pitting potential is reached, pitting damage occurs at the grain boundaries. The corrosion rate decreases by ∼five times after exposition for 720 h due to the formation of nickel and iron sulphides on the surface. Corrosion is accompanied by the absorption of 4.2–17.5 ppm hydrogen, 62…70% of which is diffusible and can cause hydrogen embrittlement. The scheme of steel corrosion under the influence of different concentrations of hydrogen sulphide is proposed.

Neural network analysis of safe life of the oil and gas industrial structures

Purpose is to study safe life of industrial (metal) structures under long-time operation in the corrosive-active media of oil and gas wells with the help of neural network analysis. Methods. The MATLAB system (MATrix LABoratory) was selected as the tool environment for interface modelling; the system is developed by Math Works Inc. and is a high-level programming language for technical computations. Of the three existing learning paradigms, we used the “with teacher” learning process, as we believed that a neural network had correct answers (network outputs) for each input example. The coefficients were adjusted so that the network gave answers being as close as possible to the known correct answers. Findings. An artificial neural network has helped obtain a generalized diagram of the expected areas of high viscoplastic characteristics of carbon steels used to manufacture metal structures in the oil and gas industry. While applying the trained neural networks, generalized dependences of the corrosion rates of structural steels on the parameters of media with different concentrations of chlorine ions, sulphate ions, hydrogen sulphide, carbon dioxide, carbon dioxide, and oxygen ions were obtained; they were the basis to predict corrosion behaviour of steels. Originality. For the first time, the possibility of applying neural network modelling to predict local corrosion damage of structural pipe steels has been shown in terms of the “steel 20 – oxygen and chloride-containing medium” system. For the first time, the technological possibility has been demonstrated to use neural network analysis for engineering predictive assessment of corrosion activity of binary systems of simulated solutions, which are most often found under industrial conditions of the oil and gas sector of the economy. Practical implications. The proposed technology of using the neural network analysis will make it possible to expand a range of predicted values beyond experimental data, i.e. to predict the value of Vcor in very dilute or concentrated salt solutions within the acidified and neutral pH ranges. It should be noted that the error of the prediction results shown by the neural network will increase along with distancing from the scope of experimental data.

Charge Density-Regulated Microchannel-Based Electrochemiluminescence Sensor for Hydrogen Sulfide Detection with a Highly Efficient Accumulation Strategy.

The electrochemiluminescence (ECL) intensity can be regulated by ionic current passing through the microchannel, which broadened the regulation of the ECL sensors. But in the early reported sensors, the electrostatic repulsion and steric hindrance caused few targets to approach the interface of the microchannel driven by concentration difference, which reduced the detection efficiency and prolonged the detection period. In this study, different accumulation strategies, such as a positive electric field and different polarity electric fields, were designed to accumulate targets in the microchannel. The interaction of azide groups and hydrogen sulfide served as a research model. Hydrogen sulfide can react with the negatively charged azide groups in the microchannel surface to produce positively charged amino groups, decreasing the negative charge density of the microchannel and thus altering the ionic current and ECL intensity. The accumulation of hydrogen sulfide at the microchannel tip can increase the collision probability with azide groups to improve the detection efficiency, and the integration of accumulation and reaction can shorten the detection period to 28 min. The hydrogen sulfide concentration on the microchannel tip accumulated by applying different polarity electric fields was 22.3-fold higher than that accumulated by applying a positive electric field. The selected research model broadened the application range of a microchannel-based ECL sensor and confirmed the universality of the microchannel-based ECL sensor.

Методика прогнозирования зон скопления сероводорода в сильвинитовых пластах калийных рудников и экспресс-определения газоносности пород по сероводороду

Intensification of potash salt mining, widespread use of high-performance continuous miners, involvement of gasbearing formations in mining are accompanied by release of natural poisonous gases into the atmosphere of mine workings, which explains the need to ensure safe working conditions for the miners. The article presents the researche results that helped to develop a methodology for predicting accumulation zones of one of the most hazardous poisonous gases, i.e. hydrogen sulfide. A correlation was established between the hydrogen sulfide concentration, presence of organic substances and the content of magnesium chloride in the rocks. The article describes methods to determine the accumulation areas of hazardous sulfurcontaining gases based on the trench sampling and laboratory test data, which makes it possible to take timely protective measures to ensure safety of the miners. The developed method is based on creation of the correlation fields for various geochemical attributes such as the NaCl, KCl, MgCl2 content and others. A close correlation between the content of organic carbon in the rocks and magnesium chloride indicates the degree of salt recrystallization, as evidenced by an increase in the hydrogen sulfide content. In addition, the article describes an express method to determine the gas content in rocks, which enables a quick and accurate assessment of hydrogen sulfide concentration directly in the mine workings, thus providing the possibility of prompt response to the hazards. Thus, the methodology proposed by the authors serves not only to identify the potentially hazardous areas, but also to prevent dangerous situations associated with the release of poisonous gases in potash mines. The research and practical approaches described in the article as well as the developed recommendations contribute to enhancing the efficiency of mine ventilation, which in turn leads to minimization of the risks to health and life of the miners.

Reliability-based life prediction method for concrete sewage pipelines under microbial attack

The durability of concrete sewage pipelines decreased for microbial attack. In this study, a method for life prediction of concrete sewage pipes under microbial-induced attack was developed by combining numerical simulation with theoretical analysis. A mathematical model of the corrosion depth of microbial erosion of concrete was constructed based on the cumulative model of sulfate concentration on the surface of sewage pipes and verified the applicability by comparing it with the experimental results. The Monte Carlo (MC) life prediction method and Fuzzy- Monte Carlo (F-MC) life prediction method for concrete sewage pipes was established based on the reliability theory and fuzzy methodology. Several factors are considered as random variables and analyzed parametrically, including hydrogen sulfide concentration (SH2S), diffusion coefficient (D), and thickness of the concrete cover (CC). In addition failure event was consider as a fuzzey event. It was found that: The increasing SH2S and D result in higher failure rates and lower service life, however as the increase of the thickness of CC, there is the opposite effect. The results of the numerical simulations revealed a NR between the three kinds of parameters and the probability of failure of sewer pipes. Compared with the MC model, the F-Mc model produces more conservative but not minimal different results, which confirms the applicability of the F-MC model.

Research on Indoor Environment Prediction of Pig House Based on OTDBO-TCN-GRU Algorithm.

Temperature and humidity, along with concentrations of ammonia and hydrogen sulfide, are critical environmental factors that significantly influence the growth and health of pigs within porcine habitats. The ability to accurately predict these environmental variables in pig houses is pivotal, as it provides crucial decision-making support for the precise and targeted regulation of the internal environmental conditions. This approach ensures an optimal living environment, essential for the well-being and healthy development of the pigs. The existing methodologies for forecasting environmental factors in pig houses are currently hampered by issues of low predictive accuracy and significant fluctuations in environmental conditions. To address these challenges in this study, a hybrid model incorporating the improved dung beetle algorithm (DBO), temporal convolutional networks (TCNs), and gated recurrent units (GRUs) is proposed for the prediction and optimization of environmental factors in pig barns. The model enhances the global search capability of DBO by introducing the Osprey Eagle optimization algorithm (OOA). The hybrid model uses the optimization capability of DBO to initially fit the time-series data of environmental factors, and subsequently combines the long-term dependence capture capability of TCNs and the non-linear sequence processing capability of GRUs to accurately predict the residuals of the DBO fit. In the prediction of ammonia concentration, the OTDBO-TCN-GRU model shows excellent performance with mean absolute error (MAE), mean square error (MSE), and coefficient of determination (R2) of 0.0474, 0.0039, and 0.9871, respectively. Compared with the DBO-TCN-GRU model, OTDBO-TCN-GRU achieves significant reductions of 37.2% and 66.7% in MAE and MSE, respectively, while the R2 value is improved by 2.5%. Compared with the OOA model, the OTDBO-TCN-GRU achieved 48.7% and 74.2% reductions in the MAE and MSE metrics, respectively, while the R2 value improved by 3.6%. In addition, the improved OTDBO-TCN-GRU model has a prediction error of less than 0.3 mg/m3 for environmental gases compared with other algorithms, and has less influence on sudden environmental changes, which shows the robustness and adaptability of the model for environmental prediction. Therefore, the OTDBO-TCN-GRU model, as proposed in this study, optimizes the predictive performance of environmental factor time series and offers substantial decision support for environmental control in pig houses.

Impacts of gaps below both door and partition walls of cubicles on odorous gas transport and respiratory infection in a public lavatory

Odorous gas transport and respiratory infection in a public lavatory are highly subject to the adopted ventilation system. The gaps below both the cubicle door and the partition walls can affect the ventilation performance. This study employed a validated computational fluid dynamics (CFD) program to investigate a public lavatory containing four cubicles with squat toilets. The airflow, concentrations of hydrogen sulfide and methyl mercaptan, and respiratory infection risk during use of the toilet were modeled. Odorous gases were released from the squat pan, while the pathogens resulting in respiratory infection were released by the exhalation of the toilet users. A total of seven different gap designs were considered, including designs without any gap, with a gap below only the cubicle door in three different gap heights, and gaps in three different heights below both the door and the partition walls. In addition, the use of a single central air exhaust and the use of multiple air exhausts were compared. The results revealed that the air from the gap below each cubicle door can effectively dilute the odorous gases released from the squat pan, whereas the gap below the partition walls was not shown to be favorable. The use of multiple air exhausts restrains the pollutant's spread and reduces the respiratory infection risk.

Effects of pockmark activity on iron cycling and mineral composition in continental shelf sediments (southern Baltic Sea)

AbstractPockmarks are formed as a result of gas (methane) or/and groundwater outflow from the sea bottom. Methane, the second most important (after CO2) greenhouse gas, has a significant impact on biogeochemical processes in the bottom sediments by affecting the cycling of some elements, e.g. C, Fe, and S. Active pockmarks may also lead to changes in water column conditions by causing nutrients release from sediments. In the present study, we have focused on the impact of biogeochemical processes in pockmarks (methanogenesis, anaerobic methane oxidation, and groundwater seepage) on the transformation of iron (Fe) and the mineral composition of the sediment. In pore water, concentrations of hydrogen sulfide, phosphate, ammonia, sulfate, chloride, dissolved inorganic carbon, iron, and methane were analyzed. In the sediment, Fe speciation was performed using sequential extraction. The mineral composition was determined using powder X-Ray diffraction and scanning electron microscopy. The results from two pockmarks (with active gas seepage and groundwater infiltration) and two reference stations in the southern Baltic Sea show that geochemical conditions in pockmark sediments are significantly different from those in the typical muddy sea bottom. Pore water in pockmarks is characterized by lower sulfate and higher dissolved carbon concentrations as compared to areas of the seafloor where such structures are absent. This is due to the outflow of groundwater, which was confirmed by lower chloride concentration. In addition, sulfate is used to oxidize methane diffusing from deeper layers. Sediments in pockmarks are enriched in Fe(II) carbonates and depleted in Fe(III) (oxy)hydroxides, resulting from the anaerobic oxidation of methane with Fe(III) (Fe-AOM). Ferrous iron produced in large quantities during Fe-AOM is precipitated with carbonates.