Hydrogen Sulfide Emissions Research Articles

Field Study of Generation and Emission of Hydrogen Sulfide in a Sanitary Sewer Network Downstream of a Long Forcemain

Field Study of Generation and Emission of Hydrogen Sulfide in a Sanitary Sewer Network Downstream of a Long Forcemain

Characterizing multifaceted environmental risks of oil and gas well leakage through soil and well methane and hydrogen sulfide emissions

Oil and gas wells (OGWs) can lead to soil and well emissions of methane (CH4), a potent greenhouse gas, and hydrogen sulfide (H2S), a highly toxic gas, both of which reduce air quality and can cause explosions when emitted into confined spaces. Developments have been occurring over OGWs, posing larger health and safety risks. However, to our knowledge, previous studies have not conjunctively analyzed well and soil emissions while considering development on or near OGWs. In this paper, we characterize 343 CH4 and H2S emission rate measurements from 67 non-producing (abandoned) and 35 producing (active) OGWs, including 205 measurements from soils surrounding 81 OGWs in Ontario and Quebec. We also provide the first emission rate estimates from an abandoned water and OGW-linked explosion and map OGWs in urban and built-up areas in Ontario and Quebec. We estimate the explosion-linked emissions to be 3,000 g CH4/hour and 7 g H2S/hour. Moreover, we find that 7,264 and 161 OGWs in Ontario and Quebec, respectively, are in urban and built-up areas, with 94% of these wells being abandoned. For the 102 wells we measured, we find OGW emission rate ranges of -16 to 47,000 mg CH4/hour and 0.001 to 3,300 mg H2S/hour, with 9% of the wells having positive detections of H2S. Although soil CH4 emissions at a 1-meter distance from the wells are most correlated with well emissions, the highest soil emission rate was observed at a 3-meter distance, indicating the potential for OGW-related emissions into buildings to occur away from the well. Overall, our multi-faceted measurement dataset provides a basis for conjunctive analysis of the broad range of environmental risks of OGWs to climate, indoor and outdoor air quality, and explosions.

PSVI-26 The benefits of probiotics (L. plantarum and L. acidophilus) supplement in growth performance, egg production, gas emission and gut microbiome diversity in Hy-Line brown laying hens

Abstract During the past few decades, antibiotics have been widely used at subtherapeutic doses to improve growth rates and performance in the poultry industry. However, antibiotics can result in side effects including bacterial resistance; these side effects often have detrimental consequences for human health. Thus, the poultry sector was urged to seek alternative strategies to promote animal performance. One environmentally friendly approach to growth promotion involves the use of probiotics, which have been used in the poultry industry for decades. Therefore, we aimed to investigate the effects of dietary supplementation with Lactobacillus spp. (L. plantarum and L. acidophilus) on growth performance, egg production, gas emission and gut microbiota diversity in laying hens. A total of 192 Hy-Line brown laying hens were randomly divided into four groups and assigned to one of four dietary treatments for 12 wk. The test treatments were basal diet (TRT1), basal + 0.25% antibiotic (TRT2), and basal + 0.1% probiotics (TRT3), and basal + 0.2% probiotics (TRT4). Laying hens fed a diet supplemented with 0.2% probiotics showed increased (P < 0.05) egg production in wk 9, 10, and 12. Moreover, fecal ammonia and hydrogen sulfide emissions were reduced (P < 0.05) in the probiotic groups. Microbiome analysis showed increased (P < 0.05) species richness in the probiotic groups, as indicated by Chao1 and Shannon indices, but a decrease (P < 0.05) in species diversity according to the Simpson index, suggesting a specific microbial community development due to probiotic supplementation. In conclusion, this study provides us with an insight into the potential use Lactobacillus spp. probiotic as a food supplement in the laying hen industry also provides us with a better understanding of the interplay between Lactobacillus spp. and the gut microbiome diversity in laying hens.

PSI-29 Enhancing growth performance and reducing environmental impact with dietary protease supplementation in growing pigs fed high- and low-density diets

Abstract Exogenous protease has emerged as a promising solution for enhancing protein digestion and utilization in animal diets, offering potential benefits for both animal performance and environmental impact mitigation in pig farming. In a 6-wk trial involving 140 growing pigs [initial body weight (BW) = 24.10 ± 1.66 kg], the effects of dietary protease supplementation on growth performance, nutrient digestibility, and noxious gas emission were investigated. Pigs were randomly assigned to one of four dietary treatments in a 2 x 2 factorial design with two levels of nutrient density and 0 or 125 g/ton supplementation of protease. The pigs were blocked by BW and housed in 28 pens with each pen consisting of 5 pigs (3 barrows and 2 gilts). The experimental design employed a randomized complete block design with 7 replicate pens per treatment. The data were analyzed using two-way ANOVA, with differences between means assessed using Tukey’s test (P < 0.05). Results revealed no significant interaction (P > 0.05) between nutrient density and protease supplementation concerning growth performance, nutrient digestibility, and noxious gas emission. Pigs subjected to high-density diets exhibited greater (P < 0.05) average daily gain (ADG) and gain-to-feed ratio (G:F) compared with those on low-density diets. While protease supplementation did not impact ADG and average daily feed intake (ADFI), there was a tendency towards reduced (P = 0.08) G:F throughout the 6-wk period. Pigs fed high-density diets demonstrated significantly greater (P < 0.05) apparent total tract digestibility (ATTD) of gross energy (GE) compared with their counterparts on low-density diets. Furthermore, the inclusion of protease significantly increased (P < 0.05) ATTD of GE. However, no discernible differences were noted among diets regarding the ATTD of dry matter and nitrogen. Regarding noxious gas emission, protease supplementation did not significantly affect total mercaptans and hydrogen sulfide (H2S) emission. Nonetheless, there was a notable trend towards reduced (P = 0.06) ammonia gas (NH3) emission with protease inclusion. Similarly, nutrient density did not exhibit a significant effect (P > 0.05) on noxious gas emission. In conclusion, the results of the study underscore the importance of nutrient density and protease supplementation in optimizing pig performance and environmental sustainability in swine production systems. Further research is warranted to elucidate the underlying mechanisms and refine strategies for maximizing the benefits of these dietary interventions.

High rates of hydrogen sulfide emissions measured from marginal oil wells near Austin and San Antonio, Texas

Marginal oil and gas wells, or wells that produce less than 15 barrels of oil equivalent per day, represent 80% of actively producing wells in the United States, although they produce less than 10% of energy supply. Marginal wells are a disproportionate source of methane (CH4) relative to their production, and they emit harmful air pollutants, such as benzene and other hydrocarbons found in oil and natural gas. We made direct measurements of CH4 and hydrogen sulfide (H2S) emissions from 46 wellheads in the Luling Field, Caldwell County, Texas, just east of the Austin/San Antonio Metroplex. We found that these wells are venting natural gas and are a large source of hydrogen sulfide (H2S), a poisonous air pollutant. Hydrogen sulfide emission rates ranged from 0 to 5 ± 0.5 g H2S hr−1 with an average emission rate of 1.6 ± 0.1 g H2S hr−1. We also found ambient concentrations of H2S at dangerous levels (>100 ppm) near many of the wells. Methane emission rates were in line with previous studies of marginal wells, ranging from 0.0 to 2770 ± 390 g CH4 hr−1, with a skewed distribution and average emission rate of 710 ± 100 g CH4 hr−1. Oil production records from Texas were incomplete: some wells had oil production data from the year of sampling, but many had no production data for several years or decades, although they were actively pumping while we were on site. Interviews with local residents indicate that the closing of the county gas processing plant and subsequent loss of gathering lines may be the cause of gas venting and CH4 and H2S emissions from production sites. This deserves further scrutiny, as marginal wells in this region are a major source of H2S, a health hazard to people living and working nearby.

Assessing sulfate-reducing bacteria influence on oilfield safety: Hydrogen sulfide emission and pipeline corrosion failure

With the further development of oilfield, excessive sulfate-reducing bacteria (SRB) has intensified odors and increased pipeline leakage incidents. Accurate predictive models of H2S emission and pipeline corrosion based on SRB content are essential for safety. This study analyzed the correlation between sulfide content and SRB content at different nodes in the injection-production system of Daqing Oilfield, and characterized the pipeline corrosion products using scanning electron microscopy (SEM), X-ray diffraction (XRD), and stereo microscope. Corrosion rates were investigated through 18 sets of orthogonal experiments, considering factors such as SRB, temperature, pH, liquid flow rate, CO2 partial pressure, and H2S partial pressure, and the main controlling factors of corrosion were identified. Finally, the risk models for H2S emission and corrosion rate based on SRB content were established under on-site operating conditions. The results show that a significantly positive correlated between SRB and sulfide content at different nodes, with the highest levels observed at the settling tank, indicating the highest risk of H2S emission. SRB contributed to corrosion in both water injection and oil collection pipelines, with more serious corrosion in the water injection pipeline. SRB and pH were identified as the main factors influencing corrosion rate. The H2S emission prediction model based on the correlation of SRB and sulfide was reliable, with an accuracy exceeding 90 % compared to the measured results. Additionally, the corrosion rate model for pipelines, related to SRB content, had an error of less than 7 %. To minimize risks, it is recommended to maintain a low risk environment in the injection-production system by sterilization and increasing the pH of water. This study has significant theoretical importance for ensuring the safe operation of injection-production systems.

Nitrite-dependent microbial utilization for simultaneous removal of sulfide and methane in sewers

Chemicals are commonly dosed in sewer systems to reduce the emission of hydrogen sulfide (H2S) and methane (CH4), incurring high costs and environmental concerns. Nitrite dosing is a promising approach as nitrite can be produced from urine wastewater, which is a feasible integrated water management strategy. However, nitrite dosing usually requires strict conditions, e.g., relatively high nitrite concentration (e.g., ∼200 mg N/L) and acidic environment, to inhibit microorganisms. In contrast to “microbial inhibition”, this study proposes “microbial utilization” concept, i.e., utilizing nitrite as a substrate for H2S and CH4 consumption in sewer. In a laboratory-scale sewer reactor, nitrite at a relatively low concentrations of 25–48 mg N/L was continuously dosed. Two nitrite-dependent microbial utilization processes, i.e., nitrite-dependent anaerobic methane oxidation (n-DAMO) and microbial sulfide oxidation, successfully occurred in conjunction with nitrite reduction. The occurrence of both processes achieved a 58 % reduction in dissolved methane and over 90 % sulfide removal in the sewer reactor, with microbial activities measured as 15.6 mg CH4/(L·h) and 29.4 mg S/(L·h), respectively. High copy numbers of n-DAMO bacteria and sulfide-oxidizing bacteria (SOB) were detected in both sewer biofilms and sediments. Mechanism analysis confirmed that the dosed nitrite at a relatively low level did not cause the inhibition of sulfidogenic process due to the downward migration of activity zones in sewer sediments. Therefore, the proposed “microbial utilization” concept offers a new alternative for simultaneous removal of sulfide and methane in sewers.

Mitigation of ammonia and hydrogen sulfide emissions during aerobic composting of laying hen waste through NaOH-modified biochar

The impact of NaOH-modified biochar on the release of NH3 and H2S from laying hens' manure was examined for 44 days, using a small-scale simulated aerobic composting system. The findings revealed that the NaOH-modified biochar reduced NH3 and H2S emissions by 40.63% and 77.78%, respectively, compared to the control group. Moreover, the emissions of H2S were significantly lower than those of the unmodified biochar group (p < 0.05). The increased specific surface area and microporous structure of the biochar, as well as the higher content of alkaline and oxygenated functional groups, were found to facilitate the adsorption of NH3 and H2S. This enhanced adsorption capability was the primary reason for the significant reduction in NH3 emissions. Furthermore, during the high-temperature phase of composting, there was a notable alteration in the microbial community. The abundance of Limnochordaceae, Savagea, and IMCC26207 increased significantly which aided in the conversion of H2S to stable sulfate. These microorganisms also influenced the abundance of functional genes involved in sulfur metabolism, thereby inhibiting cysteine synthesis, along with the decomposition and conversion of sulfate to sulfite. This led to a significant decrease in H2S emissions. This study provides valuable data for the selection of deodorizers in the composting process of egg-laying hens. The results have significant implications for the application of NaOH-modified biochar for odor reduction in aerobic composting processes.

Assessment of transient hydrogen sulfide peak emissions caused by biogas plant operation

Odor nuisance is a major impediment for public acceptance and wider implementation of biogas plants. Knowledge on composition and dynamics of emissions from these plants is highly needed for development of robust mitigation solutions. In this study, odorant emissions were investigated from two biogas plants of different sizes and capacities. Measurements using proton-transfer-reaction mass spectrometer (PTR-MS) revealed that hydrogen sulfide was the main odorant and constituted 82% and 71% of the odor activity sums (SOAV) at the two studied plants, respectively. Long-term time-resolved measurements furthermore revealed that emissions were highly dynamic with distinct short-term emission peaks. By deploying an array of electrochemical sensors, the main sources of hydrogen sulfide emission were subsequently identified and correlated with operational data to identify the major causes for the highly fluctuating emissions. Addition of biomasses in the form of animal slurry to pre-tanks, were shown to be the major cause of periodic hydrogen sulfide emission within the range of 50–1200 ppm. Such hydrogen sulfide peak emissions could challenge odor abatement from biogas plants and should be taken into account when designing odor abatement technologies for biogas plants.

The Impacts of the C/N Ratio on Hydrogen Sulfide Emission and Microbial Community Characteristics during Chicken Manure Composting with Wheat Straw

Wheat straw (WS) has long been subjected to rough treatment by traditional incineration, which not only results in the waste of biomass resources but also poses a risk of atmospheric pollution and is not conducive to the sustainable utilization of natural resources. With great humification potential, WS can be utilized as a valuable composting material. The study optimized the C/N ratio by mixing WS and chicken manure (CM) as composting raw materials, and found that this method could significantly improve the compost quality. In comparison to the conventional poplar woodchip (PW) conditioning, the incorporation of WS resulted in an elevated composting temperature, an extended high-temperature period, a more expeditious lignocellulose degradation, a notable enhancement in the organic matter content, a suppression of hydrogen sulfide production under low C/N ratio, and a promotion of elemental sulfur conversion, collectively contributing to an enhanced overall quality and environmental friendliness of the compost. Correlation analysis of microbial communities and environmental factors demonstrated that the mixed compost facilitated the growth of actinomycetes and sulfur-transforming bacteria. Additionally, structural equation model indicated that parameters such as temperature and pH value played a key role in the composting process.

Sustainable Livestock Production: Screening Analysis and Pilot Implementation of a Biofilm in Piggery Biofilters for Mitigation of Ammonia and Hydrogen Sulfide Emissions

One of the most noticeable problems associated with the close location of piggeries is gaseous compounds emission. Ammonia and hydrogen sulfide emissions affect the quality of life of people living in the vicinity of such facilities. Among the diverse methods for managing and controlling malodorous substances, biological methods, which involve the utilization of microbiological agents, are widely employed. The use of bacterial strains is a relatively simple, low-cost, and ecological method. The study aimed to conduct a preliminary evaluation of the implementation of a novel consortium of deodorizing bacteria. The study involved the selection of bacteria, assessment of the antagonistic properties, implementation of the inoculum in a mesh-filled biofilter, and analysis of ammonia, hydrogen sulfide, and fine dust content in the air before and after passing through the mature biological bed. The results obtained demonstrate the effectiveness of the biofiltration bed in reducing ammonia levels, with a maximum decrease observed at 73.90%. For hydrogen sulfide, a removal efficiency of &gt;72.08% was observed. Reduction in fine dust pollution also decreased from a level of 3.75 mg/m3 to 1.06 mg/m3. The study’s findings demonstrate the promising potential of utilizing a consortium of deodorizing bacteria as an effective approach to mitigating emissions from piggeries.

Interaction of composite fume suppression and odor elimination agents with crumb rubber modified asphalt: Inhibition behavior of volatile organic compounds (VOCs) and inorganic fume

The production and construction of crumb rubber modified asphalt (RMA) at high temperatures can produce a large amount of toxic fume, which is detrimental to human health and environment. In this study, a series of composite fume suppression and odor elimination agents (CSEAs) with both physical adsorption and chemical capture functions were adopted to reduce the emissions of volatile organic compounds (VOCs) and hydrogen sulfide (H2S). The material composition, microstructure, and specific surface area of CSEA were analyzed by using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and N2 adsorption-desorption isotherm (BET). The inhibitory effects of adding CSEA on toxic fume emissions from RMA at high temperatures were investigated through a combination of fume emission tests, H2S gas detection, gel permeation chromatography (GPC), and gas chromatography–mass spectrometry technology (GC–MS). The adsorption behavior of CSEA on H2S was analyzed through adsorption dynamics. Results showed that the physical and chemical properties of CSEA are stable while chemical adsorption dominates the CSEA's effect on H2S. ZnO and Ca(OH)2 exhibit good crystallization effects on the surface of the carrier by forming mesoporous structures mostly above 3.4 nm in size. The incorporation of CSEA significantly reduced the total emissions of RMA fume and the main components of VOCs in which the average inhibition rate of H2S can reach 44 % at an initial 30 mins.

Risk prediction for hydrogen sulfide emission based on sulfate-reducing bacteria in the water flooding oilfield

The water quality of the injection–production systems deteriorates as the water flooding oilfields are developed more deeply, and the content of sulfate-reducing bacteria (SRB) increases. Accordingly, hydrogen sulfide (H2S) emission related to SRB is intensified, which will arise safety and health problems. In order to investigate the effect of SRB on H2S emission in the water flooding oilfield, the contents of SRB and sulfide of the different nodes of a typical injection–production system of Daqing Oilfield were measured first, and then, H2S emission from water was simulated under different conditions. Consequently, a H2S emission prediction model was established based on Henry coefficient and the correlation between sulfide content and SRB content in the water. The measured sulfide contents were ranging from 0.25 to 6.34 mg/l, and the SRB contents were from 2.5 to 25 000 pcs/ml, and the highest SRB and sulfide contents were found in the settling tank. The correlation between sulfide content and SRB content was much remarkable, and the R2 value of the correlation analysis was 0.94. Henry coefficient of H2S emission was obtained from the simulated experiments under varied conditions such as sulfate content, oil content, and temperature. The established H2S emission prediction model was much reliable for predicting H2S emission for water flooding injection–production system, and the accuracy of the predicted H2S emission of four nodes of the injection–production system was larger than 95% compared to the measured results. This study provides theoretical guidance for predicting H2S emission risks in water flooding injection–production systems.

Mitigation of hazardous ammonia and hydrogen sulphide emissions using carbon based nanometal oxides adsorbents

Mitigation of hazardous ammonia and hydrogen sulphide emissions using carbon based nanometal oxides adsorbents

Supplementation of protease and different nutrient density diets in growing-finishing pigs.

This study was conducted to investigate the effects of protease supplementation and different nutrient density of diets in growing-finishing pigs. A total of one hundred-eight crossbred growing pigs ([Landrace × Yorkshire] × Duroc) with an initial body weight (BW; 18.74 ± 3.46 kg) were used for 15 weeks. Pigs were randomly assigned to six dietary treatments with 6 replicates of 3 pigs per pen in a 3 × 2 factorial through the following arrangement: Three groups of protease (1, Basal diets; 2, Protease A: 125 mg/kg protease derived from Streptomyces sps; 3, Protease B: 100 mg/kg protease derived from Bacillus licheniformis) at two different nutrient density diets (1, Basal requirement; 2, 0.94%-0.98% higher than requirement in dietary protein and 50 kcal/kg in energy). High nutrient (HN) diets showed higher average daily gain (ADG) (p < 0.05) and apparent total tract digestibility (ATTD) of crude protein (CP) (p < .0001) compared to basal nutrient (BN) diets during growing periods. Supplementation of protease showed higher BW (p < 0.05) and ADG (p < 0.05) compared to non-supplementation of protease during growing periods. Also, supplementation of protease showed higher ATTD of CP (p < 0.01), ATTD of gross energy (p < 0.05) and decreased blood urea nitrogen (BUN) level (p = 0.001) compared to non-supplementation of protease during finishing periods. Pigs which fed the protease showed decreased ammonia (NH3) emissions (p < 0.05) during experiment periods and decreased hydrogen sulfide (H2S) emissions (p < 0.01) during finishing periods. Interactions between nutrient density and protease were observed, which decreased the feed conversion ratio (p < 0.05) in HN diets without protease compared to BN diets without protease during weeks 4 to 6. Also, interaction between nutrient density and protease was observed, which resulted in improved ATTD of CP (p < 0.01) in response to PTA supplementation with HN diets during the finishing period. In conclusion, supplementation of protease reduces NH3 in feces and BUN in whole blood by increasing the digestibility of CP and improves growth performance. Also, diets with high nutrient density improved growth performance and nutrient digestibility in growing periods.

Sub-dew point claus process for reducing hydrogen sulfide emission from sulfur recovery units

Increasing the efficiency of the sulfur recovery and decreasing the hydrogen sulfide emission are significant from both economic and environmental aspects. The cold bed adsorption (CBA) process is an approach to address the above concerns. The bench scale CBA experiments including adsorption and regeneration stages at temperatures of 140 °C and 280 °C are investigated against an industrial scale modified Claus process by using a commercial Al2O3 catalyst. Implementing CBA increases the H2S conversion of a modified Claus process sulfur recovery unit about 5%, but it is not efficient to convert CS2 and COS to the elemental sulfur. Period times of 12, 7 and 3 h are appropriate for the adsorption, desorption and cooling stages, respectively. After cycles of CBA process, the surface area and pore volume of the commercial Al2O3 Claus catalyst decrease from 385 m2/g and 0.34 cm3/g to 337 m2/g and 0.31 cm3/g, respectively as a result of condensing the elemental sulfur inside its micro- and meso- pores. The proposed CBA process is applicable to reduce the H2S emission, CAPEX and OPEX of sulfur recovery units.

Рекуперация и очистка газовых выбросов целлюлозного производства

For pulp production, large-scale enterprises have been built which, while in operation, are subject to new requirements, different from the design ones, for economic efficiency, labour safety, as well as impact on the local population and the environment. Significant success in this work has been achieved by changing the liquor recovery technology, switching to burning black liquor of increased concentration, which makes it possible to almost completely eliminate the largest source of hydrogen sulfide and methyl mercaptan emissions with flue gases, reduce sulfur losses and improve energy efficiency of soda recovery boilers. Another significant source of soda recovery boiler emissions is a smelt dissolving tank vent. An important technological operation of dissolving molten sodium salts with weak white liquor supplied from the causticization shop takes place in the tank. The modern development of smelt leaching technology is related to the improvement of equipment compatible with the technology of regeneration of chemical reagents for pulp production. Heat exchangers and gas purifiers of “gas-liquid” systems, easier to adapt to technological requirements compared to other systems, are installed on the dissolving tank vent. The installation of such equipment provides the change in the smelt leaching technology, and affects the technology of causticization and lime recovery. This article covers the research of the relationship between the technical solutions ensuring the safety of personnel in the boiler shop, heat and chemicals recovery, as well as purification of gas emissions and the changes in the technology of smelt leaching in the soda recovery boiler of the pulp mill. On the basis of experimental data and a mathematical model of the movement of the vapour-gas mixture in the smelt dissolving tank vent, the technological feasibility of installing heat exchangers at different heights of the vent and the possibility of effective purification of gas emissions using a direct-flow sprayer have been considered. The applicability of the irrigation of the steam-gas flow with weak white liquor, which is formed during the cycle of chemical regeneration in pulp production, as well as the conditions for ensuring reliable operation of gas purification equipment, have been investigated. The quantitative characteristics of the necessary change in consumption and composition of weak white liquor and the methods of its supply to the dissolving tank have been obtained.

Temporal and spatial variation in hydrogen sulfide (H2S) emissions during holopelagic Sargassum spp. decomposition on beaches

BackgroundSince 2011, over 30 tropical Atlantic nations have experienced substantial landings of holopelagic Sargassum spp. Its decomposition results in the production of hydrogen sulfide (H2S), which, in elevated concentrations, can pose a threat to human health. This study aims to enhance our understanding of the temporal and spatial variability in H2S emissions during the decomposition of Sargassum on beaches. The primary objective is to assess potential exposure risks for local populations, tourists, and cleanup workers. MethodsH2S levels were monitored using a SENKO sensor (SGTP-H2S; limit of detection 0.1–100 ppm; resolution 0.1 ppm) at four distances from Sargassum accumulation points of (0, 10, 30, and 40 m) in Puerto Morelos, Mexico, during 2022 and 2023. ResultsElevated concentrations of H2S were detected beneath the Sargassum piles, with 23.5% of readings exceeding 5 ppm and occasional spikes above 100 ppm. Above the piles, 87.3% of the measurements remained below 2 ppm, and the remainder fell between 2.1 and 5.2 ppm. At 10 m from the shoreline, 90% of measurements registered below 0.1 ppm, and the remaining 10% were below 2 ppm. Readings at 30 and 40 m consistently recorded levels below 0.1 ppm. H2S concentrations positively correlated with Sargassum pile height, the temperature beneath the piles, and wind speed. ConclusionsOur findings suggest no immediate and significant exposure risk for residents or tourists. However, Sargassum cleanup workers face a higher exposure risk, potentially encountering concentrations above 5 ppm for nearly one-fourth of the working time.

Diffusive emission of carbon dioxide and hydrogen sulfide from Valley of Death, Kamchatka, Russia

Valley of Death, discovered almost half a century ago and located in the very upper reaches of the river Geysernaya, about 7 km from the Geyser Valley in Kamchatka, is famous for occurrences of dead animals there. During field work in August 2023, the soil CO2 flux was measured using the accumulation chamber method in the lower section of the Valley of Death. On an area of 6.2 × 103 m2, the flux was measured at 100 randomly distributed points. At several points a MultiGas device was used for analysis of the composition of soil gases (СО2, H2S, SO2). Data processing showed the presence of a single “hydrothermal” population of the CO2 flux. The average CO2 flux was found to be 1272 g m−2 d−1, with the maximum value of 28,984 g m−2 d−1. The average weight ratio of CO2/H2S was 14.7 ± 4, and thus, the “deadly” part of the surface of Death Valley in August 2023 emitted ∼8 t d−1 of CO2 and ∼ 0.54 t d−1 of H2S. The soil temperature at the measurement points was close to the air temperature and did not correlate with the CO2 flux. Such value of the CO2 flux corresponds not <3.5 kg s−1 of hydrothermal steam condensed beneath the degassing part of Valley of Death.

Effects of dietary multienzymes on the growth performance, digestive enzyme activity, nutrient digestibility, excreta noxious gas emission, and nutrient transporter gene expression in white feather broilers.

Adding multienzymes to poultry feed rations is recognized as a nutritional strategy aimed at improving poultry performance and health status. Nonetheless, some literatures present an ongoing debate about the extent of multienzymes beneficial impact on poultry growth performance. This study aimed to explore the impacts of dietary multienzyme supplementation on broilers, focusing specifically on growth performance, carcass characteristics, apparent nutrient digestibility, excreta noxious gas emission, and intestinal nutrient transporter gene expression. A total of 3,200 broilers were randomly assigned to five groups (eight replicates per treatment group) and treated with the following: normal control (CON), CON + 100g/t multienzyme (ME100), CON + 150g/t multienzyme (ME150), CON + 200g/t multienzyme (ME200), and CON + 250g/t multienzyme (ME250). Supplementing with multienzymes significantly influenced the feed conversion rate (linear, P = 0.007; quadratic, P = 0.024) and the European broiler index (linear, P = 0.004; quadratic, P = 0.016) in broilers. Dietary multienzymes significantly influenced apparent metabolizable energy (quadratic, P = 0.015) and neutral detergent fiber (quadratic, P < 0.001). Moreover, multienzyme supplementation in the diet also decreased the emission of ammonia (linear, P = 0.001; quadratic, P = 0.006) and hydrogen sulfide (quadratic, P = 0.006) in the excreta. In addition, dietary multi-enzyme notably elevated (P < 0.05) the mRNA expression of nutrient transporter genes, including peptide transporter 1 (PePT1), Na-dependent neutral amino acid transporter (B0AT), glucose transporter 2 (GLUT2), and fatty acid binding protein1 (FABP1). These findings suggest that dietary supplementation with multienzymes can improve the efficiency of feed utilization, and the digestion and absorption of nutrients and reduce excreta gas emission. Furthermore, this study provides a theoretical basis for advancing the use of multienzymes in broiler production.