Water-soluble Gases Research Articles

Hydrothermal liquefaction of wood using a modified multistage shrinking-core model

Wood liquefaction in hot compressed water is modeled using the hydrolysis of Cellulose, Hemicellulose, and Lignin. These three components are reacted under catalyst-free subcritical conditions in a temperature range from 553 K to 640 K, and the heating rate ranges from 2 K/min to 6 K/min. Using a simplified reaction scheme, water-soluble products11WSP: - Water soluble products (WSP), Biocrude, char, and gas are generated through intermediates with each wood component. A modified multistage shrinking core model is employed to simulate biomass particle degradation. The reaction and kinetic regime of the hydrothermal liquefaction22HTL: -Hydrothermal Liquefaction (HTL) process are treated separately for each wood component. Although the lack of initial fast reaction kinetic data limits the development of more accurate models, computed results displayed a generous fit to data from the literature. At 593 K for a 2 K/min heating rate and particle size of 0.08 mm, biocrude shows the maximum yield of 26.87% for wood liquefaction. Although lower heating rates show fast initial lignin hydrolysis, for longer residence times, and close to the critical point, yield outputs show similar yields. Meanwhile, char and gas yields of cellulose model show maximums of 55 wt% and 25 wt% respectively at 640 K with a 2 K/min heating rate. Nevertheless, char yield values become very similar at 640 K for different heating rates for the cellulose hydrolysis model. Both cellulose and lignin hydrolysis models show better hydrolysis with smaller particle sizes. Besides, lignin decomposition shows more dependence on the particle size, where it decomposes much faster with 0.08 mm particle and slower than Cellulose with the 1 mm particle.

Distribution law of helium in Leshan-Longnvsi paleo-uplift in Sichuan Basin, China

The Weiyuan and Anyue large gas fields discovered on the Leshan-Longnvsi paleo-uplift in Sichuan Basin have the oldest marine gas reservoir discovered in China so far, and Weiyuan is also the first gas field to utilize helium resources in China. The Helium in natural gas of Leshan-Longnvsi paleo-uplift belongs to crust-derived helium formed by radioactivity, and its content distribution shows obvious regularity. The content of helium is highly correlated with the age of reservoir in the same gas field, and the helium content is gradually increased from the top to the bottom. However, the content of helium in natural gas presents significantly different in various tectonic units. The content of helium in Anyue gas field developed on Gaoshiti-Moxi structure is very low. The average contents of Sinian and Cambrian are 0.0356% and 0.0078%, respectively. The content of helium in Weiyuan gas field developed on Weiyuan structure is relatively higher, and the average contents of Sinian and Cambrian are 0.28% and 0.18% respectively. The high helium content of natural gas in Weiyuan gas field is related to the large-scale granite body developed on the basement on the one hand and the water-soluble gas accumulation on the other hand. The main gas reservoirs in the Weiyuan gas field and adjacent areas are located in the Sinian system. From the slope area to the high point of the Weiyuan structure, the helium content has increased significantly. With the tectonic movement of the Himalayan period, the Weiyuan area is greatly uplifted, causing structural traps. Natural gas dissolved in the water, including helium gas, is decomposed by decompression, and the released gas is trapped, then released gases accumulated in traps and thus formed Weiyuan gas field with high content of helium.

SO2 emission measurement with the European standard reference method, EN 14791, and alternative methods – observations from laboratory and field studies

ABSTRACTEN 14791 is a European Standard Reference method for the measurement of SO2 in emissions. This standard is based on a wet-chemical method in which SO2 present in flue gases is absorbed into an absorption solution containing hydrogen peroxide, and analyzed as sulfates after sampling. This study presents the results obtained when three portable automated measuring systems (P-AMS), based on Fourier-transform infrared (FTIR) spectroscopy, non-dispersive infrared (NDIR) and ultraviolet-fluorescence (UV) techniques, were compared to the Standard Reference Method for SO2 (EN 14791) in order to verify whether they could be used as alternative methods (AM) to EN 14791. In the case of FTIR, the measurements were performed from hot and wet gas, without any conditioning. UV-fluorescence analyzers were equipped with dilution probes and one NDIR applied a permeation dryer, whereas the other had a chiller. Tests were carried out at concentration ranges from 0 to 200 mg/m3(n) and from 0 to 800 mg/m3(n) for testing of equivalency according to CEN/TS 14793 using a test bench. Equivalency test criteria were met for all tested P-AMS except for NDIR at the lower range. The SO2 results measured with NDIR and the chiller were lower compared to the set-up with NDIR and permeation. This was most probably due to the chiller causing absorption of SO2 in the condensate. Tests were also carried out at field conditions, measuring the SO2 emissions from a boiler combusting mainly bark. The same phenomena were observed in these tests as during the test bench study, i.e. the measurement set-up with NDIR and the chiller gave the lowest results. These data demonstrated that the tested alternative methods (FTIR, UV-fluorescence, and NDIR) could be used instead of the standard reference method EN 14791, thus providing real-time calibration of automated measuring systems. It must however be emphasized that when measuring water-soluble gases, such as SO2, the choice of suitable conditioning technique is critical in order to minimize losses of the studied component in the condensate.Implications: Portable automated measuring systems (P-AMS) provide real-time information about emissions and their concentrations, thus offering significant advantages compared to wet-chemical methods. This study presents results which can be used as a validation protocol to show that the tested P-AMS techniques (FTIR, NDIR, UV-fluorescence) could be used instead of EN 14791 (CEN 2017a) as alternative methods (AM), when paying attention to the selection of an appropriate conditioning technique.

Large-scale and low-cost fabrication of two functional silica sorbents by vapor condensation induced nanoemulsions and their excellent uptake performance

Effective removal of Pb(II) is a pressing global issue for both drinking water and wastewater purification. In this work, the large-scale and low-cost synthesis of two functional silica sorbents by vapor condensation induced water-in-oil (W/O) nanoemulsions (NSEs) is proposed, and the obtained high quality sorbents are applied for rapid removal of Pb(II). Tetraethoxysilane (TEOS) is diffused into the droplet of NSEs reactor, and then naked silica spheres are generated by hydrolysis and condensation at room temperature. The effects of the reaction conditions and confined space, including the stability, pumping time of water-soluble gas, and condensing time etc. on the size, morphology, and yield of main product are investigated, and the possible formation mechanism is demonstrated. Furthermore, functional silica sorbents with defined surface chemistry (i.e. Si-NH2 and Si-SH) are also synthesized via as-prepared NSEs systems. Finally, attributed to the inherent amino and mercapto terminal groups, Si-NH2 and Si-SH illuminate the maximum sorption capacity of 245.7 mg g−1 and 72.16 mg g−1 for Pb(II), respectively. Surface charge does not play a significant role in Pb(II) capture by Si-NH2, while chemisorption and electrostatic interaction both contribute to uptake performance of Si-SH. NSEs formed by condensation of water vapor do not need violent stirring and strict component proportion, which is an alternative and potential strategy to synthesize functional sorbents.

Cellulose Fibers Enable Near-Zero-Cost Electrical Sensing of Water-Soluble Gases.

We report an entirely new class of printed electrical gas sensors that are produced at near “zero cost”. This technology exploits the intrinsic hygroscopic properties of cellulose fibers within paper; although it feels and looks dry, paper contains substantial amount of moisture, adsorbed from the environment, enabling the use of wet chemical methods for sensing without manually adding water to the substrate. The sensors exhibit high sensitivity to water-soluble gases (e.g., lower limit of detection for NH3 < 200 parts-per-billion) with a fast and reversible response. The sensors show comparable or better performance (especially at high relative humidity) than most commercial ammonia sensors at a fraction of their price (<$0.02 per sensor). We demonstrate that the sensors proposed can be integrated into food packaging to monitor freshness (to reduce food waste and plastic pollution) or implemented into near-field-communication tags to function as wireless, battery-less gas sensors that can be interrogated with smartphones.

Characteristics of Aerosol Chemical Compositions and Size Distributions during a Long-Range Dust Transport Episode in an Urban City in the Yangtze River Delta

A long- and large-range heavy dust episode occurred from 3 to 8 May 2017 in China. To explore the impacts of this long-range dust transport episode on the chemical compositions and size distributions of urban aerosols, such instruments as an online analyzer for monitoring aerosols and gases (MARGA) and a wide-range particle spectrometer (WPS) were mainly used to monitor chemical components, such as PM2.5 and aerosol size distributions in the range of 10 nm to 10 μm, in Nanjing in this study. During the dust episode, the average concentrations of PM2.5 and PM10 and ions of Ca2+, Mg2+, Cl-, SO42−, NO3−, and NH4+ were 66.2, 233.9, and 1.1, 1.5, 1.1, 11.4, 7.8 and 4.4 μg·m−3, which were 4.4, 5.8, 3.7, 15, 1.38, 1.84, 1.66 and 1.83 times higher than the values observed before the episode and 2.2, 3.3, 5.5, 5.0, 1.57, 1.97, 1.39 and 1.69 times the levels after the episode. The dusts were demonstrated to have differential impacts on the water-soluble gases in the air. During the dust episode, the concentrations of HCl, SO2 and NH3 were comparably low, while the HNO2 and HNO3 concentrations were high. The diurnal variations in pollutants, including SO2, HNO3, Cl−, Ca2+, Mg2+, PM2.5 and PM10, were strongly impacted by the dust episode. However, those variations in NH3, NO3−, SO42− and NH4+ were only slightly influenced. Pollutants were distinctively featured in the various dust stages. The concentration of HNO2 was relatively high in the earliest stage but was substituted by those of SO2, PM10, PM2.5, Ca2+, Mg2+ HNO3 and Cl- in the explosion stage. The aerosol number concentrations exhibited unimodal distributions in the earliest and explosion stages but showed bimodal distributions in the duration and dissipation stages. Additionally, the aerosol size distributions were observed to shift to larger particle segments in different dust stages. The surface area concentrations exhibited four peaks in different dust stages and exhibited trimodal distributions in the non-dust episode. The surface area concentration of fine particles first increased during the earliest stage, while that of coarse particles first decreased during the dissipation stage.

A multi-instrumental geochemical approach to assess the environmental impact of CO2-rich gas emissions in a densely populated area: The case of Cava dei Selci (Latium, Italy)

The Colli Albani volcanic complex (Lazio, Italy) hosts areas characterized by anomalously high emissions of CO2-rich gases (e.g. Tivoli, Cava dei Selci, Tor Caldara, Solforata). The source of these gases is a regional aquifer within the Mesozoic carbonate rock sequences. These degassing zones release significant concentrations of H2S and other toxic gases (e.g. GEM: Gaseous Elemental Mercury, and Rn) and represent a serious hazard for local inhabitants, especially for those living at Cava dei Selci (near Rome, Italy), where the emitting areas are nested inside residential neighborhoods. In April 2016, a comprehensive geochemical survey was carried out in an abandoned stone quarry nearby the urban settlement aimed to: (i) investigate the gas composition from both punctual discharges and anomalously high diffuse soil degassing sites, and (ii) evaluate their environmental impact on the local air quality. The spatial distribution of the soil CO2 fluxes was mainly dependent on the local geostructural setting, whereas shallow secondary processes (e.g. oxidation and gas-water interaction) likely represent the main controlling factor on reactive and/or water-soluble gas species, such as CH4 and H2S. The total output of CO2 from the abandoned stone quarry accounted for 0.53% of total CO2 discharged from the whole Colli Albani volcanic district. The naturally emitted toxic gases (e.g. CO2, H2S, CH4, GEM) largely affect the air quality and pose a serious threat for the health of the local residents. A mobile multi-instrumental station able to continuously and simultaneously acquire CO2, H2S, SO2, CH4, GEM and CO was deployed to verify the concentrations of both the main deep-originated gas compounds and potential secondary gaseous contaminants (i.e. SO2) around and inside the urban settlement most exposed to the lethal gases. Hydrogen sulfide was found to be the most impacting gas, occasionally exceeding the 24-h air quality guideline for ambient air and causing odor annoyance at a distance up to more than 250 m downwind from the emitting area. In poorly ventilated basements, toxic gas accumulations up to hazardous levels were measured, producing anomalous outdoor air concentrations at the street level in front of the descending vehicular access to private garages and relatively far from the main emitting area. The geochemical survey, carried out via mobile station and soil gas measurements, resulted to be particularly efficient for evaluating the potential effects caused by gas emissions in inhabited areas. The multi-measurement approach adopted in the present study is of paramount importance for managing future urban development plans.

Overview of HOMEChem: House Observations of Microbial and Environmental Chemistry.

The House Observations of Microbial and Environmental Chemistry (HOMEChem) study is a collaborative field investigation designed to probe how everyday activities influence the emissions, chemical transformations and removal of trace gases and particles in indoor air. Sequential and layered experiments in a research house included cooking, cleaning, variable occupancy, and window-opening. This paper describes the overall design of HOMEChem and presents preliminary case studies investigating the concentrations of reactive trace gases, aerosol particles, and surface films. Cooking was a large source of VOCs, CO2, NOx, and particles. By number, cooking particles were predominantly in the ultrafine mode. Organic aerosol dominated the submicron mass, and, while variable between meals and throughout the cooking process, was dominated by components of hydrocarbon character and low oxygen content, similar to cooking oil. Air exchange in the house ensured that cooking particles were present for only short periods. During unoccupied background intervals, particle concentrations were lower indoors than outdoors. The cooling coils of the house ventilation system induced cyclic changes in water soluble gases. Even during unoccupied periods, concentrations of many organic trace gases were higher indoors than outdoors, consistent with housing materials being potential sources of these compounds to the outdoor environment. Organic material accumulated on indoor surfaces, and exhibited chemical signatures similar to indoor organic aerosol.

Chemical processing of water-soluble species and formation of secondary organic aerosol in fogs

A field study on fog chemistry and aqueous-phase processing of aerosol particles was conducted in Fresno, California's San Joaquin Valley (SJV) during wintertime. Fog droplets were collected while interstitial submicron aerosol was characterized in real time using a High Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-AMS). The fog samples were later analyzed using HR-AMS, ion chromatography (IC), and total organic carbon analyzer (TOC). Compared to interstitial aerosol, dissolved solutes in fog waters were composed of higher fractions of ammonium, nitrate, sulfate, methanesulfonic acid, and oxygenated organic compounds, likely due to aqueous formation of secondary species as well as enhanced gas-to-particle partitioning of water-soluble gases under humid conditions. The low-volatility dissolved organic matter in fog water (F-OA) was moderately oxidized with an average oxygen-to-carbon (O/C) ratio of 0.42. The chemical composition of F-OA appeared to be overall similar to that of oxygenated organic component in interstitial aerosol (OOA) and the HR-AMS mass spectra of F-OA and OOA are highly similar (r2 > 0.95). However, there are also significant chemical differences as F-OA appeared to contain a larger fraction of carboxylic functional groups than OOA, indicating enhanced organic acid formation through aqueous-phase reactions. In addition, F-OA was composed of substantially more nitrogen-containing compounds, with an average N/C ratio ∼4 times that of OOA. Most strikingly was that the F-OA spectra showed substantial enhancements of the CxHyN2+ (x ≥ 0; y ≥ 0) ions, which were likely contributed by imidazole- and/or pyrazine-based compounds formed from the aqueous reactions of aldehydes with amino compounds. The results of this study demonstrated that aqueous reactions in atmospheric droplets can significantly modify aerosol composition and contribute to the formation of oxygenated and nitrogen-containing organic compounds in atmospheric aerosol particles. This finding is important for understanding aerosol's effects on human health, air quality, and climate.

Effects of water invasion law on gas wells in high temperature and high pressure gas reservoir with a large accumulation of water-soluble gas

A high temperature and high pressure (HTHP) gas reservoir with a large accumulation of water-soluble gas contains a large amount of dissolved gas in formation water. The dissolved gas in the formation water will be released due to formation pressure depletion in the production process. At present, few researches have been done on water invasion law of gas wells regarding the released dissolved gas, especially when the change rule of water and gas is not clear in porous media after the release of water-soluble gas, which leads to the unclear water invasion law and the gas reservoirs cannot be developed efficiently. In this paper, a visualization sand filling tube is used to conduct experiments to study the effects of the dissolved gas on the law of the gas-water contact (GWC) changes in the water-soluble gas release process. The experimental results show that the release of dissolved gas leads to a GWC rise at the beginning of the depressurization process. After the pressure drops to a lower level, the GWC will decline due to a large amount of dissolved gas being released from formation water. Subsequently, numerical simulations are performed to study the effects of different solubilities of natural gas, the gas production rate, the aquifer size, and stress sensitivity on the water invasion law of the gas well. The simulation results show that a greater solubility of natural gas, a higher gas production rate, a larger aquifer size, and the existence of stress sensitivity all lead to stronger bottom water coning and an early water break-through. For the non-coning region, a greater solubility of natural gas will lead to a slower rise in the GWC. The simulation results show that the water invasion velocity with water-soluble gas is faster than the velocity without water-soluble gas.

Surface–atmosphere exchange of inorganic water-soluble gases and associated ions in bulk aerosol above agricultural grassland pre- and postfertilisation

Abstract. The increasing use of intensive agricultural practices can lead to damaging consequences for the atmosphere through enhanced emissions of air pollutants. However, there are few direct measurements of the surface–atmosphere exchange of trace gases and water-soluble aerosols over agricultural grassland, particularly of reactive nitrogen compounds. In this study, we present measurements of the concentrations, fluxes and deposition velocities of the trace gases HCl, HONO, HNO3, SO2 and NH3 as well as their associated water-soluble aerosol counterparts Cl−, NO2-, NO3-, SO42- and NH4+ as determined hourly for 1 month in May–June 2016 over agricultural grassland near Edinburgh, UK, pre- and postfertilisation. Measurements were made using the Gradient of Aerosols and Gases Online Registrator (GRAEGOR) wet-chemistry two-point gradient instrument. Emissions of NH3 peaked at 1460 ngm-2s-1 3 h after fertilisation, with an emission of HONO peaking at 4.92 ngm-2s-1 occurring 5 h after fertilisation. Apparent emissions of NO3- aerosol were observed after fertilisation which, coupled with a divergence of HNO3 deposition velocity (Vd) from its theoretical maximum value, suggested the reaction of emitted NH3 with atmospheric HNO3 to form ammonium nitrate aerosol. The use of the conservative exchange fluxes of tot-NH4+ and tot-NO3- indicated net emission of tot-NO3-, implying a ground source of HNO3 after fertilisation. Daytime concentrations of HONO remained above the detection limit (30 ng m−3) throughout the campaign, suggesting a daytime source for HONO at the site. Whilst the mean Vd of NH4+ was 0.93 mm s−1 in the range expected for the accumulation mode, the larger average Vd for Cl− (3.65 mm s−1), NO3- (1.97 mm s−1) and SO42- (1.89 mm s−1) reflected the contribution of a super-micron fraction and decreased with increasing PM2.5∕PM10 ratio (a proxy measurement for aerosol size), providing evidence – although limited by the use of a proxy for aerosol size – of a size dependence of aerosol deposition velocity for aerosol chemical compounds, which has been suggested from process-orientated models of aerosol deposition.

Study on the Effect of Toxic Gas Filter Effect of Wet Towel during Fire

화재로 인한 피해는 열상에 의한 피해보다는 연소 독성에 의한 피해가 치명적이며, 인명피해를 줄이기 위해 화재 상황에서 젖은 수건을 사용하여 화재로부터 발생되는 독성가스를 방호하도록 권장하고 있다. 본 연구에서는 젖은 수건을 통해 실제 화재에서 발생되는 가스를 대상으로 필터링 효과를 정량화하였다. 화재가스 중 세 가지 가스(CO2 , HCl, HCN)를 대상으로 젖은 수건의 필터효과를 확인하기 위해 FT-IR을 이용하여 필터를 통과한 가스를 실시간 분석 을 하였으며, 물에 잘 녹지 않는 CO2에 비해 유독가스이며, 수용성 가스인 HCl, HCN은 젖은 수건에 의해 가스가 필터링 되면서 가스 검출 시점이 지연됨을 확인하였다. 따라서 실제 화재 시 독성가스 중 특히 수용성 가스의 경우 젖은 수건을 이용하게 되면 일정 시간 피난 시간을 확보할 수 있음을 확인하였다.The damage caused by fires is fatal as opposed to the damage caused by heat, and toxic gas generated by fires can be protected against by using a wet towel. In this study, we quantified the filtration effect of gas generated by an actual fire using a wet towel. In order to confirm the filtration effect of the wet towel on three harmful gases (CO 2 , HCl, HCN), gases passed through a filter using FT-IR were analyzed in realtime. HCl and HCN, which are gases, were filtered by a wet towel, and the detection time of each gas was delayed. Therefore, it was confirmed that evacuation time can be secured by using a wet towel in the case of toxic gas, especially water-soluble gases in an actual fire.

RADON IN GROUNDWATER OF MAGADI TALUK, RAMANAGARA DISTRICT IN KARNATAKA.

Radon is a water-soluble radioactive noble gas produced from the alpha decay of 226Ra in uranium series. Its presence in drinking water and open air increases the risk of lung and intestinal cancers in human beings. In view of this, radon concentration in groundwater and its dose due to inhalation and ingestion to the population of Magadi taluk of Ramanagara district in Karnataka state, India was studied. The groundwater samples were analyzed for radon concentration using emanometry technique. The study showed that the radon concentration in this area varied from 27.4 ± 1.0 to 167.5 ± 3.9 Bq/L and the effective dose ranged from 104.2 ± 2.7 to 636.2 ± 11.0 μSv/a. The study also revealed that 95% of the 37 samples studied showed higher radon concentration compared to the UNSCEAR recommendation (40 Bq/L) and all the samples showed higher than the USEPA recommendation (11.1 Bq/L). Ten samples have concentration above the maximum permissible level prescribed by WHO (100 Bq/L). The groundwater samples are found to be slightly alkaline within the permissible limit of Indian Standards.

Detailed characterization of a mist chamber for the collection of water-soluble organic gases

Mist chambers (MC) have been used for decades to sample water-soluble gases in atmospheric studies. Herein, we characterize the use of a mist chamber for the collection of oxygenated organic gases, with a focus on intermediate solubility compounds to better constrain the transition from low-to-high collection efficiency. The investigated compounds span a range in Henry's law constants (KH, 2.5 × 101 M atm−1 to 4.1 × 105 M atm−1) and include moieties abundant in tropospheric gases (carboxylic acids, alcohols, and carbonyls). Under the configuration used here, the MC achieved greater than 90% collection efficiency for compounds with KH > 4.9 × 102 M atm−1. This represents an improvement over prior MC characterizations, likely due to the increased number of intermediate solubility compounds investigated. We apply the MC collection efficiency to simulations of VOC photooxidation. The results indicate that the MC is likely to collect the majority of gas-phase oxidation products for ten different VOCs, with the highest collection efficiency (94%) predicted for the oxidation products of α-pinene under low-NOx conditions.

Oxygenated VOCs, aqueous chemistry, and potential impacts on residential indoor air composition.

Dampness affects a substantial percentage of homes and is associated with increased risk of respiratory ailments; yet, the effects of dampness on indoor chemistry are largely unknown. We hypothesize that the presence of water-soluble gases and their aqueous processing alters the chemical composition of indoor air and thereby affects inhalation and dermal exposures in damp homes. Herein, we use the existing literature and new measurements to examine the plausibility of this hypothesis, summarize existing evidence, and identify key knowledge gaps. While measurements of indoor volatile organic compounds (VOCs) are abundant, measurements of water-soluble organic gases (WSOGs) are not. We found that concentrations of total WSOGs were, on average, 15 times higher inside homes than immediately outside (N=13). We provide insights into WSOG compounds likely to be present indoors using peer-reviewed literature and insights from atmospheric chemistry. Finally, we discuss types of aqueous chemistry that may occur on indoor surfaces and speculate how this chemistry could affect indoor exposures. Liquid water quantities, identities of water-soluble compounds, the dominant chemistry, and fate of aqueous products are poorly understood. These limitations hamper our ability to determine the effects of aqueous indoor chemistry on dermal and inhalation exposures in damp homes.

Complex accumulation and leakage of YC21-1 gas bearing structure in Yanan sag, Qiongdongnan basin, South China Sea

YC21-1 is a gas-bearing structure found within the Yanan sag in the Qiongdongnan Basin, South China Sea. While the structure bears many geological similarities to the nearby YC13-1 gas field, it nevertheless does not contain commercially viable gas volumes. The main reservoirs of the YC21-1 structure contain high overpressures, which is greatly different from those of the YC13-1 structure. The pressure coefficients from drillstem tests, wireline formation tests and mud weights are above 2.1. Based on well-log analysis, illite content and vitrinite reflectance data of mudstones in well YC21-1-2, combining with tectonic and sedimentation characteristics, the timing and causes of overpressure generation are here interpreted. The results indicate the existence of two overpressure segments in the YC21-1 structure. The first overpressure segment resides mainly within the lower and the middle intervals of the Yinggehai Formation, and is interpreted to have been mainly caused by clay diagenesis, while disequilibrium compaction and hydrocarbon generation may also have contributed to overpressure generation. The second overpressure segment comprising the Sanya Formation (Pressure transition zone) and the Lingshui and Yacheng Formations (Hard overpressure zone) is interpreted to owe its presence to kerogen-to-gas cracking. According to petrography, homogenization temperature and salinity of fluid inclusions, two stages of oil-gas charge occurred within the main reservoirs. On the basis of overpressure causes and oil-gas charge history, combining with restored tectonic evolution and fluid inclusion characteristics, a complex accumulation and leakage process in the YC21-1 gas bearing structure has been interpreted. Collective evidence suggests that the first oil charge occurred in the Middle Miocene (circa 16.3–11.2 Ma). Small amount of oil generation and absence of caprocks led to the failure of oil accumulation. Rapid subsidence in the Pliocene and Quaternary gave rise to a sharp increase in geotemperature over a short period of time, leading to prolific gas-generation through pyrolysis and, consequently, overpressure within the main reservoirs (the second overpressure segment). During this period, the second gas charge occurred in the Pliocene and Quaternary (circa 4.5–0.4 Ma). The natural gas migrated in several phases, consisting of free and water soluble phases in a high-pressure environment. Large amounts of free gas are considered to have been consumed due to dissolution within formation water in highly pressured conditions. Water soluble gas could not accumulate in high point of structure. When the pore-fluid pressures in main reservoirs reached the fracture pressure of formation, free gas could leak via opened fractures within cracked caprocks. A repeated fracturing of caprocks may have consumed natural gas stored in formation water and have made water-soluble gas unsaturated. Therefore, the two factors including caprocks fracturing and dissolution of formation water are interpreted to be mainly responsible for the failure of natural gas accumulation in the YC21-1 structure.

HYDROGEOLOGICAL CONDITIONS FOR THE PRESENCE OF OIL AND GAS IN THE WESTERN SEGMENT OF THE YENISEI-KHATANGA REGIONAL TROUGH

This article describes the petroleum potential of the Mesozoic deposits in the western segment of the Yenisei-Khatanga regional trough, as assessed from the hydrogeological data. The study area includes the Krasnoyarskregion and neighbouring zones of the Yamal-Nenets Autonomous District (Fig. 1). In tectonic terms, it is confined to the Yenisei-Khatanga regional trough and separates the Taimyr system of tectonic dislocations from the Siberian Platform [ Kontorovich, 2011; Pronkin et al ., 2012 ]. The Meso-Cenozoic section (up to 6–12 km) [ Dolmatova, Peshkova , 2001 ] is limited by the Malokhet-Rassokhin-Balakhnin deep fault and the same name system of mega-ramparts in the east. In the west, it opens up and merges with the structures of the West Siberian megabasin. The hydrogeological materials collected in the study area for almost 40 years, since 1977, remained unconsolidated, and our study did so for the first time. To date, more than 200 deep wells have been drilled in this area, and more than 25 hydrocarbon fields have been discovered. Most geologists acknowledge the leading role of water in the processes of formation, migration, accumulation and degradation of hydrocarbons: water is a medium and an active participant in mass transfer. In this regard, the compositions of groundwater, water-soluble gas and organic matter are widely discussed as hydrogeological criteria that may suggest the presence of oil and gas. The hydrogeological criteria for petroleum prospecting have been classified, and it is now possible to take into account the origin and significance of each indicator, integrate their impacts and attempt at forecasting the regional, zonal and local oil and gas fields. In the Mesozoic section, sodium chloride ground waters predominate. The inversion type of vertical hydrogeochemical zoning is dominant in the study area, and involves the entire complex of deposits: the mineralization decreases from 16–20 g/dm 3 in the Apt-Alb-Senoman complex to 5–10 g/dm 3 or less in the Jurassic aquifers (Fig. 4). The inversion is accompanied by a change in the ion-salt composition of groundwater. The concentration of HCO 3 ion increases with depth; the type of groundwater changes from predominantly sodium chloride (at a depth of ~2300 m) to chloride-hydrocarbonate sodium and hydrocarbonate-chloride sodium. Using the hydrogeological data, we assessed the petroleum potential of the sedimentary cover in the western segment of the Yenisei-Khatanga regional trough. Based on the analysis of the set of criteria and their individual contributions to the overall assessment of the prospects, we have identified 16 highly promising and 20 medium-potential structures that can substantiate further oil-and-gas prospecting, which may discover skipped and new fields. Prospecting can prove highly effective in the Cretaceous reservoirs (Upper Sukhodudinka and Lower Kheta) located in the Nadadyan, Middle Yarov, Tokachin, Turkov, Yarov and other areas (Fig. 6). The Jurassic deposits are promising for small- and medium-sized oil-and-gas reservoirs, as suggested by the geological exploration of previous years, which discovered the Zima (1966) and Khabei (1982) fields. According to the proposed set of the hydrogeological criteria, the most promising among the Jurassic reservoirs is the Malyshev reservoir in the Deryabin, Pelyatkin, Middle Yarov, Tampei and Turkov areas. Promising to a lesser extent are the Sigov (Rassokhin and Sukhodudinka areas) and Nadoyakh (Sukhodudinka area) reservoirs.

Limitations of gas filter correlation: A case study on carbon monoxide non-dispersive infrared analyzer

Two commercial Non-Dispersive Infrared (NDIR) analyzers for carbon monoxide (CO) coupled with a gas filter correlation (GFC) were used to investigate the interference effects by other gases except for CO. A stack level of particular gases including CO2, NO, NO2, SO2, and H2O (g) were mixed with CO to introduce into the analyzers. It was found that the measurement error of two analyzers were the lowest at 50ppm and 70ppm of CO, respectively. Moreover, the increase of concentrations of the interfering gases (CO2, NO, NO2, and SO2) induced an interfering effect on the performance of two analyzers. This indicated that the GFC could not cover the entire range of interfering gases. In a special case, the accuracy of the analyzers with humid mixed gases was better than that with dry mixed gases due to the absorption of water-soluble gases by condensate. However, this accuracy was only apparent with respect to low solubility of analytical target gas such as CO. The solubility of the target gas might dramatically reduce the accuracy of the analyzer.

Identifying precursors and aqueous organic aerosol formation pathways during the SOAS campaign

Abstract. Aqueous multiphase chemistry in the atmosphere can lead to rapid transformation of organic compounds, forming highly oxidized, low-volatility organic aerosol and, in some cases, light-absorbing (brown) carbon. Because liquid water is globally abundant, this chemistry could substantially impact climate, air quality, and health. Gas-phase precursors released from biogenic and anthropogenic sources are oxidized and fragmented, forming water-soluble gases that can undergo reactions in the aqueous phase (in clouds, fogs, and wet aerosols), leading to the formation of secondary organic aerosol (SOAAQ). Recent studies have highlighted the role of certain precursors like glyoxal, methylglyoxal, glycolaldehyde, acetic acid, acetone, and epoxides in the formation of SOAAQ. The goal of this work is to identify additional precursors and products that may be atmospherically important. In this study, ambient mixtures of water-soluble gases were scrubbed from the atmosphere into water at Brent, Alabama, during the 2013 Southern Oxidant and Aerosol Study (SOAS). Hydroxyl (OH⚫) radical oxidation experiments were conducted with the aqueous mixtures collected from SOAS to better understand the formation of SOA through gas-phase followed by aqueous-phase chemistry. Total aqueous-phase organic carbon concentrations for these mixtures ranged from 92 to 179 µM-C, relevant for cloud and fog waters. Aqueous OH-reactive compounds were primarily observed as odd ions in the positive ion mode by electrospray ionization mass spectrometry (ESI-MS). Ultra high-resolution Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) spectra and tandem MS (MS–MS) fragmentation of these ions were consistent with the presence of carbonyls and tetrols. Products were observed in the negative ion mode and included pyruvate and oxalate, which were confirmed by ion chromatography. Pyruvate and oxalate have been found in the particle phase in many locations (as salts and complexes). Thus, formation of pyruvate/oxalate suggests the potential for aqueous processing of these ambient mixtures to form SOAAQ.

An isotope study of the accumulation mechanisms of high-sulfur gas from the Sichuan Basin, southwestern China

The mechanism of hydrogen sulfide (H2S) generation plays a key role in the exploration and development of marine high-sulfur natural gas, of which the major targets are the composition and isotope characteristics of sulfur-containing compounds. Hydrocarbon source rocks, reservoir rocks, natural gases and water-soluble gases from Sichuan Basin have been analyzed with an online method for the content of H2S and isotopic composition of different sulfur-containing compounds. The results of comparative analysis show that the sulfur-containing compounds in the source rocks are mainly formed by bacterial sulfate reduction (BSR), and the sulfur compounds in natural gas, water and reservoir are mainly formed by thermal sulfate reduction (TSR). Moreover, it has been shown that the isotopically reversion for methane and ethane in high sulfur content gas is caused by TSR. The sulfur isotopic composition of H2S in natural gas is inherited from the gypsum or brine of the same or adjacent layer, indicating that the generation and accumulation of H2S have the characteristics of either a self-generated source or a near-source.