Increasing Gas Concentrations Research Articles

Impacts of Local and Remote SST Warming on Summer Circulation Changes in the Western North Pacific

Abstract This study explores how future SST warming in remote ocean basins may affect the western North Pacific (WNP) wet season climate by applying a high-resolution atmospheric general circulation model to conduct a series of numerical experiments. A marked precipitation and tropical cyclone (TC) activity reduction, as well as enhanced anticyclonic circulation, in the WNP is projected in AMIP experiments forced by SST change in a future warming scenario. The sensitivity experiments reveal that various SST warming phenomena (e.g., in the global SST warming pattern, the tropical ocean belt, the Indian Ocean, tropical Atlantic, the subtropical northeast Pacific) and the increase of greenhouse gas concentration could weaken the precipitation, TC activity, and circulation. By contrast, the SST warming in the WNP and eastern equatorial Pacific have opposite and mixed effects, respectively, and tend to weakly offset the dominant influences of remote ocean warming. These results indicate that the WNP, being the epicenter of the global teleconnection of divergent and rotational flow, is susceptible to the influence of the SST warming in remote ocean basins. The remote forcing as projected in future scenarios would overwhelm the enhancing effect of local SST warming and weaken the circulation, convection, and TC activity in the WNP. These findings further the understanding of how the decreased precipitation and enhanced subtropical high in the WNP may be easily triggered by remote SST warming as revealed in the AMIP-type simulations. How this effect would be affected by air-sea coupling needs further investigation.

Impacts of Local and Remote SST Warming on Summer Circulation Changes in the Western North Pacific

Abstract This study explores how future SST warming in remote ocean basins may affect the western North Pacific (WNP) wet season climate by applying a high-resolution atmospheric general circulation model to conduct a series of numerical experiments. A marked precipitation and tropical cyclone (TC) activity reduction, as well as enhanced anticyclonic circulation, in the WNP is projected in AMIP experiments forced by SST change in a future warming scenario. The sensitivity experiments reveal that various SST warming phenomena (e.g., in the global SST warming pattern, the tropical ocean belt, the Indian Ocean, tropical Atlantic, the subtropical northeast Pacific) and the increase of greenhouse gas concentration could weaken the precipitation, TC activity, and circulation. By contrast, the SST warming in the WNP and eastern equatorial Pacific have opposite and mixed effects, respectively, and tend to weakly offset the dominant influences of remote ocean warming. These results indicate that the WNP, being the epicenter of the global teleconnection of divergent and rotational flow, is susceptible to the influence of the SST warming in remote ocean basins. The remote forcing as projected in future scenarios would overwhelm the enhancing effect of local SST warming and weaken the circulation, convection, and TC activity in the WNP. These findings further the understanding of how the decreased precipitation and enhanced subtropical high in the WNP may be easily triggered by remote SST warming as revealed in the AMIP-type simulations. How this effect would be affected by air-sea coupling needs further investigation.

Fast retrieval of XCO2 over east Asia based on Orbiting Carbon Observatory-2 (OCO-2) spectral measurements

Abstract. The increase in greenhouse gas concentrations, particularly CO2, has significant implications for global climate patterns and various aspects of human life. Spaceborne remote sensing satellites play a crucial role in high-resolution monitoring of atmospheric CO2. However, the next generation of greenhouse gas monitoring satellites is expected to face challenges, particularly in terms of computational efficiency in atmospheric CO2 retrieval and analysis. To address these challenges, this study focuses on improving the speed of retrieving the column-averaged dry-air mole fraction of carbon dioxide (XCO2) using spectral data from the Orbiting Carbon Observatory-2 (OCO-2) satellite while still maintaining retrieval accuracy. A novel approach based on neural network (NN) models is proposed to tackle the nonlinear inversion problems associated with XCO2 retrievals. The study employs a data-driven supervised learning method and explores two distinct training strategies. Firstly, training is conducted using experimental data obtained from the inversion of the operational optimization model, which is released as the OCO-2 satellite products. Secondly, training is performed using a simulated dataset generated by an accurate forward calculation model. The inversion performance and prediction performance of the machine learning model for XCO2 are compared, analyzed, and discussed for the observed region over east Asia. The results demonstrate that the model trained on simulated data accurately predicts XCO2 in the target area. Furthermore, when compared to OCO-2 satellite product data, the developed XCO2 retrieval model not only achieves rapid predictions (<1 ms) with good accuracy (1.8 ppm or approximately 0.45 %) but also effectively captures sudden increases in XCO2 plumes near industrial emission sources. The accuracy of the machine learning model retrieval results is validated against reliable data from Total Carbon Column Observing Network (TCCON) sites, demonstrating its ability to effectively capture CO2 seasonal variations and annual growth trends.

Parageobacillus thermoglucosidasius Strain Engineering Using a Theophylline Responsive RiboCas for Controlled Gene Expression.

The relentless increase in atmospheric greenhouse gas concentrations as a consequence of the exploitation of fossil resources compels the adoption of sustainable routes to chemical and fuel manufacture based on biological fermentation processes. The use of thermophilic chassis in such processes is an attractive proposition; however, their effective exploitation will require improved genome editing tools. In the case of the industrially relevant chassis Parageobacillus thermoglucosidasius, CRISPR/Cas9-based gene editing has been demonstrated. The constitutive promoter used, however, accentuates the deleterious nature of Cas9, causing decreased transformation and low editing efficiencies, together with an increased likelihood of off-target effects or alternative mutations. Here, we rectify this issue by controlling the expression of Cas9 through the use of a synthetic riboswitch that is dependent on the nonmetabolized, nontoxic, and cheap inducer, theophylline. We demonstrate that the riboswitches are dose-dependent, allowing for controlled expression of the target gene. Through their use, we were then able to address the deleterious nature of Cas9 and produce an inducible system, RiboCas93. The benefits of RiboCas93 were demonstrated by increased transformation efficiency of the editing vectors, improved efficiency in mutant generation (100%), and a reduction of Cas9 toxicity, as indicated by a reduction in the number of single nucleotide polymorphisms (SNPs) observed. This new system provides a quick and efficient way to produce mutants in P. thermoglucosidasius.

Study on the Influence of Different Gas Concentrations on Coal Spontaneous Combustion

ABSTRACT The coexistence of gas and spontaneous coal combustion poses a serious threat to mine production safety. Therefore, studying the compound disaster of gas and spontaneous coal combustion and revealing the impact of gas concentration on the characteristic parameters of coal spontaneous combustion are of great significance for understanding the mechanism of compound disasters involving coal and gas and for comprehensive management. Based on theoretical analysis, this paper selects four typical types of cannel coal、non-caking coal、meager coal、anthracite coal as research subjects, and conducts programmed heating experiments on coal samples under different gas concentration conditions, aiming to provide a theoretical basis for the prevention and control of spontaneous coal combustion in a gas environment. Experimental results show that with the increase in temperature of the coal samples, the oxygen consumption rate and heating emission intensity exhibit a trend of slow increase followed by rapid increase. With the increase in gas concentration in the environment, the production of CO and CO2, oxygen consumption rate, and heat emission intensity of coal spontaneous combustion all show a decreasing trend. This is mainly because the high gas concentration occupies the adsorption sites on coal molecules, thereby hindering the reaction between coal and oxygen. Additionally, by calculating the thermodynamic parameters of the coal samples, it was found that the apparent activation energy increases with the increase in gas concentration, further confirming that the increase in gas concentration in the environment significantly inhibits the spontaneous combustion process of coal.

Design of a Portable Analyzer to Determine the Net Exchange of CO2 in Rice Field Ecosystems.

Global warming is influenced by an increase in greenhouse gas (GHG) concentration in the atmosphere. Consequently, Net Ecosystem Exchange (NEE) is the main factor that influences the exchange of carbon (C) between the atmosphere and the soil. As a result, agricultural ecosystems are a potential carbon dioxide (CO2) sink, particularly rice paddies (Oryza sativa). Therefore, a static chamber with a portable CO2 analyzer was designed and implemented for three rice plots to monitor CO2 emissions. Furthermore, a weather station was installed to record meteorological variables. The vegetative, reproductive, and maturation phases of the crop lasted 95, 35, and 42 days post-sowing (DPS), respectively. In total, the crop lasted 172 DPS. Diurnal NEE had the highest CO2 absorption capacity at 10:00 a.m. for the tillering stage (82 and 89 DPS), floral primordium (102 DPS), panicle initiation (111 DPS), and flowering (126 DPS). On the other hand, the maximum CO2 emission at 82, 111, and 126 DPS occurred at 6:00 p.m. At 89 and 102 DPS, it occurred at 4:00 and 6:00 a.m., respectively. NEE in the vegetative stage was -25 μmolCO2 m2 s-1, and in the reproductive stage, it was -35 μmolCO2 m2 s-1, indicating the highest absorption capacity of the plots. The seasonal dynamics of NEE were mainly controlled by the air temperature inside the chamber (Tc) (R = -0.69), the relative humidity inside the chamber (RHc) (R = -0.66), and net radiation (Rn) (R = -0.75). These results are similar to previous studies obtained via chromatographic analysis and eddy covariance (EC), which suggests that the portable analyzer could be an alternative for CO2 monitoring.

Mechanism of boundary bubble drag reduction of Couette flow in nano-confined domain

Bubble drag reduction technology is of great significance in improving the propulsion efficiency of underwater vehicle and reducing the comprehensive energy consumption during navigation. Bubble drag reduction is a highly effective method of reducing the frictional resistance encountered by large ships and underwater vehicles during navigation. It exhibits excellent stability in drag reduction, and has advantages such as environmental friendliness, adaptability to various flow environments, and suitability for all underwater components of ships. Therefore, it is greatly significant to conduct in-depth research on bubble drag reduction and its underlying mechanism. In this work, the flow characteristics and the boundary bubble drag reduction mechanism of gas-liquid Couette flow in parallel wall nanochannels are studied by molecular dynamics method, and the influences of surface wettability, wall roughness, and gas concentration on boundary slip velocity and bubble drag reduction effect are analyzed. The results indicate that the bubble drag reduction effect is enhanced with the increase of boundary slip velocity. In the gas-liquid two-phase flow region, with the increase of shear velocity, the lateral deformation of boundary adsorbed bubble and boundary slip velocity increase, thus enhancing the bubble drag reduction effect. The increase of solid-gas interaction strength and gas concentration can lead to the enrichment of gas atoms near the wall, improve the bubble spreading characteristics on the wall, and thus increase the slip velocity of the solid-liquid interface. The wall roughness can change the spreading characteristics of bubble, affect the boundary slip velocity, and then change the drag reduction effect of the fluid-solid interface. As the rib height increases, gas atoms accumulate in the grooves between ribs and the adsorption quantity of gas atoms on the upper surface of the rib decreases, which leads to the decrease of the boundary slip velocity of the solid-liquid interface and ultimately reduces the drag reduction effect. The research results will provide important theoretical guidance for implementing the boundary drag reduction technology in large ships and underwater vehicles.

An Internet of Things Platform for Forest Monitoring

Forests have a very important function in sustaining the natural life on our planet. However, wildfires, landslides, uncontrolled tree cutting, poaching, arson, and many other dangers threaten the forests and natural resources. Therefore, effective monitoring and observation of forests is crucial. This study explains the development and implementation of an Internet of Things (IoT)-enabled forest monitoring system as an innovative solution that will contribute to the protection of forests. The presented system provides real-time climate data in forestlands by using microcontrollers, low-cost sensors, data communication, and cloud platforms. It collects important information such as temperature, humidity, air quality, and ecological activities. Fire detection is achieved by associating the increase in CO gas concentration with the increase in temperature. Landslides are detected by measuring the acceleration of soil movement in 3 axes. Additionally, the system includes advanced machine learning-based acoustic tracking techniques to detect chainsaws, motor vehicles, screams, shouts, and gunshots. The IoT platform provides a web-based user interface and other tools to system users such as forest managers and researchers. These tools detect early signs of threats such as wildfires, landslides and illegal activities in forests. Our tests demonstrate the system's effectiveness in providing information for protecting and managing forests.

The Characteristics of Land Use in Kemiri-based Agroforestry Patterns in Maros Regency, South Sulawesi Province

One of the leading causes of global warming is land damage due to forest encroachment and the conversion of forest areas. One of the efforts to reduce the increase in greenhouse gas concentrations is maintaining carbon reserves by developing and improving forest vegetation. The agroforestry pattern can solve problems from both environmental and economic aspects in society. Candlenut plants are one of several types of plants that are usually used by applying the agroforestry model. Cenrana, Camba, Mallawa Districts, and Maros Regency are still developing and utilizing candlenut plants on community-owned land and in forest areas. This study aims to determine the spatial characteristics of the candlenut-based agroforestry pattern in Maros Regency. This research uses a quantitative method using remote sensing technology based on Google Earth Engine (GEE). The results of the study show that the agroforestry pattern in Maros Regency (Mallawa District, Camba District, Cenrana District) applies the Agrisilvicultural and Silvipastural patterns, apart from that the community's candlenut agroforestry land is located at a distance that can be reached by the community, namely 0-2 km outside the forest area. The composition of candlenut-based agroforestry and non-agroforestry patterns shows several crop combinations: horticulture, food, and plantations.

Anthropogenic Influence on Decadal Changes in Concurrent Hot and Dry Events over China around the Mid-1990s

The frequency and duration of observed concurrent hot and dry events (HDEs) over China during the growing season (April–September) exhibit significant decadal changes across the mid-1990s. These changes are characterized by increases in HDE frequency and duration over most of China, with relatively large increases over southeastern China (SEC), northern China (NC), and northeastern China (NEC). The frequency of HDEs averaged over China in the present day (PD, 1994–2011) is double that in the early period (EP, 1964–81); the duration of HDEs increases by 60%. Climate experiments with the Met Office Unified Model (MetUM-GOML2) are used to estimate the contributions of anthropogenic forcing to HDE decadal changes over China. Anthropogenic forcing changes can explain 60%–70% of the observed decadal changes, suggesting an important anthropogenic influence on HDE changes over China across the mid-1990s. Single-forcing experiments indicate that the increase in greenhouse gas (GHG) concentrations dominates the simulated decadal changes, increasing the frequency and duration of HDEs throughout China. The change in anthropogenic aerosol (AA) emissions significantly decreases the frequency and duration of HDEs over SEC and NC, but the magnitude of the decrease is much smaller than the increase induced by GHGs. The changes in HDEs in response to anthropogenic forcing are mainly due to the response of climatological mean surface air temperatures. The contributions from changes in variability and changes in climatological mean soil moisture and evapotranspiration are relatively small. The physical processes associated with the response of HDEs to GHG and AA changes are also revealed.

Impact of spacer on membrane gas separation performance

Mixing in gas separation membranes has received much less attention than in membrane liquid separation because gas molecules have much smaller viscosity, allowing them to diffuse easily through membranes without requiring significant flow mixing. However, due to advancements in membrane fabrication technologies aimed at improving material properties, concentration polarization (CP) might become an issue in gas separation due to enhanced membrane efficiency and permeability. Consequently, a 2D CFD analysis is conducted to evaluate the impact of spacer-induced mixing on membrane gas concentration polarization for typical CO2/CH4 gas separation. Results show that spacers generally enhance flux performance while reducing CP in the membrane channel when compared to the case without spacers. Furthermore, the effectiveness of spacer-flux-to-pressure-loss-ratio (SPFP) reaches a peak for a Reynolds number in the range of 5 <Reh< 200 because of the trade-off between flux and pressure drop. This mixing-induced flux enhancement is most effective under high CP conditions (less mixing) within the membrane channel. Similarly, flux enhancement due to spacers can be observed as membrane selectivity, pressure ratio and feed gas concentration increase due to enhanced CP.

Effects of the Last Deglaciation climate warming on hydrate dissociation in the northern South China Sea

Sea level and bottom water temperature variations caused by the Last Deglaciation climate warming impacted the stability of marine hydrates. In order to examine their influence on hydrate dissociation in the northern South China Sea (SCS), we conducted simulations to track the evolution of hydrate saturation and hydrate occurrence zone since the Last Deglaciation in the Dongsha Area, Shenhu Area, Xisha Area and Qiongdongnan Area. The amount of methane generated and subsequently released into seawater and atmosphere was also evaluated within the four areas. The simulation revealed the following results: (1) Hydrate dissociation induced by variations in sea level and bottom water temperature was observed in the Dongsha Area, Xisha Area and Qiongdongnan Area, but not in the Shenhu Area. (2) The water depth at which hydrate dissociation occurred ranged between 480 and 720 m, encompassing a hydrate dissociation area of approximately 1.54 × 1010 m2. This accounted for 6.68% of the northern South China Sea Area. (3) Since the Last Deglaciation, an estimation of 3.08 × 108–1.48 × 1010 m3 hydrates have dissociated, resulting in the release of 5.05 × 1010–2.43 × 1012 m3 methane. The generated methane migrated through the overlying sediments by means of central migration mode. 9.9 × 109–4.76 × 1011 m3 methane entered into the seawater, which will result in the formation of a weak acid affecting the marine environment. Meanwhile, 2.02 × 108–9.72 × 109 m3 methane entered into the atmosphere, which leads to an increase in greenhouse gas concentrations.

Assessing the Influence Factors of Agricultural Soils’ CH4/N2O Emissions Based on the Revised EDGAR Datasets over Hainan Island in China

Global warming poses a significant environmental challenge, which is primarily driven by the increase in greenhouse gas concentrations. In this study, we aimed to investigate the factors influencing CH4/N2O emissions from agricultural soils over Hainan Island, China, from 2009 to 2018. To achieve this, we selected air temperature, precipitation, and solar radiation as climate factors and categorized farmland as paddy or non-paddy, using revised EDGAR greenhouse gas datasets involving the bias correction method, and geographical detector analysis, multiple linear regression models, and bias sensitivity analysis were used to quantify the sensitivity of climate and land use. The maximum air temperature emerged as the primary factor influencing CH4 emissions, while the mean air temperature predominantly affected N2O emissions. The ratio of paddy field area to city area emerged as the second most influential factor impacting CH4/N2O emissions. The mean CH4/N2O emission intensity from paddy fields was significantly higher (0.42 t·hm−2/0.0068 t·hm−2) compared to that of non-paddy fields (0.04 t·hm−2/0.002 t·hm−2). Changes in maximum air temperature under global warming and crop irrigation practices profoundly affect greenhouse gas emissions on Hainan Island. Specifically, the emission intensities of CH4 and N2O increased by 14.2% and 11.14% for each Kelvin warmer, respectively.

Determination and analysis of macro-featured parameters based on kilogram-level coal spontaneous combustion experiment

The quantitative characterization of coal spontaneous combustion and the accurate determination of the dangerous degree are hot and difficult in the field of coal mine safety. In the paper, the experimental test analysis of Huangling No. 2 coal was carried out by a self-designed and built kilogram-level coal spontaneous combustion experimental device, and the macro featured parameters were obtained and analyzed, such as temperature field, index gas, weight, oxygen consumption rate and exothermic intensity, and spontaneous combustion limit parameters. The results show that the experimental spontaneous combustion period of Huangling No.2 coal is 34 days. When the coal temperature was below the critical temperature of 74.59 °C, the oxidation of coal samples was relatively slow, and the oxygen consumption and the production rate of gas products did not change much. After the coal temperature exceeded the critical temperature, the oxygen consumption rate and exothermic intensity increased faster and the oxidation accelerated. After reaching the dry cracking temperature of 104.93 °C, the oxidation degree accelerated sharply. CO starts to appear at the beginning of the experiment, and the increase of CO gas concentration during the heating process is exponential and can be used as an index gas. Under the temperature condition of 40 °C, the floating coal of 0.7 m needs 25.83% oxygen concentration, and the maximum air leakage intensity of the coal is negative, and no spontaneous combustion will occur. The test data and calculation results of the experiment are important for the prediction and forecast of natural fires and the determination of the risk of spontaneous combustion on site.

Study of Intra-Annual and Annual Air Temperatures Over Iraq for Period (1970 – 2021)

Abstract Iraq is one of the most vulnerable regions in the world as a result of climatic changes, the exacerbation of global warming, high temperatures, extreme weather phenomena, droughts, desertification and dust storms. Studies confirmed that the increase in greenhouse gas concentrations was a major cause of climate change in Iraq, especially in the central and southern regions, which recorded the highest concentrations of these gases in recent years. Transformational and construction. The concentration of carbon dioxide gas, to which Iraq contributes 0.00508% of global emissions, has increased by 5 times after the year 2000 compared to before, i.e., by 1.8 times. So does methane, which has increased by 0.04 ppmv annually. The research found that the amount of increase in the annual temperatures for the last fifty years is (3 °C), and with these rates of temperature rise, it is expected that the increase will be by (2 °C) by the year 2050. The highest value for the average temperature was in Basra (40 °C) compared to Mosul and Baghdad, which reach (35 °C) during the summer, which indicates that the regions of southern Iraq are the most affected by the phenomenon of global warming.

Studies on thermal, morphological, electrical conductivity and LPG sensing behavior polyaniline/In2O3 nano composites thin films

Poyaniline/In2O3 were synthesized by using the in situ polymerization method for different concentrations of nano In2O3 powder. The formation of nanocomposites and changes in the structural and micro structural properties of the materials were investigated by X-ray diffractometry (XRD). The surface morphology of PANI–In2O3 nanocomposite was elucidated using Scanning Electron Microscopy. DC conductivity studies of PANI-In2O3 composites for different wt% show thermally activated behavior. The conductivity was found to increase with the increase in temperature indicating the semiconducting behavior of all the compositions. On exposure of the composites to LPG, increase in resistance was observed with the increase in gas concentration. Maximum sensitivity for gas sensing was observed in the composite of 50 wt% In2O3 in polyaniline.

Acceleration characteristics of composite flame in the initial stage of gas/coal dust explosion and analysis of disaster intensification

To clarify the strengthening mechanism of gas/coal dust coupling explosion disasters, a 20 L spherical explosion test system, high-speed schlieren, and PIV analysis were used to study the acceleration characteristics and pressure change of composite flames in the initial stage of gas/coal dust explosion, and the flow field characteristics were also analyzed. The results showed that methane concentration had the most important influence on the formation and development of composite flame. When the methane concentration was 7.5% and 9%, the composite flame propagation showed obvious acceleration characteristics and developed spherically, the flame boundary was clear and smooth, with the whole flame being continuous and bright white. Meanwhile, the Markstein length of composite flame is positive, and increased with the increase of methane concentration and dust particle size but decreased with the increase of coal dust mass concentration, the Markstein length for 9% gas concentration was 7 times larger than 6% gas concentration, indicating the increase of gas concentration can obviously inhibit the instability of composite flame, which prolonged the residence time of coal dust particles in the composite flame, resulting in the enhancement of the pyrolysis of coal dust and improvement of explosion intensity. The PIV test results of 9% gas/coal dust explosion showed that due to the high initial explosion intensity, the negative pressure in the center of the composite flame made most of the coal dust particles undergo centripetal movement, and a large number of coal dust particles gathered around the front of the flame. At the same time, a large number of large vortices in opposite directions were formed around the front of the flame, which promoted rapid contact between the coal dust surface and oxygen and intensified the combustion reaction. The research results can provide guidance for the prevention and control of gas/coal dust composite explosion disasters.

The Effect of Natural and Anthropogenic Climate Changes on River Runoff and Snow Water Equivalent in the Lena River Basin

The hydrological models ECOMAG and HBV were used to calculate the characteristics of river flow and snow Water Equivalent in the Lena River basin. The input data included the meteorological observations and the results of calculations with global climate models with the implementation of scenarios of natural climate conditions, taking into account the anthropogenic effect on climate. The calculations were made for a historical period (1970–1999) and up to the end of the XXI century. Hydrological models for several hydrometric gages in the Lena basin were calibrated and verified. The simulation of the annual and seasonal runoff using the climate model data was evaluated by comparison with observation data. According to the results using numerical experiments over the historical period, the increase in the Lena runoff is mostly due to natural climate variations. Conversely, in the XXI century, the anthropogenic climate changes determine the specific features of the regime of river runoff and snow cover. The warming caused by an increase in greenhouse gas concentrations in the atmosphere leads to an increase in snow water equivalent and transformation of the hydrological regime in the area, in particular, to an earlier beginning of active snow melting (up to two weeks) and higher maximal discharges during spring flood. At the same time, the volume of runoff decreases in the summer and increases in the autumn and winter.

Fluxes in CO2 and CH4 and influencing factors at the sediment-water interface in a eutrophic saline lake

Although saline aquatic ecosystems are significant emitters of greenhouse gases (GHGs), dynamic changes in GHGs at the sediment-water interface remain unclear. The present investigation carried out a total of four sampling campaigns in Daihai Lake, which is a eutrophic saline lake situated in a semi-arid area of northern China. The aim of this study was to investigate the spatio-temporal dynamics of carbon dioxide (CO2) and methane (CH4) fluxes at the sediment-water interface and the influencing factors. The mean concentrations of porewater CO2 and CH4 were 44.98 ± 117.99 μmol L−1 and 124.36 ± 97.00 μmol L−1, far exceeding those in water column of 11.14 ± 2.16 μmol L−1 and 0.33 ± 0.23 μmol L−1, respectively. The CO2 and CH4 fluxes at the sediment-water interface (FS–WCO2 and FS-WCH4) exhibited significant spatial and temporal variations, with mean values of 9.24 ± 13.84 μmol m−2 d−1 and 3.53 ± 4.36 μmol m−2 d−1, respectively, indicating that sediment is the source of CO2 and CH4 in the water column. However, CO2 and CH4 fluxes were much lower than those measured at the water-air interface in a companion study (17.54 ± 14.54 mmol m−2d−1 and 0.50 ± 0.50 mmol m−2d−1, respectively), indicating that the diffusive flux of gases at the sediment-water interface was not the primary source of CO2 and CH4 emissions to the atmosphere. Regression and correlation analyses revealed that salinity (Sal) and nutrients were the most influential factors on porewater gas concentrations, and that gas fluxes increased with increasing gas concentrations and porosity. The microbial activity of sediment is greatly affected by nutrients and Sal. Additionally, Sal has the ability to regulate biogeochemical processes, thereby regulating GHG emissions. The present investigation addresses the research gap concerning GHG emissions from sediments of eutrophic saline lakes. The study suggests that controlling the eutrophication and salinization of lakes could be a viable strategy for reducing carbon emissions from lakes. However, further investigations are required to establish more conclusive results.

Enhanced Acetaldehyde Sensing Performance of Spherical Shaped Copper Doped ZnO Nanostructures

AbstractSpherical shape copper (Cu) doped ZnO nanostructures of various amount (3, 6, 9 and 12 %) were synthesized. The XRD, FTIR, UV‐Visible, HR‐TEM, FESEM, EDS, SAED and XPS were done to understand the structural, optical, morphology and shape of Cu doped ZnO nanostructures. To achieve the best gas reaction, doping concentration was optimized. ZnO and Cu doped ZnO nanostructures were exposed to various oxygenated volatile organic compounds (OVOCs) and found to be more selective towards acetaldehyde sensing. For 50 ppm acetaldehyde gas, temperature study was done at various temperatures (RT, 50, 100, 150, 200 °C) which showed optimal at 100°C for maximal gas response. The response and recovery time was 16.53 and 18.36 seconds for 50 ppm of acetaldehyde gas. The gas sensing study was carried out at different humidity rates (11, 32, 51, 63 and 84 %) using different saturated solutions. 9 % Cu doped ZnO shows maximum response (61.53 %) as compared to pure ZnO and 3, 6 and 12 % Cu doped ZnO. The spherical shape Cu doped ZnO sensing response was increases with increase in concentration of gas from 10 to 300 ppm. Acetaldehyde gas shows enhanced selectivity towards spherical shape Cu doped ZnO sensors as compared to the other OVOCs like acetone, ethyl methyl ketone, methanol, ethanol, n‐propanol, n‐butanol, formaldehyde, acetaldehyde, propionaldehyde and acrolein. The reproducibility of Cu doped ZnO was studied for 50 days. Also, after acetaldehyde gas sensing change in morphology study of sensor was done.