Dissolved Carbon Dioxide Research Articles

Assessment of amoxicillin biodegradation using a fluidized bed reactor

In recent decades, emerging pharmaceutical contaminants, such as personal care items, pharmaceuticals, and disinfectants, have increased alarmingly in aquatic ecosystems. The efficacy of wastewater treatment plants in eliminating these contaminants has been demonstrated. This study aims to find an alternative method, such as using the fluidized bed reactor (FBR) with bacteria to remove amoxicillin from wastewater. The active bacteria Acinetobacter baumannii and Klebsiella pneumoniae were isolated from one of the pharmaceutical factories in Baghdad, Iraq, from Al-Jazeera wastewater, which was used in FBR technology to decompose the antibiotic amoxicillin. The study examined several operational parameters, including pH, total organic carbon (TOC), dissolved carbon dioxide (CO2) concentration, airflow rate, amoxicillin concentration, and bacterial number, while maintaining a constant temperature. High-performance liquid chromatography (HPLC) was used to find the reaction route. The maximum amoxicillin removal efficiency was 93% and 91% for Acinetobacter baumannii and Klebsiella pneumoniae, respectively. For both bacterial species, the pH decreased due to the formation of amino acids and CO2. The suitable operation condition was 5 mg/L of amoxicillin concentration, flow rate of 30 m/s, and the number of bacteria 47 x 105 cfm/mL and 40 x 105 cfm/mL for Acinetobacter baumannii and Klebsiella pneumoniae, respectively. After treatment, the number of bacteria increased due to the degradation of amoxicillin. The steady-state time is found at 64 hours. The organic matter reaction pathway ends at the aromatic amino acid lysine, which kills gram-negative bacteria. This method was found to be successful in removing amoxicillin in low concentrations by using Acinetobacter baumannii. In the future, treating amoxicillin in wastewater using FBR technology with gram-positive bacteria is recommended.

Impacts of wastewater treatment plant effluents on dissolved inorganic carbon in highly urbanized karst rivers, Southwest China

Wastewater treatment plants (WWTPs) are an important manifestation of the impact of urbanization on aquatic ecosystems, and the influences of effluents discharge from WWTPs on receiving river carbon biogeochemical cycle processes has been a research hotspot. However, our knowledge about potential impacts of WWTP effluents on dissolved inorganic carbon (DIC) cycle in karst rivers is rather limited. This study investigates the water chemistry and carbon isotope composition (δ13CDIC) in the urbanized reach of a river that drains the world’s largest continuous karst region in Southwest China, in an attempt to determine the effects of WWTP effluents on karst river DIC cycle and source discrimination. The results reveal: (1) Partial pressure of dissolved carbon dioxide (pCO2) levels in the river increased noticeably during the dry and normal seasons after receiving WWTP effluents; (2) There existed an ionic ratio overlap between end-members of silicate rock weathering and WWTP effluents which requires caution in identifying end-members of rock weathering in urbanized karst rivers; (3) DIC in the highly urbanized karst rivers was affected by complex geochemical processes and these processes varied in different seasons; (4) The contribution of WWTP effluents to the riverine DIC pool was 21±13 %, 58±21 % and 66±33 % in the wet, dry, and normal seasons, respectively. These findings highlight the interference of WWTP effluents with DIC carbon cycling in the receiving karst rivers. Since DIC from WWTPs do not relate with consuming atmospheric or soil CO2, it is important to exclude their contribution from the watershed’s rock weathering carbon sink budget. Based on these findings, we insist that the role and effect of WWTP effluents should be carefully considered when examining DIC carbon source and cycling in rivers that drain urbanized watersheds with abundant wastewater treatment plants.

High-pressure phase equilibrium for carbon dioxide solubility with biofuels: Experimental and thermodynamic insights in 2,5-dimethylfuran and methyl levulinate

The solubility of carbon dioxide in two solvents, 2,5-dimethylfuran and methyl levulinate, were measured to high pressure, up to 9.1 MPa, at three different temperatures (283.15, 303.15 and 323.15) K. The new data were measured using both the isothermal synthetic technique and the variable volume synthetic method. Two methods were utilised to provide a level of data validation. The uncertainties in the measured data were critically estimated. The experimental phase equilibrium data were modeled using the Peng-Robinson equation of state and the Wong-Sandler mixing rule with a single set of binary interaction parameters for each system. The data indicated that the solubility of carbon dioxide in both 2,5-dimethylfuran and methyl levulinate at high pressures was relatively low, suggesting a low capacity of these biofuels to dissolve carbon dioxide at high pressure.

Quantitative analysis of dissolved carbon sources in the farmland artificial ditch drainage-Lake UlanSuhai continuum in the Hetao Irrigation District's, Inner Mongolia

Study regionAgricultural Irrigation and Drainage system - Ulansuhai Lake Continuum, located in the Hetao Irrigation District, Inner Mongolia, China. Study focusIn this study, carbon isotope tracing technology was applied to analyze the sources and migration-transformation characteristics of Dissolved Organic Carbon (DOC) and Dissolved Inorganic Carbon (DIC) in the continuous system of the agricultural irrigation and drainage system - Ulansuhai Lake in the Hetao Irrigation Area of Inner Mongolia during typical irrigation periods. New hydrological insights for the regionDuring typical irrigation periods, DOC and DIC increase simultaneously with the increase in salinity, and dissolved carbon dioxide in the irrigation and drainage channels escapes. The main sources of DOC in farmland drainage water are terrestrial C3 plants (94.00 %) and plankton (6.00 %). The primary sources of DOC in the lake are farmland drainage (98.19 %) and macroaquatic plants (1.81 %). The main sources of DIC in farmland drainage water are irrigation water from the Yellow River (64.73 %) and the equilibrium dissolution process between carbonates and soil CO₂ (35.27 %); while the primary sources of DIC in the lake are farmland drainage (93.10 %) and air-water exchange (6.90 %). Crop types in the irrigated area, soil salinization, rock weathering, metabolic processes, and the hydrological connectivity induced by irrigation from the Yellow River jointly control the sources, migration, and transformation of carbon within the continuum.

Ditch cleaning in boreal catchments: Impacts on water chemistry and dissolved greenhouse gases in runoff

Ditch cleaning (DC) is a forestry practice commonly conducted in boreal regions that aim to lower groundwater tables (GWT) in waterlogged soils, thereby maintaining or improving forest growth. However, there is limited information on the impact of DC on water chemistry and dissolved greenhouse gases (GHG) in draining ditch networks. Based on a repeated synoptic sampling of a paired catchment design we here evaluated water chemistry and GHG data in ditch waters from 25 cleaned sites (being cleaned 1–4 years prior to sampling) and 25 non-cleaned reference sites (REF). The sampled sites were further selected to test whether there were any differences in the DC effect if the operations were conducted in forested or clear-cut areas. Across all sites, we found that DC sites exhibited higher pH, sulfate and calcium concentrations than REF sites. Also, lower dissolved carbon dioxide and higher nitrous oxide concentrations were observed in DC sites. In forested areas, DC sites exhibited significantly higher calcium and potassium concentrations, along with reduced levels of methylmercury and carbon dioxide. In clear-cuts, sulfate concentrations were significantly elevated in the DC sites. We suggest that the observed differences in water chemistry and GHG´s between DC and REF sites were induced by the DC and largely driven by lower GWT following DC, resulting in deeper groundwater flow paths through more mineral-rich soil layers, and altered redox conditions. Also, the removal of organic rich sediments and vegetation from the ditches themselves may affect water chemistry and GHG´s e.g. by decreasing the formation of methylmercury and carbon dioxide.

Magnesium hydroxide addition reduces aqueous carbon dioxide in wastewater discharged to the ocean

Ocean alkalinity enhancement (OAE) reduces the concentration of dissolved carbon dioxide (CO2) in seawater, leading to atmospheric carbon dioxide removal (CDR). Here we report laboratory experiments and a field-trial of alkalinity enhancement through addition of magnesium hydroxide to wastewater and its subsequent discharge to the coastal ocean. In wastewater, a 10% increase of average alkalinity (+0.56 mmol/kg) led to a 74% reduction in aqueous CO2 (−0.41 mmol/kg) and pH increase of 0.4 units to 7.78 (efficiency 0.73 molCO2/mol alkalinity). The alkalinization signal was limited to within a few metres of the ocean discharge, evident as 27.2 μatm reduction in CO2 partial pressure and 0.017 unit pH increase, and was consistent with rapid dilution of the alkali-treated wastewater. While this proof of concept field trial did not achieve CDR due to its small scale, it demonstrated the potential of magnesium hydroxide addition to wastewater as a CDR solution.

CO2 Valorization in Deep Eutectic Solvents.

The deep eutectic solvent (DES) has emerged in recent years as a valuable medium for converting CO2 into valuable chemicals because of its easy availability, stability, and safety, and its capability to dissolve carbon dioxide. CO2 valorization in DES has evolved rapidly over the past 20 years. As well as being used as solvents for acid/base-promoted CO2 conversion for the production of cyclic carbonates and carbamates, DESs can be used as reaction media for electrochemical CO2 reduction for formic acid and CO. Among these products, cyclic carbonates can be used as solvents and electrolytes, carbamate derivatives include the core structure of many herbicides and pesticides, and formic acid and carbon monoxide, the C1 electrochemical products, are essential raw materials in the chemical industries. An overview of the application of DESs for CO2 valorization in recent years is presented in this review, followed by a compilation and comparison of product types and reaction mechanisms within the different types of DESs, and an outlook on how CO2 valorization will be developed in the future.

Acid-base disturbances and effects on oxygen uptake rates in Nile tilapia (Oreochromis niloticus) following acute and prolonged CO2 exposure

High levels of dissolved carbon dioxide (CO2) occur nightly in earthen ponds characterized by high respiration rates. Exposure to high CO2 conditions (hypercapnia) leads to acidosis in fish, which can be compensated by an accumulation of HCO3− to recover intra- and extracellular pH levels, with a capacity that appears to be species-specific. For Nile tilapia, a freshwater tropical teleost traditionally produced in earthen ponds, little information is available on the tolerance to dissolved levels of CO2 and associated acid-base disturbances. Here, we investigated first the effects of acute and progressively increasing CO2, from normocapnic conditions to 60 mg CO2 L−1, on oxygen uptake rates (MO2). This was followed by exposure to three concentrations of CO2; 10, 30, and 60 mg L−1 (equivalent to pCO2 of 5.4, 16.2, and 32.4 mmHg) against a normocapnic control (pCO2 0.3 mmHg), to investigate acute (1 h) or prolonged (24 h) effects on standard (SMR) and maximum metabolic rates (MMR), haematology, and extra- and intracellular acid-base status in adult Nile tilapia (mean BM 435 ± 16 g ± SE). Acute exposure to hypercapnia led to concentration-dependent decreases in both SMR and MMR. Fish were able to fully or partially recover MMR and metabolic scope (MS) after 24 h, while depression of SMR persisted at all CO2 levels. Acute exposure to CO2 caused intra- and extracellular pH levels to decrease by up to 0.5 units in a concentration-dependent manner. Only the lowest hypercapnic treatment (pCO2 5.4 mmHg) was able to fully recover within 24 h. Changes in haematological variables appeared minor, being restricted to increasing haematocrit, haemoglobin concentration, and mean cell volume in the highest CO2 treatments after 24 h exposure. Although the Nile tilapia is generally considered a species able to tolerate poor water quality, the modest or slow acid-base regulation following hypercapnic exposure suggests sensitivity to hypercapnia.

Reinventing shake flask fermentation: The breathable flask.

Cultivating cells in shake flasks is a routine operation that is largely unchanged since its inception. A glass or plastic Erlenmeyer vessel with the primary gas exchange taking place across various porous plugs is used with media volumes typically ranging from 100 mL to 2 L. Oxygen limitation and carbon dioxide accumulation in the vessel is a major concern for studies involving shake flask cultures. In this study, we enhance mass transfer in a conventional shake flask by replacing the body wall with a permeable membrane. Naturally occurring concentration gradient across the permeable membrane walls facilitates the movement of oxygen and carbon dioxide between the flask and the external environment. The modified flask called the breathable flask, has shown a 40% improvement in mass transfer coefficient (kLa) determined using the static diffusion method. The prokaryotic cell culture studies performed with Escherichiacolishowed an improvement of 28%-66% in biomass and 41%-56% in recombinant product yield. The eukaryotic cell culture study performed with Pichia pastoris expressing proinsulin exhibited a 40% improvement in biomass and 115% improvement in protein yield. The study demonstrates a novel approach to addressing the mass transfer limitations in conventional shake flask cultures. The proposed flask amplifies its value by providing a membrane-diffusion-based sensing platform for the integration of low-cost, noninvasive sensing capabilities for real-time monitoring of critical cell culture parameters like dissolved oxygenand dissolved carbon dioxide.

Physico-chemical parameters, heavy-metals and soil particle distribution of Liverpool axis of Badagry Creek, Lagos, South-western Nigeria

Heavy metal pollution is a serious issue of concern worldwide because it can bioaccumulate in aquatic organisms and transferred through the food chain to harm humans. Information on the heavy metal pollution of aquatic ecosystems is essential to protect life. Therefore, this study was undertaken to determine the physico-chemical parameters of surface water, soil particle distribution (SPD) and heavy metals in two shellfish species in Liverpool axis of Badagry Creek, Lagos State, Nigeria. Twelve physico-chemical parameters and four heavy metals were studied using standard methods. The results showed that maximum temperature was 31.0±1.00˚0C; turbidity, 118.00±50.90NTU; dissolved oxygen (DO), 13.3±3.8mg/l; dissolved carbon dioxide (COD), 67.7±19.1mg/l; total hardness, 173.0±63.1mg/l; conductivity, 39.2±12.2μS/cm and chloride was 2.0±0.7mg/l. Water quality parameters showed significant spatial variations (p<0.05) among sample stations. Pearson’s correction matrices revealed high correlation of DO with nitrate (r = 0.61), total hardness (r=0.62) and COD (r=0.52) at p<0.05. The heavy metal concentrations (mg/kg) in the shellfishes, Callinectes pallidus and Farfantepenaeus notialis were: lead, 0.05±0.05 and 0.04±0.02; copper, 2.03±0.17 and 0.84±0.18; zinc, 3.51±0.44 and 1.99±0.2 and cadmium, 0.02±0.02 and 0.03±0.04 respectively. These levels were not above the WHO standards (for heavy metals in fish and shell fish). The sediment particle distribution (SPD) showed that Liverpool Jetty had 19.05% coarse sand and 43.91% fine sand, while Apapa Jetty had the highest amount of clay 45.29% in the environment. Heavy metals in shellfishes were above the WHO standards.

Dispersion and fate of methane emissions from cold seeps on Hikurangi Margin, New Zealand

The influence of cold seep methane on the surrounding benthos is well-documented but the fate of dissolved methane and its impact on water column biogeochemistry remains less understood. To address this, the distribution of dissolved methane was determined around three seeps on the south-east Hikurangi Margin, south-east of New Zealand, by combining data from discrete water column sampling and a towed methane sensor. Integrating this with bottom water current flow data in a dynamic Gerris model determined an annual methane flux of 3 x 105 kg at the main seep. This source was then applied in a Regional Ocean Modelling System (ROMS) simulation to visualize lateral transport of the dissolved methane plume, which dispersed over ∼100 km in bottom water within 1 year. Extrapolation of this approach to four other regional seeps identified a combined plume volume of 3,500 km3 and annual methane emission of 0.4–3.2 x 106 kg CH4 y-1. This suggests a regional methane flux of 1.1–10.9 x 107 kg CH4 y-1 for the entire Hikurangi Margin, which is lower than previous hydroacoustic estimates. Carbon stable isotope values in dissolved methane indicated that lateral mixing was the primary determinant of methane in bottom water, with potential methane oxidation rates orders of magnitude lower than the dilution rate. Calculations indicate that oxidation of the annual total methane emitted from the five seeps would not significantly alter bottom water dissolved carbon dioxide, oxygen or pH; however, superimposition of methane plumes from different seeps, which was evident in the ROMS simulation, may have localized impacts. These findings highlight the value of characterizing methane release from multiple seeps within a hydrodynamic model framework to determine the biogeochemical impact, climate feedbacks and connectivity of cold seeps on continental shelf margins.

Ostracod Assemblages in the East Siberian Sea: A Comparative Study of River-Influenced and River-Isolated Shelf Ecosystems

The East Siberian Sea (ESS) is one of the least studied seas in terms of ostracod fauna. Ostracods are sensitive organisms to environmental changes, and detailed information on their ecology is still required. To fill this knowledge gap, we studied 33 meiobenthic dredge samples collected from the western part of the ESS and the Chaun Bay together with 17 grab samples taken from the eastern part of the sea. Quantitative analyses of the ostracod assemblages demonstrate that the river-influenced western part of the ESS is inhabited by low diverse and impoverished fauna consisting of the taxa which are able to adapt to different environmental conditions. In the isolated Chaun Bay sheltered from significant riverine influence, the ostracod assemblages contain species that prefer more stable conditions. The predominance of living specimens over dead ones and individual valves points to strong carbonate dissolution that is more pronounced in the western ESS than in the Chaun Bay. The formation of such conditions might be related to the high content of dissolved carbon dioxide resulting from bacterial remineralization of in situ produced and land-derived organic matter in the bottom sediments and low pH near the seabed. Numerous ferromanganese crusts were found on the ostracod valve surfaces and inside the shells from the Chaun Bay.

Distribution of stable Н, О and С isotopes in natural waters in the area of the Taz oil and gas condensate field (Yamalo-Nenets autonomous region)

Relevance. The study of isotopic composition of water and dissolved substances makes it possible to determine not only their genesis, but also the fractionation processes occurring in the “water–rock–gas–organic matter” system over time, i. e. as different stages of the evolution of water composition pass through. Interest in the groundwater of the Arctic regions of Western Siberia is additionally associated with the widespread occurrence of oil deposits at the depths of formation waters and the possible influence of cryogenic metamorphization processes on composition of near-surface waters. Aim. To study and compare the isotopic composition of oxygen, hydrogen and carbon in natural waters of the Yamalo-Nenets autonomous region to identify conditional isotopic markers, as well as to be able to trace the evolution of the isotopic composition of waters along a vertical section in the area of the Taz oil and gas condensate field. Objects. Surface (river, soil and lake), underground waters of the active water exchange zone of the Yamalo-Nenets autonomous region and formation waters of oil and gas deposits of the Taz field. Methods. The study of the isotopic composition of oxygen, hydrogen, and carbon of water-dissolved carbon dioxide was carried out in the Research Equipment Sharing Center at the Institute of Geology and Mineralogy SB RAS using Isotope Ratio Mass Spectrometer FinniganTM MAT 253 equipped with H/Device and GasBench II for sample preparation. Results and conclusions. The paper introduces the data on isotopic composition of O, H and C for natural waters of the Yamalo-Nenets autonomous region. The authors have determined the characteristic trends in changes in the isotopic composition of water and dissolved carbon dioxide for various water bodies. Surface and underground waters with active water exchange in terms of isotopic composition (δD and δ18О) are infiltration. As water moves down the section, with an increase in the time of interaction of the “water–rock” system and increase in temperatures, the isotopic composition becomes significantly heavier with a slope from the GMWL to the right. The authors compiled the diagram of the evolution of water-dissolved carbon isotopic composition in the region according to the obtained and some literature data. Despite the wide range of δ13C values from –30.4 to 23.6 ‰, there are, obviously, only two sources of carbon dioxide in the region: biogenic and atmospheric, with biogenic being predominant for groundwater.

Pyolytics as a product of the physical–chemical repurposing of antiseptics and an alternative to larval therapy for chronic wounds

The traditional treatment of chronic wounds involves daily cleansing of the wound surface from purulent necrotic masses using mechanical and medicinal methods, accompanied by regular replacement of wound dressing. In this case, medicinal wound cleansing lasts 10–15 mins from the time of replacement of the old wound dressing with the new one. According to established practice, medicinal sanitation of infected and purulent wounds during dressing involves irrigation of the wound surface with cleansing solutions, antiseptics, and/or antibiotics. In severe cases, the above therapy is supplemented with live larvae of the necrophage fly, which are injected into purulent necrotic masses and left in them under wound dressing until wounds are completely cleansed from pus. Nevertheless, the generally accepted course of treatment of chronic wounds remains ineffective. The use of pyolytics and their supplementation with wound dressings in the form of warm wet compresses, which create a local greenhouse effect in wounds, was reported to accelerate the healing of chronic wounds. Pyolytics are a group of antiseptics developed in Russia. They are warm alkaline solutions of hydrogen peroxide; when they interact with purulent necrotic masses, these solutions dissolve very quickly and foam them. Because of the interaction with pyolytics, thick purulent masses immediately turn into fluffy oxygenated foam. Pyolytics have been developed because of the physicochemical repurposing of aqueous solutions of sodium hydrogen carbonate and hydrogen peroxide. To accelerate the healing of chronic wounds, a recommendation was to irrigate the surface of chronic wounds with 3% hydrogen peroxide and 2–10% sodium bicarbonate solutions, heated to 37–45°C, which have alkaline activity at pH 8.4–8.5 and are enriched with dissolved carbon dioxide or oxygen (due to excess pressure of 0.2 atm). This study presented the importance of treating chronic wounds using politics and treatment outcomes using pyolytics along with warm moist dressing compresses, demonstrating a wound-healing effect. Consequently, physical and chemical reprofiling of antiseptics may make them effective pyolytics, and the combination of pyolytics with warm wound dressings such as warm moist compresses, which create a local greenhouse effect on wounds, accelerates the healing of chronic wounds.

Reservoir Drawdown Highlights the Emergent Effects of Water Level Change on Reservoir Physics, Chemistry, and Biology

AbstractWater level drawdowns are increasingly common in lakes and reservoirs worldwide as a result of both climate change and water management. Drawdowns can have direct effects on physical properties of a waterbody (e.g., by altering stratification and light dynamics), which can interact to modify the waterbody's biology and chemistry. However, the ecosystem‐level effects of drawdown remain poorly characterized in small, thermally stratified reservoirs, which are common in many regions of the world. Here, we intensively monitored a small eutrophic reservoir for 2 years, including before, during, and after a month‐long drawdown that reduced total reservoir volume by 36%. During drawdown, stratification strength (maximum buoyancy frequency) and surface phosphate concentrations both increased, contributing to a substantial surface phytoplankton bloom. The peak in phytoplankton biomass was followed by cascading changes in surface water chemistry associated with bloom degradation, with sequential peaks in dissolved organic carbon, dissolved carbon dioxide, and ammonium concentrations that were up to an order of magnitude higher than the previous year. Dissolved oxygen concentrations substantially decreased in surface waters during drawdown (to 41% saturation), which was associated with increased total iron and manganese concentrations. Combined, our results illustrate how changes in water level can have cascading effects on coupled physical, chemical, and biological processes. As climate change and water management continue to increase the frequency of drawdowns in lakes worldwide, our results highlight the importance of characterizing how water level variability can alter complex in‐lake ecosystem processes, thereby affecting water quality.

Effect of Dissolved Carbon Dioxide on Cavitation in a Circular Orifice

In this work, we investigate the effect of dissolved gas concentration on cavitation inception and cavitation development in a transparent sharp-edged orifice, similar to that previously analyzed by Nurick in the context of liquid injectors. The working liquid is water, and carbon dioxide is employed as a non-condensable dissolved gas. Cavitation inception points are determined for different dissolved gas concentration levels by measuring wall-static pressures just downstream of the orifice contraction and visually observing the onset of a localized (vapor) bubble cloud formation and collapse. Cavitation onset correlates with a plateau in wall-static pressure measurements as a function of a cavitation number. An increase in the amount of dissolved carbon dioxide is found to increase the cavitation number at which the onset of cavitation occurs. The transition from cloud cavitation to extended-sheet or full cavitation along the entire orifice length occurs suddenly and is shifted to higher cavitation numbers with increasing dissolved gas content. Volume flow rate measurements are performed to determine the change in the discharge coefficient with the cavitation number and dissolved gas content for the investigated cases. CFD analyses are carried out based on the cavitation model by Zwart et al. and the model by Yang et al. to account for non-condensable gases. Discharge coefficients obtained from the numerical simulations are in good agreement with experimental values, although they are slightly higher in the cavitating case. The earlier onset of fluid cavitation (i.e., cavitation inception at higher cavitation numbers) with increasing dissolved carbon dioxide content is not predicted using the employed numerical model.

Development of acid-free chitosan films in food coating applications: Provolone cheese as a case study

Chitosan has been extensively explored in food coatings. Still, its practical application is largely hampered by its conventional wet processing in acetic acid, whose residuals negatively impact food quality and safety. Here, we propose a new method to formulate chitosan coatings for food applications by avoiding organic acid processing and validate them on a cheese model. The procedure entails modifying a previously reported process based on HCl chitosan treatment and neutralising the resulting gel. The obtained chitosan is solubilised in water using carbonic acid that forms in situ by dissolving carbon dioxide gas. The reversibility of water carbonation allows for easy removal of carbonic acid residues, resulting in acid-free chitosan films and coatings. The performance of the coating was tested against state-of-the-art chitosan-based and polymeric coatings. We preliminarily characterised the films' properties (water stability, barrier, and optical properties). Then, we assessed the performance of the coating on Provolone cheese as a food model (mass transfer and texture profiles over 14 days). The work demonstrated the advantage of the proposed approach in solving some main issues of food quality and safety, paving the way for an effective application of chitosan in future food contact applications.

Miniature mid-infrared photoacoustic gas sensor for detecting dissolved carbon dioxide in seawater

A miniature mid-infrared photoacoustic (PA) gas sensor with a chamber volume of approximately 73 μL for detection of dissolved gases in seawater was presented. This sensor offers several advantages: small size, high sensitivity, low cost, and low power consumption. The strong absorption band of carbon dioxide (CO2) near 4.26 µm was targeted by utilizing a mid-infrared microelectromechanical system (MEMS) thermal light source and a narrow bandwidth optical filter. The thermal light source was electrically modulated, which simplified the sensor structure. Double-pass absorption was implemented to enhance the PA signal, which was detected by a small and low-cost MEMS electric microphone. The gas entered the sensor through a small hole in a diffusion manner without the need for valves or an air pump. This design feature contributes to a compact structure with dimensions of only 2.43 cm × 1.25 cm × 1.8 cm. The analysis results showed that the minimum detection limit (MDL) of CO2 reached 0.72 ppm with an averaging time of 100 s. A polydimethylsiloxane (PDMS) membrane was used as the water-gas separation unit. The performance of the designed PA sensor for detecting dissolved gases in seawater has been verified. When the flow rate of the water pump was 600 mL/min, the time for water-gas equilibrium was only 3.5 min. This can be attributed to the small size of the gas chamber and the rapid water exchange.

Response of dissolved carbon dioxide and methane concentration to warming in shallow lakes

Shallow lake ecosystems are highly sensitive to temperature fluctuation because of their high water surface-to-volume ratios. Shallow lakes have been increasingly identified as a hotspot of CO2 and CH4 emissions, but their response to temperature variation remains unclear. Here, we report from a 5-month outdoor mesocosm experiment where we investigated the impacts of a projected 3.5 °C future warming and monthly temperature changes on lake CO2 and CH4, as well as the key drivers affecting the lake carbon cycling. Our results show that CO2 and CH4 concentrations had a significantly positive correlation with monthly temperatures. CH4 concentration was primarily regulated by monthly temperature, while nutrients effects on CO2 concentration overrode climate warming and temporal temperature changes. These findings imply the varied roles that temperature and nutrient levels can play on CO2 and CH4 dynamics in shallow lake systems. The relationship between temperature and CO2 concentration was nonlinear, showing a threshold of approximately 9 °C, at which CO2 concentration could be strongly modified by nutrient level in the lake systems. Understanding this complex relationship between temperature with CO2 and CH4 concentrations in shallow lakes is crucial for effective lake management and efficient control of greenhouse gases (GHGs) emissions.

Energy harvesting and electricity production through dissolved carbon dioxide by connecting two form-stable phase change materials

Herein, we report a new solar energy harvesting approach by connecting two form-stable phase change materials in a moist environment with dissolved carbon dioxide (CO2).