CO2 Levels Research Articles

How international conflicts and global crises can intertwine and affect the sources and levels of air pollution in urban areas.

This paper analyses the intertwined impacts of the 2018 US sanctions on Iran and the COVID-19 pandemic (as examples of unplanned international conflicts and global crises) on the source and extent of air pollution in Tehran, the capital of Iran. The impacts are parametrized using the levels of criteria air pollutants (CAP) for 5years (2015-2020), which were previously deweathered using the promising machine learning technique of Random Forest (RF). The absolute principal component scores-multiple linear regression (APCS-MLR) method and the bivariate polar plot (BPP) technique are used here to analyze the source apportionment profile of the city for the business as usual (BAU; 2015 to 2018), sanctions (2019), and COVID-19 and sanctions (2020) intervals. The results show the severe impact of the 2018 US sanctions on Tehran's air quality (AQ); O3, NO2, CO, PM2.5, and PM10 levels increased by 117%, 55%, 20%, 35%, and 10%, respectively, while SO2 levels decreased by 30%. The sanctions also triggered a number of events, such as the disruption of the high-grade fuel supply chain and the Mazut crisis, which directly or indirectly accelerated the photochemical production of local tropospheric ozone to some extent. Sanctions also disrupted Tehran's AQ response to the pandemic, with CAP levels decreasing by only 2-7% during the pandemic. The ozone and PM10 BPPs show that the source apportionment profile of the city is dominated by local anthropogenic emission sources, especially urban transport, after the sanctions and the pandemic. Results also show that the impact of soft wars, such as the US sanctions against Iran, on urban air quality degradation is much stronger than that of hard wars, such as the Russia-Ukraine war.

Sugarcane Cultivation Amidst Climate Change Challenges: An in-depth Review of Mitigation Strategies and Environmental Resilience

The sugarcane (Saccharum officinarum L.) holds global significance for sugar and bioenergy production, contributing to the gross domestic product of Pakistan and generating employment. However, environmental degradation resulting from global warming, climate change, and high greenhouse gas emissions pose a critical threat to the sugarcane as well as the sugarcane industry worldwide. Developing countries, like Pakistan, India, and Bangladesh are likely to be more affected because of poor adaptability and forecasting systems, high vulnerability to disasters/extreme events, and insufficient mitigation strategies. Sugarcane production is affected by shifts in climatic conditions, such as temperature, rainfall, and CO2 level, and will continue to be affected by the onset of such events, which are directly linked to geographical areas and the capacity to adapt to such changes. This paper gives a brief description of the challenges and behavior of sugarcane crops to climate change, and the future trend of climate change with respect to sugarcane production to better quantify, comprehend, and counteract the potential negative impact by enhancing the sugarcane production on a sustainable and economically viable basis.

Assessment of Human Health Risk Caused by Heavy Metals in Kiln Dust from Coal-Fired Clay Brick Factories in Türkiye

AbstractHeavy metal (HM) pollution from natural processes and different anthropogenic activities pose significant human and environmental health risks because of their stability, non-degradable properties, and high toxicity. HM released into the air in the form of dust can enter the human body via ingestion, inhalation, and dermal contact. Keeping in mind the significance of estimating the risk from HM in different environments, the carcinogenic and non-carcinogenic health risks to workers caused by HM in kiln dust (KD) samples collected from coal-fired clay brick factories in the Western Black Sea Region of Türkiye were assessed for the first time in this study. The concentrations of major and minor oxides and HMs in the collected KD samples were analyzed using energy-dispersive X-ray fluorescence spectrometry. The average concentrations of Fe, Mn, Cr, Ni, V, Zn, Cu, As, Co and Pb analyzed in thirty-three KD samples were determined as 65444, 768, 251, 249, 248, 122, 60, 52, 42 and 16 mg/kg dw, respectively. The average levels of Ni, As, Cr, Co and Cu exceed the maximum contaminant levels recommended in the Turkish Regulation on Control of Soil Pollution. Carcinogenic and non-carcinogenic human health risk assessments for workers via three exposure pathways were carried out, estimating the hazard index (HI) and total carcinogenic risk (TCR) index, respectively. The HI values (< 1) revealed no possible non-carcinogenic health risk due to exposure to all HMs in the studied KD samples. The average TCR value revealed that the potential cancer risks for Ni, As, Cr, and Pb were slightly above the safe limit and required monitoring and further investigation for these HMs.

Recent advancements in carbon/metal-based nano-catalysts for the reduction of CO2 to value-added products

Due to the increased human activities in burning of fossil fuels and deforestation, the CO2 level in the atmosphere gets increased up to 415 ppm; although it is an essential component for plant growth, an increased level of CO2 in the atmosphere leads to global warming and catastrophic climate change. Various conventional methods are used to capture and utilize CO2, among that a feasible and eco-friendly technique for creating value-added products is the CO2RR. Photochemical, electrochemical, thermochemical, and biochemical approaches can be used to decrease the level of CO2 in the atmosphere. The introduction of nano-catalysts in the reduction process helps in the efficient conversion of CO2 with improved selectivity, increased efficiency, and also enhanced stability of the catalyst materials. Thus, in this mini-review of nano-catalysts, some of the products formed during the reduction process, like CH3OH, C2H5OH, CO, HCOOH, and CH4, are explained. Among different types of metal catalysts, carbonaceous, single-atom catalysts, and MOF based catalysts play a significant role in the CO2 RR process. The effects of the catalyst material on the surface area, composition, and structural alterations are covered in depth. To aid in the design and development of high-performance nano-catalysts for value-added products, the current state, difficulties, and future prospects are provided.

Increasing efficiency in perovskite solar cells through energy downconversion using nanoparticles

The generation of electricity through solar energy stands out as one of the fastest-growing renewable energy sources worldwide. The global demand for energy, coupled with the rising levels of CO2 in the atmosphere, highlights the need to develop renewable sources of energy. The current challenge of utilizing photovoltaic cells for electricity production lies in the efficiency of the photovoltaic conversion process occurring within the device. To enhance the efficiency of photovoltaic devices, scientists have been investigating light conversion processes to improve radiation absorption and conversion. The study and application of the downconversion process with luminescent materials have been explored to prevent energy loss in solar devices. Zinc Oxide nanoparticles (ZnO NPs) have been employed for this purpose due to their favorable optical properties for downconversion applications. Organic–inorganic perovskites, such as methylammonium lead iodide perovskite (CH3NH3PbI3), have shown promising results for power conversion efficiency, and the present study aimed to assess the increased efficiency of perovskite devices with the addition of ZnO nanoparticles on top of the device. Such optical improvement in the device can occur because high-energy photons, which would be absorbed by layers such as glass and ITO, which are not semiconductors and do not generate charge carriers, will now be absorbed by the ZnO NPs and emitted at longer wavelengths. These longer wavelengths will be absorbed in the active layer of the device, thus generating charge carriers. The obtained results demonstrated that ZnO nanoparticles with approximately 45 nm diameter can successfully produce a downconversion process, leading to improved light absorption by the active layer of the cell and consequently improving photovoltaic efficiency of a perovskite device by 5.5 %.

Plant response to decreasing soil moisture under rising atmospheric CO2 levels

Widespread drought driven by global warming is predicted across the 21st century, just as CO2 level is projected to as much as double over the same time period. However, the potential interplay between increasing CO2 and decreasing soil moisture on plant function is uncertain, as previous works have not successfully separated and quantified these two competing effects. Here we evaluated the interaction between soil moisture and CO2 using stable carbon isotope measurements of Arabidopsis grown under the simultaneous modulation of an exhaustive range of both variables. Results showed that both increasing soil water content and increasing CO2 increased isotopic discrimination, and that the soil moisture effect was not influenced by the CO2 level and vice versa. Our data confirm that changes in the carbon isotope record of terrestrial organic matter preserved within the geologic record are best interpreted as deriving from changes in atmospheric CO2.

Spatial and temporal changes of air quality in Shandong Province from 2016 to 2022 and model prediction

This study investigates the spatial and temporal dynamics of air quality in Shandong Province from 2016 to 2022. The Air Quality Index (AQI) showed a seasonal pattern, with higher values in winter due to temperature inversions and heating emissions, and lower values in summer aided by favorable dispersion conditions. The AQI improved significantly, decreasing by approximately 39.4 % from 6.44 to 3.90. Coastal cities exhibited better air quality than inland areas, influenced by industrial activities and geographical features. For instance, Zibo's geography restricts pollutant dispersion, resulting in poor air quality. CO levels remained stable, while O3 increased seasonally due to photochemical reactions in summer, with correlation coefficients indicating a strong positive correlation with temperature (r = 0.65). Winter saw elevated NO2 levels linked to heating and vehicular emissions, with an observed increase in correlation with AQI (r = 0.78). PM2.5 and PM10 concentrations were higher in colder months due to heating and atmospheric dust, showing a significant decrease of 45 % and 40 %, respectively, over the study period. Predictive modeling forecasts continued air quality improvements, contingent on sustained policy enforcement and technological advancements. This approach provides a comprehensive framework for future air quality management and improvement.

Investigation of Trace Element Levels and Toxic Metals in Obese Children: A Single-Center Experienc.

The complete role of factors contributing to the pathogenesis of childhood obesity remains to be fully elucidated. Limited research has addressed trace elements in the context of child obesity. Our objective was to assess trace element and lead (Pb), copper (Cu) (are toxic metal) levels in both healthy and obese children, and to investigate the potential correlations between these elements and obesity-related anthropometric measurements, lipid profiles, as well as insulin and glucose levels. Furnace atomic absorption spectrophotometry was employed to measure the concentrations of trace elements in the serum. Additionally, fasting glucose, insulin, and lipid levels were determined in obese children (body mass index ≥ 95th percentile for age and sex), along with 50 healthy children. Only the obesity group underwent an oral glucose tolerance test (OGTT). Significantly reduced levels of Fe, Mg, Zn, and Co were observed in obese children, whereas Cu, Pb, and Mn levels were elevated (P < .001, P <.001, P = .002, P = .008, P <.001, P = .001, P = .007, respectively). Significant positive correlations were found between the 2-hour glucose level in OGTT and Mn (P = .013), as well as between peak insulin and insulin levels at the 30th and 60th minutes, and Fe (P = .001, P = .025, P = .001). This study indicates that an imbalance in trace element levels and the accumulation of Pb may be associated with obesity, while levels of Mn and Fe may be linked to glucose intolerance.

Green biochar briquette from enzymatic pretreated biomass wastes via mild-temperature pyrolysis for eco-friendly biofuels

Abstract In this study, benefits of the enzymatic pretreatment of mixed biomass wastes to a thermochemically favourable precursor for production of ecological biofuels are demonstrated. Biochar briquettes derived from the enzymatic- hydrolysis assisted, mild-temperature pyrolysis of biomass wastes are rich in carbon, exhibit higher calorific values and emit less toxic gases during combustion. Specifically, HHV value of the pretreated briquette increases one half of that of untreated briquette. Levels of CO and CO2 emission during the production and consumption of the treated briquette are lower than those of the untreated one. The results indicate a superior performance of biochar produced from the mixtures of various biomass wastes via the combined enzymatic pretreatment and mild-temperature pyrolysis processes in sustainable applications including biofuels.

Assessment of Air Quality Index of Kolkata, Howrah, and 24 Parganas North during COVID- 19 Lockdown

In the course of COVID- 19 pandemic, a nationwide lockdown in India has been imposed from 22nd March 2020 extended to June end, thereafter a partial lockdown was enforced as a precautionary measure to confine the spread of COVID- 19. The anthropogenic activity was restricted during lockdown therefore the pollution level across many cities in India reduced drastically. This eventually led us to analyze the air quality scenario of Kolkata metropolitan city along with suburban areas of North 24 Parganas and Howrah in the state of West Bengal, India. In the present research, the air quality parameters like PM10, PM2.5, SO2, NO2, CO, O3, and NH3 were analyzed the during lockdown phase of 23rd March 2020 to 30th June 2020. A comparative study was done with the air quality data of the pre-lock down phase (March 2019 to 4th March 2020) and an Air Quality Index (AQI) was prepared. During lockdown coal/ fuel consumption was low due to the restriction of vehicle movement and road transport thus carbon emission in the air was less. AQI improved enormously with reduction of SO2 content to &lt;80 %; among other pollutants NO2 and NH3 reduced to &lt;54 % and &lt;91 % in Kolkata, Howrah, and 24 Parganas North. P.M 2.5 drastically reduced in the regions of Kolkata, Howrah, and 24 Parganas North of West Bengal effectively to &lt;81%, &lt;91 %, and &lt;95% respectively. P.M 10 reduced to &lt;75%, &lt;79%, and &lt; 81 % in Kolkata, Howrah, and 24 Parganas North. In Kolkata there was 55% reduction in the level of CO. There was 4 folds reduction of P.M2.5 and P.M10 in Kolkata compared to March- June 2019. About 50 % to 60 % improvement in air quality was identified within 7days of the lockdown. Improvement of air quality during lockdown has benefited the environment and ecology.

Species interactions amplify functional group responses to elevated CO2 and N enrichment in a 24-year grassland experiment.

Plant functional groups (FGs) differ in their response to global changes, although species within those groups also vary in such responses. Both species and FG responses to global change are likely influenced by species interactions such as inter-specific competition and facilitation, which are prevalent in species mixtures but not monocultures. As most studies focus on responses of plants growing in either monocultures or mixtures, but rarely both, it remains unclear how interspecific interactions in diverse ecological communities, especially among species in different FGs, modify FG responses to global changes. To address these issues, we leveraged data from a 16-species, 24-year perennial grassland experiment to examine plant FG biomass responses to atmospheric CO2, and N inputs at different planted diversity. FGs differed in their responses to N and CO2 treatments in monocultures. Such differences were amplified in mixtures, where N enrichment strongly increased C3 grass success at ambient CO2 and C4 grass success at elevated CO2. Legumes declined with N enrichment in mixtures at both CO2 levels and increased with elevated CO2 in the initial years of the experiment. Our results suggest that previous studies that considered responses to global changes in monocultures may underestimate biomass changes in diverse communities where interspecific interactions can amplify responses. Such effects of interspecific interactions on responses of FGs to global change may impact community composition over time and consequently influence ecosystem functions.

Níveis de CO2, quebra técnica e qualidade dos grãos de milho armazenados em diferentes condições

ABSTRACT The use of CO2 sensors has been reported as an effective tool in the early detection of signs of deterioration, allowing good accuracy in decision-making about the quality of stored grains. The objective of this study was to quantify the CO2 levels produced by maize grains stored at ambient temperature in a prototype silo, with initial moisture contents of 14, 16 and 18% w.b., and to evaluate the quality of the product over time and the technical breakage. Analyses of moisture content, ash, proteins, lipids, Hue Angle (color), germination and electrical conductivity were performed. Inside the silos, the amount of CO2, relative air humidity and temperature were monitored every hour. Grain quality evaluations were carried out at four storage times (0, 30, 60 and 90 days). A completely randomized design in a 3 × 4 factorial scheme with six replicates was used. Grains with higher moisture contents showed higher technical breakage and losses associated with CO2 emissions. Moisture content, protein, lipids, germination, bulk density, lightness and chroma decreased over time, while the electrical conductivity increased, resulting in greater damage to membranes and loss of quality of maize grains. Monitoring of CO2 in the grain mass is a good tool to assess the quality of grain, and higher initial moisture content caused greater level of CO2 emission and reduction in quality of maize grains.

Bimetallic NiSn supported on mesoporous carbon as an efficient catalyst for selective methanol synthesis from CO2

Global warming and climate change represent the most significant environmental challenges of the 21st century, primarily attributed to the rise in CO2 emission in the atmosphere. Efforts to mitigate this increase involve exploring various methods to reduce CO2 levels, with chemical reactions, such as hydrogenation, being a prominent approach. However, the stable and inert nature of CO2 necessitates the use of catalysts to facilitate its conversion. In this research, NiSn nanoparticles with varying atomic ratios were deposited onto a mesoporous carbon support and subsequently utilized as catalysts for CO2 conversion through hydrogenation reactions at ambient pressure. The diffraction patterns of NiSn/MC reveal peaks indicating the presence of a graphitic carbon structure and the existence of a nickel-tin alloy. SEM-EDX mapping and TEM characterization demonstrate the uniform dispersion of NiSn particles on the mesoporous carbon surface, without the formation of agglomerated particles. Catalytic hydrogenation reactions indicate that the atomic ratio of Ni:Sn significantly influences the catalyst activity and selectivity for methanol formation. Among the NixSny/MC catalysts and monometallic Ni/MC, Sn/MC, and NiSn NPs without support, Ni5Sn1/MC demonstrated the highest CO2 conversion of 39.9 %. Additionally, at a reaction temperature of 175 °C and a CO2:H2 gas ratio of 1:7, Ni5Sn1/MC exhibited a methanol yield of 86.31 mmol/gcat, outperforming other catalysts in the study.

Indoor Environmental Quality and Effectiveness of Portable Air Cleaners in Reducing Levels of Airborne Particles during Schools’ Reopening in the COVID-19 Pandemic

Educational buildings tend to fail in the contagion containment of airborne infectious diseases because of the high number of children, for several hours a day, inside enclosed environments that often have inadequate indoor air quality (IAQ) conditions. This study aimed to assess indoor environmental quality and test the effectiveness of portable air cleaners (PACs) in alleviating airborne particle levels in schools of Central–Southern Spain during the period of reopening after the lockdown due to the COVID-19 outbreak. To accomplish this, three sampling campaigns were organized from September to December 2020 to consistently monitor temperature and relative humidity, carbon dioxide, and particulate matter in nineteen classrooms (seven school buildings). Results showed that although the recommendation of maintaining the windows open throughout the day seemed to be effective in promoting, in general, proper ventilation conditions (based on CO2 levels). For the colder campaigns, this practice caused notorious thermal comfort impairment. In addition, a great number of the surveyed classrooms presented levels of PM2.5 and PM10, attributable to outdoor and indoor sources, which exceeded the current WHO guideline values. Moreover, considering the practice of having the windows opened, the installation of 1 unit of PACs per classroom was insufficient to ensure a reduction in particle concentration to safe levels. Importantly, it was also found that children of different ages at different education levels can be exposed to significantly different environmental conditions in their classrooms; thus, the corrective measures to employ in each individual educational setting should reflect the features and needs of the target space/building.

Changes in gill neuroepithelial cells and morphology of threespine stickleback (Gasterosteus aculeatus) to hypoxia and simulated ocean acidification.

Coastal marine environments are characterized by daily, seasonal and long-term changes in both O2 and CO2, driven by local biotic and abiotic factors. The neuroepithelial cells (NECs) of fish are thought to be the putative chemoreceptors for sensing oxygen and CO2, and, thus, NECs play a key role in detecting these environmental changes. However, the role of NECs as chemosensors in marine fish remains largely understudied. In this study, the NECs of marine threespine sticklebacks (Gasterosteus aculeatus) were characterized using immunohistochemistry. We then determined if there were changes in NEC size and density, and in gill morphology in response to either mild (10kPa) or moderate (6.8kPa) hypoxia and two levels of elevated CO2 (1,500 and 3,000 µatm). We found that the NECs of stickleback contained synaptic vesicles and were innervated, and were 50-300% larger and 2 to 4 times more abundant than in other similar sized freshwater fishes. NEC size and density were largely unaffected by exposure to hypoxia, but there was a 50% decrease in interlamellar cell mass (ILCM) in response to mild and moderate hypoxia. NECs increased in size, but not abundance in response to elevated CO2. Moreover, fish exposed to moderate or elevated CO2 had 53-78% larger ILCMs compared to control fish. Our results demonstrated that adult marine sticklebacks have NECs that can respond to environmentally relevant pCO2 and likely hypoxia, which highlights the importance of NECs in marine fishes under the heterogeneity of environmental conditions in coastal areas.

Temperature effects on chemical reactions and product yields in the Co-pyrolysis of wood sawdust and waste tires: An experimental investigation

This study investigates the effects of varying temperatures on the co-pyrolysis of wood sawdust (WS) and waste tires (WT) within a stainless steel fixed-bed reactor under a nitrogen atmosphere. The experiments were conducted at three different temperatures: 400 °C, 500 °C, and 600 °C, focusing on the thermal behavior and resultant product yields. At 600 °C, WS produced the highest oil yield (63.6 wt%), suggesting a tendency to generate more aqueous and volatile components. Conversely, WT alone showed an optimal oil yield of 46.4 wt% at 500 °C, while the WS-WT blend achieved 55.6 wt%. Gas chromatography-mass spectrometry (GC-MS) analyses of the pyrolytic oils indicated that WS-heavy mixtures were rich in aliphatic compounds, whereas WT-dominant samples had increased aromatic and phenolic contents, demonstrating the potential for creating valuable chemicals from waste. Additionally, gas analysis highlighted significant variations in syngas composition, with increased methane and decreased CO2 levels at higher temperatures, emphasizing the role of the water-gas shift reaction. These findings underscore the critical importance of temperature control in optimizing the efficiency and quality of products from co-pyrolysis, presenting a viable method for enhancing the value derived from waste materials.

The effect of polylactic acid-based blend films modified with various biodegradable polymers on the preservation of strawberries

Polylactic acid (PLA) has garnered much attention in the field of fruit and vegetable packaging. Despite its poor flexibility and water resistance, PLA film faces challenges in being used for strawberry storage and freshness preservation due to its inability to maintain flavor quality. In this study, a series of PLA-based modified films was produced by melt blending and extrusion cast processing with PLA as the main component, along with flexible biodegradable polyesters or polycarbonate as the secondary component. First, five different biodegradable polymers were used to investigate the effect of the flexibility and barrier properties of different dispersed phases on the morphology, mechanical properties, and water vapor barrier of PLA-based blend films. Next, the impact on the freshness of strawberries was assessed through examination of fruit color and weight, as well as the levels of O2 and CO2 in the packaging bags. The results showed that the size of the dispersed phase and interfacial bonding with PLA were the key factors determining the mechanical and barrier properties of the blend films. The PLA-polycaprolactone (PCL) blend showed the best compatibility among them, with PCL having the smallest dispersion size (D=0.58 µm), higher toughness than the other four PLA blends, and greater enhancement of PLA. Additionally, it exhibited a similar rate of quality loss in strawberry preservation compared to commercial PE. As a result, the color and luster were more completely preserved. The results of this study may help the future development of degradable plastics, to reduce environmental pollution.

Revitalizing IoT-based air quality monitoring system for major cities in Indonesia

An IoT-based air quality monitoring system is a technology that integrates with the internet to monitor and measure numerous air quality metrics in real-time. CO levels, dust particle levels, temperature, and humidity are the air quality characteristics that must be monitored. The air quality monitoring system in its current state requires further development, such as challenges to acquiring accurate and real-time data and difficulty in accessing reliable information. Poor air quality causes various health problems, respiratory, vision, heart disease, and even cancer. The development of air pollution producers continues to increase along with the number of oil-fueled vehicles, industries operated using petroleum-fueled engines, power plants that use energy from coal, gas and petroleum. This study presents an IoT-based air quality parameter monitoring system solution that is connected with the Blynk platform and can be accessible in real time, in an effort to assist the SDGs program, which is mandated by the global community through the UN. The research technique employed is Analysis, Design, Development, Implementation, and Evaluation. The study successfully presented an IoT-based air quality monitoring system connected with the Blynk platform, which showed great accuracy in measurement 94.34% (CO), 81.15% (dust), 99.14% (temperature), and 96.84% (humidity). These results advance urban air quality monitoring and inform sustainable technology development, contributing to environmental and health-related SDGs.

Climate change versus Mediterranean diet: A hazardous struggle for the women's heart

Climate change impacts food systems, causing nutritional deficiencies and increasing cardiovascular diseases (CVD). Regulatory frameworks like the European Farm-to-Fork Strategy aim to mitigate these effects, but current EU food safety regulations inadequately address health risks from poor diet quality and contaminants.Climate change adversely affects food quality, such as nutrient depletion in crops due to higher CO2 levels, leading to diets that promote chronic diseases, including CVD. Women, because of their roles in food production and their unique physiological responses to nutrients, face distinct vulnerabilities. This review explores the interplay between climate change, diet, and cardiovascular health in women. The review highlights that sustainable diets, particularly the Mediterranean diet, offer health benefits and lower environmental impacts but are threatened by climate change-induced disruptions. Women's adherence to the Mediterranean diet is linked to significant reductions in CVD risk, though sex-specific responses need further research.Resilient agricultural practices, efficient water management, and climate-smart farming are essential to mitigate climate change's negative impacts on food security. Socio-cultural factors influencing women's dietary habits, such as traditional roles and societal pressures, further complicate the picture.Effective interventions must be tailored to women, emphasizing education, community support, policy changes, and media campaigns promoting healthy eating. Collaborative approaches involving policymakers, health professionals, and the agricultural sector are crucial for developing solutions that protect public health and promote sustainability.Addressing the multifaceted challenges posed by climate change to food quality and cardiovascular health in women underscores the need for integrated strategies that ensure food security, enhance diet quality, and mitigate environmental impacts.

A descriptive study of carbon dioxide production and removal in full-scale RAS for Atlantic Salmon (Salmo salar L.) post-smolt: A comparison of two different measurement methods for CO2

Reliable data on metabolic rates and CO2 removal efficiency are essential for fish welfare in intensive production and RAS design. This descriptive study at a commercial post-smolt production facility evaluates two full-scale land-based RAS with different salinity levels: Module1 (M1) (2.5 ± 0.46‰ salinity) and Module2 (M2) (13.6 ± 0.46‰ salinity, with two separate RAS units, M2-RAS1, and M2-RAS2). Over eight weeks, water quality parameters were monitored in different places in the systems. CO2 concentrations were measured with an OxyGuard probe and calculated from total inorganic carbon (TIC). As fish biomass and feed load increased in both modules over time, CO2 concentrations increased and pH decreased, despite bicarbonate addition. In M1, CO2 levels increased from 6.2 to 16.4 mg L−1, while in M2, levels remained between 3.5 and 7.2 mg L−1. Apparent CO2 production, calculated from TIC, averaged at 5.2 ± 0.93 mg CO2 kg fish−1 min−1 in M1, and 3.2 ± 1.25 and 4.0 ± 1.45 mg CO2 kg fish−1 min−1 in M2-RAS1 and M2-RAS2 respectively. At the same time, the theoretical CO2 production rates showed a value of 4.4 ± 0.73, 4.2 ± 0.38, and 3.9 ± 0.71 mg CO2 kg fish−1 min−1 in M1, M2-RAS1, and M2-RAS2 respectively. The theoretical feed-to-CO2 conversion weight-to-weight ratio was estimated to be 0.345. However, M1 exhibited a higher measured feed-to-CO2 conversion ratio of 0.418, while M2-RAS1 and M2-RAS2 displayed ratios of 0.261 and 0.346, respectively. Observed CO2 (%) removal changed from 40% to 54% in M1, from 17% to 46% in M2-RAS1, and 26–44%, in M2-RAS2 over the observation period. This study suggests a significant role of the moving bed biofilter in CO2 removal, however, the effect size varied during the study and between modules, warranting further investigation. On average, 38% of CO2 removal before the degasser occurred within the biofilter in M1, and 49% in both RAS systems in M2. The total carbonate levels fluctuated over time, making it challenging to determine a clear increase or decrease, likely due to manual and varying bicarbonate additions. The two methods for assessing CO2 generally revealed minor differences and need more assessment. The prevalence of nephrocalcinosis was significantly more pronounced in M1 (73%), than in M2 (11%), which could be related to the difference in the CO2 level between the fish tanks. This study provides valuable insights into CO2 dynamics that may be useful in RAS design and operation for optimizing water quality and fish welfare.