Different Concentrations Of CO2 Research Articles

Effects of concentrated CO2 on the performance of a PBI/H3PO4 high temperature proton exchange membrane fuel cell

In this study, the impact of mimic reformate of formic acid decomposition on the anode polarization of HT-PEMFC is investigated under various operating conditions of the anode, including different concentrations of CO2, N2, CO, and humidification. Polarization curve and EIS measurements indicate that there is no significant difference (less than 5 mV when i < 0.4A/cm2) between the same concentrations of CO2 and N2 up to 75 vol%. No significant poisoning of the anode by CO2 (up to 75 vol%) has been observed, suggesting that the addition of concentrated CO2 acts more as a diluent than a poison. Upon separating the polarization effects, it is found that the oxygen reduction reaction (ORR) is a crucial step limiting the fuel cell performance, with cathodic activation losses reaching as high as 70 % at 0.8A/cm2. However, with 1 vol% CO in a H2/CO2 1/1 mixture, a significant poisoning effect on the fuel cell is observed. DRT (distribution of relaxation times) analyses reveal two peaks related to CO in high-frequency regions above 100 Hz associated with the anode polarization, with the peak integration being five times larger than in pure hydrogen. Humidification doesn't improve the voltage or mitigate CO poisoning. A one-dimensional flux model that includes the anode polarization is developed to analyze the polarizations for both cathode and anode under different concentrations of diluents, well describing the experimental results. When i < 0.8 A/cm2, the predicted values from the model closely match the measured values (within 5–10 mV). Calculations suggest that the anode polarization cannot be ignored, especially when the anode is fed with diluted gases.

Efficient and selective upgrading of biomass-derived furfural into 1,5 pentanediol by Co2+ etched ZIF-8 derived ZnCo layered double hydroxides nanoflake

Selective ring-opening hydrogenolysis of furfural (FF) to 1,5 pentanediol (1,5-PeD) is crucial for biomass valorization. However, achieving accurate bond-breaking is challenging. Herein, we report a facile method to synthesize layered double hydroxide nanoflake (ZnCo-LDH) mediated via Co2+ etching ZIF-8 with NaBH4 in water at ambient temperature. The structure, morphology, and chemical properties of synthesis catalysts with different concentrations of Co2+ were characterized. The results indicated a partial ZIF-8 structure in ZnCo-LDH, with increased Co2+ concentrations leading to catalyst agglomeration. Furthermore, the constitutive relationships between the catalyst’s properties and 1.5-PeD yields were established. Moreover, Co introduction altered the catalyst surface’s Brønsted and Lewis acids content. Density functional theory (DFT) indicated enhanced H2 adsorption and dissociation due to electro-transfer between Co and Zn species, with a tilted configuration favoring ring opening. Finally, a possible reaction mechanism was proposed. This work provides valuable insights for preparing ultrathin nanoflake ZnCo-LDH catalysts for biomass-derived furfur compound upgrading.

Research on etalon‐free CO2 measurement based on direct absorption signal fitting

AbstractThe emission of carbon dioxide (CO2) by thermal power plants is the main factor leading to the greenhouse effect. The measurement of CO2 is of great significance to carbon emission data statistics. In this paper, a measurement system based on tunable diode laser absorption spectroscopy (TDLAS) was built to measure the spectrum of CO2 near 1579 nm. To simplify the experimental system, a direct absorption signal fitting method is proposed to replace etalons for time‐frequency conversion. The method was applied to the measurement of four different concentrations of CO2 in the range of 7%–16%, and the measurement results were compared with the multipeak method, another etalon‐free method. The results show that the mean relative error of the measurement results is 4.23%, which is 1.76% lower than the measurement results of the multipeak method. The experimental research provides a feasible idea to simplify the CO2 measurement system based on TDLAS.

Development of CO2-sensitive antimicrobial bilayer films based on gellan gum and sodium alginate/sodium carboxymethyl cellulose and its application in strawberries

To effectively extend the shelf life of fruits meanwhile facilitating consumers to judge their freshness, in this work, a double-layer multifunctional film combining CO2 sensitivity and antibacterial properties was successfully prepared by adding methyl red (MR), bromothymol blue (BTB) into gellan gum (GG) as the sensing inner layer, and doping tannic acid (TA) into sodium alginate with sodium carboxymethyl cellulose (CMC) as the antimicrobial outer layer, which was applied to the freshness indication of strawberries. Microscopic morphology and spectral analysis demonstrated that the bi-layer films were fabricated successfully. The mechanical characteristics, thermal stability, water vapor resistance, and antibacterial capabilities of the bilayer films improved as TA concentration rose. They exhibited noticeable color changes at pH = 2–10 and different concentrations of CO2. Application of the prepared films to strawberries revealed that the GG-MB@SC-6%TA film performed most favorably under 4 °C storage conditions, not only monitoring strawberry freshness but also retaining high soluble solids and titratable acidity, resulting in a slight decrease in hardness and weight loss. Therefore, taking into account all of the physical-functional characteristics, the GG-MB@6%TA film has a broad application prospect for intelligent food packaging.

Comparative transcriptomic and metabolomics analysis of modified atmosphere responses in Tribolium castaneum (Coleoptera: Tenebrionidae).

Modified atmosphere is effective in controlling Tribolium castaneum Herbst, but it has adaptations. Comprehending the potential mechanism of resistance to T. castaneum in a modified atmosphere will help advance related management methods. This study conducted a comparative transcriptomic and metabolomic analysis to understand the physiological mechanism of T. castaneum in adapting to CO2 stress. Results showed that there were a large number of differentially expressed genes (DEGs) in T. castaneum treated with different concentrations of CO2. Gene ontology (GO) analysis revealed significant enrichment of DEGs mainly in binding, catalytic activity, cell, membrane, membrane part, protein-containing complex, biological regulation, and cellular and metabolic process. Kyoto Encyclopedia of Genes and Genomes analysis showed that different treatments had different effects on the metabolic pathways of T. castaneum. DEGs induced by 25% CO2 were involved in arginine and proline metabolism, and 50% air + 50% CO2 treatment affected most kinds of metabolic pathways, mainly the signal transduction pathway, including PI3K-Akt signaling pathway, AMPK signaling pathway, neurotrophin signaling pathway, insulin signaling pathway, and thyroid hormone signaling. Ribosome and DNA replication were enriched under high CO2 stress (75% and 95%). The metabolomics revealed that different concentrations of CO2 treatments might inhibit the growth of T. castaneum through acidosis, or they may adapt to anoxic conditions through histamine and N-acetylhistamine. Multiple analyses have shown significant changes in histamine and N-acetylhistamine levels, as well as their associated genes, with increasing CO2 concentration. In conclusion, this study comprehensively revealed the molecular mechanism of T. castaneum responding to CO2 stress and provided the basis for an effectively modified atmosphere in the T. castaneum.

Impact of temperature on the role of Criegee intermediates and peroxy radicals in dimer formation from β-pinene ozonolysis

Abstract. Stabilized Criegee intermediates (SCIs) and organic peroxy radicals (RO2) are critical in atmospheric oxidation processes and secondary organic aerosol (SOA) formation. However, the influence of temperature on their corresponding reaction mechanisms in SOA formation is unclear. Through utilizing formic acid as a SCI scavenger and regulating the ratio of hydroperoxyl radials (HO2) to RO2 ([HO2]/[RO2]) from ∼ 0.3 to ∼ 1.9 using different concentrations of CO, the roles of RO2 and SCIs in SOA formation were investigated from 248 to 298 K, particularly for dimer formation in β-pinene ozonolysis. The SOA yield increased by 21 % from 298 to 273 K, while it decreased by 40 % from 273 to 248 K. Both changing [HO2]/[RO2] and scavenging SCIs significantly affect SOA yield and composition. SCI reactions accounted for more than 40 % of dimer and SOA mass formation for all temperatures. Increasing [HO2]/[RO2] inhibited dimer and SOA formation, and this inhibition became larger with decreasing temperature. Compared to low [HO2]/[RO2] (0.30–0.34), the dimer abundance at high [HO2]/[RO2] (1.53–1.88) decreased by about 31 % at 298 K and 70 % at 248 K. [HO2]/[RO2] has a specific impact on SCI-controlled dimers at lower temperatures by especially influencing the C9–SCI reactions with RO2. The dimers formed from C9–SCI reactions with RO2 were estimated to decrease by 61 % at high [HO2]/[RO2] compared to low [HO2]/[RO2] at 248 K. The high reactivity and substantial contribution to SOA of β-pinene-derived SCIs at lower temperatures observed in this study suggest that monoterpene-derived SCI reactions should be accounted for in describing colder regions of the atmosphere.

Effects of carbon dioxide concentration in modified atmosphere packaging on the shelf life and quality criteria of whole wheat bread during storage

AbstractThis study aimed to determine the effects of carbon dioxide concentration in modified atmosphere packaging (MAP) on the quality criteria and shelf life of whole wheat flour bread. Four different concentrations of CO2 and N2 gases (30% CO2 + 70% N2, 50% CO2 + 50% N2, 70% CO2:30% N2 and 100% CO2) were applied to the bread samples, which were packaged with PA/EVOH/LDPE (polyamide/ethylene vinyl alcohol/low‐density polyethylene). The samples were stored at room temperature (25°C ± 1°C) for 13 days. The control group was packaged using BOPP (bi‐oriented polypropylene) under atmospheric air as in traditional current use. The effects of MAP on headspace gas analysis, pH, moisture content, water activity, water‐holding capacity, blue value, hardness, total mould and yeast count and sensory evaluation were analysed on days 0, 3, 4, 5, 7, 10 and 13. The results showed that the most effective gas combination in extending the shelf life of whole wheat bread was 100% CO2, and its shelf life was 10 days, whereas it was only 3 days for the control group. Increasing concentrations of CO2 significantly affected mould and yeast growth. As the CO2 concentration increased, the bread exhibited higher water‐holding capacity and blue values, which are important indicators for bread staling. An improved preservation of sensory properties was observed in proportion to increasing CO2 concentrations. However, the CO2 gas concentration did not affect the hardness of the bread. Overall, the study suggests that MAP technology, particularly using 100% CO2, can effectively extend the shelf life of whole wheat flour bread without the need for preservatives, not only extending the microbiological shelf life but also increasing the sensory shelf life. The species that grew in air‐packaged samples were suppressed under modified atmosphere conditions and chalk mould fungi were the dominant and shelf life‐impacting species in the MAP samples. These findings could be beneficial in reducing bread wastage, which is a critical issue in today's society due to the limited shelf life of bread caused by rapid microbiological deterioration or staling.

Catalytic activity of Co (II)-porphyrin anchored onto polymeric support of electrospun polyacrylonitrile nanofiber: synthesis and efficient green oxidation of crystal violet dye with hydrogen peroxide

AbstractA novel method was explored in this study to address water contamination challenges by utilizing nanofiber mat-supported metalloporphyrin materials. Specifically, electrospinning was employed to create various compositions of polyacrylonitrile (PAN) mixed with different concentrations of Co(II) complex of tetrakis-5, 10, 15, 20 (4-hydroxyphenyl)porphyrin Co(II)TPHPP 1 anchored to chloroacetylated poly (p-hydroxy styrene) CAPS. These resulting nanofiber mat-supported metalloporphyrin materials were comprehensively analyzed using UV, FTIR spectrum, SEM, and TGA thermographs. The study found that the designed nanofibers acted as efficient catalysts for the oxidative breakdown of crystal violet (CV) dye using H2O2 in aqueous solutions. Among these materials, the nanofiber composed of a 1:1 ratio of PAN to Co(II)TPHPP/CAPS with a lower Co(II)TPHPP loading (NF6), demonstrated the highest catalytic activity, decomposing CV completely within 60 min. Various experiments were conducted to explore the effects of H2O2 concentration, catalyst dosage, and temperature on the catalytic degradation of CV with the NF6 nanofiber mat-supported metalloporphyrin. An interesting finding was the enhanced recovery and recyclability of the catalyst due to the immobilization of metalloporphyrin on chloroacetylated polymer-supported nanofiber mats. Remarkably, even after five cycles of reuse, there was no significant degradation in the catalytic activity of the recycled catalyst. This breakthrough highlights the potential of these materials in addressing water pollution challenges efficiently and sustainably.

A multimodal lithium niobate-based SAW gas sensor for accurate detection of carbon dioxide at elevated temperature

Carbon dioxide (CO2) detection is crucial for safety control, monitoring of the environment, and other industrial applications. The diverse fields of applications make the detection of CO2 a challenging task. In this paper, a study on a multimodal surface acoustic wave (SAW) CO2 sensing system was conducted to scrutinize the sensitivity of the lithium niobate-based multimodal SAW sensor towards CO2 with temperature compensation. The study focused on developing and evaluating a SAW temperature-compensated gas sensor using time-of-flight measurements. The sensor exhibited good repeatability and sensitivity toward different concentrations of CO2.

A new method for evaluation of nanotube growth kinetics in aerosol CVD

Aerosol chemical vapor deposition (CVD) – a particular case of floating catalyst CVD method with an extreme dilution of catalyst – has been demonstrated to be one of the most advanced one-stage and continuous techniques for the production of single-walled carbon nanotubes (SWCNTs) for various applications in electronics, optics, energy storage, etc. Nevertheless, rational scaling of the aerosol CVD reactor is often limited by a fundamental problem of tracking the growth kinetics, in particular, the nanotube growth rate and the catalyst deactivation rate. We propose a robust method for the assessment of nanotube growth kinetics (growth rate and catalyst lifetime) based on the analysis of the SWCNT film equivalent sheet resistance (R90) versus residence time (τ) dependencies. We have demonstrated identical trends of R90-vs-τ and length-vs-τ curves at different concentrations of CO2 used as a promoter in the Boudouard reaction- (CO-) based synthesis. As a result, we have revealed the mechanisms behind the CO2 effect on the catalyst deactivation rate not reported before. In particular, we observed an increase in CO2 concentration to provide a faster growth rate but an earlier catalyst deactivation. We believe this work might be useful for researchers from both academia and industry and facilitate more active development of aerosol CVD methods for the production of new materials.

Construction of a Numerical Model for Flow Flash Evaporation with Non-Condensable Gas

Flash evaporation processes are widely used in petroleum, food, chemical, power, and other industries to separate products or extract heat. The liquid is often entrained by non-condensing gas components. This study develops a multiphase, multicomponent, and pressure-driven phase-change-coupled model to numerically study water flash evaporation with non-condensing CO2. The model includes the mass, momentum, energy, volume of fluid (VOF), species transport, turbulence (RNG k-ε), modified phase-change Lee, and non-condensing CO2 release governing equations. The steam generation rate and mechanism for pure water and different concentrations of CO2 are considered. The results show that the numerical model can accurately predict the flash evaporation process and has high accuracy compared with the experimental data. Both the dissolved and entrained CO2 that are released can severely disturb the flow field, leading to an increase in the steam generation rate. Under a 1–10% volume concentration of dissolved CO2 and 0.0661–0.1688% mass concentration of entrained CO2, the maximum increase ratio of steam generation can reach 20%.

PSI Photoinhibition and Changing CO2 Levels Initiate Retrograde Signals to Modify Nuclear Gene Expression.

Photosystem I (PSI) is a critical component of the photosynthetic machinery in plants. Under conditions of environmental stress, PSI becomes photoinhibited, leading to a redox imbalance in the chloroplast. PSI photoinhibition is caused by an increase in electron pressure within PSI, which damages the iron-sulfur clusters. In this study, we investigated the susceptibility of PSI to photoinhibition in plants at different concentrations of CO2, followed by global gene expression analyses of the differentially treated plants. PSI photoinhibition was induced using a specific illumination protocol that inhibited PSI with minimal effects on PSII. Unexpectedly, the varying CO2 levels combined with the PSI-PI treatment neither increased nor decreased the likelihood of PSI photodamage. All PSI photoinhibition treatments, independent of CO2 levels, upregulated genes generally involved in plant responses to excess iron and downregulated genes involved in iron deficiency. PSI photoinhibition also induced genes encoding photosynthetic proteins that act as electron acceptors from PSI. We propose that PSI photoinhibition causes a release of iron from damaged iron-sulfur clusters, which initiates a retrograde signal from the chloroplast to the nucleus to modify gene expression. In addition, the deprivation of CO2 from the air initiated a signal that induced flavonoid biosynthesis genes, probably via jasmonate production.

Effect of CO2 on the preservation effectiveness of chilled fresh boneless beef knuckle in modified atmosphere packaging and microbial diversity analysis

To explore the effect of different concentrations of CO2 in modified atmosphere packaging (MAP) on the preservation shelf life of boneless beef knuckle (BBK), and to deeply study the changes in the bacterial community. In the controlled atmosphere combination, the proportion of O2 in each group is kept at 40%, CO2: 20%–45%, and N2: 15%–60%, the blank control group is set to 40%O2+0%CO2+60%N2. Sensory evaluation, headspace gas, total colony, and physicochemical indicators were measured at the 1st, 3rd, 5th, 7th, 9th, and 11th days of storage, respectively. The results showed that group 25%CO2+35%N2 had the longest shelf life is 9 days. In the analysis of the bacterial community, CO2 significantly inhibited the growth of Pseudomonas from the 3rd day onwards in the group 25%CO2+35%N2. After 4 days of storage, Lactobacillus was the main dominant bacterium, followed by Carnobacterium. Through KEGG metabolic pathway analysis, it was found that during the storage and preservation process, the expression levels of genes related to carbohydrate metabolism and amino acid metabolism in cold fresh BBK were higher than those in other metabolites.

Inhibition of insoluble HgS and HgO generation and promotion of easy-soluble HgCl2 production for the solution washing regeneration of mercury adsorbent in syngas

Inhibiting the generation of insoluble HgO and HgS, as well as promoting the generation of HgCl2 can significantly contribute to the solution washing regeneration of adsorbent for Hg removal in syngas. In this study, CeO2-MnO2/TiO2(Ce-Mn/Ti) was chosen as the Hg adsorbent, the fixed-bed test, Hg-TPD, and characterization test (including BET, SEM-EDS, and XPS) were conducted. Firstly, the effects of different concentrations of CO, H2, NH3, and HCl on the generation of HgS, HgO, and HgCl2 on adsorbent was investigated. Although the increase of CO, H2, and NH3 concentration can inhibit the generation of HgS and HgO to different extents, and the increase of HCl concentration can promote the production of HgCl2, but they will also lead to the increase in Hg concentration to varying degrees, indicating the adjustment on syngas components and concentrations is not a feasible method. Subsequently, the effects of different concentrations of modification reagent with CuCl2 were studied. The optimal impregnation ratio of CuCl2 was determined as 10%, in which the Hg removal efficiency in H2S atmosphere could reach over 97%, and almost of the Hg-containing product was easy-soluble HgCl2. The great advantage of impregnation modification of CuCl2 is attributed to the uniform and dense distribution of CuCl2, as well as the strong activity of CuCl2 itself towards Hg0 oxidation to HgCl2. The impregnation modification of CuCl2 can significantly improve the Hg removal efficiency, inhibit the generation of HgS and HgO, and promote the generation of HgCl2, which is verified as a feasible method to improve the solution washing regeneration of Hg adsorbent.

Cobalt Impregnation on Titania Photocatalysts Enhances Vis Phenol Photodegradation.

One of the main challenges of photocatalysis is to find a stable and effective photocatalyst, that is active and effective under sunlight. Here, we discuss the photocatalytic degradation of phenol as a model pollutant in aqueous solution using NUV-Vis (>366 nm) and UV (254 nm) in the presence of TiO2-P25 impregnated with different concentrations of Co (0.1%, 0.3%, 0.5%, and 1%). The modification of the surface of the photocatalyst was performed by wet impregnation, and the obtained solids were characterized using X-ray diffraction, XPS, SEM, EDS, TEM, N2 physisorption, Raman and UV-Vis DRS, which revealed the structural and morphological stability of the modified material. BET isotherms are type IV, with slit-shaped pores formed by nonrigid aggregate particles and no pore networks and a small H3 loop near the maximum relative pressure. The doped samples show increased crystallite sizes and a lower band gap, extending visible light harvesting. All prepared catalysts showed band gaps in the interval 2.3-2.5 eV. The photocatalytic degradation of aqueous phenol over TiO2-P25 and Co(X%)/TiO2 was monitored using UV-Vis spectrophotometry: Co(0.1%)/TiO2 being the most effective with NUV-Vis irradiation. TOC analysis showed ca. 96% TOC removal with NUV-Vis radiation, while only 23% removal under UV radiation.

Determination of Co2+ ions in blood samples: A multi-way sensing based on NH2-rich carbon quantum dots

Multiple forms of detecting Co2+ are reported in this work to quantify these ions in real blood plasma samples. Carbon Quantum Dots (CQDs) were used as a fluorescent nanoprobe. The CQDs were obtained from a bottom-up approach using a hydrothermal method and choline chloride and branched poly(ethyleneimine) as precursor molecules. Several spectroscopic and structural characterizations were performed. The efficient fluorescence quenching of CQDs related to the Co2+ ion was used for the detection of the analyte, generating a sensing strategy with a limit of detection (LOD) of 0.98 μmol L−1. Furthermore, the interaction between the Co2+ ion with the CQDs resulted in the color change of the solution from colorless to pale yellow. Thus, a colorimetric Co2+ sensor was also developed, since there was an absorption band at 315 nm attributed to the formation of the complex CQD + Co2+. The colorimetric method showed an excellent sensitivity to Co2+, with a LOD of 3.01 μmol L−1. In addition, Principal Component Analysis (PCA) together with Linear Discriminant Analysis (LDA) were used successfully to distinguish different concentrations of Co2+ and different interfering ions present in the solution. Finally, a real sample of blood plasma was properly treated and doped with different concentrations of Co2+, which was successfully quantified via fluorescent method. Therefore, the CQDs obtained in this work are a powerful and versatile Co2+ detection tool.

An environmentally friendly green synthesis of Co2+ and Mn2+ ion doped ZnO nanoparticles to improve solar cell efficiency

Global warming is a threat to human health in the context of increasing organic or inorganic pollutants, which are produced by various products. The “Green synthesis” method effectively eliminates toxic and/or harmful effects that arise due to the wet-chemical synthesis process. Different concentrations of Co2+ and Mn2+ ion doped ZnO-nanoparticles (NPs) were designed at a low temperature, about 70 °C by utilizing an eco-friendly sustainable method with dandelion leaf (DL) extract as a solvent and these biosynthesized NPs were annealed to grow the crystallinity enhancement. The confirmation of NPs crystal phase, phase purity, and grain size was performed by XRD, showing the hexagonal-Wurtzite phase structure. SEM and TEM images of the NPs demonstrated sub-100 nm spherical-shaped particles. Fourier transform infrared displays characteristics band about ∼523 cm–1 which corresponds to Zn–O tetrahedron asymmetric stretching vibrations. Both UV-Visible and luminescence studies confirmed the adjacent band edge emission of ZnO and successive incorporation of Co2+ and Mn2+ ion-doped ZnO host. For improving power conversion efficiency, the polycrystalline silicon solar cells (PSSCs), different layers of Co2+ and Mn2+ ion-doped ZnO-NPs coated on bare PSSCs are promising strategies. Additionally, solar cell efficiency decreases with further coating of NPs layers and/or thickness. Optimum solar cell efficiency was observed for 5 at% Mn2+ ion-doped ZnO-NPs with three layers. Finally, Radish and Cress plants are grown, using the biosynthesized ZnO-NPs supernatant from DL extract, which showed high environmental biocompatibility.

A controllable cobalt-doping improve electrocatalytic activity of ZnO basal plane for oxygen evolution reaction: A first-principles calculation study

To design highly efficient, low-cost, and good stable electrocatalysts for the oxygen evolution reaction (OER) which is the key to the water-splitting, we doped ZnO with different concentrations of Co based on density functional theory calculations. The precise Co concentrations control from 0 % to 100 % can be achieved by cation exchange reaction in the experiment. The introduction of Co can modulate the electronic structure of ZnO, as the concentration of Co increases, the band gap greatly decreases, the system tunes from the semiconductor to the metal, and the electric conductivity is significantly improved, favoring the OER. The introduction of Co induces charge arrangement, the electrons gradually concentrate on the active site, and the bindings between the oxygen-containing intermediate and the surface are greatly improved, therefore, the potential of the OER decreases, the rate-determining step changes from the first step in pure ZnO to the third step in Co exchanged ZnO. Additionally, Co0.5Zn0.5O exhibits the favorite OER activity with the overpotential of 0.4 V. These interesting findings may simulate experimental validations and facilitate the development of more efficient OER catalysts.

System for performance evaluation and calibration of low-cost gas sensors applied to air quality monitoring

The increasing emissions of air pollutants have been a current issue and with great interest by regulatory agencies, industries, and society in general as they represent a threat to health and to the environment. The monitoring using low-cost atmospheric sensors has been an emerging alternative with great prospect of use to complement the data obtained by traditional air quality monitoring stations. However, the data obtained by these low-cost sensors are still questionable and can often be unreliable. The objective of this work was to build a system for calibration and evaluation of performance parameters of low-cost monitor comparing their results to reference analyzers. In this sense, three low-cost sensors for CO, O3 and SO2 of a monitor were calibrated and evaluated against the performance parameters defined by baseline drift, linearity, precision, bias, accuracy, response time, interference of pollutant gases and long-term drift. There was no significant deviation from baseline drift for any sensor. All sensors showed a linear profile (R2ADJ ∼1), good precision (>95%), and a response time of less than 2 min. After calibration, satisfactory accuracy (>89%) and bias (close to zero) data were obtained. The SO2 sensor showed signal disturbances in the presence of different concentrations of CO. Long-term drift suggests a calibration periodicity of less than 60 days. To use these sensors to monitor air quality, prior calibration is necessary, and the determination of performance parameters is suggested.

Exposure of insects and host plants to different concentrations of CO2 affects the performance of Mahanarva spectabilis (Hemiptera: Cercopidae) in successive insect generations.

The performance of three successive generations of Mahanarva spectabilis (Distant) (Hemiptera: Cercopidae) fed on four forages exposed to environments with different CO2 concentrations was evaluated. In the first bioassay, we utilized the following scenarios: A) plants and insects were kept at high and constant CO2 (700 ppm) and B) the insects were kept at CO2 700 ppm and fed on plants from the greenhouse (average of 390 ppm). In the second bioassay, we utilized the following scenarios: C) plants and insects were kept in a greenhouse and D) the insects were kept in the greenhouse and fed on plants kept at CO2 700 ppm. The survival and duration of the nymphal and adult stages and the number of eggs/female of M. spectabilis were evaluated. It was only possible to evaluate the cumulative effects of the increase of CO2 on three successive generations of M. spectabilis kept in a greenhouse, due to the reduced survival of the insects in the first generation in the laboratory. A greater direct than indirect effect of the CO2 level on the performance of M. spectabilis was observed. Furthermore, it should be considered that the effect of CO2 elevation on the survival, periods of development, and fecundity, when taken together, can significantly impact the population dynamics of M. spectabilis in future climate scenarios.