Measurements Of Carbon Dioxide Concentrations Research Articles

Maintaining postharvest quality of raspberries with natural volatile compounds

SummaryThe postharvest quality of raspberries (Rubus idaeus L.) was evaluated after treatment with several natural volatile compounds and storage at 0, 10 or 20 °C. At high storage temperature (20 °C), raspberries deteriorated rapidly and none of the natural volatile compounds that were used were effective in extending storage life of the fruit. At low storage temperature (0 °C), little difference could be discerned among the various volatile treatments. However, at 10 °C storage, raspberries treated with methyl jasmonate (MJ), allyl isothiocyanate (AITC), tea tree oil (TTO), or absolute ethyl alcohol had less decay. MJ‐ and TTO‐treated fruit also maintained higher levels of sugars, organic acids and oxygen radical absorbance capacity compared with untreated fruit. Samples treated with acetic acid or vinegar vapour did not differ from control fruit. Measurement of oxygen and carbon dioxide concentrations within the containers during storage revealed that none of the treatments caused accumulation or depletion of these gases to a level that would be harmful to raspberries. Colour measurements of the berries showed that all raspberry fruit became darker and less red after storage, but fruit treated with MJ were found to have the highest intensity of red colour while AITC application caused the berries to appear lighter in colour.

Carbon dioxide concentrations in the nests of the mud‐dwelling mangrove ant Polyrhachis sokolova Forel (Hymenoptera: Formicidae)

Abstract The nests of the mangrove ant Polyrhachis sokolova are found in soil in intertidal mangrove communities, and are thus inundated at high tides for several hours. Some of the nest galleries are flooded, but others retain air pockets, to which the ants retreat. During and following inundation, we measured carbon dioxide concentrations in air samples collected from different levels in the nests and from artificial ‘control’ holes in the mud. To account for the relative contribution of different sources of carbon dioxide, we also measured the carbon dioxide production by individual ants (including larvae and pupae) and small samples of mud collected near the ant nests. Nest carbon dioxide concentrations were high (2.5−11%) during and immediately following inundation, but the concentrations in the upper regions of the nest fell as soil water levels receded. However, at depths>10 cm below the level soil surface, the carbon dioxide concentrations remained relatively high and stable (at approximately 2%) over the 11 days between one high tide and the next. The contribution of the mud (and associated microorganisms) to the carbon dioxide concentration in the nests was substantial, and the contribution of the respiration of the ants was approximately 10−15% of the total. The carbon dioxide concentrations in the nests of this species during high tides are among the highest recorded for insect nests, suggesting that these ants may have unusual physiological attributes to match the behavioural and ecological challenges associated with living in the intertidal zone.

비분산 적외선 분광법을 이용한 Co2농도 고속 분석기의 Sampling Module 특성에 관한 실험적 연구

A fast response analyzer for measuring carbon dioxide concentration has been developed for transient characteristic and researches tested on internal combustion engine. The analyzer uses the well known NDIR(Non-Dispersive Infrared) method with miniaturized detection system, giving a time constant of approximately 30 microsecond, and sampling module consists of capillary tube. Since the transit time and the time constant of the sampling system depend on the sampling conditions, it is necessary to investigate the characteristics of sampling system before applied to exhaust gas measurement in engine. A unique method was designed to study the influence of the diameter of transfer sample line and operating conditions of the FRNDIR on transit time and time constant. A database of transit time and time constant was built up for different measured and simulated pressure conditions. The database can be used for correcting eventual concentration measurement.

Carbon Dioxide Levels and Summertime Ventilation Rates in UK Schools

Measurements of metabolic carbon dioxide concentration made in four classrooms in two schools are reported for both occupied and unoccupied periods. Measurements were taken for approximately one week in each classroom during the unheated season and the time-varying ventilation rates estimated. The results of the experiments show CO2 concentrations that are far beyond the guideline value of 1000 ppm (the maximum concentration during the occupied period was 3756 ppm). Calculated air supply rates vary from unacceptably low levels, to rates that are in line with guidance. The occurrence of periods with acceptable supply rates, and the rates found during purge ventilation, show that the surveyed classrooms have the potential to provide adequate fresh air. Inaccessible windows and ventilation openings, combined with lack of guidance on when and how to apply ventilation seems to be the primary reason for poor ventilation outside the heating season.

Exhaled nitric oxide as a marker of lung injury in coronary artery bypass surgery

Exhaled nitric oxide as a marker of lung injury in coronary artery bypass surgery

Maintaining quality of fresh-cut kiwifruit with volatile compounds

Kiwifruit (Actinidia deliciosa ) were cut into 5 mm slices and placed in polystyrene trays. Various volatile compounds were introduced inside the trays before the lids were covered. The development of decay and the shelf life of the slices were evaluated during storage at 10 8C. Kiwifruit slices treated with 2.24, 11.2, or 22.4 m ll � 1 methyl jasmonate maintained good quality after 3 weeks at 10 8C compared to the control slices. Comparable results were obtained with absolute ethyl alcohol (300 m ll � 1 ) or isopropyl alcohol (300 m ll � 1 ). However, 1-propanol was less effective and methyl alcohol was not effective in maintaining the quality of kiwifruit slices. Methods of application affected the efficacy of the volatile compounds. In general, suspension of the source of volatile compounds within the trays yielded better results compared to volatilization of the volatile compounds from beakers placed inside the trays. In addition to having less decay, kiwifruit slices treated with methyl jasmonate also maintained higher levels of sugars and organic acids compared to the untreated slices. Measurement of oxygen and carbon dioxide concentrations in the trays indicated that oxygen never dropped below 19.5% and carbon dioxide remained at approximately 0.8% in all treatments during the 3 weeks at 10 8C. No differences in respiration rates between methyl jasmonate treatment and control were detected. Ethylene production increased during the first 7 days and then decreased gradually. However, no differences in ethylene production between methyl jasmonate treatment and control were found. Published by Elsevier Science B.V.

Microelectrode technique for in situ measurement of carbon dioxide concentrations in xylem sap of trees.

We developed a new microelectrode technique for measuring CO2 concentration ([CO2]) in xylem sap of trees. This technique enabled us to make rapid and continuous measurements of xylem sap [CO2] in situ. In this report, we discuss the methodology and establish the feasibility of the technique. We also describe calibration procedures, temperature sensitivity, field use and other characteristics of the microelectrodes. An example of data collected in the field is provided. Microelectrode calibration was accomplished at constant temperature in air of known [CO2]. When sampling temperature differed from calibration temperature, correction was necessary. We developed an equation to correct for temperatures between 15 and 35 degrees C when calibration was conducted at 25 degrees C. Equations based on Henry's Law were used to convert measured gas phase [CO2] (%) to concentration of all products of CO2 dissolved in sap (mmol l(-1)). We inserted microelectrodes into stems of three tree species to measure diurnal changes in [CO2] in the xylem sap. A diurnal pattern with depression during the day and elevation at night was observed. Mean daily [CO2] ranged from 1.6 to 10.3 mmol l(-1). Microelectrodes were suitable for making diurnal measurements for up to 7 days without recalibration. We also used the microelectrodes to measure [CO2] of soil in situ. Soil [CO2] ranged from 1 to 4% (gas phase), with little diurnal variation.

Capnography for nonintubated patients: The wave of the future for routine monitoring of procedural sedation patients

THE USE OF procedural sedation is growing dramatically because of the increase in performance of minimally invasive procedures in nonacute and acute care settings. As anesthesia agents have been refined to provide short-acting sedation with minimal side effects, procedural sedation is becoming increasingly desirable. Procedural sedation is not only commonly used in the operating room, but has many other applications such as endoscopy, radiology, cardiology, dentistry, physicians’ offices, and pediatrics. The Joint Commission on Accreditation of Healthcare Organizations (JCAHO) defined 4 levels of sedation and anesthesia in January 2001. These defined levels made clear that because sedation-to-anesthesia is a continuum, sedation patients should be monitored and treated the same as general anesthesia patients. Capnography is the continuous measurement and display of carbon dioxide (CO2) concentration in exhaled breath. A capnogram is the graphical waveform depicting CO2 concentration throughout respiration (Table 1). A normal capnogram has a near zero baseline with a sharp rapid rise, a plateau, then a sharp rapid down shift (Fig 1). Abnormal capnograms occur for a multitude of reasons and present with varying changes from the normal (Fig 2). Table 1. Capnography Waveforms: Interpreting the Capnogram

Temporal variations in atmospheric CO 2 concentrations in Kuwait City, Kuwait with comparisons to Phoenix, Arizona, USA

Hourly atmospheric carbon dioxide (CO 2) concentration measurements are available from 1996 to present for a suburban site within the growing metropolitan area of Kuwait City. Analyses of this record reveal (a) an annual cycle with highest values in February and lowest values in September reflecting the growth and decay of vegetation in the Northern Hemisphere as well as fluctuations in motor traffic, (b) a weekly cycle with highest values during the weekdays and lowest values during weekends, and (c) a diurnal cycle with highest values after sunset when the local atmosphere becomes more stable following vehicular emission of CO 2 throughout the day and lowest values in late afternoon following several hours of relatively unstable conditions. During the daytime, CO 2 concentrations are related to wind direction, with westerly winds (coming from the desert) promoting lowest CO 2 concentrations. At night, lowest CO 2 levels are associated with higher wind speeds and winds from the north. The findings from the Kuwait City area, particularly when contrasted with the situation in Phoenix, further our understanding of the dynamics of CO 2 levels in urban environments.

Note: carbon-cycle estimation: a plea for measurement of ocean carbon dioxide concentrations

Unless an effort is made to measure the carbon dioxide content of the oceans, the ability of researchers to distinguish between absorption by oceanic and by biotic sinks related to carbon emissions will remain imperfect. This uncertainty presently limits the ability of policy-makers to set a carbon emissions target fully consistent with that for carbon dioxide concentrations.

Anthropogenic emission of mercury to the atmosphere in the northeast United States

The severity and spatial extent of the health impact of anthropogenic mercury (Hg) emission to the atmosphere depend on the emission rate and chemical form of the emitted species. The few measurements of combustion flue gas give highly variable results about how the emission is divided between the elemental (Hg°) and reactive forms and are difficult to extrapolate to a regional scale. Here we combine measurement of total gaseous mercury (TGM) and carbon dioxide (CO2) concentrations at a background site in the winter with carbon (C) emission inventory to show that at a regional (500 km) scale, the effective anthropogenic Hg° flux is 41(±2) g km−2yr−1 in the north‐east United States. This regional‐scale flux was higher under clear skies than under cloudy skies, suggesting some removal of Hg° by cloud water, but the physical mechanisms of the removal are yet to be identified.

Evaluation of the 3D-furnace simulation code AIOLOS by comparing CFD predictions of gas compositions with in-furnace measurements in a 210MW coal-fired utility boiler

The furnace of a pulverised coal-fired utility boiler with a thermal output of 210MW, with dimensions of 8m x 8m x 29m and 12 burners located on three levels, is considered. Coal combustion is described by a five-step-reaction scheme. The model covers two heterogeneous reactions for pyrolysis and char combustion and three gas phase reactions for the oxidation of volatile matter. A standard k, e-model is used for the description of turbulence. The interaction of turbulence and chemistry is modelled using the Eddy Dissipation Concept (EDC). The transport equations for mass, momentum, enthalpy and species are formulated in general curvilinear co-ordinates enabling an accurate treatment of boundaries and a very good control over the distribution of the grid lines. The discretisation is based on a non-staggered finite-volume approach and the coupling of velocities and pressure is achieved by the SIMPLEC method. Numerical diffusion is minimised by the use of the higher-order discretisation scheme MLU. The accuracy of the predictions is demonstrated by comparing the computational results with in-furnace measurements of carbon monoxide, carbon dioxide and oxygen concentrations and of temperatures.

On the modelling of coal combustion in a 550 MW<SUB align=right>el coal-fired utility boiler

The furnace of a pulverised coal-fired utility boiler with an electrical output of 550 MW, the dimensions of 19m x 15m x 48m and 32 swirl burners located on four elevations is considered. Coal combustion is described by a four-step reaction scheme. The model covers two heterogeneous reactions for pyrolysis and char combustion and three gas-phase reactions for the oxidation of volatile matter. A standard k; ε-model is used for the description of turbulence. The interaction between turbulence and chemistry is modelled using the Eddy Dissipation Concept (EDC). Radiation is computed by means of the Discrete Ordinates method. The discretisation is based on a non-staggered finite-volume approach. The coupling of velocities and pressure is achieved by the SIMPLEC-method, and the UPWIND or MLU discretisation schemes are used for the computation of the convective fluxes. All gas phase transport equations are formulated in the Eulerian way in general curvilinear co-ordinates allowing an accurate treatment of boundaries and a very good distribution of the grid lines. The coal particle phase is either treated with a Eulerian description assuming no slip between the gas and particle phase, or with a Lagrangian description. The Lagrangian approach to the particle phase is fully coupled with the gas phase using the Particle-Source-in-Cell method and taking the turbulence effects of the gas phase on particle dispersion into account. The differences in the predictions using the Eulerian and Eulerian/Lagrangian approaches are elaborated by comparing the computational results with in-furnace measurements of carbon monoxide, carbon dioxide and oxygen concentrations.

Indoor air quality in a middle school, Part I: Use of CO2 as a tracer for effective ventilation.

The overall objective of the study was to evaluate the indoor air quality at a middle school with an emphasis on characterizing baseline conditions. The focus of this article is on the relationship between occupancy and measured concentrations of carbon dioxide, and an evaluation of the use of carbon dioxide as a tracer for ventilation in the school. The school was characterized as having no health complaints, good maintenance schedules, no carpeting within the classrooms or hallways, and no significant remodeling, and its officials had agreed to allow the sampling to take place during school hours. Monitoring followed the guidelines recommended in the "Preliminary Draft: Conceptual Standardized EPA Protocol For Characterizing Indoor Air Quality in School Buildings." Four indoor locations including the cafeteria, a science classroom, an art classroom, and the lobby outside the main office, and one outdoor location were sampled for various environmental comfort and pollutant parameters for one week in February 1997. A consistent relationship between hourly occupancy and corresponding carbon dioxide concentrations was seen. Carbon dioxide concentrations in the cafeteria, art room, and lobby were within specified American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) guidelines for comfort (< 1000 ppm). The science room had the highest concentrations (frequently exceeding 1000 ppm) due to high occupancy and non-functioning unit ventilators. Measured ventilation rates were within specified ASHRAE guidelines for the art room, cafeteria, and lobby. The science room, which relied on natural ventilation only, was not able to meet the ASHRAE guideline on one of the three days studied. The use of a completely mixed space, one compartment mass balance model with estimated CO2 generation rates and measured CO2 concentrations is shown to be a useful method for evaluating ventilation. Modeled effective ventilation, air changes per hour, and mixing factors reflected measured carbon dioxide concentrations and measured ventilation in each room. Mechanical ventilation afforded better mixing than natural ventilation. This study demonstrates the usefulness of collecting indoor CO2 and occupancy data when carrying out indoor air quality evaluations in schools.

On-line estimation of the specific growth rate in the bacitracin fermentation process

An on-line estimation of the specific growth rate of an aerobic fermentation batch process was conducted based on measurements of oxygen or carbon dioxide concentrations in exhaust gas, or the concentrations of dissolved oxygen in the liquid phase in the fermentor. A simple linear model used was upgraded with a mechanism for a time-varying forgetting factor to enable good tracking of estimated parameters as well during rapid and large changes in the process. Because the measuring methods used are independent of each other and can identify the process well, mutual control of individual sensors is also possible in industrial reactors. The results from the model agree well with experimentally obtained values for bacitracin fermentation in an 80-m3 and 1.5-m3 batch bioreactor. The model provides a good basis for robust adaptive regulation of aerobic batch processes.

Carbon dioxide measurements in the nocturnal boundary layer over Amazonian forest

Abstract. Measurements of carbon dioxide concentration, temperature and windspeed were made in the nocturnal boundary layer over a tropical forest near Manaus, Brazil using a tethered balloon system. The measurements were made up to a maximum height of 300 m on ten consecutive nights in November 1995. Simultaneous surface flux and in-canopy concentration measurements were made at the surface close to the site. The observation period included several different types of conditions. Generally strong windshear and relatively weak temperature gradients prevented the formation of a strong capping inversion to the nocturnal boundary layer. On some nights, however, the inversion was sufficiently strong that the CO2 concentration at 100 m above the surface exceeded 400 ppm. The concentration within the canopy was largely controlled by the presence of an inversion very close to the canopy surface. The temperature and wind profiles are contrasted with conditions in Randônia, Brazil, where the windshear was found to be weaker and higher carbon dioxide concentrations were observed in the early morning. The difference in carbon dioxide concentrations in the nocturnal boundary layer between dusk and dawn is used to estimate the regional nighttime flux of carbon dioxide. The value obtained generally exceeds the measured surface flux and sometimes exceeds the sum of the surface flux and the in-canopy storage made at the tower site. The reasons for the discrepancy are not clear; either one of the methods is in error or the regional carbon dioxide budget differs significantly from the local budget measured at the tower site.

FTIR measurements of acid‐gas–methyldiethanolamine systems

AbstractThe standard industrial process for the purification of natural gas is to remove acid gases, mainly hydrogen sulfide and carbon dioxide, by the absorption and reaction of these gases with alkanolamines, but the lack of reliable and accurate vapor–liquid equilibrium (VLB) data impedes the commercial application of more efficient alkanolamine systems. A novel Fourier‐transform infrared (FTIR) technique was developed to make in‐situ VLE measurements of acid‐gas‐aqueous alkanolamine systems and to improve the accuracy of VLE measurements at low hydrogen sulfide and carbon dioxide concentrations. VLE measurements of low carbon dioxide and hydrogen sulfide concentrations in aqueous mixtures of methyldiethanolamine (MDEA) are reported using the new FTIR technique.

Estimation of Biokinetic Parameters for Unsaturated Soils

Model predicting gas phase concentrations of an organic substrate and of carbon dioxide in unsaturated soil microcosms was developed. The model included equilibrium partitioning of organic between soil, water, and gas phases; consumption of organic and production of carbon dioxide due to biological activity; pH-dependent carbon dioxide partitioning between the water and gas phases; and biomass growth. A Bayesian estimation method was coupled to the microcosm model to allow determination of biokinetic parameters from carbon dioxide and organic vapor concentration measurements. The Bayesian estimation method was applicable to multiresponse data with missing observations; a common occurrence in environmental monitoring. A microcosm configuration was developed for determination of biokinetic constants in unsaturated soils. Results of studies on biodegradation of toluene at two moisture contents were analyzed with the parameter estimation model. Observations of both carbon dioxide and toluene concentrations were used in parameter estimation to allow the simultaneous determination of yield and initial biomass concentrations, as well as reaction rate parameters and half-saturation constants. Parameter confidence intervals and joint confidence regions for pairs of parameters were estimated by integration of the Bayesian posterior density functions.

Error in measurement of oxygen and carbon dioxide concentrations by the DeltatracII metabolic monitor in the presence of desflurane

In experiments in dogs on the metabolic effects of inhalation anaesthetics, we noticed that in the presence of desflurane, oxygen uptake (VO2) measured with the Deltatracll metabolic monitor seemingly increased whereas it decreased when determined independently by the Fick principle. This difference remained even after correction for changes in gas concentration on addition of an inhalation anaesthetic. Therefore, we suspected that desflurane interferes with the measurement of gas concentrations. Using different precision gases, we found that desflurane disturbed both the paramagnetic oxygen sensor and the infrared carbon dioxide detector so that the measured oxygen (when FIO2 was > 0.21) and carbon dioxide concentrations were greater than expected. These errors multiply in the computing process of oxygen uptake by the DeltatracII. When the DeltatracII is to be used during inhalation anaesthesia, its results should be corrected for the presence of an anaesthetic gas. More importantly, corrections must also be made for measurement errors of the oxygen and carbon dioxide sensors, unless the device has been equipped with a modified (nickel membrane) oxygen sensor insensitive to the presence of volatile agents.

The influence of the atmospheric boundary layer on carbon dioxide concentrations over a tropical forest

Measurements of carbon dioxide concentration and flux have been made over a tropical forest in Brazil. Observations of convective and nocturnal boundary layer height made at the same site have been used to investigate the influence of the atmospheric boundary layer on the concentration measurements. The results explain some of the features of the observed trends in CO 2 concentration and illustrate the importance of taking the atmospheric boundary layer into account when interpreting surface measurements.