CO2 Measurements Research Articles

Emerging Applications of Longstanding Autonomous Ocean Carbon Observations

For over two decades, NOAA’s Pacific Marine Environmental Laboratory (PMEL) has been developing and deploying autonomous ocean carbon measurement technologies. PMEL currently maintains a network of air-sea CO2 and ocean acidification time series measurements on 33 surface buoys, including the world’s longest record of air-sea CO2 measured from a buoy. These sites are located in every ocean basin and in a variety of ecosystems, from coastal to open ocean and sub-polar to tropical. The network provides more than half of today’s ocean carbonate chemistry time-series records that qualify as long-term, publicly available, and collected at subseasonal timescales. Here, we briefly review the motivation for establishing the network, the research and applications made possible from the observations, and how sustained autonomous time series generate unique information about a changing ocean needed to inform mitigation and adaptation approaches in a changing world.

Retrospective assessment of the association between urban air pollution and children’s respiratory functions in Rome: Insights for developmental environmental health

Background & aimsNaturogenic aspects of global warming are amplified by the anthropogenic effects of the persistent exponential global population growth. Urbanization without proper planning escalates serious all-time disease pathologies in vulnerable populations, such as children, through pollution of toxic gases. We illustrate these associations with a retrospective study of respiratory heath in children living in downtown Rome when this dense urban center recorded one of the highest air pollution levels in Europe. MethodsLung and respiratory function parameters were evaluated from 2006 to 2007 in a cohort of 90 children including two age subgroups (>10 years and <10 years). Additionally, historical air pollution data from 2006 to 2008 and 2020–2021, collected from urban traffic and urban background stations in Rome, was obtained to allow for a correlational analysis between air pollution and children's respiratory health. ResultsSevere impairments on the Mead Expiratory Flow Rate were revealed alongside an increase in allergenic atopics. Historical data showed no differences between measurements from urban background and traffic stations for PM10, PM2.5, NO, and NO2, and no significant time trends. However, although both declined over time, CO measurements were consistently higher from traffic than background stations. ConclusionsOur correlational study indicates that decreases in respiratory health and function may be associated with air pollution, leading to increased susceptibility to viral infections, such as COVID-19, especially in vulnerable populations. In this context, vulnerable populations’ environmental health and disease prevention, also linked with climate change, could be addressed by focusing efforts on combatting urban pollution.

Imaging rotational energy transfer: comparative stereodynamics in CO + N2 and CO + CO inelastic scattering.

State-to-state rotational energy transfer in collisions of ground ro-vibrational state 13CO molecules with N2 molecules has been studied using the crossed molecular beam method under kinematically equivalent conditions used for 13CO + CO rotationally inelastic scattering described in a previously published report (Sun et al., Science, 2020, 369, 307-309). The collisionally excited 13CO molecule products are detected by the same (1 + 1' + 1'') VUV (Vacuum Ultra-Violet) resonance enhanced multiphoton ionization scheme coupled with velocity map ion imaging. We present differential cross sections and scattering angle resolved rotational angular momentum alignment moments extracted from experimentally measured 13CO + N2 scattering images and compare them with theoretical predictions from quasi-classical trajectories (QCT) on a newly calculated 13CO-N2 potential energy surface (PES). Good agreement between experiment and theory is found, which confirms the accuracy of the 13CO-N2 potential energy surface for the 1460 cm-1 collision energy studied by experiment. Experimental results for 13CO + N2 are compared with those for 13CO + CO collisions. The angle-resolved product rotational angular momentum alignment moments for the two scattering systems are very similar, which indicates that the collision induced alignment dynamics observed for both systems are dominated by a hard-shell nature. However, compared to the 13CO + CO measurements, the primary rainbow maximum in the DCSs for 13CO + N2 is peaked consistently at more backward scattering angles and the secondary maximum becomes much less obvious, implying that the 13CO-N2 PES is less anisotropic. In addition, a forward scattering component with high rotational excitation seen for 13CO + CO does not appear for 13CO-N2 in the experiment and is not predicted by QCT theory. Some of these differences in collision dynamics behaviour can be predicted by a comparison between the properties of the PESs for the two systems. More specific behaviour is also predicted from analysis of the dependence on the relative collision geometry of 13CO + N2 trajectories compared to 13CO + CO trajectories, which shows the special 'do-si-do' pathway invoked for 13CO + CO is not effective for 13CO + N2 collisions.

High-Resolution and Broadband Spectral Measurement of CO2 Based on Virtually Imaged Phased Array Spectrometer

High-Resolution and Broadband Spectral Measurement of CO2 Based on Virtually Imaged Phased Array Spectrometer

Measurement of CO, CO2, Particulate Matter (PM10), Cockpit and Ambient Temperature, Humidity and Noise Level at UTHM Hangar

This study is focussedon works that are done at the hangar and its effect on human health. The absence of proper air quality or noise level study at the current UTHM hangar has inspired to conduct this study. The objective of this study is to measure the emission rate of carbon monoxide (CO), carbon dioxide (CO2), particulate matter (PM10), and measure the cockpit temperature, ambient temperature, humidity, and noise level of PT6A-20 engine to obtain the data at the Universiti Tun Hussein Onn Malaysia (UTHM)Hangar. There are presence of 2 engines which are Lycoming O-360 and turboprop PT6A-20atthe hangar. Lycoming O-360 uses avgas and turboprop PT6A-20 uses jetA1 fuel type which will produce higher rate of emission and that is the reason of PT6A-20 engine being chosen. So this study aims to highlight a comprehensive data of CO, CO2,particulatematter (PM10), cockpit and ambient temperature, humidity and noise level regarding the turboprop PT6A-20 engine at hangar of UTHM to aid future researchers and ensure the air quality and safety rules of the hangar.The air quality standards areused as guideline are the Malaysia Ambient Air Quality Standard and Indoor Air Quality Standard based on the Department of Occupational Safety and Health(DOSH). Also, Occupational Safety and Health (Noise Exposure) Regulations 2019 isused as the standard for noiselevel.Q-Trak Plus IAQ Monitor model 8554 isused to measure the emission rate of CO,CO2, level of humidity and cockpit temperature. Dust Trak Aerosol Monitor isused to measure the emission rate of PM10, Pico Data Logger isused to measure the ambient temperature and finally 1352H integrating sound level meter was used to measure the noise level of PT6A-20 engine. Based on the results produced, only carbon monoxide and carbon dioxide are below than the safety limit. The othe5 parameters which are PM10, cockpit and ambient temperature, humidity and noise level are above the allowable limit according to DOSH.

The history of chemical concepts and field studies of CO2 in seawater: A tribute to Kurt Buch (1881–1967)

This review of the research on the marine CO2 system spans the time between the mid-19th century and the first years after World War II. It covers the period from the first attempts to determine the amount of CO2 dissolved in seawater to the first complete physico-chemical characterization of the marine CO2 system. The development of the latter was significantly influenced by the theoretical and experimental work of the Finnish chemical oceanographer Kurt Buch (1881–1967) during the first half of the 20th century. To acknowledge his outstanding achievements in Chemical Oceanography, this review is dedicated to him.The first part of our discussion is organized along the characteristic variables of the marine CO2 system. The analytical procedures that led successively to the definition of total CO2, alkalinity (“neutral carbonate”), the CO2 partial pressure (“CO2 tension”) and pH are briefly described. We trace the attempts to connect these variables quantitatively through the mass action law. After several failed attempts, CO2 dissociation constants were finally determined with the support of the International Council for the Exploration of the Sea (1931). Their results constituted the basis of the marine CO2 studies conducted after World War II.The second focus of our review refers to the various field studies, including early measurements of total CO2 and alkalinity during Norwegian (1878) and Danish expeditions (1895/96) in the North Atlantic and Arctic Ocean and the first measurements of surface water pCO2 in the North Atlantic, in 1902. Furthermore, we acknowledge the achievements of the German Atlantic expedition (1925–1927) for the characterization of the vertical and horizontal distribution of pH, pCO2 and CaCO3 saturation in the Atlantic Ocean. Among Buch's field studies of the CO2 system, we consider the Finnish monitoring program, in which pH and alkalinity were measured at over 70 stations in the northern Baltic Sea.Whenever it is appropriate, we show the connection between past scientific ideas, concepts and knowledge with current efforts and developments concerning the understanding of the marine carbon cycle and its response to increasing atmospheric CO2.

Enhancing the Performance of Two Different Commercial CO2 Indicators Using Digital Colourimetric Analysis, DCA

Two different, commercial colourimetric CO2 indicators are made in the lab, namely one based on an indicator in solution for monitoring the level of dissolved CO2 in an aquarium, i.e., a drop check indicator, and another based on an ink, for monitoring the level of CO2 in breath (capnography), i.e., a correct tracheal placement indicator. The selected commercial indicators are limited currently in terms of the analytical information they provide (qualitative) as they are normally assessed by eye. Thus, in each case, for both the lab-made and commercial indicators, colour photography coupled with digital image analysis, i.e., digital colour analysis (DCA), is used to convert the colour data from the indicator into a quantitative measure of CO2 and so markedly improve the quality of the analytical information provided by original indicator. This is the first time either indicator has been studied as a quantitative analytical system. The CO2 sensitivity of each of the lab-made indicators is found to match well that of its commercial counterpart. A simple program is provided to help non-experts and experts alike to apply DCA in this way. The potential of DCA to enhance the performance of other commercial indicators is discussed briefly.

A twenty year record of greenhouse gases in the Eastern Mediterranean atmosphere

Twenty years of CO2, CH4 and CO greenhouse gas atmospheric concentration measurements at Finokalia station on Crete in the Eastern Mediterranean region are presented. This dataset is the longest in the Eastern Mediterranean, based on bi-weekly grab sampling since 2002 and continuous observations since June 2014. CO2 concentrations increase by 2.4 ppm·y−1 since 2002, in agreement with the general north hemisphere trend as derived by worldwide NOAA observations. CH4 showed a mean increasing trend of 7.5 ppb·y−1 since 2002, a rate that has accelerated since 2018 (12.4 ppb·y−1). In contrast, CO has decreased by 1.6 ppb·y−1 since 2002, which resulted from a strong decrease until 2017 (2.5 ppb·y−1), followed by a small increase in the last 3 years (0.2 ppb·y−1). Both CO2 and CH4 present maxima during winter and minima during summer, in general agreement with the observations at the ICOS stations in Europe. CO also presents the highest values in winter and the lowest values in summer during June, while a secondary maximum is seen in August, which can be attributed to open fires that often occur in the area during this period. The mean summertime diurnal cycles of CH4 and CO agree with a 24-h mean OH radical concentration of the order of 0.3–1 × 107 molecules·cm−3 over the region, in general agreement with the only existing in-situ observations at Finokalia for 2001.

Simple Millimeter Wave Identification System Based on 60 GHz Van Atta Arrays.

The paper presents a proof-of-concept of a millimeter-wave identification system based on Van Atta array tags in the 60 GHz band. For interrogation of the tags, a vector network analyzer and a measurement transceiver were employed in alternative test configurations. The design, fabrication and measurements of co- and cross-polarized Van Atta arrays are presented in the paper. They can be treated as simple chipless RFID tags with frequency-response-based identification. Tags with various resonance frequencies are designed by scaling an optimized base model. The designed 57-67 GHz co-polarized and cross-polarized tags have small dimensions of approximately 23 mm × 21 mm and 40 mm × 25 mm, and they exhibit radar cross-section (RCS) levels of -16 dBsm and -21 dBsm, respectively. Owing to the retrodirective properties of Van Atta arrays, the RCS can be maintained at a high level within a broad range of angles of incidence. The system was validated in an anechoic chamber where the spectral responses of all the manufactured tags can be clearly distinguished from the environment, enabling their identification. Tests in a reflective environment were also performed, and they have shown that only the cross-polarized tags could be detected and identified in the presence of reflections from the tags' surroundings.

Ground-Based Atmospheric CO2, CH4, and CO Column Measurements at Golmud in the Qinghai-Tibetan Plateau and Comparisons with TROPOMI/S5P Satellite Observations

Ground-Based Atmospheric CO2, CH4, and CO Column Measurements at Golmud in the Qinghai-Tibetan Plateau and Comparisons with TROPOMI/S5P Satellite Observations

Contribution of Airplane Engine Emissions on the Local Air Quality around Stuttgart Airport during and after COVID-19 Lockdown Measures

Air quality investigations at airports have shown that aircrafts cause a significant increase in air pollution at and around the vicinity of the airport, which can cause adverse effects on human health. The objective of this research was to investigate the aircraft-sourced pollutant levels at the Stuttgart airport and in the surrounding areas during and after COVID-19 lockdown measures. Three phases of stationary measurements of ultrafine particles (UFP), particulate matter (PM), black carbon (BC), CO2, O3, NO, and NO2 were made at various points on the east and west sides of the airport in the extension of the airport runway. In first phase of measurement, the airport was closed for construction, and no air traffic took place. In the second phase, the airport was reopened with limited operation due to a lockdown period at the beginning of the COVID-19 pandemic. Finally, in the third phase, measurements were performed during the peak summer holiday travel season to measure the air quality during maximum air traffic, after the end of the first lockdown period. While there were fewer notable changes in the BC concentrations, coarse PM fractions, and gases across the three phases, there were significant increases in the UFP concentrations from aircraft emissions. Throughout the three phases, the peak particle concentration decreased from between 27 and 86 nm in phase 1. to between 27 and 35 nm in phase 2, to finally 11 nm in phase 3 on all days in which the aircraft plumes were measured. During flight arrivals, definite increases in UFP particle number concentration (PNC) were observed, with the majority of the particles being in the 10 nm size class. These results were measured repeatedly on both sides of the airport in the direct prolongation of the runway and even at distances of up to 3 km away in nearby neighbouring communities. While the overall PM and UFP levels are affected by vehicular traffic, the freeway measurements showed particles from aircrafts and vehicles are distinguishable using the parameters PNC and Dp. The BC concentrations were rarely influenced by aircraft activity, while only some NO and NO2 peaks were measured depending on the consistency of the wind.

Parametric evaluation of dynamic multistage centrifugal humidifier

Evaporative cooling is a passive cooling technique, which is energy efficient, sustainable, and environmentally friendly. The present work deals with the design and construction of a three-stage rotating centrifugal humidifier test rig equipped with a UV filter. Experiments are conducted varying the air velocity and the motor shaft speed. Overall cumulative performances such as DBT ratio, RH ratio, humidification effectiveness, coefficient of performance, and evaporation rate are determined with respect to Reynold’s number and stage wise. Measurements of CO 2 , Total Volatile Organic Compounds (TVOCs) and formaldehyde are performed at the exit air from the filter. Results showed maximum evaporation rate, humidification effectiveness, and coefficient of performance equal to 0.82 g s −1 , 88.74%, and 6.14, respectively. The cumulative performance improved for consecutive stages, but stagewise analysis indicated that the first stage gave a maximum performance. Exiting air quality after filtration is improved by 33%, which meets the most exigent standards in terms of the target pollutants. • Performance of a novel multistage centrifugal humidification test rig is studied. • Evaporative cooler consumes 42% less energy and saves 33% cost compared to AC unit. • Maximum humidification occurs in the first stage and reduces along stages. • Optimum values of motor speed and the Re is found to be 40 rpm and 28,949.

Short-Term Storage of Mobilized Peripheral Blood Stem Cells in a Closed System Changes the Microenvironment and May Affect the Quantity of CD34+ and CD34+CD38-CD45RA-CD90+ Cells

Hypoxic conditions preserve the multipotency and self-renewing capacity of murine bone marrow and human cord blood stem cells. Blood samples stored in sealed blood gas tubes become hypoxic as leukocytes metabolize and consume oxygen. Taken together, these observations suggest that peripheral blood stem cell (PBSC) samples stored under airtight conditions become hypoxic, and that the stem cells contained may undergo qualitative or quantitative changes. This study aimed to determine the effect of storage for 8 hours in a sealed system on PBSC samples. Granulocyte colony-stimulating factor-mobilized PBSC samples were collected prospectively from 9 patients with myeloma or amyloidosis prior to apheresis, followed by measurement of CO2, O2, hydrogen ion (pH), lactate, and glucose concentrations in the blood and immunophenotyping of stem cell and multipotent progenitor cell populations before and after 8 hours of storage in sealed blood collection tubes. Blood concentrations of O2 and glucose and pH measurements were significantly decreased, whereas concentrations of CO2 and lactate were significantly increased after storage. Significantly higher concentrations of CD34+ cells (552 ± 84 cells/106total nucleated cells [TNCs] versus 985 ± 143 cells/106TNCs; P=.03), CD34+CD38- cells (98 ± 32 cells/106TNCs versus 158 ± 52 cells/106TNCs; P=.03), CD34+CD38+ cells (444 ± 92 cells/106TNCs versus 789 ± 153 cells/106TNCs; P=.03), and CD34+CD38-CD45RA-CD90+ cells (55 ± 17 cells/106TNCs versus 89 ± 25 cells/106TNCs; P=.02) were detected after 8 hours of storage. The changes in concentrations of CD34+CD38+ cells and CD34+ cells were inversely associated with the change in glucose concentration (P=.003 and P < .001, respectively) and positively associated with the change in lactate concentration (P=.01 and P <.001, respectively) after 8 hours of airtight storage. Storage of PBSC samples in a sealed, airtight environment is associated with microenvironmental changes consistent with hypoxia and increased concentrations of immunophenotypically defined stem cells. These results may have clinical implications with regard to the collection and processing of stem cell products and warrant confirmation with functional and mechanistic studies.

Smoldering peat fire detection by time-resolved measurements of transient CO2 and CH4 emissions using a novel dual-gas optical sensor

A compact and sensitive dual-gas laser absorption sensor was developed for smoldering peat fire detection by real-time monitoring of transient CO2 and CH4 emissions from peat combustion exhaust. The sensor combines two infrared lasers to exploit CH4 and CO2 absorption lines centered at 6057.09 cm−1 and 6359.96 cm−1, respectively. Scanned-wavelength modulation spectroscopy with the second-harmonic detection (WMS-2f) and a custom-designed Herriot multipass gas cell (10.3 m path length in a 40.5 mL volume) were employed to improve detection sensitivity. The simultaneous real-time transient emissions (CH4 and CO2) were measured at an interval of 0.1 s under various smoldering peat combustion conditions in a top open cylindrical reactor. An increasing trend of CH4/CO2 ratio from 0.053 to 0.075 and the greenhouse gas (GHG) flux from 1.5 g/m2 s to 3.4 g/m2 s was observed with increasing oxygen supplies from 10 mm/s to 24 mm/s. However, a decreasing trend of CH4/CO2 ratio from 0.06 to 0.043 and GHG flux from 2.6 g/m2 s to 0.4 g/m2 s was noticed with increasing peat moisture content from 8% (dry peat) to 100%. The measurement results agree well with commercial non-dispersive infrared CO2 and CH4 analyzers which are not fast enough to capture transient emissions due to their low time response. The developed dual-gas sensor has the potential to be applied for detecting underground peatland fires and evaluating the overall GHGs emissions from smoldering wildfires due to its excellent temporal resolution, hardware simplicity, and compactness.

Opposing seasonal temperature dependencies of CO2 and CH4 emissions from wetlands.

Wetlands are critically important to global climate change because of their role in modulating the release of atmospheric greenhouse gases (GHGs) carbon dioxide (CO2 ) and methane (CH4 ). Temperature plays a crucial role in wetland GHG emissions, while the general pattern for seasonal temperature dependencies of wetland CO2 and CH4 emissions is poorly understood. Here we show opposite seasonal temperature dependencies of CO2 and CH4 emissions by using 36,663 daily observations of simultaneous measurements of ecosystem-scale CO2 and CH4 emissions in 42 widely distributed wetlands from the FLUXNET-CH4 database. Specifically, the temperature dependence of CO2 emissions decreased with increasing monthly mean temperature, but the opposite was true for that of CH4 emissions. Neglecting seasonal temperature dependencies may overestimate wetland CO2 and CH4 emissions compared to the use of a year-based static and consistent temperature dependence parameter when only considering temperature effects. Our findings highlight the importance of incorporating the remarkable seasonality in temperature dependence into process-based biogeochemical models to predict feedbacks of wetland GHG emissions to climate warming.

Using Mobile Monitoring and Atmospheric Dispersion Modeling for Capturing High Spatial Air Pollutant Variability in Cities

Air pollution is still one of the biggest environmental threats to human health on a global scale. In urban environments, exposure to air pollution is largely influenced by the activity patterns of the population as well as by the high spatial and temporal variability in air pollutant concentrations. Over the last years, several studies have attempted to better characterize the spatial variations in air pollutant concentrations within a city by deploying dense, fixed as well as mobile, low-cost sensor networks and more recently opportunistic sampling and by improving the spatial resolution of air quality models up to a few meters. The purpose of this work has been to investigate the use of properly designed mobile monitoring campaigns along the streets of an urban neighborhood to assess the capability of an operational air dispersion model as SIRANE at the district scale to capture the local variability of pollutant concentrations. To this end, an IoT ecosystem—MONICA (an Italian acronym for Cooperative Air Quality Monitoring), developed by ENEA, has been used for mobile measurements of CO and NO2 concentration in the urban area of the City of Portici (Naples, Southern Italy). By comparing the mean concentrations of CO and NO2 pollutants measured by MONICA devices and those simulated by SIRANE along the urban streets, the former appeared to exceed the simulated ones by a factor of 3 and 2 for CO and NO2, respectively. Furthermore, for each pollutant, this factor is higher within the street canyons than in open roads. However, the mobile and simulated mean concentration profiles largely adapt, although the simulated profiles appear smoother than the mobile ones. These results can be explained by the uncertainty in the estimation of vehicle emissions in SIRANE as well as the different temporal resolution of measurements of MONICA able to capture local high concentrations.

Experimental and synthetic laser-absorption-spectroscopy measurements of temperature, pressure, and CO at 1 MHz for evaluation of post-detonation fireball models

A quantum-cascade-laser-absorption-spectroscopy (QCLAS) diagnostic was used to characterize post-detonation fireballs of RP-80 detonators via measurements of temperature, pressure, and CO column pressure at a repetition rate of 1 MHz. Scanned-wavelength direct-absorption spectroscopy was used to measure CO absorbance spectra near 2008.5 cm−1 which are dominated by the P(0,31), P(2,20), and P(3,14) transitions. Line-of-sight (LOS) measurements were acquired 51 and 91 mm above the detonator surface. Three strategies were employed to facilitate interpretation of the LAS measurements in this highly nonuniform environment and to evaluate the accuracy of four post-detonation fireball models: (1) High-energy transitions were used to deliberately bias the measurements to the high-temperature outer shell, (2) a novel dual-zone absorption model was used to extract temperature, pressure, and CO measurements in two distinct regions of the fireball at times where pressure variations along the LOS were pronounced, and (3) the LAS measurements were compared with synthetic LAS measurements produced using the simulated distributions of temperature, pressure, and gas composition predicted by reactive CFD modeling. The results indicate that the QCLAS diagnostic provides high-fidelity data for evaluating post-detonation fireball models, and that assumptions regarding thermochemical equilibrium and carbon freeze-out during expansion of detonation gases have a large impact on the predicted chemical composition of the fireball.

Comparison between mainstream (Capnostat 5) and a low-flow sidestream capnometer (Capnostream) in mechanically ventilated, sevoflurane-anesthetized rabbits using a Bain coaxial delivery system

ObjectiveTo evaluate agreement between end-tidal carbon dioxide (Pe′CO2) and PaCO2 with sidestream and mainstream capnometers in mechanically ventilated anesthetized rabbits, with two ventilatory strategies. Study designProspective experimental study. AnimalsA total of 10 New Zealand White rabbits weighing 3.6 ± 0.3 kg (mean ± standard deviation). MethodsRabbits anesthetized with sevoflurane were intubated with an uncuffed endotracheal tube (3.0 mm internal diameter) and adequate seal. For Pe′CO2, the sidestream capnometer sampling adapter or the mainstream capnometer was placed between the endotracheal tube and Bain breathing system (1.5 L minute–1 oxygen). PaCO2 was obtained from arterial blood collected every 5 minutes. A time-cycled ventilator delivered an inspiratory time of 1 second and 12 or 20 breaths minute–1. Peak inspiratory pressure was initially set to achieve Pe′CO2 normocapnia of 35–45 mmHg (4.6–6.0 kPa). A total of five paired Pe′CO2 and PaCO2 measurements were obtained with each ventilation mode for each capnometer. Anesthetic episodes were separated by 7 days. Agreement was assessed using Bland-Altman analysis and linear mixed models; p < 0.05. ResultsThere were 90 and 83 pairs for the mainstream and sidestream capnometers, respectively. The mainstream capnometer underestimated PaCO2 by 12.6 ± 2.9 mmHg (proportional bias 0.44 ± 0.06 mmHg per 1 mmHg PaCO2 increase). With the sidestream capnometer, ventilation mode had a significant effect on Pe′CO2. At 12 breaths minute–1, Pe′CO2 underestimated PaCO2 by 23.9 ± 8.2 mmHg (proportional bias: 0.81 ± 0.18 mmHg per 1 mmHg PaCO2 increase). At 20 breaths minute–1, Pe′CO2 underestimated PaCO2 by 38.8 ± 5.0 mmHg (proportional bias 1.13 ± 0.10 mmHg per 1 mmHg PaCO2 increase). Conclusions and clinical relevanceBoth capnometers underestimated PaCO2. The sidestream capnometer underestimated PaCO2 more than the mainstream capnometer, and was affected by ventilation mode.

Soil greenhouse gas emissions and crop production with implementation of alley cropping in a Mediterranean citrus orchard

The implementation of alley cropping in orchards has been suggested as a sustainable strategy to increase farmer revenues by crop diversification, enhance soil organic matter (SOM) and fertility, water retention, overall biodiversity, and contribute to climate change mitigation. Thus, the objective of this study was to assess if alley cropping with annual crops can contribute to i) mitigate soil greenhouse gas (GHG) emissions, ii) enhance C sequestration in a semiarid Mediterranean irrigated citrus orchard, and iii) increase land productivity. For this, two different treatments were established: i) conventional mandarin monoculture (MC) with no alley cropping; and ii) mandarin diversified with alley cropping of barley/vetch and fava bean (DIV). Measurements of soil CO2 and N2O emissions were periodically performed (every 7–20 days) during two years. Soil CO2 emission rates followed the soil moisture trend, and showed no significant differences between treatments. As an average, soil CO2 emission rates were 147 mg m-2 h-1 in MC and 196 mg m-2 h-1 in DIV. Soil N2O emission rates were not correlated to soil moisture nor temperature, and showed average values of 0.026 mg m-2 h-1 in MC and − 0.002 mg m-2 h-1 in DIV. Alley cropping did not contribute to significantly increase soil organic C and total nitrogen in two years’ time. With regard to production, mandarin yield showed no significant differences between treatments, but alley crops contributed to complementary commodities to the main cash crop, increasing overall land productivity. Thus, alley cropping in irrigated Mediterranean orchards has no significant effect on soil C sequestration and GHG emissions at short-term, with increased land productivity owing to new commodities grown in the alleys. These results confirm that under semiarid Mediterranean climate, long periods are needed to efficiently assess soil C sequestration potential of sustainable practices in orchards.

Measurement of CO2 in Water from an Ultraviolet Oxidizer for a Space-Worthy Wastewater Recovery System Using Raman Spectroscopy.

NASA has been developing and testing a water recovery system for over two decades to minimize the amount of water required for long duration human space missions. A key system component is the total organic carbon analyzer (TOCA) that determines if the recovered water is below the toxicology-defined health limit of 5 mg/L TOC and is safe to drink. The TOCA is composed of a liquid phase loop and a gas phase loop. The TOCA employs an oxidizer to convert the organics in the liquid phase to carbon dioxide (CO2) and a liquid-gas separator to isolate the CO2 for measurement in the gas phase by infrared spectroscopy. In an effort to reduce the consumables, mass, volume, and power of the system, we investigated the ability of surface-enhanced Raman spectroscopy (SERS), and Raman spectroscopy to measure 5 mg/L carbon in water. The SERS measurement employed silver colloids to increase sensitivity, while the Raman measurements used multiple mirrors to increase sensitivity. Here, we present SERS measurements of carbonate (CO3=) at 3 mg/L carbon and Raman measurements of CO2 at 9 mg/L carbon in the effluent water of a new oxidizer being developed for a future TOCA. Both SERS and Raman techniques can determine TOC in the liquid phase, eliminating the need for the gas phase loop and associated supplies and replacement components, which could effectively decrease the size and weight of the current TOCA by as much as 50%.