Fluctuations In CO2 Concentration Research Articles

The use of novel optode sensor technologies for monitoring dissolved carbon dioxide and ammonia concentrations under live haul conditions

Fish health under live haul transportation on wellboats and in other recirculating aquaculture systems depends on frequent and reliable measurements of water quality, that may change in response to changes in the environmental conditions and treatment processes. While reliable technologies exist for sensors measuring some water quality parameters such as Oxygen concentration and salinity, there is a lack of sensor technologies for the measurement of other critical water quality parameters such as water pCO2 and NH3 concentrations. Presented is the theory of operation and performance of prototype optical sensors for the measurement of pCO2 and NH3, as well as the methods used for their calibration and characterization. In order to evaluate the sensor’s suitability for aquaculture applications we temporarily installed the sensors on a wellboat and monitored the water quality during the transportation of live mature Atlantic salmon between fish farms and slaughter facilities on the Norwegian coast. Under transportation with different stocking weights and recirculation conditions, the CO2 optode prototypes recorded measurements that coincided with measurements from standard laboratory analysis of spot samples. The pCO2 concentration in the well throughout the testing was shown to vary between approximately 300μatm and 20 000μatm. Compared to the pH derived pCO2 estimation method widely applied in aquaculture, the CO2 optode was more sensitive to small fluctuations in CO2 concentration, and gave measurements closer to the CO2 values recorded by laboratory analysis of spot samples. The NH3 optode reported measurements that were consistent with spot samples analyzed using the salicylate–hypochlorite reaction. In contrast to pCO2, the concentration of NH3 during the observed wellboat missions was found to be very low and stable at 0.8±0.3μgL−1. Once fully developed, the CO2 and NH3 optodes could contribute to better water quality control and efficiency during well boat transportations and other recirculating aquaculture systems.

Likely Effects of the Increasing Alkalinity of Inland Waters on Aquaculture

AbstractThe rising atmospheric carbon dioxide (CO2) concentration is increasing the solubility of limestone, calcium silicate, and feldspars, resulting in greater total alkalinity concentration in inland waters. This phenomenon will result in inland waters having slightly greater alkalinity concentration (and buffering capacity), higher pH when at equilibrium with atmospheric CO2, and more available carbon for photosynthesis. However, the changes in water quality will be small. Fluctuations in CO2 concentration resulting from CO2 use in photosynthesis by aquatic plants and release of CO2 by respiration, acidity resulting from nitrification of ammonia nitrogen from feeding waste and fertilizer, and application of liming materials to ponds will continue to be the dominant factors affecting pH and alkalinity in waters of inland aquaculture systems.

Liver Status Assessment by Spectrally and Time Resolved IR Detection of Drug Induced Breath Gas Changes

The actual metabolic capacity of the liver is crucial for disease identification, liver therapy, and liver tumor resection. By combining induced drug metabolism and high sensitivity IR spectroscopy of exhaled air, we provide a method for quantitative liver assessment at bedside within 20 to 60 min. Fast administration of 13C-labelled methacetin induces a fast response of liver metabolism and is tracked in real-time by the increase of 13CO2 in exhaled air. The 13CO2 concentration increase in exhaled air allows the determination of the metabolic liver capacity (LiMAx-test). Fluctuations in CO2 concentration, pressure and temperature are minimized by special gas handling, and tracking of several spectrally resolved CO2 absorption bands with a quantum cascade laser. Absorption measurement of different 12CO2 and 13CO2 rotation-vibration transitions in the same time window allows for multiple referencing and reduction of systematic errors. This FLIP (Fast liver investigation package) setup is being successfully used to plan operations and determine the liver status of patients.

Exposure Assessment for Carbon Dioxide Gas: Full Shift Average and Short-Term Measurement Approaches

Carbon dioxide (CO2) makes up a relatively small percentage of atmospheric gases, yet when used or produced in large quantities as a gas, a liquid, or a solid (dry ice), substantial airborne exposures may occur. Exposure to elevated CO2 concentrations may elicit toxicity, even with oxygen concentrations that are not considered dangerous per se. Full-shift sampling approaches to measure 8-hr time weighted average (TWA) CO2 exposures are used in many facilities where CO2 gas may be present. The need to assess rapidly fluctuating CO2 levels that may approach immediately dangerous to life or health (IDLH) conditions should also be a concern, and several methods for doing so using fast responding measurement tools are discussed in this paper. Colorimetric detector tubes, a non-dispersive infrared (NDIR) detector, and a portable Fourier transform infrared (FTIR) spectroscopy instrument were evaluated in a laboratory environment using a flow-through standard generation system and were found to provide suitable accuracy and precision for assessing rapid fluctuations in CO2 concentration, with a possible effect related to humidity noted only for the detector tubes. These tools were used in the field to select locations and times for grab sampling and personal full-shift sampling, which provided laboratory analysis data to confirm IDLH conditions and 8-hr TWA exposure information. Fluctuating CO2 exposures are exemplified through field work results from several workplaces. In a brewery, brief CO2 exposures above the IDLH value occurred when large volumes of CO2-containing liquid were released for disposal, but 8-hr TWA exposures were not found to exceed the permissible level. In a frozen food production facility nearly constant exposure to CO2 concentrations above the permissible 8-hr TWA value were seen, as well as brief exposures above the IDLH concentration which were associated with specific tasks where liquid CO2 was used. In a poultry processing facility the use of dry ice to quickly freeze product produced a nearly constant CO2 concentration that caused exposures to approach the permissible 8-hr TWA exposure value.

Simplified expressions for adjusting higher-order turbulent statistics obtained from open path gas analyzers

When density fluctuations of scalars such as CO2 are measured with open-path gas analyzers, the measured vertical turbulent flux must be adjusted to take into account fluctuations induced by ‘external effects’ such as temperature and water vapour. These adjustments are needed to separate the effects of surface fluxes responsible for ‘natural’ fluctuations in CO2 concentration from these external effects. Analogous to vertical fluxes, simplified expressions for separating the ‘external effects’ from higher-order scalar density turbulence statistics are derived. The level of complexity in terms of input to these expressions are analogous to that of the Webb–Pearman–Leuning (WPL), and are shown to be consistent with the conservation of dry air. It is demonstrated that both higher-order turbulent moments such as the scalar variances, the mixed velocity-scalar covariances, and the two-scalar covariance require significant adjustments due to ‘external effects’. The impact of these adjustments on the turbulent CO2 spectra, probability density function, and dimensionless similarity functions derived from flux-variance relationships are also discussed.

A trace-gas climatology above Zotino, central Siberia

Using light aircraft and at intervals of approximately 14 days, vertical profiles of temperature, humidity, CO2 concentration and 13C/12C and 18O/16O ratio, as well as concentrations of CH4, CO, H2 and N2O, from about 80 to 3000 m above ground level have been determined for the atmosphere above a flux measurement tower located near the village of Zotino in central Siberia (60°45′N, 89°23′E). As well as being determined from flask measurements (typically at heights of 100, 500, 1000, 1500, 2000, 2500 and 3000 m) continuous CO2 concentration profiles at 1 Hz have also been obtained using an infrared gas analyser. This measurement program is ongoing and has been in existence since July 1998. Data to November 2000 are presented and show a seasonal cycle for CO2 concentration of about 25 μmol mol−1 within the atmospheric boundary layer (ABL) and about 15 μmol mol−1 in the free troposphere. Marked seasonal cycles in the isotopic compositions of CO2 are also observed, with that of oxygen-18 in CO2 being unusual: always being depleted in the ABL with respect to the free troposphere above. This is irrespective of whether the CO2 concentration is higher or lower in the free troposphere. We interpret this as indicating a net negative discrimination being associated with the net terrestrial carbon exchange, irrespective of whether photosynthesis or respiration dominates the net carbon flux in this region. During winter flights, large fluctuations in CO2 concentration with height are often observed both within and above the stable ABL. Usually (but not always) these variations in CO2 concentrations are associated with more or less stoichiometrically constant variations in CO and CH4 concentrations. We interpret this as reflecting the frequent transport of polluted air from Europe with very little vertical mixing having occurred, despite the large horizontal distances traversed. This notion is supported by back-trajectory analyses. Vertical profiles of CO2 concentration with supplementary flask measurements allow more information on the structure and composition of an air mass to be obtained than is the case for flask measurements or for ground-based measurements only. In particular, our data question the notion that there is usually anything like “well mixed background air” in the mid-to-high northern latitudes during the winter months.

Free‐air CO2 enrichment (FACE) of a poplar plantation: the POPFACE fumigation system

Summary A new design of free‐air CO2 enrichment (FACE) is presented that has been used to expose a poplar plantation to elevated atmospheric CO2 concentrations in other‐wise unaltered conditions, in the open. This system releases pure CO2 at high velocity, through a large number of small gas jets, causing rapid mixing between CO2 and air. The theoretical and practical aspects of this design are described, with emphasis on the fluid mechanics of air–CO2 mixing in sonic jets. Field performance data, including spectral analysis of short‐term fluctuations in CO2 concentrations as well as temporal and spatial CO2 control, are reported for the European project POPFACE facility. Temporal and spatial performances of the operational POPFACE systems were adequate with average long‐term CO2 mole fractions on target. Averages over 1 min measured in the centre of the rings were within ±20% and ±10% of the target concentration for > 91% and > 75% of the time, respectively. The data presented provide convincing evidence that a pure‐CO2 FACE system can achieve reliable control, in terms of the quality of the CO2 control, with significant simplification of construction and reduced capital cost.

Effects of changes in atmospheric carbon dioxide on the location of hosts by the moth, Cactoblastis cactorum.

Sensory organs that detect CO2 are common in herbivorous moths and butterflies, but their function has been unclear until now. As the CO2 gradients in the vicinity of a host plant depend on its physiological condition, CO2 could provide a sensory cue for the suitability of the plant as a larval food source. This study investigated whether changing the atmospheric CO2 concentration affected oviposition by Cactoblastis cactorum on its host, the cactus Opuntia stricta. On host plants exposed to rapid fluctuations in CO2 concentration, the frequency of oviposition was reduced by a factor of 3.2 compared to the control. As the fluctuations mask the much smaller CO2 signals generated by the plants, this suggests that those signals constitute an important component of the host identification process. On host plants exposed to a constant background of doubled CO2, oviposition was also reduced, by a factor of 1.8. An increased background reduces host signal detectability, partially as a consequence of a general principle of sensory physiology (Weber-Fechner's law), and partially due to other factors specific to CO2-receptor neurons.

Turbulent transport of carbon dioxide over a paddy field

Turbulent fluctuations in CO2 concentrations over a paddy field are measured by a fastresponse device with an open sensing path. This IR device coupled with a sonic anemometer constitutes an eddy correlation instrument to measure CO2 fluxes. Three experiments were conducted in the surface layer over paddy 90 cm high. The stability (z − d)/L ranged from -0.14 to 0.20, where L denotes the Monin-Obukhov length.