Controlling factors of seasonal and spatial variation of riverine CO2 partial pressure and its implication for riverine carbon flux

2021 ◽  
pp. 147332
Author(s):  
Jinke Liu ◽  
Guilin Han
Keyword(s):  
Partial Pressure ◽  
Spatial Variation ◽  
Carbon Flux ◽  
Controlling Factors ◽  
Co2 Partial Pressure ◽  
Riverine Carbon Flux

Separation of carotid body chemoreceptor responses to O2 and CO2 by oligomycin and by antimycin A

1982 ◽  
Vol 242 (3) ◽  
pp. C200-C206 ◽  
Author(s):  
E. Mulligan ◽  
S. Lahiri
Keyword(s):  
Steady State ◽  
Carbonic Anhydrase ◽  
Partial Pressure ◽  
Carotid Body ◽  
Body Tissue ◽  
Antimycin A ◽  
Tissue Ph ◽  
Co2 Partial Pressure ◽  
O2 Partial Pressure ◽  
Metabolic Hypothesis

The cat carotid chemoreceptor O2 and CO2 responses can be separated by oligomycin and by antimycin A. Both of these agents greatly diminish or abolish the chemoreceptor O2 response but not the nicotine or CO2 responses. After either oligomycin or antimycin, the responses to increases and decreases in arterial CO2 partial pressure (PaCO2) consisted of increases and decreases in activity characterized respectively by exaggerated overshoots and undershoots. These were eliminated by the carbonic anhydrase inhibitor, acetazolamide, suggesting that they resulted from changes in carotid body tissue pH. The steady-state PaCO2 response remaining after oligomycin was no longer dependent on arterial O2 partial pressure (PaO2). All effects of antimycin were readily reversible in about 20 min. The separation of the responses to O2 and CO2 indicates that there may be at least partially separate pathways of chemoreception for these two stimuli. The similarity of the oligomycin and antimycin results supports the metabolic hypothesis of chemoreception.

CO2 partial pressure and CO2 emission in the Lower Mekong River

2013 ◽  
Vol 504 ◽  
pp. 40-56 ◽  
Author(s):  
Siyue Li ◽  
X.X. Lu ◽  
Richard T. Bush
Keyword(s):  
Partial Pressure ◽  
Co2 Emission ◽  
Mekong River ◽  
Co2 Partial Pressure

Corrosion Behavior of X70 Pipeline Steel and Corrosion Rate Prediction Under the Combination of Corrosive Medium and Applied Pressure

2017 ◽  
Author(s):  
Kaikai Li ◽  
Wei Wu ◽  
Guangxu Cheng ◽  
Yun Li ◽  
Haijun Hu ◽  
...  
Keyword(s):  
Natural Gas ◽  
Corrosion Rate ◽  
Tensile Stress ◽  
Partial Pressure ◽  
Corrosion Behavior ◽  
Pipeline Steel ◽  
Applied Pressure ◽  
Chloride Concentration ◽  
X70 Pipeline Steel ◽  
Co2 Partial Pressure

Natural gas transmission pipeline is prone to internal corrosion due to the combination of corrosive impurities in the pipe (such as CO2, H2S and chlorides) and applied pressure of the pipeline, which seriously affects the safe operation of the pipeline. In this work, the corrosion behavior of a typical X70 pipeline steel was investigated by using potentiodynamic polarization and electrochemical impendence spectroscopy (EIS). The polarization and EIS data under different CO2 partial pressures (0–1 atm), H2S concentrations (0–150 ppm), chloride concentrations (0–3.5 wt%) and tensile stress (0–400 MPa) were obtained. The results show that corrosion rate increases with the increase of CO2 partial pressure and chloride concentration, respectively, while first increases and then decreases with the increase H2S concentrations. The corrosion rate is less affected by elastic tensile stress. In addition, a quantitative prediction model for corrosion rate of natural gas pipeline based on adaptive neuro-fuzzy inference system (ANFIS) was established by fitting the experimental data which maps the relationship between the key influencing factors (i.e. CO2 partial pressure, H2S concentration, chloride concentration and tensile stress) and the corrosion rate. The prediction results show that the relative percentage errors of the predicted and experimental values are relatively small. The prediction accuracy of the model satisfies the engineering application requirement.

Interaction of hypoxia and hypercapnia on cerebral hemodynamics and brain electrical activity in dogs

1987 ◽  
Vol 253 (4) ◽  
pp. H890-H897 ◽  
Author(s):  
R. W. McPherson ◽  
D. Eimerl ◽  
R. J. Traystman
Keyword(s):  
Partial Pressure ◽  
Elevated Level ◽  
Severe Hypoxia ◽  
O2 Uptake ◽  
Animal Group ◽  
Moderate Hypoxia ◽  
Co2 Partial Pressure ◽  
Arterial Blood ◽  
O2 Partial Pressure ◽  
O2 Delivery

The interaction of hypoxic hypoxia, hypercapnia, and mean arterial blood pressure (MABP) was studied in 15 pentobarbital-anesthetized ventilated dogs. In one group of animals (n = 5) hypercapnia [arterial CO2 partial pressure (PaCO2) approximately 50 Torr] was added to both moderate hypoxia and severe hypoxia. Moderate hypoxia [arterial O2 partial pressure (PaO2) = 36 mmHg] increased MABP and cerebral blood flow (CBF) without changes in cerebral O2 uptake (CMRO2). Superimposed hypercapnia increased CBF and MABP further with no change in CMRO2. In another group of animals (n = 5), a MABP increase of approximately 40 mmHg during moderate hypoxia without hypercapnia did not further increase CBF, suggesting intact autoregulation. Thus, during moderate hypoxia, hypercapnia is capable of increasing CBF. Severe hypoxia (PaO2 = 22 mmHg) increased CBF, but MABP and CMRO2 declined. Superimposed hypercapnia further decreased MABP and decreased CBF from its elevated level and further decreased CMRO2. Raising MABP under these circumstances in another animal group (n = 5) increased CBF above the level present during severe hypoxia alone and increased CMRO2. The change in CBF and CMRO2 during severe hypoxia plus hypercapnia with MABP elevation were not different from that severe hypoxia alone. We conclude that, during hypoxia sufficiently severe to impair CMRO2, superimposed hypercapnia has a detrimental influence due to decreased MABP, which causes a decrease in CBF and cerebral O2 delivery.

Spatial variation in CO2 efflux from the soil in a mature beech forest ecosystem.

2021 ◽  
Author(s):  
Yihan Cai ◽  
Takahiro Nishimura ◽  
Hideyuki Ida ◽  
Mitsuru Hirota
Keyword(s):  
Spatial Variation ◽  
Temporal Variation ◽  
Forest Ecosystem ◽  
Linear Regression Analysis ◽  
Basal Area ◽  
Beech Forest ◽  
Controlling Factors ◽  
Spatial And Temporal Variation ◽  
Canopy Openness ◽  
Co2 Efflux

<p> Soil respiration (Rs) is the second largest carbon flux between the atmosphere and terrestrial ecosystem. Because of the large proportion, even small change in Rs would considerably impact the global carbon cycle. Therefore, it is important to accurately estimate Rs by taking its spatial and temporal variation into consideration. While the temporal variation of Rs and its controlling factors have been well-described, large unexplainable part still has been remained in the spatial variation of Rs especially in the forest ecosystems with complex structures. The objective of this study is to fill the knowledge gap about spatial variation of Rs and its controlling factors in a typical mature beech forest in Japan. Hypotheses of this study were, 1) Rs would show large spatial variation in the mature beech forest, 2) the spatial variation of Rs was mainly influenced by soil water content (SWC) and soil temperature (ST), 3) the two key factors were determined by the forest structures. This study was conducted in a 1- ha permanent study plot in the mature beech forest with significant gap-mosaic structures. To examine these hypotheses, Rs, SWC, ST and parameters related to forest structure, i.e. sum of basal area, diameter at breast height, number of trees, number of species within a radius of 5 m from the Rs measurement points, and canopy openness were measured at 121 points in different season between 2012 to 2013. In this study, all the measurements of Rs were conducted by using alkali-absorption technique.</p><p> Coefficient of variation of Rs was between 25 - 28 % which was similar to that of SWC in all the measurements. The spatial variation of Rs was relatively higher in July, August and September than that in June and October. There was no significant relationship in the spatial variation between Rs and ST in all the measurements, meanwhile, Rs was well explained by SWC in measurements conducted in August, September and October. Multiple linear regression analysis indicated that canopy openness and sum of basal area showed significant positive and negative correlation with SWC, respectively. And canopy openness explained SWC much more than sum of basal area did. This result suggested that SWC, the key factor determined the spatial variation of Rs, cannot be only explained by stems distribution and their characteristics, but also canopy architecture in the forest ecosystem.</p>

scholarly journals Global surface-ocean <i>p</i><sup>CO<sub>2</sub></sup> and sea–air CO<sub>2</sub> flux variability from an observation-driven ocean mixed-layer scheme

Ocean Science ◽  
2013 ◽  
Vol 9 (2) ◽  
pp. 193-216 ◽  
Author(s):  
C. Rödenbeck ◽  
R. F. Keeling ◽  
D. C. E. Bakker ◽  
N. Metzl ◽  
A. Olsen ◽  
...  
Keyword(s):  
Partial Pressure ◽  
Mixed Layer ◽  
Co2 Flux ◽  
Companion Paper ◽  
Diagnostic Model ◽  
Ocean Mixed Layer ◽  
Co2 Partial Pressure ◽  
Surface Ocean ◽  
Flux Variability ◽  
Global Surface

Abstract. A temporally and spatially resolved estimate of the global surface-ocean CO2 partial pressure field and the sea–air CO2 flux is presented, obtained by fitting a simple data-driven diagnostic model of ocean mixed-layer biogeochemistry to surface-ocean CO2 partial pressure data from the SOCAT v1.5 database. Results include seasonal, interannual, and short-term (daily) variations. In most regions, estimated seasonality is well constrained from the data, and compares well to the widely used monthly climatology by Takahashi et al. (2009). Comparison to independent data tentatively supports the slightly higher seasonal variations in our estimates in some areas. We also fitted the diagnostic model to atmospheric CO2 data. The results of this are less robust, but in those areas where atmospheric signals are not strongly influenced by land flux variability, their seasonality is nevertheless consistent with the results based on surface-ocean data. From a comparison with an independent seasonal climatology of surface-ocean nutrient concentration, the diagnostic model is shown to capture relevant surface-ocean biogeochemical processes reasonably well. Estimated interannual variations will be presented and discussed in a companion paper.

scholarly journals Maximal exercise at extreme altitudes on Mount Everest

1983 ◽  
Vol 55 (3) ◽  
pp. 688-698 ◽  
Author(s):  
J. B. West ◽  
S. J. Boyer ◽  
D. J. Graber ◽  
P. H. Hackett ◽  
K. H. Maret ◽  
...  
Keyword(s):  
Partial Pressure ◽  
Maximal Exercise ◽  
Ambient Air ◽  
O2 Uptake ◽  
Mount Everest ◽  
Air Breathing ◽  
Co2 Partial Pressure ◽  
O2 Partial Pressure ◽  
Low Levels ◽  
Arterial Po2

Maximal exercise at extreme altitudes was studied during the course of the American Medical Research Expedition to Everest. Measurements were carried out at sea level [inspired O2 partial pressure (PO2) 147 Torr], 6,300 m during air breathing (inspired PO2 64 Torr), 6,300 m during 16% O2 breathing (inspired PO2 49 Torr), and 6,300 m during 14% O2 breathing (inspired PO2 43 Torr). The last PO2 is equivalent to that on the summit of Mt. Everest. All the 6,300 m studies were carried out in a warm well-equipped laboratory on well-acclimatized subjects. Maximal O2 uptake fell dramatically as the inspired PO2 was reduced to very low levels. However, two subjects were able to reach an O2 uptake of 1 l/min at the lowest inspired PO2. Arterial O2 saturations fell markedly and alveolar-arterial PO2 differences increased as the work rate was raised at high altitude, indicating diffusion limitation of O2 transfer. Maximal exercise ventilations exceeded 200 l/min at 6,300 m during air breathing but fell considerably at the lowest values of inspired PO2. Alveolar CO2 partial pressure was reduced to 7-8 Torr in one subject at the lowest inspired PO2, and the same value was obtained from alveolar gas samples taken by him at rest on the summit. The results help to explain how man can reach the highest point on earth while breathing ambient air.

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