Carbon dioxide partial pressure and carbon fluxes of air-water interface in Taihu Lake, China

To obtain carbon dioxide （CO2） flux between water-air interface of Taihu lake, monthly water samplers at 14 sites and the local meteorological data of the lake were collected and analyzed in 1998. Carbon dioxide partial pressures （pCO2） at air-water interface in the lake were calculated using alkalinity, pH, ionic strength, active coefficient, and water temperature. The carbon fluxes at different sublakes and areas were estimated by concentration gradient between water and air in consideration of Schmidt numbers of 600 and daily mean windspeed at 10 m above water surface. The results indicated that the mean values of pCO2 in Wuli Lake,Meiliang Bay, hydrophyte area, west littoral zone, riverine mouths, and the open lake areas were 1 807.8±1 071.4（mean±standard deviation）μatm （latm=1.013 25×10^5pa）, 416.3±217.0μatm, 576.5±758.8μatm, 304.2±9.43.5μatm, 1 933.6±1 144.7 μatm, and 448.5±202.6μatm, respectively. Maximum and minimum pCO2 values were found in the hypertrophic （4 053.7μatm） and the eutrophic （3.2 μatm） areas. The riverine mouth areas have the maximum fluxes （82.0±62.8 mmol/m^2a）. But there was no significant difference between eutrophic and mesotrophic areas in pCO2 and the flux of CO2. The hydrophyte area, however, has the minimum （--0.58±12.9mmol/m^2a）. In respect to CO2 equilibrium, input of the rivers will obviously influence inorganic carbon distribution in the riverine estuary. For example, the annual mean CO2 flux in Zhihugang River estuary was 19 times of that in Meiliang Bay, although the former is only a part of the latter. The sites in the body of the lake show a clear seasonal cycle with pCO2 higher than atmospheric equilibrium in winter, and much lower than atmospheric in summer due to CO2 consumption by photosynthesis. The CO2 amount of the net annual evasion that enters the atmosphere is 28.42×10^4 t/a, of which those from the west littoral zone and the open lake account for 53.8% and 36.7%, respectively.

Changes of end-tidal carbon dioxide during cardiopulmonary resuscitation from ventricular f ibrillation versus asphyxial cardiac arrest

BACKGROUND: Partial pressure of end-tidal carbon dioxide(PETCO2) has been used to monitor the effectiveness of precordial compression(PC) and regarded as a prognostic value of outcomes in cardiopulmonary resuscitation(CPR). This study was to investigate changes of PETCO2 during CPR in rats with ventricular fi brillation(VF) versus asphyxial cardiac arrest.METHODS: Sixty-two male Sprague-Dawley(SD) rats were randomly divided into an asphyxial group(n=32) and a VF group(n=30). PETCO2 was measured during CPR from a 6-minute period of VF or asphyxial cardiac arrest.RESULTS: The initial values of PETCO2 immediately after PC in the VF group were signifi cantly lower than those in the asphyxial group(12.8±4.87 mmHg vs. 49.2±8.13 mmHg, P=0.000). In the VF group, the values of PETCO2 after 6 minutes of PC were significantly higher in rats with return of spontaneous circulation(ROSC), compared with those in rats without ROSC(16.5±3.07 mmHg vs. 13.2±2.62 mmHg, P=0.004). In the asphyxial group, the values of PETCO2 after 2 minutes of PC in rats with ROSC were signifi cantly higher than those in rats without ROSC(20.8±3.24 mmHg vs. 13.9±1.50 mmHg, P=0.000). Receiver operator characteristic(ROC) curves of PETCO2 showed signifi cant sensitivity and specifi city for predicting ROSC in VF versus asphyxial cardiac arrest.CONCLUSIONS: The initial values of PETCO2 immediately after CPR may be helpful in differentiating the causes of cardiac arrest. Changes of PETCO2 during CPR can predict outcomes of CPR.

Analysis of metabolic alterations in Arabidopsis following changes in the carbon dioxide and oxygen partial pressures

As sessile organisms,plants are subject to a multitude of environmental variations including several which directly affect their interaction with the atmosphere.Given the indiscriminant nature of Rubisco,the relative rates of photosynthesis and photorespiration are known to be responsive to changes in gas composition.However,comprehensive profiling methods have not yet been applied in order to characterize the wider consequences of these changes on primary metabolism in general.Moreover,although transcriptional profiling has revealed that a subset of photorespiratory enzymes are co-expressed,whether transcriptional responses play a role in short-term responses to atmospheric compositional changes remains unknown.To address these questions,plants Arabidopsis thaliana（Arabidopsis） ecotype Columbia（Col-O） grown under normal air conditions were transferred to different CO_2 and O_2 concentrations and characterized at the physiological,molecular,and metabolic levels following this transition.The results reveal alterations in the components,which are directly involved in,or supporting,photorespiration,including transcripts and metabolite levels.The results further highlight that the majority of the regulation of these pathways is not mediated at the level of transcription and that the photorespiratory pathway is essential also in conditions in which flux through the pathway is minimized,yet suggest that flux through this pathway is not mediated at the level of transcription.

pCO_2 and carbon fluxes across sea-air interface in the Changjiang Estuary and Hangzhou Bay

Partial pressure of CO2(pCO2) was investigated in the Changjiang(Yangtze River) Estuary,Hangzhou Bay and their adjacent areas during a cruise in August 2004,China.The data show that pCO2 in surface waters of the studied area was higher than that in the atmosphere with only exception of a patch east of Zhoushan Archipelago.The pCO2 varied from 168 to 2 264 μatm,which fell in the low range compared with those of other estuaries in the world.The calculated sea-air CO2 fluxes decreased offshore and varied from -10.0 to 88.1 mmol m-2 d-1 in average of 24.4 ± 16.5 mmol m-2 d-1.Although the area studied was estimated only 2 × 104 km2,it emitted(5.9 ± 4.0) × 103 tons of carbon to the atmosphere every day.The estuaries and their plumes must be further studied for better understanding the role of coastal seas playing in the global oceanic carbon cycle.

Temporal and spatial variability of the carbon cycle in the east of China's seas:a three-dimensional physical-biogeochemical modeling study

In the east of China＇s seas, there is a wide range of the continental shelf. The nutrient cycle and the carbon cycle in the east of China＇s seas exhibit a strong variability on seasonal to decadal time scales. On the basis of a regional ocean modeling system（ROMS）, a three dimensional physical-biogeochemical model including the carbon cycle with the resolution（1/12）°×（1/12）° is established to investigate the physical variations, ecosystem responses and carbon cycle consequences in the east of China＇s seas. The ROMS-Nutrient Phytoplankton Zooplankton Detritus（NPZD） model is driven by daily air-sea fluxes（wind stress, long wave radiation, short wave radiation, sensible heat and latent heat, freshwater fluxes） that derived from the National Centers for Environmental Prediction（NCEP） reanalysis2 from 1982 to 2005. The coupled model is capable of reproducing the observed seasonal variation characteristics over the same period in the East China Sea. The integrated air-sea CO_2 flux over the entire east of China＇s seas reveals a strong seasonal cycle, functioning as a source of CO_2 to the atmosphere from June to October, while serving as a sink of CO_2 to the atmosphere in the other months. The 24 a mean value of airsea CO_2 flux over the entire east of China＇s seas is about 1.06 mol/（m^2·a）, which is equivalent to a regional total of3.22 Mt/a, indicating that in the east of China＇s seas there is a sink of CO_2 to the atmosphere. The partial pressure of carbon dioxide in sea water in the east of China＇s seas has an increasing rate of 1.15 μatm/a（1μtm/a=0.101 325Pa）, but p H in sea water has an opposite tendency, which decreases with a rate of 0.001 3 a^（–1） from 1982 to 2005.Biological activity is a dominant factor that controls the pCO_2 air in the east of China＇s seas, and followed by a temperature. The inverse relationship between the interannual variability of air-sea CO_2 flux averaged from the domain area and Ni？o3 SST Index indicates that the carbon cycle in the east of China＇s seas has a high correlation with El Ni？o-Southern Oscillation（ENSO）.

Calcareous Sodic Soil Reclamation as Affected by Corn Stalk Application and Incubation: A Laboratory Study

A laboratory lysimeter experiment was conducted to investigate the effects of forage corn （Zea rncbys L.） stalk application on the CO2 concentration in soil air and calcareous sodic soil reclamation. The experimental treatments tested were soil exchangeable sodium percentage （ESP） levels of 1, 11, and 19, added corn stalk contents of 0 to 36 g kg^-1, and incubation durations of 30 and 60 days. The experimental results indicated that corn stalk application and incubation significantly increased CO2 partial pressure in soil profile and lowered pH value in soil solution, subsequently increased native CaCO3 mineral dissolution and electrolyte concentration of soil solution, and finally significantly contributed to reduction on soil sodicity level. The reclamation efficiency of calcareous sodic soils increased with the added corn stalk. When corn stalks were added at the rates of 22 and 34 g kg^-1 into the soil with initial ESP of 19, its ESP value was decreased by 56% and 78%, respectively, after incubation of 60 days and the leaching of 6.5 pore volumes （about 48 L of percolation water） with distilled water. Therefore, crop stalk application and incubation could be used as a choice to reclaim moderate calcareous sodic soils or as a supplement of phytoremediation to improve reclamation efficiency.

Relationship between metabolic syndrome and hypercapnia among obese patients with sleep apnea Relationship between metabolic syndrome and hypercapnia among obese patients with sleep apnea

BACKGROUND In the obese patient population,some patients have severe obstructive sleep apnea(OSA)with daytime hypoventilation.Such patients are generally identified on the basis of the presence or absence of daytime hypercapnia,and the condition is called obesity hypoventilation syndrome.However,mechanisms for such daytime hypoventilation remain unclear.AIM To investigate metabolic syndrome and daytime hypercapnia association based on hypercapnia prevalence in obese OSA patients in a nested case-control study.METHODS Consecutive obese patients(body mass index≥30 kg/m2)who underwent polysomnography due to suspected OSA were included.Among them,patients with severe OSA(apnea hypopnea index≥30/h)were divided into two groups according to the presence or absence of hypercapnia during wakefulness(arterial partial pressure of carbon dioxide≥or<45 Torr,respectively).The characteristics and clinical features of these two groups were compared.RESULTS Among 97 eligible patients,25 patients(25.8%)had daytime hypercapnia.There were no significant differences in age,gender,body mass index,apnea-hypopnea index,and Epworth Sleepiness Scale scores between the two groups.However,patients with hypercapnia had a significantly lower arterial partial pressure of oxygen level(75.8±8.2 torr vs 79.9±8.7 torr,P=0.042)and higher arterial partial pressure of carbon dioxide level(46.6±2.5 torr vs 41.0±2.9 torr,P<0.001).Additionally,patients with hypercapnia were more likely to have metabolic syndrome(72.0%vs 48.6%,P=0.043)and a higher metabolic score(the number of satisfied criteria of metabolic syndrome).In multivariate logistic regression analysis,the presence of metabolic syndrome was associated with the presence of hypercapnia(OR=2.85,95%CI:1.04-7.84,P=0.042).CONCLUSION Among obese patients with severe OSA,26%of patients had hypercapnia during wakefulness.The presence of metabolic syndrome was independently correlated with the presence of daytime hypercapnia.

Effect of sliding-cup along governor vessel on tcpO_2 and tapCO_2 in Mìngmén(命门 GV 4) point of sub-healthy humans: observation on different cupping pressure

Objective To explore the effects of sliding-cup with different parameters on energy metabolism in the body by observing the effect of sliding-cup along the governor vessel on transcutaneous partial pressures of oxygen and carbon dioxide in Mìngmén（命门 GV 4） in sub-healthy people. Methods A total of 10 sub-healthy adults at rest were observed and sliding-cup along the governor vessel were conducted with three different parameters, jar-pressure of –0.01~ –0.02 MPa with sliding-cup for 5 min, jar-pressure of –0.02~ –0.03 MPa with sliding-cup for 5 min and jar-pressure of –0.02~ –0.03 MPa with slidingcup for 3 min. Peri Flux System5000 PF5040 module was employed to monitor the changes of transcutaneous partial pressures of oxygen（tcp O2） and carbon dioxide（tcp CO2） in GV 4 at 0 min, 5 min, 10 min, 15 min, 20 min, 25 min and 30 min after sliding-cup with above different interventions in sub-healthy subjects. Results After sliding-cup, tcp O2 increased at first and then decreased over time; there was no difference in tcp O2 after sliding-cupping with different parameters（all P0.05）. After sliding-cup, tcp CO2 decreased; there was no difference in tcp CO2 after sliding-cup with different parameters（all P0.05）. Conclusion Sliding-cup has a sustained effect on the body and can speed up the energy metabolism in the body.