Increase In HCO3 Research Articles

Seasonal variations in the vertical structure of pelagian water stratum in the Southern Baikal

For the first time, T,S-analysis was used to determine the specifics of seasonal variations in the vertical structure of Lake Baikal active layer. In the under-ice period, the active layer includes the under-ice, top winter, and upper intermediate water masses. The under-ice water mass, unlike other masses, shows an increase in mineralization to 100.74 mg/kg, which corresponds to a release of 71.1 g salt under 1 m2 of water surface in a layer 0–40 m in the process of salt freezing out during ice cover formation and accretion. In the phases of mixing (homothermy), the water masses of the active layer transform into a surface homogeneous mass. In summer and autumn, surface and upper intermediate water masses, separated by a water mass of summer thermocline can be identified. A specific feature of the summer thermocline water mass is the increased sum of ions because of an increase in HCO 3 - concentration at the decay of organic matter accumulating in the bottom part of the thermocline. The existence of the under-ice water mass and the water mass of summer thermocline was established in Lake Baikal for the first time. In the deep-water zone (>250 m), except for the bottom parts, the lower water masses (the lower intermediate and the deep) are permanent, their characteristics remaining stable during the year. The changes in the bottom water mass are due to the character of the processes of bottom water renewal.

Dynamic modeling reveals a three-step response of Saccharomyces cerevisiae to high CO2 levels accompanied by increasing ATP demands.

Saccharomyces cerevisiae is often applied in large-scale bioreactors where gradients of dissolved CO2 exist. Under high CO2 pressure, the dissolved gas enters the microbe, causing multifold intracellular responses such as decrease of pH, increase of HCO3- and changes of ion balance. Effects of varying CO2 concentrations are multifold, hard to scale and hardly investigated. Hence, the multi-level response to CO2 shifts was summarized in a predicting ODE model with mass action kinetics, balancing electrochemical charges in steady-state growth conditions. Compared to experimental observations, the simulated dynamics of ion concentrations were found to be consistent. During CO2 shifts, the model predicts the initial depolarization of the membrane potential, the temporal pH drop and the activation of countermeasures such as Pma1-mediated H+ export and Trk1,2-mediated K+ import. In conclusion, extracellular cation concentrations and the cellular pH regulation are critical factors that determine physiology and cellular energy management. Consequently, pressure-induced CO2 gradients cause peaks of ATP demand which may occur in cells circulating in large-scale industrial bioreactors.

Dissolution sequestration mechanism of CO2 at the Shiqianfeng saline aquifer in the Ordos Basin, northwestern China

This study focused on the target injection layers of deep saline aquifers in the Shiqianfeng Fm. in the Carbon Capture and Sequestration (CCS) Demonstration Projects in the Ordos Basin, northwestern China. The study employed a combination method of experiments and numerical simulation to investigate the dissolution mechanism and impact factors of CO2 in these saline aquifers. The results showed (1) CO2 solubility in different types of water chemistry were shown in ascending order: MgCl2-type water < CaCl2-type water < Na2SO4-type water < NaCl-type water < Na2CO3-type water < distilled water. These results were consistent with the calculated results undertaken by TOUGHREACT with about 5% margin of error. CO2 solubility of Shiqianfeng Fm. saline was 1.05 mol/L; (2) compared with distilled water, the more complex the water’s chemical composition, the greater the increase in HCO3 −concentration. While the water’s composition was relatively simple, the tested water’s HCO3 −concentrations were in close accord with the calculated value undertaken by the TOUGHREACT code, and the more complex the water’s composition, the poorer the agreement was, probably due to the complex and unstable HCO3 − complicating matters when in an aqueous solution system including both tested HCO3 −concentration and calculated HCO3 −concentration; (3) the CO2 solubility in the saline at the temperature conditions of 55 °C and 70 °C were 1.17 and 1.02 mol/L. When compared with the calculated value of 1.20 and 1.05 mol/L, they were almost the same with only 1 and 3% margin of error; concentrations of HCO3 − were 402.73 mg/L (0.007 mol/L) and 385.65 mg/L (0.006 mol/L), while the simulation results were 132.16 mg/L (0.002 mol/L) and 128.52 mg/L (0.002 mol/L). From the contrast between the tested data and the calculated data undertaken by the TOUGHREACT code, it was shown that TOUGHRACT code could better simulate the interaction between saline and CO2 in the dissolution sequestration capacity. Therefore, TOUGHREACT code could be used for the inter-process prediction of CO2 long-term geological storage of CO2; (4) The Ca2+ concentration and SO4 2−concentration in saline water had less effect on the solubility of CO2 and HCO3 −concentration. In addition, TDS and pH values of saline affected not only the solubility of CO2, but also the conversion of CO2 to HCO3 − due to that they can affect the activity and acid-base balance. So in fact, we just need to consider that the TDS and pH values are main impact factors in the dissolution sequestration capacity of CO2 geological sequestration in deep saline aquifers.

Changes in the geochemical parameters of karst lakes over the past three decades – The case of Plitvice Lakes, Croatia

One of the major reasons for the increase in global air temperature since the early 20th century is considered to be the increase in the atmospheric CO2 concentration. Karst relief is considered an important carbon sink, but it can also be a natural source of carbon and CO2 emission. Aquatic systems in karst areas facilitate carbon exchange between the karst and the atmosphere, often through groundwater geochemical carbonate rock dissolution (carbon sink) and in the form of secondary calcium carbonate precipitation (possible carbon source).The protected area of Plitvice Lakes National Park, located in the karst region of Croatia, was chosen as a case study on karst geochemical processes. The lakes are also specific for their authigenic calcite precipitation in the form of tufa barriers and lake sediment. Physical and chemical data (temperature, pH, Ca2+, HCO3−, Mg2+ and CO2 concentrations, calcite saturation index (SIcalc), calcite dissolution ionic ratio (IRcalc), and Mg/Ca ratio) from water samples collected at 8 locations (2 springs, 2 rivers, and 4 lakes) from 1981 to 2014 were studied.The data were not collected systematically, so long-term changes have been mostly assessed through comparison between parameters from two selected periods (1981–1986 and 2010–2014) and through temporal correlations for each observed parameter in each calendar month.For the 33 years studied, an increase in air and water temperature, Ca2+ and HCO3− concentrations, calcite saturation index (SIcalc), calcite dissolution ionic ratio (IRcalc), and a decrease in the Mg/Ca ratio were observed. No statistically significant change was observed for pH or CO2 and Mg2+ concentrations. Average discharge rates did not display any significant change over the past three decades, however there was a change in their seasonal distribution.The significant increase in Ca2+ and HCO3− concentrations at lake locations were primarily caused by an increase in Ca2+ and HCO3− values in the water of the springs. Simultaneously, Mg2+ concentrations remained constant, which indicates higher levels of limestone (calcite) dissolution than dolomite dissolution. One of the reasons for this could be higher air/soil temperatures, resulting in higher soil CO2 production, which appears to result in the higher dissolution of calcite exclusively. An increase in HCO3− concentrations at the springs implies that karst groundwater is a carbon sink. Furthermore, the fact that the spatial decrease in HCO3− concentration in downstream waters was the same during the 1981–1986 and 2010–2014 periods implies that the entire observed karst lake system itself is a carbon sink.Temporal and spatial changes in SIcalc and IRcalc values in surface waters were mainly attributed to an increase in the intensity of bioactivity, which is in turn connected with an increase in water temperature.

Efficiency of acidemia correction on intermittent versus continuous hemodialysis in acute methanol poisoning

Context: Acidemia is a marker of prognosis in methanol poisoning, as well as compounding formate-induced cytotoxicity. Prompt correction of acidemia is a key treatment of methanol toxicity and methods to optimize this are poorly defined.Objective: We studied the efficiency of acidemia correction by intermittent hemodialysis (IHD) and continuous renal replacement therapy (CRRT) in a mass outbreak of methanol poisoning.Methods: The study was designed as observational cohort study. The mean time for an increase of 1 mmol/L HCO3–, 0.01 unit arterial blood pH, and the total time for correction of HCO3– were determined in IHD- and CRRT-treated patients.Results: Data were obtained from 18 patients treated with IHD and 13 patients treated with CRRT. At baseline, CRRT group was more acidemic than IHD group (mean arterial pH 6.79 ± 0.10 versus 7.05 ± 0.10; p = 0.001). No association was found between the rate of acidemia correction and age, weight, serum methanol, lactate, formate, and glucose on admission. The time to HCO3– correction correlated with arterial blood pH (r= −0.511; p = 0.003) and creatinine (r = 0.415; p = 0.020). There was association between the time to HCO3– correction and dialysate/effluent and blood flow rates (r= −0.738; p < 0.001 and r= −0.602; p < 0.001, correspondingly).The mean time for HCO3– to increase by 1 mmol/L was 12 ± 2 min for IHD versus 34 ± 8 min for CRRT (p < 0.001), and the mean time for arterial blood pH to increase 0.01 was 7 ± 1 mins for IHD versus 11 ± 4 min for CRRT (p = 0.024). The mean increase in HCO3– was 5.67 ± 0.90 mmol/L/h for IHD versus 2.17 ± 0.74 mmol/L/h for CRRT (p < 0.001).Conclusions: Our study supports the superiority of IHD over CRRT in terms of the rate of acidemia correction.

Bicarbonate enhanced removal of triclosan by copper(II) catalyzed Fenton-like reaction in aqueous solution

The antimicrobial and preservative agent triclosan (TCS) is an emerging and persistent pollutant, and is ubiquitous in the environment. Low cost and efficient removing technology for TCS in water has been the target of many researches. In this study, effective removal of TCS from water was achieved by Cu2+/H2O2 system in the presence of environmental relevant concentration of bicarbonate (HCO3−). The removal efficiency of TCS increased with the increase of HCO3− concentration from 0 to 2.0mM, while further increase of the HCO3− concentration caused the decrease of removal efficiency. TCS (0.01mM) could be totally removed over 120min when HCO3− was 2.0mM (pH 8.72) in the presence of 0.01mM Cu2+ ions at 25.0°C. In order to explore the reaction mechanism, radical scavenging technologies, molecular probe compound p-Chlorobenzoic acid (PCBA) and cyclovoltammetric (CV) experiments were employed to determine the reactive oxygen species (ROS), the steady-state concentrations of OH and Cu2+-complex, respectively. The results suggested that the Cu2+-complex formed between Cu2+ and HCO3− could catalyze H2O2 to produce O2−· and OH, which were responsible for the removal of TCS. Based on the reaction mechanism and identified intermediates of the oxidation process using TOF–LC–MS techniques, the reaction pathways for the oxidation of TCS were proposed including the cleavage of the ether bond, hydroxylation and polymerization. Finally, evaluation on the toxicity change of TCS reaction solution mediated by Cu2+/H2O2-HCO3− system with the freshwater green alga Scenedesmus obliquus showed significant detoxification of TCS.

The Effect of Light Stress and Other Culture Conditions on Photoinhibition and Growth of Dunaliella tertiolecta.

This work aimed to examine the effects of high light stress as well as other culture conditions including HCO3 − concentration, temperature, salinity, and pre-acclimation on photoinhibition and growth of halotolerant alga Dunaliella tertiolecta. Significant photoinhibition of D. tertiolecta was observed during a short period of exposure (6 hours) to high intensity of lights (1000, 1500, and 2000 μmol photons m-2 s-1); however, after 2 days of continuous light exposure, the alga adapted to high light stress and reached similar growth rates as low light exposure. The increase in HCO3 − concentration in the culture medium did not reduce photoinhibition, but the growth rate and chlorophyll contents increased with increasing HCO3 − concentrations. Temperature had significant effects on photoinhibition. Combined high temperature and high light intensity led to more serious photoinhibition and reduced cell growth rates, so did combined low salinity and high light intensity. Pre-acclimation by 50, 200, or 500 μmol photons m-2 s-1 each for 1, 3, or 6 hours (a total of nine treatments) did not significantly influence photoinhibition or cell growth of D. tertiolecta, probably because the acclimation periods were not long enough.

Analysis of acid–base balance as well as hematological and biochemical parameters in horses of combined driving discipline

Abstract. The aim of this study was to evaluate the effect of training on hematological and biochemical blood indices and acid–base balance as well as to attempt an assessment of the degree of driving horses' training based on examined parameters during the training cycle. The study was conducted on eight Polish Halfbred driving horses (aged 6–12 years). Each four-horse harness included two geldings and two mares. Blood was collected before and directly after training as well as after a 30 min recovery period. Blood samples were analyzed for hematological and biochemical parameters, as well as acid–base balance and glutathione peroxidase activity. The data were processed using a general linear model (ANOVA) procedure in Statistica v10. A significant (P &lt; 0.01) post-exercise increase in heart rate and respiratory rate was noted. Changes (P &lt; 0.01) in red blood cells (RBC), hemoglobin (HGB), glucose (GLU) and nonesterified fatty acids (NEFA) were observed after exercise. Correctness of the exercises affects the rate of recovery to rest values. The fastest recovery to the values of the rest period was noted in the case of RBC, HGB, LYM (lymphocytes), TCO2 (total carbon dioxide), HCO3− (bicarbonate concentration), GLU and NEFA. Training load did not cause acid–base balance disturbance, with visible compensation during the recovery period (increase in HCO3− and extracellular base excess (BE)). Changes in GPx activity were not confirmed statistically; however an increasing tendency was observed after training. Long-term exercises of driving horses cause significant lipomobilization. This study enables an evaluation and comparison of physical preparation to effort and intensity of driving horses' training. In the case of driving horses' training, there is a need to accept lower lactic acid (LA) (&lt; 4 mmol L−1) values in aerobic–anaerobic threshold interpretation.

A HCO3−-dependent mechanism involving soluble adenylyl cyclase for the activation of Ca2+ currents in locus coeruleus neurons

Hypercapnic acidosis activates Ca2+ channels and increases intracellular Ca2+ levels in neurons of the locus coeruleus, a known chemosensitive region involved in respiratory control. We have also shown that large conductance Ca2+-activated K+ channels, in conjunction with this pathway, limits the hypercapnic-induced increase in firing rate in locus coeruleus neurons. Here, we present evidence that the Ca2+ current is activated by a HCO3−-sensitive pathway. The increase in HCO3− associated with hypercapnia activates HCO3−-sensitive adenylyl cyclase (soluble adenylyl cyclase). This results in an increase in cyclic adenosine monophosphate levels and activation of Ca2+ channels via cyclic adenosine monophosphate-activated protein kinase A. We also show the presence of soluble adenylyl cyclase in the cytoplasm of locus coeruleus neurons, and that the cyclic adenosine monophosphate analogue db-cyclic adenosine monophosphate increases Ca2+i. Disrupting this pathway by decreasing HCO3− levels during acidification or inhibiting either soluble adenylyl cyclase or protein kinase A, but not transmembrane adenylyl cyclase, can increase the magnitude of the firing rate response to hypercapnia in locus coeruleus neurons from older neonates to the same extent as inhibition of K+ channels. This article is part of a Special Issue entitled: The role of soluble adenylyl cyclase in health and disease.

CO2 leakage in a shallow aquifer – Observed changes in case of small release

CO2 leakage in a shallow aquifer – Observed changes in case of small release

202

Introduction: THAM has been suggested as an alternative buffer to NaHCO3, particularly in respiratory acidosis since it has the advantage to act as a pure proton acceptor. In a previous experiment using a porcine respiratory acidosis lung injury model we, however, recognized a somewhat lower PvCO2-PaCO2 difference during THAM infusion as well as a higher PaCO2 than in the controls after concluded infusion. We studied this now in more detail with a higher dose of THAM. Methods: In 12 anesthetized, lung lavaged, endotracheally intubated and mechanically ventilated piglets we induced hypercapnic acidosis by reducing tidal volume from 6ml/kg to 3 ml/kg. In 6 piglets we infused 3.3mM THAM (3 ml/kg/h) in a central vein for 3 h followed by 3 hours observation, whereas the others served as controls. Hemodynamics and blood gases were obtained at 8 occasions during the first 2 h, and then every h until the end of the experiment. Results: In the THAM group the PvCO2-PaCO2 difference was 1.5 ± 4.2 mmHg (mean±SD) at end of infusion and increased to 7.3 ± 5.6 mmHg at 6 h. In the controls these differences were 16.1 ± 5.2 and 15.9 ± 5.8 respectively (p<0.001 compared with THAM). This resulted in significantly higher PaCO2 at the end of the experiment in the THAM group (169 ± 12.5 vs. 103 ± 11.5 mmHg in controls p=0.001) despite similar pH (7.16 ± 0.035) as in the controls caused by the expected increase in HCO3 (55.6 ± 2.7 vs. 31.5 ± 2.7mmol/L in controls, p=0.001) Conclusions: Our study suggests that pulmonary CO2 removal is reduced during central venous infusion of THAM for buffering of respiratory acidosis. The reason for this result is unknown, but might be due the increased HCO3 reducing the solubility of CO2, reduction of blood CO2 as well a drag of CO2 from the alveolar space by THAM or inhibition of carbon anhydrase in the erythrocytes.

CO2 -concentrating mechanisms in three southern hemisphere strains of Emiliania huxleyi.

Rising global CO2 is changing the carbonate chemistry of seawater, which is expected to influence the way phytoplankton acquire inorganic carbon. All phytoplankton rely on ribulose-bisphosphate carboxylase oxygenase (RUBISCO) for assimilation of inorganic carbon in photosynthesis, but this enzyme is inefficient at present day CO2 levels. Many algae have developed a range of energy demanding mechanisms, referred to as carbon concentrating mechanisms (CCMs), which increase the efficiency of carbon acquisition. We investigated CCM activity in three southern hemisphere strains of the coccolithophorid Emiliania huxleyi W. W. Hay & H. P. Mohler. Both calcifying and non-calcifying strains showed strong CCM activity, with HCO3 (-) as a preferred source of photosynthetic carbon in the non-calcifying strain, but a higher preference for CO2 in the calcifying strains. All three strains were characterized by the presence of pyrenoids, external carbonic anhydrase (CA) and high affinity for CO2 in photosynthesis, indicative of active CCMs. We postulate that under higher CO2 levels cocco-lithophorids will be able to down-regulate their CCMs, and re-direct some of the metabolic energy to processes such as calcification. Due to the expected rise in CO2 levels, photosynthesis in calcifying strains is expected to benefit most, due to their use of CO2 for carbon uptake. The non-calcifying strain, on the other hand, will experience only a 10% increase in HCO3 (-) , thus making it less responsive to changes in carbonate chemistry of water.

Dynamic modulation of ANO1/TMEM16A HCO 3 − permeability by Ca 2+ /calmodulin

Anoctamin 1 (ANO1)/transmembrane protein 16A (TMEM16A) is a calcium-activated anion channel that may play a role in HCO(3)(-) secretion in epithelial cells. Here, we report that the anion selectivity of ANO1 is dynamically regulated by the Ca(2+)/calmodulin complex. Whole-cell current measurements in HEK 293T cells indicated that ANO1 becomes highly permeable to HCO(3)(-) at high [Ca(2+)](i). Interestingly, this result was not observed in excised patches, indicating the involvement of cytosolic factors in this process. Further studies revealed that the direct association between ANO1 and calmodulin at high [Ca(2+)](i) is responsible for changes in anion permeability. Calmodulin physically interacted with ANO1 in a [Ca(2+)](i)-dependent manner, and addition of recombinant calmodulin to the cytosolic side of excised patches reversibly increased P(HCO3)/P(Cl). In addition, the high [Ca(2+)](i)-induced increase in HCO(3)(-) permeability was reproduced in mouse submandibular gland acinar cells, in which ANO1 plays a critical role in fluid secretion. These results indicate that the HCO(3)(-) permeability of ANO1 can be dynamically modulated and that ANO1 may play an important role in cellular HCO(3)(-) transport, especially in transepithelial HCO(3)(-) secretion.

Groundwater composition and pollution due to agricultural practices at Sete Cidades volcano (Azores, Portugal)

Groundwater is a strategic resource of the Azores archipelago given that agriculture is a major economic activity. A field study was undertaken at Sete Cidades volcano (São Miguel, Portugal) to characterize the composition of soil water at several depths in two sites: one without anthropogenic pressure (village site) and the other pasture land (Pa I site), and groundwater in the saturated zone of both sites. The composition of groundwater from springs discharging on the volcano flanks and inside the summit caldera is similar, composed principally of poorly mineralized Na–HCO3 and Na–HCO3–Cl water types, as suggested by median electrical conductivity values. Samples of groundwater collected in seven piezometers spread inside the Sete Cidades caldera are characterized by a conductivity between 95 and 232μS/cm and the dominant water type is Na–HCO3.Soil water at the Sete Cidades village site is of Na–Cl type and its compositional similiarity to rain water suggests control by evapotranspiration. The limited soil depth of the site, as well as the high precipitation and soil hydraulic conductivity, cause vertical homogenization of soil water composition. In contrast, soil water sampled at the pasture site (Pa1) shows greater mineralization when compared to the previous site, and waters are mainly HCO3 to HCO3–Cl types with a Mg–Ca trend for cations. A trend was indicated for the relative soil water composition at site Pa I, from the more superficial suction cup (G1) to the deeper G14–15. This is an evolution similar to perched-water bodies inside the Sete Cidades Caldera. The Mg–Ca-dominated composition at lower depth is explained by the application of fertilizers. Nevertheless, other processes are also influencing water chemistry evolution, and the observed relative decreases in Ca, Mg and K with depth may result from clay formation and the uptake by ion exchange of Ca2+ and Mg2+ for Na+. Although, the relative increase in Na could also result from silicate weathering. Besides contributing to the Na content, silicate dissolution may also explain the relative increase in HCO3, both being associated with silica in solution.The impact of the excessive application of fertilizers is reflected by the NO3 contents of soil water at Pa I and the village sites, as values are higher where agriculture is developed, with a similar trend being observed in the saturated zone.

Enhanced inorganic carbon uptake by Chlorella sp. IMMTCC-2 under autotrophic conditions for lipid production and CO2 sequestration

To achieve sustainable production of biofuel from microalgae, a well-optimized and sustained biomass production is prerequisite. The major factor determining the higher productivity of algae is the availability and uptake of CO2 for biomass growth. In this study, an improved CO2 sequestration method leading to improved biomass yields has been investigated. The ability of OH− ions in fixing dissolved CO2 in form of HCO 3 − in algal growth medium was studied using a Chlorella sp. and scaled-up in a photobioreactor. It was observed that a critical concentration of 0.005 M OH− is required for HCO 3 − formation and utilization by algae. HCO 3 − uptake was enhanced by 70.8% (in presence of 0.01 M NaOH) with a sixfold increase in growth rate compared with only CO2 system. In mineral carbon systems such as NaHCO3 and Na2CO3, increase in HCO 3 − uptake was enhanced by 65.4% and 63.4%, respectively. The maximum rate of CO2 fixation of 6.6 mg L−1 h−1 was obtained with 0.01 M NaOH which was 1.5 times compared with mineral carbon sources. The biomass from scale-up experiment contained 16.3% lipid (by weight) of which 75% is unsaturated fatty acids (in total lipids). This supports the idea that fixing the dissolved CO2 in the form of bicarbonate using alkali helps in increased biomass productivity rather than CO2 itself, forms a precursor for biodiesel, and increases CO2 sequestration in a cyclic process.

Adaptation to different salinities exposes functional specialization in the intestine of the sea bream (Sparus aurata L.)

The processing of intestinal fluid, in addition to a high drinking rate, is essential for osmoregulation in marine fish. This study analyzed the long-term response of the sea bream (Sparus aurata L.) to relevant changes of external salinity (12, 35 and 55 p.p.t.), focusing on the anterior intestine and in the less-often studied rectum. Intestinal water absorption, epithelial HCO(3)(-) secretion and gene expression of the main molecular mechanisms (SLC26a6, SLC26a3, SLC4a4, atp6v1b, CFTR, NKCC1 and NKCC2) involved in Cl(-) and HCO(3)(-) movements were examined. The anion transporters SLC26a6 and SLC26a3 are expressed severalfold higher in the anterior intestine, while the expression of Atp6v1b (V-type H(+)-ATPase β-subunit) is severalfold higher in the rectum. Prolonged exposure to altered external salinity was without effect on water absorption but was associated with concomitant changes in intestinal fluid content, epithelial HCO(3)(-) secretion and salinity-dependent expression of SLC26a6, SLC26a3 and SLC4a4 in the anterior intestine. However, the most striking response to external salinity was obtained in the rectum, where a 4- to 5-fold increase in water absorption was paralleled by a 2- to 3-fold increase in HCO(3)(-) secretion in response to a salinity of 55 p.p.t. In addition, the rectum of high salinity-acclimated fish shows a sustained (and enhanced) secretory current (I(sc)), identified in vitro in Ussing chambers and confirmed by the higher expression of CFTR and NKCC1 and by immunohistochemical protein localization. Taken together, the present results suggest a functional anterior-posterior specialization with regard to intestinal fluid processing and subsequently to salinity adaptation of the sea bream. The rectum becomes more active at higher salinities and functions as the final controller of intestinal function in osmoregulation.

P267 Association of the length of non-invasive ventilation (NIV) with arterial bicarbonate level in COPD patients with acute hypercapnic respiratory failure (AHRF)

IntroductionFollowing the British Thoracic Society (BTS) NIV audit 2011 we noted that our institution's length of stay was longer than the national average. Factors related to length of stay are...

Dolomite Versus Calcite Weathering in Hydrogeochemically Diverse Watersheds Established on Bedded Carbonates (Sava and Soča Rivers, Slovenia)

The relative contributions of dolomite to calcite weathering related to riverine fluxes are investigated on a highly resolved spatial scale in the diverse watersheds of Slovenia, which previous work has shown have some of the highest carbonate-weathering intensities in the world and suggests that dolomite weathering is favored over limestone weathering in mixed carbonate watersheds. The forested Sava and Soca River watersheds of Slovenia with their headwaters in the Julian Alps drain alpine regions with thin soils (<30 cm) and dinaric karst regions with thicker soils (0 to greater than 70 cm) all developed over bedded Mesozoic carbonates (limestone and dolomite), and siliclastic sediments is the ideal location for examining temperate zone carbonate weathering. This study extends previous work, presenting geochemical data on source springs and documenting downstream geochemical fluctuations within tributaries of the Sava and Soca Rivers. More refined sampling strategies of springs and discrete drainages permit directly linking the stream Mg2+/Ca2+ ratios to the local bedrock lithology and the HCO3 − concentrations to the relative soil depths of the tributary drainages. Due to differences in carbonate source lithologies of springs and tributary streams, calcite and dolomite weathering end members can be identified. The Mg2+/Ca2+ ratio of the main channel of the Sava River indicates that the HCO3 − concentration can be attributed to nearly equal proportions by mass of dolomite relative to calcite mineral weathering (e.g., Mg2+/Ca2+ mole ratio of 0.33). The HCO3 − concentration and pCO2 values increase as soil thickness and alluvium increase for discrete spring samples, which are near equilibrium with respect to calcite. Typically, this results in approximately 1.5 meq/l increase in HCO3 − from the alpine to the dinaric karst regions. Streams in general do not change in HCO3 −, Mg2+/Ca2+, or Mg2+/HCO3 − concentrations down course, but warming and degassing of CO2 produce high degrees of supersaturation with respect to calcite. Carbonate-weathering intensity (mmol/km2-s) is highest within the alpine regions where stream discharge values range widely to extreme values during spring snowmelt. Overall, the elemental fluxes of HCO3 −, Ca2+, and Mg2+ from the tributary watersheds are proportional to the total water flux because carbonates dissolve rapidly to near equilibrium. Importantly, dolomite weathers preferentially over calcite except for pure limestone catchments.

High sodium intake increases HCO3−absorption in medullary thick ascending limb through adaptations in basolateral and apical Na+/H+exchangers

A high sodium intake increases the capacity of the medullary thick ascending limb (MTAL) to absorb HCO(3)(-). Here, we examined the role of the apical NHE3 and basolateral NHE1 Na(+)/H(+) exchangers in this adaptation. MTALs from rats drinking H(2)O or 0.28 M NaCl for 5-7 days were perfused in vitro. High sodium intake increased HCO(3)(-) absorption rate by 60%. The increased HCO(3)(-) absorptive capacity was mediated by an increase in apical NHE3 activity. Inhibiting basolateral NHE1 with bath amiloride eliminated 60% of the adaptive increase in HCO(3)(-) absorption. Thus the majority of the increase in NHE3 activity was dependent on NHE1. A high sodium intake increased basolateral Na(+)/H(+) exchange activity by 89% in association with an increase in NHE1 expression. High sodium intake increased apical Na(+)/H(+) exchange activity by 30% under conditions in which basolateral Na(+)/H(+) exchange was inhibited but did not change NHE3 abundance. These results suggest that high sodium intake increases HCO(3)(-) absorptive capacity in the MTAL through 1) an adaptive increase in basolateral NHE1 activity that results secondarily in an increase in apical NHE3 activity; and 2) an adaptive increase in NHE3 activity, independent of NHE1 activity. These studies support a role for NHE1 in the long-term regulation of renal tubule function and suggest that the regulatory interaction whereby NHE1 enhances the activity of NHE3 in the MTAL plays a role in the chronic regulation of HCO(3)(-) absorption. The adaptive increases in Na(+)/H(+) exchange activity and HCO(3)(-) absorption in the MTAL may play a role in enabling the kidneys to regulate acid-base balance during changes in sodium and volume balance.

Effect of HCO&lt;sub&gt;3&lt;/sub&gt;Concentration on CO&lt;sub&gt;2&lt;/sub&gt; Corrosion for Q235 Steel

The effects of HCO3- concentration on CO2 corrosion for Q235 steel were investigated by weight loss tests and potentiodynamic polarization curve and EIS (Electrochemical Impedance Spectroscopy) techniques. The results showed that the corrosion rate of Q235 steel decreased wih on increase of HCO3- concentration when [HCO3-] was lower than 600mg/L. An evident active-passive behavior exhibited in anodic process at 1000mg/L·HCO3- .The cathodic reactions were promoted by increasing [HCO3-] when it reached 1000mg/L, H2CO3 and HCO3- become the most important cathodic reaction. Anodic behavior was an active process at higher [HCO3-] concentration and the anodic current density increased with the increase of [HCO3-] concentration.