Increase In Bicarbonate Concentration Research Articles

Quantifying genome-specific carbon fixation in a 750-meter deep subsurface hydrothermal microbial community.

Dissolved inorganic carbon has been hypothesized to stimulate microbial chemoautotrophic activity as a biological sink in the carbon cycle of deep subsurface environments. Here, we tested this hypothesis using quantitative DNA stable isotope probing of metagenome-assembled genomes (MAGs) at multiple 13C-labeled bicarbonate concentrations in hydrothermal fluids from a 750-m deep subsurface aquifer in the Biga Peninsula (Turkey). The diversity of microbial populations assimilating 13C-labeled bicarbonate was significantly different at higher bicarbonate concentrations, and could be linked to four separate carbon-fixation pathways encoded within 13C-labeled MAGs. Microbial populations encoding the Calvin-Benson-Bassham cycle had the highest contribution to carbon fixation across all bicarbonate concentrations tested, spanning 1-10mM. However, out of all the active carbon-fixation pathways detected, MAGs affiliated with the phylum Aquificae encoding the reverse tricarboxylic acid (rTCA) pathway were the only microbial populations that exhibited an increased 13C-bicarbonate assimilation under increasing bicarbonate concentrations. Our study provides the first experimental data supporting predictions that increased bicarbonate concentrations may promote chemoautotrophy via the rTCA cycle and its biological sink for deep subsurface inorganic carbon.

Serum Bicarbonate Levels Among Patients on Venovenous Extracorporeal Membrane Oxygenation for Acute Respiratory Distress Syndrome With and Without Kidney Replacement Therapy

OBJECTIVES: For patients with acute respiratory distress syndrome (ARDS) receiving venovenous extracorporeal membrane oxygenation (ECMO) who develop acute kidney injury (AKI) requiring kidney replacement therapy (KRT), the inability to renally compensate for respiratory acidosis could result in increased sweep gas flow to normalize arterial pH. Our objective was to examine the relationship of serum bicarbonate levels, arterial pH, sweep gas flow, and Paco 2. DESIGN: This is a retrospective cohort study. We compared patients who received KRT while undergoing venovenous ECMO to patients who did not. SETTING: Vanderbilt University Medical Center, February 2019 to February 2022. PATIENTS: We examined data from adult patients receiving venovenous ECMO for ARDS. INTERVENTIONS: Values for serum bicarbonate, arterial pH, Paco 2, and sweep gas flow were collected daily from time of cannulation until the earlier of decannulation, 30 days, or death. MEASUREMENTS AND MAIN RESULTS: Of the 126 patients included, 53 (42.1%) received KRT and 73 (57.9%) did not. In patients who received KRT, mean serum bicarbonate levels remained between 22 and 28 mmol/L throughout the study period. Patients who did not receive KRT experienced an increase in mean serum bicarbonate levels over time up to 40 mmol/L (mean difference = –4.4 mmol/L [95% CI, –6.3 to –2.5 mmol/L]; p < 0.0001). Mean values for Paco 2 (–5.2 [95% CI, –8.8 to –1.7]; p = 0.004) and pH (–0.03 [95% CI, –0.03 to –0.02]; p < 0.0001) were lower in patients who received KRT than in patients who did not, despite higher sweep gas flow rates in patients who received KRT than in patients who did not (mean difference = 1.5 [95% CI, 0.8–2.3]; p < 0.001). CONCLUSIONS: ARDS patients on venovenous ECMO with preserved kidney function experience an increase in bicarbonate concentration over time, compared to patients with AKI on KRT. Whether this increase in bicarbonate concentration increases pH, decreases sweep gas flow requirements, and facilitate weaning from venovenous ECMO requires examination in future research.

Carbon dioxide/bicarbonate is required for sensitive inactivation of mammalian glyceraldehyde-3-phosphate dehydrogenase by hydrogen peroxide

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) contains an active site Cys and is one of the most sensitive cellular enzymes to oxidative inactivation and redox regulation. Here, we show that inactivation by hydrogen peroxide is strongly enhanced in the presence of carbon dioxide/bicarbonate. Inactivation of isolated mammalian GAPDH by H2O2 increased with increasing bicarbonate concentration and was sevenfold faster in 25 mM (physiological) bicarbonate compared with bicarbonate-free buffer of the same pH. H2O2 reacts reversibly with CO2 to form a more reactive oxidant, peroxymonocarbonate (HCO4-), which is most likely responsible for the enhanced inactivation. However, to account for the extent of enhancement, we propose that GAPDH must facilitate formation and/or targeting of HCO4- to promote its own inactivation. Inactivation of intracellular GAPDH was also strongly enhanced by bicarbonate: treatment of Jurkat cells with 20 µM H2O2 in 25 mM bicarbonate buffer for 5 min caused almost complete GAPDH inactivation, but no loss of activity when bicarbonate was not present. H2O2-dependent GAPDH inhibition in bicarbonate buffer was observed even in the presence of reduced peroxiredoxin 2 and there was a significant increase in cellular glyceraldehyde-3-phosphate/dihydroxyacetone phosphate. Our results identify an unrecognized role for bicarbonate in enabling H2O2 to influence inactivation of GAPDH and potentially reroute glucose metabolism from glycolysis to the pentose phosphate pathway and NAPDH production. They also demonstrate what could be wider interplay between CO2 and H2O2 in redox biology and the potential for variations in CO2 metabolism to influence oxidative responses and redox signaling.

Bicarbonate Effects on Antibacterial Immunity and Mucus Glycobiology in the Cystic Fibrosis Lung: A Review With Selected Experimental Observations.

The primary defect in cystic fibrosis (CF) is abnormal chloride and bicarbonate transport in the cystic fibrosis transmembrane conductance regulator (CFTR) epithelial ion channel. The apical surface of the respiratory tract is lined by an airway surface liquid layer (ASL) composed of mucin comprising mainly MUC5A and MUC5B glycoproteins. ASL homeostasis depends on sodium bicarbonate secretion into the airways and secretion deficits alter mucus properties leading to airway obstruction, inflammation, and infections. Downstream effects of abnormal ion transport in the lungs include altered intrinsic immune defenses. We observed that neutrophils killed Pseudomonas aeruginosa more efficiently when it had been exposed to sodium bicarbonate, and formation of neutrophil extracellular traps (NETs) by neutrophils was augmented in the presence of increasing bicarbonate concentrations. Physiological levels of bicarbonate sensitized P. aeruginosa to the antimicrobial peptide cathelicidin LL-37, which is present in both lung ASL and in NETs. Sodium bicarbonate has various uses in clinical medicine and in the care of CF patients, and could be further explored as a therapeutic adjunct against Pseudomonas infections.

Bromate formation during oxidation of bromide-containing water by the CuO catalyzed peroxymonosulfate process

Bromate formation has been found in the SO4•−-based oxidation processes, but previous studies primarily focused on the bromate formation in the homogeneous SO4•−-based oxidation processes. The kinetics and mechanisms of bromate formation are poorly understood in the heterogeneous SO4•−-based oxidation processes, although which have been widely studied in the eliminations of micropollutants. In this work, we found that the presence of CuO, a common heterogeneous catalyst of peroxymonosulfate (PMS), appreciably enhanced the bromate formation from the oxidation of bromide by PMS. The conversion ratio of bromide to bromate achieved over 85% within 10 min in this process. CuO was demonstrated to play a multiple role in the bromate formation: (1) catalyzed PMS to generate SO4•−, which then oxidizes bromide to bromate; (2) catalyzed the formed free bromine to disproportionate to bromate; (3) catalyzed the formed free bromine to decomposed back into bromide. In the CuO-PMS-Br system, bromate formation increases with increasing CuO dosages, initial CuO and bromide concentrations, but decreases with increasing bicarbonate concentrations. The presence of NOM (natural organic matter) resulted in a lower formed bromate accompanied with organic bromine formation. Notably, CuO catalyzes PMS to transform more than 70% of initial bromide to bromate even after recycled used for six times. The formation of bromate in the PMS catalysis by CuO system was also confirmed in real water.

Transmembrane Transport of Bicarbonate Unravelled*.

Anion receptors can be used to transport ions across lipid bilayers, which has potential for therapeutic applications. Synthetic bicarbonate transporters are of particular interest, as defects in transmembrane transport of bicarbonate are associated with various diseases. However, no convenient method exists to directly observe bicarbonate transport and study the mechanisms involved. Here, an assay is presented that allows the kinetics of bicarbonate transport into liposomes to be monitored directly and with great sensitivity. The assay utilises an encapsulated europium(III) complex, which exhibits a large increase in emission intensity upon binding bicarbonate. Mechanisms involving CO2 diffusion and the dissipation of a pH gradient are shown to be able to lead to an increase in bicarbonate concentration within liposomes, without transport of the anion occurring at all. By distinguishing these alternative mechanisms from actual bicarbonate transport, this assay will inform the future development of bicarbonate transporters.

Modeling acid-base balance during continuous kidney replacement therapy.

Clinical studies have suggested that use of bicarbonate-containing substitution and dialysis fluids during continuous kidney replacement therapy may result in excessive increases in the carbon dioxide concentration of blood; however, the technical parameters governing such changes are unclear. The current work used a mathematical model of acid-base chemistry of blood to predict its composition within and exiting the extracorporeal circuit during continuous veno-venous hemofiltration (CVVH) and continuous veno-venous hemodiafiltration (CVVHDF). Model predictions showed that a total substitution fluid infusion rate of 2 L/h (33% predilution) with a bicarbonate concentration of 32mEq/L during CVVH at a blood flow rate of 200mL/min resulted in only modest increases in plasma bicarbonate concentration by 2.0mEq/L and partial pressure of dissolved carbon dioxide by 4.4mmHg in blood exiting the extracorporeal circuit. The relative increase in bicarbonate concentration (9.7%) was similar to that in partial pressure of dissolved carbon dioxide (8.2%), resulting in no significant change in plasma pH in the blood exiting the CVVH circuit. The changes in plasma acid-base levels were larger with a higher infusion rate of substitution fluid but smaller with a higher blood flow rate or use of substitution fluid with a lower bicarbonate concentration (22mEq/L). Under comparable flow conditions and substitution fluid composition, model predicted changes in acid-base levels during CVVHDF were similar, but smaller, than those during CVVH. The described mathematical model can predict the effect of operating conditions on acid-base balance within and exiting the extracorporeal circuit during continuous kidney replacement therapy.

Change in plants as bicarbonate rises

Freshwater Ecology Freshwater plants can be broadly divided into two major categories according to their photosynthetic traits: Some use carbon dioxide as their carbon source, whereas others use bicarbonate. Iversen et al. found that the relative concentrations of these two inorganic carbon forms in water determine the functional composition of plant communities across freshwater ecosystems (see the Perspective by Marce and Obrador). They created global maps revealing that community composition is structured by catchment geology and not climate (in contrast to the terrestrial realm, where the trait composition is structured by temperature and rainfall). Anthropogenic influences from land-use change are causing large-scale increases in bicarbonate concentrations in freshwater catchments and are thus leading to wholesale changes in the composition of their aquatic plant communities. Science , this issue p. [878][1]; see also p. [805][2] [1]: /lookup/doi/10.1126/science.aay5945 [2]: /lookup/doi/10.1126/science.aaz9096

Catchment properties and the photosynthetic trait composition of freshwater plant communities.

Unlike in land plants, photosynthesis in many aquatic plants relies on bicarbonate in addition to carbon dioxide (CO2) to compensate for the low diffusivity and potential depletion of CO2 in water. Concentrations of bicarbonate and CO2 vary greatly with catchment geology. In this study, we investigate whether there is a link between these concentrations and the frequency of freshwater plants possessing the bicarbonate use trait. We show, globally, that the frequency of plant species with this trait increases with bicarbonate concentration. Regionally, however, the frequency of bicarbonate use is reduced at sites where the CO2 concentration is substantially above the air equilibrium, consistent with this trait being an adaptation to carbon limitation. Future anthropogenic changes of bicarbonate and CO2 concentrations may alter the species compositions of freshwater plant communities.

Investigation of the hydrogen evolution phenomenon on CaCO3 precipitation in artificial seawater

Precipitation of CaCO3, as the most important part of scales, causes a serious problem in industrial equipment such as pipelines and desalination plants. The effect of the hydrogen evolution phenomenon on the electrochemical precipitation was studied through varying different factors including cathodic potential (CP), bicarbonate concentration, and solution temperature. The application of CP from −0.8 VSCE to −1.2 VSCE, an increase in bicarbonate concentration and temperature elevation from 25 °C to 45 °C led to the increase of scaling time (ts) and residual current density (ir). In all cases, it was indisputably found that the hydrogen evolution phenomenon had a predominant effect on the calcium carbonate precipitation. The surface analyses by means of scanning electron microscopy (SEM) showed formation of crystals in two defined forms of calcite and aragonite. Moreover, the energy dispersive spectroscopy (EDS) technique confirmed the formation of CaCO3 crystals.

Quantification of kinetic rate law parameters for the dissolution of natural autunite in the presence of aqueous bicarbonate ions at high concentrations

Uranium is a key contaminant of concern in the groundwater at U.S. Department of Energy (DOE) facilities within the United States and is a potential source of groundwater contamination and a risk to human health and the environment through discharges to surface water. Dissolved inorganic carbon (bicarbonate/carbonate) has a high affinity for complexing with uranium that is present as sorbed or unique uranium-bearing mineral phases within the sedimentary matrix. This process can result in the formation of soluble uranyl carbonate aqueous species, which are mobile under circumneutral pH conditions. This study was conducted to quantify the rate of release of uranium from the autunite mineral, (Ca[(UO2)(PO4)]2•3H2O), that was formed during polyphosphate injection to remediate uranium; the dissolution of uranium was studied as a function of the aqueous bicarbonate concentration, ranging from 25 to 100 mM. Experiments were carried out in the pH range from 7 to 11 in the temperature range of 23–90 °C via single-pass flow-through testing. Consistent with the results of previous studies (Gudavalli et al., 2013a, 2013b), the rate of uranium release from autunite exhibited minimal dependency on temperature, but was strongly dependent on pH and increasing concentrations of bicarbonate in the solution. Data obtained during these experiments were compared with results of previous experiments conducted using a low-concentration range of bicarbonate solutions (0.5–3.0 mM). An 8- to 30-fold increase in the rate of uranium release was observed in the presence of high bicarbonate concentrations at pH 7–8 compared to low bicarbonate values, while at pH 9–11, there was only a 5-fold increase in uranium rate of release with an increase in bicarbonate concentrations. The rate of uranium release was calculated to be between 5.18 × 10−8 and 1.69 × 10−7 mol m−2 s−1. The activation energy values at high and low bicarbonate concentrations were similar, with ratio values in the range of 0.6–1.0.

Erratum to: Patterns of coccolithophore pigment change under global acidification conditions based on in-situ observations at BATS site between July 1990–Dec 2008

Coccolith production is an important part of the biogenic carbon cycle as the largest source of calcium carbonate on earth, accounting for about 75% of the deposition of carbon on the sea floor. Recent studies based on laboratory experiment results indicated that increasing anthropogenic CO2 in the atmosphere triggered global ocean acidification leading to a decrease of calcite or aragonite saturation and calcium carbonate, and to decreasing efficiency of carbon export/pumping to deep layers. In the present study, we analyzed about 20 years of field observations of coccolithophore pigment, dissolved inorganic carbon (DIC), nutrients, and temperatures from the Bermuda Atlantic Time-series Study (BATS) site and satellite remote sensing to investigate the variable tendency of the coccolithophore pigment, and to evaluate the influence of ocean acidification on coccolithophore biomass. The results indicated that there was a generally increasing tendency of coccolithophore pigment, coupled with increasing bicarbonate concentrations or decreasing carbonate ion concentration. The change of coccolithophore pigment was also closely associated with pH, nutrients, mixed layer depth (MLD), and temperature. Correlation analyses between coccolithophores and abiotic parameter imply that coccoliths production or coccolithophore pigment has increased with increasing acidification in the recent 20 years.

Corrosion of New-Generation Steel in Outer Oil Pipeline Environments

New-generation high-strength pipeline steels are susceptible to corrosion attacks at their outer surfaces, from bicarbonate and carbonate in the hydrated soils in which pipelines are buried. The nature of the corrosion attacks requires implementing modified electrochemical methods by which the corrosion reactions can be studied comprehensively. From that, the findings can be linked to the alloying elements of the new pipeline materials, to modify them from both the strength and corrosion resistance perspectives. This paper presents an electrochemical study on the corrosion of API-X100 steel, in aerated bicarbonate-carbonate solutions, with cyclic voltammetry. At a fast 10 mV/s scan, over ten cycles, the passive films appeared as transparent layers, regardless of bicarbonate and carbonate concentrations. The surface controlled the reactions more than the passive films. The passive films showed evidence of forming gradually with increased cycling. Carbonate competed with bicarbonate during dissolution, decreasing its rate and making passivation faster. Bicarbonate in carbonate solutions catalyzed dissolution and disrupted passivation. The passive films with increased bicarbonate concentrations had higher transpassivation potentials.

Layered Double Hydroxide and Its Calcined Product for Fluoride Removal from Groundwater of Ethiopian Rift Valley

In this study, batch experiments have been carried out to investigate the mechanism of fluoride uptake by layered double hydroxide (LDH) and calcined layered double hydroxide (CLDH). Furthermore, practical use of these synthetic minerals was studied in continuous mini-column experiments. In these column studies, groundwater from Ethiopia was tested. LDH and CLDH were synthesized with Mg/Al mole ratio of 2. From batch experimental study, LDH and CLDH have shown maximum removal capacity of 84 and 222 mg F−/g from aqueous solution, respectively. It was observed that fluoride removal was pH dependent with favorable pH range of 5–7 (max. at pH 6). The mechanism of removal is suggested to be ion exchange for LDH and a memory effect followed by surface precipitation reaction for CLDH. The presence of other anions lowered defluoridation capacity of LDH in the order of PO4 3− > SO4 2− > NO3 − ≈ Cl−. From continuous experiments at 1 mM NaHCO3, LDH showed maximum defluoridation capacity of 1.3 mg/g and CLDH up to 20 mg/g. It was also observed that increase of bicarbonate concentration to 10 mM lowered the fluoride uptake capacity of CLDH to 4 mg/g. The presence of 1 mM H4SiO4 further reduced fluoride uptake capacity to 3 mg/g. CLDH column tested with groundwater from the Rift Valley with 10.5 mg F−/L has shown maximum removal capacity of 2.2 mg F−/g. Regeneration of this column indicated that CLDH has a good potential to be re-used.

Dose-Response of Sodium Bicarbonate Ingestion Highlights Individuality in Time Course of Blood Analyte Responses.

To defend against hydrogen cation accumulation and muscle fatigue during exercise, sodium bicarbonate (NaHCO3) ingestion is commonplace. The individualized dose-response relationship between NaHCO3 ingestion and blood biochemistry is unclear. The present study investigated the bicarbonate, pH, base excess and sodium responses to NaHCO3 ingestion. Sixteen healthy males (23 ± 2 years; 78.6 ± 15.1 kg) attended three randomized order-balanced, nonblinded sessions, ingesting a single dose of either 0.1, 0.2 or 0.3 g·kg-1BM of NaHCO3 (Intralabs, UK). Fingertip capillary blood was obtained at baseline and every 10 min for 1 hr, then every 15 min for a further 2 hr. There was a significant main effect of both time and condition for all assessed blood analytes (p ≤ .001). Blood analyte responses were significantly lower following 0.1 g·kg-1BM compared with 0.2 g·kg-1BM; bicarbonate concentrations and base excess were highest following ingestion of 0.3 g·kg-1BM (p ≤ .01). Bicarbonate concentrations and pH significantly increased from baseline following all doses; the higher the dose the greater the increase. Large interindividual variability was shown in the magnitude of the increase in bicarbonate concentrations following each dose (+2.0-5; +5.1-8.1; and +6.0-12.3 mmol·L-1 for 0.1, 0.2 and 0.3 g·kg-1BM) and in the range of time to peak concentrations (30-150; 40-165; and 75-180 min for 0.1, 0.2 and 0.3 g·kg-1BM). The variability in bicarbonate responses was not affected by normalization to body mass. These results challenge current practices relating to NaHCO3 supplementation and clearly show the need for athletes to individualize their ingestion protocol and trial varying dosages before competition.

In-situcharacterization of the early stage of pipeline steel corrosion in bicarbonate solutions by electrochemical atomic force microscopy

An electrochemical atomic force microscope was used to characterize the early stage of corrosion of an X100 pipeline steel in bicarbonate solutions with varied concentrations by synchronous measurements of electrochemical potential of the steel and its topographic evolution with time. Upon immersion of the steel in 0.01 M NaHCO3 solution, both electrochemical potential and topographic profile are associated with the dissolution of air-formed oxides present on the steel surface. The potential drops and the surface roughness increases rapidly. When corrosion of the steel occurs, the potential further drops and the surface roughness of the steel increases gradually. As the steel corrosion achieves a steady state, the generation of corrosion products reaches a dynamic equilibrium state. The surface roughness maintain an approximately stable value. In solutions containing increased bicarbonate concentrations, such as 0.1 M and 0.5 M NaHCO3, the steel can be passivated. The formed passive film can eliminate some surface features and improves the surface roughness. The topographic profile of the steel surface in 0.5 M NaHCO3 solution is smoother than that in 0.1 M solution. The surface features within 20 nm become eliminated after 4500 s of immersion in 0.1 M NaHCO3 solution, while larger features within 50 nm in size are eliminated in 0.5 M NaHCO3 solution in the same time period. Copyright © 2016 John Wiley & Sons, Ltd.

Water Quality Impact from the Discharge of Coal Mine Wastes to Receiving Streams: Comparison of Impacts from an Active Mine with a Closed Mine

This study examined two underground coal mines in the Sydney basin and investigated the water chemistry impact from their wastewater discharges to surface receiving waters. One mine closed 17 years prior to the study, and the other was still active. The geology of both mine locations shared many similarities and some important differences that influenced their wastewater chemistry and its subsequent impact on receiving waterways. Water quality of wastewater discharges from the two mines and their receiving waterways was investigated over a 6-month period. Both mine discharges caused comprehensive modification to receiving water chemistry. The closed mine increased electrical conductivity (EC) 3.3 times from upstream (33 μS/cm) compared to downstream (108 μS/cm). In comparison, the active mine increased EC by 9.4 times (173 μS/cm) upstream to 1628 μS/cm downstream. Both coal mine wastes increased the concentration of different contaminants to levels that are potentially hazardous for receiving water ecosystems. The active mine increased bicarbonate concentration in the receiving water by more than 60 times to 743 mg/L. The closed mine increased zinc and nickel concentrations in its receiving stream by 70 and 20 times to 318 and 360 μg/L. The active coal mine discharge was dominated by sodium and bicarbonate ions compared to magnesium and sulphate ions in the closed mine drainage. Although both receiving waters were sodium and chloride dominated upstream of the mine waste, their ionic composition was strongly modified due to the inflow of coal mine wastes. Results from this study are a reminder that water pollution from coal mines is important for both active mines and for closed mines decades after mining activity ceases.

Low Alloy X100 Pipeline Steel Corrosion and Passivation Behavior in Bicarbonate-Based Solutions of pH 6.7 to 8.9 with Groundwater Anions: An Electrochemical Study

This research investigates the fundamental corrosion and passivation processes occurring on API-X100 pipeline steels before, during, and after passive layer formation in bicarbonate-based simulated soil solutions of pH 6.7 to 8.9. Free corrosion potentials decrease exponentially with bicarbonate (and pH), owing to increased water and bicarbonate reduction in more alkaline conditions and the coupled iron oxidation reaction. Active corrosion rates at potentials slightly above open circuit potential increase with bicarbonate, until a concentration of 1.68 g L−1 sodium bicarbonate (plus dilute amounts of chlorides/sulfate) at which first signs of film formation appear. Thereon, increased bicarbonate concentration generally decreases current densities and resists ferrous-oxide product formations due to improved iron carbonate formation conditions precipitating more durable passive layers. Potentiodynamic polarization in the anodic regime reveals varying electrochemical processes involving interactions between hydroxide, carbonate, and oxide complexes with ferrous, with diverse pH and potential dependencies. The products of corrosion reactions were investigated by scanning electron microscopy, X-ray diffraction, and/or X-ray photoelectron spectroscopy.

Corrosion Cyclic Voltammetry of Two Types of Heat-Affected Zones (HAZs) of API-X100 Steel in Bicarbonate Solutions

This paper examined the electrochemical corrosion behavior and corrosion products of two types of heat-affected HAZs made from API-X100 steel. Cyclic voltammetry, with different scan rates and potential ranges at 10 cycles, was applied to analyze the interdependent corrosion reactions of cathodic reduction, anodic dissolution, passivation, and transpassivation. The HAZ cooled at 60 K/s, from a peak temperature of 1470 K (1197 °C) that was held for 15 seconds, exhibited better passivation and lower cathodic activity than the HAZ cooled at 10 K/s. Increasing bicarbonate concentration, from 0.05 and 0.2 to 0.6 M, increases the anodic activity and cathodic reduction, but accordingly protects the active surfaces and enhances passivation.

Effect of Ammonium:Nitrate Ratios in the Response of Strawberry to Alkalinity in Hydroponics

Strawberry (Fragaria ananasa) plants were grown in hydroponics in a greenhouse, where the supply of different ammonium (NH4+): nitrate (NO3−) ratios, was investigated to reduce the negative effect of alkalinity in nutrient solutions. The experiment was arranged in factorial combination with two factors, NH4+:NO3− ratios (0%:100%, 25%:75%, 50%:50%, 75%:25%, and 100%:0%) and bicarbonate (0, 25, 50, and 75 mM; NaHCO3). Plants treated with increasing bicarbonate concentrations exhibited significantly inhibited growth. In plants treated with NH4+ and NO3− simultaneously, there was a counteraction of the bicarbonate-induced growth suppression. Sole NO3− application in the presence of high bicarbonate resulted in poor growth and plant death due to high alkalinity. The adverse effect of alkalinity on SPAD values and maximal quantum yield of PSII photochemistry (Fv/Fm) alleviated with increasing proportion of NH4+ in nutrient solutions. The results showed that fruit numbers and yield of strawberry increased with elevation of NH4+ in nutrient solutions.