scholarly journals Redox potential, nitrate content and pH in flooded Eutric Cambisol during nitrate reduction

2008 ◽  
Vol 53 (No. 1) ◽  
pp. 20-28 ◽  
Author(s):  
T. Wlodarczyk ◽  
P. Szarlip ◽  
M. Brzezinska ◽  
U. Kotowska
Keyword(s):  
Statistical Analysis ◽  
Redox Potential ◽  
Nitrate Reduction ◽  
Narrow Range ◽  
Acid Soils ◽  
Nitrate Content ◽  
Soil Flooding ◽  
Ph Values ◽  
Curvilinear Relation

Topsoils from 16 arable Cambisols developed from sand, loam and silt were used to study soil ability to nitrate reduction under flooding conditions. The strongest drop of redox potential (Eh) was observed during the first day of soil flooding. Decreasing tendency in pH values was observed of alkaline and neutral soils, and an increase in pH of acid and strongly acid soils, accompanied by a fall in Eh values. Redox potential was negatively correlated with the pH values (R<sup>2</sup> = 0.3041; <i>p</i> < 0.001). The fall of NO<sub>3</sub><sup>&minus;</sup> varied from 20 to 100% depending on the type of soil and on the time of incubation. With a decrease of nitrate content within the range from 100 to 10 mg NO<sub>3</sub><sup>&minus;</sup>-N/kg, the value of redox potential decreased from 250 to 190 mV. The highest reduction of nitrates coincided with Eh values within a narrow range between 200 and 210 mV. Statistical analysis of redox potential in the function of the content of nitrates showed a curvilinear relation (R<sup>2</sup> = 0.3823; <i>p</i> < 0.001).

Strategies for Optimized Nitrate Reduction with Primary Denitrification

1992 ◽  
Vol 26 (5-6) ◽  
pp. 1087-1096 ◽  
Author(s):  
J. Londong
Keyword(s):  
Adaptive Control ◽  
Feedback Control ◽  
Redox Potential ◽  
Nitrate Reduction ◽  
Treatment Plant ◽  
Nitrate Content ◽  
Biodegradable Materials ◽  
Feasible Method ◽  
Nitrate Load ◽  
Full Scale Tests

Full-scale tests carried out for the extension of a 700 000 PE treatment plant are used to show the consequences of advanced denitrification requirements. Three nitrate recirculation strategies were tested: feedback control via the nitrate content at the denitrification zone outflow, control via the redox potential and adaptive control of the recirculated nitrate load in accordance with the input of biodegradable materials, estimated on the basis of a BOD-MS measurement (3 minute BOD). In a situation in which advanced, process-stable primary denitrification has to be carried out in a restricted space, especially in large treatment plants, controlled nitrate recirculation oriented on the requirement for biodegradables is a feasible method. If denitrification is limited by lack of biodegradable substrate, supplements in line with denitrification requirements will be needed. The necessary control can be implemented via a measurement of BOD-M3 in the influent and measurement of nitrate content in the effluent from the activated sludge tank.

scholarly journals Aferição do pH de diferentes agentes clareadores indicados para o clareamento intracoronário

2018 ◽  
Author(s):  
João Felipe Besegato ◽  
Gabriela Dos Santos Ribeiro Rocha ◽  
Marlene De Sousa Amorim ◽  
Fabio Martins Salomão ◽  
Daniel Poletto ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Statistical Analysis ◽  
Multiple Comparisons ◽  
The Other ◽  
Sodium Perborate ◽  
Distilled Water ◽  
Friedman Test ◽  
Time Intervals ◽  
Ph Values ◽  
Evaluation Time

Objective: to measure pH values of bleaching agents that are indicated to intracoronal bleaching technique in different time intervals. Methods: Each group (G) received five samples (n=5): G1 – distilled water (AD); G2 – hydrogen peroxide (H2O2) 30%; G3 – sodium perborate (PbS) + AD; G4 – PbS + H2O2 30%; G5 – sodium percarbonate (PcS) + AD; and G6 – PcS + H2O2 30%. pH values were stated using a digital pHmeter, in different time intervals: immediately after handling (T0), 24 hours (T1) and 168 hours after handling (T2). The results were submitted to statistical analysis through Kruskal-Wallis and Mann Whitney tests, in this order, allowing multiple comparisons among the groups. To verify the effect of time in each group, Friedman test was applied. Results: In the evaluation of the effect of time in each group, it was observed that G2 presented acid behavior, while the other groups exhibited values close to neutrality or alkaline. Conclusions: H2O2 30% was the only agent that showed acidic behavior in every evaluation time. Meanwhile, PcS + H2O had the highest pH values.

scholarly journals The effect of dissolved organic carbon on pelagial and near-sediment water traits in lakes

2011 ◽  
Vol 74 (2) ◽  
pp. 133-139 ◽  
Author(s):  
Krzysztof Banaś
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Redox Potential ◽  
Environmental Conditions ◽  
Calcium Concentration ◽  
Total Hardness ◽  
Sediment Layer ◽  
Ph Values ◽  
Doc Concentration ◽  
Good Transparency

The effect of dissolved organic carbon (DOC) on the environmental conditions of macrophytes has been studied in 35 lakes divided into soft- and hardwater: oligohumic (&lt;4.0 mg C dm<sup>-3</sup>), α-mesohumic (4.0-8.0 mg C dm<sup>-3</sup>), β-mesohumic (8.1-16.0 mg C dm<sup>-3</sup>) and polihumic (&gt;16.0 mg C dm<sup>-3</sup>). The optimum environmental conditions for macrophytes have been found in oligohumic lakes, characterised by low water colour and its good transparency. In soft- and hardwater lakes increasing concentration of DOC is accompanied with an increase in the colour (r=0.95), while the visibility decreases. With increasing DOC in the near-sediment layer the pH values decrease while the concentration of nitrogen increases and the concentration of phosphorus slightly increases. In hardwater lakes with increasing DOC concentration, the redox potential, conductivity, total hardness and calcium concentration in the near-sediment water decrease, whereas the content of CO<sup>2</sup> remains at a very low level.

scholarly journals Chemical Reduction of Nitrate by Zero-Valent Iron: Shrinking-Core versus Surface Kinetics Models

2020 ◽  
Vol 17 (4) ◽  
pp. 1241 ◽  
Author(s):  
Maria Villen-Guzman ◽  
Juan Manuel Paz-Garcia ◽  
Brahim Arhoun ◽  
Maria del Mar Cerrillo-Gonzalez ◽  
Jose Miguel Rodriguez-Maroto ◽  
...  
Keyword(s):  
Nitrate Reduction ◽  
Chemical Reduction ◽  
Permeable Reactive Barriers ◽  
Zero Valent Iron ◽  
Sound Design ◽  
Surface Kinetics ◽  
Ph Values ◽  
Stirred Reactor ◽  
Constant Ph ◽  
Shrinking Core

Zero valent iron (ZVI) is being used in permeable reactive barriers (PRB) for the removal of oxidant contaminants, from nitrate to chlorinated organics. A sound design of these barriers requires a good understanding of kinetics. Here we present a study of the kinetics of nitrate reduction under relatively low values of pH, from 2 to 4.5. We use a particle size of 0.42 mm, which is within the recommended size for PRBs (0.2 mm to 2.0 mm). In order to avoid possible mass-transfer limitations, a well-stirred reactor coupled with a fluidized bed reactor was used. The experiments were performed at constant pH values using a pH controller that allows to accurately track the amount of acid added. Since the reduction of H + to H 2 by the oxidation of ZVI will always be present for these pH values, blank experiments (without nitrate) were performed and the rate of this H + reduction obtained. This rate of reduction was studied using three kinetic models: a regular empirical one, the Shrinking-Core Model (SCM), and the Surface Kinetics Model (SKM). The best performance was obtained from the SKM model. Therefore, this model was also used to study the results for the nitrate reduction, also with satisfactory results. In both cases, some assumptions are introduced to maintain a moderate number of fitting parameters.

Use of an industrial by-product as a liming source

1969 ◽  
Vol 78 (3-4) ◽  
pp. 73-86
Author(s):  
Miguel A. Muñoz ◽  
Lourdes Peña ◽  
Julia M. O’Hallorans
Keyword(s):  
Moisture Content ◽  
Production Process ◽  
Industrial Waste ◽  
Soil Acidity ◽  
Agricultural Soils ◽  
Acid Soils ◽  
Incubation Experiment ◽  
Short Term ◽  
Ph Values ◽  
Acetylene Production

Calcium hydroxide [Ca(OH)2], a by-product of the acetylene production process, is a potential liming source for acid agricultural soils. The material as generated has a moisture content of 80%, which decreases to about 50% after settling in a collecting pond. Air dried Ca(OH)2 (2.63% moisture), ground to pass a 300 µm sieve, had a CaCO3 equivalent of 120%, Commercial CaCO3 (1.53% moisture) had a pure CaCO3 equivalent of 84%. Both liming sources were evaluated in laboratory incubation studies using four acid soils; Corozal clay (Ultisol), Mariana (Inceptisol), Bayamón (Oxisol) and Alonso (Ultisol). The industrial waste [Ca(OH)2] was as effective as CaCO3 in neutralizing soil acidity. An application of 8.0 meq/100g of both liming sources increased the pH of Mariana soil from 4.65 to 6.07, Corozal soil from 4.13 to 4.92 and Alonso soil from 4.74 to 6.48. The pH of Bayamón soil increased from 4.39 to 6.65 with the application of 8.0 meq of CaCO3; however, the same amount of Ca(OH)2 increased the pH to 6.92. Exchangeable Al3+ levels were close to zero in Mariana, Bayamón and Alonso soils at pH values between 6.0-6.3. Exchangeable Al3+ in Coroza! soil decreased from 934.37 mg/kg to 269.79 mg/kg as the pH increased from 4.13 to 4.92. in a short term incubation experiment (5 days), Ca(OH)2 reacted faster than CaCO3 to neutralize soil acidity. Samples of Mariana, Alonso and Bayamón soils treated with 8.0 meq/100g of Ca(OH)2 reached pH values around 6,00 after one day of incubation, whereas CaCO3-treated samples reached similar pH values only after the second or third day of incubation.

The effect of soil pH on potassium intensity and release of non-exchangeable potassium to ryegrass

1970 ◽  
Vol 75 (3) ◽  
pp. 571-576 ◽  
Author(s):  
A. Islam ◽  
J. Bolton
Keyword(s):  
Soil Ph ◽  
Sandy Soil ◽  
Acid Soils ◽  
The Other ◽  
Exchangeable Potassium ◽  
Air Drying ◽  
Ph Values ◽  
Small Constant ◽  
Activity Ratios ◽  
Exchangeable Form

Ryegrass was used to remove potassium from two acid soils limed to different pH values. Most non-exchangeable potassium was removed from the unlimed soils (pH 4·5) but differences in removal between pH 5·5 and 7·0 were small. Air-drying the soils after cropping released further potassium into the exchangeable form in amounts independent of soil pH.Equilibrium potassium activity ratios (ARK) after each out declined to small constant values characteristic of the soils. A sandy soil (Woburn) initially contained less exchangeable potassium than a soil with more clay (Sawyers), but after a few crops, ARK, % K in the grass and K uptakes per cut were larger from Woburn soil, showing that non-exchangeable potassium was being released faster than in the other soil.

Soil pH and aluminium and their spatial variation in Western Australian acidic soils

1990 ◽  
Vol 30 (5) ◽  
pp. 637 ◽  
Author(s):  
PJ Dolling ◽  
WM Porter ◽  
AD Robson
Keyword(s):  
Spatial Variation ◽  
Soil Ph ◽  
Surface Soil ◽  
Acid Soils ◽  
Poor Correlation ◽  
Ph Values ◽  
Coefficients Of Variation ◽  
Subsurface Soil ◽  
The Relationship ◽  
Surface Soil Ph

Thirty-eight sites on acid soils (pH<5.5, 1:5 in water) in the medium rainfall region of Western Australia were sampled to examine spatial variation in soil pH and 0.01 mol/L CaCl2-extractable aluminium. We also examined the relationship between (i) the A1 and A2 horizon soil pH, (ii) the A1 and A2 horizon extractable aluminium, (iii) surface and subsurface soil pH and (iv) surface soil and subsurface soil-extractable Al. Soil at each site generally had a light-textured layer overlying a clay layer at varying depths (30-70 cm) and was classified as either Dy 5.21 or Dy 5.41 (Northcote 1979). Over 80% of the sites had surface soil pH values 4.8 or lower and extractable aluminium concentrations 2 �g/g or higher. There was a very poor correlation (r2 = 0.21) between the A1 horizon soil aluminium extracted in 0.01 mol/L CaCl2 and the pH measured in 0.01 mol/L CaCl2 over 1 ha sites. The relationship was slightly improved in the A2 horizon (r2 = 0.49). The coefficients of variation of soil pH varied from 1.2 to 5.1%, while the coefficients of variation for CaCl2-extractable aluminium varied from 10 to 50%. At many of the sites, low pH values and high aluminium concentrations extended down to 35-45 cm. At the B horizon the pH values generally increased and the aluminium concentrations decreased. The surface soil pH and extractable aluminium were not good indicators (r2 = 0.09-0.60) of the subsurface soil pH and extractable aluminium.

Selenium fortification of hydroponically grown corn salad (Valerianella locusta)

2015 ◽  
Vol 66 (11) ◽  
pp. 1128 ◽  
Author(s):  
Nicola Tomasi ◽  
Roberto Pinton ◽  
Stefano Gottardi ◽  
Tanja Mimmo ◽  
Matteo Scampicchio ◽  
...  
Keyword(s):  
Amino Acids ◽  
Nutritional Value ◽  
Narrow Range ◽  
Essential Element ◽  
Leafy Vegetables ◽  
Nitrate Content ◽  
Protein Thiols ◽  
Pigment Contents ◽  
Hydroponically Grown ◽  
Edible Parts

There is increasing interest in the hydroponic technology to produce leafy vegetables for ready-to-eat salads. Optimisation of the growing system can lead to higher yield and/or improved nutritional value of the product. Selenium (Se) is an essential element for animal and humans, with quite a narrow range between deficiency and toxicity, whereas it is assumed beneficial for plants. In the present study, two cultivars (Gala and Baron) of corn salad (Valerianella locusta (L.) Laterr.) were used to test the possibility to increase Se content in the edible parts (leaves). Effects on yield, nitrate content, and accumulation of sulfur (S) and S-containing amino acids and Se and Se-containing amino acids were studied. Results showed that corn salad tolerates selenate (Na2SeO4) concentrations ranging from 10 to 40 µm in the nutrient solution, with plants accumulating Se at levels compatible with the need in human diets at 10 µm selenate. Se-treated plants showed some benefits with respect to a decrease of nitrate concentration and increase of pigment contents (chlorophylls and carotenoids). At 10 µm selenate, Se-cysteine and Se-methionine were produced, without affecting non-protein thiols or cysteine and methionine contents. At the higher Se supply, sulfate accumulated in the leaves with a parallel decrease in the amount of S-amino acids and a rise in the relative amount of Se-amino acids. Based on the chemical analyses, cv. Gala showed better tolerance than cv. Baron to moderate selenate supply (40 µm).

The pH of Puerto Rican Soils Used for Principal Crops

1969 ◽  
Vol 46 (2) ◽  
pp. 107-119
Author(s):  
George Samuels
Keyword(s):  
Puerto Rico ◽  
Puerto Rican ◽  
Soil Ph ◽  
Acid Soils ◽  
Soil Series ◽  
Root Crop ◽  
Ph Values ◽  
Ph Range ◽  
The Relationship ◽  
Acid Range

The pH values of the soils of Puerto Rico were determined with the following results: 1. About 80 percent of the soils were acid (below pH 7) and 50 percent were below pH 6, which was acid enough to require liming. 2. Most of the soils planted to bananas were pH 6 and above. 3. The pH range for brushland was wide, extending from acid to alkaline. 4. Eighty percent of the soils of the coconut plantations were above pH 6. 5. Coffee soils, in general, were acid, with 63 percent below pH 6, of which 49 percent were in the range pH 5.0 to 5.9 and 13 percent in the very acid range of pH 4.0 to 4.9. 6. The pH of soils planted to corn varied widely. 7. The small cotton acreage had a pH range of 5.0 to 5.9. 8. The soils planted to grapefruit had 57 percent of their acreage at pH 4.0 to 4.9 and 29 percent in the range pH 5.0 to 5.9. 9. The natural pastures had 75 percent of their soil at pH below 6, whereas improved and rotational pastures had only 39 percent below pH 6. 10. Pineapples were planted in acid soils, 75 percent of which were below pH 6. 11. The majority, 68 percent, of the plantains were grown in acid soils below pH 6. 12. Root-crop soils had a systematic distribution throughout the range of pH from below 4 to above 8. 13. Most soils used for soilage (cut grass) had a pH above 6. 14. Eighty-one percent of the sugarcane acreage was found to be in the range of pH 5 to 8. About 36 percent of the cane acreage was below pH 5.5 and in need of liming. 15. Tobacco was grown primarily on acid soils, with 61 percent of its acreage on those below pH 6. 16. No vegetables were found in soils with a pH below 5, and 50 percent were planted in soils with a pH above 6. 17. The pH range for woodland soil was distributed rather evenly from a pH 5 to 7.9. 18. The average pH and range of pH of the soils of Puerto Rico are presented, by soil series, and several examples are given of the relationship between soil pH and soil series.

The heat stability of milk as affected by variations in pH and milk salts

1969 ◽  
Vol 36 (3) ◽  
pp. 343-351 ◽  
Author(s):  
P. A. Morrissey
Keyword(s):  
Calcium Phosphate ◽  
Calcium Ion ◽  
Narrow Range ◽  
Heat Stability ◽  
Salt Composition ◽  
Ion Concentrations ◽  
Ph Values ◽  
Soluble Calcium ◽  
Β Lactoglobulin ◽  
Minimum Heat

SummaryThe maximum and minimum heat stability exhibited by most milks over a relatively narrow range of pH values is shown also by synthetic colloidal calcium caseinate-calcium phosphate systems and even by simple caseinate systems, provided all possess adequate contents of β-lactoglobulin, soluble calcium and phosphate. The phenomenon is not, however, dependent on the presence of the characteristic micellar structure of the casein of milk. The minimum stability observed, usually around pH 6·9, is the most characteristic feature of the phenomenon and arises from heat induced deposition of calcium phosphate on a caseinate/β-lactoglobulin complex. This reaction, which tends to occur to a marked degree at relatively high pH values and calcium ion concentrations, sensitizes the complex to precipitation by calcium ions. The precise pH values at which the maximum and minimum stabilities occur can vary depending on the salt composition of the serum, since the latter can influence the solubility of calcium phosphate.

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