scholarly journals Denitrification in nitric-acid-treated cattle slurry during storage

1993 ◽  
Vol 41 (2) ◽  
pp. 63-80 ◽  
Author(s):  
O. Oenema ◽  
G.L. Velthof
Keyword(s):  
Nitric Acid ◽  
Ph Dependence ◽  
N2o Emission ◽  
Low Ph ◽  
Nh3 Volatilization ◽  
Cattle Slurry ◽  
N2o Production ◽  
Ph Range ◽  
On Farm ◽  
Complete Homogenization

Lowering the pH of cattle slurry with HNO3 was used to reduce NH3 volatilization during storage and after application. Incubation studies were carried out to examine possible NO3 losses and N2O emission from HNO3 treated slurry during storage. Batches of cattle slurry were treated with various amounts of HNO3 to obtain a pH range of 6.0 to 3.0. The slurries were stirred once or twice a week and stored for 6 months at 15 degrees C. Changes in pH, Eh, NO3- and NH4+ concn, and emissions of N2O, CO2 and CH4 were monitored. The loss of NO3- and the emission of N2O were related to slurry pH, being lowest at low pH. Cumulative loss of NO3- ranged from ~40 mmol/kg for slurries of target pH < or =>5.0 to ~400 mmol/kg for slurries of target pH 6.0. Homogenization of the slurries via stirring and addition of H2O2 decreased NO3- loss and H+ consumption. The strong pH dependence of NO3- loss, the production of N2O and the stoichiometry of H+ consumption and NO3- loss indicated that the loss of NO3- was mainly due to microbiological denitrification. Similar N2O production rates in the presence and absence of C2H2 indicated that nitrification was not an important source of N2O. It is concluded that lowering the pH to values 4.5 as well as regular and complete homogenization of the slurry via stirring are important for the success of the on-farm treatment of slurry with HNO3.

scholarly journals Studies of an acid-induced species of purple membrane from Halobacterium halobium

1978 ◽  
Vol 171 (2) ◽  
pp. 469-476 ◽  
Author(s):  
T A Moore ◽  
M E Edgerton ◽  
G Parr ◽  
C Greenwood ◽  
R N Perham
Keyword(s):  
Phase Transition ◽  
New Species ◽  
Temperature Dependence ◽  
Ph Dependence ◽  
Low Ph ◽  
Purple Membrane ◽  
Halobacterium Halobium ◽  
Temperature Dependent ◽  
Ph Range ◽  
Increasing Temperature

A new spectral species of the purple membrane of Halobacterium halobium has been observed below pH 3.2. The formation of this new species is temperature-dependent and is favoured by increasing temperature up to the physiological range of the organism. The rate of formation at pH 3.0 and 22 degrees C is 7.9 × 10-3s-1. The spectral distribution and temperature-dependence of the new species suggest that it may be phototransiet O, stabilized by low pH. Flash-photolytic experiments in the pH range 7.2-2.7 show a pH-dependence corresponding to the static events and are consistent with a single protonation of bacteriorhodopsin below pH 3.22. These results can also be interpreted in terms of the stabilization of phototransient O at low pH. The temperature-dependence of the formation of the acid-induced species may reflect a relationship with the phase transition of the membrane.

Electroanalytical chemistry of vanadium complexes: Electrochemical oxidation of [V(IV)O(nta)(H2O)]-

1989 ◽  
Vol 54 (1) ◽  
pp. 64-69 ◽  
Author(s):  
Roland Meier ◽  
Gerhard Werner ◽  
Matthias Otto
Keyword(s):  
Cyclic Voltammetry ◽  
Electrochemical Oxidation ◽  
Ph Dependence ◽  
Differential Pulse ◽  
Nitrilotriacetic Acid ◽  
Reduced Form ◽  
Vanadium Complexes ◽  
Differential Pulse Polarography ◽  
Electroanalytical Chemistry ◽  
Ph Range

Electrochemical oxidation of [V(IV)O(nta)(H2O)]- (H3nta nitrilotriacetic acid) was studied in aqueous solution by means of cyclic voltammetry, differential pulse polarography, and current sampled DC polarography on mercury as electrode material. In the pH-range under study (5.5-9.0) the corresponding V(V) complex is produced by one-electron oxidation of the parent V(IV) species. The oxidation product is stable within the time scale of cyclic voltammetry. The evaluation of the pH-dependence of the half-wave potentials leads to a pKa value for [V(IV)O(nta)(H2O)]- which is in a good agreement with previous determinations. The measured value for E1/2 is very close to the formal potential E0 calculated via the Nernst equation on the basis of known literature values for log Kox and log Kred, the complex stability constants for the oxidized and reduced form, respectively.

scholarly journals Common Loon, Gavia immer, Breeding Success in Relation to Lake pH and Lake Size Over 25 Years

2009 ◽  
Vol 123 (2) ◽  
pp. 146 ◽  
Author(s):  
Robert Alvo
Keyword(s):  
Breeding Success ◽  
Low Ph ◽  
Single Pair ◽  
Gavia Immer ◽  
Common Loon ◽  
Sulphur Deposition ◽  
Acidic Lakes ◽  
Ph Range ◽  
Lake Size ◽  
Critical Ph

I monitored Common Loon (Gavia immer) breeding success in relation to lake pH (range 4.0–8.5) between 1982 and 2007 on 38 single-pair lakes (5–88 ha) in the Sudbury, Ontario, area. No chicks fledged on lakes with pH < 4.4. Chicks fledged on lakes with slightly higher pH only if the lakes were relatively large. Acidic lakes became less acidic as sulphur dioxide emissions from the Sudbury smelters and sulphur deposition from other long-range sources decreased. Two lakes initially too acidic to support successful loon reproduction eventually had successful reproduction. One loon pair used two large acidic lakes (combined area 140 ha) connected by shallow rapids, and one of the adults made extremely long dives (average = 99 s) while foraging for the chicks. One chick died on that lake after apparently ingesting a very large food item; the lack of smaller items was attributed to the lake’s acidity. My results suggest that a shortage of food for chicks is the main reason why low pH reduces breeding success. I suggest that, for lakes without high levels of dissolved organic carbon (DOC), the critical pH for loon breeding success is approximately 4.3, and the suboptimal pH is approximately 4.4–6.0.

Field study on N2O emission from subsurface wastewater infiltration system under variable loading rates and drying-wetting cycles

2017 ◽  
Vol 76 (8) ◽  
pp. 2158-2166 ◽  
Author(s):  
Ying-Hua Li ◽  
Hai-Bo Li ◽  
Xin-Yang Xu ◽  
Si-Yao Xiao ◽  
Si-Qi Wang ◽  
...  
Keyword(s):  
Field Study ◽  
Conversion Rate ◽  
Oxygen Demand ◽  
N2o Emission ◽  
Conversion Ratio ◽  
Gas Chromatograph ◽  
Variable Loading ◽  
N2o Production ◽  
Loading Rates ◽  
Operation Conditions

In this field study, the impacts of influent loadings and drying-wetting cycles on N2O emission in a subsurface wastewater infiltration (SWI) system were investigated. N2O emitted under different operation conditions were quantified using static chamber and gas chromatograph techniques. N2O conversion rate decreased from 6.6 ± 0.1% to 2.7 ± 0.1% with an increase in hydraulic loading (HL) from 0.08 to 0.24 m3/m2·d. By contrast, N2O conversion rate increased with increasing pollutant loading (PL) up to 8.2 ± 0.5% (PL 4.2 g N/m2·d) above which conversion rate decreased, confirming that N2O production was under the interaction of nitrification and denitrification. Taking into consideration the pollutants (chemical oxygen demand (COD), NH4+-N, NO3−-N and total nitrogen (TN)) removal ratio and N2O emission, optimal loading ranges and drying-wetting modes were suggested as HL 0.08–0.12 m3/m2·d, PL 3.2–3.7 g N/m2·d and 12 h:12 h, respectively. The results revealed that in SWI systems, conversion ratio of influent nitrogen to N2O could be between 4.5% and a maximum of 7.0%.

scholarly journals Managing Ammonia Emissions from Dairy Cows by Amending Slurry with Alum or Zeolite or by Diet Modification

2001 ◽  
Vol 1 ◽  
pp. 860-865 ◽  
Author(s):  
John J. Meisinger ◽  
Alan M. Lefcourt ◽  
Jo Ann S. Van Kessel ◽  
Victor Wilkerson
Keyword(s):  
Dairy Cows ◽  
Nitrogen Sources ◽  
Neutral Detergent Fiber ◽  
Wind Tunnels ◽  
Conservation Strategies ◽  
Nh3 Volatilization ◽  
Available N ◽  
Lactating Dairy Cows ◽  
Potential Contributor ◽  
On Farm

Animal agriculture is a significant source of atmospheric ammonia. Ammonia (NH3) volatilization represents a loss of plant available N to the farmer and a potential contributor to eutrophication in low-nitrogen input ecosystems. This research evaluated on-farm slurry treatments of alum or zeolite and compared three diets for lactating dairy cows in their effectiveness to reduce NH3 emissions. NH3 emissions were compared using a group of mobile wind tunnels. The addition of 2.5% alum or 6.25% zeolite to barn-stored dairy slurry reduced NH3 volatilization by 60% and 55%, respectively, compared to untreated slurry. The alum conserved NH3 by acidifying the slurry to below pH 5, while the zeolite conserved ammonia by lowering the solution-phase nitrogen through cation exchange. The use of alum or zeolite also reduced soluble phosphorus in the slurry. NH3 loss from fresh manure collected from lactating dairy cows was not affected by three diets containing the same level of crude protein but differing in forage source (orchardgrass silage vs. alfalfa silage) or neutral detergent fiber (NDF) content (30% vs. 35% NDF). NH3 losses from the freshly excreted manures occurred very rapidly and included the urea component plus some unidentified labile organic nitrogen sources. NH3 conservation strategies for fresh manures will have to be active within the first few hours after excretion in order to be most effective. The use of alum or zeolites as an on-farm amendment to dairy slurry offers the potential for significantly reducing NH3 emissions.

scholarly journals Impact of rice-fish/shrimp co-culture on the N2O emission and NH3 volatilization in intensive aquaculture ponds

2019 ◽  
Vol 655 ◽  
pp. 284-291 ◽  
Author(s):  
Fengbo Li ◽  
Jinfei Feng ◽  
Xiyue Zhou ◽  
Chunchun Xu ◽  
M. Haissam Jijakli ◽  
...  
Keyword(s):  
N2o Emission ◽  
Nh3 Volatilization ◽  
Aquaculture Ponds ◽  
Rice Fish ◽  
Intensive Aquaculture

pH dependence of kinetics and steady-state block of cardiac sodium channels by lidocaine

1993 ◽  
Vol 264 (5) ◽  
pp. H1588-H1598 ◽  
Author(s):  
D. J. Wendt ◽  
C. F. Starmer ◽  
A. O. Grant
Keyword(s):  
Steady State ◽  
Sodium Channel ◽  
Local Anesthetic ◽  
Ph Dependence ◽  
Membrane Depolarization ◽  
Low Ph ◽  
Proton Exchange ◽  
Phasic Block ◽  
Cardiac Sodium Channels ◽  
External Ph

The local anesthetic-class antiarrhythmic drugs produce greater depression of conduction in ischemic compared with normal myocardium. The basis for this relatively selective action is uncertain. A model of the pH-dependent interaction of tertiary amine drugs with the sodium channel suggests that the low pH occurring during ischemia slows drug dissociation from the channel by changing the drug's protonation. The importance of the proton exchange reaction and the effect of overall slowing of drug dissociation on steady-state sodium channel blockade is uncertain. We have measured whole cell sodium channel current in rabbit atrial myocytes during control and exposure to lidocaine while external pH was varied between 6.8 and 7.8 at membrane potentials of -140, -120, and -100 mV. Tonic blockade was little influenced by external pH. Decreasing the external pH from 7.8 to 6.8 slowed both the rate of development of phasic block and recovery from the block. Decreasing the membrane potential from -140 to -100 mV increased the degree of phasic block attained in the steady state. Block was further enhanced when low pH was combined with membrane depolarization. Experiments in which deuterium ions were substituted for protons suggest that the kinetics of proton exchange is not rate limiting in the dissociation of drugs from the sodium channel. We conclude that it is the combined effect of low pH and membrane depolarization that may be critical in the enhanced blocking action of local anesthetic-class drugs during ischemia.

Oxidation of Nickel(II) and Manganese(II) by Peroxodisulfate in Aqueous Solution in the Presence of Molybdate. Crystal Structure of the (NH4)6[NiMo9O32].6H2O Product

1992 ◽  
Vol 45 (12) ◽  
pp. 1943 ◽  
Author(s):  
SJ Dunne ◽  
RC Burns ◽  
GA Lawrance
Keyword(s):  
Rate Constant ◽  
Linear Dependence ◽  
Ph Dependence ◽  
Order Rate Constant ◽  
X Ray Diffraction ◽  
X Ray ◽  
First Order ◽  
Oxidant Concentration ◽  
Ph Range ◽  
Kinetics Of

Oxidation of Ni2+,aq, by S2O82- to nickel(IV) in the presence of molybdate ion, as in the analogous manganese system, involves the formation of the soluble heteropolymolybdate anion [MMogO32]2- (M = Ni, Mn ). The nickel(IV) product crystallized as (NH4)6 [NiMogO32].6H2O from the reaction mixture in the rhombohedra1 space group R3, a 15.922(1), c 12.406(1) � ; the structure was determined by X-ray diffraction methods, and refined to a residual of 0.025 for 1741 independent 'observed' reflections. The kinetics of the oxidation were examined at 80 C over the pH range 3.0-5.2; a linear dependence on [S2O82-] and a non-linear dependence on l/[H+] were observed. The influence of variation of the Ni/Mo ratio between 1:10 and 1:25 on the observed rate constant was very small at pH 4.5, a result supporting the view that the precursor exists as the known [NiMo6O24H6]4- or a close analogue in solution. The pH dependence of the observed rate constant at a fixed oxidant concentration (0.025 mol dm-3) fits dequately to the expression kobs = kH [H+]/(Ka+[H+]) where kH = 0.0013 dm3 mol-1 s-1 and Ka = 4-0x10-5. The first-order dependence on peroxodisulfate subsequently yields a second-order rate constant of 0.042 dm3 mol-1 s-1. Under analogous conditions, oxidation of manganese(II) occurs eightfold more slowly than oxidation of nickel(II), whereas oxidation of manganese(II) by peroxomonosulfuric acid is 16-fold faster than oxidation by peroxodisulfate under similar conditions.

scholarly journals Modelling of pH-dependence to develop a strategy for stabilising mAbs at acidic steps in production

2019 ◽  
Author(s):  
Max Hebditch ◽  
Ryan Kean ◽  
Jim Warwicker
Keyword(s):  
Experimental Data ◽  
Design Principle ◽  
Ph Dependence ◽  
Low Ph ◽  
Viral Clearance ◽  
Acidic Ph ◽  
Antibody Therapeutics ◽  
Acid Environment ◽  
Pass Through ◽  
Acid Stable

AbstractEngineered proteins are increasingly being required to function or pass through environmental stresses for which the underlying protein has not evolved. A major example in health are antibody therapeutics, where a low pH step is used for purification and viral clearance. In order to develop a computational model for analysis of pH-stability, predictions are compared with experimental data for the relative pH-sensitivities of antibody domains. The model is then applied to proteases that have evolved to be functional in an acid environment, showing a clear signature for low pH-dependence of stability in the neutral to acidic pH region, largely through reduction of saltbridges. Interestingly, an extensively acidic protein surface can maintain contribution to structural stabilisation at acidic pH through replacement of basic sidechains with polar, hydrogen-bonding groups. These observations form a design principle for engineering acid-stable proteins.

scholarly journals THE ABSORPTION SPECTRUM OF VISUAL PURPLE

1938 ◽  
Vol 21 (4) ◽  
pp. 411-430 ◽  
Author(s):  
Aurin M. Chase ◽  
Charles Haig
Keyword(s):  
Absorption Spectrum ◽  
Absorption Spectra ◽  
Light Transmission ◽  
Low Ph ◽  
The Other ◽  
Distilled Water ◽  
Color Purity ◽  
Chemical Combination ◽  
Ph Range ◽  
Sensitive Group

The absorption spectra of visual purple solutions extracted by various means were measured with a sensitive photoelectric spectrophotometer and compared with the classical visual purple absorption spectrum. Hardening the retinas in alum before extraction yielded visual purple solutions of much higher light transmission in the blue and violet, probably because of the removal of light-dispersing substances. Re-extraction indicated that visual purple is more soluble in the extractive than are the other colored retinal components. However, the concentration of the extractive did not affect the color purity of the extraction but did influence the keeping power. This suggests a chemical combination between the extractive and visual purple. The pH of the extractive affected the color purity of the resulting solution. Over the pH range from 5.5 to 10.0, the visual purple color purity was greatest at the low pH. Temperature during extraction was also effective, the color purity being greater the higher the temperature, up to 40°C. Drying and subsequent re-dissolving of visual purple solutions extracted with digitalin freed the solution of some protein impurities and increased its keeping power. Dialysis against distilled water seemed to precipitate visual purple from solution irreversibly. None of the treatments described improved the symmetry of the unbleached visual purple absorption spectrum sufficiently for it to resemble the classical absorption spectrum. Therefore it is very likely that the classical absorption spectrum is that of the light-sensitive group only and that the absorption spectra of our purest unbleached visual purple solutions represent the molecule as a whole.

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