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Query: UMLS:C0847097 (acidity)
 15,165 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Annular denuder-filter pack sampling systems were used to make indoor and outdoor measurements of aerosol strong H+, SO4(2-), NH4+, NO3- and NO2-, and the gaseous pollutants SO2, HNO3, HONO and NH3 during summer and winter periods in Boston, Massachusetts. Outdoor levels of SO2, HNO3, H+ and SO4(2-) exceeded their indoor concentrations during both seasons. Winter indoor/outdoor ratios were lower than during the summer, probably due to lower air exchange rates during the winter period. During both monitoring periods, indoor/outdoor ratios of aerosol strong H+ were 40-50 percent of the indoor/outdoor SO4(2-) ratio. Since aerosol strong acidity is typically associated with SO4(2-), this finding is indicative of neutralization of the acidic aerosol by the higher indoor NH3 levels. Geometric mean indoor/outdoor NH3 ratios of 3.5 and 23 respectively were measured for the summer and winter sampling periods. For HONO, NH3, NH4+ and NO2-, indoor concentrations were significantly higher than ambient levels. Indoor levels of NO3- were slightly less than outdoor concentrations.
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PMID:Indoor and outdoor concentrations of inorganic acidic aerosols and gases. 205 63

Reactions of cis-diamminedichloroplatinum(II) with phosphonoformic acid (PFA), phosphonoacetic acid (PAA), and methylenediphosphonic acid (MDP) yield various phosphonatoplatinum(II) chelates which were characterized by phosphorus-31 NMR spectroscopy. The P-31 resonances for the chelates appear at 6-12 ppm downfield as compared to the uncomplexed ligands. All complexes exhibit monoprotic acidic behavior in the pH range 2-10. The chemical shift-pH profiles yielded acidity constants, 1.0 x 10(-4), 1.5 x 10(-4), and 1.3 x 10(-6) M-1, for the PFA, PAA, and MDP chelates. In addition to the monomeric chelate, MDP formed a bridged diplatinum(II,II) complex when it reacted with cis-Pt (NH3)2(H2O)2(2)+. The P-31 resonance for this binuclear complex appears at 22 ppm downfield from the unreacted ligand. Rate data for the complexation reactions of the phosphonate ligands with the dichloroplatinum complex are consistent with a mechanism in which a monodentate complex is formed initially through rate-limiting aquation process of the platinum complex, followed by a rapid chelation. For the PFA and PAA complexes, initial binding sites are the carboxylato oxygens. Implications of the various binding modes of the phosphonates in relationship to their antiviral activities are discussed.
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PMID:Phosphonato complexes of platinum(II): kinetics of formation and phosphorus-31 NMR characterization studies. 215 Aug 56

Atmospheric gaseous pollutants (NO2, SO2, NH3, HNO3) and related ionic species in water-soluble fine particulates and rainwater were monitored from September 1986 to January 1987 with the aim of estimating the acid deposition over a rural area near Rome. A wet-only rain collector and an annular denuder-filter pack sampling system for gases and aerosols were employed to avoid chemical artifact formation. A comparison of the wet and dry deposition rates indicates that atmospheric removal by precipitation was the dominant sink for sulfate and nitrate at the sampling site. Ion balance analysis showed that the main compounds present in aerosols were (NH4)2SO4 and NH4NO3, since the ammonium neutralization factor approached 100% and the acidity content was very low. The marked enrichment of H+, SO4(2-) and NO3- in precipitation compared with NH4+ could be explained by assuming either that SO2 and NO2 are oxidized in cloud droplets or that acidic sulfate and nitrate are scavenged directly in-cloud or below-cloud.
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PMID:Characterization of a rural area in terms of dry and wet deposition. 285 79

Mineralocorticoid plays a role in urinary acidification and acid-base balance, but the response of the inner medulla to aldosterone has not been elucidated. A model of selective aldosterone deficiency (SAD) with hyperkalemia and hyperchloremic metabolic acidosis was employed to assess segmental acidification by measuring in situ pH, titratable acidity (TA) and total ammonia (Am). Hydrogen ion secretion was also examined as a function of the increment in in situ PCO2 in the collecting duct during bicarbonate loading. SAD rats were compared to ADX controls that received adrenalectomy and chronic replacement of gluco- and mineralocorticoid and to rats with chronic metabolic acidosis induced by oral NH4Cl (CMA). Both fractional and absolute delivery of Am to the loop of Henle was lower in SAD vs. CMA rats (1.34 to 3.63 mM, P less than 0.01). Delivery of Am to the base and tip collecting duct (BCD and TCD) was also markedly lower in SAD (1.50 vs. 0.52 and 1.77 vs. 0.47 mM, respectively, P less than 0.01). Net addition of Am and net acid between BCD and TCD, observed in CMA rats, was not observed in SAD despite equivalent degrees of systemic metabolic acidosis. Similarly, the concentration gradient favoring transfer of NH3 between loop of Henle and CD was reduced in SAD. During bicarbonate loading the increment in PCO2 at BCD, TCD and in final urine was significantly lower in SAD rats than in adrenal intact bicarbonate-loaded rats. Therefore, the acidification defect in this model of SAD appears to be a result of a decrease in ammonia production and delivery to the loop of Henle, impaired transfer from loop to collecting duct and reduction in the rate of H+ secretion by the collecting duct.
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PMID:Effect of selective aldosterone deficiency on acidification in nephron segments of the rat inner medulla. 318 58

Ammonia excretion rates of channel catfish, Ictalurus punctatus, little skate (Raja erinacea), and blue crab (Callinectes sapidus) were measured in experimental regimes which permitted simultaneous assessment of the partial pressure gradients for nonionized NH3 and the chemical concentration gradients of NH4+. Under conditions of low external ammonia, the average ammonia excretion was +295 microM kg-1 h-1 for catfish, +149 microM kg-1 h-1 for blue crabs, and +59 microM kg-1 h1 for skates with partial pressure gradients of +72.5 mu Torr, +413 mu Torr, and +24.4 mu Torr, respectively; and [NH4+] gradients of +189 microM l-1, +643 microM l-1, and +107 microM l-1 (positive indicating greater from inside to medium). When the external ammonia was increased to 1.15 mM l-1, both gradients were reversed, and the net ammonia movement was initially from the external water into all three species. In the catfish the inward movement ceased, however, and ammonia excretion eventually resumed in the face of reversed gradients of both NH3 partial pressure and [NH4+]. Unidirectional Na+ influx, indicative of a Na+/NH4+ exchange, did not increase. The ammonia data, changes in titratable acidity, and net apparent H+ efflux were all consistent with a linked extrusion of internal NH4+ for external H+. Incorporation of such an exchange into a computer simulation model of the ammonia equilibrium and exchange system duplicated the experimental data. Other hypotheses failed to match experimental data, or failed to predict internal ammonia levels lower than outside. In the crab, internal ammonia levels rose rapidly to concentrations and partial pressures above the external medium until excretion was reestablished, with no evidence of maintenance of a reversed gradient. In the skate, internal concentrations rose appreciably in the first hour and continued to rise for 6-8 h, with no resumption of ammonia excretion. The interspecies differences appear to be due at least partly to differences in ammonia permeability of the gills.
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PMID:Responses to reversed NH3 and NH4+ gradients in a teleost (Ictalurus punctatus), an elasmobranch (Raja erinacea), and a crustacean (Callinectes sapidus):evidence for NH4+/H+ exchange in the teleost and the elasmobranch. 374 31

It is known that Pi normally provides the major source of non-NH3 urinary buffer and that Pi-buffered renal H+ excretion (titratable acidity, TA) accounts for a large fraction of daily renal net acid excretion (NAE). Whether the presence of luminal non-NH3 buffers is a prerequisite to normal renal regulation of systemic acid-base equilibrium under any conditions has not been investigated. Accordingly, I investigated whether chronic renal regulation of plasma (p) [HCO3] might be impaired under conditions of normophosphatemic hypophosphaturia (NHP) produced by short-term dietary Pi restriction. During a steady-state of HCl-induced acidosis in NaCl-replete NHP dogs (group 1A, N = 6), [HCO3-]p averaged 14.1 +/- 0.6 mEq/liter and arterial (a) [H+] averaged 54 +/- 2 nEq/liter. Substitution K+ 2.5 mEq/kg as neutral Pi for equivalent dietary KCl for 7 to 8 days resulted in significant amelioration of acidosis (delta [HCO3-]p + 2.2 +/- 0.5 mEq/liter, P less than 0.01; delta [H+]a -6 +/- 2 nEq/liter, P less than 0.01) in association with a cumulative increment (sigma delta) in TA excretion (+ 103 mEq, P less than 0.001) and NAE (+ 22 mEq). To investigate whether Pi-induced amelioration of acidosis was related to enhanced urinary buffer capacity, an additional group (group 1B, N = 5) with NHP and chronic HCl acidosis was administered the non-Pi buffer, neutral creatinine (5.0 mmoles/kg daily). As with Pi, acidosis was ameliorated by creatinine administration and sigma delta NAE increased.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Hypophosphaturia impairs the renal defense against metabolic acidosis. 651 76

A large number of studies have indicated associations between particulate air pollution and adverse health outcomes. Wintertime air pollution in particular has been associated with increased mortality. Identification of causal constituents of inhalable particulate matter has been elusive, although one candidate has been the acidity of the aerosol. Here we report measurements of acidic aerosol species made for approximately 1.5 years in Erfurt, Germany, and Sokolov, Czech Republic. In both locations, the burning of high-sulfur coal is the primary source of ambient air pollution. Twenty-four-hour average measurements were made for PM10, [particulate matter with an aerodynamic diameter (da) < or = 10 microns], as well as fine particle (da < 2.5 microns) H+ and SO4(2-) for the entire study. Additionally, separate day and night measurements of fine particle H+, SO4(2-), NO3-, and NH4+ and the gases, SO2, HNO3, HONO, and NH3 were collected with an annular denuder/filter pack system over a 7-month (late winter-summer) period with additional measurements during pollution episodes the following winter. At both sites, 24-hr SO2 (mean concentrations of 52 micrograms/m3, with peak levels of > 585 micrograms/m3) and PM10 (mean concentration 60 micrograms m3) concentrations were quite high. However, aerosol SO4(2-) concentrations (mean concentration of approximately 10 micrograms/m3) were not as great as expected given the high SO2 concentrations, and acidity was very low (mean concentration of < 1 microgram/m3, with peak levels of only 7 micrograms/m3). Low acidity is likely to be the result of NH3 neutralization and slow conversion of SO2 to SO4(2-).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Measurement of acidic aerosol species in eastern Europe: implications for air pollution epidemiology. 765 78

Indoor acid aerosol, nitric acid (HNO3), and ammonia (NH3) concentrations were measured in 47 homes in State College, Pennsylvania, during the summer of 1991. From each home, 12-hour indoor, 12- and 24-hour outdoor, and 12-hour air exchange samples were collected continuously over a 5-day period. Additionally, questionnaires were administered daily by field technicians to obtain information on house occupant number, ventilation, gas stove use, pets, and other housing characteristics. In this paper, we discuss the relationship between NH3 and corresponding concentrations of aerosol strong acidity (H+) and HNO3 inside these homes. As part of this analysis, we also examined indoor/outdoor concentration relationships and identified housing factors that may influence indoor levels. In State College, indoor NH3 concentrations were higher than corresponding outdoor levels, with air conditioner use, air exchange rates, and occupant number identified as important determinants of indoor levels. Indoor concentrations of both H+ and HNO3 were substantially lower than outdoor levels, as homes with air exchange rates less than one exchange per hour were found to have essentially no acid indoors. These low H+ and HNO3 levels likely resulted from their reaction with indoor NH3 and with indoor surfaces. Indoor NH3 concentrations were higher than outdoor levels, indicating the presence of indoor NH3 sources; however, correlations between indoor NH3 and both pets and occupants, its primary indoor sources, were weak and negative, respectively. Mass balance models that included an NH3 neutralization term were found to predict indoor H+ concentrations reasonably well, representing a substantial improvement over outdoor concentrations alone. The accumulation of NH3 indoors was found to be the primary determinant of indoor H+ and HNO3 levels.
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PMID:The relationship between airborne acidity and ammonia in indoor environments. 789 66

Naturally contaminated yellow corn containing 12500 ng/g of aflatoxin B1 (AFB1) was ground and blended with non-contaminated corn to obtain various levels of AFB1 (7500, 6300, 400, 354, and 17 ng AFB1/g). All samples were exposed to ammonia treatment under various conditions for 60 min. Treatment variables included ammonia concentration, moisture level of the corn, temperature, and pressure applied. The moisture content of the corn (8%) was adjusted to 12% and 16%, respectively. Four ammonia treatments were conducted for each moisture level: (a) 1.5% and 2.0% gaseous NH3 at 40-45 degrees C and 55 psi; (b) aqueous NH4OH (2.0% as NH3) at 121 degrees C and 17 psi; (c) sequential treatment of (a) and (b); and (d) aqueous NH4OH (2.0% as NH3) at 25 degrees C and 55 psi. For the treatment with 2% gaseous NH3, the reduction in levels of AFB1 in samples containing 12% moisture ranged from 52.7 to 67.7%, while in samples containing 16% moisture, the reduction ranged from 79.4 to 93.1%. Treatment with NH4OH alone at elevated temperatures (b) or following gaseous NH3 treatment (c) resulted in a reduction of the AFB1 content by greater than 99%. Treatment with NH4OH at 25 degrees C (d) showed a lower efficiency in reducing AFB1 levels. The permanency of the process, i.e. reversion of inactivated AFB1 to the parent compound, was studied by exposing the ammonia-treated corn to HCl (pH = 2.0 at 37 degrees C for 2 h) to simulate stomach acidity. The results showed no significant reversion of aflatoxin (reversibility less than 0.05%). These findings suggest that at high temperature aqueous NH4OH or gaseous NH3 can be used effectively to reduce AFB1 in corn. The present study also revealed that the moisture level of the product and holding temperature were the crucial factors that influenced the efficacy of aflatoxin decontamination by ammoniation.
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PMID:Efficacy and permanency of ammonia treatment in reducing aflatoxin levels in corn. 789 70

Third-crop mixed grass-legume forage and corn were ensiled in 70-tonne bunker silos to evaluate the effects of a commercial carbohydrase enzyme-inoculant mixture (220 ml/tonne) and an experimental enzyme-inoculant mixture (264 ml/tonne) on silage fermentation and composition, ruminal degradation, and milk production. Twelve Jersey and 24 Holstein early lactation cows were fed one of four TMR at 32.5:32.5:35.0 haycrop silage:corn silage:concentrate (DM basis) containing a combination of treated and untreated silages from d 2 to 100 of lactation. Bunker silages were incubated twice in situ in fistulated cows in each dietary treatment to determine rates of DM and NDF degradation. Treatment of haycrop silage significantly reduced silage pH and acetic acid concentration and increased titratable acidity, lactic acid concentration, lactate: acetate ratio, and DM and NDF disappearances after 24 h of ruminal incubation. Treated haycrop silage increased DMI:BW ratio and daily production of milk, milk protein, and SNF of early lactation cows. Application of the experimental mixture to corn silage did not change silage fermentation or composition, except that the concentration of NH3 was reduced. Enxyme-treated corn silage did not improve DMI and slightly reduced daily milk production in early lactation cows.
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PMID:Effects of enzyme-inoculant systems on preservation and nutritive value of haycrop and corn silages. 818 74


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