SEARCH · PubMed Health

Results for “NITRIC ACID”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 505 records · Page 28Linked to original sources

PubMed2001

Determination of lead in fine particulates by slurry sampling electrothermal atomic absorption spectrometry.

A simple method for determining lead in fine particulates (PM2.5) by using electrothermal atomic absorption spectrometry (ETAAS) has been developed. Particulates collected on Nuclepore filter by using a dichotomous sampler were suspended in diluted nitric acid after ultrasonic agitation. The dislodging efficiency is nearly 100% after agitation for 5 min. In order to study the suspension behavior of PM2.5 in solvents, a Brookhaven ZetaPlus Particle Size Analyzer was used to determine the particle size distribution and suspension behavior of air particulates in the solvent. The pre-digestion and modification effect of nitric acid would be discussed. Palladium was added as a chemical modifier and the temperature program of ETAAS was changed in order to improve the recovery. The slurry was introduced directly into a graphite tube for atomization. The metal content in the sample was determined by the standard addition method. In addition, a conventional acid digestion procedure was applied to verify the efficiency of the slurry sampling method. It offers a quick and efficient alternative method for heavy metal characterization in fine particulates.

Environmental Pollution↗

PubMed2006

Effect of postinjury intravenous or intrathecal methylprednisolone on spinal cord excitatory amino-acid release, nitric oxide generation, PGE2 synthesis, and myeloperoxidase content in a pig model of acute spinal cord injury.

STUDY DESIGN: Prospective, randomized, in vivo acute spinal cord injury in pigs. SETTING: Department of Anesthesiology, University of Washington, Seattle, WA, USA. OBJECTIVES: To determine whether postinjury methylprednisolone could reduce the generation of known mediators of secondary neurological injury. METHODS: Intrathecal microdialysis probes were used to sample cerebrospinal fluid (CSF) for measurement of PGE(2), glutamate, and citrulline (a byproduct of nitric oxide generation), before and after spinal cord injury in anesthetized pigs. The spinal cord was removed at the end of the study for measurement of myeloperoxidase and methylprednisolone concentrations. Animals were randomly allocated to receive intravenous methylprednisolone (30 mg/kg bolus then 3.4 mg/kg/h), intrathecal methylprednisolone (5 mg bolus then 5 mg/h), or saline, beginning 30 min after the spinal cord was injured by using a modification of the Allen weight drop technique. RESULTS: Spinal cord injury significantly increased the amount of glutamate, PGE(2), myeloperoxidase, and citrulline, recovered from the CSF dialysates. However, neither intravenous nor intrathecal methylprednisolone administered after injury had any effect on the magnitude of the increase in any of the measured biochemicals. Intrathecal methylprednisolone administration produced a spinal cord methylprednisolone concentration that was eight times greater, and a plasma concentration that was 32 times less, than that achieved with intravenous administration. CONCLUSIONS: Contrary to earlier animal studies in which methylprednisolone was administered either before or immediately after spinal cord injury, we found no effect of intravenous or intrathecal methylprednisolone on any of the parameters measured when administered 30 min postinjury.

Analysis of Variance↗

PubMed2004

Preconcentration of gallium by coprecipitation with synthetic zeolites prior to determination by electrothermal atomic absorption spectrometry.

Synthetic zeolites were dissolved in nitric acid, and the resulting solution used as a coprecipitant for the preconcentration of trace amounts of gallium in water samples prior to determination by electrothermal atomic absorption spectrometry (ETAAS). The gallium preconcentration conditions and the ETAAS measurement conditions were optimized. Gallium was quantitatively concentrated with the zeolites coprecipitate from pH 6.0 to 8.0. The coprecipitate was easily dissolved in nitric acid, and an aliquot of the resulting solution was introduced directly into a tungsten metal furnace. The atomic absorbance of gallium in the resulting solution was measured by ETAAS. An ashing temperature of 400 degrees C and an atomizing temperature of 2600 degrees C were selected. The calibration curve was linear up to 3.0 microg of gallium and passed through the origin. The detection limit (S/N > or = 3) for gallium was 0.08 microg/100 cm3. The relative standard deviation at 1.0 microg/100 cm3 was 3.0% (n = 5). The proposed method has been successfully applied to trace gallium analysis in environmental water samples.

Journal Article↗

PubMed1998

Ultrasonic extraction and field-portable anodic stripping voltammetry for the determination of lead in workplace air samples.

An on-site, field-portable analytical method for the determination of lead in workplace air samples, based on the use of ultrasonic extraction and anodic stripping voltammetry (ASV), was evaluated. Workplace air samples were obtained using a standard method involving particulate collection onto mixed cellulose ester membrane filters. Samples were collected at work sites where airborne particulates were generated from the abrasive blasting of lead-containing paint on highway bridges. Ultrasonic extraction (UE) of air filter samples in diluted nitric acid, followed by portable ASV, was used for the determination of lead. Also, performance evaluation samples consisting of reference materials of known lead concentration were subjected to the UE-ASV procedure for lead determination. Confirmatory analyses of the air filters and performance evaluation samples subjected to the UE-ASV lead measurement method were conducted by hotplate digestion in concentrated nitric acid and 30% hydrogen peroxide, followed by inductively coupled plasma-atomic emission spectrometric (ICP-AES) determination of lead. Recoveries of lead from performance evaluation materials (when using the UE-ASV method) were found to be quantitative. The performance of the UE-ASV method for lead in air filters was found to be acceptable, as evaluated by comparison with results from hotplate strong acid digestion followed by ICP-AES analysis. Based on the results of this study, the ultrasonic extraction/portable ASV procedure demonstrates potential for the on-site determination of lead in personal breathing zone and area air samples.

Air Pollutants, Occupational↗

PubMed1981

Zinc determined in 10-microL serum or urine samples by flameless atomic absorption spectrometry.

We describe a precise flameless atomic absorption spectrometric method requiring only 10 microL of sample, which thus permits repeated measurements in the neonate. Standard curves covering the range of 0 to 30 mg of zinc per liter, with standards in various matrixes (albumin, glycerol, serum, or nitric acid) had slopes ranging from 0.49 to 1.17, relative to that for aqueous standards. We prepared low-zinc matrixes, which had slopes similar to that of serum, by dialyzing serum or a 50 g/L solution of albumin vs a buffered zinc-free dialysis fluid containing appropriate inorganic constituents. Use of thoroughly de-ionized water, reagent-grade chemicals, "ultrapure" nitric acid, specified disposable plastic ware, and appropriate pipet tip-rinsing techniques minimized extraneous contamination with zinc. Concentrations of zinc in serum calculated from a "rational-method" calibration algorithm fit to the standard curve agreed well with independent determinations by flame atomic absorption spectrometry.

Humans↗

PubMed2001

The detection of large HNO3-containing particles in the winter Arctic stratosphere.

Large particles containing nitric acid (HNO3) were observed in the 1999/2000 Arctic winter stratosphere. These in situ observations were made over a large altitude range (16 to 21 kilometers) and horizontal extent (1800 kilometers) on several airborne sampling flights during a period of several weeks. With diameters of 10 to 20 micrometers, these sedimenting particles have significant potential to denitrify the lower stratosphere. A microphysical model of nitric acid trihydrate particles is able to simulate the growth and sedimentation of these large sizes in the lower stratosphere, but the nucleation process is not yet known. Accurate modeling of the formation of these large particles is essential for understanding Arctic denitrification and predicting future Arctic ozone abundances.

Journal Article↗

PubMed1992

Pharmacokinetics of the organic nitrates trans-2-amino-2-methyl-N-(4- nitroxycyclohexylmethyl)-propionamide in dogs, and of 4-(2-nitroxyethyl)-piperidine in dogs and in monkeys.

The plasma concentrations of the organic nitrates (nitric acid esters) trans-2-amino-2-methyl-N-(4-nitroxycyclohexylmethyl)-propionamide (BM 12.1200) and of 4-(2-nitroxyethyl)-piperidine (BM 12.1173, CAS 129999-77-5) were determined in dog plasma by capillary gas chromatography with electron capture detection (GC-ECD). Intra- and interassay variation coefficients of the gas chromatographic analysis lay between 2.9 and 8.8%; recoveries amounted to 50-62%. Both nitric acid esters were absorbed quickly and attained maximum plasma levels within 1 h. The total bioavailability of BM 12.1200 is > 55%, and that of BM 12.1173 is 63%; their elimination half-lives are, respectively, 4.2 h and 1.3-1.4 h. Thus, BM 12.1173 and the reference substance IS-5-MN (isosorbide-5-mononitrate) show corresponding elimination half-lives. These results regarding the pharmacokinetic parameters of BM 12.1173 were confirmed by cross-over application of BM 12.1173 and IS-5-MN to Macaca Arctoides. In comparison to all species which have been treated with IS-5-MN thus far, the shortest elimination half-life (t1/2 = 0.6 h) is found in monkeys.

Administration, Oral↗

PubMed1983

[60-CO organic complexes formed in the seawater by the addition of amino acids and their pretreatment for chemical analysis].

By sodium nickel ferrocyanide coprecipitation, 60Co and 137Cs are simultaneously collected by nearly 99% recoveries from the unaged seawater. But this coprecipitation is not effective for the recovery of the 60Co complexed with organic ligands which would exist in natural seawater. In order to obtain the effective recoveries for these complexed 60Co, various pretreatments were investigated by using model samples containing the 60Co aged with several amino acids. In the acidification of these samples by nitric acid as 1 pretreatment, a large portion of these complexed 60Co was dissociated, especially by heating samples at 90-95 degrees C. The recoveries of 60Co were ranging from 90 to 97%. On the other hand, the usage of potassium peroxodisulfate (4.0 x 10(-4)-2.0 x 10(-2) M) as another pretreatment method elevated the recoveries of these complexed 60Co by more than 99% by heating samples above 90 degrees C. These 2 pretreatment methods were also effective for recoveries of 137Cs ion.

Amino Acids↗

PubMed2001

Gaseous and particulate air pollutants in the Northeastern Mediterranean Coast.

The concentrations of sulfur dioxide (SO2), ammonia (NH3) and particulate matter were measured for a 6-month period and the concentration of gas phase nitric acid (HNO3) was measured for a 1-month period in the North-eastern Mediterranean atmosphere (Küçük Calticak, Antalya) using a 'filter pack' system that was developed and optimised in our laboratory. Among all the gas phase pollutants, HNO3 had the lowest concentration (0.42 microg m(-3)) followed by ammonia. Most of the measured parameters showed variation in time depending on strengths of source regions and meteorological conditions. Nitric acid is found mostly in particulate form, but gas to particulate partitioning of SO2 shows seasonal variation. Wind trajectory analyses indicate that the major contribution to the observed concentrations come mostly from Eastern Europe and Blacksea regions as well as the southern sector.

Journal Article↗

PubMed2001

[Upper gastrointestinal tract injury caused by ingestion of caustic substances].

BACKGROUND: To determine the distribution, extension and severity of injuries produced by the ingestion of caustic substances in the upper gastrointestinal tract, and to assess the relationship of these factors with the type of caustic substance ingested, whether intake was accidental or deliberate and the appearance of strictures or death. PATIENTS AND METHOD: Between 1993 and 1999, 138 patients (74 males and 84 females) who underwent upper gastrointestinal endoscopy in our unit within the first 24 hours after ingestion of caustic substances were included in the study. Mean age was 47 years (14-97 years). The severity of caustic injury was evaluated using the classification of Showkat et al. RESULTS: The type of caustic substance ingested was as follows: lye in 84 patients (53%), nitric acid in 21 (13%), different caustic mixtures in 43 (27%) and unknown in 10 patients (6%). Lesions were grade I in 51 patients(32%), grade II in 33 (21%) and grade III in 20 (13%). No lesions were seen in 54 patients (34%). Of the 158 patients, gastric injury was found in 91 (57.5%), esophageal burn in 72 (45.5%) and duodenal injury in 28 (18%). Ingestion was accidental in 80 patients (51%) and voluntary in 62 (39%); the reasons for ingestion were unclear in 16 patients (10%). Voluntary ingestion and acid use were associated with greater severity of lesions (p < 0.0005). Eight patients (5.0%) died, 10 patients (6.3%) required emergency surgery, and 7 (4.4%) developed esophageal-gastric strictures that required surgery or endoscopic treatment. CONCLUSIONS: The most common type of caustic substance ingested was lye. In 66% of the patients, lesions were absent or superficial. The more severe injuries, producing strictures and higher mortality, were related to voluntary and nitric acid ingestion. The part of the digestive tract most frequently affected after lye and acid ingestion was the stomach.

Adolescent↗

PubMed1984

Determination of copper in biological materials by atomic absorption spectroscopy: a reevaluation of the extinction coefficients for azurin and stellacyanin.

A new method for the determination of copper in biological materials by graphite furnace atomic absorption spectroscopy is presented. This new procedure is an extension of the classic method of standard additions, where the analyte concentration is determined in a series of identical samples to which various amounts of metal standard have been added. The concentration of metal in the original sample is determined from an extrapolation of a plot of absorbance versus added analyte. In the new method, the amount of copper is determined by the method of standard additions for different concentrations of the sample under investigation as well. From an extrapolation of the data, the concentration of copper in the absence of interfering matrix is obtained. Studies with fetal bovine serum demonstrate that the new extrapolation technique is precise. Furthermore, considerably more copper is detected than by the classic method of standard additions applied to a nitric acid treated sample. The matrix effects of phosphate, nitrate, albumin, and serum were also examined. Both phosphate and serum, at physiological pH, decrease the detectability of added copper, while nitrate and albumin were without effect. The accuracy of this method has been verified by determining the extinction coefficients of stellacyanin and azurin. The values obtained, 4.33 X 10(3) and 3.75 X 10(3) M-1 cm-1, respectively, are considerably different from those determined by the method of standard additions on nitric acid digests of these proteins, but were close to values previously reported and determined colorimetrically.

Animals↗

PubMedDate not supplied

Graft copolymerization of ethyl acrylate onto cellulose using ceric ammonium nitrate as initiator in aqueous medium.

Ceric ammonium nitrate (CAN) in the presence of nitric acid has been used as efficient initiator for graft copolymerization of the ethyl acrylate onto cellulose at 35.0 +/- 0.1 degrees C. Graft copolymerization of ethyl acrylate onto cellulose has taken place through the radical initiation process. The graft yield and other grafting parameters have been evaluated by varying concentration of ethyl acrylate from 2.5 x 10(-1) to 15.0 x 10(-1) mol dm(-3) and ceric ammonium nitrate from 5.0 x 10(-3) to 25.0 x 10(-3) mol dm(-3) at constant concentration of the nitric acid (8.0 x 10(-2) mol dm(-3)). The rate of graft copolymerization has shown 1.5 order with respect to the concentration of the ceric ammonium nitrate. The graft copolymerization data obtained at different temperatures were used to calculate the energy of activation, which has been found to be 28.9 kJ mol(-1) within the temperature range from 20 to 50 degrees C. The effect of addition of cationic and anionic surfactants on graft copolymerization has also been studied. On the basis of the experimental observations, reaction steps have been proposed and a suitable rate expression for graft copolymerization has been derived.

Acrylates↗

PubMed1980

Improvements to assisted distillation cleanup of pesticide residues in animal fats.

The assisted distillation technique, which was developed for the cleanup of pesticide residues from animal fats, has been improved. Nitric acid cleaning of distillation tubes resulted in a significant improvement in the recoveries of hexachlorobenzene (HCB) and lindane (from 76 to 92% and 84 to 89%, respectively). A larger U-tube condenser was developed that condensed 100% of all pesticides studied. With this new condenser, a study of distillation tube flow rates showed that pesticide recoveries at 600 mL nitrogen/min were generally better than those obtained at any other flow rate although recoveries were satisfactory at 400 and 800 mL/min. Recoveries of pesticides at distillation temperatures of 210-240 degrees C were obtained with tubes cleaned with nitric acid, and using the larger U-tube condenser. The distillation temperature of choice was again 230 degrees C because there was little variation from 220 to 240 degrees C.

Adipose Tissue↗

PubMedDate not supplied

Di- and trinitrophenanthrenes: synthesis, separation, and reduction property.

Although nitrated polycyclic aromatic hydrocarbons (nitrated PAHs), specifically, dinitrated PAHs, have been indicated as potent mutagenic and carcinogenic environmental pollutants, only a few di- and trinitrophenanthrenes (DNPHs and TNPHs) have been reported up to the present time. Methods for the preparation of DNPHs and TNPHs by direct nitration of phenanthrene were established in this study. The reaction of phenanthrene with fuming nitric acid in acetic anhydride gave a complex mixture of DNPHs. Eleven DNPHs were isolated by using preparative HPLC with a total of 62.6% yield. Their chemical structures were determined using 1H NMR and electron impact mass spectrometry (EI-MS). The isolated DNPHs and their yields were 2,10-DNPH (14.2%), 1,10-DNPH (8.0%), 3,10-DNPH (6.9%), 3,6-DNPH (6.6%), 2,9-DNPH (5.3%), 1,6-DNPH (5.1%), 3,5-DNPH (4.6%), 4,9-DNPH (3.2%), 4,10-DNPH (3.1%), 1,5-DNPH (2.8%), and 2,6-DNPH (2.8%). Similarly, nine TNPHs were obtained from the nitrated reaction mixture of phenanthrene with fuming nitric acid without solvent: 3,6,9-TNPH (9.2%), 2,6,9-TNPH (9.0%), 1,6,9-TNPH (8.2%), 1,5,10-TNPH (9.0%), 2,6,9-TNPH (9.0%), 1,6,9-TNPH (4.0%), 1,7,9-TNPH (3.4%), 2,5,10-TNPH (2.5%), 2,6,10-TNPH (2.4%), 3,5,10-TNPH (1.8%), and 2,7,9-TNPH (0.2%) in 46.5% of the total yield. The reduction properties of the DNPHs and TNPHs were examined using cyclic voltammetry. The LUMO energy levels of the DNPHs and TNPHs calculated by the AM1 method were correlated to the first reduction potentials (E1/2). The coplanar or noncoplanar conformations of the nitro substituents to the phenanthrene ring system were also discussed.

Molecular Conformation↗

PubMed2006

Pore surface fractal analysis of palladium-alumina ceramic membrane using Frenkel-Halsey-Hill (FHH) model.

The alumina ceramic membrane has been modified by the addition of palladium in order to improve the H(2) permeability and selectivity. Palladium-alumina ceramic membrane was prepared via a sol-gel method and subjected to thermal treatment in the temperature range 500-1100 degrees C. Fractal analysis from nitrogen adsorption isotherm is used to study the pore surface roughness of palladium-alumina ceramic membrane with different chemical composition (nitric acid, PVA and palladium) and calcinations process in terms of surface fractal dimension, D. Frenkel-Halsey-Hill (FHH) model was used to determine the D value of palladium-alumina membrane. Following FHH model, the D value of palladium-alumina membrane increased as the calcinations temperature increased from 500 to 700 degrees C but decreased after calcined at 900 and 1100 degrees C. With increasing palladium concentration from 0.5 g Pd/100 ml H(2)O to 2 g Pd/100 ml H(2)O, D value of membrane decreased, indicating to the smoother surface. Addition of higher amount of PVA and palladium reduced the surface fractal of the membrane due to the heterogeneous distribution of pores. However, the D value increased when nitric acid concentration was increased from 1 to 15 M. The effect of calcinations temperature, PVA ratio, palladium and acid concentration on membrane surface area, pore size and pore distribution also studied.

Journal Article↗

PubMed2002

Bladder cancer among chemical workers exposed to nitrogen products and other substances.

OBJECTIVE: To investigate further bladder cancer mortality excess based on four deaths observed among the internal comparison population of a previous historical cohort study of workers from a chemical plant in Lima, Ohio. The internal population mainly comprised workers from the Nitrogen Products (NP) Division. METHODS: The original Lima cohort was expanded to include all workers (n = 1,841) employed between 1955 and 1996. A subcohort of workers employed mainly in the NP Division (NP Subcohort) was identified and used as the primary study population and as the source of cases and controls for a matched case-control study of bladder cancer. All death records were reviewed for any mention of bladder cancer; all available personnel, medical, and insurance files were reviewed to identify any current or former employees with an existing diagnosis of bladder cancer. A qualitative exposure assessment of all cases and controls was performed to evaluate an exploratory hypothesis that the bladder cancer excess may be associated with work histories involving both NP and urea, specifically, nitric acid and urea. RESULTS: We identified 96 new deaths among the expanded Lima cohort and obtained cause of death for 90. One additional bladder cancer death and one living case were identified and these were members of the original Lima cohort. The bladder cancer standardized mortality ratio (SMR) for the NP Subcohort (SMR = 3.31, 95%CI = 0.90-8.47) fell between the SMRs observed for all workers in the original and expanded Lima cohort (SMR = 3.93, 95%CI = 1.07-10.06 and 3.10, 95%CI = 1.01-7.24, respectively), but was markedly less than the SMR observed for corresponding subcohort of AN-unexposed workers in the original Lima cohort (SMR = 7.01, 95%CI = 1.91-17.96). Sparse data and a high prevalence of exposure among controls precluded an informative statistical analysis of the possible association between work histories involving both nitric acid and urea and bladder cancer risk. CONCLUSIONS: This study confirms that bladder cancer mortality is elevated among persons who worked mainly in the NP Division of the Lima plant, but at a lower, less statistically significant level than indicated by the original cohort study. No occupational risk factors considered to be causally related to the bladder cancer excess could be identified by this intensive investigation; other possible reasons for the excess are suggested by the descriptive data.

Adult↗

PubMed2005

Fatty acid transduction of nitric oxide signaling: multiple nitrated unsaturated fatty acid derivatives exist in human blood and urine and serve as endogenous peroxisome proliferator-activated receptor ligands.

Mass spectrometric analysis of human plasma and urine revealed abundant nitrated derivatives of all principal unsaturated fatty acids. Nitrated palmitoleic, oleic, linoleic, linolenic, arachidonic and eicosapentaenoic acids were detected in concert with their nitrohydroxy derivatives. Two nitroalkene derivatives of the most prevalent fatty acid, oleic acid, were synthesized (9- and 10-nitro-9-cis-octadecenoic acid; OA-NO2), structurally characterized and determined to be identical to OA-NO2 found in plasma, red cells, and urine of healthy humans. These regioisomers of OA-NO2 were quantified in clinical samples using 13C isotope dilution. Plasma free and esterified OA-NO2 concentrations were 619 +/- 52 and 302 +/- 369 nm, respectively, and packed red blood cell free and esterified OA-NO2 was 59 +/- 11 and 155 +/- 65 nm. The OA-NO2 concentration of blood is approximately 50% greater than that of nitrated linoleic acid, with the combined free and esterified blood levels of these two fatty acid derivatives exceeding 1 microm. OA-NO2 is a potent ligand for peroxisome proliferator activated receptors at physiological concentrations. CV-1 cells co-transfected with the luciferase gene under peroxisome proliferator-activated receptor (PPAR) response element regulation, in concert with PPARgamma, PPARalpha, or PPARdelta expression plasmids, showed dose-dependent activation of all PPARs by OA-NO2. PPARgamma showed the greatest response, with significant activation at 100 nm, while PPARalpha and PPARdelta were activated at approximately 300 nm OA-NO2. OA-NO2 also induced PPAR gamma-dependent adipogenesis and deoxyglucose uptake in 3T3-L1 preadipocytes at a potency exceeding nitrolinoleic acid and rivaling synthetic thiazo-lidinediones. These data reveal that nitrated fatty acids comprise a class of nitric oxide-derived, receptor-dependent, cell signaling mediators that act within physiological concentration ranges.

3T3-L1 Cells↗

PubMed2006

Do NAD and NAT form in liquid stratospheric aerosols by pseudoheterogeneous nucleation?

Laboratory data of the freezing of nitric acid hydrates (NAD, NAT) from HNO(3)/H(2)O and HNO(3)/H(2)SO(4)/H(2)O solution droplets have been evaluated with respect to a "pseudoheterogeneous" (surface-induced) nucleation mechanism of NAD and NAT, which has been argued to possibly lead to the formation of polar stratospheric clouds (PSCs). In addition, a parametrization of pseudoheterogeneous nucleation of NAD and NAT suggested recently (Tabazadeh et al. J. Phys. Chem. A 2002, 106, 10238-10246) has been analyzed, showing that this parametrization should not be used in stratospheric modeling studies. The analysis of several laboratory data sets yields an upper limit of the pseudoheterogeneous nucleation rate coefficient of NAD of 2.2 x 10(-5) cm(-2) s(-1). In contrast, the upper limit of the pseudoheterogeneous nucleation rate coefficient of NAT could not be constrained satisfactorily, since formation of NAT has not been observed at stratospheric conditions in laboratory experiments applying small droplets. Maximum NAD production rates of 9.6 x 10(-9) cm(-3) (air) h(-1) in the stratosphere have been estimated assuming a pseudoheterogeneous nucleation mechanism that is constrained by the experimental observations. If maximum NAD supersaturation persisted for 4 weeks in the polar stratosphere the corresponding NAD particle number densities are estimated to be about 6 x 10(-6) cm(-3). These particle number densities are 3 orders of magnitude lower than particle number densities recently observed in the stratosphere. In conclusion, on the basis of laboratory data it is found that a pseudoheterogeneous nucleation mechanism is not sufficient to explain recent observations of large nitric acid containing particles in the polar stratosphere.

Journal Article↗