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At least 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Fluid mechanics simulation of fog formation associated with polluted atmosphere produced by energy related fuel combustion

It is noted that large quantities of atmospheric aerosols with composition SO4(-2), NO3(-1), and NH4(+1) have been detected in highly industrialized areas. Most aerosol products come from energy-related fuel combustion. Fluid mechanics simulation of both microphysical and macrophysical processes is considered in studying the time dependent evolution of the saturation spectra of condensation nuclei associated with polluted and clean atmospheres during the time periods of advection fog formation. The results demonstrate that the condensation nuclei associated with a polluted atmosphere provide more favorable conditions than condensation nuclei associated with a clean atmosphere to produce dense advection fog, and that attaining a certain degree of supersaturation is not necessarily required for the formation of advection fog having condensation nuclei associated with a polluted atmosphere.

Hung, R. J.↗
NASA NTRS1981

Acid rain at Kennedy Space Center, Florida - Recent observations

During the period July, 1977 to September, 1979, rainfall was collected in the vicinity of the Kennedy Space Center and subjected to appropriate chemical analysis for purposes of characterization of general composition and acidity. Results obtained form the basis for future comparisons, should significant alteration of the chemical composition of rain occur during the space shuttle era. Acidity extremes calculated on a monthly basis from event samples collected from five sites within a 200 sq km area varied from pH 5.1 in November, 1977, and April, 1978 to pH 4.3 in July, 1978 and July, 1979. Weighted average pH for the entire period was 4.55. Acidity was due to the presence of sulfuric and nitric acids. The mole ratio of excess SO4(-2):NO3(-) was typically greater than one. Monthly weighted average Cl(-) concentrations ranged from 20-240 micromoles/liter. The Cl(-):Na(+) ratio was slightly lower than that present in sea water.

Madsen, B. C.↗
NASA NTRS1981

Atmospheric cycles of nitrogen oxides and ammonia

The atmospheric cycles of nitrogenous trace compounds for the Northern and Southern Hemispheres are discussed. Source strengths and destruction rates for the nitrogen oxides: NO, NO2 and HNO3 -(NOX) and ammonia (NH3) are given as a function of latitude over continents and oceans. The global amounts of NOX-N and NH3-N produced annually in the period 1950 to 1975 (34 + 5 x one trillion g NOx-N/yr and 29 + or - 6 x one trillion g NH3-N/yr) are much less than previously assumed. Globally, natural and anthropogenic emissions are of similar magnitude. The NOx emission from anthropogenic sources is 1.5 times that from natural processes in the Northern Hemisphere, whereas in the Southern Hemisphere, it is a factor of 3 or 4 less. More than 80% of atmospheric ammonia seems to be derived from excrements of domestic animals, mostly by bulk deposition: 24 + or - 9 x one trillion g NO3 -N/yr and 21 + or - 9 x one trillion g NH4+-N/yr. Another fraction may be removed by absorption on vegetation and soils.

Bottger, A.↗
NASA NTRS1982

H2O2 levels in rainwater collected in south Florida and the Bahama Islands

Measurements of H2O2 in rainwater collected in Miami, Florida, and the Bahama Islands area indicate the presence of H2O2 concentration levels ranging from 100,000 to 700,000 M. No systematic trends in H2O2 concentration were observed during an individual storm, in marked contrast to the behavior of other anions for example, NO3(-), SO4(-2), and Cl(-). The data suggest that a substantial fraction of the H2O2 found in precipitation is generated by aqueous-phase reactions within the cloudwater rather than via rainout and washout of gaseous H2O2.

Zika, R.↗
NASA NTRS1982

Precursor gases of aerosols in the Mount St. Helens eruption plumes at stratospheric altitudes

Nineteen stratospheric samples from the eruption plumes of Mount St. Helens were collected in five flight experiments. The plume samples were collected at various altitudes from 13.1 to 20.7 km by using the Ames cryogenic sampling system on board the NASA U-2 aircraft. The enriched, cryogenically collected samples were analyzed by chromatography. The concentrations of aerosols precursor gases (OCS, SO2, and CS2), CH3Cl, N2O, CF2Cl2, and CFCl3 were measured by gas chromatography. Large enhancement of the mixing ratio of SO2 and moderate enhancement of CS2 and OCS were found in the plume samples compared with similar measurement under pre-volcanic conditions. A fast decay rate of the SO2 mixing ratio in the plume was observed. Measurement of Cl(-), SO2(2-), and NO3(-) by ion chromatography was also carried out on water solutions prepared from the plume samples. The results obtained with this technique imply large mixing ratios of HCl, (NO + NO2 + HNO3), and SO2, in which these constituents are the respective sources of the anions. Measurement of the Rn222 concentration in the plume was made. Other stratospheric constituents in the plume samples, such as H2O, CO2, CH4, and CO, were also observed.

Inn, E. C. Y.↗
NASA NTRS1982

Plant growth in controlled environments in response to characteristics of nutrient solutions

Plant growth in controlled environments in response to characteristics of nutrient solutions is discussed. Descriptions of experimental results concerning root acclimation to temperature, root and shoot acclimation to nitrogen stress, and growth response to NH4(+) and NO3(-) nutrition are included. A preliminary model validation to changing temperatures is presented.

Raper, C. D., Jr.↗
NASA NTRS1983

Chemical weathering and diagenesis of a cold desert soil from Wright Valley, Antarctica - An analog of Martian weathering processes

Weathering, diagenesis, and chemical alteration of a soil profile from the Dry Valleys of Antarctica are investigated as an analog to soil development within the Martian regolith. Soil samples from a soil pit one meter deep on Prospect Mesa, Wright Valley, are examined for their major element concentrations, water-soluble cations and anions, carbon, sulfur, and water concentrations, and related petrographic characteristics of weathering in a cold, dry environment. A petrographic study of the samples suggests that most silicate mineral and lithic fragments exhibit some degree of alteration. Chemical alteration occurs both in samples above and within the permanently frozen zone. The concentrations of water-soluble cations, for example, Na(+), K(+), Ca(2+), and anions, Cl(-), SO4(2-), NO3(-), are found to decrease significantly from the surface to the permanently frozen zone, suggesting a major movement of water-soluble species. It is also found that enrichments in secondary mineral abundances correlate with the water soluble ion concentrations. The formation of zeolites is seen throughout the soil column; these, it is thought, may be reservoirs for volatile storage within the regolith.

Gibson, E. K.↗
NASA NTRS1983

Influence of the Mediterranean outflow on the isotopic composition of neodymium in waters of the North Atlantic

Measurements of the Nd-143/Nd-144 ratio, expressed as epsilon-Nd(0), made in sea water samples obtained at depths from 0 to 4850 m at stations 95, 101, and 30 of North-Atlantic cruise 109-1 of the RV Atlantis II are reported and analyzed. In the 1000-m sample at station 95, determined by salinity, O2, PO4, NO3, SiO2, potential-temperature, and pressure profiles to correspond to the core of the Mediterranean outflow, an epsilon-Nd(0) value of -9.8 + or - 0.6 was found, a significant increase over the layers above and below, where epsilon-Nd(0) is about -12. Mixing estimations give a value for pure Mediterranean waters of approximately -6; continental drainage or volcanic deep-sea sediments are considered possible sources for this more radiogenic Nd. The epsilon-Nd(0) peak in the western North Atlantic (station 30) is found at the surface, and the deep waters are less radiogenic than in the eastern North Atlantic, suggesting multiple Nd sources. Possible origins and distribution mechanisms are discussed.

Piepgras, D. J.↗
NASA NTRS1983

Proceedings of a Workshop on Assessment of Techniques for Measuring Tropospheric N sub x O sub y

Human impact on the troposphere, particularly on the regional to global scale is assessed. One area of required research is instrumentation development, which is aimed at improving the capability to measure important trace gases and aerosols which are key species in the major atmospheric biogeochemical cycles. To focus on specific needs, the Instrumentation Workshop for NxOy Tropospheric Species was conducted. The workshop discussed measurement needs and instrument capabilities for NxOy species, including NO, NO2, HNO3, HNO2, PAN, and NO3 aerosols. The status and measurement capabilities of various techniques (operational as well as conceptual) were discussed, along with future instrument and technology needs.

Source record↗
NASA NTRS1984

Nitrate in the Greenland ice sheet in the years following the 1908 Tunguska event

The Tunguska event on June 30, 1908 has been subjected to much speculation within different fields of research. Publication of the results of the 1961 expedition to the Tunguska area (Florensky, 1963) supports the view that a cometary impact caused the event. Based on this interpretation, calculations of the impactor energy release and explosion height have been reported by Ben-Menahem (1975), and velocity, mass, and density of the impactor by Petrov and Stulov (1975). Park (1978) and Turco et al. (1981, 1982) used these numbers to calculate a production of ca. 30,000,000 tons of NO during atmospheric transit. This paper presents a high-resolution study of nitrate concentration in the Greenland ice sheet in ca. 10 years covering the Tunguska event. No signs of excess nitrate are found in three ice cores from two different sites in Greenland in the years following the Tunguska event. By comparing these results with results for other aerosols generally found in the ice, the lack of excess NO3(-) following the Tunguska event can be interpreted as indicating that the impactor nitrate production calculated by Park (1978) and Turco et al. (1981, 1982) are 1-2 orders of magnitude too high. To explain this, it is suggested, from other lines of reasoning, that the impactor density determined by Petrov and Stulov (1975) probably is too low.

Rasmussen, K. L.↗
NASA NTRS1984

Optical Studies of Nitrogen Oxides in the Stratosphere

Several observational approaches were used to study the oxides of nitrogen in the stratosphere. Two species are accessible in the visible range: NO2 (400 to 450 nm) and NO3 (620 to 670 nm). In the infrared NO, NO2 and HNO3 can be studied easily only if measurements are made from above the tropopause where the water density becomes low. Measurements were carried out both by ground-based techniques as well as aircraft and balloons.

Noxon, J. F.↗
NASA NTRS1983

MAP/GLOBUS campaign 1983

The major scientific objectives of the campaign are the accurate measurement of ozone and its short-term variability together with the determination of members of the NO sub x family as NO, NO2, NO3, N2O5, and HNO3. Related important solar fluxes (including scattered fluxes) shall be measured as much as possible. Other important trace species (as H2O) shall be determined simultaneously. The detailed scientific objectives for the ozone and NO sub x measurements are given. A further scientific objective is the study of atmospheric dynamics, especially of the meteorological background. Therefore special analysis will be performed of the data of respective network stations and satellites. Local wind and turbulence measurements will also be performed.

Offerman, D.↗
NASA NTRS1985

Role of chemotaxis in the ecology of denitrifiers

It has been recognized that the process of denitrification represents a major sequence in the nitrogen cycle. It involves the anaerobic reduction of nitrate or nitrite to nitrous oxide or elemental nitrogen. This process is responsible for significant losses of nitrogen from agricultural soils. Up to now, little attention has been paid to the ecology of the organisms responsible for denitrification. It is pointed out that chemotaxis would probably offer a strong competitive mechanism for denitrifiers, since chemotaxis would allow denitrifiers to actively reach nitrate by directed motility, rather than by random movement or diffusion of nitrate. The present investigation was initiated to examine the chemotactic responses of several denitrifiers to nitrate and nitrite. Attention is given to bacterial strains, culture media and cell preparation, chemotaxis assays, and competition experiments. It was found that several denitrifiers, including P. aeruginosa, P. fluorescens, and P. Stutzeri, were strongly attracted to NO3(-) and NO2(-).

Kennedy, M. J.↗
NASA NTRS1985

Tentative identification of the 780/cm nu-4 band Q branch of chlorine nitrate in high-resolution solar absorption spectra of the stratosphere

According to models of the photochemistry of the stratosphere, chlorine nitrate (ClONO2) is an important temporary reservoir of stratospheric chlorine. At night, ClO is believed to combine in a three-body reaction with NO2 to form chlorine nitrate. During daylight, chlorine nitrate is destroyed by photolysis to form free chlorine and NO3. Infrared spectroscopy has the potential to provide a technique for conducting important quantitative measurements of stratospheric chlorine nitrate. The present paper reports a detailed study of spectra in the 780/cm region. This study has led to the tentative identification of the nu-4 band Q branch of ClONO2 as a significant contributor to the observed stratospheric absorption near 780.21 per cm.

Rinsland, C. P.↗
NASA NTRS1986

Production rates of neon xenon isotopes by energetic neutrons

As a first step in an experimental program to study the behavior of noble gases produced in situ in minerals, a suite of minerals and pure chemicals were irradiated with 14.5 MeV neutrons at LLNL's Rotating Target Neutron Source (RTNS-II) and production rates for noble gases were determined. While neutron effects in meteorites and lunar samples are dominated by low-energy neutron capture, more energetic cosmic-ray secondary neutrons can provide significant depth-dependent contributions to production of cosmogenic nuclides through endothermic reactions such as (n,2n), (n,np), (n,d) and (n,alpha). Production rates for nuclides produced by cosmic-ray secondary neutrons are therefore useful in interpreting shielding histories from the relative abundances of cosmogenic nuclides. Absolute production cross sections were calculated from isotope dilution analyses of NaCl, Mg, CsCl, and Ba(NO3)2 samples, assuming purity, stoichiometry, and quantitative noble gas retention and extraction. Relative production cross sections determined from neon isotopic ratios in the mineral samples were also considered in evaluating the neon production cross sections. Results are presented.

Leich, D. A.↗
NASA NTRS1985

Evaluation of a catalytic reduction technique for the measurement of total reactive odd-nitrogen NOy in the atmosphere

The suitability of a technique for the measurement of total reactive odd-nitrogen NOy-containing species in the atmosphere has been examined. In the technique, an NOy component species, which may include NO, NO2, NO3, HNO3, peroxyacetyl nitrate, and particulate nitrate, are catalytically reduced by CO to form NO molecules on the surface of a metal converter tube, and the NO product is detected by chemiluminescence produced in reaction with O3. Among the catalysts tested in the temperature range of 25-500 C, Au was the preferred catalyst. The results of laboratory tests investigating the effects of pressure, O3, and H2O on NOy conversion, and the possible sources of interference, have shown that the technique is suitable for atmospheric analyses. The results of a test in ambient air at a remote ground-based field site are included.

Fahey, D. W.↗
NASA NTRS1988

Photochemistry of biogenic emissions over the Amazon forest

The boundary layer chemistry over the Amazon forest during the dry season is simulated with a photochemical model. Results are in good agreement with measurements of isoprene, NO, ozone, and organic acids. Photochemical reactions of biogenic isoprene and NOx can supply most of the ozone observed in the boundary layer. Production of ozone is very sensitive to the availability of NOx, but is insensitive to the isoprene source strength. High concentrations of total odd nitrogen (NOy) are predicted for the planetary boundary layer, about 1 ppb in the mixed layer and 0.75 ppb in the convective cloud layer. Most of the odd nitrogen is present as PAN-type species, which are removed by dry deposition to the forest. The observed daytime variations of isoprene are explained by a strong dependence of the isoprene emission flux on sun angle. Nighttime losses of isoprene exceed rates of reaction with NO3 and O3 and appear to reflect dry-deposition processes. The 24-hour averaged isoprene emission flux is calculated to be 38 mg/sq m per day. Photooxidation of isoprene could account for a large fraction of the CO enrichment observed in the boundary layer under unpolluted conditions and could constitute an important atmospheric source of formic acid, methacrylic acid, and pyruvic acid.

Jacob, Daniel J.↗
NASA NTRS1988

Biomass-burning emissions and associated haze layers over Amazonia

The characteristics of haze layers, which were visually observed over the central Amazon Basin during many of the Amazon Boundary Layer Experiment 2A flights in July/August 1985, were investigated by remote and in situ measurements, using the broad range of instrumentation and sampling equipment on board the Electra aircraft. It was found that these layers strongly influenced the chemical and optical characteristics of the atmosphere over the eastern Amazon Basin. Relative to the regional background, the concentrations of CO, CO2, O3, and NO were significantly elevated in the plumes and haze layers, with the NO/CO ratio in fresh plumes much higher than in the aged haze layers. The haze aerosol was composed predominantly of organic material, NH4, K(+), NO3(-), SO4(2-), and organic anions (formate, acetate, and oxalate).

Andreae, M. O.↗