High Emission Regions Research Articles

A study of new particle formation and growth involving biogenic and trace gas species measured during ACE 1

Measurements are presented of ambient nanoparticle distributions (2.7 to 10 nm diameter) in regions of high biogenic emissions encountered during the First Aerosol Characterization Experiment (ACE 1), November 15 to December 14, 1995. Large numbers of newly formed nanoparticles were observed directly downwind of penguin colonies on Macquarie Island (54.5°S, 159.0°W). In these regions, nanoparticle concentrations were also correlated with sulfuric acid (H2SO4(g)) gas concentrations. The measurements show that biogenic species, possibly ammonia (NH3), either by itself or with H2SO4, nucleated to form new particles at rates much higher than bimolecular H2SO4/H2O nucleation. Nanoparticle distributions evolved as air was advected away from the island showing clear evidence of growth of the newly formed particles. Observed growth rates were in the range of 2 to 5 nm h−1 and were about a factor of 4 to 17 times higher than the growth by condensing H2SO4(g) and associated water. The cause for fast growth of the newly formed particles is unknown.

Optical, radio, and X-ray structure in NGC 1275.

view Abstract Citations (49) References (63) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Optical, radio, and X-ray structure in NGC 1275. McNamara, Brian R. ; O'Connell, Robert W. ; Sarazin, Craig L. Abstract We have compiled U, I, Hα, radio, and x-ray maps of NGC 1275 in order to study the galaxy's structure and color distribution. There are strong indications that the radio source is interacting with the gaseous medium in NGC 1275. A ~2 mag spread in U-I color is found across the face of the galaxy. The brightest and bluest structure in the U-band image is located along the northern radio lobes and cavity walls in the x-ray emission. Correspondingly bright features are absent along the southern radio lobe. The low velocity Hα emission avoids the cavities in the x-ray emission occupied by the radio lobes. The global distribution of excess blue light, Hα emission, and brightest x-ray emission occur over similar spatial scales (~30-40 kpc). However, the x-ray and optical structures are not correlated in detail. We have detected a faint blue continuum from the outer, "crab-like" low velocity filaments, which may signal ongoing star formation there. In addition, we have detected blue continuum toward the high velocity emission regions, perhaps from stars associated with the high velocity gas. Dark features, probably associated with dust, surround the nucleus and extend in filaments to the north- west. We suggest the dust surrounding the nucleus is associated with NGC 1275 itself, whereas the dust to the north-west may be associated with the high velocity system. The color distribution is consistent with population ages ranging from ~10 Myr to 1 Gyr superposed on an older, elliptical background population. The formation of the youngest (brightest, bluest) population along the radio lobes may have been induced by shock compression of cold gas along the northern radio lobe. This interpretation is complicated, however, by the superposition of light toward both high and low velocity gas to the north-west of the nucleus and the pole-on aspect of the radio source. The cooling rate of the x-ray-emitting gas in the central 20 kpc or so is comparable to the estimated star formation rates over the past several hundred Myr. However, the x-ray structure is more complicated than simple cooling flow models would predict, and there are indications that the dense x-ray structures are falling into the galaxy and have not had time to cool. A merger with a gas-enriched galaxy [Holtzman et al. AJ, 103,691(1992)] may have contributed to the structure. Publication: The Astronomical Journal Pub Date: July 1996 DOI: 10.1086/117991 Bibcode: 1996AJ....112...91M Keywords: GALAXIES: INDIVIDUAL: NGC 1275; X-RAYS: GALAXIES; RADIO LINES: GALAXIES; GALAXIES: ACTIVE full text sources ADS | data products SIMBAD (3) NED (1)

Long‐range transport of ozone in the East Asian Pacific rim region

Measurements of surface ozone were conducted at three remote island sites in the East Asian Pacific rim region during the Pacific Exploratory Mission‐West (A) campaign period in September–October, 1991. The ozone concentrations observed at the three measurement stations at Oki and Okinawa, Japan, and Kenting, Taiwan, had similar ranges varying between 6–63, 8–58, and 4–65 ppb, respectively, except for one event of short‐range transport of polluted air at Kenting. Day‐to‐day variations have been analyzed by using backward air parcel trajectories on isentropic surfaces. The results showed that continental air masses which originated from northwestern Asia and passed through the high anthropogenic emission region of East Asia contained the highest concentration of ozone, 30–60 ppb with an average of 43–45 ppb at the three stations. In contrast, the lowest concentrations were observed for air parcels originating from the mid‐Pacific and transported without mixing with the continental outflow. These parcels contained 5–20 ppb of ozone with the average of 11, 15, and 9 ppb at Oki, Okinawa, and Kenting, respectively. The air parcels from the South China Sea contained 22 and 18 ppb of ozone at Okinawa and Kenting, respectively, which were higher than those from mid‐Pacific. Continental air mass from the north‐northeast to Oki containing 35–40 ppb ozone with the average of 37 ppb was recognized as continental “background.” The high ozone concentrations in the northwesterly continental outflow exceeding the background was ascribed to photochemical buildup in the planetary boundary layer.

On-Road Emission Performance of Late-Model TWC-Cars as Measured by Remote Sensing

During three days in September 1991, the Denver University remote sensor (FEAT) was used to measure the CO and HC emissions from 10,000 gasoline passenger cars on a freeway ramp in Goteborg, Sweden. The data have been used to study the emission performance of late-model three-way catalyst (TWC) cars as a function of age and as compared with earlier model years of non-catalyst cars. Regulations requiring the use of TWCs on all new gasoline passenger cars were adopted in Sweden beginning with model year 1989. Due to sales encouragement, a major fraction of model years 1987 and 1988 are also TWC-cars. The results show that the average volume %CO emissions were approximately 90 percent lower for the model years with exclusively TWC-cars compared to the pre-1987 (non-catalyst) model years. The figure deduced from the remote sensing readings for the corresponding reduction of average volume %HC emissions is uncertain due to liquid water occasionally present in the exhaust of some late-model cars, and interfering with the HC measurements. In the high emission region, no major differences in emission performance were observed between model years with exclusively TWC-cars. 16 refs., 10 figs., 1 tab.

The relationship between upwind SO 2 emissions and SO 4– concentrations in precipitation at six sites in the eastern U.S.A.

A method for estimating the upwind SO 2 emissions associated with individual wet SO 4 2− deposition events has been developed. The relationship between these estimates and wet SO 4 2− concentrations was examined at six Utility Acid Precipitation Study Program Sites (UAPSP) for the 1979–1986 period. Using Spearman correlation coefficients and the Bonferroni experimentwise criterion for statistical significance it was found that upwind emissions and concentrations were significantly related ( p < 0.05). However, correlation's were sensitive to site location, time upwind of the emissions and season, and ranged from −0.03 to 0.50. Correlations were weaker at sites located west of the high emission region in the midwestern U.S.A. and stronger at sites further away and to the east of this region. There was a decrease in the strength of the correlations from the warm season to the cold season. It was also found that differences in meteorology between events obscured the relationship between emissions and concentrations. The effects of variations in ambient temperature and precipitation amount on wet SO 4 2− concentrations were taken into account by calculating partial correlation coefficients. A higher percentage of the resulting correlations were found to be statistically significant and the differences between sites decreased. This suggested that meteorological variability had a confounding influence on the detection of a link between concentrations and emissions. This influence should be considered when studying source-receptor relationships.

Use of Cluster Analysis to Define Periods of Similar Meteorology and Precipitation Chemistry in Eastern North America. Part II: Precipitation Patterns and Pollutant Deposition

Abstract The precipitation chemistry associated with the flow patterns of transport-derived clusters has been examined. Cluster analysis was applied to transport vectors, derived from there years of daily trajectories arriving at monitoring sites, in order to define a synoptic climatology of representative three-day periods of air mass movement. The resulting clusters were successful in defining wet, dry, polluted and nonpolluted clusters, as shown by the spatial patterns of median deposition and by statistical testing. The highest pollutant depositions over the widest areas resulted from mean transport patterns with large areas of slow air mass movement over the regions of high sulfur emissions and which were frequently persistent over several periods or followed persistent clusters. There was a large amount of overlap among the chemistry distributions and large variation within most of the clusters. Seasonal differences exist within each cluster, with sulfur deposition within a given cluster generally b...

Ionization of liquid metals, gallium

Field ionization of a liquid metal, such as Ga or In, has attracted considerable interest since it could become a source of strong focused ion emission. We have studied this phenomenon using the improved magnetic-sector atom-probe field ion microscope. The energy distributions of field ionization of Ga and critical energy deficits are measured as a function of surface temperature and electric field. The field ionization of Ga can be divided into a low and a high emission region. In the low emission region Ga+ ions are emitted at a field of approximately 0.5 V/A when the emitter is heated to approximately 600 °C. The intensity of this Ga+ emission is sufficient to yield a desorption image of the emitter surface. This implies that the ion flux is ∠103 ions/atomic site/second. When the emitter is kept at low tempertures (78 K) the emission is predominately Ga++. In both cases the ions display a sharp energy distribution (?1.5 eV FWHM) and a small energy deficit (?2.1 eV). In the high emission regime Ga++ ions are produced with a broad energy distribution (?12 eV FWHM). The total current ranges from 10−8 A or less in the low emission regime up to or greater than 10−5 A in the high emission regime.

Eleven-years inversion of the green corona emission

A cross correlation analysis of coronal green line intensity (5303A) and interplanetary magnetic field polarity for the period 1947-1970 shows that the coronal features are organized in a constant pattern with respect to the 4-sector structure through the solar cycle. A sudden inversion of the coronal pattern with respect to the sector structure takes place at the solar minima. The high emission regions of the green corona are located near the solar magnetic sector boundaries having polarities (-,+), (+,-), (-,+) during cycles 18, 19, 20 respectively in the Northern Hemisphere, and (+,-), (-,+), (+,-) in the Southern Hemisphere.