Edgar R. Stephens

Fluorocarbons in the Los Angeles Basin

Ambient air concentrations of fluorocarbon 11 (fluorotrichloromethane) and fluoro-carbon 12 (dichlorodifluoromethane) have been measured using a gas chro-matograph equipped with a pulsed, electron capture detector. Air samples taken on a moderately smoggy day in July 1970, at several locations near Los Angeles gave average readings of fluorocarbon 12, 0.7 ppb and fluorocarbon 11, 0.56 ppb. These readings were contrasted with those taken in early February 1973 when the air was clear and marked with turbulence due to several seasonal rain storms. The readings of both fluorocarbon 1 1 and 12 averaged about 25% less during clear weather than those taken during moderate smog. The effects of weather conditions on the concentration were also dramatically pointed out by the February samples, in that as much as a tenfold change in concentrations of both fluorocarbons from location to location and from day to day at the same location was observed. A concentration versus altitude study clearly revealed that fluoroca...

Analysis of the atmosphere for light hydrocarbons

A procedure has been developed for the analysis of trace quantities of light hydrocarbons in air. A freezetrap filled with chromatographic packing was installed in place of the gas sample loop of a flame ionization chromatograph. An air sample 0.1–0.5 liter volume was passed through the trap which was chilled with liquid oxygen. The trap wasthen brought to ice temperature and its contents simultaneously swept into the column. The resulting chromatogram could be used to determine about 25 hydrocarbons through n-hexane. The minimum detectable concentration was below 1 ppb for these hydrocarbons. With such sensitivity it is possible to make useful measurements even on samples of light air pollution. Air samples from the Riverside area were analyzed in this fashion starting in the summer of 1965. The relative amounts of these hydrocarbons were then compared with the distribution reported for the various known hydrocarbon sources. The attenuation of the more reactive hydrocarbons by photolysis was also observe...

The formation of molecular oxygen by alkaline hydrolysis of peroxyacetyl nitrate

Abstract Alkaline hydrolysis of peroxyacetyl nitrate (PAN) vapor was found to produce molecular oxygen in mole for mole yield. This accounts for the oxygen which was missing in the hydrolysis experiments of Nicksic, Harkins and Mueller.

Fluorocarbon air pollutants II.

Improvements in previously reported techniques now make it possible to routinely measure fluorocarbon 11 and 12 at 1.0 × 10−12 by volume and 10 × 10−12 by volume, concentrations well below typical levels of background unpolluted air. Irradiation of fluorocarbons 11, 12, 113 and 114 in ambient Riverside air, simulated heavy smog, and simulated heavy smog plus SOx indicated that these compounds were photochemically very stable, and show no measurable tendency to decompose. Fluorocarbons 11 and 12 were used to provide a good label for following the movement of polluted air inland from Los Angeles.

Background and vertical atmospheric measurements of fluorocarbon-11 and fluorocarbon-12 over Southern California

Abstract Sample tubes containing air analyzed for fluorocarbon-11 and fluorocarbon-12 were collected in a twin-engined aircraft. The samples were collected at altitudes ranging from ground level to 22000 ft (MSL) over the Southern California area. Background levels of fluorocarbon-11 and fluorocarbon-12 were determined to be 0.060 and 0.090 ppb, respectively. Simultaneous ozone measurements suggest that these fluorocarbons can be used to trace polluted air below the inversion layer.

Smog Aerosol: Infrared Spectra

Infrared spectra of smog aerosol are similar to those of sulfuric acid aerosol, but they do not show the prominent CH and carbonyl bands of organic aerosols from terpenes. Some features of the smog aerosol spectra are not present in the spectra from either type of synthetic aerosol.

Comparison of synthetic and smog aerosols

Abstract Aerosols resembling those observed in polluted air have been generated photochemically in several laboratories in the past 15 years. But the importance of such mechanisms in real polluted air in comparison with aerosols emitted directly from sources has not been easy to evaluate. An optical particle counter and a technique for obtaining infrared spectra of aerosols have now been used to compare these synthetic laboratory aerosols with smog aerosols from the Riverside, California area. The dirty air conditions studied were photochemical smog, dust storm, and orchard heater smoke. The clean air conditions examined were rainstorm, Santa Ana wind, and morning radiation inversion. Aerosol generated photochemically appears to account for most of the visibility loss in smog which is due to particles in the 0. 3-1.0 μm diameter range. This portion of the aerosol can be accounted for as sulfuric acid, and auto exhaust alone is sufficient to account for it if the sulfur in gasoline is oxidized to sulfuric acid efficiently. Infrared analysis shows sulfate bands and additional bands which are ascribed to a nitrate. Particles larger than 1 or 2 μ may account for much of the weight of particulate matters but not much of the visibility loss. Many of these are solid in contrast to the smaller particles which appear to be liquid. Sandstorm aerosols are much larger in size while orchard heater smoke looks like particulate carbon and has no infrared bands.

A Search for Some Nitro-Oleflns in Polluted Air

An electron capture chromatographic method of detecting nitro-ethylene and 1-nitro-lpropene was developed and applied to ambient air samples, photolyzed propene/nitrogen dioxide mixtures and auto exhaust. No trace of either compound was found in ambient air or in the photolyzed mixtures. The detection limit was estimated to be 1 ppb. A single sample of auto exhaust showed several small peaks which, if attributed to nitroolefin, would amount to insignificant traces

Atmospheric Photochemical Reactions Inhibited by Iodine

The inhibition by iodine of the atmosphere photochemical reaction of olefin with nitrogen dioxide has been confirmed. The presence of iodine in concentrations comparable to those of the reactants retards the formation of aldehyde, peroxyacetyl nitrate, and aerosol as well as the disappearance of olefin. The reaction of iodine with atomic oxygen may account for this inhibition. A number of other potential inhibitors were found to be ineffective.

Infrared absorptivity of the 9.6 μm ozone band as a function of spectral resolution and abundance

Abstract The i.r. absorptivity of the R -branch maximum (9.48 μm) of gaseous ozone was determined at 25°C as a function of spectral resolution and absorbance a/a total pressure of 735 torr of dry air. Ozone samples produced by a high voltage discharge in oxygen, and measured accurately by either a pressure or volume change, were spectroscopically measured in a 57741. environmental chamber at paths up to 69.17 m. A linear relation between spectral slit (Δ v ) and the ratio of the absorbances ( R v/p ) of the observed absorption minimum between the R and Q branches to the absorption maximum of the R -branch was found for cm -1 v -1 and for absorption up to 48%. The i.r. absorptivity varied approx. 20% (from 3.9 to 4.8 cm -1 STP) over the range of values for R v/p studied. Absorptivity was weakly dependent on ozone abundance ( w ) for w ⩽0.03 cm STP.