PANs in the Atmosphere

The types of PANs and PBzNs present or possibly present in the ambient atmosphere are discussed. Biological activities of the PANs and PBzNs are briefly considered. The concentration and composition of PANs in the atmosphere are discussed and calculations made of the production of RGO radicals from precursor alkanes, alkenes and aromatic hydrocarbons present in the atmosphere. Lifetimes of PANs are estimated, and the effects of transport on the composition of PANs is evaluated.     

Carbon Monoxide in the Atmosphere

A carbon monoxide analyzer has been developed which is capable of continuous measurement of the carbon monoxide concentration in the atmosphere. The operating principle of the instrument is the reaction of carbon monoxide with hot mercuric oxide followed by the photometric determination of the mercury vapor produced. Oxygenated hydrocarbons and olefins are quantitatively detected. Those normally present are in the ambient atmosphere in low concentrations relative to CO. Hydrogen and methane in the atmosphere do not interfere with the CO analysis. Measurements of atmospheric CO concentrations in California, Greenland, and Oregon seem to indicate that CO content is an air mass characteristic. North Pacific marine air mass concentrations may be as low as about 0.040 parts per million (ppm) CO, while the air mass over continental California seems to be characterized by CO levels of 0.5-1.0 ppm or greater.     

Particulate Elemental Carbon in the Atmosphere

This report summarizes the important results which were presented at an international symposium on particulate elemental carbon in the atmosphere. The “Particulate Carbon: Atmospheric Life Cycle” symposium was sponsored by General Motors Research Laboratories on October 12–14, 1980. Supplemental background data are included.     

Atmosphere and agriculture in the new millennium

Effects of changing climate (CO(2), O(3), aerosols, UV-B radiation, temperature and precipitation) on crops are predominantly based on univariate studies. Limited bivariate studies suggest rising CO(2) levels would be beneficial to crops but may be offset by adverse O(3) effects. Elevated UV-B and ambient crop yields are difficult to project due also to limited research. Climate warming concerns, using average daily temperatures may be less important than the effects of rising nocturnal temperatures on crop growth. Traditional approaches of examining air pollutant-induced visible foliar injury or the effects of single air pollutants on crop productivity need to be redirected to the analysis of integrated holistic systems. In that context, present and future agriculture in India and the USA are compared.     

Long Range Cloud Diffusion in the Lower Atmosphere

Previous attempts to measure heavy metals in air are discussed with particular reference to lead. A polarographic method was developed for lead in air samples taken on glass fiber sheet. Using this method, the distribution of lead across the glass fiber sheet was investigated, and within experimental error, found to be uniform. Air samples from 18 Ontario cities, previously analyzed for benzo [a]pyrene content were analyzed.     

Contaminant Concentrations in the Atmosphere of Los Angeles County

Sampling for nitrogen and sulfur dioxides was initiated at several National Air Sampling Network stations in 1959 using a sampler developed for that purpose. In 1961 the Gas Sampling Network was expanded to its maximum of 49 stations. Sampling equipment and collecting solutions are supplied and chemical analyses performed by the network laboratories. Sampling and analysis procedures are described briefly. Average and maximum 24-hour concentrations of nitrogen dioxide and sulfur dioxide observed at 48 stations during 1961-1963 are presented.     

Ambient Carbon Monoxide And Its Fate in the Atmosphere

Carbon monoxide, the most abundant air pollutant found in the atmosphere generally exceeds that of all other pollutants combined (excluding C0₂). An estimated tonnage of >87 X 10⁶ of CO was emitted in the United States from major technological sources alone during 1966. More than 90% of the total CO emitted from fossil fuels is derived from gasoline powered motor vehicles. Other sources of CO include emissions from coal and fuel oil burning, aircraft and open burning. Some CO is also formed by certain vegetation and marine invertebrates (siphonophores). Chemical reactions of CO in the upper and lower atmosphere are discussed. Chemical oxidation of CO in the lower atmosphere by molecular oxygen is very slow. The exact duration of CO in the lower atmosphere is not known with certainty; however, the mean residence time has been variously estimated to be between 0.3 and 5.0 years. In the absence of scavenging processes the estimated world-wide CO emission would be sufficient to raise the’atmospheric level by 0.03 ppm per year, yet the background levels of CO in clean air do not appear to be increasing. Several potential sinks are discussed. Knowledge of the mechanism of process of removal of CO from the lower atmosphere is unsatisfactory; the process, at the present time, cannot be identified with certainty.     

Viable Microorganisms in an Urban Atmosphere

The microbial population (types and numbers) of a vertical profile of air in an industrial area of the Twin Cities was determined between May and November 1967. No consistent relationships could be shown to exist between the microbial contamination and the meteorological parameters concurrently measured. The mean viable counts ranged from 58/ft³ at grade level to 22/ft³ at 500 ft. Regardless of altitude, molds constituted approximately 70% of the total airborne microflora, bacteria between 19 and 26%, and yeasts and actinomycetes the remainder. The particle size with which the viable population was associated showed a consistent peak in the 3 – 5 μ range.     

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 chrómatogram 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 observed. A system for irradiating trapped air samples was also constructed. Samples were collected in 5-gallon borosilicate bottles which were then irradiated with ultraviolet radiation and the concentration changes followed.     

Variation of Different Pollutants in the Atmosphere of Mexico City

The first regional warning system was developed by the New York-New Jersey Cooperative Committee on Air Pollution and was put into operation in 1964. In 1967, new criteria were adopted based on recommendations of a workshop sponsored by City College of New York at the request of State agencies. With the passage of time, it has been recognized that the criteria necessary to call an alert required updating and strengthening. In recognition of this, the Commission sponsored a workshop of government officials to evaluate the criteria and levels of the sulfur dioxide, carbon monoxide, and particulate parameters used in the system and to consider the addition of other parameters.     

Fine Particle Receptor Modeling in the Atmosphere of Mexico City

Abstract

Source apportionment analyses were carried out by means of receptor modeling techniques to determine the contribution of major fine particulate matter (PM_2.5) sources found at six sites in Mexico City. Thirty-six source profiles were determined within Mexico City to establish the fingerprints of particulate matter sources. Additionally, the profiles under the same source category were averaged using cluster analysis and the fingerprints of 10 sources were included. Before application of the chemical mass balance (CMB), several tests were carried out to determine the best combination of source profiles and species used for the fitting. CMB results showed significant spatial variations in source contributions among the six sites that are influenced by local soil types and land use. On average, 24-hr PM_2.5 concentrations were dominated by mobile source emissions (45%), followed by secondary inorganic aerosols (16%) and geological material (17%). Industrial emissions representing oil combustion and incineration contributed less than 5%, and their contribution was higher at the industrial areas of Tlalnepantla (11%) and Xalostoc (8%). Other sources such as cooking, biomass burning, and oil fuel combustion were identified at lower levels. A second receptor model (principal component analysis, [PCA]) was subsequently applied to three of the monitoring sites for comparison purposes. Although differences were obtained between source contributions, results evidence the advantages of the combined use of different receptor modeling techniques for source apportionment, given the complementary nature of their results. Further research is needed in this direction to reach a better agreement between the estimated source contributions to the particulate matter mass.     

Methane emission from lakes

A physico-chemical model to describe methane and carbon dioxide emission from lakes was developed. The model describes the emission by diffusion, bubbles and plants. The intensity of the fluxes can be calculated either for total or particular emission in dependence on gas bubbles composition. It was found, that diffusional (Q) and bubble (J) fluxes depend on the methane molar ratio (X) in bubbles as follows: [formula: see text]. The model allows to estimate the role of the methane oxidation by atmospheric oxygen in the total methane flux. It was shown, that the methane oxidation does not influence much methane fluxes to the atmosphere for most of the experimentally observed situations.     

Methane fluxes from tundra soils and snowpack in the maritime Antarctic

Methane fluxes were measured from three exposed tundra sites and four snowpack sites on the Fildes Peninsula in the maritime Antarctic in the summertime of 2002. The average fluxes at two normal tundra sites were −15.3 μg m⁻² h⁻¹ and −14.3 μg m⁻² h⁻¹, respectively. The fluxes from tundra site with fresh penguin dropping addition showed positive values with the average of 36.1 μg m⁻² h⁻¹, suggesting that the deposition of fresh droppings greatly enhanced CH₄ emissions from the poor Antarctic tundra during penguin breeding periods. The summertime variation in CH₄ flux was correlated with surface ground temperature and the precipitation. The correlation between the flux and PT₀, which is the product of the precipitation and surface ground temperature, was quite strong. The diurnal cycle of CH₄ flux from the tundra soils was not obtained due to local fluky weather conditions. The fluxes through four snowpack sites were also obtained by the vertical CH₄ concentration gradient and their average fluxes were −46.5 μg m⁻² h⁻¹, −28.2 μg m⁻² h⁻¹, −46.4 μg m⁻² h⁻¹ and −17.9 μg m⁻² h⁻¹, respectively, indicating that tundra soils under snowpack also consume atmospheric CH₄ in the maritime Antarctic; therefore these fluxes could constitute an important part of the annual CH₄ budget for Antarctic tundra ecosystem.     

Mercury Concentration in the Atmosphere in Chicago A New Ultrasensitive Method Employing Amalgamation

During the past two years, the Chicago Department of Environmental Control chemistry laboratory has developed a prototype sensor for measuring low levels of mercury found in the free or ambient atmosphere. Earlier studies of mercury in the Chicago area postulated that most of the mercury in the atmosphere should condense onto particulates and be collectable on filters. The results of the work presented here show that this may not occur. Analysis of composites of Chicago high volume particulate filters results in an average of 4 nanograms/m³ (range 2-10 nanograms/m³). This compared with a typical average of elemental mercury measurements of 22 nanograms/m³ (range 5-60 nanograms/m³). Thus, it is obvious that particulate borne mercury, at least as analyzed from a high volume filter paper, is not as significant as the total or elemental mercury existing in the metropolitan area. A direct method for collecting mercury and measuring in a flameless atomic absorption unit yields very good results.