A Study of Ozone Levels in a Maritime and Land Environment

During the summer of 1976, a comparison was made between ozone measurements for a coastal industrial concentration area (Norfolk/Virginia Beach, Virginia) and an offshore station (Chesapeake Light Station, 15 miles out to sea). The anticipated dominance of high offshore ozone readings with offshore flow was not observed. A surprising number of high O₃ concentrations were observed at both the offshore and land sites with northeasterly and easterly winds. This suggests that the phenomenon of long range transport of contaminants from highly urbanized centers in the northeast to the mid-Atlantic states via an offshore sea route must be given careful consideration. The body of information presented in this paper points out the need for a clearer understanding of the complex urban/rural O₃ problem coupled with transport effects before costly control strategies are to be implemented.     

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.     

Mass and Elemental Composition of Fine and Coarse Particles in Six U.S. Cities

Inhalable particulate matter (IP) samples have been collected in six U.S. cities in conjunction with an air pollution health study. The IP were collected using dichotomous virtual impactors in two size ranges: fine particles (FP) having aerodynamic diameter (d_a) <2.5 μm, and coarse particles (CP) with 2.5 μm < da < 15 μm. The mass measurements were determined by beta-gauge attenuation. The elemental composition of the FP and CP were determined by X-ray fluorescence. The means and distributions for FP and CP and selected elemental data highlight the similarities and differences that exist among these cities in the health study. Examining the temporal variations gives additional information on the meteorology and sources influencing the FP and CP fractions of Inhalable particle mass.

Differences in the concentration (and ratios) of selected elements have indicated the varying presence of crustal, steel industry, automotive, oceanic and fuel combustion sources in these cities. The noted variation in the concentrations and character of ambient aerosols in these cities are pertinent to interpreting differences in population exposures.     

The Coefficient of Haze as a Measure of Particulate Elemental Carbon

The technique to measure the coefficient of haze (COH) was developed in 1953 and was widely employed as a surrogate technique to measure total suspended particulate matter (TSP) in the 1960s. Because of the physical design of the sampler (known as the AISI Tape Sampler) used to measure COH, it was postulated that COH was directly related to the mass of fine elemental carbon particles (EC) with diameters less than 2.5 μm. To test the hypothesis, simultaneous samples of COH and EC were collected and analyzed during the 1981 Summer Study in Detroit. Regression analysis indicates that the two quantities are linearly related over the concentration range observed. Additional analyses indicate that COH is not related to TSP, fine particle mass, or light-scattering aerosol. Calculation of specific light absorption coefficients for EC from the COH data support the hypothesis that the tape sampler responds only to fine EC. A brief examination of historical COH data from Detroit suggests that the EC concentration has declined since 1972. This should be regarded as a preliminary assessment, however, until further verification of the COH-EC connection can be made.     

Evaluation of Trickle Bed Air Biofilter Performance as a Function of Inlet VOC Concentration and Loading,and Biomass Control

ABSTRACT

The 1990 Amendments to the Clean Air Act have stimulated strong interest in the use of biofiltration for the economical, engineered control of volatile organic compounds (VOCs) in effluent air streams. Trickle bed air biofilters (TBABs) are especially applicable for treating VOCs at high loadings. For long-term, stable operation of highly loaded TBABs, removal of excess accumulated bio-mass is essential. Our previous research demonstrated that suitable biomass control for TBABs was achievable by periodic backwashing of the biofilter medium. Backwashing was performed by fluidizing the pelletized biological attachment medium with warm water to about a 40% bed expansion. This paper presents an evaluation of the impact of backwashing on the performance of four such TBABs highly loaded with toluene. The inlet VOC concentrations studied were 250 and 500 ppmv toluene, and the loadings were 4.1 and 6.2 kg COD/m³ day (55 and 83 g toluene/m³ hr). Loading is defined as kg of chemical oxygen demand per cubic meter of medium per day. Performance deterioration at the higher loading was apparently due to a reduction of the specific surface of the attached biofilm resulting from the accumulation of excess biomass. For a toluene loading of 4.1 kg COD/m³ day, it was demonstrated that the long-term performance of biofilters with either inlet concentration could be maintained at over 99.9% VOC removal by employing a backwashing strategy consisting of a frequency of every other day and a duration of 1 hr.     

Thermal Exploitation of Wastes with Lignite for Energy Production

Abstract

The thermal exploitation of wastewood with Greek lignite was investigated by performing tests in a laboratory-scale fluidized bed reactor, a 1-MW_th semi-industrial circulating fluidized bed combustor, and an industrial boiler.

Blends of natural wood, demolition wood, railroad sleepers, medium-density fiberboard residues, and power poles with lignite were used, and the co-combustion efficiency and the effect of wastewood addition on the emitted pollutants were investigated. Carbon monoxide, sulfur dioxide, and oxides of nitrogen emissions were continuously monitored, and, during the industrial-scale tests, the toxic emissions (polychlorinated dibenzodioxins and dibenzofurans and heavy metals) were determined. Ash samples were analyzed for heavy metals in an inductively coupled plasma-atomic emission spectroscopy spectrophotometer.

Problems were observed during the preparation of wastewood, because species embedded with different compounds, such as railway sleepers and demolition wood, were not easily treated. All wastewood blends were proven good fuels; co-combustion proceeded smoothly and homogeneous temperature and pressure profiles were obtained. Although some fluctuations were observed, low emissions of gaseous pollutants were obtained for all fuel blends. The metal element emissions (in the flue gases and the solid residues) were lower than the legislative limits. Therefore, wastewood co-combustion with lignite can be realized, provided that the fuel handling and preparation can be practically performed in large-scale installations.