A Microprocessor-Based Air Quality Monitoring System

Portable air quality monitoring systems may be required to supplement fixed installations or to provide for quick response to a transient situation, possibly at a remote location. A microprocessor-based monitoring unit has been developed for use with existing sensors. The unit is portable and its operational sequence can be programmed to adapt it to any unique requirements existing at the deployment site. Selectable on-site calculations are performed on raw data, and a hard copy or tape record of results can be produced.     

Estimate of Contribution of Jet Aircraft Operations To Trace Element Concentration at or near Airports

Samples of ASTM type A jet fuel were analyzed for trace element content by instrumental neutron activation techniques. Forty-nine elements were sought. Only ten, aluminum, gold, indium, lanthanum, titanium, vanadium, barium, dysprosium, tellurium, and uranium, were observed at levels above the detection limits encountered; of these only aluminum, titanium, and barium were present at concentrations greater than 0.1 ppm. Estimates of exhaust gas. concentrations are made, and the ambient contribution at or near airports is calculated by using the Los Angeles International Airport dispersion model. It is shown that the ambient contribution is about an order of magnitude below typical urban levels for virtually all elements sought.     

The Impact of Gold Smelter Emissions on Vegetation and Soils of a Sub-Arctic Forest-Tundra Transition Ecosystem

Gold smelters near Yellowknife in Canada's Northwest Territories have emitted large quantities of sulfur dioxide and arsenic since inception of roasting in 1941. Although particulate wastes are well contained by baghouse fitters in the one remaining operating smelter, significant gaseous emissions continue. Soil and vegetation were sampled at 52 sites over an area of about 40 km radius from the source. Plant ecology was studied at 43 of those sites. After preliminary multi-element screening that indicated only arsenic was a serious persistent contaminant, x-ray fluorescence was used to measure arsenic content in sampled materials. The plant ecology data were synthesized into an Index of Vitality with numerical ratings of pertinent factors. In the marginal forests and rocky outcrops of the area, indicator species of vegetation permitted a division into zones of severe, moderate, mild, or no impact in order of increasing distance from the current center of emissions. Severe impact, including killing of trees, is local only. Analyses of foliage indicate little uptake of arsenic which, together with the presence of S0₂ symptoms, point to S0₂ as the main factor causing decline of vegetation. A separate study, abstracted here, supports this view by providing data that show a frequency of at least 2 significant fumigation episodes per growing season. Soil analyses indicate extremely high arsenic contamination near the stack. A monotonie pattern of dispersion yielded a function explainable in terms of rapid condensation of gaseous emissions. The relationship of arsenic in surface soil and vegetation to distance is approximately an inverse square.     

The Effects of Precipitation on Aquatic and Terrestrial Ecosystems: A Proposed Precipitation Chemistry Network

Precipitation is one of the most important factors determining the nature and productivity of terrestrial and aquatic ecosystems. Detailed historical and contemporary records are available indicating the amount of water deposited at thousands of locations throughout the world. Comparatively, however, knowledge of the changing chemistry of precipitation has developed only recently and is still very fragmentary. Our present ignorance of the total impact of changes in precipitation quality on the productivity and stability of ecosystems is especially profound. This paper has a fourfold purpose: (1) to describe the myriad of trace chemical constituents transferred from the atmosphere into the biosphere of the earth; (2) to define the range of beneficial and injurious ecological effects of perturbations in atmospheric deposition; (3) to explain the concepts of sensitive areas, life stages, and life forms; and (4) to describe briefly plans for a National Deposition Network and associated research on the terrestrial and aquatic ecosystems of the United States.     

A New Real-Time Isokinetic Dust Mass Monitoring System

A new real-time dust mass monitor has been developed by combining an automatic isokinetic sampling probe with a tapered element oscillating microbalance (TEOM). Fly ash from a room temperature wind tunnel is sampled through the isokinetic sampler and collected on an astroquartz mat filter in the TEOM detector. The filter is first excited and oscillated at low frequency (about 200 Hz). As the particles deposit on the filter, the mass increase of the filter is reflected in a frequency reduction which yields the collected particle mass directly in real time. The TEOM detector normally has a high mass resolution (10^?9 g) and wide dynamic range (105⁵–106⁶). It is desensitized for high particle loading applications. Good agreement has been obtained between the mass collected through the isokinetic sampling system and the weight loss of the dust feeder, in real time. The body of information presented in this paper is directed to those concerned with particle emission and control in fossil fuel combustion systems.     

An Overview of EPA’s Quality Assurance Program

Quality Assurance has been defined in many different ways to express concern for the “quality” of the output of some operation or function. For the purpose of this presentation, quality assurance is defined as the sum of those activities within an environmental monitoring or measurement program which are primarily for the purpose of documenting the precision, accuracy, representativeness, and completeness of the data that are produced. Further, we view quality assurance as a management tool which encompasses both administrative and technical functions which generally fall into three categories: (1) Prevention which includes those activities carried out prior to the proper placement and operation of the measurement system; (2) Evaluation which includes the continuous overview and checks on the performance of the systems and operators; and (3) Correction which includes changes made to improve or stabilize the capability and performance of the system.     

A Comparison of Two Techniques for the Collection and Analysis of Polynuclear Aromatic Compounds in Ambient Air

A demonstration of the GHEMFIX solidification/stabilization process was conducted under the United States Environmental Protection Agency’s (EPA) Superfund Innovative Technology Evaluation (SITE) program. The demonstration was conducted in March 1989, at the Portable Equipment Salvage Company (PESC) uncontrolled hazardous waste site in Clackamas, Oregon. Waste containing lead, copper, and polychlorinated biphenyls (PCBs) from four different areas of the site were treated. Results showed substantial reduction of leachable lead and copper between the untreated waste and treated waste utilizing the EPA Toxicity Characteristics Leaching Procedure (TCLP) test. The effectiveness of this process for immobilizing PCBs could not be determined since the raw waste did not leach PCBs at high concentrations, utilizing the TCLP test. Data from other leaching tests for lead and copper would need to be utilized as input into a site specific groundwater model to determine whether solidification/stabilization would be an acceptable remedy for the site. Physical testing results indicated durability in exposed conditions.     

Electrostatic Stimulation of Fabric Filtration

The concept of electrostatic stimulation of fabric filtration (ESFF) has been investigated at pilot scale. The pilot unit consisted of a conventional baghouse in parallel with an ESFF baghouse, allowing direct comparison. All results reported in this paper are for pulse-cleaned bags in which the electric field was maintained parallel to the fabric surface. The performance of the ESFF baghouse has been superior to the parallel conventional baghouse by several measures. The ESFF baghouse demonstrated: (1) a reduced rate of pressure drop increase during a filtration cycle, (2) lower residual pressure drop, (3) stable operation at higher face velocities, and (4) improved particle removal efficiency. These benefits can be obtained with only minor modifications to conventional pulse-jet hardware and at low electrical power consumption. The indicated ability to operate at increased face velocities with only modest expenditure for electrical hardware leads to very favorable economic projections.