National Air Sampling Network Research Articles

Sampling Frequencies for Determining Long-Term Average Concentrations of Atmospheric Participate Sulfates

On the basis of simple statistical analysis preliminary conclusions and recommendations may be made on the ambient sampling strategy of particulate sulfates. The results are applicable to obtaining 24 hr average sulfate samples from high-volume particulate samplers. Two basic conclusions are: (1) A seasonally dependent sampling frequency appears desirable for sulfate monitoring. There are large seasonal variations during the warm months and relatively low and less variable values in the colder parts of the year. If one is interested only in the annual average, a constant sampling frequency of once every three days is allowable for a 90% confidence level. (2) To date, nearly all sulfate measurements available from the public domain are from exposed high-volume particulate filters. Federal and state routine sampling programs have largely followed the sampling rate of once every 6 days for total suspended particulates. Sulfate measurements are available from the National Air Sampling Network (NASN) at a frequency of once every 6 or 12 days. Annual or seasonal averages of sulfate concentrations derived from NASN stations in the midwest and northeast would not be acceptable in terms of this study. To obtain acceptable annual means from the NASN stations, it will be necessary to usemore » data for two or more years, provided the temporal distribution of sulfate concentrations is similar from year to year. Present knowledge of long-term sulfate variation is not complete enough to allow this assumption without qualification.« less

Routine assessment of the particle size-weight distribution of urban aerosols

A sampling method for measuring the aerodynamic particle size-weight distribution of atmospheric suspended particulates is described. The method should prove valuable for routine use by control agencies, where rugged instruments and simple sampling procedures are required. An entry cover designed to simulate the aerosol entry conditions of the high volume sampler used in the National Air Sampling Network (NASN) was mounted to a 6 stage Andersen cascade impactor with back-up filter. The system maintained a constant sampling flow rate (1 cfm) over a 24-hr period using a critical orifice and a durable high efficiency vacuum pump. The amount of material collected on each of the 6 impaction plates and the membrane back-up filter were weighed to establish the aerodynamic particle size-weight distribution of an atmospheric aerosol.

Determination of lead in airborne particulates in Chicago and Cook County, Illinois, by atomic absorption spectroscopy

A simple precise procedure for determining the lead content of suspended particulate samples collected from the air uses atomic absorption spectroscopy. It is necessary to utilize the standard additions technique to overcome matrix effects. Analyses of 38 samples collected in the Chicago and Cook County area on March 31, 1966, as a part of the National Air Sampling Network, yielded values from 0.10 to 3,18 g. of Pb per cubic meter of air. Results obtained by the referee method of polarography showed substantial agreement with atomic absorption values. Possibilities of employing atomic absorption for the determination of other metals found in suspended particulates are currently being investigated. 12 references, 4 figures, 2 tables.

New and improved procedures for gas sampling and analysis in the national air sampling network.

The NASN sampler for the collection of gaseous pollutants has been modified to increase its versatility and efficiency. Oxides of nitrogen are collected in bubblers employing a 70-100 μ frit with a collection efficiency of approximately 50% depending upon the frit porosity. Included in the sampler is a bubbler for the collection of aldehydes in which the aldehyde-MBTH complex is stable at least two weeks. This inert bubbler, which is constructed of polypropylene and Teflon, makes it possible for samples to be collected over the network and analyzed at a central laboratory. In addition, gaseous ammonia is collected in 0.1N H2SO4. This collecting system has an efficiency of greater than 85%. Low-level samples are analyzed automatically employing Nesslerization, whereas high-level samples from source emissions may be collected in indicating boric acid and titrated with 0.02N H2SO4. The sampler will accommodate either 50 or 100 ml polypropylene collecting tubes.

A factor analysis model of large scale pollution

Based on data obtained from the U.S. Public Health Service National Air Sampling Network for the years 1957–1961, factor analysis techniques were used to produce a pollution model for 30 U.S. cities. Orthogonal models obtained from Varimax and Quartimax solutions and an oblique solution (Oblimax) were similar. The first four principal factors were tentatively assigned to pollution from (I) heavy industry, (II) automobiles, (III) fuel burning, and (IV) petroleum refining on the basis of their chemical composition. These four factors account for about 70 per cent of the variance while another 20 per cent appears to be due to widespread use of plating materials. Regression of the derived factors (factor scores) on the 30 sampling locations indicates general agreement with the known character of the sites and with other studies of individual pollution components.

Application of Polyurethane Foam Filters for Respirable Dust Separation

Polyurethane foam was incorporated as a prefilter on standard hi-volume samplers of the National Air Sampling Network (NASN) in an exploratory study. The foam selectively filtered particles of various sizes. The characteristics of the particles passing through the foam approached the respirable size fraction as defined by reports of the Atomic Energy Commission. The respirable fraction was then collected on a glass-fiber filter. Parameters such as pore size and thickness of the foam, air flow rates, and loadings were studied to determine their effects on the filtration of “respirable” dust. Ambient air was the particulate source, and sizing was accomplished by an Andersen sampler coupled with nephelometric analyses. Some sizing was also done microscopically. The foam was evaluated at several locations to account for possible variations in ambient air over areas of different industrial complexity.

RESULTS OF FIVE YEARS' OPERATION OF THE NATIONAL GAS SAMPLING NETWORK.

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.

CINCINNATI'S RADIOACTIVE FALLOUT MONITORING PROGRAM.

Two aspects of Cincinnati's fallout monitoring program are discussed: monitoring in the event of a nuclear attack and routine daily monitoring of fallout. The hlstory of the Hamilton County civil defense and Cincinnati air pollution organizations is described. The network of monitoring stations and the training program are discussed. A continuous air monitor for beta activity is described. Fallout data collected as a part of the National Air Sampling Network are given. (D.L.C.)

Choosing an aerometric data system.

Since air pollution studies vary in complexity, their data systems vary also. Small studies may involve a few dustfall results taken monthly; complex studies, such as the Continuous Air Monitoring Program, may involve data generated at the rate of 14,000 numbers per day. Small studies may require only paper and pencil; complex ones may require a variety of data processing equipment, including electronic computers. The choice of the proper data system is important, for data processing and analysis costs may be one-third to one-half of the total study cost. Brief descriptions are given of data unit operations (record, punch, verify, sort, tabulate, and calculate) and the machines that are used to perform them. Examples of systems using various components are cited, including systems used in the National Air Sampling Network, The Continuous Air Monitoring Program, and the Louisville and Nashville air pollution studies. Sources and rental costs are given for the various data machines.

Evaluation of air particulate sampling equipment.

Abstract Techniques used by the National Air Sampling Network for the collection of samples of suspended particulate matter for subsequent analysis are discussed. Sampling equipment, particularly the Hi-Vol sampler and a vacuum pump sampler using membrane filters for extended sampling periods, is described and data on sampler performance are presented.

Analytical Aspects of the Use of Glass Fiber Filters for the Collection and Analysis of Atmospheric Particulate Matter

Abstract Characteristics of the ideal sampling medium, required by the Public Health Service National Air Sampling Network's program of sampling and analysis, are described. The chemical and physical properties of a glass fiber filter web are contrasted with these ideal characteristics. The importance of quality control by the supplier is emphasized by describing problems arising from variations in filter quality. Amounts of benzene-soluble organics, water soluble alkali and alkaline-earth salts, and metals in currently available brands are compared.

Airborne particulate beta radioactivity measurements of the National Air Sampling Network--1953-1959.

Abstract The air-borne particulate radioactivity data of the National Air Sampling Network have been summarized for the period October, 1953, through December, 1959. Sampling and counting procedures are described, and the decay rates of fission products are considered. Radioactivity of particulates is presented relative to source and distribution.

Research in the Radioactive Contamination of the Environment

Research activities of the Division of Radiological Health, Robert A. Taft Sanitary Engineering Center, Public Health Service, Cincinnati, Ohio, are described. The Center operates three national networks in cooperation with state and municipal agencies. These include the National Air Sampling Network, which comprises 161 stations from which 24-hr samples of air particulates are collected on a statistically random basis at least bi-weekly; the Water Quality Basic Data Network, which collects weekly samples from 50 stations on the principal U. S. streams; and a National Milk Surveillance Network, which provides monthly samples from each of 10 milk sheds. Gross beta determinations are made on the air and stream samples; gross alpha determinations on one-fourth of the stream samples; and specific radionuclide analyses are made on all milk samples. Representative data on the Cincinnati area are included. (C.H.)

ParticulatePollutantsIn TheAirOF TheUnited States

In operation since 1953, the National Air Sampling Network has collected a large quantity of data concerning the concentrations of suspended particulate air pollutants in the United States. This paper reports the results of statistical analyses of the suspended particulated data and treats in succession three major topics: establishment of the mathematical form of the distribution of particulate levels, discussion of parameters which may be used to defined these distributions, and use of the descriptive parameters in drawing conclusions as to the suspended particulate pollution in the air of the United States. 5 references, 7 figures, 9 tables.

Results of Three Years of Operation of the National Air Sampling Network

Results of Three Years of Operation of the National Air Sampling Network