Areawide Trace Metal Concentrations Measured by Multielement Neutron Activation Analysis

A suite of 24 hour high volume air particulate samples, collected June 11–12,1969, at 25 locations in the Northwest Indiana area, has been analyzed by nondestructive neutron activation analysis for 30 trace elements. The use of Ge(Li) gamma-ray spectrometry and computer assisted data reduction, combined with 2-4 replications of each analysis, yielded precise results which allowed a study of the geographical distribution patterns of the elements. Some elements, such as Na, K, Ti, Al, Sm, and Eu, show only minor concentration variations over the area,while others, such as Cu, W, Cr, Zn, Sb, Ga, Br, Ag, Fe, and Ce, show large variations, indicative of important local sources. Similar distribution patterns and high correlation coefficients suggest common sources for several elements. The variations of most heavy elements significantly exceed previously reported variations of total particulate, indicating the latter to be an unsatisfactory guide for elemental distribution, especially near pollution sources. Three representative locations for measurement of elemental abundances in the area are suggested. The influence of meteorological conditions and the potential Lake Michigan pollution hazard are discussed     

Measuring Concentrations of Volatile Organic Compounds in Vinyl Flooring

ABSTRACT

The initial solid-phase concentration of volatile organic compounds (VOCs) is a key parameter influencing the emission characteristics of many indoor materials. Solid-phase measurements are typically made using solvent extraction or thermal headspace analysis. The high temperatures and chemical solvents associated with these methods can modify the physical structure of polymeric materials and, consequently, affect mass transfer characteristics.

To measure solid-phase concentrations under conditions resembling those in which the material would be installed in an indoor environment, a new technique was developed for measuring VOC concentrations in vinyl flooring (VF) and similar materials. A 0.09-m² section of new VF was punched randomly to produce ~200 0.78-cm² disks. The disks were milled to a powder at -140 °C to simultaneously homogenize the material and reduce the diffusion path length without loss of VOCs. VOCs were extracted from the VF particles at room temperature by fluidized-bed desorption (FBD) and by direct thermal desorption (DTD) at elevated temperatures. The VOCs in the extraction gas from FBD and DTD were collected on sorbent tubes and analyzed by gas chromatog-raphy/mass spectrometry (GC/MS). Seven VOCs emitted by VF were quantified. Concentration measurements by FBD ranged from 5.1 |ig/g VF for n-hexadecane to 130 |Jg/g VF for phenol. Concentrations measured by DTD were higher than concentrations measured by FBD. Differences between FBD and DTD results may be explained using free-volume and dual-mobility sorption theory, but further research is necessary to more completely characterize the complex nature of a diffusant in a polymer matrix.     

Measuring Ammonia Concentrations and Emissions from Agricultural Land and Liquid Surfaces: A Review

Abstract

Aerial ammonia concentrations (C _g) are measured using acid scrubbers, filter packs, denuders, or optical methods. Using C _g and wind speed or airflow rate, ammonia emission rate or flux can be directly estimated using enclosures or micrometeorological methods. Using nitrogen (N) recovery is not recommended, mainly because the different gaseous N components cannot be separated. Although low cost and replicable, chambers modify environmental conditions and are suitable only for comparing treatments. Wind tunnels do not modify environmental conditions as much as chambers, but they may not be appropriate for determining ammonia fluxes; however, they can be used to compare emissions and test models. Larger wind tunnels that also simulate natural wind profiles may be more useful for comparing treatments than micrometeorological methods because the latter require larger plots and are, thus, difficult to replicate. For determining absolute ammonia flux, the micrometeorological methods are the most suitable because they are nonintrusive. For use with micrometeorological methods, both the passive denuders and optical methods give comparable accuracies, although the latter give real-time C _g but at a higher cost. The passive denuder is wind weighted and also costs less than forced-air C _g measurement methods, but it requires calibration. When ammonia contamination during sample preparation and handling is a concern and separating the gas-phase ammonia and aerosol ammonium is not required, the scrubber is preferred over the passive denuder. The photothermal interferometer, because of its low detection limit and robustness, may hold potential for use in agriculture, but it requires evaluation. With its simpler theoretical basis and fewer restrictions, the integrated horizontal flux (IHF) method is preferable over other micrometeorological methods, particularly for lagoons, where berms and land-lagoon boundaries modify wind flow and flux gradients. With uniform wind flow, the ZINST method requiring measurement at one predetermined height may perform comparably to the IHF method but at a lower cost.     

Diurnal Variation of Aerosol Trace Element Concentrations In Livermore,California*

Concentrations of 15 atmospheric aerosol trace elements in Livermore, California, were measured by neutron activation analysis in 2–hour filter samples for 58 hours during 3 typical summer days. All elements showed cyclic patterns with concentration variations of factors of 3 to 10. Three basic patterns were seen: (1) Na and Cl in phase with each other and nearly perfectly out of phase with the others, with a late night maximum for both; (2) All other elements except Br, showing a midafternoon maximum; and (3) Br, which had morning and evening peaks suggestive of automotive sources. Details of the patterns suggest a diurnal circulation model for the Livermore Valley involving alternation between fresh and aged marine air. Comparison of the trace element patterns with those of CO, NO₂, and “oxidant” was not definitive.     

A Fast Gas Chromatographic Method for Measuring C2-C6 Alkanes and Alkenes in Air

The Environmental Protection Agency is responsible for establishing, reviewing, and revising standards of performance for new stationary sources of air pollution. Since this federal program was authorized in 1970, standards of performance (commonly referred to as new source performance standards or NSPS) have been developed for 34 categories of stationary sources. These regulations have focused primarily on large new sources of particulate matter, NO _x , and SO₂ emissions. Recently, work has begun on NSPS for a number of source categories that emit volatile organic compounds. Environmental professionals in these industries and in many regulatory agencies have little direct experience with the NSPS program and are unaware of the detailed engineering, cost, and economic information available with each proposed rulemaking. This article, therefore, reviews the purposes, procedures, and benefits of the NSPS program. A summary of the NSPS that have been promulgated through February 1983 are presented in tabular form.     

Quality Assured Measurements of Animal Building Emissions: Gas Concentrations

Abstract

Comprehensive field studies were initiated in 2002 to measure emissions of ammonia (NH₃), hydrogen sulfide (H₂S), carbon dioxide (CO₂), methane (CH₄), nonmethane hydrocarbons (NMHC), particulate matter <10 µm in diameter, and total suspended particulate from swine and poultry production buildings in the United States.

This paper focuses on the quasicontinuous gas concentration measurement at multiple locations among paired barns in seven states. Documented principles, used in air pollution monitoring at industrial sources, were applied in developing quality assurance (QA) project plans for these studies. Air was sampled from multiple locations with each gas analyzed with one high quality commercial gas analyzer that was located in an environmentally controlled on-farm instrument shelter. A nominal 4 L/min gas sampling system was designed and constructed with Teflon wetted surfaces, bypass pumping, and sample line flow and pressure sensors. Three-way solenoids were used to automatically switch between multiple gas sampling lines with ≥10 min sampling intervals. Inside and outside gas sampling probes were between 10 and 115 m away from the analyzers. Analyzers used chemiluminescence, fluorescence, photoacoustic infrared, and photoionization detectors for NH₃, H₂S, CO₂, CH₄, and NMHC, respectively. Data were collected using personal computer-based data acquisition hardware and software. This paper discusses the methodology of gas concentration measurements and the unique challenges that livestock barns pose for achieving desired accuracy and precision, data representativeness, comparability and completeness, and instrument calibration and maintenance.     

A New Catalytic Reactor for Nitrogen Oxides Removal

The body of information presented in this paper is directed to those individuals concerned with the catalytic NO_x removal reactor for a dirty (containing dust) flue gas. In the case of treating a dirty flue gas, the concentration of dust is the most important factor. While the dirty gas passes through the catalytic reactor, dust particles deposit and plug up the catalyst causing the reactor pressure loss to rise. As a result, the NO_x reduction efficiency decreases more and more, and continuous operation becomes impossible. A new type of NO_x removal reactor for dirty flue gas, the intermittent moving bed reactor, has been developed. The following characteristics have been evaluated: (1) method of calculating reactor pressure loss caused by dust particles, (2) static pressure distribution across the catalyst bed in the reactor, (3) method of evaluating uniform movement of catalyst and (4) reentrainment pattern of dust by catalyst movement. After carrying out various successful pilot plant tests, the information needed for construction and operation of a commercial plant has been developed.     

Relationship of Indoor N02 Concentrations to Use of Unvented Gas Appliances

In preparation for a prospective study of the relationship of residential nitrogen dioxide exposure and respiratory infections in infants, we conducted a pilot study to assess NO₂ concentrations in a sample of homes in Albuquerque, New Mexico. The methods used to characterize concentrations are described. Three locations in 144 homes were monitored with passive diffusion samplers for two two-week cycles during November and December 1984. Two-week average NO₂ concentrations in the activity room ranged from 2.0 to 168.7 ppb. NO₂ concentrations in the activity room and the infant’s bedroom were fivefold higher in homes with gas stoves than in homes with electric stoves. Sixty-four percent of homes with gas stoves had activity room concentrations that exceeded the highest outdoor concentration. Multiple regression models Indicated that the outdoor concentration, use of a gas stove, particularly one with pilot lights, presence of a gas dryer in the living area, and use of a floor or wall furnace contributed to NO₂ concentrations. Use of a toaster or microwave oven in a house with a gas stove reduced NO₂ concentrations. The results of this study demonstrate a broad range of NO₂ concentrations in Albuquerque. We conclude with suggestions for an exposure assessment strategy that would be valid and feasible in the context of a large epidemiologic study of the health effects of NO₂.     

Evaluation of Virtual Source Beam Configurations for Rapid Tomographic Reconstruction of Gas and Vapor Concentrations in Workplaces

Abstract

Beam path average data from an Open Path Fourier Transform Infrared (OP-FTIR) spectrometer can be used to reconstruct two-dimensional concentration maps of the gas and vapor contaminants in workplaces and the environment using computed tomographic (CT) techniques. However, a practical limitation arises because in the past, multiple-source and detector units were required to produce a sufficient number of intersecting beam paths in order to reconstruct concentration maps. Such a system can be applied to actual field monitoring situations only with great expense and difficulty. A single monostatic OP-FTIR system capable of rapid beam movement can eliminate this deficiency. Instead of many source and detector units, a virtual source arrangement has been proposed using a number of flat mirrors and retroreflectors to obtain intersecting folded beam paths.

Three virtual source beam configurations generated for a single-beam steerable FTIR system were tested using 54 flat mirrors and four retroreflectors or 54 flat mirrors and 56 retroreflectors mounted along the perimeter walls of a typical 24- x 21-ft test room. The virtual source CT configurations were numerically evaluated using concentration maps created from tracer gas concentration distributions measured experimentally in a test chamber. Synthetic beam path integral data were calculated from the test maps and beam configurations. Computer simulations of different beam configurations were used to determine the effects of beam geometry. The effects of noise and peak-reducing artifacts were evaluated. The performance of the tomographic reconstruction strategy was tested as a function of concentration and concentration gradients.     

A New Gas-Liquid Interphase Reactor

A first-order differential equation describes the dynamic response of many continuous air sampling instruments: C_t = C_i + p(dC_i/dt), where C_t is true concentration, C_i is indicated concentration, p is the time constant, and t is time. The time constant, lag time, delay time, and response time are all functions of the volume and flow through the sensor reservoir. All of them can be expressed by the same general equation: t = k₃V/Q, where t is the selected time variable, k₃ is a constant appropriate to the particular system and selected time variable, V is sensor reservoir volume, and Q is the flow rate through the reservoir. The time constant is the time a sampler takes to indicate 63.2 percent of its final response. Select time constants equal to about half of the shortest desired averaging time. Solve the second equation for the reagent flow to give the desired time constant. Selection of such a time constant eliminates spurious “noise” produced by a fast-responding system. It also provides values within 5 percent of true for atmospheres that change markedly between successive intervals. If a slow-responding system must be used, use the first equation to increase apparent response time. A digital computer can be programmed to automatically correct all measured values. Similarly, analog circuitry can be installed in an air sampling instrument to increase or decrease response time. The analog circuitry to increase response time will continuously solve and plot the first equation.     

Analysis of Sampling Strategies for Estimating Annual Average Indoor NO2 Concentrations in Residences with Gas Ranges

Abstract

Range gas consumption in households tends to follow an annual cycle resembling a sinusoid, with peak consumption during the winter. When outdoor NO2 concentrations have a constant or small impact, the resulting indoor NO2 concentrations also tend to resemble an annual sinusoid. Optimal monitoring strategies can be designed to take advantage of this knowledge to obtain a better estimate of the true annual average gas consumption or indoor NO2 concentration. Gas consumption data, together with measured outdoor concentrations, house volumes, sampled emission rates, air exchange rates, and NO2 decay rates, are used to model weekly indoor NO2 concentrations throughout the year. Based on the modeling results, various monitoring strategies are evaluated for their accuracy in estimating the annual mean. Analysis of the results indicates that greater accuracy is attained using samples equally spaced throughout the year. In addition, the expected error for various monitoring strategies and various numbers of equally spaced samples is quantified, and their ability to classify homes into correct concentration categories is assessed.     

Design and Verification of a Programmable Gas Dispensing System for Exposing Plants to Dynamic Concentrations of Air Pollutants

Abstract

Landfills represent a source of distributed emissions source over an irregular and heterogeneous surface. In the method termed “Other Test Method-10” (OTM-10), the U.S. Environmental Protection Agency (EPA) has proposed a method to quantify emissions from such sources by the use of vertical radial plume mapping (VRPM) techniques combined with measurement of wind speed to determine the average emission flux per unit area per time from nonpoint sources. In such application, the VRPM is used as a tool to estimate the mass of the gas of interest crossing a vertical plane. This estimation is done by fitting the field-measured concentration spatial data to a Gaussian or some other distribution to define a plume crossing the vertical plane. When this technique is applied to landfill surfaces, the VRPM plane may be within the emitting source area itself. The objective of this study was to investigate uncertainties associated with using OTM-10 for landfills. The spatial variability of emission in the emitting domain can lead to uncertainties of –34 to 190% in the measured flux value when idealistic scenarios were simulated. The level of uncertainty might be higher when the number and locations of emitting sources are not known (typical field conditions). The level of uncertainty can be reduced by improving the layout of the VRPM plane in the field in accordance with an initial survey of the emission patterns. The change in wind direction during an OTM-10 testing setup can introduce an uncertainty of 20% of the measured flux value. This study also provides estimates of the area contributing to flux (ACF) to be used in conjunction with OTM-10 procedures. The estimate of ACF is a function of the atmospheric stability class and has an uncertainty of 10–30%.     

Predictions of Maximum Ground-Level H2S Concentrations Resulting from Two Sour Gas Well Blowouts

Alberta has recently experienced two sour gas well blowouts: Lodgepole and Claresholm. Sulphur emissions associated with the blowouts were about 1400 and 2 tonnes per day, respectively. The Lodgepole blowout was not only of much greater magnitude but also lasted significantly longer than the Claresholm blowout (67 vs. 4 days). Special air quality monitoring with respect to H₂S was conducted to assess impacts of the blowouts. Monitoring was especially extensive for the Lodgepole incident. Maximum observed ground-level H₂S concentrations were compared to predictions obtained using a Gaussian model which makes allowance for the effects of sonic exit velocity on plume spread and the effects of wind shear on plume transport. There was appreciable agreement between predicted and observed values.     

Determination of Multiple Atmospheric Diffusion Coefficients Using the Carbon Hollow Tube Gas Chromatography Method

Gaseous organic species were collected by carbon hollow tube pairs. Diffusion coefficients (D_a) of anhydrous and hydrated organic species were then determined by measuring the ratio of each component that adsorbed in the collection tubes. In controlled experiments, the precision and accuracy of D_a determinations were 12 percent and 9.1 percent respectively. Ternary mixtures of airborne compounds were separated and quantified using gas chromatography. Observed D_as for each component of these mixtures were similar to those obtained for individual components. This method was applied to volatile organic species in marine air, soil air, and cigarette effluents.     

A Device for Measuring Volatile Organic-Carbon Emissions from Cooling-Tower Water

A manual method for measuring reduced sulfur compounds in kraft pulp mill and sulfur recovery plant emissions was evaluated. The method involves removing SO₂ from the gas stream (if present) with a citric acid-potassium citrate buffer that passes reduced sulfur compounds; thermal oxidation of all reduced sulfur compounds to SO₂; collection of the SO₂ in H₂O₂; and a titrimetric analysis of the H₂O₂ for SO₄ ^2?. A heated filter removes alkaline particulate matter that would produce a negative interference if absorbed by the buffer. When used at kraft pulp mills, the method agrees closely with Reference Method 16, provided that nonregulated reduced sulfur compounds, such as carbonyl sulfide, are not present in the emissions. At sulfur recovery plants, nonregulated reduced sulfur compounds, such as thiophene, are likely to be present in the emissions and will produce a positive bias in the results obtained with this method. The precision of the method ranges from 1 to 7 percent relative standard deviation.     

A Simple Technique for Measuring Mean H2S Concentration

Lead acetate impregnated ceramic tiles are useful devices for determining H₂S levels in the outdoor air. The exposure of tiles in simple shelters and for an overnight period is effective in an areawide sampling program to determine: (1) whether a significant H₂S source exists, (2) the source location, (3) the area affected, and (4) the relative intensity pattern.

On the basis of an overnight exposure, tiles can “see” a mean H₂S concentration range of 0.003 to 0.3 ppm. The lower level of sensitivity is near 0.03 ppm X hr. Hence, tiles offer a way to verify whether hourly air quality standards are being exceeded.

Tiles can be qualitatively evaluated against: experience, known effects, or by ranking against each other. Tiles can be semi-quantitatively evaluated by visual grading against painted standards developed by exposing tiles of particular manufacture to known H₂S dosages.