Determination of Volatile Organic Compounds in the Atmosphere Using Two Complementary Analysis Techniques

ABSTRACT

During a preliminary field campaign of volatile organic compound (VOC) measurements carried out in an urban area, two complementary analysis techniques were applied to establish the technical and scientific bases for a strategy to monitor and control VOCs and photochemical oxidants in the Autonomous Community of the Basque Country. Integrated sampling was conducted using Tenax sorbent tubes and laboratory analysis by gas chromatography, and grab sampling and in situ analysis also were conducted using a portable gas chromatograph. With the first technique, monocyclic aromatic hydrocarbons appeared as the compounds with the higher mean concentrations. The second technique allowed the systematic analysis of eight chlorinated and aromatic hydrocarbons. Results of comparing both techniques, as well as the additional information obtained with the second technique, are included.     

Modeling of Solid Particle Flow and Heat Transfer in Rotary Kiln Calciners

Abstract

Contaminated solid wastes exist in many industrial sites, gas plants, and oil refineries. One method of decontaminating the soil is to subject it to high temperatures in a rotary calciner in an anaerobic environment. Preliminary results from a computational model are presented in this paper for the flow and heat transfer from granular solid particles under treatment in a rotary kiln calciner. A fluidization model using kinetic theory of granular flow has been employed to solve the particle flow and heat transfer problem. While a two-dimensional model is used to predict the rotation induced flow of the solid particles, a pseudo three-dimensional model for heat transfer is developed where the axial bulk temperature gradient is obtained from a one-dimensional energy balance model. The model predictions indicate interesting features of the flow and temperature fields in the bed material. Future tasks include the development of a devolatilization model to study the decontamination of waste soil in the rotary calciner.     

A Comparative Analysis of Emissions Deterioration for In-Use Alternative Fuel Vehicles

Abstract

Although there have been several studies examining emissions from in–use alternative fuel vehicles (AFVs), little is known about the deterioration of these emissions over vehicle lifetimes and how this deterioration compares with deterioration from conventional vehicles (CVs). This paper analyzes emissions data from 70 AFVs and 70 CVs operating in the federal government fleet to determine whether AFV emissions deterioration differs significantly from CV emissions deterioration. An analysis is conducted on three alternative fuel types (natural gas, methanol, and ethanol) and on four pollutants (carbon monoxide, total hydrocarbons, non-methane hydrocarbons, and nitrogen oxides). The results indicate that for most cases studied, deterioration differences are not statistically significant; however, several exceptions (most notably with natural gas vehicles) suggest that air quality planners and regulators must further analyze AFV emissions deterioration to properly include these technologies in broader air quality management schemes.     

Development of a Sample Equilibration System for the TEOM Continuous PM Monitor

ABSTRACT

In recent years, scientific discussion has included the influence of thermodynamic conditions (e.g., temperature, relative humidity, and filter face velocity) on PM retention efficiency of filter-based samplers and monitors. Method-associated thermodynamic conditions can, in some instances, dramatically influence the presence of particle-bound water and other light-molecular-weight chemical components such as particulate nitrates and certain organic compounds. The measurement of fine particle mass presents a new challenge for all PM measurement methods, since a relatively greater fraction of the mass is semi-volatile.

The tapered element oscillating microbalance (TEOM) continuous PM monitor is a U.S. Environmental Protection Agency (EPA) PM₁₀ equivalent method (EQPM-1090-079). Several hundred of these monitors are deployed throughout the United States. The TEOM monitor has the unique characteristic of providing direct PM mass measurement without the calibration uncertainty inherent in mass surrogate methods. In addition, it provides high-precision, near-real-time continuous data automatically. Much attention has been given to semi-volatile species retention of the TEOM method.

While using this monitor, it is desirable to maintain as low an operating temperature as practical and to remove unwanted particle-bound water. A new sample equilibration system (SES) has been developed to allow conditioning of the PM sample stream to a lower humidity and temperature level. The SES incorporates a special low-particle-loss Nafion dryer. This paper discusses the configuration and theory of the SES. Performance results include high time-resolved PM_2.5 data comparison between a 30 °C sample stream TEOM monitor with SES and a standard 50 °C TEOM monitor. In addition, 24-hr integrated data are compared with data collected using an EPA PM_2.5 Federal Reference Method (FRM)-type sampler. The SES is a significant development because it can be applied easily to existing TEOM monitors.     

Aerosol Research and Inhalation Epidemiological Study (ARIES): Air Quality and Daily Mortality Statistical Modeling— Interim Results

ABSTRACT

The Aerosol Research and Inhalation Epidemiological Study (ARIES) is an EPRI-sponsored project to collect air quality and meteorological data at a single site in northwestern Atlanta, GA. Seventy high-resolution air quality indicators (AQIs) are used to examine statistical relationships between air quality and health outcome end points. Contemporaneous mortality data are collected for Fulton and DeKalb counties in Georgia. Currently, 12 months of air quality and weather data are available for analysis, from August 1998 through July 1999.

The interim mortality analysis used Poisson regression in generalized additive models (GAMs). The estimated log-linear association of mortality with various AQIs was adjusted for smoothed functions of time and meteorological data. The analysis considered daily deaths due to all nonaccidental causes, deaths to persons 65 years or older, and deaths in each of the two constituent counties. The fine particle effect associated with the four mortality subgroups, using only today (lag 0), yesterday (lag 1), 2-day average (average of today and yesterday), and first difference (today minus yesterday) measurements of the air quality relative to today's number of deaths was positive for lag 0, lag 1, and 2-day average and positive only for decedents at least 65 years of age using first difference. The t values ranged from 0.81 to 1.15 for lag 0, 1.04 to 1.53 for lag 1, 1.10 to 1.66 for 2-day average, and -0.32 to 0.33 for first difference with 346 or 347 days of data. No statistically significant estimate of the linear coefficient was found for the other 14 air quality variables in our interim analysis for the four mortality subgroups. We discuss diagnostics to support these models.

These interim analyses did not include an evaluation of sensitivity to a larger set of lag structures, nonlinear model specifications, multipollutant analyses, alternative weather model and smoothing model specifications, air pollution imputation schemes, or cause-specific mortality indicators, nor did they include a full reporting of model selection or goodness-of-fit indicators. No conclusion can be drawn at this time about whether the findings from subsequent studies have sufficiently greater power to detect effects comparable to those found in other U.S. cities including at least 2 or 3 years of data.     

Biological Removal of Gaseous Ammonia in Biofilters: Space Travel and Earth-Based Applications

ABSTRACT

Gaseous NH₃ removal was studied in laboratory-scale biofilters (14-L reactor volume) containing perlite inoculated with a nitrifying enrichment culture. These biofilters received 6 L/min of airflow with inlet NH₃ concentrations of 20 or 50 ppm, and removed more than 99.99% of the NH₃ for the period of operation (101, 102 days). Comparison between an active reactor and an autoclaved control indicated that NH₃ removal resulted from nitrification directly, as well as from enhanced absorption resulting from acidity produced by nitrification. Spatial distribution studies (20 ppm only) after 8 days of operation showed that nearly 95% of the NH₃ could be accounted for in the lower 25% of the biofilter matrix, proximate to the port of entry. Periodic analysis of the biofilter material (20 and 50 ppm) showed accumulation of the nitrification product NO₃ ^- early in the operation, but later both NO₂ ^- and NO₃ ^- accumulated. Additionally, the N-mass balance accountability dropped from near 100% early in the experiments to ~95 and 75% for the 20- and 50-ppm biofilters, respectively. A partial contributing factor to this drop in mass balance accountability was the production of NO and N₂O, which were detected in the biofilter exhaust.     

Characterization of Fine Particulate Matter Produced by Combustion of Residual Fuel Oil

ABSTRACT

Combustion experiments were carried out on four different residual fuel oils in a 732-kW boiler. PM emission samples were separated aerodynamically by a cyclone into fractions that were nominally less than and greater than 2.5 |j.m in diameter. However, examination of several of the samples by computer-controlled scanning electron microscopy (CCSEM) revealed that part of the PM_2.5 fraction consists of carbonaceous cenospheres and vesicular particles that range up to 10 |j.m in diameter. X-ray absorption fine structure (XAFS) spectroscopy data were obtained at the S, V, Ni, Fe, Cu, Zn, and As K-edges and at the Pb L-edge. Deconvolution of the X-ray absorption near edge structure (XANES) region of the S spectra established that the dominant molecular forms of S present were sulfate (26-84% of total S) and thiophene (13-39% of total S). Sulfate was greater in the PM_2.5 samples than in the PM₂₅₊ samples. Inorganic sulfides and elemental sulfur were present in lower percentages. The Ni XANES spectra from all of the samples agreed fairly well with that of NiSO₄, while most of the V spectra closely resembled that of vanadyl sulfate (VO?SO₄?xH₂O). The other metals investigated (i.e., Fe, Cu, Zn, and Pb) also were present predominantly as sulfates. Arsenic was present as an arsen-ate (As⁺⁵). X-ray diffraction patterns of the PM_2.5 fraction exhibit sharp lines due to sulfate compounds (Zn, V, Ni, Ca, etc.) superimposed on broad peaks due to amorphous carbons. All of the samples contain a significant organic component, with the loss on ignition (LOI) ranging from 64 to 87% for the PM_2.5 fraction and from 88 to 97% for the PM_2.5+ fraction. Based on ¹³C nuclear magnetic resonance (NMR) analysis, the carbon is predominantly condensed in graphitic structures. Aliphatic structure was detected in only one of seven samples examined.     

Comparison of Short-Term Variations (15-Minute Averages) in Outdoor and Indoor PM2.5 Concentrations

ABSTRACT

Measurements of 15-min average PM_2.5 concentrations were made with a real-time light-scattering instrument at both outdoor (central monitoring sites in three communities) and indoor (residential) locations over two seasons in the Minneapolis-St. Paul metropolitan area. These data are used to examine within-day variability of PM_2.5 concentrations indoors and outdoors, as well as matched indoor-to-outdoor (I/O) ratios. Concurrent gravimetric measurements of 24-hr average PM_2.5 concentrations were also obtained as a way to compare real-time measures with this more traditional metric. Results indicate that (1) within-day variability for both indoor and outdoor 15-min average PM_2.5 concentrations was substantial and comparable in magnitude to day-to-day variability for 24hr average concentrations; (2) some residences exhibited substantial variability in indoor aerosol characteristics from one day to the next; (3) peak values for indoor short-term (15-min) average PM_2.5 concentrations routinely exceeded 24-hr average outdoor values by factors of 3-4; and (4) relatively strong correlations existed between indoor and outdoor PM_2.5 concentrations for both 24-hr and 15-min averages.     

Objectives and Design of Central California's 1995 Integrated Monitoring Study of the California Regional PM10/PM2.5 Air Quality Study

ABSTRACT

The 1995 Integrated Monitoring Study (IMS95) is part of the Phase 1 planning efforts for the California Regional PM_10/PM_2.5 Air Quality Study. Thus, the overall objectives of IMS95 are to (1) fill information gaps needed for planning an effective field program later this decade; (2) develop an improved conceptual model for pollution buildup (PM10, PM2.5, and aerosol precursors) in the San Joaquin Valley; (3) develop a uniform air quality, meteorological, and emissions database that can be used to perform initial evaluations of aerosol and fog air quality models; and (4) provide early products that can be used to help with the development of State Implementation Plans for PM_10. Consideration of the new particulate matter standards were also included in the planning and design of IMS95, although they were proposed standards when IMS95 was in the planning process.     

Estimates of Particle Hygroscopicity during the Southeastern Aerosol and Visibility Study

ABSTRACT

Aerosol water content was determined from relative humidity controlled optical particle counter (ASASP-X) size distribution measurements made during the Southeastern Aerosol and Visibility Study (SEAVS) in the Great Smoky Mountains National Park during summer 1995. Since the scattering response function of the ASASP-X is sensitive to particle refractive index, a technique for calibrating the ASASP-X for any real refractive index was developed. A new iterative process was employed to calculate water mass concentration and wet refractive index as functions of relative humidity. Experimental water mass concentrations were compared to theoretically predicted values assuming only ammonium sulfate compounds were hygroscopic. These comparisons agreed within experimental uncertainty. Estimates of particle hygroscopicity using a rural aerosol model of refractive index as a function of relative humidity demonstrated no significant differences from those made with daily varying refractive index estimates. Although aerosol size parameters were affected by the assumed chemical composition, forming ratios of these parameters nearly canceled these effects.