A wealth of air toxics monitoring data has been collected by state and local agencies in support of various monitoring programs including the 2001/2002 10-city pilot monitoring project. To assist in developing the national air toxics monitoring network design guidelines, Battelle and STI previously conducted analyses of these data. In this project for the Lake Michigan Air Directors Consortium (LADCO), STI validated the data and provided data validation guidelines to the states. STI also developed, performed, and documented descriptive analyses, including spatial and temporal variation in concentrations and trends of air toxics data across the U.S., and compared ambient measurements to air toxics and model output for a few cities. Some analyses focused on the relationship between elemental carbon and diesel emissions. ArcGIS Spatial Analyst was used to investigate potential spatial variations in exposure to mobile source toxic emissions and evaluate candidate monitoring locations. STI also performed source apportionment of toxics data using positive matrix factorization. Results were presented to stakeholders in a workbook and in two workshops held in 2003 and 2004 (http://www.ladco.org/toxics.html).
In ongoing support to the Arizona Department of Environmental Quality, STI staff validated hazardous air pollutant (HAP) data collected in Phoenix, Arizona, and investigated the spatial and temporal characteristics of toxic pollutants to assess future data collection needs. We assessed the adequacy of current toxic measurements and determined the frequency, sample duration, and pollutants to meet the network monitoring objectives. We developed and selected weighting schemes for the various layers to be used in a suitability analysis including selected population segments, mobile source activity, point source emissions density, and meteorology. This resulted in a map showing highly suitable monitoring locations that met monitoring goals. STI scientists conducted a workshop on the assessment and prepared a quality assurance project plan for the HAP monitoring program.
STI conducted a 2-day data validation workshop in Chicago, Illinois, at U.S. EPA Region V headquarters. Data validation guidelines and local examples were provided for criteria pollutant, speciated PM2.5, hydrocarbon, air toxics, surface meteorological, and special studies (e.g., continuous mass, organic carbon/elemental carbon) data. Hands-on training was provided on validation tools including VOCDat.
In ongoing support to the Arizona Department of Environmental Quality's Phoenix area Photochemical Assessment Monitoring Stations (PAMS) program, STI validated volatile organic compound data collected from 1998 to 2003. Valid data were then used to perform the U.S. EPA's prescribed analyses for the PAMS program including characterizing spatial and temporal trends.
From 1997 through 1999, Baylor University flew over 160 aircraft flights collecting air quality data in Texas. STI scientists analyzed the aircraft data from 36 selected flights, in conjunction with meteorological and emissions data. STI characterized the three-dimensional distributions of ozone, oxides of nitrogen, and sulfur dioxide concentrations and interpreted the distributions to improve the understanding of ozone sources and transport in Texas. The findings from the analysis supported the development of a conceptual model of the chemical and meteorological processes that influence ozone concentrations in the Houston-Galveston Bay, Dallas-Fort Worth, and San Antonio metropolitan areas and the amount each area contributes to downwind concentrations.
CRPAQS was designed to improve the scientific understanding of excessive PM concentrations in central California. STI's involvement in the data analysis phase of CRPAQS included assessing technical issues associated with the accuracy, precision, and representativeness of air quality and meteorological measurements; analysis of boundary and background particulate matter (PM) and precursor concentrations; analysis of PM and precursor concentrations in the "vertical dimension"; reconciling emission estimates with ambient data and reconciling ambient measurement variations and observations of emissions-related activities; evaluation of air pollutant transport including an assessment of the spatial, temporal, and chemical characteristics of visibility; and analyses of PM phases (gas vs. liquid vs. aerosol), secondary formation limitations, and nitric acid formation. (Read more about CRPAQS.)
Baylor University performed aircraft-based sampling with two aircraft in 2003 in Texas to support a tracer release study at an industrial facility, characterize point source emissions and their effect on ozone production, and document/quantify regional ozone transport. STI provided project and flight planning, and preparation support; revised the quality assurance project plan; installed, tested, and calibrated instrumentation on two aircraft; developed data processing software; processed and validated data; and prepared various data analysis products including spatial and temporal depictions of the data. This work was performed for the Texas Commission on Environmental Quality under contract to Baylor University.
In this study for the Texas Commission on Environmental Quality, STI acquired, validated, and interpreted hourly automated-gas chromatograph (auto-GC) data from 1998-2001 for the Houston area. Data were summarized by individual compounds, species groups, and TNMOC concentrations by site, year, season, month, and time of day. Similar summaries were prepared on weight percent and reactivity-weighted bases. STI performed case study analyses of ozone episode days and of wind direction dependence to characterize the potential role of individual compounds in ozone formation. Positive matrix factorization and other factor analysis tools were applied to the ambient data to improve the understanding of emission sources impacting air quality monitoring sites.
STI validated precipitation and speciated particulate matter data collected as part of an air pollutant deposition study at Freeport, Maine, near Casco Bay. We characterized nitrogen, mercury, and fine particle data including assessing seasonal trends and comparing Casco Bay data to data collected at other Maine sites. We computed wet deposition rates and estimated dry deposition rates for nitrogen (nitrate and ammonia) and mercury. We also compared total (wet plus dry) deposition estimates to estimates from other studies and to the emission inventory. Results were reported at a public meeting regarding Casco Bay pollution. This project was performed for the U.S. EPA under contract to the University of Southern Maine.
To assist in developing the national air toxics monitoring network design guidelines, STI characterized typical seasonal and diurnal patterns for air toxics and illustrated the effects of meteorological conditions on concentration variability. Some analyses focused on the relationship between elemental carbon and diesel emissions. ArcGIS Spatial Analyst was used to explore the placement of monitors in one pilot city to assess exposure to mobile source toxic emissions. STI also performed source apportionment of toxics data using positive matrix factorization. This project was performed for the U.S. EPA under contract to the Lake Michigan Air Directors Consortium (LADCO).
STI worked with Battelle staff for the U.S. EPA to develop and analyze an integrated database of criteria pollutants, their precursors and chemical components, and air toxics to evaluate the potential intersection of the nation's ozone, PM2.5, and air toxics problems. The team investigated the possibility that some emissions sources contribute to multiple air quality problems through exploratory (i.e., broadly applied to pollutants and sites) and focused (i.e., more in-depth assessment of selected sites and pollutants) analyses including source apportionment, spatial/temporal correlation, and ensemble backward trajectory applications.
STI developed data validation guidelines for air toxics and applied them to data collected from 2001 to 2003 at two sites in Phoenix, Arizona. We also developed and conducted a series of prescribed analyses that address basic policy questions. To identify areas with high exposure to Diesel Particulate Matter (DPM) we conducted spatial analysis using geographic information system (GIS) capabilities. Source apportionment of PM2.5 was conducted using Positive Matrix Factorization to identify, quantify, and evaluate the impact of individual source types on PM2.5 levels in Phoenix. This work was performed for the Arizona Department of Environmental Quality.
During the 1997 Southern California Ozone Study, 26 radar wind profilers with radio acoustic sounding systems and 6 sodars collected upper-air wind and temperature data. STI and team members performed objective and subjective quality control on these raw data. The quality control effort identified erroneous measurements due to radio interference, spurious radar returns from birds and aircraft, ground clutter, noise, etc. The subjective reviews involved examination of the hourly data for both internal and external consistency and meteorological reasonableness, and the data were edited as needed. The end product was a high quality, validated data set. This work was performed for the South Coast Air Quality Management District.