Impact/Purpose:

The purpose of this two (2) year study (one year field program) is to characterize the chemical composition and sources of coarse particles (PMc, particles between PM2.5 and PM10) in a rural area of increasing population growth, including the influence of specific source areas, such as, nearby areas influenced by mining and agricultural activity.

Description:

Characterization of PMc is critical to the understanding of recently observed adverse health effects (e.g., asthma, reduced cardiac variability, etc) from coarse particles in ambient air. PMc mass an (PMc, particles between PM2.5 and PM10) in a rural area of increasing population d chemical composition data will be obtained at 3 sites in Pinal County, Arizona. Unique, first time information on the organic composition and semi-volatile nature of PMc will be obtained at these three sites. New samplers and sampling methods will be evaluated as part of this study. Data from the existing IMPROVE and Pinal county monitoring networks will be integrated to obtain PM2.5 mass and chemical speciation data to augment the PMc data. A limited number of PM2.5 samples will be analyzed for chemical composition to verify the representativeness of the study sites relative to the IMPROVE and Pinal County sites. Temporal and spatial characteristics of the data will be evaluated and an estimate of sources influencing PMc concentrations will be obtained using receptor modeling methods. These data will begin to increase EPA’s understanding of the potential toxicity of rural PMc, which is of interest not only to EPA and the scientific community in preparation for the next review of the PM NAAQS, but also to Region 9 air districts, state agencies, tribes and other stakeholders for their current and future efforts to better understand and control the impact of rural PMc concentrations, particularly in areas of increasing populations. Pinal County, Arizona was selected for this study because multiple monitoring sites currently exceed the 24-hour PM10 standard (150 ug/m3). The county is largely rural with a growing population (229,549 in 2005 estimated-population; 2000 sq. mi. The population of the state of Arizona is projected to increase by 29.4% in the decade between 2000 and 2010.) Sites will be selected to represent up to three separate areas of the county with differing source-mixes (residential, agricultural, and mining-related). Sites will be chosen with the assistance of the Pinal County Air Quality Control District (District) and Arizona Department of Environmental Quality (ADEQ). The District and ADEQ will also assist with providing sampling equipment, installation, and operation of the equipment and sampler operations. Four dichotomous virtual impactor (DVI) samplers will be operated at each site to allow for comprehensive chemical determination of PMc on an estimated 80% of the collected filters. PMc and PMf mass will be obtained for all sampling periods. PMf filters will be archived initially and a limited number will be analyzed later in the study to determine representativeness with other nearby monitoring networks (e.g., IMPROVE and Pinal County). Two samplers (fine and coarse sides) will be equipped with Teflon filters and two with quartz filters. One PMc Teflon filter will be analyzed for mass (gravimetrically) and ions (ion chromatography) and one for trace elements (ICP-MS). One PMc quartz-fiber filter will be analyzed for OC/EC (by thermal optical absorption) and the other for OC species, the latter will be composites of samples collected monthly. A single continuous dichotomous sampler (TEOM 1405-DF Dichotomous Ambient Particulate Monitor with FDMS, FDMS TEOM) will be operated at one of the sites to obtain a continuous record of PMc and PMf mass on an hourly basis. Initially 10 days of collocated sampling over about 1 month to allow for an estimate of overall precision. Chemical analysis data will be obtained within 30 days of sampling to allow for any modifications to samplers. Sampling periods will be 24-hr for filter based time-integrated samplers and hourly averaged for the continuous FDMS TEOM . FDMS TEOM continuous data will be averaged to respective 24-hr average data for comparison to filter-based DVI data. This evaluation is especially important for the newly commercialized FDMS TEOM. Following preliminary sampler performance evaluation, the sampling frequency will be one 24-hour average sample every six days coinciding with the STN/IMPROVE sampling schedule so direct comparisons can be made with IMPROVE and Pinal County PM2.5 speciation and mass samples and PM10 mass samples as well as urban sampling in Phoenix and Tucson and special study data from the Yuma border area. Integration of other networks will allow for a regional characterization and determination of representativeness of the sites chosen for this study. Chemical analysis data will be available no more than 2 months after the quarter it was collected to allow for initial evaluations and quality assurance. These data will be made available to all participants. This proposal includes laboratory analytical services to chemically characterize PMc collected on filters for mass, metals, ions, and major carbon components and individual species. PM2.5 mass will be obtain on all samples and if budget allows, a limited number of PM2.5 samples will be analyzed to confirm representativeness of the chemical components of PM2.5 at the study sites relative to the other networks. The EPA protocol for PM10 sampling will be followed. Independent quality assurance will be conducted by the Region 9 Quality Assurance Office (chemical analysis methods) and ORIA, Las Vegas by the QA field manager for the STN network for the field measurements. Special studies including collocated sampling PMc and PM2.5 mass, and PMc chemical composition will be considered as funding allows. Use of the continuous FDMS TEOM will allow for examination of the volatile components of PMc as well as a detailed examination of the variability of PMc on an hourly basis over the one-year period, and measurements of OC species and trace elements by ICP-MS will allow for an examination of source markers developed through receptor modeling (e.g., PMF) and an estimate of source types impacting the sites. The project includes data analysis to evaluate the results and receptor modeling to give a sense of the source types impacting PMc concentrations at the sites. The policy objective of this two year study is to more fully characterize the chemical composition of coarse particles in a rural area with high PMc levels and increasing population and to attempt to link PMc concentrations to source types over a variety of spatial and temporal scales. This objective will help provide guidance to Regions 8 & 9, Pinal County, and Arizona DEQ on likely sources and source strengths and how they vary by season and by day of the week. Research objectives include the spatial and temporal variability (seasonally, daily, diurnally) of PMc and its relationship to PM2.5 by integration with nearby PM2.5 monitoring; examining specific spatial and temporal differences in PMc influenced by specific source types (residential, agricultural, mining-related); identification of possible organic species and trace element source markers; and evaluation of the semi-volatile nature of PMc components.

Record Details: