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FIELD EVALUATION OF A HIGH-VOLUME DICHOTOMOUS SAMPLER
Citation:
SARDAR, S. B., B. CHAKRABARTI, M. D. GELLER, C. SIOUTAS, AND P. A. SOLOMON. FIELD EVALUATION OF A HIGH-VOLUME DICHOTOMOUS SAMPLER. Presented at American Association of Aerosol Research 2005, Atlanta, GA, February 07 - 11, 2005.
Impact/Purpose:
The PM Supersites Program is an ambient monitoring program intended to address the scientific uncertainties associated with fine particulate matter. The main objectives of the Supersites Program are as follows: 1) characterize particulate matter in a way that contributes to the understanding of source-receptor relationships and supports development of State Implementation Plans (SIPs), 2) develop and test advanced measurement methods for potential use in national monitoring networks, and 3) support health and exposure studies by providing detailed chemical and physical data at one or more central monitoring sites.
The specific objectives of this task are to provide scientific review and coordination of the technical aspects of the Supersites Program. This includes coordination among all Supersites projects and other projects which support Supersites objectives, overseeing of the data management, and coordinating the communication of data analysis and modeling results to the scientific community and other stakeholders. Products include a number of peer-reviewed journal articles (approaching 200 or more), final reports from each project, a relational database than includes not only Supersites data, but most aerometric data collected in the continental US and SE Canada during the period July 2001 to August 2002, and a policy relevant findings synthesis entitled Key and Policy Relevant Findings from the Supersites Program and Related Studies. Also supporting the synthesis is a major international conference where results will be presented from air quality methods, measurements, modeling, and data analysis studies with similar objectives to the Supersites program and during the time period of the Supersites Program, i.e., the last 5-7 years.
Description:
This study presents the field evaluation of a high-volume dichotomous sampler that collects coarse (PM10-2.5) and fine (PM2.5) particulate matter. The key feature of this device is the utilization of a round-nozzle virtual impactor with a 50% cutpoint at 2.5 5m to split PM10 into its coarse and fine fractions at a very high flow rate. The high-volume dichotomous sampler operates at a total flow rate of 1100 lpm with major and minor flows of 1000 and 100 lpm, respectively. The virtual impactor was characterized in the Particle Instrumentation Unit of the Southern California Particle Center and Supersite (SCPCS), with ambient aerosols before it was put into its current configuration. Furthermore, to evaluate its performance, the virtual impactor was connected to a 100 lpm virtual impactor (2.5 5m cut point) in series, and ambient aerosols were measured using an aerodynamic particle sizer (APS, Model 3320, TSI Inc).
By connecting the two virtual impactors in series, concentration enrichment of 150 times ambient was achieved. The high-volume dichotomous sampler was then collocated with a MOUDI (Micro Orifice Uniform Deposit Impactor, Model 110, MSP Corporation, Minneapolis, MN) and a dichotomous PM10 Partisol sampler (Model 2025, R & P) at the University of Southern California in Los Angeles. The MOUDI and the high-volume sampler agreed well, with an average ratio (N = 19) of high-volume to MOUDI measured coarse PM concentration being 0.84 1 0.08. Similarly, good agreement was also observed between the high-volume dichotomous sampler and the Partisol (Ratio of the high-volume to Partisol is found to be 0.86 1 0.1). In addition to time-integrated coarse PM mass measurements, filter and impaction substrate samples were analyzed for inorganic ions (nitrate and sulfate), elemental carbon (EC) and organic carbon (OC) and will also be compared as part of further investigation in this study. The ultimate goal of this study was to demonstrate the feasibility of using this high-volume dichotomous sampler as an effective system to collect simultaneously sufficient coarse and fine mass samples for improving the sensitivity for organic aerosol speciation and the measurement of potentially toxic compounds and to allow for comprehensive standard chemical analysis over short time intervals as may be desired from one filter set for source apportionment studies or other data analysis and modeling efforts. Subsequent analysis of the filters may then lend itself to quick speciation/identification of ambient PM.
Although this work was reviewed by EPA and approved for publication, it may not necessarily reflect official Agency policy.