Comparison of integrated samplers for mass and composition during the 1999 Atlanta Supersites project

Abstract

[1] The first of the U.S. Environmental Protection Agency's (EPA) Particulate Matter (PM) Supersites projects was established in Atlanta, GA, during the summer of 1999 in conjunction with the Southern Oxidants Study. The short-term primary focus was a one month intensive field campaign to evaluate advanced PM measurement methods for measuring PM mass and the chemical and physical properties of PM. Long-term objectives are being met through coordination and cooperation with existing programs in Atlanta and the southeastern United States. Three categories of PM instruments were deployed during August 1999: time-integrated or discrete filter-based methods like those used in EPA's PM2.5 Chemical Speciation Network; continuous or semicontinuous species specific methods, most of which are still in development; and single particle mass spectrometers, the most advanced methods looking at the chemical composition of single particles. The focus of this paper is on comparison of the discrete filter-based methods. Samples were collected by 12 discrete filter-based samplers on an every other day basis during the study period at the Jefferson Street Southeastern Aerosol Research and Characterization (SEARCH) study site. Samples were analyzed for PM2.5 mass, sulfate, nitrate, ammonium, organic carbon, elemental carbon, and trace elements, the latter by XRF. Samplers used a variety of filters; denuder-filter combinations in the case of nitrate and organic carbon, particle size fractionating devices, and flow rates. Ambient concentrations for most species were sufficiently above detection limits for testing comparability among samplers, with nitrate being the most notable exception for the major components having an average reported value of 0.5 mg/m 3 . Several trace species, e.g., As and Pb, also were often below limits of detection of the analysis method. Results indicate that real differences exist among the samplers tested for most species, with sulfate and ammonium being the exceptions, under the conditions tested. Differences are due to sampler design, and in the case of elemental carbon, also due to the use of different chemical analysis methods. Comparability among most of the samplers for a given species was: mass (±20%); sulfate (±10%); nitrate (±30-35%); ammonium (±10-15%); organic carbon either with or without denuders (±20%) or including samplers both with and without denuders (±35-45%); elemental carbon (±20 to ±200%, the latter if different analysis methods are used); and minor and trace elements (±20-30%). A net organic carbon-sampling artifact on quartz-fiber filters was estimated from the comparison of denuded versus undenuded samples and is in the range of 1-4 mg/m 3 .

U.S. National PM2.5Chemical Speciation Monitoring Networks—CSN and IMPROVE: Description of networks

“…The variation between the two approaches for OC measured on typical urban and rural samples ranges from about 10 to 30%; for EC the difference can be up to a factor of 2 or more for the different analytical protocols used in the comparison studies (Solomon et al, 2000;Chow et al, 2001;Schmid et al, 2001;Solomon et al, 2003;Chow et al, 2004;Watson et al, 2005;Chow et al, 2008;Cheng et al, 2011). Total carbon (TC), equal to the sum of OC and EC, usually agrees to within 10-15%.…”

“…(Clark, 2002b;Gutknecht et al, 2001). URG relative to the other samplers, since nitrate can volatilize off the Teflon filter during analysis by energy-dispersive x-ray fluorescence (EDXRF), which occurs prior to analysis for ions (Solomon et al, 2000;Solomon et al, 2003, Yu et al, 2006. In February 2007, CSN began transitioning sampling on QFF for carbonaceous components to the URG 3000N sampler (EPA, 2007b;EPA, 2012e).…”

“…Quality assurance helps to identify factors that can increase uncertainty and, once minimized, ensures those uncertainty levels are maintained by establishing a set of performance criteria or data quality objectives (DQOs) (EPA, 1999b;White et al, 2005). For historical purposes, Table 8 lists the performance criteria recommended for the CSN and IMPROVE networks in developing the joint networks (Koutrakis, 1999;Solomon et al, 2000, Solomon et al, 2003.…”

“…Studies examined uncertainty issues in only one network or the other, whereas other studies examined it between networks. These studies include the initial CSN intercomparisons (Solomon et al, 2000;Coutant and Stetzer, 2001;Solomon et al, 2003), estimating the overall measurement uncertainty for mass or one or more chemical components for CSN and IMPROVE (Solomon et al, 2000;Chow et al, 2001;Solomon et al, 2003;Ashbaugh et al, 2004aAshbaugh et al, , 2004bChow et al, 2004;Watson et al, 2005;White et al, 2005;Yu et al, 2006;Smiley, 2013;Hyslop and White, 2008b), and estimating different uncertainty components (blanks, MDL, sampling artifacts) for OC, mass, ions, and elements by EDXRF (Iyer et al, 2000;Gutknecht et al, 2001;Kim et al, 2001;Lewtas et al, 2001;Fehsenfeld et al, 2004;Subramanian et al, 2004;Gego et al, 2005;Kim et al, 2005;Gutknecht et al, 2006;Zhao et al, 2006;Chow et al, 2008;Hyslop and White, 2008a;Watson et al, 2009;Chow et al, 2010;Gutknecht et al, 2010;Cheng et al, 2011;Maimone et al, 2011;Malm et al, 2011). Several special EPA Office of Air Quality Planning and Standards (OAQPS) studies also were conducted to examine sampling artifacts associated with QFF medium caused by a specific filter cassette (Clark, 2002b); the effect of QFF filter type (manufacturer) for collection and analysis of OC and EC (Peterson et al, 2007); the extraction efficien...…”

“…Three prototype and commercially available chemical speciation samplers were initially evaluated for use in the CSN (Solomon et al, 2000;Solomon et al, 2003). The prototype samplers were the MetOne SASS (Spiral Ambient Speciation Sampler), the URG MASS (University Research Glassware Mass Aerosol Speciation Sampler), and the Thermo Anderson RAAS (Reference Ambient Air Sampler).…”