Methods to Assess Carbonaceous Aerosol Sampling Artifact for 

IMPROVE and Other Long-Term Networks 

Prepared by: 

Judith C. Chow, John G. Watson, and L.-W. Antony Chen 

With contributions from 

Dana Trimble, Steven S.H. Ho, and Konstantinos Veropoulos 

Division of Atmospheric Sciences 

Desert Research Institute 

2215 Raggio Parkway, Reno, Nevada, U.S.A. 

Prepared for: 

Neil Frank 

U.S. Environmental Protection Agency (MD-14) 

Office of Air Quality Planning & Standards 

4201 Alexander Dr., Room 463 

Research Triangle Park, North Carolina, U.S.A. 

August 22, 2008 
 

ii

TABLE OF CONTENTS 

Table of Contents...................................................................................................................... ii 

List of Tables ........................................................................................................................... iii 

List of Figures............................................................................................................................v 

Carbon Nomenclature ............................................................................................................ viii 

1. Introduction..................................................................................................................... 1-1 

1.1 Background.............................................................................................................. 1-1 

1.2 Objectives................................................................................................................ 1-3 

1.3 Hypotheses .............................................................................................................. 1-3 

1.4 Report Structure....................................................................................................... 1-4 

2. Methods to Compensate for Organic Sampling Artifacts............................................... 2-1 

2.1 Blank Subtraction Approach ................................................................................... 2-1 

2.2 Denuder Approach................................................................................................... 2-1 

2.3 Backup Filter Approach .......................................................................................... 2-2 

2.4 Slicing Approach..................................................................................................... 2-2 

2.5 Regression Intercept Approach ............................................................................... 2-3 

3. Blank Carbon Data Analysis .......................................................................................... 3-1 

3.1 IMPROVE Blank and Backup Filter Analysis........................................................ 3-1 

3.2 MARCH-Atlantic Blank and Backup Filter Analysis............................................. 3-3 

3.3 Denuder/Backup Filter Approach............................................................................ 3-6 

3.4 Sliced Filter Approach............................................................................................. 3-7 

3.5 Regression/Intercept Approach ............................................................................... 3-8 

3.6 Composition of Adsorbed Organic Gases ............................................................... 3-9 

4. Summary, Conclusions, and Recommendations ............................................................ 4-1 

5. References....................................................................................................................... 5-1 
 

iii

LIST OF TABLES 

Page

Table 3-1. Summary of field blanks acquired at 181 sites (plus six collocated sites) in the 

IMPROVE Network from 1/1/2005 to 12/31/2006. 3-39 

Table 3-2. Average field blank concentration by carbon fraction at 181 (plus 6 collocated) 

sites in the IMPROVE network from 1/1/2005 to 12/31/2006. 3-42 

Table 3-3. Organic carbon comparison between the quartz-fiber front (QF, no blank 

subtraction) and quartz-fiber backup behind quartz-fiber (QBQ) filter 

concentrations collected at the six sites in the IMPROVE network with secondary 

filters behind quartz-fiber front filters for the period from 1/1/2005 though 

12/31/2006. Blank values taken from Table 2. 3-46 

Table 3-4. Comparison of concurrent OC concentration at quartz-fiber front filter (QF), 

quartz-fiber backup filter behind quartz-fiber filter (QBQ), front field blank 

(bQF), and backup field blank (bQBQ) filters at the six sites with secondary 

filters behind quartz-fiber front filters in the IMPROVE network. 3-47 

Table 3-5. Number of samples acquired from the SEARCH network during 2005 and 2006. 

(dQF, dQBQ, and bQF are not necessarily obtained on the same days.) 3-48 

Table 3-6. Original and sliced filter mass and concentration (the circular filter punch size is 

0.5 cm2

). 3-49 

Table 3-7. Average carbon fractions for top and bottom sliced quartz-fiber front (QF) and 

concurrent backup (QBQ) filters. 3-50 

Table 3-8. Robust regression intercept of quartz-fiber front (QF) organic carbon (OC; y-axis) 

versus PM2.5 mass (x-axis) averaged over all IMPROVE sites for each season 

during the period from 1/1/2005 through 12/31/2006. 3-51 

Table 3-9. Lower quantifiable limits (LQLs) of polycyclic aromatic hydrocarbons (PAHs), 

phthalates, alkanes, alkenes, hopanes, and steranes by thermal desorption-gas 

chromatography/mass spectrometry (TD-GC/MS). 3-52 

Table 3-10. Summary of organic concentrations (ng/cm2

) on the front (QF) and backup 

(QBQ) filters at four IMPROVE sites (MORA, HANC, CHIR, OKEF) during 

winter 2005. 3-53 
 

iv

LIST OF TABLES, continued 

Page

Table 3-11. Summary of organic concentrations (ng/cm2) on the front (QF) and backup 

(QBQ) filters at four IMPROVE sites (MORA, HANC, CHIR, OKEF) during 

summer 2005. 3-57 

Table 4-1. Summary of major findings for the seven hypotheses. 4-4 
 

v

LIST OF FIGURES 

Page

Figure 1-1. Sampling sites in the IMPROVE network from VIEWS (2007). The circled sites 

are locations where secondary filters (i.e., quartz-fiber backup filters [QBQ]) are 

acquired ~6% of the time: #78 (MORA) Mount Rainier National Park; #96 

(YOSE) Yosemite National Park; #48 (HANC) Hance Camp at Grand Canyon 

National Park; #39 (CHIR) Chiricahua National Monument; #6 (SHEN) 

Shenandoah National Park; and #16 (OKEF) Okefenokee National Wildlife 

Refuge. Site IDs in Table 3-1 are followed by a 1 to represent the original 

location within the Class I area. Numbers >1 indicate that the site was relocated 

within the area. Collocated sites are indicated with an X......................................... 1-5 

Figure 1-2. The SEARCH network, consisting of: Mississippi pair: urban Gulfport (GLF) in 

Gulfport and rural Oak Grove (OAK) near Hattiesburg; Alabama pair: urban 

Birmingham (BHM) in North Birmingham and rural Centreville (CTR) south of 

Tuscaloosa; Georgia pair: urban Jefferson Street (JST) in Atlanta and rural 

Yorkville (YRK) northwest of Atlanta; and Florida pair: urban Pensacola (PNS) 

in Pensacola and suburban outlying field (OLF) northwest of Pensacola................ 1-6 

Figure 3-1. Site-averaged blank carbon fractions in the IMPROVE network. (Includes 77 

sites with data from > 5 field blanks sorted by site from lowest to highest total 

carbon content. The bottom panel is an extension of the top panel.) .................... 3-13 

Figure 3-2. Distribution of average field blank TC (μg/filter) for 181 IMPROVE sites for the 

period from 1/1/2005 to 12/31/2006....................................................................... 3-14 

Figure 3-3. Seasonal averages of field blank carbon fractions for 77 IMPROVE sites with > 5 

blanks(725 total) for the period from 1/1/2005 to 12/31/2006 (spring: March, 

April, May; summer: June, July, August; fall: September, October, November; 

winter: December, January, February).................................................................... 3-15 

Figure 3-4. Averaged blank total carbon concentration (BLKTC) compared with concurrent 

averaged front filter carbon loading in the IMPROVE network between 1/1/2005 

and 12/31/2006. Only 77 sites with data from > 5 blanks are included. ................ 3-16 

Figure 3-5. Comparison of site-averaged carbon fractions from field blank and quartz-fiber 

front filters at 77 sites with more than five field blanks in the IMPROVE network 

for the period from 1/1/2005 through 12/31/2006.................................................. 3-17 

Figure 3-6. Average carbon concentration from the quartz-fiber backup filter (QBQ) 

compared with concurrent quartz-fiber front filter (QF) carbon fraction 

concentrations for six sites in the IMPROVE network. ......................................... 3-18 
 

vi

LIST OF FIGURES, continued 

Page

Figure 3-7. Site-averaged quartz-fiber backup (QBQ) carbon fractions at six sites in the 

IMPROVE network. ............................................................................................... 3-19 

Figure 3-8. Carbon fractions of concurrent QBQ and bQF filters from six IMPROVE anchor 

sites. (MORA: Mount Rainier National Park, 5 samples; YOSE: Yosemite 

National Park, 4 samples; HANC: Hance Camp at Grand Canyon National Park. 

3 samples; CHIR: Chiricahua National Monument, 5 samples; SHEN 

Shenandoah National Park, 9 samples; and OKEF Okefenokee National Wildlife 

Refuge, 1 sample). .................................................................................................. 3-20 

Figure 3-9. Time series of quartz-fiber front filter (QF), quartz-fiber backup filter (QBQ), and 

field blank (bQF) OC concentrations at six sites in the IMPROVE network for 

the period from 1/1/2005 through 12/31/2006. A small number of field blanks 

was available at each of the backup filter sites....................................................... 3-21 

Figure 3-10. Comparison of field blank OC (bQF) with backup blank OC (bQBQ) 

concentrations at six sites in the IMPROVE network. ........................................... 3-22 

Figure 3-11. Comparisons of averaged OC concentrations in quartz-fiber front filters (QF), 

quartz-fiber backup filters (QBQ), front field blanks (bQF) and backup field 

blanks (bQBQ) for the concurrent sampling of 22 sample sets for the period from 

1/1/2005 through 12/31/2006 at six sites in the IMPROVE network..................... 3-23 

Figure 3-12. Comparison of seasonally averaged OC on quartz-fiber front filter (QF), quartzfiber backup behind Teflon-membrane front filter (QBT), quartz-fiber backup 

behind quartz-fiber front filter (QBQ), and blank filters (bQF and bQBQ) for: a) 

Day 1 (24 hr sampling on first day followed by a 48 hr passive period), and b) 

Day2 (24 hr sampling on second day with 24 hr passive period before and after 

sampling) samples acquired from Fort Meade, MD. (spring: April; summer: July; 

fall: October; winter: January.) ............................................................................... 3-24 

Figure 3-13. Average and standard deviation (bar) for organic carbon fraction concentrations 

on quartz-fiber front filters (QF), quartz-fiber backup behind Teflon-membrane 

(QBT), and quartz-fiber backup behind quartz-fiber (QBQ) for summer 1999 at 

Fort Meade, MD (36 24-hr samples). ..................................................................... 3-25 

Figure 3-14. Estimated negative sampling artifact (OC loss) from Teflon-membrane and 

quartz-fiber filters against particulate OC (pOC + pSVOC) loading at FME for: 

a) summer (July) and b) winter (January) seasons. The edges of scatter are 

determined from the regression of data with the lowest 10% 

OC_loss/(pOC+pSVOC) ratio................................................................................ 3-26 
 

vii

LIST OF FIGURES, continued 

Page

Figure 3-15. The fraction of pOC, retained pSVOC, and volatilized pSVOC or gSVOC from 

Teflon-membrane and quartz-fiber filters at FME during summer and winter 

seasons. ................................................................................................................... 3-27 

Figure 3-16. Average backup (dQBQ) and blank (bQF) TC compared with dQF carbon 

fractions for the SEARCH network. The first site at each pair is the urban site, 

while the other is suburban or rural site. (The number of data points is shown in 

Table 3-5.)............................................................................................................... 3-28 

Figure 3-17. Average carbon fractions on quartz-fiber backup filters (dQBQ following 

preceding organic denuders) in the SEARCH network from 1/1/2005 through 

12/31/2006. (Sites are arranged according to Table 3-5.)....................................... 3-29 

Figure 3-18. Averaged carbon fractions of quartz-fiber blank filters in the SEARCH network 

from 1/1/2005 to 12/31/2006. (Sites are arranged according to Table 3-5.)........... 3-30 

Figure 3-19. Comparison of concurrent SEARCH quartz-fiber front (QF), quartz-fiber 

backup (QBQ), and quartz-fiber blank (bQF) filter OC concentrations................. 3-31 

Figure 3-20. Comparison of original and sliced filter mass (in mg) with carbon loading (in 

μg). Diamonds and circles indicate front (QF) and backup (QBQ) filters, 

respectively. The upper and lower triangles indicate top (QFtop) and bottom 

halves (QFbottom) of slices, while rectangles represent the original filter punch (0.5 

cm

2

). In Cases (a) and (b), the bottom halves of QF contains similar carbon 

concentrations as those on backup filters. In Cases (c) and (d), the bottom-half of 

QF contains higher carbon concentrations than QBQ slices. ................................. 3-32 

Figure 3-21. Robust regression intercepts (bars) and slopes (lines) for quartz-fiber front filter 

OC (y-axis) versus PM2.5 mass (x-axis) for all IMPROVE sites during: a) spring 

(April), b) summer (July), c) fall (October), and d) winter (January). IMPROVE 

data from 1/1/2005 to 12/31/2006. ......................................................................... 3-33 

Figure 3-22. Gas chromatograms of front (QF) and backup (QBQ) quartz-fiber samples for 

the: (a) Mount Rainier, WA (MORA), (b) Chiricahua, AZ (CHIR), (c) Grand 

Canyon, AZ (HANC), and (d) Okefenokee, GA (OKEF) sites in the IMPROVE 

network on selected days of summer and winter 2005........................................... 3-35 
 

viii

CARBON NOMENCLATURE 

VOC:...................................................................................................Volatile Organic Compounds 

SVOC:....................................................................................... Semi-Volatile Organic Compounds 

gSVOC:............................................................ Gaseous-Phase Semi-Volatile Organic Compounds 

pSVOC:..............................................................Particle-Phase Semi-Volatile Organic Compounds 

TC: ....................................................................................................Total Carbon (TC = OC + EC) 

OC:...........................................................................................................................Organic Carbon 

pOC:........................................................................... Non-Volatile Particle-Phase Organic Carbon 

EC: ........................................................................................................................Elemental Carbon 

QBT:..........................................Quartz-Fiber Backup Filter behind Teflon-Membrane Front Filter 

QBQ:................................................. Quartz-Fiber Backup Filter behind Quartz-Fiber Front Filter 

bQBQ:.....................................Blank Quartz-Fiber Backup Filter behind Quartz-Fiber Front Filter 

dQBQ:................................Denuded Quartz-Fiber Backup Filter behind Quartz-Fiber Front Filter 

QBQtop:.............Top Half of a Sliced Quartz-Fiber Backup Filter behind Quartz-Fiber Front Filter 

QBQbott:......Bottom Half of a Sliced Quartz-Fiber Backup Filter behind Quartz-Fiber Front Filter 

QF: .............................................................................................................Quartz-Fiber Front Filter 

bQF ...............................................................................................Field Blank (Quartz-Fiber Filter) 

dQF ............................................................................................ Denuded Quartz-Fiber Front Filter 

QFtop .................................................................................... Top Half of a Quartz-Fiber Front Filter 

QFbottom.......................................................................... Bottom Half of a Quartz-Fiber Front Filter 
 

1-1

1. INTRODUCTION 

1.1 Background 

When particles are collected onto quartz-fiber filters, some of the organic vapors in the 

air are adsorbed onto the fibers. This adsorption also occurs passively when filters are exposed to 

the atmosphere with no air drawn through them. These vapors leave the sample during thermal 

analyses (Watson et al., 2005) and are interpreted as part of the measured organic carbon (OC). 

This positive OC “artifact” yields higher values for OC in PM2.5 and PM10 samples than are 

actually in ambient air (Kukreja and Bove, 1976). The adsorbed VOCs also char within the filter, 

thereby causing differences in elemental carbon (EC) levels determined by transmittance and 

reflectance corrections (Chen et al., 2004; Chow et al., 2004). Semi-volatile organic compounds 

(SVOCs) can be collected as particles, but portions of them can evaporate and leave the particle 

in the gas stream owing to increases in temperature or decreases of their gas phase 

concentrations in the sampled air (Galasyn et al., 1984). Evaporated SVOCs yield a negative OC 

artifact because they should have been reported as part of the PM2.5 or PM10 mass (Obeidi and 

Eatough, 2002). 

Several U.S. networks, including the Interagency Monitoring of Protected Visual 

Environments (IMPROVE) network (Figure 1-1; Watson, 2002), the Maryland Aerosol Research 

and Characterization (MARCH-Atlantic) study (Chen et al., 2001; 2002; 2003), and the 

Southeastern Aerosol Research and Characterization (SEARCH) network (Figure 1-2; Hansen et 

al., 2003; 2006), use quartz-fiber front filters (QF) to collect OC and EC and use backup filters 

and/or field blanks to correct for the OC artifact. The urban Speciation Trends Network (STN) 

(Flanagan et al., 2006) obtains field blanks, no backup filters, and does not make corrections for 

adsorbed organic vapors. Positive and negative sampling artifacts are among several causes of 

poor agreement in carbon interlaboratory and intermethod comparisons (Chow et al., 2001; 2004; 

Watson et al., 2005). In summary, the measured carbon consists of: 1) non-volatile particulate 

organic carbon (pOC) and EC; 2) volatile organic compounds (VOCs) that adhere to quartz 

fibers under most ambient conditions; and 3) SVOCs that migrate between the gas and particle 

phases depending on ambient temperature, aerosol compositions and concentrations, gas-phase 

concentrations in the air, and availability of heterogeneous surfaces on which to adsorb. 

Hereafter, SVOCs are referred to as pSVOCs, which would be measured with pOC, and 

gSVOCs, the portion that evaporates and constitutes the negative artifact. 
 

1-2

With sufficient exposure time, adsorbed VOCs may reach equilibrium with VOCs in the 

airstream passing through it (Storey et al., 1995; Mader and Pankow, 2001a; 2001b; 2002). The 

time to reach this “saturation” depends on ambient temperature, sampling train configuration 

(e.g., preceding organic denuder, filters in series), available surface area in the filter, ambient 

VOC/SVOC/pOC composition and concentration, exposure of the filter to air before and after 

sampling, sample volumes, and the velocity of air drawn through the filter. Field blanks and 

backup filters without preceding organic denuders can yield similar carbon loadings when 

adsorbed VOC dominates (i.e., positive artifact). Filter cross-sections show that pOC is 

collected on the upper third of the front quartz-fiber filter (Chow et al., 2004). The level of 

saturation may change, however, with changes in the environment. Heating the filter removes 

adsorbed material. It is also possible that passing VOC-free air through the filter (as might 

happen with an efficient denuder) would cause previously adsorbed VOCs and SVOCs to be 

removed from a backup filter. Owing to this changing equilibrium, it would be expected that as 

field blanks and backup filter are exposed to ambient air over longer time periods, their adsorbed 

VOC levels will become more similar. Because it is a more inert material and has a much 

smaller internal surface area, Teflon filters are expected to pass more VOCs to a quartz backup 

filter. Less of the gSVOC is retained on the Teflon, but it is available for adsorption on the 

backup. 

The IMPROVE network acquires quartz-fiber backup filters behind quartz-fiber front 

filters (QBQ) at the six sites in Figure 1-1: (i.e., Mt. Rainier National Park [MORA]; Yosemite 

National Park [YOSE]; Hance Camp at Grand Canyon National Park [HANC], Chiricahua 

National Monument [CHIR], Shenandoah National Park [SHEN]; and Okefenokee National 

Wildlife Reserve [OKEF]). Approximately 60 QBQ samples are analyzed each month, and 

monthly median OC concentrations are used for blank subtraction. Field blanks are sent to and 

received from all IMPROVE sites along with the regular sample shipments. About 2% of all 

samples are field blanks, and these are randomly assigned to sample shipments. 

Samples from the IMPROVE, MARCH-Atlantic, and SEARCH networks provide an 

opportunity to study the magnitude of positive and negative artifacts and different artifact 

correction strategies for a wide variety of non-urban and urban atmospheres. These networks use 

different filter samplers, filter sizes, and sampling configurations. Sample remnants are stored 

under refrigeration after analysis, and these remnants can be used for further tests. Sample, field 
 

1-3

blank, and backup filters from these networks are analyzed for OC, EC, and seven thermal 

carbon fractions: OC1, OC2, OC3, and OC4 at 120, 250, 450, and 550 °C in a 100% helium 

atmosphere; EC1, EC2, and EC3 at 550, 700, and 800 °C in a 2% oxygen/98% helium 

atmosphere. OPR represents pyrolyzed carbon determined by filter reflectance following the 

IMPROVE thermal/optical reflectance (TOR) protocol implemented on DRI/OGC carbon 

analyzers (Chow et al., 1993; Watson et al., 1994; Chen et al., 2004; 2005). The IMPROVE_A 

thermal/optical protocol yields comparable OC1, OC2, OC3, and OC4 at 140, 280, 480, and 

580 °C in a 100% helium atmosphere, and EC1, EC2, and EC3 at 580, 740, and 840 °C in a 2% 

oxygen/98% helium atmosphere. Pyrolyzed OC is reported as OPR for TOR and as OPT for 

simultaneously measured thermal/optical transmittance (TOT). IMPROVE_A is applied to 

IMPROVE samples acquired after 1/1/2005 using the DRI Model 2001 thermal/optical carbon 

analyzer (Chow et al., 2007a). Chow et al. (2007a) showed that the OC/EC split remains 

consistent between the IMPROVE and IMPROVE_A protocols and that the seven carbon 

fractions are also comparable. 

1.2 Objectives 

The goal of this study is to better understand, using samples from existing networks, the 

magnitude and variability of organic gases adsorbed onto quartz-fiber filters and to evaluate 

methods to compensate for these artifacts in long-term PM2.5 networks. Specific objectives are: 

• Analyze existing data bases on field blanks and backup filters from the IMPROVE and 

other networks to evaluate magnitudes and variability of adsorbed carbon in different 

carbon fractions and determine how they differ by location, season, and source 

contributions. 

• Compare the magnitudes of sampling artifacts estimated by different methods, such as 

field blank, quartz behind Teflon (QBT) or quartz behind quartz (QBQ), sliced top and 

bottom half of the front filter, and regression methods. 

• Perform laboratory analyses on selected archived samples to determine the 

homogeneity of adsorbed organic gases within a filter, relationships between artifacts 

on front and backup filters, and on the bottom half of the front filters. 

• Evaluate alternative estimates for sampling artifact based on thermal carbon fractions 

on the bottom half of front filters and backup filters. 

• Identify the adsorbed organic species composition on front and backup filters by 

exploratory chemical analysis. 

1.3 Hypotheses 

Seven hypotheses were formulated to address the study objectives: 
 

1-4

A. Quartz backup filters and field blanks contain the same quantities of adsorbed 

VOC and OC fractions. 

B. Nearly all of the adsorbed VOCs and gSVOCs are in the IMPROVE OC1, OC2, 

and OC3 fractions. 

C. Adsorbed VOCs are similar among blanks and backups and for different sampling 

locations, times, and OC aerosol loadings. 

D. Quartz behind Teflon yields the same amounts in carbon fractions as quartz 

behind quartz. 

E. Front and backup quartz-fiber filters are saturated with adsorbed organic vapors 

only for high loading samples, and before saturation the front filter captures more 

gSVOC than the backup filter. 

F. Analysis of a small number of backup filters can be extrapolated to a large 

number of samples with appropriate stratification by sampling site, sampling time, 

and OC loading. 

G. Adsorbed VOCs are different from organic compounds in the sampled aerosol. 

1.4 Report Structure 

Section 1 states the background, objectives, and hypotheses being tested. Section 2 

describes five approaches that have been used to compensate for organic sampling artifacts in 

different networks or in different studies. Carbon fractions from field blanks, denuder sampling, 

backup filters, filter slicing, and intercept approaches are examined. Section 3 documents data 

analysis of blank and backup filter measurements acquired from the IMPROVE, MARCHAtlantic, and SEARCH networks. Section 4 relates these observations to the hypotheses being 

tested and summarizes conclusions on the findings. Section 5 provides references and a 

bibliography. 
 

1-5

MORA

YOSE

HANC

CHIR

SHEN

OKEF

MORA

YOSE

HANC

CHIR

SHEN

OKEF

Figure 1-1. Sampling sites in the IMPROVE network from VIEWS (2007). The circled sites are 

locations where secondary filters (i.e., quartz-fiber backup filters [QBQ]) are acquired ~6% of 

the time: #78 (MORA) Mount Rainier National Park; #96 (YOSE) Yosemite National Park; #48 

(HANC) Hance Camp at Grand Canyon National Park; #39 (CHIR) Chiricahua National 

Monument; #6 (SHEN) Shenandoah National Park; and #16 (OKEF) Okefenokee National 

Wildlife Refuge. Site IDs in Table 3-1 are followed by a 1 to represent the original location 

within the Class I area. Numbers >1 indicate that the site was relocated within the area. 

Collocated sites are indicated with an X.
 

1-6

Figure 1-2. The SEARCH network, consisting of: Mississippi pair: urban Gulfport (GLF) in 

Gulfport and rural Oak Grove (OAK) near Hattiesburg; Alabama pair: urban Birmingham 

(BHM) in North Birmingham and rural Centreville (CTR) south of Tuscaloosa; Georgia pair: 

urban Jefferson Street (JST) in Atlanta and rural Yorkville (YRK) northwest of Atlanta; and 

Florida pair: urban Pensacola (PNS) in Pensacola and suburban outlying field (OLF) northwest 

of Pensacola. 
 

2-1

2. METHODS TO COMPENSATE FOR ORGANIC SAMPLING 

ARTIFACTS 

Several methods are used to compensate for organic sampling artifacts. These include: 1) 

field blank subtraction (Blank Subtraction Approach), 2) gaseous organic denuders prior to the 

filter (Denuder Approach), 3) filters or absorbent materials following the front filter (Backup 

Filter Approach), 4) removal and analysis of the bottom half of the front filter (Slicing 

Approach), and 5) regressing OC on PM2.5 to find the intercept (Intercept Approach). Each of 

these methods is applied and evaluated to appropriate data from the IMPROVE, MARCH, and 

SEARCH networks. 

2.1 Blank Subtraction Approach 

Filters that accompany the sampled filters through all processes except having ambient 

air drawn through them are subject to passive deposition and adsorption of materials that are not 

necessarily in the sampled air (Bruckman and Rubino, 1976; Sweitzer, 1980; Swinford, 1980; 

Chow et al., 1994; 1996). Average field blank levels can be subtracted from those measured on 

the sampled filters. The uncertainty of this average is represented by its standard deviation, 

which should be incorporated into the reported measurement precision and lower quantifiable 

limit (LQL) (Watson et al., 2001). Properly handled field blanks usually show low particle 

deposition (as indicated by low EC and trace elements) but substantial OC adsorption 

(Kirchstetter et al., 2003; Eatough et al., 2003a; Kim et al., 2005; Offenberg et al., 2007). 

2.2 Denuder Approach 

Organic carbon denuders (Bertoni et al., 1984; Eatough et al., 1987; Fitz, 1990; Krieger 

and Hites, 1992; 1993; Gundel et al., 1995; Cui et al., 1997; Mader et al., 2001; Ding et al., 

2002a; 2002b; 2003; Fan et al., 2003; Viana et al., 2006) allow VOCs to diffuse to an absorbing 

surface while permitting small particles to pass through to the filter. Baked quartz-fiber filter 

strips (Fitz, 1990), XAD resin (Gundel et al., 1995), and activated carbon impregnated filter 

strips (Eatough et al., 1993) have been used as absorbents. These denuders remove VOC and 

gSVOC, thereby reducing the equilibrium vapor pressure over the pSVOC and enhancing its 

volatilization both within the denuder and on the filter. OC on backup filters comes from a 

portion of the gSVOC, a negative artifact, and VOCs not removed by the denuder. Quartz 

backup filters probably do not capture all of the gSVOC, as indicated by activated charcoal 

impregnated backup filters (Eatough et al., 2003b). Denuders are not 100% efficient, so some 
 

2-2

VOCs that might be adsorbed also reach the backup filters. Chow et al. (2006) showed that in 

the denuded channel (dQF), pOC agreed most closely with the difference between non-denuded 

front and backup filter OC (i.e., QF minus QBQ) at the Fresno Supersite. Differences between 

the denuded quartz-fiber front filter OC (dQF) followed by the backup filter (dQBQ) method and 

the non-denuded quartz-fiber behind Teflon (QBT) and QBQ methods were within their 

measurement uncertainties. 

2.3 Backup Filter Approach 

A quartz-fiber filter is placed behind the front filter, which may be a Teflon-membrane or 

quartz-fiber filter. It is assumed that the OC measured on the backup is also uniformly adsorbed 

within the front filter, so it should be subtracted from the front filter OC. OC on quartz- and 

glass-fiber backup filters behind front filters was first observed by Cadle et al. (1983) and more 

systematically studied by McDow and Huntzicker (1990). Using QBT and QBQ on parallel 

channels at Los Angeles, CA, Turpin et al. (1994) reported that backup filter saturation was 

attained for QBT before QBQ. Turpin et al. (1994) suggested that QBT provides a more 

accurate estimate of the positive OC artifact. However, QBT often yields higher OC on the 

backup than does QBQ (Turpin et al., 1994; Chen et al., 2002; Chow et al., 2006). More of the 

pSVOC collected on the front Teflon-membrane filter may leave the filter because Teflonmembrane adsorbs less of these vaporized gases than quartz-fiber. It is uncertain whether the 

QBT OC should be added to or subtracted from pOC. Owing to the inert nature of Teflon, 

pSVOC volatilization from it could be substantial. Without a preceding denuder, Chow et al., 

(2006) found that QBT OC was nearly twice that of QBQ at the Fresno Supersite. Average OC 

on QBT and QBQ were 2.1 ± 0.3 and 1.28 ± 0.45 μg/m3

 during winter and 1.84 ± 0.28 and. 0.91 

± 0.46 μg/m3

 during summer; with an average of 1.75 ± 0.27 vs. 0.91 ± 0.45 μg/m3. Compared to 

QF loadings, the extent of organic adsorption was also much higher for QBT than for QBQ. The 

QBT/QF vs. QBQ/QF ratios were 24 vs. 10.9% for winter and 44% vs. 24% during summer, 

with an average of 34% vs. 17.5% from December 1999 to February 2001 at the Fresno 

Supersite. 

2.4 Slicing Approach 

Fung et al. (2004) developed a jig and sharp blade to slice the filter through its crosssection into nearly equal front and back halves. Both halves can be weighed to scale OC on the 

bottom half to the whole filter. Assuming that the pOC is collected only on the top half and that 
 

2-3

the adsorbed vapor is distributed uniformly throughout the filter depth, OC on the bottom half 

should provide an estimate of the adsorbed organic vapor throughout the filter. This method is 

the same as the backup filter approach, but without two quartz-fiber filters in series. Microscopic 

examination of filter cross-sections shows that few particles penetrate into the bottom half of a 

filter (Chow et al., 2004). 

2.5 Regression Intercept Approach 

If the positive OC artifact at a monitoring site is relatively constant for all seasons and 

concentration levels, it should provide a constant increment over the mass measured on the 

Teflon-membrane filter. Calculating a linear regression line of OC vs. PM2.5 or PM10 mass 

results in an intercept at zero mass that would indicate the magnitude of the artifact OC (White 

and Macias, 1989). This method assumes that PM mass and OC are highly correlated and span a 

wide range of concentrations. 
 

3-1

3. BLANK CARBON DATA ANALYSIS 

The IMPROVE, MARCH-Atlantic, and SEARCH networks used one or more of the 

approaches in Section 2 to correct for OC artifacts. Each of these networks followed the 

IMPROVE or IMPROVE_A TOR protocol, yielding seven thermal carbon fractions. Field blank 

and backup filter data were readily available, and sample remnants were kept in cold storage and 

could be submitted to additional analyses. 

3.1 IMPROVE Blank and Backup Filter Analysis 

Between 1/1/2005 and 12/31/2006, 44,016 samples from the IMPROVE network were 

analyzed for OC and EC following IMPROVE_A with. 959 (2.2% of the total) field blanks 

(bQF) collected at 187 sites (including six collocated sites). During the same period, 1,406 

backup filters (i.e., QBQ) were acquired at six sites (i.e., MORA, YOSE, HANC, CHIR, SHEN, 

and OKEF). 

Locations of each IMPROVE site along with the six backup filter sites are shown in 

Figure 1-1. Table 3-1 shows that from one to 17 field blanks were taken at individual sites with 

the number varying by season and location. Zero to six field blanks were acquired at individual 

sites during each season. Field blanks covered many sites, but for limited times. The frequency 

of backup filters was ~10 per site per month. 

Passive adsorption, as indicated by field blanks, accounts for part of the positive artifact. 

Turpin et al. (1994) and Subramanian et al. (2004) suggest that quartz-fiber (front and backup) 

filters might reach equilibrium/saturation within 24 hours. They did not examine the extent to 

which this conjecture might apply to field blanks that contain no active sample flow (zero face 

velocity). The positive OC artifact should be equal to or greater than OC measured on the field 

blanks. 

Figure 3-1 shows average field blank carbon concentrations for the thermal fractions by 

site (see Table 3-1 for site names). As expected for filters without a deposit, EC levels are 

negligible. Most of the adsorbed OC is in the OC1 and OC2 fractions (evolving at < 280 °C), but 

there is still a substantial amount in the OC3 (380 °C) fraction. Lot-by-lot differences for quartzfiber filters were observed by Kirchstetter et al. (2001), but this is not the cause of differences 

among the sites because filters from each lot are distributed to all sites. To minimize the 

influence of outliers, only sites that obtained more than five blanks are included in Figure 3-1. 
 

3-2

For most sites, average blank TC levels ranged from 7 to 10 μg/25 mm filter as shown in Figure 

3-2. 

Table 3-2 quantifies the blank OC distribution among the OC1 (140 °C), OC2 (280 °C), 

and OC3 (480 °C) fractions, each of which contributes 2 – 3 μg/filter for IMPROVE with very 

low concentrations found in other carbon fractions. Most of the OC4 is <0.5 μg/filter, compared 

to < 0.1 μg/filter for EC1, EC2, and OP. EC3 concentrations are not detected. Positive levels for 

EC1 and EC2 are caused by charring of some of the adsorbed organic vapors rather than particle 

deposits (Chow et al., 2004), but this charring is compensated for by the TOR correction when 

EC is reported. Among the 181 IMPROVE sites, field blank TC and OC can be considered 

equivalent within analytical uncertainties. Field blank TC is highest at the Indian Gardens 

(INGA) site in AZ, in the range of 8.6 – 19.7 μg/filter, and lowest at the Blue Mounds (BLMO) 

site in MN, in the range of 4.5 – 6.5 μg/filter. Figure 3-3 shows that the average field blank TC 

concentration is higher during summer than during the other seasons, ranging from 7.0 ± 2.5 

μg/filter in winter to 12.3 ± 14.6 μg/filter in summer. For OC2 and OC3, the winter/summer 

ratios are 0.71 and 0.73, respectively. Higher temperatures in summer would be expected to 

lower the equilibrium saturation ratio, but summertime photochemical activity might also create 

heavier VOCs (Pandis et al., 1992) that might adhere to the filters. Wildfires are also more 

prevalent during dry summer and early fall periods at many of these sites. 

Figure 3-4 shows that the average field blank TC is relatively consistent with respect to 

the average concentrations of TC and carbon fractions at the site. The ratio of the 90th percentile 

to the 10th percentile TC is only ~1.5 for field blanks, compared to 3.5 for TC on the front filters. 

This is a small variability for most of the field blanks considering the variety of environments in 

which these sites are located. At sites with low OC concentrations, such as Hawaii Volcano 

National Park (HAVO1, #102 in Figure 1-1), field blank TC (~10 μg/filter) accounts for most of 

the front filter TC (Figure 3-4). In the medium loading range (20 – 40 μg/filter), field blank TC is 

comparable to OC1 + OC2 on the front filter. For higher loadings ( > 40 μg/filter), however, 

field blank TC is much less than OC1+OC2. 

Figure 3-5 shows that field blank OC1, OC2, and OC3 levels are similar across the 

IMPROVE network and are not related to ambient concentrations above ~3 μg/filter. OC1, OC2, 

and OC3 on the front filter are not exclusively due to adsorbed VOC. 
 

3-3

Table 3-3 shows site-averaged backup filter (QBQ) OC levels of 8 to 13 μg/filter, which 

are 2 to 4 μg/filter above field blanks from the same sites, but they are comparable to the 8.4 ± 

1.6 μg/filter all-site average in Table 3-2. The relatively small number of field blanks may bias 

the site-to-site comparison with backup filters. Figure 3-6 shows that site-averaged QBQ TC 

does not depend on average carbon concentrations at the six sites, similar to the findings for field 

blanks in Figure 3-4). Figure 3-7 shows how backup filter OC is distributed among the carbon 

fractions, again illustrating that most of the material is in the OC1, OC2, and OC3 fractions and 

that the OC is equivalent to TC after TOR charring corrections. The most visible differences 

between backup filters and field blanks (Figure 3-1) are the higher OC4 (580 °C), EC1 [580 °C], 

and EC2 [740 °C]) abundances in QBQ. Figure 3-8 compares the carbon fractions of QBQ and 

bQF filters taken at the same site on the same day, demonstrating that the OC4 abundance is the 

same or higher for QBQ filters. The EC fraction is mostly caused by charring, (e.g., OP, 

included in EC1). 

The use of monthly median QBQ concentrations from the six sites is supported by Figure 

3-9, showing that OC concentrations on front filters, backup filters, and field blanks (where 

available) vary by month at each site. All sites except OKEF show higher front filter OC 

concentrations in summer than in winter, with QBQ and bQF showing a similar month-to-month 

variability. The agreement between OC levels on corresponding field blanks and backup filters 

shown in Figure 3-10, and the similarity of the all site average field blank OC (8.4 ± 1.6 

μg/filter; n=959,) and six-site average backup filter OC (10.03 ± 5.04 μg/filter; n=1406) 

concentrations, indicates that QBQ subtraction would be only slightly more than a bQF 

subtraction, and the difference would be within the propagated precision of blank subtraction. 

Examining this in more detail, Figure 3-11 shows that OC on blank filters (bQF or 

bQBQ) agrees within ±15% with OC on backup filters (QBQ) at all but the YOSE site. Average 

OC levels on YOSE field blanks (bQF and bQBQ) are ~35% (~3.4 μg/filter) lower than OC on 

backup filters. Front filter average OC concentrations are also highest (59.3 ± 14.5 μg/filter) at 

the YOSE site, which is known to have regularly experienced wildfires throughout the 2005 – 

2006 measurement period. 

3.2 MARCH-Atlantic Blank and Backup Filter Analysis 

MARCH-Atlantic samples from Fort Meade (FME), MD, used 47 mm QBT and QBQ 

configurations (Chen et al., 2002) from July 1999 to July 2002, including 10 intensive sampling 
 

3-4

months for the four seasons. The FME site was located on a military base approximately halfway 

between Baltimore, MD, and Washington, DC and represents an urban-scale mixture of PM2.5

carbon contributions. The site is within the zone of influence of several primary carbon sources 

such as vehicle exhaust and residential wood combustion. 

Three filter sets were obtained for three days of consecutive 24-hr sampling. The first two 

sample sets (i.e., Day 1, Day 2) remained at the site for 72 hrs (irrespective of sampling period), 

which is consistent with the passive period of the field blanks. These samples are used to 

evaluate how the positive OC artifact might change with atmospheric exposure before and after 

sampling. 

Seasonal average OC levels from front (QF), backup (QBQ and QBT), and blank filters 

(bQF and bQBQ) are compared in Figure 3-12. OC concentrations at FME were much higher in 

summer than during other seasons. The volatility of organic aerosol is also expected to be higher 

in summer, as is the presence of heavy VOCs that might have an affinity to quartz, resulting in 

higher positive and negative artifacts compared to other seasons. Field blank OC (bQF and 

bQBQ) shows summer vs. winter differences, ranging from 10.5 to 15.7 μg/47mm filter, which 

is equivalent to 2.7 to 4.0 μg/25mm IMPROVE filter. This seasonal variation is consistent with 

that found in the IMPROVE network (Figure 3-3). VOC adsorption may attain saturation on 

these field blanks over the 72-hr exposure time. 

Both QBQ and QBT backup filters show substantially higher OC than field blanks (bQF, 

bQBQ), in contrast to the comparison for IMPROVE samples. This may be attributed to the 

urban-rural difference, as SVOC is probably more abundant in urban atmospheres. There is no 

difference between Day 1 (24-hr sampling on the first day, followed by 48-hr passive adsorption) 

and Day 2 (remained in the sampler for 24-hr before 24-hr sampling on the second day, followed 

by a 24-hr passive period) in Figures 3-12a and 3-12b, respectively. In spring and summer, 

average QBT OC is > 60% of QF OC. This difference reduces to < 50% in winter and spring. 

QBQ OC is between QBT and field blank OC (bQF and bQBQ). Turpin et al. (1994) attribute 

this to a slow saturation of the tandem quartz-quartz filter configuration. Chow et al. (2006), on 

the other hand, conjecture that this is mostly due to the volatilization of pSVOC from the front 

Teflon-membrane filters, which has been observed and quantified by Subramanian et al. (2004) 

using the denuder method. 
 

3-5

Average OC thermal fractions for the front (QF) and backup (QBT and QBQ) filters for 

summer 1999 are compared in Figure 3-13, representing the warmest period during MARCHAtlantic. OC1, OC2, and OC3 levels for QBT are similar to those on QF, while corresponding 

levels on QBQ are half these amounts. There is more charring (OP) for the QBT than for the 

QBQ, which might be associated with semi-volatile polar compounds (Yu et al., 2002). These 

results support the hypothesis that much of the QBT comes from pSVOC evaporating from 

particles collected on the Teflon-membrane filters. QBQ shows 30 – 40% lower OC2 and OC3, 

and nearly zero OP compared with the QBT values. 

An ideal case may be considered where higher QBT and QBQ OC relative to field blank 

OC (bQF and bQBQ) results from the negative OC artifact. This is possible when all the backup 

and blank filters are saturated by VOC and/or gSVOC adsorption. Since QBT OC is likely to 

overestimate positive OC artifacts due to the negative artifact from Teflon-membrane filters, 

only QBQ OC is considered. Particle-phase OC (pOC + pSVOC) in the atmosphere is estimated 

by: 

pOC + pSVOC = OCQF + OCQBQ - 2 × OCbQF (1) 

Assuming that all the volatilized OC is recaptured by the quartz-fiber backup filters, the 

negative OC artifact from Teflon (TOCloss) and quartz-fiber filter (QOCloss) is estimated by: 

 TOCloss = OCQBT – OCbQF (2) 

 QOCloss = OCQBQ – OCbQF (3) 

TOCloss and QOCloss are plotted against pOC plus pSVOC in Figures 3-14a and 3-14b. 

TOCloss and QOCloss should only depend on the pSVOC concentration. The upper edges of in 

Figures 3-14a and 3-14b reveal the TOCloss/pSVOC and QOCloss/pSVOC ratio. In summer, the 

slope is ~0.71 and ~0.29, meaning that, on average, 71% and 29% of pSVOC have volatilized 

from the front Teflon-membrane and quartz-fiber filters, respectively. During winter, the fraction 

of volatilized pSVOC was 59% from front Teflon-membrane and 21% from front quartz-fiber 

filters. 

From the ratio, pSVOC and pOC concentrations can be estimated from Eq. (1). Figure 3-

15 shows the partition of pOC, retained pSVOC, and volatilized pSVOC (negative artifact) at the 

FME site. For Teflon-membrane filters, the negative artifacts are 45% and 31% of the total (i.e., 

pOC plus pSVOC) in summer and winter, respectively. For quartz-fiber filters, the negative 
 

3-6

artifacts are 18% and 11% for summer and winter, respectively. These fractions are higher than 

those reported by Subramanian et al. (2004) for Pittsburgh, but the difference could be due to 

varying ambient conditions and carbon chemical compositions between FME and the Pittsburgh 

Supersite. This illustrates the need to obtain information over a wide range of environments and 

to refrain from over-generalizing results from a single experiment. The above analyses suggest 

that quartz-fiber behind Teflon-membrane (QBT) is an inaccurate measure of the positive OC 

artifact, but that it may be used in conjunction with collocated QBQ filters to estimate the 

negative OC artifact, at least in an environment similar to that of the FME site. 

3.3 Denuder/Backup Filter Approach 

As shown in Figure 1-2, the SEARCH network (Hansen et al., 2003) contains four urban 

vs. rural (or suburban) pairs of sampling sites (i.e., Mississippi pair: urban Gulfport (GLF) in 

Gulfport and rural Oak Grove (OAK) near Hattiesburg; Alabama pair: urban Birmingham 

(BHM) in North Birmingham and rural Centreville (CTR) south of Tuscaloosa; Georgia pair: 

urban Jefferson Street (JST) in Atlanta and rural Yorkville (YRK) northwest of Atlanta; and 

Florida pair: urban Pensacola (PNS) in Pensacola and suburban outlying field (OLF) northwest 

of Pensacola). SEARCH particle composition monitors (PCM3; Edgerton et al., 2005) contain a 

carbon denuder upstream of the QBQ filter packs. Since the denuder is believed to remove most 

of the VOC and gSVOC created during particle transit, the positive OC artifact should be 

minimized, and the QBQ OC should be dominated by the negative OC artifact. In contrast to the 

IMPROVE network’s one-week exposure, SEARCH field blanks are placed in the sampler for 1 

– 15 minutes before removal, so passive adsorption periods are much shorter. 

The numbers of sample, backup, and blank filters at eight SEARCH sites during 2005 – 

2006 are listed in Table 3-5, with their averages compared in Figure 3-16. These filter samples 

and field blanks were not necessarily collected on the same days. While dQBQ TC are close to 

dQF OC1 concentrations, the areal densities in μg/cm2

 (the SEARCH filter deposit area [7.12 

cm2

] is about twice the IMPROVE filter deposit area [3.53 cm2]) are 30 – 50% lower than the 

IMPROVE blank TC. This is consistent with the lower positive OC artifact, due to the preceding 

organic denuder in the PCM. This also explains the substantial negative artifact (up to ~16% of 

dQF OC) at the JST and YRK sites. Blank (bQF) TC is generally lower than dQBQ TC. 

Thermal carbon fractions for SEARCH dQBQ and bQF are shown in Figure 3-17 and 3-

18, respectively. Except for the urban-rural pair in GA (JST and YRK), all SEARCH sites show 
 

3-7

enriched OC2 and OC3 relative to OC1. At the GLF, OAK, PNS, and OLF sites OC1 is < 0.2 

μg/filter on dQF. This is consistent with VOC being removed from the sampling stream. 

Adsorbed SVOC (negative OC artifact) should have more OC2 – OC4 than OC1 (positive OC 

artifact). At the JST and YRK sites, however, high OC1 may indicate VOC denuder 

breakthrough when VOC concentrations are high. Elevated OC3 (1.4 to 2.4 μg/filter) is 

observed in bQF at the GLF, OAK, PNS, and OLF sites, warranting further investigation of 

VOC composition at the SEARCH sites. 

Only three SEARCH samples contain concurrent dQF, dQBQ, and bQF measurements, 

two from the JST site and one from the OAK site. Although the limited data set prevents any 

conclusions from being drawn, dQBQ OC and bQF OC appear to be similar for the three 

samples (Figure 3-19). 

3.4 Sliced Filter Approach 

When backup filters are used, it is assumed that the filter is saturated and that the 

distribution of adsorbed organic vapors is uniformly distributed. The top-half (QFtop) of a blank 

filter should yield the same OC as the bottom half (QFbott) and analysis of a punch from the left 

side should yield the same results as a punch from the right side. Otherwise, the distribution of 

SVOC, particularly the negative OC artifact, within a front or backup filter may be described by 

a gradient (i.e., decreasing with the increasing penetration depth). Therefore, the OC artifact 

from high to low should follow the sequence of: QFbott > QBQtop > QBQbott > bQF > bQBQ. 

Fourteen of the IMPROVE samples that contain front and backup filters were sliced and weighed, 

with their top- and bottom-halves analyzed separately for carbon fractions. The following 

procedure was applied: 

• Conduct gravimetric and carbon analyses on the front circular punch of 0.5 cm2

. 

• Acquire a second circular punch from the same filter for weighing and carbon analysis. 

• Slice the second punch and weigh the top and bottom halves. 

• Analyze both halves for carbon fractions. 

• Estimate the sampling artifact by scaling carbon measured on the bottom-half filter to the 

whole filter. 

Table 3-6 shows that the slicing experiment conserved filter mass (with average percent 

difference of -3.3 to +5.3%). Figure 3-20 shows two typical comparisons, demonstrating a 

gradient of carbon distribution from top to bottom of the filter stack. On average, QFbott contains 

higher OC and TC concentrations than do the top and bottom halves of the QBQ filters in terms 
 

3-8

of μgC per mg filter (Table 3-7). The difference is more pronounced for higher-temperature OC 

fractions (e.g., OC3, OC4), especially when the QF OC loading is high (e.g., the YOSE and 

SHEN sites). 

The number of cases studied in this experiment is too small to generalize, but the results 

in Table 3-7 indicate that deviations from the assumptions that the backup filter adsorption 

equals that of the front filter, and that adsorption is uniform throughout the filter, are not 

universally valid. 

3.5 Regression/Intercept Approach 

As noted earlier, this method calculates a linear regression slope, intercept, and 

correlation of OC regressed on PM2.5 (White and Macias, 1989; Solomon et al., 2004). If there 

were no positive or negative OC artifact, the regression line intercept would be zero, within the 

estimated standard error. A significant (greater than two or three standard errors) intercept 

quantifies the excess carbon on all of the samples. This method assumes: 1) the sum of positive 

and negative artifacts is constant for all samples (within measurement uncertainties; 2) the OC 

artifact is the dominant reason for lack of mass closure; and 3) PM2.5 and OC concentrations are 

highly correlated (i.e., OC constitutes a reasonably consistent fraction of PM2.5). PM2.5 mass 

data were acquired from VIEWS (2007) and linked to the OC concentration from quartz-fiber 

front filters (QF). OC, on average, accounts for a larger fraction of PM2.5 in summer (~20%) than 

winter (15%). 

It is shown in previous sections that positive and negative OC artifacts differ by season 

and location, so the OC-PM2.5 pairs were segregated by site and by season for regression analysis. 

Ordinary non-weighted least squares regression slopes and intercepts were strongly influenced 

by a few outliers. Therefore, a robust ordinary least squares regression (ROR; Dutter and Huber, 

1981) algorithm was applied that uses an iteratively re-weighted least squares algorithm. The 

ROR algorithm is also used in multivariate factor-analysis models such as positive matrix 

factorization (PMF; Paatero, 1997). 

Figure 3-21 shows a wide range of intercepts, including negative intercepts. The OC 

artifact has been found to be higher in summer, but 14 IMPROVE sites (9%) experience negative 

OC intercepts. In winter, negative intercepts appear at 6 IMPROVE sites (4%). One explanation 

is that summer sulfate is so high that the OC vs. PM2.5 relationship is biased, i.e., the OC artifact 

becomes a minor factor for determining the regression statistics. 
 

3-9

The network average and standard deviation of OC vs. PM2.5 regression intercepts is 

shown in Table 3-8. These values (11.2 – 18.2 μg/filter) are higher than either the blank or 

backup OC concentrations. This is consistent with a negative OC artifact for Teflon-membrane 

filters. The intercept method, if applied, will likely overestimate the positive OC artifact and 

overcorrect the OC concentration. However, considering that PM2.5 mass closure is usually 

attained with respect to PM2.5 measured on Teflon-membrane filters, the intercept method may 

yield better mass closure than field blank or backup filter corrections, giving the correct answer 

for the wrong reason. 

3.6 Composition of Adsorbed Organic Gases 

A full understanding of positive and negative OC artifacts will not be obtained until the 

organic compounds associated with them are identified and quantified. There have been few 

attempts to do this because large quantities of material are needed for solvent extraction followed 

by concentration of the extract and gas chromatographic/mass spectrometric (GC/MS) analysis 

(Mazurek et al., 1987). An alternative to solvent extraction is thermal desorption (TD)-GC/MS 

that removes particulate and adsorbed organic compounds from the filter by heating and sends 

the evolved gases directly through the GC/MS (Hays and Lavrich, 2007; Chow et al., 2007b). 

TD-GC/MS is currently applied to daily samples taken in SEARCH and other long-term 

networks (Schnelle-Kreis et al., 2005a; 2005b; Sklorz et al., 2007), with nearly 5,000 of these 

measurements reported worldwide. 

In TD-GC/MS, a small portion of the quartz-fiber filter, similar to that used for 

IMPROVE TOR analysis, is heated to evaporate and quantify ~130 non-polar organic 

compounds, including polycyclic aromatic hydrocarbons (PAH) n-alkanes, iso/anteiso-alkanes, 

hopanes, steranes, methyl-alkanes, branched-alkanes, cycloalkanes, alkenes, and phthalates. 

Mauderly and Chow (2008) provide a simple summary of these and other organic compound 

categories and methods for their quantification. Most of the detected compounds have boiling 

points < 250 °C and are often classified as pSVOCs. Compounds are listed in order of 

increasing carbon number, which generally corresponds to a higher boiling point within each 

category. Feasibility for analyzing polar compounds has been demonstrated (Hays, 2007), and 

this might be usefully applied in the future to explain a larger fraction of the adsorbed organic 

vapors. 
 

3-10

TD-GC/MS following the method of Ho and Yu (2004a; 2004b) was applied to a few of 

the IMPROVE front and backup filters to evaluate its feasibility and to provide some initial 

insight into the chemical composition of the organic artifacts. This method heats the sample to 

275 °C within the GC injection port, thereby characterizing the OC1+OC2 fraction. The evolved 

organic gases concentrate at the entry to the GC column, which then is ramped to 400 °C so that 

the organic compounds can be separated as they pass through the column in an inert helium 

carrier gas for detection and identification by the mass spectrometer. Table 3-9 lists the species 

that were quantified and their LQLs. Reference materials added to the sample prior to heating 

are used to normalize the peak areas and elution times. The gas chromatograms and mass 

spectra contain more information than is reported here in terms of unidentified peaks and shapes 

of the underlying “unresolved” fraction that merit further investigation for understanding organic 

artifacts and source apportionment (Watson and Chow, 2007), but this potential is not explored 

here. 

Tables 3-10 and 3-11 summarize organic concentration densities (ng/cm2 of filter) on 

sampled front and backup filters from several IMPROVE sites for winter (four filter sets) and 

summer (six filter sets) periods, respectively. The final row in each table presents the sum of all 

quantifiable organic compounds on QF, which range from 18.5 (MORA) to 116.3 (CHIR) 

ng/cm2

 during winter and from 36.1 (CHIR) to 124.5 (MORA) ng/cm2 during summer. These 

are small fractions of OC1 + OC2 on the same filters, which range from 0.8 (MORA) to 9.0 

(OKEF) μg/cm2 in winter and from 1.2 (MORA) to 11.6 (OKEF) μg/cm2 during summer. The 

final rows of Table 3-10 show that the backup filter accounts for 90% of the front filter organic 

compounds at the OKEF site, but only 20% of front filter deposit at the CHIR site during winter. 

The high retene (2.1 ng/cm2

) level for the winter CHIR sample is indicative of contributions 

from vegetative burning (Ramdahl, 1983), and many of the other organic concentration densities 

are large for this sample. During summer, the sum of organic compounds on the backup filter 

account for 50 – 90% of the front filter concentrations except for the OKEF sample (20%). 

Ratios of backup to front filter concentrations are also given for each sample set in Tables 

3-10 and 3-11. These ratios should be > 1 if the front filter needs to achieve saturation before the 

backup filter (QBT or QBQ). This is not always the case, as evidenced by backup to front filter 

ratios as high as 12.8 for wintertime squalane (12/21/2005) at the OKEF site. Both the front and 

backup filter levels are low, and measurement uncertainties are high for this and other 
 

3-11

compounds with high backup to front filter ratios. There is nearly always an important or major 

amount (30% to 200%) of a compound on the backup filter when the front filter concentration 

density exceeds 1 ng/cm2. OC1 + OC2 backup to front ratios exceed unity for most of these 

filters, indicating that there are many more compounds being adsorbed on the backup filter than 

are quantified here. 

The TD analysis shows that ambient concentrations of the target organic compounds are 

at almost equal levels between front and backup filters in cases of low filter loading. This is 

supported by both the gas chromatograms (Figure 3-22) and the measurements of the OC1 and 

OC2 concentrations in Tables 3-10 and 3-11, respectively. In the case of the OKEF site where 

OC1 and OC2 show high loadings, regardless of season, concentrations of the target compounds 

in the front filter are higher than those in the backup filter for most of the species. 

Most of the PAHs remain on the front filter, especially for the winter CHIR samples 

affected by vegetative burning where their concentration densities are highest. The n-alkanes up 

to octacosane (n-C28) show large fractions of the total on backup filters, often at levels twice the 

concentration densities on the front filter (OKEF winter). Higher n-alkanes (e.g., > n-C35, 

pentatriacontane) are rarely detected on the backup filters. Hopanes and steranes, which are 

believed to derive from engine lubricating oils (Fujita et al., 2007a; 2007b), do not show high 

levels on the backup filters even when they are detected on the front filters. Front filter 

concentration densities are low for these non-urban samples. Methyl-alkanes, branched-alkanes, 

alkenes, and pthalates are not detected at high levels during winter and have variable ratios of 

backup to front filter densities. For the highest concentrations measured at CHIR during winter 

(1/19/2005), backup filter levels are relatively low except for bis(2-ethylrexgl)phthalate (0.41 

ng/cm2

). Summer samples generally show higher backup to front filter concentration densities 

for these categories, especially for n-alkanes, but there is much variability among the samples. 

There might be more evaporation of these compounds (i.e., negative OC artifact) from the front 

filter during the summer than during winter owing to the higher daytime temperatures. 

The small number of chemical compounds measured (relative to all of those that might be 

adsorbed), locations, and sampling dates do not permit generalization of these findings. It is 

apparent, however, that backup filters sometimes contain more material than the front filter. 

Front and backup filters are not necessarily saturated and they may not adsorb organic vapors 
 

3-12

uniformly across their surface or through their depths. There could also be migration of SVOC 

from front to backup filters during sampling. 
 

3-13

0

5

10

15

20

25

30

PITT1

BOAP1

FOPE1

HEGLX

WIMO1

EVERX

SHRO1

GRBA1

MOZI1

CABA1

HALE1

CACR1

ADPI1

CRLA1

AGTI1

SIME1

MKGO1

LYBR1

BIBE1

DETR1

YELL1

GRSM1

CEBL1

ATLA1

BRMA1

MOHO1

BRCA1CRES1

SIKE1

HEGL1

CAPI1

DOUG1

NOCA1

FRES1

VIIS1

SAMA1

DENA1

MELAX

R

Blank Carbon Concentration (

AFA1

μg/filter)

OC1 OC2

OC3 OC4

EC1 EC2

EC3 OC by Reflectance (OCR)

(a) 

0

5

10

15

20

25

30

MOOS1

HAVO1

BRIG1

JOSH1

COGO1

WHPA1

ROMA1

REDW1

PHOE1

PASA1

CHAS1

BADL1

DOSO1

MONT1

ELLI1

CANY1

INGA1

GUMO1

HECA1

SYCA1

ULBE1

MEVE1

FLAT1

TUXE1

PEFO1

CADI1

SAWEX

EVER1

HOOVX

BLIS1

THBA1

CORI1

BAND1

ELDO1

SENEX

LABE1

ISLE1

PETE1

SNPA1

HOOV1

SHEN1

SAWE1

Blank Carbon Concentration (

μg/filter)

OC1 OC2

OC3 OC4

EC1 EC2

EC3 OC by Reflectance (OCR)

(b) 

Figure 3-1. Site-averaged blank carbon fractions in the IMPROVE network. (Includes 77 sites 

with data from > 5 field blanks sorted by site from lowest to highest total carbon content. The 

bottom panel is an extension of the top panel.) 
 

3-14

0

10

20

30

40

50

60

70

80

90

100

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34

Total Carbon Concentration (μg/filter)

 Number of Sites

Figure 3-2. Distribution of average field blank TC (μg/filter) for 181 IMPROVE sites for the 

period from 1/1/2005 to 12/31/2006. 
 

3-15

0

2

4

6

8

10

12

14

16

18

20

Spring Summer Fall Winter

Blank Carbon Concentration (

μg/filter)

EC3

EC2

EC1

OC4

OC3

OC2

OC1

OC by Reflectance

Figure 3-3. Seasonal averages of field blank carbon fractions for 77 IMPROVE sites with > 5 

blanks(725 total) for the period from 1/1/2005 to 12/31/2006 (spring: March, April, May; 

summer: June, July, August; fall: September, October, November; winter: December, January, 

February).
 

3-16

0

20

40

60

80

100

120

140

160

180

200

HAVO1

VIIS1

DENA1

TUXE1

MOZI1

SYCA1

HOOVX

BLIS1

CANY1

BRMA1

SENEX

SAWEX

SAWE1

RAFA1

SHEN1

MOOS1

EVERX

DOSO1

HEGL1

LABE1

AGTI1

CHAS1

DOUG1

MKGO1

PITT1

PHOE1

Sampling Sites

Carbon Concentration (

μg/filter)

EC3

EC2

EC1

OC4

OC3

OC2

OC1

blk TC (BLKTC)

Active Sampling Passive

Deposition

Figure 3-4. Averaged blank total carbon concentration (BLKTC) compared with concurrent 

averaged front filter carbon loading in the IMPROVE network between 1/1/2005 and 12/31/2006. 

Only 77 sites with data from > 5 blanks are included.
 

3-17

0

5

10

15

20

0 5 10 15 20

Carbon Fractions on Front Filter (μg/filter) 

Carbon Fractions on Blank Filter 

(μg/filter)

OC1

OC2

OC3

Figure 3-5. Comparison of site-averaged carbon fractions from field blank and quartz-fiber front 

filters at 77 sites with more than five field blanks in the IMPROVE network for the period from 

1/1/2005 through 12/31/2006. 
 

3-18

0

20

40

60

80

100

120

140

160

180

200

MORA

YOSE

HANC

CHIR

SHEN

OKEF

Sampling Sites

Carbon Concentration (

μg/filter)

EC3

EC2

EC1

OC4

OC3

OC2

OC1

QBQ

Figure 3-6. Average carbon concentration from the quartz-fiber backup filter (QBQ) compared 

with concurrent quartz-fiber front filter (QF) carbon fraction concentrations for six sites in the 

IMPROVE network. 
 

3-19

0

5

10

15

20

25

MORA

YOSE

HANC

CHIR

SHEN

OKEF

Sampling Sites

Backup Carbon Concentration 

(μg/filter)

OC1 OC2 OC3 OC4 EC1 EC2 EC3 Avg. Backup OC

Figure 3-7. Site-averaged quartz-fiber backup (QBQ) carbon fractions at six sites in the 

IMPROVE network. 
 

3-20

0%

20%

40%

60%

80%

100%

MORA (QBQ)

MORA (bQF)

YOSE (QBQ)

YOSE (bQF)

HANC (QBQ)

HANC (bQF)

CHIR (QBQ)

CHIR (bQF)

SHEN (QBQ)

SHEN (bQF)

OKEF (QBQ)

OKEF (bQF)

Carbon Fractions (%)

EC2

EC1

OC4

OC3

OC2

OC1

Figure 3-8. Carbon fractions of concurrent QBQ and bQF filters from six IMPROVE anchor 

sites. (MORA: Mount Rainier National Park, 5 samples; YOSE: Yosemite National Park, 4 

samples; HANC: Hance Camp at Grand Canyon National Park. 3 samples; CHIR: Chiricahua 

National Monument, 5 samples; SHEN Shenandoah National Park, 9 samples; and OKEF 

Okefenokee National Wildlife Refuge, 1 sample).
3-21

1

10

100

1000

1/1/2005

3/1/2005

5/1/2005

7/1/2005

9/1/2005

11/1/2005

1/1/2006

3/1/2006

5/1/2006

7/1/2006

9/1/2006

11/1/2006

Date

OC Concentration (μg/filter)

QFQBQbQF

MORA

1

10

100

1000

1/1/2005

3/1/2005

5/1/2005

7/1/2005

9/1/2005

11/1/2005

1/1/2006

3/1/2006

5/1/2006

7/1/2006

9/1/2006

11/1/2006

Date

OC Concentration (μg/filter) QF QBQ bQF YOSE

1

10

100

1000

1/1/2005

3/1/2005

5/1/2005

7/1/2005

9/1/2005

OC Concentration (μg/filter)

HANC

1

10

100

1000

1/1/2005

3/1/2005

5/1/2005

7/1/2005

9/1/2005

11/1/2005

1/1/2006

3/1/2006

5/1/2006

7/1/2006

9/1/2006

11/1/2006

Date

OC Concentration (μg/filter)QF QBQ bQF CHIR

1

10

100

1000

1/1/2005

3/1/2005

5/1/2005

7/1/2005

9/1/2005

11/1/2005

1/1/2006

3/1/2006

5/1/2006

7/1/2006

9/1/2006

11/1/2006

Date

OC Concentration (μg/filter)QF QBQ bQF SHEN

1

10

100

1000

1/1/2005

3/1/2005

5/1/2005

7/1/2005

9/1/2005

OC Concentration (μg/filter) 

OKEF

Figure 3-9. Time series of quartz-fiber front filter (QF), quartz-fiber backup filter (QBQ), and field blank (bQF) six sites in the IMPROVE network for the period from 1/1/2005 through 12/31/2006. A small number of field b

each of the backup filter sites. 
3-22

y = 0.94x

R2

 = 0.57

0

5

10

15

0 5 10 15

Field Blank OC (μg/filter)

Backup Blank OC (

μg/filter)

N = 22

Figure 3-10. Comparison of field blank OC (bQF) with backup blank OC (bQBQ) 

concentrations at six sites in the IMPROVE network. 
3-23

 

0

20

40

60

80

100

120

MORA1 YOSE1 HANC1 CHIR1 SHEN1 OKEF1

OC Concentration (

μg/filter)

QF

QBQ

bQF

bQBQ

Figure 3-11. Comparisons of averaged OC concentrations in quartz-fiber front filters (QF), 

quartz-fiber backup filters (QBQ), front field blanks (bQF) and backup field blanks (bQBQ) for 

the concurrent sampling of 22 sample sets for the period from 1/1/2005 through 12/31/2006 at 

six sites in the IMPROVE network. 
3-24

0

20

40

60

80

100

120

140

160

spring summer fall winter

Organic Carbon Concentration (μg/filter)

QF_Day1

QBT_Day1

QBQ_Day1

bQF

bQBQ

(a) 

0

20

40

60

80

100

120

140

160

spring summer fall winter

Organic Carbon Concentration (μg/filter)

QF_Day2

QBT_Day2

QBQ_Day2

bQF

bQBQ

(b) 

Figure 3-12. Comparison of seasonally averaged OC on quartz-fiber front filter (QF), quartzfiber backup behind Teflon-membrane front filter (QBT), quartz-fiber backup behind quartzfiber front filter (QBQ), and blank filters (bQF and bQBQ) for: a) Day 1 (24 hr sampling on first 

day followed by a 48 hr passive period), and b) Day2 (24 hr sampling on second day with 24 hr 

passive period before and after sampling) samples acquired from Fort Meade, MD. (spring: 

April; summer: July; fall: October; winter: January.)
3-25

-10

0

10

20

30

40

50

60

70

OC1 OC2 OC3 OC4 OP

Carbon Concentration (

μg/filter)

QF

QBT

QBQ

Figure 3-13. Average and standard deviation (bar) for organic carbon fraction concentrations on 

quartz-fiber front filters (QF), quartz-fiber backup behind Teflon-membrane (QBT), and quartzfiber backup behind quartz-fiber (QBQ) for summer 1999 at Fort Meade, MD (36 24-hr samples). 
3-26

0

20

40

60

80

100

120

140

0 200 400 600 800

pOC + pSVOC (μg/filter)

Volatilized OC Loss (

μg/filter)

Toc_loss

Qoc_loss

(a) 

0

20

40

60

80

100

120

140

0 200 400 600 800

pOC + pSVOC (μg/filter)

Volatilized OC Loss (

μg/filter)

Toc_loss

Qoc_loss

(b) 

Figure 3-14. Estimated negative sampling artifact (OC loss) from Teflon-membrane and quartzfiber filters against particulate OC (pOC + pSVOC) loading at FME for: a) summer (July) and b) 

winter (January) seasons. The edges of scatter are determined from the regression of data with 

the lowest 10% OC_loss/(pOC+pSVOC) ratio. 

 TOCloss

 QOCloss

 TOCloss

 QOCloss
3-27

(40)

(20)

0

20

40

60

80

100

120

140

160

Teflon Quartz Teflon Quartz

Summer Winter

OC Concentration (

μg/filter)

pSVOC (volatilized)

pSVOC (retained)

pOC

VOC and gSVOC (adsorption)

Figure 3-15. The fraction of pOC, retained pSVOC, and volatilized pSVOC or gSVOC from 

Teflon-membrane and quartz-fiber filters at FME during summer and winter seasons. 
3-28

0

20

40

60

80

100

120

140

160

180

200

GLF

OAK

BHM

CTR

JST

YRK

PNS

OLF

Sampling Sites

Carbon Concentration (

μg/filter)

EC3

EC2

EC1

OC4

OC3

OC2

OC1

TC (dQBQ)

TC (bQF)

Georgia 

Pair

Alabama 

Pair

Mississippi 

Pair

Florida 

Pair

Mississippi Pair: urban Gulfport [GLF] in Gulfport; and rural Oak Grove [OAK] near Hattiesburg 

Alabama Pair: urban Birmingham [BHM] in North Birmingham and rural Centreville [CTR] south of Tuscaloosa 

Georgia Pair: urban Jefferson Street [JST] in Atlanta and rural Yorkville [YRK] northwest of Atlanta 

Florida Pair: urban Pensacola [PNS] in Pensacola and suburban outlying field [OLF] northwest of Pensacola 

Figure 3-16. Average backup (dQBQ) and blank (bQF) TC compared with dQF carbon fractions 

for the SEARCH network. The first site at each pair is the urban site, while the other is suburban 

or rural site. (The number of data points is shown in Table 3-5.)
3-29

0

5

10

15

20

25

GLF

OAK

BHM

CTR

JST

YRK

PNS

OLF

Sampling Sites

Backup Carbon Concentration (

μg/filter)

OC1 OC2

OC3 OC4

EC1 EC2

EC3 OC by Reflectance (OCR)

Mississippi

Pair

Alabama

Pair

Georgia

Pair

Florida

Pair

Figure 3-17. Average carbon fractions on quartz-fiber backup filters (dQBQ following 

preceding organic denuders) in the SEARCH network from 1/1/2005 through 12/31/2006. (Sites 

are arranged according to Table 3-5.) 
3-30

0

5

10

15

20

25

GLF

OAK

BHM

CTR

JST

YRKPNS

OLF

Sampling Sites

Blank Carbon Concentration (

μg/filter)

OC1 OC2

OC3 OC4

EC1 EC2

EC3 OC by Reflectance (OCR)

Mississippi

Pair

Alabama

Pair

Georgia

Pair

Florida

Pair

Figure 3-18. Averaged carbon fractions of quartz-fiber blank filters in the SEARCH network 

from 1/1/2005 to 12/31/2006. (Sites are arranged according to Table 3-5.) 
3-31

0

10

20

30

40

50

60

70

80

90

100

30-Nov-05 20-Feb-06 01-Dec-06

JST JST OAK

OC Concentration (

μg/filter)

QF

QBQ

bQF

Figure 3-19. Comparison of concurrent SEARCH quartz-fiber front (QF), quartz-fiber backup 

(QBQ), and quartz-fiber blank (bQF) filter OC concentrations. 
3-32

(a) (b) 

(c) (d) 

Figure 3-20. Comparison of original and sliced filter mass (in mg) with carbon loading (in 

μg). Diamonds and 

(QF) and backup (QBQ) filters, respectively. The upper and lower triangles indicate top (QFtop) and bottom halv

while rectangles represent the original filter punch (0.5 cm2). In Cases (a) and (b), the bottom halves of QF co

concentrations as those on backup filters. In Cases (c) and (d), the bottom-half of QF contains higher carbon conslices. 

YOSE1 2006/2/16 (R14098)

05

1015202530

0123

Slice Mass (mg)

Carbon Loading (ug)

SHEN1 5/17/2005 (Q93898)

0

102030405060

01234

Slice Mass (mg)

Carbon Loading (ug) Front Filter Backup Filter

CHIR1 2005/4/7(Q94596)

05

10152025

0123

Slice Mass (mg)

Carbon Loading (ug)

SHEN1 2005/1/13 (Q89488)

0

10203040506070

01234

Slice Mass (mg)

Carbon Loading (ug)
 

3-33

-20

0

20

40

60

80

100

Intercept (

μg/filter)

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

Slope

Spring

(a) 

-20

0

20

40

60

80

100

Intercept ( μg/filter)

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

Slope

Summer

(b) 

Figure 3-21. Robust regression intercepts (bars) and slopes (lines) for quartz-fiber front filter OC 

(y-axis) versus PM2.5 mass (x-axis) for all IMPROVE sites during: a) spring (April), b) summer 

(July), c) fall (October), and d) winter (January). IMPROVE data from 1/1/2005 to 12/31/2006.
 

3-34

-20

0

20

40

60

80

100

Intercept (

μg/filter)

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

Slope

Fall

(c) 

-20

0

20

40

60

80

100

Intercept (

μg/filter)

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

Slope

Winter

(d) 

Figure 3-21. Continued. 
 

3-35

(a) 

MORA

(8/5/2005)

0

500000

1000000

1500000

2000000

2500000

6.09

7.5

8.9210.311.813.214.6

16

17.418.820.321.723.124.525.927.328.830.231.6

33

34.435.837.338.740.141.542.944.345.847.248.6

50

51.452.854.355.7

Retention Time (minutes)

Abundance

QF

QBQ

Summer 

MORA

(1/28/2005)

0

200000

400000

600000

800000

1000000

1200000

1400000

6.09

7.5

8.9210.311.813.214.6

16

17.418.820.321.723.124.525.927.328.830.231.6

33

34.435.837.338.740.141.542.944.345.847.248.6

50

51.452.854.355.7

Retention Time (minutes)

Abundance

QF

QBQ

Winter 

Figure 3-22. Gas chromatograms of front (QF) and backup (QBQ) quartz-fiber samples for the: 

(a) Mount Rainier, WA (MORA), (b) Chiricahua, AZ (CHIR), (c) Grand Canyon, AZ (HANC), 

and (d) Okefenokee, GA (OKEF) sites in the IMPROVE network on selected days of summer 

and winter 2005. 
 

3-36

 (b) 

CHIR

(7/27/2005)

0

500000

1000000

1500000

2000000

2500000

3000000

3500000

4000000

6.09

7.5

8.9210.311.813.214.6

16

17.418.820.321.723.124.525.927.328.830.231.6

33

34.435.837.338.740.141.542.944.345.847.248.6

50

51.452.854.355.7

Retention Time (minutes)

Abundance

QF

QBQ

Summer 

CHIR

(1/19/2005)

0

500000

1000000

1500000

2000000

2500000

3000000

6.09

7.5

8.9210.311.813.214.6

16

17.418.820.321.723.124.525.927.328.830.231.6

33

34.435.837.338.740.141.542.944.345.847.248.6

50

51.452.854.355.7

Retention Time (minutes)

Abundance

QF

QBQ

Winter 

Figure 3-22. Continued. 
 

3-37

(c) 

HANC

(8/2/2005)

0

500000

1000000

1500000

2000000

2500000

3000000

3500000

6.097.088.079.0710.111.1

121314151617181920212223242526

26.927.928.929.930.931.932.933.934.935.936.937.938.939.940.9

Retention Time (minutes)

Abundance

QF

QBQ

Summer 

HANC

(1/7/2005)

0

200000

400000

600000

800000

1000000

1200000

1400000

6.097.088.079.0710.111.1

121314151617181920212223242526

26.927.928.929.930.931.932.933.934.935.936.937.938.939.940.9

Retention Time (minutes)

Abundance

QF

QBQ

Winter 

Figure 3-22. Continued. 
 

3-38

(d) 

OKEF

(8/20/2005)

0

2000000

4000000

6000000

8000000

10000000

12000000

6.097.538.9710.411.913.314.716.217.619.120.5

22

23.424.926.327.729.230.632.133.5

35

36.437.839.340.742.243.645.146.547.949.450.852.353.755.2

Retention Time (minutes)

Abundance

QF

QBQ

Summer 

OKEF

(12/21/2005)

0

200000

400000

600000

800000

1000000

1200000

6.09

7.5

8.9210.311.813.214.6

16

17.418.820.321.723.124.525.927.328.830.231.6

33

34.435.837.338.740.141.542.944.345.847.248.6

50

51.452.854.355.7

Retention Time (minutes)

Abundance

QF

QBQ

Winter 

Figure 3-22. Continued.
 

3-39

Table 3-1. Summary of field blanks acquired at 181 sites (plus six collocated sites) in the 

IMPROVE Network from 1/1/2005 to 12/31/2006.

 Sampling Period Total Field # of Field Blanks by Season 

SiteID Name State From To Blanks Spring Summer Fall Winter 

ACAD1 Acadia NP ME 1/13/2005 1/5/2006 3 1 0 0 2 

ADPI1 Addison Pinnacle NY 1/13/2005 5/11/2006 6 3 1 1 1 

AGTI1 Agua Tibia CA 5/19/2005 11/16/2006 7 1 1 5 0 

AREN1 Arendtsville PA 1/13/2005 3/30/2006 5 2 0 0 3 

ATLA1 Atlanta GA 1/13/2005 11/19/2006 8 3 1 2 2 

BADL1 Badlands NP SD 1/13/2005 12/7/2006 7 1 1 1 4 

BALD1 Mount Baldy AZ 3/17/2005 6/1/2006 5 2 1 1 1 

BALT1 Baltimore MD 1/13/2005 12/15/2005 4 1 1 0 2 

BAND1 Bandelier NM NM 3/17/2005 12/28/2006 9 3 2 2 2 

BIBE1 Big Bend NP TX 3/17/2005 8/24/2006 7 3 2 2 0 

BIRM1 Birmingham AL 1/13/2005 8/24/2006 5 1 1 1 2 

BLIS1 Bliss SP (TRPA) CA 3/17/2005 10/26/2006 10 3 1 5 1 

BLMO1 Blue Mounds MN 1/13/2005 1/5/2006 4 2 0 0 2 

BOAP1 Bosque del Apache NM 1/13/2005 12/7/2006 8 0 3 2 3 

BOND1 Bondville IL 3/17/2005 11/16/2006 5 3 0 1 1 

BOWA1 Boundary Waters Canoe Area MN 3/30/2006 9/14/2006 3 2 0 1 0 

BRCA1 Bryce Canyon NP UT 7/21/2005 11/16/2006 5 0 2 3 0 

BRET1 Breton LA 2/3/2005 2/3/2005 1 0 0 0 1 

BRID1 Bridger Wilderness WY 5/19/2005 12/7/2006 2 1 0 0 1 

BRID9 Bridger Wilderness WY 1/13/2005 1/13/2005 1 0 0 0 1 

BRIG1 Brigantine NWR NJ 2/3/2005 5/11/2006 6 3 1 0 2 

BRMA1 Bridgton ME 1/13/2005 10/26/2006 6 2 0 2 2 

CABA1 Casco Bay ME 5/19/2005 12/28/2006 6 2 2 0 2 

CABI1 Cabinet Mountains MT 5/19/2005 2/16/2006 3 1 1 0 1 

CACO1 Cape Cod MA 10/13/2005 12/28/2006 2 0 0 1 1 

CACR1 Caney Creek AR 1/13/2005 9/14/2006 7 3 2 1 1 

CADI1 Cadiz KY 5/19/2005 11/16/2006 7 3 0 3 1 

CANY1 Canyonlands NP UT 7/21/2005 10/5/2006 9 1 3 3 2 

CAPI1 Capitol Reef NP UT 3/17/2005 12/7/2006 6 1 2 2 1 

CEBL1 Cedar Bluff KS 1/13/2005 10/26/2006 10 2 3 2 3 

CHAS1 Chassahowitzka NWR FL 6/9/2005 10/5/2006 8 3 2 2 1 

CHER1 Cherokee Nation OK 10/13/2005 9/14/2006 3 1 0 2 0 

CHIC1 Chicago IL 1/13/2005 3/17/2005 2 1 0 0 1 

CHIR1 Chiricahua NM AZ 1/13/2005 8/24/2006 5 2 2 0 1 

CLPE1 Cloud Peak WY 3/17/2005 4/20/2006 3 2 0 1 0 

COGO1 Columbia Gorge #1 WA 3/17/2005 10/5/2006 6 3 0 2 1 

COHI1 Connecticut Hill NY 7/21/2005 12/15/2005 3 0 1 1 1 

COHU1 Cohutta GA 3/17/2005 3/17/2005 1 1 0 0 0 

CORI1 Columbia River Gorge WA 3/17/2005 12/7/2006 5 2 1 1 1 

CRES1 Crescent Lake NE 3/17/2005 6/1/2006 6 4 1 1 0 

CRLA1 Crater Lake NP OR 5/19/2005 12/7/2006 7 1 3 1 2 

CRMO1 Craters of the Moon NM ID 3/17/2005 5/11/2006 4 3 0 1 0 

DENA1 Denali NP AK 5/19/2005 12/28/2006 7 1 3 0 3 

DETR1 Detroit MI 4/7/2005 12/31/2006 8 2 2 2 2 

DEVA1 Death Valley NP CA 3/17/2005 10/5/2006 4 1 1 2 0 

DOME1 Dome Lands Wilderness CA 12/15/2005 12/28/2006 4 0 1 0 3 

DOSO1 Dolly Sods Wilderness WV 3/17/2005 9/14/2006 9 3 2 2 2 

DOUG1 Douglas AZ 1/13/2005 12/28/2006 6 1 2 1 2 

EGBE1 N/A 9/1/2005 10/5/2006 5 1 2 2 0 

ELDO1 El Dorado Springs MO 7/21/2005 7/13/2006 6 2 2 1 1 

ELLI1 Ellis OK 3/17/2005 5/11/2006 7 3 1 2 1 

EVER1 Everglades NP FL 1/13/2005 9/14/2006 6 1 1 2 2 

EVERX Everglades NP (collocated) FL 1/13/2005 10/5/2006 9 4 0 2 3 

FLAT1 Flathead MT 1/13/2005 10/5/2006 8 1 3 2 2 

FOPE1 Fort Peck MT 3/17/2005 11/16/2006 6 1 2 2 1 

FRES1 Fresno CA 5/19/2005 11/16/2006 7 2 2 3 0 

FRRE1 Frostburg MD 5/19/2005 8/3/2006 4 1 2 0 1 

GAMO1 Gates of the Mountains MT 5/19/2005 10/13/2005 2 1 0 1 0 

GICL1 Gila Wilderness NM 4/7/2005 7/13/2006 4 1 2 0 1 

GLAC1 Glacier NP MT 1/13/2005 11/16/2006 5 2 1 1 1 

GRBA1 Great Basin NP NV 1/13/2005 12/28/2006 10 2 2 2 4 

GRGU1 Great Gulf Wilderness NH 1/13/2005 3/9/2006 5 2 1 0 2 

GRRI1 Great River Bluffs MN 5/19/2005 12/15/2005 3 1 1 0 1 

GRSA1 Great Sand Dunes NM CO 10/13/2005 10/5/2006 3 1 0 2 0 
 

3-40

Table 3-1. Continued Sampling Period Total Field # of Field Blanks by Season 

SiteID Name State From To Blanks Spring Summer Fall Winter 

GRSM1 Great Smoky Mountains NP TN 1/13/2005 10/26/2006 6 2 1 1 2 

GRSM9 Great Smoky Mountains NP TN 1/13/2005 1/13/2005 1 0 0 0 1 

GUMO1 Guadalupe Mountains NP TX 7/21/2005 12/28/2006 5 1 3 0 1 

HALE1 Haleakala NP HI 3/17/2005 12/28/2006 8 2 1 1 4 

HANC1 Hance Camp at Grand Canyon NP CO 1/13/2005 4/20/2006 3 1 0 0 2 

HAVO1 Hawaii Volcanoes NP HI 1/13/2005 12/28/2006 8 0 3 3 2 

HECA1 Hells Canyon OR 1/13/2005 11/16/2006 7 3 1 2 1 

HEGL1 Hercules-Glades MO 1/13/2005 11/16/2006 7 2 2 1 2 

HEGLX Hercules-Glades (collocated) MO 1/13/2005 11/16/2006 14 4 6 2 2 

HOOV1 Hoover CA 1/13/2005 9/14/2006 8 1 4 1 2 

HOOVX Hoover (collocated) CA 1/13/2005 12/7/2006 13 4 3 0 6 

HOUS1 Houston TX 5/19/2005 7/21/2005 2 1 1 0 0 

IKBA1 Ike's Backbone AZ 12/15/2005 12/15/2005 1 0 0 0 1 

INGA1 Indian Gardens AZ 2/3/2005 9/14/2006 6 0 2 2 2 

ISLE1 Isle Royale NP MI 1/13/2005 11/16/2006 6 2 0 3 1 

JARI1 James River Face Wilderness VA 1/13/2005 6/1/2006 5 1 1 1 2 

JOSH1 Joshua Tree NP CA 1/13/2005 7/13/2006 6 3 1 0 2 

KAIS1 Kaiser CA 1/13/2005 1/5/2006 5 1 1 1 2 

KALM1 Kalmiopsis OR 1/13/2005 11/16/2006 4 0 1 1 2 

LABE1 Lava Beds NM CA 1/13/2005 5/11/2006 7 4 0 2 1 

LASU2 Lake Sugema IA 1/13/2005 12/15/2005 3 0 0 1 2 

LAVO1 Lassen Volcanic NP CA 1/13/2005 1/5/2006 3 0 0 1 2 

LIGO1 Linville Gorge NC 3/17/2005 4/20/2006 5 3 0 1 1 

LIVO1 Livonia IN 1/13/2005 5/19/2005 2 1 0 0 1 

LOST1 Lostwood ND 5/19/2005 11/16/2006 5 2 0 3 0 

LYBR1 Lye Brook Wilderness VT 1/13/2005 12/7/2006 6 1 1 1 3 

MACA1 Mammoth Cave NP KY 5/19/2005 12/7/2006 5 2 1 0 2 

MAVI1 Martha's Vineyard MA 5/19/2005 7/13/2006 5 3 1 0 1 

MEAD1 Meadview AZ 5/19/2005 5/19/2005 1 1 0 0 0 

MELA1 Medicine Lake MT 3/17/2005 8/24/2006 3 2 1 0 0 

MELAX Medicine Lake (collocated) MT 1/13/2005 12/7/2006 8 3 2 0 3 

MEVE1 Mesa Verde NP CO 1/13/2005 12/28/2006 9 1 4 2 2 

MING1 Mingo MO 5/19/2005 9/14/2006 4 1 0 2 1 

MKGO1 M.K. Goddard PA 3/17/2005 8/24/2006 7 4 1 2 0 

MOHO1 Mount Hood OR 1/13/2005 8/24/2006 7 3 1 2 1 

MOMO1 Mohawk Mt. CT 3/17/2005 12/7/2006 4 1 0 0 3 

MONT1 Monture MT 1/13/2005 11/16/2006 7 2 2 2 1 

MOOS1 Moosehorn NWR ME 1/13/2005 12/7/2006 7 2 1 1 3 

MORA1 Mount Rainier NP WA 1/13/2005 11/16/2006 5 2 1 1 1 

MORA9 Mount Rainier NP WA 1/13/2005 1/13/2005 1 0 0 0 1 

MOZI1 Mount Zirkel Wilderness CO 3/17/2005 11/16/2006 8 4 1 3 0 

NEBR1 Nebraska NF NE 1/13/2005 6/22/2006 5 1 2 0 2 

NEYO1 New York City NY 5/19/2005 12/15/2005 3 1 1 0 1 

NOAB1 North Absaroka WY 3/30/2006 10/5/2006 3 1 1 1 0 

NOCA1 North Cascades WA 3/17/2005 12/28/2006 7 2 2 2 1 

NOCH1 Northern Cheyenne MT 9/1/2005 10/5/2006 3 1 0 2 0 

OKEF1 Okefenokee NWR GA 6/1/2006 6/1/2006 1 0 1 0 0 

OLTO1 Old Town ME 5/19/2005 4/20/2006 4 2 0 1 1 

OLYM1 Olympic WA 2/3/2005 2/16/2006 2 0 0 0 2 

OMAH1 Omaha NE 3/17/2005 10/5/2006 4 1 1 2 0 

ORPI1 Organ Pipe AZ 3/17/2005 11/16/2006 5 2 0 2 1 

PASA1 Pasayten WA 5/19/2005 10/5/2006 6 1 1 3 1 

PEFO1 Petrified Forest NP AZ 3/17/2005 12/7/2006 6 3 1 1 1 

PENO1 N/A 3/30/2006 8/24/2006 2 1 1 0 0 

PETE1 Petersburg AK 4/7/2005 9/14/2006 8 3 1 2 2 

PHOE1 Phoenix AZ 1/13/2005 5/11/2006 6 2 0 2 2 

PHOE5 Phoenix AZ 1/13/2005 5/11/2006 5 1 0 1 3 

PINN1 Pinnacles NM CA 3/9/2006 5/11/2006 2 2 0 0 0 

PITT1 Pittsburgh PA 1/13/2005 12/10/2006 8 2 2 2 2 

PMRF1 Proctor Maple R. F. VT 3/17/2005 7/13/2006 4 2 1 1 0 

PORE1 Point Reyes National Seashore CA 7/21/2005 11/16/2006 4 1 1 2 0 

PRIS1 Presque Isle ME 2/3/2005 4/20/2006 3 2 0 0 1 

PUSO1 Puget Sound WA 3/17/2005 1/5/2006 2 1 0 0 1 

QUCI1 Quaker City OH 10/5/2006 10/5/2006 1 0 0 1 0 

QURE1 Quabbin Summit MA 1/13/2005 2/16/2006 4 0 0 2 2 
 

3-41

Table 3-1. Continued Sampling Period Total Field # of Field Blanks by Season 

SiteID Name State From To Blanks Spring Summer Fall Winter 

QUVA1 Queen Valley AZ 3/17/2005 11/16/2006 3 1 0 2 0 

RAFA1 San Rafael CA 1/13/2005 12/7/2006 7 1 1 2 3 

REDW1 Redwood NP CA 1/13/2005 12/7/2006 6 1 1 1 3 

ROMA1 Cape Romain NWR SC 1/13/2005 7/13/2006 5 3 1 0 1 

ROMO2 Cape Romain NWR SC 1/13/2005 1/13/2005 1 0 0 0 1 

RUBI1 Rubidoux CA 3/17/2005 7/21/2005 3 2 1 0 0 

SACR1 Salt Creek NM 1/13/2005 8/3/2006 5 1 1 2 1 

SAFO1 Sac and Fox KS 1/13/2005 2/16/2006 4 0 1 1 2 

SAGA1 San Gabriel CA 1/13/2005 10/5/2006 4 2 0 1 1 

SAGO1 San Gorgonio Wilderness CA 3/17/2005 9/14/2006 4 3 0 1 0 

SAGU1 Saguaro NM AZ 1/13/2005 11/16/2006 2 0 0 1 1 

SAMA1 St. Marks FL 5/19/2005 11/16/2006 7 2 2 2 1 

SAPE1 San Pedro Parks NM 3/17/2005 2/16/2006 3 2 0 0 1 

SAWE1 Saguaro West AZ 1/13/2005 6/1/2006 7 4 1 1 1 

SAWEX Saguaro West (collocated) AZ 1/13/2005 8/24/2006 16 5 6 1 4 

SAWT1 Sawtooth NF ID 1/13/2005 11/16/2006 4 0 1 2 1 

SENE1 Seney MI 3/17/2005 11/16/2006 3 1 0 2 0 

SENEX Seney (collocated) MI 1/13/2005 12/7/2006 13 3 2 4 4 

SEQU1 Sequoia NP CA 12/15/2005 11/16/2006 4 0 0 2 2 

SEQU9 Sequoia NP CA 1/13/2005 1/13/2005 1 0 0 0 1 

SHEN1 Shenandoah NP VA 1/13/2005 1/5/2006 9 6 0 0 3 

SHMI1 Shamrock Mine CO 5/19/2005 5/11/2006 2 2 0 0 0 

SHRO1 Shining Rock Wilderness NC 3/17/2005 5/11/2006 6 4 0 1 1 

SIAN1 Sierra Ancha AZ 7/21/2005 10/5/2006 4 1 1 1 1 

SIKE1 Sikes LA 1/13/2005 8/3/2006 6 0 2 1 3 

SIME1 Simeonof AK 1/13/2005 10/5/2006 7 2 2 2 1 

SIPS1 Sipsy Wilderness AL 5/19/2005 12/7/2006 3 1 0 0 2 

SNPA1 Snoqualmie Pass WA 7/21/2005 12/28/2006 7 0 1 4 2 

SPOK1 Spokane Res. WA 5/19/2005 6/9/2005 2 1 1 0 0 

STAR1 Starkey OR 2/3/2005 12/7/2006 4 1 1 0 2 

SULA1 Sula Peak MT 5/19/2005 11/16/2006 3 1 0 1 1 

SWAN1 Swanquarter NC 3/17/2005 3/9/2006 5 2 2 1 0 

SYCA1 Sycamore Canyon AZ 1/13/2005 9/14/2006 6 1 1 1 3 

TALL1 Tallgrass KS 1/13/2005 11/16/2006 5 0 1 2 2 

THBA1 Thunder Basin WY 5/19/2005 11/16/2006 8 2 2 2 2 

THRO1 Theodore Roosevelt ND 5/19/2005 5/19/2005 1 1 0 0 0 

THSI1 Three Sisters Wilderness OR 1/13/2005 12/28/2006 5 1 1 0 3 

TONT1 Tonto NM AZ 12/15/2005 12/28/2006 5 1 1 1 2 

TRCR1 Trapper Creek AK 3/17/2005 9/14/2006 4 1 0 2 1 

TRIN1 Trinity CA 1/13/2005 7/21/2005 4 2 1 0 1 

TUXE1 Tuxedni AK 6/9/2005 11/16/2006 7 1 3 2 1 

ULBE1 UL Bend MT 1/13/2005 12/7/2006 7 1 1 1 4 

UPBU1 Upper Buffalo Wilderness AR 3/17/2005 9/14/2006 5 1 3 1 0 

VIIS1 Virgin Islands NP VI 3/17/2005 11/16/2006 8 1 2 3 2 

VILA1 Viking Lake IA 1/13/2005 7/13/2006 4 0 1 0 3 

VOYA1 Voyageurs NP #1 MN 1/13/2005 7/13/2006 5 2 1 0 2 

WARI1 Walker River Paiute Tribe NV 5/19/2005 10/13/2005 4 1 1 2 0 

WASH1 Washington D.C. DC 12/7/2006 12/7/2006 1 0 0 0 1 

WEMI1 Weminuche Wilderness CO 1/13/2005 2/16/2006 4 1 0 1 2 

WHIT1 White Mountain NM 5/19/2005 11/16/2006 4 1 1 2 0 

WHPA1 White Pass WA 3/17/2005 7/13/2006 7 3 1 1 2 

WHPE1 Wheeler Peak NM 4/16/2005 4/8/2006 3 2 1 0 0 

WHRI1 White River NF CO 3/17/2005 12/7/2006 4 1 1 1 1 

WICA1 Wind Cave SD 1/13/2005 12/7/2006 4 2 0 0 2 

WIMO1 Wichita Mountains OK 7/21/2005 11/16/2006 6 1 1 4 0 

YELL1 Yellowstone NP 1 WY 1/13/2005 9/14/2006 6 2 0 2 2 

YOSE1 Yosemite NP CA 3/17/2005 8/24/2006 4 1 2 0 1 

ZICA1 Zion Canyon UT 2/3/2005 12/7/2006 5 0 2 1 2 

Total 959 291 194 217 257 

a

 Spring = March, April, May 

 Summer = June, July, August 

 Fall = September, October, November 

 Winter = December, January, February
3-42

Table 3-2. Average field blank concentration by carbon fraction at 181 (plus 6 collocated) sites in the IMP1/1/2005 to 12/31/2006. 

 Sampling Period Total # Carbon Concentrations (μg/filter) 

Site ID Site Name State From To of Field Blanks TC OC EC OC1 OC2 OC3 OC4 

ACAD1 Acadia NP ME 1/13/2005 1/5/2006 3 8.8 ± 2.25 8.61 ± 2.01 0.2 ± 0.34 1.98 ± 0.34 2.85 ± 0.73 3.25 ± 0.96 0.53 ± 0.26 ADPI1 Addison Pinnacle NY 1/13/2005 5/11/2006 6 7.36 ± 1.02 7.36 ± 1.02 0 ± 0 1.84 ± 0.4 2.68 ± 0.56 2.56 ± 0.45 0.24 ± 0.22 AGTI1 Agua Tibia CA 5/19/2005 11/16/2006 7 11.04 ± 2.71 10.95 ± 2.71 0.1 ± 0.09 3.2 ± 1.12 3.66 ± 0.74 3.54 ± 1.18 0.5 ± 0.21 AREN1 Arendtsville PA 1/13/2005 3/30/2006 5 7.16 ± 3.13 7.01 ± 2.99 0.15 ± 0.22 2.06 ± 1 2.32 ± 1.29 2.18 ± 0.89 0.45 ± 0.4 ATLA1 Atlanta GA 1/13/2005 11/19/2006 8 8.14 ± 1.92 8.07 ± 1.93 0.08 ± 0.14 2.07 ± 0.74 2.96 ± 0.75 2.58 ± 0.57 0.45 ± 0.25 BADL1 Badlands NP SD 1/13/2005 12/7/2006 7 11.17 ± 3.67 10.99 ± 3.44 0.18 ± 0.32 3.78 ± 2.65 3.19 ± 0.86 3.41 ± 1.13 0.61 ± 0.38 BALD1 Mount Baldy AZ 3/17/2005 6/1/2006 5 7.74 ± 2.94 7.7 ± 2.89 0.05 ± 0.06 2.66 ± 1.18 2.18 ± 0.85 2.54 ± 0.82 0.31 ± 0.29 BALT1 Baltimore MD 1/13/2005 12/15/2005 4 7.81 ± 1.51 7.74 ± 1.42 0.07 ± 0.1 2.21 ± 0.68 2.69 ± 0.5 2.52 ± 0.46 0.32 ± 0.2 BAND1 Bandelier NM NM 3/17/2005 12/28/2006 9 9.94 ± 2.93 9.85 ± 2.81 0.09 ± 0.17 3.23 ± 0.82 3.09 ± 1.16 3.08 ± 1 0.45 ± 0.29 BIBE1 Big Bend NP TX 3/17/2005 8/24/2006 7 8.48 ± 2.41 8.11 ± 1.62 0.37 ± 0.98 2.19 ± 0.46 2.73 ± 0.69 2.79 ± 0.47 0.4 ± 0.2 BIRM1 Birmingham AL 1/13/2005 8/24/2006 5 7.94 ± 1.45 7.93 ± 1.46 0.01 ± 0.02 2.35 ± 0.55 2.84 ± 0.62 2.47 ± 0.66 0.28 ± 0.2 BLIS1 Bliss SP (TRPA) CA 3/17/2005 10/26/2006 10 9.48 ± 2.24 9.26 ± 2.07 0.22 ± 0.28 2.25 ± 1.1 2.75 ± 0.54 3.6 ± 1.53 0.66 ± 0.37 BLMO1 Blue Mounds MN 1/13/2005 1/5/2006 4 5.4 ± 0.8 5.42 ± 0.83 0 ± 0 1.47 ± 0.47 1.65 ± 0.41 2.14 ± 0.74 0.19 ± 0.09 BOAP1 Bosque del Apache NM 1/13/2005 12/7/2006 8 11.03 ± 4.81 10.58 ± 4.22 0.45 ± 0.65 2.3 ± 0.84 3.47 ± 1.37 3.83 ± 1.81 0.99 ± 0.86 BOND1 Bondville IL 3/17/2005 11/16/2006 5 6.67 ± 3.27 6.54 ± 3.18 0.14 ± 0.12 1.45 ± 0.83 2.15 ± 1.01 2.48 ± 1.23 0.46 ± 0.27 BOWA1 Boundary Waters Canoe Area MN 3/30/2006 9/14/2006 3 7.1 ± 2.55 6.87 ± 2.2 0.23 ± 0.4 1.49 ± 0.33 2.49 ± 0.72 2.41 ± 0.74 0.48 ± 0.49 BRCA1 Bryce Canyon NP UT 7/21/2005 11/16/2006 5 10.96 ± 3.7 10.59 ± 3.2 0.37 ± 0.59 3.31 ± 1.52 3.4 ± 0.88 3.19 ± 0.56 0.69 ± 0.34 BRET1 Breton LA 2/3/2005 2/3/2005 1 8.19 ± 0 8.19 ± 0 0 ± 0 2.11 ± 0 2.74 ± 0 3.09 ± 0 0.24 ± 0 BRID1 Bridger Wilderness WY 5/19/2005 12/7/2006 2 8.64 ± 1.79 8.42 ± 1.39 0.25 ± 0.35 1.98 ± 0.77 3.1 ± 0.33 2.94 ± 0.63 0.47 ± 0.22 BRID9 Bridger Wilderness WY 1/13/2005 1/13/2005 1 9.25 ± 0 8.72 ± 0 0.53 ± 0 2.19 ± 0 3.06 ± 0 2.71 ± 0 0.76 ± 0 BRIG1 Brigantine NWR NJ 2/3/2005 5/11/2006 6 7.42 ± 2.86 7.39 ± 2.84 0.03 ± 0.08 2.02 ± 1.03 2.69 ± 1.3 2.46 ± 0.78 0.22 ± 0.21 BRMA1 Bridgton ME 1/13/2005 10/26/2006 6 7.72 ± 3.06 7.61 ± 2.82 0.11 ± 0.27 1.65 ± 0.8 2.51 ± 0.52 2.9 ± 1.31 0.52 ± 0.58 CABA1 Casco Bay ME 5/19/2005 12/28/2006 6 8.94 ± 2.41 8.9 ± 2.36 0.04 ± 0.07 2.63 ± 0.78 3.19 ± 0.69 2.69 ± 0.84 0.39 ± 0.25 CABI1 Cabinet Mountains MT 5/19/2005 2/16/2006 3 7.34 ± 2.32 7.25 ± 2.22 0.1 ± 0.15 2.37 ± 0.6 2.03 ± 0.99 2.47 ± 0.47 0.39 ± 0.23 CACO1 Cape Cod MA 10/13/2005 12/28/2006 2 6.81 ± 1.72 6.72 ± 1.63 0.09 ± 0.09 2.16 ± 0.15 2.4 ± 1.07 1.94 ± 0.55 0.21 ± 0.18 CACR1 Caney Creek AR 1/13/2005 9/14/2006 7 9.12 ± 2.53 8.56 ± 2.01 0.57 ± 0.89 1.69 ± 0.6 2.76 ± 1.04 3.49 ± 1.02 0.61 ± 0.26 CADI1 Cadiz KY 5/19/2005 11/16/2006 7 7.65 ± 1.87 7.56 ± 1.76 0.1 ± 0.14 1.96 ± 0.61 2.7 ± 0.82 2.53 ± 0.71 0.36 ± 0.33 CANY1 Canyonlands NP UT 7/21/2005 10/5/2006 9 9.29 ± 4.01 8.93 ± 3.59 0.36 ± 0.74 2.67 ± 1.39 2.79 ± 1.09 2.92 ± 0.95 0.54 ± 0.45 CAPI1 Capitol Reef NP UT 3/17/2005 12/7/2006 6 9.7 ± 2.96 9.59 ± 2.97 0.11 ± 0.17 2.91 ± 1.47 3.05 ± 0.88 3.05 ± 0.91 0.57 ± 0.36 CEBL1 Cedar Bluff KS 1/13/2005 10/26/2006 10 7.13 ± 2.45 7.11 ± 2.41 0.02 ± 0.05 2 ± 0.66 2.25 ± 0.95 2.55 ± 0.73 0.31 ± 0.3 CHAS1 Chassahowitzka NWR FL 6/9/2005 10/5/2006 8 7.06 ± 1.9 6.92 ± 1.76 0.14 ± 0.22 1.56 ± 0.56 2.35 ± 0.61 2.71 ± 0.76 0.3 ± 0.2 CHER1 Cherokee Nation OK 10/13/2005 9/14/2006 3 7.4 ± 1.24 7.4 ± 1.24 0 ± 0 1.85 ± 0.55 2.7 ± 0.73 2.55 ± 0.34 0.3 ± 0.17 CHIC1 Chicago IL 1/13/2005 3/17/2005 2 8.06 ± 1.44 8.06 ± 1.44 0 ± 0 2.51 ± 0.11 2.62 ± 0.03 2.6 ± 1.35 0.32 ± 0.17 CHIR1 Chiricahua NM AZ 1/13/2005 8/24/2006 5 7.89 ± 3.33 7.87 ± 3.33 0.02 ± 0.03 2.49 ± 1.64 2.63 ± 0.86 2.43 ± 0.73 0.31 ± 0.21 CLPE1 Cloud Peak WY 3/17/2005 4/20/2006 3 6.59 ± 2.01 6.56 ± 1.99 0.02 ± 0.02 1.98 ± 0.98 2.21 ± 0.5 2.2 ± 0.56 0.17 ± 0.15 COGO1 Columbia Gorge #1 WA 3/17/2005 10/5/2006 6 8.52 ± 1.68 8.4 ± 1.63 0.12 ± 0.21 2.42 ± 0.76 2.96 ± 0.64 2.57 ± 0.41 0.44 ± 0.22 COHI1 Connecticut Hill NY 7/21/2005 12/15/2005 3 10.53 ± 3.09 10.39 ± 2.86 0.14 ± 0.24 3.51 ± 0.71 3.34 ± 1.07 3.06 ± 1.05 0.48 ± 0.21 COHU1 Cohutta GA 3/17/2005 3/17/2005 1 15.7 ± 0 14.96 ± 0 0.74 ± 0 6.25 ± 0 3.98 ± 0 4.06 ± 0 0.68 ± 0 CORI1 Columbia River Gorge WA 3/17/2005 12/7/2006 5 7.96 ± 3.2 7.79 ± 3 0.16 ± 0.21 2.03 ± 1.12 2.82 ± 1.18 2.54 ± 0.88 0.4 ± 0.29 CRES1 Crescent Lake NE 3/17/2005 6/1/2006 6 7.57 ± 1.23 7.55 ± 1.2 0.02 ± 0.04 2.45 ± 0.6 2.57 ± 0.36 2.31 ± 0.39 0.21 ± 0.14 CRLA1 Crater Lake NP OR 5/19/2005 12/7/2006 7 7.88 ± 4.04 7.84 ± 3.99 0.04 ± 0.06 2.7 ± 1.58 2.47 ± 1.22 2.38 ± 1.06 0.29 ± 0.31 CRMO1 Craters of the Moon NM ID 3/17/2005 5/11/2006 4 7.51 ± 2.65 7.5 ± 2.64 0.01 ± 0.01 2.26 ± 0.66 2.52 ± 0.86 2.51 ± 1.01 0.2 ± 0.22 DENA1 Denali NP AK 5/19/2005 12/28/2006 7 10.24 ± 1.64 10.2 ± 1.64 0.04 ± 0.04 3.14 ± 0.97 3.39 ± 0.47 3.19 ± 0.49 0.49 ± 0.13 DETR1 Detroit MI 4/7/2005 12/31/2006 8 7.64 ± 3.66 7.37 ± 3.07 0.27 ± 0.64 1.57 ± 0.35 2.34 ± 1.06 2.83 ± 1.27 0.63 ± 0.71 DEVA1 Death Valley NP CA 3/17/2005 10/5/2006 4 8.58 ± 4.33 7.67 ± 2.65 0.91 ± 1.71 1.57 ± 0.3 2.47 ± 0.82 2.95 ± 0.9 0.68 ± 0.79 DOME1 Dome Lands Wilderness CA 12/15/2005 12/28/2006 4 10.36 ± 6.12 10.2 ± 5.8 0.16 ± 0.32 2.6 ± 1.18 3.19 ± 1.14 3.77 ± 2.69 0.64 ± 0.84 DOSO1 Dolly Sods Wilderness WV 3/17/2005 9/14/2006 9 9.83 ± 3.39 9.43 ± 2.74 0.4 ± 0.85 2.71 ± 0.91 2.84 ± 1.09 3.22 ± 0.98 0.66 ± 0.4 DOUG1 Douglas AZ 1/13/2005 12/28/2006 6 10.28 ± 4.22 10.17 ± 3.96 0.13 ± 0.29 3.25 ± 1.87 3.19 ± 0.87 3.14 ± 1.1 0.61 ± 0.41 EGBE1 N/A 9/1/2005 10/5/2006 5 8.49 ± 2.1 8.36 ± 1.94 0.12 ± 0.18 1.95 ± 0.77 3.06 ± 0.67 2.9 ± 0.56 0.46 ± 0.19 ELDO1 El Dorado Springs MO 7/21/2005 7/13/2006 6 7.72 ± 2.64 7.61 ± 2.55 0.1 ± 0.13 2.03 ± 1.03 2.46 ± 0.9 2.68 ± 0.76 0.43 ± 0.24 ELLI1 Ellis OK 3/17/2005 5/11/2006 7 9.85 ± 1.29 9.73 ± 1.27 0.12 ± 0.1 2.61 ± 0.77 3.01 ± 0.58 3.26 ± 0.5 0.75 ± 0.67 EVER1 Everglades NP FL 1/13/2005 9/14/2006 6 9.52 ± 1.75 9.45 ± 1.74 0.07 ± 0.14 2.41 ± 0.98 4.24 ± 1.27 2.44 ± 0.64 0.36 ± 0.24 EVERX Everglades NP FL 1/13/2005 10/5/2006 9 8.3 ± 1.13 8.2 ± 1.01 0.1 ± 0.15 1.95 ± 0.44 3.05 ± 0.65 2.79 ± 0.57 0.41 ± 0.21 FLAT1 Flathead MT 1/13/2005 10/5/2006 8 8.82 ± 2.84 8.77 ± 2.84 0.05 ± 0.09 2.59 ± 0.97 2.96 ± 0.92 2.79 ± 0.92 0.44 ± 0.37 FOPE1 Fort Peck MT 3/17/2005 11/16/2006 6 10.08 ± 2.33 9.98 ± 2.32 0.1 ± 0.14 2.97 ± 1.45 3.49 ± 1.03 3.06 ± 0.37 0.46 ± 0.1 FRES1 Fresno CA 5/19/2005 11/16/2006 7 9.11 ± 1.76 8.99 ± 1.56 0.12 ± 0.25 2.38 ± 0.49 3.03 ± 0.72 3 ± 0.58 0.58 ± 0.3 FRRE1 Frostburg MD 5/19/2005 8/3/2006 4 9.93 ± 3.56 9.8 ± 3.45 0.13 ± 0.17 2.97 ± 1.07 2.98 ± 1.17 3.25 ± 0.97 0.6 ± 0.45 GAMO1 Gates of the Mountains MT 5/19/2005 10/13/2005 2 8.75 ± 1.26 8.75 ± 1.26 0 ± 0 2.73 ± 0.56 2.9 ± 0.19 2.81 ± 0.42 0.3 ± 0.09 
3-43

Table 3-2. Continued. 

 Sampling Period Total # Carbon Concentrations (μg/filter) 

Site ID Site Name State From To of Field Blanks TC OC EC OC1 OC2 OC3 OC4 

GICL1 Gila Wilderness NM 4/7/2005 7/13/2006 4 7.98 ± 3.34 7.98 ± 3.34 0 ± 0.01 2.56 ± 1.14 2.46 ± 1.06 2.7 ± 1.02 0.26 ± 0.32 GLAC1 Glacier NP MT 1/13/2005 11/16/2006 5 8.69 ± 1.94 8.66 ± 1.89 0.03 ± 0.06 2.54 ± 0.63 3.13 ± 0.58 2.65 ± 0.62 0.34 ± 0.33 GRBA1 Great Basin NP NV 1/13/2005 12/28/2006 10 8.74 ± 1.5 8.7 ± 1.46 0.04 ± 0.12 2.6 ± 0.8 3.18 ± 0.66 2.58 ± 0.47 0.34 ± 0.18 GRGU1 Great Gulf Wilderness NH 1/13/2005 3/9/2006 5 10.02 ± 1.65 9.75 ± 1.81 0.27 ± 0.22 2.9 ± 0.61 3.32 ± 0.94 2.94 ± 1 0.56 ± 0.19 GRRI1 Great River Bluffs MN 5/19/2005 12/15/2005 3 8.47 ± 3.48 8.29 ± 3.18 0.17 ± 0.3 2.29 ± 1.25 2.75 ± 1.11 2.74 ± 0.89 0.52 ± 0.21 GRSA1 Great Sand Dunes NM CO 10/13/2005 10/5/2006 3 11.7 ± 2.07 11.48 ± 1.9 0.22 ± 0.25 3.71 ± 0.86 3.35 ± 0.49 3.81 ± 0.53 0.61 ± 0.1 GRSM1 Great Smoky Mountains NP TN 1/13/2005 10/26/2006 6 7.7 ± 3.42 7.62 ± 3.38 0.08 ± 0.12 1.78 ± 0.92 2.41 ± 0.99 2.92 ± 1.26 0.52 ± 0.35 GRSM9 Great Smoky Mountains NP TN 1/13/2005 1/13/2005 1 16.09 ± 0 15.41 ± 0 0.68 ± 0 2.61 ± 0 4.53 ± 0 6.65 ± 0 1.63 ± 0 GUMO1 Guadalupe Mountains NP TX 7/21/2005 12/28/2006 5 12.54 ± 2.8 12.15 ± 2.6 0.38 ± 0.31 4.1 ± 0.81 3.52 ± 1.14 3.75 ± 0.69 0.78 ± 0.37 HALE1 Haleakala NP HI 3/17/2005 12/28/2006 8 7.36 ± 1.6 7.31 ± 1.57 0.06 ± 0.08 1.42 ± 0.68 2.74 ± 0.52 2.79 ± 0.57 0.36 ± 0.2 HANC1 Hance Camp at Grand Canyon NP AZ 1/13/2005 4/20/2006 3 7.6 ± 2.42 7.51 ± 2.35 0.09 ± 0.15 2.17 ± 1.45 2.17 ± 0.85 2.88 ± 0.76 0.31 ± 0.27 HAVO1 Hawaii Volcanoes NP HI 1/13/2005 12/28/2006 8 6.62 ± 2.16 6.6 ± 2.15 0.02 ± 0.03 1.68 ± 0.73 2.38 ± 0.84 2.31 ± 0.63 0.24 ± 0.16 HECA1 Hells Canyon OR 1/13/2005 11/16/2006 7 7.17 ± 3.02 7 ± 2.92 0.16 ± 0.31 1.38 ± 0.42 2.2 ± 0.45 3.08 ± 1.96 0.35 ± 0.34 HEGL1 Hercules-Glades MO 1/13/2005 11/16/2006 7 7.51 ± 2.81 7.37 ± 2.64 0.14 ± 0.19 2.3 ± 0.62 2.2 ± 1.02 2.51 ± 0.88 0.36 ± 0.32 HEGLX Hercules-Glades MO 1/13/2005 11/16/2006 14 8.6 ± 3.01 8.43 ± 2.86 0.17 ± 0.29 2.36 ± 0.89 2.77 ± 0.86 2.83 ± 1.06 0.46 ± 0.39 HOOV1 Hoover CA 1/13/2005 9/14/2006 8 8.4 ± 2.12 8.31 ± 2.01 0.09 ± 0.22 2.54 ± 0.94 2.59 ± 0.59 2.83 ± 0.62 0.36 ± 0.23 HOOVX Hoover CA 1/13/2005 12/7/2006 13 6.41 ± 2.01 6.4 ± 2.01 0.01 ± 0.03 1.77 ± 0.81 2.09 ± 0.71 2.25 ± 0.59 0.28 ± 0.18 HOUS1 Houston TX 5/19/2005 7/21/2005 2 12.15 ± 3.09 11.51 ± 2.18 0.64 ± 0.91 2.44 ± 0.39 3.89 ± 0.89 4.05 ± 0.89 1.12 ± 0.79 IKBA1 Ike's Backbone AZ 12/15/2005 12/15/2005 1 6.17 ± 0 6.12 ± 0 0.05 ± 0 2.55 ± 0 1.26 ± 0 2.06 ± 0 0.26 ± 0 INGA1 Indian Gardens AZ 2/3/2005 9/14/2006 6 13.32 ± 3.86 13 ± 3.64 0.32 ± 0.31 4.2 ± 1.38 4.28 ± 1.45 3.77 ± 1.01 0.74 ± 0.52 ISLE1 Isle Royale NP MI 1/13/2005 11/16/2006 6 5.42 ± 2.29 5.41 ± 2.26 0.02 ± 0.04 1.26 ± 0.49 1.9 ± 0.95 2.04 ± 0.76 0.21 ± 0.21 JARI1 James River Face Wilderness VA 1/13/2005 6/1/2006 5 8.53 ± 3.32 8.48 ± 3.25 0.05 ± 0.08 2.49 ± 1.4 3.03 ± 1.09 2.59 ± 0.73 0.37 ± 0.23 JOSH1 Joshua Tree NP CA 1/13/2005 7/13/2006 6 9.19 ± 0.97 9.13 ± 0.94 0.06 ± 0.1 2.64 ± 0.69 2.87 ± 0.98 3.25 ± 0.36 0.38 ± 0.24 KAIS1 Kaiser CA 1/13/2005 1/5/2006 5 10.31 ± 2.45 10.19 ± 2.38 0.12 ± 0.12 2.88 ± 0.89 3.51 ± 0.9 3.28 ± 0.79 0.51 ± 0.25 KALM1 Kalmiopsis OR 1/13/2005 11/16/2006 4 7.99 ± 0.77 7.89 ± 0.67 0.1 ± 0.13 1.89 ± 0.46 2.59 ± 0.3 2.97 ± 0.74 0.43 ± 0.3 LABE1 Lava Beds NM CA 1/13/2005 5/11/2006 7 6.74 ± 1.69 6.64 ± 1.55 0.1 ± 0.15 1.98 ± 0.61 2.14 ± 0.44 2.24 ± 0.51 0.27 ± 0.24 LASU2 Lake Sugema IA 1/13/2005 12/15/2005 3 7.82 ± 2.99 7.81 ± 2.98 0.01 ± 0.02 2.18 ± 0.46 2.76 ± 1.36 2.63 ± 1.18 0.24 ± 0.2 LAVO1 Lassen Volcanic NP CA 1/13/2005 1/5/2006 3 6.15 ± 2.08 6.04 ± 1.89 0.11 ± 0.19 1.37 ± 0.64 1.79 ± 0.58 2.68 ± 2.06 0.2 ± 0.34 LIGO1 Linville Gorge NC 3/17/2005 4/20/2006 5 7.91 ± 1.58 7.82 ± 1.46 0.09 ± 0.13 2.37 ± 0.56 2.23 ± 0.54 2.69 ± 0.54 0.53 ± 0.32 LIVO1 Livonia IN 1/13/2005 5/19/2005 2 12.08 ± 6.11 11.11 ± 4.74 0.97 ± 1.38 1.53 ± 0.56 2.79 ± 0.13 5.43 ± 3.57 1.35 ± 1.59 LOST1 Lostwood ND 5/19/2005 11/16/2006 5 7.9 ± 4.05 7.83 ± 3.94 0.07 ± 0.15 2.54 ± 1.66 2.52 ± 1.24 2.41 ± 0.84 0.35 ± 0.3 LYBR1 Lye Brook Wilderness VT 1/13/2005 12/7/2006 6 7 ± 2.17 6.95 ± 2.11 0.05 ± 0.08 1.91 ± 0.66 2.55 ± 0.66 2.24 ± 0.7 0.25 ± 0.31 MACA1 Mammoth Cave NP KY 5/19/2005 12/7/2006 5 7.94 ± 1.75 7.94 ± 1.75 0 ± 0 2.56 ± 0.79 2.36 ± 0.35 2.62 ± 0.53 0.4 ± 0.2 MAVI1 Martha's Vineyard MA 5/19/2005 7/13/2006 5 6.85 ± 2.47 6.72 ± 2.2 0.13 ± 0.29 1.71 ± 0.45 1.96 ± 0.57 2.7 ± 1.3 0.34 ± 0.38 MEAD1 Meadview AZ 5/19/2005 5/19/2005 1 8.87 ± 0 8.87 ± 0 0 ± 0 2.75 ± 0 3.06 ± 0 2.75 ± 0 0.3 ± 0 MELA1 Medicine Lake MT 3/17/2005 8/24/2006 3 7.62 ± 1.65 7.48 ± 1.44 0.14 ± 0.21 1.8 ± 0.32 2.4 ± 0.1 2.92 ± 1.3 0.36 ± 0.4 MELAX Medicine Lake MT 1/13/2005 12/7/2006 8 7.92 ± 5.29 7.79 ± 4.99 0.13 ± 0.31 2.02 ± 0.78 2.03 ± 0.79 3.45 ± 3.42 0.29 ± 0.2 MEVE1 Mesa Verde NP CO 1/13/2005 12/28/2006 9 9.58 ± 3.14 9.53 ± 3.1 0.05 ± 0.12 3.03 ± 1.06 3.21 ± 1.04 2.85 ± 0.94 0.44 ± 0.35 MING1 Mingo MO 5/19/2005 9/14/2006 4 6.99 ± 1.06 6.96 ± 1.05 0.03 ± 0.03 1.9 ± 0.57 2.18 ± 0.49 2.5 ± 0.6 0.38 ± 0.1 MKGO1 M.K. Goddard PA 3/17/2005 8/24/2006 7 8.12 ± 2.33 7.8 ± 1.82 0.32 ± 0.57 2.16 ± 0.71 2.9 ± 0.63 2.41 ± 0.41 0.31 ± 0.26 MOHO1 Mount Hood OR 1/13/2005 8/24/2006 7 7.13 ± 2.27 7.08 ± 2.23 0.05 ± 0.09 1.78 ± 0.63 2.57 ± 0.68 2.46 ± 0.84 0.28 ± 0.3 MOMO1 Mohawk Mt. CT 3/17/2005 12/7/2006 4 5.75 ± 1.24 5.68 ± 1.17 0.07 ± 0.08 1.8 ± 0.7 1.86 ± 0.43 1.88 ± 0.25 0.13 ± 0.15 MONT1 Monture MT 1/13/2005 11/16/2006 7 8.77 ± 3.22 8.56 ± 3.02 0.21 ± 0.36 2.34 ± 1.04 2.74 ± 0.97 2.81 ± 1.01 0.51 ± 0.51 MOOS1 Moosehorn NWR ME 1/13/2005 12/7/2006 7 8.52 ± 1.45 8.44 ± 1.46 0.08 ± 0.13 2.65 ± 0.89 2.52 ± 0.77 2.84 ± 0.52 0.44 ± 0.2 MORA1 Mount Rainier NP WA 1/13/2005 11/16/2006 5 6.33 ± 2.19 6.26 ± 2.18 0.07 ± 0.16 2.03 ± 1.21 1.83 ± 0.75 2.23 ± 1 0.17 ± 0.18 MORA9 Mount Rainier NP WA 1/13/2005 1/13/2005 1 5.01 ± 0 5.01 ± 0 0 ± 0 1.29 ± 0 1.45 ± 0 2.26 ± 0 0 ± 0 MOZI1 Mount Zirkel Wilderness CO 3/17/2005 11/16/2006 8 9.88 ± 1.35 9.85 ± 1.33 0.03 ± 0.08 2.89 ± 0.67 3.4 ± 0.56 3.03 ± 0.46 0.53 ± 0.13 NEBR1 Nebraska NF NE 1/13/2005 6/22/2006 5 11.11 ± 3.88 10.83 ± 3.72 0.28 ± 0.27 3.36 ± 1.89 3.4 ± 0.71 3.31 ± 0.95 0.76 ± 0.53 NEYO1 New York City NY 5/19/2005 12/15/2005 3 8.61 ± 1.7 8.49 ± 1.5 0.12 ± 0.2 2.69 ± 0.87 3 ± 0.7 2.44 ± 0.26 0.36 ± 0.25 NOAB1 North Absaroka WY 3/30/2006 10/5/2006 3 8.81 ± 3.8 8.56 ± 3.37 0.25 ± 0.43 2.1 ± 0.54 2.57 ± 0.4 3.41 ± 1.99 0.47 ± 0.46 NOCA1 North Cascades WA 3/17/2005 12/28/2006 7 9.25 ± 2.49 8.93 ± 2.4 0.32 ± 0.28 2.45 ± 1.02 2.87 ± 0.7 3.15 ± 0.8 0.45 ± 0.32 NOCH1 Northern Cheyenne MT 9/1/2005 10/5/2006 3 7.82 ± 1.2 7.82 ± 1.2 0 ± 0 2.24 ± 0.57 2.51 ± 0.57 2.65 ± 0.25 0.42 ± 0.17 OKEF1 Okefenokee NWR GA 6/1/2006 6/1/2006 1 10.57 ± 0 10.57 ± 0 0 ± 0 3.64 ± 0 3.04 ± 0 3.18 ± 0 0.7 ± 0 OLTO1 Old Town ME 5/19/2005 4/20/2006 4 6.8 ± 1.12 6.79 ± 1.11 0.01 ± 0.02 2.08 ± 0.09 2.2 ± 0.95 2.3 ± 0.13 0.21 ± 0.2 OLYM1 Olympic WA 2/3/2005 2/16/2006 2 5.99 ± 3.11 5.76 ± 2.86 0.23 ± 0.25 1.43 ± 0.9 1.61 ± 0.2 2.29 ± 1.16 0.43 ± 0.61 OMAH1 Omaha NE 3/17/2005 10/5/2006 4 8.13 ± 1.14 8.13 ± 1.14 0 ± 0 2.12 ± 0.88 3.1 ± 0.3 2.63 ± 0.34 0.29 ± 0.2 ORPI1 Organ Pipe AZ 3/17/2005 11/16/2006 5 7.14 ± 1.38 7.07 ± 1.26 0.07 ± 0.15 1.78 ± 0.29 2.5 ± 0.52 2.56 ± 0.57 0.23 ± 0.18 PASA1 Pasayten WA 5/19/2005 10/5/2006 6 8.07 ± 1.68 7.92 ± 1.72 0.15 ± 0.22 2.09 ± 0.56 2.47 ± 0.59 2.93 ± 0.87 0.43 ± 0.27 PEFO1 Petrified Forest NP AZ 3/17/2005 12/7/2006 6 7.58 ± 2.3 7.48 ± 2.14 0.1 ± 0.2 1.99 ± 0.81 2.09 ± 0.68 2.89 ± 1.01 0.51 ± 0.52 PENO1 N/A 3/30/2006 8/24/2006 2 9.46 ± 0.69 9.45 ± 0.7 0.01 ± 0.01 2.54 ± 0.66 2.93 ± 0.24 3.48 ± 0.09 0.51 ± 0.11 
3-44

Table 3-2. Continued. 

 Sampling Period Total # Carbon Concentrations (μg/filter) 

Site ID Site Name State From To of Field Blanks TC OC EC OC1 OC2 OC3 OC4 

PETE1 Petersburg AK 4/7/2005 9/14/2006 8 6.56 ± 2.15 6.5 ± 2.08 0.05 ± 0.12 1.98 ± 0.62 2.15 ± 0.8 2.15 ± 0.61 0.23 ± 0.23 PHOE1 Phoenix AZ 1/13/2005 5/11/2006 6 9.95 ± 3.59 9.65 ± 3.3 0.3 ± 0.46 2.66 ± 1.1 3.26 ± 0.91 3.11 ± 0.91 0.55 ± 0.55 PHOE5 Phoenix AZ 1/13/2005 5/11/2006 5 8.57 ± 0.96 8.55 ± 0.95 0.02 ± 0.03 2.62 ± 0.83 2.73 ± 0.38 2.77 ± 0.52 0.44 ± 0.11 PINN1 Pinnacles NM CA 3/9/2006 5/11/2006 2 6.81 ± 0.18 6.81 ± 0.18 0 ± 0 1.77 ± 0.36 2.38 ± 0.02 2.49 ± 0.42 0.17 ± 0.22 PITT1 Pittsburgh PA 1/13/2005 12/10/2006 8 8.67 ± 3.05 8.39 ± 2.59 0.28 ± 0.52 2.43 ± 1.01 2.48 ± 0.47 2.88 ± 0.89 0.61 ± 0.69 PMRF1 Proctor Maple R. F. VT 3/17/2005 7/13/2006 4 9.03 ± 1.44 9.03 ± 1.43 0.01 ± 0.01 2.69 ± 0.79 3.18 ± 0.66 2.79 ± 0.27 0.36 ± 0.11 PORE1 Point Reyes National Seashore CA 7/21/2005 11/16/2006 4 7.77 ± 3.21 7.69 ± 3.08 0.08 ± 0.15 2.25 ± 1.35 2.49 ± 1.03 2.53 ± 0.65 0.35 ± 0.29 PRIS1 Presque Isle ME 2/3/2005 4/20/2006 3 8.6 ± 0.99 8.57 ± 0.99 0.03 ± 0.05 2.79 ± 0.49 3 ± 0.55 2.47 ± 0.34 0.3 ± 0.28 PUSO1 Puget Sound WA 3/17/2005 1/5/2006 2 8.73 ± 2.76 8.54 ± 2.49 0.19 ± 0.27 2.04 ± 0.29 3.1 ± 1.07 2.75 ± 0.66 0.64 ± 0.48 QUCI1 Quaker City OH 10/5/2006 10/5/2006 1 10.51 ± 0 10.26 ± 0 0.25 ± 0 2.33 ± 0 3.5 ± 0 3.88 ± 0 0.55 ± 0 QURE1 Quabbin Summit MA 1/13/2005 2/16/2006 4 8.26 ± 3.06 8.25 ± 3.06 0 ± 0.01 1.56 ± 1.19 2.72 ± 1.04 3.8 ± 2.37 0.17 ± 0.11 QUVA1 Queen Valley AZ 3/17/2005 11/16/2006 3 9.27 ± 3.21 9.25 ± 3.19 0.02 ± 0.03 2.59 ± 1.47 3.25 ± 1.16 3.11 ± 0.69 0.31 ± 0.14 RAFA1 San Rafael CA 1/13/2005 12/7/2006 7 9.91 ± 2.41 9.82 ± 2.38 0.09 ± 0.09 3.23 ± 0.68 3.27 ± 0.8 2.87 ± 0.75 0.45 ± 0.32 REDW1 Redwood NP CA 1/13/2005 12/7/2006 6 8.02 ± 1.38 7.95 ± 1.3 0.07 ± 0.15 2.14 ± 0.61 2.88 ± 0.39 2.56 ± 0.53 0.37 ± 0.26 ROMA1 Cape Romain NWR SC 1/13/2005 7/13/2006 5 8.17 ± 4.04 7.59 ± 3.16 0.58 ± 1.15 1.77 ± 1.19 2.54 ± 1.24 2.69 ± 0.55 0.58 ± 0.54 ROMO2 Rocky Mountain NP CO 1/13/2005 1/13/2005 1 10.7 ± 0 10.58 ± 0 0.11 ± 0 2.31 ± 0 3.71 ± 0 3.91 ± 0 0.65 ± 0 RUBI1 Rubidoux CA 3/17/2005 7/21/2005 3 10.33 ± 2.14 10.18 ± 1.95 0.14 ± 0.25 2.58 ± 0.83 3.53 ± 0.42 3.54 ± 0.45 0.53 ± 0.35 SACR1 Salt Creek NM 1/13/2005 8/3/2006 5 7.97 ± 2.78 7.93 ± 2.71 0.04 ± 0.08 2.08 ± 0.86 3 ± 0.85 2.56 ± 0.84 0.28 ± 0.27 SAFO1 Sac and Fox KS 1/13/2005 2/16/2006 4 8.35 ± 2.64 8.17 ± 2.45 0.18 ± 0.25 1.88 ± 0.46 2.58 ± 1.2 3.28 ± 1.07 0.42 ± 0.25 SAGA1 San Gabriel CA 1/13/2005 10/5/2006 4 9.85 ± 1.36 9.76 ± 1.29 0.09 ± 0.1 3.1 ± 0.81 3.33 ± 0.39 2.83 ± 0.37 0.51 ± 0.23 SAGO1 San Gorgonio Wilderness CA 3/17/2005 9/14/2006 4 8.77 ± 0.26 8.7 ± 0.16 0.07 ± 0.11 2.13 ± 0.4 3.42 ± 0.31 2.75 ± 0.36 0.41 ± 0.07 SAGU1 Saguaro NM AZ 1/13/2005 11/16/2006 2 9.75 ± 2.33 9.75 ± 2.33 0 ± 0 2.04 ± 1.17 2.81 ± 0.25 4.01 ± 2.31 0.65 ± 0.58 SAMA1 St. Marks FL 5/19/2005 11/16/2006 7 9.57 ± 4.38 9.43 ± 4.2 0.14 ± 0.3 2.54 ± 1.57 3.12 ± 1.32 3.21 ± 1.19 0.57 ± 0.47 SAPE1 San Pedro Parks NM 3/17/2005 2/16/2006 3 7.37 ± 1.96 7.25 ± 1.85 0.13 ± 0.11 1.74 ± 0.54 2.14 ± 0.58 3.12 ± 1.19 0.24 ± 0.21 SAWE1 Saguaro West AZ 1/13/2005 6/1/2006 7 9.16 ± 2.35 9.13 ± 2.27 0.04 ± 0.08 2.63 ± 1.3 3.07 ± 0.64 2.99 ± 0.68 0.47 ± 0.28 SAWEX Saguaro West AZ 1/13/2005 8/24/2006 16 9.21 ± 3.55 9.06 ± 3.15 0.15 ± 0.53 2.39 ± 0.67 2.95 ± 0.93 3.11 ± 1.36 0.57 ± 0.49 SAWT1 Sawtooth NF ID 1/13/2005 11/16/2006 4 7.8 ± 2.17 7.79 ± 2.16 0.01 ± 0.02 2.34 ± 0.64 2.66 ± 0.7 2.46 ± 0.67 0.33 ± 0.26 SENE1 Seney MI 3/17/2005 11/16/2006 3 7.74 ± 2.53 7.53 ± 2.35 0.2 ± 0.18 1.6 ± 0.3 2.58 ± 0.81 2.85 ± 1.06 0.5 ± 0.43 SENEX Seney MI 1/13/2005 12/7/2006 13 6.9 ± 3.28 6.87 ± 3.33 0.03 ± 0.1 2.08 ± 1.41 2.28 ± 1.12 2.23 ± 0.84 0.27 ± 0.21 SEQU1 Sequoia NP CA 12/15/2005 11/16/2006 4 7.52 ± 1.11 7.48 ± 1.13 0.04 ± 0.04 1.82 ± 0.3 2.64 ± 0.37 2.62 ± 0.27 0.39 ± 0.26 SEQU9 Sequoia NP CA 1/13/2005 1/13/2005 1 7.87 ± 0 7.73 ± 0 0.14 ± 0 2.68 ± 0 2.4 ± 0 2.29 ± 0 0.36 ± 0 SHEN1 Shenandoah NP VA 1/13/2005 1/5/2006 9 8.34 ± 3.1 8.21 ± 2.94 0.15 ± 0.27 1.82 ± 0.81 2.89 ± 0.97 2.98 ± 1.3 0.55 ± 0.46 SHMI1 Shamrock Mine CO 5/19/2005 5/11/2006 2 9.05 ± 0.39 9.01 ± 0.23 0.08 ± 0.11 2.84 ± 0.75 2.92 ± 0.48 2.9 ± 0.35 0.41 ± 0.21 SHRO1 Shining Rock Wilderness NC 3/17/2005 5/11/2006 6 10.26 ± 1.16 9.99 ± 0.96 0.27 ± 0.23 3.06 ± 0.59 3.27 ± 0.35 3.07 ± 0.44 0.58 ± 0.18 SIAN1 Sierra Ancha AZ 7/21/2005 10/5/2006 4 10.12 ± 2.11 9.91 ± 1.97 0.21 ± 0.16 2.63 ± 0.8 3.01 ± 0.63 3.69 ± 1.24 0.58 ± 0.23 SIKE1 Sikes LA 1/13/2005 8/3/2006 6 9.03 ± 2.31 8.8 ± 2.15 0.24 ± 0.34 2.19 ± 0.29 2.89 ± 0.92 3.17 ± 1.04 0.55 ± 0.22 SIME1 Simeonof AK 1/13/2005 10/5/2006 7 6.4 ± 2.11 6.4 ± 2.11 0.02 ± 0.03 1.59 ± 0.91 2.3 ± 0.6 2.31 ± 0.63 0.22 ± 0.19 SIPS1 Sipsy Wilderness AL 5/19/2005 12/7/2006 3 7.94 ± 2.78 7.79 ± 2.61 0.15 ± 0.19 2.84 ± 0.99 2.38 ± 1.13 2.2 ± 0.8 0.37 ± 0.17 SNPA1 Snoqualmie Pass WA 7/21/2005 12/28/2006 7 8.2 ± 3.17 8.17 ± 3.13 0.03 ± 0.06 2.5 ± 1.32 2.71 ± 0.96 2.55 ± 0.82 0.41 ± 0.23 SPOK1 Spokane Res. WA 5/19/2005 6/9/2005 2 6.13 ± 5.13 6.03 ± 4.89 0.13 ± 0.19 1.7 ± 1.24 2.03 ± 1.78 1.97 ± 1.3 0.41 ± 0.48 STAR1 Starkey OR 2/3/2005 12/7/2006 4 8.36 ± 4.59 8.05 ± 3.98 0.31 ± 0.63 2.47 ± 1.19 2.33 ± 0.99 2.8 ± 1.52 0.45 ± 0.38 SULA1 Sula Peak MT 5/19/2005 11/16/2006 3 7.27 ± 1.63 7.27 ± 1.63 0 ± 0 1.96 ± 0.73 2.68 ± 0.54 2.31 ± 0.34 0.31 ± 0.04 SWAN1 Swanquarter NC 3/17/2005 3/9/2006 5 7.69 ± 1.52 7.63 ± 1.41 0.07 ± 0.11 1.97 ± 0.49 2.83 ± 0.65 2.51 ± 0.47 0.35 ± 0.32 SYCA1 Sycamore Canyon AZ 1/13/2005 9/14/2006 6 6.73 ± 1.91 6.62 ± 1.74 0.11 ± 0.19 1.56 ± 0.6 1.95 ± 0.57 2.76 ± 0.77 0.36 ± 0.31 TALL1 Tallgrass KS 1/13/2005 11/16/2006 5 7.84 ± 2.47 7.79 ± 2.51 0.05 ± 0.08 2.03 ± 0.61 2.64 ± 1.06 2.76 ± 1.02 0.34 ± 0.28 THBA1 Thunder Basin WY 5/19/2005 11/16/2006 8 8.04 ± 2.14 7.97 ± 2.1 0.07 ± 0.09 2.35 ± 0.74 2.71 ± 0.75 2.51 ± 0.66 0.39 ± 0.19 THRO1 Theodore Roosevelt ND 5/19/2005 5/19/2005 1 7.53 ± 0 7.6 ± 0 0 ± 0 2.13 ± 0 2.88 ± 0 2.47 ± 0 0.27 ± 0 THSI1 Three Sisters Wilderness OR 1/13/2005 12/28/2006 5 6.86 ± 2.36 6.73 ± 2.13 0.12 ± 0.24 1.83 ± 0.4 2.33 ± 0.73 2.32 ± 0.79 0.26 ± 0.5 TONT1 Tonto NM AZ 12/15/2005 12/28/2006 5 6.96 ± 0.84 6.91 ± 0.84 0.05 ± 0.08 1.71 ± 0.54 2.04 ± 0.27 2.75 ± 0.59 0.41 ± 0.24 TRCR1 Trapper Creek AK 3/17/2005 9/14/2006 4 5.71 ± 1.31 5.72 ± 1.35 0.01 ± 0.01 1.43 ± 0.41 2.09 ± 0.6 2.11 ± 0.39 0.12 ± 0.11 TRIN1 Trinity CA 1/13/2005 7/21/2005 4 6.66 ± 1.93 6.6 ± 2.01 0.06 ± 0.12 1.83 ± 1.06 2.22 ± 0.81 2.32 ± 0.37 0.22 ± 0.18 TUXE1 Tuxedni AK 6/9/2005 11/16/2006 7 7.24 ± 2.67 7.21 ± 2.61 0.04 ± 0.08 1.83 ± 1.27 2.51 ± 0.74 2.6 ± 0.57 0.27 ± 0.23 ULBE1 UL Bend MT 1/13/2005 12/7/2006 7 7.86 ± 1.74 7.69 ± 1.72 0.17 ± 0.19 2.19 ± 0.73 2.47 ± 0.69 2.53 ± 0.51 0.5 ± 0.26 UPBU1 Upper Buffalo Wilderness AR 3/17/2005 9/14/2006 5 12.06 ± 1.92 11.69 ± 1.73 0.37 ± 0.4 3.29 ± 1.16 3.58 ± 0.63 4.05 ± 0.75 0.76 ± 0.3 VIIS1 Virgin Islands NP VI 3/17/2005 11/16/2006 8 6.15 ± 2.7 5.95 ± 2.43 0.2 ± 0.32 0.85 ± 0.63 2.48 ± 0.73 2.33 ± 1.01 0.28 ± 0.41 VILA1 Viking Lake IA 1/13/2005 7/13/2006 4 8.22 ± 1.68 8.09 ± 1.64 0.13 ± 0.09 2.78 ± 0.32 2.32 ± 0.76 2.58 ± 0.51 0.41 ± 0.14 VOYA1 Voyageurs NP #1 MN 1/13/2005 7/13/2006 5 8.19 ± 2.47 8.11 ± 2.39 0.08 ± 0.12 2.29 ± 0.68 2.73 ± 0.79 2.73 ± 1.11 0.36 ± 0.28 WARI1 Walker River Paiute Tribe NV 5/19/2005 10/13/2005 4 9.32 ± 0.98 9.22 ± 0.92 0.1 ± 0.19 2.72 ± 0.25 3.31 ± 0.46 2.81 ± 0.27 0.38 ± 0.12 WASH1 Washington D.C. DC 12/7/2006 12/7/2006 1 12.45 ± 0 11.74 ± 0 0.71 ± 0 4 ± 0 3.74 ± 0 2.92 ± 0 1.08 ± 0 WEMI1 Weminuche Wilderness CO 1/13/2005 2/16/2006 4 8.59 ± 1.89 8.58 ± 1.88 0.01 ± 0.01 2.63 ± 0.37 2.98 ± 1.06 2.75 ± 0.69 0.23 ± 0.1 WHIT1 White Mountain NM 5/19/2005 11/16/2006 4 9.95 ± 3.44 9.77 ± 3.25 0.18 ± 0.22 2.63 ± 1.02 3.19 ± 0.76 3.48 ± 1.42 0.47 ± 0.32 WHPA1 White Pass WA 3/17/2005 7/13/2006 7 9.15 ± 2.78 9.1 ± 2.81 0.05 ± 0.07 2.84 ± 1.25 3 ± 0.89 2.89 ± 0.74 0.37 ± 0.27 
3-45

Table 3-2. Continued. 

 Sampling Period Total # Carbon Concentrations (μg/filter) 

Site ID Site Name State From To of Field Blanks TC OC EC OC1 OC2 OC3 OC4 

WHPE1 Wheeler Peak NM 4/16/2005 4/8/2006 3 7.75 ± 1.77 7.77 ± 1.74 0 ± 0 2.36 ± 0.89 2.64 ± 0.87 2.63 ± 0.31 0.19 ± 0.13 WHRI1 White River NF CO 3/17/2005 12/7/2006 4 9.75 ± 1.1 9.47 ± 0.96 0.27 ± 0.27 2.05 ± 0.83 2.96 ± 0.45 3.36 ± 0.25 0.74 ± 0.35 WICA1 Wind Cave SD 1/13/2005 12/7/2006 4 6.05 ± 2.6 5.96 ± 2.53 0.09 ± 0.09 1.97 ± 1.02 1.64 ± 0.49 2.18 ± 1.09 0.17 ± 0.17 WIMO1 Wichita Mountains OK 7/21/2005 11/16/2006 6 9.29 ± 1.58 9.27 ± 1.59 0.02 ± 0.03 2.57 ± 0.73 3.33 ± 0.53 2.97 ± 0.42 0.4 ± 0.17 YELL1 Yellowstone NP 1 WY 1/13/2005 9/14/2006 6 9.25 ± 1.8 9.04 ± 1.56 0.22 ± 0.26 2.67 ± 0.65 3.04 ± 0.44 2.92 ± 0.58 0.41 ± 0.21 YOSE1 Yosemite NP CA 3/17/2005 8/24/2006 4 6.4 ± 2.39 6.37 ± 2.39 0.03 ± 0.06 1.87 ± 1.44 2.17 ± 0.47 2.16 ± 0.53 0.17 ± 0.14 ZICA1 Zion Canyon UT 2/3/2005 12/7/2006 5 7.53 ± 2.13 7.51 ± 2.08 0.02 ± 0.05 2.21 ± 0.92 2.64 ± 0.57 2.44 ± 0.71 0.23 ± 0.21 Total 959 8.48 ± 1.67 8.35 ± 1.59 0.14 ± 0.16 2.32 ± 0.63 2.75 ± 0.52 2.84 ± 0.57 0.43 ± 0.2 
3-46

Table 3-3. Organic carbon comparison between the quartz-fiber front (QF, no blank subtraction) 

and quartz-fiber backup behind quartz-fiber (QBQ) filter concentrations collected at the six sites 

in the IMPROVE network with secondary filters behind quartz-fiber front filters for the period 

from 1/1/2005 though 12/31/2006. Blank values taken from Table 2. 

Organic Carbon Concentration (μg/filter, avg±std) 

Sitea Front Filter (QF) 

Backup Filter 

(QBQ) 

Number 

of QBQ 

Field Blanks 

(bQF) 

Number 

of Field 

Blanks 

MORA 41.89 ± 32.76 8.22 ± 3.48 237 6.26 ± 2.18 5 

YOSE 45.04 ± 33.54 10.34 ± 4.26 228 6.37 ± 2.39 4 

HANC 29.02 ± 35.25 8.74 ± 4 243 7.51 ± 2.35 3 

CHIR 24.15 ± 11.85 8.06 ± 2.8 228 7.87 ± 3.33 5 

SHEN 45.07 ± 27.1 11.74 ± 6.01 230 8.21 ± 2.94 9 

OKEF 76.28 ± 43.54 13.07 ± 4.71 240 10.57 1 

All Sites 42.69 ± 35.39 10.03 ± 5.04 1406 7.52 ± 2.69 27 

a MORA: Mount Rainier National Park 

 YOSE: Yosemite National Park 

 HANC: Hance Camp at Grand Canyon National Park 

 CHIR: Chiricahua National Monument 

 SHEN: Shenandoah National Park 

 OKEF: Okefenokee National Wildlife Refuge 
3-47

Table 3-4. Comparison of concurrent OC concentration at quartz-fiber front filter (QF), quartzfiber backup filter behind quartz-fiber filter (QBQ), front field blank (bQF), and backup field 

blank (bQBQ) filters at the six sites with secondary filters behind quartz-fiber front filters in the 

IMPROVE network. 

Organic Carbon Concentration (μg/filter) 

 QF QBQ bQF bQBQ 

Site Code Site Name # of samples Conc. ± StDev Conc. ± StDev Conc. ± StDev Conc. ± StDev 

MORA Mount Rainier NP 5 29.81 ± 19.63 7.33 ± 3.57 6.26 ± 2.18 6.00 ± 3.98 

YOSE Yosemite NP 4 58.99 ± 39.05 9.75 ± 4.86 6.37 ± 2.39 6.82 ± 1.69 

HANC 

Hance Camp at 

Grand Canyon NP 3 16.80 ± 6.43 6.38 ± 0.96 7.51 ± 2.35 5.79 ± 1.3 

CHIR Chiricahua NM 5 25.06 ± 15.64 8.10 ± 2.07 7.87 ± 3.33 7.59 ± 2.3 

SHEN Shenandoah NP 4 36.45 ± 11.39 8.21 ± 2.39 7.06 ± 3.33 6.96 ± 2.63 

OKEF Okefenokee NWR 1 30.13 10.83 10.57 11.13 

All Sites 22 33.48 ± 23.50 8.13 ± 2.19 7.16 ± 2.64 6.89 ± 2.63 

a MORA: Mount Rainier National Park 

 YOSE: Yosemite National Park 

 HANC: Hance Camp at Grand Canyon National Park 

 CHIR: Chiricahua National Monument 

 SHEN: Shenandoah National Park 

 OKEF: Okefenokee National Wildlife Refuge 
3-48

Table 3-5. Number of samples acquired from the SEARCH network during 2005 and 2006. 

(dQF, dQBQ, and bQF are not necessarily obtained on the same days.) 

Site Name/State Site Code Site Type Number 

of dQFa

Number 

of dQBQb

Number 

of bQFc

Gulfport, MS GLF Urban 275 28 14 

Oakgrove, MS OAK Rural 247 30 19 

North Birmingham, AL BHM Urban 496 50 9 

Centreville, AL CTR Rural 275 25 23 

Jefferson Street, GA JST Urban 814 77 13 

Yorkville, GA YRK Rural 283 26 20 

Pensacola, FL PNS Urban 261 20 24 

Outlying Field, FL OLF Suburban 257 21 22 

a QF: Quartz-fiber front filter behind the preceding organic denuders 

b QBQ: Quartz-fiber filter behind quartz-fiber front filter behind the preceding organic denuders (representing 

~10% of the samples randomly selected for carbon analysis) c bQF: Quartz-fiber front field blank (collected at ~10% of total) 
3-49

Table 3-6. Original and sliced filter mass and concentration (the circular filter punch size is 0.5 

cm

2

). 

 Mass Concentration (ng/punch) 

 Sample Original Front Back SUM Average % 

Site ID Site Name Type Date (F + B) Difference 

MORA1 Mount Rainier NP QF 5/19/2005 3.5 1.9 1.6 3.5 -0.7% 

MORA9 Mount Rainier NP QF 1/13/2005 3.5 2.4 1.2 3.6 0.5% 

YOSE1 Yosemite NP QF 2/16/2006 3.7 1.4 2.3 3.7 -0.2% 

HANC1 Hance Camp at Grand Canyon NP QF 1/13/2005 3.1 2.1 1 3.1 0.2% 

HANC1 Hance Camp at Grand Canyon NP QF 2/3/2005 3.7 2.2 1.5 3.7 -0.7% 

CHIR1 Chiricahua NM QF 1/13/2005 3.3 1.2 2.1 3.3 0.0% 

CHIR1 Chiricahua NM QF 4/7/2005 3.3 1.9 1.4 3.3 -0.6% 

CHIR1 Chiricahua NM QF 3/30/2006 3.5 1.7 1.8 3.5 -0.1% 

SHEN1 Shenandoah NP QF 2/3/2005 3.2 1.5 1.9 3.4 5.3% 

SHEN1 Shenandoah NP QF 3/17/2005 3.5 1.5 2.1 3.5 -0.3% 

SHEN1 Shenandoah NP QF 1/5/2006 3.8 2.5 1.3 3.8 0.0% 

SHEN1 Shenandoah NP QF 1/13/2005 3.6 1.7 1.9 3.6 -0.5% 

 

MORA1 Mount Rainier NP QBQ 5/19/2005 3.5 1.7 1.8 3.5 -0.2% 

MORA9 Mount Rainier NP QBQ 1/13/2005 3.7 2.3 1.5 3.7 0.1% 

YOSE1 Yosemite NP QBQ 2/16/2006 3.5 1.5 2 3.4 -0.9% 

HANC1 Hance Camp at Grand Canyon NP QBQ 1/13/2005 3.1 1.7 1.4 3 -3.3% 

HANC1 Hance Camp at Grand Canyon NP QBQ 2/3/2005 3.8 2 1.7 3.7 -1.0% 

CHIR1 Chiricahua NM QBQ 1/13/2005 3.4 1.4 1.9 3.4 -0.2% 

CHIR1 Chiricahua NM QBQ 4/7/2005 3.4 1.1 2.4 3.4 -0.1% 

CHIR1 Chiricahua NM QBQ 3/30/2006 3.7 1.6 2 3.6 -0.8% 

SHEN1 Shenandoah NP QBQ 2/3/2005 3.2 2 1.2 3.2 -0.9% 

SHEN1 Shenandoah NP QBQ 3/17/2005 3.6 2 1.6 3.6 -0.5% 

SHEN1 Shenandoah NP QBQ 1/5/2006 3.6 1.8 1.9 3.6 0.2% 

SHEN1 Shenandoah NP QBQ 1/13/2005 3.8 1.8 1.8 3.7 -2.4% 

a 100

2

Original Sum

Original Sum

×

⎟

⎠

⎞ ⎜

⎝

⎛ +

−
3-50

Table 3-7. Average carbon fractions for top and bottom sliced quartz-fiber front (QF) and concurrent backup (QB

Carbon Loading (μgC/mg filter) 

Site 

(No. of Samples) Sliced Filter OC EC TC OC1 OC2 OC3 OC4 OP EC

MORA (2) QF_top 4.30 0.43 4.73 0.04 0.79 2.10 0.77 0.59 0.8

 QF_bottom 3.32 0.36 3.69 0.02 0.78 2.14 0.39 0.00 0.3 QBQ_top 2.52 0.00 2.52 0.38 0.91 1.09 0.15 0.00 0.0 QBQ_bottom 2.09 0.00 2.10 0.06 0.70 1.27 0.06 0.00 0.0

YOSE (1) QF_top 10.71 1.95 12.67 0.00 1.75 3.88 2.19 2.90 4.4

 QF_bottom 4.10 0.49 4.59 0.45 1.15 1.91 0.59 0.00 0.3 QBQ_top 2.02 0.00 2.02 0.24 0.69 1.09 0.00 0.00 0.0 QBQ_bottom 1.76 0.00 1.76 0.33 0.57 0.77 0.09 0.00 0.0

CHIR (3) QF_top 5.95 1.28 7.24 0.28 1.41 2.57 0.95 0.74 1.6

 QF_bottom 3.96 0.18 4.13 0.59 1.25 1.80 0.32 0.00 0.1 QBQ_top 2.36 0.00 2.36 0.09 0.74 1.52 0.02 0.00 0.0 QBQ_bottom 2.56 0.01 2.57 0.33 0.78 1.34 0.11 0.00 0.0

HANC (2) QF_top 7.90 1.71 9.61 0.47 1.90 3.91 1.41 0.22 1.6

 QF_bottom 8.54 0.77 9.31 0.00 1.42 6.24 0.87 0.00 0.7 QBQ_top 5.90 0.43 6.33 0.31 1.10 3.87 0.63 0.00 0.4 QBQ_bottom 6.36 0.62 6.98 0.03 1.22 4.40 0.71 0.00 0.6

SHEN (4) QF_top 13.98 5.12 19.10 0.33 3.08 3.66 3.52 3.38 7.6

 QF_bottom 5.57 1.57 7.14 0.21 1.62 1.64 0.77 1.34 1.7 QBQ_top 3.14 0.13 3.27 0.45 0.85 1.60 0.25 0.00 0.1 QBQ_bottom 1.96 0.00 1.96 0.17 0.63 1.13 0.04 0.00 0.0
 

3-51

Table 3-8. Robust regression intercept of quartz-fiber front (QF) organic carbon (OC; y-axis) 

versus PM2.5 mass (x-axis) averaged over all IMPROVE sites for each season during the period 

from 1/1/2005 through 12/31/2006. 

Intercept (μg/filter) Springa Summer Fall Winter 

Number of pairs 8898 7184 4372 7311 

Average Intercept OC 12.44±6.43 18.18±15.13 15.23±10.45 11.20±7.63 

Average blank OC 8.44 10.17 8.14 7.08 

Average backup OCb 8.88 12.68 10.23 7.78 a

 Spring = March, April, May 

 Summer = June, July, August 

 Fall = September, October, November 

 Winter = December, January, February 

b

 From six sites 
 

3-52

Table 3-9. Lower quantifiable limits (LQLs) of polycyclic aromatic hydrocarbons (PAHs), 

phthalates, alkanes, alkenes, hopanes, and steranes by thermal desorption-gas 

chromatography/mass spectrometry (TD-GC/MS). 

LQL LQL LQL LQL 

Compounds (ng/cm2

) (ng/cm2)

a Compounds (ng/cm1

) (ng/cm2)

 a

PAHs Alkanes 

acenaphthylene 0.66 0.07 n-Alkanes (n-C14 to n-C44) 

acenapthene 0.52 0.06 tetradecane (n-C14) 0.41 0.04 

fluorene 0.25 0.03 pentadecane (n-C15) 0.24 0.03 

phenanthrene 0.12 0.01 hexadecane (n-C16) 0.25 0.03 

anthracene 0.05 0.01 heptadecane (n-C17) 0.22 0.02 

fluoranthene 0.07 0.01 octadecane (n-C18) 0.19 0.02 

pyrene 0.11 0.01 nonadecane (n-C19) 0.14 0.02 

chrysene 0.11 0.01 icosane (n-C20) 0.14 0.02 

benzo[b]fluoranthene 0.23 0.02 heneicosane (n-C21) 0.24 0.03 

benzo[k]fluoranthene 0.08 0.01 docosane (n-C22) 0.18 0.02 

benzo[a]pyrene 0.25 0.03 tricosane (n-C23) 0.21 0.02 

perylene 0.27 0.03 tetracosane (n-C24) 0.16 0.02 

indeno[1,2,3-cd]pyrene 0.12 0.01 pentacosane (n-C25) 0.17 0.02 

dibenzo[a,h]anthracene 0.27 0.03 hexacosane (n-C26) 0.17 0.02 

benzo[ghi]perylene 0.18 0.02 heptacosane (n-C27) 0.08 0.01 

coronene 0.21 0.02 octacosane (n-C28) 0.21 0.02 

dibenzo[a,e]pyrene 0.08 0.01 triacontane (n-C30) 0.27 0.03 

 hentriacotane (n-C31) 0.22 0.02 

1-methylnaphthalene 0.13 0.01 dotriacontane (n-C32) 0.25 0.03 

2-methylnaphthalene 0.04 0.00 tritriactotane (n-C33) 0.16 0.02 

2,6-dimethylnaphthalene 0.25 0.03 tetratriactoane (n-C34) 0.19 0.02 

9-fluorenone 0.28 0.03 hexatriacontane (n-C36) 0.24 0.03 

9-methylanthracene 0.26 0.03 tetracontane (n-C40) 0.24 0.03 

anthroquinone 0.14 0.01 Methyl-alkanes 

1,8-napthalic anhydride 0.24 0.03 2-methylnonadecane 0.25 0.03 

methylfluoranthene 0.08 0.01 3-methylnonadecane 0.27 0.03 

retene 0.34 0.04 Branched-alkanes 

cyclopenta[cd]pyrene 0.08 0.01 pristine 0.28 0.03 

benz[a]anthracene-7,12-dione 0.29 0.03 phytane 0.28 0.03 

methylchrysene 0.12 0.01 squalane 0.28 0.03 

 Cyclohexanes 

Phthalates octylcyclohexane 0.27 0.03 

dimethylphthalate 0.16 0.02 decylcyclohexane 0.20 0.02 

diethyl phthalate 0.25 0.03 tridecylcyclohexane 0.37 0.04 

di-n-butyl phthalate 0.13 0.01 n-heptadecylcyclohexane 0.24 0.03 

butyl benzyl phthalate 0.24 0.03 nonadecylcyclohexane 0.20 0.02 

bis(2-ethylhexyl)phthalate 0.21 0.02 

di-n-octyl phthalate 0.24 0.03 Alkenes 

 squalene 0.16 0.02 

1-octadecene 0.23 0.02 

 Hopanes Steranes 

22,29,30-trisnorphopane (Tm) 0.14 0.02 ααα 20R-Cholestane 0.07 0.01 

αβ-norhopane (C29αβ-hopane) 0.09 0.01 αββ 20R-Cholestane 0.19 0.02 

βα -norhopane (C29βα -hopane) 0.39 0.04 αββ 20S 24S-Methylcholestane 0.23 0.02 

αβ-hopane (C30αβ-hopane) 0.30 0.03 ααα 20R 24R-Methylcholestane 0.16 0.02 

βα-hopane (C30βα-hopane) 0.33 0.04 ααα 20S 24R/S-Ethylcholestane 0.22 0.02 

αβS-homohopane (C31αβS-hopane) 0.24 0.03 αββ 20R 24R-Ethylcholestane 0.10 0.01 

αβR-homohopane (C31αβR-hopane) 0.24 0.03 ααα 20R 24R-Ethylcholestane 0.10 0.01 

a

 Assumes a sampled air volume 32.7 m3, and 0.5 cm2 of the 3.53 cm2 of the exposed area used in TD-GC/MS 

analysis 
3-53

Table 3-10. Summary of organic concentrations (ng/cm2) on the front (QF) and backup (QBQ) filters at 

(MORA, HANC, CHIR, OKEF) during winter 2005. 

Site Mount Rainier, WA (MORA) Grand Canyon, AZ (HANC) Chiricahua, AZ (CHIR) 

 Sampling Date 1/28/2005 1/28/2005 Back/Front 1/7/2005 1/7/2005 Back/Front 1/19/2005 1/19/2005 Back/Front 12/2 Filter Type QF QBQ Ratio QF QBQ Ratio QF QBQ Ratio QF Carbon Fractions (μg/cm2)  OC 13.3 12.4 0.9 6.6 7.5 1.1 33.2 8.8 0.3  EC 1.7 0.3 0.2 1.2 0.0 0.0 10.5 0.1 0.0  TC 15.0 12.7 0.8 7.8 7.5 1.0 43.7 8.9 0.2  O1 0.2 1.7 9.5 0.6 1.8 3.0 1.0 2.1 2.2  O2 2.8 3.3 1.2 3.0 2.9 1.0 7.7 2.8 0.4  O3 6.1 5.7 0.9 1.8 2.3 1.3 8.5 3.1 0.4  O4 1.7 1.8 1.0 0.3 0.4 1.1 7.0 0.8 0.1  E1 2.9 0.3 0.1 0.9 0.1 0.1 18.1 0.1 0.0  E2 1.2 0.0 0.0 1.2 0.0 0.0 1.5 0.1 0.0  E3 0.0 0.0 - 0.0 0.0 - 0.0 0.0 - Organic Compounds (ng/cm2) ID PAHs P02 acenaphthylene nd nd - nd nd - 0.157 nd - nd P03 acenapthene nd nd - nd 0.097 - 0.005 nd - nd P04 fluorene nd nd - nd nd - 0.095 nd - P05 phenanthrene nd nd - nd nd - 0.737 nd - P06 anthracene 0.104 0.093 0.890 0.051 0.015 0.286 0.206 0.072 0.347 P07 fluoranthene 0.020 nd - nd nd - 1.064 nd - nd P08 pyrene nd nd - nd nd - 0.755 nd - nd P09 benzo[a]anthracene nd nd - nd nd - 0.026 nd - nd P10 chrysene nd nd - nd nd - 0.575 nd - nd P11 benzo[b]fluoranthene nd nd - nd nd - 0.374 nd - nd P12 benzo[k]fluoranthene nd nd - nd nd - 0.434 nd - nd P13 benzo[a]fluoranthene nd nd - nd nd - 0.026 nd - nd P14 benzo[e]pyrene nd nd - nd nd - 0.547 nd - nd P15 benzo[a]pyrene nd nd - nd nd - 0.140 nd - nd P16 perylene nd nd - nd nd - 0.095 nd - nd P17 indeno[1,2,3-cd]pyrene nd nd - nd nd - nd nd - nd P18 dibenzo[a,h]anthracene nd nd - nd nd - nd nd - nd P19 benzo[ghi]perylene nd nd - nd nd - 0.221 nd - nd P20 coronene nd nd - nd nd - nd nd - nd P21 dibenzo[a,e]pyrene nd nd - nd nd - nd nd - nd P22 2-methylnaphthalene nd nd - nd nd - 0.197 nd - nd P23 1-methylnaphthalene nd nd - nd nd - nd nd - nd P24 2,6-dimethylnaphthalene nd nd - nd nd - 0.467 nd - nd P25 9-fluorenone nd nd - nd nd - 0.191 nd - nd P26 9-methylanthracene nd nd - nd nd - 0.581 nd - nd P27 anthroquinone nd nd - nd nd - 0.133 nd - nd P29 methylfluoranthene nd nd - nd nd - nd nd - nd P30 retene 0.158 0.033 0.210 0.077 nd - 2.086 0.045 0.022 nd P31 cyclopenta[cd]pyrene nd nd - nd nd - nd nd - nd P32 benz[a]anthracene-7,12-dione nd nd - nd nd - nd nd - nd 
3-54

Table 3-10. Continued 

Site Mount Rainier, WA (MORA) Grand Canyon, AZ (HANC) Chiricahua, AZ (CHIR) 

 Sampling Date 1/28/2005 1/28/2005 Back/Front 1/7/2005 1/7/2005 Back/Front 1/19/2005 1/19/2005 Back/Front 12/2 Filter Type QF QBQ Ratio QF QBQ Ratio QF QBQ Ratio QF P33 methylchrysene nd nd - nd nd - 0.031 nd - nd P34 picene nd nd - nd nd - nd nd - nd 

n-alkanes 

NA01 tetradecane (n-C14) nd nd - nd nd - nd nd - nd NA02 pentadecane (n-C15) 2.650 0.740 0.279 0.886 1.148 1.296 1.661 1.405 0.845 NA03 hexadecane (n-C16) 1.492 1.007 0.675 0.922 1.168 1.268 2.403 0.538 0.224 NA04 heptadecane (n-C17) 1.651 1.066 0.646 1.378 1.213 0.880 2.909 1.524 0.524 NA05 octadecane (n-C18) 2.451 1.689 0.689 1.698 1.620 0.954 2.731 0.917 0.336 NA06 nonadecane (n-C19) 1.204 0.793 0.659 0.778 0.631 0.811 0.523 0.753 1.441 NA07 icosane (n-C20) 1.510 1.088 0.721 1.147 1.088 0.949 1.842 1.228 0.667 NA08 heneicosane (n-C21) 1.045 0.672 0.643 0.650 0.437 0.672 5.679 0.649 0.114 NA09 docosane (n-C22) 2.136 1.165 0.546 1.053 0.769 0.730 3.264 1.005 0.308 NA10 tricosane (n-C23) 1.549 0.927 0.598 0.774 0.441 0.569 4.351 0.876 0.201 NA11 tetracosane (n-C24) 1.413 0.732 0.518 0.843 0.415 0.492 5.213 0.987 0.189 NA12 pentacosane (n-C25) 1.378 0.899 0.653 0.958 0.449 0.469 7.469 1.134 0.152 NA13 hexacosane (n-C26) 0.833 0.499 0.599 0.733 0.327 0.446 7.879 0.850 0.108 NA14 heptacosane (n-C27) 0.720 0.267 0.371 0.405 0.158 0.389 7.187 0.994 0.138 NA15 octacosane (n-C28) 0.243 0.088 0.361 0.086 0.106 1.235 5.932 0.365 0.062 NA16 nonacosane (n-C29) 0.854 0.056 0.065 0.150 0.095 0.636 11.887 0.329 0.028 NA17 triacontane (n-C30) 0.158 nd - nd nd - 3.512 0.052 0.015 NA18 hentriacotane (n-C31) 0.162 nd - nd nd - 8.384 nd - NA19 dotriacontane (n-C32) 0.027 nd - nd nd - 1.635 nd - NA20 tritriactotane (n-C33) nd nd - nd nd - 1.763 nd - NA21 tetratriactoane (n-C34) nd nd - nd nd - 0.552 nd - nd NA22 pentatriacontane (n-C35) nd nd - nd nd - 0.566 nd - nd NA23 hexatriacontane (n-C36) nd nd - nd nd - 0.486 nd - nd NA24 heptatriacontane (n-37) nd nd - nd nd - nd nd - nd NA25 octatriacontane (n-38) nd nd - nd nd - nd nd - nd NA26 nonatriacontane (n-39) nd nd - nd nd - nd nd - nd NA27 tetracontane (n-C40) nd nd - nd nd - nd nd - nd NA28 hentetracontane (n-41) nd nd - nd nd - nd nd - nd NA29 dotetracontane (n-42) nd nd - nd nd - nd nd - nd 

iso/anteiso-alkanes 

IAA01 iso-nonacosane (iso-C29) 0.257 nd - nd nd - 0.505 nd - nd IAA02 anteiso-nonacosane (anteiso-C29) 0.248 nd - nd nd - 0.079 nd - nd IAA03 iso-triacontane (iso-C30) 0.178 nd - nd nd - 0.160 nd - nd IAA04 anteiso-triacontane (anteiso-C30) 0.112 nd - nd nd - 0.068 nd - nd IAA05 iso-hentriacotane (iso-C31) nd nd - nd nd - 0.256 nd - nd IAA06 anteiso-hentriacotane (anteiso-C31) nd nd - nd nd - 0.076 nd - nd IAA07 iso-dotriacontane (iso-C32) nd nd - nd nd - 0.070 nd - nd IAA08 anteiso-dotriacontane (anteiso-C32) nd nd - nd nd - 0.079 nd - nd IAA09 iso-tritriactotane (iso-C33) nd nd - nd nd - 0.079 nd - nd IAA10 anteiso-tritriactotane (anteiso-C33) nd nd - nd nd - 0.053 nd - nd IAA11 iso-tetratriactoane (iso-C34) nd nd - nd nd - nd nd - nd 
3-55

Table 3-10. Continued 

Site Mount Rainier, WA (MORA) Grand Canyon, AZ (HANC) Chiricahua, AZ (CHIR) 

 Sampling Date 1/28/2005 1/28/2005 Back/Front 1/7/2005 1/7/2005 Back/Front 1/19/2005 1/19/2005 Back/Front 12/2 Filter Type QF QBQ Ratio QF QBQ Ratio QF QBQ Ratio QF IAA12 anteiso-tetratriactoane (anteiso-C34) nd nd - nd nd - nd nd - nd IAA13 iso-pentatriacontane (iso-C35) nd nd - nd nd - nd nd - nd IAA14 anteiso-pentatriacontane (anteiso-C35) nd nd - nd nd - nd nd - nd IAA15 iso-hexatriacontane (iso-C36) nd nd - nd nd - nd nd - nd IAA16 anteiso-hexatriacontane (anteiso-C36) nd nd - nd nd - nd nd - nd IAA17 iso-heptatriacontane (iso-37) nd nd - nd nd - nd nd - nd IAA18 anteiso-heptatriacontane (anteiso-37) nd nd - nd nd - nd nd - nd 

hopanes 

HOP01 22,29,30-trisnorneophopane (Ts) 0.040 nd - nd nd - 0.097 nd - nd HOP02 22,29,30-trisnorphopane (Tm) 0.018 nd - nd nd - 0.074 nd - nd HOP03 αβ-norhopane (C29αβ-hopane) 0.072 nd - 0.067 nd - 0.445 nd - nd HOP04 29Ts 0.015 nd - 0.018 nd - 0.136 nd - nd HOP05 βα-norhopane (C29βα -hopane) 0.054 nd - 0.019 nd - 0.088 nd - nd HOP06 αβ-hopane (C30αβ -hopane) 0.055 nd - 0.092 nd - 0.326 nd - nd HOP07 30αα nd nd - 0.007 nd - 0.031 nd - nd HOP08 βα-hopane (C30βα -hopane) nd nd - nd nd - 0.043 nd - nd HOP09 αβS-homohopane (C31αβS-hopane) nd nd - nd nd - 0.326 nd - nd HOP10 αβR-homohopane (C31αβR-hopane) nd nd - nd nd - 0.282 nd - nd HOP11 αβS-bishomohopane (C32αβS-hopane) nd nd - nd nd - 0.086 nd - nd HOP12 αβR-bishomohopane (C32αβR-hopane) nd nd - nd nd - 0.074 nd - nd HOP13 22S-trishomohopane (C33) nd nd - nd nd - 0.113 nd - nd HOP14 22R-trishomohopane (C33) nd nd - nd nd - 0.092 nd - nd HOP15 22S-tretrahomohopane (C34) nd nd - nd nd - nd nd - nd HOP16 22R-tetrashomohopane (C34) nd nd - nd nd - nd nd - nd HOP17 22S-pentashomohopane(C35) nd nd - nd nd - nd nd - nd HOP18 22R-pentashomohopane(C35) nd nd - nd nd - nd nd - nd 

steranes 

STE01 ααα 20S-Cholestane nd nd - nd nd - nd nd - nd STE02 αββ 20R-Cholestane nd nd - nd nd - nd nd - nd STE03 αββ 20s-Cholestane nd nd - nd nd - nd nd - nd STE04 ααα 20R-Cholestane nd nd - nd nd - 0.048 nd - nd STE05 ααα 20S 24S-Methylcholestane nd nd - nd nd - 0.078 nd - nd STE07 αββ 20R 24S-Methylcholestane nd nd - nd nd - nd nd - nd STE08 αββ 20S 24S-Methylcholestane nd nd - nd nd - nd nd - nd STE09 ααα 20R 24R-Methylcholestane nd nd - nd nd - nd nd - nd STE10 ααα 20S 24R/S-Ethylcholestane nd nd - nd nd - 0.224 nd - nd STE11 αββ 20R 24R-Ethylcholestane nd nd - nd nd - 0.149 nd - nd STE12 αββ 20S 24R-Ethylcholestane nd nd - nd nd - 0.128 nd - nd STE14 ααα 20R 24R-Ethylcholestane nd nd - nd nd - 0.097 nd - nd 

methyl-alkanes 

MA01 2-methylnonadecane 0.052 0.073 1.393 0.187 nd - 0.140 0.065 0.462 MA02 3-methylnonadecane 0.079 0.034 0.427 0.035 nd - 0.204 0.029 0.144 

branched-alkanes 

BA01 pristane 3.218 2.179 0.677 2.161 2.157 0.998 4.026 2.248 0.558 BA02 phytane 2.016 1.460 0.724 1.513 1.368 0.904 2.518 1.168 0.464 BA03 squalane 0.136 0.013 0.095 0.022 0.013 0.574 0.145 0.020 0.140 
3-56

Table 3-10. Continued 

Site Mount Rainier, WA (MORA) Grand Canyon, AZ (HANC) Chiricahua, AZ (CHIR) 

 Sampling Date 1/28/2005 1/28/2005 Back/Front 1/7/2005 1/7/2005 Back/Front 1/19/2005 1/19/2005 Back/Front 12/2 Filter Type QF QBQ Ratio QF QBQ Ratio QF QBQ Ratio QF 

cycloalkanes 

CA01 octylcyclohexane 0.091 0.107 1.175 0.622 0.189 0.303 1.749 0.309 0.177 CA02 decylcyclohexane 0.204 0.096 0.472 0.794 0.084 0.106 1.878 0.082 0.044 CA03 tridecylcyclohexane 0.158 0.056 0.354 0.062 0.050 0.807 0.260 0.090 0.348 CA04 n-heptadecylcyclohexane 0.221 0.097 0.438 0.011 0.094 8.882 1.459 0.091 0.063 CA05 nonadecylcyclohexane 0.075 0.023 0.311 0.044 nd - 0.317 0.039 0.122 

alkene 

AE02 1-octadecene 0.433 0.327 0.754 0.215 0.321 1.495 0.640 0.253 0.396 

phthalates 

PH01 dimethylphthalate 0.100 nd - nd nd - 0.459 nd - PH02 diethyl phthalate nd nd - nd nd - 0.333 nd - nd PH03 di-n-butyl phthalate 0.045 nd - nd 0.007 - 0.733 0.008 0.011 PH04 butyl benzyl phthalate nd nd - nd nd - nd nd - nd PH05 bis(2-ethylhexyl)phthalate 0.140 nd - nd nd - 0.122 0.406 3.320 nd PH06 di-n-octyl phthalate 0.086 nd - nd nd - nd nd - nd nd: not detected 
3-57

Table 3-11. Summary of organic concentrations (ng/cm2) on the front (QF) and backup (QBQ) filters at four IM

HANC, CHIR, OKEF) during summer 2005. 

 Site Mount Reinier, WA (MORA1) Grand Canyon, AZ (HANC1) Chiricahua, AZ (CHIR1)  Sampling Date 8/5/2005 8/5/2005 Back/Front 7/21/2005 7/21/2005 8/2/2005 8/2/2005 7/27/2005 7/27/2005 7/21/2005 7/21/2005  Filter Type QF QBQ Ratio bQF bQBQ QF QBQ QF QBQ bQF bQBQ  OC 126.1 19.3 0.2 126.1 19.3 0.2 33.0 18.1 0.5 26.7 16.8 0.6 10.4 10.3  EC 29.2 1.7 0.1 29.2 1.7 0.1 2.9 1.9 0.6 2.7 0.7 0.2 0.0 0.0 -  TC 155.3 21.0 0.1 155.3 21.0 0.1 35.9 19.9 0.6 29.4 17.5 0.6 10.4 10.3  OC1 2.6 3.3 1.3 2.6 3.3 1.3 2.3 4.4 1.9 1.1 5.2 4.6 2.5 2.9  OC2 31.9 6.2 0.2 31.9 6.2 0.2 8.2 5.4 0.7 7.8 4.9 0.6 3.5 3.6  OC3 47.1 7.1 0.2 47.1 7.1 0.2 11.0 6.3 0.6 7.4 4.4 0.6 4.0 3.1  OC4 27.1 2.7 0.1 27.1 2.7 0.1 4.8 2.0 0.4 3.2 1.5 0.5 0.4 0.7  EC1 40.4 0.8 0.0 40.4 0.8 0.0 6.0 1.0 0.2 6.5 0.6 0.1 0.0 0.0 -  EC2 5.5 0.9 0.2 5.5 0.9 0.2 3.3 0.8 0.3 3.4 0.8 0.3 0.0 0.0 -  EC3 0.7 0.0 0.0 0.7 0.0 0.0 0.3 0.0 0.0 0.0 0.1 - 0.0 0.0 - 

Compound

ID PAHs P02 acenaphthylene 0.140 nd - nd 0.029 - 0.056 nd - nd 0.033 - 0.126 0.050 P03 acenapthene nd nd - nd nd - nd 0.009 - nd nd - nd nd - P04 fluorene 0.111 0.026 0.235 0.107 0.071 0.659 0.029 nd - 0.039 0.178 4.578 0.298 0.090 P05 phenanthrene 0.382 0.031 0.080 0.044 nd - 0.054 0.028 0.513 0.097 0.020 0.208 0.025 0.008 P06 anthracene 0.106 0.037 0.343 0.027 0.042 1.590 0.039 0.039 1.008 0.046 0.032 0.689 0.011 0.026 P07 fluoranthene 0.275 nd - nd nd - 0.019 nd - nd nd - 0.030 nd - P08 pyrene 0.229 nd - nd nd - nd nd - nd nd - nd nd - P09 benzo[a]anthracene nd nd - nd nd - nd nd - nd nd - nd nd - P10 chrysene nd nd - nd nd - nd nd - nd nd - nd nd - P11 benzo[b]fluoranthene nd nd - nd nd - nd nd - nd nd - nd nd - P12 benzo[k]fluoranthene nd nd - nd nd - nd nd - nd nd - nd nd - P13 benzo[a]fluoranthene nd nd - nd nd - nd nd - nd nd - nd nd - P14 benzo[e]pyrene nd nd - nd nd - nd nd - nd nd - nd nd - P15 benzo[a]pyrene nd nd - nd nd - nd nd - nd nd - nd nd - P16 perylene nd nd - nd nd - 0.017 nd - nd nd - nd nd - P17 indeno[1,2,3-cd]pyrene nd nd - nd nd - nd nd - nd nd - nd nd - P18 dibenzo[a,h]anthracene nd nd - nd nd - nd nd - nd nd - nd nd - P19 benzo[ghi]perylene nd nd - nd nd - nd nd - nd nd - nd nd - P20 coronene nd nd - nd nd - nd nd - nd nd - nd nd - P21 dibenzo[a,e]pyrene nd nd - nd nd - nd nd - nd nd - nd nd - P22 2-methylnaphthalene nd nd - nd nd - nd nd - nd nd - nd nd - P23 1-methylnaphthalene nd nd - nd nd - nd nd - nd nd - nd nd - P24 2,6-dimethylnaphthalene 0.410 0.112 0.274 nd nd - 0.108 0.061 0.561 nd 0.069 - nd nd - P25 9-fluorenone nd nd - nd nd - nd nd - nd nd - 0.034 nd - P26 9-methylanthracene nd nd - nd nd - 0.031 nd - nd 0.103 - nd nd - P27 anthroquinone nd nd - nd nd - nd nd - nd nd - nd nd - P29 methylfluoranthene nd nd - nd nd - nd nd - nd nd - nd nd - P30 retene 0.100 0.070 0.701 nd 0.013 - 0.102 0.034 0.333 0.292 0.021 0.071 0.081 0.014 P31 cyclopenta[cd]pyrene nd nd - nd nd - nd nd - nd nd - nd nd - P32 benz[a]anthracene-7,12-dione nd nd - nd nd - nd nd - nd nd - nd nd - P33 methylchrysene nd nd - nd nd - nd nd - nd nd - nd nd - P34 picene nd nd - nd nd - nd nd - nd nd - nd nd - 

n-alkanse 

NA01 tetradecane (n-C14) nd nd - nd nd - nd nd - nd nd - nd nd - NA02 pentadecane (n-C15) 1.092 0.430 0.393 1.487 1.430 0.961 0.740 0.351 0.474 1.315 0.464 0.353 1.780 1.142 NA03 hexadecane (n-C16) 2.224 1.730 0.778 1.458 1.668 1.144 0.914 1.687 1.846 1.738 2.719 1.565 3.721 1.749 NA04 heptadecane (n-C17) 2.019 1.623 0.804 1.014 1.601 1.578 1.482 2.229 1.504 1.671 2.206 1.320 2.999 1.312 NA05 octadecane (n-C18) 3.897 2.908 0.746 1.905 2.019 1.060 2.465 3.068 1.244 2.427 2.704 1.114 2.923 2.447 NA06 nonadecane (n-C19) 1.846 1.911 1.035 1.346 0.905 0.672 1.302 2.130 1.636 0.900 2.039 2.265 1.865 1.067 NA07 icosane (n-C20) 5.993 4.364 0.728 2.993 1.862 0.622 3.216 3.531 1.098 3.130 3.095 0.989 3.028 1.873 NA08 heneicosane (n-C21) 2.536 3.237 1.276 1.483 0.696 0.469 1.527 2.270 1.487 1.318 1.907 1.448 1.339 0.978 NA09 docosane (n-C22) 5.553 5.511 0.993 3.364 1.488 0.442 4.282 4.375 1.022 3.221 4.860 1.509 2.244 1.376 NA10 tricosane (n-C23) 6.333 18.055 2.851 1.311 0.586 0.447 5.146 5.309 1.032 3.304 4.677 1.416 0.904 0.682 NA11 tetracosane (n-C24) 3.881 8.342 2.150 1.000 0.460 0.461 2.419 1.607 0.664 2.233 1.623 0.727 0.652 0.517 NA12 pentacosane (n-C25) 10.178 2.551 0.251 0.868 0.432 0.497 3.969 1.222 0.308 3.031 2.087 0.689 0.898 0.540 NA13 hexacosane (n-C26) 6.433 7.448 1.158 0.399 0.354 0.888 1.172 0.375 0.320 0.829 1.138 1.372 0.553 0.146 
3-58

Table 3-11. Continued.  Site Mount Reinier, WA (MORA1) Grand Canyon, AZ (HANC1) Chiricahua, AZ (CHIR1)  Sampling Date 8/5/2005 8/5/2005 Back/Front 7/21/2005 7/21/2005 8/2/2005 8/2/2005 7/27/2005 7/27/2005 7/21/2005 7/21/2005  Filter Type QF QBQ Ratio bQF bQBQ QF QBQ QF QBQ bQF bQBQ NA14 heptacosane (n-C27) 13.584 13.124 0.966 0.377 0.157 0.417 1.739 0.212 0.122 2.634 1.034 0.393 0.712 0.288 NA15 octacosane (n-C28) 3.687 0.967 0.262 0.359 0.502 1.397 0.553 0.042 0.076 0.619 0.333 0.538 0.226 0.375 NA16 nonacosane (n-C29) 8.578 1.658 0.193 0.231 nd - 1.867 nd - 4.115 0.311 0.076 0.102 nd - NA17 triacontane (n-C30) 1.836 6.209 3.382 0.272 0.611 2.245 0.364 nd - 0.248 0.083 0.333 nd 0.190 - NA18 hentriacotane (n-C31) 10.026 0.574 0.057 0.050 nd - 0.521 nd - 0.504 0.032 0.064 nd nd - NA19 dotriacontane (n-C32) 0.487 2.442 5.011 0.076 0.217 2.838 0.115 nd - 0.050 nd - nd 0.060 - NA20 tritriactotane (n-C33) 0.816 0.815 0.999 0.081 nd - nd nd - nd nd - nd nd - NA21 tetratriactoane (n-C34) 0.345 0.019 0.056 0.127 nd - nd nd - nd nd - nd nd - NA22 pentatriacontane (n-C35) 0.320 0.128 0.399 nd nd - nd nd - nd nd - nd nd - NA23 hexatriacontane (n-C36) 0.171 nd - nd nd - nd nd - nd nd - nd nd - NA24 heptatriacontane (n-37) nd nd - nd nd - nd nd - nd nd - nd nd - NA25 octatriacontane (n-38) nd nd - nd nd - nd nd - nd nd - nd nd - NA26 nonatriacontane (n-39) nd nd - nd nd - nd nd - nd nd - nd nd - NA27 tetracontane (n-C40) nd nd - nd nd - nd nd - nd nd - nd nd - NA28 hentetracontane (n-41) nd nd - nd nd - nd nd - nd nd - nd nd - NA29 dotetracontane (n-42) nd nd - nd nd - nd nd - nd nd - nd nd - 

iso/anteiso-alkanes 

IAA01 iso-nonacosane (iso-C29) 0.212 nd - 0.212 nd - nd nd - nd nd - nd nd - IAA02 anteiso-nonacosane (anteiso-C29) 0.256 nd - 0.256 nd - nd nd - nd nd - nd nd - IAA03 iso-triacontane (iso-C30) 0.180 nd - 0.180 nd - nd nd - nd nd - nd nd - IAA04 anteiso-triacontane (anteiso-C30) 0.101 nd - 0.101 nd - nd nd - nd nd - nd nd - IAA05 iso-hentriacotane (iso-C31) 0.054 nd - 0.054 nd - nd nd - nd nd - nd nd - IAA06 anteiso-hentriacotane (anteiso-C31) 0.029 nd - 0.029 nd - nd nd - nd nd - nd nd - IAA07 iso-dotriacontane (iso-C32) 0.097 nd - 0.097 nd - nd nd - nd nd - nd nd - IAA08 anteiso-dotriacontane (anteiso-C32) 0.065 nd - 0.065 nd - nd nd - nd nd - nd nd - IAA09 iso-tritriactotane (iso-C33) nd nd - nd nd - nd nd - nd nd - nd nd - IAA10 anteiso-tritriactotane (anteiso-C33) nd nd - nd nd - nd nd - nd nd - nd nd - IAA11 iso-tetratriactoane (iso-C34) nd nd - nd nd - nd nd - nd nd - nd nd - IAA12 anteiso-tetratriactoane (anteiso-C34) nd nd - nd nd - nd nd - nd nd - nd nd - IAA13 iso-pentatriacontane (iso-C35) nd nd - nd nd - nd nd - nd nd - nd nd - IAA14 anteiso-pentatriacontane (anteiso-C35) nd nd - nd nd - nd nd - nd nd - nd nd - IAA15 iso-hexatriacontane (iso-C36) nd nd - nd nd - nd nd - nd nd - nd nd - IAA16 anteiso-hexatriacontane (anteiso-C36) nd nd - nd nd - nd nd - nd nd - nd nd - IAA17 iso-heptatriacontane (iso-37) nd nd - nd nd - nd nd - nd nd - nd nd - IAA18 anteiso-heptatriacontane (anteiso-37) nd nd - nd nd - nd nd - nd nd - nd nd - 

hopanes 

HOP01 22,29,30-trisnorneophopane (Ts) 0.094 0.069 0.741 0.094 0.069 0.741 nd nd - 0.019 nd - 0.006 0.053 HOP02 22,29,30-trisnorphopane (Tm) 0.060 0.069 1.145 0.060 0.069 1.145 nd nd - 0.011 nd - 0.007 nd - HOP03 αβ-norhopane (C29αβ-hopane) 0.182 0.167 0.919 0.182 0.167 0.919 nd nd - 0.082 nd - 0.030 0.039 HOP04 29Ts 0.100 0.026 0.262 0.100 0.026 0.262 nd nd - 0.049 nd - 0.015 0.025 HOP05 βα-norhopane (C29βα -hopane) 0.080 0.019 0.240 0.080 0.019 0.240 nd nd - nd nd - nd nd - HOP06 αβ-hopane (C30αβ -hopane) 0.165 0.063 0.386 0.165 0.063 0.386 nd nd - 0.051 nd - 0.029 0.038 HOP07 30αα 0.012 0.009 0.772 0.012 0.009 0.772 nd nd - nd nd - nd nd - HOP08 βα-hopane (C30βα -hopane) 0.019 nd - 0.019 nd - nd nd - nd nd - nd nd - HOP09 αβS-homohopane (C31αβS-hopane) 0.158 nd - 0.158 nd - nd nd - nd nd - nd nd - HOP10 αβR-homohopane (C31αβR-hopane) 0.121 nd - 0.121 nd - nd nd - nd nd - nd nd - HOP11 αβS-bishomohopane (C32αβS-hopane) 0.056 nd - 0.056 nd - nd nd - nd nd - nd nd - HOP12 αβR-bishomohopane (C32αβR-hopane) 0.057 nd - 0.057 nd - nd nd - nd nd - nd nd - HOP13 22S-trishomohopane (C33) 0.056 nd - 0.056 nd - nd nd - nd nd - nd nd - HOP14 22R-trishomohopane (C33) 0.036 nd - 0.036 nd - nd nd - nd nd - nd nd - HOP15 22S-tretrahomohopane (C34) nd nd - nd nd - nd nd - nd nd - nd nd - HOP16 22R-tetrashomohopane (C34) nd nd - nd nd - nd nd - nd nd - nd nd - HOP17 22S-pentashomohopane(C35) nd nd - nd nd - nd nd - nd nd - nd nd - HOP18 22R-pentashomohopane(C35) nd nd - nd nd - nd nd - nd nd - nd nd - 

steranes 

STE01 ααα 20S-Cholestane 0.046 nd - 0.046 nd - 0.031 nd - nd nd - nd nd - STE02 αββ 20R-Cholestane nd nd - nd nd - 0.029 nd - nd nd - nd nd - STE03 αββ 20s-Cholestane nd nd - nd nd - 0.080 nd - nd nd - nd nd - STE04 ααα 20R-Cholestane nd nd - nd nd - 0.062 nd - nd nd - nd nd - STE05 ααα 20S 24S-Methylcholestane nd nd - nd nd - 0.083 nd - nd nd - nd nd - 
3-59

Table 3-11. Continued.  Site Mount Reinier, WA (MORA1) Grand Canyon, AZ (HANC1) Chiricahua, AZ (CHIR1)  Sampling Date 8/5/2005 8/5/2005 Back/Front 7/21/2005 7/21/2005 8/2/2005 8/2/2005 7/27/2005 7/27/2005 7/21/2005 7/21/2005  Filter Type QF QBQ Ratio bQF bQBQ QF QBQ QF QBQ bQF bQBQ STE07 αββ 20R 24S-Methylcholestane nd nd - nd nd - nd nd - nd nd - nd nd - STE08 αββ 20S 24S-Methylcholestane 0.019 nd - 0.019 nd - nd nd - nd nd - nd nd - STE09 ααα 20R 24R-Methylcholestane 0.240 nd - 0.240 nd - nd nd - nd nd - nd nd - STE10 ααα 20S 24R/S-Ethylcholestane nd nd - nd nd - nd nd - nd nd - nd nd - STE11 αββ 20R 24R-Ethylcholestane nd nd - nd nd - nd nd - nd nd - nd nd - STE12 αββ 20S 24R-Ethylcholestane nd nd - nd nd - nd nd - nd nd - nd nd - STE14 ααα 20R 24R-Ethylcholestane 0.080 0.141 1.760 0.080 0.141 1.760 nd nd - nd nd - nd nd - 

methyl-alkanes 

MA01 2-methylnonadecane 0.281 0.023 0.083 0.281 0.023 0.083 0.120 0.130 1.080 0.131 0.079 0.601 0.175 0.060 MA02 3-methylnonadecane nd nd - nd nd - 0.141 0.204 1.449 0.094 0.091 0.970 0.311 0.158 

branched-alkanes 

BA01 pristane 0.630 0.242 0.384 0.630 0.242 0.384 2.649 3.248 1.226 2.398 3.457 1.442 4.720 3.739 BA02 phytane 0.699 0.226 0.324 0.699 0.226 0.324 2.180 2.938 1.348 2.135 2.880 1.349 2.846 2.003 BA03 squalane 0.175 0.317 1.815 0.175 0.317 1.815 0.037 0.022 0.603 0.011 0.016 1.464 0.014 0.018 

cycloalkanes 

CA01 octylcyclohexane nd nd - nd nd - 1.046 0.495 0.473 1.586 0.352 0.222 0.839 0.241 CA02 decylcyclohexane 0.477 0.564 1.181 0.477 0.564 1.181 1.254 0.290 0.232 2.028 0.154 0.076 0.604 0.336 CA03 tridecylcyclohexane nd nd - nd nd - 0.157 0.180 1.149 0.167 0.167 1.001 0.339 0.265 CA04 n-heptadecylcyclohexane 1.660 0.028 0.017 1.660 0.028 0.017 0.190 0.260 1.369 0.125 0.160 1.280 0.138 0.080 CA05 nonadecylcyclohexane 1.440 2.894 2.010 1.440 2.894 2.010 0.068 0.018 0.264 0.036 0.072 2.002 0.014 nd - 

alkene 

AE02 1-octadecene 6.624 0.222 0.034 6.624 0.222 0.034 0.502 0.783 1.560 0.831 0.509 0.612 0.442 0.345 

phthalates 

PH01 dimethylphthalate 0.638 0.011 0.017 0.638 0.011 0.017 1.024 0.012 0.012 0.118 0.007 0.060 0.023 0.207 PH02 diethyl phthalate 1.081 2.172 2.010 1.081 2.172 2.010 0.517 0.858 1.662 0.090 0.379 4.193 0.400 0.015 PH03 di-n-butyl phthalate 3.057 4.341 1.420 3.057 4.341 1.420 0.491 2.292 4.667 0.046 0.036 0.781 0.193 0.023 PH04 butyl benzyl phthalate nd 0.097 - nd 0.097 - nd 0.059 - nd nd - nd nd - PH05 bis(2-ethylhexyl)phthalate 11.605 0.389 0.034 11.605 0.389 0.034 0.151 0.107 0.707 nd nd - 0.367 nd - PH06 di-n-octyl phthalate nd 0.186 - nd 0.186 - nd nd - nd nd - nd nd - nd: not detected 
 

4-1

4. SUMMARY, CONCLUSIONS, AND RECOMMENDATIONS 

Table 4-1 addresses the hypotheses specified in Section 1 with information generated in 

Section 3. Positive OC artifacts occur when VOCs adsorb onto quartz-fiber filters. Negative OC 

artifacts occur when particulate organic compounds evaporate during active sampling. Some of 

these evaporated compounds may also be adsorbed within the quartz-fiber filters. Positive and 

negative artifacts compete with each other, but it appears from blank and backup filters that the 

positive artifact is most often larger than the negative artifact. 

For the IMPROVE network, 959 field blanks acquired at 181 sites during 2005 and 2006 

yield an average positive OC artifact of 8.4 ± 1.6 μg/filter (2.4 ± 0.45 μg/cm2

). For 1,406 quartzfiber backup behind quartz-fiber front filters six non-urban locations, the average positive OC 

artifact was 10.0 ± 5.0 μg/filter. Backup filter averages ranged from 8.1 ± 2.8 μg/filter at 

Chiricahua to 13.1 ± 4.7 μg/filter at Okefenokee. Average backup IMPROVE filters were up to 

19% higher, and more variable, than the field blanks. The difference is within the standard 

deviation of the average, and they could be used interchangeably to adjust for the positive OC 

artifact in the non-urban IMPROVE sites. Since the IMPROVE network also includes urban 

sites (e.g., Washington, DC) where positive and negative artifacts might differ from non-urban 

sites, more spatial coverage on the backup filters is recommended. A systematic protocol to 

acquire field blanks (e.g., once/month at the beginning or end of each month with ~7 days in the 

passive deposition period) would obtain a better record of the seasonal variability than is 

currently provided by the random field blank placement. 

The IMPROVE positive OC artifact is dominated by the OC1, OC2, and OC3 thermal 

fractions. Sectioning of front filters from top to bottom demonstrates that areal densities of these 

OC fractions may decrease with depth through the filter. The assumption that VOC and SVOC 

adsorption on the backup filter equals that on the front filter is not generally met in the 

IMPROVE network, at least for the filters examined here. The causes for the unequal 

distribution are not known, but they could be caused by inhomogeneities in the filter material, as 

deviations from the assumption of complete saturation of the quartz fibers. Analysis of a small 

number of front and backup filters for 130 SVOCs showed higher quantities on the backup filter 

than on the front filter, also consistent with deviations from the saturation assumption. This 
 

4-2

indicates a migration of gSVOC through the filter material with time during sampling, similar to 

the migration of organic compounds through the gas chromatograph during analysis. 

Quartz-fiber behind Teflon-membrane filters showed twice the OC adsorption as quartzfiber behind quartz-fiber front filters at the MARCH-Atlantic urban-scale monitor. Quartz-fiber 

backup behind quartz-fiber front filters showed twice the OC levels of the field blanks, in 

contrast to the similarity between these estimators from the IMPROVE samples. This difference 

could be caused by: 1) larger concentrations of adsorbable VOCs in urban areas, which might 

have deposited or reacted before arriving at remote IMPROVE sites; 2) greater abundances of 

SVOCs at the urban site, which might have largely evaporated from particles during transport; 

and/or 3) a longer residence period for the IMPROVE field blanks in the sampler (~ 7 days) than 

for the MARCH-Atlantic field blanks (~ 3 days). 

The SEARCH network uses an organic carbon denuder upstream of the front and backup 

filters, and backup filter levels are only slightly higher than field blank levels. Since the denuder 

removes most of the VOC and gSVOC atmosphere from the air stream, the backup should 

consist mostly of material evaporated from the front aerosol deposit and be an indication of the 

negative OC artifact. This negative OC artifact may be more prevalent in urban than in nonurban areas. 

The IMPROVE method of adjusting for the OC artifact appears to be the best that can be 

done within the constraints of current understanding. Given the non-urban nature of most 

measurement locations, organic carbon denuders appear to be unnecessary. The negative OC 

artifact appears to be partially compensated for by recapture of material within the bottom half of 

the front filter. The backup filter and field blanks appear to retain approximately that which 

would represent the positive OC artifact. The small exposure area (3.53 cm2

) of the 25 mm filter 

relative to the deposit also makes the artifact correction less important for samples with OC 

levels > 20 μg/filter. 

Urban samples appear to be more complex, owing to the dynamic nature of the aerosol 

both in the atmosphere and once it has been collected on a filter. A denuder/backup filter system 

appears to be the most accurate approach, and SEARCH shows that the backups and field blanks 

are similar with this configuration. Parallel quartz-fiber backup behind Teflon-membrane front 

and quartz-fiber backup behind quartz-fiber front filters offer the opportunity to separate the 

adsorbed VOCs from the evaporated and re-adsorbed gSVOCs. Each of these approaches 
 

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requires more resources in terms of filter handling and analysis. At the least, field blanks should 

spend as much time in the sampling system as the active samples and should be subtracted from 

the carbon measurements with their uncertainties propagated. 
4-4

Table 4-1. Summary of major findings for the seven hypotheses. Hypothesis Major Findings A: Quartz backup filters and field blanks contain the same quantities of adsorbed OC and OC fractions. 

When field blanks have a long exposure times (3 to 7 days) at non-urban IMappears to be true. The six site-averaged OC concentrations on QBQ fall wit

averaged field blank OC across the IMPROVE network. However, the FME OC was be much higher (122%) than field blank OC, and the QBT OC was emay be more heavy VOCs amenable to adsorption and more evaporated SVOThis hypothesis could not be evaluated at the SEARCH sites because the fiel

exposed for 15 minutes, too short to attain equilibrium with the environment

B: Nearly all of the adsorbed organic vapors are in the IMPROVE OC1, OC2, and OC3 fractions.

This is true for field blanks and partially true for backup filters from the IMP

field blanks, carbon mass is almost equally distributed between OC1, OC2, a

filters, however, substantial OC4 and EC fractions (caused by OP; up to 32% observed at SHEN. At SHEN, average backup filter OC was 19% higher than 

and this could be explained by additional SVOC adsorption by backup filters

C: Adsorbed organic gas concentrations are similar among field blanks and backup filters and for different sampling locations, times, and OC aerosol loadings.

Adsorbed OC on backups and field blanks is higher during summer than durat both urban and non-urban sites. There is evidence of month-to-month var

D: Quartz behind Teflon yields the same amounts in carbon fractions as quartz behind quartz.

This is not true for data from the FME urban site that compared side-by-side from a similar experiment at the Fresno Supersite (Watson and Chow, 2002). contained 30-40% higher OC than QBQ, especially for OC2 and OC3. OC3, fractions were also higher, an indication of SVOC adsorption. Data were insthis for the non-urban IMPROVE sites. 
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Table 4-1. Continued. Hypothesis Major Findings E: Front and backup quartz-fiber filters are saturated with adsorbed organic vapors only for high loading samples, and before saturation the front filter captures more SVOC than the backup filter. 

This is not universally true. According to the sliced filter experiment, OC is 

distributed through the depth and width of the filter. The bottom half of QF 

concentration either higher than or similar to those on QBQ filters. The numthese tests were insufficient to determine how homogeneity might be related 

loading. 

F: Analysis of a small number of backup filters can be extrapolated to a large number of samples with appropriate stratification by sampling site, sampling time, and OC loading.

Based on the six IMPROVE network sites with backup filters, the QBQ OC 

vary much. Field blank and backup filter concentrations are similar among dsites with a ratio of the 90th percentile to the 10th percentile TC of ~1.5 for IMblanks. The subtraction of a monthly median determined from backup filters used to correct for the positive organic artifact in IMPROVE seems to be the done with the existing data. Evidence does not support this method at urban data shows QBQ to have even more variability than field blanks. This may bquantities of VOC and SVOC in urban atmospheres that requires active sampbackup filter) for adsorption. Some of the IMPROVE urban sites should incobtain a larger data base, as the currently used method may be less accurate ienvironments. 

G: Adsorbed organic gases are different from organic compounds in the sampled aerosol.

This is not true for the 130 SVOCs analyzed. Concentrations for nearly all 

in the front and backup filters, sometimes with higher concentrations on 

number of samples and compounds quantified is too small to generalize

SVOCs may be in continuous flux, evaporating from one part of the filter on

another part of the filter. This indicates that the equilibrium/saturation 

limited, and that the dynamics of this process needs to be considered in a mo

Filter Abbreviations

QF: Quartz-fiber front filter QBQ: Quartz-fiber backup filter behind quartz fiber front filter VOC: Volatile organic compounds SVOC: Semi-volatile organic compounds gSVOC: Gaseous-phase SVOCs pSVOC: Particle-phase SVOCs pOC: Non-volatile particle-phase organic carbon 

Six IMPROVE sites where secondary filters were collected

MORA: Map (Figure 1-1) location #78 - Mount Rainier NaYOSE: Map location #96 - Yosemite National Park HANC: Map location #48 - Hance Camp at Grand CanyCHIR: Map location #39 - Chiricahua National MonumenSHEN: Map location #6 - Shenandoah National Park OKEF: Map location #16 - Okefenokee National Wildlife R
 

5-1

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