2012 Progress Report: Development and Deployment of an Instrumentation Suite for Comprehensive Air Quality Characterization Including Aerosol ROS

EPA Grant Number: R834799C001
Subproject: this is subproject number 001 , established and managed by the Center Director under grant R834799
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).

Center: The Southeastern Center for Air Pollution and Epidemiology: Multiscale Measurements and Modeling of Mixtures
Center Director: Tolbert, Paige
Title: Development and Deployment of an Instrumentation Suite for Comprehensive Air Quality Characterization Including Aerosol ROS
Investigators: Weber, Rodney J. , Bergin, Michael , Mulholland, James , Nenes, Athanasios , Sarnat, Stefanie Ebelt , Sarnat, Jeremy , Strickland, Matthew J
Institution: Georgia Institute of Technology , Emory University
Current Institution: Georgia Institute of Technology , Duke University , Emory University , University of Nevada - Reno
EPA Project Officer: Chung, Serena
Project Period: January 1, 2011 through December 31, 2016
Project Period Covered by this Report: August 1, 2011 through July 31,2012
RFA: Clean Air Research Centers (2009) RFA Text |  Recipients Lists
Research Category: Health Effects , Air


To provide a chemically comprehensive data set on ambient particle composition at various sites relative to roadway emissions that will be used by other SCAPE Projects. As a part of this effort, our goal is to develop new instruments and analytical methods to quantify concentrations of particle-bound reactive oxygen species (ROS) and the ability of aerosols to catalyze the production of ROS through interactions with antioxidants to determine their sources.

Progress Summary:

1. Design and testing of the particle-bound ROS system: Construction of an ambient ROS instrument to be extensively deployed during SCAPE was completed during this reporting period. The system is based on collection of total (gas + particle) ROS and gas ROS by a mist chamber scrubber. Particle ROS is determined by difference. This method was chosen following tests that showed gas phase ROS concentrations were substantially higher than particle phase (factor of 10 or so), and no suitable coating was found for effective gas denuding. This makes exclusive particle collection systems (e.g., PILS) susceptible to substantial positive bias due to artifacts from gas interferences. In addition to the particle collection system, the ROS analytical method was finalized and was based on a syringe pump system with external mixing vial. This was a change from the original design based on mixing within the mist chamber, which experiments showed led to substantial chemical contamination due to carry-over between successive mist-chamber sample runs. This instrument underwent trial testing in February 2012 and to date has been running for two months as part of the SCAPE Project 1 field sampling. Continued refinements are being made to the instrument. 


2. Assessment of ACSM performance through two ambient inter-comparisons studies: An Aerodyne Inc. Aerosol Chemical Speciation Monitor (ACSM) was purchased for deployment during SCAPE to measure particle composition. As this is a relatively new instrument, an assessment of the instrument’s quantitative performance during two seasons (August 2011, February 2012) was undertaken through comparisons with other online aerosol composition monitors (i.e., PILS-IC for anions/cations, Sunset Labs OCEC for organic matter). The results showed significant discrepancies existed and that these differences change under different sampling conditions (seasons). Part of this is due to the ACSM measuring PM1.0, whereas all other instruments measure PM2.5, as per EPA standards. Other factors are related to variability in the AMS collection/measurement efficiency. The results of these tests suggest that the ACSM data will need to be checked and possibly scaled to other traditional measures of aerosol composition when deployed during SCAPE. A poster on this topic will be presented at the Oct 2012 AAAR conference (Kotra et al., 2012). Selected results are also included in a paper currently under review (Verma et al., 2012). 


3. Development of a ROS system for quantifying the ability of particles to catalyze ROS production based on the DTT assay: Following suggestions from SCAPE’s Science Advisory Committee, an additional ROS analytical system was developed and tested. In contrast to the online particle-bound ROS system described in Part 1 above, this instrument was designed for analysis of filter extracts. This acellular assay, in contrast to the particle-bound measurement, quantifies the ability of particles to generate ROS by interactions with antioxidants and is based on the dithiothreitol (DTT) assay. Substantial effort was required to develop and verify a DTT ROS measurement protocol. The method was extended from published approaches to include analysis of methanol filter extracts (i.e., non-water soluble species) and the hydrophobic and hydrophilic organic aerosol sub-fractions of both water and methanol filter extracts. As a preliminary study prior to our intensive SCAPE sampling, filters collected at the Jefferson Street SEARCH site (JST) during January-February 2012 were analyzed. The results are summarized in a manuscript submitted to Environmental Science and Technology (Verma et al., 2012) and will be presented at the October 2012 AAAR conference (Verma et al., 2012).

a. Key findings from this study include: Methanol filter extracts, which include water-insoluble and some fraction of the water-soluble aerosol components, have substantially higher PM2.5 mass-normalized DTT activity relative to water-soluble extracts. Thus, there are insoluble aerosol species that are DTT active. A correlation analysis indicated that the DTT activity of both extracted fractions were linked to organic species since the methanol extracted DTT activity was correlated with the water-insoluble organic carbon mass fraction, whereas the water-soluble DTT activity was correlated with the water-soluble organic carbon mass fractions. Overall, these results demonstrate the importance of both insoluble and soluble organics as potential aerosol toxic species through their ability to generate ROS. Further identification of possible DTT active organic species responsible for this potential toxicity was assessed through the isolation of hydrophobic and hydrophilic fractions. For both extracts (i.e., methanol or water extracts) the hydrophobic fraction (based on separation via C-18 SPE column) contained compounds that were the most DTT active. This result is consistent with aromatic compounds being exclusively associated with the hydrophobic fraction, which includes PAHs and quinones, both thought to be toxic through their ability to participate in REDOX reactions. For the water-soluble extract, however, additional soluble organics other than aromatics appear to be DTT active either by themselves or associated with some other component (e.g., possible organic-metal complex) since a non-trivial component of the overall DTT activity was associated with hydrophilic organics.

b. Since extensive DTT analysis of Project 1 filters is now planned, construction of an automated DTT analytical system was undertaken during this performance period. Equipment has been purchased (see section 4 below) and construction and testing of a DTT-ROS analytical system for high filter sample throughput has been undertaken. It is anticipated that this analysis system will be an integral part of Project 1 and Project 2. 


4. Start of Project 1 Ambient Sampling Program: The main goal of Project 1 is to provide roughly two years of detailed ambient aerosol characterization. An existing Georgia Tech sampling trailer was acquired and retrofitted this spring to serve as our mobile sampling platform. The table below lists the various instruments deployed in the paired sites (fixed site and satellite site). In addition to the preliminary January-February 2012 deployments. Two months of Project 1 paired measurements have been completed (JST fixed site and trailer co-located at JST; JST fixed site and trailer at Yorkville SEARCH site (YRK)). Preparations for near-road and road-side deployments are underway. 


List of instruments installed and operation at the Jefferson  Street (JST) fixed site and the mobile trailer site


Trailer (Satellite) Site

Jefferson Street (Fixed Site)

Met Station

Met Station*

TEOM (PM2.5)

TEOM (PM2.5)

Compact OPC (PM2.5,PM10)

Compact OPC (PM2.5,PM10)

OCEC (Sunset labs)

TC (Sunset labs)*

BC (7 lambda aeth.)


WSOC and brown carbon

WSOC and brown carbon



ROS-DCFH (total, gas)


SMPS (size dist.)

SMPS (size dist.)




NOx *

High Volume Sampler

High Volume Sampler

2-Channel Filters (PCM)

2-Channel Filters (PCM)

VOC Whole Air Canisters

VOC Whole Air Canisters

*Instruments/data as part of SEARCH network.


Future Activities:

  1. Continue extensive field measurements with a suite of instruments at paired sites, including JST as the main site and satellite sites (trailer-based measurements) at YRK, near-roadside and roadside. Three weeks of measurements will also be conducted in other cities: St. Louis and Birmingham.
  2. Determine the importance of particle-bound ROS (e.g., typical ambient concentrations).
  3. Perform extensive measurements of ROS oxidative potential via DTT assay on various filter extracts to determine specific groups of organic species responsible for toxicity. Also, determine if water-soluble redox active metals and hydrophobic organics (e.g., HULIS) synergistically combine to produce more ROS then either species alone based on authentic ambient aerosols.
  4. Explore other possible cellular assays on a limited set of filters for comparison with acellular particle-bound ROS and DTT-ROS.
  5. Present results at meetings and prepare and publish manuscripts.


Journal Articles on this Report : 1 Displayed | Download in RIS Format

Other subproject views: All 62 publications 17 publications in selected types All 17 journal articles
Other center views: All 334 publications 136 publications in selected types All 132 journal articles
Type Citation Sub Project Document Sources
Journal Article Verma V, Rico-Martinez R, Kotra N, King L, Liu J, Snell TW, Weber RJ. Contribution of water-soluble and insoluble components and their hydrophobic/hydrophilic subfractions to the reactive oxygen species-generating potential of fine ambient aerosols. Environmental Science & Technology 2012;46(20):11384-11392. R834799 (2012)
R834799 (2013)
R834799 (2014)
R834799 (2015)
R834799 (2016)
R834799 (Final)
R834799C001 (2012)
R834799C001 (2013)
R834799C001 (2014)
R834799C001 (2015)
R834799C001 (Final)
  • Abstract from PubMed
  • Full-text: ES&T-Full Text PDF
  • Abstract: ES&T-Abstract
  • Other: ResearchGate-Full Text PDF
  • Supplemental Keywords:

    reactive oxygen species, ROS, oxidative stress, oxidative potential , Health, Scientific Discipline, Health Risk Assessment, Risk Assessments, Biochemistry, Environmental Monitoring, children's health, particulate matter, ambient air monitoring, climate change, air pollution, airshed modeling, ambient particle health effects, human health risk

    Relevant Websites:

    Southeastern Center for Air Pollution & Epidemiology - Emory/Georgia Tech EPA Clean Air Research Center Exit

    Progress and Final Reports:

    Original Abstract
  • 2011
  • 2013 Progress Report
  • 2014 Progress Report
  • 2015 Progress Report
  • Final Report

  • Main Center Abstract and Reports:

    R834799    The Southeastern Center for Air Pollution and Epidemiology: Multiscale Measurements and Modeling of Mixtures

    Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
    R834799C001 Development and Deployment of an Instrumentation Suite for Comprehensive Air Quality Characterization Including Aerosol ROS
    R834799C002 Examining In-Vehicle Pollution and Oxidative Stress in a Cohort of Daily Commuters
    R834799C003 Novel Estimates of Pollutant Mixtures and Pediatric Health in Two Birth Cohorts
    R834799C004 A Multi-City Time-Series Study of Pollutant Mixtures and Acute Morbidity