Alexander torres tami bond advisor christopher lehmann co advisor october 26 2011
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Evaluation of Methods for Measuring Carbonaceous Aerosol in Rainwater PowerPoint PPT Presentation

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Alexander Torres Tami Bond , Advisor Christopher Lehmann , Co-advisor October 26, 2011. University of Illinois at Urbana-Champaign Civil and Environmental Engineering NADP Annual Meeting and Scientific Symposium. Evaluation of Methods for Measuring Carbonaceous Aerosol in Rainwater.

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Evaluation of Methods for Measuring Carbonaceous Aerosol in Rainwater

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Alexander Torres

Tami Bond, Advisor

Christopher Lehmann, Co-advisor

October 26, 2011

University of Illinois at Urbana-Champaign

Civil and Environmental Engineering

NADP Annual Meeting and Scientific Symposium

Evaluation of Methods for Measuring Carbonaceous Aerosol in Rainwater

Carbonaceous Aerosol

  • Black Carbon (BC)

    • Byproduct of the incomplete combustion of fossil fuels and biomass

    • Absorbs visible light and warms the atmosphere

    • 85% of the emitted mass is in particles < 0.2 µm diameter

    • Atmospheric concentrations range:

      • 0.2 to 2.0 µg/m3(rural)

      • 1.5 to 10 µg/m3 (urban)

BC particles collected on a Millipore filter

Diesel engines: high emitter

Carbonaceous Aerosol

  • Organic Carbon (OC)

    • Primary sources:

      • Combustion of fuels and biomass

      • Commercial products

      • Biogenic material

    • Secondary Source:

      • Oxidation of VOCs

    • Atmospheric concentrations range:

      • ~3.5 µg/m3 (rural)

      • 5 to 20 µg/m3 (urban)

    • Reflect light and coolthe atmosphere

OC particles collected on a Millipore filter

Fireplace: high emitter

Wet Deposition (WD) of Carbon Aerosols

  • Importance of the study:

    • WD is the most uncertain parameters in global circulation modeling of carbonaceous aerosols

    • Carbon particles comprises 25-70% of PM2.5 in USA

    • Measurements of OC and BC together are limited

    • Removal rates of OC and BC are different (70% of OC and 10% of BC is water soluble)

    • High variability in the reported BC lifetime: 40 hours to 1 month

Objectives of the study

  • Evaluate different analytical techniques to measure particulate and dissolved carbon in rain

  • Measure concentration of BC and OC in rain

  • Match precipitation data with atmospheric concentration which yields insights into BC and OC removal

Bondville Environmental and Atmospheric Research Station, IL

Analytical Approach

Rain Sample

Rain Sample


Dissolved Carbon

Particulate Carbon

Quartz Fiber Filters

Particulate Organic Carbon

Black Carbon

Dissolved Organic Carbon


Organic Carbon

Black Carbon: Analytical Method

  • Thermal-Optical Method (OC-EC Analyzer)

    • Measures particulate OC and BC

    • Samples are collected on a quartz fiber filter

    • Temperature ramps are used to desorb OC (O2-free environment) and BC (O2/He environment) and converted to CO2

    • Light absorbance is used to separate OC and BC

Quartz fiber membrane

OC-EC Aerosol Analyzer, Sunset Laboratory

Black Carbon: Method Limitations

  • Experimental limitations

    • BC particles (in water) are too small to be collected on quartz fiber filters

    • Large biogenic material interferes with the analysis

    • BC concentration in rain is too low to be detected using 45 mm filters.

Nuclepore filter (8 µm pore size)

Black Carbon: Method Improvement

  • Work-around

    • Pre filtration of the sample is necessary to remove biogenic material

    • Filtration area has to be reduced to get a low detection limit (140 ng/L)

    • Addition of a ionic compound is necessary to induce the BC particles agglomeration

Funnel with fritted glass disk

(~ 50 µm pore size)

Small filtration device

(filtration area= 0.7 cm2)

Adding 3 drops of H3PO4 (25% v/v)

Adding 1 g of (NH4)2SO4 / 100 mL

Filtration Setup

Black Carbon: Method Improvement

  • Collection efficiency of the quartz fiber filter after adding a ionic compound

No addition

Black Carbon: Method Improvement

  • Determination of the optimum amount of (NH4)2SO4 to be added to the rain sample

0.5 g

Dissolved Organic Carbon (DOC): Analytical Method

  • Total Organic Carbon (“TOC”) Analyzer

    • Combustion catalytic oxidation method

    • Low detection limit (4 µg/L)

  • Limitations

    • Requires 30 mL of sample

    • Susceptibility of the analysis to contamination

  • Work-around

    • Use rain samples with large volume

    • Use nitric acid bath for 24 hours and/or muffling at 450°C for 5 hours

Shimadzu TOC 5000 Carbon Analyzer

Dissolved Organic Carbon:Preliminary Results

  • Comparison of the monthly mean concentration of DOC in rain vs. historical record of OC in air measured at Bondville, IL.

Dissolved Organic Carbon:Preliminary Results

  • Comparison of the measured DOC vs. concentration of ions in precipitation

Dissolved Organic Carbon:Preliminary Results

  • Mean mass fraction of DOC in precipitation measured at Bondville, IL

Dissolved Organic Carbon:Preliminary Results

  • Comparison of the DOC measurements vs. Ion Percent Difference (IPD)

… an Indicator of the “missing” anions in the CAL’s measurements


  • Sampling of particulate BC and OC in rain employing quartz fiber membranes requires the reduction of the filtration area and the addition of a “salt”

  • Adding ionic compounds stimulates the BC particles interaction and agglomeration

  • Pre filtration, decontamination, and proper handling and conservation of rain samples is required to avoid contamination with OC

  • DOC in rain correlates with SO42-, NO3-, and Total Ions.

  • Organic compounds contributes to the ion balance of rain samples.


  • Illinois State Water Survey (National Atmospheric Deposition Program)

  • EPA STAR Fellowship Program

  • University of Puerto Rico at Mayaguez (UPRM)

  • Tami Bond research group at UIUC (

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