Alexander torres tami bond advisor christopher lehmann co advisor october 26 2011
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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

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

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 aerosol1

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

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

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

Analytical Approach

Rain Sample

Rain Sample

Pre-filtration

Dissolved Carbon

Particulate Carbon

Quartz Fiber Filters

Particulate Organic Carbon

Black Carbon

Dissolved Organic Carbon

Dissolved

Organic Carbon


Black carbon analytical method

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

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

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 improvement1

Black Carbon: Method Improvement

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

No addition


Black carbon method improvement2

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

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

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 results1

Dissolved Organic Carbon:Preliminary Results

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


Dissolved organic carbon preliminary results2

Dissolved Organic Carbon:Preliminary Results

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


Dissolved organic carbon preliminary results3

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


Conclusions

Conclusions

  • 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.


Acknowledgments

Acknowledgments

  • 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 (http://hiwater.org/)


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