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

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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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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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