Correlation between Graphitic Carbon and Elemental Carbon in Diesel Particulate Matter in Workplace Atmospheres

Area of Science:

• Environmental Science
• Analytical Chemistry
• Occupational Health

Background:

• Diesel particulate matter (DPM) contains elemental carbon (EC), a key component of air pollution.
• Accurate measurement of EC is crucial for assessing workplace exposure and health risks.
• Traditional EC measurement methods can be time-consuming and require laboratory analysis.

Purpose of the Study:

• To evaluate graphitic carbon (GC) measured by Raman spectroscopy as a surrogate for elemental carbon (EC) in diesel particulate matter (DPM).
• To assess the feasibility of using portable Raman spectrometry for onsite EC determination in workplace aerosols.
• To establish a calibration method for GC-based EC estimation.

Main Methods:

• Raman spectroscopy was employed to quantify graphitic carbon (GC) in DPM, analyzing D and G modes.
• Certified DPM standards, engine exhaust soot, and workplace aerosols were analyzed.
• A calibration curve was developed correlating GC measurements with EC concentrations determined by NIOSH Method 5040.
• GC-EC estimates were compared with traditional EC measurements.

Main Results:

• GC quantification using Raman spectroscopy showed low uncertainty (6.0-6.9%) across various aerosol types.
• A strong agreement was observed between GC-based EC estimates and NIOSH Method 5040 results for filter loadings below 2.86 microg/cm².
• The study demonstrated the potential of GC as a surrogate for EC in DPM.

Conclusions:

• Graphitic carbon (GC) measured by Raman spectroscopy is a suitable surrogate for elemental carbon (EC) in diesel particulate matter (DPM).
• Portable Raman spectrometers can enable rapid, onsite assessment of EC in workplace environments.
• Appropriate sample collection is essential to avoid high filter mass loadings for accurate results.