[Organic and element carbon in foliar smoke]

Area of Science:

• Environmental Chemistry
• Atmospheric Science
• Combustion Science

Background:

• Foliar smoke is a significant source of atmospheric carbonaceous aerosols.
• Understanding the composition of foliar smoke is crucial for air quality modeling and climate studies.
• Previous research has not fully characterized the organic and elemental carbon fractions under different combustion regimes.

Purpose of the Study:

• To investigate the mass fractions and distribution of Organic Carbon (OC) and Elemental Carbon (EC) in foliar smoke.
• To compare the carbonaceous composition of foliar smoke generated under flaming versus smoldering conditions.
• To determine emission factors (EF) for particulate matter, OC, and EC from burning green leaves.

Main Methods:

• A custom combustion and sampling apparatus was used to burn green leaves.
• Smoke was collected and analyzed using an Organic/Elemental Carbon (OC/EC) Analyzer with the IMPROVE thermal-optical reflectance (TOR) method.
• Mass fractions, carbon fraction distributions, and emission factors were quantified.

Main Results:

• Smoldering foliar smoke showed higher mean OC (48.9%) and OC/EC ratios (11.5) compared to flaming smoke (OC 44.9%, OC/EC 4.8).
• Flaming conditions yielded higher mean EC (10.9%) and char-EC (10.7%) mass fractions.
• Emission factors for particulate matter, OC, and EC differed significantly between smoldering and flaming combustion.

Conclusions:

• Foliar smoke composition, particularly OC and EC fractions, is highly dependent on combustion conditions (smoldering vs. flaming).
• Smoldering conditions favor higher OC content and OC1/OC2 ratios, while flaming conditions lead to greater char-EC and char-EC/soot-EC ratios.
• The carbonaceous composition of foliar smoke varies by tree species and combustion type, differing notably from other biomass smoke.