Climatology

Ecology

Biology

Materials science

Levoglucosan

Absorption (acoustics)

Geology

Organic chemistry

Particulates

Environmental chemistry

Biomass (ecology)

Environmental science

Composite material

Aerosol

Chemistry

Seasonality

Atmospheric sciences

Biomass burning

Environmental Science & Technology

Brown carbon (BrC) has recently emerged as an important light-absorbing aerosol. This study provides interannual and seasonal variations in light absorption properties, chemical composition, and sources of water-soluble BrC (WS-BrC) based on PM10 samples collected in Godavari, Nepal, from April 2012 to May 2014. The mass absorption efficiency of WS-BrC at 365 nm (MAE365) shows a clear seasonal variability, with the highest MAE365 of 1.05 ± 0.21 m2 g–1 in premonsoon season and the lowest in monsoon season (0.59 ± 0.16 m2 g–1). The higher MAE365 values in nonmonsoon seasons are associated with fresh biomass burning emissions. This is further substantiated by a strong correlation (r = 0.79, P < 0.01) between Abs365 (light absorption coefficient at 365 nm) and levoglucosan. We found, using fluorescence techniques, that humic-like and protein-like substances are the main chromophores in WS-BrC and responsible for 80.2 ± 4.1% and 19.8 ± 4.1% of the total fluorescence intensity, respectively. BrC contributes to 8.78 ± 3.74% of total light absorption over the 300–700 nm wavelength range. Considering the dominant contribution of biomass burning to BrC over Godavari, this study suggests that reduction in biomass burning emission may be a practical method for climate change mitigation in South Asia.

Water-Soluble Brown Carbon in Atmospheric Aerosols from Godavari (Nepal), a Regional Representative of South Asia