Absorption Ångström Exponent Values to Identify Light-absorbing Carbonaceous Aerosol Sources in Blantyre, Malawi
Abstract Ambient aerosols, particularly light-absorbing carbonaceous (LAC) particles, which includes black and brown carbon, poses health risks and contributes to global warming. LAC particles emissions in residential areas of Blantyre, Malawi are associated with driving old vehicles, cooking with s...
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| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Springer
2024-09-01
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| Series: | Aerosol and Air Quality Research |
| Subjects: | |
| Online Access: | https://doi.org/10.4209/aaqr.240095 |
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| Summary: | Abstract Ambient aerosols, particularly light-absorbing carbonaceous (LAC) particles, which includes black and brown carbon, poses health risks and contributes to global warming. LAC particles emissions in residential areas of Blantyre, Malawi are associated with driving old vehicles, cooking with solid biofuels, and waste burning. Identifying the sources of ambient LAC aerosols is crucial for informed policymaking. Rather than using costly laboratory methods, we tested the use of the MA200 micro-aethalometer and the resulting Absorption Ångström Exponent (AAE) values to identify LAC aerosols sources. AAE is a parameter reflecting the wavelength-dependent light absorption by particles and typically varies between 1–2. We conducted field experiments to determine the AAE values of local pollution sources. We then verified the use of derived AAE to identify the LAC particles sources by mobile and personal monitoring in the areas with known dominant air pollution sources. The AAE470/880 of fossil-fuel-related emission (AAEff) (vehicular emissions: 1.07 ± 0.14, plastics burning: 1.30 ± 0.08, synthetic textiles burning: 1.17 ± 0.05) were closer to 1 while those of biomass-based emission (AAEbb) (garden waste burning: 1.92 ± 0.10, cardboard and paper burning: 1.90 ± 0.45, cooking using firewood: 1.78 ± 0.04) were closer to 2. When comparing the AAEff with AAEbb, a p-value of < 0.01 suggested statistical dissimilarity. The results were used to propose ranges of AAE470/880 corresponding to the predominant LAC source: < 1.29 for fossil-fuels, > 1.63 for biomass, and 1.29–1.63 for the mix of two. The mobile and personal monitoring results supported these ranges, showing AAE values < 1.29 on busy roads and > 1.63 in areas where cooking or biomass-burning occurred. This study highlighted the utility of AAE in differentiating between fossil-fuel and biomass-based sources of LAC particles in Malawi. However, contextual knowledge is required to identify the specific combustion source. This simple approach provides a low-cost alternative to expensive techniques and could be applied in similar contexts. |
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| ISSN: | 1680-8584 2071-1409 |