Biomass burning declines lead to large net reductions in NO2 concentrations over north equatorial Africa in spite of growing fossil fuel emissions
Abstract
Socio-economic development in low and middle-income countries has been accompanied by increased emissions of air pollutants such as nitrogen oxides (NOx: nitrogen dioxide (NO2) + nitric oxide (NO)), which affect human health. In sub-Saharan Africa, fossil fuel combustion has nearly doubled since 2000. At the same time, biomass burning—another important NOx source—has declined in Africa's northern biomass burning region, attributed to changes in climate and anthropogenic fire management associated with agricultural development. However, the effects of this contrasting trends in emissions have not been evaluated. Here we use observations of tropospheric NO2 vertical column densities (VCDs) from the Ozone Monitoring Instrument and burned area from the Global Fire Emissions Database version 4s to identify NO2 trends and drivers over Africa. Across the three northern ecoregions in Africa where biomass burning occurs—home to 400 million people—mean annual tropospheric NO2 VCDs decreased by 7.5 ± 5.0%, 17.6 ± 5.8%, and 11.3 ± 12.2% over 2005 to 2017. Reductions in burned area explained the majority of the decrease. A residual trend not explained by our burned area-based model is largely negative and largely restricted to the biomass burning season, suggesting that increasing fossil fuel emissions were small relative to declining biomass burning emissions. Negative spatial correlations between NO2VCDs and population density in the northern fire region confirm that anthropogenic fire management at higher population densities reduces overall emissions. In contrast to the widely-held perception that socio-economic development worsens air quality in low and middle-income nations, our results suggest that many African countries are following a fundamentally different pathway, resulting in regional air quality benefits. However, these benefits may be lost with increasing fossil fuel use.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.A13D..01H
- Keywords:
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- 0305 Aerosols and particles;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0322 Constituent sources and sinks;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0345 Pollution: urban and regional;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0365 Troposphere: composition and chemistry;
- ATMOSPHERIC COMPOSITION AND STRUCTURE