Rapidly increasing ethanol concentrations in rainwater and air

• Published in: NPJ climate and atmospheric science 2019-01, Vol.2 (1), Article 3
• Main Authors: Willey, Joan D., Avery, G. Brooks, Felix, J. David, Kieber, Robert J., Mead, Ralph N., Shimizu, Megumi S.
• Format: Article
• Language: English
• Subjects: 704/172/169/824; 704/47; Acetaldehyde; Air pollution; Air quality; Alkenes; Atmosphere; Atmospheric Protection/Air Quality Control/Air Pollution; Atmospheric Sciences; Biodiesel fuels; Biofuels; Biomass; Climate Change/Climate Change Impacts; Climatology; Combustion; Earth and Environmental Science; Earth Sciences; Emissions; Environmental impact; Ethanol; Fuels; Greenhouse effect; Greenhouse gases; Hydroxyl radicals; Oxidation; Peroxyacetyl nitrate; Photochemicals; Rain; Rain water; Sinkholes; Vapor phases; Water pollution
• ISSN: 2397-3722; 2397-3722
• DOI: 10.1038/s41612-018-0059-z

Rainwater and gas phase ethanol concentrations increased approximately fourfold between 2010 and 2017 in Wilmington, NC, USA. This 8-year study demonstrates that the gas phase and rainwater concentrations of ethanol have risen due to increased production and use of ethanol as a biofuel. Rainwater ethanol concentrations are close to equilibrium with local atmospheric gas phase concentrations and have increased in proportion to increased air concentrations. Ethanol emissions are important because they impact the oxidizing capacity of the atmosphere due to the reactivity of the alcohol towards hydroxyl radical. Gas phase ethanol contributes to air pollution through oxidation to acetaldehyde, with subsequent production of ozone, and in high NO x regions production of peroxyacetyl nitrate (PAN). However, combustion of ethanol can also lower emissions of acetaldehyde precursors such as alkenes, suggesting that the potential impact of ethanol combustion is complex. The large increase in the concentration of ethanol in both the gas and condensed phases indicates that existing sinks are not sufficient to remove the excess alcohol being added to the atmosphere from biofuel use. This suggests that the projected growth of ethanol as a biofuel will result in considerable increases in atmospheric concentrations within the next few years with direct ramifications on a host of fundamentally important atmospheric processes. Atmospheric science: ethanol increases Concentrations of ethanol have increased in both rain water and the atmosphere due to the use of ethanol biofuels. Biofuel use has doubled in the past decade as a means to reduce transport-related greenhouse gas emissions. However, the corresponding impact on ethanol sources and sinks remains largely unquantified. Joan Willey from the University of North Carolina Wilmington, and colleagues, investigate these changes using a unique record of rainwater and atmospheric ethanol concentrations from Wilmington, NC. From 2010 to 2017, atmospheric and rainwater ethanol concentrations have increased fourfold, suggesting current sinks are insufficient in removing ethanol at the rate at which it is being added, impacting air quality and other atmospheric processes. As ethanol concentrations are projected to increase further through the continued expansion of biofuels, more work is needed to fully examine their environmental impacts.