Wintertime ammonium nitrate aerosol pollution in urban areas: NOx and VOC control as mitigation strategies
Abstract
Wintertime particulate matter (PM2.5) pollution remains one of the most significant air quality problems in the US and in parts of Asia, but the chemical mechanisms leading to PM2.5 are still not well understood. Salt Lake City, UT frequently experiences ammonium nitrate aerosol levels in excess of ambient air quality standards, typically during persistent cold air pools (PCAPs). During a PCAP, vertical mixing is largely suppressed and pollutants are concentrated near the surface where they react over the course of many days. The 2017 Utah Winter Fine Particulates Study aimed to develop a better understanding of the chemical mechanisms driving the buildup of ammonium nitrate aerosol so that more effective mitigation strategies may be employed. We will present a photochemical box model that reproduced the buildup of aerosol from emissions of NOx and VOCs in the same way that O3 buildup is typically treated. The key parameter was total Ox (= O3 + NO2 + 2*NO3 + 3*N2O5 + ClNO2 + 1.5*HNO3 + 1.5*NO3-), which is a marker for photochemical nitric acid formation. The model indicates that the Salt Lake Valley is in a NOx-saturated regime, where NOx reductions may initially increase the ammonium nitrate aerosol. Therefore VOC control would be a more effective initial strategy for controlling PM2.5 in the greater Salt Lake region and other valleys with similar PM2.5 pollution.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.A42A..05W
- Keywords:
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- 0305 Aerosols and particles;
- ATMOSPHERIC COMPOSITION AND STRUCTUREDE: 0317 Chemical kinetic and photochemical properties;
- ATMOSPHERIC COMPOSITION AND STRUCTUREDE: 0345 Pollution: urban and regional;
- ATMOSPHERIC COMPOSITION AND STRUCTUREDE: 0365 Troposphere: composition and chemistry;
- ATMOSPHERIC COMPOSITION AND STRUCTURE