Using the Multicomponent Aerosol FORmation Model (MAFOR) to Determine Improved VOC Emission Factors in Ship Plumes
Lea Fink1, Matthias Karl1, Volker Matthias1
1Helmholtz-Zentrum Hereon, Department of Coastal Environmental Chemistry, 21052 Geesthacht, Germany.
Toxics
|June 26, 2024
Summary
International shipping emissions significantly impact air quality. Adjusting volatile organic compound (VOC) emission factors for ships, particularly for low-volatility compounds, improves air quality models and reveals potential PM2.5 changes.
Area of Science:
- Atmospheric Chemistry
- Environmental Science
- Marine Pollution
Background:
- International shipping contributes significantly to global anthropogenic emissions, including particulate matter (PM).
- Ship emissions of volatile organic compounds (VOCs) are crucial precursors to secondary fine particulate matter (PM2.5) formation.
- Understanding the impact of VOC emission factors (EF) on PM2.5 is vital for air quality assessments.
Purpose of the Study:
- To investigate the influence of varying VOC emission factors for ship engines on secondary PM2.5 formation in ship exhaust plumes.
- To refine aerosol box models by adjusting VOC EFs to match observed particle number size distributions.
- To assess the regional impact of adjusted VOC ship emissions on PM2.5 concentrations over the Mediterranean Sea using a chemistry transport model (CTM).
Main Methods:
- Utilized an aerosol box model for near-plume scale simulations of ship exhaust.
- Adjusted VOC emission factors, focusing on intermediate-, low-, and extremely low-volatility compounds.
- Integrated near-plume model results into a regional-scale chemistry transport model (CTM).
Main Results:
- Agreement between measured and modeled particle number size distributions improved significantly with adjusted VOC EFs.
- The study found that the VOC EF needed to be scaled by a factor of 3.6 compared to literature values.
- Regional CTM simulations showed up to a 5% change in PM2.5 concentrations along major shipping routes and near harbor cities during summer.
Conclusions:
- Adjusting VOC emission factors, especially for low-volatility compounds, is crucial for accurate modeling of secondary PM2.5 from ship emissions.
- While regional impacts can be noticeable (up to 5%), the overall effect of VOC EF changes on PM2.5 is moderated by rapid dilution in larger CTM grid cells.
- This research highlights the importance of accurate VOC emission data for ship pollution and its contribution to atmospheric particulate matter.
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