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Regional air quality impacts of ship emissions from megaports in the Yangtze River Delta, China, and in Northern Europe

Subject Area Atmospheric Science
Term from 2018 to 2023
Project identifier Deutsche Forschungsgemeinschaft (DFG) - Project number 392026931
 
Final Report Year 2023

Final Report Abstract

In ShipCHEM for the first time the impact of shipping emissions on air quality in Europe and China was investigated in a harmonized way with the same set of model systems. For this purpose, the Modular Ship Emission model System (MoSES) was developed and applied to calculate ship emissions for 2015 based on ship position data, technical ship specifications and most recent emission factors. The ship emission data was combined with other land based emission data and then fed into the regional scale chemistry transport modeling (CTM) system CMAQ. The CTM results showed that shipping contributes significantly to increased NO2 and PM2.5 concentrations in coastal areas with higher absolute contributions in China compared to Europe. However, in Europe shipping has a higher share in the air pollutant concentrations levels, because of the typically cleaner air in Europe. MoSES can also be used to generate future emission scenarios for investigating changes in the ship fleet, ship fuels in use and exhaust gas abatement technologies. Small scale model studies about the dispersion of ship exhaust in the vicinity of large ships revealed a significant downward dispersion behind the ship caused by the obstacle effect. A parameterization was developed that can be used for an improved representation of the vertical ship exhaust distribution in approx. 100 m behind the ship. The formula considers meteorological conditions as well as exhaust gas specifications. In an urban scale model application, it was shown that simulated concentration levels in 1 – 2 km distance to the ship depend highly on the consideration of the downward dispersion. Much higher ground level pollutant concentrations resulting from ship emissions must be expected in short distances from the ship, even when the ship has a high stack. This indicates that better results for ground level air pollutant concentrations can be achieved with urban sale chemistry transport models when the ship plume parameterization scheme is applied. Shipping can be the dominating source of air pollutants in big harbor cities. Results of both model studies help to better quantify this impact of shipping emissions in coastal areas and specifically in megaports. Consequently, measures to reduce air pollution in cities can be better planned and justified, e.g. the construction of onshore power supply units that provide electricity for ships at berth. In addition, the results from future ship emission scenarios contribute to decisions about the use of new fuels with much lower greenhouse gas emissions in shipping. Some of these fuels may still contribute to air pollution, e.g. ammonia. The effectiveness of exhaust gas aftertreatment systems and of new regulations, e.g. on NOx emissions from shipping, can be quantified.

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