2008 年 43 巻 6 号 p. 934-937
The International Maritime Organization (IMO) is working for the further advancement of regulation in NOx emission reduction for ship's diesel engines. As for Tier III, which is assumed to be entering into force in 2015, two proposals were discussed at the 11th meeting of BLG Subcommittee in February 2008. One was a uniform regulation over the world with 40% to 50% reduction from the Tier I regulations. The other was a geographically controlled regulation with an 80%, or higher, reduction for a designated area. Tier II level for others are applied. In the present study, a simple diffusion model is employed to estimate the NOx concentration over the land area for the case that each regulation is applied. Simulation studies have revealed that an appropriate distance given as the boundary in the geographical regulation could reduce the NOx concentration over a land area, to a comparable level as the uniform regulation can be estimated to achieve.