Water-borne transportation plays an important role in the economic and social development and contributes greatly to air pollution in China as well. An effective regulating policy is dependent on accurate estimation in terms of sorts, quantification and location of emissions. However, there is insufficient real and reliable data source for China's marine diesel engines and vessels. In order to employ fuel-based approach and ship activity-based approach to estimate accurately the exhaust emissions from water-borne transportation sector in China, emission factors of different types of marine diesel engines were investigated. Based on statistical analysis on Parent Engine emission test reports of 76 and 113 marine diesel engines manufactured by China's engine makers in accordance with IMO NOx TierⅠ and TierⅡ standards respectively as defined in MARPOL(International Convention for the Prevention of Pollution from Ships) Annex VI, abnormal data were statistically identified and eliminated by Grubbs' criterion method, fuel-based emission factors and energy-based emission factors of NOx, CO, HC and CO2 for 2-Stroke main engines, 4-Stroke main engines and 4-Stroke auxiliary engines were determined respectively. The results showed that fuel-based emission factors of NOx, CO, HC and CO2 for different types of marine diesel engines were 30.67-76.55, 3.01-6.13, 1.25-2.24 and 3141.15-3165.63 kg·t-1 respectively. Energy-based emission factors of NOx, CO, HC and CO2 for different types of marine diesel engines were 6.83-13.64, 0.61-1.35, 0.21-0.50 and 534.04-745.18 g·(kW·h)-1 respectively. In addition, the relationships of energy-based emission factors against engine load were expressed by power function or quadratic polynomial and the algorithm coefficients were determined. In addition, it is difficult to obtain the true emission levels of marine diesel engines in China through simple modification of emission factors reported by foreign institutes. In particular,considering the diversity of diesel engines onboard China's coastal and inland vessels, more samples and tests in terms of types and operational conditions are necessary to provide basic data for marine emission inventories in China. The results could provide applicable data for estimation of marine emissions in China.
Keywords: energy-based emission factor; exhaust emissions; fuel-based emission factor; marine diesel engine; water-borne transportation.