Study on ship emissions and its impact to air quality in Hong Kong

Abstract

Hong Kong is one of the busiest ports in the world, but it is lacking in sophisticated maritime emission inventory and air quality assessment inside or near the port area. Most of the shipping activities in Hong Kong waters occur within a couple of kilometers from the community, and the emissions from ships may cause adverse health effects on the public. The current research focuses on two areas: (i) developing emission inventory on ocean-going vessels (OGVs) and (ii) investigating the contribution of ship emission to the air quality of a community near the international container port. The speed profiles of vessels on different shipping routes in Hong Kong waters were determined with Automatic Identification System. Compared with the emissions estimated using the speed limits of control zones, the ship emissions estimated using vessel speed profiles could provide results with up to 88% higher accuracy. Uncertainty analysis and sensitivity of the model demonstrated the significance of improvement of vessel speed resolution. The vessel speed profiles derived were applied to the ship emission estimation. Based on maritime emission inventory developed with activity-based approach in the current study, the total ship emissions from OGVs in 2007 were 17097, 8190, and 1035 tonnes accounting for 17%, 11%, and 16% of total emissions of NOx, SO₂, and PM₁₀ in Hong Kong, respectively. From the emission spatial allocation, the shipping route along the East Lamma Channel and the berthing location of the Kwai Chung and Tsing Yi Container Port were the regions with the highest emissions. The OGV emissions in Hong Kong contributed 0.07% NOx, 0.05% SO₂, and 0.06% PM₁₀ out of the global total shipping emissions in 2007. Fine particulates (PM₂.₅) was collected near the Kwai Chung and Tsing Yi Container Terminals (KTCT) during the two study periods, i.e., (1) 14 August to 2 October 2009 for summer and (2) 26 January to 1 March 2010 for winter. The average PM₂.₅ concentration was 30.5 μg/m³. The chemical composition of the PM₂.₅ collected was characterized. The dominant species was determined to be sulfate (34%), followed by organic matter (19%) and elemental carbon (12%). The major PM₂.₅ sources, with particular emphasis on those associated with ship emissions, were identified using positive matrix factorization (PMF). The emissions of residual oil combustion and marine diesel oil combustion from ship engines contributed 12% (3.6 μg/m³) and 7% (2.3 μg/m³) of the total PM₂.₅ in the area near KTCT. The secondary sulfate associated with ship emission was determined, and its contribution to PM₂.₅ was 6% (1.8 μg/m³). Together with the primary ship emissions, the total ambient PM₂.₅ mass associated with ship emissions at the sampling site was 7.6 μg/m³ (25%).