Abstract
Abstract. The North Sea is one of the areas with the highest ship traffic densities worldwide. At any time, about 3000 ships are sailing its waterways. Previous scientific publications have shown that ships contribute significantly to atmospheric concentrations of NOx, particulate matter and ozone. Especially in the case of particulate matter and ozone, this influence can even be seen in regions far away from the main shipping routes. In order to quantify the effects of North Sea shipping on air quality in its bordering states, it is essential to determine the emissions from shipping as accurately as possible. Within Interreg IVb project Clean North Sea Shipping (CNSS), a bottom-up approach was developed and used to thoroughly compile such an emission inventory for 2011 that served as the base year for the current emission situation. The innovative aspect of this approach was to use load-dependent functions to calculate emissions from the ships' current activities instead of averaged emission factors for the entire range of the engine loads. These functions were applied to ship activities that were derived from hourly records of Automatic Identification System signals together with a database containing the engine characteristics of the vessels that traveled the North Sea in 2011. The emission model yielded ship emissions among others of NOx and SO2 at high temporal and spatial resolution that were subsequently used in a chemistry transport model in order to simulate the impact of the emissions on pollutant concentration levels. The total emissions of nitrogen reached 540 Gg and those of sulfur oxides 123 Gg within the North Sea – including the adjacent western part of the Baltic Sea until 5° W. This was about twice as much of those of a medium-sized industrialized European state like the Netherlands. The relative contribution of ships to, for example, NO2 concentration levels ashore close to the sea can reach up to 25 % in summer and 15 % in winter. Some hundred kilometers away from the sea, the contribution was about 6 % in summer and 4 % in winter. The relative contribution of the secondary pollutant NO3− was found to reach 20 % in summer and 6 % in winter even far from the shore.
Highlights
Land-based sources of SO2 and NOx have decreased substantially in Europe during the last 20 years, partly because of technical progress in the sectors of traffic, heating and industrial production, and partly because of the political and economic changes in eastern Europe since 1990
Ship traffic in the North Sea is recognized by its adjacent states as a relevant source of air pollutants because future projections show that this traffic is likely to grow further during the coming decades (Project, 2014)
Because, according to Zeretzke (2013), the nitrogen content of heavy fuel oil (HFO) of up to 0.6 % should not be neglected, our model considers NOx emissions of 5.6 g kg−1 HFO burned
Summary
Land-based sources of SO2 and NOx have decreased substantially in Europe during the last 20 years, partly because of technical progress in the sectors of traffic, heating and industrial production, and partly because of the political and economic changes in eastern Europe since 1990. When little was known about ship activities and the emission behavior of their engines, the only way to estimate emissions of air pollutants from ships was to estimate fuel consumption by means of fuel sales numbers and multiply them by emission factors per units of fuel burned This method is described in the CORINAIR guidelines (EEA, 2013), and it is partly used to date by the European member states in order to report national emissions to the European Union. (2012) used the MARIN emission inventory for a study about the impact of introducing a Nitrogen Emission Control Area (NECA) on the environment and human health in the North Sea. In 2012, Jalkanen et al (2012) published a study about a ship emission model (STEAM2) that followed an approach similar to the one presented here, combining AIS signals with a ship characteristics database. The plausibility of the ship emissions presented here and their contribution to air pollution were evaluated by performing statistical tests with observed concentrations available from the European Monitoring and Evaluation Programme (EMEP) network (EMEP, 2015)
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