Abstract. Ship emissions in and around ports are of interest for
urban air quality management in many harbour cities. We investigated the
impact of regional and local ship emissions on urban air quality for
2012 conditions in the city of Gothenburg, Sweden, the largest cargo
port in Scandinavia. In order to assess the effects of ship emissions, a
coupled regional- and local-scale model system has been set up using ship
emissions in the Baltic Sea and the North Sea as well as in and around the
port of Gothenburg. Ship emissions were calculated with the Ship Traffic
Emission Assessment Model (STEAM), taking into account individual
vessel characteristics and vessel activity data. The calculated
contributions from local and regional shipping to local air pollution in
Gothenburg were found to be substantial, especially in areas around the city
ports. The relative contribution from local shipping to annual mean NO2 concentrations was 14 % as the model domain average, while the
relative contribution from regional shipping in the North Sea and the Baltic
Sea was 26 %. In an area close to the city terminals, the contribution of
NO2 from local shipping (33 %) was higher than that of road
traffic (28 %), which indicates the importance of controlling local
shipping emissions. Local shipping emissions of NOx led to
a decrease in the summer mean O3 levels in the city by 0.5 ppb
(∼2 %) on average. Regional shipping led to a slight
increase in O3 concentrations; however, the overall effect of
regional and the local shipping together was a small decrease in the summer
mean O3 concentrations in the city. In addition, volatile organic compound (VOC) emissions from
local shipping compensate up to 4 ppb of the decrease in summer O3
concentrations due to the NO titration effect. For particulate matter with a median
aerodynamic diameter less than or equal to 2.5 µm (PM2.5), local
ship emissions contributed only 3 % to the annual mean in the model domain,
while regional shipping under 2012 conditions was a larger contributor, with
an annual mean contribution of 11 % of the city domain average. Based on the modelled local and regional shipping contributions, the health
effects of PM2.5, NO2 and ozone were assessed using the
ALPHA-RiskPoll (ARP) model. An effect of the shipping-associated PM2.5
exposure in the modelled area was a mean decrease in the life expectancy by
0.015 years per person. The relative contribution of local shipping to
the impact of total PM2.5 was 2.2 %, which can be compared to the 5.3 % contribution from local road traffic. The relative contribution of
the regional shipping was 10.3 %. The mortalities due to the exposure to
NO2 associated with shipping were calculated to be 2.6 premature deaths yr−1. The relative contribution of local and regional
shipping to the total exposure to NO2 in the reference simulation was
14 % and 21 %, respectively. The shipping-related ozone exposures were
due to the NO titration effect leading to a negative number of premature
deaths. Our study shows that overall health impacts of regional shipping can
be more significant than those of local shipping, emphasizing that abatement
policy options on city-scale air pollution require close cooperation across
governance levels. Our findings indicate that the strengthened Sulphur
Emission Control Areas (SECAs) fuel sulphur limit from 1 % to 0.1 % in
2015, leading to a strong decrease in the formation of secondary particulate
matter on a regional scale was an important step in improving the air
quality in the city.
Supplementary material to "The impact of ship emissions on air quality and human health in the Gothenburg area – Part I: 2012 emissions"