Impact of a nitrogen emission control area (NECA) on the future air quality and nitrogen deposition to seawater in the Baltic Sea region

Abstract

Abstract. Air pollution due to shipping is a serious concern for coastal regions in Europe. Shipping emissions of nitrogen oxides (NOx) in air over the Baltic Sea are of similar magnitude (330 kt yr−1) as the combined land-based NOx emissions from Finland and Sweden in all emission sectors. Deposition of nitrogen compounds originating from shipping activities contribute to eutrophication of the Baltic Sea and coastal areas in the Baltic Sea region. For the North Sea and the Baltic Sea a nitrogen emission control area (NECA) will become effective in 2021; in accordance with the International Maritime Organization (IMO) target of reducing NOx emissions from ships. Future scenarios for 2040 were designed to study the effect of enforced and planned regulation of ship emissions and the fuel efficiency development on air quality and nitrogen deposition. The Community Multiscale Air Quality (CMAQ) model was used to simulate the current and future air quality situation. The meteorological fields, the emissions from ship traffic and the emissions from land-based sources were considered at a grid resolution of 4×4 km2 for the Baltic Sea region in nested CMAQ simulations. Model simulations for the present-day (2012) air quality show that shipping emissions are the major contributor to atmospheric nitrogen dioxide (NO2) concentrations over the Baltic Sea. In the business-as-usual (BAU) scenario, with the introduction of the NECA, NOx emissions from ship traffic in the Baltic Sea are reduced by about 80 % in 2040. An approximate linear relationship was found between ship emissions of NOx and the simulated levels of annual average NO2 over the Baltic Sea in the year 2040, when following different future shipping scenarios. The burden of fine particulate matter (PM2.5) over the Baltic Sea region is predicted to decrease by 35 %–37 % between 2012 and 2040. The reduction in PM2.5 is larger over sea, where it drops by 50 %–60 % along the main shipping routes, and is smaller over the coastal areas. The introduction of NECA is critical for reducing ship emissions of NOx to levels that are low enough to sustainably dampen ozone (O3) production in the Baltic Sea region. A second important effect of the NECA over the Baltic Sea region is the reduction in secondary formation of particulate nitrate. This lowers the ship-related PM2.5 by 72 % in 2040 compared to the present day, while it is reduced by only 48 % without implementation of the NECA. The effect of a lower fuel efficiency development on the absolute ship contribution of air pollutants is limited. Still, the annual mean ship contributions in 2040 to NO2, sulfur dioxide and PM2.5 and daily maximum O3 are significantly higher if a slower fuel efficiency development is assumed. Nitrogen deposition to the seawater of the Baltic Sea decreases on average by 40 %–44 % between 2012 and 2040 in the simulations. The effect of the NECA on nitrogen deposition is most significant in the western part of the Baltic Sea. It will be important to closely monitor compliance of individual ships with the enforced and planned emission regulations.

Effects of ship emissions on air quality in the Baltic Sea region simulated with three different chemistry transport models

“…Wet deposition of gases and particles is computed by the resolved cloud model of CMAQ, which estimates how much certain vertical model layers contributed to the precipitation (Foley et al, 2010). Sea salt emissions were calculated in line by the parameterization of Gong (2003) (as described in Kelly et al, 2010). Sea salt surf zone emissions were deactivated because of considerable overestimations in some coastal regions (Neumann et al, 2016).…”

Urban population exposure to NO<sub><i>x</i></sub> emissions from local shipping in three Baltic Sea harbour cities – a generic approach

“…In a fourth step, we assembled generic diurnal variation in population activity for each ME to temporally distribute the population to all MEs because no specific information exists for Rostock, Riga or the Gdańsk-Gdynia area. The generic time profiles are mainly derived from diurnal variation in population activity in the Helsinki metropolitan area in four MEs: home, workplace, traffic and other (Kousa et al, 2002;Soares et al, 2014). Soares et al (2014) derived information on the Helsinki population from annually collected data of the municipalities of the Helsinki metropolitan area.…”

Effects of strengthening the Baltic Sea ECA regulations

“…They found that the implementation of the stricter SECA regulations in the BAS and the NOS would result in substantial health improvements in Europe. Karl et al (2019b) compared the effects of BAS shipping calculated by three different chemistry transport models using year 2012 emissions and meteorology. They found that in the entire BAS region the average contribution from ships to PM 2.5 is in the range of 4.3 %-6.5 % for the three CTMs, and deposition of oxidised nitrogen to the Baltic Sea is in the 20-24 kt N per year range.…”