Abstract
Abstract. The ecological status of the Baltic Sea has for many years been affected by the high input of both waterborne and airborne nutrients. The focus here is on the airborne input of nitrogen (N) and the projected changes in this input, assuming the new National Emission Ceilings directive (NEC-II), currently under negotiation in the EU, is fulfilled towards the year 2020. With a set of scenario simulations, the Danish Eulerian Hemispheric Model (DEHM) has been used to estimate the development in nitrogen deposition based on present day meteorology combined with present day (2007) or future (2020) anthropogenic emissions. Applying a so-called tagging method in the DEHM model, the contribution from ship traffic and from each of the nine countries with coastlines to the Baltic Sea has been assessed. The annual deposition to the Baltic Sea is estimated to 203 k tonnes N for the present day scenario (2007) and 165 k tonnes N in the 2020 scenario, giving a projected reduction of 38 k tonnes N in the annual load in 2020. This equals a decline in nitrogen deposition of 19%. The results from 20 model runs using the tagging method show that of the total nitrogen deposition in 2007, 52% came from emissions within the bordering countries. By 2020, this is projected to decrease to 48%. For some countries the projected decrease in nitrogen deposition arising from the implementation of the NEC-II directive will contribute significantly to compliance with the reductions agreed on in the provisional reduction targets of the Baltic Sea Action Plan. This underlines the importance of including projections like the current in future updates of the Baltic Sea Action Plan.
Highlights
The atmosphere is an important pathway for transport of nutrients to the marine areas (see Krishnamurthy et al (2010) and references therein) as well as for inner waters like e.g. the Kattegat Sea (Spokes et al, 2006) and the Baltic Sea (HELCOM, 2005)
The aim of this study is to investigate the changes in nitrogen deposition if the new National Emission Ceilings (NECII) directive for 2020 is adopted
Thereafter we describe the set of scenario simulations we have performed to investigate the changes in nitrogen deposition if the National Emission Ceilings directive (NEC-II) directive for 2020 is adopted as well as the meteorological data and emissions applied for these scenario simulations
Summary
The atmosphere is an important pathway for transport of nutrients to the marine areas (see Krishnamurthy et al (2010) and references therein) as well as for inner waters like e.g. the Kattegat Sea (Spokes et al, 2006) and the Baltic Sea (HELCOM, 2005). For the Baltic Sea, about 25 % of the total reactive nitrogen load is deposited directly from the atmosphere (HELCOM, 2005). In order to re-establish good ecological status of the Baltic marine environment, the countries around the Baltic Sea have adopted the HELCOM Baltic Sea Action Plan (BSAP) (see http://www.helcom.fi/ BSAP/ActionPlan/en GB/ActionPlan/). The countries in the Baltic Sea catchment area have agreed to take actions no later than 2016 to reduce the nutrient load from waterborne and airborne inputs.
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