Atmospheric Deposition of Nitrogen to the OSPAR Maritime Area in the period 1995-2014
One of the important tasks of the Convention for the Protection of the Marine Environment of the North-East Atlantic (OSPAR) is to protect the OSPAR Maritime Area from eutrophication. This requires analysis of the role of nutrient emissions, discharges losses and inputs into the OSPAR area. In addition to riverine and direct inputs, atmospheric nitrogen input plays an important role for some regions of the OSPAR Maritime Area. Therefore, actions and measures to reduce nitrogen input may need to be formulated.
Nitrogen deposition to the OSPAR Maritime Area has been a subject of a cooperation between Meteorological Synthesizing Centre – West (MSC-W) of EMEP and OSPAR since 2003, starting with the first EMEP report for OSPAR (Bartnicki and Fagerli. 2003). This cooperation has continued and been documented (Bartnicki and Fagerli, 2004a, 2004b; Bartnicki and Fagerli, 2006).
The EMEP report for OSPAR is an evaluation of nutrient inputs to the OSPAR Maritime Area from land-based sources (via atmospheric transport and deposition) and directly from the atmosphere. This evaluation has been performed for the entire OSPAR Maritime Area and for individual OSPAR Regions. The five OSPAR Regions are shown in Figure 1.
EMEP prepared data and a report for the following tasks and products at the OSPAR Region level:
Task 1: Time series of atmospheric deposition to OSPAR Regions (with the understanding that the EMEP grid does not fully cover the whole of Region V, I and IV). Data for 1995–2014 for NHx and NOx.
Task 2: Weather-normalised total (sum of NOx and NHx) nitrogen deposition to each OSPAR Region for 1995–2014, based on the source-receptor matrices for oxidised and reduced nitrogen, including calculation of new source-receptor matrices for selected OSPAR Regions 1995–2014.
Task 3: Use the source-receptor matrices calculated in Task 2, conduct source apportionment by country (and shipping, non-OSPAR sources etc.) of the atmospheric deposition (total nitrogen) to each OSPAR region for the period 1995–2014.
Task 4: A synthesis of the results from Tasks 1-3, discussing major sources, changes, influence of EU and international agreements, likely developments.
Task 5: Time series of emissions (NOx and NHx) from each Contracting Party divided by SNAP sector.
In the above tasks, the source apportionment (Task 3) was calculated using the source-receptor matrices and was performed on actual data (not weather-normalised). Emission sources from all countries (OSPAR Contracting Parties and non-Contracting Parties) were included directly in the calculations performed with the EMEP/MSC-W model. The emissions sources located outside the EMEP domain (e.g. nitrogen emission sources in the United States and Canada) were not included directly in the calculations, but taken into account indirectly, in the lateral boundary conditions to the EMEP/MSC-W model.
Figure 1 OSPAR Maritime Area and Regions. I: Arctic Waters, II: Greater North Sea, III: Celtic Seas, IV: Bay of Biscay and V: Wider Atlantic. Available via https://odims.ospar.org/layers/geonode:ospar_regions_2017_01_001
Nitrogen emissions for 2014 have been derived from the 2016 official data submissions to UNECE CLRTAP as of May 2016. The gridded distributions of the 2014 emissions were provided by the EMEP Centre on Emission Inventories and Projections (CEIP). The emissions for the period of 2000–2013 were derived from the data submissions to UNECE CLRTAP as of May 2015. Re-submissions of emission data in 2016 were not included since the gridded data set for 2000–2013 had not been updated by CEIP in 2016. This is the reason for differences in nitrogen emissions officially submitted by some countries (e.g. Germany) to UNECE and emissions used for the EMEP/MSC-W model calculations presented here.
The EMEP/MSC-W (Simpson et al. 2012) model was used for all nitrogen computations presented here. The latest available model version rv4.9 was used for the deposition calculations. This version is described in the EMEP Status Report 1/2016 and the results of model verification for 2014 can be found in the Supplementary material to the EMEP Status Report 1/2016. The model was run on 50 × 50 km in the EMEP domain. Meteorology, emissions, boundary conditions and forest fires for 2014 have been used as input. In addition, the SO2 emissions from the Holuhraun eruption in 2014 were included in the emission inventories. For the first time, DMS emissions are created ’on-the-fly’ e.g. they are meteorology dependent. Analysis of this model version performance and comparison of the model results with measurements can be found in Supplementary material to EMEP Status Report 1/2016.
In 2008, the Steering Body of EMEP adopted an extension of the official EMEP domain to facilitate the inclusion of countries in Eastern Europe, Caucasus and Central Asia (EECCA) in the EMEP calculations (ref. ECE/EB.AIR/GE.1/2007/9). Thus from 2008, the official 50 x 50 km2 polar stereographic EMEP grid has been extended from 132 × 111 to 132 × 159 grid cells following Stage 1 in ECE/EB.AIR/GE.1/2007/9. In geographical projection, it leads to an extension eastward as well as northward.
All nitrogen depositions presented in the present report were computed in the domain that covers most of the OSPAR Maritime Area, but unfortunately not all of them. Therefore, some underestimation of the computed depositions can be expected mainly in Region V, but also to a less extent in the Regions I and III. The maxima of these underestimations were evaluated based on the boundary depositions as 10% for Region V, 5% for Regions I and 3% for Region III.
The main subject of the present report is atmospheric nitrogen deposition to the OSPAR Maritime Area. However, one of the most important inputs to EMEP/MSC-W model for calculating deposition is nitrogen emissions. Therefore, annual nitrogen emissions from all OSPAR Contracting Parties in the period 1995-2014 are presented in an Appendix.