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Atmospheric nitrogen depositions to the Baltic Sea during 1995-2008
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Key message
The total deposition of nitrogen to the Baltic Sea in 2008 was 216 ktonnes, 2.5% lower than in 1995 and 8% lower than in 2000.
There is a continuous (app. 20%) increase in oxidised, reduced and total nitrogen deposition into the Baltic Sea in the period 2002 – 2008. In sub-basins Gulf of Finland and Gulf of Riga annual depositions of oxidised, reduced and total nitrogen are higher in 2008 than in 1995 and in 2000.
Results and Assessment
Relevance of the indicator for describing the developments in the environment
This indicator shows the levels and trends in oxidised, reduced and total atmospheric nitrogen depositions to the Baltic Sea. The depositions of nitrogen compounds represent the pressure of emission sources on the Baltic Sea basin and catchment.
Policy relevance and policy reference
The HELCOM Ministerial Declaration of 1988 called for a 50 % reduction in discharges of nutrients to air and water by 1995 with 1987 as a base year. The 1992 Helsinki Convention and the 1998 Ministerial Declaration reaffirmed the need to further reduce discharges; leading to the adoption of several relevant Recommendations concerning measures to reduce emissions from point sources and diffuse sources. In 1990, HELCOM adopted its first Recommendation on Monitoring of Airborne Pollution Load (HELCOM Recommendation 11/1) which was later superseded by the Recommendations 14/1 and 24/1.
Assessment
Atmospheric deposition of oxidised and reduced nitrogen was computed with the latest version of the new unified model developed at MSC-W of EMEP. The latest available emission data for the HELCOM countries and all other EMEP sources have been used in the model calculations.
Calculated annual oxidised, reduced and total nitrogen depositions to the entire Baltic Sea basin in the period 1995 – 2008 are shown, in per cent of 1995 value, in Figure 1.
Figure 1. Atmospheric deposition of oxidised, reduced and total nitrogen to the entire Baltic Sea basin for the period 1995-2008 in per cent of 1995 value.
No significant trends could be determined for nitrogen loads entering the Baltic Sea in the considered period, except for the recent period 2002 – 2008 when all kinds of nitrogen deposition are increasing.
Mainly because of interannual changes in meteorological conditions, annual nitrogen deposition to the Baltic Sea and its sub-basins varies significantly from one year to another in the period 1995 - 2008. Maximum annual deposition of oxidised and reduced nitrogen deposition to the Baltic Sea takes place in the year 1998 and 2000, respectively. Minimum annual deposition can be noticed in the year 2002 for both oxidised and reduced nitrogen. Annual depositions of oxidised, reduced and total nitrogen in 2008 are respectively 2.6%, 2.3% and 2.5% lower than in 1995.
Average annual atmospheric nitrogen deposition into the Baltic Sea is 206 kt over the period 1995 – 2008 with approximately 9% standard deviation. The annual total nitrogen deposition consisted of slightly more (2-6%) of oxidised than reduced nitrogen.
Calculated annual total nitrogen depositions to the six sub-basins of the Baltic Sea in the period 1995 – 2008 are presented in Figure 2.
Figure 2. Atmospheric deposition of oxidised, reduced and total nitrogen to six sub-basins of the Baltic Sea for the period 1995 - 2008. Units: ktonnes N/year. Note: the scales for the sea regions are different!
No significant trends can be recognized in nitrogen depositions to sub-basins of the Baltic Sea in the Period 1995 – 2008. Annual deposition of oxidised nitrogen is lower in 2008 than in 1995 in sub-basins Belt Sea, Kattegatt, Baltic Proper and Gulf of Bothnia. Deposition of reduced nitrogen is lower in 2008 than in 1995 in only three out of six sub-basins: Belt Sea, Kattegatt, Baltic Proper and Gulf of Bothnia. All kinds of nitrogen depositions are higher in 2008 than in 1995 in sub-basins Gulf of Finland and Gulf of Riga.
Compared to 2007, all kind of nitrogen depositions are higher in 2008 in the North-East subbasins Gulf of Bothnia, Gulf of Finland and Gulf of Riga, as well as in the Kattegat sub-basin. The deposition increase from 2007 to 2008 in the Gulf of Finland is significant: 31% and 19%, for oxidised and reduced nitrogen respectively. The deposition increase was not caused by the emission increase which in all HELCOM sources was slightly lower in 2008 than in 2007. It was caused by the interannual variation of meteorological conditions, mainly higher precipitation over the Baltic Sea - especially North East Baltic and higher average temperature.
Data
Table 1. Annual depositions of oxidised nitrogen to the sub-basins and the entire basin of the Baltic Sea in the period 1995-2008. Units: kt N per year and basin.
| Year | BAP | BES | GUB | GUF | GUR | KAT | BAS |
| 1995 | 69 | 9,7 | 20,5 | 8 | 6 | 9,1 | 122,3 |
| 1996 | 72,1 | 10 | 19 | 8,7 | 5,7 | 9 | 124,5 |
| 1997 | 60,1 | 8,5 | 15,7 | 6,6 | 5,3 | 8,1 | 104,3 |
| 1998 | 74,6 | 10,6 | 20,8 | 8,1 | 5,4 | 9,5 | 129 |
| 1999 | 66 | 10 | 19,8 | 7,5 | 5,3 | 9,6 | 118,1 |
| 2000 | 68,8 | 9,9 | 23 | 8,6 | 5,7 | 10,2 | 126,2 |
| 2001 | 64,1 | 9,9 | 18,6 | 6,6 | 4,7 | 8,6 | 112,5 |
| 2002 | 55,1 | 8,4 | 14,2 | 5,6 | 4,3 | 7,5 | 95 |
| 2003 | 58 | 7,7 | 18,9 | 7,1 | 4,9 | 8 | 104,7 |
| 2004 | 56,9 | 8,4 | 15,8 | 7,4 | 5 | 7,5 | 100,8 |
| 2005 | 56,7 | 7,7 | 16,4 | 7 | 4,8 | 7,9 | 100,4 |
| 2006 | 61 | 8,8 | 16,7 | 7,2 | 5,5 | 8,1 | 107,1 |
| 2007 | 63,2 | 9 | 13,9 | 7,1 | 4,8 | 7,7 | 105,7 |
| 2008 | 67,7 | 7,9 | 19,5 | 9,1 | 6,3 | 8,6 | 119,1 |
Table 2. Annual depositions of reduced nitrogen to the sub-basins and the entire basin of the Baltic Sea in the period 1995-2008. Units: kt N per year and basin.
| Year | BAP | BES | GUB | GUF | GUR | KAT | BAS |
| 1995 | 52,2 | 13,1 | 14,5 | 5,2 | 4 | 9,9 | 98,9 |
| 1996 | 52,4 | 12 | 12,7 | 6,1 | 4 | 9,4 | 96,6 |
| 1997 | 45,9 | 12,2 | 9,3 | 3,9 | 3,5 | 9,3 | 84,1 |
| 1998 | 59 | 14,7 | 13,9 | 4,8 | 3,6 | 11 | 107 |
| 1999 | 51,3 | 14 | 13 | 4,2 | 3,5 | 10,7 | 96,7 |
| 2000 | 58,4 | 14,4 | 17,5 | 5,4 | 4 | 11,9 | 111,7 |
| 2001 | 51,9 | 13,6 | 13,1 | 4,2 | 3,5 | 9,5 | 95,8 |
| 2002 | 44,2 | 12,1 | 10,2 | 3 | 2,8 | 8,7 | 81,1 |
| 2003 | 46,1 | 11,2 | 13,6 | 4,2 | 3,4 | 8,8 | 87,3 |
| 2004 | 48,1 | 13,1 | 10,5 | 4,3 | 3,6 | 9,2 | 88,8 |
| 2005 | 50,2 | 13,1 | 11,3 | 4,9 | 3,8 | 9,4 | 92,7 |
| 2006 | 50,1 | 14,2 | 10,4 | 4,4 | 3,8 | 9,5 | 92,4 |
| 2007 | 56,4 | 14,1 | 9,7 | 4,6 | 3,5 | 8,3 | 96,6 |
| 2008 | 53,1 | 12,4 | 11,6 | 5,5 | 4,2 | 9,9 | 9 |
Table 3. Annual depositions of total nitrogen to the sub-basins and the entire basin of the Baltic Sea in the period 1995-2008. Units: kt N per year and basin.
| Year | BAP | BES | GUB | GUF | GUR | KAT | BAS |
| 1995 | 121,2 | 22,9 | 35,1 | 13,2 | 10 | 19 | 221,3 |
| 1996 | 124,5 | 22 | 31,7 | 14,8 | 9,8 | 18,4 | 221,1 |
| 1997 | 105,9 | 20,6 | 25,1 | 10,5 | 8,8 | 17,5 | 188,4 |
| 1998 | 133,6 | 25,4 | 34,7 | 12,9 | 9 | 20,4 | 236 |
| 1999 | 117,3 | 24 | 32,8 | 11,7 | 8,8 | 20,2 | 214,9 |
| 2000 | 127,2 | 24,3 | 40,5 | 14 | 9,7 | 22,1 | 237,9 |
| 2001 | 116 | 23,5 | 31,6 | 10,8 | 8,2 | 18 | 208,2 |
| 2002 | 99,4 | 20,5 | 24,4 | 8,6 | 7 | 16,2 | 176,1 |
| 2003 | 104,1 | 18,9 | 32,5 | 11,2 | 8,4 | 16,8 | 192 |
| 2004 | 105 | 21,4 | 26,2 | 11,7 | 8,5 | 16,7 | 189,6 |
| 2005 | 106,9 | 20,8 | 27,7 | 11,9 | 8,6 | 17,3 | 193,2 |
| 2006 | 111,1 | 23 | 27 | 11,6 | 9,2 | 17,5 | 199,5 |
| 2007 | 119,6 | 23,1 | 23,5 | 11,7 | 8,3 | 16 | 202,3 |
| 2008 | 120,8 | 20,3 | 31,1 | 14,7 | 10,5 | 18,5 | 215,8 |
Metadata
Technical information
1. Source: EMEP/MSC-W.
2. Description of data: The atmospheric depositions of oxidised and reduced nitrogen were calculated with the latest version of EMEP Unified model developed at EMEP/MSC-W in Oslo. The latest available official emission data for the HELCOM countries have been used in the model computations. Emissions of two nitrogen compounds for each year of this period were officially reported to the UN ECE Secretariat by several HELCOM Contracting Parties. Missing information was estimated by experts. Both official data and expert estimates were used for modelling atmospheric transport and deposition of nitrogen compounds to the Baltic Sea - http://www.ceip.at/ .
3. Geographical coverage: Atmospheric depositions of oxidised and reduced nitrogen were computed for the entire EMEP domain, which includes Baltic Sea basin and catchment.
4. Temporal coverage: Time series of annual atmospheric depositions are available for the period 1995 – 2008.
5. Methodology and frequency of data collection: Atmospheric input and source allocation budgets of nitrogen (oxidised, reduced and total) to the Baltic Sea basins and catchments were computed using the latest version of EMEP Unified model. EMEP Unified model is a multi pollutant, three-dimensional Eulerian model which takes into account processes of emission, advection, turbulent diffusion, chemical transformations, wet and dry depositions and inflow of pollutants into the model domain. Complete description of the model and its applications is available on the web http://www.emep.int.
Calculations of atmospheric transport and depositions of nitrogen compounds are performed annually two years in arrears on the basis of emission data officially submitted by Parties to CLRTAP Convention and expert estimates.
Quality information
6. Strength and weakness:
Strength: annually updated information on atmospheric input of oxidised and reduced nitrogen to the Baltic Sea and its sub-basins.
Weakness: gaps and uncertainties in officially submitted time series data of nitrogen emissions to air by countries.
7. Uncertainty: The results of the EMEP Unified model are routinely compared with available measurements at EMEP and HELCOM stations. The comparison of calculated versus measured data indicates that the model predicts the observed air concentrations and depositions of nitrogen compounds within the accuracy of approximately 30%.8. Further work required: Further work is required on reducing uncertainties in emission data and better parametrization of physical processes in the EMEP Unified model.
For reference purposes, please cite this Baltic Sea Environment Fact Sheets as follows:
[Author’s name(s)], [Year]. [Baltic Sea Environment Fact Sheets title]. HELCOM Baltic Sea Environment Fact Sheets 2010. Online. [Date Viewed], http://www.helcom.fi/environment2/ifs/en_GB/cover/.
Last updated: 12 November 2010