Atmospheric depositions of heavy metals to the Baltic Sea

	Author: Alexey Gusev, EMEP MSC-E

Key message

Total annual atmospheric depositions of heavy metals to the Baltic Sea have decreased in period from 1990 to 2002 by 38% for cadmium, 40% for mercury, and 67% for lead.  

Results and Assessment

Relevance of the indicator for describing the developments in the environment

This indicator shows the levels and trends in cadmium, mercury, and lead atmospheric depositions to the Baltic Sea. The depositions of heavy metals represent the pressure of emission sources on the Baltic Sea aquatic environment.

Policy relevance and policy reference

HELCOM adopted a Recommendation in May 2001 for the cessation of hazardous substance discharges/emissions by 2020, with the ultimate aim of achieving concentrations in the environment near to background values for naturally occurring substances and close to zero for man-made synthetic substances.

Assessment

Total annual atmospheric depositions of heavy metals to the surface of the Baltic Sea have substantially decreased in period 1990-2002 (Figure 1). The most significant drop in depositions over the Baltic Sea is obtained for lead (67%). The decrease of cadmium and mercury depositions is amounted to 38% and 40%, respectively. On the level of individual sub-basins the most significant drop in cadmium and lead depositions can be noted for the Kattegat, by 79% and 50%, respectively (Tables 1-3, Figures 2-4). Largest decrease in mercury depositions is obtained for the Belt Sea (63%).

The reduction of atmospheric input of lead, cadmium, and mercury to the Baltic Sea is a result of abatement measures as well as of economic contraction and industrial restructuring in Poland, Estonia, Latvia, Lithuania, and Russia in early 1990s.

Among the HELCOM countries the most significant contributions to depositions over the Baltic Sea belong to Poland, Germany, and Russia (Table 4). In spatial distribution of heavy metals depositions on the Baltic Sea the highest levels can be noted for the southern-western part of the Baltic Sea (the Belt Sea and the Baltic Proper). Significant levels of lead and cadmium depositions can also be noted for the Gulf of Riga.

Figure 1: Computed total annual atmospheric depositions of cadmium, mercury, and lead to the Baltic Sea for the period 1990-2002, (% of 1990).

Click the image to enlarge!

Figure 2:  Time-series of computed total annual atmospheric deposition of cadmium to six sub-basins of the Baltic Sea for the period 1990-2002 in tonnes/year as bars (left axis) and total deposition fluxes in g/km2/year as lines (right axis). Note that different scales have been used for total depositions in tonnes/year and the sames scales for total deposition fluxes.  

Click the image to enlarge!

Figure 3:  Time-series of computed total annual atmospheric deposition of lead to six sub-basins of the Baltic Sea for the period 1990-2002 in tonnes/year as bars (left axis) and total deposition fluxes in kg/km2/year as lines (right axis). Note that different scales have been used for total depositions in tonnes/year and the sames scales for total deposition fluxes.  

Click the image to enlarge!

Figure 4:  Time-series of computed total annual atmospheric deposition of mercury to six sub-basins of the Baltic Sea for the period 1990-2002 in tonnes/year as bars (left axis) and total deposition fluxes in g/km2/year as lines (right axis). Note that different scales have been used for total depositions in tonnes/year and the sames scales for total deposition fluxes. Click on the map to see enlarged version.

References

Ilyin I., O. Travnikov, W. Aas, W. Aas, K. Breivik, S. Manø [2004] Heavy metals: transboundary pollution of the  environment. MSC-E and CCC. EMEP status report 2/2004. June 2004. (http://www.msceast.org/reps/2_2004.pdf)

Data

Table 1. Computed total annual depositions of cadmium to six Baltic Sea sub-basins for period 1990-2002. Units: tonnes/year

Table 2. Computed total annual depositions of lead to six Baltic Sea sub-basins for period 1990-2002. Units: tonnes/year

Table 3. Computed total annual depositions of mercury to six Baltic Sea sub-basins for period 1990-2002. Units: tonnes/year

Table 4. Contributions (in %) of the HELCOM countries to total annual depositions over the Baltic Sea.

Metadata

Technical information

1. Source: EMEP/MSC-E

2. Description of data: The atmospheric depositions of heavy metals were obtained using the latest version of MSCE-HM model developed at EMEP/MSC-E (Ilyin et al., 2004). The latest available official emission data for the HELCOM countries have been used in the model computations. Emissions of all three metals for each year of this period were officially reported to the UN ECE Secretariat by most of HELCOM countries (EB.AIR/GE.1/2004/1). Some of the countries, in particular, Germany, Lithuania, Russia, and Poland submitted part of the data for this period. Missing information was obtained on the basis of official data by interpolation or extrapolation. These data were used for modelling of transboundary air pollution by heavy metals within European region including the Baltic Sea and its catchment area (Ilyin et al., 2004).

3. Geographical coverage:   Atmospheric depositions of lead, cadmium, and mercury were obtained for the European region.

4. Temporal coverage: Timeseries of annual atmospheric depositions are available for the period 1990 – 2002.

5. Methodology and frequency of data collection: 

Atmospheric input and source allocation budgets of heavy metals (cadmium, lead, and mercury) to the Baltic Sea and its catchment area were computed using the latest version of MSCE-HM model. MSCE-HM is the regional-scale model operating within the EMEP region. This is a three-dimensional Eulerian model which includes processes of emission, advection, turbulent diffusion, chemical transformations of mercury, wet and dry depositions, and inflow of pollutant into the model domain. Horizontal grid of the model is defined using stereographic projection with spatial resolution 50 km at 60º latitude. The description of EMEP horizontal grid system can be found in the internet (http://www.emep.int/grid/index.html). Vertical structure of the model consists of 15 non-uniform layers defined in the terrain-following sigma coordinates and covers almost the whole troposphere. Meteorological data used in the calculations for 2002 are based on the Re-analysis project data prepared by National Centers for Environmental Predictions together with National Center of the Atmospheric Research (NCEP/NCAR) in the USA. Detailed description of the model can be found in EMEP reports (Ilyin et al., 2002; Ilyin et al., 2003) and in the Internet on EMEP web page http://www.emep.int under the link to information on Heavy Metals.

Calculations of atmospheric transport and depositions of lead, cadmium, and mercury are provided on the regular basis annually two years in arrears on the basis of emission data officially submitted by Parties to CLRTAP Convention.

Quality information

6. Strength and weakness:

Strength: annually updated information on atmospheric input of lead, cadmium, and mercury to the Baltic Sea and its sub-basins

Weakness: gaps and uncertainties in officially submitted by countries time series of heavy metal emissions to air

7. Uncertaity:

The MSCE-HM model has been verified in a number of intercomparison campaigns with other regional models [Sofiev et al., 1996; Gusev et al., 2000; Ryaboshapko et al., 2001] and has been qualified by means of sensitivity and uncertainty studies [Travnikov, 2000]. It was concluded that the results of heavy metal airborne transport modeling are in satisfactory agreement with available measurements and discrepancy does not exceed on average a factor of two. The comparison of calculated versus measured data indicates that the model predicts the observed air concentrations of lead and cadmium within the accuracy of 30%. For concentrations in precipitation the difference between calculated and measured values may reach two times. Computed mercury concentrations deviate from measured values within a factor of two.

8. Further work required:

Further work is required on reducing uncertainties in emission data and modeling approaches used in MSCE-HM model.