Waterborne inputs of heavy metals to the Baltic Sea
In 2006 the reported waterborne load of mercury entering the Baltic Sea was 10.8 tonnes. The 2006 load figure for lead was 274 tonnes and for cadmium 47.5 tonnes. During the period 1994-2006 riverine annual heavy metal loads (notably Cd and Pb) seem to have decreased for most of Contracting Parties. However, incomplete data from some countries makes it difficult to draw conclusions concerning the total heavy metal load into the Baltic Sea.
Results and assessment
Relevance of the indicator for describing developments in the environment
High concentrations of heavy metals in biota of the Baltic Sea is mainly caused by pollution loads originating from land-based sources. Of the total loads in 2006, about 87% of the cadmium, 54% of lead, and 76% of mercury entered the Baltic Sea via rivers or as direct waterborne discharges. The rest originated from atmospheric deposition.
Policy relevance and policy references
Excessive heavy metal concentrations may pose a health risk to marine biota and to humans. In the Baltic Sea, high concentrations of mercury, cadmium and lead have been measured in fish, in birds' eggs and in the seal tissue for instance. Measured concentrations of heavy metals have typically been as much as an order of magnitude higher than concentrations in the North Sea. The main reason behind these high concentrations in the Baltic Sea is intense industrial activity, high population in the catchment area, and above all the long renewal time of the seawater. Quantified annual information on the waterborne inputs of heavy metals is needed for evaluation of long-term changes of heavy metal concentrations in biota and the state of marine environment.
Due to the incomplete data on heavy metals, a good quantitative picture of the loads entering the Baltic Sea cannot be given. Shortcomings in national monitoring programs and the lack of proper laboratory equipment meant that heavy metal figures were not obtained in many cases, or that the loads reported are not fully reliable (no harmonized detection limits in all HELCOM countries). Also different calculation methods have been used in the countries if the measured concentrations have been below the detection limit. The datasets for unmonitored rivers and coastal areas are even more incomplete.
The riverine heavy metal loads vary to some extent with runoff from year to year, but not to the same extent as nutrient loads do, mainly due to their origin (industry, waste water treatment plants). To be able to evaluate the reductions in waterborne loads of heavy metals from land-based sources, comparable, reliable and extensive long-term data (since early '80s) should be made available.
Figure 1. Direct inputs of Lead in t/a to the Baltic Sea and the river, coastal and direct point and diffuse source flow in m3/s of 1994-2006 of the 9 riparian countries. (Note variable scales in the graphs). Click image to enlarge.
Figure 2. Direct inputs of Cadmium in t/a to the Baltic Sea and the river, coastal and direct point source flow in m3/s of 1994-2006 of the 9 riparian countries. (Note variable scales in the graphs) Click image to enlarge.
Figure 3. Direct inputs of Mercury in t/a to the Baltic Sea and the river, coastal and direct point source flow in m3/s of 1994-2006 of the 9 riparian countries. (Note variable scales in the graphs) Click image to enlarge.
Time series of riverine, coastal and direct point source inputs to the Baltic Sea for Lead, Cadmium and Mercury including the river and coastal flow in 1994-2006.
Table 1. Riverine, coastal and point source flow to the Baltic Sea of 9 countries in 1994-2006, m3/s
|Total Baltic Sea||15088.1||16077.6||11900.9||14004.6||18423.0||16521.8||17778.0||16645.5||14449.5||10624.6||14970.2||15830.2||13614.1|
Table 2. Direct inputs of lead of 9 countries in 1994-2006 as totals, t/a.
Table 3. Direct inputs of cadmium of 9 countries in 1994-2006 as totals, t/a.
Table 4. Direct inputs of mercury of 9 countries in 1994-2006 as totals, t/a.
HELCOM PLC data base
1) Data have been collected by the Contracting Parties of HELCOM and submitted to the Pollution Load Compilation database (PLC database). The data base is located in the Finnish Environment Institute (SYKE).
2) Description of data:
The data are based on annual average concentrations (mg/l) of nutrients and their fractions (Ptotal-PO4-P, PO4-P, Ntotal, NH4-N, NO2-N, NO3-N and NO2,3-N), concentrations of heavy metals (Cd, Pb and Hg) and mean flows (m³/s). The contracting parties have calculated the annual loads (t/a) of monitored and unmonitored rivers, coastal areas and direct point sources (Wastewater treatment plants, industries and fish farms). From 2003 on also loads on direct diffuse sources have been collected. The data have been pooled together as total loads to the Baltic Sea by country.
Monitored river loads and most of the point source data are based on measurements, and unmonitored river catchment, coastal area loads and direct diffuse loads on estimates, respectively.
The fractions in the nitrogen graph (Figure 1) have been calculated by deducting the reported loads of NH4-N, and NO2-N, NO3-N, or NO2,3-N as a sum, from the reported total nitrogen (Ntotal) load resulting in the fractions of NH4-N, NO2,3-N and organic nitrogen.
Apart from the above, in the table 2 only the reported total nitrogen (Ntotal) has been used not the sum of fractions.
In the phosphorus graph (Figure 2) total phosphorus load have been divided into two fractions Ptot and PO4-P
As for the Ntotal, only the reported total phosporus (Ptotal) load have been used in the table 3.3) Spatial coverage: drainage of the Baltic Sea of 9 riparian countries; Denmark, Estonia, Finland, Germany, Latvia, Lithuania, Poland, Russia and Sweden, including the drainages of the Baltic Sea in Belarus, Czech Republic, Norway, Slovakia and Ukraine.
4) Transboundary rivers:
For the transboundary rivers, the following loads have been used:
- River Tornio (Finland)/Torne älv (Sweden): in the Swedish data
- River Narva (Russia and Estonia): in the Estonian data
- River Oder (Poland and Germany): in the Polish data
6) Russian data includes also the loads of the Kaliningrad Region, if reported.
1) Methodology and frequency are variable, but the methods used have been agreed on the PLC-5 guidelines. For monitored rivers daily flow and concentration regression or monthly flow and concentrations, and for unmonitored areas loads based on the surface area comparison with a similar monitored area have been used for calculations.
2) Data are heterogeneous in space and time, which may cause some variation between years. Due to robust analysing methods in some countries reported loads might be too high.
Only the missing data of all sources, i.e. monitored rivers, coastal area and direct point and diffuse sources, have been listed below. Therefore, more data may be partially missing.
No data of 1994-1999 from the Kaliningrad region of Russia and no Latvian data of costal areas in 1994-2003
Most of the data of 1994-2003 from the Kaliningrad region of Russia and Russian data of 1994-1999 and Ntot data of 2005 from the Gulf of Finland.
It should be noted, that due to the missing Russian riverine Ntotal load to the Gulf of Finland in 2005, the difference between the calculated sum of Nitrogen fractions (Figure 1) and the reported Ntotal load (Table 2) is evident. Only the total loads of direct point sources have been included.
Most of the data of 1994-2006 from the Kaliningrad region of Russia.
No data of 1994, 1996-1999, 2002-2003 and 2005-2006 from Denmark, no data of 1995-1999 and 2001-2003 from Estonia and no data from Lithuania 2006.
No data of 1994, 1996-1999 and 2005-2006 from Denmark, no data of 1995-1999 and 2001-2003 from Estonia, no data from Russia 2003.
No data of 1994, 1996-1999 and 2005-2006 from Denmark, no data of 1995-1999 and 2001-2003 from Estonia, no data of 1994-2000 and 2002-2004 from Latvia, no data from Lithuania of 1994-1997, 2002 and 2006, and no data from Sweden 1994.
Analysis method of Mercury was changed in Finland in 2000.
Missing data have been listed in table 5.
Table 5. Years of the missing data by parameter and country.
|Denmark||1994, 1996-1999, 2002-2003, 2005-2006||1994, 1996-1999, 2005-2006||1994, 1996-1999, 2005-2006|
|Estonia||1995-1999, 2001-2003||1995-1999, 2001-2003||1995-1999, 2001-2003|
|Latvia||BAP, GUR COASTAL AREA 1995-2003||1994-2000, 2002-2004|
|Lithuania||COASTAL AREA 1994-1995||2006||1994-1997, 2002, 2006|
|Russia||BAP 1994-1999, COASTAL AREA 1994-2006||BAP MONITORED (Kaliningrad) 1994-2003, GUF 1994-1999; BAP and GUF COASTAL AREA 1994-2006||MOST OF THE DATA OF BAP (Kaliningrad Region)||2003|
For reference purposes, please cite this indicator fact sheet as follows:
[Author’s name(s)], [Year]. [Indicator Fact Sheet title]. HELCOM Indicator Fact Sheets 2008. Online. [Date Viewed], http://www.helcom.fi/environment2/ifs/en_GB/cover/.
Last updated: 30 June 2009