Waterborne inputs of heavy metals to the Baltic Sea

	Authors: HELCOM PLC-Group, Data Consultant SYKE

Key message

In 2008 the reported waterborne load of mercury entering the Baltic Sea was 0.9 tonnes. The 2008 load figure for lead was 164 tonnes and for cadmium 15.2 tonnes. The incompleteness of data from some countries makes it difficult to draw conclusions concerning the total heavy metal load, as well as changes in loads over time, 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. According to available data on loads for 2008, about 69% of the cadmium, 46% of lead, and 22% 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.

Assessment

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 means that figures for heavy metal loads have not been 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 1994-2008 Of the 9 riparian countries. (Note variable scales in the graphs)

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 1994-2008 of the 9 riparian countries. (Note variable scales in the graphs)

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 1994-2008 of the 9 riparian countries. (Note variable scales in the graphs)

Data 

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 1994-2008.

Table 1. Riverine, coastal and point source flow to the Baltic Sea of 9 countries in 1994-2008, m³/s

Table 2. Direct inputs of lead of 9 countries in 1994-2008 as totals, t/a.

Table 3. Direct inputs of cadmium of 9 countries in 1994-2008 as totals, t/a.

Table 4. Direct inputs of mercury of 9 countries in 1994-2008 as totals, t/a.

Meta data

Technical Information:

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 (P_total-PO₄-P, PO₄-P, N_total, NH₄-N, NO₂-N, NO₃-N and NO_2,3-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 NO_2,3-N as a sum, from the reported total nitrogen (N_total) load resulting in the fractions of NH₄-N, NO_2,3-N and organic nitrogen.

Apart from the above, in the table 2 only the reported total nitrogen (N_total) have been used not the sum of fractions.

In the phosphorus graph (Figure 2) total phosphorus load have been divided into two fractions P_tot and PO₄-P

As for the N_total, only the reported total phosporus (P_total) load have been shown 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

5) Temporal coverage: nutrients 1994-2008 and harmful substances 1994-2008

6) Russian data includes also the loads of the Kaliningrad Region, if reported.

Data Quality:

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 the years. Due to robust analysing methods in some countries reported loads might be too high.

Missing data

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. Missing data have been listed in table 5.

FLOW

Russia:

-Data of 1994-1999 from the Kaliningrad Region (BAP)
-Data of coastal areas 1994-2008
-All data of 2008

Latvia: Data of coastal areas in 1994-2003 and 2007-2008.

Germany: Most of the data of 2008 (i.e. many rivers of Baltic Proper, all coastal areas and direct point sources).

NITROGEN

Russia:

-All data of 2008
-data of rivers in 1994-2003 and 2007-2008 from the Kaliningrad region
-data of 1994-1999, 2005, 2008 from the Gulf of Finland
-All data of coastal area 1994-1999, 2001-2007

Due to the missing Russian riverine N_total load to the Gulf of Finland in 2005, the difference between the calculated sum of Nitrogen fractions (Figure 1) and the reported N_total load (Table 2) in 2005 is evident. Only the total loads of direct point sources have been included.

Germany: Most of the N_tot, NH₄, NO₂₃, NO₂ and NO₃ data of 2008 of rivers, all data of coastal areas Direct point source data of 2007-2008 of N_tot, NH₄, NO₂₃, NO₂ and NO₃.

Poland: NH₄, (NO₂₃) and NO₂ data of 2008

In general, many countries have gaps in the point source data in different N-fractions (NH₄, NO₂₃, NO₂ and NO₃) over the years.

PHOSPHORUS

Russia:

-Most of the data of 1994-2008 from the Kaliningrad region of Russia.
-All data of 2008

Germany:

-Most of the data of 2008 (i.e. many rivers of Baltic Proper, all coastal areas and direct point sources).
-Point source data of 2007-2008

In general, many countries have gaps in the point source phosphorus data (P_tot, PO₄,) over the years.

LEAD

Denmark: data of 1994, 1996-1999, 2002-2003 and 2005-2008

Estonia: data of 1995-1999 and 2001-2003

Lithuania: data of 2007

Poland: data of 2008

Russia: data of 2008

CADMIUM

Denmark: data of 1994, 1996-1999 and 2005-2008

Estonia: data of 1995-1999 and 2001-2003

Poland: data of 2008

Russia: data of 2003 and 2008

MERCURY

Denmark: data of 1994, 1996-1999 and 2005-2008

Estonia: data of 1995-1999 and 2001-2003, 2007-2008

Lithuania: data of 1994-1997, 2002, 2006-2008

Latvia: data of 1994-2000 and 2002 and 2004

Poland: data of 2008

Russia: data of 2008

Sweden: data of 1994

Analysis method of Mercury was changed in Finland  in 2000.

Table 5. Years of the missing data by parameter and country.

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: 1 December 2010