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2.6. Heavy metals and persistent organic pollutants
In recent years special attention has been paid within the frames of United Nations (UN)/European Economic Committee on persistent organic pollutants and heavy metals.
Two protocols have been adopted within the frames of the convention of long-range transportation of air pollution, on which basis production and use of several persistent compounds is intended to prohibit or restrict (Executive Body decisions: 1998/2 persistent organic compounds, 1998/1
- heavy metals). Estonia is planning to join these protocols in 2001/2002.
By the beginning of new millennium 36 countries have undersigned the protocols, including Latvia and Lithuania, but only five countries have ratified them (Canada, Norway, Sweden, Netherlands and Luxembourg).
There are 12 prohibited persistent organic compounds (Annex 1 to the protocol): aldrin, endrin, chlordane, DDT, dieldrin, heptachlorine, hexachlorine benzene, hexabromide biphenyl, chlorine decon, mirex, toxaphen and polychlorinated biphenyls. Twelve compounds were selected from 107 persistent compounds as most hazardous to peoples health (Roots, 1999). Annex 2 to the protocol (list of compounds with prohibited or restricted use) includes in addition to DDT and polychlorinated biphenyls also hexachloro-cyclohexane. Belonging of DDT simultaneously into two annexes is justified with the fact that until now no substitute has been found for that compound in battle with malaria and encephalitis. In Estonia the import of chlorine organic pesticides is prohibited with Government regulation from October 21, 1967.
For heavy metals, main attention of UN/EEC is paid on three metals: cadmium, lead and quicksilver.
2.6.1. Heavy metal pollution precipitating through the air
Atmospheric heavy metal pollution has been monitored in Estonia for ten years with the method of bio-indication, using ordinary heath moss (Pleurozium schreberi), which accumulates heavy metals proportionally with their content in the air.
In 1990 Estonia joined the European project of bio-indicational heavy metal monitoring, where 28 countries are participating and which is coordinated by Lund University in Sweden. According to the project, distribution of Cd, Cr, Cu, Fe, Ni, Pb, V and Zn and, if possible, also AS and Hg content in moss is mapped with interval of 5 years simultaneously in different countries (figure 2.28). In Estonia the network of monitoring of heavy metals distribution consists of 100 moss sampling points fixed with geographical coordinates, with intervals of 30 km. Heavy metal content has been measured according to that network pitch in Estonia in 1990 and 1995 (Liiv etc. 1996). For the region remaining under greater pollution load, North-East Estonia, such monitoring network is insufficient, therefore in that region heavy metal pollution has been evaluated in 1992 and 1997 on the basis of intensified monitoring programme (Monitoring
sub-programme, 1998). Collection and processing of moss samples and measuring of their content of elements is proceeding from internationally accepted methodology (Rühling, A., Steinnes, E., 1998).
Figure 2.28. Cd content in moss in Europe in 1995 (Rühling, A., Steinnes, E., 1998).
Average Cd content in moss was relatively low in Estonia in 1995 - 0.189 µg/g. Cd content in moss was relatively uniformly distributed in Estonia
- there are only two separated zones on the map of territorial Cd distribution. In 1990 Cd content in moss was higher than in 1995. For comparison
- in Poland and Romania Cd content in moss extends to 2 µg/g.
Hg content in Estonia was relatively low in 1995 - average of Estonia was 0.0796 µg/g. Hg content in moss was the highest in Kohtla-Nõmme (North-East Estonia) and Rocca-al-Mare
- over 0.1000 µg/g. In most European countries Hg content in moss remains below 0.1 µg/g. In 1990 Hg content in moss was not measured in Estonia.
Average Pb content in mossin Estonia in 1995 was 7.349 µg/g, the highest Pb content (20.0 µg/g) in moss samples was measured in Kunda. For comparison
- in Tallinn Pb content in moss is twice as high at places, up to 41.5 µg/g in Pelgulinn (Mäkinen, Liiv, 1995). In 1995 Pb content was lower in Estonia than in 1990.
North-East Estonia 1992-1997
Cd, Cr, Cu, Fe, Ni, Pb, V and Zn content in the moss of 36 sampling points located in North-East Estonia was in most cases over average level of Estonia in 1992 as well as in 1997. On the transect of sampling points starting from the Estonian Power Station (EPS) to North-East and South-West as well as from Kunda-Nordic cement factory to East and West common rule can be observed that the content of heavy metals in moss is decreasing along the increase of distance of sampling points from the pollution source. At the same time content of elements in moss is not the highest in sampling points located closer to EPS, but only in the moss of sampling point located 3 km to North-East, where probably largest amount of solid waste is precipitating from high plant pipes. As a rule, content of elements will decrease to average level of Estonia 10 km to South-West from EPS.
2.6.2. Emissions of heavy metals
Emissions of heavy metals have been calculated proceeding from fuel combustion in 1990-1998 (table 2.12). Figure 2.29 includes the emissions of lead, cadmium and mercury by type of fuel in 1998. Greater part of heavy metals is produced at oil shale burning in large power stations. Another large pollution source is burning of wood and wood waste in small boiler houses. In 1990-1998 emissions were reduced two times, which is caused by the decrease of the amount of burnt fuel.
Table 2.12. Emissions of heavy metals from fuel combustion, kg.
Figure 2.29. Emissions of lead, cadmium and mercury by type of fuel in 1998.
Table 2.13 shows emissions of lead from different pollution sources. Largest amounts of lead are emitted from fuel combustion and transport (figure 2.30). Figure 2.31 shows that in 1990 the emission of lead from transport was twice as large as from oil shale combustion. In 1998 this relation has changed. Lead was emitted from transport three times less, compared to oil shale combustion. This is caused by remarkable decrease of the use of petrol with lead content (only 10% in 1998).
Table 2.13. Emission of lead in tons.
Figure 2.30. Distribution of lead emissions between main pollution sources in 1998.
Figure 2.31. Distribution of lead emissions between pollution sources 1990-1998.
2.6.3. Persistent organic pollutants
Government Regulation from October 21, 1967 prohibited import of chlorine organic pesticides to Estonia (Müür, 1996). Estonia itself is not manufacturing chlorine organic pesticides.
By now the use (and import) of all toxic chlorine organic pesticides belonging into the protocol adopted by UNECE in 1998 is prohibited in Estonia. According to the data of the Estonian Inspectorate of Vegetation Protection 1.1 tons of DDT is currently stored under control.
Unfortunately, toxic organic compounds reach the Estonian territory through long-range transportation of air pollution. Toxic compounds reach the Baltic Sea mainly through atmosphere and rivers. For example, correspondingly 20 and 3 kg of DDT with precipitations and by rivers water brought into the Baltic Sea; also 230 and 50 kg of another toxic pesticide, hexachlorocyclohexane (HCH) and 390 and 330 kg of polychlorined biphenyls (PCB) with industrial origin (Agrell, 1999).
Due to the programme of the Nordic Council of Ministers
"Environmental Research in the Baltic Sea Region" measurement of the content of toxic chlorine organic compounds was carried through for the first time in the atmospheric air of the Gulf of Liivi region (figure 2.32). In comparison, data of Hällestad station in Sweden have been given. Pärnu station was located in Tahkuse (Nordic Environmental Research Programme for 1993-1997, 1999).
Figure 2.32. PCB and DDT content in the air of the Gulf of Liivi region according to the data of the programme of the Nordic Council of Ministers "Environmental Research in the Baltic Sea Region".
When PCB showed up decrease of compound content from local pollution
source in Salaspils (Latvia) towards Saaremaa, corresponding geometric
average contents of toxicants in the air were 0.6 ng/m3
and 0.05 ng/m3, distribution of summary DDT to Saaremaa
region is probably caused by long-range transportation of air pollution
(Nordic Environmental Research Programme for 1993-1997, 1999). In
addition to toxic chlorine organic pesticides the list of extremely
hazardous organic compounds includes also polychlorined biphenyls
(PCB), furans and dioxins. The mentioned compounds contain correspondingly
209, 175 and 75 isomers with different toxic level, which makes analysis
expensive and requires also availability of excellent equipment and
analyzing staff. Currently PCB analyses are conducted in Estonia,
but there is no possibility to analyze dioxins and furans.
In result of joint project of Estonia and Denmark analysis of polychlorined biphenyls (PCB) in old transformer oils was carried through. Order of the treatment of waste containing polychlorined biphenyls and polychlorined terphenyls has been developed for elimination of those compounds from use (basis: EC directive 96/59/EU).
In Estonia there are no known pollution sources of dioxins and furans, as main emission sources of toxicants are combustion of waste (69%) and black metallurgy (10%). 38% of annual emission of furans and dioxins comes from Japan, 26% from USA (Dioxin and Furan Inventories, 1999).
Researches by German scientists of dioxin and furan contents of milled oil shale taken into the furnace of the Estonian Power Station and volatile ash caught with electric filter, carried through within the frames of the European Dioxin Project, showed that contents of toxicants in the oil shale power station were insignificant, compared to amounts emitted from waste combustion plants, and were comparable with those found in brown coal dust in Germany, remaining in case of many isomers of dioxin and furan below determination level (Dioxin research in oil shale based power station,
1998).
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