Arkona Basin
Arkona Basin |
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It is estimated that annual average pollution loads carried by the Odra/Oder at the mouth of the lagoon are some 56 000 tons of BOD, (23 percent of total discharges in the basin), 24 000 tons of tot-N (21 percent), 7 000 tons of tot-P (44 percent), 920 tons of heavy metals (59 percent) and 2 630 000 tons of chlorides and sulfates (100 percent). It should be noted that the river still has a significant self-purification potential and that sedimentation of heavy metals is significant (almost all of them are deposited in the Odra/Oder River below its confluence with the Warta). The pollution loads reaching the Baltic are less than the above values due to the effect of the lagoon.
The catchment area of the Arkona Basin covers the territories of new Federal Länder of Mecklenburg-Vorpommern immediately bordering the sea, and that of Brandenburg and Saxony. These Länder cover 60 percent and 22 percent of the German catchment area of the Baltic Sea respectively. In the new Länder, about 86 percent of the population of larger urban centers (more than 20 000 population) are connected to municipal treatment plants. In smaller communities this percentage is usually much lower - around 25 percent. A low percentage of biological treatment is characteristic for municipal sewage treatment plants (on average, only 12 percent of the population is connected to biological treatment facilities). The remainder of the population is connected to mechanical treatment only, or none at all. There are no facilities for elimination of nutrients.
The population of the Danish part of the area is about 100 000 inhabitants. However, in the summer period this figure may perhaps be higher by 50 000 as the islands of Bornholm, Lolland and Mon are popular holiday areas with many vacation houses and camping areas. In 1990, nitrogen discharge was 470 tons and phosphorus 110 tons. Most Danish wastewater treatment plants discharging to the Baltic Sea have been or are being upgraded to meet the requirements of the National Action Plan for the Marine Areas. The extended capacity and capability shall be fully developed by 1993.
Sweden In the Swedish part of the catchment area, there are 22 coastal municipalities, of which 10 are larger than 10 000 p.e. Almost all those living in densely populated areas are served by biological and chemical treatment plants. There are several municipalities inland (the largest city Kristianstad of 160 000 inhabitants), all provided with similar sewage treatment facilities. Improvements being introduced currently should result in a further reduction of phosphorus and nitrogen discharges.
Industrial wastewater discharges in the German part of the catchment area were significant due to obsolete production technologies, excessive water use, low water recirculation rates and insufficient capacities of existing wastewater treatment plants. This situation, however, changed rapidly during the last two years. For example, it is estimated that production cutbacks, shutdowns, and changes of industrial production profiles have reduced annual BOD5 discharges by about 7 800 t/y as compared to the 1987 levels (more than 62 percent).
The Danish part of the catchment area has little industry; the total direct discharge amounts to less than 500 p.e.
The Swedish industrial plants
include, among others, four pulp and
paper mills (three of them located on the
coast), several small glassworks, a scrap
aluminium smelter and a number of food
manufacturing plants. The pulp and
paper mills discharge large quantities of
nutrients and oxygen-consuming
material. Two of them manufacturing
bleached chemical pulp discharge
chlorinated organic substances. Further
reduction of nutrients and chlorinated
organic substances is necessary, in
particular to offset eutrophication in Hanö
Bay.
Agriculture
The German part of the catchment area draining to the Bornholm Basin is a region of intensive farming. In the new Länder, cattle stocks were concentrated in mass farms with a high output of liquid manure. Storage capacities were insufficient and there were no adequate transportation and distribution facilities. Additional risks were posed by open air fertilizer and pesticide storage spaces and by trench silos.
Economic conditions following German re-unification have brought about changes in agricultural infrastructure and some reconstruction of existing plants. German expertise has become available to the new German Länder, but to reach the level of the old German Länder will require some time.
While comparable to agriculture elsewhere in Denmark, the area of the catchment is small. In 1990 total input to the Baltic Sea was 1 840 tons of nitrogen and 41 tons of phosphorus.
Farming in the Swedish part of the catchment area is quite intensive. To reduce the agricultural pollution load, Sweden has decided (target year 1995) to reduce livestock density, to build storage capacity of 8 months for cattle manure and 10 months for pigs and poultry, to prohibit manure application during winter and autumn, and to require that at least 60 percent of arable land has growing crops in autumn and winter.
Substantial inputs of nutrients by agriculture, industries and municipalities. A large proportion of the pollution load reaches Bornholm Basin by atmospheric deposition. This is estimated to be on the order of 55 000 tons per year for nitrogen and 600 tons per year for phosphorus. There is a substantial deposition of heavy metals. Information on pesticide residues is lacking.
Source: The Baltic Sea Joint Comprehensive Environmental Action Programme. Helsinki, 1993. (Balt. Sea Environ. Proc. No. 48), pp. 3-11 - 3-14
