Köphultssjöns tillstånd och omgivningens påverkan
Sammanfattning: The condition of the lake Köphultssjön in southern Småland, Sweden, has been investigated. The lake is acidified and has been treated with lime. The natural conditions that could be expected were assessed. The possible effects from land use (forestry, agriculture and peat extraction) acid rain, treatment with lime and discharge from sewage works were studied. Water samples were taken in the lake system, Köphultssjön, Fedingesjön and Hannabadssjön. Sediment from Köphultssjön and Hannabadssjön (downstream) was analyzed. The extent of the drainage basins was assessed with the help ofa topographic map and the directions of the streams in the area. The results show that Köphultssjön is still acidified, partly owing from drainage from bogs and humus rich soil. Acid rain greatly affects the area, because of the poor buffering capacity of the rock. The other two lakes are less acidified since they receive less water from bogs and Hannabadssjön receives a more constant lime dosage. Lime has improved the quality of the water in Köphultssjön, but can lead to an increase in the level of nutrients in sediments with the subsequent expansion of macrophytes such as reeds. The nutrient content of the lake was higher than expected since the area is poor in nutrients. This is due to the discharge from sewage works, agriculture, forestry, peat extraction and also to nitrogen pollution from the air. The sediment layer in Köphultssjön is thick and compared with that in Hannabadssjön is more organic because of the supply of peat and humus. The acidity of the lake increases the precipitation of the organic substances. The surface of Köphultssjön was lowered about 100 years ago which, together with present activities, has lead to the acceleration of the expansion of vegetation at the expense of the lake.
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