Freshwater - State and impacts (Sweden)
For the most part, Sweden’s water bodies are not rich in nutrients, except in agricultural and metropolitan areas. Acid fallout has decreased by more than 90 % during the past ten years. There are still no clearly established explanations for the high con
b) What are the state (S) and impacts (I) related to this theme, including impacts on the natural environment and human health/human well-being, both at national level as well as in transboundary terms?
For the most part, Sweden's water bodies are not rich in nutrients, except in agricultural and metropolitan areas. This points to the areas in Sweden where we can find bodies of water with excessive nutrients. At the same time as we are seeing a positive trend in water quality, eutrophication of new bodies of water is occurring. One explanation is that while agricultural acreage is decreasing, loading from other sources, such as runoff and traffic, is increasing. In addition, nitrogen and sulphur continue to be introduced from distant sources within and outside the country.
Acidification varies between areas
Acidification is caused by national and international anthropogenic loads. Acid fallout has decreased by more than 90 % during the past ten years. One source of acidifying pollutants that is becoming increasingly important is shipping. Differences within Sweden are large. This is clearly shown in the figure.
How various toxic substances are distributed among water, sediment and organisms depends on the substances' characteristics, such as whether they bind with humus and whether or not they are fat-soluble. Many substances have not been produced, used or spread within the country but have been conveyed through atmospheric fallout. These substances often occur in a gradient from south to north and can be found in otherwise unpolluted water bodies.
Other substances have a particular area of usage or are produced as by-products within industries and occur in more limited places, such as large cities, mining areas, agricultural areas or other specific areas. If these substances are detected in high concentrations, it is often possible to find a way to deal with the pollution since the source can usually be found, the exception being those groups of substances that accumulate in the food chain.
Mercury occurs naturally in high concentrations in Sweden. However, there are still no clearly established explanations for the high concentrations that exist today in almost all Swedish freshwater bodies. There are hundreds of small, seemingly unpolluted forest lakes where the mercury concentration in fish is too high for human consumption of the fish.
The large hydroelectrical constructions and dams in northern Sweden cause enormous impact on the environment. The hydromorphology of many smaller rivers and lakes has also been changed due to hydropower, timber floating, trenching, etc. These changes are often quite old and can be difficult to evaluate. They are also expensive to remediate.