In 40% of Europe's lakes, water quality is not up to the EU Water Framework Directive standard, this is primarily due to phosphorus pollution. It's a big problem for water quality and biodiversity in lakes and society, and we have to get a handle on how we restore these lakes, says associate professor and co-editor of the special issue, Kasper Reitzel, Department of Biology, University of Southern Denmark. Together with colleagues, Sara Egemose and Henning S. Jensen, who are experts in lake restoration, they are associated with Villum Kann Rasmussen Centre of Excellence, Centre for Lake Restoration (CLEAR). The special issue of Water Research regarding this topic has contributions from 60 authors from 12 countries.
Risen to alarming levels
In a press release, the journal writes:
"Phosphorus is the main cause of deterioration of water quality around the world. This results in "dead zones", toxic algal blooms, loss of biodiversity and increased health risks for plants, animals and people who come in contact with contaminated water.
After decades of runoff from agriculture, sewers and industry, the content of phosphorus in our lake beds has risen to alarming levels. The extent of the problem is daunting, and although attempts to reduce runoff have been made, about 10 million tonnes of extra phosphorous is released into our fresh water every year. Long-term monitoring activities show that plant and animal life is often not restored, even as the phosphorus input decreases. This is because the phosphorus is superimposed in sediment, from which it may be released back to the lake water. "
Geo-engineering can help the lakes
Geo-engineering covers the methods used to restore the lakes for phosphorus pollution.
Often the methods attempt to change the chemical bonding of phosphorus in the lake bed, for example, by adding aluminium salts or modified clay to the lake.
But the results are not always good. For example, geo-engineering is sometimes used indiscriminately in lakes because the external phosphorus load has not been reduced enough, because of economic reasons, or have used low doses, says Sara Egemose, Department of Biology, University of Southern Denmark. In the special issue presents a scientific assessment of the various geo-engineering methods. This knowledge, scientists from CLEAR in collaboration with Nature Agency translated into a set of guidelines for restoration of Danish lakes.