Olika våtmarkstypers påverkan på CH 4 , N 2 O och CO 2 utsläpp, och upptag av N 2

Wetlands are constructed for uptake of nutrients in areas that have exceeded critical loads of nitrogen and also for promoting biological diversity. Wetlands have not only positive effects, they have some negative environmental effects as they emit the greenhouse gases methane (CH4), carbon dioxide (CO2) and nitrous oxide (N2O). There are different ways to construct wetlands which gives different types of consequences. The vegetation in the wetlands has also proved to be important for both the uptake of nitrogen and for the emissions of greenhouse gases. Four types of constructed wetlands have been compared, to see which is best suited for maximum uptake of nitrogen and minimum emissions of greenhouse gases. The different types are: the wetlands with free water surface (FWS), horizontal subsurface flow (HSSF), vertical subsurface flow (VSSF) and hybrid systems. The hybrid system consisting of one vertical- horizontal subsurface flow wetland was found to be the best alternative regarding the uptake of nitrogen. If the purpose is to have as little greenhouse gas emissions as possible the free water surface is the most effective type of wetland.