Green roofs are one of the method of recovering green space in urban are-as. They are also effective in improvement of air quality and local climate as well as play an important role in thermal insulation of buildings. The most important role they play in urban areas is rain water retention and delaying of the runoff. The main goal of the research was to estimate potential influence of the green roof substrate on runoff water quality. Preliminary results show increase of the con-centration of phosphates and total solids in leachate. Mean concentration of solids in intensive roof substrate leachate amounted 231 mg dm-3 and in extensive sub-strate leachate 274 mg dm-3, comparing to concentration 6-7 mg dm-3 in simulated rain. Phosphorus concentration in intensive and extensive substrate runoff amounted 0,112 mgPO4-P dm-3 and 0,126 mgPO4-P dm-3 respectively. Phosphorus concentration in simulated rain amounted 0,056 mgPO4-P dm-3. Even if the concentrations in substrate leachate are low, phosphorus can still be an important factor influencing green roofs runoff receiver quality.
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