綠屋頂利用屋頂閒置空間提供綠化植栽，以減少都市熱島效應，或是藉由過濾、吸收或滯留雨水，減少暴雨之逕流水量。綠屋頂在國外已實施多年，國內近年亦出現許多實例，例如新北市政府大力推廣綠屋頂計畫。然而，國內對於綠屋頂的相關功能，卻鮮少有本土性監測數據，尤其針對綠屋頂的水文水質影響，幾乎沒有實場研究。因此本研究選取台北市三個薄層綠屋頂，分析其降雨逕流水質。三個實場樣區位在台北市信義區公所、信義國中、松山工農，另外亦採取一般住宅大樓裸露屋頂一處，以及雨水水樣。實驗期間共採了9次降雨，分析水質項目包括溶氧、導電度、酸鹼值、硝酸鹽、氨氣、總磷、化學需氧量及懸浮固體。結果顯示，除溶氧外，綠屋頂其他逕流水質濃度都比裸露屋頂的逕流水質高，尤其總磷與懸浮固體物高出10倍以上，硝酸鹽也有8倍之多。監測結果顯示綠屋頂設置後若缺乏適當維護，尤其過濾層若沒有發揮作用導致土壤隨逕流沖出，將使逕流水水質濃度提高，可能成為潛在的都市非點源污染來源。
Green roofs utilize unused roof space to build a green space with plantations, which can mitigate urban heat island effects as well as retain and detain storm water. Green roofs are widely applied around the world. In recent years, the development of green roof is highly promoted by local governments in Taiwan. However, on the contrary to the blooming practical cases the local monitoring data is very less; especially the lack of water quality monitoring. This study is the very first experience on green roof water quality analysis in Taiwan. Three extensive green roofs in Xinyi district in Taipei city were estimated. They are the Xinyi district office, Xinyi junior high school, SongShan high school of Agriculture and Industry. One general bare roof and rainwater were sampled as compare groups. The total nine storm events were collected and dissolved oxygen (DO), conductivity, pH, nitrate (NO3), ammonia nitrogen, total phosphorous (TP), chemical oxygen demand, and suspended solid (SS) were analyzed for water quality. The results showed that all water quality concentration from green roof runoff were higher than that from bare roof except DO. The TP and SS of green roof runoff were higher than 10 times and the NO3 is higher than 8 times of that of bare roof water. It implies that the improper management of green roof might cause it as potential water pollution sources in urban area.
