[Fluorescence properties of lake water]

Fluorescence spectrum technique has advantages of high sensitivity, high selectivity and quick-and-easy detection, and excitation-emission matrix (EEM) can provide abundant information. Fluorescence spectrum is unique for each water sample and is named as "fluorescence fingerprint". In the present paper, excitation-emission matrix was used to study the variability of water quality from spring to winter of two neighboring lakes in an urban park in Beijing. There was typical protein-like and humic-like fluorescence in the EEMs of the two lakes and the intensity of the protein-like fluorescence was significantly stronger. The close relationships between the fluorescence intensities and natural/anthropogenic activities showed that the water quality changed obviously with the season: the water quality in spring and summer was better than in autumn and winter. Natural factor like the growth of algae and plants etc was the major impact factor for the lake for pleasure boats, and anthropogenic factor such as planting was significantly important for the lake with ornamental plants. So the variability of water quality of lake is determined by the function of lake. To remove the remains of algae and plants in spring and autumn benefits the water quality of the lakes.