Relationship between Algal Chlorophyll Concentration and Spectral Reflectance of Inland Water
内陆水体藻类叶绿素浓度与反射光谱特征的关系

Algal chlorophyll measurement is usually used to assess trophic status of lakes. The development of hyperspectral imaging enable it possible to detect spectral features of algal chlorophyll with high spectral resolution and to map the spatial distribution of algae in large lakes with great precision. This study was conducted to establish correlation between hyperspectral reflectance and algal chlorophyll concentration. The problem is complicated by the numerous suspensions and dissolved organic matters in inland water because optical effects of these pollutant substances often overwhelm spectral features of algae. The area studied in this paper is the Lake Taihu in the Yantze river delta, which becomes enriched quickly in nutrients and supports excessive growths of blue alga in summer. Reflectance spectrum of water in the range of 350 to 1050nm was measured by a GER\|1500 radiometer with a bandwidth of 1.6nm. The water was also sampled simultaneously to determine algal chlorophyll concentration and other water quality parameters in the laboratory. The position of reflectance peak near 700nm and reflectance ratio of R 705nm / R 675nm were found to be significantly correlated with algal chlorophyll concentration. Chlorophyll algorithms based on these spectral features are presented.