内陆水体藻类叶绿素浓度与反射光谱特征的关系

Relationship between Algal Chlorophyll Concentration and Spectral Reflectance of Inland Water

通过研究内陆水体反射光谱特征与藻类叶绿素浓度之间的关系，建立藻类叶绿素高光谱定量遥感模型。在实验地太湖地区，采用高分辨率地物光谱仪实地测量了湖水在可见光和近红外波段（３００—１１００ｎｍ）的反射光谱曲线，并且同时采样分析叶绿素、总悬浮固体物质浓度等水质参数。研究发现在叶绿素浓度较高时（ ＞ ５μｇ／Ｌ），水体光谱反射比Ｒ７０５ｎｍ／Ｒ６７５ｎｍ 、叶绿素在７００ｎｍ 附近反射峰的位置等与叶绿素浓度有较好的相关性。

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.