分别于2004—06和2004—08在太湖的21个固定监测站点进行原位水质取样分析和波谱实测,进而利用地面实测高光谱数据评价太湖水体富营养化状态.水体富营养化程度的评价指标为营养状态指数(TSI).首先,根据太湖水体固有光学特性,用分析模型的方法建立水体反射率模拟模型,进而用求解优化函数的方法,利用Matlab软件反演叶绿素a浓度;其次,利用反演的叶绿素a浓度,计算采样点位的营养状态指数,并利用ArcView软件进行插值,制作太湖富营养状态评价图.结果表明.2004-06和2004-08太湖富营养化程度差异显著:6月,中营养水平湖区所占比例最大,其面积占总面积的61%;8月,轻度富营养水平湖区所占比例最大,其面积占总面积的52%.总体上,富营养化程度最严重的区域为太湖北部,由北向南富营养化程度逐渐减弱,东部的富营养化水平最低.
In situ experiments including water quality analyzing and spectra measuring were conducted on Jun. , 2004 and Aug. , 2004 in Taihu Lake for 21 samples. Then eutrophic state of Taihu Lake was evaluated by measured hyperspectra data, and the evaluating index was eutrophic state index (TSI). Firstly, the simulation model of water reflectance was built by analytic model using inherent optical properties (IOPs). Then Chlorophyll a content (Chl-a) was inversed by optimizing method by Matlab software; Secondly, TSI was calculated by inversed Chl-a, and the eutrophic state of Taihu Lake was evaluated by using ArcView' s interpolation function. The evaluation figures show that: there are notable differences between Jun. , 2004 and Aug. , 2004. The proportion of mesotropher state is as high as 61% in June, while the proportion of light eutrophic is as high as 52% in August. In totally, the most serious eutrophic state occurs in north of Taihu Lake. Eutrophic state wears off from north to .south. The lowest eutrophic region is in the east of Taihu Lake.