基于反射率的太湖典型湖区溶解性有机碳的反演

RETRIEVING OF DISSOLVED ORGANIC CARBON BASED ON IRRADIANCE REFLECTANCE IN TYPICAI LAKE ZONES OF LAKE TAIHU

2004年4月基于野外水下辐照度的测定及实验室溶解性有机碳(DOC)的分析,通过研究典型湖区水体中DOC浓度与反射率之间的关系,选择DOC浓度反演的最佳波段,建立了DOC浓度的遥感定量反演模型。结果表明,DOC浓度在6.60～17.17mg/L(均值为9.99mg/L,方差为2.48mg/L)之间;反射率的峰值出现在560～590nm;红光波段与绿光波段反射率的对数值能较好的估计DOC浓度,其中又以lg(R670/R530)与lg(DOC)相关程度最高,决定系数为0.82;DOC浓度反演的经验模型为:lg(DOC)=0.654(±0.012)lg[R(670)/R(530)]+1.007(±0.086)。对模型进行检验,最小误差为6.7%、最大误差为20.3%,平均误差为12.3%。

Underwater irradiance and irradiance reflectance in typical lake zones of Lake Taihu were measured using a Macam SR9910 scanning spectroradiometer in April 2004. Extensive water quality parameters such as Total Suspended Solids (TSS), Dissolved Organic Carbon (DOC) and chlorophyll a (Chl-a) were measured simultaneously with the spectral data. The features of the spectral irradiance reflectance of the lake waters are discussed. An optimum band combination is found and a local algorithm model for DOC concentration estimation is developed. The results show that DOC concentration ranges from 6.60 to 17.17 mg/L with an average of 9.99 mg/L. Most peaks of subsurface irradiance reflectance are recorded between 560 and 590 nm. The ratio of irradiance reflectance of red waveband to green waveband can be used to estimate DOC concentration satisfactorily. Determination coefficients between lg(R670/R530) and lg(DOC) is 0.82. The retrieving model of DOC concentration is: lg(DOC)=0.654( 0.012)lg\R(670)/R(530)\]+1.007( 0.086). The maximal, minimal and average relative errors of model are 20.3%, 6.7% and 12.3%, respectively. This paper has demonstrated the potential of the method for deriving CDOM and DOC from measurements of irradiance reflectance in lake Taihu. The accuracy of the method needs to be improved if it is to be of practical use, and this will involve more and careful measurements.