Quantitative estimation of chlorophyll-a concentration in the northern part of Lake Taihu using spectral reflectance

Abstract

利用地物光谱仪研究了太湖水体的反射光谱特征与叶绿素a浓度之间的定量关系,结果表明太湖水体的叶绿素a浓度可以用720 nm附近的反射率估算,同时也可以用806 nm和571 nm两个波段的反射率比值来估算,前者建立的估算模型具有较好的通用性,而后者只能较好的估算<10μg/L的叶绿素a浓度;通过对光谱微分的分析,发现叶绿素a浓度与690 nm附近的一阶微分和702 nm附近的二阶微分相关性最好,但基于反射光谱一阶微分的叶绿素a浓度估算模型,并没有显著的提高太湖叶绿素a浓度的估测精度,二阶微分后的估测精度好于一阶微分,但其估测精度仍没有利用720 nm反射光谱的反演模型高．太湖水体的叶绿素a浓度可以利用720 nm附近的反射光谱有效地估算．;The quantitative relationship between Spectral Reflectance (SR) characteristics of water and chlorophyll-a( Chi. a) concentration in Lake Taihu was analysed based on the in-situ data collected by ASD FieldSpec Hand-Held Spectroradiometer. The results reveal that the Chi. a concentration can be quantitative retrieved using SR at wavelength of 720 nm，or using the ratio of SR at wavelength of 806 nm and 507 nm. The model using SR at wavelength of 720 nm is an effective retrieval model whether Chi. a concentration > 10ug/L or Chi. a concentration < 10 ug/L, while the model using the ratio only retrieve Chi. a concentration effectively for Chi. a concentration < 10ug/L. It was found that there is high correlation between Chi. a and the first derivative at 690 nm, also high correlation between Chi. a and the second derivative at 702 nm through spectral derivative method，but the model retrieve accuracy using the first derivative or the second derivative is not significantly improved compared to the model directly using SR. But the retrieval accuracy using the second derivative is a little higher than the model using the first derivative. So it was concluded that the Chi. a Concentration in Lake Taihu can be retrieved using SR at wavelength 720.