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Hyperspectral features about suspended substance in some representative areas, Lake Taihu, China

Three campaigns including 37 valid samplings were made to measure field spectra together with some water quality parameters including suspended substance concentration and other data. Field spectra were measured with a portable Field Spec FR spectroradiometer (ASD Inc.), in a wavelength range of 350-2500 nm. And the concentrations of water quality parameters were measured according to the corresponding investigation criteria about lakes of China. Based on the correlative analysis between field spectra and suspended substance concentrations of different ranges, we divided all the 37 samples into different groups according to the analyzed threshold concentrations. Then some reflectance variables at some bands were used to do the correlative analysis with suspended substance concentrations of different groups to find out the better indicative bands. Because of no evident indicative bands existing with the general method in some groups, the first and second derivative method was also used. The results showed that the best variable is not a constant when the concentration is low and the range or span is narrow. Otherwise, the best variable is the reflectance first derivative near 878 nm, and then the average reflectivity in the range of 810-820 nm, or the reflectivity at 820 nm. Generally, the derivative method is better to estimate suspended substance concentration with hyperspectra.