Hyperspectral feature analysis of chlorophyll a and suspended solids using field measurements from Taihu Lake, eastern China

摘要

We report results of three field campaigns conducted at 39 stations. At each station, we measured reflectance spectra in situ and collected water samples for measuring chlorophyll a (CHL) and suspended solids (SS) concentrations in the laboratory. To identify the indicative bands and develop suitable estimation models for CHL (C_(CHL)) and SS (C_(SS)) concentrations in Taihu Lake, a spectral-feature method and a derivative method were applied. The following conclusions were drawn: (a) the critical C_(CHL) and C_(SS) probably causing their spectral variation are, respectively: 0, 10, 50 and 75 μg L~(-1), and 0, 10, 50 and 100 mg L~(-1); (b) the derivative method is better than the spectral-feature method for estimating C_(CHL) and C_(SS); (c) the optimal variable for CHL is a reflectance second-order derivative at 501 nm or a reflectance first-order derivative at 698 nm; the optimal variable for SS can change when its concentration is low and the range is narrow; otherwise, the optimal variable is a reflectance first-order derivative at 878 nm; and (d) the CHL and SS have an effect on one another's retrieval. The C_(CHL) estimation accuracy would benefit from narrowing the C_(SS) range. With C_(CHL) increasing and its range broadening, the corresponding C_(SS) estimation accuracy decreases gradually.