Beijing Key Laboratory of Remote Sensing and Digital City Environment

Beijing, China

Beijing Key Laboratory of Remote Sensing and Digital City Environment

Beijing, China

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Zhu Y.,Beijing Normal University | Zhu Y.,Beijing Key Laboratory of Remote Sensing and Digital City Environment | Qu Y.,Beijing Normal University | Qu Y.,Beijing Key Laboratory of Remote Sensing and Digital City Environment | And 3 more authors.
Journal of Remote Sensing | Year: 2014

The leaf reflectance spectra of plants polluted with heavy metal copper exhibit abnormal behavior. This paper investigates the spectral changes in copper-polluted leaves using seven spectral signatures and the spectral angle method. Wheat and lettuce were selected as the experimental subjects and were cultured in copper-polluted soil. Leaf spectra reflectance and scanning electron micrograph of ten copper treatment groups were measured in four regular periods. The reflectance spectra of the leaves were obtained using an ASD Field Spectrometer. Results showed that the irregular spectral changes of copper-polluted leaves depend on crop growth stages and crop types. The spectral angle, a simple method of comparing the vector angle of the leaf spectra with the given threshold values, has been justified as an efficient method of describing the spectral differences between copper-polluted leaves and healthy leaves. The method is very sensitive to light and the severity of copper pollution. Results also show that the leaf structural parameter (N) of copper-polluted leaves is larger than that of healthy leaves. The linear relationship between N and the reflectance value of the red shoulder was fitted with a correlation coefficient of 0.978. As a result, the deduced N from the leaf reflectance spectra may be used as an indicator to reflect the leaf structure distortion under copper pollution conditions. The significance of this study lies in its provision of data asbasis and theoretical support for the construction of a copper-polluted leaf reflectance spectral model.


Zhu Y.,Beijing Normal University | Zhu Y.,Beijing Key Laboratory of Remote Sensing and Digital City Environment | Qu Y.,Beijing Normal University | Qu Y.,Beijing Key Laboratory of Remote Sensing and Digital City Environment | And 3 more authors.
International Journal of Remote Sensing | Year: 2014

This study intended to investigate the reflectance model for a crop stressed by the heavy metal copper. Forty-six groups of copper-treated leaves were measured in a laboratory experiment. Through these measurements, we obtained leaf reflectance spectra from 400 to 2500 nm, information on the biochemical components of leaves, and their corresponding scanning electron microscopy images. We then developed a new reflectance spectral model based on the classic broadleaf radiative transfer model - PROSPECT. Compared with the PROSPECT model, the new model primarily considers the addition of the specific absorption coefficient of the copper ion. The scattering process is described by a refractive index (n) and a leaf structure parameter (N). The absorption is modelled with pigment concentration, water content, dry matter content, copper ion contamination, and the corresponding specific spectral absorption coefficients (Kab, Kw, Kd and Kcu). Thus, reflectance spectral modelling is an inversion procedure to calculate the above six parameters accurately. For model validation, 16 leaves from the laboratory experiment were used. The validation showed that the inversion values for agree very well with the published absorption spectra of cupric chloride solutions. The linear regression analysis between the simulated and measured reflectance values provides a correlation coefficient of approximately 0.9441, and the root-mean-square error was less than 0.1 from 400 to 2500 nm. © 2014 © 2014 Taylor & Francis.

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