铜污染植被指数的玉米叶片污染程度探测模型

doi:10.3964/j.issn.1000-0593(2020)01-0209-06

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Abstract The use of hyperspectral remote sensing to monitor heavy metal pollution in crops has become an important part of remote sensing research. The difference in the amount of heavy metal content in the contaminated crop leaves mapped to the spectrum is weak, so it is challenging to dig sensitively the value information contained in it. In this paper, based on the spectrum of crop leaves, a pollution detection model of copper pollution vegetation index (CPVI) was proposed by combining multiple spectral feature bands to characterize the pollution degree of heavy metal copper on crops. Firstly, a pot experiment was conducted to add CuSO₄·5H₂O powder with different concentration gradients to the soil to simulate copper-contaminated soil environment and stress corn growth. The spectra of old, middle and new leaves at the ear of corn were collected, and the Cu²⁺ content and relative chlorophyll concentration in the leaves were determined. Then, using 58 randomly selected corn leaf spectra as experimental data, the spectral reflectances of the two groups of wavelengths λ₁ and λ₂ were selected in the wavelength range of 380~900 nm. The Pearson correlation coefficient between CPVI [λ₁, λ₂] and Cu²⁺ content in the corresponding leaves was calculated, and the absolute value matrix of correlation characteristics was obtained. Secondly, according to the obtained correlation feature matrix, the characteristic band of 690 and 465 nm with high correlation coefficient was extracted and combined with the band 850 nm to establish the Copper pollution index of maize (CPVI_m). After that, CPVI_m index was verified based on 26 other groups of data, and Normalized difference vegetation index (NDVI), MERIS terrestrial chlorophyll index (MTCI) and other conventional vegetation indexes were compared to verify the effectiveness and superiority of CPVI_m. The results showed that the highest correlation coefficient between NDVI, MTCI, REP, DVI and Cu²⁺ content in leaves was 0.68, and the lowest residual sum of squares was 70.99. However, CPVI_m was significantly negatively correlated with Cu²⁺ content in leaves. The correlation coefficient was -0.80, and the residual sum of squares was 48.52, which were better than conventional indexes such as NDVI and MTCI. It proved that CPVI_m is more sensitive to heavy metal stress. At the same time, the robustness of CPVI_m index was verified by using the spectral data of different varieties of maize in different years. The correlation coefficient of CPVI_m and Cu²⁺ content were -0.90 and -0.96, respectively, which were significantly correlated. It shows that CPVI_m is still suitable for detecting the pollution degree of different maize varieties. In addition, using Cu²⁺ content, CPVI_m and chlorophyll relative concentration in maize leaves, a three-dimensional analysis model was constructed, which reflected the correlation between them from a spatial point of view. The CPVI detection model based on the combination of spectral characteristic bands can be used as a reference method to evaluate the pollution degree of heavy metals in crops. The CPVI_m index based on this method can effectively identify the degree of heavy metal Cu²⁺ pollution in maize.

Key words：Spectrum; Maize leaves; Pearson correlation coefficient matrix; Copper pollution vegetation index; Chlorophyll

Received: 2018-11-17 Accepted: 2019-03-25

ZTFLH:

TP7

Corresponding Authors: YANG Ke-ming E-mail: ykm69@163.com

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https://www.gpxygpfx.com/EN/10.3964/j.issn.1000-0593(2020)01-0209-06 OR https://www.gpxygpfx.com/EN/Y2020/V40/I01/209