重金属铜污染植被光谱响应特征研究

重金属铜污染植被的反射光谱特性会发生明显改变。在本研究中,采用不同程度的铜污染土壤作为培养基质,选择春小麦、上海青两种农作物进行铜胁迫实验,获取了4个不同生育期、10个不同铜污染强度下的植被叶片的反射光谱,并采用铜污染叶片7个特征波段和光谱角的方法研究了铜污染叶片的光谱特征。结果表明,铜污染叶片光谱差异与作物时期和作物类型有关,可以采用叶片光谱角描述铜污染叶片与健康叶片的光谱差异。该方法只需与阈值做简单的比较,方法简便易行,而且对轻度及重度铜污染十分敏感。叶片光谱辐射传输模型反演结果表明铜污染叶片内部结构参数N明显变大,这也证明了铜污染使叶片内部结构更加散乱无序。在此基础上进一步建立了N与红肩处反射率值的线性关系,相关系数为0.978。本文为铜污染叶片光谱反射模型的建立提供了初步的数据基础与理论支持。

Spectral response of wheat and lettuce to copper pollution

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.