藻类水体离水辐射光谱的荧光偏振识别研究

发布时间：2018-11-29 12:14

【摘要】：富营养化水体中,藻类和其它浮游植物会大量繁殖,而藻类细胞中叶绿素所占的比例比较稳定,因此叶绿素浓度是反映水体富营养化程度的一个重要指标。藻类细胞内的叶绿素分子吸收光能后,会以释放能量的形式发射叶绿素荧光,因此叶绿素荧光可以作为近似估算叶绿素浓度的一个重要参数,准确提取离水辐射中的叶绿素荧光对遥感监测水体中的叶绿素浓度并且对水环境评价等具有重大的理论意义和广泛的应用前景。在大气海洋系统中,入射的太阳光会被大气海洋系统的各种分子、气溶胶和水溶胶散射,同时被海表反射,这些过程都会改变光的偏振态。被散射和反射的太阳光是部分偏振光,并且包含了能够反映大气海洋系统中的气溶胶和悬浮物的本质特征的信息。水中颗粒物的弹性散射光是部分偏振光,而叶绿素荧光则是非偏振光,基于该特征并利用偏振技术可从总离水辐射信息中分离出荧光,从而达到遥感反演叶绿素浓度的目的。但对于近岸复杂水体,该方法能否适用并不清楚,基于此,实验通过偏振测量系统,具体分析了不同叶绿素浓度和无机颗粒物浓度,以及光源入射角,水表面有风情况对偏振分离方法的影响。本文选用抑食金球藻,强壮前沟藻和海洋原甲藻作为试验藻种,利用地物光谱仪结合偏振器通过两种观测方式完成了室内条件下叶绿素荧光偏振分离实验。结果表明,斜入射情况下,光源入射天顶角在30°-60°时,测量结果更为可信,入射角为45°时分离效果最好。对含不同浓度叶绿素的藻类水体,均能较好地分离出叶绿素荧光,但叶绿素浓度过低时,分离结果的误差较大,相较而言,高浓度叶绿素水体的分离结果更为可靠。对含不同浓度无机颗粒物的藻类水体,分离出的荧光峰会随浓度增加有降低趋势,但是当颗粒物浓度达到3×105mg/m3时,反演结果仍然可靠。表面有风情况下,测量出的光谱曲线波动较大,但是并不影响荧光分离。同时也在秦皇岛海域进行了赤潮水体和悬浮泥沙水体的现场偏振测量,结果表明对赤潮水体,偏振分离荧光方法仍然具有一定的适用性,表明利用偏振方法分离叶绿素荧光对遥感探测近岸水体的叶绿素浓度及赤潮监测均具有重要意义。对现场测量悬浮泥沙水体,本文对比分析了偏振度光谱特征与遥感反射率的关系,发现上行辐亮度偏振度与遥感反射率光谱呈现反相关系,表明在获取海洋水色信息方面,偏振度具有同遥感反射率类似的能力。
[Abstract]:Algae and other phytoplankton proliferate in eutrophication water, but the percentage of chlorophyll in algae cells is stable. Therefore, chlorophyll concentration is an important index to reflect the eutrophication degree of eutrophication. Chlorophyll molecules in algae cells emit chlorophyll fluorescence in the form of energy release after absorption of light energy, so chlorophyll fluorescence can be used as an important parameter to approximate estimate chlorophyll concentration. Accurate extraction of chlorophyll fluorescence from off-water radiation has great theoretical significance and wide application prospect for remote sensing monitoring of chlorophyll concentration in water body and evaluation of water environment. In the atmospheric ocean system, the incident solar light will be scattered by various molecules, aerosols and hydrosol in the atmospheric ocean system, and also reflected by the sea surface. These processes will change the polarization state of the light. The scattered and reflected sunlight is partially polarized and contains information that can reflect the essential characteristics of aerosols and suspended matter in atmospheric and oceanic systems. The elastic scattering light of particulate matter in water is partially polarized, while chlorophyll fluorescence is non-polarized light. Based on this characteristic and using polarization technique, fluorescence can be separated from the information of total off-water radiation, so that the chlorophyll concentration can be retrieved by remote sensing. However, it is not clear whether this method can be applied to the inshore complex water. Based on this, the different chlorophyll concentration, inorganic particle concentration and incident angle of light source are analyzed by polarization measurement system. The influence of wind on the polarization separation method. In this paper, Chlorella aurantia, Chlorophyta roxburghii and Prorocentrum were selected as experimental algae. The experiment of chlorophyll fluorescence polarization separation under indoor conditions was carried out by means of ground object spectrometer combined with polarizer. The results show that the measurement results are more reliable when the incident zenith angle of the light source is 30 掳-60 掳, and the separation effect is the best when the incidence angle is 45 掳. For algae with different concentrations of chlorophyll, chlorophyll fluorescence can be well separated, but when the concentration of chlorophyll is too low, the error of the separation results is larger, compared with that of high concentration of chlorophyll water, the separation results are more reliable. For algae with different concentrations of inorganic particles, the fluorescence summit showed a decreasing trend with increasing concentration, but when the concentration of particulate matter reached 3 脳 105mg/m3, the inversion results were still reliable. In the case of surface wind, the measured spectral curves fluctuate greatly, but do not affect the fluorescence separation. At the same time, the polarization measurements of red tide water and suspended sediment water are also carried out in Qinhuangdao Sea area. The results show that the polarization separation fluorescence method is still applicable to the red tide water. The results show that the polarization method of chlorophyll fluorescence separation is of great significance for remote sensing detection of chlorophyll concentration and red tide monitoring in coastal waters. In this paper, the relationship between polarization spectral characteristics and remote sensing reflectance is compared and analyzed for the measurement of suspended sediment in situ. It is found that the upstream radiance polarization degree and remote sensing reflectance spectrum are inversely related to each other, which indicates that in the aspect of obtaining ocean water color information, The degree of polarization has a capability similar to that of remote sensing reflectivity.
【学位授予单位】：大连海事大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X52

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