| Soil can provide plant with esssential water and nutrients, so it is known as the "home of plants". And plants can offer different kinds of nutrients for human beings to satisfy their need of survival and development. Hence soil environment and plant growth are closely related to humans. The heavy metal pollution of soil mainly comes from sedimentation of atmospheric dust, wastewater irrigation and sludge accumulation, usage of fertilizer and pesticide, etc. Heavy metal attracts much attention for its difficulty in degrading, stronger toxicity, easy accumulation, etc.Among of them, study focus of many scholars lies in Cd specifically, a heavy metal with strong biology transfering property, which is easily absorbed and accumulated by plants. This paper offers quantitative inversion to Cd content in soil and rice plant,SPAD of leaf is as well, through monitoring the heavy metal content in soil and rice plant of different Cd gradient paddies, monitoring spectrum of rice plant, using spectroscopy technology combined with mathematical statisticsmethod. This is significant for discovering and determing the pollution levels of soil and rice timely,and securing grain safety of our nation. This paper aimes to research thepollution status of Cd in soil, by studying the spectral characteristics of rice in visible light-near infrared spectrum, extracting variables of the spectral characteristics of rice,setting up ground spectral model which is combined with the remote sensing images,and then offer ideas and methods for the technology of remote sensing monitoring on soil pollution of large areas. The main contents are as follows:Collecting 27 soil samples from surrounding areas of Gui xi in Jiangxi province as the research object, the author uses inductively coupled plasma mass spectrometry determined of soil samples of Cu, Pb, Zn, Cd and their effective state, through doing difference significancy analysis, selecting the three Cd gradient of the soil as the research object. By studying the relationship among heavy metal content in rice plants,heavy metal content in soil and rice leaf SPAD levels, analysing the law that rice plant spectral curve changes according to heavy metal content in soil and rice plants, rice leaf SPAD levels, finding out the sensitive spectral characteristic value, the research aims to establish the model among heavy metal content in rice plants, heavy metal content in soil and the sensitive spectral characteristic value, set up the relationship between the ground spectrum characteristic value and high spectrum monitoring datawith aerial image statistics, and finally offer scientific basis for the realization of aerial remote sensing monitoring soil pollution.The experimental results show that:(1)The heavy metal elements in rice plant are mainly absorbed from soil.(2)(2)Rice leaf SPAD levels has a negtive corelation with Cd content in rice plant, that means rice leaf SPAD levels can indicate the polution of the heavy metal Cd in soil and rice plant.(3)Rice leaf SPAD levels has a positive corelation with the depth of blue valley andthe peak of red edge. Establishing regression model between rice leaf SPAD levels and the depth of blue valley andthe peak of red edge in leaf spectral characteristic, the fitting coefficient is perfect to some degree, according to regression Coefficent R2.(4) The spectrum characteristic value of rice leaf are affected by the Cd elementin soil and rice plants, which is most closely related to the fact that the most distivtive change occurs in the depth of blue valley and the peak of red edge.(5)Rice leaf spectral characteristic parameters from remote sensing indicates that the depth of blue valley and the peak of red edge can be used to monitor the degree of the Cd pollution degree of soil and of rice which are affected by the Cd element. At the same time, it's possible to forecast Cd content in soil and rice palnts,by establishing regression model among SPAD of rice plant, Cd content in soil and rice plants, and rice leaf spectrum. |
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