The Inversion Of Relative Content Of Heavy Metals In Water,Soil And Vegetation In The Tianfu New District Management Using Field Hyperspectral Method

With the development of the industrialization,modernization and urbanization,China's resource consumption is in a period of rapid growth.The consumption of resources will produce a large amount of residual heavy metal,those heavy metal soak into and gather in the soil,water and vegetation through atmospheric deposition,rainwater,etc.Then,the accumulation of heavy metals in soil,water and vegetation can threaten human health through contaminating the food chain.Thus,the monitoring of heavy metal concentration is very important in soil,water and vegetation.Although direct sampling can provide an accurate measurement of soil contaminants at specific sites,however,these procedures are often time-consuming,and it can only analyze the point and profile of samples but can't analyze the distribution in studied area from the macroscopic.In addition,the heavy metal transfer so rapidly in soil that a certain lag in the acquisition time of heavy metal concentration through the traditional method,especially in water.The development of remote sensing technology,especially hyperspectral provides a possibility for the rapid and large-scale distribution of heavy metals in soil,water and vegetation,which can acquire the continuous spectrum of the target.The Tianfu New District Management in Chengdu,Sichuan Province is selected as study area,and the spectral data of four crops,water and soil samples was collected by ASD Field Pro III in July,2017.This thesis intends to establish inversion models of heavy metal concentration through spectral analysis.Considering there is no geochemical analysis data caused by objective factors,,this thesis presents a method that only use the characteristic bands to estimate the heavy metal stress in the vegetation qualitatively and evaluate the relative concentration of heavy metals in soil and water semi-quantitatively.This method can analysis the vegetation stress trends and establish inversion models of the relative concentration of heavy metals by corresponding the heavy metal concentration of soil and water in 2004,based on the assumption that the contents of the four elements of heavy metals AS,Cd,Mn and Pb in 2017 are basically the same as those in 2004.Then,the environmental evaluation map of the study area can be made.The main work and achievements of this thesis are shown below:(1)The four high concentration and large differences in distribution heavy metal elements such as As and Cd in soil,Pb and Mn in water in the study area are selected as the object in this thesis.The inversion models of the heavy metals relative concentration were established based on the spectral band response curve of the four elements on soil or water in the literature without geochemical analysis data.According to the application of these models in soil,water,and vegetation,the relative concentration maps of soil and water in the study area and the vegetation stress trends were obtained.(2)Through analyzing the field spectral data of soil,the spectral features of As are: 454 nm,504nm,554 nm,604nm,754 nm,1395nm,1759 nm,1894nm,2198 nm,2300nm,and 2320nm;the spectral features of Cd are: 433 nm,504nm,654 nm,764nm,1250 nm,1290nm,1444 nm,1887nm,2100 nm,2192nm,2210 nm,and 2260 nm.The distributions of the relative concentration of the two heavy metals in soil can be obtained.The results indicate that the relative concentration of As in soil of the urban areas and the mountainous regions of the study area are low,and in the mainly agricultural hills and plains area of Xinxing Town,Baisha Town,Xinglong Town and Jiancha Town are high.The relatively concentrations of Cd of the hills and plains of the study areas are low,and the cities expanding currently in Zhonghe Town,Huayang Town,Zhengxing Town and Xinglong Town are high.(3)Through analyzing the field spectral data of water,the spectral features of Pb are: 497 nm,540nm,612 nm,620nm,669 nm,677nm,738 nm,748nm,813 nm,and 987nm;the spectral features of Mn are: 539 nm and 904 nm.The distributions of the relative concentration of the two heavy metals in water indicate that the relative contents of the two heavy metals are little difference.The relative concentration of Pb and Mn of the Zhonghe Town and Xinxing Town in the northwes.The relative concentration of the two heavy metals decreases with the flow of water.(4)For the vegetation in the study area,the red borders of the main vegetation sweet potato leaves,pumpkin leaves,fragrant leaves and Tianxiang rice leaves were extracted.Combined with the relative contents of heavy metals As and Cd in the soil,the heavy metal stress tendency of the vegetation was analyzed,and the Cd elements in the soil of the study area were found.The relative content of heavy metals promoted the growth of sweet potato leaves,fragrant leaves and Tianxiang rice leaves.As element inhibited the leaves of Tianxiang rice,leaves and sweet potato,but promoted the growth of pumpkin.