Studying On Retrieval Of Soil Heavy Metal Content In Kun Shan Using The Organic Matter Diagnosis Index

Hyperspectral remote sensing is characterized by high spectrum resolution, and has a great potential to quantitatively identify soil component through inverse analysis. Organic matter as the main component of soil has unique spectrum characteristic. Heavy metal as the trace element does not have obvious spectrum characteristic. Soil organic matter plays a key role in immobilizing heavy metals. So there are some correlations between soil organic matter and heavy metals. To a certain extent, using spectrum characteristic of soil organic matter to estimate the content of heavy metals is feasible.This paper takes paddy soil in Kunshan as study object. Through investigating soil reflectance Spectroscopy, the sensitive band and the absorption parameter of organic matter are extracted based on mathematic analysis of soil reflectance. And several diagnostic models for soil organic matter are made through regression analysis. Then we attempt to estimate the content of heavy metals by soil organic matter diagnostic index. The dissertation concentrates on the following aspects:1. In the field, the spectrum of soils samples were measured by ASD Fieldspec Pro FR in the range of 350～2500 nm. Through soil spectral and chemical analysis, it is found that the soil reflectance increases quickly in the visible spectrum, but slowly in the near-infrared spectrum. With increasing organic matter, the soil reflectance spectral curve goes downward.2. Methods as derivative, logarithm and standardized ratio transformation may weaken the background noise effectively to the spectrum data. Especially using the ratio of the reflectance to the average of 450～750 nm may obviously enhance the correlation between soil organic matter and soil reflectance. According to the result of the correlation analysis, the 511 nm is regarded as the best detecting band for soil organic matter content. Moreover, based on the Organic matter Diagnosis Index (ODI) in the 507～516 nm the linear retrieval model is made.3. Continuum-removal is an effective method in soil spectral analysis. In this study, it is observed that there is a strong absorption around 511 nm due to organic matter. Based on the absorption area in the 450～580 nm regions, the content of organic matter is calculated accurately.4. Based on the absorption low of heavy metal, using the best organic matter diagnosis index make a model of estimating the content of heavy metal in soil. But the practicability of this method still needs further validated.