Study on the Characteristics and Mechanism of Visible and Near Infrared Reflectance Spectra of Soil Heavy Metals
CHENG Hang1,2, WAN Yuan3, CHEN Yi-yun2,4,5*, WAN Qi-jin1,6,7*, SHI Tie-zhu8, SHEN Rui-li9, GUO Kai2, HU Jia-meng2
1. School of Chemistry and Environmental Engineering,Wuhan Institute of Technology,Wuhan 430073, China
2. School of Resource and Environmental Science,Wuhan University,Wuhan 430079, China
3. College of Urban and Environmental Sciences,Hubei Normal University,Huangshi 435002, China
4. State Key Laboratory of Soil and Sustainable Agriculture,Nanjing 210008, China
5. Suzhou Institute of Wuhan University,Suzhou 215123, China
6. Key Laboratory for Green Chemical Process of Ministry of Education,Wuhan Institute of Technology, Wuhan 430073, China
7. Hubei Key Lab of Novel Reactor & Green Chemical Technology,Wuhan 430073, China
8. College of Life Sciences, Shenzhen University,Shenzhen 518060, China
9. Hubei Academy of Environmental Sciences,Wuhan 430072, China
Abstract:In this paper, the reflectance spectral features of chromium(CrCl3), copper chloride(CuCl2) and zinc chloride (ZnCl2) were measured by using visible and near-infrared reflectance spectroscopy (VNIRS). Thus, the spectra features integrating with the state of electrons arranged of heavy metal elements, and combined with the Crystal Field Theory were used to analyze where and why the wavebands of spectral features occurred. With the soil samples collected from Daye City, CrCl3, CuCl2 and ZnCl2 were added to them with different concentrations, and measured their VNIRS to study the impacts of different concentrations of heavy metals on soil reflectance spectra. Besides, the spectral data were transformed via different spectra pre-processing methods to explore the linear correlations between heavy metal concentrations and the reflectance spectra of the soil samples, and to study on where and why the Pearson’s significantly correlated wavebands (p<0.05) appeared and its potential mechanism. The results showed that the reflectance spectra in the range of visible and shortwave near-infrared of heavy metal compounds are related to the whether the 3d orbits of heavy metal elements filled by electron or not. The reflectance spectra of soil samples have been affected by the heavy metal compounds which were added, and negative correlations were revealed between the reflectance spectra data and the heavy metal concentrations. The maximum of the negative values of Pearson correlation coefficient were -0.788, -0.880, -0.824, respectively. There were some changes with the linear correlation between the heavy metal concentrations and the reflectance spectra, and the information of Pearson’s significantly correlated wavebands (p<0.05) became richer and more obvious after the reflectance spectra being pre-processed. This research indicated that the VNIRS of heavy metals are closely related to their electronic structure; the high concentrations of heavy metals in soils could be detected by the VNIRS technique, which has great potential in predicting soil heavy metal contents with rapid and efficient, non-destructive and cost-effective. Based on the VNIRS characteristics of some heavy metals, this paper integrated with the Crystal Field Theory to provide a theoretical basis and experimental reference for qualitative and quantitative analysis of reflectance spectroscopy of soil heavy metals.
Key words:Visible and near-infrared reflectance spectroscopy; Soil heavy metals; Pretreatment; Crystal field theory; Linear correlation
程 航,万 远,陈奕云,万其进,石铁柱,申锐莉,郭 凯,胡佳蒙. 部分土壤重金属可见-近红外反射光谱特征及机理研究[J]. 光谱学与光谱分析, 2018, 38(03): 771-778.
CHENG Hang, WAN Yuan, CHEN Yi-yun, WAN Qi-jin, SHI Tie-zhu, SHEN Rui-li, GUO Kai, HU Jia-meng. Study on the Characteristics and Mechanism of Visible and Near Infrared Reflectance Spectra of Soil Heavy Metals. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2018, 38(03): 771-778.