Abstract
Near InfraRed Spectroscopy (NIRS) has become an extremely important analytical technique in recent years and been applied in various geoscience areas such as mineral exploration and environmental studies. It is used for studying the physico-chemical properties of earth materials by enabling the interpretation of mineral composition and the study of its variability based on the diagnostic of spectral features. In this research, the application of laboratory reflectance spectroscopy in assessing heavy metals pollution is investigated. The potential use of reflectance spectroscopy in detecting Fe-related and clay minerals as well as the quantitative characterization of pollutants is studied for the mine waste of Jalta and Bougrine in the North of Tunisia. Mining activities of lead/Zn, have led to extensive pollution. The analysis of geochemical results outlined the level and spatial pattern of pollutants concentration. Results of the study showed that a relationship exists between reflectance spectra and geochemical measures of pollutants. The Spectral interpretation of Fe-related minerals and clay minerals showed that they are related to the pollutants and can be used as indirect spectral indicators of the pollution. The Fe-minerals include: jarosite, goethite, hematite/goethite, and hematite; clay minerals and feature-less (aspectral) materials. A direct quantitative relationship between pollutants and spectral parameters shows that Pb-Zn-Mn are the best correlated with a ratio of 610/500 nm range while Ni-Cr have a best correlation with a slope around 980 nm. Outputs from Partial Least Square Regression (PLSR) confirmed these relationships and also indicated that spectral parameters and reflectance values within 400 - 2500 nm range can better predict the contamination for Mn, Pb and Zn than for Ni and Cr but not for Fe, Cu, Cd, EC and pH.
Highlights
In the abondoned waste mines, acid water drainage can adversely impact the quality of drinking water and the health of riparian ecosystems
In contrast to previous studies, we focused more on modeling the relations between reflectance spectroscopy and geochemical variables of the waste mines by the use of Partial Least Square Regression (PLSR)
The results concerning the relationships between spectral parameters and heavy metals concentration indicate that Fe oxides play an important role in the prediction of soil heavy metals using reflectance spectra
Summary
In the abondoned waste mines, acid water drainage can adversely impact the quality of drinking water and the health of riparian ecosystems. The Acidic water formed by sulfide oxidation can relatively generate soluble and insoluble secondary Fe-related minerals which are controlled by pH, level of oxidation, moisture content, and solution composition ([1] FRITZE et al, 1994; [2] DAVIES, 2001). The secondary Fe-related minerals are of special interest to this study since they have specific spectral features. Near-InfraRed Spectroscopy (NIRS) reflectance is a quantitative and qualitative technique that gives good resuts for the determination of various parameters in food, agriculture, textile, petrochemical, and pharmaceutical industries. NIRS has given good outcomes for the determination of physical, chemical, and biological soil properties such as moisture; total C, N, and P contents; mineral N; quality of organic matter; and biological parameters of soil such as respiration and microbial biomass
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