Estimating leaf mercury content in Phragmites australis based on leaf hyperspectral reflectance

Introduction:Highmercury(Hg)concentrations affect the chlorophyll in leaves,therebymodifying leaf spectra.Hyperspectra is a promising technique for the rapid,nondestructive evaluation of leaf Hg content.In this study,we investigated Hg contents and reflective hyperspectra of reed leaves(Phragmites communis)in a gold mining(Jilin province,China).Spectral parameters sensitive to Hg content were identified through basic spectral transformations,continuous wavelet transformation(CWT),and spectral indices techniques.Leaf Hg inversion models were developed using stepwise multiple linear regression,partial least squares regression,and random forest algorithms.Outcomes:The results indicated that:1)leaf Hg content decreased with increasing distance from the mine:Jiapigou(JPG)>Erdaocha(EDC)>Laojingchang(LJC)>Erdaogou(EDG)>Lingqian(LQ)>Weishahe(WSH).2)Hg–sensitive wavelengths were primarily in the visible region;CWT increased the correlation between hyperspectral data and leaf Hg content,and improved the regression and accuracy of inversion;3)the continuumremoval–CWT–stepwise multiple linear regression was better for estimating low leaf Hg content;while the differential spectral index–partial least squares regression was better for estimating high leaf Hg content.Conclusion:These hyperspectral inversion methods could be used for rapid,nondestructive monitoring of wetland plants.

Kerogen——as a sort of organic bearer of gold in gold-bearing formations

Organic component, organic carbon and gold content analyses were used to study the relationship between gold mineralization and organic matter in major host rocks of three different chronological gold-bearing formations of South China. The results show that the organic matter of host rocks in various chronological major gold-bearing formations of South China has associated with gold mineralization in genesis. There is a positive correlation between gold and organic carbon in the host rocks of gold-bearing formations. Gold element was mainly enriched in insoluble organic matter——kerogen. Gold content of the kerogen is commonly higher from a few tens to several hundred times than that of the whole rocks, up to 5%—40% gold of the whole rocks. Gold remaining in the kerogen was considered an organic group of the kerogen to combine with ionic gold in solution through surface absorption, ion exchange complex reaction and chelation so that the kerogen could have become an important sort of organic bearer