Assessing Metal-Induced Changes in the Visible and Near-Infrared Spectral Reflectance of Leaves: A Pot Study with Sunflo
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RESEARCH ARTICLE
Assessing Metal-Induced Changes in the Visible and Near-Infrared Spectral Reflectance of Leaves: A Pot Study with Sunflower (Helianthus annuus L.) Paresh H. Rathod1,4 • Carsten Brackhage2 • Ingo Mu¨ller3 • Freek D. Van der Meer1 • Marleen F. Noomen1 Received: 2 July 2016 / Accepted: 23 August 2018 / Published online: 12 October 2018 Ó Indian Society of Remote Sensing 2018
Abstract The aim of this study was to monitor changes in leaf spectral reflectance due to phytoaccumulation of trace elements (Cd, Pb, and As) in sunflower mutant (M5 mutant line 38/R4-R6/15-35-190-04-M5) grown in spiked and in situ metalcontaminated potted soils. Reflectance spectra (350–2500 nm) of leaves were collected using portable ASD spectroradiometer, and respective leaves sample were analyzed for total metal contents. The spectral changes were quite noticeable and showed increased visible and decreased NIR reflectance for sunflower grown in soil spiked with 900 mg As kg-1, and in in situ metal-contaminated soils. These changes also involved a blue-shift feature of red-edge position in the first derivatives spectra, studied vegetation indices and continuum removed absorption features at 495, 680, 970, 1165, 1435, 1780, and 1925 nm wavelength. Correlograms of leaf-metal concentration and reflectance values show highest degrees of overall correlation for visible, near-infrared, and water-sensitive wavelengths. Partial least square and multiple linear regression statistical models (cross-validated), respectively, based on Savitzky–Golay filter first-order derivative spectra and combination of spectral feature such as vegetation indices and band depths yielded good prediction of leaf-metal concentrations. Keywords Metal-contaminated soils Sunflower Spectral reflectance Phytoremediation Visible and near-infrared spectroscopy
Introduction Looking at the environmental consequences associated with metal-contaminated sites, remediation has become an important task. Many physicochemical methods have been
& Paresh H. Rathod [email protected] 1
Department of Earth Systems Analysis, Faculty of Geoinformation Science and Earth Observation, University of Twente, 7514AE Enschede, The Netherlands
2
Institute for General Ecology and Environmental Protection, Technical University, TU Dresden, 01737 Tharandt, Germany
3
Saxon State Office for Environment, Agriculture and Geology, 09599 Freiberg, Germany
4
Present Address: Anand Agricultural University, Anand, Gujarat State, India
materialized for remediating metal-contaminated sites, and phytoremediation (i.e., cleaning-up process that employs various types of plants to remove, transfer or stabilize metals in the soil) is among the most emphasized ecofriendly and inexpensive method (Cundy et al. 2016; Mench et al. 2010; Pilon-Smits 2005; Vangronsveld et al. 2009). However, like any remediation system, phytoremediation does have shortcomings: (1) there are only few recognized hyperaccumulators, i.e., exceptional plant species, which tolerate as well as accumulate large amount
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