Abstract
Ore processing is a source of soil heavy metal pollution. Vegetation traits (structural characteristics such as spatial cover and repartition; biochemical parameters—pigment and water contents, growth rate, phenological cycle…) and plant species identity are indirect and powerful indicators of residual contamination detection in soil. Multi-temporal multispectral satellite imagery, such as the Sentinel-2 time series, is an operational environment monitoring system widely used to access vegetation traits and ensure vegetation surveillance across large areas. For this purpose, methodology based on a multi-temporal fusion method at the feature level is applied to vegetation monitoring for several years from the closure and revegetation of an ore processing site. Features are defined by 26 spectral indices from the literature and seasonal and annual change detection maps are inferred. Three indices—CIred-edge (CIREDEDGE), IRECI (Inverted Red-Edge Chlorophyll Index) and PSRI (Plant Senescence Reflectance Index)—are particularly suitable for detecting changes spatially and temporally across the study area. The analysis is conducted separately for phyto-stabilized vegetation zones and natural vegetation zones. Global and specific changes are emphasized and explained by information provided by the site operator or meteorological conditions.
Highlights
The state of vegetation, its survey and mapping are of growing interest to local territory stakeholders
The main purpose of this study is to propose an unsupervised methodology applied on multispectral satellite time series to monitor vegetation for several years from the closure and revegetation of an ore processing site
The main site purpose this study is to analyze the temporal evolution of vegetation growing in an related to meteorological conditions) and the longer-term change related to vegetation response ore processing site after closure and detect abrupt change related to one-time events
Summary
The state of vegetation, its survey and mapping are of growing interest to local territory stakeholders. The presence of pollutants in the growth medium (soil or water) can prove stressful for the vegetation and have direct physiological effects on plants (visual symptoms, photosynthetic process alteration, impact on development...). These effects result from the contact of the pollutants with the plants’ roots and their assimilation in the tissues [2,3,4]. Vegetation is considered as an indicator of soil pollution which can be detected by means of optical imaging, with the changes in the characteristics of vegetation (pigment content, cell structure, water content, physiological state...) altering its optical properties [6,7,8,9,10,11,12]
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