Figure 1
From: Retrieving zinc concentrations in topsoil with reflectance spectroscopy at Opencast Coal Mine sites
The geographical location of the study area and spatial distribution of the in-situ sampling sites are classified by pollution level. (a), (b), and (c) represent the actual conditions of the study area. (Note: soil samples were classified into three types based on the background value (BV)15 of the Inner Mongolia Autonomous Region using the contamination factor method61,62, including clean (Zn ≤ 48.6 mg kg−1), low pollution (48.6 ≤ Zn ≤ 97.2 mg kg−1), and moderate pollution (97.2 ≤ Zn ≤ 145.8 mg kg−1), respectively. The Fig. 1 was generated by ArCGIS 10.0 that was obtained from https://www.esri.com/en-us/arcgis/products/arcgis-desktop/, and the satelite image used in Fig. 1 (sub Fig. 5) was downloaded from Google Earth (https://earth.google.com/)).
