Use of environmental forensics to assess land sustainability: a case study on a former coal mining site

Abstract

A comprehensive environmental forensics investigation has been done on a former coal mining site in NE England, and now a country park used for recreation, but which lacks the ability to grow vegetation in certain areas. Initial mapping of the site was done using an unmanned aerial vehicle (UAV) with multispectral imaging (MSI) capability, followed by determination of 7 vegetation indices (VIs). The use of the VIs allowed a direct comparison between the two field sites and provided an indicator of vegetative stress. This was followed by field sampling and laboratory analyses using EX-XRF for metal analyses, soil property determination (pH, CEC and organic matter), metabolomic determination of the main soil metabolites using Hydrophilic Liquid Interaction Chromatography Hi-Resolution Mass Spectrometry, and a comprehensive investigation of soil bacteria and fungi using metagenomics. The results indicate how the soil environment of the top field has recovered to allow an abundance of flora in Spring and Summer, despite the soil having a low pH (4.0) and a high Pb concentration (94.0 mg kg⁻¹) but counterbalanced by the presence of natural plant and soil metabolites, and a high abundance of nutrient producing bacteria. In contrast, the bottom field is characterised by a sparse vegetation coverage on a harsher soil environment reminiscent of marshland, with a soil pH of 6.2, but a lower Pb concentration (58.4 mg kg⁻¹) contrasted with soil with a high sodium content (2050 mg kg⁻¹), the presence of man-made anthropogenic metabolites, and bacteria capable of undertaking soil remediation.