Remote Sensing of Explosives-Induced Stress in Plants: Hyperspectral Imaging Analysis for Remote Detection of Unexploded Threats

Paul V Manley,Felix B Fritschi,Vasit Sagan,Joel G Burken

doi:10.3390/rs11151827

Abstract

Explosives contaminate millions of hectares from various sources (partial detonations, improper storage, and release from production and transport) that can be life-threatening, e.g., landmines and unexploded ordnance. Exposure to and uptake of explosives can also negatively impact plant health, and these factors can be can be remotely sensed. Stress induction was remotely sensed via a whole-plant hyperspectral imaging system as two genotypes of Zea mays, a drought-susceptible hybrid and a drought-tolerant hybrid, and a forage Sorghum bicolor were grown in a greenhouse with one control group, one group maintained at 60% soil field capacity, and a third exposed to 250 mg kg−1 Royal Demolition Explosive (RDX). Green-Red Vegetation Index (GRVI), Photochemical Reflectance Index (PRI), Modified Red Edge Simple Ratio (MRESR), and Vogelmann Red Edge Index 1 (VREI1) were reduced due to presence of explosives. Principal component analyses of reflectance indices separated plants exposed to RDX from control and drought plants. Reflectance of Z. mays hybrids was increased from RDX in green and red wavelengths, while reduced in near-infrared wavelengths. Drought Z. mays reflectance was lower in green, red, and NIR regions. S. bicolor grown with RDX reflected more in green, red, and NIR wavelengths. The spectra and their derivatives will be beneficial for developing explosive-specific indices to accurately identify plants in contaminated soil. This study is the first to demonstrate potential to delineate subsurface explosives over large areas using remote sensing of vegetation with aerial-based hyperspectral systems.

Highlights

Environmental contamination by explosives and energetics has resulted from widespread production, testing and partial detonations, unexploded ordnance (UXO), and improper disposal
The effects of drought conditions and exposure to Royal demolition explosive (RDX) in soil were hypothesized to be discernable from controls but not each other
The results presented validate methods to delineate subsurface explosives over large areas at a canopy scale using the remote sensing of vegetation with aerial-based hyperspectral systems

Summary

Introduction

Environmental contamination by explosives and energetics has resulted from widespread production, testing and partial detonations, unexploded ordnance (UXO), and improper disposal. Unique to these constituents, threats exist for acute and chronic health concerns [1], and even physical threats by UXO. Landmines are of specific concern as over 110 million have been laid in more than 70 countries since the 1970s [2]. An estimated 15,000 to 20,000 people are injured or killed each year from remnant landmines, with children accounting for one in five of those deaths [3]. It is estimated that in the US alone 10 million hectares need remediation [4]. Royal demolition explosive (RDX; hexahydro-1,3,5-trinitro-1,3,5-triazine) is commonly found with trinitrotoluene (TNT)

Methods

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Discussion

Conclusion