Spectral and Growth Characteristics of Willows and Maize in Soil Contaminated with a Layer of Crude or Refined Oil

Abstract

Remote sensing holds great potential for detecting stress in vegetation caused by hydrocarbons, but we need to better understand the effects of hydrocarbons on plant growth and specific spectral expression. Willow (Salix viminalis var. Tora) cuttings and maize (Zea mays var. Lapriora) seedlings were grown in pots of loam soil containing a hydrocarbon-contaminated layer at the base of the pot (crude or refined oil) at concentrations of 0.5, 5, or 50 g·kg−1. Chlorophyll concentration, biomass, and growth of plants were determined through destructive and nondestructive sampling, whilst reflectance measurements were made using portable hyperspectral spectrometers. All biophysical (chlorophyll concentration and growth) variables decreased in the presence of high concentrations of hydrocarbons, but at lower concentrations an increase in growth and chlorophyll were often observed with respect to nonpolluted plants, suggesting a biphasic response to hydrocarbon presence. Absorption features were identified that related strongly to pigment concentration and biomass. Variations in absorption feature characteristics (band depth, band area, and band width) were dependent upon the hydrocarbon concentration and type, and showed the same biphasic pattern noted in the biophysical measurements. This study demonstrates that the response of plants to hydrocarbon pollution varies according to hydrocarbon concentration and that remote sensing has the potential to both detect and monitor the variable impacts of pollution in the landscape.

Updating risk remediation-endpoints for petroleum-contaminated soils? A case study in the Ecuadorian Amazon region

“…Agathokleous et al (2020) [ 40 ] highlighted hormesis as a prevalent yet underexplored phenomenon in their review of 43 papers. Additionally, hormesis in plants growing on oil-polluted soils, such as Medicago sativa [ 39 ], Salix viminalis , and Zea mays [ 41 ], further corroborates its significance. Agathokleous et al (2020) [ 42 ] further underpin this by examining 33 plant species and over 20 stress-inducing agents, affirming hormesis as a multifaceted response mechanism in plants, particularly driven by low-level stressors stimulating chlorophyll production to counteract higher stress scenarios.…”

Maize Characteristics Estimation and Classification by Spectral Data under Two Soil Phosphorus Levels

“…Based on published literature and the sensitivity of optical and polarization features to LAI and yield, optical spectral vegetation indexes were used to estimate LAI and yield. The leaf area index and yield of crops can be estimated from seven bands of red spectra (600 nm, 603 nm, 636 nm, 639 nm, 642 nm, 666 nm, and 669 nm), four bands of near infrared (738 nm, 741 nm, 744 nm, and 747 nm) and two bands close to the edge of blue and green spectra (498 nm and 501 nm) [2,[26][27][28][29][30]. In this paper, 15 vegetation indexes from the spectral data were selected to evaluate the characters of maize, as shown in Table 2.…”