Fusing chlorophyll fluorescence and plant canopy reflectance to detect TNT contamination in soils
TNT is released into the soil from many different sources, especially from military and mining activities, including
buried land mines. Vegetation may absorb explosive residuals, causing stress and by understanding how plants respond
to energetic compounds, we may be able to develop non-invasive techniques to detect soil contamination. The
objectives of our study were to examine the physiological response of plants grown in TNT contaminated soils and to
use remote sensing methods to detect uptake in plant leaves and canopies in both laboratory and field studies.
Differences in physiology and light-adapted fluorescence were apparent in laboratory plants grown in N enriched soils
and when compared with plants grown in TNT contaminated soils. Several reflectance indices were able to detect TNT
contamination prior to visible signs of stress, including the fluorescence-derived indices, R740/R850 and R735/R850, which
may be attributed to transformation and conjugation of TNT metabolites with other compounds. Field studies at the
Duck, NC Field Research Facility revealed differences in physiological stress measures, and leaf and canopy reflectance
when plants growing over suspected buried UXOs were compared with reference plants. Multiple reflectance indices
indicated stress at the suspected contaminated sites, including R740/R850 and R735/R850. Under natural conditions of
constant leaching of TNT into the soil, TNT uptake would be continuous in plants, potentially creating a distinct
signature from remotely sensed vegetation. We may be able to use remote sensing of plant canopies to detect TNT soil
contamination prior to visible signs.