Detecting contamination-induced tree stress within the Chernobyl exclusion zone

The radioactive contamination from the 1986 accident at the Chernobyl Nuclear Power Plant (CNPP) caused significant change in the abundance and distribution of tree species in the exclusion zone. Some 400 ha of Scots pine (Pinus sylvestris) were killed from high levels of contamination and these areas have since been recolonised by silver birch (Betula pendula). Much work has shown that changes in leaf pigments (chlorophyll a and b, carotenoids) and biomass as a result of water and nutrient deficiencies and other environmental influences can be detected through spectral reflectance characteristics of leaves. This paper presents the results of a reconnaissance study showing that spectral reflectance measurements can also be used to detect the effect of radionuclide contamination on the vegetation in the Chernobyl exclusion zone. Through laboratory and in situ spectroradiometry of silver birch and Scots pine, we demonstrate that the chlorophyll red edge and the Three Channel Vegetation Index (TCHVI) correlate well with specific activities of 90Sr and 137Cs in leaves, γ-dose rates and 137Cs inventories in soil. The results show that remote sensing has the potential of providing a valuable monitoring technique for assessing the ecological impact of radionuclide contamination.