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metal sources (ie. coal mines, ore-dressing enterprises,
lants, thermal power stations, chemical factories, highways
etc ). 1350 samples of soil and plants were analyzed for their
heavy metal content. Simultaneously from an altitude of
150 m airborne high spectral resolution data were acquired
by an airborne spectrometer ,Quartz' with the following
parameters:
- spectral range 410-770 nm
- spectral resolution 1 nm
- spectrum registration period 0.5 s
- angle of viewing field of 0.05 rad 2
- radiance range (0.16-52.08) 10" W/sr m".
The results showed a similar 10 - 20 nm „blue shift“ for the
red edge” in the reflectance spectra for wheat, corn, barley,
alfalfa, and fodder grass under metal-induced stress
conditions (Lyalko, 1992). A correlation was observed
between the ,blue shift" value and aggregated heavy metal
content in the plants. This correlation and spectral ratios
(NIR/RED, RED/GREEN) allowed to map the Western
Donbas area according to ist heavy metal pollution levels.
These findings were proved by laboratory vegetation
experiments with winter wheat, corn, and alfalfa. After the
soluble compounds of Be, Zn and Sn had been added in
increasing concentrations changes in spectral brightness and
shape of wheat spectral function appeared.
The vegetation experiments for corn and alfalfa were
performed on substrata of different soil types (i.e. carbonate
chernozem, leached chernozem, gray forest soil).
Various amounts of Ni, Cr, Cd were added to the substrata
which the plants grew on. During the process of plants
growth measurements of the spectral reflectance factor at
the 448, 530, 563, 620, 682, 747, 785, 885, 970 and
1025 nm bands as well as of the chlorophylls a and b, the
carotenoids, the bulk of green and air-dry amounts of the
plants and their roots were performed. The results of the
Study show a regular decrease of pigment contents
(chlorophylls a, b, carotenoids) and green and air-dry weight
of the roots under higher heavy metal concentration for
chernozem soil (pH 7.5). Under low concentration of heavy
metals in the substratum a slight stimulation of the plant
growth was observed on acid gray forest soil (pH 5.5), where
the migration of heavy metal compounds is higher and
induces some increase of the pigments and phytomass
amount. Under higher contents of heavy metals in gray
forest soil substratum a decrease of pigments content, green
amount of plants and their roots could be observed similar to
that from the experiment with plants on chernozem soil
Substrata. The spectrometric data obtained during the
vegetation experiments with corn and alfalfa showed that
spectral reflectance factor of plants increases in the spectral
bands from 680 to 1025 nm. This supports the use of
Spectrometric and multispectral remote sensing data for
localization of heavy metal contaminated areas by
measuring spectral features of vegetation cover.
The obtained rules and facilities developed for data
Processing of airborne spectrometric data have been used to
determine the levels of heavy metal pollution in the northern
part of the Ukraine in the hazardous zone of the Chernobyl
Nuclear Power Plant.
The program package applied was developed to determine
the changes in vegetation reflectance spectra as a result of
metal-induced stress. The package installed on IBM-
Compatible PCs consists of programs performing
computation of spectral brightness coefficients, spectral
smoothing, first and second derivatives of spectral functions
aswell as the | blue shift" value.
455
The results of processing remote sensing data were verified
by ground truth data obtained on heavy metal polluted sites
and by analysis of the pollutants composition from the 30 km
Chernobyl zone towards Kiev. The spectral analysis data for
950 samples of soils and plants growing on these soils
allows the following conclusions about the pollution level to
be made:
- 75% of the soil samples investigated exeed the maximum
permissible concentrations (MPC) of Cu (approved in the
Ukraine) by more than 10 times, of Zn by more than 2-4
times respectively
- 50% of soil samples exceed the MPC of Ni by more than
2-5 times
- 1596 of soil samples exceed MPC of Pb and Mn by more
than 2-3 times.
Maximum permissible concentrations of other heavy metals
in soils have not yet approved in the Ukraine. Therefore it is
not possible to assess the pollution levels for many chemical
elements which directly originated in the reactor and
indirectly from emissions induced by the melted metal
construction of the damaged reactor block.
The MPC's for widespread agricultural crops in the Ukraine
have been approved only for Pb, Cu and Zn. The vegetation
cover of the test site exceeded the MPC's
- of Pb by more than 2-5 times in 5096 of the crop samples
- of Cu and Zn by more than 2-3 times in 896 of the crop
samples.
The critical content level of toxicant chemical elements, when
crop yield decreases for more than 1096 was exceeded in
- 5096 of the crop samples for Mn and in
- 15-2096 of the crop samples for Ni, Ti, V and Cr.
The results obtained show that the area of the Ukrainian
Polissin have been exposed to pollution by a heavy metal
complex after the Chernobyl accident. The character of the
pollution and the level of toxic impact in combination with the
radioactive contamination require studies and assessments.
The use of remote sensing methods for the solution of these
problems allows to coordinate and intensify long-term and
extensive field studies required.
3. ESTIMATION OF RADIONUCLIDE CONTAMINATION
ON AREAS USING MULTISPECTRAL SPACE IMAGERY
The use of multispectral remotely sensed data is based on a
closed correlation between the environmental conditions and
vegetation state. Growth and development of vegetation are
connected with metabolism processes and depend on
environmental conditions such as light, temperature,
moisture, fertility of soil, and of course, on toxicants presence
or absence.
The spectral characteristics of plants, as shown in other
publications (Vygodskny et al., 1987; Kronberg, 1988; Lyalko
et al., 1992 and others) depend on the ability of foliage and
neadles to reflect, absorb and transmit solar energy.
The plots of spectral reflection for separated species and
different vegetation communities have their own features in
certian wavelengths both for maximum and for the shape of
spectral reflectance curve (Krinov, 1947; Kronberg, 1988).
The physiological stress of the plants leads to changes of
their spectral characteristics in visible range, because
chlorophyl reacts to each change of metabolism and
degrades under unfavorable conditions.
The radionuclides released during the Chernobyl disaster are
also toxicants though the character of contamination caused
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B7. Vienna 1996
