Full text: Resource and environmental monitoring

  
  
reactors encouraged the migration of these particles to the eastern 
part of the reservoir. 
The image (from pair 1986 - 1988) shows the changes in the 
ecological situation as of the third year after the accident. 
The pine forests have undergone clear changes everywhere, 
taking on a blotched appearance. The greatest changes can be 
seen on the northern edges of the forests. There are no substantial 
changes in the condition of deciduous forests. There is a clear 
change in the dead 'red' forest, especially in those areas where the 
trees were uprooted and soil removed. 
The condition of vegetation in the town of Pripyat has 
deteriorated noticeably. The most contaminated part of the 
cooling water reservoir is that into which used process water is 
released. 
The image (from pair 1986 - 1995) shows the ecological changes 
which have occurred up to the present day.  Radionuclides 
produced by human activity have had an impact on pine forest 
everywhere, and the ecological 
situation has improved only in places. The general condition of 
deciduous forests has not seen any substantial changes. Grass 
vegetation has proved to be the most resistance to the impact of 
radionuclides. The water in the Chernobyl NPP cooling reservoir 
has become noticeably cleaner, and the condition of vegetation in 
the town of Pripyat has improved. 
2.2 Classification 
First of all, before starting the studying of environment state 
influence on vegetation, it is necessary to divide vegetation on 
homogeneous parts as precise as possible, using ground truth 
and remote sensing data. This problem is very difficult because 
of all the forests are mixture within the area and influence of 
toxicants on some species of vegetation 
is different. The landscapes classifiction had been carried out 
using modules of ERDAS IMAGINE software. It was indicated 
all types of landscapes on classified multiband images for 
example on SPOT 23.08.95. Besides this it was shown the 
peculiarities of distribution of some type of vegetation which are 
absent on initial vegetation map, used for supervised 
classification. For example, it was shown the heterogeneous 
character of some kinds of vegetation cover which cause the 
specific spot view of classified images. It was observed the 
replacing of the pine tree forests with deciduous forests on the 
edge of pine tree forests, along the roads etc. It was specified 
limits of some forests with complicate boundaries. The big 
variety of vegetation species was observed within the long-fallow 
lands and meadows. But, the influence of radionuclide 
pollution on spectral characteristics of vegetation more week 
than influence on ones of species peculiarities. 
2.3 The vegetation spectral reflectance research 
The studying of spectral reflectance of vegetation of multiband 
multitemporal images was carried out using set of ground truth 
observation . The map of soil radioactive pollution with Cs-137, 
created using soil sample analisys, had been used. The analysis 
carried out for multitemporal images have shown the 
dependencies between spectral characteristics of major 
boiocenouses in the test sites in red and near-infrared bands on 
the one hand and the soil content of CS-137 on the other. All the 
Intemational Archives of Photogrammetry and Remote Sensing. Vol. XXXII, Part 7, Budapest, 1998 
plots show a quite simple unimodal relation between the 
analyzed values. According to these plots one can conclude that, 
the higher the contamination of soils by radionuclides, the higher 
the spectral brightness of plant in each band. For pine tree forest 
this relation is manifested most clearly (Lyalko et. al. 1996 . The 
radionuclides influence content of chlorophyll in plant as well as 
structure of cells. The maximum distinctions for anomaly and 
background values of radionuclide content in soil are observed 
for 1986 year and the minimum one for 1995 year. The reduction 
of distinctions connected with increasing of background values 
because of radionuclides migration. Over 10 years, it is going the 
relaxing of radionuclides influence on plant, but vegetation is 
not fully recovered. 
It was developed another approach using the analysis of 
determination of shift of red edge position (REP) of the one 
dimensional plots of spectral reflectance and wavelength. The 
values of spectral reflectance had been taken from Landsat TM 
multiband image (29.05.1988) for sites with different level of 
contamination by Cs-137. It is known the REP of spectral 
reflectance is the source of information about ecological state 
(Collins, et. al, 1983; Horler et. al. 1983; Demetriades-Shah et. 
al., 1992; Baret et al., 1992; Lyalko et. al., 1992, et. al.). REP is 
the value of wavelength in interval 680 -760 nm, where first 
derivative of spectral plot is maximum, that is mean that second 
derivative at this point is equal to zero. The approach of REP 
determination had been developed using Landsat TM data for 
spectral reflectance of pine tree forest. To examine the method, 
the sites with concentration of Cs-137 from 5 up to 25 Ci/sq.km 
were measured. For this sites, the plots of spectral reflectance 
had been done using Landsat TM 2,3,4,5 band data. For plot 
construction, according to method, 1t was supposed the possibility 
of using of supplementary data which produced from initial data. 
As a result the 11 points are used for plot construction with 
values of wavelength from 520 up to 830 nm: 520, 560, 600, 
610, 630, 660, 690, 710, 760, 830 nm. The centered values of 
spectral brightness were used in points with wavelength 610 and 
710 nm . This values are approximated using sum of Chebyshev 
polynomials from 1 to 4 degrees (Sportjuk et. al. 1993). The 
initial values and approximated curve are shown ın figure 1. For 
approximated curve the first derivative of reflectance spectra had 
been determined in interval 660 - 760 nm and the point of first 
derivative maximum had been indicated. This approach had been 
used for REP determination of average spectral curve obtained 
from summarizing of 65 initial spectral curves for sites with 
level of Cs-137 contamination in soil about 5 Ci/ sq.km. The 
same procedure had been carried out for 7 spectral curves 
connected with level of Cs-137 contamination 25 Ci/sq.km 
approximately. For two average curves the plots of first 
derivatives and REP are demonstrated in figure 2. The REP is 
equal to 725 nm (for lowS Ci/sq.km) and 721.5 nm (for 25 
Ci/sq.km) according to calculations. Of course, this result will be 
tested for another vegetation species but it demonstrate potential 
possibility of indication of polluted sites of homogeneous forests 
using REP determination on the basis of Landsat TM data. 
The relationship between the spectral brightness values of 
various forms of vegetation and the Cs-137 content in the soils 
was used as a basis for a map showing the contamination of soil 
with toxicants, principally Cs-137, in the zone affected by the 
  
  
  
   
  
     
    
   
    
    
   
    
  
   
    
   
     
   
    
   
    
    
    
    
   
    
     
   
    
  
   
   
    
     
   
  
  
     
   
   
    
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