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2. Study area, material and methods

Material was collected in the Gomel Region, 30 km away from the CNPP in 1986–2000 applying usual pedobiological techniques (soil samples and Barber’s pitfall traps) at reference points subjected to radioactive contamination. 105 pitfall traps were used every year. They were emptied 15 times from the middle of April till the end of October, i.e. during the active period in the life of soil-dwelling arthropods. The pitfall traps were plastic cups measuring 72 mm in diameter. They were set at intervals of several meters away from each other. The traps were filled with 4% formalin. The species of the animals collected were identified. At present, the Polessky Radiological Ecological Reserve is located in this site with a contamination level equal to 1500 kBq × m-². Gamma-radiation at the soil surface was measured with SRP 68–01 and DRG 01T radiometers. As controls, similar biotopes in the Pripaytsky National Park located 150 km to the west of the study area were chosen. In this area, the contamination level was nearly the same as the natural background. The samples of animals, soil and litter were collected in cylindrical plastic containers. The volume of each container varied from 100 to 250 ml. Sometimes, 50-ml containers were used. The containers were placed directly on an ORTEC Ge detector connected to a Canberra 80 series multichannel analyser system. Efficiency calibrations of the detector to all geometries used had previously been performed and checked at intervals with standardised solution of 137 Cs.

The 137 Cs deposition density at reference point (v. Babchin, pine forest) recalculated as to 1991 was 1110,0 kBq/m2 , 90 Sr – 77,7 kBq/m2. The 137 Cs deposition density at reference point (v. Lomachi, oak forest) recalculated as to 1991 was 2331,0 kBq/m2, 90 Sr – 284,0 kBq/m2.

3. Results and discussion

The studies of zoocenotic characteristics such as population density, trophic structure and species composition of soil invertebrates inhabiting biogeocenoses are aimed at obtaining the definite relations and parameters characterizing the state of soil invertebrate communities - most sensitive to radioactive contamination. Those studies are based on comparing certain parameters characterizing the vital activities of soil fauna in biogeocenoses under contamination with control areas situated far from contamination sources.

The results of out gamma-survey of soil as the invertebrate’s habitat show that contamination of soil cover is inhomogeneous in different biogeocenose types. A wide range of gamma-activity and radionuclide content in the soil and years was obtained in biogeocenoses with radioactive contamination. A general trend of maximum radionuclide concentration in a 10–cm soil layer was found for forest biogeocenoses.

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After 5 – 6 years marked differences between soil invertebrate populations in contaminated and control biogeocenoses were found, but species diversity in contaminated soils was five times lower.

After 9 – 10 years the species diversity of invertebrate community was still reduced by 60 %.

During last years it was observed a slow return of animal diversity and community structure to the initial parameters. Secondary changes and side-effects were registered for phytophagous and saprophagous.

3.2. TROPHIC STRUCTURE

The dynamics of the trophic structure whose changes are indicative of drastic disturbance in the soil invertebrate communities, is an even better indication than density and zoomass. The trophic groups have characterized based on density and zoomass.

It was found that in the soils of studied biogeocenoses (in 1986 – 1989) the density, and, consequently, zoomass decreased in all trophic groups, namely phytophagous, saprophagous (disappear at all) and zoophagous.

We carried out the pedobiological research ( in 1994 – 1996) in the forest biogeocenoses with different gamma-radiation background: 1) the weak radioactive contamination (0,15 – 0,19 mr/hr) 2) the strong radioactive contamination (2,28 – 5,58 mr/hr). In the zone of weak radioactive contamination the zoophagous are dominants. In the zone of strong radioactive contamination phytophagous are dominants, but the zoophagous are subdominants.

3.3. RADIONUCLIDE ACCUMULATION

The results of the studies on 90Sr and 137 Cs content in the soil, litter and invertebrates in the exclusion zone of the CNPP have been analysed. The dependence of radionuclide accumulation factors on the peculiarities of morphological structure, functional ecology and nutrition type of soil invertebrates was found. The dynamics of 137 Cs content in some species of invertebrates was studied (Fig. 1, 2).

The highest contamination level in the invertebrates was found in the year of the accident. It has been found that a year after accident the invertebrates gammaactivity dropped considerably, then its decrease was slower. Similar changes were also observed for gamma radionuclides in the litter and in the soil, but the contents of gamma-radiators in the litter being higher.

For the 90 Sr accumulation in the invertebrates, we can arrange in the following decreasing order: Diplopoda (millipedes) – Shelled mollusks – Insecta (insects) – Lumbricidae (earthworms). For 137 Cs accumulation in the invertebrates, we can compose the following decreasing order: Insecta – Diplopoda – Shelled mollusks – Lumbricidae.

The radionuclide loading is caused by ecological biotopic and food characteristics and it depends on species of soil animals: saprophagous, which are

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3.4. CHANGES IN THE HEMOLYMPH

Hemolymph of the invertebrates performs vital functions, metabolic, homeostatic and protective, and its cellular composition is a reliable indicator of the population viability.

We carried out the morphological and cytological investigation of the hemolymph of the invertebrates under different radioactive level (table. 2).

Table 2. Correlation between haemocytes in Diplopoda species under different doses.

Pr – proleukocytes; Ma – macronucleocytes; Mi – micronucleocytes; E – enocytoides; Fa – active phagocytes; Fp – passive phagocytes; DC – dead cells.

In the hemolymph of both normal and irradiation-exposed invertebrates, five haemocyte types were revealed: proleukocytes, macronucleocytes, micronucleocytes, enocytoides; phagocytes (active and passive) (classification of [4]). The proportion of haemocytes varies with the physiological condition. The most typical sings of pathological change of hemolymph are an increase of the amount of dead cells (in control – 2 – 3) and decrease of the amount of proleukocytes (in control 10 – 12).

Morphological changes are as follows: lysis, fission shift of the nucleus to the cell periphery, disturbance of circular shape in some cells, elongation, cytoplasm budding and vacuolisation. Cytoplasm of some cells loses its granular texture, becomes homogeneous, while staining it turns dark blue and the nucleus acquires reddish tinge.

The largest changes in the hemolymph were found at a higher radiation dose absorbed by the objects.

4. Conclusions

Thus, our studies allowed us to estimate correctly the changes induced by radioactive contamination caused by Chernobyl nuclear accident at the level of soil invertebrate communities and to reveal the pattern of their disturbance under constant radiological pressure. All evidence shows that soil mezofauna complexes in different biogeocenoses exposed to irradiation for a long time react clearly by a noticeable suppression. It is concluded from the results that the haematological

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characteristics can serve as convenient bioindicators of the radioactive contamination in the biogeocenoses. Percentages of all cell types observed and their structural changes may be recommended as criteria for comparison.

5.References

1.M.I. Kuzmenko Radioecological problems in Ukrainian water reservoirs . Gidrobiol. Zh. 34 (6), 1998, pp. 95 – 119 (in Russian).

2.M.S. Ghilarov, D.A. Krivolutsky Radioecological investigations in soil zoology. Zool. Zh. 50 (3), 1971, pp. 329 – 342 (in Russian).

3.D.A. Krivolutsky Radioecology of communities of terrestrial animals. M: Energoatomizdat, 1983, 88 pp. (in Russian).

4.M.I. Sirotina Genesis of blood cells in normal and icteric oak eggar moth larvae and butterflies. Dokl. VASKhNIL, 4, 1965, pp. 22 – 28 (in Russian).

Part 4.

Problems of Estimation of Risks from Different Factors

GENERALIZED ECOSYSTEM INDICES: ECOLOGICAL SCALING AND ECOLOGICAL RISK

V. GEORGIEVSKY

Russian Research Center “Kurchatov Institute”, Moscow, RUSSIA

1. Introduction

There are two problems regarding analysis of data for ecological monitoring:

ξ Reduction of dimensionality data. There it is necessary to convert the contamination data of few ecological chains by few pollutants to system characteristics. It is may be realized by Multidimensional Analysis (Discriminant Analysis, Factor Analysis, Cluster Analysis, etc);

ξ Interpretation of results of Multidimensional Analysis. This is a key problem for ecological monitoring and is to be considered as a problem of ecological scaling.

Two examples cover the wide spectrum of ecological situations concerning the monitoring of the radioactive contamination territories:

ξ Analysis of monitoring data in Rovenskaia Area of Ukraine; contamination data of several ecosystem’ chains by single radionuclide contamination of soil, milk, potatoes by 137Cs for 236 settlements have been analysed and

ξ Analysis of monitoring data in Kievskaia Area of Ukraine; contamination data

of single ecosystem’ chains by several radionuclides (soil contamination by 90Sr, 134Cs, 137Cs, 106Ru. 144Ce for 122 settlements) have been analysed.

2.Methodology

1.The attribute of data from ecological monitoring is the following. Many variables in noise condition are measured but among these variables there is not a key variable. The ecological data are “symptoms” only. The state of ecosystem is determined by effect of all data on the system, not by any particular measured variable. This is in analogy with diagnostics in medicine where it is necessary to indicate disease condition using circumstantial symptoms.

There is apparently a possibility to introduce the Ecological Index as a system characteristics and to develop the ecological scale for ranking the ecological conditions, for the formalization of the concept of ecological risk and for the decision-making [1, 2, 3].

2.The development of ecological scale consists of following steps:

ξ Reduction of dimensionality of initial data of monitoring and convert it to small system parameters,

ξ Discrimination and classification, ξ Clusterization,

ξ Development of Multidimensional Reference Ecological Image (MREI),

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ξ Scaling the ecological conditions in terms of MREI.

In the ecological scale the Scaling Factor is introduced where it acts like a kind of “ecological thermometer”.

An analysis of ecological conditions and ecological decision-making may be realized on the base of this model (“ecological thermometer”) by analysis of the ordering and evolution of the ecosystem position on the scale.

single value).

Note: This methodology is some variant of the Multidimensional scaling for ecosystem conditions in terms of Multidimensional Reference Ecological Image (indicated 0, 1, 2. by experts).

4. This Analysis has been founded on the next hypothesis:

ξ It is supposed that the ecological conditions depend on distances between the points inside clusters and between the points of different clusters.

ξ It is supposed that the linear combination of ecological parameters is the approximation to whichever dependency of the ecological conditions on distance.

ξ The Euclidean distance is used because the canonic roots, which are used for clusterisation, are uncorrelated.

5. As it is known the Linear Regression is used in the Discriminant Analysis for the classification. Roughly speaking, there the regression function is passed between clusters. In our method the regression functions are used twice:

ξ on the first stage, it is used for classification (Discrimination Analysis) and there the regression functions pass between clusters, and