THE IMPACTS OF THE CHERNOBYL NUCLEAR DISASTER ON THE FOREST VEGETATION
OF THE POLISSYA REGION OF UKRAINE
Dr. Mykolai Kaletnik
Director of Research, Ukrainian Ministry of Forestry, Kyyiv, Ukraine
Dr. Petro Pasternak
Research Associate, Ukrainian Research Ecology Laboratory,
Institute of Forest Management and Amelioration,
Ukrainian Ministry of Forestry, Kharkiv, Ukraine
Dr. Serhei Hrisiuk
Research Associate, Department of Radiobiology,
Ukrainian State Agricultural University, Kyyiv, Ukraine
Yurij Bihun
Forest Stewardship Program Associate, School of Forest Resources,
The Pennsylvania State University, University Park, PA USA
ABSTRACT
In the spring of 1986, the aftermath of the Chernobyl nuclear explosion
left a substantial portion of the forested area of the Ukrainian Polissya
region contaminated with radioactive fallout. Although less than 14.5% of
Ukraine is forested, nearly one-quarter (24.2%) of its woodlands (appox.
2,371,600 ha) are located in the Polissya region. Common pine (Pinus
sylvestris) is the primary species with associated boreal hardwoods, birch
(Betuala spp.), aspen (Populus spp.), and alder (Alnus spp.) characteristic of
this transition forest zone. Of the four oblasts (provinces) showing evidence
of radioactive fallout, damage was concentrated primarily in two provinces:
Kyyiv and Zhitomir. Weather patterns as well as the forest of the Polissya
region of Ukraine and neighboring republic of Byelorus played a major role in
ameliorating the radioactive atmospheric desposition on agricultural areas and
urban centers.
Impacts of the fallout have been monitored in forest zones since shortly
after the catastrophic event, but detailed scientific studies of the effects
on forest vegetation and forest soils were not initiated until 1990. Results
and analysis from these preliminary studies are available. Patterns of
fallout, interception of particulate mattter by the forest canopy, and impact
on understory flora were recorded. The migration, accumulation and
persistence of radioactive materials in roots, boles, leaf litter and soils
is reported.
Radioactive deposition followed a mosaic pattern depending on the proximity
to the center of the explosion and prevailing winds. In spite of the erratic
distribution and the variable size of the contaminated units, the affected
area was stratified into five levels or zones of contamination with
corresponding management and utilization strategies for each zone. Entry
into highly contaminated areas is restricted and the degree of contamination
determines access which, in turn, dictates management activities for grazing,
timber harvesting, foraging and hunting. The needs for long-term monitoring
and inventory methods are discussed.
INTRODUCTION
On April 26, 1986, 1:24 am Moscow time, two explosions in quick succession
blew the roof off Block No. 4 reactor building of the V. I. Lenin Chernobyl
Nuclear Power Reactor in the then Ukrainian SSR and sent shockwaves around the
world. The cloudless spring days of April could not foretell the worst man-
made nuclear catastrophe and the massive misfortune which came upon the
Ukrainian land. According to the Ukrainian Academy of Science researchers
(personal communication, Grodzhinsky et al., Ukrainian Academy of Science,
1993), the ecological and economic conditions of Ukraine today are among the
worst in Europe and the Chernobyl accident exacerbated these conditions
immeasurably.
This report reflects a compendium of the preliminary research on the
effects of Chernobyl nuclear disaster on the forest vegetation (primarily
trees or the woody vegetation) of the Polissya region of Ukraine. The report
does not attempt to be a comprehensive study on the subject, therefore, the
following presentation will concentrate on:
<> a general overview of the event
<> a physiographic and biogeographical description of the site
<> inventory technology and monitoring methods
<> impacts on the woody vegetation of the region
<> effectiveness of design and methods
<> problems, recommendations and conclusion
Although considerable contamination occurred in Russia and Byelorus, this
discussion will concentrate on the forested territory of the Ukrainian
Polissya and will not dwell on the human health, political or social impacts
of the accident.
THE EVENT
The aftermath of the Chernobyl nuclear explosion left a substantial portion
of the forested area of the Ukrainian Polissya region contaminated with
radioactive fallout. The extremely heterogeneous nuclide deposition in the
affected area has made monitoring and inventory procedures extremely complex.
Over a ten-day period, two periods of intensive deposition of airborne
radionuclides, April 26-27, 1986 and May 2-6, 1986, were critical.
Radioactive fallout followed a mosiac pattern depending on the proximity to
the center of the explosion and prevailing winds.
"After the explosion, the heat from the fire increased the release rates
of radioiodine (I-131, I-133), a substantial fraction of the volatile
metallic elements including radiocesium (Cs-134, Cs-137) and somewhat
lesser fraction of other radionuclides normally found in the fuel of
a reactor that has been in operation for several years (IAEA, 1991)."
Patterns of Fallout
Although surface winds at the time of the accident were light and variable,
the initial explosion and heat from the fire carried some of the radioactive
materials to a height of 1500 m where winds were 8-10 m/s from the southeast
and from where the jet stream transported flow over the western part of the
former USSR towards Finland and Sweden ( Figure 1). Regional distribution of
radioactive fallout affected most of eastern Europe, central Europe, and
Scandinavia.
"Changing meteorological conditions, with winds in different directions
at different altitudes and continuing release over a ten-day period,
resulting in a very complex disperion pattern (IAEA, 1991)..."
Due to prevailing winds, ground contamination was concentrated N, NW
(Gomel, Byelorus) and NE (Bryansk, Russia) of the reactor site. Of the four
oblasts (provinces) in Ukraine: Kyyiv, Zhitomir, Rovno, and Chernihiv showing
evidence of radioactive fallout, damage was concentrated primarily in two
provinces: Kyyiv and Zhitomir. Physio-chemical changes from the reactor
emission and weather patterns as well as the forests of the Polissya region of
Ukraine (and neighboring republics of Byelorus and Russia) played a major role
in ameliorating the radioactive atmospheric deposition on agricultural areas
and urban centers; particulary Kyyiv, a major city of over 2.5 million people,
less than 160 km away.
Deposition
The deposition of radioactive fallout was primarily in the form of:
<> Cs, Sr, I, Pu
<> Within 30 km - 80% contaminated with Cs-134 and Cs-137.
<> Outside the 30-km zone - areas where 100% of the radiation is
derived from cesium isotoopes (IAEA, 1991).
Eventually a 30 km "dead zone" was established around the damaged reactor site
and is maintained to this day. Most research activities, monitoring and data
collection are restricted from the 30 km zone.
SITE DESCRIPTION
Present-day Ukraine occupies 603.7 million km, the largest country in
Europe with a population of approximately 52 million people. The town of
Chernobyl is located in the Kyyiv Oblast in the Polissya (Polis ye) region of
Ukraine ( Figure 2). Polissya is a geographical area that straddles the
northern border of Ukraine, southeastern Byelorus and southern Russia. A land
of lakes, forests, swamplands, and peat bogs that drain from the Pripyat
marshes. The soil in the area is a mosaic layered soil cover that is chiefly
a podzolic soddy soil on sandy clay bottom with an aerated water regime
(personal communication, Grodzhinsky, 1993). Physiographically, Polyissya
(19% of the territory of Ukraine), is characterized by low relief, high
groundwater table and contental climate with precipitation level of 500-700 mm
from east to west (Bazhan, 1984).
"Chernobyl, a small city known since antiquity, derives its bitter name
from the commmon wormwood. Chernobyl...a pleasant little provincial
Ukranian town, swath in green full of cherry and apple trees. In the
summertime many people from Kiev, Moscow and Leningrad loved to holiday
here. They came here for a long time, not infrequently for the entire
summer and with their children and members of their households, they
rented dachas - rooms in wooden one-storied buildings, prepared pickles
and preserves for winter, picked mushrooms, which were found in
abundance in the local woods and sunbathed on the blinding clean
sandy banks of the Kiev Sea, and fished in the beauty of the Polissyan
nature..."
Dr. Iurii Shcherbak, contemporary author, physician, member of Ukrainian
Academy of Sciences and former Minister of Environment (Shcherbak, 1989).
Contamination was considerable in the Polissya region, the largest 'swamp'
in Europe - a territory which is 32.1% forested wetlands (the word 'lis' -
meaning forest; Polissya - the woodlands). The Pripyat marshes and forests
of the Polissya absorbed a significant part of the first eruption of
radionuclides (Medvedev, 1990).
Forests of Polissya
Unlike Russia, which contains the world's greatest concentration of
coniferous biomass, Ukraine is known primarily as an agricultural country of
prairies or steppes. Nonetheless, forests occupy approximately 14.3% of the
territory (see Table 1) or 10 m ha (the size of Hungary). Of this area,
nearly one-quarter (24.2%) of its woodlands (approx. 2,371,600 ha) are located
in the Polissya region. Ukrainian forests represent less than 1.0% of the
former USSR (Barr, 1989), however, in terms of site quality, growth rate (the
average annual increment of wood per ha was twice as great as USSR) and
quality hardwoods (52% of Ukrainian forests are hardwoods), Ukraine's forests
are far more productive than the boreal forests of Russia (Backman, 1990).
Although the Polissya region is classified as 'mixed-forest' zone, nearly
64.5% of the forest land is covered with conifers. Common pine (Pinus
sylvestris) is the primary species with associated boreal or shade intolerant
hardwoods: English (common) oak (Quercus robur) 18%, birch (Betuala
verrucosa) 11%, alder (Alnus spp.) 7%, aspen (Populus spp.) 2%, and hornbeam
(Carpinus betulus) 0.6% characteristic of this transition forest zone. Shade
tolerant hardwoods such as maple (Acer platanoides), basswood (Tilia spp.),
beech (Fagus sylvestris) and European spruce (Picea abies) are associated
components of the forest zone (Henciryk, 1992). Although figures are variable
depending on site and geographical location, average yield/ha is 125 cu. m.
and annual growth/ha approximately 4.2 cu. m. (Grodzhinsky, 1993).
Table 1. Five forest zones of Ukraine.
<> Ukrainian Carpathians (45%)
<> northern mixed forest (36.6%)
<> southern Crimean mountains (25%)
<> forest-steppe (12%)
<> steppe (3%)
INVENTORY TECHNOLOGY AND MONITORING METHODS
Although various Soviet, Russian, Byelorussian and international research
organizations were involved in collecting data, the forest management aspect
of this discussion will focus on the findings of the Ukrainian government
Ministry of Forestry.
Shortly after the accident in 1986, two research laboratories organized to
collect data and two mobile field laboratories to monitor radiation in forest
zones were established by the Ukrainian Ministry of Forestry (Kaletnik, 1992).
Initial monitoring of radiation in the forest was restricted to its potential
impact on human health. In 1991 radiological monitoring began at the
Ukrainian Ministry of Forestry at all their research stations and collective
forest stations; in 1992, full scale monitoring of 2.7 million ha of
forestland for three radionuclides: Cs-137, St-90, and Pu. At present nearly
50 forest collectives are involved in the monitoring program.
The deposition of radionuclides on terrestrial surfaces can result in
delivery of radiation doses to man through:
<> external radiation exposure
<> food chain contamination
<> inhalation of suspended particles
Wind-driven redistribution of surface-deposited radioactivity is a major
health concern (Anspaugh, 1973), particularly in agricultural and forestry
operations. The goal of the Ministry of Forestry program is to minimize
radioactive exposure to forest workers to expected norms established by health
officials.
Soviet Methodology for Mapping Field of Environmental Contamination
Table 2. Post-accident phase: large scale survey of global regions
<> Initial airborne external radiometric survey with Soviet airplanes
carrying gamma spectrometers.
<> Spatial resolution of potentially affected areas 5-10 km between
transects (information on the calibration procedures unavailable).
<> Based on initial aerial surveys, Soviet helicopters with gamma
spectrometers scanned special subregions of the global region from
an altitude of 1-2 km.
<> Survey represents an average field with a radius of 50-250 m.
<> Biannual aerial surveys to update database of the spatial variation.
<> Airborne scanning complemented by biannual soil sampling program.
<> Samples taken in approx. 500 settlements; depending on number of
inhabitants and the variability of the nuclide deposition pattern.
<> Data on concentration in soil samples and data on radiation field from
airborne measurements are combined to derive maps of regional nuclide
deposition by using scaling methods in order to match the two data sets
(IAEA, 1992).
IMPACTS ON THE FOREST VEGETATION
Interception of Particulate Matter by the Forest Canopy
The forests of Polissya functioned as a physical barrier and filtration
system to prevent mass transferance of radioactive isotopes great distances
contaminating major urban areas and productive agricultural areas. Radiation
contamination was five times higher in the forest than in surrounding
hayfields, cultivated pastures or croplands (Kaletnik, 1991).
Trees have greater surface area and conifers retained the radioactive
particulate matter longer (persistence of needles). Tree crowns and the rough
coniferous bark served to accumulate particulate matter and screen open areas.
Trees still act as a screen during agricultural production when radioactive
substances in the soil are disturbed and carried as airborne particles of
dust, etc.
Table 3. Total area contaminated with Cs-137 (curies/sq. km.)
Level or land-type Area
------------------ --------------
> 1 ci 37,000 sq. km.
5-15 ci 1,960 sq. km.
15-40 ci 820 sq. km.
> 40 ci 640 sq. km.
Agricultural land 8.6 million ha.
Forest land 1.5 million ha.
More than 70% of plantations have >1 ci/sq.km.; 1.55% >15 ci/sq.km. Wood,
in the form of cut logs or log decks without bark, was 2.5 less contaminated
than wood with bark. Outside the 30 km zone, areas in the Zhitomir province
have the greatest concentration of radionuclides. Firewood with greater than
5 ci/sq.km. is not recommended, but frequently firewood with 5-6 ci/sq.km. is
utilized for heating (Kaletnik, 1992). Slabs from sawmilling process, often
the most contaminated part of the logs, are often left at the mill site or
used for firewood.
Migration, Accumulation and Persistence of Radioactive Materials in Trees,
Litter and Soils
In 1986, after the initial reaction, 80-95% of the radioactive deposition
was in the crown, foliage or bark. By 1990, only 5-10% remained in the tree
and most had migrated to the forest litter and upper soil horizon. A very
small percentage absorbed through stomata in foliage. By 1991, about 90% of
the radioactive isotopes have migrated into the forest litter and 0-5 cm of
the 'A' horizon of the soil. Most recent measurements indicate that migration
of radionuclides in the soil has descended to 10 cm (98% of the radionuclides
are within the 15 cm of the soil profile (Kaletnik, 1992). The velocity of
migration of radioactive isotopes depends on physical and chemical soil
characteristics such as texture, organic matter content and porosity (personal
communication, Serhei Hrisiuk, radiobiologist, Ukrainian State Agricultural
University (USAU), 1993). Radionuclides tend to migrate through sandy,
impoverished soils with greater velocity than finer soils with organic matter
that bind the radioactive microelements. Clay content (cation exchange) and
water are also important, and there are indications of a tentatively
exponential relationship with pH (lower pH giving faster migration). At
present, the penetration of the radioactive isotopes have begun through into
the root systems of woody plants and trees, with migration from the root
system into the wood where they are beginning to accumulate in the various
organs of the trees (Hrisiuk, 1993).
A number of confounding characteristics make it difficult to predict the
rate of uptake or transfer coefficient.
"A fraction of activity present in soil is taken up by the roots of a
plant and transferred to its aerial parts. Short-lived radionuclides
decay before they can be absorbed. Long-lived radionuclides are more
persistent. The magnitude of transfer depends on:
+ physical and chemical characteristics of the radioactive compounds
+ 'age' of radioactive contamination
+ species and age of tree
+ physical and chemical characteristics of the soil
+ meteorological conditions
+ climatic conditions
(IAEA, 1991)."
Cs-137 uptake in agricultural crops can be reduced by a factor of 3.5 by
application of large quantities of fertilizer and lime - depending on
biological characteristics of the crop or pasture (IAEA, 1991).
Hardwoods tend to lose contamination with annual leaf fall; however, the
platy, rough bark of the conifers sequesters particulate matter and persistent
foliage continues to show contamination. The effects, if any, of uptake into
the trees is not apparent and is the subject of current research at the
Ukrainian Academy of Science, USAU and Ministry of Forestry (as well as Russia
and Byelorus).
Effects of Irradiation on Terrestrial Ecosystems
Effects of irradiation on terrestrial ecosystems may be masked for the
first several years but follow a pattern as predictable as the patterns of
plant succession and clear stages in the impoverishment of natural communities
(Woodwell and Houghton, 1986):
"The overriding principle is that acute and chronic disturbance favors
populations of small bodies, rapid reproducers that have a broad
tolerance of habitats"
Forests are generally more sensitive than agricultural communities. 'Short-
term' or acute exposures of toxin differ in that with increasing time beyond
some point they diminish as repair progresses. Larger bodied plants (i.e.
trees) are more vulnerable and more susceptible to secondary pathogens that
may be the causal agent in mortality (Woodwell and Houghton, 1986). The first
sorting - elimination of the normally dominant species; the second sorting -
advent of new species and species resistant to disturbance; that marked
changes along a gradient of exposure. Houghton suggests that stability is not
reached after a short period of time and mortality occurs along the continuum.
The Red Forest
Following the pattern of acute or chronic radiation exposure, coniferous
trees close to the immediate source absorbed a dose of 100-150 Gy (most of it
as beta radiation) and within days turned chlorotic and brown (Woodwell and
Houghton's first sorting). North of Chernobyl, near entrance to Pripyat, a
tall stand of Scots Pine that looked like 'burnt' pine wood and was referred
to in the early reports as the rust colored or 'red forest,' absorbed the
highest radioactive fallout:
"...pronounced morphological changes were observed in the dose range
from 3-10 Gy. Other species present in the damaged pine area (mainly
beech, aspen, and oak) suffered practically no damage, and no obvious
morphological changes were apparent in herbaceous plants (IAEA, 1991)."
The Soviet press reported rather casually that the pine forest around the
Chernobyl plant died within a few days of the accident (Medvedev, 1990).
Various sources later confirmed that between 400 and 600 ha of Scots pine
forest died of acute irradiation and was buried near the plant by June 1987.
"The dead wood was covered with sand, was cut down in stages by construction
machinery and treated with chemical preservative." The 'hot' parts of the
trees were placed in containers and buried in concrete (Marples, 1988).
Burying contaminated debris may cause long-term problems.
Damage to the broadleaved and coniferous vegetation in the 1986-1990 period
was variable depending on the dosage and distance from the Chernobyl plant
site (Hrisiuk, 1993). Immediately after the event, there was a great fear of
forest fires because of the potential of radioactive aerosol re-emitted during
combustion. In the winter of 1986-87, firewood used by the local citizens was
replaced by coal to reduce the number of mini-nuclear explosions in the
villagers' woodstoves (Shcherbak, 1988).
Table 5. Observed symptoms of radioactivity on tree morphology in the
Chernobyl zone.
<> necrosis of new shoots
<> chlorotic foliage
<> branch deformation (akin to herbicide damage)
<> premature foliage abscission
<> anomalies in reproductive organs
<> reduced growth rate
<> elongation of shoots (foxtailing)
<> bud abortions
<> leaf shape distortion (oaks - loss of distinct sinus in leaf margins)
<> premature cone dropping
<> decrease in cone formation and seed production
Impact on Understory Flora
Depending on species, mushrooms are extremely sensitive to radionuclides
and radioactive cesium in the soil is readily and rapidly taken up by
mushrooms even in minute concentrations. Although fungi and lichens function
as good indicators of radioactivity, contamination is a serious problem
because mushrooms are freely available and are an important part of the diet
and local culture. Considered a delicacy, mushrooms are frequently pickled
and featured in the local cuisine and a traditional family activity in the
forests of eastern Europe (IAEA, 1991).
Wild berries and wild fruits also have elevated levels of radiocesium in
comparison with cultivated foodstuffs. These wild foods are important because
they supplement the diet and are a feature of local cuisine and lifestyles.
Restrictions on mushrooms and wild berries also shape people's perceptions of
the safety of their living conditions and environmental hazard of the
surrounding forests (IAEA, 1991).
EFFECTIVENESS OF INVENTORY METHODS
Since 1986, dozens of Soviet and former Soviet research institutes as well
as western organizations have been collecting data and analyzing the
environmental impact of the Chernobyl disaster. These ongoing research
activities, some independent, some cooperative have given us a broad based
picture of the environmental impacts. Long-term study of forest vegetation
and forest soil has begun in earnest in the early 1990s and is still being
monitored. The 1991 IAEA-sponsored inter-comparison exercise showed that most
of Soviet and NIS data was reliable. Equipment and analytical procedures for
gamma spectrometry were generally considered adequate for providing
representative averages. However, some concern was raised about soil
laboratory techniques in terms of inadequate dissolution procedures in
underestimating radionuclides in soil (IAEA, 1991).
Table 5. Representative samples of inventory methods for forest ecosystems.
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Soil-
+ Multiple in situ gamma dose rate measurements with alpha and gamma
spectrometers are used to screen for 'hot spots' in sample area
(usually at 1 m above the ground level).
+ If results are positive, the area is unsuitable for sampling. Hot
spot perimeters are surveyed and marked.
+ If results are negative, multiple gamma dose rate measurements with
alpha and gamma spectrometers are used to identify soils suitable
as sampling sites.
+ When a suitable site is chosen, one to six soil samples are taken
along the contour of an area of interest to obtain a representative
sample of the area using the 100 sq.m. 'rectangular envelope'
technique.
+ Three stepped 'disk' shaped and 'brick-shaped' samples:
a) disk-shaped sample: initial phases - metal sampling ring
collected a soil disk with a diameter of 14 cm and thickness
of 5 cm; recently - steel ring depth to 10 cm or 15 cm in
sandy soils.
b) brick-shaped sample: five representative brick-shaped soil
samples 10 cm (width) x 20 cm (length) x 6 cm (thickness).
According to IAEA assessments (IAEA,1991), deliberate discrimination
against hot spots limits the usefulness of soil sampling techniques
on a small scale. For large scale average assessment of surface
deposition, these methods can be considered adequate. Some uncertainty
is associated with accuracy of Soviet fallout maps not known at this
time. Spatial resolution on the order of several hundred meters can be
assumed for official maps.
Surface and groundwater- not included for present study, however, along
the Dnieper River, dissolved phase water and sediments have been
extensively monitored.
Air- not included for present study; detailed information available from
various Soviet and western sources.
Vegetation- carried out jointly with soil samples. Bark, foliage, and
to a lesser extent the bole, were analyzed. Lichen was removed and
sampled. Multiple gamma dose rate measurements with alpha and gamma
spectrometers using the envelope technique. Vegetation samples (clover)
were analyzed for maps of Cs-134, Cs-137, Sr-90 and K. Forty-four
percent of the monitoring area has > 1 ci/sq.km.. Based on the
migration patterns, root system and stem analysis will be the next
logical progression for detailed analysis.
Foodstuffs- in the case of mushrooms, medicinal herbs and berries in the
forest, contamination maps for Cs-137, Sr-90 and Pu were produced and
available. Local monitoring with dosimeters is done on a large scale
by people who depend on these foodstuffs as supplemental sources for
diet.
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CONCLUDING REMARKS
Problems
Notwithstanding the data available, there are serious complications in
analyzing/monitoring the event:
1) unevenness or mosaic pattern of the fallout
2) difficulty in collecting data on the ground due to health reasons
3) organization - piecemeal, contradictory data and interpretation
4) calibration and equipment
5) politics - simplification, calming anxieties, playing down seriousness
of the event.
Recommendations
Foresters, forest engineers, rangers and forest workers have the greatest
threat of radiation exposure in the forest or in the open fields (Kalentnik,
1992). This group has 1.5-2.5 times higher doses than other inhabitants of
the contaminated zones ( Figure 3).
Table 6. Recommendations for decresing risk of radiation exposure to
forestry personnel.
<> Limit exposure
<> Rotation of workers
<> Winter of snow conditions
<> Maximize mechanization, sanitary and prophylactic conditions for
forest workers (sealed cabs for trucking and harvesting machinery).
<> Monitor exposure on a regular basis
<> Train and employ skilled radiologists in forest research and operations
<> Increse number of laboratories and monitoring stations
<> Certificates for radioactivity clean wood products and foodstuffs
<> Wood products -
3 ci/km - optional
3-5 ci/km - random control
>5 ci/km - strict control of all materials
15-30 ci/km - prohibited or severely restricted
Depends on soil conditions (clay vs sand, organic content, etc.)
<> Wild foodstuffs -
>2 ci/km - not recommended
1-2 ci/km - radiological controls
0.5-1.0 ci/km - radiological controls on organic soils
Recommendations for limiting exposures have been formulated by the Ukrainian
Ministry of Forests based on detailed zonation maps (Table 7).
Table 7. Forest zonation based on the amount of Cs-137 contamination; the
most dangerous of the long-lasting elements to human health thrown
into the atmosphere by the Chernobyl reactor.
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Zone VI (>40 ci/sq.km.) - extemely contaminated. Severe restrictions on
on entry as well as silvicultural treatments and standard forest management
activities. Clearcutting and intermediate cuts prohibited. Berry picking,
mushroom collecting, grazing, pine tar collection and shearing of evergreen
materials for horticultural needs are prohibited. Access to medicinal
herbs and fodder restricted. Firefighting activities, pest management and
fire suppression should be done with airplanes or helicopters.
Zone V (15-40 ci/sq.km.) - restricted access. Some silvicultural
activities permitted. Silvicultural treatments such as thinnings and
sanitation cuts should be done under winter conditions with snow or wet
conditions to minimize disturbance to radioactive particulate matter
settled in the canopy of the trees and soil. Maximize mechanized
harvesting operations. Berry picking, mushroom collecting, grazing,
pine tar, collection of evergreen materials for horticultural needs are
prohibited. Access to medicinal herbs and fodder restricted. Firefighting
activities, pest management and fire suppression should be done with
airplanes or helicopters.
Zone IV (10-15 ci/sq.km.) - moderate restrictions. Harvesting permitted
under snow conditions, but processing of wood products is not recommended.
Berry picking, mushroom collecting, grazing, collection of evergreen
materials for horticultural needs are still prohibited.
Zone III (5-10 ci/sq.km.) - moderate restrictions. Berry picking,
medicinal herbs, birch sap, firewood cutting, mushroom collecting, grazing,
collection of evergreen materials for horticultural needs are still
prohibited. Licensed hunting under supervision is allowed and game can be
taken after radiological inspections. Limited silvicultural and
agricultural activities allowed.
Zone II (2-5 ci/sq.km.) - light restrictions. Silvicultural activities
allowed, but logging under wet or snowy conditions and use of mechanized
operations still recommended. Grazing and haying prohibited. Using and
preparing berries, medicinal herbs, birch sap, mushrooms and use of
evergreen materials are allowed with radiological inspection.
Zone I (< 2 ci/sq.km.) - No restrictions on silvicultural and agricultural
use of these areas. Depending on area and soils, using and preparing
berries, medicinal herbs, birch sap, mushrooms and use of evergreen
materials are allowed with radiological inspection.
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Afforestation in the Chernobyl Zone
The forest research station at Pripyat and Staropetrivsk is growing pine
seed taken from the contaminated zone 1986 and 1987 and doing experiments to
compare germination, survival, and juvenile growth tests with controlled seed.
Experiments have also been conducted to determine the utility of timber grown
on these lands, and research has demonstrated that pulpwood containing Cs-137
is usable as the radionuclides are separated during the pulp dilution phase in
acid solution (Grodzhinsky, 1993). However, the health and safety conditions
of workers harvesting and handling the woody materials poses an unanswered
question and possible additional hazard. Reforestation on these areas would
disturb the upper layers of the soil and could possibly increase exposure to
radiation. Contaminated farmlands and agricultural areas should be abandoned
and allowed to revert to natural vegetation, primarily brushy hardwoods and
boreal hardwoods. Aerial seeding of pine and other conifers is not extremely
effective but could be used to augment natural regeneration.
Conclusions
The data presented in this paper represent a very cursory examination of
the impacts of the Chernobyl disaster on the forests of northern Ukraine. A
more detailed examination of original data from Russian, Byelorussian,
Ukrainian and western sources should be compiled in a more systematic manner
emphasizing concerns with ongoing monitoring and analysis.
Zonation recommendations outlined by the Ukrainian Ministry of Forestry
should be carried out carefully with continual monitoring and revision.
Contamination of the groundwater table is a major concern and should be
sampled frequently to assess the radionuclide migration through the soil
profile. Growth and yield studies, disease impact studies, and root systems
and stem analysis on a site specific basis should accompany these studies.
A geographic information system (GIS) would be the most effective method to
update these records and make data available for analysis. GIS would provide
ready access to maps and data, thereby facilitating recommendations for forest
and natural resource management. GIS would also take into account concerns
for risk management, health and human safety throughout the contaminated
region.
LITERATURE CITED
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Environmental behavior of radionuclides released in the nuclear industry.
Symposium proceedings Aix-En-Provence. Vienna: International Atomic
Energy Association, pp. 34-47.
Backman, Charles and T. R. Waggener. 1990. Soviet forests at the crossroads:
emerging trends at the time of economic and political reform. CINTRAFOR:
Working Paper No. 28. Seattle: College of Forest Resources; University
of Washington. 382 p.
Bazham, M. P., Ed. 1982. Soviet Ukraine. The Ukrainian Soviet Encyclopedia.
Ukrainian Academy of Sciences: Kyyiv. 572 p.
Barr, Brenton M. and Kathleen E. Braden. 1989. The disappearing Russian
forest: a dilemma in Soviet resource management. London: Rowan &
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