In April 1986, the Chernobyl nuclear power plant located near Pripyat in Ukraine exploded. This accident was the most severe in the history of nuclear power industry, resulting in a huge release of radionuclides over large areas of Belarus, Ukraine, and the Russian Federation and changing the lives of more than 4 million people living in those areas. The lighter radioactive particles and mixture of gases released by the plant were carried to all countries in the Northern Hemisphere, deposited on the ground and on surface waters. For the purpose of this article, the environmental consequences at the time of the disaster and those still continuing today are described here.
The Chernobyl disaster has both short-term and long-term impacts in terms of radionuclide effects on environment. During weeks and months after the accident, levels of radioactivity in drinking water caused concern in the most affected areas of Ukraine. The initial levels were caused primarily by direct deposition of radionuclides on the surface of rivers and lakes. After this initial period, radioactivity in aquatic systems was generally below drinking water guideline limits. Bioaccumulation of radioactivity in fish showed the concentrations that were significantly above the permissible levels for consumption in the most affected areas. In some 'closed' lakes in Ukraine, Belarus, and the Russian Federation, these problems continue even today.
The radiation-induced acute effects on plants and animals were observed in the highly contaminated areas. No radiation-induced acute effects in plants and animals have been reported outside the 'exclusion zone'. After the disaster, 4 km2 of pine forest in the immediate vicinity of the nuclear plant turned ginger brown and died. In the worst-contaminated areas, some animals also died or stopped reproducing. Some domestic animals left on an island in the Pripyat River 6 km from the power plant died when their thyroid glands were destroyed by high levels of radiation doses.
During the first few years after the accident, the impact of irradiation in both somatic and germ cells have been observed in plants and animals of the exclusion zone. The relationship between the observed cytogenetic anomalies in somatic cells and ecological significance is now known.
Following the natural reduction of exposure levels due to decay of short-lived isotopes and migration, wildlife populations have been recovering from the acute radiation-induced effects. Population viability of plants and animals has recovered substantially due to the combined effects of reproduction and immigration from less-affected areas.
In the years since the disaster, the recovery of biota in the exclusion zone abandoned by humans has facilitated these areas become a haven for wildlife. As a result, populations of many species of wild animals and birds, which were never seen in the area prior to the disaster, are now plentiful and it has become a unique sanctuary for biodiversity, due to the absence of human activities.
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