Radiochronological Methods as Tools to Study Environmental Pollution

Abstract

The study of the environmental impact of natural and anthropogenic events forms the essence of environmental pollution considerations. The nature of the polluting species as well as their time distributions are of primary importance with respect to identifying the polluting sources. Sediments are the most frequently used materials in such studies. Sediments act as the ecological memories of the environments of their formation. Besides classical chronological methods, radiochronological methods developed recently gave a big impetus to environmental pollution studies. One of the key radioisotopic technique is to utilize Pb-210, a product of the U-235 radioactive series to date the last 200 years of the sediments. A number of supporting indicators are also utilized. One of them being anthropogenic Cs-137 which is used as a time-marker. Large amounts of Cs-137 radioactivity was released to the environment during 1954-1963, in time of the most intense atmospheric nuclear arms testing and again in 1986 during the Chernobyl nuclear accident. These intense Cs-137 activities form time-markers throughout sediment cores corresponding to their release years. During our studies extending over several years we have used radiochronological methods in dating several sediment cores from Zurich and Constance Lakes in Switzerland from east coast of Spain, Sea of Marmara, from the Black Sea region, Southern coast of Turkey and from North Cyprus. The distribution of several elemental concentrations of importance in pollution considerations along sediment cores were also determined. These studies allowes proposing time frames to pollution events and help inqueries in tracing possible sources of pollution.