The Enhanced Deposition Of (Cs)-C-137 Fallout In Tropical Cloud Forests

Cesium-137 (Cs-137) is an artificial radionuclide which did not exist in the environment until man began atmospheric testing for nuclear weapons development. The phrase "cloud forest" and its' characteristics are very ambiguous and can be misleading, thus care needs to be taken into account when this term is encountered. The activity of Cs-137 was determined mainly in surface soils, as well as mosses, lichens and other types of vegetation. The Cs-137 activities (Bq kg(-1)) were measured by high energy resolution gamma-ray spectroscopy employing reference materials as comparators.In this chapter, the spatial distribution of Cs-137 in various tropical cloud forests, foggy areas and their surrounding areas in Venezuela will be presented, in order to show the effect that cloud forests and foggy areas had on the deposition of radioactive fallout. The relationship between the Cs-137 activities in the surface soils and the elevations of their sampling sites not only clearly showed the effect that the cloud forests had on the enhancement of Cs-137 but also can be used to estimate the base of the cloud cover. Cloud forests were usually considered to be in mountainous areas at high altitudes, but the peaks of some of the tropical cloud forests discussed herein were located at relatively low elevations. Finally, the Cs-137 activities in soils, mosses and lichens collected along the Caruay River will be presented with respect to its surrounding area. The area along the river had similar characteristics to a tropical cloud forest, but this was due to the fog which was produced daily.In conclusion, it is very important to consider the effect of cloud forests and other similar pathways, such as foggy areas, in which Cs-137 can be directly deposited from the atmosphere at much higher concentrations than by rainfall, or one could report anomalously high activity values, which could suggest that more Cs-137 has been recently introduced into the environment.