The distribution of fallout 137Cs in Costa Rica.
Baseline levels of 137Cs on different sites throughout the Costa Rican territory are presented in this study from local and undisturbed soils. They are believed to represent the fallout input to the land surface. Seventy samples were collected from September 1991 to December 1993, and analyzed by gamma spectroscopy. The territory was divided in three regions, Caribbean, Pacific, and Central, based on meteorological and geographical conditions to study spatial distribution of cesium. The results show a higher activity in the Caribbean region perhaps due to the wind influence and higher rain precipitation throughout the year. No relevant time variation of the activity levels for each location was found. The highest value of 17.6 Bq kg(-1) of 137Cs is compared with its generalized derived limit, being only 1.97% of the generalized derived limit value. The mean country activity value ranges from 0.4 to 17.8 Bq kg(-1) with an average of 3.7 Bq kg(-1).