Assessing the artificial radionuclide Cesium-137 spatial distribution in the Southern Hemisphere from lake sediment records

When supported by a reliable geochronology, lake sediments provide important archives for environmental and climatic changes. Artificial radionuclides in general, and cesium-137 ( 137 Cs) in particular, are frequently used to validate sediment chronologies over the past century. This review and meta-analysis assessed the spatial distribution and variability of 137 Cs in lake records from the Southern Hemisphere, while also identifying geographical data gaps. The 137 Cs profile shapes and inventories were compared and categorized, and their relationships with environmental variables were tested. The spatial distribution of available data reveals an imbalance in studies available across the Southern Hemisphere, with South America showing the greatest research coverage. While the sedimentation rate was identified as a key factor of 137 Cs variability, two groups identified from the database presented high peak activities regardless of sedimentation rate, particularly in lakes located between 40°S and 50°S in Chile and Argentina. Lake geographic location (and their distance from nuclear test sites) appears to be the most influential factor explaining disparities in 137 Cs deposition. Surprisingly, neither precipitation nor lake elevation showed a significant correlation with 137 Cs peak activity. • The median 137 Cs activity peaks is about ten times lower than those recorded in Northern Hemisphere lakes. • 137 Cs peak activity and sedimentation rate differentiate lake 137 Cs profiles based on cluster analysis. • Latitude and distance to nuclear weapon test sites are the most relevant explanatory variables for 137 Cs distribution.