Geochemical baselines for the radioelements K, U, and Th in the Campania region, Italy: a comparison of stream-sediment geochemistry and gamma-ray surveys

Abstract

This paper presents new data on the baseline concentrations of U, Th and K in 2389 stream sediments over the whole Campania region. These data, based on systematic sampling and analysis, are compared with those obtained by gamma-ray spectrometry surveys. Variations in the U, Th and K concentration in the surficial environment of the Campania region appear to be related to bedrock lithology. Generally, high U, Th and K values in stream sediments correspond well with the occurrence of volcanic rocks in the central-western part of the region, whereas low values are found in areas characterized by silico-clastic and carbonate deposits, occurring mostly in the southern and eastern part of the region. Gamma-ray spectrometry maps show a similar pattern, although the distribution of the highest radioactivity levels define more restricted areas than the ones resulting from mapping stream sediment geochemistry. Particularly high 40K radioactivity levels delimit all the known eruptive centers (Roccamonfina, Campi Flegrei and Somma–Vesuvius), including the fissural sources of Campania Ignimbrites, much better than U and Th radioactivity. One of the concerns for human health in the Campania region is the total gamma radiation and Rn potential related mostly to alkaline volcanics of the Neapolitan volcanological province. In particular, geothermal activity occurring in all the Campanian volcanic areas represents a potential hazard for Rn gas.