Natural and artificial radionuclides in rocks and soils of the Galápagos Islands

Abstract

For the first time on the Galápagos Islands, we conducted a systematic study of the levels of natural and anthropogenic radionuclides in lava and soils. We used newly collected lava samples as well as soil samples from previous studies, including a soil chronosequence with soil ages up to 1070 ka and an elevation sequence covering an arid-to-humid climate gradient.

The levels of most natural radionuclides were higher in the topsoils than in the lava samples, probably due to residual accumulation during weathering, with concentrations increasing from young to old soils. Concentrations of ⁴⁰K showed an opposite trend, likely due to its high mobility after release from primary minerals through weathering processes. The inventories of ¹³⁷Cs (36.9–380 Bq m⁻²) and ²¹⁰Pb_ex (573–7764 Bq m⁻²) correlated significantly, with rainfall being an influencing factor. Comparison of the ¹³⁷Cs inventories in the studied soils with those found across South America shows a similar range as reported for the area between 3° northern and 10° southern latitude in Brazil.

Overall, the levels of natural and anthropogenic radionuclides in the soils of the Galápagos Islands are rather low compared to other regions of the world. An elevated contribution to the population radiation dose is not to be expected.