Environmental radioactivity in atmospheric dust deposition samples from Northern Algeria

Abstract

The Sahara Desert is the main source of global atmospheric mineral dust, with nearby regions, such as Algeria, within those with the highest dust deposition fluxes reported worldwide. This work aims to study environmental radioactivity and depositional fluxes in dust fallout in northern Algeria. Dust deposition samples were collected monthly using an artisan collector in Algiers from May 2014 to June 2018, and for six months in Chréa National Park. They were analyzed by gamma spectrometry for ⁷Be, ⁴⁰K, ¹³⁷Cs, ²¹⁰Pb, ²²⁶Ra, and ²²⁸Th, and by WDXRF for major and trace elements. The monthly amount of dust fallout ranged from 0.5 to 33.2 g m⁻², acting as an efficient trap of atmospheric ⁷Be and ²¹⁰Pb, with average concentrations of 15 ± 10 and 2.9 ± 1.3 kBq kg⁻¹, respectively. About 98 % of ²¹⁰Pb was in excess with respect to ²²⁶Ra. Wind variability results in different dust provenances, with varying chemical compositions and varying sorption capacities for ⁷Be and ²¹⁰Pb. Pearson's correlation matrices for temperature, rainfall, radionuclides, major, and trace elements, revealed interesting features on the behavior of the studied tracers in fallout dust. The annual ²¹⁰Pb fluxes associated with dust fallout were estimated to be 186.3 ± 2.4 Bq m⁻²y⁻¹ for surfaces with a retention capacity for deposited dust similar to that of the sampling device.