Assessing natural radioactivity risks and heavy metals pollution in Al-Lisi volcanic mountain, Dhamar city, Yemen

Abstract

Studying the radiation hazards in volcanic environments is of paramount importance due to the often-present thermal activity, exemplified by phenomena like hot springs, fumaroles, and geysers. These features contribute to the release of radioactive elements and heavy metals, presenting significant threats to both human health and the environment. This study aims to assess the concentration of natural radiation and heavy metals and the associated environmental hazards in the Al-Lisi volcanic mountain in Dhamar city, Yemen. Nineteen different samples, including hot spring water, soil, plants, and groundwater, were collected. These samples were detected using a high-purity germanium detector. The concentrations of ²²⁶Ra in these samples were measured at 185.91 Bq L⁻¹ in water, 373.95 Bq kg⁻¹ in soil, 111.10 Bq kg⁻¹ in plants, and 1.44 Bq L⁻¹ in groundwater; for ²³²Th, concentrations were 138.62 Bq L⁻¹, 507.08 Bq kg⁻¹, 141.5 Bq kg⁻¹, and 1.77 Bq L⁻¹; and for ⁴⁰K, concentrations were 448.47 Bq L⁻¹, 1084.45 Bq kg⁻¹, 928.07 Bq kg⁻¹, and 13.08 Bq L⁻¹, respectively. Radium equivalent activity and absorbed gamma dose in the air due to these nuclides, as well as external hazard index, and annual effective dose, were calculated for all samples, the overall results indicated that the study area poses higher radiological hazards than the globally recommended values. Moreover, variations in environmental pollution levels due to heavy metal concentrations were observed. The results are concerning, and we suggest detailed geological and radiological analyses to understand, address, and devise appropriate solutions.