MMs (metals and metalloids) based 238U, 226Ra, 232Th,40 K contamination and health risk assessments in different surface soils near an uranium mine of Southeast China

Abstract

Purpose

The radionuclides pollution base on MMs (metals and metalloids) near uranium mines has been drawing broad attention, but the extent of their impact on soil and human health is still unclear. Therefore, the aim of this study was to investigate the distribution and health risk assessments of ²³⁸U, ²²⁶Ra, ²³²Th and ⁴⁰ K base on MMs (Cr, Ni, Cu, Zn, As, Cd, and Pb) in different surface soils near an uranium mine.

Materials and methods

Surface soil samples were extracted from 35 representative sites near the Lefu uranium mine. Radionuclides and MMs were measured using high-purity germanium (HPGe) N-type coaxial detector and inductively coupled plasma mass spectrometer, respectively. Pollution status was evaluated using D_R, Ra_eq, AEDE, H_ext, and ELCR for radionuclides and P_i, I_geo, RI and health risk index for MMs. Their correlation was analyzed through Pearson/Spearman correlation analysis.

Results and discussion

The average activity concentration of ²³⁸U, ²²⁶Ra, ²³²Th, and ⁴⁰ K are 504, 1227, 118, and 769 Bq·kg⁻¹ respectively and the average concentration of Cr, Ni, Cu, Zn, As, Cd, and Pb are 200, 33.9, 41.3, 132, 18.4, 0.26, and 78.7 mg·kg⁻¹, respectively. Values of D_R, Ra_eq, AEDE, H_ext, and ELCR all exceed the world average to varying degrees and values of P_i, I_geo, RI and the health risk index are within the acceptable ranges. Correlation analyses showed that ²³⁸U, ²²⁶Ra, ²³²Th and Pb are strongly correlated (correlation coefficient > 0.6) with each other.

Conclusions

On the basis of the obtained values, it can be concluded that generally higher radionuclides and MMs were distributed near the Lefu uranium. There are potential health risks associated with the elevated radioactivity. The overall situation of MMs is controllable, however, particular attention is warranted for Cr and Cd, as they approach values-at-risk. The strong correlations between ²³⁸U, ²²⁶Ra, ²³²Th and Pb imply a uniform pollution level or a possible shared source.