Assessment of heavy metals and radionuclides in dust fallout in the West Rand mining area of South Africa

Violet P Dudu,Munyaradzi Manjoro,Manny Mathuthu

doi:10.17159/2410-972x/2018/v28n2a17

Violet P Dudu, Munyaradzi Manjoro + Show 1 more

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https://doi.org/10.17159/2410-972x/2018/v28n2a17

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Abstract

Windblown dust can contain radioactive materials from mining. These radionuclides when inhaled in dust produce ionizing radiation which damages the cells and tissues in the body. The aim of this study was to assess dust fallout radionuclides in the West Rand mining area of South Africa. Dust fallout monitoring was done using the method (ASTM) D-1739 of 1998 employing multi-directional buckets. Results show that all 9 locations investigated in the different seasons recorded dust fallout rates within stipulated residential limit according to the National Dust Control Regulations (NDCR) (Government Gazette 36974, 1 Nov 2013). Locations 3 in spring (301.93 mg/m2/day) and 6 in winter (589.8 mg/m2/day) recorded dust fallout rates with values above the target value of 300 mg/m2/day according to guidelines by South African Standards (SANS 1929:2011). The ANOVA tests (p-value < 0.05) indicate that the mean dust fallout rate is significantly different across the seasons, mean dust fallout rate in summer is significantly (p-value < 0.05) more than the autumn by 103.15 mg/m2/day. Moderate, positive correlations (0.4 ≤ r < 0.7) exist between average dust fallout rate and wind speed. A weak, negative correlation exist between average dust fallout rate and rainfall with a value of -0.393. All the investigated elements had Enrichment Factor (EF) greater than 1. Cadmium (Cd) and lead (Pb) were extremely enriched (68.36 and 43.48, respectively), whereas Thorium (Th) (7.26) and Chromium (Cr) (9.79) had significant enrichment. Activity concentrations obtained for 226Ra, 238U, 232Th and 40K were 53.59 ± 20.45 Bq/kg, 15.20 ± 6.74 Bq/kg, 6.62 ± 2.76 Bq/kg and 278.51 ± 84.39 Bq/kg, respectively. Activity concentrations were within world averages except 226Ra which exceeded the 32 Bq/kg world average. Statistically significant (p-value < 0.05), strong (0.7≤ r< 0.9) and positive correlation exists between 226Ra and 40K. A moderate, positive correlation (0.4 ≤ r < 0.7) exist between 238U and 232Th. Since EF values showed that the elements in the dust had anthropogenic influence, further studies should look at contributions of different sources to the elements found in dust.

Highlights

Mining activities pose a great threat to the environment including contamination of the environment
Results for the ANOVA test (Appendix B) for significant difference across locations and seasons indicate that the mean dust fallout rate is significantly different across the seasons (p-value < 0.05)
Seasonal variation of dust fallout rates and relationship with meteorological parameters All 9 locations in summer, autumn, winter and spring did not exceed the permissible residential limit of 600 mg/m2/day according to National Dust Control Regulations (Figure 2)

Summary

Introduction

Mining activities pose a great threat to the environment including contamination of the environment. Some contaminants produced from mining contain toxic substances for example radioactive elements which can be trapped in dust particles (Csavina et al 2012). These radionuclides may be carcinogenic it is considered that there is no threshold below which adverse effects occur (Cothern 1990, Fadol et al 2015, Taskin et al 2009). While radionuclides occur naturally in soils and rocks as a result of radioactive decay, most environmental releases are due to industrial processes such as mining and processes

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