Assessment of asbestos contamination in soils at rehabilitated and abandoned mine sites, Limpopo Province, South Africa.

Prior to its termination, asbestos mining in South Africa was centred on the large crocidolite fields of the present day Northern Cape, the amosite (grunerite)-crocidolite fields of Limpopo, and chrysotile fields of Mpumalanga provinces. The legacy of these activities continues to affect surrounding communities in contemporary South Africa. The asbestos fields of Limpopo host two important former mining areas at Penge and at the Bewaarkloof near Chuenespoort. A large abandoned site is located southeast of Penge at Weltevreden, where there is no evidence of any rehabilitation. Two former mines, Lagerdraai and Uitkyk, are rehabilitated sites in an extensive string of closed mines that operated in the southern Bewaarkloof. Samples from the abandoned and rehabilitated mine sites were studied using semi-quantitative X-ray powder diffraction (XRD) to determine asbestos contamination levels in soils, and to assess distribution patterns of asbestos mineral species in the surrounding soils. Only where below detection (typically 1-3 mass%) from XRD, samples were assessed optically. The Weltevreden site, with no observable rehabilitation efforts, contrasts with the rehabilitated sites at Lagerdraai and Uitkyk. The predominant asbestiform mineral species at each site were successfully identified, with underlying geological asbestos mineral distribution trends recognised in the soils at the Bewaarkloof. Trace amounts of asbestiform minerals were identified in soils downstream of the Weltevreden mine, as well as in surrounding hillsides. The results indicate that XRD is a potentially useful tool for benchmarking sites yet to be rehabilitated as well as monitoring the effectiveness of previous rehabilitation efforts. The method is also a suitable first-pass for target areas that may require more detailed, time-consuming, and costly analysis.

Diamond fingerprinting for source discrimination using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and Fourier transform infrared spectrometry (FTIR).

The Kimberley Process Certification Scheme (KPCS) was established in 2000 as a means of controlling the flow of conflict diamonds, mostly, from the African continent. In 2013, the KPCS imposed an embargo on diamonds from the Central African Republic (CAR). Since then the embargo has been lifted in certain prefectures of the country, however, smuggling is suspected from non-compliant areas. Three parcels of diamonds suspected to have mining origins in the CAR, were analysed. These diamonds were investigated for their morphological and chemical characteristics, to establish a diamond fingerprint and to determine if these diamonds had the same fingerprint as previously analysed diamonds from CAR or the Democratic Republic of the Congo (DRC). The analyses of these diamonds were included in the already established diamond database of rough diamonds from the African continent. The morphological characteristics identified included the mass (ct), colour, surface coatings, dominant, secondary and tertiary form, shape, breakage, inclusions, abrasion and surface features that are specific to octahedral, dodecahedral and cubic shapes. The morphological characteristics determined from the diamonds revealed that morphology alone cannot be used as a discriminatory method for diamond fingerprinting. Fourier transform infrared spectroscopy (FTIR) identified the nitrogen concentration and aggregation state of that N. This allowed for the typing of the diamonds as Type I (containing N) and Type II (containing no measureable N). The concentration of N in the three parcels is less than 600 ppm. Further classification of Type I diamonds was performed according to the N aggregation state as single, double or four-fold. The vast majority of diamonds show a combination of nitrogen aggregation states while few were classified as Type II. Fourier transform IR showed no discernible trends between the current study and the established database. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was used as a means of determining the trace element concentrations of 69Ga, 88Sr, 89Y, 90Zr, 93Nb, 133Cs, 137Ba, 139La, 140Ce, 141Pr, 146Nd, 147Sm, 153Eu, 157Gd, 159Tb, 163Dy, 165Ho, 166Er, 169Tm, 172Yb, 175Lu, 178Hf, 181Ta, 232Th and 238U. Laser ablation ICP-MS determined that not all elements produce statistically viable data, however, the data could still be used to discern trace element differences and trends among the parcels. In the current set of diamonds, laser ablation ICP-MS data for parcels A and B showed an excellent agreement with each other as well as those from diamonds previously analysed from CAR. None of the three parcels showed any similarity to data from Bria River or the DRC. It is concluded that the diamonds from parcels A and B are very likely to have mining origins in the same area in the CAR, whereas parcel C is distinct and of possible mixed origin.