Hydrogeochemical and hydrogeological baseline study following the mining of asbestos at the Havelock Mine, Bulembu, eSwatini

Abstract

This study examined the hydrogeological and hydrochemical conditions around Bulembu, eSwatini, two decades post-closure of the Havelock asbestos mine. On-site parameters and water samples underwent chemical and stable isotope analysis, supplemented by flow measurements and tracer tests with NaCl and uranine. Multivariate statistical analysis and PHREEQC modelling identified three water groups: i) low mineralised surface water (32 mg/L TDS), ii) mining-influenced water from the Havelock mine pool (212 mg/L TDS), and iii) tailings seepage water (411 mg/L TDS). All are earth alkaline, hydrogen carbonate-dominant, dominated by Mg and hydrogen carbonate ions. Surface water complies with WHO standards, except for elevated As in the mine pool and Cr in waste rock seepage. Chemical and tracer test results indicate a well-mixed, low-residence-time mine pool. Both the Tutusi river catchment and the upper Nkomazana catchment as well as water courses downstream of the abandoned mine exhibit pristine water quality. The authors propose inclusion of the area in a trans-boundary national park with the Barbeton Makhonjwa Mountains UNESCO World Heritage Site. They recommend amelioration of tailings, not remining, to safeguard the environment and local population from asbestos exposure.