Dealing with elemental mercury on a Western Cape legacy site has rendered the area suitable for redevelopment. Explosives were once manufactured there, mainly for use in the Second World War.
"What was interesting about this project is that the toxicity of mercury is very dependent on the chemical speciation – on whether it is organic mercury, elemental mercury, immobile mercury salts or mercury sulfide," says Richard O'Brien, principal environmental geochemist at SRK Consulting’s Cape Town office.
"While elemental mercury is highly toxic if inhaled, organic mercury is far more toxic if you ingest it; mercury sulfide, on the other hand, presents very little risk to human health," he expands.
Speaking at the annual conference of the Network for Industrially Contaminated Land in Africa in 2018, O'Brien noted that an innovative approach was taken to establish the precise nature of the risk that the project team was dealing with. The mercury has contaminated both the soil and the groundwater, with concentrations in soil ranging from less that 5 mg/kg up to 780 mg/kg, exceeding the US Environmental Protection Agency (EPA) residential soil screening level of 10mg/kg.
