Geochemistry of groundwater in an intensely urbanised karst area (Lusaka, Zambia)

The capital of Zambia Lusaka (about 2 million inhabitants) is built on a plateau where dolomitic marbles widely crop out. The carbonate formation hosts a very intensively exploited karstic groundwater resource. Considering the fast urban expansion and the lack of environmental control, this resource is in serious danger of pollution that could compromise the social and economical development of the capital. In this paper the geochemistry of the ground water is for the first time being analysed on the basis of a small number of samples taken in July 2001 in order to get a preliminary idea of the water quality. In some samples the concentrations of reduced nitrogen species and mercury exceed the guidelines proposed by the WHO for drinking water. Lusaka is a good example of the potential human impact on a vulnerable karst environment, and if no measures will be taken in the very near future, the quality of life in the city will be at serious risk.