Hydrogeochemical processes in the Kafue River upstream from the Copperbeltmining area, Zambia

Frequent sampling during an annual cycle of dissolved (<0.45 mum) and suspe nded (>0.45 mum) elements has been conducted in the Kafue River at Raglan's Farm, upstream from the mining activities within the Copperbelt Province, Zambia. Additional sampling of sediment and interstitial pore water was con ducted during low water discharge. The presence of carbonates within the dr ainage basin naturally gives rise to high element concentrations in the dis solved phase (Ca = 626, Mg = 494, Na = 360 and K = 24 mmol l(-1)). During t he rainy season the relative composition of the dissolved elements indicate d a wash out of accumulated weathering products and mineralised organic mat erial from the unsaturated zone of the soil profile. High concentrations of dissolved Al, Fe and Mn were measured during high water discharge. At low water discharge the sediment was a major source of Fe, Mn and associated Co and Cu to the water column. Enhanced concentrations of dissolved and suspe nded S, Co and Cu during the rainy season indicated that atmospheric deposi ted particles from the mining area were washed out into the river. Autochth onous formation of particles rich in Si indicated diatom production during low water discharge.