Status of aluminium in environmental compartments contaminated by acidic mine water

Investigations were conducted to characterize aluminium in the affected stream and soils downstream of a mine site discharging acidic mine water. The water-borne Al exhibited a highly non-conservative behaviour at water pH below 3.8 in the 0–3.9km reach and a much more conservative behaviour in the reaches with higher water pHs downstream of the 3.9km station. The concentration of water-borne Al was higher at the medium flow event than at the flood event in the 0–9km reach while the opposite was observed for the 16–56km reach. Transport of Al associated with suspended materials was only observed during the flood event. The amount of Al carried by per unit weight of suspended particles was smaller in the 0–16km reach than in the 25–56km reach. The sediment-borne Al increased downstream with maximum Al accumulation occurred in the 25–29km reach. The residual Al dominated Al fractions in the streambed sediments. The NH4Cl-extractable Al in the affected soils decreased with increasing distance from the acidic irrigation water source. In contrast, both the water-extractable and total Al in the soils showed no clear distribution pattern. The NH4Cl-extractable Al was closely correlated with soil acidity while neither total Al nor water-extractable Al was correlated with soil acidity. The vertical distribution of NH4Cl-extractable Al was regulated by pH with certain influence from soil clay abundance