Retention and chemistry of aluminium in groundwater discharge areas

Abstract

The concentration of different fractions of Al were measured in seven micro (3–4 m 2) discharge areas using extraction methods on the upper layer of the soil. The areas were situated in two catchments subjected to different levels of acidic deposition. The Al fractions were determined by separate extractions with 1m KCl, 0·5m CuCl 2 and 0·2 m (NH 4) 2C 2O 4. The fractions associated with the different extraction reagents are preferentially exchangeable, organically bound and amorphous hydroxide, although a complete separation cannot be made. The total amount of Al was determined after dry ashing. The results show that the levels of total Al in the peat were high when compared to ombrotrophic peatlands. The quantity and characteristics of the organic material and the acidity of the soils in the discharge zone could be decisive in determining which fractions of Al occur. The high levels of total Al in the soil indicate that the discharge zone could be an important trap for the element.