Response of heavy metal sorption to soil management and soil development

Wien

2007

Artikel aus einer ZeitschriftUnselbständiges Werk

200138914

Adsorption onto soil organic matter (SOM) and mineral surfaces are the major controlling factors governing the bioavailability and leaching behaviour of pollutants in soils. Altering the general chemical properties of soil has a major impact on the sorption capacity. In a serious of studies we examined the impact of 1) soil development, 2) soil management (e.g. fertilisation, manuring) and 3) land use (arable land, permanent pasture, floodplain forest) on the sorption capacity of selected heavy metals (Cd, Cu, Zn). The investigated soil samples were obtained from two long-term field experiments, located in Ultuna (Sweden, set up in 1956) and Gumpenstein (Austria, set up in 1962). In both long-term experiments the quantity and quality of the SOM as well as the pH-values were influenced by long-term management practices. However, no significant impact on the mineral phase was found. Another set of samples was derived from three chronosequences of floodplain soils in the Elbe, Ebro and Danube basin. The soil profiles in the floodplains turned out to be of largely varying age according to the abundances of natural and artificial radionuclides present in the different horizons, from ages of a few decades to thousands of years. Batch sorption experiments as well as sequential extractions were conducted following standard procedures. In the adsorption experiments high metal loadings were added to soil. Experiments were performed with bulk soils, metal spiked soils and the particle size fractions in theses soils. Sorption isotherms revealed enhanced metal retention with increasing soil pH and SOM content in the long-term field experiments. In the Ultuna soils, for instance, sorption increased among the investigated farming practices in the following order: sewage sludge < fallow < inorganic fertiliser < without N ~ green manure < peat < Ca(N03)2 < animal manure < grassland/extensive pasture. Amounts of retained Cu, Cd and Zn differed by a factor of 2.5 to 3 among soils, when the highest concentration of metal was added to soil. Sorption experiments with floodplain soils clearly demonstrated that sorption capacity increases with soil age. Soil pH and the content of carbonate as well as the SOM content seemed to be the main factors controlling the sorption capacity for the selected heavy metals in floodplain soils.