Die Bodenkultur - Journal for Land Management, Food and Environment
R. Jandl, M. Fürhacker, A. Weingartner and M. Pollak:
Evaluation of a soils suitability to apply sewage sludge
We simulated the chemical composition of the soil solution of an agricultural soil under the assumption of an annual application of sewage sludge. Our goal was to estimate both the consequences of long term sludge application and the time frame available to exhaust the trace metal retention capacity of the soil. Our scenarios included changes in soil pH as consequence of land use change. At low soil pH (pH =3) a substantial portion of lead and copper was tied up in organic complexes, whereas cadmium and nickel remained in solution as free ions; at high pH (pH =7) even cadmium and nickel formed complexes with organic ligands. The trace metal retention capacity of the soil was high and allows a continuous application of sewage sludge for many decades. Concentrations of trace metals in the soil solution are rising, but deep soil profiles make the retention capacity apparently inexhaustible. These conclusions apply for the chosen parameters in our study. Preferential water flow is not considered in our models and may cause deviations between simulations and field measurements. Based on our results we consider modeling a valuable tool to evaluate the human impact on soil processes.
Key words: sewage sludge, trace metals, model, simulation, MINTEQA2, WHAM.