Initial Changes in Refilled Lysimeters Built with Metal Polluted Topsoil and Acidic or Calcareous Subsoils as Indicated by Changes in Drainage Water Composition |
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Authors: | Jörg Luster Manoj Menon Sandra Hermle Rainer Schulin Madeleine S Günthardt-Goerg Bernd Nowack |
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Institution: | 1.Swiss Federal Institute for Forest, Snow, and Landscape Research,Birmensdorf,Switzerland;2.Institute of Terrestrial Ecosystems,ETH Zurich,Zürich,Switzerland;3.Department of Geological Sciences and Engineering,University of Nevada,Reno,USA;4.EMPA – Swiss Federal Laboratories for Materials Testing and Research,St. Gallen,Switzerland |
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Abstract: | Soil translocation for recultivation of soil removed from construction sites and for the preparation of refilled lysimeters
inevitably involves disturbance of soil structure, and, if intermediate storage is included, also drying and rewetting of
the soil. We report on an experiment with model forest ecosystems, where uncontaminated forest subsoils were covered with
non-contaminated or freshly heavy metal (mainly Zn and Cu) contaminated topsoil in large lysimeters. Monitoring of the chemical
composition of the drainage water revealed two distinct soil conditioning phases. During an initial phase of about a year
strongly elevated nitrate and sulfate concentrations occurred that were attributed to a mineralisation flush caused by the
increased accessability of mineralisable nitrogen and sulfur in destroyed aggregates. These effects were significantly larger
in lysimeters with calcareous subsoil than in those with acidic subsoil. The second phase was characterised by a gradual decrease
in dissolved organic carbon and sulfate concentrations, in particular in the acidic subsoil. This decrease may be attributed
to the depletion of pools made accessible during aggregate destruction or the formation of new aggregates. These chemical
changes had only little effects on the concentrations of copper and zinc in the drainage water. Based on our results, it can
be concluded that large refilled lysimeters can be used for many purposes without risk of compromised results, if a conditioning
phase of about 1 year with sufficiently moist soil conditions is respected. Nevertheless, gradual changes in soil chemical
characteristics still occur after this initial phase. Implications for the recultivation of sites using relocated soils are
discussed. |
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Keywords: | Drying and rewetting of soils Heavy metals Mineralisation of soil organic matter Refilled lysimeters Soil relocation Soil solution Soil structure |
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