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Content archived on 2024-04-19

The role of exchange processes on controlling ion transport in forest soils and catchments


Ion exchange processes are of great importance in soil.
While the soil solution instantaneously riflects the changes imposed to the ecosystem, the exchange complex maintains the memory of these changes. Acid deposition in the northern hemisphere has left an inprint on the exchangeable complex as an increase of exchangeable acidity. Models for predicting acidification of ecosystem waters are presently inadeguate because the exchange coefficients are assumed to be constant across a wide pH range.
Also the role of DOC, is not considered in the models.
To obviate these problems we propose to conduct basic experiments on exchange reactions specifically on the nature of the charges under different acidity levels, the anion exchange reaction and the role of DOC in the mobility of base cations.
A new approach is introduced to consider the inhomogeneous distribution of ions in soil aggregates; the aggregates represents a fundamental component in the rhizosphere between the roots and the percolating soils solution. Diffusion from the inside to outside of aggregates will be evaluated. An other aspect is the role of the coarse soil fraction ( 2mm) in exchange processes.
Preliminary data show that rocks that have weathered and acquired porosity have relatively high cation exchange capacity.
These measurements will be extended to other stony soils.
Collection of ecosystem solutions will occur at sites located in Sweden, France, Germany and Italy.
This north and south transect will allow to compare processes in different environments.
The data previously collected at Gardsjon and Aubure and Conventwald will provide the input for the revised models.

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Università degli Studi di Firenze
EU contribution
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Piazzale delle Cascine 15
50144 Firenze

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Participants (3)