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Thorough wetting and drainage of a peat lysimeter in a climate change scenario |
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| Authors: | Maurizio Previati Davide Canone Edoardo Iurato Davide Gisolo Stefano Ferrari Pietro Teatini Mario Putti Stefano Ferraris |
| Institution: | 1. Interuniversity Department of Regional and Urban Studies and Planning (DIST), Politecnico di Torino and Università di Torino, Torino, Italy;2. Interuniversity Department of Regional and Urban Studies and Planning (DIST), Politecnico di Torino and Università di Torino, Torino, Italy
EnviCons s.r.l., Lungo Po Antonelli 21, Torino, Italy;3. Department of Civil, Environmental and Architectural Engineering (DICEA), Università di Padova, Padova, Italy;4. Department of Mathematics, Università di Padova, Padova, Italy;5. Interuniversity Department of Regional and Urban Studies and Planning (DIST), Politecnico di Torino and Università di Torino, Torino, Italy Institute of Geosciences and Earth Resources (IGGd), Consiglio Nazionale delle Ricerche, Pisa, Italy |
| Abstract: | A peat deposit (Zennare basin, Venice coastland, Italy) was monitored in previous field studies to investigate the hydrological response of organic soil to meteorological dynamics. Field tests and modelling predictions highlighted the risk of the complete loss of this peat layer during the next 50 years, due to oxidation enhanced by the increased frequency of warmer periods. Unfortunately, despite the considerable impacts that are expected to affect peat bogs (in this area and worldwide), only a few experimental studies have been carried out to assess the hydrologic response of peat to severe water scarcity. Because of that, an undisturbed 0.7 m3 peat monolith was collected, transferred to the laboratory and instrumented. The total weight (representative of the water content dynamics of the peat monolith as a whole), and two vertical profiles of matric potentials and water content were monitored in controlled water-scarce conditions. After an extended air-drying period, the monolith was used as an undisturbed peat lysimeter and a complete cycle of wetting and drainage was performed. Supplementary measurements of matric potential ψ and water content θ were collected by testing peat subsamples on a suction table apparatus. A set of water retention curves was determined in a range of matric potentials broader (ψ down to ?7 m) than the current natural conditions in the field (minimum ψ = ?1 m). While water content at saturation showed values similar to those in the original natural conditions (θ ? 0.8), a remarkable loss of water holding capacity (even for low potentials) has been highlighted, especially in deep layers that are now permanently below the water table. The retention curves changed shape and values, with a more pronounced hysteresis visible in an increasing distance between wetting and drying data. Hydraulic non-equilibrium between the water content and water potential could be a possible cause and it is worth modelling in future studies. The parameters of the van Genuchten retention curves were obtained for the wetting and the drying phases. |
| Keywords: | Peatland peat soil hydrology lysimeter wetlands hydro-physical properties experiment climate change |