Phosphorus release within the soil matrix caused by the changed redox conditions due to re-establishment of a riparian wetland can be critical for the aquatic environment. However, phosphorous released in the soil will not always result in an immediate contribution to this loss to the aquatic environment. Lowland soils are primarily peat soils, and only a minor part of the total soil volume of peat soils is occupied by macropores (>30 µm). Since water primarily flows in these macropores, the majority of the soil matrix is bypassed (the immobile domain). Phosphorus released in the immobile domain is not actively transported out of the system, but is only transported via diffusion, which is a very slow process. Thus it is interesting to investigate the size of the active pore volume in peat soils. The hypothesis of this study is that the active pores volume of a peat soil can be expressed using bulk density as a key parameter. This hypothesis is investigated using intact soil cores (d:6 cm; h: 15 cm) from 20 Danish peat soil locations. The volume of macropores was determined for samples, drained to a matrix potential of pF 2, using a pycnometer. Furthermore, retention curves were conducted using 100 cm3 intact soil samples. Finally, breakthrough of tritium (3H2O) was used to construct breakthrough curves for each peat soil, which indicates the flow pattern in the soil. A mobile-immobile domain model (MIM-model) in CXTFIT was used to derive parameters describing the size of the immobile and mobile domains as well as the exchange between the two domains. Finally, the samples were dried in the own for determination of the bulk density. The bulk density was correlated to parameters from the MIM-model and to the macropore volume to determine, whether bulk density can be used as a key parameter.
Proceedings From the 7th Sws 2012 European Chapter Meeting: Wetland Restoration – Challenges and Opportunities, 2012
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Society of Wetland Scientists meeting European, 2012
Aarhus University, DCE - Danish Centre for Environment and Energy