A constant head permeameter experiment was done to quantify changes in hydraulic conductivity for highly and barely decomposed organic soil as a result of salinity. Furthermore, transport parameters including retardation factor, fraction of mobile water and mass transfer coefficient were studied, by fitting analytical solutions to the breakthrough curves.
Effects of Salinity in Organic Soils
Floating fen areas in the Netherlands are threatened by salt intrusion because of climate change. Hydrology is very important in the formation and control of these fens. In order to estimate the extent of the exposure and the risk of salt intrusion, we need to understand the physical properties that affect flow and transport through the organic soils. Therefore this research aims to tell if hydraulic conductivity changes with salinity and provide solute transport parameters.
A constant head permeameter experiment was conducted, and showed that hydraulic conductivity increases or stays the same with increasing salinity and hydraulic conductivity decreases or stays the same with decreasing salinity. No difference in hydraulic conductivity was found for highly and barely decomposed organic soils.
Breakthrough curves of CaCl2 and NaCl were fitted to an analytical mobile-immobile model (MIM), using the CXTFIT code, in order to estimate transport parameters- retardation factor, fraction of mobile water and mass transfer coefficient. The model was sensitive to mobile volume, and we found that the variation of this factor was quite big between columns. Decomposition degree did not affect the estimate of mobile volume and the retardation factor. Only the salt type influenced the retardation factor; R of calcium was larger than the one of sodium. The model was not sensitive to dispersivity. These results could help to understand the water flow process in this area.