Modelling and mapping the processes and distribution of salt affected soils in semi-arid areas

School of Geography, University of Leeds

Student

Ruth Schofield

Supervisors

Prof Mike Kirkby

Dates

1st October 1997 - 30th September 2001

Grants

University of Leeds Studentship

Summary

Salt affected areas can be found on every continent, with approximately 10% of the total land surface of the globe affected. The Phd Research involves the modelling and mapping of salt affected soils under both contemporary and possible climate change scenarios. The modeling is the primary focus of the research, and the field work provides sample studies from different saline environments to provide validation to the principles and parameters incorporated in the models. Field studies have been carried out in three very different salt affected environments of a Tunisian Chott system, an irrigated agricultural valley with anthropogenically induced salt affected soils in SE Spain and finally a selection of sodium dominated salt affected soils in Hungary. Of Relevance to salt affected soils are the following ions essentially Na⁺ Mg₂⁺ Ca₂⁺ K⁺ Cl^- SO₂4 HCO^-3 CO₂3^-. These ions are extracted using a 1:5 soil:water extract. This filtered extract can then be analysed for the cations (Na⁺ Mg₂⁺ Ca₂⁺ K⁺ ) on the ICP and the anions (Cl^- and SO₂4 ) on the Dionex, with the HCO^-3 and CO₂3^-, being determined by titrations with HCl. The ion make up of the water samples are also determined using the same equipment for the relevant cations and ions. The fieldwork involves sampling soil pits to a depth of 3m ⁺ and where possible irrigation, meteoric and groundwater samples are also taken. The soil and water samples then undergo physico^-chemical analysis in the laboratories in Leeds. The soil salinity is determined by analysing the conductivity of a saturated soil extract, with the salinity of the water being taken directly as a measure of conductivity in mS/cm. The modeling component of the research has developed both a one dimensional profile model, with a vertical component, and a spatial model which takes account of topography, these models therefore reflect the salinity distribution down the profile and across the landscape respectively. The one dimensional profile model is built and run through an Excel macro with the spatial model developed using C++, AML, ARCINFO and ARCVIEW.