Sediment Fingerprinting Tracer Conservativeness: Exploring the In-Channel Soil Properties variability

Abstract

<p>Soil properties' conservative behaviour is essential in sediment tracing research. To compare suspended sediment and soil samples, it is necessary that soil properties remain stable or vary in a predictable way during its transfer from sources to deposition areas. Conservative behaviour of soil properties has been largely focused on the differences in particle size and organic matter. However, in-channel biochemical alterations are also known to occur, but further research is needed considering the wide variety of fluvial regimes. Here is presented an experiment to investigate variations of in-channel soil properties' by using the most common soil properties used as tracers in sediment fingerprinting studies; i.e., colour, fallout radionuclides and geochemical elements. Twenty-eight soil samples collected from different land uses were introduced in an intermittent stream channel of a small Mediterranean catchment. Samples were extracted at different time intervals (i.e. 7, 30, 60, 90, 150, 210, 270 and 365 days) during one year. Results showed that changes on soil properties -average coefficient of variation 8.1 ± 8.8%- were generally lower than its spatial variability within the catchment (average coefficient of variation 16.3 ± 18.5%); being the colour properties the most stable tracers with an average coefficient of variation 2.6 ± 2.2%. The general low variability observed in the investigated soil properties and its strong correlations with specific surface area and carbon content seems to emphasize the role of particle size and organic matter in the conservative behaviour of soil properties. The exploration of in-channel soil properties variability can improve the selection of tracers in future suspended sediment fingerprinting studies in Mediterranean catchments.</p>