Suspended sediment source tracing at the Juksan Weir in the Yeongsan River using composite fingerprints

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Since 2008, the Yeongsan River in South Korea has experienced significant environmental changes, such as the dredging of its riverbed and the construction of large weirs. The quantity and quality of the fine sediments that provide adsorptive surfaces for pollutants has an influence on water quality, human health, and aquatic organisms. To determine the dominant contributors and seasonal variation in suspended sediment at the Juksan Weir in the Yeongsan River, reservoir sediments were obtained at monthly intervals using a time-integrated suspended sediment sampler. We applied a fingerprinting procedure combined with a multivariate mixing model to discriminate between different types of land use and to apportion sediment sources. Cropland topsoils, forest topsoils and channel bank materials were selected as end-members, and fallout radionuclides, geochemical elemental concentrations and the magnetic properties of each source material were used as diagnostic tracer properties. According to the mixing model results, channel bank materials were the dominant source of reservoir sediment during the entire monitoring period. In winter, there was a slight increase in the contribution from forest topsoils, which could have been influenced by freeze–thaw processes. Despite the high proportion of agricultural land use in the study catchment and its proximity to the river, there was a small sediment contribution from the cropland topsoils. There were uncertainties resulting from an imperfect classification due to the spatial distributions of forest and cropland and the combination of the mixing model with the fingerprinting procedure. The results provide the basis for developing strategies for sediment control and reservoir management.