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Sediment transport in fluvial systems is a key driver of basin-wide global soil loss, river sedimentation, and the movement and transformation of organic, inorganic, and nutrient materials, all of which can contribute to severe eco-environmental degradation. Since the late 1800s, much research effort has focused on the physics of sediment entrainment, transport, and deposition by river flows. This paper reviews ongoing research aimed at considering the simultaneous physical, chemical and biological processes that characterize riverine sediment flux. Four related issues are considered: riverine sediment flux; soil erosion and chemical transport; fluxes of dissolved organic carbon; and sediment-induced CO2 emission/sequestration. Modelling of sediment flux has moved beyond empirical and statistical approaches to that of a generalized form of the universal integral solution of the basic flux equation, which is now anticipated to lead to a wide range of applications. Whereas soil erosion and riverine chemical transport are now known to cause soil degradation and reduced water quality, limited progress has been made to date on the quantification of erosion rates. As soils erode, CO2 is emitted at erosion and transport sites and sequestered at deposition sites, the net effect being carbon sequestration. However, the rates of CO2 emission/sequestration vary widely, owing to the large spatial variations in soil type, land-slope, rainfall intensity, etc. It is now well established that dissolved organic carbon (DOC) concentrations and fluxes have been increasing over the past two decades, due to reduced atmospheric sulphur concentration, climate warming, and changes in precipitation patterns. The research discussed herein provides insight into the interaction between sediment and multiple material substances, leading to a better understanding of fluvial river ecosystems, which is essential for maintaining river health.
Keywords: sediment flux, soil erosion, environmental implication, chemical transport, dissolved organic carbon, CO2 flux