The characteristics of composite suspended sediment particles transported during storm events in the river Exe, Devon, U.K

Abstract

Abstract Particle size is one of the most important factors controlling the behaviour of fluvial suspended sediment and its role in different environmental and geomorphological processes. Primary mineral particles are frequently transported as composite particles or aggregates, which consist of different sized mineral particles combined with organic matter and biogenic material. The formation and behaviour of such aggregates are controlled by physical, chemical and biological factors which act independently and also in combination at different spatial and temporal scales. This paper examines the nature and behaviour of the composite suspended sediment particles transported by the River Exe, Devon, U.K. during several storm events. Effective size (undispersed) fractions were separated in situ using a field-portable water elutriation apparatus. The absolute (chemically dispersed) grain size composition of each effective size class was examined, in order to provide information on the proportion of the sediment transported as aggregates. In addition, the influence of a number of factors in controlling the occurrence and behaviour of aggregates during storm events has been examined. More detailed information concerning the character and structure of the composite particles has been obtained using Scanning Electron Microscope observation and Energy Dispersive X-Ray analysis (SEM/EDAX).