tailieunhanh - Flocculation In Natural And Engineered Environmental Systems - Chapter 3

Trầm tích hạt mịn ( | 3 Intra-Storm and Seasonal Variations in the Effective Particle Size Characteristics and Effective Particle Density of Fluvial Suspended Sediment in the Exe Basin Devon United Kingdom John M. Phillips and Desmond E. Walling CONTENTS Introduction. 48 The Study Sites . 49 Methodology. 51 Results and Discussion. 52 The Degree of Aggregation of Suspended Sediment in the Study Area. 52 Short-Term Variability in the EPSD. 54 Intra-Storm Variability in the EPSD and Associated DOA. 55 Inter-Storm and Seasonal Variability in the EPSD and Associated DOA. 60 Effective Particle Density. 65 Sources of Aggregated Sediment in the Exe Basin . 66 Conclusion. 67 Acknowledgments . 68 References . 68 1-56670-615-7 05 2005 by CRC Press 47 Copyright 2005 by CRC Press 48 Flocculation in Natural and Engineered Environmental Systems INTRODUCTION Fine-grained m sediment-associated transport dominates the land-ocean flux of many natural1 and anthropogenically derived nutrients and contaminants to the fluvial Globally transport during storm events dominates the suspended sediment flux of most In addition to its role in the sediment-associated transport of nutrients contaminants and other geochemical materials suspended sediment frequently represents a significant form of nonpoint source pollution in its own right with both environmental for example ref. 6 7 and economic The hydrodynamic properties of suspended sediment particles are determined primarily by their size diameter density and shape. Of these parameters particle size represents the principal physical factor controlling both the hydrodynamic properties and chemical activity of fluvial suspended sediment particles. Particle size is a key variable in many numerical models of the transport and geochemical dynamics of fine sediment. A sound understanding of the in situ particle size characteristics of fluvial suspended sediment is .