Rivers and streams are the corridors of material transport from land to sea. Solutes and particles experience a range of environments as they traverse the river network, many of which are highly reactive, and reaction rates are localized to specific regions. The interfacial region between the river and its underlying sediments, or the hyporheic zone, is particularly reactive due to the diversity of chemical environments and the abundance of life in stream sediments. The overall transformation of reactive materials in streams and rivers is therefore closely linked to their transport to, and retention within, the hyporheic zone. However, hyporheic transport processes are difficult to elucidate because stream and rivers are highly heterogeneous. Transport mechanisms are not only active over a broad range of spatial and temporal scales in these systems, but they also co-vary. To accurately predict material movement in this environment, transport models must capture the full distribution of scales over which these processes are active, as well as the coupling between them. Such an effort requires detailed observations of the mechanisms that dominate hyporheic transport, many of which are difficult to measure within sediments. This dissertation is motivated by the need for parsimonious, mechanistic models describing solute and particle transport at the sediment-water interface. To this end, we combine experiments and modeling to advance understanding of several transport processes that have not been observed or incorporated into current modeling frameworks. Specifically, we study the role of turbulence in regulating hyporheic transport in coarse-grained streambeds (Chapters 2-3), the controls of microbial biomass on fine particle transport (Chapter 4), and the reworking of interfacial sediments by the aquatic worm Lumbriculus variegatus (Chapter 5). Together, our findings advance understanding of interfacial solute and fine particle transport by providing novel observations of several physical processes that regulate interfacial dynamics, as well as strategies for how these processes can be incorporated into multi-scale transport modeling frameworks.

Last modified

• 11/01/2018

Creator

• Kevin R. Roche

DOI

• https://doi.org/10.21985/N2P16B

Keyword

• stochastic model
• hyporheic exchange
• bioturbation
• sediment-water interface
• environmental transport

Date created

• 2017-01-01

Resource type

• Dissertation

Rights statement

• In Copyright