Abstract
Interfacial solute fluxes from sediment cores enclosed in stirred chambers were compared with solute fluxes from a reference core inserted In a flume simulating in si tu conditions with unidirectional boundary-layer flow. Utilizing Rhodamine-WT dye as conservative solute, and quantifying the hydrodynamic driving forces by hot film anemometry and a highly sensitive wet/wet d~fferential pressure transducer, the pathways of solutes in chamberand flume-confined cores are ~dentified. The critical parameter limiting confined-core flux techniques is the sediment permeability, with equivalency between experimental techniques and natural, smooth bottoms found for impermeable sediments only, where bottom stress and Schmidt number act as the controlling parameters permitting use of diffusive laws. In contrast, pressure gradients, induced by edge and sidewall effects in cores under unidirectional flow and by circular flow patterns in stirred chambers, being ineffective for impermeable sediments, generate non-negligible advective porewater flows in permeable sediments. For fine sandy sediment (4 = 2.2; permeability K = 15 Darcy, D), stirred-chamber circular flow enhanced solute release up to 6-fold over that from the reference core exposed to 2-dimensional flow, with intruding supernatant water reaching up to 8-fold deeper ~ n t o the porespace. Consequences of these advective exchange processes include release of anoxic porewater and increased oxygen uptake in permeable cores, with shifts in redox isolines affecting biological and geochemical processes in the sediment. Results suggest that chamber fluxes are both siteand device-dependent and cannot be automatically equated with In si tu fluxes.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.