FILTERING COASTAL SEDIMENTS

In exposed shallow coastal environments well-sorted sands produce highly permeable sediments that are characterized by rapid fluid exchange with the overlying water column. This exchange is driven by pressure gradients produced by wind, tide and wave induced bottom currents interacting with the seabed. The ensuing pore water exchange is tightly linked to the topography of the sediment and responds quickly to any changes in the sediment relief and bottom flow velocity. This presentation summarizes the influence of the interfacial pore water flows on solute and particle transport into and from permeable shelf sediments and discusses the consequences of the spatial and temporal dynamics of these processes for the biogeochemical reactions in the sands. Results from flume and chamber experiments are compared with in-situ observations. We discuss the contribution of the advective pore water exchange to the mineralization of deposited organic matter and its potential influence on coastal water quality.