The project integrated field and laboratory studies to demonstrate a linear relationship and empirical functions can be derived by combining raw (uncalibrated) signals of at least one pair of optical and acoustic (O/A) sensors to infer the fraction of sand/mud (f_sand) and SPMC of a suspension. This two-year project consists of three work packages (WP).
WP1: to conduct two 2-week field campaigns at MOW1, W05, W08 stations in the Belgian coastline to quantify the responses of O/A signals associated with the alteration of SMPC and SPM compositions, i.e. particle sizes and f_sand.
The project went above and beyond this plan, conducting two campaigns throughout the North Sea along the coastline of France, the UK, Germany and Belgium. The campaigns collected water and bed samples and measured hydrodynamic data. Some examples of hydro-sedimentary data collected are flow velocity, water temperature, pH, salinity, particle size and concentration in full or haft tidal cycle period. Some biological data were also collected, including but not limited to phytoplankton pigments, organic matter, POC, PON, DOC, and transparent exopolymer particles. One of the important data is the f_sand was not obtained due to the technical drawback of using Niskin bottles to collect water samples, which let the sands settle before they can be captured.
WP2: to conduct laboratory experiments using suspended sediments collected during the field campaigns to quantify the degree to which total concentration, flocculation, f_sand and particle size dictate O/A sensors’ behaviours.
A series of experiments were conducted in IFREMER, France. Bed sediments collected from the campaigns in WP1 and phytoplankton provided by PELAGOS, IFREMER were used. Different mixtures of sediments and phytoplankton at various concentrations were tested. Apparently, the O/A sensors used in the experiments were unable to detect
any changes with different concentrations of phytoplankton. It is suspected that the types and/or the size of phytoplankton might not respond strong enough to the frequency/wavelength of the O/A sensors used in these experiments. This observation needs to be further investigated.
WP3: to test the functionality and efficiency of the empirical functions established from WP1 and WP2 with field data collected from different parts of Europe provided by TU Delft and CAU.
Currently, the empirical functions derived from WP1 and WP2 are being tested with field measurement data from the station MOW1, Belgium. The results suggest that it is applicable to other data sets. Since data set with f_sand information was not available, producing a readily applicable functions for all cases is impossible. Hence, in order to apply the empirical functions (from WP1 and WP2) at least three water samples are needed for calibration purposes.
