Observations of the effects of turbulence on particle size distributions in an estuarine bottom boundary layer

Here we present continuous, concurrent observations of dynamics and suspended particulate matter (SPM), performed in the bottom boundary layer (bbl) of a macrotidal estuary during a 24-day period. Turbulence parameters were found to vary on both a quarter-diurnal and a spring-neap tidal timescales. An approximate local balance between the shear production and dissipation of turbulent kinetic energy (TKE) was also found. The concentration of SPM in the bbl varied on similar timescales, but diurnal and synoptic scale variations were also found to be important. The size distribution of SPM observed is strongly linked to the Kolmogorov microscale and turbulent shear rate, suggesting that turbulence is playing a significant role in regulating the extent of SPM flocculation.