POSSIBILITIES AND LIMITATIONS OF SEDIMENT TRAPS TO MEASURE SEDIMENTATION AND RESUSPENSION

Settling flux of particulate matter measured by sediment traps in shallow and turbulent waters considerably exceeds settling flux calculated from mass balances. Theoretical consideration on sinking distance and particle settling leads to the conclusion that traps overtrap particles in even moderately turbulent waters. The disappearance of turbulent diffusion and bottom shear stress within the traps causes the high rates of 'trapping', whereas their presence in natural water bodies hampers sedimentation. The use of sediment traps may be restricted to the identification of rapidly sinking particles, measurement of sinking velocities of well defined types of particles, and estimation of resuspension.