Short experiments (1421 days) were carried out during autumn 1998 and spring 1999 at one selected site of the Venice Lagoon to measure bioturbation activities and mixing rates, as well as to obtain quantitative information on benthos functionality. Fluorescent sediment particles (luminophores, 63350 µm) were introduced as pulse inputs at the sediment surface. The concentrationdepth profiles of the tracer were simulated with a new advection diffusionnon local model applied under non-steady state conditions. This allowed the quantification of the mixing parameters associated with different mechanisms: biodiffusion (Db), bioadvection (W) and non-local mixing (Ke, z1, z2). A parameter RS (removed sediment) was also calculated to account for the flux of sediment due to nonlocal transport. Results show that bioturbation was dominated by biodiffusion in autumn and by bioadvection in spring. Mean mixing parameters Db, W, and RS changed from 3.09 to 0.87 cm2 y-1, from 0.93 to 15.50 y-1 and from 5.85 to 7.79 g cm-2 y-1, respectively.
Bioturbation experiments in the Venice Lagoon
M Frignani;L G Bellucci
2003
Abstract
Short experiments (1421 days) were carried out during autumn 1998 and spring 1999 at one selected site of the Venice Lagoon to measure bioturbation activities and mixing rates, as well as to obtain quantitative information on benthos functionality. Fluorescent sediment particles (luminophores, 63350 µm) were introduced as pulse inputs at the sediment surface. The concentrationdepth profiles of the tracer were simulated with a new advection diffusionnon local model applied under non-steady state conditions. This allowed the quantification of the mixing parameters associated with different mechanisms: biodiffusion (Db), bioadvection (W) and non-local mixing (Ke, z1, z2). A parameter RS (removed sediment) was also calculated to account for the flux of sediment due to nonlocal transport. Results show that bioturbation was dominated by biodiffusion in autumn and by bioadvection in spring. Mean mixing parameters Db, W, and RS changed from 3.09 to 0.87 cm2 y-1, from 0.93 to 15.50 y-1 and from 5.85 to 7.79 g cm-2 y-1, respectively.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.