Abstract:

We studied the effect of tubificid density and overlying water pH on the behavior of tubificid bioturbation and on migration of Cu and Cd from overlying water to the sediment through laboratory simulation of sediment/water system in tubificid bioturbation processes. The results show that bioturbation can significantly increase the migration rate of both Cu and Cd to the sediment, and the effect increases with increased density of tubificid. The influence of bioturbation on migration rate of Cu is greater than Cd. Acid and alkali induced stress can enhance the bioturbation. This enhancement of bioturbation is more significant under alkaline conditions. The presence of tubificid bioturbation can significantly enhance the acidbase buffering capacity of the experimental systems, and make the pH  of systems to be uniform and neutral. Both the changes of pH and the bioturbation in the systems affect the migration rate of Cu and Cd.
 Generally, the migration rate of the metals increases with the increase of overlying water pH. The promotion effect of bioturbation on migration rate of Cd is greater than Cu.

Key words: tubificid, bioturbation, sediment, heavy metal, migration, pH