Study On The Influence Factors Of The Speciation And Release Of Heavy Metals In Sediment With Tubificid Bioturbation

In aquatic environment, heavy metals are widespread but important pollutants, and their environmental behaviors are influenced by a variety of solid substances in water environment (including biological and abiotic matters) significantly. After the heavy metals and other pollutants are discharged into the water body, natural colloidal would will take a series of physical and chemical reactions such as adsorption, complexation, distribution, degradation, precipitation reactions, affecting the environmental behavior of pollutants and chemical speciation, which play very important role in the distribution, migration and transformation and the fate of heavy metals. The presence of tubificid worm makes the water/sediment interface complex, the physical, chemical, and biological benthic irrigation, bio-sedimentation, respiration and biological vertical transport and mixing on the role of sediment pore water and overlying accelerate water exchange of material flux. The results show that biotuabation have promoted the vertical and horizontal exchange of sediment particles and the pollutants exchange between the pore water and the overlying water. On the other hand, their metabolic activities, including defecating, respiring, and feeding, absorbing oxygen and nutrient, while producing carbon dioxide and excretion. It will consequentially change the physical properties, structure, chemical composition, pH, redox conditions and pollutants distribution of sediment. All these factors will play their role in the fate, speciation and bioavailability of pollutants.The results showed that Cd, Zn, Pb, Cu concentrations in overlying water were influenced to some extent by the chatter of earthworm bioturbation, but because of their physical and chemical properties of different metals are affected to different extent and manner different, this change is the role of biological disturbance, and this with the redox conditions of heavy metals in interstitial water, AVS result of the role. Overall, the role of biological disturbance that residue of heavy metals were significantly decreased, while the exchangeable and Fe-Mn oxide fraction increased significantly.Biological disturbance, physical disturbance and the role of the irrigation flutter earthworm heavy metals in the sediment convection-diffusion and molecular diffusion occurs, leading to higher levels of heavy metals in interstitial water, and then continued under the concentration gradient to migrate to the overlying water. One, Pb migration into mainly done early in the experiment, biological disturbance on the pore water of the impact of the migration of Pb in the sediments more significant than 5cm; in the migration process of Cu concentration gradient caused by molecular diffusion plays an important role, and biological disturbance on dissolved Cu from the sediment pore water diffusion to play a positive role; AVS content of carbonate Cd, Fe and Mn oxide bound Pb, the carbonate bound Zn, the impact of residual Zn large; in the biological perturbations, Cd in the water/sediment interface migration more particles as a carrier through the passive transport; flutter earthworm bioturbation can affect the existing form of heavy metals, thereby affecting heavy metals in overlying water concentration and forms.