Study on enhancement effect of benthic animals addition and in situ passivation on sediment dredging
In this study,the West Chaohu Lake was the research object,the effect of enhanced dredging was stydied through adding Lanthanum modified bentonite(LMB,Phoslock®),Bellamya aeruginosa,Corbicula fluminea,the combination of Bellamya aeruginosa and Corbicula fluminea to the dredged column samples by indoor simulation experiment.The contents of NH4+-N and soluble reactive phosphorus(SRP)in pore water were measured by pore water balance technique(Peeper)and the exchange fluxes at sediment-water interface were calculated.The phosphorus forms of sediment were analyzed by fractional extraction experiments.The results showed that the contents of TP and SRP in the overlying water and the diffusion flux of NH4+-N and SRP in pore water were decreased significantly,and the contents of TN was 1.3 times of that in the dredging group,on the basis of dredging.Compared with the dredging group,when adding benthic animals the concentrations of nitrogen and phosphorus in the overlying water and the diffusion flux of NH4+-N in pore water increased in varying degrees,the diffusion flux of SRP was reduced by 3.6%～53.6%.The addition of Phoslock and benthic animals could further reduce the contents of TN,TP and OM in the dredged sediment by 4.8%～12.3%,14.2%～39.2%and 4.5%～20.1%,respectively.The results of phosphorus forms showed that Phoslock and Corbicula fluminea could reduce the proportion of mobile phosphorus in total phosphorus in sediment by 25.9%and 22.4%,while the proportion of mobile phosphorus of Bellamya aeruginosa was 1.3 times of that in dredging groups.The above studies showed that Phoslock could further enhanced the control effect of dredging on nitrogen and phosphorus in sediment;the addition of benthic animals reduced the contents of pollutants in sediment and the diffusion flux of SRP in the pore water,while the concentration of nitrogen and phosphorus in the overlying water and the diffusion flux of NH4+-N at the sediment-water interface increased,so the effect of enhanced dredging was unsatisfactory.
West Chaohu Lakeendogenous pollutiondredgingpassivation materialsbenthic animals
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NSTL
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