Study On The Distribution Mechanism Of Heavy Mental In Tidal Flat Of Dagu Estuary In Jiaozhou Bay By Simulated Test On Laboratory

Jiaozhou Bay is a semi-enclosed bay which has relatively independent natural conditions.Dagu River is the largest river in Jiaozhou Bay,whoes estuary is intertidal regions of high extent of isolation and the ideal site for intertidal investigation.In this study,Fe was the key factor of heavy metal distribution by correlation analysis.The most significant correlation was found between Fe and Cr,so they were taken as the research objects.The object of the subject was to investigate the influence of Fe to the distribution of Cr in the estuary where pH and salinity changed significantly.It was conducted by laboratory simulation experiment,supplemented by a variety of characterization techniques(XRD,SEM–EDX,XPS).The results from our study indicated that:(1)Fe into the estuary could hydrolyzed completely to ferric hydroxide with the increase of pH and salinity.The hydrolysis rate increased with pH,but was little influenced by salinity.(2)The removal rate of Cr by ferric hydroxide decreased with increasing pH from weak acid to weak alkaline from river water to seawater in estuary;this is because pH changed the Zeta potential of ferric hydroxide.(3))The removal rate of Cr by ferric hydroxide firstly decreased and then increased with increasing salinity,as well from 0 to 30 from river water to seawater in estuary.On the hand,Na+ entering the sliding surface,which could improve Zeta potential and stability of ferric hydroxide colloid.That leads to the amount of Cr removal by colloid aggregation decreased.On the other hand,there was competitive adsorption between Cl-and CrO42-/HCrO4-.So When the salinity was 10,the removal rate of Cr is less than 10 percent.(4)Ferric hydroxide generated in estuary would experience three stages:flcos formation,growth and reduction.The larger salinity was,the faster colloid aggregated,the larger size grain had,and the more closely grain combined,the harder floc reduction started and the larger size grain had after flcos reduction,the more uniformit was dispersed.(5)Cr(VI)was removed by electrostatic force,and Cr(III)was removed by entrainment in ferric hydroxide flocs and co-precipitation in flocs surface.It was released again easily which was entrained in ferric hydroxide flocs caused by flocs reduction.Fe-Cr oxide and hydroxide would not be generated.