| The issue of sediment deposit in the Yangtze River has become a key element to restrain the development of navigation.Study on the effect of fine sediment's physical and chemical performance on flocculating settling thus has many significant meanings,such as promoting the recognition of sediment deposit in the Three Gorges Reservoir Area and advancing the treatment of channel dredging.This work presented in this paper took five different sediment samples as research target,which were taken from Zhongxien Kounty(Chongqing,China).Specifically,the five sediment samples have been named as S1,S2,S3,S4 and S5 respectively.And some performances such as distribution of grading,organic content,elemental composition,cation exchange capacity and PH have been analyzed according specific methods such as X-ray diffraction(XRD),Inductively Coupled Plasma(ICP)and Laser Granulometric Analysis.We further analyzed the effects of grading,organic content,Zeta electric potential,Cation Exchange Capacity(CEC)and elemental composition on sediments flocculating settling respectively.The results obtained from this research could be summarized as following:there were two kinds of sediment grains,namely cosmid and silt,whose grain size ranges from 2 to 120?m.These sediment grains scattered sparsely,accelerating the dispersion of sediments.Besides,their grain size and distribution were centralized,mainly at the range of 7.0~8.0 and 10~30?m respectively.The sediments were neutral partial alkali,whose PH value is mainly range from 7.5~8.5.The surface of sediments was negative charge with the maximum Zeta potential at 13.68 mv and the minimum at 7.21 mv.The change of CEC was greatly.The CEC of the S2-05 reached 34.4 cmol/kg,while the S1-1 was 25.7 cmol/kg.The organic content of every section was huge with little change,and the organic content mainly scattered in the range of 3.0%~4.0%.there were many elements contained in sediments,including Ca,Fe,K,Ti,Cl,Mn,Ba,Cr,Zr,Sr,Zn,Rb,Cu,Pb,As and Mo.For each element,the content was different hugely.Specifically,the content of Ca and Fe could reached 140g/Kg and 108g?Kg-1 respectively,while the content of Mn was only 3g / Kg.We came to the conclusion after analyzing that Fe could affect the amount of sediments.According to SPSS method,things could be figured out such as there was a positive correlation between grain size and organic content,with the coefficient of 0.807,while there was anegative correlation between cation exchange capacity and Zeta potential,with the coefficient of-0.756.Additionally,there was a positive correlation between pH and the content of Ca,with the coefficient of 0.791.Things such as grain size,organic content,Zeta potential and CEC had a significant effect on flocculation settling.With grain size increasing from 10.83 to 15.21 um,the velocity of flocculation settling will decrease from 0.56 to 0.34 mm/s.There was a positive correlation between organic content and flocculation settling.With the increase of organic content,from 3.04% to 3.41%,the velocity of flocculation settling will increasingly become small,namely from 0.67 from 0.38 mm/s.However,the greater the Zeta potential is,the smaller the flocculation settling of the sediment is,specifically,with the value of the Zeta potential increasing from 11.64 to 16.93 mv,the velocity of flocculation settling will decrease from 0.59 to 0.39 mm/s.Similarly,the velocity of flocculation settling will increasingly become small,from 0.45 to 0.29 mm/s,with the increase of CEC from 32.2 to 36.7cmol/Kg.It has a great practical meaning to investigate the effect of fine sediment's physical and chemical performance on the flocculating settling of sediments.What's more,from the physical and chemical performance of sediment to analyze those factors' effect on flocculating settling is the precondition to demonstrate the aggradation pattern of the Three Gorges Reservoir Area and to supply the traditional Sediment flocculation theory. |
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