| Taihu Lake is strongly disturbed by wind and waves with sediment resuspension and particle size sorting,affecting the migration and transformation of various pollutants.We sieved sediments of Taihu Lake into different size-grouped particles,extracted their fractions of metals with Tessier method,conducted adsorption experiments,and evaluated ecological risk of heavy metals under sediment resuspension.Our research has important implication in the prevetion on metal pollution in the shallow lakesThreee sampling sites,in the Meiliang Bay,center of Taihu Lake,east of Taihu Lake respectievley,were set for study.Five groups of particles,including 30-50 μm,10-30μm,5-10 μm,2.5-5 μm and<2.5 μm 5,were obtained to analyze their metals and related physical and chemical indicators,including organic matter(OM),oxides of iron(Fe)and aluminum(Al).Then adsorption kinetics and isothermal adsorption of Cu and Pb on particles were conducted.Finally,assessment of metal pollution were evaluated by the methods of secondary phase versus primary value method,land accumulation index method,potential ecological hazard index method and thin film gradient diffusion technique(DGT).The relevant research results are shown as follows:(1)The chemical parameters of particles with different sizes showed an increasing trend with the decrease of particle sizes,with ranges of 0.15～5.27%for organic matter,4953.52-31877.56 mg/kg for free iron oxides,672.10～4772.20 mg/kg for amorphous iron oxides,2975.85～28303.39 mg/kg for free aluminum oxides,and amorphous 313.60～3846.70 mg/kg for aluminum oxide.(2)There is an increasing concentration on particles with decareased size,with Zn in ranges of 31.66～210.65 mg/kg,Cu in ranges of 8.67～67.37 mg/kg,and Cd in ranges of 0.09～0.73 mg/kg.The proportion of effective concentrations of Cu,Ni,Pb and Zn to their total concentratins ranged from 30%to 60%,mainly bound to iron and manganese oxides and organic compounds.The effective concentration of Cd accounted for more than 90%of its total concentration.The residual is the larger proportion for As and Cr,with 90%of the proportion.(3)Cu and Pb were selected to conduct adsorption experiments on the five goups of particles.The quasi-first-order and quasi-second-order models were used to fit the adsorption kinetics,showing a better fit with quasi-second-order model.The Langmuir and Freundlich model were used to fit adosorption isotherms,showing a bettern fit with the Langmuir model.The adsorption capacity of Cu and Pb increases with the decrease of particle size,with binding campacity of Pb 3-4 times Cu under the same conditions.The adsorption of heavy metal particles was correlated with their occurrence forms(4)The pollution risk of metals increased with decareased particle sizes,with a risk of particles<2.5 μm having 3～8 times higher than that of particles in ranges of 30～50μm.The results evaluated by DGT method indicated that the release risk of Cu was smaller,while the risk of Cd and Fe was larger.Figure 47 table 22 reference 114... |
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