| The distribution process and driving mechanism of phosphorus on different size particles under suspension disturbance were researched through the traditional extraction and phosphorus species adsorption methods.The particles phosphorus supply capacity for cyanobacteria with different sizes was studied by algae culture experiment to making further investigations of encological risk of sediment suspension.It provides important research ideas and scientific basis for further assessment of internal risk of phosphorus in sediment and management of lake eutrophication.The water quality and sediment of the Zhenjiang-Wuxi Great Canal were investigated,and five size particles(50-150 ?m,30-50 ?m,10-30 ?m,5-10 ?m and < 5 ?m)were separated.The physicochemical properties,the adsorption-desorption ability of phosphorus and the growth response of algae on different size particles were researched at the same time.Three Columns(Column 1: disturbance suspension,Column 2: disturbance suspension plus phosphorus,Column 3: disturbance suspension plus phosphorus and carbon source)were designed for 90 days experimental.Phosphorus and iron in overlying and pore water was monitored and phosphorus fractions on particles due to 90 d suspension was extracted to analysis the distribution process of phosphorus on different size particles.The results as shown follows:(1)The canal overlying water quality of the canal is IV according the standard with weakly alkaline,high DO and serious pollution of nitrogen and phosphorus.The median diameter of suspended particles is about 10 ?m,and the sediment TP pollution increases from 343.4 mg/kg in the upstream to 2703.1 mg/kg in the downstream,indicated the extraneous pollutants most enriched in the sediment.(2)The coarse particle groups(10-150 ?m)mainly mineral composition is silica,and the fine particles(< 10 ?m)contain more mineral components and organic matter than coarse particles.And the concentration of iron,aluminum and organic matter tends to increase with the decrease of particle size.The results of phosphorus fraction also showed that fine particles enriched more active phosphorus and higher risk of releasing under anaerobic condition.(3)Under 90 days disturbance distribution experiment,bioavailable phosphorus(BAP) ratio of five groups of particle size(50-150 ?m,30-50 ?m,10-30 ?m,5-10 ?m and <5 ?m)are 14.7%,17.0%,16.6%,22.9% and 28.8% respectively under aerobic condition;with 9.6%,19.5%,19.5%,25.4% and 26.0% respectively under anaerobic condition.BD-P and Na OH25-P are the main enriched forms on the particles,and BDP have a tendency to transformed to Na OH25-P due to continuous suspension and sedimentation.Redox conditions controlled by organic matter reactivate the sediment under the action of microorganisms.The iron or aluminum minerals are activated increase the deposit ability of phosphorus,and increase the risk of phosphorus explosive release under suspended condition.The distribution of phosphorus on the particles is mainly controlled by iron,aluminum minerals and organic matter and rarely affected by calcium compounds.(4)Fine particles(<10 ?m)have high adsorption rate,adsorption capacity and lower release risk of phosphorus;The P release amount of < 5 ?m particle is 404.3 mg/kg with 10 times compared with 30-50 ?m particles at p H=10,indicating that the release of fine particle phosphorus is extremely sensitive to the environmental p H increased;the algae culture experiment found that the fine particles have stronger P supply capacity to algae.< 5 ?m particles as a phosphorus source promoted algae growth with 5.6 times than 30-50 ?m particles.Algae growth increased environment p H,due to large amount Na OH25-P accumulated on the fine particles and released,resulting in algae burst growth and eutrophication of the water body.Figure 37 Table 11 Reference 92... |
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