【作者】 陈昌仁；

【导师】 万福绪； 陶长生；

【作者基本信息】 南京林业大学 ， 水土保持与荒漠化防治， 2011， 博士

【摘要】 我国长江中下游地区浅水湖泊众多,拥有面积1km2以上的湖泊651个,占全国淡水湖泊总面积的60%。大量研究表明,浅水湖泊沉积物易受波浪和湖流的共同作用而频繁发生再悬浮-沉降的交替过程,造成上覆水中污染物浓度突然上升。同时,水生植物是湖泊生物圈层中重要的结构组成部分,在营养盐的循环、迁移和归宿中扮演了重要的角色。因此,水动力作用下水生植物对沉积物磷素环境效应的研究具有重要的理论和实践意义。本文以太湖为研究对象,通过野外采样和室内模拟实验相结合的方法,采用沉积物再悬浮装置模拟研究大型水生植物对太湖沉积物再悬浮的抑制以及对磷素的环境效应。室内模拟采用一种自行研制的串联圆筒式的再悬浮模拟装置,设计在0.2～0.5 N.m"2的切应力和60～1800s的振荡持续时间条件下,对太湖沉积物类原状样本的再悬浮特征开展室内模拟实验研究,从引起沉积物再悬浮的水动力学机制出发,构建水体底部切应力水平和作用时间与沉积物再悬浮通量的定量关系,并揭示沉积物—水界面底泥再悬浮过程中磷素的释放特征。本文实验重点根据太湖水生植物种群分布特征,选择伊乐藻和芦苇两种太湖水生植物优势种,分别作为沉水植物和挺水植物的代表,并通过水培试验,每种水生植物设置不同种群密度的三种对照(伊乐藻覆盖度90%、60%、30%,芦苇种植密度150棵/m2、80棵/m2、50棵/m2),包括无植物在内,共设置七组对照,研究不同水生植被种群密度对沉积物再悬浮及上覆水中磷素含量的影响。实验研究发现,悬浮物浓度随扰动时间呈缓慢上升的趋势,随着切应力的逐渐增大,上升趋势更加明显；有植物对照的SPM浓度随时间的增加幅度明显小于无植物对照。太湖悬浮物静沉降特征显示,沉积物被扰动后SPM的静沉降过程总体上呈现前期快速下降、中期缓慢下降和后期基本稳定三个阶段。相对于无植物对照,有植物对照的缓慢下降过程的持续时间有所缩短,基本在5h浓度即达到稳定。在沉积物再悬浮和沉降随时间变化特征研究的基础上,分析了水生植物种群密度对悬浮物分布特征的影响机制。结果表明：随伊乐藻覆盖度的不断增加,各切应力对应的上覆水中SPM浓度呈逐渐下降的趋势；随着切应力增加,上覆水中SPM浓度随水生植物种群密度的增加而下降的幅度逐渐增大；并且挺水植物芦苇对沉积物再悬浮较强的抑制作用强于沉水植物伊乐藻。水生植物对SPM浓度垂向分布特征的研究表明,水生植物对SPM浓度的垂向分布具有一定的抑制作用,水生植物的存在干扰了外力扰动产生的能量向下传递,使得上覆水SPM浓度降低并趋于均化。随着外力扰动的进一步增强,各种对照情况的垂向梯度均不明显。总磷、磷酸盐、BAP三种形态磷素在有无植物对照的条件下,其浓度与切应力和外力扰动时间的关联不大。对比各形态磷素浓度可知,上覆水总磷浓度显著高于磷酸盐,BAP浓度亦普遍高于磷酸盐。BAP与磷酸盐的比值随植株密度的增加而减小,随切应力增加而增大。更多还原

【Abstract】 There are many shallow lakes in the middle or lower reaches of the Yangtze river, own more than 1km2 lakes 651, accounting for 60% of the total freshwater lakes. A mass of researches indicated that sediment in shallow lakes were vulnerable to waves and lake flows joint with action and frequent suspension, the alternate process caused water pollutant concentration rised abruptly. Meanwhile, aquatic plants plays an important role in the biological epitomizes, cycle of nutrient, migration and inmigration of lakes. Therefore, the research on phosphorus of sediments by aquatic plants to environmental effects under dynamic actions of important theoretical and practical significance.This paper take Tai Lake as the research object, through field sampling and indoor simulation experiments, using the method that combining sediments suspended device simulate large aquatic plants in Tai Lake against sediment suspension and phosphorus environmental effects. A series of cylindrical suspended analogue devices developed for indoor simulation, designed 0.2～0.5 N·m-2 shear and 60～1800s oscillations duration condition, to study the sediment suspension characteristics of original core samples from Tai Lake, from a water resuspension caused by sediments, based on dynamic mechanism of constructing water bottom shear stress level and duration and sediment resuspension the quantitative relation flux, and reveals sediments-water process of sediment suspension again interface phosphorus release features.The experiment of aquatic plants on population distribution according to the characteristics of Tai Lake, choosing waterweeed and reed from Tai Lake, submerged plant and quite as representatives of water plants, and through the hydroponic experiments, each aquatic plant set up different population density contrast (waterweeed coverage 90%,60%,30%, reed planting density 150 trees/m2,80 trees/m2,50 trees/m2), including no plants as constrast, totally seven groups, The effects on phosphorus content of different aquatic vegetations density to sediment resuspension and overlying water.This study found that suspended sediment concentration rised slowly with disturbing time, remarkbally rise with shear stress increased; The concentration of a plant controls over time SPM rises obviously less than no plant controls. Tai Lake suspended sediment characteristics shows, static settlement after static SPM is disturbed presents on the settlement of the overall process of falling fast, medium-term slow drop and later basically stable three stages. No plants comparison, relative to a plant controls the duration of slow drop process shorten, somewhat 5h concentration achieve namely in basically stable.Again in sediment suspension and settlement changes with time characteristics on the basis of study of aquatic plants, analyzes the population density distribution characteristics of the mechanism of the effect of material. Results show that:waterweeed growing algae coverage, the shear stress overlying water corresponding SPM a trend of gradual decrease concentration; Along with the shear stress overlying water increased, with aquatic plants SPM concentration of population density decreases gradually increased the range; And quite water plants of sediment suspension again reed strong inhibition submerged plant waterweeed better than them. Aquatic plants SPM concentration of the vertical distribution characteristics of aquatic plants study shows that the concentration of SPM vertical distribution has certain inhibition and aquatic plants exists interfere with external disturbance energy produced downward transmission, makes the overlying water and tends to reduce SPM concentration homogenization. Along with the further strengthen external disturbance, various control situation are not obvious vertical gradient.The total phosphorus, phosphate, BAP without plants, have no relevant with shear stress and external disturbances time. Compared with different forms of phosphorus concentration, overlying water total phosphorus significantly higher than phosphates, BAP phosphate of general prep above also. BAP and phosphate decreased with plant density ratio increasing and increased with of shear stress enhance.更多还原