摘要
水体富营养化是当今世界可临的一个严重环境问题。造成富营养化的限制因子主要是N和P，尤其是P。对于大多数外源磷得到控制的水体来说。底泥磷的释放对长期维持藻类生长，促进湖泊富营养化的发展具有举足轻重的作用。但是，底泥对磷的释放与吸收是有条件的，它受到多种因素的影响，包括底泥本身的理化性质和其它环境条件，如氧化还原状况、pH值、温度等。本研究以重庆龙水湖作为紫色土酸雨区湖泊的代表，采用野外调查、采样分析和室内模拟相结合的方法，以研究其底泥及其磷的性质为重点，同时对其水质进行初步评价，旨在揭示紫色土酸雨区底泥的特点以及释磷吸磷的规律，为防止该地区湖泊富营养化提供参考。
对龙水湖的调查与分析显示，该湖泊水质季节变化明显，春季好于夏季，受温度和pH值影响较大。夏季湖水呈弱碱性，pH值平均为9.11，湖水pH值的上升主要是藻类活动引起的。由国内外相关标准，夏季水中的总磷浓度处于中营养化水平。底泥中铁的含量为28717.87-44650.00mg.kg~(-1)，平均39493.04mg.kg~(-1)；镁的含量也较高，为5004.95-8957.45mg.kg~(-1)，平均6538.83mg.kg~(-1)；钙和锰的含量则较低，但都明显高于周围土壤值。
对磷的形态分析表明，湖泊底泥总磷最高为571.00mg.kg~(-1)，最低为304.71mg.kg~(-1)，平均为442.04mg.kg~(-1)。无机磷的形态以Fe-P和闭蓄态磷为主，Fe-P平均为89.75mg.kg~(-1)，占TP的20％左右；Ca-P和Al-P含量较低，平均含量分别为29.50mg.kg~(-1)、5.21mg.kg~(-1)，TP、Fe-P和有机质、铁、镁的含量呈极显著关系。
热力学实验表明，底泥鲜样的吸附能力明显强于干样。以干样来说，对磷的吸附容量范围为454-1667mg.kg~(-1)。平均为1042mg.kg~(-1)。该湖泊底泥对磷的吸持能力不强，吸持率平均只有72％左右。影响底泥吸附容量的因素主要是有机质、铁、镁和粘粒等。
通过底泥的吸附动力学发现，该湖泊底泥对磷的吸附初始阶段的速率非常大。一般来说，底泥吸附容量越大，其吸附速率也越大，达到平衡的时间也越短。影响底泥吸附速率的因素主要是有机质、Fe、Ca、Mg和Mn等元素，粒径对磷的吸附也有重要影响。所有动力学方程中，Elovich方程拟合最好。
该湖泊底泥生物有效磷(BAP)平均为138.53mg.kg~(-1)，占TP的31.34％；磷吸持指数(PSI)和磷的最大吸附量(S_(max))之间存在极显著关系，相关系数r=0.991…，可以作为一种快速测定底泥磷的最大吸附量的方法。该湖泊底泥磷吸持饱和度(DPS)处在一个相对较低的水平，平均为15.17％。表明该湖泊底泥对磷的吸持强度较大，磷的流失和释放风险较小。底泥有效磷(Olsen-P)平均为9.76mg.kg~(-1)，反映该湖泊底泥供磷水平较低。
室内模拟实验表明，厌氧条件下，上覆水和底泥pH值出现波动，但总的变化趋势是下降；氧化还原电位(Eh)变化不大，说明该湖泊底泥在春末夏初Eh处于最低稳定状态；厌氧有利于底泥磷的释放，但磷的释放量是先上升后下降，最后稳定在高于初始阶段水体TP的水平。
西南农业大学硕士论文摘要
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微生物对底泥磷的释放影响是复杂的，影响也是巨大的，它可以分解矿化底泥的有机磷
为可溶性无机态而返回到上覆水中。微生物是促进上覆水中的TP上升还是下降要视具体情况
而论，由于本湖泊底泥吸附容量大且藻类数量较少，上覆水的TP反而下降。
pH值对底泥释磷产生重要影响。在碱性条件下，龙水湖底泥释磷量明显增加，在pH值
为5~8时，底泥释磷量较少;在pH值为5时底泥释磷量最小，当pH>8时，底泥释磷量开始
增加。另外，在影响底泥性质的诸多因子中，活性铁和活性铝的作用不突出，并不表明它和
底泥的许多性质(如磷的最大吸附量)没有关系，而是因为它们含量太少以至作用显现不出
来。
总的来说，龙水湖底泥对磷的吸附容量和吸附速率都很大，磷吸附容量远未饱和，所以
对进入水库的营养物质有很强的缓冲作用，这在一定程度上可以缓解水体富营养化的发生，
在近期发生富营养化的风险很小.但是，该湖泊底泥源于紫色土中的红紫泥，团粒结构和水
稳性差，分散性强，当湖泊由于风、船等扰动时，富含磷的底泥容易泛起，加上该地区湖泊
底泥铁的含量较高，Fe一P所占TP比例较大，磷的吸持率低，如果湖泊内源磷不加控制持续增
加，一旦条件有利，这种形式的磷将重新进入水中，被藻类利用，所以降低底泥内源磷负荷
对防止富营养化发生非常重要。
Eutrophication of surface waters is a serious problem in many parts of the world. Internal load of nitrogen and phosphorus especially P play a major role in eutrophication. Phosphorus release in sediment is very important to support algae during eutrophication. But, release and sorption of phosphorus was controlled by many factors, including physico-Chemical characteristics of sediment and other environmental conditions, such as redo condition, pH, temperature and so on. As represent of purple soil, Long-shui Lake is selected. The means is about field research, sample analyse and simulation of study in lab. The study on character of sediment and phosphorus release is primary. At the same time, evaluation of water quality will be done. The aim is open out the characteristic of sediment and law of phosphorus release and sorption. The study should benefit the precaution of eutrophication in this area.
Research and analyse indicated, water quality in this lake changed evidence in different seasons, and, water quality in spring was better than in summer that effected by temperature and pH. In summer, lake water was alkalescence with the value of pH 9.11 caused by algae. According to Chinese and foreign criterion about lake, Long-shui lake was in mesotrophication.
Iron (Fe) ranged from 28717.87mg.kg-1 to 44650.00 mg.kg-1 sediment, averaged 39493.04 mg.kg-1.Mg had a high level (5004.95-8957.45 mg.kg-1 sediment), averaged 6538.83 mg.kg-1.Ca and Mn had few but more than the values of soil background. From the analyse of phosphorus fraction, we found sediment total P ranged from 304.71 mg.kg-1 to 571.00 mg.kg-1 (mean=442.04 mg.kg-1). Fe-P and O-P (Occluded P) represented major fraction in inorganic phosphorus. Fe-P averaged 89.75 mg.kg-1 (20% of TP). The contents of Ca-P (mean=29.50 mg.kg-1) and Al-P (mean=5.21 mg.kg-1) were rather low. The correlation between TP, Fe-P and organic matter contents, the amount of Fe and Mg, was very significant.
The experiment of thermodynamics showed, P sorption capacity of fresh sediment was higher than dry sediment. P sorption maxima (Smax) ranged from 454.00 mg.kg-1 to 1667.00 mg.kg-1 sediment (mean=1042.00 mg.kg-1). While phosphorus retention was only 72% of P adsorbed. Organic matter content, Fe, Mg and clay could play a significant role in determining Smax.
The P sorption speed in first phase showed very fast. In general, the more sediment absorbed, the faster sorption speed is, and then the fewer balanceable time will be. The factors affecting sediment sorption speed included OM, Fe, Ca, Mg and Mn. Clay content also play significant role. Elovich equation was the best among the fitted model equations.
Biologically available phosphorus (BAP) averaged 138.53 mg.kg-1 sediment (31.34% of TP).Phosphorus sorption index (PSI) and phosphorus sorption capacity in sediment were well
correlated (r=0.991...) suggesting that PSI could be an effective means to rapidly screen sediments for their phosphorus sorption capacity. While the degree of P saturation (DPS) in sediment showed low level (mean=15.17%) and suggested to have a lower susceptibility to P losses than those with higher DPS values. Sediment available phosphorus (Olsen extracted P) averaged 9.76 mg.kg-1 and explained the level of supplying P from sediment was very low.
Under anaerobic conditions, the values of pH both in overlying water and sediment indicated fluctuate but with downside. Redox potential (Eh) in sediment changed a little and showed it was stabilization from the end of spring to the beginning of summer. Phosphorus should release from sediment under anaerobic conditions with a progress from raise to descend. The equilibrium P concentrations in overlying water were higher than total P in first phase.
Microbe can make organic P into inorganic P by its catabolism, and returned to overlying water again. The effect to sediment P release of microbe was complex and tremendous. Total P in water sometimes raised and sometimes descended in different conditions because of the effect of microbe. In this experiment, t
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