【作者】 董林林；

【导师】 迟杰；

【作者基本信息】 天津大学 ， 环境科学， 2007， 硕士

【摘要】 “水—沉积物”界面是水与沉积物之间的转换区,是水环境的一个特殊而重要的区域。沉水植物作为这一区域生态系统的重要组成部分,对“水—沉积物”界面磷的迁移、转化起到了调控作用。本课题以“水—沉水植物—沉积物”体系为研究对象,选取敬业湖为采样现场,现场与实验室模拟相结合,进行了沉水植物与沉积物作用对富营养化湖泊磷循环的影响的研究。采样期间敬业湖上覆水总氮浓度为6.21 mg/L～2.70 mg/L,总磷浓度为0.18 mg/L～0.12 mg/L,总氮和总磷浓度都远远超过了富营养化的发生浓度。菹草生长期间,除溶解性有机磷以外,敬业湖上覆水中总氮、总磷、颗粒态总磷、可溶性总磷和溶解性活性磷浓度都随菹草生物量的增加而降低,而菹草衰败后又开始升高。表层水和间隙水的碱性磷酸酶活性也呈现相同的变化趋势,而且表层水的碱性磷酸酶活性始终大于间隙水,说明沉水植物对碱性磷酸酶活性的抑制作用是沉水植物净化水质的重要特征之一。采样期间敬业湖藻型沉积物中的交换态磷、铁结合磷和碎屑磷含量始终高于草型沉积物,而闭蓄态磷、自生磷和有机磷含量则刚好相反,两沉积物中铝结合磷均未检出。由此可以得出,菹草自身生长吸收上覆水及表层沉积物中的生物可利用磷,其促淤作用又使得动植物残体及其中的磷在表层沉积物中蓄积(TOC含量为6.26 %～8.89 %,有机磷含量为25.4 mg/kg～62.8 mg/kg),同时通过改变表层沉积物的理化环境抑制表层沉积物中生物难利用磷的释放,从而间接地降低了上覆水中磷的浓度。因此,我们可以通过定期打捞衰老菹草降低水中磷的浓度,而且菹草的存在使得对富营养化有重要贡献的内源磷稳定地存在于沉积物中。可见,沉水植物菹草通过对敬业湖“水—沉积物”界面磷循环的调控,对敬业湖的富营养化状况起到了一定的控制作用。实验室研究表明,有机质对沉积物中磷的释放有明显的促进作用,随着TOC含量的增加,释放量也增加。而相对于腐殖酸,蓝藻更容易促进磷的释放,这是因为腐殖酸在释放与Fe3+、Al3+等阳离子结合的PO43-、SO42-等阴离子的同时,与活性磷发生了反应。更多还原

【Abstract】 The water-sediment interface is the transformation-zone between water and sediments, a special and important area of aquatic environment. As the concernful composition in the ecosystem, submerged macrophytes have a dominative effect on the removal and transformation of phosphorus between the water-sediment interface. In this work, Jingye lake, a water-submerged macrophyte-sediment ecosystem, was selected as the sampling field to investigate the effect of submerged macrophytes together with sediments on the circulation of phosphorus of eutrophic lakes, and further lab-simulating experiments was also carried out.During the sampling period, the concentrations of TN and TP of overlying water of Jingye lake ranged from 6.21 mg/L to 2.70 mg/L, and 0.18 mg/L to 0.12 mg/L respectively, and both of which were beyond the limiting concentration of eutrophication. When the Potamogeton crispus was growing, the concentrations of TN, TP, PP, TDP and SRP of overlying water except DOP decreased with the increase of biomass of Potamogeton crispus, while increased when the biomass of Potamogeton crispus began to decline. The same change trend was also found with the alkaline phosphatase activity in surface and pore water, and the alkaline phosphatase activity in surface was higher than that in the pore water, sugesting that restraint in the alkaline phosphatase activity by submerged macrophytes is an important characteristic of decontamination of water.During the sampling period, the concentrations of Ex-P, Fe-P and Ca-P of algae type sediments were higher than that of grass type sediments of Jingye lake, whereas the concentrations of Oc-P, De-P and Or-P were reverse. Al-P was not detected in both type of sediments. So it can be concluded that Potamogeton crispus absorbs the bioavailable phosphorus from overlying water and surface sediments and accelerates the accumulation of propagation residues and its phosphorus in the surface sediments (TOC: 6.26～8.89 %; organic phosphorus: 25.4～62.8 mg/kg). Meanwhile, by changing the physical and chemical characteristics of surface sediments, Potamogeton crispus restrains the desorption process of bio-unavailable phosphorus, decreases the phosphorus concentration of overlying water indirectly. Consequently, we can decrease the phosphorus concentration in water by removing the dead Potamogeton crispus termly. The live plant makes the sediment-bound phosphorus, which made great contribution to the eutrophication, exist in the sediments steadily. Therefore, Potamogeton crispus plays the role to some extent in controlling the degree of eutrophication of Jingye lake by influencing the circulation of the phosphorus of water-sediment interface.Lab-simulating investigation indicated that organic matter can accelerate the P desorption process greatly, and the desorption capacity had the same trend as TOC concentration. Meanwhile, cyanobacteria worked better by compared with humous acids. It is because that humous acids accelerated PO4- and SO42- desorption, as well as reacted with bioavailable phosphorus.更多还原