长江中游水体颗粒磷与悬沙定量关系及其通量变化研究

发布时间：2018-05-07 10:09

本文选题：悬沙 + 颗粒磷　；参考：《长江科学院》2014年硕士论文

【摘要】：三峡水库是举世瞩目的大型水利枢纽，研究三峡水库蓄水以来长江中游河段悬浮泥沙环境效应，具有重要的学术价值。本文在前人研究的基础上，通过设计完整的室内动态吸附实验，分析了长江中游悬浮泥沙粒径、含沙量以及磷浓度对泥沙吸附颗粒磷的影响，并系统分析了未来20年长江中游颗粒磷通量的变化情况，指出三峡水库淤积泥沙影响营养盐的输移，对长江中下游生态环境也产生一定影响。主要研究内容及结论包括以下几个方面：（1）总结了长江中游水体悬沙与颗粒磷的时空分布现状。水库蓄水以来，长江中游悬沙和颗粒磷通量大幅降低，宜昌至汉口河段，蓄水后均值低于蓄水前，坝下均值低于库区均值；蓄水前后，悬沙和颗粒磷通量都具有季节性变化，丰水期输送通量占了全年的80%以上，但是建库后季节性变化幅度较小，，峰值较低。（2）通过长江中游泥沙与颗粒磷的室内吸附实验，揭示了总吸附量和单位质量泥沙吸附量随悬沙含量、粒径、磷酸盐浓度和温度改变的规律。可得总吸附量随着含沙量和初始磷浓度的增加而增加；单位质量泥沙吸附量随含沙量和粒径的增加而递减，随温度和初始磷浓度的增加而增大，有最大吸附容量。（3）泥沙吸附磷达到平衡状态时，磷在水沙两相之间的分配关系可以分别用Freundfich吸附等温式和Langmuir吸附等温式来表达，两种吸附等温模型拟合结果均满足精度要求，Langmuir模型只考虑两个变量，含沙量和平衡时水相磷浓度，拟合方便简单。（4）基于实测资料，率定并验证了长江中游颗粒磷与悬沙的定量关系式，Cs=k*S~(1-n)*C_w(1+k'*S~(-n)*C_w)，并依据该方程，对未来20年长江中游颗粒磷通量变化情况进行了预测。结果表明，短时间内长江中游颗粒磷通量仍然低于蓄水以前的水平，因而造成坝下水体磷缺失，这在一定程度上会抑制四大家鱼等水生生物的生长。（5）对进一步研究温度和粒径对泥沙吸附磷的影响，以及两岸排污、农村面源污染等的影响进行了展望。
[Abstract]:The three Gorges Reservoir is a large water conservancy project that attracts worldwide attention. It is of great academic value to study the environmental effect of suspended sediment in the middle reaches of the Yangtze River since the three Gorges Reservoir was impounded. On the basis of previous studies, the effects of suspended sediment particle size, sediment content and phosphorus concentration on the adsorption of particulate phosphorus by sediment in the middle reaches of the Yangtze River are analyzed by designing a complete indoor dynamic adsorption experiment. The change of particulate phosphorus flux in the middle reaches of the Yangtze River in the next 20 years is analyzed systematically. It is pointed out that sediment deposition in the three Gorges Reservoir affects the transport of nutrients and the ecological environment in the middle and lower reaches of the Yangtze River. The main contents and conclusions include the following: The temporal and spatial distribution of suspended sediment and particulate phosphorus in the middle reaches of the Yangtze River are summarized. Since the reservoir was impounded, suspended sediment and particulate phosphorus fluxes in the middle reaches of the Yangtze River have been greatly reduced. The mean values of suspended sediment and particulate phosphorus fluxes in the reach of Yichang to Hankou are lower than those before and after impounding, and the mean value under the dam is lower than that in the reservoir area before and after impounding. In the high water period, the transport flux accounted for more than 80% of the whole year, but the seasonal variation range was small and the peak value was lower after the establishment of the reservoir. 2) through the indoor adsorption experiments of sediment and particulate phosphorus in the middle reaches of the Yangtze River, the regularity of the change of total adsorption capacity and sediment adsorption capacity per unit mass with suspended sediment content, particle size, phosphate concentration and temperature was revealed. The total adsorption capacity increases with the increase of sediment content and initial phosphorus concentration, and decreases with the increase of sediment content and particle size, and increases with the increase of temperature and initial phosphorus concentration, with the maximum adsorption capacity. 3) when phosphorus adsorption reaches equilibrium, the distribution of phosphorus between water and sediment phases can be expressed by Freundfich adsorption isotherm and Langmuir adsorption isotherm, respectively. The fitting results of the two isothermal adsorption models meet the precision requirements. The Langmuir model only considers two variables, sediment content and phosphorus concentration in water phase at equilibrium. The fitting is convenient and simple. Based on the measured data, the quantitative relationship between particulate phosphorus and suspended sediment in the middle reaches of the Yangtze River is determined and verified. Based on this equation, the variation of particulate phosphorus flux in the middle reaches of the Yangtze River in the next 20 years is predicted. The results show that the particulate phosphorus flux in the middle reaches of the Yangtze River is still lower than that before the water storage in a short period of time, resulting in phosphorus deficiency under the dam, which to some extent inhibits the growth of aquatic organisms such as the four big domestic fish. The effects of temperature and particle size on phosphorus adsorption by sediment, sewage discharge from both banks and non-point source pollution in rural areas are prospected.
【学位授予单位】：长江科学院
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TV14

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