【作者】 王岩；

【导师】 程国玲； 姜霞；

【作者基本信息】 东北林业大学 ， 环境科学， 2014， 硕士

【摘要】 湖泊作为地球表面一个重要的自然生态系统,承载着人类历史的发展,具有多种重要的服务功能。近几十年来,人口的激增以及人类活动的加剧,导致湖泊污染严重、生态环境日益恶化、灾害频发,所引起的经济损失剧增,湖泊已成为区域环境变化和人与自然相互作用响应最为敏感、影响最为深刻、治理难度最大、投入资金最多的地理单元之一。其中,湖泊富营养化是目前湖泊污染治理过程中最主要的问题之一,而氮、磷是水体浮游藻类的限制性营养元素,是湖泊富营养化的关键因子。因此了解湖泊的氮磷含量分布、季节变化特征以及水体营养状态特征,对于湖泊富营养化的预防和治理具有重要意义。本文以洞庭湖及湘江、资江、沅水、澧水4条入湖支流为主要研究对象,通过历史数据的收集及分析测定水体和沉积物中的氮、磷含量,对水体及沉积物中的氮、磷时空分布特征进行了系统的研究,并对洞庭湖水体营养状态特征及沉积物粒径大小进行了分析；同时将洞庭湖与太湖、巢湖等水华频繁暴发的长江中下游湖泊进行对比分析,讨论了洞庭湖水华暴发的主要条件；此外,对洞庭湖沉积物进行了初步的生态风险评价。得出如下主要结论：(1)洞庭湖水体ρ(TN)为1.35～2.98mg/L,平均值为2.34mg/L;c(TP)为0.02～0.22mg/L,平均值为0.06mg/L;c(NH4+-N)为0.03～0.68mg/L,平均值为0.27mg/L;c(NO3--N)为0.07～0.9.1mg/L,平均值为0.54mg/L。沉积物w(TN)为558.08～2846.51mg/kg,平均值为1220.47mg/kg；w(TP)为357.74-998.25mg/kg,平均值为678.97mg/kg；w(NH4+-N)为11.92～78.12mg/kg,平均值为28.94mg/kg；w(NO3--N)为0.92～19.37mg/kg,平均值为4.41mg/kg。全湖TLI(∑)均值为45.93,已达中营养水平,局部地区已达富营养水平。(2)洞庭湖水体、沉积物中氨氮、硝氮、TN、TP含量的水期特征均表现为6月>1月；且在洞庭湖入湖河口断面污染较大：东洞庭湖区污染较西洞庭湖区和南洞庭湖区严重。富营养化程度6月较1月严重。(3)洞庭湖水体中ρ (TN)、ρ(TP)较高,已具备了发生藻华的营养条件,但目前仍未发生大面积蓝藻水华暴发现象,可能还有其它因素导致,如过水型湖泊特殊的水文水动力条件导致叶绿素含量偏低。(4)洞庭湖沉积物粒径分布由东向西呈现增大趋势,东洞庭湖区沉积物粒径最细。(5)生态风险评价结果显示,洞庭湖各断面沉积物TN的标准指数基本均大于1,即洞庭湖沉积物中TN含量多数超标,环境质量受氮的污染严重；TP的标准指数变化大于或等于1,TP含量水平也较高,尤其入湖支流及东洞庭湖区的TP标准指数相对更高,构成了一定的污染。按照美国EPA制定的沉积物分类标准,洞庭湖沉积物TN含量处在最低级别生态风险效应和严重级别之间；TP的浓度部分已具有生态效应,对环境产生了一定的危害。更多还原

【Abstract】 As an important natural ecosystem of the earth, lakes are the force of the society development and have many important functions of services. In recent decades, the intensification of human activities is causing lakes pollution, ecological environment deterioration, disasters and economic losses. Lakes have become one of the most sensitive areas in the interaction between man and nature, which needs more money and time to deal with. Eutrophication is one of the most important lakes pollution problems. The concentration of nitrogen and phosphorus are the key factors of the planktonic algae growth and eutrophication. Therefore, there is an important significance to explore the distribution of nitrogen and phosphorus contents, seasonal variation and nutritional characteristics of water for the prevention and treatment of lakes eutrophication.This paper made the Dongting Lake and four rivers as the research object, through collecting the history data, analyzing nitrogen and phosphorus contents of the overlying water and sediments, discussing the nutrient spatial and temporal distribution and nutritional characteristics, exploring the particle size and assessing the ecological risk, we draw the following main conclusions:(1) The concentration of total nitrogen (TN), total phosphorus (TP), ammonia (NH4+-N) and nitrate (NO3--N) in the overlying water were1.35～2.98mg/L,0.02～0.22mg/L,0.03～0.68mg/L and0.07～0.91mg/L, respectively. The average concentration of TN, TP, NH4+-N and NO3--N were2.34mg/L,0.06mg/L,0.27mg/L and0.54mg/L, respectively. The content of TN, TP, NH4+-N and NO3-N in sediments were558.082846.51mg/L,357.74～998.25mg/L,11.92～78.12mg/L and0.92～19.37mg/L, respectively. The average content of TN, TP, NH4+-N and NO3-N were1220.47mg/L,678.97mg/L,28.94mg/L and4.41mg/L, respectively.(2) The concentration of nitrogen and phosphorus in June generally are higher than that in January. Higher concentration of phosphorus and nitrogen occurred in the estuary of inflowing river. The average concentration of phosphorus and nitrogen in East Dongting Lake were highest compared with other regions of Dongting Lake. The comprehensive nutrition state index in June is higher than that in January.(3) Compared with other eutrophic lakes, alga blooms in large scale did not happen with relatively higher concentration of TN and TP in overlying water and sediments in Dongting Lake, which could be explained by the special conditions of hydrology and hydrodynamic force causing lower content of chlorophyl.(4) The particle size is increasing from east to west. The particle size of the Esat Dongting Lake is the smallest.(5) Ecological risk assessment showed that the standard index of TN in sediments in Dongting Lake is greater than1. It means the content of TN in sediments is excessive and the pollution of nitrogen is severely. The standard index of TP is equal or greater than1. It means the content of TP in sediments also is higher, especially in the estuary of tributaries and the East Dongting Lake. According to the criteria of sediment classification which was made by the U.S. EPA, the content of TN in sediments in Dongting Lake is between the lowest level of ecological risk and severity of effects. The content of TP has been ecological effects on the environment of certain hazards.更多还原