【摘要】 洞庭湖水体主要污染物为氮和磷,而有关洞庭湖营养盐赋存形态与叶绿素a的关系鲜有报道。为研究洞庭湖氮与磷的时空分布特征及其对叶绿素a（Chl-a）的影响,2017年在洞庭湖湖体、出湖口及8条入湖河流共20个断面采集了水样,分析了水体中不同形态氮、磷和Chl-a的质量浓度。结果表明,洞庭湖水体中总氮（TN）、溶解态总氮（DTN）、氨氮（NH₄⁺-N）、硝酸盐氮（NO₃^--N）质量浓度年均值分别为1.83、1.69、0.26、1.27 mg·L^-1,总磷（TP）、溶解态总磷（DTP）、磷酸盐（DPO）、颗粒态磷（PP）质量浓度年均值分别为0.081、0.059、0.049、0.022 mg·L^-1,Chl-a质量浓度平均值为4.84μg·L^-1。空间分布上,各形态氮和磷的质量浓度总体表现为:入湖口>出湖口>湖体,其中,区间入湖口水体中ρ（TN）、ρ（NH₄⁺-N）、ρ（TP）、ρ（PP）最高,而ρ（NO₃^--N）、ρ（DTP）、ρ（DPO）在松滋口最高。ρ（Chl-a）表现为区间>湖体>出湖口>松滋口>四水。时间分布上,各形态氮与磷的质量浓度具有明显的季节变化特征,均表现为枯水期>平水期>丰水期;ρ（Chl-a）总体上呈现丰水期>平水期>枯水期的趋势。可见入湖河流对洞庭湖氮与磷的时空分布起了至关重要的作用,入湖污染负荷和人类活动（包括采沙和生产生活）是洞庭湖氮与磷空间分布的重要影响因素,而入湖水量可在一定程度上解释洞庭湖氮与磷的时间分布。总体而言,洞庭湖未出现明显的富营养化现象,这可能得益于其独特的水文条件（水循环周期短,流速较快）,但流速较低的六门闸和大小西湖断面ρ（Chl-a）较高,夏季水华频发,应引起高度重视。更多还原

【Abstract】 Nitrogen and phosphorus were the major pollutants in Dongting Lake. However, the relationships between concentration of nutrients in various forms and chlorophyll a in Dongting Lake were seldom studied. To study the temporal and spatial distributions of nitrogen（N） and phosphorus（P） as well as their relationship with chlorophyll a（Chl-a） in Dongting Lake, samples of surface water from 20 typical sections including lake region, outflow river and eight inflow rivers were collected in 2017, and different forms of N, P and Chl-a concentrations were analyzed. The results showed that the average concentrations of total nitrogen（TN）, dissolved total nitrogen（DTN）,ammonia（NH₄⁺-N） and nitrate（NO₃^--N） were 1.83, 1.69, 0.26 and 1.27 mg·L^-1, respectively. The average concentrations of total phosphorus（TP）, dissolved total phosphorus（DTP）, phosphate（DPO） and particulate phosphorus（PP） were 0.081, 0.059, 0.049 and 0.022 mg·L^-1, respectively. The average of Chl-a concentration was 4.84 μg·L^-1. Spatially, the concentrations of different forms of N and P ranked as an order: inflow rivers>outflow river>lake region. In details, the highest concentrations of TN, NH₄⁺-N, TP and PP were determined in Qujiang rivers, while the highest concentrations of NO₃^--N, DTP and DPO occurred in Songzi outlet. Chl-a concentrations decreased in the order of Qujian rivers>lake region>outflow river>Songzi outlet>Four rivers. In addition, an obvious seasonal variation was observed in terms of N and P concentrations. Various forms of N and P concentrations were ranked as an order as follow: the dry season>the normal season>the wet season. An inverted order was found in terms of Chl-a concentrations in temporal. Therefore, inflow rivers played an important role in the spatial and temporal distributions of N and P in Dongting Lake. Pollution load from inflow rivers and human activities（including sand dredging, human production and living） were considered as important factors affecting the spatial distribution of N and P in Dongting Lake. The inflow volume can explain the temporal distribution of N and P in Dongting Lake to some extent. Shortly, no serious eutrophication was detected in Dongting Lake, which might owe to its unique hydrological conditions with shorter hydraulic retention time and higher flow velocity. Algal bloom in summer and high Chl-a concentration were observed in the sections Liumenzha and Daxiaoxihu with lower flow velocity, which should be paid more attention.更多还原