乌溪江水库富营养化程度及其影响因子时空分布探讨

为了解乌溪江水库主要水质指标的时空分布特征，探究其营养化程度的变化趋势，2019-2020年，对丽水市乌溪江水库的7个采样点（S1-S7）的水温、pH、总氮、总磷、叶绿素a等理化因子进行了监测。分析对比了综合营养指数和理化因子等关键指标在不同时期的分布特征。结果表明，乌溪江水库的营养盐浓度呈现出春夏高秋冬低、从上游（S1）至下游（S7）逐渐下降的趋势，平均综合营养指数也从47.1（S1）下降到32.5（S7），整体上属于中营养化水库。总磷浓度在0.002-0.040mg/L间，平均值为0.012mg/L；总氮浓度在0.412-2.826mg/L间，氮的主要赋存形式为硝酸盐。叶绿素a含量均值为3.77 ug/L，河流区的叶绿素a含量显著高于下游的过渡区和湖泊区。分析表明：汛期地表径流带来的富营养化压力最大，同时也是氮磷等外源性营养盐输入水体的主要途径；WD、pH、TP和叶绿素a含量中等程度相关，水库生态系统具备很强的净化能力。但近年来富营养化程度加剧。

Temporal and Spatial Distribution and Influencing Factors of Eutrophication Degree of Wuxi River Reservoir

From the 2019 to 2020, the water quality physicochemical parameters such as water temperature (WT), pH, total nitrogen (TN), total phosphorus (TP), and chlorophyll a (Chl-a) were monitored at 7 sampling points (S1-S7) of Wuxi-jiang Reservoir in Lishui City, for the purpose of studying the spatial and temporal distribution characteristics of the main water quality indicators and the tendency of trophic degree within the reservoir. The research has compared the distribution characteristics of key indicators such as comprehensive nutritional index and physicochemical factors in different periods. The result showed that the nutrient concentration of Wuxi-jiang Reservoir had a decreasing trend from upstream (S1) to downstream (S7), and the average comprehensive nutrient index also decreased from 47.1 (S1) to 32.5 (S7), which can be regarded as an indicator of mesotrophic water state. Total phosphorus concentration ranged from 0.002-0.040 mg/L, with a mean value of 0.012 mg/L. Total nitrogen concentration ranged from 0.412-2.826 mg/L, and the main fugitive form of nitrogen was nitrate. Besides, the mean value of Chl- a content was 3.77 ug/L, and Chl-a content in the river area was significantly higher than that in the downstream transition area and lake area. The analysis results indicated that the eutrophication pressure brought by surface runoff during the precipitation period had the highest influence; the contents of WT, pH, TP and Chl-a were moderately correlated, and the reservoir ecosystem had a strong purification ability. Our findings showed that the degree of eutrophication has intensified in recent years.