香溪河夏季水华暴发差异性研究及其机制分析

Regional Differences and Mechanism Analysis of Summer Blooms in Xiangxihe Reservoir Bay

三峡水库支流水华已成广泛关注问题,香溪河在同一时期不同空间暴发了不同藻类水华。2017年6-7月对香溪河水华藻种进行连续跟踪监测,分析水华藻种和环境因子的变化及其关系。结果表明:香溪河总氮平均浓度为2.212 mg/L,总磷平均浓度为0.071 mg/L,表层水温在24.95~29.93℃之间。总磷浓度从上游到下游呈递减趋势,总氮从上游到下游呈递增趋势。监测期间中下游暴发了蓝藻水华,叶绿素a最高浓度为69.62μg/L;上游暴发了甲藻水华,叶绿素a最高浓度为100.56μg/L,水华的优势藻种呈现空间差异性。这种藻类空间分布的差异性主要受中层倒灌异重流影响,倒灌的范围同时也决定了2种水华的暴发范围。中下游水体高浓度氮与中层倒灌异重流是蓝藻水华暴发的关键。上游区间具有特殊的循环水流与高浓度磷是甲藻水华暴发的关键。

The tributary of the Three Gorges Reservoir has become a widespread concern, and the Xiangxi River Reservoir has experienced different algal blooms in different spaces during the same period.From June to July 2017, continuous tracking and monitoring of the water bloom algae in Xiangxi River was carried out to analyze the changes and relationships between the algae species and environmental factors. The results showed that the average concentration of total nitrogen in Xiangxi River Reservoir was 2.212 mg/L, the average concentration of total phosphorus was 0.071 mg/L, and the surface water temperature was between 24.95 and 29.93 ℃.The total phosphorus concentration showed a decreasing trend from upstream to downstream, and the total nitrogen increased from upstream to downstream.During the monitoring period, cyanobacteria bloom broke out in the middle and lower reaches, and the highest concentration of chlorophyll a was 69.62 μg/L.There was an outbreak of dinoflagellate bloom in the upstream, the highest concentration of chlorophyll a was 100.56 μg/L,and the dominant algae species in the bloom presented spatial differences.The spatial distribution of this algae is mainly affected by the middle layer backflow heterogeneous flow, and the range of back irrigation also determines the extent of the two blooms.The high concentration of nitrogen in the middle and lower reaches of the river and the heterogeneous flow in the middle layer are the key to the outbreak of cyanobacteria blooms. The upstream zone has a special circulating water flow and high concentration of phosphorus is the key to the outbreak of dinoflagellate blooms.