Lake water quality observed after extreme rainfall events: implications for water quality affected by stormy runoff
Lake water quality observed after extreme rainfall events: implications for water quality affected by stormy runoff
复制标题
DOI：
10.1007/s42452-021-04823-x
复制
发表时间：
2021-10
影响因子：
2.6
通讯作者：
T. Fukushima;T. Kitamura;B. Matsushita
中科院分区：
文献类型：
--
作者：
T. Fukushima;T. Kitamura;B. Matsushita
为探讨极端降雨事件对湖泊水质的影响，对近入流河流监测站逐月监测数据进行了分析。我们检验了这样一个假设，即影响取决于降雨量、季节、与河流的距离等。采水日前10天的降雨量与多个水质指标的相关性最高；即与Na+、Cl−、叶绿素a （Chla）和COD呈负相关，与正磷酸盐呈正相关。由于某些EREs的Na+、Cl−和Chla阈值很低（≤25百分位），我们采用降雨量≥140 mm的阈值来选择EREs并评价这种情况下的水质。满足上述阈值的事件样本（1组；G1）可能代表EREs期间的流入水量（一般发生在10 - 5月），其他事件样本（2组；G2）表明湖泊（6 - 9月）的变化显著，可能取决于湖泊的初级生产状态。在降雨量较低的情况下（50 ~ 140 mm， 10天），即使在10 ~ 5月，藻类产量也会快速恢复。G1条件下的COD、总磷和正磷酸盐值高于基流条件下的河流水质值，而G1和基流条件下的氮值几乎相同。从时间-纵向分布、未来监测和气候变化等方面讨论了ERFs对湖泊水质的影响。
To investigate the effects of extreme rainfall events (EREs) on lake water quality, we analyzed the lake monthly monitoring data at the stations close to inflow rivers. We tested the hypothesis that the effects depend on rainfall magnitude, season, distance from the rivers, etc. The highest correlations with many water-quality indicators were obtained for the rainfall amount for the preceding 10 days before the water sampling days; i.e., negatively with Na+, Cl−, chlorophyll a (Chla), and COD, and positively with ortho-phosphate. We used the threshold of rainfall amount ≥ 140 mm to choose EREs and evaluate the water quality on such occasions because quite low values of Na+, Cl−, and Chla thresholds (≤ 25th percentile) were observed in some of the EREs. The event samples (group 1; G1) meeting the above thresholds probably represented the inflow waters during EREs (generally occurred in Oct–May), and the others (group 2; G2) indicated significant changes in the lakes (Jun to Sep), probably depending on the lake’s state of primary production. In the events of lower rainfall events (50 mm to 140 mm for 10 days), fast recoveries of algal production usually occurred even in Oct to May. The values of COD, total phosphorus, and ortho-phosphate in G1 were higher than the values of river water quality in the baseflow conditions, whereas both the G1 and baseflow values of nitrogen were nearly the same. The effects of ERFs on lake water quality from the viewpoints of tempo-longitudinal distributions, future monitoring, and climate change were discussed.