强降雨对沙河水库的水质及其藻类群落结构的影响

Effects of heavy rainfall on water quality and algal community structure in Shahe Reservoir

汛期强降雨往往对河流水质产生重要影响,而关于不同类型强降雨对河流水质及藻类群落的影响值得深入探讨.以北运河上游沙河水库及其支流为研究对象,对比分析2019年和2020年汛期不同类型强降雨对沙河水库水质的影响.通过对2019年强降雨(累计降雨量达51.6mm·d^(-1)和降雨强度12.9 mm·h^(-1),历时4 h)和2020年强降雨后(累计降雨量193.8 mm·d^(-1)和降雨强度16.15 mm·h^(-1),历时12 h)的沙河水库及其支流进行连续6 d追踪监测,考察和比较强降雨后沙河水库及其支流的主要水质及藻类群落特征,明确强降雨对沙河水库水质波动和藻类群落的影响.研究结果表明,累计降雨量大、降雨强度大和历时长的强降雨对沙河水库及其支流的水质影响大,并造成了藻类群落结构的明显差异.与2019年相比,2020年强降雨引起水体TN和TP的浓度升高,南沙河较为显著,但整体上COD和氨氮浓度基本达地表水环境质量标准(GB3838-2002)的IV类标准.2019年与2020年降雨后水质的波动差异主要是不同类型强降雨导致地表径流所携带的面源污染负荷不同所致.东沙河和退水口的藻类群落多样性、丰富度较高;2020年降雨后库区的藻类群落多样性和丰富度均出现上升,其中沙河水库区域优势藻类属于硅藻门和蓝藻门.两场降雨后1~3 d,蓝藻门出现明显的增加和替代趋势,在库区与退水口更加显著,富营养化指示藻-微囊藻在库区的丰度高于其他监测点,且2020年比2019年更加显著.雨量的大小改变了藻类群落与环境因子的相关性,雨量越大,TP易成为藻类群落的主要影响因素.

Heavy rainfall during the flood season typically has an important impact on river water quality,and the impact of different types of heavy rainfall on river water quality and algae communities is worthy of in-depth discussion.In this study,the Shahe Reservoir and its tributaries in the upper reaches of the North Canal were selected as the research objects to compare and analyze the impact of different types of heavy rainfall on the water quality of the Shahe Reservoir in the flood seasons in 2019 and 2020.Through tracking and monitoring the Shahe Reservoir and its tributaries after heavy rainfall in 2019(cumulative rainfall of 51.6 mm·d^(-1) and rainfall intensity of 12.9 mm·h^(-1),lasting 4 h)and 2020(cumulative rainfall of 193.8 mm·d^(-1) and rainfall intensity of 16.15 mm·h^(-1),lasting 12 h)for six consecutive days,the effects of heavy rainfall on the main water quality and algae community characteristics of Shahe Reservoir and its tributaries were investigated and clarified.The results demonstrated that heavy accumulated rainfall,high rainfall intensity,and long-lasting heavy rainfall have a significant influence on the water quality of the Shahe Reservoir and its tributaries,and could cause obvious differences in the structures of the algae community.Compared with 2019,heavy rainfall in 2020 resulted in the increase of the concentrations of TN and TP in the water body and the effect on the Nansha River was more significant.However,the overall COD and ammonia nitrogen concentrations could still basically reach the Class IV standard of the surface water environmental quality standard(GB3838-2002).The discrepancy of water quality after rainfall in 2019 and 2020 was mainly due to the different non-point source pollution load carried by surface runoff caused by different types of heavy rainfall.The diversity and abundance of algae communities in Dongsha River and Retreats are relatively high^(-1) the diversity and abundance of algae communities in the reservoir area increased after the 2020 rainfall.Among them,the dominant algae in the Shahe Reservoir area belonged to the Diatom and Cyanophyta.1~3 days after the two rains,there was a significant increase and replacement trend of the Cyanophyta,which was more significant in the reservoir area and the outlet.The abundance of the eutrophication indicator algae i.e.,Microcystis in the reservoir area was higher than that in other monitoring points,and such phenomenon in 2020 was more significant than 2019.The amount of rainfall changed the correlation between the algae community and environmental factors.The TP was more likely to become the main influencing factor of the algae community at greater rainfall conditions.