In order to explore the spatial and temporal distribution characteristics and influencing factors of chloro-phyll a(Chl-a)concentration and eutrophication in the middle reaches(from mouth of the Honghe River to the exit of Hongze Lake)of the Huaihe River,water quality was investigated in 28 sampling sections in the middle reaches of the Huaihe River in June 2019,September 2019 and February 2020,and the relationship between the spatial and temporal distribution of Chl-a and environmental factors were analyzed by principal component analysis and multiple linear stepwise regression analysis.The results showed that there was obvious spatial and temporal distribu-tion characteristics of concentration of Chl-a in the middle reaches of the Huaihe River,with the annual mean value of(20.12±7.25)μg/L,with the variation range from 2.97 μg/L to 80.61 μg/L.The descending order of the spatial variation was expressed as Linhuaigang Sluice>from Linhuaigang Sluice to Bengbu Sluice>under Bengbu Sluice.Principal component analysis showed that Chl-a concentrations on Linhuaigang Sluice were positively corre-lated with transparency and dissolved oxygen level(P<0.05),but negatively correlated with nitrous nitrogen(P<0.05),and Chl-a concentrations from Linhuaigang Sluice to Bengbu sluice were significantly positively correlated with dissolved oxygen concentration and pH value(P<0.05),and Chl-a concentrations under Bengbu Sluice were positively correlated with permanganate index and total phosphorus(P<0.05).The multiple linear stepwise regres-sion analysis revealed that pH,total phosphorus and total nitrogen were the main environmental factors affecting the concentration of Chl-a in the middle reaches of Huaihe River,pH being the passive factor for the change in Chl-a concentrations.There were obvious differences in the correlation between total nitrogen and concentration in differ-ent hydrological periods,and total phosphorus concentration was the limiting nutritional factors of phytoplankton in the middle reaches of Huaihe River.The water in the middle reaches of the Huaihe River was dominated by mild eutrophication,and the temporal and spatial variation characteristics of the comprehensive trophic status index(TLI)were similar to the changes in Chl-a concentration.The Linhuaigang Sluice and the confluence of the main stream of the Huaihe River with the Yinghe River and the Wuhe River were the main mutation points of water quali-ty change.It was found that the total nitrogen concentration mainly exceeded the standard in the middle reaches of Huaihe River,and the changes in the hydrological situation of the river caused by dams,tributary inflows and non-point source pollution were the main influencing factors causing the change in the TLI.
维普
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