Effect of Planktonic Algae on Iron Variation In Plain Reservoirs, North China Plain

The seasonal high iron concentration in reservoirs in North China Plain causes staining and taste, thus impacting consumer acceptance of drinking water. To elucidate the regularities and causes of the variations of iron concentration, our study summarized and analyzed the iron distribution of a typical plain reservoir during the three years from 2020 to 2022 and analyzed its correlation with environment variables and other water quality indicators. Statistical analysis showed that the increase of iron concentration in the plain reservoir mainly occurred between May and November, and it usually peaked in September, the maximum exceeds 1mg/L. Iron element in overlying water existed mainly in an insoluble state. Iron concentration exhibited a positive correlation with turbidity, water temperature, permanganate index, chlorophyll a and algae count (P<0.01). Furthermore, iron concentration had a significant correlation with the amount of Microcystis, Eudorina, Euglena, and Cryptomonas. It can be inferred that the increase in iron concentration in the plain reservoir is caused by the growth and reproduction of planktonic algae. Temporal and spatial variations of planktonic algae also gradually affect the iron content in sediment. Our study highlights the interaction between planktonic algae and iron concentration, and planktonic algae inhibition is important in controlling iron concentration.