Sediment pH structures the potential of the lake's internal P pollution involved in different types of P reactivation.

Internal P pollution in lakes is being increasingly recognized as a dominant cause of eutrophication. Lake geo-engineering is a commonly used method to accelerate P deposition and control pollution. This study aimed to bridge the gap between the theory and practice of such geo-engineering methods based on a comprehensive investigation of sediment P reactivation using 171 samples from 64 lakes in China. Given the importance of pH on sediment P lability, sediment pH was hypothesized to structure the potential of the lake's internal P pollution. The results showed that the reactivation of sediment P tended to be promoted by lower Al, Fe, and Ca and higher loss of ignition (LOI) at different sediment pH; it was also promoted with increasing pH at sediment pH < 7 and with decreasing pH at sediment pH > 7. Notably, the key properties, besides total P, affecting the release of soluble P from sediments under anoxic conditions were pH at sediment pH > 7 and Fe content at sediment pH < 7. The factors affecting the potential sediment P pool available for Microcystis aeruginosa were LOI and pH at sediment pH > 7 and LOI, pH, Fe, and Ca at sediment pH < 7. These results verified our hypothesis and suggested that the mechanisms affecting bioavailable P pollution were more complex compared to those of soluble P. The sediment pH effect was further verified owing to the varied coupling of sediment properties with P distributions at different pH. Therefore, the sediment pH effect on the potential of internal P pollution should be taken into full consideration to design appropriate geo-engineering methods for lake restoration. [Display omitted] • Sediment P reactivation mechanism was studied based on 171 samples from 64 lakes. • Key sediment properties affecting P re-activation varied at different sediment pH. • Sediment mobile P and bioavailable P had different key affecting properties. • Sediment pH could be the fundamental data to develop lake geo-engineering. Accordingly, higher Al, Fe, Ca, and pH, as well as lower LOI and TP reduced the release of soluble P and the potential of M. aeruginosa to utilize P from sediments at pH > 7. Similar trends were observed in sediments at pH < 7, except that higher pH was favorable for P reactivation in sediments with pH < 7. Based on the best correlations determined here, the key properties (besides TP) affecting the soluble P release were pH at sediment pH > 7 and Fe at sediment pH < 7; those affecting the available P pool in sediment for M. aeruginosa were LOI and pH at sediment pH > 7 and LOI, pH, Fe, and Ca at sediment pH < 7. [ABSTRACT FROM AUTHOR]