Response of Magnetite/Lanthanum hydroxide composite on cyanobacterial bloom

Magnetite/lanthanum hydroxide composite (MLC-10) was applied in simulate natural water, sediment and cyanobacteria (WSC) system to evaluate its effect on cyanobacterial bloom in this study. According to the results, the addition of MLC-10 showed a good performance on inhibition of cyanobacterial bloom in systems. The cyanobacteria density of WSC-0.5 and WSC-1.0 (adding 0.5 g and 1.0 g MLC-10) at 30 day was 99.39% and 99.84% less than that in WSC-C (adding no MLC-10 in WSC system), respectively. The addition of MLC-10 could form a phosphorus-binding layer that adsorbed soluble reactive phosphate (SRP) in overlying water, improved the release of internal phosphorus (P) from sediment to pore water then blocked SRP release from pore water to overlying water, especially in WSC-0.5 and WSC-1.0. The results may be due to the high adsorption capacity of MLC-10 to phosphorus. Additionally, oxidative stress and oxidative damage of cyanobacteria were observed after exposing to MLC-10, and oxidative damage degree increased with the elevated amount of MLC-10. MLC-10 addition showed a slight effect on microbial community of surface sediment. Phosphorus limitation, cell damage and limited cells' floating performance were the possible mechanisms of cyanobacterial bloom controlling by MLC-10. Based on these results, MLC-10 could be used as a potential P-inactive material for cyanobacterial bloom controlling.