Elevated nano-α-FeO enhances arsenic metabolism and dissolved organic carbon release of Microcystis aeruginosa under a phytate environment.

Little information is available on the effects of nano-α-FeO on arsenic (As) metabolism of algae and potential associated carbon (C) storage in As-contaminated water with dissolved organic phosphorus (DOP) as a phosphorus (P) source. In this study, Microcystis aeruginosa (M. aeruginosa) was used to investigate impacts of nano-α-FeO on cell growth and As metabolism of algae under a phytate (PA) environment as well as potential associated C storage. Results showed that nano-α-FeO had a subtle influence on algal cell growth in a PA environment. Herein, algal cell density (OD) and chlorophyll a (Chla) were inhibited at elevated nano-α-FeO levels, which simultaneously limited the decrease of Yield. As suggested, the complexation of PA with nano-α-FeO could alleviate the negative influence on algal cell growth. Furthermore, the elevated nano-α-FeO increased As methylation in the PA environment due to higher monomethylarsenic (MMA) and dimethylarsenic (DMA) concentrations in the test media. Additionally, microcystins (MCs) in the media changed consistently with UV, both of which were relatively lower at 10.0 mg·L nano-α-FeO. Enhanced As(V) methylation of algal cells was found to simultaneously reduce the release risk of As(III) and MC while increasing dissolved organic carbon (DOC) content in media, suggesting unfavorable C storage. Three-dimensional fluorescence analysis revealed that the main DOC constituent was the tryptophan-like component in aromatic proteins. Correlation analysis showed that decreases in pH and the zeta potential and an increase in Chla may lead to metabolic As improvements in M. aeruginosa. The obtained findings highlight the need for greater focus on the potential risks of DOP combined with nano-α-FeO on algal blooms as well as the biogeochemical cycling processes of As and C storage in As-contaminated water with DOP as the P source.