Combined effects of arsenate and benzene on Microcystis aeruginosa growth and arsenic metabolism

Abstract

To comprehensively understand the ecological risks of the coexistence of organic pollutants benzene and inorganic arsenate (As(V)) in the aquatic environment, Microcystis aeruginosa, one of the dominant algal species in eutrophic waters, was taken as the experimental alga to explore their growth response, arsenic (As) metabolism and the dissolved organic matter (DOM) changes in water under individual and combined pollution for benzene and As, respectively. The results showed that the algal cells of M. aeruginosa could proliferate normally. No significant differences were found among treatments after 96 h exposure to benzene and As(V) individual or combined. Intracellular As(V) accumulation was the main metabolism path for this alga and was significantly correlated to As(V) concentration but not benzene in the environment under different treatments. Benzene could promote As accumulation in algae and the total As metabolism amount in an individual algal cell at low As(V) levels. Meanwhile, only low benzene concentration showed As accumulation promotion at high As(V) levels. Microcystins (MCs) release in media affected by As(V) was different with benzene concentrations. There were no significant differences of UV254 in media among different treatments which represented macromolecular organic matters and aromatic compounds containing CC and CO bonds. Total organic carbon (TOC) was relatively higher in benzene media than in other treatments. The infrared spectrum characteristics of dissolved organic matter (DOM) confirmed that benzene was degraded and converted obviously at high levels in media by algal cells. Meanwhile, the three-dimensional fluorescence spectrum analysis showed that benzene in media could restrict proteins released in DOM caused by algae cells. The results are of great significance to the application of microalgae in water bioremediation and the comprehensive understanding of the ecological effects and risks in aquatic ecosystems.