Ecotoxicological analysis of fly ash and rice-straw black carbon on Microcystis aeruginosa using flow cytometry

Black carbon (BC) has a strong affinity for hydrophobic organic compounds (HOCs), and it is a potential material to control HOCs pollution in aquatic ecosystems. Here, flow cytometry (FCM) was used to evaluate the ecotoxicological effect of fly ash, rice-straw ash, and their acid-demineralised products on the growth of Microcystis aeruginosa. It was found that the BCs had little negative effect on cyanobacteria, when the content of BCs was not above 1 mg ml−1. However, higher doses of BCs (>2 mg ml−1) had an obvious negative effect on cell density and esterase activity, especially for BCs with acid treatment, which greatly inhibited cell density caused by its high adsorptivity for cyanobacteria. The BCs had little impact on the fluorescence intensity, only with a slight stimulation in later period, so the fluorescence intensity was a less sensitive indicator than cell density and esterase activity. Considering ecotoxicological effect of BCs on the algae, the application concentration of BCs for HOCs pollution control as in situ remediation material would better not exceed 1 mg ml−1.

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► The toxic effects of different BCs on cyanobacteria were evaluated by flow cytometry.
► Cell density and esterase activity were more sensitive than fluorescence intensity.
► Low-doses BCs had little adverse effect on cyanobacteria.
► High-doses BCs with acid treatment could adsorb cyanobacteria and influence growth.
► The concentration of BCs in HOCs pollution control would better not exceed 1 mg ml−1.