The reactivity of dissolved organic matter (DOM) in forming disinfectant byproducts (DBPs) is promoted when using copper-based algaecides for controlling algae bloom triggered by the elevated nutrients levels after wildfires. Here, we cultivated Microcystis aeruginosa with black (BE) and white (WE) ash water extracts under 0, 0.5, and 1.0 mg-Cu/L for 4 d and employed Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) for the DBPs precursors characterization. The disappeared DOM during disinfections was mainly composed of O1-14, N1O1-14 and N2O1-14. It had a higher average molecular weight (MW) and double-bond equivalent (DBE), relative to DOM after incubation, regardless of disinfects and Cu2+, indicating the assigned features with larger MW and more double bonds/rings as preferable DBP precursors. A larger number of disappeared assigned features with low DBE of 1-10 in control without Cu2+ addition possibly explained lower DOM chlorine reactivity in forming carbonaceous and oxygenated DBPs, relative to the treatments with Cu2+ addition. A larger number of O1-14 and N1O1-14 with DBE=5-16 in the treatments potentially accounted for higher DOM chloramine reactivity in forming N-nitrosodimethylamine (NDMA), compared to the control. Our study suggests the oxygen- and nitrogen-containing organic compounds with more double bonds/aromatic rings as potential DBP precursors in source water after applying copper sulfate to control post-fire algae blooms.

Using APPI(-) and ESI(-) FT-ICR MS to characterize disinfection byproduct precursors from wildfire-induced Microcystis aeruginosa blooms controlled by copper sulfate

ACS Fall 2021

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