Abstract
Algicides, like hydrogen peroxide and copper sulfate, are commonly applied to recreational waters and drinking water sources to mitigate cyanobacterial blooms. In this work, the effects of hydrogen peroxide and copper sulfate were evaluated in two natural bloom samples (collected from Canadian and American waterbodies) and one lab-cultured Microcystis aeruginosa suspended in Colorado River water. Five algicide to dissolved organic carbon (DOC) dose ratios were evaluated during an initial exposure period of 24 h. One dose ratio (0.4 H2O2:DOC or 0.25 CuSO4:DOC) was then evaluated during stagnation after quenching (hydrogen peroxide) or extended exposure (copper sulfate) for up to 96 or 168 h. During the initial hydrogen peroxide exposure, the CA bloom had no release of intracellular microcystins (MCs) and the USA bloom only releasedMC at 4 H2O2:DOC. The reverse occurred with copper sulfate, where the CA bloomreleasedMCs at 0.6 CuSO4:DOC but the USA bloom had no detectable extracellularMCs. ExtracellularMC was released from the lab-culturedMicrocystis at the lowest hydrogen peroxide and copper sulfate doses. In the hydrogen peroxide stagnation experiment, intracellular MC decreased in the USA bloom after 168 h despite the low dose applied. Similarly, the extended copper sulfate exposure led to intracellularMC decreases in both bloomsamples after 168 h, despite showing no impact during the initial 24 h monitoring period. The lab-cultured Microcystis was again less resistant to both algicides, with releases observed after less than 2 h of stagnation or exposure. The damage to cells asmeasured by pigments during these experiments did not match the MC data, indicating that blooms with depressed pigment levels can still be a risk to nearby drinking water sources or recreational activities. These results provide insight on the timeline (up to one week) required for monitoring the potential release of MCs after algicide application.
Original language | English |
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Article number | 1105 |
Number of pages | 12 |
Journal | Water (Switzerland) |
Volume | 12 |
Issue number | 4 |
DOIs | |
Publication status | Published - 13 Apr 2020 |
Externally published | Yes |
Keywords
- Copper sulfate
- Cyanobacteria
- Hydrogen peroxide
- Microcystins
- Stagnation