Unraveling the source-water fishy odor occurrence during low-temperature periods: Odorants identification, typical algae species and odor-producing potential

In this study, odor characteristics and phytoplankton composition were systematically investigated in two winter periods in a reservoir with fishy odor in north China. Ten potential fishy odor-producing algae were isolated and odorant-producing potentials were evaluated. Olfactometry profile and odorant composition of water samples were analyzed using GC-Olfactometry combined with GC × GC-TOFMS. The results showed that 2,4-heptadienal and hexanal were major fishy odor contributors. The abundance of Uroglena sp., Synura sp. and Peridinium sp. was negatively correlated with total dissolved organic carbon, ammonia nitrogen, and nitrate, illustrating nutrient level might be major drivers for the succession of fishy odor-producing algae. Dinobryon sp. and Uroglena sp. made the greatest contribution to fishy odor, followed by Peridinium sp., Synura sp., and Ochromonas sp. Fishy odor in 2016 winter and the early of 2017 winter was mainly caused by Dinobryon sp., while Uroglena sp. contributes mostly in March in 2017 winter. This study demonstrates the main odorants and algae causing fishy odor in reservoir, which will provide a scientific basis for the management of seasonal fishy odor problems in water source.