Seasonal dynamics of odor compounds concentration driven by phytoplankton succession in a subtropical drinking water reservoir, southeast China

Occurrences of odor compounds in drinking water reservoirs are considered as a nuisance by the water industry. Through the high-frequency monitoring of Tianmuhu Reservoir, a drinking water source for a city with a population of 700,000, we found that odor compounds seasonal dynamics were significantly related to phytoplankton succession, which was controlled by hydrometeorological process. 2-Methylisoborneol (2-MIB) was significantly related to Aphanizomenon sp. (r = 0.51). When the surface water temperature exceeded 12 degrees C, 2-MIB concentration may exceed the odor threshold concentration. With the proliferation of Aphanizomenon sp. in spring, 2-MIB concentration reached 87.22 ng/L. After late spring heavy rain, 2-MIB concentration sharply decreased to 3.19 ng/L. As the temperature increased at the end of the rainy season, Aphanizomenon sp. biomass increased to 2.09 mg/L, and 2-MIB concentration increased to 40.16 ng/L. These results showed that the concentration of odor compounds in shallow layer varied greatly because odor compounds mainly originated from phytoplankton and were susceptible to short-term hydrometeorological processes. However, the concentrations of odor compounds in deep layer were relatively insensitive to short-term weather processes. This study will improve the understanding of seasonal changes in odor compounds at different depths, and provide useful information for reservoir managers to prevent odor problems.