Occurrence of algae and algae-related taste and odour (T&O) compounds in the Qingcaosha Reservoir, China

This study examined the temporal and spatial variations in the occurrence of major algae and algae-related taste and odour (T&O) compounds in Qingcaosha Reservoir, China. Water samples were collected monthly from seven sites in the reservoir and analysed using solid phase microextraction combined with gas chromatography-mass spectrometry. Results showed that green algae were dominant over the 9-month study. In addition, cyanobacteria in the summer and early autumn peaked at 3.2 ∼ 9.6 × 10⁶ cell/L. Among the four most common algae-related T&O compounds, dimethyl trisulphide was undetectable at any of the sampling sites, and 2-methylisoborneol (2-MIB), geosmin and β-cyclocitral were frequently over their respective odour threshold levels from August through October. β-cyclocitral concentration was linearly correlated with the concentration of cyanobacteria (R² = 0.9831). The peak β-cyclocitral concentrations varied from 452 to 1,293 ng/L and were observed close to the water table. In contrast, high concentrations of 2-MIB and geosmin occurred in the water overlying sediments, probably because some of the 2-MIB and geosmin came from the micro-organisms in the sediments. These results provide important information regarding algae and algae-related T&O compounds in a typical reservoir in estuary and coastal areas, and will be helpful for developing appropriate strategies to minimize undesirable T&O issues in water sources.