Isolation and Identification of Odourous Compounds from a Lake Subject to Cyanobacterial Blooms

Buffalo Pound Lake in southern Saskatchewan, Canada, is subject to heavy blooms of blue-green algae, mainly Anabaena, Oscillatoria and Aphanizomenon. The occurrence of any of these species is usually followed by the appearance of pronounced tastes and odours. Water samples were extracted using a Likens- Nickerson or continuous liquid-liquid apparatus and capillary GC of the extracts showed that a large number of compounds are always present although the taste and odour vary in intensity. Many of these compounds have been identified using capillary GC-MS. Geosmin, which imparts a muddy flavour to water, was detected but methylisoborneol was absent. Other compounds present in the water included alkanes, alkylbenzenes, acetophenone, cyclohexanone, phenylacetonitrile, and α-pinene, some of which could affect the palatability of the water. Although some water samples had a musty odour extracts were frequently dominated by a pungent, smoky or tobacco flavour consistent with the presence of β-cyclocitral which was also indicated by GC-MS.