MICROCYSTIS BLOOMS INFLUENCING VOLATILE ORGANIC COMPOUNDS CONCENTRATIONS IN LAKE TAIHU

Taste and odor (T&O) due to several odorous compounds are frequently recorded during cyanobacterial bloom in natural waters. However, the seasonal variations and the key water quality variables connected with these cyanobacterial metabolites are relatively unknown. In this study, eight odorous compounds and water quality variables in Lake Taihu were evaluated monthly from January to December 2009. Dissolved odorous compounds were found at very low levels throughout the year whereas higher values were detected in the particulate fractions, with the peak values 242.4 ng/L for dimethyl trisulfide (DMTS), 395.6 ng/L for 2-methylisoborneol (MIB), 47.3 ng/L for 2-isobutyl-3-methoxypyrazine (IBMP) and 11 ng/L for 2-isopropyl-3-methoxypyrazine (IPMP), 2072 ng/L for beta-cyclocital, 573 ng/L for beta-ionone, respectively, far exceeding their respective odor thresholds. Microcystis biomass, TP, chl-a, and PO4-P contributed significantly to the variations of T&O compounds. Microcysitis biomass explained most of the variations of T&O compounds, with a proportion of 87.4 % and were positively correlated with DMS (r=0.26, p <0.01), MIB (r=0.24, p <0.01), geosmin (r=0.31, p <0.01), beta-cyclocitral (r=0.76, p <0.01) and beta-ionone (r=0.74, p <0.01). This study indicates that particulate compounds should be taken into account as a potential source of odorants and that the concentrations of taste and odor compounds could be predicted by Microcysitis biomass in Lake Taihu.