## 2 Results and Discussion  
In the eastern drinking water source of Chaohu Lake, the concentrations of dissolved and particulate T/O compounds displayed intricate seasonal variations (Figure 1). Geosmin exhibited its highest concentration in March (39.7 \(\pm\) 10.6 ng\(\cdot\)L\({}^{-1}\)), with particulate concentrations consistently below 2 ng\(\cdot\)L\({}^{-1}\). The concentrations of MIB were notably elevated from May to October, peaking at 180.5 ng\(\cdot\)L\({}^{-1}\) in July 2012. The maximum concentration of MIB in both the dissolved and particulate forms was recorded at 164.0 ng\(\cdot\)L\({}^{-1}\) (July 2012) and 20.7 ng\(\cdot\)L\({}^{-1}\) (June 2012), respectively. The average values for the total concentration of CYC in the investigated drinking water source exhibited three peaks in January 2012 (105.6 ng\(\cdot\)L\({}^{-1}\)), March (53.5 ng\(\cdot\)L\({}^{-1}\)), and June (54.0 ng\(\cdot\)L\({}^{-1}\)), respectively, with both the dissolved and particle concentrations reaching their zenith in January 2012. Two distinct peaks in the total concentrations of ION were evident in December (53.3 ng\(\cdot\)L\({}^{-1}\)) and June 2012 (136.6 ng\(\cdot\)L\({}^{-1}\)), respectively. Although there is a limited body of literature specifically investigating T/O compounds in Chaohu Lake, it is evident that T/O issues are pronounced in this lake. This is manifested both by the reported maximum concentrations of four T/O compounds, with respective values of 1300 (GSM), 180.5 (MIB), 800 (ION), and 8300 ng\(\cdot\)L\({}^{-1}\), and the presence of significant olfactory problems in both the eastern and western regions of the lake (Refs. [11; 22; 33; 42] and this study). The seasonal variations in the concentrations of T/O compounds within the eastern drinking water source of Chaohu Lake might be attributed to meteorological conditions, water temperature fluctuations, and biological activities [44; 54]. Concerning the distribution between the dissolved and particulate forms, varied patterns were evident among different T/O compounds (Figure 1). Specifically, the four examined T/O compounds exhibited distribution patterns ranging from 11% to 91% outside cellular structures throughout the year, except for December, when no dissolved substance was detected. More than 79% of both GSM and MIB were found in the dissolved form, except for December, when the proportions were 0% for the former and 5% for the latter in June. Over the entire year, the average proportion of particulate CYC was 45%, comprising approximately 20% from September to November, 4-35% from February to May, and 62-100% in the remaining months. The majority of ION was observed within cellular structures, with an average particulate ratio of 71% throughout the year. Exceptions included 11-25% in April, September, and October and 59-78% in March, July, and August, with concentrations reaching 97-100% in the remaining months. Overall, GSM and MIB predominantly existed in dissolved form, while CYC and ION exhibited notable variations in their distribution between dissolved and particulate forms. The aggregate concentrations of the four T/O compounds, encompassing both dissolved and particulate fractions, within the three designated sampling sites exhibited a range of 8.9-292.6 ng\(\cdot\)L\({}^{-1}\) (Figure 1). The concentrations of dissolved GSM, MIB, CYC, and ION surpassed their respective OCCs [36] in 75%, 42%, 25%, and 33% of the months, respectively. In terms of the overall concentrations, the proportions of GSM and MIB exceeding OTCs remained relatively constant, while those of CYC and ION increased to 75% and 100%, respectively. Hence, the concentrations of dissolved GSM, MIB, CYC, and ION surpassed their respective odor threshold concentrations in certain months, potentially impacting the perception and acceptability of water quality.