## 2 Results and Discussion
### Characteristics of the T/O Compounds in Freshwaters of the World  
#### 2.4.1 Spatiotemporal Distribution of T/O Compounds in Freshwater Sources Worldwide  
We compiled a review of the literature spanning from 1986 to 2023 that documented the presence of typical cyanobacteria-derived T/O compounds, namely GSM, MIB, CYC, and ION, in freshwater bodies worldwide (Table 3). The findings revealed prevalent T/O issues in raw water sourced from drinking water treatment plants, lakes, reservoirs, rivers, aqueducts, and fishponds, with manifestations reported in diverse regions, including China, Egypt, Germany, Italy, Japan, Korea, Spain, Switzerland, Thailand, the United States of America, and North America. These freshwater bodies exhibited variability in T/O types, concentrations, and the months of maximum occurrence. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline  & **Geosmin** & **2-Methyl Isoborneol** & \(\mathbf{\beta}\)**-Cyclocitral** & \(\mathbf{\beta}\)**-Ionone** & **MC-LR** & **MC-RR** & **MC-YR** \\ \hline geosmin & \(1\) & & & & & & \\ MIB & \(0.288\) & \(1\) & & & & & \\ \(\beta\)-cyclocitral & \(0.660\)** & \(0.256\) & \(1\) & & & & \\ \(\beta\)-ionone & \(0.408\)* & \(0.169\) & \(0.654\)** & \(1\) & & & \\ MC-LR & \(-0.183\) & \(0.228\) & \(0.239\) & \(0.014\) & \(1\) & & \\ MC-RR & \(-0.136\) & \(0.217\) & \(0.157\) & \(0.077\) & \(0.802\)** & \(1\) & \\ MC-YR & \(-0.368\)* & \(0.128\) & \(-0.019\) & \(-0.265\) & \(0.817\)** & \(0.643\)** & \(1\) \\ \hline \hline \end{tabular} Note: Correlation significance is denoted with * \(p<0.05\) or ** \(p<0.01\).  
\end{table} 
Table 2: Correlation coefficients between concentrations of T/O compounds and microcystin congeners (MC-LR, MC-RR, and MC-YR) from September 2011 to August 2012 in the eastern drinking water source of Chaohu Lake. \begin{table}
\begin{tabular}{l l l l l l l l} \hline \hline
**Country and Region** & **Sampling Site** & **Sampling Time** & **Geosmin (ng.\(\mathbf{L^{-1}}\))** & **2-Methyl Isobomed** & **\(\beta\)-Cyclotatat** & **\(\beta\)-Ionene** & **Reference** \\  & & & & **ng.\(\mathbf{L^{-1}}\))** & **(ng.\(\mathbf{L^{-1}}\))** & **(ng.\(\mathbf{L^{-1}}\))** & **(ng.\(\mathbf{L^{-1}}\))** & **(ng.\(\mathbf{L^{-1}}\))** & **(ng.\(\mathbf{L^{-1}}\))** \\ \hline China & Eastern Chachu Lake & August 2012, & 0-1300 (August 2021) & 0 & 0–800 & 0-8300 & \\  & Drinking water intakes & December 2012 & & & (August 2012) & (December 2012) & [33] \\  & in the Eastern Chachu & August 2011 & 0.3-3.97 & & 11-13.05,6 & 8.5-136 & \\  & Lake & August 2012 & & 0–180.5 (July 2012) & 0–11.3-105,6 & 8.5-136 & \\  & Western Chachu Lake & July 2013 & 0–28.3 & 0–4.18 & 0–7714.8 & 0–211.2 & \\  & December 2013 & & (December 2013) & (August 2013) & (September 2013) & [42] \\  & Chaohu Lake & September 2017 & 3-8.0 & 0–5.95 & & 9.4-280 & \\  & & & (September 2017) & (September 2017) & (September 2017) & [22] \\  & & & 0-30 & 0–450 & 20–450 & 40–570 & \\  & & & (October 2003) & (July 2003) & (September 2003) & (September 2003) & [46] \\  & Donglu Lake & May 1995-April 1996 & 0–3.3 & 10–317 & & & [56] \\  & & & (June 1995) & (January 1996) & & & [56] \\ Feng-Shen Reservoir & December 2000- & & 0–185 & & & [57] \\  & July 2003 & & 0–71 & & & [58] \\  & January 2009- & & 0–17 & & & [59] \\  & December 2009