## 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
In China, GSM concentrations have reached noteworthy peaks, including 1300 ng\(\cdot\)L\({}^{-1}\) in Chaohu Lake in August 2012 [33], 2711.5 ng\(\cdot\)L\({}^{-1}\) in Xionghe Lake in July 2007, 826.7 ng\(\cdot\)L\({}^{-1}\) in the same lake in November 2007 [66], and the aforementioned 7200 ng\(\cdot\)L\({}^{-1}\) in the YH Reservoir. Additionally, GSM concentrations exceeding 600 ng\(\cdot\)L\({}^{-1}\) have been documented in various countries, such as Germany, Japan, Korea, and the USA. MIB concentrations have also been reported at high levels in China, with Chaohu Lake recording a maximum concentration of 180.5 ng\(\cdot\)L\({}^{-1}\) in August 2012 [11]. Many other water bodies in China, including Dianchi Lake, Donghu Lake, Taihu Lake, Xionghe Reservoir, and a landscape lake in Beijing, have exhibited MIB values over 20 times the OTC. For example, MIB concentrations reached 450 ng\(\cdot\)L\({}^{-1}\) in Dianchi Lake in July 2003 [46], 317 ng\(\cdot\)L\({}^{-1}\) in Donghu Lake in January 1996 [56], 325 ng\(\cdot\)L\({}^{-1}\) in Taihu Lake in September 2009 [23], and 5302.7 ng\(\cdot\)L\({}^{-1}\) in a fishpond in July 2006 [70]. In other countries and regions, MIB concentrations generally ranged from 0 to 289 ng\(\cdot\)L\({}^{-1}\), except for Japan, where a concentration of 1400 ng\(\cdot\)L\({}^{-1}\) was reported [78]. These high concentrations of GSM and MIB not only indicate potential risks to water quality but also suggest the need for continued monitoring and management efforts to mitigate their impacts on drinking water supplies and aquatic ecosystems. In contrast, both CYC and ION were reported in only 15 studies, encompassing seven water bodies (Table 3). Regarding CYC, it is noteworthy that in seven Chinese reservoirs [21] and the Llobregat River in Spain [81], CYC was not detected. However, the recorded peak values exceeded the OTC of 19.3 ng\(\cdot\)L\({}^{-1}\) in 14 publications, spanning seven water bodies. Specifically, in China, Eastern Chaohu Lake, a drinking water source, recorded concentrations as high as 800 ng\(\cdot\)L\({}^{-1}\) in August 2012 [33]. Western Chaohu Lake had a concentration of 105.6 ng\(\cdot\)L\({}^{-1}\) in January 2012 [11], while Eastern Chaohu Lake again reached 714.8 ng\(\cdot\)L\({}^{-1}\) in September 2013 [42]. Elevated concentrations were also reported in other Chinese lakes, including Dianchi Lake (450 ng\(\cdot\)L\({}^{-1}\) in September 2003 [46]), Taihu Lake (2080 ng\(\cdot\)L\({}^{-1}\) in September 2009 [23]), and landscape lakes in Beijing, reaching a remarkable 6000 ng\(\cdot\)L\({}^{-1}\) in May 2016 [45;69]. In different geographical regions, CYC has also been detected. For instance, [PERSON] et al. (1997) reported concentrations ranging from 0 to 57 ng\(\cdot\)L\({}^{-1}\) in the Arno River in Japan in May 1995 [34], while [PERSON] et al. (1999) found 133 ng\(\cdot\)L\({}^{-1}\) in Winnebago Lake in the USA in August 1996 [40]. These findings highlight the widespread occurrence of CYC and the potential need for further investigation and monitoring in diverse aquatic systems. Regarding ION, the reported maximum concentrations in 14 publications, inclusive of the current study, exceeded the odor threshold concentration (OTC) of 7 ng\(\cdot\)L\({}^{-1}\). Notably, ION was not detected in seven significant reservoirs located in eastern China, as reported by [PERSON] et al. (2021)[21], and concentrations in the Arno River in Italy ranged from 0 to 7 ng\(\cdot\)L\({}^{-1}\), as documented by [PERSON] et al. (1997) [34]. Among the various water bodies studied, Chaohu Lake and Taihu Lake stand out as having been extensively investigated. Chaohu Lake recorded a peak concentration of 8300 ng\(\cdot\)L\({}^{-1}\) in December 2012 [33], while Taihu Lake exhibited a peak concentration of 1976.4 ng\(\cdot\)L\({}^{-1}\) in September 2017 [22]. These high concentrations indicate potential environmental concerns in these regions. In addition to Chaohu and Taihu lakes, other Chinese water bodies also showed elevated ION concentrations.