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In this study, samples from the Yangtze River, Han River, and Liangzi Lake in Wuhan City were utilized to characterize the formation of disinfection by-products (DBPs) from chlorine-based disinfection residues in drinking water sources. The results indicated that the main DBPs in drinking water sources were trichloromethane (TCM) and trichloroacetic acid (TCAA). The generation of DBPs was significantly positively correlated with oxidative substances, aromatic compounds, pH, and ammonia nitrogen (NH3-N) content in the water. The concentration of TCAA increased from 0 to 2.45 ± 0.31 mg/L when the reaction time increased to 72 h. As the NaClO concentration increased from 5 mg/L to 15 mg/L, the concentrations of TCAA, TBM, and DCAN increased from 2.03 ± 0.04 mg/L, 0 mg/L, and 0 mg/L to 2.49 ± 0.34 mg/L, 0.21 ± 0.07 mg/L, and 0.10 ± 0.04 mg/L before decreasing to 1.75 ± 0.19 mg/L, 0.17 ± 0.07 mg/L, and 0.04 ± 0.05 mg/L, respectively. The orthogonal experimental results showed that Br−, NH3-N, and pH all had significant influences on the TCM generation, whereas temperature affected the formation of TCAA in the Han River. This work reveals the factors influencing the generation of DBPs from chlorine-based disinfection residues, offering a prevention and control method for DBPs in drinking water sources from a theoretical perspective.

Seawater stratification is an important ecological indicator and typical feature in the marine environment, which is of great significance to the material cycle and distribution of organisms. In March 2016, a survey was conducted in the M2 seamount of the Western Pacific Ocean, seawater stratification of temperature, salinity, dissolved oxygen (DO), nutrients, bacteria, and the impact of the M2 seamount were discussed. It is found that the seawater stratification of each parameter is obvious in this area. At the depth of 0–75 m, there is a mixed layer, and these parameters remain relatively stable; at 75–500 m, there are obvious thermocline, gradient layer of bacteria, and nutricline; at the depth deeper than 500 m, these parameters remain relatively stable. In addition, at 75–150 m, there is a high-salt zone dominated by the North Pacific Tropic Water, while at 270–1370 m, there is an oxygen minimum zone with low DO. There is a close relationship in seawater stratification of different parameters. At 75–500 m, the density gradient dominated by the thermocline limits the water exchange, then directly controls the gradient layer of DO, nutrients, and bacteria. Additionally, the double actions of the high-salt zone and thermocline affect the stratification of other parameters. At 0–75 m, due to the abundant DO, sufficient carbon source, and low nutrients, the bacteria could grow largely, while at 75–500 m, bacteria could consume a large amount of DO to decompose organic matter, leading to a decrease in DO and an increase of nutrients. Although the M2 seamount is a shallow seamount, there is no upwelling around it, which weakly influences the seawater stratification of different parameters. This study will provide a new perspective on seawater stratification and its ecological effects.

Transparent exopolymer particle (TEP) is a transparent jellylike substance characterized with high carbon concentration, playing an important role in the marine carbon cycle. Based on a survey of the East China Sea coast in summer of 2020, the distribution, controlling factors of TEP and its impact on marine carbon transportation were discussed. The results showed that the TEP in the surface decreases from northwest to southeast gradually with an average concentration of 214.90 µg Xeq./L, which is basically consistent with the distribution of POC, Chl a and NO3-N. The TEP in the water of 10 m, 20 m, and 30 m also gradually decreases from northwest to southeast horizontally, while it is high in the surface and bottom layer, and low in the middle water layer vertically. The hydrological situation of the study area is complex and is the main factor affecting the distribution of various parameters including TEP. The TEP in the seawater has the characteristics of high TEP-C/POC, low settling ratio and high degradation ratio. The TEP-C/POC in the seawater is 32.03%, which is extremely higher than that of 14.46% in the surface sediments; the settling ratio of TEP is 17.67%, which is extremely lower than that of 50.31% for POC; the degradation ratio of TEP is 82.79%, which is extremely higher than that of 49.69% for POC. These results together indicated that TEP in the seawater has a longer residence time and is more easily degraded than other forms of POC.