Different characteristics of wastewater have different effects on the diversity and abundance of bacteria and archaea in rivers. There are many creeks around Taihu Lake, and they receive a large volume of industrial wastewater and domestic sewage, which is discharged into these creeks, and finally into Taihu Lake. The present study determined Illumina reads (16S rRNA gene amplicons) to analyze the effects of industrial wastewater and domestic sewage on the bacterial and archaeal communities at the different sampling sites along two creeks. The bacterial and archaeal diversity of the creek receiving sewage was higher than that of the creek receiving industrial waste. Proteobacteria dominated the microbial communities of all samples in both creeks. Betaproteobacteria dominated in the sewage creek, and its abundance declined along the creek. Certain pollutant-resistant classes were more abundant at the site near to the pollution source of the industry creek (e.g., Epsilonproteobacteria and Flavobacteria). Halobacteria belonging to the phylum Euryarchaeota was the dominant archaea at all sites in both creeks, while Methanobacteria was more abundant in the industry creek. The bacterial community was more affected by the distance between the sampling site and the pollutant source than the archaeal community, indicating that bacterial diversity and abundance could be a good index to distinguish domestic and industrial pollution, especially when the main pollution sources are difficult to identify.

Taihu Lake is the third largest freshwater lake in China. Due to rapid economic development and excessive nutrient discharges, there is serious eutrophication in the northern part of the lake. Nitrogen (N) is one of the key factors for eutrophication in Taihu Lake, which mainly comes from the rivers around the lake. Samples from four inflowing rivers were analysed for δ¹⁵N and δ¹⁸O isotopes in December 2013 to identify the different sources of nitrogen in the northern part of Taihu Lake. The results indicated that the water quality in Taihu Lake was clearly influenced by the water quality of the inflowing rivers and nitrate (NO₃⁻-N) was the main component of the soluble inorganic nitrogen in water. The soil organic N represented more than 70% of the total NO₃⁻-N loads in the Zhihugang. Domestic sewage was the major NO₃⁻-N source in the Liangxi river, with a contribution of greater than 50%. Soil organic N and domestic sewage, with contributions of more than 30% and 35% respectively, were the major NO₃⁻-N sources in the Lihe river and Daxigang river. Denitrification might be responsible for the shifting δ¹⁵N-NO₃⁻ and δ¹⁸O-NO₃⁻ values in the Daxigang river, and a mixing process may play a major role in N transformations in the Lihe river in winter. The results of this study will be useful as reference values for reducing NO₃⁻ pollution in the inflowing rivers in the north of Taihu Lake.

Water nitrogen and phosphorus may exhibit pronounced diel changes as affected by diel temperature and DO fluctuations due to algal productivity (photosynthesis and respiration) in eutrophic lakes. Here, we used a laboratory experiment to evaluate the diel dynamics of water ammonium (NH4 +), nitrate (NO3 -), and soluble reactive phosphorus (SRP) in different periods of algal bloom in the highly polluted region of Taihu Lake, China. Results showed that diel changes of water NH4 +, NO3 -, and SRP depended on the different periods of algal bloom. Diel variations of NH4 +, NO3 -, and SRP showed increased trends during algal decomposition, and decreased trends at the beginning of algal growth, suggesting that their diel variations were mainly controlled by algae self through nutrients released by decomposing algae or algal assimilation. However, water NH4 +, NO3 -, and SRP decreased from predawn maxima to afternoon minima and subsequently increased when Chl-a was high, which might be governed by the combined effects of algal assimilation and geochemical processes (e.g., nitrification, denitrification, and Fe-bound P cycles). Overall, the diel biogeochemical cycles of inorganic nitrogen and SRP have important implications for the accuracy of pollution assessment and provide important support for the control and management of eutrophic lakes.

Nickel titanate (NiTiO₃) semiconductors and graphitic carbon nitride (g-C₃N₄) have attracted great attention as photocatalysts in the degradation of environmental pollutants because of their visible-light-driven activity. But the utilizations of both semiconductors are limited by their low specific surface area. In this study, a nano-NiTiO₃/g-C₃N₄ photocatalyst was successfully synthesized by optimizing the preparation method of photocatalyst precursors. Compared with the bulk g-C₃N₄ and bulk NiTiO₃/g-C₃N₄ composite photocatalysts, the nano-NiTiO₃/g-C₃N₄ composite catalyst displayed a larger specific surface area, a more abundant pore size structure, and superior carrier separation capabilities. According to the pseudo-first-order, the degradation rate of MB was more than 2.5–19.7 times higher than that of previous studies. The superoxide radicals (·O₂⁻) and holes (h⁺) played significant roles in the photocatalytic reaction of MB. This study provides a new idea for the synthesis of photocatalysts and the improvement in photocatalytic performance.