Abstract
Along with urbanization, the intensified nitrogen pollution in urban rivers and the form of black-odor rivers has become one of the biggest concerns. Better understanding of the nitrogen transformations and microbial mechanisms occurring within urban rivers could help to manage their water quality. In this study, pollution characteristics, potential nitrogen removal rate, composition and function of bacterial community, and abundance of functional genes associated with nitrogen transformation were comparatively investigated in a typical urban river (FC) and a suburban river (LH). Compared with LH, FC was characterized by higher content of nutrients, lower potential nitrogen removal rate and lower abundance of functional genes associated with nitrogen transformation in both overlying water and sediment, especially in summer. Sediment dissolved organic matter characterized by excitation−emission matrix (EEM) showed that FC was more severely polluted by high nitrogen organic matter. Our results revealed that anammox was the main nitrogen removal pathway in both rivers and potential nitrogen removal rates decreased significantly in summer. Bacterial community analysis showed that the benthic communities were more severely influenced by the pollutant than aquatic ones in both rivers. Furthermore, the FC benthic community was dominated by anaerobic respiring, fermentative, sulfate reduction bacteria. Quantitatively, the denitrification rate showed a significant positive correlation with the abundance of denitrification genes, whilst the anammox rate was significantly negatively correlated with bacterial diversity. Meanwhile, NH4+-N had a significant negative correlation to both denitrification and anammox in sediment. Taken together, the results indicated that the increased nitrogen pollutants in an urban river altered nitrogen removal pathways and bacterial communities, which could in turn exacerbate the nitrogen pollution to this river.
Highlights
Fast growth of population and urbanization cause urban areas to produce more and more pollution
The contents of total nitrogen (TN), Total phosphorus (TP), NH4+-N, and NO3—N in FCS (FC sediment) were significantly higher than LHS (LH sediment) (p < 0.05) (Fig 2), indicating that more pollutants accumulated in urban center river sediment compared with the suburban one
In LHS, the contents of TN, TP and Total organic carbon (TOC) in summer were significantly higher than spring (p < 0.05), which was consistent with the higher load as observed in overlying water in summer
Summary
Fast growth of population and urbanization cause urban areas to produce more and more pollution. Insight into the nitrogen accumulation in urban center river source pollution, nonpoint source pollution, such as surface runoff caused by rainfall events, as well as endogenous release of the sediment pollutants persist to increase the levels of pollution in urban rivers [1,2,3,4]. Many rivers heavily polluted by organic matter, nitrogen, phosphorus, and heavy metals often resulted in excessive oxygen consumption and production of blackening and stinking pollutants, which caused rivers to become black and odor smell, especially in summer [6,7,8]. Improving urban river water quality, especially elimination of black-odor phenomenon in rivers, is an urgent need for sustainable city development
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
