Influence of rapid rural-urban population migration on riverine nitrogen pollution: perspective from ammonia-nitrogen
China is undergoing a rapid transition from a rural to an urban society. This societal change is a consequence of a national drive toward economic prosperity. However, accelerated urban development resulting from rapid population migration from rural to urban lands has led to high levels of untreated sewage entering aquatic ecosystems directly. Consequently, many of these regions have been identified as hot spots of riverine nitrogen (N) pollution because of the increasing level of urban point-source discharge. In order to address this concern, we assessed effects of urban development on ammonia-nitrogen (AN) loads using a panel data regression model. The model, expressed as an exponential function of anthropogenic N inputs multiplied by a power function of streamflow, was applied to 20 subwatersheds of the Huai River Basin for the years 2003–2010. The results indicated that this model can account for 81% of the variation in annual AN fluxes over space and time. Application of this model to three scenarios of urban development and sewage treatment (termed urbanization priority, sustainable development, and environmental priority) suggests that future N pollution will inevitably deteriorate if current urban environmental management and investment are not significantly improved. Stronger support for environmental management is very critical to alleviate N pollution and improve water quality. More effort should focus on improving sewage treatment and the N removal rate of the current sewage system in light of the increasing degree of urbanization.
KeywordsNet anthropogenic nitrogen input (NANI) Nitrogen (N) Urbanization Sewage treatment Panel data model
The authors wish to express their gratitude to Huai River Basin Water Resources Protection Bureau and Hydrologic Information Center of Huai River Commission for providing water quality and hydrological data. We also thank the reviewers for their valuable comments.
This study was financially supported by National Nature Science Foundation of China (NO. 41771531 and 41701040), the State Key Laboratory of Urban and Regional Ecology scientific project (NO. SKLURE2017-1-05), Talents-Import Program in Nanjing Institute of Geography and Limnology (NO. NIGLAS2016QD04), and Natural Science Foundation of Jiangsu Province of China (NO. BK20171100).
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