title: Investigating the spatial-temporal variation of nitrogen cycling in an urban river in the North China Plain.
abstract: Urban rivers are essential in retaining nutrients, but little is known about nitrogen cycling in these rivers in semiarid areas. We measured chemical and isotopic compositions of ammonium (NH4(+)-N) and nitrate (NO3(-)-N) to investigate spatial-temporal variation of nitrogen cycling in the Fuhe River in the North China Plain. Nitrogen pollution in the river was mainly induced by extra NH4(+)-N inputs which come from the discharges of urban sewage and effluents of wastewater treatment plants in upstream. NH4(+)-N obtained from decomposing organic matter of sediments can diffuse into the overlying water. Intense nitrification then occurs at the terrestrial-aquatic interface. Due to less vegetation in spring and autumn, loss of NH4(+)-N is mainly caused by nitrification. In contrast, significant NH4(+)-N is absorbed by plants in summer. NO3(-)-N generated from nitrification can be denitrified during the study period. The highest NO3(-)-N loss (about 86.3%) was observed in summer. The contribution of NO3(-)-N loss due to denitrification is 44.6%. The remaining 55.4% is due to plant uptake. The results suggested that nitrogen cycling in the river is related to temperature and dry-wet cycles. And vegetation restoration along the river could benefit the incremental improvements to the aquatic ecosystem.
authors: The Key Laboratory of Water and Sediment Sciences, Ministry of Education, School of Environment, Beijing Normal University, Beijing 100875.
authors: J
authors: J
authors: Wang
authors: Y S
authors: YS
authors: Pei
authors: K J
authors: KJ
authors: Zhang
authors: G
authors: G
authors: Gao
authors: Z F
authors: ZF
authors: Yang
mesh_terms: D002681:China; D004784:Environmental Monitoring; D009584:Nitrogen / Q000737:chemistry*; D058458:Nitrogen Cycle; D000644:Quaternary Ammonium Compounds; D045483:Rivers / Q000737:chemistry*; D012621:Seasons; D013997:Time Factors; D014506:Urban Renewal; D014874:Water Pollutants, Chemical / Q000737:chemistry
chemical_list: D000644:Quaternary Ammonium Compounds; D014874:Water Pollutants, Chemical; D009584:Nitrogen