title: Contribution of urban runoff in Taipei metropolitan area to dissolved inorganic nitrogen export in the Danshui River, Taiwan.
abstract: A previous study has demonstrated that Danshui River has almost the highest dissolved inorganic nitrogen (DIN) yield in the world and exports most of the DIN in the form of ammonium unlike the world's large rivers. However, the DIN sources are poorly constrained. In this study, the contributions of major sources in the Taipei metropolitan area to the DIN export in the Danshui River were investigated. It is observed that ammonium is the major DIN species in the downstream reaches, resulting from the ammonium-dominated inputs of the effluents of wastewater treatment plants (WWTP) and rain water pumping stations (RWPS). DIN concentrations in the downstream (urban) reaches are substantially elevated. The upstream tributaries annually discharge ∼2709 t DIN to the downstream reaches. However, the DIN discharge off the downstream reaches rises to ∼17,918 t, resulting from the contribution of RWPS-collected water, i.e., ∼14,632 t, and the effluents of two WWTP, i.e., ∼577 t. RWPS-collected water inherently contains the contribution of atmospheric deposition, ∼2937 t DIN. This finding implies that ∼11,695 t (∼66 % of the downstream output) DIN flux off the Danshui River is from urban runoff and can be attributed to human activities in the Taipei metropolitan area. To improve the water quality in the Danshui River, water quality controls in urban runoff are important.
authors.affiliation: Department of Geography, National Taiwan Normal University, Taipei, Taiwan.
authors.forename: Nae-Wen
authors.initials: NW
authors.lastname: Kuo
authors.affiliation: Department of Soil and Water Conservation, National Pingtung University of Science and Technology, Pingtung, Taiwan.
authors.forename: Shih-Hao
authors.initials: SH
authors.lastname: Jien
authors.affiliation: Graduate Institute of Earth Science, Chinese Culture University, Taipei, Taiwan.
authors.forename: Nien-Ming
authors.initials: NM
authors.lastname: Hong
authors.affiliation: Department of Geography, National Taiwan Normal University, Taipei, Taiwan.
authors.forename: Yao-Te
authors.initials: YT
authors.lastname: Chen
authors.affiliation: Department of Geography, National Taiwan Normal University, Taipei, Taiwan. tylee@ntnu.edu.tw.
authors.forename: Tsung-Yu
authors.identifier: http://orcid.org/0000-0002-5203-470X
authors.initials: TY
authors.lastname: Lee
mesh_terms: D002947:Cities; D004784:Environmental Monitoring; D009584:Nitrogen / Q000032:analysis*; D011891:Rain; D045483:Rivers / Q000737:chemistry*; D013624:Taiwan; D062065:Wastewater; D014874:Water Pollutants, Chemical / Q000032:analysis*; D060753:Water Quality
chemical_list: D009584:Nitrogen; D062065:Wastewater; D014874:Water Pollutants, Chemical
keywords: Nonpoint source pollution; Rain water pumping station; Urban runoff; Urbanization; Wastewater treatment plant; Water pollution control