title: Field scale interaction and nutrient exchange between surface water and shallow groundwater in the Baiyang Lake region, North China Plain.
abstract: Fertilizer input for agricultural food production, as well as the discharge of domestic and industrial water pollutants, increases pressures on locally scarce and vulnerable water resources in the North China Plain. In order to: (a) understand pollutant exchange between surface water and groundwater, (b) quantify nutrient loadings, and (c) identify major nutrient removal pathways by using qualitative and quantitative methods, including the geochemical model PHREEQC) a one-year study at a wheat (Triticum aestivum L.) and maize (Zea mays L.) double cropping system in the Baiyang Lake area in Hebei Province, China, was undertaken. The study showed a high influence of low-quality surface water on the shallow aquifer. Major inflowing pollutants into the aquifer were ammonium and nitrate via inflow from the adjacent Fu River (up to 29.8mg/L NH4-N and 6.8mg/L NO3-N), as well as nitrate via vertical transport from the field surface (up to 134.8mg/L NO3-N in soil water). Results from a conceptual model show an excess nitrogen input of about 320kg/ha/a. Nevertheless, both nitrogen species were only detected at low concentrations in shallow groundwater, averaging at 3.6mg/L NH4-N and 1.8mg/L NO3-N. Measurement results supported by PHREEQC-modeling indicated cation exchange, denitrification, and anaerobic ammonium oxidation coupled with partial denitrification as major nitrogen removal pathways. Despite the current removal capacity, the excessive nitrogen fertilization may pose a future threat to groundwater quality. Surface water quality improvements are therefore recommended in conjunction with simultaneous monitoring of nitrate in the aquifer, and reduced agricultural N-inputs should be considered.
authors.affiliation: Department of Environmental Engineering, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark; State Key Laboratory of Water Cycle and Related Land Surface Processes, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China; Sino-Danish Center for Education and Research, 8000 Aarhus C, Denmark. Electronic address: benb@env.dtu.dk.
authors.forename: Bentje
authors.initials: B
authors.lastname: Brauns
authors.affiliation: Department of Environmental Engineering, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark.
authors.forename: Poul L
authors.initials: PL
authors.lastname: Bjerg
authors.affiliation: State Key Laboratory of Water Cycle and Related Land Surface Processes, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China.
authors.forename: Xianfang
authors.initials: X
authors.lastname: Song
authors.affiliation: Geological Survey of Denmark and Greenland, 1350 Copenhagen, Denmark.
authors.forename: Rasmus
authors.initials: R
authors.lastname: Jakobsen
mesh_terms: D000383:Agriculture / Q000706:statistics & numerical data; D002681:China; D004784:Environmental Monitoring; D005308:Fertilizers / Q000706:statistics & numerical data; D060587:Groundwater / Q000737:chemistry*; D060106:Lakes / Q000737:chemistry*; D009566:Nitrates / Q000032:analysis; D009584:Nitrogen / Q000032:analysis*; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D005308:Fertilizers; D009566:Nitrates; D014874:Water Pollutants, Chemical; D009584:Nitrogen
keywords: Anammox; Groundwater pollution; Nitrogen; North China Plain; Surface water–groundwater interaction; Wheat–maize double cropping