title: Nitrogen transport and transformation in the saturated-unsaturated zone under recharge, runoff, and discharge conditions.
abstract: Water level (WL) changes are an important factor in the fate and transport of nitrogen in the saturated-unsaturated zone. In this study, the fate of nitrogen was investigated under simulated conditions of replenishment, runoff, and discharge. Three patterns of water level changes of ascent, stability, and descent were simulated under laboratory conditions to study nitrogen transport and transformation. Three columns (I, II, and III) were used to simulate the conditions of replenishment, steady water level, and discharge, respectively. The nitrate-nitrogen (NO3 (-)-N), nitrite-nitrogen (NO2 (-)-N), and ammonia-nitrogen (NH4 (+)-N) concentrations observed at different depths were compared among the three columns at 46.5 and 251.5 h. The results indicated that the NO3 (-)-N concentration decreased with time in both the saturated and unsaturated zones of the three columns (columns I, II, and III). The maximum decreasing concentrations of NO3 (-)-N in the three columns were 14.3, 37.97, and 38.17 mg/L, respectively. However, NH4 (+)-N in the saturated zone increased with time, whereas the NH4 (+)-N concentration decreased in both the saturated and unsaturated zones of other columns. No significant change in NO2 (-)-N concentration was observed in the experiment. These results suggest that water level changes must be considered in the remediation of groundwater nitrate pollution in the field.
authors.affiliation: School of Environment, Beijing Normal University, Beijing, 100875, China.|State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing, 100012, China.|State Environmental Protection Key Laboratory of Simulation and Control of Groundwater Pollution, Chinese Research Academy of Environmental Sciences, Beijing, 100012, China.
authors.forename: Zhifei
authors.initials: Z
authors.lastname: Ma
authors.affiliation: State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing, 100012, China.|State Environmental Protection Key Laboratory of Simulation and Control of Groundwater Pollution, Chinese Research Academy of Environmental Sciences, Beijing, 100012, China.
authors.forename: Xinying
authors.initials: X
authors.lastname: Lian
authors.affiliation: State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing, 100012, China.|State Environmental Protection Key Laboratory of Simulation and Control of Groundwater Pollution, Chinese Research Academy of Environmental Sciences, Beijing, 100012, China.
authors.forename: Yonghai
authors.initials: Y
authors.lastname: Jiang
authors.affiliation: State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing, 100012, China.|State Environmental Protection Key Laboratory of Simulation and Control of Groundwater Pollution, Chinese Research Academy of Environmental Sciences, Beijing, 100012, China.
authors.forename: Fanhua
authors.initials: F
authors.lastname: Meng
authors.affiliation: State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing, 100012, China. xibeidou@263.net.|State Environmental Protection Key Laboratory of Simulation and Control of Groundwater Pollution, Chinese Research Academy of Environmental Sciences, Beijing, 100012, China. xibeidou@263.net.
authors.forename: Beidou
authors.initials: B
authors.lastname: Xi
authors.affiliation: State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing, 100012, China.|State Environmental Protection Key Laboratory of Simulation and Control of Groundwater Pollution, Chinese Research Academy of Environmental Sciences, Beijing, 100012, China.
authors.forename: Yu
authors.initials: Y
authors.lastname: Yang
authors.affiliation: State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing, 100012, China.|State Environmental Protection Key Laboratory of Simulation and Control of Groundwater Pollution, Chinese Research Academy of Environmental Sciences, Beijing, 100012, China.
authors.forename: Zhiye
authors.initials: Z
authors.lastname: Yuan
authors.affiliation: State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing, 100012, China.|State Environmental Protection Key Laboratory of Simulation and Control of Groundwater Pollution, Chinese Research Academy of Environmental Sciences, Beijing, 100012, China.
authors.forename: Xiangjian
authors.initials: X
authors.lastname: Xu
mesh_terms: D004784:Environmental Monitoring; D060587:Groundwater / Q000737:chemistry; D009566:Nitrates / Q000032:analysis; D009573:Nitrites; D009584:Nitrogen / Q000032:analysis*; D058458:Nitrogen Cycle; D014872:Water Movements; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D009566:Nitrates; D009573:Nitrites; D014874:Water Pollutants, Chemical; D009584:Nitrogen
keywords: Environmental Fate; Fluctuate; Groundwater; Nitrogen; Water level