Nitrate Accumulation and Leaching in Surface and Ground Water Based on Simulated Rainfall Experiments.
To evaluate the process of nitrate accumulation and leaching in surface and ground water, we conducted simulated rainfall experiments. The experiments were performed in areas of 5.3 m2 with bare slopes of 3° that were treated with two nitrogen fertilizer inputs, high (22.5 g/m2 NH4NO3) and control (no fertilizer), and subjected to 2 hours of rainfall, with. From the 1st to the 7th experiments, the same content of fertilizer mixed with soil was uniformly applied to the soil surface at 10 minutes before rainfall, and no fertilizer was applied for the 8th through 12th experiments. Initially, the time-series nitrate concentration in the surface flow quickly increased, and then it rapidly decreased and gradually stabilized at a low level during the fertilizer experiments. The nitrogen loss in the surface flow primarily occurred during the first 18.6 minutes of rainfall. For the continuous fertilizer experiments, the mean nitrate concentrations in the groundwater flow remained at less than 10 mg/L before the 5th experiment, and after the 7th experiment, these nitrate concentrations were greater than 10 mg/L throughout the process. The time-series process of the changing concentration in the groundwater flow exhibited the same parabolic trend for each fertilizer experiment. However, the time at which the nitrate concentration began to change lagged behind the start time of groundwater flow by approximately 0.94 hours on average. The experiments were also performed with no fertilizer. In these experiments, the mean nitrate concentration of groundwater initially increased continuously, and then, the process exhibited the same parabolic trend as the results of the fertilization experiments. The nitrate concentration decreased in the subsequent experiments. Eight days after the 12 rainfall experiments, 50.53% of the total nitrate applied remained in the experimental soil. Nitrate residues mainly existed at the surface and in the bottom soil layers, which represents a potentially more dangerous pollution scenario for surface and ground water. The surface and subsurface flow would enter into and contaminate water bodies, thus threatening the water environment.
Institute of Soil and Water Conservation, Chinese Academy of Sciences and Ministry of Water Resources, Yangling, Shaanxi Province, China; University of Chinese Academy of Sciences, Beijing, China.
Hong
H
Wang
Institute of Soil and Water Conservation, Chinese Academy of Sciences and Ministry of Water Resources, Yangling, Shaanxi Province, China; Institute of Soil and Water Conservation, Northwest A&F University, Yangling, Shaanxi Province, China; College of Water Resources and Architectural Engineering, Northwest A&F University, Yangling, Shaanxi Province, China.
Jian-en
JE
Gao
College of Water Resources and Architectural Engineering, Northwest A&F University, Yangling, Shaanxi Province, China.
Xing-hua
XH
Li
College of Water Resources and Architectural Engineering, Northwest A&F University, Yangling, Shaanxi Province, China.
Shao-long
SL
Zhang
College of Water Resources and Architectural Engineering, Northwest A&F University, Yangling, Shaanxi Province, China.
Hong-jie
HJ
Wang
D003198:Computer Simulation; D005308:Fertilizers / Q000032:analysis; D060587:Groundwater / Q000737:chemistry*; D015233:Models, Statistical; D009566:Nitrates / Q000032:analysis*; D011891:Rain; D013997:Time Factors
D005308:Fertilizers; D009566:Nitrates