Abstract
In order to understand the migration process of nitrate-nitrogen pollutants in the shallow unsaturated zone of the soil, the Tianjin coastal dredger and typical fluvo-aquic soils in North China were used as the research objects. The Hydrus-1D software was used to establish a numerical model to simulate nitrate. The pollution process of nitrogen pollutants in the unsaturated zone of soil, the results show that: during the migration process of the two kinds of shallow vadose zones of soil, the nitrate-nitrogen pollutants migrate downward at the maximum concentration before reaching the maximum concentration. After the maximum concentration, the concentration of nitrate nitrogen in the soil no longer increases; due to the difference in the average particle size of the soil, the migration rate of nitrate nitrogen in fluvo-aquic soil is significantly greater than that in artificial dredger soil. Nitrate nitrogen is in the simulation period completely passing through the simulated soil layer, the fluvo-aquic soil is completely passed through by nitrate nitrogen at 2d, and the artificial dredge fill is completely passed through by nitrate nitrogen at 2.5d.
Highlights
The Scholars have conducted a large number of studies on the migration and accumulation of nitrogen pollutants in the soil
In the continuous field experiment, the effects of different nitrogen application contents on the accumulation and leaching of soil nitrate nitrogen were studied; Zhang Xuexue et al [2] studied the irrigation and silt soil under different irrigation water amounts and fertilization conditions based on the soil column simulation method, results show: the amount of nitrogen applied has the greatest impact on the cumulative effect of nitratenitrogen migration in the soil; Yang Ruxin [3] et al used numerical simulation analysis to study the soil moisturenitrate nitrogen dynamic transport law in different fertilization conditions and irrigation intensity scenarios
The percentage of sand (0.05~0.5mm) is 2.7%, and the percentage of powder (0.002~0.05mm) is the percentage is 83.3%, and the percentage of clay particles (0.0001~0.002mm) is 14% [5]; the basic data of the typical fluvo-aquic soil in North China is obtained through experiments by Guo Zifan et al, and the percentage of sand particles (0.05~0.5mm) is 26%, the percentage of powder particles (0.002~0.05mm) is 67.5%, and the percentage of clay particles (0.0001~0.002mm) is 6.5%[6]
Summary
The Scholars have conducted a large number of studies on the migration and accumulation of nitrogen pollutants in the soil. Numerical simulation analysis method has become one of the main methods to study the accumulation and change of nitrogen pollution in soil due to its advantages such as good economy, fast speed and good visualization effect [4]. Hydrus-1D was used to simulate and compare the one-dimensional vertical migration and accumulation process of nitrate-nitrogen pollutants in the typical artificial dredger fill soil in Tianjin coastal area and the typical fluvo-aquic soil in the unsaturated zone of the North China Plain, and analyze their accumulation characteristics and differences
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