土壤空间变异对溶解性有机氮淋失风险影响的模拟研究

Assessing the influence of soil spatial variability on water leakage and dissolved organic nitrogen leaching through simulation

本文应用COMSOL软件对土壤中溶解性有机氮(DON)的迁移转化过程进行了模拟,采用局部敏感性分析和全局敏感性分析两种方法,探究了土壤初始状态和土壤水力学参数的空间变异对土壤水分渗漏和DON淋失的影响。结果表明:土壤累积水分渗漏量与初始基质势的大小正相关,累积DON淋失量的大小与初始基质势以及DON初始含量的大小正相关。土壤在弱变异条件下,累积水分渗漏量的不确定性主要是由饱和导水率(K_(s))和饱和含水率(θ_(s))的空间变异引起的,累积DON淋失量要受到K_(s)的影响;在中等变异条件下,累积水分渗漏量和累积DON淋失量都对K_(s)的波动更为敏感。对于大尺度地区,土壤在弱变异条件下,大部分区域水分渗漏和DON淋失程度一致,在中等变异条件下,土壤水分渗漏和DON淋失量空间分布不均匀性增大,部分区域会发生大规模的水氮淋失。在水氮管理中考虑土壤空间变异特征,有利于降低土壤水分渗漏和DON淋失量,减轻土壤养分的流失,进而降低DON向地下水的淋失风险。

The processes of transportation and transformation of dissolved organic nitrogen(DON) in soil were simulated in this paper using the COMSOL software.The influence of spatial variability of soil initial state and soil hydraulic parameters on water leakage and DON leaching were investigated using the local sensitivity analysis and global sensitivity analysis.The results indicated that the soil water leakage was positively correlated with soil initial matrix potential and the soil DON leaching was positively correlated with soil initial matrix potential and DON initial content.For the clay with a low spatial variability,the uncertainty of soil water leakage was mainly caused by the spatial variability of saturated water conductivity and saturated water content while it was mainly caused by the spatial variability of saturated water conductivity when the spatial variability of soil reached a medium level.The DON leaching was more sensitive to the fluctuations of the saturated water conductivity at different degrees of spatial variability.For large-scale coastal areas,the degree of water leakage and DON leaching was the same in most regions for the region with a low spatial variability while the spatial distribution of soil water leakage and the DON leaching would be more uneven.Substantial water and nitrogen leaching would occur in some areas for the region with a medium spatial variability.Considering the characteristics of soil spatial variation in water and nitrogen management is helpful to reduce the loss of soil nutrients and then reduce the risk of the DON leaching to groundwater.