再生水灌溉条件下氮磷运移转化实验与数值模拟

Simulation of Nitrogen and Phosphorus Transport and Transformation in Saturated-Unsaturated Soil

利用二维饱和-非饱和土壤氮磷运移转化模型nitrogen-2D对污水灌溉试验的实测数据进行了分析,结果证明所提出的模型可以较好的描述土壤中的水分运动和氮的转化运移过程,土壤含水量及铵态氮剖面模拟值与实测数据吻合程度较好.用检验过的数学模型模拟了不同污水灌溉方案下土壤及地下水中不同形态氮及磷的变化情况,分析了不同灌溉方案下土壤的氮磷平衡和农田养分平衡状况,结果表明:适度的污水灌溉,硝态氮和无机磷不会淋溶出1.5m土层,不会对地下水造成氮磷污染;施入土壤的铵态氮,由于有较强的吸附性,不易被作物直接吸收,49%转化成硝态氮,作物根系吸收以硝态氮为主,氮肥当季利用率为23.3%;反硝化是进行污水灌溉时旱地土壤氮素的主要损失形式,约占施入氮量的12.6%.

Nitrogew2D is a physically-based model developed on the basis of SWMS-2D to predict the fate of nitrogen and phosphorus following irrigation with effluent, To test the model, a sewage effluent irrigation experiment was conducted. In this paper, the nitrogen-2D model is extended and tested with data from four effluent-irrigated winter wheat plantations. The results show that, on the whole, measured and simulated values are in reasonably good agreement, especially soil water content and soil ammonia content, which indicates that it can offer reliable prediction of the fate of water and nitrogen in spite of the relative simplicity of the model. The model is then used to estimate the soil nitrogen and phosphorus behavior in winter wheat field under the same situation with different concentrations of nitrogen and phosphorus in the sewage effluent. The results show that under the simulated conditions, no nitrogen or phosphorus leaching happened at 1.5 m depth in the period, and because of the strong adsorbability of the soil, 49% of the ammonia following irrigation with effluent was turned into nitrate by nitration instead of uptake. Denitrification of nitrate is the maior channel resulting in loss of soil nitrogen fertilizer with a volume of about 12.6% of the input nitrogen. Nitrate is much more available for crop than ammonia and the current fertilization utilization rate is 23.3%.