滇池湖滨农业污染土壤的硝化过程及控制方法

Nitrification Process and Control Method of Soils in Dianchi Lakeside of Agricultural Pollution Environment

通过对流经农业区的河流水质监测、不同土地利用方式的土壤现场采样分析、室外大型人工模拟装置和室内土柱的试验,研究了农业生产过程施肥与农村生活污水进入农田后,有机态和铵态氮素在土壤内的硝化过程特点以及减少硝态氮通过径流向水体迁移的方法。结果表明,耕层和不同深度土层中土壤有机态氮和铵态氮有少量积累,但在旱作时期又被消耗,且土壤矿质N素在这个时期发生NH+4-N向NO-3-N的转化,主要存在0￣60cm土层中。硝化作用强度与土壤水分、氮负荷率、停留时间和土壤有机质等因素有关。利用滇池流域湖滨区土壤潜水位埋深浅的自然特征,控制入渗水的深度和停留时间可有效地减少土壤硝态氮向地表水中迁移。

Through monitoring water quality of river in agricultural watershed, analysis for field soil samples under different land utilization modes and the experiments in a large scale artificial simulated equipment and in the laboratorial soil column, we researched on the characteristics of nitrification process of organic nitrogen and ammonium nitrogen in soil when fertilizer and rural wastewater were used and the control method for reducing the nitric nitrogen in soil transferring into water bodies by runoff. The results indicated that there existed a little accumulation of organic nitrogen and ammonium nitrogen in the cultivated layer and various depth of soil layer during the rice growth, and this accumulative nitrogen would be depleted during dry season. The transformations of mineral nitrogen in soil from NH+4-N to NO+4-N during this period occurred mainly in 0~60 cm soil layer. Part of nitric nitrogen could be moved from upper bed soil to bottom soil under irrigation water and rainwater eluviations, but the lower concentration of NO+4-N was monitored in 1.0~1.5 m horizon of soil. The maximal content of NO+4-N was only 0.67 mg·L-1 in 1.0~1.5 m layer of soil, varied usually from 0.16 to 0.39 mg·L-1. These results suggested that the higher denitrification intensity of soils in Dianchi lakeside had important functions to reduce the nitrate ion concentration. The nitrification intensity related to the water content of soil, nitrogen loading rate, the retention time and the soil organic matter. Based on the nature characteristic of lakeside soil with shallow buried depth of ground water table in catchments of Dianchi Lake, controlling the depth and retention time of seepage water in soil could availably reduce the soil nitrate moving to surface water.