通过野外采样及室内化验,利用紫外可见分光光度法测定土壤、地下水中硝态氮浓度,并分析干旱绿洲灌区硝态氮淋失因素及对地下水的污染情况。结果表明:硝态氮在土壤剖面中的淋失受土壤质地、水位埋深、灌水量、施氮量等多种因素影响,人为因素—灌溉和施肥是影响硝态氮向地下水迁移的重要因素。其中,冬灌是硝态氮淋失最直接的影响,不同定额对土壤硝态氮的淋洗效果在表层最显著。逐年增大的氮肥施用量是影响潜水水质不断恶化的重要因素,其正在以平均每年15.50 kg/hm2的速度迅速增加,已造成潜水硝态氮浓度每年增加0.22 mg/L的趋势。灌区浅层地下水已受到硝态氮污染,超标率(超限值>10 mg/L)达11.67%,严重超标率(超限值>20 mg/L)达1.7%,且主要分布在土壤质地为砂砾石的区域,中深层地下水硝态氮的浓度虽未超标,但已具有受潜在污染的风险。
To study the factors affecting the leaching of nitrate nitrogen in farmland soil in arid oasis irrigation area and the pollution of groundwater. Through field sampling and laboratory analysis, and analysis of leaching of nitrate nitrogen the concentration of nitrate nitrogen in soil and groundwater was determined by UV spectrophotometry. The results of the study indicate the leaching loss of nitrate nitrogen in the soil profile is influenced by various factors such as the lithology of the gas zone, the depth of the water level, the irrigation and the amount of nitrogen. Human factors-Irrigation and fertilization are important factors affecting the migration of nitrate nitrogen to groundwater. Inside, winter irrigation is the most direct effect of nitrate leaching, different ration of soil nitrate nitrogen leaching effect in the most significant surface. The increasing amount of nitrogen fertilizer applied year by year is an important factor that affects the continuous deterioration of diving water quality. It is increasing rapidly with an average annual rate of 17.3kg/hm2, which has resulted in an annual increase of 0.22mg/L of nitrate nitrogen concentration in phreatic water. The shallow groundwater in the irrigation area has been contaminated. The exceeding standard rate (overrun value >10mg/L) reaches 11.67%, and the severe exceeding standard rate (>20 mg/L) reaches 1.7%, which is mainly distributed in the gravel area of the vadose zone. Although the concentration of nitrate nitrogen in middle deep groundwater is not over standard, it has the potential pollution risk.