宁夏引黄灌区日光温室集约种植区浅层地下水硝态氮含量与耕层土壤硝态氮含量的关系

  目的  探讨宁夏引黄灌区日光温室集约种植区地下水硝态氮污染现状及其与土壤硝态氮含量之间的关系，为有效防治地下水硝态氮污染及土壤盐渍化提供理论依据。  方法  通过抽样调查方法，采集7个典型日光温室集约种植区不同时期的214个地下水样及102个0 ~ 20 cm土壤样品，分析了地下水和土壤的硝态氮含量及电导率等。  结果  地下水样本硝态氮含量超过Ⅲ类水标准的达53.3%；近80%的土壤样本呈现出不同程度的盐渍化，其中中度盐化土占57%。当地下水硝态氮含量大于40 mg L?1时，地下水电导率、土壤电导率和土壤硝态氮含量均随地下水硝态氮浓度增加而急剧增加。土壤电导率与土壤硝态氮含量之间呈极显著线性函数关系，决定系数达0.376。土壤硝态氮含量与地下水硝态氮含量之间呈极显著的指数函数关系，土壤电导率与地下水电导率之间呈极显著的线性函数关系。  结论  宁夏典型日光温室集约种植区的地下水硝态氮污染和次生盐渍化严重，并与土壤硝态氮含量和盐渍化密切相关。

Relationship between Nitrate Nitrogen Content in Shallow Groundwater and Soil in Intensive Greenhouse System of the Ningxia Yellow River Irrigation Region

  Objectives  With the adjustment of agricultural cultivation structure in Ningxia Yellow River Irrigation Region, the area of greenhouse increased greatly. The objectives of this study were to investigate the nitrate nitrogen (N) pollution in shallow groundwater and to analyze its relationship with soil nitrate N in intensive greenhouse planting areas, and then to provide theoretical basis for effective control of groundwater nitrate N pollution in Ningxia and other similar areas of China.   Methods  A total of 214 groundwater samples and 102 soil samples were obtained from seven typical greenhouse intensive planting areas in different periods, and the contents of nitrate N and salts of groundwater and soil were analyzed.  Results  Results showed that the contents of nitrate N in groundwater samples exceeded the grade III standard of groundwater by 53.3% and there were great differences in the pollution degree of groundwater nitrate N among the 7 intensive planting areas. The contents of groundwater nitrate N increased from summer and autumn fallow period to winter planting period. There was a significant positive correlation between groundwater salinity and groundwater nitrate N concentration in intensive greenhouse planting area, especially when the groundwater nitrate N content was greater than 40 mg L?1, and the groundwater salinity increased dramatically. From the aspect of soil salinity, nearly 80% of the samples showed different degrees of salinization, in which moderate salinization accounted for 57.12%. There was an extremely significant linear relationship between soil salinity and nitrate N content in 0 – 20 cm soil, with a determination coefficient of 0.376. Meanwhile, there was a very significant exponential function relationship between soil nitrate N content and groundwater nitrate N content and an extremely significant linear function relationship between soil salinity and groundwater salinity.   Conclusion  The groundwater nitrate N pollution in typical greenhouse intensive planting areas in Ningxia is considerably serious. The accumulation of nitrate N in soil and soil salinization are partly caused by nitrate N content and salinity of groundwater, and the large accumulation of soil nitrate N might be the main source of groundwater nitrate N.