摘要:我国农业生产过程造成的地下水硝酸盐污染问题备受关注，作为硝态氮累积和存储的重要场所和硝酸盐淋失进入地下水的主要通道，包气带土壤中硝酸盐存储分布特征与地下水硝酸盐污染密切相关。本文以北方典型黑土、潮土和褐土区农田为研究对象，建立了北方地下水硝酸盐监测网（东北、华北、西北），通过对不同区域地下水的采样和测定，比较了地下水硝酸盐污染的区域差异，结合历史数据对地下水硝酸盐时空变化进行了分析。进一步选择华北平原作为厚包气带的代表区域，实地取样分析了包气带硝态氮累积存储和分布特征。结果表明：东北黑土区地下水硝酸盐超标率最高，达39.6%；其次为华北潮土区，超标率为19.3%；西北褐土区的地下水硝态氮超标率最低，为14.9%。随时间推移，华北平原区域尺度浅层地下水硝酸盐超标率有增长趋势，2016—2018年403个采样点地下水超标率为18.9%，高于1998年的11.8%。华北平原区域厚包气带硝酸盐存贮总量可达1854万t，粮食种植对区域包气带硝酸盐累积存储的平均贡献率为78.3%；包气带0~6 m是华北平原区硝酸盐存储的主要土层，这部分存储的硝态氮对地下水构成了潜在的威胁。
关键词:面源污染/
区域尺度/
地下水/
包气带/
硝酸盐存储
Abstract:Nitrate leaching from Chinese farmland causes non-point source pollution and is an increasingly serious issue. The vadose zone is an important place for nitrate nitrogen accumulation and storage and a common way for nitrate to leach into the groundwater. Nitrate spatial-temporal changes in the underground water and vadose zones were analyzed in this study. Farmlands in black soil, fluvo-aquic soil, and cinnamon soil in northern China were investigated by monitoring underground water nitrate and water level changes to determine the underground water nitrate contents. The results showed that the black soil region (Northeast China) had the highest groundwater nitrate content with excess standard rate of 39.6%, followed by the fluvo-aquic soil region (North China) (19.3%); the cinnamon soil region (Northwest China) had the lowest rate (14.9%). In the North China Plain, the excess standard rates of nitrate in shallow underground water trended upward over the years; the groundwater nitrate excess standard rate was 11.8% in 1998 and 18.9% from 2016 to 2018. The underground water nitrate excess standard rate was higher in vegetable-planting areas than in grain crop-planting areas. Soil nitrate was distributed and accumulated in the vadose zone before being leached into the underground water. Nitrate accumulation increased with vadose zone thickness; the total nitrate-N storage in the North China Plain deep vadose zone was up to 18.54 million tons. Nitrate accumulated mainly at a depth of 0–6 m, and crop production contributed, on average, 78.3% toward the regional vadose zone nitrate storage.
Key words:Non-point source pollution/
Regional scale/
Ground water/
Vadose zone/
Nitrate storage
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