王士军, 田路遥, 刘丙霞. 地下水浅埋区层状土壤结构对包气带硝态氮累积和淋失的影响[J]. 中国生态农业学报 (中英文), 2023, 31(1): 125−135. DOI: 10.12357/cjea.20220409
引用本文: 王士军, 田路遥, 刘丙霞. 地下水浅埋区层状土壤结构对包气带硝态氮累积和淋失的影响[J]. 中国生态农业学报 (中英文), 2023, 31(1): 125−135. DOI: 10.12357/cjea.20220409
WANG S J, TIAN L Y, LIU B X. Effects of layered soil on the accumulation and leaching of nitrate-nitrogen in shallow groundwater regions[J]. Chinese Journal of Eco-Agriculture, 2023, 31(1): 125−135. DOI: 10.12357/cjea.20220409
Citation: WANG S J, TIAN L Y, LIU B X. Effects of layered soil on the accumulation and leaching of nitrate-nitrogen in shallow groundwater regions[J]. Chinese Journal of Eco-Agriculture, 2023, 31(1): 125−135. DOI: 10.12357/cjea.20220409

地下水浅埋区层状土壤结构对包气带硝态氮累积和淋失的影响

Effects of layered soil on the accumulation and leaching of nitrate-nitrogen in shallow groundwater regions

  • 摘要: 农业过量施肥造成包气带硝态氮(NO3-N)累积与地下水NO3-N污染加剧, 明确非均质层状土壤结构对NO3-N迁移过程的影响对防止地下水硝酸盐污染具有重要意义。华北低平原区非均质层状土壤结构分布广泛, 地下水埋藏浅, NO3-N淋滤路径短, 是地下水污染的敏感区域。本研究选择位于河北省沧州市南皮县的3个非均质层状土壤结构剖面(P1: 含多个薄黏壤土夹层的无施肥草地; P2: 含多个薄黏壤土夹层的农田; P3: 含140 cm厚黏壤土夹层的农田)和1个对照剖面(P4: 相对均质的粉壤土农田), 研究层状土壤结构以及农业施肥对包气带NO3-N累积与淋失规律的影响。结果表明, NO3-N累积分布层位与黏壤土层深度和厚度相关, 3个非均质层状土壤剖面NO3-N含量均高于相对均质粉壤土剖面, 且非均质农田中P3剖面NO3-N含量峰值(238 mg∙L−1)和累积层厚度(100~250 cm)均最大。2018年雨季8—9月含黏壤土夹层剖面NO3-N淋失量: P3 (319.2 kg∙hm−2) <P1 (383.9 kg∙hm−2)<P2 (554.7 kg∙hm−2), 说明在雨季含厚黏壤土夹层剖面对包气带NO3-N淋失的阻控效果显著优于含多个薄黏壤土夹层的剖面(P<0.05)。受层状沉积结构和地下水浅埋深的影响, P2浅层地下水NO3-N浓度的超标率与平均增长速率(93%和2.14 mg∙L−1∙d−1)显著高于P4 (21%和0.53 mg∙ L−1∙d−1) (P<0.05)。研究明确了层状土壤剖面对NO3-N运移具有阻滞作用且黏壤土夹层越厚阻滞作用越强, 地下水NO3-N浓度受包气带层状土壤结构和地下水埋深二者的综合控制。研究结果可为地下水浅埋区地下水硝酸盐污染防治提供科学依据。

     

    Abstract: Excessive nitrogen application in agriculture causes the accumulation of nitrate-nitrogen (NO3-N ) in the vadose zone and intensifies nitrate pollution in groundwater. Heterogeneous layered soil is relatively common in nature and plays an important role in controlling pollutants entering groundwater from the surface. Heterogeneous layered soil exists in the low plain area of North China which is sensitive to groundwater pollution owing to its shallow groundwater burial and short nitrate leaching path. Thus, it is important to clarify the influence of the heterogeneous layered soil structure on the NO3-N migration process to prevent nitrate pollution in groundwater. In this study, four typical soil profiles, heterogeneous and relatively homogeneous, and two land use types were selected in Nanpi County, Hebei Province. The four typical soil profiles included three heterogeneous layered soils (P1, P2, P3), one relatively homogeneous profile (P4), and two land uses, which were unfertilized grassland with multiple 30 cm thin clay soil interlayers (P1), fertilizing farmland with multiple 30 cm thin clay soil interlayers (P2), fertilizing farmland with 140 cm thick clay soil interlayers (P3), and fertilizing farmland with relatively homogeneous silty loam (P4). The effect of layered soil on the accumulation and leaching of NO3-N was studied by analyzing the relationship between the physical and chemical properties of different layered soil profiles and NO3-N content in soil profiles and groundwater. The results showed that the vertical distribution of NO3-N was affected by the depth and thickness of the clay loam soil layer. The NO3-N contents in the three heterogeneous layered soil profiles were higher than that in the homogeneous profile with silt loam. In the three heterogeneous layered soil profiles, P3 with a 140-cm clay soil interlayer, its’ peak content of NO3-N (238 mg·L–1) and the accumulation layer thickness (100–250 cm) were the highest. In the rainy season of 2018 (from August to September), the leaching amounts of NO3-N in the heterogeneous profiles were P3 (319.2 kg·hm–2) < P1 (383.9 kg·hm–2) < P2 (554.7 kg·hm–2), which indicated that the control effect of the layered soil profile with a thick clay loam interlayer on NO3-N leaching was significantly better than that with multiple thin clay loam interlayers (P<0.05). NO3-N in shallow groundwater was affected by the soil deposition structure of the aquifer. The over-limit ratio and average increasing rate under a heterogeneous deposition profile with clay loam interlayers (P2, 93% and 2.14 mg·L–1·d–1) were significantly higher than those of the homogeneous deposition profile with silt loam (P4, 21% and 0.53 mg·L–1·d–1). This study verified that layered soil profiles have a blocking effect on soil water and NO3-N migration; and thicker the clay loam interlayer, the stronger is the blocking effect of soil water and NO3-N migration. The interaction of soil water and solution between the vadose zone and groundwater is frequent in shallow groundwater regions; thus, the NO3-N concentration in groundwater is controlled by the structure of the layered soil in the vadose zone and the depth of groundwater. These results provide a scientific basis for the prevention and control of nitrate pollution in shallow groundwater regions.

     

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