Vertical Spatial Distribution of Denitrification Intensity in the Vadose Zone of Typical Sections of Chaobai River Alluvial Fan

Abstract

In this study, the Chaobai River alluvial fan area, Beijing City, was chosen as the study area, and two typical profiles (S6 and S8) were selected to determine the denitrification intensity value of the vadose zone at different sampling depths (0-10 m). The vertical spatial distribution of denitrification in the vadose zone was analyzed, and the influencing factors of the vertical distribution of denitrification strength in the aeration zone were identified. The results showed that the NO3--N concentrations in the denitrification process of soil samples in different vadose zones experienced three main stages:rising, falling, and rising. The vadose zone denitrification intensities in S6 and S8 ranged from 0.0026 to 0.0185 mg·(kg·d)-1 and 0.0017 to 0.0233 mg·(kg·d)-1, respectively. That the overall denitrification intensity was low. The denitrification intensity of the vertical space showed an "S"-type trend. The main controlling factors for denitrification intensity in S6 and S8 vadose zones included clay, nitrate, and nitrite and showed significant correlations with the diversity of microorganisms, such as the ACE and Shannon indices, and the nitrate reductase (nirK) gene of denitrifying bacteria at a certain depth range.