Isotopic Biogeochemical Indicators of Evapotranspiration and Nitrogen Flows in a Check-Dam Catchment in the Loess Plateau, China,Land Degradation & Development

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Isotopic Biogeochemical Indicators of Evapotranspiration and Nitrogen Flows in a Check-Dam Catchment in the Loess Plateau, China
Land Degradation & Development ( IF 4.7 ) Pub Date : 2018-08-02 , DOI: 10.1002/ldr.3090
Shibo Chen _{1,

2} , Yong Huang ₂ , Linhua Wang ₂ , Weiliang Chen _{2,

3} , Yafeng Wang ₁ , Yang Gao _{3,

4}

Affiliation

The increasingly fragile environment and associative nitrogen (N) biogeochemical cycle have become critical environmental and ecological issues in China's Loess Plateau. However, N flow and N source for typical catchments remain poorly understood in the Loess Plateau. In this study, we measured concentrations and isotopic signatures of N, hydrogen (H), and oxygen (O) in both rainfall and river water. Results showed that baseflow variation in total nitrogen (TN) concentrations ranged from 0.16 to 32.70 mg L⁻¹. The monthly TN deposition flux and monthly TN wet deposition concentration to river water were shown significant variations between rainy and dry seasons. The range of variation in δ²H values for rainfall and baseflow was from −90.0‰ to 19.8‰ and from −67.2‰ to −38.4‰, respectively, whereas δ¹⁸O–H₂O values ranged from −12.1‰ to +2.7‰ and from −9.3‰ to −3.6‰, respectively. The Local Meteoric Water Line in the check‐dam catchment was δ²H = 7.35 δ¹⁸O + 2.29 (R² = 0.93). Furthermore, NO₃⁻ δ¹⁵N and δ¹⁸O values in baseflow ranged from −2.0‰ to +20.5‰ and from +8.0‰ to +15.6‰, respectively. The results indicated that rainfall was affected by below‐cloud secondary evaporation and caused strong isotopic kinetic fractionation to occur during the precipitation process. The NO₃⁻ in runoff was mainly derived from the nitrification of soil organic matter and manure or sewage, for which the proportion of manure or sewage was from 50.5% to 83%.

更新日期：2018-08-02

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