title: Geochemical isotopic composition in the Loess Plateau and corresponding source analyses: A case study of China's Yangjuangou catchment.
abstract: Isotopic fractionation technology is widely used in identifying sources and the speciation of geochemical isotopic elements. With the increase in human activity, geochemical element transport by soil erosion has become the most critical environmental problem in the Loess Plateau, so tracing the geochemical element source would help in the identification and management of local soil erosion. In this study, we investigated the spatial distribution of carbon (C), nitrogen (N), oxygen (O), and hydrogen (H) isotopes in water and then further analyzed13C and15N in soil and vegetation to better understand the C and N sources and their biogeochemical cycling function in the Loess Plateau. Results showed that mean dual isotopic values of δ15N-NO3-and δ18O-NO3-in the watershed streams were 11.44±6.15‰ and -11.29±2.52‰, respectively, and that N wet deposition, fertilizers, and manure were the three main pollution sources. The mean dual isotopic value of δ13C in the water was -5.36±0.28‰, indicating that δ13C-DIC in the Yangjuangou Catchment of China's Loess Plateau is mainly controlled by carbonate weathering or soil erosion. The severe erosion in this region has typically occurred in grassy (C4) land-use types devoid of woody vegetation (C3), and this has led to a discrepancy in δ13C between soil and water. We found δ18O and δ2D in water to be -7.87±0.85‰ and -61.49±3.25‰, respectively, and to show a high positive correlation (r2=0.81). This suggests that summer rainstorms lead to soil erosion and runoff, which cause a wide range of isotopic values to occur across the Loess Plateau.
authors.affiliation: State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Yafeng
authors.initials: Y
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Liding
authors.initials: L
authors.lastname: Chen
authors.affiliation: Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China; College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China. Electronic address: gaoyang@igsnrr.ac.cn.
authors.forename: Yang
authors.initials: Y
authors.lastname: Gao
authors.affiliation: College of Geoscience and Surveying Engineering, China University of Mining and Technology (Beijing), Beijing 100083, China.
authors.forename: Shibo
authors.initials: S
authors.lastname: Chen
authors.affiliation: State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Weiliang
authors.initials: W
authors.lastname: Chen
authors.affiliation: Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China; College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Zhuo
authors.initials: Z
authors.lastname: Hao
authors.affiliation: Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China; College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Junjie
authors.initials: J
authors.lastname: Jia
authors.affiliation: Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China; College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Ning
authors.initials: N
authors.lastname: Han
keywords: Carbon; Hydrogen; Isotopic fractionation; Loess Plateau; Nitrogen; Oxygen