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Chinese Journal of Applied Ecology ›› 2019, Vol. 30 ›› Issue (6): 1840-1846.doi: 10.13287/j.1001-9332.201906.013

• Special Features of Stable Isotope Ecology • Previous Articles     Next Articles

Effects of extraction methods on soil water isotope and plant water source segmentation.

MA Xiao-jun1,2, JIN Jing-jing3, SI Bing-cheng1,2,3,*, XIANG Wei1,2, WANG Hong-xiu1,2   

  1. 1College of Water Resources and Architectural Engineering, Northwest A & F University, Yangling 712100, Shaanxi, China;
    2Key Laboratory of Agricultural Soil and Water Engineering in Arid and Semi-arid Areas of Ministry of Education, Yangling 712100, Shaanxi, China;
    3Institute of Water-saving Agriculture in Arid Areas of China, Northwest A & F University, Yangling 712100, Shaanxi, China
  • Received:2018-11-19 Online:2019-06-15 Published:2019-06-15
  • Supported by:
    This work was supported by the National Natural Science Foundation of China (K305021308) and the Special Fund for Thousand-Talent Plan (Z111021308)

Abstract: We used two types of soil with different physicochemical properties (loam and sand), oven-dried them, and then added the known isotopic composition mineral water that was reference water to compose the soil-water mixture with different soil water contents (loam: 0.15, 0.20, 0.30 g·g-1; sand: 0.10 g·g-1). After that, we set up different equilibrium time (loam: 3, 6, 12, 24, 48, 72, 96 h; sand: 96 h) to ensure that the dry soil particles were well mixed with the added water. The soil water was extracted by mechanical centrifugation and cryogenic vacuum extraction after equilibrium, and their isotope composition was analyzed. Results showed that the isotopic values of soil water extracted by mechanical centrifugation method had no significant difference in same water content with different equilibration times, but were more enriched compared with the reference water isotopic value. The maximum enrichment for hydrogen and oxygen isotope was 7.38‰ and 1.24‰, respectively. In contrast, cryogenic vacuum extraction method resulted in more depleted soil water isotopes than reference water, with the maximum depletion for hydrogen and oxygen isotope being 6.27‰ and 1.03‰, respectively. Moreover, the degree of depletion increased with the increases of equilibrium time (less than 24 h) at low water content, and became stable after 24 h. With the increases of soil water content, the isotopic composition of the extracted soil water was less affected by the two extraction methods. The water isotope value of loam that had high clay content, was more sensitive to the extraction method than the sandy soil that had low clay content. The difference of isotopic composition caused by extraction methods did not affect the plant water source segmentation.