Exploring the contribution of precipitation to water within the active layer during the thawing period in the permafrost regions of central Qinghai-Tibet Plateau by stable isotopic tracing

Xiaofan Zhu; Tonghua Wu; Lin Zhao; Chengsong Yang; Huiwen Zhang; Changwei Xie; Ren Li; Weihua Wang; Guojie Hu; Jie Ni; Yizhen Du; Shuhua Yang; Yuxin Zhang; Junming Hao; Cheng Yang; Yongping Qiao; Jianzong Shi

doi:10.1016/j.scitotenv.2019.01.064

Exploring the contribution of precipitation to water within the active layer during the thawing period in the permafrost regions of central Qinghai-Tibet Plateau by stable isotopic tracing

Sci Total Environ. 2019 Apr 15:661:630-644. doi: 10.1016/j.scitotenv.2019.01.064. Epub 2019 Jan 14.

Authors

Xiaofan Zhu¹, Tonghua Wu², Lin Zhao³, Chengsong Yang⁴, Huiwen Zhang⁵, Changwei Xie³, Ren Li³, Weihua Wang⁶, Guojie Hu³, Jie Ni¹, Yizhen Du¹, Shuhua Yang¹, Yuxin Zhang¹, Junming Hao¹, Cheng Yang¹, Yongping Qiao³, Jianzong Shi³

Affiliations

¹ Cryosphere Research Station on the Qinghai-Tibet Plateau, State Key Laboratory of Cryospheric Science, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China; University of Chinese Academy of Sciences, Beijing 100049, China.
² Cryosphere Research Station on the Qinghai-Tibet Plateau, State Key Laboratory of Cryospheric Science, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China. Electronic address: thuawu@lzb.ac.cn.
³ Cryosphere Research Station on the Qinghai-Tibet Plateau, State Key Laboratory of Cryospheric Science, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China.
⁴ State Key Laboratory of Frozen Soil Engineering, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China.
⁵ State Key Laboratory Breeding Base of Desertification and Aeolian Sand Disaster Combating, Gansu Desert Control Research Institute, Lanzhou 730070, China.
⁶ State Key Laboratory of Desert and Oasis Ecology, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi 830011, China.

PMID: 30682613
DOI: 10.1016/j.scitotenv.2019.01.064

Abstract

Stable isotopic tracing has proven to be a useful tool for assessing surface water source dynamics and hydrological connectivity in permafrost regions. This study has investigated the contribution of precipitation to water within the active layer at three long-term observation sites, including Fenghuoshan (FHS), Hoh Xil (KKXL) and Wudaoliang (WDL), by using isotopic tracer technique and two-component mixing model. The results showed that precipitation was the predominant source for water within the active layer, permafrost and ground ice near permafrost table at the three sites. Precipitation in August was the predominant source for water within the active layer at FHS, and precipitation in September was the main source at KKXL and WDL. The variation of isotopic values at different levels indicated that the water sources within the active layer could vary as the depth increases. The evaporation fractionation of water within the active layer at WDL was noticeable at depths of 0-50 cm, and the evaporation intensity decrease gradually from late June to late September. The relationship of isotopic tracing values between precipitation and water within the active layer at depths of 0-50 cm becomes more significant as the amount of the recently-occurring precipitation increases. Moreover, the relatively higher d-excess in precipitation indicates that local recycled moisture has greater contribution to precipitation. The differences of d-excess in most water within the active layer, permafrost and ground ice near permafrost table revealed that there were isotopic fractionation when precipitation supplying to above-mentioned three water bodies. The precipitation event amounted to 8.1 mm at KKXL can exert 49% ± 7.1% and 30.8% ± 3.6% contribution to water within the active layer at depths of 0-10 cm and 10-20 cm, respectively. While the long-period contribution cannot be identified because of the impact of evaporation. The results would provide new insights into the contribution of precipitation to water within the active layer on the QTP, which is also helpful to improve process-based hydrological models in the permafrost regions.

Keywords: Active layer; Permafrost; Precipitation; Qinghai-Tibet Plateau; Stable isotopic tracing.