Effect of coal mining subsidence fractures on source of water absorption of Artemisia Desertorum

Ground fissures caused by coal mining subsidence are not only a serious geological hazard, but also affect the growth and development of vegetation in the mining area and damage the mining ecosystem. To investigate the quantitative influence of coal mining subsidence fractures on the source of water uptaken by Artemisia Desertorum, the simulated precipitation tests of isotopically-labeled water were conducted in three test areas influenced by coal mining subsidence fractures to different degrees on 22312-working face of Huojitu mine field in Shendong mining area. The three test areas were divided according to the distance between Artemisia Desertorum and the fractures, where the coal mining subsidence conditions were classified as the virgin zone (where the Artemisia Desertorum was over 50 m away from the cracks in the test area), the zone affected by coal mining subsidence without obvious fractures (hereinafter referred to as fracture-free zone, where Artemisia Desertorum was more than 5 m away from the fractures in the test area) and the fracture zone (where the fractures with a width of about 15 cm passed through the test area at 0-20 cm away from Artemisia Desertorum). In this test, six pieces of Artemisia Desertorum were selected as the research objects and divided into six soil profiles. Then, the δ¹⁸O and δ²H isotope contents of soil water and xylem water of plant samples in different soil layers were calculated with LGR liquid water isotope analyzer and Isoprime 100 isotope ratio mass spectrometer (IRMS) respectively. In addition, the contribution of different soil layers to the water uptaken by Artemisia Desertorum after precipitation was quantified with the MixSIAR Bayesian mixture model of R script, and to explore the mechanism of soil water recharge and the source of plant water. The results show that: (1) The proportion of preferential flow in the subsidence fracture zone is 18.2%, (2) 59.7% of water uptaken by Artemisia Desertorum comes from the 10‒20 cm soil layer in the virgin area, (3) 46.6% and 39.4% of water comes from the 40‒60 cm and 0‒10 cm soil layers in the fracture-free zone, respectively, and (4) 85.9% of water uptaken by Artemisia Desertorum is mainly derived from the 40-60 cm soil layer in the subsidence fracture zone. The research results are significant to reveal the mechanism of soil water recharge and the water uptake pattern of plants in subsidence fracture zone of coal-mining areas.