BACKGROUNDHydrogen and oxygen isotopes can be used to identify water sources and trace water cycles and have been used in hydrogeochemistry since the 1950s. Studies have been carried out on stable isotopes of atmospheric precipitation, rivers and lakes in Xinjiang.However, the research on hydrogen and oxygen isotopes of waters in Altay is scarce, except for atmospheric precipitation. Researchers found that the rainfall in the Altai Mountains during the warm season (April-October) increased significantly from 1959 to 2014. Due to this background of climate condition changes, it is meaningful to study the hydrogen and oxygen isotope compositions of various types of water bodies in the Altay region, at the southern foot of the Altai Mountains.

OBJECTIVESTo obtain the basic data of hydrogen and oxygen isotopic composition of water in Altay and reveal their spatial distribution characteristics.

METHODSHydrogen and oxygen isotope compositions of river water, lake water, spring water, snow water, and water from a mine pit in the Altay region of Xinjiang were determined by liquid water laser isotope analyzer (LGR DT100, America). The dissolved oxygen (DO), TDS, T, and pH of the water samples were measured using the German WTW3430 multi-parameter water quality analyzer. The concentrations of Na⁺, K⁺, Ca²⁺, and Mg²⁺ were analyzed by inductively coupled plasma-optical emission spectrometry (PE8300, PerkinElmer, USA). The concentrations of HCO₃^- and CO₃^2- were determined by alkali titration method. Cl^- and SO₄^2- concentrations were analyzed by ion chromatography method.

RESULTSThe results showed that the ranges of δ¹⁸O and δD of the waters in the Altay area were from -15.4‰ to -5‰ and from -121‰ to -49‰, respectively. The hydrogen and oxygen isotope content of various types of water in the Altay region were significantly different. The δ¹⁸O and δD values of river waters varied from -15.4‰ to -11.5‰ and from -114‰ to -100‰, respectively, and the deuterium excess parameter varied from -12.4‰ to 12.4‰. The δ¹⁸O and δD of Ulungur Lake were much higher than those of surface rivers, with an average value of -5.95‰ and -78.5‰, respectively. The deuterium excess parameter of Ulungur Lake was much lower than those of surface rivers, with an average value of -30.9‰. The δ¹⁸O value (-14.9‰ and -11.8‰) of groundwater was similar to that of surface rivers, but δD (-114‰ and -121‰) was slightly higher than that of surface rivers, indicating that groundwater was supplied by surface rivers but may be affected by water-rock reactions. The δ¹⁸O and δD values of snow water and the water from a mine pit were -11.8‰ and -90‰, -11.6‰ and -106‰, respectively. The fitting lines for hydrogen and oxygen isotopes of the Irtysh River and Ulungur River were δD=1.7297δ¹⁸O-83.879 and δD=1.986δ¹⁸O-76.5, respectively. Surface rivers were remarkably different from the global and Urumqi atmospheric precipitation lines, indicating that apart from atmospheric precipitation, surface rivers were also recharged by glacier meltwater, and underwent evaporation and isotope fractionation during the water cycle.Due to the temperature and latitude effect of hydrogen and oxygen isotopes, the δD and δ¹⁸O showed significant positive correlation relationships with T, TDS, and the molar concentration of major ions such as Na⁺, K⁺, Ca²⁺, Cl^-, and SO₄^2-, also showing a significant negative correlation with the latitude of the sampling sites and DO (P < 0.05, n=32).

CONCLUSIONSThe hydrogen and oxygen isotope composition characteristics obtained in this study provide basic data for the stable isotope research of various types of water bodies in the Altay area.The precipitation in Altay has increased significantly in recent decades. Due to this background, it is indeed necessary to continue to conduct long-term and in-depth systematic research on the composition of hydrogen and oxygen isotopes in Altay's atmospheric precipitation and other types of water bodies.