Stable isotopic characteristics of precipitation in Lanzhou City and its surrounding areas, Northwest China.

Based on the precipitation samples obtained at Lanzhou City (36°06′N, 103°44′E, 1,548 m a.s.l.) in western China and its surrounding counties (Yongdeng, Gaolan, and Yuzhong) from April 2011 to February 2013, the characteristics of stable isotopes in precipitation and the correlations between δO and meteorological factors were analyzed. The LMWL (local meteoric water line) of Lanzhou City and its surrounding areas was calculated, and the order of LMWL slopes in the four stations is Yuzhong (7.70) > Lanzhou (7.57) > Yongdeng (7.24) > Gaolan (6.80). Both the slope and intercept of the LMWLs for each station are less than those of the global meteoric water line. There is a weakly positive correlation between δO and air temperature, and the correlation between δO and precipitation amount is weakly negative. Evidenced from the slope and intercept of LMWL and the relationship between δO and relative humidity, there is secondary evaporation when the precipitation falls from clouds to the ground. [ABSTRACT FROM AUTHOR]