Lead isotopic composition of insoluble particles from widespread mountain glaciers in western China: Natural vs. anthropogenic sources Guangming Yu a , Jianzhong Xu a, * , Shichang Kang b , Qianggong Zhang b , Jie Huang b , Qian Ren a , Jiawen Ren a , Dahe Qin a a State Key Laboratory of Cryospheric Sciences, Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, No 360 Donggang West Road, Lanzhou 730000, PR China b Key Laboratory of Tibetan Environment Changes and Land Surface Processes, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100101, PR China highlights  Snowpit samples were collected in mountain glaciers of Western China.  Lead (Pb) isotopic compositions in insoluble particle of snow samples show geographic trend.  The anthropogenic lead contributions in snow samples are observed and assessed. article info Article history: Received 27 November 2012 Received in revised form 2 April 2013 Accepted 8 April 2013 Keywords: Stable lead isotopes Insoluble particles Snowpit Qinghai-Xizang (Tibet) Plateau Western China abstract Stable lead (Pb) isotopic fingerprints provide opportunities to trace natural and anthropogenic Pb sources in the environment. In order to evaluate Pb deposition from different sources over mountainous areas of western China, Pb isotopic compositions were characterized from modern aeolian dust in 15 snowpit samples collected from 13 typical mountain glaciers between 2008 and 2010. Most of the snowpits sampled cover more than a whole year of accumulation and overlap with each other on deposition date. Pb isotopic variability among all the samples is small, varying in the range of 18.1399e18.9199 for 206 Pb/ 204 Pb, 15.5979e15.8743 for 207 Pb/ 204 Pb, 38.2272e39.9453 for 208 Pb/ 204 Pb, 1.1605e1.2009 for 206 Pb/ 207 Pb and 2.4433e2.5182 for 208 Pb/ 207 Pb. Three isotopic plots of the different Pb isotope ratios ( 207 Pb/ 204 Pb vs. 206 Pb/ 204 Pb, 208 Pb/ 204 Pb vs. 206 Pb/ 204 Pb, and 208 Pb/ 207 Pb vs. 206 Pb/ 207 Pb) in all the sam- ples show identical geographic trends, with more radiogenic in the south and less in the north. This trend is consistent with the distribution of natural dust sources and supports the interpretation of a regional/ local source for insoluble particles (IP) to snow/glaciers in this region. Comparison with the Pb isotope results from potential dust sources, however, it shows that the Pb isotopic compositions of IP samples in snow samples are relatively less radiogenic. Parts of these less-radiogenic Pb isotopes are comparable with the ice core results during recent decades, which are shown to be influenced by anthropogenic sources. At sites located along the periphery of western China, the Pb isotopic compositions are much closer to anthropogenic results. Natural and anthropogenic Pb sources are roughly assessed using a simple binary model. The sites with a high anthropogenic fraction are at lower elevations and are relatively close to population centers. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction Western China defined herein as the area encompassing the Qinghai-Xizang (Tibet) Plateau (QXP) and northwestern China, covers more than 4,500,000 km 2 , almost half of China’s land area. It is a region of widespread mountains and arid/semi-arid areas. The QXP, a vast highland surrounded by the earth’s highest mountains including the Himalayas, Pamir, and Kunlun Shan, and sometimes called earth’s “third pole”, has an area of around 2,500,000 km 2 with an average elevation exceeding 4,500 m a.s.l. The region of northwestern China lies to the north of the QXP, and consists of two large deserts, the Taklimakan Desert and the Gurbantunggut Desert, which are separated by the Tienshan Mountains. The huge highland and mountainous areas of the QXP exert a profound * Corresponding author. Tel.: þ86 931 4967352. E-mail address: jzxu@lzb.ac.cn (J. Xu). Contents lists available at SciVerse ScienceDirect Atmospheric Environment journal homepage: www.elsevier.com/locate/atmosenv 1352-2310/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.atmosenv.2013.04.018 Atmospheric Environment 75 (2013) 224e232