Sediment records of Sb and Pb stable isotopic ratios in Lake Qinghai Libin Xu a , Fengchang Wu a, ⁎, Jian Zheng b , Qianli Xie c , Huixian Li a , Haiqing Liao a , Xiaoli Zhao a , Fei Guo a a State Environmental Protection Key Laboratory for Lake Pollution Control, Chinese Research Academy of Environmental Sciences, Beijing 100012, China b Nakaminato Laboratory for Marine Radioecology, Environmental Radiation Effects Research Group, National Institute of Radiological Sciences, Hitachinaka, Ibaraki, 311-1202, Japan c Worsfold Water Quality Centre, Trent University, Peterborough, ON, Canada K9H 7B8 abstract article info Article history: Received 25 January 2010 Received in revised form 11 May 2010 Accepted 25 May 2010 Available online 4 June 2010 Keywords: Antimony Sediment Lake Qinghai Pb isotopic ratios A sediment core in Lake Qinghai in northwest China was collected in 2006. 137 Cs and 210 Pb activities were analyzed to investigate the chronology of the sediment core. Sb and Pb concentrations, and Pb stable isotopic ratios were analyzed to study the historical atmospheric deposition records and sources of Sb over the past 15 centuries. The Sb concentration was 4.21 ± 1.52 μg/g in the sediments, its vertical distribution of Sb shows three large peaks in the recent two centuries, 1799, 1896 and 1944, coincided with Sb contamination from large wars, respectively. The peak in 1920 responded the large earthquake that happened in northern China, which was not far away from Lake Qinghai. The Sb/Pb ratio, 206 Pb/ 207 Pb and 208 Pb/ 206 Pb results suggest that Sb and Pb were probably from the ores in South China and coals in North China before 1965, but obviously from uses of leaded gasoline after 1965. © 2010 Elsevier B.V. All rights reserved. 1. Introduction Antimony (Sb) is increasingly being identified as a toxic environmental pollutant and has been implicated in cancer develop- ment [1–3]. It is ubiquitous in the environment, but has not been paid enough attention until recently. Growing body of evidence suggests that human activities have had, and continue to have, a tremendous influence on its environmental geochemical cycle [4,5]. Antimony is commonly enriched in practically all metal sulfide ores (especially those of Pb, Fe and Cu) as well as coal, and it is mainly used in storage batteries, antifriction alloys, cable sheathing, electrodes, type-metal, small arms and tracer bullets, and flame retardants. Sb studies of peat bog profiles from both Switzerland [6] and Faroe Islands [4] showed remarkable atmospheric Pb and Sb contaminations in the Roman Period, which not only indicated the long history of atmospheric Sb contamination in Europe, but also the significance of long range atmospheric transport of Sb from smelting of lead ores [4]. The comparison of Sb and Pb profiles over the past 2500 years in peat bog of Scotland also showed discernible peaks during both Mediaeval and Roman/pre-Roman periods, with evidence from Pb isotopic ratios indicating the source of Pb ores indigenous to Britain [7]. Antimony research of sediment cores in Sweden suggested that the impact of diagenesis on Sb redistribution was minor, and Sb concentration showed intense accumulation after Second World War [8]. China has the biggest Sb reserves in the world [9], but there were no studies on the Sb history in China yet. In this study, we focused on the sediment core of Lake Qinghai in Qinghai Province, which is the biggest inland lake in China, and our aim is to study the historical use and also the source origins of Sb in China. 2. Sampling and methods Lake Qinghai (N: 36°32′–37°15′, E: 99°36′–100°16′) is the biggest inland lake in China with an area of 4583 km 2 in the northeast of Qinghai Plateau. It is also a salty lake with mountains surrounding it. Its main supplies are precipitation and snow-ice melt water. There are no big cities and few people lived around it. So the main source of Sb and Pb was atmospheric deposition. A sediment core (48 cm) named QH-5 (N: 36°46′7.8″, E: 100°15′ 34.9″) was collected with a gravity corer in Lake Qinghai in August of 2006 (Fig. 1). The tube was airproofed on site and kept in frozen environment and then transported to laboratory for processing. They were sliced in 0.5 or 1 cm subsamples before freeze-dried and homogenized in a mortar. Sb, Pb and Pb isotopic ratios (including 204 Pb/ 208 Pb, 206 Pb/ 208 Pb and 207 Pb/ 208 Pb) were analyzed in Trent University of Canada. Metal analyses were made with ICP-MS (ELEMENT 2, Finnigan MAT GmbH, Bremen, Germany) in a clean room using an ultrasonic nebulizer (USN6000AT, Cetac Technologies, Omaha, NE, USA). External calibra- tion was applied while using 103 Rh as internal standard. Quality assurance included the analysis of certified reference material (NIST- 2709). ICP-MS measurements of Pb isotopic ratios used the common lead reference from the National Institute of Standard Technology (NIST SRM 981) for mass bias correction. The analysis was repeated when the differences between the measured and certified values of the standard reference materials exceeded 0.5%. The Pb counts of the Microchemical Journal 97 (2011) 25–29 ⁎ Corresponding author. Tel.: +86 10 84915312. E-mail address: wufengchang@vip.skleg.cn (F. Wu). 0026-265X/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.microc.2010.05.012 Contents lists available at ScienceDirect Microchemical Journal journal homepage: www.elsevier.com/locate/microc