A Muztagata ice core recovered at 7010 m altitude in East Pamirs provides a Pb concentration record from 1955 to 2000. The result reveals in- creasing Pb concentrations from 1955 to 1993, with two Pb concentration peaks in 1980 and 1993. After 1993, Pb concentrations in ice core show an obvi- ously declining trend. Analysis shows that the lead in the Muztagata ice core mainly came from anthropo- genic emissions from countries in Central Asia, while the local emission had little contribution.
Vertical distribution of the main bacteria isolated from the Muztagata ice core (about 22.4 m) was investigated by means of cultivation and 16S rRNA sequence analysis. The results showed that the amount of culturable bacteria fluctuated with ice core depth, and was more in dirty layer than in clean ice, which suggested the close corresponding relationship between high input of the bacteria deposited by wind and snowflow and dirty layer. Most of the bacteria were psychrophiles and psychrotolerants, including α- and γ-proteobacteria, Cryobacterium psychro-philum, CFB (Cytophaga-Flavobacterium-Bacteroides) group, high-G+C gram-positive bacteria (HGC). Acinetobacter sp. and HGC repeatly occurred in different ice depths, and their quantita-tive distribution was consistent with the change of the total amount of culturable bacteria with depth, which suggested the main bio-indicator; while Flavobacterium, Cryobacterium psychro-philum, and α-proteobacteria, also functioned as a secondary indicator of climatic and environ-mental changes. This study is the first report concerning continuous quantitative variation and pattern of the main culturable bacteria in ice core section.
XIANG Shurong1, YAO Tandong1, 2, AN Lizhe1, 3, WU Guangjian2, XU Baiqing2, MA Xiaojun 3, LI Zhen1, WANG Junxia1 & YU Wusheng1 1. Key Laboratory of Ice Core and Cold Regions Environment, Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou 730000, China
The paleoclimate data recovered from ice cores, tree rings and lake sediments indicate regional features of climatic change on the Tibetan Plateau (TP) during the last 2000 years. The composite temperature reconstructions indicate that several main climatic episodes, such as the 揕ittle Ice Age?between 1400 and 1900, the 揗edieval Warm Period?in 1150—1400, a less warm period in 800—1100, and an earlier cold period between the 3rd and 5th centuries, occurred in the TP. In addition, temperature varied from region to region. The period from AD 800 to 1100, which was warm in northeastern TP, was contemporaneous with cooling in the western and southern TP. The southern TP experienced warming between 1150 and 1400. For western TP, the d 18O records of the Guliya ice core indicate that the period 1250—1500 witnessed a clear warming. Large-scale trends in the temperature history from northeastern TP are more similar to those in eastern China than are the trends from the Guliya ice cap far to the west and southern TP. The most prominent similarities between the temperature variations of the TP and eastern China are such cold phases as 1100—1150, 1500—1550, 1650—1700 and 1800—1850, and the latter three cold events match with three widespread glacial advances which occurred on the TP during the Little Ice Age.
