Houyun Zhou

Arsenic in a Speleothem from Central China: Stadial-Interstadial Variations and Implications

In a pilot study, arsenic in a stalagmite (SJ3) collected from Central China was measured, and its association with past climate and environment was explored. Most of the SJ3 arsenic concentrations ranged from 120 to 320 ppb with the highest concentrations associated with relatively warm and humid climatic phases and lowest concentrations with cold and dry phases. The SJ3 arsenic record was very similar to the manganese record of SJ3. Variations of arsenic in SJ3 might be controlled by metal oxides of iron, manganese, and aluminum in karst groundwater at the study site, which in turn were closely related with changes in past climate and environment. A considerable proportion of arsenic was in excess over manganese in SJ3, which might be related with incorporation of arsenic into the calcite lattice during the formation of SJ3. It was speculated that more arsenic was released due to stronger weathering of the surface soils and sequestrated by metal oxides in karst groundwater under warm-humid climatic phases than under cold-dry phases. This suggested that climate shift might alter arsenic balance in sedimentary areas and aquifer systems and potentially exert significant influence on global arsenic contamination.

Age dating of lacustrine sediments in Lake Tianshuihai of the Tibetan Plateau by using U-series isochron method and its significance

The age of the clastic-clay sediments with varied content of carbonate in core TS95 taken from the Lake Tianshuihai in the northwest of the Tibetan Plateau was determined successfully by using the total sample dissolution U-series isochron method for the first time. With this method, the serial absolute timescale (isotope time scale) covered the last 240 ka in the main body of the Tibetan Plateau with a sea level up to 4000 m is also established for the first time, thereby laying the foundation for the research on the paleoclimate and palaeoenvironment in the Lake Tianshuihai region as well as the relationship between evolution of the Tibetan Plateau and global changes. In addition to a brief introduction of the basic principles, the procedures of experiments, and the results, this note also presents the adaptability and superiority of this method as well as its possible problems.

R/S analyses of some geochemical indexes for Tianshuihai Lake core in West Kunlun Mountain and their environmental implications

With the decrease of global temperature, glacial epoch came over the earth and global climate fluctuated over a great range since the beginning of Quaternary. Paleoclimotologists of various countries have focussed attention to the periodic characteristics and dynamics of climatic fluctuation in the past many years (Berger, 1977; Imbrie and Hays, 1984; Ding Zhongli et al., 1990; Yu Zhiwei et al., 1992; Liu Youmei et al., 1996). Although some of the workers have paid their attention to the nonlinear characteristics of the global Quaternary environmental evolution (Nicolis and Nicolis, 1984; Lu Houyuan et al., 1993), it is worth while to do this kind of work in some special areas in the world, for example the Qinghai-Tibet Plateau.UsingR/S analysis, the authors calculated the Hurst indexesH of some geochemical proxies, including organic carbon, FeO, Fe2O3 and FeO/ Fe2O3, from the Tianshuihai Lake core in West Kunlun Mountain of the Qinghai-Tibet Plateau. The proxies satisfy the Hurst law withHorg.carbon = 0.735,HFe2O3 = 0.757,HFeO = 0.848 andHFeO/Fe2O3 = 0.646. All the indexes are greater than 0.5, meaning that from 240 to 15 ka B. P., there were some long-run dependencies-persistence in the climatic and environmental evolution around the Tianshuihai Lake area. This is in accordance with the climate there from 240 to 15 ka B. P. (Yu Suhua et al., 1996). The paleo-climate and paleo-environment evolution around the Tianshuihai Lake area is of persistence as well as of fluctuation and is a combination of these two components. There are some differences between the four Hurst indexes, which probably resulted from the different intensities of persistence of the four proxies, organic carbon, FeO, Fe2O3 and FeO/ Fe2O3, or from the change of drainage system around the Tianshuihai Lake area from openness to closeness(Li Bingyuan et al., 1991; Sun Honglie, 1996; Shi Yafeng et al., 1998).The Qinghai-Tibet plateau was the starter and sensor of the climatic and environmental variation of the surrounding areas (Yao Tandong et al., 1991; Feng Song et al., 1998) and some other scientists even regarded it as the driver and amplifier of global climatic variations (Pan Baotian and Li Jijun, 1996). The persistence in which the climate and environment around the Tianshuihai Lake area evolved from 240 to 15 ka B. P. is probably a function of the continuous uplift of the plateau in the same period of time.