Determination Of Trace Elements In Stalagmites By ICP-MS And The Research For Paleoclimate Reconstruction In Western Of Henan Province,China During MIS8/9

The past climate change is one of the most important parts in the investigation of the global changes.Exploring how the climate changed in the geological period does benefit to the prediction of the climate change in the future which has been very emergent beeause of the serious environmental crisis now.There are many advantages to research past global changes in China, on the one hand, which have some global general climatic characteristics induced by global atmospheric physical system; on the other hand, which have some unique climatic characteristics induced by special geographical location. Therefore, researching past global climate changes of China have very significant advances on establishing global climate changes model and forecasting local climate changes in China. Along with the research of the cave secondary sediment deposition process, people come to realize that like deep sea and lakes chemical sediment core, loess, ice core, tree wheel, and coral, cave is also an important natural environmental history file. There has nothing geological records can replace it in the annual and seasonal time scale reconstruction of climate and environment change, and it has become the ideal carrier in the comprehensive research of climate and ecological environment change since hundreds of thousands years.This research set stalagmites of Laomu Cave as the main research object which located in Luanchuan, Henan Province, southeastern coast of the loess plateau. Through discussing modern monitoring data for the Jiguan Cave of Luanchuan area, we can explored the relationship between the precipitation and cave drops and the response mechanism of cave drops of trace elements to the modern environmental change.We also discussed the testing technology of ICP-MS for trace elements to providing technical support for more index comparison of stalagmites. Based on the above content analysis, we use oxygen、carbon isotopes and trace elements of the stalagmites of Laomu Cave recoverying the ancient climate change history during 315～257 ka BP. After preliminary discussed the possible driving mechanism of the climate change and control factors of trace elements.we conclude that:(1) For more stalagmites index comparison of reconstruction of ancient climate, testing technology of trace elements of stalagmites providing a very important actual significance.ICP-MS technology has its unique advantages in the inspection of testing trace elements of stalagmite. On the basic of understand the ICP-MS detection technology principle and master the analysis performance, we discussed the analysis method of stalagmites’ trace elements, such as Mg、Sr、Ba、U、Mn、Al、V、Li.(2) The precipitation of the study area Luanchuan is mainly concentrated in the June to October, and less in November to next May, accounting for only 20% of the annual precipitation.The variable characteristic of precipitation oxygen isotope in Luanchuan is generally lighter in summer than in winter. Judging from the full-year scale, Oxygen isotope values have the obvious effect of precipitation, butδ18O of precipitation has little temperature effect. Drop rate of dripping water can be rapid response to changes in precipitation in Jiguand cave, but we can not rule out the retention of water enter water droplets. So when we restore the ancient climate information, we must take the impact of mixed water into account. The contents and ratios of trace element in dripping water are basically controlled by precipitation in Jiguan cave within the observation period, so it can be better reflect the seasonal changes in precipitation and have certain indicating significance on special climate phenomenon. But there are still many unexplained phenomena what we need further research. Moreover, by monitoring two drop water from Jiguan caves, we can find:due to differences of environmental conditions in the overlying cave and differences of the supply path of each dropping water, the drop rate have wide difference in same cave. Bcause factors affecting trace elements in stalagmite is more complex, and the contents and ratios of trace element in each dropp water have some differences, so when using trace elements in stalagmite to reconstruct the paleoclimate, we must carefully select the samples. But long-term drop rates observations show that cave dripp water have obvious response to the change of the climate, it is the feasible foundation that we use stalagmite to reconstruct paleoclimate.(3) Based on 205 oxygen and carbon isotopic dates a record of internal structures and variation features of the Asian Summer Monsoon(ASM) in the Northern of China was reestablished during the Antepenultimate Glacial MIS8/9 from stalagmite LM-1 in Laomu Cave, the west of Henan Province, China. Theδ180 value of stalagmite LM-1 is similar to that of the stalagmite LZ-15, in Shennongjia, Hubei Province, China. The record of the two stalagmites have some correlation with the same period of summer solar radiation of north latitude 65, which shows that the southeast of the Loess Plateau and the middle and lower reaches of the Yangtze River are controlled by the same climate system in the MIS8/9 and solar radiation is still the direct factor of variation of the Asian Monsoon in the orbital scale. Theδ13C record is similar to theδ180 record of stalagmite LZ-15, and both with typical precession cycle, and show that temperatures and changing of rainfall by the orbit driven are main factor. During the transition of MIS8/9, the record of LM-1 shows the same trends with the decline of CO2 content from the Ice core Vostok, Antarctic. So we can infer that the content of CO2, CH4 and NO2 changing may amplify the climate fluctuation caused by the orbit driven.(4) The trace elements of stalagmite of Laomu Cave is better responded to the changes of external climatic conditions, it can also refers to ancient climate with a good significance. Through the combine of stalagmite stable isotope with trace elements, we can complete the reconstruction of the change of the old climate. The relationship between Mg/Ca andδ13C is positive correlation. The temperature lead the change of LM-1 carbon isotope and magnesium partly coefficient, but it isn’t the main factor of the change of ratio of Mg/Ca. The Degassing of CO2 and the prior calcite precipitation (PCP) of carbonate may be the main fators that lead the relationship betweenδ13C and Mg/Ca. Therefore, the change ratio of Mg/Ca is mainly controled by the PCP which is caused by change of precipitation. At the same time, the trends of Sr/Ca、Ba/Ca and U/Ca have showed a high degree of consistency, they also have a good correlation coefficient, this imply that the three factors my be controled by the common factors, the change of this three is absolutely the same with the change ofδ18O, therefore, we can infer that the change of Sr/Ca、Ba/C and U/Ca are mainly controled by percipitation and the PCP. In the same time, the surface vegetation、overlying soil and atmospheric dust can also effect them. The trend of the change of Mn/Ca、Al/Ca、V/Ca and Li/Ca are absolutely same, whose characteristic is the same as pulse, and it have some relationships with the growth rate, so we can deduce that it has some response relationships with the climate change, it is also affected by precipitation, colloidal/particle phases of elements and hydrodynamic. In view of the trace element’s complexity in the Karst Dynamic System, we should enhance the mechanism research in the work of future.