Study Of Oxygen And Hydrogen Isotopes Feature In Tamarix Cone And Environmental Change In Lop Nur Region

Lop Nur region is located in the hinterland of the Eurasian continent, and it is an extreme arid zone in the world. It is adjacent to Aljin Mountain in the south, and Kuruktag Mountain in the north, the Yumen Guan and Yang Guan in the east, the Taklimakan Desert in the west. Lop Nur is the accordant junction area of every river in Tarim Basin. The change of the environment in Lop Nur is a symbol for that of all the area in Tarim Basin and mountanious region around.Arid zone is an important part of the earth surface system. It has a unique characteristic of environmental change. New research for this area is needed to complete the global change science system. Tamarix Cone is a kind of biological landform and it provide a new means for the climatic factors of ancient environment reconstructiong from the two aspects both high-resolution dating and information in the carrier.Tamarix Cones in Lop Nur region are mainly distributed in the south and west and northwest, along the river, lake coastal and delta regions. Tamarix Cone is mainly deposited by the twigs and leaves of Tamarix and sand layers. Mostly, the Tamarix Cone has clear sediment layer, like tree-rings. And it has a function of exactly dating and environmental information storage.In this paper, the Tamarix Cone is the main object of study. Moving average method is used in this paper to pretreatment the data ofδD values andδ¹⁸O values, and then through the correlation analysis, the result thatδD0 andδ¹⁸O₀ has a prominent correlation (r=0.32, p=0). Then the theoretical relationships between hydrogen isotope and air temperature, RH and precipitation are analysed, and also the oxygen isotope. The course of environment change in Lop Nur area in the last more than 160 years is sutdied. And the main process and conclusions are as follows:(1) Through the correlation analysis betweenδDma and the monthly mean minimum temperature, relative humidity, it is demonstrated that the relationship ofδD and the minimum temperature in the season when the Tamarix is growing bloomly is positive correlation. And that is negative correlation betweenδD and RH. The results are all the same as the previous study.(2)δDma as well asδ¹⁸Oma has a negative correlationship with precipitation in Tamarix growing season, which reveals the effect of the precipitation rain fall. This is related with the surroundings where the Tamarix growing.(3) The average minimum temperature in March is reconstructed. And the change scope of the average minimum temperature in March is less than 1℃in the last more than 160 years. That is because the information of temperature changing is easily lost in the Tamarix growing time.(4) The average RH from February to April is also reconstructed. And it reveals that the change of average RH from February to April has a certain periodity, but the periods has an attenuation phenomena, indicating human activities affecting the climate in the region is increasingly apparent.(5) Based on the changing trend of the mean temperature in March, three phases is divided as follows:â‘ 1844¹927, the temperature fluctuation is small, and there are several alternation between the cold and the warm periods;â‘¡T he period of 1828¹963 is an obviously warm time which lasted reach to 36 years;â‘¢It can be ensured that the period of 1964²006 is totally cold time, but in the time of 1969¹973 and 2002²006, the air temperature has a rising trend which are short durations.(6) Through the study, we found that in a longer time scale, the climate of Lop Nur region before the middle of the 1960s is relatively dry; after the middle of the 1960s, the precipitation began to increase in the region, and this time totally belongs to the relative wet period. In this paper, the total precipitation in July can serve as a basis for division of the wet and the dry period, with which the wet and dry periods of Lop Nur area is reconstructed.