| Since the inception of mankind on Earth, human activity has gradually become an impact factor in the process of environmental change, and this influence becomes larger and larger. Especially since the Industrial Revolution, The world industrialization level is in rapid development as well as the growth of the world population. With human’s excessive development and utilization on resources and environment, it has caused a series of environmental problems such as global warming; desertification intensified environmental pollution; ecological environmental imbalance; reduction of the forest-steppe, species extinction; soil erosion; water scarcity; the frequency and degree of natural disasters increased and so on. All these issues threaten human’s survival environment hardly. In the need of human’s survival and development, they pay much attention on the change of future global environment or climate and eager to predict the future trend of them. In order to predict future’s global change better, it’s important to have a deep understanding on the past climate and environmental conditions. With the constantly updated and improved of analytical techniques, new discoveries and theories emerge in large numbers which make the studying on paleoclimatic and paleoenvironmental evolution to be the most active areas of international geo-scientists academic atmosphere and have received wide attention all over the world. Since the1980s, the international academic community had carried out a series of global change researches such as:the International Geosphere-Biosphere Plan IGBP, International Human Dimensions Programme on Global Environmental Change IHDP, the World Climate Research Programme WCRP and the DIVERSTITAS, whose purpose is to reveale the global variation and forecast future global trends.The Holocene (from11500years ago to the present) is the second epoch of Quaternary which is the youngest geological epoch. The change of Holocene climate is closely related to the development of human society, all the prosperity, development, advances, prosperous and strong of human civilization are occurred in the Holocene. So it has an important guiding significance for people to treat the Holocene climate as the key research object to human studying of the climate change. Volcanic activity is one of the driving forces in global climate change; it has a profound impact on the human living environment and climate change in spite of the fact that it’s a short but intense geological phenomenon. A Strong volcanic eruption could destroy the city, buried the village, and even lead to regional or global climate change. Therefore, it a key point to obtain a kind of environmental events archival material for studying which has a complete record of the Holocene climate change and volcanic eruption event. Peat is formed in the Quaternary, especially in the Holocene. Its formation and accumulation mainly is controlled by climate, then by the geology, geomorphology, hydrology and other factors. The process of peat formation contains a large number of evolution information of palaeoclimate and paleoenvironment; therefore, as an important research material to recover past global changes, peat plays an important role in the study of global changes.This article took the peat sediment in Northeast China as the research object, which contains palaeoclimatical information, volcanic eruptions and other environmental events. The article discussed the Holocene climate change in Hani peatland and compared it with other regions’ diverse climate proxies, and proved the response relationship between the climate proxies of Hani peat and abrupt climate change events. Meanwhile, we extracted the volcanic ash from Hani and Jinchuan peat profiles, identified relevant volcanic eruption events, explored the relationship between volcanic eruptions and climate changes, compared the volcanic eruption events and information of climate evolution, interpreted and recovered the impact of climate change from Holocene volcanic eruptions, that is, the research of volcanic activity’s climate effects provides some new ways and methods.The major research contents and conclusions of the paper are listed as follows:1.This paper firstly describes the meaning of peat and peatland:peat is organic sediment formed by the plant remains through biochemical action having different degree of decomposition, soft and full of water, the process is under the environment that full of water and anaerobic katolysis; the peatland means habitat of peat. Secondly, this paper analysis the distribution of the peatlands both home and abroad; investigate the relationship between peat and environment; summarize the progress of Holocene climate changes use peat as climate proxies, provide the evidence that peat not only can be used as the archives of climate events, but also provite favourable record through volcanic eruptions.2.In this paper, we chose Northeast China as survey region, select the dammed lake peatland in Hani regions and Maar lake type peatland in Jinchuan as the object of study, describe the study area in geology, geomorphology, hydrology, climate and other conditions detailedly, and summarize the methods and techniques ofresearch.3.In this paper, we establish14C chronology framework through Hani and Jinchuan peat profile:describe the collected peat profile detailedly based on its color and lithologic characters at the sampling lacation of Jinchuan and Hani peatland, and establish lithologic horizon’s control points, get the Hani peat profile geochronologic framework through the AMS14C dating of peat plant cellulose in control points,the9meters long Hani peatland constantly deposited for11930±172years, the age of10meter peat column in Jinchuan peatland profile is6922aB.P.Using the CALIB4.3software regulate the peat’s age, and calculate the relationship between the Hani peat profile correction age and the depth:y=16.78x-619.4, R2=0.992; and the relationship between the Jinchuan peat profile correction age and the depth:y=9.132x, R2=0.934.Use the interpolation method to calculate peat deposition rate of Hani peatland, maximum deposition rate is1.75cm/yr, while the minimum deposition rate is0.07cm/yr; the deposition rate of Jingchuan peat profile is0.663cm/yr as maximum value, the minimum is0.07cm/yr。4. Volcanic ash was identified and extracted from Hani and Jinchuan peat profile respectively, and the methods of extracting volcanic ash from sediments that predecessors had done were summarized. To extract volcanic ash, acidification method was selected in Hani peatland, while thin alkali method in Jinchuan peatland. Volcanic glasses were identified through a polarizing microscope, and the environmental scanning electron microscope was used to analysis the morphology of volcanic ash:under the scanning electron microscope, the surface of the volcanic ash is full of stomata structure with multi-edges and fragmental, overlaped and embedded tightly. The main elements of volcanic ash was measured by electron microprobe technique.resulting that volcanic ash is mainly rock debris, type of trachyte with low potassium content, which shows that volcano eruption is neutraland belongs to mid-term development in which process the early basic rock was carried out5.The absorbance and transmittance of Hani peatland were measured,together with813C and δ18O. Choose absorbance to characterize peat humification, the significance of813C and δ18O to ancient climate were discussed. Combining with the data previously analysised the significance of Hani peat humification to the ancient climate. High value of peat humification indicates warm climate..It goes opposite for the carbon isotopic variation trend with the peat humification.6.On the basis of time series curve of peat humification and the time series curve of δ13C and δ18O of peat cellulose, using multi-index method the Holocene climate evolution of Hani regions was rebuilt, which was mainly divided into six stages:12000aB.P～11200aB.P with the climate of dry and cold,l1500～9800aB.P with the climate of warm and wet,9800～9000aBwith the climate of sharply cooling and dry cleaning,9000～4800kaB.P with the climate of warm,and wet,4800～1800aB.P with the climate of fluctuations between dry and cold with warm and humid;1800～OaB.P with the climate of dry and cold.7. The response of Hani peatlandon8.2ka and4.2ka events of Holocene climate were studied; δ18O time series of Hani peat shows thatit appears a wide δ18O trough on the curve during the period of8.3ka B.P. Further study showed a series of decrease point of δ18O at the period of8.3ka B.P, indicating the existing of a small decline of the δ18O peak. Compare with the813C time series, during about8.1-8.3ka BP δ13C of Hani has three peaks and appears a peak value at8.3ka, which indicated a relatively dry climate. It shows a slightly undulating broad trough in the peat humification curve which shows a long term dry and cold climate during7.8ka-8.3ka period. Contrasted by multi-index in this study has further evidence for the response of the Hani peatland climate proxies to8.2ka climate abrupt events. The4.2ka event response shows that δ13C sequence change strongly and the value increased largely between4.2-4.8ka, which indicated the dry climate. The δ18O curve showed lifting combinations of repeated constantly changes between4.0-5.0ka, at the point of4.3ka the most strongly sharp decline performance that the climate is relatively cold; the values of Hani peat humification fluctuate abnormally during this period with two troughs, and continuously about300a.8.Comparing the climate changes during the three periods in Holocene of Hani peat in regions. Using different regional climate files to discuss the Holocene climate changes from different stages,12.8-11.2ka B.P, Younger Dryas (9.7-11.0ka B.P14C age);11.2-8.0ka B.P, the Early Holocene (7.0-9.7ka B.P14C age);8.0-3.0ka B.P, the Middle Holocene(2.8-7.0ka B.P14C age);3.0-0ka B.P.The Late Holocene(0-2.8ka B.P14C age) shows that as paleoclimate file, Hani peatland not only record climate changes in the region, but also respond to global climate changes,which provide evidence for the researches of global climate changes.9.The distribution characteristics of Holocene volcano in the world and China weresummarized, and the volcanoes condition of northeast China was introduced. This paper reviews the development of volcano climatology, whose method is statistical and numerical simulation. The relationships between volcanic eruption and climate change show in three aspects, which are collection and analysis of basic data, the radioactive effect of volcano aerosol and the climate effect of volcano activity. We have built the time sequence of volcanic eruptions such as (the time sequence of volcanic eruptions in East Asia, VEI>3; the time sequence of volcanoes in Northeast China) and we product the different time scales of the volcano eruption times and VEI cumulative curves. These curves show the trend of Holocene volcano eruption activity, representative of the period4000-4300a B.P.10.Combined with the14C dating data of peat cellulose, using the age-depth modeling, volcanic ash layers have been traced, the age of Jinchuan tephra layer can be calculated to2300-2315a B.P (AMS14C age) and the age of Hani tephra layer is8352±76a B.P.-9604±80a B.P.(AMS14C age). We study the geochemical composition of the tephra, speculated that the tephra of Jinchuan peatland came from the Long-gang volcano group Jinlongdingzi volcanic eruption andthe tephra of Hani peatland came from Changbaishan Tianchi volcanic eruption. The tephra in peat layers deposited represents the dry-cold climate condition, which shows that the volcano eruption event response to climate change.Comparing a series of East Asia volcanic eruption events in δ18O and δ13C and the humification degree curves of peatland from Jinchuan and Hani peatland, we found thatthe neighboring or large scale volcanic eruptions precisely responded to the minimum temperature and humidity. The results show that peatland can conserve Holocene widely volcanic eruption events, and these eruptions can cause the regional climate change, temperature and humidity decrease. Therefore, it is a feasible method to extract tephra and recognize volcanic eruption from peat to analyze the relationship between the climate changes and volcanic eruptions. |
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