| Abrupt paleo-climate and-environment events occurred in the history, one of the key points in the paleoclimate research, are strongly important for further understanding of the mechanisms for the global climate change. As the time goes by, the climate and environment condition becomes much more complex. Since the mid-20th century, climate and environment events related to both nature and human reasons have occurred much frequently. Researchers paid much more attentions to these events. More proper materials and suitable indicators are needed to distinguish the nature and anthropogenic reasons for these events in different study areas and would be useful for better understanding the impact process.In the present study, the desiccation cracks discovered in Zhoushan Archipelago, East China Sea, the sediment core named38002, collected from Northern Yellow Sea Mud, as well as moss, topsoils, and a peat bog named BI, collected from Ny-Alesund, Arctic, were studied. Combining with the chronological, mineralogical, palynological, and geochemical results, the climate and environment change events could be reconstructed from these materials. In this paper, we tried to find more reliable materials and proxies for the further understanding of the thousand-year time-scale paleoclimate shift event and the climate and environment change events caused by nature and anthropogenic reasons during these centuries. It might be helpful for the climate prediction in the future. At the same time, different kinds of proxies and sampling methods were considered according to the environment and time-scales.The main contents are summarized as follows:1. Climate shift event recorded in the desiccation cracks discovered in Zhujiajian Island, Zhoushan Archipelago, Zhejiang ProvinceDesiccation crack, a kind of common and clear structures of ancient strata, has mainly been used as an evidence for sedimentary sequences. Few works have been done on the applications in paleoclimate and paleoenvironment research. Furthermore, the chronology character of desiccation cracks has been limited reported.Large desiccation cracks, discovered in the intertidal zone of Zhujiajian Island, Zhejiang Province, were performed with chronological, palynological, mineralogical, and elemental geochemical analyses. By contrasting with the different proxies’results of the host sediment, the overlying sediment and filling sediment, we reconstructed the formation of the desiccation cracks.Results showed that, the desiccation crack found in Zhujiajian Island, formed around31.2-30.4cal ka B.P., was very likely the production of an abrupt climate shift event. During the cracks period, the climate condition seemed to be much colder and more arid, with a decline in vegetation. The desiccation crack reflected a sudden climate change of the local ecosystem. Compared with different results indicated from other proxies, the climate event, inferred from the desiccation cracks in Zhujiajian Island, is quite likely linked to Heinrich event3via the East Asian Monsoon.Desiccation cracks may provide a new proxy material for study paleoclimate and paleoenvironment in the Quaternary.2. Climate and environment events recorded in the sediment core from Northern Yellow Sea Mud The reconstruction of the climate and environment events related to natural and anthropogenic reasons could provide useful scientific formation to discuss the principles and mechanisms. However, different proxies from the environment materials might be with different sensitivities to different events.In the present study, a sediment core, named38002, was collected from the Northern Yellow Sea Mud. The sedimentary analyses, including the chronology information, grain size, as well as the elements contents, were performed. Combining with the former researches, the climate and environment events suggested in the sediment core were discussed.The chronology result showed that, the average sedimentation rate was0.13cm/yr, therefore, the time span of the core is1755-2009AD. The sediment might provide the climate and environment change information during the past250years in the study area. The sedimentary characteristics showed that the study area was strongly influenced by the rivers surrounding Bohai Sea, and especially by Yellow River during the past150years.The variation of different proxies from the sediment core might provide some information of the climate and environment change event occurred in the Chinese Mainland. The characters of sort coefficient of grain size, the organic proxies (TOC, TN and TOC/TN), and kinds of elements ratios (Ni/Al, Mn/Al, Cr/Al, Co/Al, and Se/Al) showed great variation in the depth of21cm, indicating the relocation of the Yellow River in1855AD. The relocations of the Yellow River entrance in1938AD and1978AD were also found in the sediment core according to the sort coefficient. The increasing trends of the elements (Pb, Zn, Se, TOC, TC, TN, and so on) changed a lot in the surface10cm (1950AD), suggesting the development of China.The sedimentary characteristics of sediment core collected from Northern Yellow Sea Mud were considered as the implication for several major historical events occurred in China. Furthermore, these events might provide an accurate dating method in the study area.3. Climate and environment records achieved in moss, topsoils, and peat bogs from Ny-Alesund, ArcticNy-Alesund, Arctic was far from the human society, with no obvious local pollution source. Contracting with other places at the same latitude, there were much more plants and animals in Ny-Alesund. Therefore, it was considered as one of the most important areas for the study of global climate change and the distribution and spread of pollutions.1) The moss(Dicranum angustum) and topsoil samples were collected in both disturbed and undisturbed areas in Ny-Alesund. Sb concentrations in all the samples as well as coal and gangue were examined. We discuss the biogeochemical process of Sb in different materials, and try to explain the Sb distribution in the study area.Results show that the average Sb concentration of coal and gangue from Ny-Alesund is only0.1mg/kg (mean value). Therefore, the weathering process of local coal bed could not contribute to the increase of Sb concentrations in topsoil and moss in the study area.The reference value of Sb in the topsoils from Ny-Alesund is0.313mg/kg, which is much lower than the predicted baseline Sb concentration for soil, suggesting that the Sb level in soil is unlikely to be hazardous. The distribution of Sb in topsoil samples was partially associated with traffic and historical mining activities. In addition, the decrease of Sb content in topsoil may be caused by the washing of snow water and seawater.The reference value of Sb in moss from Ny-Alesund is0.108mg/kg. The appearance of the peak value of Sb concentration in moss was related with the location of sampling sites and wind field in the study area. Compared with topsoils, Sb in moss could reflect its accumulation on a larger and longer scale. Therefore, moss could be used to estimate Sb pollution level in both highly and lightly polluted areas.2) The peat bog named BI was collected in Juttahomen Island, Arctic. The analysis of210Pb,137Cs, and elements were performed to the subsamples. The expression process of major pollution element in the peat bog was discussed.The peat bog sediments were composed of the vegetations, sedentary product of local bedrock, and droppings of seabirds. Since the210Pb and137Cs results were strongly influenced by the vegetations, and the contents of the vegetations changed a lot in the profile, the results of these radio isotopes should be calibrated before the establishment of sediment chronology.The concentrations of the elements, as well as the Factor analysis results showed that Hg, Pb, and Sb accumulated in the samples were mainly transported via atmosphere. The contents of Hg and Pb might be influenced by the activities of seabirds via the droppings. However, the variation of Sb content is mainly correlated with local vegetations, and influenced by the absorption of moss. |
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