Lake Sediments Response To Climate Change For The Past 54 Years In Yangcheng,Shanxi Province.

Paleoclimate reconstruction is of great significance and basis for current understanding global changes and environment evolution in the future.However,the climatic significances of the common geochemical indicators in lake sediments are still multiplicity and uncertainty.Furthermore,there are few studies for lacustrine sediments in Northern China,mainly due to the less lakes as well as great impacts from human activities,which are certain difficulties in carrying out paleoclimate research.Herein,we analysis the meteorological data since Yangcheng Meteorological Station in Shanxi Province.It mainly focus on the the annual variation,seasonal variation,mutation and extreme climate events of meteorological indicators,including precipitation,temperature,wind speed and sunshine hours.Combined with the organic carbon content?TOC?,nitrogen content?TN?,carbon/nitrogen ratio?C/N?,organic carbon isotope(?¹³C),total nitrogen isotope(?¹⁵N)and element abundances in sediments of the Niangniang Lake in Shengwangping,Yangcheng.The results of XRF scanning elements such as Al,K,Ca,Ba,Rb,Si,Sr,and Zr were analyzed,and the potential relationship between the meteorological data and the sediment geochemical indicators is investigated.Through the comparative study for different indicators,we obtained the following preliminary results:?1?The inter-annual variation of meteorological elements in the Yangcheng of Shanxi since 1957 have significant fluctuations,and the annual and seasonal variations of precipitation,temperature,wind speed and sunshine hours are significantly different.The correlation between annual precipitation and extreme precipitation index is high.The extreme precipitation index is supposed to be a good indicator for the annual precipitation in Yangcheng area.The temperature trend in the Yangcheng is accompanied with the global warming trend,with the largest increase in the winter and spring.?2?TOC and TN displayed similar trends and began to rise rapidly after 1980,which was related to the increase in annual average temperature in Yangcheng area and the gradual strengthening of human activities.The C/N ratio indicates that the source of organic matter in the sediments of the SHENG Wangping Lake in mainly comes from lake aquatic algae and various aquatic plants.The trend of TOC and TN is consistent with the trend of growth season length?GSL?.?3?The?¹³C value indicates that the vegetation is dominated by C3 plants.The?¹⁵N value has a tendency of overall positive deviation,indicating the trend of eutrophication of the water in Sheng Wangping Niangniang Lake.The?¹³C index shows a gradual negative trend in the whole core,and there is a certain relationship with the annual precipitation and extreme precipitation index,especially in comparison with spring and summer precipitation have many details?4?Elements such as Ti,Al,K,Ba and Rb derived from weathering of rock and soil which respond to changes in average temperature difference in Yangcheng,especially similar to the spring average temperature difference.?5?There is a strong correlation between Ca/Sr,Ti/Sr,Ca/Zr and Ti/Zr,which is consistent with the annual average temperature,annual precipitation and the temperature of growth period trend.When the climate is relatively warm and humid,the ratios of Ca/Sr,Ti/Sr,Ca/Zr,Ti/Zr are relatively high,and when the climate is relatively cold and dry,Ca/Sr,Ti/Sr,Ca/Zr,Ti/The Zr ratio is relatively low.?6?The relative abundance of Si,Sr and Zr elements responds well to changes in wind speed.Among them,annual average wind speed and spring average wind speed have the greatest influence on the content of Si,Sr and Zr elements.Zr is also affected by annual precipitation and extreme precipitation index.