Research On The Interannual Variability Of Cave Climatic Environment And Trace Elements Of Drip Water In Kaiyuan Cave, Shandong, China

In recent years,many important achievements in the study of paleoclimate and paleoenvironment had been obtained with the help of speleothem records in karst cave.Large amounts of paleoclimatic and paleoenvironmental information were recorded by stalagmites in Karst cave,but the climatic and environmental implications of these proxies were still uncertainly using these records to reconstruct the paleoclimate and paleoenvironment,and need to be corrected by modern environment and monitoring technology.Some important achievements of the reconstruction of the paleoclimate and paleoenvironment in Shandong Peninsula Some had been obtained based on the study of the thickness of laminae,the ?13C and ?18O ratios,and the trace elements in the stalagmite of Kaiyuan cave.The speleothems in the cave were formed by the dissolution and deposition of drip water,and the change information of the paleoclimate and paleoenvironment outside the cave were recorded by speleothems through drip water.The monitoring of internal cave environment and the research on the change of cave drip water hydrochemistry indexes are helpful for clarifying the change and influence mechanism between hydrogeochemical properties of the cave drip water and the climate and environment outside the cave.It is important to extract paleoclimate and paleoenvironment information which is recorded by speleothems.The accuracy of the interpretation of alternative indexes can also be improved.This paper chose Kaiyuan cave as the research object which cave is located in Shandong Province,had a 3-year continuous monitoring of the cave air environment indicators and drip water in Kaiyuan Cave since December 31,2011.The main monitoring indicators included caves air temperature,relative humidity,CO₂ concentration,drip rates,conductivity,pH values and trace elements ion concentration(Ca²⁺,Ba²⁺,Mg²⁺,Sr²⁺)and its ratios?Mg/Ca,Sr/Ca,Ba/Ca?,the variations and their influencing factors of the indicators of the cave climatic environment and drip water in Kaiyuan Cave were also analyzed in the aspects of hydrology and hydrochemistry.Furthermore,the atmospheric temperature and precipitation of the local meteorological stations during the cave monitoring period were also collected.According to the comparative analysis of the above indicators,the variations of trace elements and their relation with the external climate and environment were also explored.The main results of this paper are as follows.?1?The variation of cave air temperature in the cave was small,there were obvious seasonal variations of high in summer and low in winter,and the interannual variations were not obvious.The spatial differentiation between the monitoring points' temperature in the cave showed that KY1 which is near the entrance of the cave had larger fluctuation change.The changing trend of the relative humidity in the cave was on the contrary to the temperature.The relative humidity of summer was lower than winter.On the interannual timescale,it had a low relative humidity in 2014.?2?The variations of CO₂ concentration inside the cave showed a trend with high in summer and low in winter,and the fluctuation change of summer and autumn were greater,and it was stable in winter.But the interannual variations were not obvious,it had no significant spatial differences.?3?The variation of atmospheric precipitation played a major role in controlling the drip rates in Kaiyuan cave.During the 3-year monitoring period,the seasonal variations of drip rate and the interannual variation of the five drip points in Kaiyuan cave were obvious.The variations of drip rate in the cave had some lagging effects on the responsing to precipitation.The seasonal variations of pH values and conductivities in the drip water of Kaiyuan Cave were also affected by the change of the climate and environment outside the cave.?4?The concentration of Ca²⁺,Mg²⁺,Sr²⁺ and Ba²⁺ in the samples of drip water collected from the three drip monitoring points in Kaiyuan cave had obvious differences in range and mean value,but they had some same seasonal and interannual variabilities.The concentration of Ca²⁺,Mg²⁺,Sr²⁺ and Ba²⁺ in the samples of drip water may be effect by the changes of the climate and environment outside the cave and also need further monitoring and discussion.?5?The variations of Mg/Ca,Sr/Ca and Ba/Ca ratios in drip water of the three monitoring sites were similar in Kaiyuan Cave,which had a probable response to the change of precipitation,further monitoring studies should be done to research the seasonal and interannual variabilities and their implications.