Climate Response Model Of Cave Water In Karst Cave Group Of Jinhua North Mountain

In the study of caves,a lot of work has been carried out on secondary sediments inside karst caves.The cave water plays a key role as an"input source"in the formation of the cave's secondary sediments.Modern cave system monitoring work is of great significance for understanding the specific climate significance,stalagmite deposition mechanism,and contemporary cave environment of various environmental alternative indicators in cave stalagmites in specific areas.This paper takes the Shuanglong Cave and Erxian Cave in the North Mountain of Jinhua as research objects.The hydrogeochemical properties of the cave water(including Ca²⁺,Mg²⁺,Ba²⁺,Sr²⁺and their ratios?Mg/Ca,Sr/Ca,Ba/Ca?,rainwater isotope?Stable isotopes of cave water?were continuously monitored to analyze the geochemical changes of the cave water in the North Mountain of Jinhua.At the same time,combined with the meteorological data of Jinhua City,the characteristics and indications of the response of the geochemical changes of the cave water to the external climate change were revealed.The research results are as follows:?1?Affected by the seasonal and inter-annual differences in precipitation,migration paths,water-soil,water-rock interaction and other factors,the cations of the cave water in Jinhua Beishan have obvious differences with the external climate response mode,mainly in The relationship between precipitation.If the Ca²⁺concentration shows a"bimodal"variation characteristic,it indicates that the external precipitation is increased in spring and summer,and the autumn and winter precipitation has less climate information;if the Ca²⁺concentration shows a"single peak"variation characteristic,it indicates that the external Climate information with little annual precipitation;if the Ca²⁺concentration shows a slight rise and then decreases to maintain a low value,it indicates that there is a climatic feature that the external precipitation is stable and continuous.At the multi-year average scale,the Ca²⁺concentration of Beishan cave water can respond to changes in spring and summer precipitation,that is,with the increase of external precipitation and temperature,the Ca²⁺concentration shows a slight upward trend;but with the decrease of precipitation,the Ca²⁺concentration of cave water is higher than that of the previous period?January-June?decline.The concentration of Mg²⁺in the cave water can reflect the change of the outside dry humidity,which is inversely related to the precipitation.If the concentration of Sr²⁺exhibits a"bimodal"change trend during the year,it indicates that the external precipitation is gradually increasing in spring and summer,and the seasonal characteristic of the precipitation decreasing after autumn.However,the"precipitation effect"of Ba²⁺is not obvious.?2?Mg/Ca and Sr/Ca in the cave water of Jinhua Beishan well indicate the change of external precipitation.The specific performance is as follows:the lower Mg/Ca can respond to external heavy precipitation events;the higher Mg/Ca can indicate the stable and continuous climate characteristics of external precipitation in a certain period.The response of cave water Sr/Ca to external precipitation is similar to Mg/Ca:at the annual average scale,the"precipitation effect"of dripping Sr/Ca is not obvious,only in the dry season?July-December?,slightly higher Sr/Ca can Climatic information indicating that there is little outside precipitation.The cave water Ba/Ca has a"precipitation effect",but the drip Ba/Ca does not indicate a strong precipitation event outside the dry period.?3?The precipitation?¹⁸O of Jinhua North Mountain is affected by the amount of precipitation,the source of water vapor,the migration path,etc.The mean value and variation range of the precipitation?¹⁸O show the spatial difference.However,the precipitation?¹⁸O in each year showed a positive change in winter and a negative change in summer,and the"precipitation effect"was obvious.?4?When the cave drip?¹⁸O responds to the external precipitation,it will be affected by the seasonal distribution of regional precipitation,the time that the drip lags behind atmospheric precipitation,and the mixing effect of"new and old water",which will lead to interannual differences.The?¹⁸O amplitude of each drip point in Jinhua Beishan is even smaller than that of outside atmospheric precipitation,but the?¹⁸O value of the drip point can reflect its corresponding average state of?¹⁸O of atmospheric precipitation.Due to the difference in drip point in the thickness of the overlying rock layer,migration path,position from the opening,ventilation conditions,etc.,the drip point near the opening and the thinner overlying rock layer will have a corresponding?¹⁸O in response to external atmospheric precipitation.Dexterity,the inheritance of atmospheric precipitation?¹⁸O and temperature“negative temperature effect”is good,and the inheritance of dripping water?¹⁸O inside the cave is poor.Due to the difference in precipitation in different years,the correlation between the dripping point?¹⁸O and the temperature in the cave shows a difference,specifically as follows:?1?In the years with less precipitation,?¹⁸O and temperature have a positive correlation;?2?Precipitation In the years with large quantities,the relationship between?¹⁸O and temperature has inherited the“negative temperature effect”of atmospheric precipitation and temperature.In addition,at the multi-year average scale,the drip point deep in the cave can reflect the"temperature effect"of the outside temperature.