Response Of Cave Dripping Water And Modern Sediments In Guilin To Climate Change

With global warming,climate weather events have occurred frequently in recent years,and how to effectively predict future climate change is getting more attention.The time of historical environmental information recorded by the instrument is short,so it is necessary to interpret the evolution of the paleo-climate information that accurately and continuously recorded in stalagmites.Cave system monitoring is an important basis for interpreting stalagmite records environmental information and building bridges between measurement information,and important basis for establishing the connection between the sensor measurement record and the environmental substitution index.This study systematically monitors precipitation,cave environment,drip water and modern sediments in Liangfeng?LF?Cave,Guilin city.Finally,the monitoring result interprets respond rules to environmental information.The monitoring results mainly draw the following conclusions:?1?Cave temperature present seasonal variation that affect by the atmospheric temperature.The cave temperature from the outside to the inside gradually decreases that affected by the structure of the cave.On the seasonal scale,the lag time of the cave temperature rise period is long,and the lag time of the cooling time is short,which is related to the“buffering effect”of the structure in the cave.The pCO₂ in this cave is high in summer and low in winter.Moreover,the main controlling factors of pCO₂ in caves are also different that affected by seasonal changes in the atmospheric environment.?2?The conductivity of cave drip,Ca²⁺and HCO₃^-are the same variation.In summer,soil CO₂ is increased,infiltration water erosion ability is enhanced,conductivity,Ca²⁺,HCO₃^-appear peak,and in winter it is opposite.Mg/Ca,Sr/Ca and SO₄^2-all have seasonal variation characteristics in drip water.The Mg/Ca and SO₄^2-can clearly indicate the variation characteristics of precipitation amount.But Mg/Ca,Sr/Ca and SO₄^2-differ in its response time to the climate information variation that affected by the different runoff paths;?3?The?D and?¹⁸O of precipitation area showed obvious seasonal variation in Guilin.Due to the difference of water vapor source,the values of?D and?¹⁸O were negative in summer and positive in winter.The meteoric water line in the region is:?D=8.12?¹⁸O+12.9.The?D and?¹⁸O of drip water are also display seasonally variation that affected by the precipitation isotope value.The mixing of"new water"and"old water"on the top of the cave,the?¹⁸O value variation range of drip water is much smaller than precipitation.And the response time of drip water to precipitation is different in dry season and wet season.The?¹³C_DIC of cave drip is mainly affected by soil CO₂ in the rainy season.The precipitation amount is the key factor to control the?¹³C_DIC value in the dry season;?4?The modern sediments amount is high in summer and low in winter.The?¹⁸O value of modern sediments negative variation indicates strong summer monsoon,precipitation amount increased,while the positive variation of?¹⁸O value indicates the weak summer monsoon,precipitation amount reduced.The?¹³C of modern sediment can be used to reflect the?¹³C variation in soil CO₂ on seasonal scale and to reflect the drought events caused by precipitation amount variation in interannual scale;?5?Drip water can respond to extreme precipitation events very quickly?less than 24 h?.The isotope composition of modern sediments also has obvious variation during ENSO,indicating that the event-scale climatic events can be recorded in drip water and modern sediments.However,different drip water have different response time to extreme events which caused by the difference the storage capacity and runoff path in epikarst on the top of the LF cave.