EFFECT OF EXTREME PRECIPITATION ON STABLE ISOTOPE COMPOSITIONS OF DRIP WATER AND SEDIMENT DURING AUTUMN AND WINTER IN LIANGFENG CAVE AT GUILIN, SOUTHWEST CHINA

In recent years, extreme weather events occur multiple times which make us to effectively predict extreme events. However, meteorological data recording time is short, therefore, stalagmites can be used to reconstruct ancient climate change that precise continuous record of extreme events, and we can use information to effectively explain the variation of extreme events. This project monitor’s stalagmite systems mainly include precipitation, dripwater and sediment in Liangfeng cave. To establish the hydrogen, oxygen and carbon isotopes in atmospheric precipitation, dripwater and sediments, and analysis climate information recorded in those environment substitute index. In order to research stable isotope composition and variability in dripwater and sediment during a short time scale. Through establish the relationship between precipitation, dripwater and sediment, quantitative reconstruction stable isotope values variation during three medium. And then discusses the extreme precipitation events in the stalagmite.

In this study, precipitation, drip water and sediment were high resolution monitored from September 2017 to January 2018 in Liangfeng Cave, Guilin city, SW China. The precipitation samples are measured δD and δ¹⁸O isotope values. The result indicated that δD and δ¹⁸O isotope compositions of precipitation have obvious positive variations which caused by water vapor source in the study area. The local meteoric water line (LMWL) is δD = 8.8δ¹⁸O + 16.38. The precipitation was the only source for Liangfeng cave, its oxygen isotope signals were reflected in the drip waters, and recorded in the sediment. But cave drip waters may be mixed as precipitation which rain in the olden days before entering into the cave, and precipitation which rain in the olden days affected by evaporation effect through the epikarst. So that δ¹⁸O values of drip water were more positive excursion than precipitation. However, δ¹⁸O of the sediment response time of extreme precipitation events were different that effected by different hydrogeochemical process. Therefore, monitoring δ¹⁸O of drip water and sediment response process to environmental information, it can provide accurately interpreting paleoclimate information in the stalagmite which recorded by oxygen isotope.