Dissolved inorganic carbon isotope compositions of drip water in Panlong cave, southwest China

Abstract

High-resolution carbon and oxygen isotope records in stalagmites provide significant information for quantitative paleo-reconstructions of past temperature and precipitation. This paper describes results of isotopic analysis of dissolved inorganic carbon (DIC) in Panlong Cave water (from drips and shallow pools). Cave water was sampled monthly throughout 2012 and analyzed for δ13CDIC composition. The values of δ13CDIC in drip water were in the range of −10.42 to −16.07 ‰, while the values of δ13CDIC in pool water were in the range of −1.88 to −6.94 ‰. Dissolved inorganic carbon isotope records showed a gradual stepwise negative excursion from January to August, and a gradual stepwise positive excursion from September to December. δ13CDIC in cave water showed remarkable seasonal variations, which were negative excursion from 2 to 5 ‰ in rainy season than in dry season. A negative δ13CDIC excursion in summer was not the result of vegetation types, which was contributed to enhance root respiration and decomposition of soil organic matter. A correlation between δ13CDIC values of perennial drip water and pool water samples with air temperature and precipitation amount suggests that these negative excursions were caused by increasing air temperature during rainy season. Negative excursions in δ13CDIC values of seasonal drip water were correlated with monthly precipitation, caused by the influx of soil organic matter into the cave. Hence, this paper provides an important framework and an empirical basis for reconstructing temperature from stalagmites and drip water in this region.