We analyzed variations in the Sr/Ca, Ba/Ca, REE/Ca (REE: rare earth element), Zn/Ca, and Pb/Ca ratios preserved in an annually layered stalagmite, XL21, from central China. The stalagmite record spans the 95year period AD 1914-2008. The Sr/Ca and Ba/Ca ratios have a significant positive correlation with the stalagmite's growth rate, suggesting that they were primarily controlled by growth-rate variations. Variations in REE/Ca ratios are consistent with local temperature changes, suggesting temperature influenced REE concentrations in the stalagmite over decadal to annual timescales. Higher temperature in this humid area can increase vegetation cover, microbial activity, and organic decomposition in the soil, resulting in enhanced pCO2, organic matter concentration and reduced pH, and consequently increased REE mobilization from the overlying soil layer and host rock. Higher temperatures may also increase the natural Zn mobilization from the overlying soil mediated by organic matter and consequently may have led to increased Zn retention in XL21. An increasing trend is seen in the Pb/Ca ratios from XL21 since 1985, which is consistent with increased lead production in this area, and indicates an increase in mine-derived lead pollution in the local environment over the past 30years.
Bibliographical noteFunding Information:
We acknowledge A. Osincev, S. Breitenbach and H. Zhang for surveying and drawing the cave. The final version of the manuscript benefited for constructive suggestions from two anonymous reviewers and Prof. Alan Gillespie and Prof. John Dodson. This work was supported by the National Basic Research Program of China (grant 2013CB955902 ; 2010CB833405 ); Key Program of the Chinese Academy of Sciences (grant KZZD-EW-04-01 ); and National Science Foundation of China (grant 41023006 ; 41230524 ; 41001061 ; 41372192 ). We also thank financial supported by Taiwan NSC ( 98-2116-M002-012 , 99-2628-M002-012 , 99-2611-M002-005 , and 100-3113-M-002-002 to CCS) and National Taiwan University ( 101R7625 to CCS).
- Annually layered stalagmite
- Central China
- Climate change
- Environmental pollution
- REE geochemistry
- Trace elements