Transportation characteristics of δ^(13)C in the plants-soil-bedrock-cave system in Chongqing karst area  

作　　者：Li TingYong Li HongChun Xiang XiaoJing Kuo Tz-Shing Li JunYun Zhou FuLi Chen HongLi Peng LingLi 

机构地区：[1]School of Geographical Sciences,Southwest University,Chongqing 400715,China [2]State Key Laboratory of Loess and Quaternary Geology,Institute of Earth Environment,Chinese Academy Sciences,Xi'an 710075,China [3]Key Laboratory of the Three Gorges Reservoir Region's Eco-Environment,Chongqing University and Southwest University,Ministry of Education,Chongqing 400715,China [4]Department of Geosciences,Taiwan University,Taipei 10617,Taiwan [5]Department of Earth Sciences,Cheng-Kung University,Tainan 70101,Taiwan

出　　处：《Science China Earth Sciences》2012年第4期685-694,共10页中国科学（地球科学英文版）

基　　金：supported by Open Foundation of the Karst Dynamics Laboratory,China (Grant Nos.GKN0842008 and KDL2008-08);National Natural Science Foundation of China (Grant Nos.40802035,41030103,41172165 and 40971122);Open Foundation of the State Key Laboratory of Loess and Quaternary Geology,Institute of Earth Environment,CAS,China (Grant No. SKLLQG0907);Key Project of Special Research Foundation of Southwest University,China (Grant Nos. XDJK2009B016 and XDJK2009C106)

摘　　要：Here we use an analytical method to determine δ^13C in local plants and organic matter in the soils above Furong cave, Chong- qing, China. We also monitored d13C in dissolved inorganic carbon （DIC） of drip water, δ^13C of active deposits under the drip waters, and the concentration of air CO2 （PCO2）. Based on these, we preliminarily studied the transportation characteristics of stable carbon isotope （^13C） in cave system of the subtropical karst area. The average δ^13C value of 27 local plant samples, which belong to 16 families, was -32% and the weighted δ^13C for surface dry biomass was -33%0. We found that for 54 soil samples collected from 5 soil profiles, δ^13C of soil organic matters was -22%o, which could be attributed to the different trans- portation rates of stable carbon isotopes during the decomposition of plants and organic matters in soils. The relatively lighter 12C tended to transfer into gaseous CO2, which made the relatively heavier ^13C concentrated in the soils. On the basis of moni- toring of DIC- δ^13C in drip waters from July 2009 to June 2010, we found that values in winter months were heavier and values in summer months were lighter in general, the reason of which was that in summer months, both the temperature and the hu- midity were comparatively higher, resulted in more CO2 with lighter δ^13C generated from organic matters decomposition and plants respiration. The average DIC- δ^13C value was -11%o, about 11%o heavier than the δ^13C of organic matters in soils, which proved that part of DIC in cave drip water was sourced from dissolution of inorganic carbonate （host rock, with heavier δ^13C. As for the δ^13C of active deposits at five drip water sites in Furong cave, they had almost the same variation with relatively light values. In other words, these active speleothems were deposited at equilibrium conditions for isotopic fractionation. These results suggest that the carbon isotopic information of speleothems could be used to track the evolution of localHere we use an analytical method to determine δ13C in local plants and organic matter in the soils above Furong cave,Chongqing,China.We also monitored δ13C in dissolved inorganic carbon(DIC) of drip water,δ13C of active deposits under the drip waters,and the concentration of air CO2(PCO2).Based on these,we preliminarily studied the transportation characteristics of stable carbon isotope(13C) in cave system of the subtropical karst area.The average δ13C value of 27 local plant samples,which belong to 16 families,was -32‰ and the weighted δ13C for surface dry biomass was -33‰.We found that for 54 soil samples collected from 5 soil profiles,δ13C of soil organic matters was -22‰,which could be attributed to the different transportation rates of stable carbon isotopes during the decomposition of plants and organic matters in soils.The relatively lighter 12C tended to transfer into gaseous CO2,which made the relatively heavier 13C concentrated in the soils.On the basis of monitoring of DIC-δ13C in drip waters from July 2009 to June 2010,we found that values in winter months were heavier and values in summer months were lighter in general,the reason of which was that in summer months,both the temperature and the humidity were comparatively higher,resulted in more CO2 with lighter δ13C generated from organic matters decomposition and plants respiration.The average DIC -δ13C value was -11‰,about 11‰ heavier than the δ13C of organic matters in soils,which proved that part of DIC in cave drip water was sourced from dissolution of inorganic carbonate(host rock,with heavier δ13C).As for the δ13C of active deposits at five drip water sites in Furong cave,they had almost the same variation with relatively light values.In other words,these active speleothems were deposited at equilibrium conditions for isotopic fractionation.These results suggest that the carbon isotopic information of speleothems could be used to track the evolution of local vegetation in certain situations.

关 键 词：karst area δ^13 PLANT soil organic matter DIC-δ^13 in drip water active speleothems 

分 类 号：P531[天文地球—古生物学与地层学] S153.61[天文地球—地质学]