酸雨对桂林枯水期岩溶地下水δ^(13)C_(DIC)及碳汇效应的影响  

Impact of Acid Rain to δ^(13)C_(DIC) of Karst Groundwater and Carbon Sink in Dry Season in Guilin

作　　者：黄奇波[1,2,3] 覃小群[2,3] 刘朋雨[2,3] 唐萍萍[2,3] 

机构地区：[1]中国地质大学环境学院,湖北武汉430074 [2]中国地质科学院岩溶地质研究所,广西桂林541004 [3]国土资源部广西岩溶动力学重点实验室,广西桂林541004

出　　处：《地球科学（中国地质大学学报）》2015年第7期1237-1247,共11页Earth Science-Journal of China University of Geosciences

基　　金：中国地质调查项目(No.12120113005200);国家自然科学基金项目(No.41302211)

摘　　要：定量评价硫酸对岩溶碳汇效应的影响有助于提高岩石风化碳汇通量估算精度,对当前全球气候变化研究意义重大.选取受酸雨影响的桂林岩溶区为研究对象,在枯水期对研究区14个岩溶大泉和15条地下河水化学成分和碳同位素进行了测试分析,结果表明:岩溶大泉和地下河中阳离子以Mg2+和Ca2+为主,阴离子以HCO3-为主,分别占阳离子和阴离子组成的90%以上,SO42-含量较低,其含量范围为0.004~0.213mmol/L;所占阴离子组成比例为0.12%~6.11%;δ13CDIC、[Ca2++Mg2+]/[HCO3-]更偏向于碳酸溶解端元,离硫酸溶解端元距离远,证实硫酸参与碳酸盐岩的溶解对地下水无机碳(dissolved inorganic carbon,简称DIC)及δ13CDIC的影响有限;与Sr2+/Ca2+值一样,δ13CDIC主要受径流条件控制,其大小可以反映地下水径流条件的强弱.利用化学计量关系计算出由硫酸溶蚀碳酸盐岩的平均比例为22.64%,产生的DIC(HCO3-H2SO4)占总DIC的平均比例为13.04%,碳酸产生的DIC(HCO3-H2CO3)占地下水总DIC的比例为86.96%,其中来源于土壤大气中的HCO3-比例为43.48%.因此,扣除硫酸对地下水中DIC的贡献后,岩溶碳汇效应将减少13.04%.Quantitative evaluation of the impact of sulfuric acid to karst carbon sink not only improves the estimation accuracy of karst carbon sinks, but also facilitates research on global climate change. In this paper, Guilin karst area affected by acid rain is selected for studying. The results of testing and analysis of the chemical composition and inorganic carbon isotope in 14 karst spring and 15 subterraneans show that in both karst spring and subterranean, Mg^2＋ and Ca^2＋ are the main negative ions, and HCO^3- is the main positive ion ,which were accounted for more than 90% of negative ion and positive ion respectively, and SO4^2- has a lower content, which content range was 0.004-0.213 mmol/L and the composition ratio was 0.12%-6. 11%; Theδ^13CCD1C , [Ca^2＋ Mg^2＋ ]/[HCO3^-] are more inclined to carbonate dissolution endmemher, and the longer distance from sulfuric acid dissolution endmember indicates the limited impact of sulfuric acid dissolution of carbonate rocks involved in groundwater inorganic carbon （DIC） and 81aCDlc. Same as the situation of Sre＋/Ca2＋ values, ~la CDtC could reflect the ron-off condition of groundwater to some degree. Using the stoichiometry method calculate, the average proportion of DIC （HCO3-H2SO4 ） produced by sulfuric acid gained by stoichiometric relationship is 22.64%, accounts for 13.04%, while that produced by carbonic acid accounts for 86.96%, of which 43.48% comes from the soil atmosphere. Deducting DIC contribution of sulfuric acid to the groundwater, 13.04%0 karst carbon sink will be reduced.

关 键 词：岩溶碳汇 硫酸 溶解无机碳同位素 Sr2+/Ca2+桂林岩溶区 地下水 

分 类 号：P631[天文地球—地质矿产勘探]