岩溶地下河补给的地表溪流溶解无机碳及其稳定同位素组成的时空变化  

Temporal and Spatial Variations of Dissolved Inorganic Carbon and Its Stable Isotopic Composition in the Surface Stream of Karst Groundwater Recharge

作　　者：李丽[1,2] 蒲俊兵[1] 李建鸿[1] 张陶[1,2] 

机构地区：[1]中国地质科学院岩溶地质研究所/国土资源部,广西岩溶动力学重点实验室,桂林541004 [2]西南大学地理科学学院,重庆400715

出　　处：《环境科学》2017年第2期527-534,共8页Environmental Science

基　　金：国家自然科学基金项目(41572234,41202185);中国地质科学院基本科研业务费项目(YYWF201636)

摘　　要：岩溶水体中溶解无机碳(DIC)主要以HCO_3^-形式存在,其同位素(δ^(13)CDIC)被广泛用于示踪DIC的不同来源及其影响因素.为了解亚热带典型岩溶溪流溶解无机碳及其稳定同位素的分布规律,本文以广西柳州官村地下河补给的地表溪流为研究对象,对其水化学特征和δ^(13)CDIC进行分析.结果表明,溪流上游和下游的DIC与δ^(13)CDIC都表现出明显的时空变化特征,地下河出口(G1点)HCO_3^-旱季浓度变化范围为(4.73±0.14)mmol·L^(-1),而雨季为(4.23±0.68)mmol·L^(-1).溪流下游(G2点)HCO_3^-旱季浓度变化范围为(4.56±0.23)mmol·L^(-1),而雨季为(4.20±0.59)mmol·L^(-1).溪流上游的旱季δ^(13)CDIC变化范围为-12.22‰±0.49‰,雨季的变化范围为-12.28‰±0.82‰;溪流下游的旱季变化范围为-10.73±0.71‰,雨季的变化范围为-11.10‰±0.90‰.两个点水体DIC含量旱季均高于雨季,且G1点要高于下游G2点.两个点水体δ^(13)CDIC值旱季较雨季偏重,且G2点水体δ^(13)CDIC值显著高于G1点δ^(13)CDIC值.地下河水和溪流DIC主要来源于土壤CO2和碳酸盐岩溶蚀,但是溪流上游与下游DIC和δ^(13)CDIC值差异表明水体的CO2脱气作用,水生植物的光合作用显著影响了水体DIC和δ^(13)CDIC值.Stable carbon isotope of dissolved inorganic carbon （ δ^13CDIC ）, which is mainly constituted by HCO -3 in karst water, is widely used to trace the different sources and influential factors of dissolved inorganic carbon （ DIC）. In order to understand the distribution of DIC and δ^13CDIC in subtropical karst area, this paper researched the water chemistry and δ^13CDIC in a karst surface stream in detail, which is fed by Guancun subterranean stream in Liuzhou City, Guangxi Province, in the southwest of China. The results showed that the contents of DIC in subterranean stream outlet （G1 site） ranged from 4. 60 to 4. 90 mmol·L ^- 1 with an average of 4. 73 mmol·L ^- 1 in dry season, and from 2. 80 to 4. 70 mmol·L ^- 1 with an average of 4. 23 mmol·L^ - 1 in rainy season. The contents of DIC in 1. 35 km downstream site （G2 site） ranged from 4. 30 to 4. 90 mmol·L^ - 1 with an average of 4. 56 mmol·L ^- 1 in dry season, and from 3. 00 to 4. 70 mmol·L ^- 1 with an average of 4. 20 mmol·L - 1 in rainy season. The δ^13CDIC of subterranean stream outlet （G1 site） varied from - 12. 8‰ to - 11. 53‰ with an average of - 12. 22‰ in dry season, and from - 13. 12‰ to - 11. 01‰ with an average of - 12. 28‰ in rainy season. The δ^13CDIC of stream downstream site （G2 site） ranged from - 11. 71‰ to - 9. 55‰ with an average of - 10. 73‰ in dry season, and ranged from - 12. 18‰ to - 9. 85‰ with an average of - 11. 10‰ in rainy season. The contents of DIC of G1 site were higher than those of G2 site. The DIC contents in dry season in both G1 and G2 site were higher than those in rainy season. The values of δ^13CDIC of G1 and G2 site in dry season were more positive than those in rainy season. The δ^13CDIC value of G1 site was more negative than that of G2 site. The main sources of DIC in underground river and surface stream were soil CO2 and carbonate dissolution. However, the differences of DIC and δ13CDIC between G1 and G2 site showed that CO2 degassing and photosynthesis

关 键 词：岩溶地表溪流 溶解无机碳(DIC) δ^13CDIC 碳酸盐岩风化 广西 

分 类 号：X523[环境科学与工程—环境工程]