| 亚热带典型岩溶溪流水气界面CO2交换通量变化过程及其环境影响 |
| 摘要点击 1925 全文点击 1209 投稿时间：2016-01-06 修订日期：2016-03-03 |
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| 中文关键词 岩溶地表溪流 CO2脱气 通量 影响因素 官村岩溶地表溪流 |
| 英文关键词 karst surface stream CO2 degassing fluxes influencing factors Guancun karst subterranean stream |
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| 中文摘要 |
| 具有较高水体CO2分压(pCO2)的岩溶地下水出露地表后常与大气形成较高的正向CO2浓度梯度,因此评价岩溶水体水气界面CO2交换通量对于岩溶碳循环过程研究具有重要意义.本文以广西柳州官村地下河补给的地表溪流为研究对象,详细讨论了岩溶溪流水-气界面CO2交换通量.使用静态箱法和手持式二氧化碳测量仪GM70对脱气通量进行检测,结果表明,溪流的CO2交换通量以脱气为主,地下河出口(G1点)脱气通量变化范围为139.48~890.84 mg·(m2·h)-1,平均值为445.72 mg·(m2·h)-1,溪流下游(G2点)脱气通量变化范围为16.54~844.18 mg·(m2·h)-1,平均值为159.81 mg·(m2·h)-1,脱气通量的时空变化特征表现为雨季要大于旱季,地下河出口地区要大于下游地区.溪流CO2脱气会对附近空气中CO2气体碳同位素(δ13C-CO2)产生影响,使溪流附近空气中CO2气体碳同位素(δ13C-CO2)值逐渐偏负,并表现出明显的时空变化,即δ13C-CO2雨季偏负于旱季,G1点δ13C-CO2偏负于G2点.并且由于脱气作用的进行,溪流的水化学性质沿流程变化,表现为HCO3-沿流程逐渐降低,pH值升高,电导率降低,pCO2沿流程递减,常见碳酸盐矿物的饱和指数SIc逐渐升高,δ13C-DIC值逐渐偏正. |
| 英文摘要 |
| CO2 cycle process or sources/sinks are not only the basis of understanding and responding to global climate change, but also the core of the current global climate change research. Gas exchange across water-air interface in terrestrial surface water is an important way of nutrient elements (carbon, nitrogen) exchange between aquatic ecosystems and ambient air. Escaping CO2 gas from surface water is also actively involved in the modern carbon cycle. In the material cycle in karst regions, CO2 plays a key role in karst processes, driving the formation of karst features. Karst groundwater with high water CO2 partial pressure (pCO2) often shows highly positive CO2 concentration gradient to atmosphere after it is discharged to surface, so the evaluation of CO2 exchange fluxes across karst water-air interface is important for karst carbon cycle research. This paper researched CO2 exchange fluxes across water-air interface in the karst surface stream in detail which was fed by Guancun subterranean stream in Liuzhou city, Guangxi province. Closed static chamber method and portable hand-holding CO2 sensor (GM70) were both employed in CO2 exchange fluxes monitoring. The results showed that CO2 degassing was the mainly form of CO2 exchange across the steam water-air interface. CO2 degassing flux in subterranean stream outlet (G1 site) ranged from 139.48 to 890.84 mg·(m2·h)-1 with an average of 445.72 mg·(m2·h)-1. CO2 degassing flux in stream downstream site (G2 site) ranged from 16.54 to 844.18 mg·(m2·h)-1 with an average of 159.81 mg·(m2·h)-1. The CO2 degassing flux in G1site was higher than that in G2 site. CO2 degassing fluxes in rainy season in both G1 and G2 site were higher than those in dry season. Stable carbon analysis of CO2 gas (δ13C-CO2) found that CO2 degassing from karst stream might influence air CO2 carbon isotope near water surface, which resulted in the more negative δ13C-CO2 value with the increase of CO2 degassing flux. Significant spatio-temporal variations of δ13C-CO2 were found, and the δ13C-CO2 in the rainy season was more negative than that in dry season and δ13C-CO2 in G1 site was more negative than that in G2 site. As a result of stream CO2 degassing, the hydrochemical characteristics of steam varied along stream running, which resulted in decrease of HCO3-, EC and pCO2 and increase of pH, SIc and δ13C-DIC in the stream. |
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