广西桂林漓江典型河段水化学昼夜动态变化 及其对岩溶碳循环的影响
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引用本文:章程,肖琼,苗迎,郭永丽,汤庆佳,郝玉培.2018.广西桂林漓江典型河段水化学昼夜动态变化 及其对岩溶碳循环的影响[J].地球学报,39(5):613-621.
DOI:10.3975/cagsb.2018.042001
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作者单位E-mail
章程 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
联合国教科文组织国际岩溶研究中心 
chzhang@karst.ac.cn 
肖琼 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
联合国教科文组织国际岩溶研究中心 
 
苗迎 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
联合国教科文组织国际岩溶研究中心 
 
郭永丽 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
联合国教科文组织国际岩溶研究中心 
 
汤庆佳 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
联合国教科文组织国际岩溶研究中心 
 
郝玉培 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
联合国教科文组织国际岩溶研究中心 
 
基金项目:中国地质科学院基本科研业务费项目(编号: YYWF201639)
中文摘要:岩溶区河流水化学昼夜动态变化的研究, 对年际尺度河流监测计划制定、碳循环研究及其通量估算具有重要作用与意义。本文选择桂江上游漓江典型岩溶河流, 开展不同河段水化学高分辨率监测和高频水样取样工作, 分析了水化学的昼夜动态变化、沿流程变化及其影响因素, 探讨了水化学昼夜循环的生物代谢过程与光合作用机理。结果表明, 硅酸盐岩分布河段与碳酸盐岩分布河段水化学存在显著差异, 且具有不同的昼夜变化规律。总体上, 受补给流域地质背景控制, 从北部硅酸盐岩山区到南部峰林平原区, 即从上游到下游, 水温、pH、SpC、Ca2+和HCO– 3离子含量逐渐升高, 升高幅度分别为3.63 ℃、1.99、125.23 μS/cm、22.42 mg/L、73.32 mg/L。DO、pH、SpC、Ca2+、HCO– 3及δ13CDIC等指标昼夜变化主要受水生植物光合作用控制, 最大昼夜变幅分别为19.4 mg/L、2.02、56.4 μS/cm、12 mg/L、48.8 mg/L、–2.05‰。K+、Na+和 NO– 3离子含量昼夜变化主要受生物代谢过程(同化作用)控制。桂林河段水生植物光合作用消耗水体DIC及伴随的Ca沉降能显著影响水体饱和度和CO2分压, 白天CO2分压下降, 水体处于过饱和状态, 对水气界面脱气过程发生具有抑制作用。阳朔河段水体均处于过饱和状态, CO2分压处于与大气平衡的临界线附近, 意味着随着流程的增加, 水体产生脱气的可能性在减小, 说明秋冬季由岩溶作用溶蚀产生的碳汇是相对稳定的。
中文关键词:水化学  昼夜动态变化  光合作用  流域地质背景  桂林漓江
 
Day and Night Aqueous Chemical Changes and Their Impact on Karst Carbon Cycle at Typical Monitoring Sites of the Lijiang River, Guilin, Guangxi
Abstract:The study of day and night aqueous chemistry in karst region provides the foundation for river monitoring planning at the yearly scale and flux estimation of carbon cycling. The Lijiang River, a typical medium river in southwest China karst region, was selected in this study. 2-day monitoring work with high resolution data logger and high frequency sampling at 2-hour interval was conducted at four sites of the Lijiang River. Day and night change of hydrochemistry and its variation along the river flow were investigated and the influences of geological background, photosynthesis and metabolism were analyzed. The results show that the changes in aqueous chemistry at four sites are quite different with varied day and night cycling features. Total ion concentration in the reaches charged by silicate-dominant rock area is much lower than that in the reaches of carbonate-dominant rock area. Controlled directly by geological background, water temperature, pH value, specific conductivity, and concentrations of Ca2+ and HCO– 3 increase from northern mountain area to southern karst peak-forest plain, i.e., from the upstream area to the downstream area, by 3.63 ℃, 1.99, 125.23 μS/cm, 22.42 mg/L, and 73.32 mg/L respectively. Day and night changes of dissolved oxygen, pH, specific conductivity, concentrations of Ca2+ and HCO– 3, δ13CDIC are mainly caused by photosynthesis of aquatic vegetation, with maximum amplitude being 19.4 mg/L, 2.02, 56.4 μS/cm, 12 mg/L, 48.8 mg/L, and –2.05‰ respectively. Con-centration changes of K+, Na+, NO– 3 are mainly controlled by the metabolism process (assimilation). Along the reaches near Guilin City, vegetation photosynthesis consumes dissolved inorganic carbon simultaneously with calcite precipitation, which can influence saturation with respect to calcium and partial pressure of CO2 and result in decrease of pCO2 pressure and the formation of over-saturated waterbody during the daytime, thus inhibiting the degassing process in the water-gas interface. Moreover, at the downstream area near Ynagshuo Town, waterbody is over-saturated during the monitoring period and pCO2 values are close to the value equivalent to atmospheric CO2, suggesting the decrease of degassing potentiality with the increase of waterflow path. This means that carbon sink resulting from karst processes is relatively stable during the winter season in Lijiang watershed.
keywords:aqueous chemistry  day and night changes  photosynthesis  watershed geological background  Lijiang of Guilin
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