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岩溶水体溶解无机碳(DIC)的转化过程是评价岩溶碳汇稳定性及效应的重要指标之一,为了解其在岩溶地下水补给的地表溪流中的变化特征和影响因素,于2013年7月8~14日对广西融安县官村地下河水补给的地表溪流进行7昼夜定位连续监测,利用高分辨率自动监测仪器每15分钟测定pH、溶解氧(DO)、水温(T)、电导率(SpC)等参数,人工每2小时采集水样用于测定常规离子和δ~(13)C_(DIC)等指标。结果表明溪流水体T,pH,DO,SpC,DIC(以HCO_3~-表示),Ca~(2+),δ~(13)C_(DIC),方解石饱和指数(SIc)以及水体二氧化碳分压(pCO_2)等水化学指标均表现出明显的昼夜变化过程。SpC,DIC,Ca~(2+)和pCO_2等指标白天降低,夜间升高;T,pH,DO,δ~(13)C_(DIC)和SIc等指标白天升高,夜间降低。SIc变化范围为0.70~0.89,表明溪流中可能发生了碳酸盐的沉积。通过热力学参数计算表明水温(昼夜变化幅度为5.8℃)对水体pCO_2的昼夜变化影响率为27.48%~54.88%。反映水体水生植物新陈代谢过程(光合作用和呼吸作用过程)的水体DO指标和水体δ~(13)C_(DIC)均在白天上升,夜间下降,而δ~(13)C_(DIC)和水体DIC呈明显负相关关系(R~2=0.71),这也证明溪流水体DIC的变化过程受到水生植物新陈代谢过程的影响,白天水生植物以光合作用为主,消耗DIC,释放O_2,水体δ~(13)C_(DIC)上升;晚上以呼吸作用为主,消耗O_2,释放CO_2,增加DIC,水体δ~(13)C_(DIC)下降,其对水体pCO_2的昼夜变化影响率为45.12%~72.52%。通过研究表明溪流溶解无机碳变化过程受到物理因素(太阳辐射和水温等)和生物作用(呼吸作用和光合作用)的共同影响,这为进一步了解岩溶地下水出露地表后溶解无机碳转化过程及岩溶碳汇稳定性评价提供了依据。
Karst water dissolved inorganic carbon (DIC) conversion process is to evaluate the stability of karst carbon sink and effect of one of the important indicators, in order to understand its surface karst groundwater recharge characteristics and changes in surface water streams, in July 2013 8 The surface stream of underground river water supply in Guantun underground village, Rongan County, Guangxi Province, was continuously monitored for 7 days and nights using a high resolution automatic monitoring instrument. The pH, dissolved oxygen (DO), water temperature (T), and electrical conductivity ) And other parameters, artificial every 2 hours to collect water samples for determination of conventional ions and δ ~ (13) C_ (DIC) and other indicators. The results showed that there was no significant difference in the water body T, pH, DO, SpC, DIC (expressed as HCO 3 -), Ca 2+, δ 13 CICIC, pCO_2) and other water chemical indicators showed a significant diurnal course. The indexes of SpC, DIC, Ca 2+ and pCO 2 decreased at daytime and increased at night. The indexes of T, pH, DO, δ ~ (13) C_ (DIC) and SIc increased during the day and decreased at night. The SIc ranged from 0.70 to 0.89, indicating that carbonate deposition may have occurred in streams. The calculation of thermodynamic parameters showed that the influence of water temperature (diurnal variation of 5.8 ℃) on the diurnal variation of pCO_2 was 27.48% ~ 54.88%. The DO and δδ (13) C_ (DIC) of water body reflect the metabolic process (photosynthesis and respiration) of aquatic plants increased during the day and decreased at night, while δ ~ (13) C_ (DIC) and DIC (R ~ 2 = 0.71). This also proves that the change of DIC in stream water is affected by the metabolism process of aquatic plants. During the day, the photosynthesis of aquatic plants is dominated, DIC is consumed, O_2 is released, δ ~ (13) (DIC) increased. At night, the effect of respiration was mainly O_2, CO_2 was released, DIC was increased, δ 13 C_ (DIC) of water was decreased, and its effect on diurnal variation of pCO_2 was 45.12% -72.52% . The results show that the process of dissolved inorganic carbon changes in streams is influenced by physical factors (solar radiation and water temperature) and biological effects (respiration and photosynthesis). This is the first step to understand the process of dissolved inorganic carbon conversion and karst Carbon sink stability evaluation provides the basis.