摘要:
基于对广西弄拉表层岩溶泉水文动态自动化监测研究,发现在良好的森林植被覆盖条件下,泉域内水资源的排泄方式在不同季节差异较大。丰水期主要以泉口径流排泄为主,而枯水期则以泉域内生态需水消耗为主。4至8月降水量占全年总量的66.24%,泉口水资源输出量却高达全年总量的90.89%。与之相对应,碳输出量占全年总量的90.46%。上述数据说明岩溶碳汇过程主要发生在径流系数较高的丰水季节。在碳汇方式上,碳汇过程明显受到雨水稀释效应、CO2效应及水岩相互作用的控制。在降水初期,受到雨水的混合稀释, HCO3-浓度明显下降。期间受到CO2效应及水岩相互作用的影响,使HCO3-浓度波动较大。但随着流量的衰减,水岩相互作用重新又占主导地位, HCO3-浓度动态变化趋于平稳。根据近十年来的监测结果表明,在次生森林植被覆盖条件恢复下,岩溶动力系统中的 Ca2+、Mg2+和 HCO3-离子浓度均明显增高。以HCO3-浓度增长最为明显,2003-2005年平均值为356.55 mg/L,而2012年上升为432.97 mg/L,其差值76.42 mg/L,十年间增幅达21.4%。
Abstract:
Based on years’ automatic monitoring of dynamic hydrological state of an epikarst spring in Nongla, Guangxi, the authors found that, under the good vegetation coverage, the discharge mode is different in different seasons. It is mainly the runoff discharge by spring in the wet season and consumption of ecological water requirement in the dry season. In 2012, the precipitation from April to August accounted for 66.24%of the whole year. At the same time, the discharge of spring accounted for 90.89% and the karst carbon sink accounted for 90.46%of the whole year. It is evident that the karst carbon sink occurs mainly in the wet season because of the higher runoff coefficient. In the study area, carbon sink is controlled by rainwater dilution, CO2 effect and water-rock interaction (WRI). At the beginning of precipitation, the concentration of HCO3- is continuously reduced, controlled by rain dilution. However, it is also obviously affected by CO2 effect and WRI. HCO3-concentration fluctuation with time. At the later stage of spring discharge, WRI is dominant again and HCO3-concentration tends to be somewhat stable. From the monitoring data obtained in the past decade, the concentrations of Ca2+, Mg2+ and HCO3- in the karst dynamic system were significantly increased with the recovery of the secondary forest vegetation. With the concentration of HCO3- as an example, the average value was 356.55 mg/L during the period of 2003-2005, whereas it was 432.97 m/L in 2012, the difference being 76.42 mg/L, and the value was increased by 21.4%during the ten years.
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