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基于水-岩-气-生相互作用的碳酸盐风化碳汇模型表明,陆地碳酸盐风化碳汇是大气CO_2汇的重要组成部分;然而,碳酸盐风化碳汇的过程、机制和控制因素仍有待进一步的研究。本文采用野外监测、现场滴定和样品室内测试相结合的方法,对珠江流域支干流分旱季和雨季进行了4次野外监测取样,研究其水化学组成的时空变化特征。结果表明:珠江流域支干流的水化学组成受流域岩石风化、气候和水生光合作用的共同影响,并具有明显的时空变化特征。空间上,南盘江下游双江口段至红水河上游蔗香段,水流较慢,水质清澈,水生光合作用强烈,电导率、[HCO_3~-]和[Ca~(2+)]的空间变化主要受水生光合作用控制;从红水河上游蔗香段至肇庆西江大桥监测点,反映的是流域岩石风化对水化学空间变化的影响。季节变化上,西江的电导率、[HCO_3~-]和[Ca~(2+)]呈现出夏季低、冬春季高的特征,主要反映稀释效应的控制。西江干流河水的溶解氧具有明显的季节变化,在上述南盘江下游双江口段至红水河上游蔗香段,DO是夏季高冬季低,其他监测点是冬季高而夏季低;DO的季节变化受水生光合作用强度的控制。在南盘江下游双江口段至红水河上游蔗香段,温度是光合作用强度的限制因子,而其他监测点的光合作用限制因子为浊度影响的光照。造成上述差异的原因是监测点的水文环境不同。通过对梧州水文站流量和[HCO_3~-]变化的分析发现,[HCO_3~-]的季节变化幅度相对流量小得多,显示在西江流域中,HCO_3~-也存在化学稳定性行为。因此在西江流域中,流量变化是岩溶碳汇通量变化的主控因子。研究还发现,西江流域中具有强烈的生物碳泵效应,由内源有机碳形成的碳汇通量约占传统计算模式碳汇(溶解无机碳-DIC)通量的40%。因此,在估算珠江流域碳酸盐风化碳汇时,必须考虑水生生态系统光合生物对DIC的利用形成的有机碳的贡献。
Carbonate weathering carbon sink models based on water-rock-gas-gas interactions suggest that overland carbonate carbon sequestration is an important component of atmospheric CO 2 sinks; however, the process, mechanism and control of carbonate weathering of carbon sinks Factors still need further study. In this paper, field monitoring, on-site titration and sample indoor testing were combined to conduct 4 field monitoring samplings in dry and rainy season in the mainstream of the Zhujiang River Basin, and to study the spatio-temporal variations of its chemical composition. The results show that the hydrochemical composition of the main stream in the Pearl River Basin is affected by rock weathering, climate and photosynthesis in the watershed, and has obvious temporal and spatial variation characteristics. Spatially, the space between the Shuangjiangkou section of the lower reaches of the Nanpanjiang River and the upper section of the Hongshuihe cane segment is characterized by slow water flow, clear water quality, strong photosynthesis of aquatic photosynthesis, electrical conductivity, [HCO 3 ~ -] and [Ca 2+] Changes are mainly controlled by photosynthesis; from the upper reaches of Hongshui River sugarcane to Zhaoqing Xijiang River Bridge monitoring point, reflecting the watershed rock weathering chemical changes in water space. Seasonal changes, the conductivity of the Xijiang, [HCO_3 ~ -] and [Ca ~ (2+)] showed the characteristics of low summer and high winter and spring, mainly reflecting the dilution effect. The dissolved oxygen in the mainstream of the Xijiang River has obvious seasonal changes. In the upper reaches of the Shuangjiangkou section of the upper reaches of the Nanpanjiang River to the upper reaches of the Hongshui River, DO is high in summer and low in winter, while the other monitoring sites are high in winter and low in summer; Changes are controlled by the intensity of photosynthesis. The temperature is the limiting factor of photosynthesis intensity in Shuangjiangkou section of the lower reaches of Nanpanjiang River to the upper section of Hongshui River, and the limiting factor of photosynthesis in other monitoring sites is the light affected by turbidity. The reason for the above difference is that the hydrological environment of the monitoring sites is different. Through the analysis of the change of flow and [HCO_3 ~] in Wuzhou Hydrologic Station, the seasonal change of [HCO_3 ~] is much smaller than that of HCO_3 ~ -, indicating that HCO_3 ~ - is also chemically stable in the Xijiang River Basin. Therefore, in the Xijiang River basin, the change of flux is the main controlling factor of the change of carbon flux in the karst area. The study also found that there is a strong biochar pumping effect in the Xijiang River Basin. The carbon flux formed by endogenous organic carbon accounts for about 40% of the flux of the conventional computational model carbon sink (dissolved inorganic carbon-DIC). Therefore, the contribution of aquatic ecosystem photosynthetic organisms to the organic carbon formed by the utilization of DIC must be taken into account when estimating carbonate carbon sequestration in the Pearl River Basin.