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为探究筑坝对河流溶解性无机碳(DIC)地球化学行为的影响,对乌江流域的水库及河流进行了半月1次为期1年的现场监测和取样分析.相对于入库河流,库区叶绿素a浓度平均提高了5.6倍,库区表层DIC中HCO3和溶解CO2比重下降,CO32比重和DIC碳同位素值(δ13CDIC)上升,而水库下泄水中DIC各组分却表现出与库区表层相反的地球化学行为.δ13CDIC变化范围为10.2‰~2.5‰,表明碳酸盐岩风化、光合作用及呼吸作用共同控制了δ13CDIC的变化.河流筑坝后浮游植物生物活动增强,显著影响了原始河流DIC的地球化学行为,δ13CDIC可以用来判断这种变化过程.河流-水库水体高频率监测对于准确评估筑坝河流CO2释放通量和明确碳循环过程中的源汇关系是非常必要的.
In order to explore the effect of dam construction on the geochemical behavior of dissolved inorganic carbon (DIC) in rivers, a one-year on-site monitoring and sampling analysis was carried out on the reservoirs and rivers in the Wujiang River basin for one year for a period of one year. Relative to the inflow rivers, a concentration increased 5.6 times on average, the proportion of HCO3 and dissolved CO2 decreased, the proportion of CO32 and DIC carbon isotope value (δ13CDIC) increased in the DIC in the reservoir area, while the DIC components in the DIC discharged from the reservoir showed opposite earth surface Chemical behavior.The δ13CDIC ranged from 10.2 ‰ to 2.5 ‰, indicating that the weathering, photosynthesis and respiration of carbonates controlled the δ13CDIC changes.The biological activity of phytoplankton increased after the river dammed, which significantly affected the DIC of the original river Chemical behavior, δ13CDIC can be used to judge the change process.The high frequency monitoring of river-reservoir water body is very necessary for accurate assessment of CO2 emission flux in dammed river and clarifying the relationship of source and sink in carbon cycle.