西江源区河水水化学和碳同位素地球化学特征及物源分析

发布时间：2018-04-01 01:19

  本文选题：河流碳　切入点：碳同位素　出处：《中国地质大学(北京)》2016年博士论文

【摘要】：河流系统是全球生物地球化学循环的重要环节,是将陆地侵蚀物质输入海洋的主要通道。最新研究表明,河流每年的CO_2释放量(1.8 Pg C)是入海碳通量(0.9 Pg C)的2倍,占内陆水体(河水,湖水和湿地)释放总量的43%,是大气碳平衡的重要成分。河流碳为水生生物提供能量,并影响水生环境的地球化学性质。中国西南喀斯特流域以突出的地球化学敏感性和生态脆弱性为特征,自然风化是其物源的主要营力,人为扰动使河水的成分更加复杂。仅仅依靠离子组成难以区分河流碳的不同来源,而稳定碳同位素(δ~(13)C)成为示踪河水物源的重要手段。本文利用δ~(13)C对比分析西江源区南、北盘江流域物源特征,深入讨论影响这些变异的机制和控制因素,并查明西江源区在整个西江水系乃至世界河流的碳收支中所扮演角色。结果表明：1.离子组成分析和相关性分析表明,南、北盘江离子成分受控于碳酸作用下碳酸盐岩的风化。硫酸和农业肥料作为媒介参与了流域内碳酸盐矿物的风化,尤其是在北盘江流域。南盘江河水受城镇工农业和生活污水的影响较大,而北盘江河水成分除了农业污染之外,还来源于煤炭产业废水的排放。2.南、北盘江δ~(13)CPOc和C/N分异明显,悬浮态的土壤有机碳是POC的主要来源。然而,北盘江POC一部分来源于陆生高等植物,而南盘江受自源浮游生物的影响较大。土壤有机碳的淋滤可能是北盘江DOC的重要来源,土壤在河道的输移过程发生的降解作用是南盘江DOC的来源之一。此外,北盘江山区支流水土流失强烈,DOC/POC比值低至0.18；南盘江受沿程蓄水工程的影响,河水DOC/POC比值普遍高于1。DOC与Cl-、NO3-口SO42-三种污染物特征离子的相关性表明,人为活动不仅影响南、北盘江水化学成分,还使河水有机碳的来源更加复杂。3.南、北盘江δ~(13)CDIC变化范围为-13.9‰～-8.1‰。碳酸盐矿物的溶解和土壤CO_2是河水DIC的主要来源。pCO_2跟DIC和SIc分别呈正、负相关性,pCO_2显著影响水中碳酸盐矿物的溶解过程。南盘江上游河段城市化程度较高,pC02和DIC普遍高于其他以碳酸盐岩地层为主的西江河段。光合作用的增强、基流和汇流中的土壤CO_2混入以及有机碳的氧化是影响南盘江河水pCO_2分布的因素之一。北盘江河水pCO_2跟硫酸的参与、风景区人为活动的输入以及地下水的混合密切相关。有机碳的氧化是维持北盘江河水pC02的主要动力。南盘江δ~(13)CP1C值和PIC含量普遍低于北盘江流域,海相碳酸盐的风化是北盘江河水PlC的重要来源。4.南盘江流域CO_2的逸出量高于北盘江流域,且普遍高于西江中、下游流域。与世界其他气候类型的流域相比,南、北盘江流域CO_2的逸出量低于热带流域,普遍高于温带流域,而和世界其他亚热带流域相近。
[Abstract]:The river system is an important part of the global biogeochemical cycle, and is the main channel of the terrestrial erosion material into the ocean.The latest research shows that the annual CO_2 release of rivers is twice as much as that of the amount of carbon fluxes (0.9 PG C) released into the sea, accounting for 43% of the total amount released from inland waters (rivers, lakes and wetlands), which is an important component of the atmospheric carbon balance.River carbon supplies energy to aquatic organisms and affects the geochemistry of aquatic environments.Karst basin in southwestern China is characterized by prominent geochemical sensitivity and ecological vulnerability. Natural weathering is the main source of the water and the composition of the river is complicated by artificial disturbance.It is difficult to distinguish the different sources of carbon from rivers only by ion composition, and stable carbon isotope (未 ~ (13) C) is an important means to trace the source of river water.In this paper, the provenance characteristics of the southern and northern Panjiang basins in Xijiang source region are analyzed by means of 未 ~ (13) C, the mechanism and controlling factors affecting these variations are discussed in depth, and the role of Xijiang source region in carbon budget of the whole Xijiang river system and even the rivers of the world is found out.The result shows that 1: 1.The ion composition analysis and correlation analysis show that the ion composition of Pangjiang is controlled by the weathering of carbonate rock under carbonation.Sulphuric acid and agricultural fertilizers are involved in the weathering of carbonate minerals in the basin, especially in the Beipanjiang basin.Nanpanjiang River is greatly affected by urban industrial, agricultural and domestic sewage, while the composition of Beipanjiang River is derived from coal industry wastewater discharge in addition to agricultural pollution.The 未 ~ (13) C ~ (13) C ~ (3 +) and C / N in the south and north of Panjiang are distinct, and the suspended soil organic carbon is the main source of POC.However, some of the POC in Beipanjiang are derived from terrestrial higher plants, while the Nanpanjiang is greatly influenced by autoplankton.The leaching of soil organic carbon may be an important source of DOC in Beipanjiang River, and the degradation of soil in the course of channel transport is one of the sources of DOC in Nanpan River.In addition, the ratio of soil and water loss in tributaries of Beipanjiang River is as low as 0.18.The DOC/POC ratio of Nanpanjiang River is generally higher than that of 1.DOC and the characteristic ions of so _ 42- in Cl-no _ 3- mouth, which indicates that anthropogenic activities affect not only the south, but also the south.The chemical composition of the Beipanjiang River also makes the source of organic carbon in the river more complicated. 3.In the south and north of Panjiang River, the variation range of CDIC is from -13.9 鈥，

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