【作者】 魏秀国；

【导师】 沈承德；

【作者基本信息】 中国科学院研究生院（广州地球化学研究所） ， 地球化学， 2003， 博士

【摘要】 本文以珠江水体、悬浮物为研究对象，通过对西江马口、北江河口、东江博罗断面水体取样，分析水体中不同形态碳含量，测定碳同位素值，并计算了河流碳通量值；还对珠江流域的侵蚀状况及植被分布对流域侵蚀的影响进行了探讨。得出如下的结论： 珠江水体HCO₃^-离子含量在一个水文年中发生显著变化，特别是丰水期与枯水期之间波动幅度较大；无机碳含量西江含量最高，其次是北江，东江最低；西江无机碳主要来源于岩溶作用，由于受河流冲刷效应影响，丰水期HCO₃^-离子含量升高；东江流域无机碳主要来源于硅酸盐岩的碳酸盐风化过程，丰水期HCO₃^-离子含量无显著变化；北江无机碳来源于岩溶作用和硅酸盐岩的碳酸盐风化过程，受稀释效应影响，无机碳含量随水量增加而降低。 珠江水体中DOC含量属热带-亚热带河流的下限值水平。其含量顺序与DIC相反，即东江＞北江＞西江。 与世界其它河流相比，珠江POC含量较低；三条河流中，以西江最高，东江次之，北江最低。珠江流量存在很大的季节变化，汛期拥有超过60％的年度总径流量，DOC和POC在高流量时骤增，DOC含量增加约20-90％，而POC含量最大则可能增加6倍，与山区河流的特征相似。 2000-2001水文年度珠江河流碳通量为1.355×10⁴kg·km^-2·a^-，比1997-1998水文年度的碳通量(2.741×10⁴kg·km^-2·a^-)结果低，这与本年度流域缺乏强暴雨冲刷过程有直接的联系。 珠江水体悬浮物POC稳定同位素值介于-18～-28‰之间，西江、北江、东江三个断面平水期的POC δ¹³C值的变化范围分别介于-23.09‰～-20.66‰、-27.25‰～-18.77‰、-24.10‰～-21.83‰之间；丰水期POC δ¹³C值的变化范围分别介于-23.75‰～-22.59‰、-25.36‰～-22.65‰、-23.17‰～-20.80‰之间；丰水期向枯水期过渡期间三江不同断面水体中POC δ¹³C值的变化范围分别处于-22.95‰～-20.32‰、-24.39‰～-22.13‰、-24.39‰～-22.31‰之间；枯水期水体POC δ¹³C值的变化范围分别介于-23.15‰～-20.06‰、-24.34‰～-22.87‰、-26.67‰～-23.60‰之间。 珠江水系各断面水体中悬浮物含量及POC δ¹³C值的季节变化是其物质来源季节变化的反映。在珠江流域中，东江水体POC受C₄植物草类以及作物的影响明显，δ¹³C值比西江、北江偏重。北江流域森林覆盖率较高，受C₃植物影响明显，故北江水体中POC δ¹³C值最轻。西江水体中有机质受C₃、C₄植物共同影响，其δ¹³C值介于北江、东江之间。 珠江水体悬浮物POC¹⁴C表观年龄介于540～2050a之间，西江、北江悬浮物POC年龄相对较老，东江悬浮物POC年龄较为离散，既有较为年轻的样品，又有较老的样品，但以较年轻的样品为主。珠江水体中POC以现代碳源为主，其含量在不同支流及全年内相当恒定，全部样品的现代碳含量超过75％。 珠江水体悬浮物中POCΔ¹⁴C与δ¹³C之间接近正相关关系，反映的是大河汛期悬浮物碳同位素的对应表征值，是流域侵蚀和植被覆盖现状、历史情况的综合反映。 珠江流域侵蚀比较严重，其中以西江流域为甚，东江流域整体状况较好，但中下游地区由于受人类扰动的影响，水土流失仍较严重；北江流域侵蚀总体较轻。更多还原

【Abstract】 This paper researches on the water and suspension in Zhujiang (Pearl) River and her three branches, sampling in Makou Hydrological gorge station of Xijiang River, Hekou Hydrological gorge station of Beijiang River and Boluo Hydrological gorge station of Dongjiang River. The author calculated the riverine carbon flux and measured the content of different carbon forms and carbon isotope composition. Furthermore, the author also studied drainage basin erosion and the influence of vegetation distribution on erosion. The main conclusions are as follows:The HCO3- ion content of Zhujiang River changes notably in one hydrological year, especially in wet season and dry season. As for the content of inorganic carbon, that of the Xijiang River is the highest, then the Beijiang River, and then the Dongjiang River. The Xijiang River’s inorganic carbon source was major from karst process in the drainage basin. Due to the "washing effect" , the content of HCO3- ion increased in the wet season. The HCO3- of Dongjiang River originates mostly from the weathering process of silicate, and its content changes little. The HCO3-of Beijiang River originates primarily from the weathering process of silicate and karst process. Influenced by the " dilution effect" , its content decreased while its runoff increased.The content of dissolved organic carbon (DOC) in Zhujiang River only reached the lowest value standard only in the tropical-subtropical zone. Among the three rivers, the DOC content of Dongjiang River is the highest, then the Beijiang River, and then the Xijiang River.Paniculate organic carbon (POC) content of Zhujiang River is lower than that of other rivers in the world. Among the three branches, the content in Xijiang River is the highest, then the Dongjiang River, and then the Beijiang River. The runoff of Zhujiang River has very great seasonal change. DOC and POC increased dramatically at high runoff in these rivers. The DOC content increased 20-90%, POC content probably increased 6 times. This indicates that Zhujiang River has the characteristics of mountainous rivers.The riverine carbon flux of the Zhujiang River is about 1.355 104kg-km-2-a- in hydrological year 2000-2001, lower than the result in hydrological year 1997-1998. It was due to fewer storms and lack of stronger erosion process.The stable isotope value of POC in Zhujiang River is between -18~-28%. The stable isotope value of POC in the three hydrological station sections in the normal season is between -23.09 %~-20.66%, -27.25%~-18.77% and -24.10%~-21.83%, respectively. The change in scope of POC 8 13C value in the wet season is between 23.75%~- 22.59%, -25.36%-~-22.65% and -23.17%~--20.80%. The POC 13C value in the period of the transition from the wet season to the dry season is between -22.95%~-20.32%, -24.39%~~-22.13% and -24.39%~-22.31%, respectively. The change in scope of POC 13C value in the dry season in the three hydrologicalstation section is between -23.15% ~-20.06%, -24.34%~-22.87% and -26.67%~-23.60%, respectively.The seasonal change of POC 13C value of suspension in Zhujiang River is the reflection of the suspended source in every season. POC in the Dongjiang river was influenced mainly by C4 plant such as grass and crops, and POC 6 13C value was heavier than that in the Xijiang and Beijiang Rivers. The forest cover rate of the Beijiang River drainage basin is higher. Affected by C3 plant, its POC 8 13C value was lighter. Influenced by C3 and C4 plant in the Xijiang River, its POC 6 13C value is between Dongjiang and Beijiang Rivers’.The POC14C apparent age of Zhujiang River suspension is between 540 and 2050 a. Among the three branches, Xijiang and Beijiang River suspensions are older. The 14C apparent age value of Dongjiang River is comparatively scattered-it not only has considerably younger samples but also the older ones. POC of Zhujiang River was mainly from modern carbon, the content of which was fairly constant in different branches all year round.The erosion of Zhujiang River drainage basin is relativel更多还原