重新评估河流输入陆源有机碳对海洋碳循环的贡献和影响

Rivers are the major conduits for the transport of land materials to the ocean. It is estimated that the world rivers deliver about 0.45 Gt of terrestrial organic carbon to the ocean each year. This large amount of terrestrial organic carbon transported by rivers, thus, could have important influence to the carbon cycle and biogeochemical processes in marginal seas. Our understanding to the organic carbon transported by rivers, however, is still limited to the concentration and flux studies. In the recent years, radiocarbon measurement has been shown to be a very powerful and sensitive tool to study the geochemistry of riverine organic carbon. In this proposed study, we will use carbon isotope (13C and 14C) technique to study organic carbon transported in the major rivers in China. We will (1) measure both 13C and 14C for POC and DOC; and for SPE-DOC and Permeate-DOC as separated using solid phase extraction (SPE) method; (2) to quantitatively determine the particulate black carbon (PBC) and dissolved black carbon (DBC) and their isotopic signatures in the rivers; and (3) to quantitatively determine the abundance and isotopic compositions of DOC, SPE-DOC, Permeate-DOC, PBC and DBC in the ocean. The results obtained from this study will provide not only new data for our understanding of the sources, age and cycling time scales of organic carbon in the rivers, but insight of the importance of riverine organic carbon to the carbon cycle in the ocean. This study will also provide useful information towards a synthesis of black carbon transported by the rivers in the world. It will enhance our international collaboration and contribute significantly to the geochemical studies of organic carbon transported by rivers in China.

河流作为陆源物质输送的主要通道，每年向海洋输送0.45 Gt的有机碳，对边缘海的碳循环及生物地球化学过程具有重要影响。目前，我们对河流输送陆源有机碳的认识很大程度上仍停留于浓度和通量研究的基础上。近年来，利用碳-14方法研究河流有机碳成为一强有力的手段。该研究将应用碳同位素（14C和13C）方法对我国主要河流输送有机碳进行深入研究。我们将（1）测定河流POC和DOC的14C和13C，并通过固相萃取（SPE）法，分离DOC测定其不同组分（SPE-DOC, Permeate-DOC）的同位素值；（2）定量分析和测定河流输送颗粒态和溶解态黑碳（PBC，DBC）的含量和同位素值；（3）测定海洋DOC及不同组分，及PBC和DBC的含量和14C、13C分布。研究结果对认识我国河流输送有机碳的来源、年龄及循环时间尺度会提供全新的认识，对深入了解河流输送陆源有机碳对海洋碳循环的贡献具有重要意义。

河流是承载和输送陆源有机碳的主要通道，河流，特别是大河流每年向海洋输送的大量陆源有机碳和无机碳，对海洋，特别是对边缘海的碳循环和生物地球化学过程具有重要意义和影响。该项目通过四年的努力，系统研究了我国4条大河流：长江、珠江、黄河、黑龙江以及台湾地区3条小型山区河流输送陆源有机碳和无机碳的来源、通量和碳-14年龄。顺利完成了预期的研究目标和任务。我们利用碳同位素方法结合浓度分析，系统研究了我国4条大河流：长江、珠江、黄河、黑龙江以及台湾地区3条小型山区河流输送陆源有机碳和无机碳的来源、通量和碳-14年龄。通过比较，揭示了不同河流的流域自然环境、地质条件、植被覆盖以及人类活动等因素对河流输入陆源碳的影响。通过碳-14年龄揭示了不同河流输送陆源有机碳和无机碳的来源差异及循环时间尺度的不同，以及对边缘海的碳循环及生物地球化学过程中的影响。该研究项目是对我国主要河流输送陆源碳的一个综合研究，很多数据均为首次获得，对深入认识河流输送陆源碳及其对边缘海碳循环的影响具有实际意义。项目目前已发表前三标注SCI文章9篇，包括Nature Communications文章两篇和一区文章4篇, 另有2篇一区文章将近期发表。