【作者】 王亮；

【导师】 张龙军；

【作者基本信息】 中国海洋大学 ， 环境科学， 2014， 博士

【摘要】 河流是陆源物质向海洋输运的主要通道。当今，以水库修建、农业灌溉引水等为主的人为影响日益加剧，改变了河流自然状态下的物质输运规律，对河流流域的碳收支平衡以及源/汇格局产生重要影响。黄河是中纬度干旱半干旱地区高浑浊度河流的典型代表，也是受人类活动影响最为严重的河流之一。对其碳输运规律及影响因素的探讨，对于讨论同类河流碳输运行为具有重要的借鉴意义。本文通过2003年至2012年间黄河干流的多个航次以及花园口（全年）和利津站（调水调沙及24小时连续站）的观测数据，探讨了黄河各形态碳的输运特征和季节变化规律，特别关注自然过程变化和人为活动对其影响，主要结果如下：（1）与世界河流有机碳输运以溶解态（DOC）为主不同的是，黄河有机碳输运以颗粒态（POC）为主。且超过85%的POC集中在粒径小于32μm的颗粒物上，自兰州至利津不同粒径悬浮颗粒物承载POC的输运规律是一致的。黄河DOC浓度从上游至下游呈现逐渐升高的趋势，城市污水排放和农业灌溉退水污染的影响也不可忽视，这与大多数河流污染输入的DOC主要来自于城市污水排放不同。另外，全球变暖可能会导致青藏高原河段水体中DOC浓度升高。（2）虽然当前黄河水体中有机碳主要来源于黄土母质以及具有难降解的特性。然而黄河水库库容极大，水库对颗粒物的滞留、沉积，使得库区自生源有机碳贡献增加而导致降解率升高，对高浑浊度的黄河来说，库区对河流自身有机碳输运规律产生的影响远远高于其他河流。短时期来看，黄河流域水库因沉积作用已经作为一个稳定的碳汇存在，然而调水调沙工程却在不到一个月的时间里，将超过全年35%和56%的DOC和POC输运入海，瞬时流量和TSS浓度甚至可分别高达4100m3/s和27×103mg/L。（3）黄河DIC浓度高达3mmol/L，在世界河流中位居前列。尽管青藏高原亚流域的面积仅占全流域的30%，但作为黄河的主要水源区，强烈的淋溶作用导致该亚流域拥有全流域最高的化学风化速率，其岩石风化大气CO2消耗量也占到全流域的64%；而在占全流域面积近70%黄土高原亚流域，较高的蒸降比限制了化学风化速率，较小的地表径流限制了风化产物向黄河干流的输运，其岩石风化大气CO2消耗量仅占全流域的35%。因此，青藏高原亚流域是黄河水体中高浓度DIC的主要来源。而以往的研究认为“黄土中较高的碳酸岩含量是导致黄河水体中高浓度DIC的原因”。此外，随着全球变暖以及黄土高原干旱的程度增加，青藏高原亚流域对黄河DIC输运入海通量的贡献在未来将呈现上升趋势。（4）与世界河流一样，黄河也表现为大气CO2的源。但与大多数河流有机物降解是提供CO2主要来源不同的是，强烈化学风化过程维持的河水高DIC浓度的碳酸盐体系是影响黄河水体pCO2分布的主要因素。黄河水体中TSS含量极高，水体的透光性差，浮游植物的光合作用受到限制，生物固碳能力较弱。（5）黄河的DIC收支出现不平衡，进入黄河水体的DIC量大于黄河输运入海通量。水库滞留，农业灌溉取水对河流DIC的清除作用显著。更多还原

【Abstract】 Rivers play an important role in the global carbon cycle by linking land andocean systems, which are the two largest carbon reservoirs on the earth’s surface.Nowadays, under server human influences such as reservoir construction andagriculture irrigation, natural ways of riverine material transport are totally changed,so are the carbon input/output balance and sink/source patterns. The Yellow Riverrepresents typically rivers which are located in arid and semiarid regions and holdhigh turbidity. Studies on carbon cycles and influence factors in the Yellow Riverestuary can provide some meaningful advice to other rivers with the samecharacteristics.Using data from field investigations between2003and2012along the YellowRiver mainstream and some continuous observations at the Huayuankou and Lijinstation, we examined the transport features and seasonal variations of organic andinorganic carbon, with a focus on contrasting the impacts of human activities withthose of natural processes. Conclusions are as follows:(1) Different from other large rivers, organic carbon is mainly transported in theparticulate form, and85%of the POC is concentrated in particles with grain sizesmaller than32μm. Due to natural and human influences, DOC correlates weaklywith discharge and it varied as a result of human activities such as agriculturalirrigation and pollution in the whole basin except for the upstream Qinghai-TibetPlateau, where DOC may be influenced by global warming. Organic carbon in theYellow River originates mainly from loess and possesses refractory feature. Labilepart of the organic carbon in reservoirs is much higher compared with that in themainstream, due to more autochthonous contributions.(2) CO2consumption by chemical weathering in the Yellow River basinachieves101.8×109mol/a, to which80%and20%are contributed by carbonate andsilicate, respectively. In addition, although the Qinghai-Tibet Plateau only accountsfor30%of the whole basin area, its CO2consumption by chemical weatheringoccupies more than60%of the total. The Qinghai-Tibet Plateau is probably the originof high HCO3-in the Yellow River and contributes about66%of the riverine DIC flux.The contribution from the Loess Plateau was overestimated in the previous studies. Inaddition, we also speculate that, due to global warming, contributions from the Qinghai-Tibet Plateau to the chemical weathering and DIC flux of the Yellow Riverwill probably increase in the future.(3) In the Yellow River, inorganic carbon is mainly transported in the dissolvedform. High DIC in the Qinghai-Tibet Plateau is due to the high chemical weatheringrate, and abundant carbonate in the loess is probably the reason that DIC stays at thehigh level in the middle reach. In addition, influcences of high evaporation in theLoess Plateau can not be neglected. The Yellow River acts as a CO2source comparedwith atmosphere, carbonate system is the main control mechanism.(4) Monthly fluxes of all kinds of carbon in the Yellow River show the samepattern: high in the wet season and low in the dry season. Total carbon flux of theYellow River amonts to133.8×104tC/a, mainly in inorganic and particulate forms.The water and sediment regulation scheme transports about one-third of the annualDOC flux and one half of the POC flux in about20days. In the whole Yellow Riverbasin, inorganci carbon input is much higher that its output, probably due to carbondepositon in the resevoirs and the downstream river channel. As a result, the naturalriverine transport patterns have been altered and ecosystems in the estuarine andcoastal areas have been influenced.更多还原