西江流域的有机碳侵蚀通量

在西江下游的马口水文站对径流进行了4个季节的有机碳采样分析。研究表明,西江径流有机碳的断面构成在各个季节均较为一致;季节性变化表现为,有机碳和悬浮物含量随流量的增加而增加。随着水体悬浮物含量的增加,悬浮物的有机碳含量呈对数趋势降低。西江流域的有机碳侵蚀通量为10.18×106gC/km2·yr.,是全球外流域有机碳侵蚀通量的2～3倍,其中以颗粒有机碳的侵蚀通量为主,达到8.30×106gC/km2·yr.,溶解有机碳的侵蚀通量为1.88×106gC/km2·yr.。反映了流域内较强的机械剥蚀过程,这与西江流域典型的季风气候、较大的地形高差,以及农业耕作历史长久、土地利用强度较大等因素有关。     

乌裕尔河流域颗粒有机碳的来源：碳同位素证据

以2008、2009年所采集的乌裕尔河9个点位水体中的悬浮物为研究对象,对丰、枯水期颗粒有机碳（POC）含量、碳同位素组成（^13C、^14C）及表观年龄进行了系统测试与分析,以期探讨河流中颗粒有机碳来源与流域土壤侵蚀的关系。研究结果表明,该河流中颗粒有机碳（POC）主要来源于未受玉米残体及根系输入影响的深层土壤,且土...     

黄河口有机碳的时空输运特征及其影响因素分析

通过2004年4月,2004年9月,2005年9月,2006年4月4个航次,结合2003年8月对河道感潮带的连续同步观测,对低流量下黄河口有机碳的输运特征进行了考察。结果发现:黄河输入至河口的悬浮物中颗粒有机碳(POC)含量约为0.51%,主要以陆源输入为主,几乎不受季节变化影响,由于大量POC含量低的陆源泥沙的稀释作用,浮游植物对总颗粒有机碳的贡献只有在悬浮物含量(TSS)<200mg/L时才能显现出来;黄河口TSS超过455mg/L时,有机碳入海以颗粒有机碳为主;反之,以溶解有机碳为主。黄河口悬浮物在低盐度区沉降作用前后的中值粒径降低,Φ>16μm的悬浮物的沉降作用比Φ<16μm的悬浮物更为剧烈,POC含量随悬浮物粒径的降低而升高,黄河携带的颗粒有机碳80%以上集中在Φ<16μm的TSS中;低流量下,黄河口最大混浊带对POC的过滤效率为65%,混浊带对POC的过滤效应能造成黄河口POC的有效通量被高估;由于受黄河口沉积物向水体解析DOC的影响,在盐度小于10时,DOC几乎不受海水稀释作用的影响,但在盐度大于10的区域DOC与盐度表现出良好的负相关关系,黄河口枯、丰水期淡水端溶解有机碳的有效浓度分别高于实测最高值20%和10%左右,从而造成黄河口DOC有效通量被低估。     

珠江水体悬浮物碳稳定同位素组成与流域土壤侵蚀研究

以珠江流域水体悬浮物为研究对象,对其碳稳定同位素组成(δ13C)及颗粒有机碳(POC)的含量进行了测定和研究。结果表明:河流悬浮物同位素组成与珠江流域植被分布格局、土壤有机质密切相关;珠江悬浮物碳同位素组成主要受C3植被影响,其中,西江悬浮物碳同位素组成表现出较强的C4植被特征。东江水体悬浮物碳同位素组成在洪水季节表现出较强的C4植被特征,其它季节则表现出C3植被特征;北江水体悬浮物碳同位素组成无明显的C4植被特征。东江悬浮物样品POCδ13C值呈逐年上升趋势,与近年来流域内植被破坏和土壤侵蚀加剧相对应,并显示其侵蚀程度超过西江流域。     

河流碳通量与陆地侵蚀研究

河流碳通量系陆地侵蚀产物,它构成全球碳循环的一个重要环节。河流碳通量在数量上远小于全球碳循环的其他环节,但由于与陆地生态系统联系密切,故对它的研究尤为重要。全球每年河流碳通量约为1GtC（10⁹t碳）,其中约60％为无机碳、40％为有机碳。溶解态有机碳和颗粒状有机碳主要来源于土壤侵蚀,另有一部分有机碳来源于河湖中的浮游植物;溶解态无机碳主要源于大气中CO₂和碳酸盐;颗粒无机碳主要指未溶解的碳酸盐。亚洲季风区河流对全球河流碳通量具有较大贡献,而对其研究程度较低。河流碳通量研究既可为流域治理提供基础资料,也是进一步了解人为CO₂“未知汇”的途径之一。     

三峡水库建设对长江下游颗粒有机碳通量及碳同位素组成的影响

2008年4月至2009年4月,在南通长江干流每周采集一次表层悬浮物样品,共51个,分析了其粒度、颗粒有机碳(POC)、颗粒氮(PN)含量以及有机碳同位素(δ13Corg)组成,研究了下游干流颗粒有机碳组成的季节性变化特征.悬浮物的平均粒径在一年内变化不明显,而POC和PN含量呈现洪季缓慢减小,枯季增加的趋势;δ13C...     

长江干流颗粒有机碳及其同位素组成的季节性输送特征

2007年夏季和冬季对长江干流悬浮物进行了季节性采样,系统分析了悬浮物颗粒有机碳含量及稳定碳同位素的组成,研究了其空间分布以及季节变化特征。结果显示,长江干流夏季颗粒有机碳含量在0．4％～1．3％,冬季含量在0．7%-2．2％。冬季和夏季颗粒有机碳平均δ^13C值分别为-24．74‰和～24．83‰,季节性差异不大,在...     

增江颗粒有机碳同位素的AMS研究初报

全球河流每年向海洋输送约1Gt(10¹⁵g)的碳,其中40%为有机碳。然而,在海洋沉积物中却难以寻找到足量的陆地碳的生物地球化学标记[1]。显然,陆地碳在河流搬运过程中经历了复杂的生物地球化学变化,乃至“踪迹全无”。河流有机碳可大体上划分为颗粒态(POC)和溶解态(DOC)两种基本类型。就全球范围讲,河流输送的POC和DOC在数量上相当或DOC略高些。但在一些高浑浊的河流,尤其是亚洲季风区的河流中,POC在有机碳中却占绝对优势。如珠江干流水体中POCDOC比值高达5.0左右^[2]。因此,亚洲季风区河流中所搬运的POC对其注入水域的生物地球化学过程影响深远。河流有机质的来源复     

河流碳循环模型研究进展

河流是连接陆地和海洋两大碳库的“重要管道”和“生物反应器”,深入理解河流碳循环过程并建立河流碳循环模型是估算区域尺度河流碳通量的重要手段。当前,对河流碳循环模型构建与应用的探讨还较为缺乏。通过文献调研对河流碳循环机理和已有模型研究进行回顾和总结,首先归纳了河流中颗粒有机碳、溶解有机碳和溶解无机碳的主要来源及相关迁移转化过程,然后对经验统计和机理过程两大类河流碳循环模型的模拟方法、应用现状和优缺点进行了综述。经验统计模型采用统计或机器学习方法建立河流碳通量与环境因子的关系,建模较为简单,但普适性和外推性较差;机理过程模型在陆面模式或水文模型中耦合河流碳循环相关过程,物理性和可靠性较强,但较为复杂。不同模型的侧重点和对河流碳循环过程的表达各不相同,适用场景也不相同。河流碳循环模拟研究目前尚处于起步阶段,现有模型对陆地和水体碳循环过程以及人类活动影响的表达普遍不足,无法准确模拟和预测河流碳循环过程的长期变化。今后应加强对河流碳循环过程的观测,提高对陆地和水体碳循环机理的认识,进而完善其在模型中的表达,提高河流碳循环模拟的精度,为中国实现“双碳”目标提供科学支撑。     

全球变化背景下北方泥炭地释放溶解有机碳的驱动机制

泥炭地（peatland）是一类储碳效率很高的特殊陆地生态系统,其碳储量约占全球土壤碳库的近1／3,对全球碳循环有着举足轻重的作用。有证据表明在过去20余年,北半球大范围的天然水体中溶解有机碳的浓度呈显著增升趋势。普遍认为与全球变化背景下北方泥炭地大规模释放溶解有机碳有关,但其驱动机制尚不十分清楚。已经提出的具有代表性...     

Riverine organic carbon in the Xijiang River (South China): seasonal variation in content and flux budget

. Riverine water samples were collected from the lower reach hydrometric station Makou of the Xijiang River, in four hydrological seasons during 1997 and 1998. The samples were analyzed for their particulate and dissolved organic carbon. The contents of riverine particulate and dissolved organic carbon changed synchronously during different hydrological processes. The contents of organic carbon and total suspended substances in the riverine water increased with increasing discharge. The mass of organic carbon in the total suspended substances decreased logarithmically with increasing total suspended substances. The transported flux of organic carbon in the Xijiang River drainage is about 10.18᎒⁶ g of C km^–2 year^–1, which is two to three times larger than that of the average value in other river systems. Particulate organic carbon is the main component of riverine organic carbon, with a flux of about 8.30᎒⁶ g of C km^–2 year^–1.     

珠江流域的化学侵蚀

是流域化学侵蚀过程的主要输出物质。在珠江的马口站、河口站两个断面进行了一个完整水文年(包括4个水文季节)的采样,用容量法对78组样品进行了含量分析。结果表明,珠江径流的含量在一个水文年中发生约36%的变化,汛期含量大于枯水期含量。径流含量与悬浮物含量之间存在相同的变化趋势。在同一水文季节,西江马口站断面径流含量较为均一,而北江河口站断面各采样点的含量相差较大。西江和北江流域侵蚀通量分别为1103×103mol/km2·a和1289×103mol/km2·a。影响珠江流域侵蚀通量的主要因素是流域内碳酸盐岩的出露面积和径流深度过度的土地开垦和酸雨等现代环境问题也是造成流域化学侵蚀强度增加的主要原因。     

Increased concentrations of dissolved trace metals and organic carbon during snowmelt in rivers of the alaskan arctic

Arctic rivers typically transport more than half of their annual amounts of water and suspended sediments during spring floods. In this study, the Sagavanirktok, Kuparuk and Colville rivers in the Alaskan Arctic were sampled during the spring floods of 2001 to determine levels of total suspended solids (TSS) and dissolved and particulate metals and organic carbon. Concentrations of dissolved organic carbon (DOC) increased from 167 to 742 μmol/L during peak discharge in the Sagavanirktok River, at about the same time that river flow increased to maximum levels. Concentrations of dissolved Cu, Pb, Zn and Fe in the Sagavanirktok River followed trends observed for DOC with 3- to 25-fold higher levels at peak flow than during off-peak discharge. Similar patterns were found for the Kuparuk and Colville rivers, where average concentrations of dissolved trace metals and DOC were even higher. These observations are linked to a large pulse of DOC and dissolved metals incorporated into snowmelt from thawing ponds and upper soil layers. In contrast with Cu, Fe, Pb and Zn, concentrations of dissolved Ba did not increase in response to increased discharge of water, TSS and DOC. Concentrations of particulate Cu, Fe, Pb and Zn were more uniform than observed for their respective dissolved species and correlated well with the Al content of the suspended particles. However, concentrations of particulate Al were poorly correlated with particulate organic carbon. Results from this study show that >80% of the suspended sediment and more than one-third of the annual inputs of dissolved Cu, Fe, Pb, Zn and DOC were carried to the coastal Beaufort Sea in 3 and 12 d, respectively, by the Kuparuk and Sagavanirktok rivers.     

Modern carbon burial in Lake Qinghai,China

The quantification of carbon burial in lake sediments, and carbon fluxes derived from different origins are crucial to understand modern lacustrine carbon budgets, and to assess the role of lakes in the global carbon cycle. In this study, we estimated carbon burial in the sediment of Lake Qinghai, the largest inland lake in China, and the carbon fluxes derived from different origins. We find that: (1) The organic carbon burial rate in lake sediment is approximately 7.23 g m⁻² a⁻¹, which is comparable to rates documented in many large lakes worldwide. We determined that the flux of riverine particulate organic carbon (POC) is approximately 10 times higher than that of dissolved organic carbon (DOC). Organic matter in lake sediments is primarily derived from POC in lake water, of which approximately 80% is of terrestrial origin. (2) The inorganic carbon burial rate in lake sediment is slightly higher than that of organic carbon. The flux of riverine dissolved inorganic carbon (DIC) is approximately 20 times that of DOC, and more than 70% of the riverine DIC is drawn directly and/or indirectly from atmospheric CO₂. (3) Both DIC and DOC are concentrated in lake water, suggesting that the lake serves as a sink for both organic and inorganic carbon over long term timescales. (4) Our analysis suggests that the carbon burial rates in Lake Qinghai would be much higher in warmer climatic periods than in cold ones, implying a growing role in the global carbon cycle under a continued global warming scenario.     

Transformation of phosphorus in the Elbe estuary

The distribution of dissolved and particle-bound phosphorus (P) was investigated in the Elbe estuary during March 1995. The forms of particulate P were studied with a sequential extraction technique. Organic P dominated particle-bound P in the outer reaches of the estuary (52%), decreased to a minimum of 21% in the turbidity zone, and increased to 33% further upstream. Fe-bound P was the second most important P species in the outer reaches (27%) and dominated in the turbidity zone (up to 57%) and upstream of the turbidity zone (up to 48%). The P:Fe ratio increased with decreasing salinity, from 0.11 in the outer reaches to about 0.22 at zero salinity. Dissolved inorganic P release from reverine suspended matter was about two to three times larger than release, from marine suspended matter and was dominated by release of Fe-bound P. Dissolved inorganic P release from marine and from riverine organic matter were of equal importance. Because marine suspended matter dominates in the estuary, this suggests riverine organic matter is remineralized much faster than marine organic matter. This is in line with the refractory nature of marine organic matter (no phytoplankton bloom) and the easily degradable character of the riverine suspended matter (phytoplankton bloom) in the Elbe estuary during March 1995.     

Stable isotope analysis of carbon cycling in the Perdido estuary, Florida

Stable carbon isotope (δ¹³C) analysis was used in the Peridido Estuary, Florida U.S. to determine the predominant carbon source that supports the bacterial assemblage. Stable carbon isotope values were measured in the suspended particulate matter (SPM), dissolved organic and inorganic matter, and bacteria. Stable nitrogen isotope (δ¹⁵N) ratios were measured in SPM and nitrate to assist in understanding carbon cycling through the estuary. Analyses were conducted on samples from riverine, coastal, and anthropogenic sources and compared with samples from the bay. Stable isotope ratio analysis was coupled with estimates of mixing of riverine and coastal waters into the bay. Preliminary observation of the °¹³C data indicates that terrestrial organic matter is the primary carbon source that is assimilated by bacteria in the ecosystem. Stable isotope data from carbon and nitrogen pools in combination with analysis of estuarine current velocities indicates that primary production is an important factor in the carbon cycle. This study demonstrates the importance of stable isotope analysis of multiple carbon and nitrogen pols to assess sources and cycling of organic matter.     

Speciation of dissolved selenium in the Kaoping and Erhjen rivers and estuaries,southwestern Taiwan

Analytical methods of dissolved Se species in river water and seawater were established and applied to study dissolved Se speciation in the Kaoping and Erhjen rivers and estuaries, southwestern Taiwan. The Kaoping and Erhjen rivers and estuaries were respectively in relatively oxygenated and oxygen-deficient conditions as revealed from the distributions of dissolved oxygen, DOC, nutrients, and dissolved Mn. Concentrations of dissolved total Se increased downstream in the riverine sections, ranging from 0.6 nM to 1.2 nM for the Kaoping River and from 0.8 nM to 1.05 nM for the Erhjen River. The dissolved total Se was only slightly higher in the Erhjen middle estuary than in the Kaoping middle estuary in spite of heavier pollution in the former. The dissolved total Se behaved rather conservatively in the Kaoping estuary but nonconservatively in the Erhjen estuary resulting from anthropogenic inputs, and in this respect showed similarities with the behavior of redox-sensitive Mn. The predominant species of selenium were Se(VI) and organic Se in the Kaoping River and Se(VI) in the Kaoping estuary. The elevated concentration of Se(VI) in the Kaoping estuary may stem from the degradation of organic Se and oxidation of Se(IV). On the other hand, Se(IV) and organic Se were equally dominant in the Erhjen River, and Se(IV) was predominant through most of the Erhjen estuary. The elevated distribution of Se(IV) in the Erhjen middle estuary may result mostly from partial decomposition of organic Se, but further oxidation of Se(IV) was inhibited in reducing waters. However, Se(VI) became dominant at Erhjen outer estuary where water was oxygenated by the replacement of intruded coastal seawater. Apparently, the speciation of dissolved Se was mainly controlled by the biological and redox processes in the Kaoping and Erhjen rivers and estuaries.     

唐古拉山冬克玛底冰川流域河水总溶解固体和悬移质的变化特征

通过2013年6-9月对唐古拉山冬克玛底冰川流域河水的逐日定时样品采集,并结合流域水文与气象资料,对径流的总溶解固体（TDS）和悬移质的变化特征进行分析。结果表明：2013年消融期的平均气温为3.7℃,消融期降水量为546 mm,7月和8月两个月径流量占消融期总径流量的63%。消融期逐日的TDS变化范围为31~140 mg·L^-1,平均值为60 mg·L^-1,TDS随径流变化显著,表现为消融强烈时（7-8月） TDS浓度较低,消融初期（6月）和末期（9月）时TDS浓度较高;径流中TDS与悬移质浓度（SSC）变化表现出相反变化趋势,即消融强烈时悬移质浓度较高,而消融初期与末期悬移质浓度较低,消融期平均悬移质浓度为122.8 mg·L^-1,流量-SSC时序关系表现为以顺时针滞后事件为主。2013年冬克玛底冰川流域消融期的化学侵蚀总量和物理侵蚀总量分别为2.214×10³ t和6.722×10³ t,化学侵蚀与物理侵蚀率的比值为0.33。