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1.
腾冲新生代火山区温泉CO2气体排放通量研究 总被引：6，自引：6，他引：0
近期研究表明,不仅火山喷发期会向当时的大气圈输送大量的温室气体,火山间歇期同样会释放大量的温室气体。在火山活动间歇期,火山区主要以喷气孔、温(热)泉以及土壤微渗漏等形式向大气圈释放温室气体。腾冲是我国重要的新生代火山区,同时也是重要的水热活动区,那里出露大量的温泉,然而目前未见腾冲火山区温泉气体排放通量的研究报道。本文利用数字皂膜通量仪测量了腾冲新生代火山区温泉中CO2的排放通量。研究结果表明,腾冲新生代火山区温泉向当今大气圈输送的CO2通量达3.58×103 t·a-1,相当于意大利锡耶纳Bassoleto地热区温泉中CO2的排放规模。腾冲火山区温泉的CO2释放通量主要受深部岩浆囊、断裂分布、地下水循环、围岩成分等多方面因素的影响。本文根据温泉中CO2的排放特征,将腾冲温泉分为南北两区,南区温泉CO2通量远高于北区的温泉,热海地热区的通量为腾冲CO2通量的最大值。在北温泉区,CO2通量主要受控于断裂的分布;而在南温泉区,除受到断裂控制外,热海地热区底部的岩浆囊及其与围岩的相互作用成为CO2气体的重要物质来源,同时高温的岩浆囊为温泉及CO2的形成提供了重要热源。 相似文献
2.
云贵高原湖泊CO2的地球化学变化及其大气CO2源汇效应 总被引：3，自引：0，他引：3
湖泊是大气CO2的源还是汇,长期以来一直都存有争议。云贵高原地区的湖泊由于受流域碳酸盐岩风化作用的影响,使这一问题就显得更特殊,也更复杂。本次研究通过化学平衡计算和气相色谱测定两种方法得到了比较一致的湖水CO2浓度结果。研究发现,在夏季强烈的光合作用消耗了湖水CO2,致使湖水中CO2浓度降低。在贵州草海、百花湖以及云南的泸沽湖、杞麓湖,表层湖水CO2分压(为便于与大气CO2比较,文中湖水CO2用分压单位表示)小于200μatm,远低于大气CO2分压,湖泊正不断地从大气中吸收CO2,从而构成大气CO2的汇。 相似文献
3.
4.
北京斋堂黄土中主要温室气体组分特征 总被引：4，自引：3，他引：1
根据极地冰芯等资料已经重建了过去大气温室气体（主要是CO2,CH4）浓度的变化。由于人类活动的影响,温室气体的含量自工业革命以来有了明显的上升,其影响表现为全球变暖。如果维持现在的CO2产放水平,根据气候模式预测到下个世纪末全球温度将增加l-3.5℃,可能极大地改变人类生存的环境。但是预测结果还存在着很大的不确定性,其中一个重要因素是对温室气体的源和汇的理解还不完善,有相当数量的CO2声向不明（即未知汇）.目前倾向认为,在北半球的中纬度地带可能存在着一个巨大的陆地生态系统汇（植被和土壤）.中国黄土分布在北半球中纬度,实际上是在干旱一半干旱气候条件下形成的一套巨厚的成土作用较弱的黄土一古土壤序列。 相似文献
5.
大气细粒子(PM2.5)污染是全球尤其是我国许多城市的重要环境问题。利用示踪物质识别和估算大气颗粒物来源是公认的可靠技术,纤维素可以作为示踪物质表征一次颗粒物的天然植被排放来源。本文针对大气细粒子中纤维素含量低、全程序空白相对较高等难点,优化建立了纤维素酶水解、GOD-苯酚-四氨基安替比林测糖法,在我国首次应用于测定大气PM2.5中纤维素的含量,估算天然植被排放源的贡献。方法检出限为0.26 μg/m3(纤维素),可以满足大气PM2.5纤维素测定要求;而且有效地降低了空白,全程序空白值(36.5 μg葡萄糖)低于文献方法空白值(53.8 μg葡萄糖),使之更适合于PM2.5的测定。使用本方法对2012年5月至6月采集的北京市大气PM2.5样品进行分析,纤维素检出率为96%,纤维素的平均含量为(0.573±0.17) μg/m3,折合为天然植被排放量占PM2.5质量浓度的1.37%±0.65%;天然植被排放源对有机碳的平均贡献率为4.4%,最大达到9.2%,反映出天然植被排放是北京市PM2.5的重要来源之 一。本研究方法为我国城市大气颗粒物(包括总悬浮颗粒物、PM10、PM2.5等)来源识别提供了新的手段。 相似文献
6.
岩溶区碳循环与大气CO2的源汇关系：以贵州岩溶区为例 总被引：1，自引：0，他引：1
全球碳循环的研究表明，人为ＣＯ２收支存在不平衡现象，据不同的估算，其未知汇为（１．８±１．４）×１０＾１５ｇＣ／ａ或（２．０～４．７）×１０＾１５ｇＣ／ａ。通过对贵州高原岩溶区岩溶作用带及其相邻圈层碳循环的观测，研究表明，岩溶作用带的碳循环强度与其相邻圈层（土壤层，生物圈，大气圈）的碳循环强度密切相关，表层带岩溶泉水中的ＨＣＯ＾－３与上部圈层的ＣＯ２浓度呈较好的正相关关系。同时，在不同生态，地质条 相似文献
7.
周口店地区的古环境变化研究多数研究集中在中更新世时期,而缺乏对早更新世时期环境变化的研究。这主要是由于缺少保存完好的早更新世沉积记录造成的。随着对20世纪80年代在周口地区发现的东洞剖面,发现这是一个保存完好的早更新世剖面,为研究早更新世时期的古环境变化特征提供了良好的研究材料。为了重建早更新世时期的古环境变化特征,利用XRF对东洞洞穴沉积物的主要元素（SiO2,Al2O3,Fe2O3和CaO）的化学组成进行了高分辨率分析,同时对沉积物中的FeO含量进行了测试。结果显示东洞剖面沉积物的主要化学组成为SiO2,占41.6%～58.9%,其次是Al2O3和Fe2O3,其含量的变化范围分别为13.69%～29.63%和5.00%～9.81%。Al2O3和Fe2O3在剖面上与SiO2含量成明显的镜像变化关系,显示出Al2O3和Fe2O3对沉积物中SiO2含量的稀释作用。另外,Fe2O3与Al2O3在剖面上具有很好的相关性,表明Fe2O3主要富集在富铝的矿物中。从元素含量在剖面的上分布看,东洞剖面的化学组成发生3次大的波动,主要表现为SiO2和FeO含量增高,而Fe2O3与Al2O3含量的减少。这3次波动分别出现在剖面的15.3～14.6m,11.0～9.9m和8.40～7.84m深度处。在3次化学组成的波动出现的同时,指示沉积物风化程度和温度变化的Si/Al（SiO2/Al2O3）和FeO/Fe2O3比值也发生了明显变化,比值增高,指示了3次大的干冷事件。另外,在剖面上部（10.00～7.84m,即第2次事件以后）SiO2/Al2O3和FeO/Fe2O3比值变高且波动频繁,表明自第2次干冷事件后沉积区的环境变得不稳定,逐渐向冷干气候转变。东洞剖面的地球化学记录（SiO2/Al2O3和FeO/Fe2O3）与泾川黄土剖面的粒度曲线具有较好的对比性,支持了东洞剖面记录的环境信息与黄土沉积记录的环境变化具有一致性。通过与泾川粒度曲线的对比发现,东洞剖面记录的3次干冷事件在时段上分别对应于黄土-古土壤序列中的L26,L15和L13。 相似文献
8.
河流碳通量与陆地侵蚀研究 总被引：29，自引：2，他引：29
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。 相似文献
9.
测定了新疆罗布泊地区湖相沉积物CK-2钻孔样品的总有机碳含量（TOC）及其同位素组成、碳酸盐含量和C/N比值等环境代用指标,以及石膏矿物的质谱-铀系年龄。测试结果表明,20～9kaB.P.期间沉积物δ13Corg.在-23.4‰～-16.1‰之间波动且阶段性明显,与TOC呈现良好的相关关系,整体变化趋势同南极Dome C冰芯中记录的全球大气CO2浓度一致;C/N比值表明有机碳来源主要是陆生高等植物。因此大气CO2浓度变化是影响20～9kaB.P.期间罗布泊湖相沉积物δ13Corg.值变化的主导因素,周围山体上C3/C4植物相对生物量的变化则是另一重要因素。依据δ13Corg.的变化序列将此时间段湖区古环境的演化分成6个阶段:20.0～14.1kaB.P.期间受到末次盛冰期的影响,气温偏低,湖水丰沛;14.1～13.3kaB.P.是一个气候不稳定期,冷暖波动较频繁,但以暖为趋势;13.3～12.8kaB.P.期间经历了一段冷期,于12.8kaB.P.结束了末次冰期,随后气候开始转暖至11.8kaB.P.;其后气温再次变冷并维持到10kaB.P.;最后从10kaB.P.进入全新世暖期。δ13Corg.序列明显向偏负方向变化,表明该地区变暖的趋势相当明显。罗布泊地区日益干旱化是全球气候变化的结果,尤其是受到全球CO2浓度的不断升高所制约。 相似文献
10.
本次研究选择中国东部一个生态和环境空间分异极大的浅水湖泊（太湖）以及周围河流,分别于2003年7月和9月两次采集湖水和河水样品,分析其中的N2O浓度,并利用扩散模型公式估算水-气界面N2O交换通量。结果显示N2O饱和度的空间变化从70％不饱和到2708％过饱和变化范围很大。N2O饱和度的空间分布,N2O与CH4、无机氮、TDS（总溶解固体物质）之间的相关性都表明： 太湖重度富营养区N2O的产生极大地受到人为N输入的影响。然而,初步的通量分析显示湖泊N2O的释放因子不超过0.63％,小于河流中的默认值,N2O产率也略低于水环境中的平均值,太湖以面积为权重的释放通量平均值并不高,在7月和9月分别为14.0μmol/m2·d和9.7μmol/m2·d。这些结果表明流域人为N输入对整个湖泊N2O的促进作用是有限的,预计未来湖泊N2O释放不会因为人为活动增加而出现大幅度增加的状况。流域内各生态景观N2O释放量的比较,也表明富营养湖泊总体上仍然是一个十分有限的大气N2O释放源。相反,太湖周围河流存在较大的N2O释放速率,在7月和9月估算的N2O释放通量分别为142.1μmol/m2·d和28.8μmol/m2·d。将这一释放速率推广到整个流域后,预计河网的N2O释放量将占到耕作土壤的10％～50％,显示了河流对区域N2O质量平衡具有较重要的影响。 相似文献
11.
本文介绍了国外利用AMS14C法研究极冰、海水中溶解的碳、大气中含碳,深海沉积含碳物等的最新进展和成果。这些成果表明,由于AMS14C法测定需要的样品量仅是常规测定用量的千分之一,因而为在地学领域中的应用开辟了广阔的前景。我国的AMS14C方法研究已经起步,新方法的建成和使用必将推动有关学科的进一步发展。 相似文献
12.
Release of CO2 from surface ocean water owing to precipitation of CaCO3 and the imbalance between biological production of organic matter and its respiration, and their net removal from surface
water to sedimentary storage was studied by means of a quotient θ = (CO2 flux to the atmosphere)/(CaCO3 precipitated). θ depends not only on water temperature and atmospheric CO2 concentration but also on the CaCO3 and organic carbon masses formed. In CO2 generation by CaCO3 precipitation, θ varies from a fraction of 0.44 to 0.79, increasing with decreasing temperature (25 to 5°C), increasing atmospheric
CO2 concentration (195–375 ppmv), and increasing CaCO3 precipitated mass (up to 45% of the initial DIC concentration in surface water). Primary production and net storage of organic
carbon counteracts the CO2 production by carbonate precipitation and it results in lower CO2 emissions from the surface layer. When atmospheric CO2 increases due to the ocean-to-atmosphere flux rather than remaining constant, the amount of CO2 transferred is a non-linear function of the surface layer thickness because of the back-pressure of the rising atmospheric
CO2. For a surface ocean layer approximated by a 50-m-thick euphotic zone that receives input of inorganic and organic carbon
from land, the calculated CO2 flux to the atmosphere is a function of the CaCO3 and Corg net storage rates. In general, the carbonate storage rate has been greater than that of organic carbon. The CO2 flux near the Last Glacial Maximum is 17 to 7×1012 mol/yr (0.2–0.08 Gt C/yr), reflecting the range of organic carbon storage rates in sediments, and for pre-industrial time
it is 38–42×1012 mol/yr (0.46–0.50 Gt C/yr). Within the imbalanced global carbon cycle, our estimates indicate that prior to anthropogenic
emissions of CO2 to the atmosphere the land organic reservoir was gaining carbon and the surface ocean was losing carbon, calcium, and total
alkalinity owing to the CaCO3 storage and consequent emission of CO2. These results are in agreement with the conclusions of a number of other investigators. As the CO2 uptake in mineral weathering is a major flux in the global carbon cycle, the CO2 weathering pathway that originates in the CO2 produced by remineralization of soil humus rather than by direct uptake from the atmosphere may reduce the relatively large
imbalances of the atmosphere and land organic reservoir at 102–104-year time scales. 相似文献
13.
Steven W. Leavitt 《Environmental Geology》1982,4(1):15-21
Continuing interest in the effects of carbon dioxide on climate has been promoted by the exponentially increasing anthropogenic
production of CO2. Volcanoes are also a major source of carbon dioxide, but their average input to the atmosphere is generally considered minor
relative to anthropogenic input. This study examines eruption chronologies to determine a new estimate of the volcanic CO2 input and to test if temporal fluctuations may be resolved. Employing representative average values of 2.7 g cm−3 as density of erupted material, 0.2 wt percent CO2 in the original melt, 60 percent degassing during eruption, and an average volume of 0.1 km3 for each of the eruptions in the recently published eruption chronology of Hirschboeck (1980), a volcanic input of about
1.5 · 1011 moles CO2 yr−1 was determined for the period 1800–1969. The period 1800–1899 had a somewhat lower input than 1900–1969, which could well
be related more to completeness of observational data than to a real increase in volcanic CO2. This input is well below man's current CO2 production of 4–5 · 1014 moles CO2 yr−1.
The average values above together with specific volumetric estimates were employed to calculate CO2 input from individual historic eruptions, massive flood basalts, and ash-flow eruptions. Total CO2 release from the largest of flood basalt and ash-flow sequences was 1015-1016 moles of CO2. The impact of these sources on global atmospheric CO2 and climate, however, will be limited by the duration and spacing of the major individual eruptive periods in the sequences. 相似文献
14.
Marcelo F. L. Souza Viviane R. Gomes Simone S. Freitas Regina C. B. Andrade Bastiaan Knoppers 《Estuaries and Coasts》2009,32(1):111-122
Net ecosystem metabolism (NEM) was measured in the Piauí River estuary, NE Brazil. A mass balance of C, N, and P was used to infer its sources and sinks. Dissolved inorganic carbon (DIC) concentrations and fluxes were measured over a year along this mangrove dominated estuary. DIC concentrations were high in all estuarine sections, particularly at the fluvial end member at the beginning of the rainy season. Carbon dioxide concentrations in the entire estuary were supersaturated throughout the year and highest in the upper estuarine compartment and freshwater, particularly at the rainy season, due to washout effects of carbonaceous soils and different organic anthropogenic effluents. The estuary served as a source of DIC to the atmosphere with an estimated flux of 13 mol CO2 m?2 year?1. Input from the river was 46 mol CO2 m?2 year?1. The metabolism of the system was heterotrophic, but short periods of autotrophy occurred in the lower more marine portions of the estuary. The pelagic system was more or less balanced between auto- and heterotrophy, whereas the benthic and intertidal mangrove region was heterotrophic. Estimated annual NEM yielded a total DIC production in the order of 18 mol CO2 m?2 year?1. The anthropogenic inputs of particulate C, N, and P, dissolved inorganic P (DIP), and DIC were significant. The fluvial loading of particulate organic carbon and dissolved inorganic nitrogen (DIN) was largely retained in two flow regulation and hydroelectric reservoirs, promoting a reduction of C:N and C:P particulate ratios in the estuary. The net nonconservative fluxes obtained by a mass balance approach revealed that the estuary acts as a source of DIP, DIN, and DIC, the latter one being almost equivalent to the losses to the atmosphere. Mangrove forests and tidal mudflats were responsible for most of NEM rates and are the main sites of organic decomposition to sustain net heterotrophy. The main sources for this organic matter are the fluvial and anthropogenic inputs. The mangrove areas are the highest estuarine sources of DIP, DIC, and DIN. 相似文献
15.
Greenhouse gases and greenhouse effect 总被引：1，自引：0，他引：1
G. V. Chilingar O. G. Sorokhtin L. Khilyuk M. V. Gorfunkel 《Environmental Geology》2009,58(6):1207-1213
Conventional theory of global warming states that heating of atmosphere occurs as a result of accumulation of CO2 and CH4 in atmosphere. The writers show that rising concentration of CO2 should result in the cooling of climate. The methane accumulation has no essential effect on the Earth’s climate. Even significant
releases of the anthropogenic carbon dioxide into the atmosphere do not change average parameters of the Earth’s heat regime
and the atmospheric greenhouse effect. Moreover, CO2 concentration increase in the atmosphere results in rising agricultural productivity and improves the conditions for reforestation.
Thus, accumulation of small additional amounts of carbon dioxide and methane in the atmosphere as a result of anthropogenic
activities has practically no effect on the Earth’s climate. 相似文献
16.
G. Brey 《Contributions to Mineralogy and Petrology》1976,57(2):215-221
CO2 solubility has a slight negative temperature dependence in olivine melilitite at 30 kb with 9% CO2 dissolved at 1,450 °C, 8.5% at 1,550 °C and 8.3% at 1,650° C. CO2 is dissolved as the carbonate molecule (CO
3
2–
) only. Feldspar melts (albite-anorthite) dissolve much less CO2 at 30 kb (around 2%) with a slight increase with increasing anorthite content. A CO2 absorption peak in infrared spectra of albite-rich glasses diappears in favour of the CO
3
2–
peak with increasing anorthite content. It is inferred that CO2 was present as CO
3
2–
in albite-rich melts also, but reverts to CO2 during quenching because of bonding differences related to Ca2+ and Na+ in the melts. 相似文献
17.
The main aim of this study was to assess the natural and anthropogenic contributions of CO2 in the urban atmosphere of Wrocław City (SW Poland) using combined quantitative (CO2 concentrations) and qualitative analysis (δ13C of CO2). Between 21 January 2011 and 22 December 2011, 17 sampling campaigns were performed at 3-week intervals and in total 255 samples were collected. The mean CO2 concentration was 469 ± 71 ppm and the mean δ13C(CO2) was −10.8 ± 1‰.The measured δ13C(CO2) values of major end-members for two winter heating seasons (−25.7‰ in January–March of 2011 and −27.6 ‰ in October–December of 2011) and for one vegetative season (−20.4‰ in April–September of 2011) suggest soil respiration as a main source of atmospheric CO2 during the vegetative season, and a very significant impact of fossil fuel combustion during the winter heating seasons. There were significant increases of CO2 concentrations at many sampling locations after the opening of a new motorway on 31 August 2011. The authors hypothesise that the new motorway contributes to the increase of CO2 across the city. 相似文献
18.
Faxiang Tao 《中国地球化学学报》2017,36(4):658-666
The carbon cycle of global inland waters is quantitatively comparable to other components in the global carbon budget. Among inland waters, a significant part is man-made lakes formed by damming rivers. Man-made lakes are undergoing a rapid increase in number and size. Human impacts and frequent algae blooms lead to it necessary to make a better constraint on their carbon cycles. Here, we make a primary estimation on the air–water CO2 transfer flux through an algae bloom year for a subtropical man-made lake—Hongfeng Lake, Southwest China. To do this a new type of glass bottles was designed for content and isotopic analysis of DIC and other environmental parameters. At the early stage of algae bloom, CO2 was transferred from the atmosphere to the lake with a net flux of 1.770 g·C·m?2. Later, the partial pressure (pCO2) of the aqueous CO2 increased rapidly and the lake outgassed to the atmosphere with a net flux of 95.727 g·C·m?2. In the remaining days, the lake again took up CO2 from the atmosphere with a net flux of 14.804 g·C·m?2. As a whole, Lake Hongfeng released 4527 t C to the atmosphere, accounting for one-third of the atmosphere/soil CO2 sequestered by chemical weathering in the whole drainage. With an empirical mode decomposition method, we found air temperature plays a major role in controlling water temperature, aqueous pCO2 and hence CO2 flux. This work indicates a necessity to make detailed and comprehensive carbon budgets in man-made lakes. 相似文献
19.
Weathering of rocks that regulate the water chemistry of the river has been used to evaluate the CO2 consumption rate which exerts a strong influence on the global climate. The foremost objective of the present research is to estimate the chemical weathering rate (CWR) of the continental water in the entire stretch of Brahmaputra River from upstream to downstream and their associated CO2 consumption rate. To establish the link between the rapid chemical weathering and thereby enhance CO2 drawdown from the atmosphere, the major ion composition of the Brahmaputra River that drains the Himalaya has been obtained. Major ion chemistry of the Brahmaputra River was resolved on samples collected from nine locations in pre-monsoon, monsoon and post-monsoon seasons for two cycles: cycle I (2011–2012) and cycle II (2013–2014). The physico-chemical parameters of water samples were analysed by employing standard methods. The Brahmaputra River was characterized by alkalinity, high concentration of Ca2+ and HCO3 ? along with significant temporal variation in major ion composition. In general, it was found that water chemistry of the river was mainly controlled by rock weathering with minor contributions from atmospheric and anthropogenic sources. The effective CO2 pressure (log\({{\text{P}}_{{\text{C}}{{\text{O}}_{\text{2}}}}}\)) for pre-monsoon, monsoon and post-monsoon has been estimated. The question of rates of chemical weathering (carbonate and silicate) was addressed by using TDS and run-off (mm year?1). It has been found that the extent of CWR is directly dependent on the CO2 consumption rate which may be further evaluated from the perspective of climate change mitigation The average annual CO2 consumption rate of the Brahmaputra River due to silicate and carbonate weathering was found to be 0.52 (×106 mol Km?2 year?1) and 0.55 (×106 mol Km?2 year?1) for cycle I and 0.49 (×106 mol Km?2 year?1) and 0.52 (×106 mol Km?2 year?1) for cycle II, respectively, which were significantly higher than that of other Himalayan rivers. Estimation of CWR of the Brahmaputra River indicates that carbonate weathering largely dominates the water chemistry of the Brahmaputra River. 相似文献
20.
Oceania supplies ∼40% of the global riverine flux of organic carbon, approximately half of which is injected onto broad continental shelves and processed in shallow deltaic systems. The Gulf of Papua, on the south coast of the large island of New Guinea, is one such deltaic clinoform complex. It receives ∼4 Mt yr−1 particulate terrestrial organic carbon with initial particle Corg loading ∼0.7 mg m−2. Corg loading is reduced to ∼0.3 mg m−2 in the topset-upper foreset zones of the delta despite additional inputs of mangrove and planktonic detritus, and high net sediment accumulation rates of 1-4 cm yr−1. Carbon isotopic analyses (δ13C, Δ14C) of ΣCO2 and Corg demonstrate rapid (<100 yr) remineralization of both terrestrial (δ13C <−28.6) and marine Corg (δ13C ∼−20.5) ranging in average age from modern (bomb) (Δ14C ∼60) to ∼1000 yr (Δ14C ∼−140). Efficient and rapid remineralization in the topset-upper foreset zone is promoted by frequent physical reworking, bioturbation, exposure, and reoxidation of deposits. The seafloor in these regions, particularly <20 m, apparently functions as a periodically mixed, suboxic batch reactor dominated by microbial biomass. Although terrestrial sources can be the primary metabolic substrates at inshore sites, relatively young marine Corg often preferentially dominates pore water ΣCO2 relative to bulk Corg in the upper foreset. Thus a small quantity of young, rapidly recycled marine organic material is often superimposed on a generally older, less reactive terrestrial background. Whereas the pore water ΣCO2 reflects both rapidly cycled marine and terrestrial sources, terrestrial material dominates the slower overall net loss of Corg from particles in the topset-upper foreset zone (i.e. recycled marine Corg leaves little residue). Preferential utilization of Corg subpools and diagenetic fractionation of C isotopes supports the reactive continuum model as a conceptual basis for net decomposition kinetics. Early diagenetic fractionation of C isotopes relative to the bulk sedimentary Corg composition can produce changes in 14C activity independent of radioactive decay. In the Gulf of Papua topset-upper foreset, Δ14C of pore water ΣCO2 averaged ∼ 300‰ greater than Corg sediment between ∼1-3 m depth in deposits. Diagenetic fractionation and decomposition aging of sedimentary Corg compromises simple application of 14C for determination of sediment accumulation rates in diagenetically reactive deposits. 相似文献