海洋沉积物中色素生物标志物研究进展

海洋沉积物中的光合色素包含着水体、沉积物中浮游和底栖植物以及微生物群落的丰富信息,能表征特定生物来源,在埋藏到沉积物甚至发生某些改变之后仍然保留其源信息,是一类重要的化学生物标志物.结合总有机碳、总氮等其他海洋地球化学参数,沉积色素可用来研究海洋浮游植物和光合细菌的群落组成和丰度,反演海洋初级生产、水体富营养化水平及其历史趋势,指示水体和沉积物氧化还原条件,揭示海域气候条件等现状及其历史变化.沉积色素的研究,对于掌握海洋中碳的生物地球化学循环过程,回溯古环境、古海洋、古生态以及古气候记录,制定合理的海洋管理政策具有十分重要的意义.阐述了沉积物中色素的分类、来源、性质和分析方法,分析了色素在沉积物中的保存和变化规律,探讨总结了沉积色素作为化学生物标志物在海洋学研究中的应用.     

Selective preservation of soil organic matter in oxidized marine sediments (Madeira Abyssal Plain)

In ocean margin sediments both marine and terrestrial organic matter (OM) are buried but the factors governing their relative preservation and degradation are not well understood. In this study, we analysed the degree of preservation of marine isoprenoidal and soil-derived branched glycerol dialkyl glycerol tetraethers (GDGTs) upon long-term oxygen exposure in OM-rich turbidites from the Madeira Abyssal Plain by analyzing GDGT concentrations across oxidation fronts. Relative to the anoxic part of the turbidites ca. 7-20% of the soil-derived branched GDGTs were preserved in the oxidized part while only 0.2-3% of the marine isoprenoid GDGT crenarchaeol was preserved. Due to these different preservation factors the Branched Isoprenoid Tetraether (BIT) index, a ratio between crenarchaeol and the major branched GDGTs that is used as a tracer for soil-derived organic matter, substantially increases from 0.02 to 0.4. Split Flow Thin Cell (SPLITT) separation of turbidite sediments showed that the enhanced preservation of soil-derived carbon was a general phenomenon across the fine particle size ranges (<38 μm). Calculations reveal that, despite their relatively similar chemical structures, degradation rates of crenarchaeol are 2-fold higher than those of soil-derived branched GDGTs, suggesting preferential soil OM preservation possibly due to matrix protection.     

Alkyl amides in two organic-rich anoxic sediments: A possible new abiotic route for N sequestration

Fixed nitrogen (N) plays an integral role in global cycling; while most is recycled to refuel primary productivity, a small fraction escapes to be preserved and stabilised in sediments. Despite decades of research, the functionality and reactivity of this sequestered organic N has been poorly understood. This study was undertaken to shed light on this problem by characterising the bulk sediment organic matter using nuclear magnetic resonance (NMR), followed by molecular level analysis using ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). We studied two organic-rich anaerobic sediments, one from a freshwater system and another from a marine paralic basin. Mangrove Lake, Bermuda (marine) and Mud Lake, Florida (freshwater) have been shown in past studies to contain high levels of N-containing organic matter. Our resulting multidimensional NMR data suggests the existence of a new type of amide functionality in both these lake sediments, and we investigated this further using FT-ICR-MS and gas chromatography mass spectrometry (GC-MS). FT-ICR-MS confirmed the existence of homologous series of CHNO containing compounds, whose structures are verified using GC-MS as alkyl amides. Model reactions involving naturally occurring esters and ammonia suggest the source of alkyl amides to be amidation of esters with sedimentary ammonia derived from anaerobic degradation of organic matter. This expands upon previous hypotheses for preservation of amide containing compounds that call upon biological/abiological protection of proteins and peptides or the formation of refractory nitrogenous adducts.     

Elucidation of different forms of organic carbon in marine sediments from the Atlantic coast of Spain using thermal analysis coupled to isotope ratio and quadrupole mass spectrometry

Analysis of river, estuary and marine sediments from the Atlantic coast of Spain using thermogravimetry–differential scanning calorimetry–quadrupole mass spectrometry–isotope ratio mass spectrometry (TG–DSC–QMS–IRMS) was used to (a) distinguish bulk chemical hosts for C within a sediment and humic acid fraction, (b) track C pools with differing natural C isotope ratios and (c) observe variation with distance from the coast. This is the first application of such a novel method to the characterisation of organic matter from marine sediments and their corresponding humic acid fractions. Using thermal analysis, a labile, a recalcitrant and a refractory carbon pool can be distinguished. Extracted humic fractions are mainly of recalcitrant nature. The proportion of refractory carbon is greatest in marine sediments and humic acid fractions. Quadrupole mass spectrometry confirmed that the greatest proportion of m/z 44 (CO₂) and m/z 18 (H₂O) were detected at temperatures associated with recalcitrant carbon (510–540 °C). Isotope analysis detected progressive enrichment in δ¹³C for the sediment samples with an increase in marine influence. Isotopic heterogeneity in the refractory organic matter in marine sediments could be due to products of anthropogenic origin or natural combustion products. Isotope homogeneity of humic acids confirms the presence of terrigenous C in marine sediments, allowing the terrestrial input to be characterised.     

海相沉积物碳酸盐相中微量元素的分析方法研究

海相沉积物中自生沉积碳酸盐相的微量元素携带极为丰富的原始地质信息,然而海相沉积物中碳酸盐相的测定还没有建立统一的标准方法.本文以修正的Tessier七步提取流程为基础,以电感耦合等离子体质谱法(ICP-MS)为检测手段,针对海相沉积物碳酸盐相组分中V、Cr、Co、Ni、Sr五种微量元素建立了分级提取方法.实验以海相沉积物样品和标准物质作为参考样品,对比了NaAc和EDTA提取碳酸盐相的效果.结果表明,NaAc不能完全提取出沉积物碳酸盐相中的微量元素;EDTA可以较好地提取自生海相沉积物碳酸盐相中的微量元素,但是由于其络合能力太强还会提取有机物结合态的金属元素.本研究确定的分级提取方法是:首先用中性盐NaC1去除离子交换态,然后用提取专一性较强的焦磷酸钠(pH =10)去除有机态,再用EDTA提取仅自生海相沉积物的碳酸盐相.方法精密度(RSD)均＜5％,各元素的检出限在0.5～ 4.3 ng/g之间,回收率在88.0％ ～ 101.6％之间,方法的选择性和稳定性能够满足地球化学样品形态分析的要求.     

The lignin component of humic substances: Distribution among soil and sedimentary humic,fulvic, and base-insoluble fractions

Vanillyl, syringyl and cinnamyl phenols occur as CuO oxidation products of humic, fulvic and base-insoluble residual fractions from soils, peat and nearshore marine sediments. However, none of these lignin-derived phenols were released by CuO oxidation of deepsea sediment or its base-extractable organic fractions. Lignin analysis indicated that peat and coastal marine sediments contained significantly higher levels of recognizable vascular plant carbon (20–50%) than soils and offshore marine sediments (0–10%).Although accounting for less than 20% of the total sedimentary (bulk) lignin, lignin components of humic acid fractions compositionally and quantitatively resembled the corresponding bulk samples and baseinsoluble residues. Recognizable lignin, presumably present as intact phenylpropanoid units, accounted for up to 5% of the carbon in peat and coastal humic acids but less than 1% in soil humic acids. Fulvic acid fractions uniformly yielded less lignin-derived phenols in mixtures that were depleted in syringyl and cinnamyl phenols relative to the corresponding humic acid fractions.Within the vanillyl and syringyl families the relative distribution of acidic and aldehydic phenols is a sensitive measure of the degree of oxidative alteration of the lignin component The high acid/aldehyde ratios and the low phenol yields of soils and their humic fractions compared to peat and coastal sediments indicate extensive degradation of the lignin source material. Likewise, the progressively higher acid/aldehyde ratios and lower phenol yields along the sequence: plant tissues (plant debris)-humic acids-fulvic acids suggest that this pattern represents the diagenetic sequence for the aerobic degradation of lignin biopolymers.     

Reactivity of organic matter in aquifer sediments: geological and geochemical controls

Reduction rates in aquifers are commonly carbon limited, but little is known about the molecular composition and degradability of sedimentary organic matter (SOM) in aquifer sediments. The composition, source and degradation status of SOM in aquifer sediments of fluvio-glacial (Pleistocene) and shallow marine (Pliocene) origin, were determined using flash pyrolysis-gas chromatography/mass spectrometry. Incubation experiments (106 d) were used to assess the reactivity of SOM towards molecular oxygen. A dominance of lignin-derived components and long chain odd-over-even predominant alkanes indicate that terrestrial higher land plants were the main source of SOM even in the shallow marine sediments, while bacterial lipid-derived hopanoids and iso- and anteiso-C₁₅ and C₁₇ fatty acids indicate a minor contribution of microbial biomass. No compositional difference was observed between SOM present in the fine (<63 μm) and coarse fraction (63-2000 μm). A significant part of SOM was not present as low-molecular-weight compounds but was macromolecularly bound. For the fluvio-glacial sediments, a relatively higher abundance of resistant macromolecular compounds was in agreement with stronger signs of aerobic lignin, alkane and hopanoid oxidation. The more degraded status of SOM in the fluvio-glacial sediments was consistent with their significantly lower SOM mineralization (2-6%) during incubation, as compared with the shallow marine sediments (9-14%). The reactivity towards oxygen of SOM was controlled by the extent of past aerobic oxidation. Not the age of SOM, but the extent of oxygen exposure during syn- and postdepositional conditions seems most important in affecting the degradation status of SOM in aquifer sediments and thus their ability to reduce oxidants.     

Possible carotenoid-derived structures in fossil kerogens

The unique KMnO₄ degradation products of β-carotene, previously identified as 2,2-dimethyl succinic acid (C₆) and 2,2-dimethyl glutaric acid (C₇) have been found in the oxidation products of Green River shale (Eocene, 52 × 10⁶yr) and Tasmanian Tasmanite (Permian, 220−274 × 10⁶yr) kerogens. These two compounds were also detected in KMnO₄ degradation products of young kerogens from lacustrine and marine sediments. The results indicate that kerogens incorporated carotenoids (possibly β-carotene) at the time of kerogen formation in surface sediments. Both acids are useful markers to obtain information on biological precursors contributing to the formation of fossil kerogens.     

Short chain ladderanes: Oxic biodegradation products of anammox lipids

Anammox, the microbial anaerobic oxidation of ammonium by nitrite to produce dinitrogen gas, has been recognized as a key process in both the marine and freshwater nitrogen cycles, and found to be a major sink for fixed inorganic nitrogen in the oceans. Ladderane lipids are unique anammox bacterial membrane lipids that have been used as biomarkers for anammox bacteria in recent and past environmental settings. However, the fate of ladderane lipids during diagenesis is as of yet unknown. In this study, we performed oxic degradation experiments (at 20-100 °C) with anammox bacterial biomass to simulate early diagenetic processes occurring in the water column and at the sediment-water interface. Abundances of C₁₈ and C₂₀ ladderane lipids decreased with increasing temperatures, testifying to their labile nature. The most abundant products formed were ladderane lipids with a shorter alkyl side chain (C₁₄ and C₁₆ ladderane fatty acids), which was unambiguously established using two-dimensional NMR techniques on an isolated C₁₄-[3]-ladderane fatty acid. The most pronounced production of these short-chain lipids was at 40 °C, suggesting that degradation of ladderane lipids was microbially mediated, likely through a β-oxidation pathway. An HPLC-MS/MS method was developed for the detection of these ladderane alteration products in environmental samples and positively tested on various sediments. This showed that the ladderanes formed during degradation experiments also naturally occur in the marine environment. Thus, short-chain ladderane lipids may complement the original longer-chain ladderane lipids as suitable biomarkers for the detection of anammox processes in past depositional environments.     

Formation of pristane from α-tocopherol under simulated anoxic sedimentary conditions: A combination of biotic and abiotic degradative processes

Incubation of intact and oxidized α-tocopherol (vitamin E) in anaerobic sediment slurries allowed us to demonstrate that, as previously suggested by Goossens et al. (1984), the degradation of α-tocopherol in anoxic sediments results in the formation of pristane. The conversion of α-tocopherol to this isoprenoid alkane involves a combination of biotic and abiotic degradative processes, i.e. the anaerobic biodegradation (which seems to be mainly induced by denitrifying bacteria) of trimeric structures resulting from the abiotic oxidation of α-tocopherol. On the basis of the results obtained, it is proposed that in the marine environment most of the α-tocopherol present in phytoplanktonic cells should be quickly degraded within the water column and the oxic zone of sediments by way of aerobic biodegradation, photo- and autoxidation processes. Abiotic transformation of this compound mainly results in the production of trimeric oxidation products, sufficiently stable to be incorporated into anoxic sediments and whose subsequent anaerobic bacterial degradation affords pristane. These results confirm that the ratio pristane to phytane cannot be used as an indicator of the oxicity of the environment of deposition; in contrast, they support the use of PFI (Pristane Formation Index) as a proxy for the state of diagenesis of sedimentary organic matter.     

The use of hydroxyacids as geochemical indicators

The distributions of hydroxyacids in a variety of Recent and ancient sediments have been determined by gas chromatography-mass spectrometry. A lacustrine sediment (Rostherne Mere, U.K.) and two marine situations (Cariaco Trench, Black Sea) were analyzed as examples of Recent depositional environments. β-hydroxyacids occurred in all of the Recent sediments, consistent with their presumed microbial origin, whereas di- and trihydroxyacids were present in the sediments with a significant higher plant input (Black Sea and Rostherne Mere sediments). The two ancient (Eocene) sediments examined, viz. the Greene River (U.S.) and Messel (Germany) oil-shales, contained only trace amounts of hydroxyacids. These results provide evidence that hydroxyacids are in general not well preserved over geological time.     

From land to sea: provenance,composition, and preservation of organic matter in a marine sediment record from the North-East Greenland shelf spanning the Younger Dryas–Holocene

The organic matter content of marine sediments is often used to infer past changes in ocean conditions. However, the organic carbon pool preserved in coastal sediments is a complex mixture derived from different sources and may not reflect in situ processes. In this study, we combine taxonomic identification of reworked palynomorphs with pyrolysis organic geochemistry and reflected-light organic petrographic microscopy to investigate the provenance, composition and preservation of organic matter in a marine sediment core retrieved from the NE Greenland shelf. Our study reveals continuous yet variable input of land-derived organic carbon to the marine environment throughout the late Younger Dryas–Holocene, with the highest input of inert carbon in the late Younger Dryas. Although the sediments contain some recent marine palynomorphs, there is no other evidence of fresh marine organic carbon. In contrast, our results indicate that these shelf sediments represent a significant sink of recycled organic carbon. The results of pyrolysis geochemistry revealed that ~90% of the total organic carbon in the sediments is inert. The organic petrography analyses revealed that >70–84% of the organic carbon in the sediment core is terrigenous. Reworked dinoflagellate cysts showed a continuous provenance of Cretaceous land-derived material, most likely from the nearby Clavering Island. Our study points to the importance of constraining the organic matter origin, composition and preservation in marine sediments to achieve more accurate palaeoenvironmental reconstructions based on organic proxies.     

The chronology, palaeogeography and archaeological significance of the marine quaternary record of the West Sussex coastal plain, Southern England, U.K.

The Quaternary sediments of the West Sussex Coastal Plain have produced a wide range of floral, faunal and archaeological remains. These sediments consist of marine sands and gravels exhibiting transgressive and regressive trends which occur from present day sea-level to c. +43.0 m O.D. and are overlain by terrestrial silts and cold climate periglacial sediments. At the present day coastline, channel fill deposits occur below modern beach levels. New field observations, coupled with a re-investigation of old sites and literature, suggest that five discrete high stands of sea-level may be preserved in the area of the West Sussex Coastal Plain. Age estimates for these deposits suggest that they span large parts of the Middle and Upper Pleistocene (Oxygen Isotope Stages 13 to 5). Conformable relationships between many of the marine and terrestrial sediments suggest that the potential exists within the area to correlate the marine and terrestrial Quaternary stratigraphic records. In addition sediments associated with two of these high sea-level stands are associated with extensive buried landsurfaces covering large areas of the coastal plain. At some locations these intact landsurfaces are associated with evidence for human activity and represent stratigraphic and cultural resources of international importance.     

Depositional environments of Late Eocene lignite-bearing strata, east-central Texas

Late Eocene lignites in the Brazos River Valley area occur in parasequence-scale cycles containing mostly marine sediments. Lignite is present at the base of the marine interval and forms the base of the cycle in a majority of cases. Less frequently, lignite is underlain by a thin interval of nonmarine deposits that form the base of the cycle. In both situations, the lignite is part of a thin transgressive interval. Cycles are separated by an exposure surface, usually marked by plant rooting and/or development of a paleosol in the top of the underlying sediments. Peat accumulated on top of these exposure surfaces and lignite is preserved where marine flooding allowed ocean waters to cover the peat deposits with fine grained sediments, producing high-ash lignite horizons of great lateral extent but variable thickness and quality. This strandplain model of lignite occurrence provides a better understanding of Late Eocene lignites in Texas than the deltaic or fluvial-deltaic models previously used. The strandplain model of lignite occurrence is appropriate for most of the Yegua-Jackson lignites (Middle-Late Eocene) of Texas and should be considered when evaluating depositional conditions of Paleogene lignites in the northern Gulf Coast region. A re-evaluation of Late Eocene stratigraphy of the Brazos Valley area accompanies the documentation of depositional environments.     

The development of a sterile,PAH-spiked,aged marine sediment for biodegradation experiments: chemical results

The fate of polycyclic aromatic hydrocarbon (PAH) mixtures in marine sediments can be difficult to determine due to extraction, analytical and matrix barriers. The purpose of this work was to develop and validate methods to kill indigenous microorganisms in marine sediments, to spike the sediments with a mixture of PAHs in a minimally invasive fashion and to age the treated sediments while following the effects of the treatments on the PAHs and several groups of microorganisms. Following gamma irradiation (0.0, 2.5, 3.5 and 5.0 Mrad), the sediments were mixed with known amounts of PAHs that had been coated onto fine-grained sand. During the subsequent ageing process, levels of extractable PAHs and numbers of microorganisms were monitored. The addition of PAHs to the unirradiated sediment seemed to rapidly induce the degradation of phenanthrene, fluoranthene and pyrene, while these PAHs decreased to a much smaller extent in the irradiated sediments in the 376 days of the experiment. The heavier PAHs, chrysene and benzo(a)pyrene, showed slight decreases in extractable concentrations at all irradiation levels, suggesting PAH sequestration/ageing over time. While some microbial populations recovered rapidly, culturable PAH degraders did not recover at any irradiation level tested and concentrations of light molecular weight PAHs in sediments irradiated at all levels dropped only slightly. This suggests that even the lowest dose (2.5 Mrad) may inhibit PAH degradation sufficiently to permit ageing of the spiked sediments for 6 months to a year. The methods described show promise for the generation of realistic, well-characterized spiked sediments for use in biodegradation and bioavailability experiments.     

Behavior of Hydrocarbons in the Mouth Parts of Arctic Rivers

The paper reviews data (acquired in 2007–2016) on aliphatic and polycyclic aromatic hydrocarbons in comparison with data on concentrations of lipids, C_org, and chlorophyll a in the water and bottom sediments the river–sea geochemical barrier (for the Northern Dvina, Ob, Yenisei, and Lena rivers). It was established that the concentrations of anthropogenic hydrocarbons decrease and these compounds precipitate like other organic compounds and particulate matter, where riverine and marine waters mix. Relatively pure water flows in the pelagic zones of seas. In spite of low temperatures in the Arctic, anthropogenic hydrocarbons transform so rapidly that natural compounds dominate in the water and bottom sediments: autochthonous in the seawater and allochthonous in the bottom sediments.     

南海北部白云凹陷08CF7岩心沉积物的磁化率特征及其意义

海洋沉积物的磁性异常与甲烷渗漏活动及其产物密切相关。为揭示南海北部天然气水合物区沉积物磁化率的变化特征及其意义,对白云凹陷08CF7岩心331个沉积物样品的磁化率进行测定和分析。08CF7岩心沉积物磁化率变化范围为554×10-6~2656×10-6SI,平均值为1141×10-6SI。磁化率随深度变化可分为0~188 cm、188~240 cm及240 cm以下等3段,分别与硫酸盐富集带、硫酸盐-甲烷转换界面(SMT)的上部过渡带及SMT相对应。研究表明,海底天然气渗漏是08CF7岩心沉积物磁化率异常变化的可能原因,其机理是：在强烈的还原环境中,甲烷厌氧氧化反应的产物HS-与沉积物中的Fe3+发生反应,形成顺磁性的黄铁矿。沉积物磁化率变化能快速了解SMT状况及其深度,提供了一种识别南海北部天然气水合物的间接方法。     

Uppermost Triassic to Lower Jurassic stratigraphy in the Lough Foyle Basin of County Londonderry,Northern Ireland

The Lough Foyle Basin is a half-graben that straddles the border between Northern Ireland and the Republic of Ireland and contains sediments that range in age from Lower Carboniferous to Holocene. The basin’s post-rift succession is represented by sediments of the Penarth Group and Lias Group. The lithostratigraphy and biostratigraphy of that interval are revised using new borehole material and existing outcrop. Palaeontological data provide a chronostratigraphic framework and aid palaeoenvironmental interpretations. Foraminifera, ostracods, palynomorphs indicate a nearshore, marginal marine depositional setting throughout much of the Rhaetian with a more marine, shelf and nearshore depositional setting for the Lias Group. The Penarth Group succession is similar to that elsewhere in Northern Ireland but the Lias Group (Waterloo Mudstone Formation) differs in that five distinct members can be recognised (Clooney Mudstone, Drummans Siltstone, Gortmore Mudstone, Tircreven Sandstone and Ballyleighery Mudstone), four of which are newly described. The deltaic and shelf sandstones of the Tircreven Sandstone Member are the only such examples preserved in the Jurassic strata of Northern Ireland and are some of the oldest in the Jurassic of the UK and Ireland, providing evidence of the proximity of the nearby Irish Landmass and representing a useful comparison for Early Jurassic sandstone reservoirs in offshore basins.     

太湖全新世沉积物的古盐度指标及其环境意义

沉积物中的Ｃａ／（Ｆｅ＋Ｃａ）比值和硼含量随水体含盐度的高低而相应增减，它们都是较好的古盐度指标。本文对太湖全新世的沉积物进行了古盐度指标的分析。并与现代湖泊和海洋沉积物作了对比，结果反映东太湖为陆相沉积环境，而西太湖则主要为海相沉积环境。此结论与古生物化石的结论一致，从而证明了太湖地区于全新世期间经历了大规模的海侵，并形成海湾－湖环境。同时也证明了这些古盐度指标是行之有效的。     

Patterns of organic and inorganic sulfur transformations in sediments

Two new methods for analysis of sedimentary sulfur employing sensitive flame photometric detection have been developed and applied to a study of marine, estuarine and freshwater sediments. Volatile organosulfur compounds generated from freeze-dried sediments upon heating in a H₂ atmosphere reflect the distribution and extent of degradation of detrital organic matter. Regions of biogeochemical sulfur transformations, as characterized by the presence of SO₂ progenitors, sulfite and thiosulfate, are also depicted. Scrubbing of sediment slurries treated with the reducing agent, acidic Cr(II) solution, releases H₂S and CH₂SH from their metal-complexed forms. CH₃SH is a common constituent of marine and estuarine sediments at sub-ppm concentrations.