海南儋州湾红树林区沉积有机质来源及碳储量

本文测定了海南儋州湾南岸柱状沉积物的粒度、总有机质参数(TOC、C/N和 δ13C)和类脂生物标志物含量,并通过端元混合模型使用红树植物特征标志物蒲公英萜醇含量、长链正构烷烃含量和δ13C值半定量区分了海南儋州湾南岸沉积有机质来源,尤其是红树林的贡献.另外,通过估算沉积物的有机碳储量来评估儋州湾红树林区域的储碳能力.在...     

Sources and distributions of terrigenous organic matter in a mangrove fringed small tropical estuary in South China

The sources and distributions of terrigenous organic matter (OM) were investigated in a small tropical estuary in the Hainan Island, South China. Plants, suspended particulate matter (SPM), and surface sediments samples in the estuary and coast were collected. Bulk properties [organic carbon (OC%), total nitrogen (TN%), stable carbon isotope (δ13C) and grain size] and lignin phenol concentrations were measured. OC% of mangrove plants was (43.4 ± 2.1)%, which is similar to the values reported for mangrove plants in other regions. OC% of sediment samples ranged from 0.07% to 1.42%, and they were related to the sediment texture. Lignin phenols in the sediment ranged from 5.16 mg/100 mg OC in the uppermost station to 0.51mg/100mg OC in the coast. The molar ratio of organic carbon to total nitrogen (C/N) (～7) and δ 13 C (～-31.1×10-3 ) of riverine SPM revealed that the major OM sources of riverine SPM were aquatic OM (phytoplankton and/or bacteria). Moreover, the lower lignin concentration (Λ8) and higher (Ad/Al)v of lignin phenols suggest that terrestrial OM in riverine SPM were mainly from soil. Furthermore, C/N ratio, δ13C and lignin phenols reveal that mangrove plants were the predominant OM sources of mangrove surface sediment. Based on the δ13C and lignin phenols, it can be concluded that the major OM sources in estuarine and coastal surface sediments were marine phytoplankton, riverine SPM and mangrove surface sediment. In addition, the higher (Ad/Al)v of lignin phenols in those coastal sediments indicate that seagrass might be a potential OM source in coastal sediments, however, the lower (Ad/Al)v in the estuarine sediments in turn suggests that seagrass could not be transported to the mangrove fringed region. A three-end-member model which is based on lignin concentrations and δ13C was applied to evaluate the contribution of mangroves to the organic matter preserved in the surface sediments. Around the mangrove fringed region, mangrove could contribute more than 50% to the sedimentary OM, and this value is much higher than riverine OM. Nevertheless, mangrove OM could not be efficiently transported to the coastal region. Our study suggests that mangrove forest is an important OM source in this small estuary.     

Microbial biomass response to different quantities and sources of organic matter in Brazilian coastal sediments

This study investigates the benthic microbial responses to organic matter (OM) variations in quantity and sources in two shallow water bays (Fortaleza and Ubatuba Bays) on the SE coast of Brazil on six occasions during the year. The pelagic and benthic compartments of the bays were evaluated by: (i) nutrients and chlorophyll a (Chl a) in the water column; (ii) quantity and sources of OM in the sediment (Chl a, total organic carbon and total nitrogen and lipid biomarker composition); and (iii) microbial biomass in sediments as an indicator of active benthic response. Although there were changes in water‐column nutrients during the year, Chl a was fairly constant, suggesting a regular supply of microalgae‐derived OM to the sea bottom. Based on the composition of lipid biomarkers in sediments, OM sources were classified as mostly marine and with high contributions of labile (microalgae‐derived) OM. Labile OM composition varied from diatoms in the summer to phytoflagellates in the winter and tended to accumulate in areas protected by physical disturbances in one of the bays. Microbial biomass followed this trend and was 160% higher in protected than in exposed areas. This study suggests that the coupling between labile OM and benthic microbial biomass occurs primarily in protected areas, irrespective of the time of the year. Since meio‐ and macrofaunal assemblages depend upon secondary microbial production within the sediments, this coupling may have an important role for the benthic food‐web.     

Composition of the organic matter of the water,suspended matter,and bottom sediments in Nha Trang Bay in Vietnam in the South China Sea

Research has been conducted in Nha Trang Bay (Southern Vietnam, the South China Sea) at the section from the estuary of the Cai River to the marine part of the bay, as well as in the area of coral reefs. The objects of the studies are the river and sea waters, the suspended matter, and the bottom sediments. Data on the dissolved organic carbon and the total nitrogen in the water are obtained. The organic carbon content is estimated in the suspended matter; the organic carbon and the molecular and group composition of the n-alkanes are determined in the bottom sediments. The molecular and group composition of the n-alkanes in the bottom sediments of the landfill have made it possible to identify three types of organic matter (OM): marine, mixed, and of mainly terrigenous origin. All the types of OM are closely related to the specificity of the sedimentation and the hydrodynamics of the waters in this water area.     

Geochemistry and organic petrography of Cretaceous sediments of the Calabar Flank,southeastern, Nigeria

Detailed bulk geochemistry and organo-petrography of outcrop Cretaceous sediments (with no significant effects of weathering) from the Calabar Flank, southeast Nigeria were performed to understand the organic carbon source, accumulation and degradation, and paleo-climatic, paleoceanographic and paleoenvironmental conditions in West Africa during Early Cretaceous (Aptian) to Maastrichtian times. This study was based on microscopic, elemental analyses (organic carbon, nitrogen, iron and sulphur), Rock-eval pyrolysis and carbon-isotope analyses. In general, the Calabar Flank shales are characterised by highly variable total organic carbon (TOC) contents, which range between 0.1% in Aptian–Albian Mfamosing Limestone and 9.9% in the Awi Formation sediments. The organic matter (OM) is a mixture of immature to early-mature marine and terrigenous OM of types III and IV. This is indicated by low hydrogen indices (HI value (10–190 mg HC/g TOC), T_max (417–460 °C), vitrinite reflectance %R_o (0.39–0.62 %R_o), low to high C/N ratios (3.4–1158.0) and high amounts of terrigenous macerals (vitrinite + inertinite). Based on carbon isotope, C/N ratios and sulphate reduction index (SRI), OM degradation (up to 70%, SRI > 2.5) is most pronounced for shales deposited in a marine environment. The geochemical and petrographic data indicate that local factors such as low bioproductivity, down slope transport and redeposition of sediments from a fluvial–deltaic basin to nearshore facies, shallower, oxic and mildly oxygen-deficient environments, humid–arid paleogeographic conditions, specifically controlled the amount and quality of the OM during Aptian–Mastrichtian stages where marine sediments have been assumed to be deposited during the global anoxic events. Therefore, the order of the main factors controlling OM content in sediments are: input of terrigenous material transported from the land > low OM productivity by marine photoautotrophs > low preservation.     

Characterizing the depositional settings for sedimentary organic matter distributions in the Lower Yangtze River-East China Sea Shelf System

Grain-size distributions, total organic carbon (TOC) and total nitrogen (TN) concentrations, and TOC/TN ratios (C/N) were analysed for surface sediments from the Lower Yangtze River-East China Sea (ECS) shelf system. Hierarchical cluster analysis of grain-size parameters (mode, mean, sorting, skewness and kurtosis) has been employed to characterize grain-size compositions. The results suggest there are five grain-size compositional types (type-I–V) that fingerprint distinct depositional conditions. In areas with high sedimentation rates, hydrological sorting preferentially enriches the fraction coarser than 6.4ø (12 μm) in shallow seafloor sediments (water depth<30 m) by transporting the finer fraction to the deeper seafloor (water depth>30 m), and thus forms grain-size compositional type-I (shallow) and type-II (deep). In the open shelf, where modern sediment supply is very limited, grain-size types-III–V are identified according to different winnowing intensity. Overall TOC contents significantly correlate with mud proportions, suggesting muddy sediments are the primary control on OM accumulation. However, de-association of terrestrial OM from fine sediments in the Estuary and the occurrence of presumably relict OM in the open shelf exert additional controls on OM dispersal and carbon cycling in the ECS. By considering geography, oceanography, sediment source, and the relation between sedimentation conditions and sedimentary OM distributions, we define six depositional settings: the lower river, the estuary, the coast, the offshore upwelling area, the erosional area, and the open shelf. These settings describe the sediment dispersal and associated organic matter cycling in the Lower Yangtze River-ECS shelf system.     

Geochemistry of polycyclic aromatic hydrocarbons in the bottom sediments of the eastern Arctic shelf

Sources and pathways of supply of polycyclic aromatic hydrocarbons (PAH) in the surface sediments of the Laptev and East Siberian seas were identified based on an analysis of the lithological-geochemical characteristics and distribution of organic matter (OM). The distribution of organic carbon, humic acids, bitumoids, and hydrocarbons demonstrates the determining role of the riverine runoff in the formation of the recent sediments. The total average content of PAH in the sediments of this region approximates 37 ng/g, not exceeding 80 ng/g of dry sediment. The biogenic components of the PAH (alkylphenanthrenes, alkylchrysenes, perylene) dominate in the estuarine-shelf and coastal-shelf sediments enriched with plant detritus and significantly decrease in the pelagic zone. The anthropogenic influence is observed in sediments of the port of Tiksi, where the total content of PAH with dominant pyrogenic components is two orders of magnitude higher as compared with the background values in the study region.     

Deep-sea terrigenous organic carbon transfer and accumulation: Impact of sea-level variations and sedimentation processes off the Ogooue River (Gabon)

Sedimentary, isotopic and bulk geochemical proxies measured in sediment samples of five gravity cores collected in the distal part of the Ogooue turbidite system (around 4000 m-depth) were used to develop a conceptual model to describe the accumulation of terrigenous organic matter (OM) during the last 200,000 yrs BP in the eastern part of the Gulf of Guinea. This model takes into account the influence of the different depositional processes (turbiditic vs hemipelagic sedimentation), geomorphological features and sea-level variations.Total organic carbon (TOC) and the stable organic carbon isotopes of the OM (δ¹³C) variability follow the highstand/lowstand (interglacial/glacial) cyclicity with a very low accumulation rate of terrigenous OM during periods of high sea-level and higher accumulation rate during period of low sea-level. A sea-level of 80–120 m below present day seems to favor the transfer of terrigenous sediments to the deep offshore environment through the turbidite system and thanks to the connection of the canyons heads with the river system presently located at the shelf edge at −120 m water depth.In this system, terrigenous OM matter delivered by the river accumulate in the sediments via two main processes. Indeed, a part of the terrigenous OM settles in combination with the finest particles forming hemipelagites, while another part, formed of very well preserved land plant debris, is transported and deposited far offshore with turbidity currents. The proportion of terrigenous OM accumulated due to turbidity currents is important as it can represent more than 70% of the carbon accumulated during sea-level lowstand. Moreover, terrigenous OM seems to preferentially accumulate in the levees and the lobes of the system notably due to the higher frequency of organic-rich turbidites.This study demonstrates that gravity flows, influenced by the sea-level variations, can significantly affect the terrigenous OM budget of the deep offshore Atlantic margins and that channel-levee complexes as well as turbidite lobes can be regarded as good sink for terrestrial organic carbon. These processes should be taken into consideration in the context of source rocks exploration but also for the estimation of the general carbon accumulation in ocean sediment.     

Organic matter origin and distribution in suspended particulate materials and surficial sediments from the western Adriatic Sea (Italy)

In this study, organic carbon (OC), total nitrogen (TN), stable carbon isotopic (δ¹³C_OC) and CuO reaction product compositions were used to identify the sources of organic matter (OM) and to quantify the relative importance of allochthonous and autochthonous contributions to the western Adriatic Sea, Italy. Suspended particulate material (195 samples) and surficial sediments (0–1 cm, 70 samples) from shallow cross-shelf transects were collected in February and May 2003, respectively. Vertical water column profiles were acquired along the same transects. Data include depth, potential temperature, salinity, density and chlorophyll fluorimetry.Along the western Adriatic shelf in the near-shore region, the phytoplankton growth was influenced by dynamics of the buoyant plumes from the Po and Appennine rivers. A small amount of very fine terrigenous material remained suspended within the coastal current and was exported southward along the shelf to the slope. High variability in the bulk composition was detected in the Po prodelta surficial sediments, whereas the western Adriatic shelf, although a larger area, exhibited a narrower range of values.A significant decoupling was observed between suspended particles in the water column and surficial deposits. The organic material collected in the water column was compositionally heterogeneous, with contributions from marine phytoplankton, riverine–estuarine phytoplankton and soil-derived OM. Frequent physical reworking of surficial sediments likely leads to the efficient oxidation of marine OC, resulting in the observed accumulation and preservation of refractory soil-derived OC delivered by the Po and Appennine rivers.     

Total hydrolysable amino acid mineralisation in sediments across the northeastern Atlantic continental slope (Goban Spur)

Total hydrolysable amino acids (THAA), individual amino acid distributions, total organic carbon (TOC) and total nitrogen (TN) were measured in sediments across the Goban Spur continental slope at water depths of 651, 1296 and 3650 m. Objectives were to examine (1) differences in organic matter (OM) degradation state in surface sediments across the slope from sedimentary amino acid compositions, and (2) whether these differences are related to particle size distributions. Application of a ‘reaction–diffusion’ model to the sediment concentration profiles showed that TOC and THAA degradation rate constants decreased with increasing water depth. Ratios of degradation rate constants of THAA over TOC indicated that THAA turn over faster than TOC at 651 and 1296 m water depth only. From estimates of degradation rate constants of individual amino acids, it was concluded that with increasing water depth fewer amino acids contribute to overall THAA degradation. The contribution of THAA to TOC mineralisation decreased from the upper to the lower slope. Since at all three sampling stations the amino acids with the highest relative contribution to THAA had a higher abundance in sediments with reduced THAA mineralisation rates, we conclude that the overall amino acid reactivity decreases with increasing water column depth. A principal component analyses, carried out on normalised amino acid mole percentages, established significant shifts in amino acid compositions and confirmed that (1) OM degradation state increased from 651 to 3650 m and (2) that OM in the finest fraction at the shallowest station appeared to be considerably less degraded than in the coarser fractions or any size fractions at the deeper stations. Therefore, we conclude that downslope transport, sorting and accumulation of fine particles with continuous mineralisation of OM attached to the particles during vertical and lateral transport results in an increasing organic matter degradation state from the upper slope to the abyssal plain.     

Concentration and Isotopic and Elemental Composition of Organic Matter in Subsea Thawed and Permafrost Deposits of Buor-Khaya Bay

Oceanology - A comparative analysis of the content and composition of organic matter (OM) in samples of bottom sediments and subaqueous permafrost rocks by the concentration of organic carbon (OC),...     

Sources and distribution of organic matter in a river-dominated estuary (Winyah Bay, SC, USA)

The sources and distribution of organic matter (OM) in surface waters and sediments from Winyah Bay (South Carolina, USA) were investigated using a variety of analytical techniques, including elemental, stable isotope and organic biomarker analyses. Several locations along the estuary salinity gradient were sampled during four different periods of contrasting river discharge and tidal range. The dissolved organic carbon (DOC) concentrations of surface waters ranged from 7 mg l⁻¹ in the lower bay stations closest to the ocean to 20 mg l⁻¹ in the river and upper bay samples. There was a general linear relationship between DOC concentrations and salinity in three of the four sampling periods. In contrast, particulate organic carbon (POC) concentrations were significantly lower (0.1–3 mg l⁻¹) and showed no relationship with salinity. The high molecular weight dissolved OM (HMW DOM) isolated from selected water samples collected along the bay displayed atomic carbon:nitrogen ratios ([C/N]a) and stable carbon isotopic compositions of organic carbon (δ¹³C_OC) that ranged from 10 to 30 and from −28 to −25‰, respectively. Combined, such compositions indicate that in most HMW DOM samples, the majority of the OM originates from terrigenous sources, with smaller contributions from riverine and estuarine phytoplankton. In contrast, the [C/N]a ratios of particulate OM (POM) samples varied significantly among the collection periods, ranging from low values of 5 to high values of >20. Overall, the trends in [C/N]a ratios indicated that algal sources of POM were most important during the early and late summer, whereas terrigenous sources dominated in the winter and early spring.In Winyah Bay bottom sediments, the concentrations of the mineral-associated OM were positively correlated with sediment surface area. The [C/N]a ratios and δ¹³C_OC compositions of the bulk sedimentary OM ranged from 5 to 45 and from −28 to −23‰, respectively. These compositions were consistent with predominant contributions of terrigenous sources and lesser (but significant) inputs of freshwater, estuarine and marine phytoplankton. The highest terrigenous contents were found in sediments from the river and upper bay sites, with smaller contributions to the lower parts of the estuary. The yields of lignin-derived CuO oxidation products from Winyah Bay sediments indicated that the terrigenous OM in these samples was composed of variable mixtures of relatively fresh vascular plant detritus and moderately altered soil OM. Based on the lignin phenol compositions, most of this material appeared to be derived from angiosperm and gymnosperm vascular plant sources similar to those found in the upland coastal forests in this region. A few samples displayed lignin compositions that suggested a more significant contribution from marsh C₃ grasses. However, there was no evidence of inputs of Spartina alterniflora (a C₄ grass) remains from the salt marshes that surround the lower sections of Winyah Bay.     

Experimental evidence for an effect of early-diagenetic interaction between labile and refractory marine sedimentary organic matter on nitrogen dynamics

In most natural sedimentary systems labile and refractory organic material (OM) occur concomitantly. Little, however, is known on how different kinds of OM interact and how such interactions affect early diagenesis in sediments. In a simple sediment experiment, we investigated how interactions of OM substrates of different degradability affect benthic nitrogen (N) dynamics. Temporal evolution of a set of selected biogeochemical parameters was monitored in sandy sediment over 116 days in three experimental set-ups spiked with labile OM (tissue of Mytilus edulis), refractory OM (mostly aged Zostera marina and macroalgae), and a 1:1 mixture of labile and refractory OM. The initial amounts of particulate organic carbon (POC) were identical in the three set-ups. To check for non-linear interactions between labile and refractory OM, the evolution of the mixture system was compared with the evolution of the simple sum of the labile and refractory systems, divided by two. The sum system is the experimental control where labile and refractory OM are virtually combined but not allowed to interact. During the first 30 days there was evidence for net dissolved-inorganic-nitrogen (DIN) production followed by net DIN consumption. (Here ‘DIN’ is the sum of ammonium, nitrite and nitrate.) After  30 days a quasi steady state was reached. Non-linear interactions between the two types of OM were reflected by three main differences between the early-diagenetic evolutions of nitrogen dynamics of the mixture and sum (control) systems: (1) In the mixture system the phases of net DIN production and consumption commenced more rapidly and were more intense. (2) The mixture system was shifted towards a more oxidised state of DIN products [as indicated by increased (nitrite + nitrate)/(ammonium) ratios]. (3) There was some evidence that more OM, POC and particulate nitrogen were preserved in the mixture system. That is, in the mixture system more particulate OM was preserved while a higher proportion of the decomposed particulate N was converted into inorganic N. It can be concluded that during the first days and weeks of early diagenesis the magnitude and composition of the flux of decompositional dissolved N-compounds from sediments into the overlying water was influenced by non-linear interactions of OM substrates of different degradability. Given these experimental results it is likely that the relative spatial distributions of OM of differing degradability in sediments control the magnitude and composition of the return flux of dissolved N-bearing compounds from sediments into the overlying water column.     

Origin of sedimentary organic matter in the north-western Adriatic Sea

In order to evaluate the origin and the transformation of organic matter on the shallow shelf of the NW Adriatic Sea, organic carbon, total nitrogen and stable isotope ratios of organic carbon were analysed in riverine suspended matter and sediments as well as in marine suspended and sedimentary organic matter, in marine phytoplankton and zooplankton.The deposition of organic matter is influenced by fine sediment concentration. Surface sediments were characterised by highly variable biogeochemical conditions on the sea floor, whereas sub-surface sediments showed a more homogeneous hypoxic/anoxic environment.Low C_org/N ratio and high organic carbon and nitrogen concentrations in riverine suspended organic matter indicate an important contribution of freshwater phytoplankton within rivers, particularly during low flow regimes, which adds to the marine phyto- and zooplankton at shelf locations.In order to evaluate the importance of terrestrial, riverine and marine sources of OM in shelf sediments, a three end-member mixing model was applied to shelf surface sediments using ¹³C/¹²C values for organic matter and N/C ratios. The model showed an elevated contribution of terrestrial organic substances at intermediate depths (10–15 m), mostly corresponding to an area of coarser grain-size, whereas the riverine and marine organic fractions were mainly accumulating near the coast and offshore, respectively.     

Lipid biomarker composition in surface sediments from the Carlsberg Ridge near the Tianxiu Hydrothermal Field

Hydrothermal venting has a profound effect on the chemical and biological properties of local and distal seawater and sediments. In this study, lipid biomarkers were analyzed to examine the potential influence of hydrothermal activity on the fate of organic matter(OM) in surface sediments around Tianxiu Hydrothermal Field in the Carlsberg Ridge(CR), Northwest Indian Ocean. By comparing the biomarker distributions of the samples with that of other typical hydrothermal sediments in the mid ocean ridge, it is shown that the location of the samples is not affected by the hydrothermal activity. The relatively low abundances of terrestrial n-alkyl lipids and riverine1,15-C32 diol suggested a minor contribution of terrigenous OM to the study area. The bacteria contributed predominantly to sedimentary marine OM; however, other marine source organisms, e.g., eukaryotes(i.e.,phytoplankton and fungi) could not be completely neglected. The marine-originated biomarkers showed significantly variable distributions between the two sediments, suggesting different dynamic physical and biogeochemical processes controlling the fate of marine OM. This study identified various diagnostic biomarkers(5,5-diethyl alkanes, diols and β-OH FAs), which may have significant environmental implications for future works in this region.     

Bacterial response to seasonal changes in labile organic matter composition on the continental shelf and bathyal sediments of the Cretan Sea

Bacterial abundance, biomass and cell size were studied in the oligotrophic sediments of the Cretan Sea (Eastern Mediterranean), in order to investigate their response to the seasonal varying organic matter (OM) inputs. Sediment samples were collected on a seasonal basis along a transect of seven stations (ranging from 40 to 1570 m depth) using a multiple-corer. Bacterial parameters were related to changes in chloroplastic pigment equivalents (CPE), the biochemical composition (proteins, lipids, carbohydrates) of the sedimentary organic matter and the OM flux measured at a fixed station over the deep basin (1570 m depth). The sediments of the Cretan Sea represent a nutrient depleted ecosystem characterised by a poor quality organic matter. All sedimentary organic compounds were found to vary seasonally, and changes were more evident on the continental shelf than in deeper sediments. Bacterial abundance and biomass in the sediments of the Cretan Sea (ranging from 1.02 to 4.59 × 10⁸ cells g⁻¹ equivalent to 8.7 and 38.7 μgC g⁻¹) were quite high and their distribution appeared to be closely related to the input of fresh organic material. Bacterial abundance and biomass were sensitive to changes in nutrient availability, which also controls the average cell size and the frequency of dividing cells. Bacterial abundance increased up to 3-fold between August '94 and February '95 in response to the increased amount of sedimentary proteins and CPE, indicating that benthic bacteria were constrained more by changes in quality rather than the quantity of the sedimentary organic material. Bacterial responses to the food inputs were clearly detectable down to 10 cm depth. The distribution of labile organic compounds in the sediments appeared to influence the vertical patterns of bacterial abundance and biomass. Cell size decreased significantly with water depth. Bacterial abundance and biomass were characterised by clear seasonal changes in response to seasonal OM pulses. The strong coupling between protein flux and bacterial biomass together with the strong bacterial dominance over the total biomass suggest that the major part of the carbon flow was channelled through the bacteria and the benthic microbial loop.     

Degradation of organic pollutants in near shore marine sediments: Part I—breakdown of pulp mill fibre

Cellulose levels in the sediments of Loch Linnhe and Loch Eil were measured over a period of years following the introduction of pulp mill effluent to system. Cellulose levels in experimental sediment systems subjected to pulp fibre inputs at levels simulating various possible loch input levels were measured and compared. No permanent build up of cellulose in either the loch systems or the experimental systems was observed, even at high input levels.Pulp fibre degradation rates were measured experimentally using two different techniques. No difference was found between the degradation rates of wet and predried fibre.Degradation rates equivalent to 0·2 g dry fibre m^?2 day^?1 were found in areas of low fibre input and 0·5 g dry fibre m^?2 day^?1 in areas of high input were recorded. These rates were of the same order as, but somewhat lower than, the probable input rates to the sediments in Loch Eil. Speculations as to possible reasons for this are advanced.     

Aliphatic biomarker signatures of early Oligocene-early Miocene source rocks in the central Qiongdongnan Basin: Source analyses of organic matter

The geochemical signatures of fifty-four rock samples and three supplementary drill stem test(DST) oils from the Yacheng-Sanya formations in the central Qiongdongnan Basin(CQB) were analysed. Reconstruction of the early Oligocene-early Miocene(36–16 Ma) palaeovegetation and source analyses of organic matter(OM) were conducted using aliphatic biomarkers in ancient sediments and DST oils. Both the interpreted aquatic and terrigenous OM contributed to the CQB source rocks(SRs) but had varying relat...     

Spatial distribution of gut juice extractable Cu,Pb and Zn in sediments from the Pearl River Estuary,Southern China

In this study, we compared the spatial distribution of total metals (Cu, Pb, and Zn) and bioaccessible metals, which were quantified by incubating sediments with the digestive fluid of sipunculans Sipunculus nudus, in natural sediments of the Pearl River Estuary (PRE). The spatial distribution of bioaccessible metal was not the same as that of total metals in PRE sediments, which were mainly controlled by fine-grained size, total organic carbon (TOC) and Fe. Geochemical factors were important in interpreting this different spatial variation. The similar spatial variations of bioaccessible Cu and total Cu were related to TOC in PRE sediments. Differently from the total Zn, a higher bioaccessible Zn was detected near the West Channel of PRE because of a lower TOC. However, the distribution of bioaccessible Pb was not significantly related to any sediment geochemistry. This study provides a more accurate view of metal pollution in the PRE natural sediments.     

Cohesive sediments in scottish freshwater lochs and reservoirs

The cohesive nature of sediments coating the floors of Scottish freshwater lochs and reservoirs is illustrated through microscopic observations, settling velocity experiments, geophysical remote sensing, and rheology. Preliminary results confirm 1) the occurrence of natural sedimentary aggregates, 2) the importance of organic matter in aggregate formation and rheological behavior, and 3) the shear thinning, thixotropic character of the deposits.