渤海湾表层沉积物元素地球化学分布特征与影响因素

对取自渤海湾的307个表层沉积物进行了元素测试和粒度分析。渤海湾表层沉积物的常微量元素呈现4种组合:富集于粗粒沉积区的SiO_2、Na_2O亲碎屑元素组合;富集于细粒沉积区的以Al_2O_3和重金属元素为代表的亲黏土元素组合;与缺氧环境有关的MnO、V、TOC元素组合和与河流输入有关的陆源CaO、TiO_2元素组合。粒度粗细主导了渤海湾元素含量分布的整体格局;海域河流物源供应不同较大影响了渤海湾南部(富Na_2O、CaO和SiO_2)和北部(富Ba和P_2O_5)在元素含量上的差异;高流速潮流对海底的冲刷再分配导致曹妃甸南侧Sr、Ca元素的条带状富集异常;有机质在细粒沉积区的富集导致缺氧环境的形成和K_2O、Mn、V、自生黄铁矿的海洋自生化学沉积;人类活动导致以Pb为代表的重金属污染在河流入海口、港口及沿岸海域的元素分布异常;曹妃甸沙坝内侧的泻湖(海洋钙质生物沉积)与沙坝外侧水下岸坡(陆源碎屑沉积)的截然不同的物源,导致了独特地貌沉积环境下元素分布的局部差异。     

Geochemistry of muds from a shallow restricted estuary,Australia

Sediments from a shallow, restricted estuary in southeast Australia were analysed for Ti, V, Cr, Mn, Fe, Co, Cu, Ni, Zn, P₂O₅ and organic carbon. Subjective interpretation of factor analysis on a geochemical basis, indicates that the dominant controls on the distribution and concentration of these metals and P₂O₅ in the mud sediments are the mineralogy of land-derived detritus and the chemical conditions of the environment in which the sediments are deposited. None of the transition-metal contents of the sediments, apart from Cr and possibly Cu, can be directly attributed to enrichment over that due to areal variation in detrital mineralogy. Chromium may be precipitated from the water column as a hydroxide in reducing environments, and Cu may be supplied to some extent by organic matter. Phosphate is enriched in the sediment through its association with organic matter. Manganese concentrations are depleted from the surface sediments of reducing environments. Iron sulphide and associated Ni and Zn sulphides are probably formed largely through early diagenetic reactions involving the mobilization of these metals from detrital mineral phases into authigenic phases. Evidence for the presence of these authigenic phases is found in sediments from areas where reducing conditions are likely to be most prevalent.     

Voltammetric study of adsorption of cu(II) species on solid particles added to seawater

The adsorption on solid particles of natural organic ligand in seawater of Cu(II) ions, and of the inert Cu(II) complexes has been studied. Model solids, γ-Al₂O₃, Na⁺-0.392-γ-Al₂O₃, ‘Aerosil 200’, chrysotile, northupite and CaCO₃ were added to seawater. It was observed that at pH 8 natural organic matter was strongly adsorbed on chrysotile and was not adsorbed on Na⁺ -0.392-γ-Al₂O₃; it was also adsorbed on γ-Al₂O₃ over the range of 3 < pH < 7. In this pH range, the complexing capacity and adsorption of Cu is at a minimum because Cu(II) is not adsorbed on γ-Al₂O₃ and natural organic matter is adsorbed. Inert CuL complexes were adsorbed at pH 8.0 on γ-Al₂O₃, ‘Aerosil 200’, CaCO₃, and chrysotile but they were not adsorbed on northupite. The voltammetric method can be recommended for use in natural waters for distinguishing between metal ionic and metal inert complex species which are adsorbed from solution onto various solid particles.     

Pyrite formation under conditions approximating those in anoxic sediments: II. Influence of precursor iron minerals and organic matter

In the paper (Wang and Morse, 1996) that preceded this study, we presented results of experiments performed using a silica gel crystal growth technique to produce pyrite under conditions approximating those commonly occurring in anoxic marine sediments. The primary focus of that study was on the chemical pathways that pyrite formation follows and how differing conditions influenced reaction kinetics and morphology of pyrite crystals. In this paper, we present results of further long-term (up to 1 y) studies of pyrite formation, using the silica gel experimental technique, in which we investigated the role that different precursor iron (hydr)oxide minerals and marine organic matter play in pyrite formation. The minerals studied were akaganeite (β-FeOOH), ferrihydrite (Fe₅HO₈ · 4H₂O), goethite (α-FeOOH), hematite (α-Fe₂O₃), lepidocrocite (γ-FeOOH), and magnetite (Fe₃O₄). Marine organic matter used in this study was freeze-dried plankton collected from near-surface water in the Gulf of Mexico. The influence of precursor iron (hydr)oxide mineralogy, although important for initial iron sulfidization rates, was relatively minor compared to other variables, such as solution pH and sulfide concentration, in controlling the rate of pyrite formation. Consequently, major variations in the observed rate of pyritization of different iron (hydr)oxide minerals in sediments (e.g., Canfield and Berner, 1987) may reflect large differences in surface areas of the minerals rather than their intrinsic reactivity and is a confirmation of the estimates of Canfield et al. (1992) that most iron oxides have similar reactivity. The presence of marine organic matter (freeze-dried plankton) caused an increase in the sulfidization rate of goethite and a major (about 20 ×) decrease in the rate of pyrite formation. This can be interpreted as indicating that organic matter-iron interactions are important in both iron (hydr)oxide dissolution, and pyrite nucleation and growth. A possible explanation for this behavior is that dissolved organic matter produced during the long experiments (up to 1 year) increased the rate of goethite dissolution while inhibiting pyrite nucleation and growth by complexing iron. The lessons learned in the study of other mineral reaction kinetics (e.g., calcite and aragonite), that rates determined in pure inorganic systems, may not always be reliably applied to natural systems where organic matter can significantly influence mineral dissolution and growth rates, are, alas, repeated here for pyrite.     

Uranium in coastal sediments of Tokyo Bay and Funka Bay

The sediment cores from Tokyo Bay and Funka Bay were analyzed for U and its isotopic ratio,²³⁴U/²³⁸U, after dissolving them in 0.1 M HCl, and 30% H₂O₂ in 0.05 M HCl. A small fraction of U in the anoxic sediments was dissolved in 0.1M HCl and even the added yield tracer,²³²U, was lost. The isotopic ratio of H₂O₂ soluble U in the sediments was equal to that of seawater, suggesting that the H₂O₂ soluble U in the sediments is authigenic. The 6M HCl solution dissolved part of the lithogenic U besides the authigenic U. The depth profiles of U from the two bays resembled each other. The authigenic U comprised more than half of the total U even at the surface and increased with depth down to 70 cm, showing small maxima at about 20 cm. The concentration of refractory U was nearly constant with depth and similar to that of the pelagic sediments. The highest U concentration, 6 µg g^–1 which was about 5 times that of the pelagic sediments, was observed in the layer between 70 and 160 cm depth in Tokyo Bay. The annual sedimentation rates of U in the Tokyo Bay sediments were 2.6 tons at the surface and 7.0 tons at the 70–160 cm depth. The increase in U with depth should be due to the deposition of interstitial U either diffusing downward from the surface indicating the trapping of seawater U, or otherwise diffusing upward from the deeper layer indicating the internal cycling of U within the sediments.     

Phosphorus and metals bound to organic matter in coastal sediments - An investigation of complexes of P,Cu, Zn,Fe, Mn,Ni, Co and Ti by inductively coupled plasma-atomic emission spectrometry with sephadex gel chromatography

Phosphorus and metals bound to organic matter were separated from coastal sediments of Harima Sound in Seto Inland Sea, Japan by extraction with NaOH and fractionated by Sephadex G-25 chromatography. Phosphorus and metals were determined in the eluates by a multi-channel, inductively coupled plasma-atomic emission spectrometer. Phosphorus and Cu, Zn, Fe, Mn, Ni, Cr, Co and Ti bound to organic matter with high molecular weights (OMHMW) (MW ? 5000) were found to be present in the sediments, but no Mo or V were found. The technique provides minimum estimates of the amounts of P and metals bound to organic matter. These organic complexes show surface enrichment in a sediment core (0–20 cm) and their contents decrease with depth. Also, the amounts of eighteen elements, namely: P, Fe, Mn, Zn, Cu, Si, Al, Ti, Pb, Co, Ni, Cr, Mo, V, Na, K, Ca and Mg, in H₂O, ammonium acetate at pH 7 and 5, hydrogen peroxide, hydroxylamine hydrochloride and hydrogen fluoric acid soluble fractions have been determined with a selective chemical leaching technique for the ²¹⁰Pb-dated sediment core sample. Considerable amounts of P (6–19%) and Cu (5–21%) were associated with organic matter, in contrast to other metals such as Fe, Mn, Zn, Ni, Cr, Co and Ti which were associated with sulfide and silicate.     

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.     

Phosphorus regeneration and burial in near-shore marine sediments (the Gulf of Trieste, northern Adriatic Sea)

According to bioassay studies and high dissolved nutrient N/P ratios in the seawater column, phosphorus (P) is thought to control marine productivity in the northern Adriatic Sea. P in near-shore marine sediments of the Gulf of Trieste, the northernmost part of the Adriatic Sea, was investigated using pore water P distributions, and benthic P flux studies under oxic and anoxic conditions. The data show that P regeneration is up to three-fold more extensive in sediments overlain by oxygen-depleted waters and proceeds in parallel with Fe and Mn enhanced benthic fluxes. It appears from the incubation experiments that degradation of sedimentary organic matter is the main contribution to the flux of P at the sediment–water interface, while the release of phosphate adsorbed on the iron oxide surface is of minor importance.It appears that about 50% of P in the Gulf of Trieste is retained within in the sediments, probably bonded to clay minerals and carbonate grains or precipitated as fluoroapatite. In these sediments total P (P_tot) is preserved preferentially over organic C (C_org). P regenerated from surficial sediments contributes about 1/3 of the P that is assimilated by benthic microalgae. The phytoplankton P requirement should be entirely supplied from fresh-water sources. These results suggest that oxygen depletion in coastal areas caused by eutrophication enhances P regeneration from sediments, providing the additional P necessary for increased biological productivity. The development of anoxic bottom waters in coastal areas enhances the recycling of P, exacerbating the nutrient requirement in the area. A geochemical record of P burial in a longer sedimentary sequence revealed an increasing trend of P_tot and organic P (P_org) contents occurring approximately 50 years BP (after 1950), probably due to increasing use of inorganic fertilizers and detergents in the area.     

渤海湾北部和西部海域表层沉积物中无机碳形态研究

采用氯化钠(NaC1)、氨水(NH3·H2O)、氢氧化钠(NaOH)、盐酸羟胺(NH2OH·HC1)溶液对渤海湾北部和西部海域表层沉积物中无机碳进行了连续浸取,并将无机碳分为5种赋存形态:交换态(NaCl相)、弱碱结合态(NH3·H2O相)、强碱结合态(NaOH相)、弱酸结合态(NH2OH·HCl相)和残渣态.同时,结...     

The partitioning of organic carbon fluxes and sedimentary organic matter decomposition rates in the ocean

The partitioning of annual organic carbon fluxes from five stations located in the vicinity of the Pacific-Antarctic Ridge and the Peru continental margin suggests that 35–85% of the total near-bottom organic carbon flux is utilized at or near the sediment-water interface. These estimates have large uncertainties, but illustrate that assessments of organic carbon utilization can be made by several stepwise approaches which are generally applicable to a wide spectrum of marine environments.In one approach, the mineralization of organic carbon from the sediments was predicted from both sedimentary organic carbon and pore water nutrient profiles with comparable results. Neglecting sediment mixing, the rate constants of the anoxic sediments off Peru range from 0.1 × 10^?3 to 4 × 10^?3 y^?1, and rate constants derived for oxic SW Pacific sediments range from 3 × 10^?4 to 7 × 10^?4 y^?1. As with other values reported for sulfate reducing sediments by Toth and Lerman (1977) and for oxic central Pacific sediments by Müller and Mangini (1980), log-log plots of rate constants vs. sedimentation rate define two parallel linear relationships for oxic and anoxic sediments, respectively. The apparently enhanced rates for oxic environments may result from large benthic organisms which redistribute a portion of the available detritus and in doing so convert it into more easily accessible and metabolizable organic matter. In low-oxygen environments, bottom feeders and infauna are less abundant and more likely to irrigate rapidly accumulating sediments.     

C25 and C30 biogenic alkenes in sediments and detritus of a New England salt marsh

As part of a geochemical study of C₂₅ and C₃₀ biogenic alkenes in estuarine environments, distributions of these compounds in detritus and sediments collected from a New England salt marsh (Round Swamp on Conanicut Island in Narragansett Bay, Rhode Island) have been determined. The alkene assemblages detected, consisting primarily of four acyclic C₂₅ dienes and trienes and a C₃₀ bicyclic diene, qualitatively resemble those previously reported for other sediments in which anoxic conditions were prevalent. These similarities exist despite significant differences in the principal sources of sedimentary organic matter, suggesting that the occurrence of these specific alkenes is more likely associated with an in situ process common to anoxic environments than with a direct input from a specific source. Size fractionation (> 840 μm and < 840 μm to 1·2 μm) of marsh detritus revealed that the larger size fraction, consisting primarily of decaying Spartina debris, contains significant amounts of alkenes. This result, together with alkene subsurface profiles which show high surface concentrations decreasing to near-background levels by 20 cm, suggest that anaerobic bacteria are mediating in situ production of these compounds. Previous studies of bacterial hydrocarbons have not reported the presence of these C₂₅ and C₃₀ alkenes, although similar compounds have been isolated from several species of methanogenic bacteria. However, attempts to induce alkene synthesis by decomposing Spartina anaerobically in the laboratory were unsuccessful. In light of this result, the exact source of alkenes in marsh sediments remains uncertain. The absence from marsh sediments of other C₂₅ alkenes whose sedimentary distributions had been previously correlated with the presence of marine (planktonic) organic matter implies the existence of different origins for structurally related constituents of this hydrocarbon series.     

Enhanced preservation of organic matter in sediments deposited within the oxygen minimum zone in the northeastern Arabian Sea

The presence of a strongly developed oxygen minimum zone (OMZ; [O₂]<2 μM) in the northeastern Arabian Sea affords the opportunity to investigate whether oxygen deficiency in bottom waters enhances the preservation of organic matter in the underlying sediments. We explored if the observed patterns of organic matter accumulation could be explained by differences in productivity, sedimentation rate, water depth, and mineral texture. The differences in the burial rates of organic matter in sediments deposited within or below the OMZ could not be explained on the basis of these factors. All collected evidence points to a coupling of low oxygen concentrations and enhanced organic matter preservation. Under more oxygenated conditions bioturbation as well as the presence of labile manganese and iron oxides are probably important factors for a more efficient microbially mediated degradation of organic matter. Pore water profiles of dissolved Mn²⁺ and Fe²⁺ show that reduction of manganese and iron oxides plays a minor role in sediments lying within the OMZ and a larger role in sediments lying below the OMZ.     

沉积物中磷的存在形态及其生物可利用性研究

用MgCl₂,NaOH和HCl对大亚湾的大鹏澳、南海的珠江口、厦门湾的胡里山沉积物进行了逐级提取和总磷分析,并以这3种沉积物为惟一磷源培养小球藻和球等鞭金藻,估算了藻类对沉积物中磷的可利用量.结果表明,3种沉积物总磷含量分别为449.3,650.1和643.9mg/kg;MgCl₂和NaOH提取的生物可利用的非磷灰石无机磷分别为168.8,146.6和118.1mg/kg.非磷灰石无机磷占总磷的18.3%～32.6%.3种提取剂对3种沉积物提取的磷是HCl提取相最大,NaOH提取相次之,MgCl₂提取相最小.小球藻和球等鞭金藻在3种沉积物中的最大相对生长率为4.3%～26.9%,两种藻在3种沉积物中的生长与非磷灰石无机磷和藻类可利用的颗粒磷量相对应.颗粒磷占非磷灰石无机磷的42.4%～78.2%,占沉积物中总无机磷的21.1%～27.1%,占总磷的11.8%～20.3%.     

Alkaline leaching characteristics of biogenic opal in Eocene sediments from the central Arctic Ocean: a case study in the ACEX cores

Accurate knowledge of the extent of biogenic opal preservation in marine sediment cores is important for paleoceanographic reconstructions. The alkaline leaching method is widely employed for %biogenic opal analysis due to its ease and speed. In this study, a revised method for measuring %biogenic opal in sediment from arctic coring expedition samples was suggested. The studied middle Eocene sediments from the central Arctic Ocean presented a problem in insufficiently leaching biogenic opal with a Na₂CO₃ solution. Based on XRD analysis, it was suggested that such an alkaline resistance results from slight diagenesis of biogenic opal. In order to solve this problem, an alkaline leaching method utilizing a 2 M NaOH solution was suggested for the accurate measurement of %biogenic opal in the Eocene sediments from the central Arctic. Furthermore, dissolution rates from lithogenic matter by NaOH solution were measured in order to correct the %biogenic opal values.     

Origin of organic matter and paleoenvironment conditions of the Late Jurassic organic-rich shales from shabwah sub-basin (western Yemen): Constraints from petrology and biological markers

Late Jurassic organic-rich shales from Shabwah sub-basin of western Yemen were analysed based on a combined investigations of organic geochemistry and petrology to define the origin, type of organic matter and the paleoenvironment conditions during deposition. The organic-rich shales have high total sulphur content values in the range of 1.49–4.92 wt. %, and excellent source rock potential is expected based on the high values of TOC (>7%), high extractable organic matter content and hydrocarbon yield exceeding 7000 ppm. The high total sulphur content and its relation with high organic carbon content indicate that the Late Jurassic organic-rich shales of the Shabwah sub-basin were deposited in a marine environment under suboxic-anoxic conditions. This has been evidenced from kerogen microscopy and their biomarker distributions. The kerogen microscopy investigation indicated that the Late Jurassic organic-rich shales contain an abundant liptinitic organic matter (i.e., alginite, structureless (amorphous organic matters)). The presence of alginite with morphology similar to the lamalginite alga and amorphous organic matter in these shale samples, further suggests a marine origin. The biomarker distributions also provide evidence for a major contribution by aquatic algae and microorganisms with a minor terrigenous organic matter input. The biomarkers are characterized by unimodal distribution of n-alkanes, low acyclic isoprenoids compared to normal alkanes, relatively high tricyclic terpanes compared to tetracyclic terpanes, and high proportion of C₂₇ and C₂₉ regular steranes compared to C₂₈ regular sterane. Moreover, the suboxic to anoxic bottom water conditions as evidenced in these Late Jurassic shales is also supported based on relatively low pristane/phytane (Pr/Ph) ratios in the range of 0.80–1.14. Therefore, it is envisaged here that the high content of organic matter (TOC > 7 wt.%) in the analysed Late Jurassic shales is attributed to good organic matter (OM) preservation under suboxic to anoxic bottom water conditions during deposition.     

Source rock characteristics and biostratigraphy of the Lower Silurian (Telychian) organic-rich shales at Akyaka, central Taurus region, Turkey

The Akyaka section in the central Taurus region in the southern part of Turkey includes the organic matter and graptolite-rich black shales which were deposited under dysoxic to anoxic marine conditions in the Early Silurian. A biostratigraphical analysis, based on graptolite assemblages, indicates that the sediments studied may well be referable to the querichi Biozone and early Telychian, Llandovery. A total of 15 samples have been subjected to Leco and Rock-Eval pyrolysis and graptolite reflectance measurements for determination of their source rock characteristics and thermal maturity. The total organic carbon content of the graptolite-bearing shales varies from 1.75 to 3.52 wt% with an average value of 2.86 wt%. The present Rock-Eval pyrolytic yields and calculated values of hydrogen and oxygen indexes imply that the recent organic matter type is inert kerogen. The measured maximum graptolite reflectance (G_Rmax %) values are between 5.04% and 6.75% corresponding to thermally over maturity. This high maturity suggests a deep burial of the Lower Silurian sediments resulting from overburden rocks of Upper Paleozoic to Mesozoic Upper Cretaceous and Middle-Upper Eocene thrusts occurred in the region.     

Oxygen and organic carbon fluxes in sediments of the Bay of Biscay

The relationship between particulate organic carbon (POC) concentrations measured in modern sediment and fluxes of exported POC to the sediment surface needs to be understood in order to use POC content as a proxy of paleo-environmental conditions. The objective of our study was to compare POC concentrations, POC mineralization rates calculated from O₂ consumption and POC burial rates. Benthic O₂ distributions were determined in 58 fine-grained sediment cores collected at different periods at 14 stations in the southeastern part of the Bay of Biscay with depths ranging from 140 to 2800 m. Depth-dependent volume-specific oxygen consumption rates were used to assess rates of aerobic oxidation of organic matter (OM), assuming that O₂ consumption solely was related to heterotrophic activity at the sediment–water interface. Heterogeneity of benthic O₂ fluxes denoted changes in time and space of fresh organic material sedimentation. The most labile fraction of exported POC engendered a steep decrease in concentration in the upper 5 mm of vertical O₂ profiles. The rupture in the gradient of O₂ microprofile may be related to the bioturbation-induced mixing depth of fast-decaying carbon. Average diffusive O₂ fluxes showed that this fast-decaying OM flux was much higher than buried POC, although diffusive O₂ fluxes underestimated the total sediment oxygen demand, and thus the fast-decaying OM flux to the sediment surface. Sedimentary POC burial was calculated from sediment mass accumulation rate and the organic carbon content measured at the top of the sediment. The proportion of buried POC relative to total exported POC ranged at the most between 50% and 10%, depending on station location. Therefore, for a narrow geographic area like the Bay of Biscay, burial efficiency of POC was variable. A fraction of buried POC consisted of slow-decaying OM that was mineralized within the upper decimetres of sediment through oxic and anoxic processes. This fraction was deduced from the decrease with depth in POC concentration. At sites located below 500 m water depth, where the fast-decaying carbon did not reach the anoxic sediment, the slow-decaying pool may control the O₂ penetration depth. Only refractory organic material was fossilized in sedimentary records at locations where labile OM did not reach the anoxic portion of the sediment.     

Sources and preservation of organic matter in Plum Island salt marsh sediments (MA, USA): long-chain n-alkanes and stable carbon isotope compositions

Elemental (TOC, TN, C/N) and stable carbon isotopic (δ¹³C) compositions and n-alkane (nC_16–38) concentrations were measured for Spartina alterniflora, a C₄ marsh grass, Typha latifolia, a C₃ marsh grass, and three sediment cores collected from middle and upper estuarine sites from the Plum Island salt marshes. Our results indicated that the organic matter preserved in the sediments was highly affected by the marsh plants that dominated the sampling sites. δ¹³C values of organic matter preserved in the upper fresh water site sediment were more negative (−23.0±0.3‰) as affected by the C₃ plants than the values of organic matter preserved in the sediments of middle (−18.9±0.8‰) and mud flat sites (−19.4±0.1‰) as influenced mainly by the C₄ marsh plants. The distribution of n-alkanes measured in all sediments showed similar patterns as those determined in the marsh grasses S. alterniflora and T. latifolia, and nC₂₁ to nC₃₃ long-chain n-alkanes were the major compounds determined in all sediment samples. The strong odd-to-even carbon numbered n-alkane predominance was found in all three sediments and nC₂₉ was the most abundant homologue in all samples measured. Both δ¹³C compositions of organic matter and n-alkane distributions in these sediments indicate that the marsh plants could contribute significant amount of organic matter preserved in Plum Island salt marsh sediments. This suggests that salt marshes play an important role in the cycling of nutrients and organic carbon in the estuary and adjacent coastal waters.     

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.