Trace elements in suspended matter from the anoxic hypersaline Tyro and Bannock Basins (eastern Mediterranean)

In the anoxic hypersaline Tyro and Bannock Basins of the eastern Mediterranean, extremely high concentrations of Co (0.015%), Cu (1.35%) and Zn (0.28%) were found in suspended matter collected at the sharp interface between seawater and the anoxic brine. The high particulate Co, Cu and Zn concentrations can be explained by the sharp increase in dissolved sulphide at these interfaces, and the resultant precipitation of metal sulphides. The particulate As, Sb and Mo concentrations also showed a sharp maximum at or close to the interface. However, the contributions of As, Sb and Mo contents in suspended matter to the total concentrations in the water column are small. Scanning electron microscopy-energy-dispersive X-ray analysis (SEM-EDAX) of suspended particulate matter from the Tyro Basin revealed spherical particles strongly enriched in Fe, Cu and Zn at the seawater-brine interface.     

Recycling of manganese in the coastal sea,Funka Bay,Japan

The downward flux of Mn through the water column was directly measured using sediment traps. The Mn flux from the bottom sediment to the water column, and the removal rate of Mn in the bottom water were estimated from Mn gradients in the bottom water. The sediment traps were deployed more than ten times at the same station in Funka Bay, Japan. The trapped settling matter and filtered suspended matter samples were analyzed for Mn, Fe, Al and ignition loss. The observed downward flux of Mn through the water column in winter (1.3–2.8 μg/cm² /day) was generally an order of magnitude larger than that in summer (0.13–0.45 μg/cm² /day), and the Mn fluxes for both seasons were also greater than the accumulation rate of Mn in the bottom sediments (0.10 μg/cm ²/day). More Al was contained in the trapped settling matter than in the suspended matter, while Mn showed the opposite behavior. The Fe/Mn ratio of the residual fraction (obtained by subtracting the sediment component of the settling matter) was rather well correlated with the corresponding ratio in suspended matter. Settling particles are expected to scavenge suspended matter during their passage through the water column. The flux of Mn across the sediment—water interface was estimated from its vertical profiles in the water column to be 0.1–0.3 μg/cm² day. The residence time of Mn in bottom water was about one to several months. These results suggest that Mn is actively recycled between the water column and the sediments of the coastal sea.     

Chlorinated hydrocarbons in the open mediterranean ecosystem and implications for mass balance calculations

Studies on the biogeochemical cycling of organic contaminants in the Mediterranean have demonstrated the importance of polychlorinated biphenyls (PCBs) as relatively stable markers of recent anthropogenic influence in ocean systems. This paper presents results of hydrocarbon analyses of deep water profiles, sediments and their associated surface flocculent layers, and zooplankton samples collected in the western basin. Seawater concentrations were higher than those previously reported for the eastern basin and were consistent with the presence of industrial sources in the northwestern segment. In the water column, the percent of PCBs associated with filterable particles was related to the ambient concentrations of total suspended matter, distance from coastal input sources and on depth. The occurrence of deep water residues primarily in the dissolved phase and observations of subsurface maxima in seawater concentrations during a season of high surface productivity were consistent with the predictions of vertical transport models based on residues associated with sinking particles and equilibrium partitioning. Flocculent layers at the sea/sediment interface contained two and three orders of magnitude, respectively, more PCBs and petroleum hydrocarbons (PHCs) than their associated surface sediments. The flocculent particles also contained several biogenic hydrocarbons presumably originating from plankton and relatively soluble and labile contaminants such as hexachlorohexane isomers (HCH) and hexachlorobenzene (HCB), thus confirming that the majority of the flux of hydrocarbons to sediments is carried on rapidly settling large particles. By combining the sediment and flocculents data with published sedimentation rates for the deep basins of the Mediterranean, a yearly flux rate of PCBs to the open sea sediments was estimated as 13 μg m⁻² yr⁻¹ or less than half of the rate measured in a coastal sediment trap experiment. Analytical results are placed in the context of other distribution data for PCBs and long-term flux studies to construct a partial mass balance budget for this semi-enclosed sea. The computed coastal inventory showed that about 35% remains suspended in the water column while the majority of residues are deposited in coastal sediments. However in the open sea, the deep water column may contain up to 70% of the total inventory and may be a continually increasing reservoir of stable organic contaminants reaching the ocean. The budget shows that priority for improved research and monitoring efforts in ocean systems should be given to continued advancement in techniques for the precise measurement of deep water concentrations and for measuring current atmospheric inputs and sedimentation rates in order to develop more accurate ocean flux models.     

Metal distributions and their fluxes at the coastal boundary of a semi-enclosed ria

Water column samples have been collected in the outer channel of the Ferrol Ria (NW Spain) during four occasions over a tidal cycle. The objective was to study the exchange of dissolved and particulate Cd, Cu, Pb and Zn and particulate Al, Fe and Si between the ria and the adjacent coastal waters. This study provides the first extensive dataset on dissolved and particulate metal concentrations in the water column of a Galician ria. Typical concentrations of dissolved Cd (96 ± 31 pM), Cu (8 ± 4 nM), Pb (270 ± 170 pM) and Zn (21 ± 10 nM) were similar than in other European Atlantic shelf and coastal waters. The fraction of metals in the particulate phase followed the trend: Pb > Cu Zn > Cd. The outgoing water from the ria was enriched in dissolved and particulate Cu, Pb and Zn compared with incoming waters, whereas Cd concentrations were similar for both waters. The suspended particulate matter was composed of a mixture of marine and continental material. The latter end-member was found to arise from the metal-rich ria bed sediments, which is diluted by the dominant metal-poor marine end-member. The net output flux of Cu from the channel is balanced by the freshwater inputs to the ria, and the net Zn flux gave a positive output to coastal waters. For Pb, the net flux to the coastal waters is less than that input from the rivers, as a result of its particle reactivity and deposition in sediments. On the contrary, a net input flux of dissolved Cd from coastal waters was observed, highlighting the oceanic source of this metal in the Galician rias. Results from the budget calculations are in agreement with the differential geochemical behavior of these elements in coastal waters.     

The nutrient and trace metal geochemistry of a dredge plume

Field sampling of the dissolved and particulate material field downstream of a large volume bucket dredge operating in the lower Thames River estuary near New London, Connecticut, was conducted in order to examine the magnitude and character of the dredge-induced resuspension. These data indicate that large amounts of dissolved phosphate, ammonia, silica, manganese, copper and particulate materials are released into the water column, whereas cadmium concentrations were unaffected. Concentrations in the vicinity of the dredge exceed background levels by two to nine times for the dissolved materials and by two orders of magnitude for particulates. During the ebb cycle, downstream material concentrations decrease rapidly to background within approximately 180 m for dissolved materials and 700 m for particulates.Two mechanisms were found to control the distribution of materials downstream of the dredge: (a) physical transport, including advection, turbulent mixing and diffusion, and (b) geochemical processes (i.e. adsorption, desorption, precipitation, dissolution, etc.). The concentration of dissolved materials downstream of the dredge decrease at a first order exponential rate. The downstream distribution of the dissolved ammonia and silica was found to be consistent with the reactivity experiments (Figure 8) which predicted that PO₄ would undergo a decay in concentration in the presence of suspended sediments. Absorption of phosphate onto suspended sediments and gravitational settling of the suspended particulates were the processes. Manganese and copper underwent a dual transformation which involved an initial dissolution, followed by flocculation and possible coprecipitation as MnO₂. Cadmium concentrations in the water column were unaffected by the dredging process due to low pore water concentrations.The observed spatial distribution indicates that dredge-induced injection of dissolved and particulate materials is primarily a near field phenomenon producing relatively minor variations as compared to those caused by naturally occurring storm events. These latter systems have been shown (Tramontano, 1978; Bohlen et al., 1979) to produce estuary-wide variations in suspended materials, PO₄ and NH₄ concentrations increasing the mass of materials in suspension by at least a factor of two. This increase in total suspended load, PO₄ and NH₄, is nearly an order of magnitude larger than that produced by the dredge.     

The effect of manganese oxide scavenging on molybdenum in saanich inlet,British Columbia

A simple colorimetric method was developed for determining molybdenum in seawater by solvent extraction of its dithiolate and was then applied during a nine month study of Saanich Inlet. This inlet is a fjord on the coast of Vancouver Island, British Columbia, in which the bottom waters alternate between a weakly oxygenated and anoxic state. Results are given for the concentrations of dissolved and suspended molybdenum, suspended manganese, dissolved oxygen and of salinity measurements. Salinity-molybdenum correlations demonstrate that the deep waters are deficient in molybdenum, a conclusion consistent with reports that the sediments deposited in the reducing zone are enriched with molybdenum precipitated from the anoxic bottom waters. Suspended manganese, which occurs in large amounts as a result of the oxidative precipitation of dissolved Mn(II) diffusing from anoxic waters, has a distribution that is directly correlated to that of suspended molybdenum and which tends to be inversely related to that of dissolved molybdenum, suggesting that molybdenum is being coprecipitated with manganese oxides. Such a hypothesis is supported by the fact that the average molybdenum to manganese weight ratio of suspended matter closely approximates that of local manganese nodules, and by a mathematical analysis of the distribution data which includes development of a model for scavenging. Computations using the model relationships indicate that manganese oxide scavenging tends to concentrate molybdenum in the reducing waters where the anoxic processes responsible for its deposition in the sediments become operative. Additional calculations based upon current estimates of oceanic residence times suggest that manganese-oxide scavenging operating on an oceanic scale could be removing approximately 10% of the molybdenum being added to the oceans.     

Origin and fate of particulate organic matter in the southern Beaufort Sea – Amundsen Gulf region,Canadian Arctic

To establish the relative importance of terrigenous and marine organic matter in the southern Beaufort Sea, we measured the concentrations and the stable isotopic compositions of organic carbon and total nitrogen in sediments and in settling particles intercepted by sediment traps. The organic carbon content of surface sediment in the Chukchi and southern Beaufort Seas ranged from 0.6 to 1.6% dry wt., without a clear geographical pattern. The C_ORG:N_TOT ratio ranged from 7.0 to 10.4 and did not vary significantly downcore at any one station. Values of δ¹³C_ORG and δ¹⁵N_TOT in the sediment samples were strongly correlated, with the highest values, indicative of a more marine contribution, in the Amundsen Gulf. In contrast, the organic matter content, elemental (C_ORG:N_TOT ratio) and isotopic (δ¹³C_ORG and δ¹⁵N_TOT) composition of the settling particles was different from and much more variable than in the bottom sediments. The isotopic signature of organic matter in the Beaufort Sea is well constrained by three distinct end-members: a labile marine component produced in situ by planktonic organisms, a refractory marine component, the end product of respiration and diagenesis, and a refractory terrigenous component. A three-component mixing model explains the scatter observed in the stable isotope signatures of the sediment trap samples and accommodates an apparent two-component mixing model of the organic matter in sediments. The suspended matter in the water column contains organic matter varying from essentially labile and marine to mostly refractory and terrigenous. As it settles through the water column, the labile marine organic matter is degraded, and its original stable isotope signature changes towards the signature of the marine refractory component. This process continues in the bottom sediment with the result that the sedimentary organic matter becomes dominated by the refractory terrigenous and marine components.     

Cycles of chemical substances in the atmosphere,the Sea and the sea-floor

Since 1960 when I was a senior student, I have studied natural phenomena observed in the hydrosphere and atmosphere by means of chemical elements. Each of the phenomena is, in general, very complicated and so I have attempted to depict the whole picture of material circulation in the marine environment by studying its various aspects at the same time. My chief strategy has been to use natural radio-nuclides as clocks of various phenomena, and to use sediment traps for the determination of vertical fluxes in the ocean. The many results I have obtained can be summarized as follows. 1. I have found that several sporadic events control the material exchange through the atmosphere. These include the strong winter monsoon and typhoons that transport sea-salt particles to the Japanese Islands, theKosa episodes that transport soil dust to the ocean, and storms that result in exchange of sparingly soluble gases such as oxygen and carbon dioxide at the air-sea interface. I have also proved quantitatively that the source of aluminosilicate material in pelagic sediments is air-borne dust. 2. I have proposed a model,Settling model, for the removal of chemical substances from the ocean and found various lines of evidence supporting the model. This model predicts the reversibility in the existing state of insoluble chemical elements in seawater among large settling particles, small suspended particles and colloidal particles that pass through a membrane filter and explains well their behavior in the ocean. I have first precisely measured calcium and iodine in the ocean and have explained their distributions on the basis of the solution and redox equilibria. 3. Using chemical tracers, I have estimated the vertical eddy diffusion coefficients to be 1.2 cm²sec⁻¹ for the Pacific deep water, 0.5 cm²sec⁻¹ for the deep Bering Sea water and 3–80 cm²sec⁻¹ for the Pacific surface water, and have studied the structure of water masses in the western North Pacific and the Sea of Japan. I have also invented and applied a method for the calculation of the age of deep waters using radiocarbon. 4. I have calculated the rates of decomposition of organic matter and the regeneration rates of chemical components in the deep and bottom waters as well as coastal waters by modelling water circulation and mixing. Particulate fluxes and regeneration rates are larger in the deep waters beneath the more biologically productive surface waters. I have stressed the role of silicate in the marine ecosystem, especially in the succession of phytoplankton species. 5. I have quantitatively studied the migration of chemical elements during the early diagenesis of bottom sediments especially manganese using chemical and radiochemical techniques. Manganese is being actively recycled not only in coastal seas but also in pelagic sediments except in the highly oligotrophic subtropical ocean. This recycling can explain the formation of manganese nodules and enables us to balance the manganese budget in the ocean.     

Sediment trap comparison experiments

Four types of sediment traps which are different in their shapes were simultaneously deployed in Funka Bay, Hokkaido or open ocean, in order to compare the quantity and quality of settling particles collected at the same time. In Funka Bay, the larger total particulate fluxes were observed with the sediment traps having the larger height to width ratios. The settling particles collected with the narrower sediment traps were somewhat similar to suspended particle enriched in organic matter, phosphorus and Mn. These results suggest that the narrower sediment trap more effectively collects fine and light particles similar to suspended particles.     

Some peculiarities of the trace-metal distribution in Baltic waters and sediments

Between 1980 and 1984 extensive studies were carried out in the Baltic Sea on trace metals (Cd, Co, Cu, Fe, Hg, Mn, Ni, Pb and Zn) in water, suspended matter and sediments. The results enabled the influence of different factors on metal distribution patterns to be considered. The vertical profiles of dissolved and particulate metals in waters of the central deep basins reflect influences caused by oxygen deficiency and anoxic conditions in near-bottom water layers. Peculiarities at Station BY15 in the Gotland Deep included high dissolved Fe, Mn and Co concentrations and remarkable enrichment of Zn (0.64%), Cd (51 μg g⁻¹) and Cu (0.15%) in particulate matter from the anoxic zone. Manganese-rich particles were accumulated above this layer.In fine-grained soft sediments below anoxic deep waters, maximum contents of Cd, Cu and Zn were observed, relative to other coring sites, between Bothnian Bay and Lübeck Bight. The Hg content in sediments probably reflects the joint flocculation with organic matter. Land-based sources seem to play the leading part for maximum lead contents.     

海洋雾状层的成因及其对海洋碳循环过程的影响

海洋雾状层既是陆源物质进入海底的输送通道,又是海洋水体中沉降颗粒及底部再悬浮颗粒物的停留场所。雾状层物质来源主要有陆源、生源以及海底表层沉积物的再悬浮,不同海区、不同层位的雾状层的物质来源有所差异;雾状层的成因具有复杂性,既有物理作用,又有生物及化学作用,大量研究表明,海底洋流、内波(潮)等物理作用是雾状层形成的主要控制因素。雾状层中碳的存在形态主要有颗粒有机碳(POC)、溶解有机碳(DOC)、胶体有机碳(COC)以及无机碳,雾状层与其上下海水之间、雾状层与海底表层沉积物之间不同形态碳在生物-化学-物理动力系统作用下不断发生物质交换与迁移,对海洋碳循环生物地球化学过程起重要的控制作用,是整个海洋碳循环的一个不可忽视的环节。     

Measurements of suspended particulate matter with laser in-situ scattering and transmissometry in the Jiaozhou Bay in China

1 IntroductionKnowledge of suspended particle size and distri-bution is the key elements for better understandingthe sediment transport processes ( Wang et al.,2004), primary production (Ning et al., 2004),water quality controlling and pollution predictio…     

Early diagenesis in recent bottom sediments of the Dvina Bay (White Sea)

Investigations in the water column and bottom sediments including entrapped water were carried out on expeditions of the P.P. Shirshov Institute of Oceanology in the Dvina Bay, the White Sea. We studied the transformation of particulate organic matter at the biogeochemical barrier between the water and bottom and in the underlying Holocene sediments. Low rates of the early diagenesis of sediments caused by low values of primary production in the conditions of high fluxes of terrigenous organic matter were established. The low temperatures of microorganisms habitat play the secondary role.     

A study of the geochemistry of suspended particulate matter in coastal waters

The concentrations of Si, Al, Ti, Fe, K, Ca, Mg, P and Mn, before and after chemical leaching, in particulate matter from waters off the west coast of Scotland have been measured in vertical profiles at two seasons. The distribution of Si and Ca are shown partly to reflect temporal changes in biological production in different waters. The distributions of Al, Ti, Fe, K and Mg have been used to distinguish different sources and types of suspended alumino-silicates, and to trace probable circulation patterns in the water mass.While Si and Ti contents of the particulate matter are unaffected by mild chemical leaching, large amounts of other elements, notably Mg, K and Al, can be removed by this treatment. Presumably, these losses indicate preferential release of these elements from octahedral and interlayer sites in clay mineral lattices.The distribution of particulate P covaries with non-silicate Fe in the surface waters, while in bottom waters, high concentrations of particulate Fe and Mn are associated. The relationship of Fe and P is considered to be due to the presence of particulate ferriphosphates derived from runoff. The particulate Mn and Fe in deep waters is produced by the precipitation of dissolved metals released from bottom sediments by diagenesis.     

Optical,biological, and chemical properties ofAoshio,hypoxic milky blue-green water,observed at the head of Tokyo Bay

Aoshio-hypoxic water which can be distinguished from surrounding coastal water by its milky blue-green color-is often observed at the head of Tokyo Bay when coastal upwelling of sulfidic bottom water occurs during summer and early autumn. Optical properties and the biological-chemical composition of suspended matter in theaoshio water were investigated using nearby “normal” coastal water as a reference. Suspended matter in theaoshio water contributed to the large beam-attenuation coefficient and also to the strong upward radiance with maximal intensity around 550 nm as a result of the scattering process. No significant difference in bacterial density was observed between samples ofaoshio water and reference coastal water. The low chlorophylls concentration inaoshio water samples indicates that biological pigments may not play a dominant role in the color of theaoshio events. The suspended particles inaoshio water samples had much higher contents of sulfur and manganese and a lower silicon content than those in reference coastal water samples. The colloidal elemental sulfur and manganese-rich particles identified in theaoshio water appear to be oxidation products of dissolved sulfide and manganese (II) in the anoxic water. On the basis of these findings, it may be concluded that there is a high probability that elemental sulfur and manganese-rich particles are responsible for the color and turbidity inaoshio.     

Vertical Patterns of Suspended Matter Characteristics Along a Coastal-basin Transect in the Western Baltic Sea

Suspended particulate matter samples were collected from the water column, the bottom nepheloid layer and the ‘ fluffy layer ’ from four stations along a coastal-basin transect in the Pomeranian Bight, western Baltic Sea. Sampling was performed nine times between October 1996 and December 1998 for various analyses, including electron probe x-ray micro analysis for detailed mineralogical investigations.Specific vertical patterns of clay mineral distributions were found. Suspended particulate matter (SPM) in the bottom nepheloid layer and the ‘ fluffy layer ’ overlying sediments was enriched in organic carbon and hydrated three layer clay minerals, whereas the non-aggregated SPM was dominated by quartz and biogenic opal. It appears that separation effects operate during aggregation of mineral particles and organic matter in repeated cycles of resuspension and settling. No clear seasonal variations in the composition of the SPM were found, in spite of high spatial and temporal variability of biological and physical variables. The results suggest that preferential incorporation, possibly aided by microbiological colonization, of hydrated three layer silicates into the organic flocs is a process that occurs under a wide range of conditions. Because aggregates sink faster than individual particles, aggregate formation led to a relative enrichment of illite and smectite in the near-bottom layers. Considering the affinity of organic contaminants and heavy metals to organic matter, the selective removal of aggregated organic matter and hydrated three-layer clay minerals from the water column and enhanced transport in the near-bottom fluffy layer may be a natural cleansing mechanism operating in the shallow waters of the bight.     

太平洋悬浮体特征及近底雾状层(雾浊层)探讨

2005年在太平洋12个测站分层采集了悬浮体水样及连续的水体温度、盐度、深度等数据.利用水体悬浮体含量在垂向上的分布特征初步分析了大洋雾状层的特点,并讨论了水体中悬浮体颗粒物质的来源,对不同海洋环境中悬浮体分布进行了对比,发现大洋水体中悬浮体含量总体很小,一般不超过0.30mg/dm3,但在一定水层内悬浮体含量相对较高,形成雾状层.雾状层在大洋内广泛分布,一般以表层雾状层和近底雾状层形式存在.大洋水体中悬浮体颗粒物来源广泛.表层雾状层的形成主要受透光层内生物作用的影响,而底质沉积物的再悬浮是影响底部雾状层形成的重要因素.因受水体物理海洋环境和物质来源的影响,不同区域水体中悬浮体含量不同,雾状层的分布不同.海山顶部受水流及岩石基底影响雾状层分布不明显,海山底部与开辟区洋盆海域雾状层更普遍.开辟区东西区由于物源差异水体中悬浮体含量差别明显,靠近火山喷口的西区水体中悬浮体含量明显高于东区的.     

Continental runoff of solid matter as a source of dissolved calcium in the ocean

It was found in the experiments that the transfer of calcium from the solid phase to the dissolved state took place under the interaction of terrigenous matter (bottom sediments from the freshwater lake) with the solutions modeling the interstitial waters of the sediments of high-productive regions of the ocean. This calcium might later bind the autochthonous CO₂ formed in the ocean under the oxidation of organic matter. According to the data of the three-week experiment, 1 g of the terrigenous matter evolved on average ～2.3 mg Ca²⁺ into interstitial solutions, which conforms to the involving of exclusively surface layers of the grains of the solid phase into the reaction. In view of the true rate of halmyrolysis of the grains of terrigenous silicates (a few μm/year), at the value of the continental runoff of solid matter being equal to 16 billion t/year, the amount of dissolved calcium supplied to the ocean as a result of the transformation of the terrigenous sedimentary matter at the stage of diagenesis amounts to 250–440 million t/year and over. These values are 3- to 5-fold higher that the amount of calcium in the continental runoff of dissolved matter supplied by the erosion of silicates and capable of forming carbonate sediments in the ocean under the interaction with autochthonous CO₂, unlike the calcium that is product of the dissolution of carbonate rocks.     

Carbon inputs and distribution in estuaries of turbid rivers: the Yang Tze and Yellow rivers (China)

Particulate and dissolved organic and inorganic carbon concentrations were measured in the Yang Tze (Changjiang) and Huanghe (Yellow) river estuaries, during two different seasons. During the winter, the organic matter in the suspended load of both estuarine systems was dominantly of terrestrial origin, while in the summer, there were significant contributions from aquatic production. In these turbid rivers, there is a strong positive correlation between the concentrations of total suspended matter and particulate organic carbon, probably because biological production is inhibited when turbidity exceeds a certain limit. Dissolved organic carbon (DOC) does not exhibit a conservative behavior in these estuarine systems. High dissolved organic carbon values in bottom water samples suggest remobilization of DOC from near-surface, bottom sediments. Dissolved inorganic carbon concentrations were very high in the Huanghe River, and the trend in the calculated saturation indices for calcite suggests precipitation of carbonate in this estuarine system. There is no such evidence for carbonate precipitation in the Yang Tze River.     

The behavior of iron,manganese and silicon in the Peconic River estuary,New York

The behavior of dissolved and particulate iron and manganese and dissolved silicon has been studied as a function of chlorinity in the Peconic River estuary, New York. This study sought to identify important geochemical processes in a relatively pristine estuary facing increasing anthropogenic impact.Dissolved iron behaved in the classical non-conservative manner exhibiting removal of nearly 80% at very low chlorinities, while particulate iron increased by a corresponding amount over the same chlorinity range. Dissolved manganese was enriched by up to 200% over its predicted concentration at low and intermediate chlorinities by desorption from suspended particulates and by a probable benthic flux. Dissolved silicon was enriched by up to 100% at low and intermediate chlorinities also from a probable benthic flux. These fluxes were estimated to be 5 μg cm^?2 day^?1 for dissolved manganese and 70 μg cm^?2 day^?1 for dissolved silicon.The quantity of both particulate iron and manganese increased at high chlorinities due to an influx of suspended inorganic particulates. In the intermediate to high chlorinity region, oxidation of sediment-derived manganese is believed to contribute to the observed increase in particulate manganese.Total iron was essentially conservative throughout most of the estuary, while total manganese was non-conservative presumably due to extensive remobilization of dissolved manganese from the sediments.