Distributions of trace metals Co, Cu and Cd in northern Sagami Bay, Japan and their relationship to estuarine variables

Concentrations of the trace metals Co, Cu and Cd in dissolved (0.2 mm) phases in surface waters were determined to test whether DOC, which is an indicator of dissolved organic matter (DOM), and organic matter (OM) in suspended particulate matter (SPM) act as important estuarine variables controlling the distributions of these metals in the estuarine zone. Although the dissolved metals in the surface waters from the Sagami River to northern Sagami Bay had different behaviors in June, August, and November, 2008, concentrations of dissolved Co and Cu linearly correlated with DOC concentration, but with different slopes for fresh (salinity of0.1) waters. This difference in the water regime between those two metals and the DOC in Sagami Bay indicates that there are differences in composition between riverine and estuarine DOM, due to change of the composition by biogeochemical processes and the presence of additional sources, or that seawater cations are competing for binding sites of DOM during the estuarine mixing. As for particulate phase, there was no relationship between the concentrations of particulate metals and that of OM in SPM at low river flows (i.e., June and November surveys). It is thought that change of the OM composition by the additional SPM sources (anthropogenic discharge and resuspension from the seabed) contributes to the affinity of trace metals for sorption sites on the surfaces of the SPM, thereby making the evaluation of importance of OM in SPM difficult. On the other hand, at high river flow (August survey), riverine SPM significantly contributed to the estuarine SPM and it entered northern Sagami Bay with negligible composition change; however, there were weak correlation coefficients of particulate Co and Cd to OM in SPM, and there was no linear relationship between particulate Cu and OM in SPM. This can be attributed to the imbalanced competition between particle sorption and organic/inorganic complexation for Co and Cd, and prevention of particle sorption by binding Cu more strongly to dissolved organic ligands

R/V SHINSEI MARU Cruise Report KS-21-23

調査海域: 常磐沖 / Area: Off Joban ; 期間: 2021年10月7日～2021年10月17日 / Operation Period: October 7, 2021～October 17, 2021http://www.godac.jamstec.go.jp/darwin/cruise/shinsei_maru/ks-21-23/

Effect of aging time on the availability of freshly precipitated ferric hydroxide to coastal marine diatoms

Cell growth and iron uptake of the coastal marine diatoms Chaetoceros sociale and Thalassiosira weissflogii were studied in the presence of short-aged amorphous ferric hydroxide (am-Fe(III)) media. These were prepared by aging for 1 day, 3 days, and 3 weeks after adding a small amount of ferric iron acidic stock solution to autoclaved filtered seawater and were experimentally measured in culture experiments at 10 degrees C for C. sociale and 20 degrees C for T. weissflogii. The order of cell yields for both species was: 1-day aged am-Fe(III) > 3-day aged am-Fe(III) >> 3-week aged am-Fe(III) media. The iron uptake rates by C. sociale during 0-1 day in 1 day and 3-day aged am-Fe(III) media were about two-thirds and one-fourths, respectively, lower than that in the direct Fe(III) input medium containing C. sociale into which an acidic Fe(III) stock solution was added directly. The longer aging time of am-Fe(III) in media results in reducing the supply of bioavailable iron in the media by the slower dissolution rate of am-Fe(III) with the longer aging time. These results suggest that the chemical and structural changes of freshly precipitated amorphous ferric hydroxide with short aging time affect their ability, such as iron solubility and dissolution rate to supply bioavailable iron for the phytoplankton growth. The chemical and structural conversion of solid iron phases with time is one of the most important processes in changing the supply of available iron to marine phytoplankton in estuarine and coastal waters and in iron fertilization experiments

Determination of Trace Levels of Yttrium and Rare Earth Elements in Estuarine and Coastal Waters by Inductively Coupled Plasma Mass Spectrometry Following Preconcentration with NOBIAS-CHELATE Resin

The use of a solid-phase extraction column packed with a polyamino-polycarboxylic acid chlating resin (NOBIASCHELATE resin) for separation and concentration of trace levels of yttrium (Y) and rare earth elements (REEs) from estuarine andcoastal water samples is described. The Y and REE recoveries from the resin were pHdependent; at pH 5.7, Y and REEs were extracted from the resin with almost 100% recovery. Barium, which has the potential to interfere with the analysis of REEs by inductively coupled plasma mass spectrometry (ICP-MS) because of the formationof oxide complexes, was not recovered from the column at pH 5.7. In addition, the reproducibility of the results for Y and REEs was not affected by variationsin salinity or by high concentrations of heavy metals,such as Fe, Mn, and Mo. The method was verified by the analysis of a coastal water standard reference material (NRCC CASS-4). The values obtained with the present method were comparable to previously reported values obtained by standardanalytical techniques. We used this simple, quick method to determine the concentrations of Y and REEs in estuarine and coastal waters of the MabechiRiver and off Aomori, Japan

Processes controlling cobalt distribution in two temperate estuaries, Sagami Bay and Wakasa Bay, Japan

Concentrations of cobalt (Co) in surface waters from the Sagami River to northern Sagami Bay and from the Yura River to southwestern Wakasa Bay in Japan were determined in order to investigate the factors governing the distribution of this metal during estuarine mixing. Dissolved (0.2 um) Co showed non-conservative mixing behavior with low or mid-salinity maxima within those two estuarine regions, indicating benthic remobilization and/or sewage input apart from riverine input during the estuarine mixing. These results are supported by a suite of complementary measurements of other parameters, such as manganese, phosphate, and suspended particulate matter concentrations. In addition, the concentration ratio of dissolved Co to total Co (dissolved plus particulate) increased along the salinity gradient, implying the potential for desorption of this metal from suspended particulate matter on estuarine mixing. To identify desorption of this metal from suspended particulate matter by salinity changes, laboratory desorption experiments were undertaken by mixing unfiltered river water and filtered estuarine water samples with a different volume of each water sample. The mixed water samples for the experiments had different salinity values of 4.0, 17, and 30. Although dissolved Co and particulate Co concentrations at salinity 4.0 were almost constant from 2 min after starting the experiment to 120 h, dissolved Co concentrations at salinities 17 and 30 increased with time in the experimental period. Declines in particulate Co concentrations were observed in those salinities. Also, a relatively high percentage of Co in the solid phase at salinity 30, as compared to the percentage at salinities 4.0 and 17, was desorbed from the particles. Furthermore, these experiments showed the potential for desorption of Co from riverine suspended particulate matter. It is suggested that changes in salinity contributed to the particle-solution exchange of Co. Thus, the combination of benthic remobilization, desorption from suspended particulate matter, and/or sewage input could be responsible for the non-conservative behavior of Co during the estuarine mixing in both estuarine areas

Influence of dissolved organic matter on particle-water interactions of Co, Cu and Cd under estuarine conditions

Influence of dissolved organic matter (DOM) on particle-water interactions of trace metals (Co, Cu, and Cd) between particulate (>0.2 um) and dissolved (<0.2 um) phases has been investigated along a salinity gradient using samples from the estuarine area of northern Sagami Bay, Japan. Partitioning experiments were performed by mixing riverine suspended particles with the mixtures of different proportions of river and marine end-members and determining concentrations of Co, Cu and Cd in particulate and dissolved phases. Concentrations and distribution coefficients (Kds) between particulate and dissolved phases of Co and Cu were dependent on the presence of DOM. The Kds of Co and Cu in the mixtures in the presence of DOM were lower than those in mixtures that had been ultraviolet-irradiated (UV-irradiated) (absence of DOM), throughout the salinity gradient. In addition, speciation calculations estimated that a greater fraction of Co and Cu in the dissolved phase was present in organic form throughout the salinity gradient, while the seawater ion concentrations and ligand competition (e.g., competition from Ca and Mg and formation of stable and soluble chloro-, sulphato-, and carbonato complexes) had a small effect on the speciation of Co. These results indicate that DOM may play an important role in controlling the speciation and the particle-water interactions of Co and Cu in the estuarine waters. As for Cd, the effect of DOM on the interactions of this metal was less intense than for Co and Cu. Seawater ions appeared to act as an important variable for controlling the particle-water interactions of Cd in the estuarine waters

Contribution of 137Cs-enriched particles to radiocesium concentrations in seafloor sediment: Reconnaissance experiment.

Autoradiography was used to detect 137Cs-enriched particles in sediment samples. The contributions of 137Cs-enriched particles to 137Cs concentrations in sediment samples ranged from 9% to 64%. These experiments revealed that the variability of 137Cs concentrations was due mainly to the heterogeneous distribution of 137Cs-enriched particles in the samples. Therefore, the heterogeneous distribution of 137Cs-enriched particles is probably one of the main factors responsible for the temporal and spatial variations of 137Cs concentrations in sediment samples

Concentrations of stable elements and uranium in estuarine areas of Japan

The geochemistry of stable elements can be a good analogue for understanding the behavior of radionuclides in estuarine and coastal environments. In this study, the behavior of major ions (Na, Mg, K, and Ca), nutrients (NO3 + NO2, PO4, and Si(OH)4), U, and heavy metals was observed in several estuarine and coastal regions of Japan. We also collected data on salinity, pH, and suspended particle matter (SPM). Nutrient concentrations followed conservative dilution lines in these estuaries, and concentrations of dissolved Fe decreased as salinity increased from 0 to 20. In general, most of the dissolved Fe in estuaries is in colloidal form. The behavior of dissolved Fe might reflect a loss of colloidal Fe through coagulation in this salinity range. Dissolved Co and Ni concentrations followed approximate dilution lines from the rivers to the seawater end-members, suggesting that they were quasi-conservative in these estuarine systems. A rapid increase in dissolved Cd concentrations was observed at low levels of salinity (<1). Estimated fluxes of dissolved Cd to the estuarine and coastal regions showed that the salt-induced desorption of Cd from particles constitutes a significant source of dissolved Cd

Influence of Dissolved Organic Matter on the Partitioning of Cobalt and Copper between Particles and Estuarine Seawater

To investigate the function of dissolved organic matter in the partitioning of cobalt and copper between particulate (>0.2um) and dissolved (<0.2 um) phases, mixing experiments have been carried out by introducing riverine suspended particulate matter into ultra violet (UV)-irradiated estuarine seawater and non UV-irradiated estuarine seawater, collected from northern Sagami Bay, Japan. Distribution coefficients, Kd, between particulate and dissolved phases for the metals in the non UV-irradiation estuarine seawater including dissolved organic matter, were lower than those in the UV-irradiated estuarine seawater. When fulvic acid was added to the mixture of UV-irradiated estuarine water and riverine suspended particulate matter, a decrease in Kds was observed with increasing concentrations of fulvic acid. This indicated that the complexation of the metals with dissolved organic ligands was likely to be one of the important factors decreasing the Kds.11th International Conference on the Biogeochemistry of Trace Element