Trace metal speciation in coastal and off-shore sediments from Ross Sea (Antarctica)

The information on total metal concentration in sediments is not sufficient to assess the metal behaviour in the environment, while speciation studies are more effective in estimating environmental impact of contaminated sediments. Concerning metal distribution in Antarctic marine sediments, several studies reported total or extractable (by means of a unique reagent) content, but only few publications dealt with metal speciation.This work presents the total content and speciation pattern of Al, Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn in 12 cm sediment cores, sampled both in coastal and off-shore sites of the Ross Sea shelf area, within the framework of the Italian National Antarctic Programme (PNRA). The total content results of metals are comparable with the background values and the speciation highlights good environmental quality of the studied areas. Only Cd and Pb, in fact, are present in significative amount in non residual phases (acid-extractable and reducible, respectively).     

Modeling of 137Cs migration in cores of marine sediments of Mumbai Harbor Bay

The vertical concentration profile of ¹³⁷Cs in cores of marine sediment of Mumbai Harbor Bay has been studied by the compartment and the diffusion-convection models. Based on the measured concentrations of ¹³⁷Cs in the sediment layers, the various transport parameters such as sedimentation rate, residence half- time, effective migration velocity, diffusion coefficient and the convective velocities were determined. The sedimentation rate was determined to be 1.61, 1.03 0.69 and 1.25 cm year^?1 from the slope of lines obtained from the depth profile of ¹³⁷Cs in cores using a least-square fitting method at site 1, 2, 3 and 4 respectively. The mean residence half-times, ranging from 11 to 35 years were observed to be the highest at the upper layers (up to 8 cm) of all sites and decreased with sediment depth. Subsequently, the ranges of mean value of effective vertical migration velocity in the same layers were between 0.15 and 0.46 cm year^?1. As expected, the vertical migration in the upper sediment layers was very slow and thereafter increased slowly in the succeeding layers (12 cm onwards) of all sites with a mean ranging from 1.11 to 4.13 cm year^?1. The obtained migration velocities were quite higher than those reported in literatures for global fallout. The convective velocity and diffusion coefficient at each site were assumed to be constant in the whole depth and calculated under the assumption of steady state. Using a depth-zoned bioturbational mixing model, the estimated biological diffusion coefficients ranged from 7 × 10^?7 to 3.8 × 10^?6 cm² s^?1 which were within the literature values reported for shallow coastal environments and deep sea.     

Evaluation of volatile chlorinated hydrocarbons distribution along depth profiles in the Ross Sea, Antarctica

The presence and the distribution along depth profiles of volatile chlorinated hydrocarbons (VCHCs) were evaluated in seawater samples collected in the Ross Sea (Southern Ocean, Antarctica) during the 2002-2003 Italian expedition. Sampling areas were located where the Circumpolar Deep Water interacts with the shelf waters that supply the Ross Sea.The VCHCs investigated were: 1,1,1-trichloroethane (C₂H₃Cl₃), tetrachloromethane (CCl₄), trichloroethylene (C₂HCl₃), tetrachloroethylene (C₂Cl₄). The analytical procedure consisted of a liquid-liquid extraction carried out with n-hexane directly in Antarctica, followed by gas chromatographic analysis with electron capture detection carried out in Italy.Concentration levels for the VCHCs analysed ranged from digits to hundreds of ng/L according to the station, depth and substance considered. Important differences in concentration levels between the three stations near the Ross Ice Shelf and the two stations located in the Cape Adare area were observed. In particular the stations situated in the Cape Adare zone, at certain depths, showed a thermal inversion due to the mixing of the Circumpolar Deep Water with the waters generated inside the Ross Sea Basin. The lowest concentration levels were recorded at this temperature increase.     

Horizontal and vertical distributions of Biogenic and Anthropogenic Organic compounds in the Ross Sea (Antarctica)

Horizontal and vertical distributions of organic compounds extractable with n-hexane were investigated at five sampling stations (Ross Sea) during the Italian Antarctic Expedition 1997/98. Samples were collected from seven depths under pack ice and from two or three depths at the other stations located at different distances from the coast. The lowest concentrations of biogenic and anthropogenic compounds were found at station Y3, the furthest from the coast, while the highest concentrations were observed under pack ice (B2-2 station) or in the Polynya zone (Y1 station). The levels of organic compounds in the particulate phase were higher than those in the dissolved phase for all the investigated samples. Concentrations of biogenic organic compounds (long-chain aldehydes and alcohols, fatty acid esters and n-alkanes) were well related to fluorescence intensity, which is usually reported as a biological activity index. The odd-to-even carbon-number ratio for n-alkanes was lower than 1 at stations B2-2, Y1, Y5 and Y6 (located less than 150?km far from the coast) with the predominance of n-C16, n-C24 and n-C28, indicative of autochthonous pelagic species. An odd-to-even ratio higher than unity and a different n-alkane profile were observed at station Y3 (about 300?km from the Ross Ice Shelf and 600?km from Terra Nova Bay). Low levels of pollutants (i.e. phthalates) were found, mainly in the particulate phase up to a depth of 50?m, confirming a local source of the phthalates found at significant concentrations during previous expeditions.     

Natural radionuclides and 137Cs activity concentration in the bottom sediment cores from Kuwait Bay

Summary The activity concentration of natural radionuclides and ¹³⁷Cs in the bottom sediments cores from Kuwait Bay have been determined by γ-ray spectrometry. Particular attention was devoted to the exact determination of two uranium isotopes: ²³⁵U and ²³⁸U in order to find any presence of depleted uranium dispersed during the 1991 Gulf War. The calculated ²³⁸U/²³⁵U activity ratios for all the surface (15 cm) as well as the core profile (up to 70 cm in depth) samples were within the limit of one standard deviation close to the value of 21.5 for natural uranium. Simultaneous instrumental determination of the unsupported ²¹⁰Pb and ²²⁶Ra in a few sediment core profiles was used for quantification of sediment accumulation rates. The calculated sedimentation rates (for the constant atmospheric ²¹⁰Pb flux rate - CRS model) ranged from 0.2 to 0.6 cm ^. y^-1 and were close to the data calculated by the Weibull distribution of ¹³⁷Cs in undisturbed sediment cores.     

Distribution and speciation of metals in surface sediments of Taranto [corrected] gulf (Ionian Sea, Southern Italy)

Concentrations of metals (Al, Fe, Ti, Ni, Mn, Cr, Zn, Cu, Pb) were determined in surface sediments from Taranto gulf (Ionian Sea, Southern Italy) in order to assess the distribution and the bioavailability of metals. Total metal content and speciation of Fe, Ni, Mn, Zn, Cu and Pb were determined. Sediment cores were also sampled in some stations of particular interest. The analytical results show that metals distribution does not show significant variations in relation to depth. Metal distribution in the Taranto gulf is mainly influenced by industrial wastes from Taranto town, by rivers of the Basilicata region and by prevailing anticlockwise marine currents. These factors cause an accumulation of metals in the sediments near to the coasts of Calabria. The statistical analysis, effected by HCA and PCA methods, can be considered a good starting point in order to classify sediment samples and to locate accumulation areas. Metal speciation shows that Fe, Ni and Zn are present in sediments mainly as sulphides, Mn is present principally in an ion-exchange form or bound to carbonate, while Cu and Pb are mainly present in the fraction bounds to humic acids.     

HPLC approach for revealing age-related changes of aquatic dissolved organic matter in sediment core

Analytical method based on HPLC has been used to characterize aquatic dissolved organic matter (DOM) from sediment core of Lake Võrtsjärv, South- Estonia. High-performance size exclusion chromatography (HPSEC) as separation method was coupled with diode-array detection (DAD) and separated molecular fractions of DOM were subject to qualitative and semi-quantitative analysis. Qualitative analysis based on UV- spectra revealed the presence of proteins and humic constituents in separated high molecular weight fraction and aromatic constituents in low molecular weight fraction. Statistical data treatment methods enabled clustering sediment layers into 4 periods according to sediment depth and age. The upper 0-30 cm sediment DOM had statistically relevant differences in comparison to other periods as revealed by lower total peak and humic substances (HS) fraction areas, and molecular weights. Samples from 80-120 cm depth differed from others by decreased low molecular weight (LMW) fraction content. The observed down-core trends suggest polymerization of LMW organic constituents and increasing humification. The statistical analyses revealed that some chromatographic and spectrometric parameters can be used to differentiate between sediment layers and to evaluate environmental changes.     

Distribution of137Cs and239,240Pu in the sediment of the Seto Inland Sea

The contents and distribution patterns of¹³⁷Cs and^239,240Pu in the sediments of the Seto Inland Sea were determined. In most of the sediment columns, approximately uniform concentrations were found to a depth of around 20 cm, probably due to bioturbation. Total amounts of¹³⁷Cs in the sediment column are considerably lower than the global fallout inputs. It is suggested that a significant portion of¹³⁷Cs input was removed from the Seto Inland Sea to the open ocean. Large excess inventories of^239,240Pu over fallout input were observed in the investigated sediment columns.     

Material transport between the atmosphere and sediment of the Lake Balaton

A monitoring system was developed to gain information on the present level of pollutants in the Lake Balaton, Hungary. Determination of 13 polycyclic aromatic hydrocarbons (PAHs) and inorganic pollutants (mostly toxic metals) in aerosol, precipitation and sediment samples was carried out. The aim of collecting aerosol and precipitate samples in the same site at the same period was to determine the distribution of elements in two depositions. For the fractionation by particle size, aerosols were sampled by a cascade impactor. A simple three-stage sequential leaching procedure was applied to establish the distribution of metals among environmentally mobile, bound to carbonates and oxides, and environmentally immobile, (bound to silicates) fractions in aerosols. Sediment samples were collected from 17 different sites inside of the lake and 10 sites at harbors at 30–70 cm in depth. Core samples were cut to 10-cm pieces, dried at room temperature, and finally passed through a 63-μm sieve. Total concentrations of elements were determined by atomic absorption spectrometry (AAS) after an acidic digestion. The concentrations of PAHs were determined by HPLC method with fluorescence detection.In aerosol samples collected from September 6, 2002 to January 26, 2003, concentration of Cd was <0.1 μg/m³, and the majority of Cd has been found in the mobile fraction. Cadmium was associated to particles between 0.25 and 2 μm indicating the anthropogenic origin. Similar distribution of Pb was obtained in all seasons, and the highest concentration of Pb was found as 8.6 ng/m³ in particle size of 0.7 and 1.4 μm. Results of total concentration of elements of bottom sediments of the Lake Balaton and harbors were compared to Interim Sediment Quality Guideline (ISQG) values and the Probable Effect Level (PEL) values. Data showed that the average concentrations of elements were usually less than those of ISQGs and other background data for soils and geochemical values. The sediment is not polluted and its disposal is feasible. There is no direct correlation between the concentration of elements deposited onto the surface of the lake from dry and wet deposition and the upper part of the sediment. So, from the budget of the deposition, the concentration of elements in the upper layer of the sediment cannot be predicted.Seasonal changes of the concentration of PAHs in aerosol was observed, samples collected at winter contained the highest values. In December–January 2002/2003, the wet deposition was found as 64 μg/m² period. Among the individual compounds, the wet deposition rate of phenantrane, fluoranthene and pyrene was dominant, while for dry deposition, these compounds were fluoranthene and pyrene. The concentrations of ∑PAHs found for all sites and depth of sediment samples ranged from 11 to 1734 μg/kg dry weight with an average of 132 μg/kg. These values represent a quite low pollution level compared to other sediment with anthropogenic influence. Based on the results, it can be definitely confirmed that the chemical quality of the water and sediment of the Lake Balaton is satisfactory.     

Chemical characterization and recent sedimentation rates in sediment cores from Rio Grande reservoir,SP, Brazil

The Rio Grande reservoir lies southeast of the Metropolitan Area of São Paulo. In order to evaluate if the sediments contain a historical registration of anthropogenic activity, four sediment cores were sampled from the reservoir. In these cores the Hg concentration was determined by the CV AAS technique, major and trace elements by instrumental neutron activation analysis and the sedimentation rates by the ²¹⁰Pb method. The results obtained for Hg are much higher than expected, showing an anthropogenic contribution. As a general trend, the elemental concentration decreases with depth, indicating recent contamination.     

Sediment Assessment of the Pchelina Reservoir,Bulgaria

The temporal dynamics of anthropogenic impacts on the Pchelina Reservoir is assessed based on chemical element analysis of three sediment cores at a depth of about 100–130 cm below the surface water. The ¹³⁷Cs activity is measured to identify the layers corresponding to the 1986 Chernobyl accident. The obtained dating of sediment cores gives an average sedimentation rate of 0.44 cm/year in the Pchelina Reservoir. The elements’ depth profiles (Ti, Mn, Fe, Zn, Cr, Ni, Cu, Mo, Sn, Sb, Pb, Co, Cd, Ce, Tl, Bi, Gd, La, Th and U_nat) outline the Struma River as the main anthropogenic source for Pchelina Reservoir sediments. The principal component analysis reveals two groups of chemical elements connected with the anthropogenic impacts. The first group of chemical elements (Mn, Fe, Cr, Ni, Cu, Mo, Sn, Sb and Co) has increasing time trends in the Struma sediment core and no trend or decreasing ones at the Pchelina sampling core. The behavior of these elements is determined by the change of the profile of the industry in the Pernik town during the 1990s. The second group of elements (Zn, Pb, Cd, Bi and U_nat) has increasing time trends in Struma and Pchelina sediment cores. The increased concentrations of these elements during the whole investigated period have led to moderate enrichments for Pb and U_nat, and significant enrichments for Zn and Cd at the Pchelina sampling site. The moderately contaminated, according to the geoaccumulation indexes, Pchelina Reservoir surface sediment samples have low ecotoxicity.     

INAA applied to the multielemental characterization of a sedimentary column: a contribution to oceanographic studies

The environmental changes that occurred in different periods can be identified through the increase or decrease of the concentrations of metals and other substances throughout sediment cores. The purpose of this study was to determine Al, As, Ba, Br, Cs, Eu, K, La, Mn, Sb, Sc, Sm, Th, Ti, U and V in a sediment core collected from S?o Paulo State South Seashore. Instrumental neutron activation analysis followed by gamma-ray spectrometry was the analytical method used. Results showed an abrupt decrease in the concentration of all elements in the 132–134 cm layer depth. This finding indicates an impact of anthropic activity.     

Determination of Pu isotopes in sediment cores in the Sea of Okhotsk and the NW Pacific by sector field ICP-MS

Summary Studies on the environmental behavior of plutonium in the marine environment require an analytical method with high sensitivity and capability to provide the isotopic composition of Pu in marine samples. In this work, as part of our on-going project on Pu environmental behavior in the Pacific Ocean, a sector field ICP-MS method combined with an off-line anion-exchange chromatography system was optimized for the determination of Pu and its atomic ratio of ²⁴⁰Pu/²³⁹Pu in sediment core samples. Using a conical concentric nebulizer and 150-second counting time, we were able to lower the detection limit of Pu down to 0.35 fg. The mass discrimination effect was evaluated using a mixed Pu isotope standard solution with certified a ²⁴⁰Pu/²³⁹Pu isotope ratio (NBS-947). The overall performance of the analytical method was validated by the determination of Pu and its isotope composition in an ocean sediment reference material (IAEA-368). Both the ^239+240Pu activity and ²⁴⁰Pu/²³⁹Pu atomic ratio were found to be in good agreement with the certified and/or literature values. As an important application, we employed the analytical method to investigate the vertical profiles of ^239+240Pu activity and ²⁴⁰Pu/²³⁹Pu atomic ratio in sediment cores in the Sea of Okhotsk and the NW Pacific. It was found that the Bikini close-in fallout Pu could be transported as far as the Sea of Okhotsk. The results provided evidence to support our hypothesis on the oceanic current transportation of Bikini close-in fallout Pu in the NW Pacific and its marginal seas.     

沱江流域Pb、Cd的环境污染化学行为研究

对沱江流域金堂、简阳、内江三地河流沉积物中重金属Pb和Cd含量及其时空分布特征进行了研究,并结合与沉积物中Fe、Mn和LOI等参数的相关性对河流沉积物中Pb和Cd地球化学性质进行了初步的分析和讨论。结果表明,沱江三地沉积物中Cd、Pb含量不高,平均含量按上、中、下游次序逐渐降低;从垂向分布行为看,Cd在上游金堂地区上部含量高于下部,而中、下游两地则相反,而Pb均随着深度的增加而减少,反映了近年来人类活动所产生Pb污染的加剧;TOC、沉积物性状和上覆水体中的物化性质对于其垂向分布有着较大影响。对于深入揭示水环境中重金属的环境地球化学循环有着重要的指导意义。     

Plutonium characteristics in sediments of Hiroshima Bay in the Seto Inland Sea in Japan

Sediment core samples were collected from Hiroshima Bay in the Seto Inland Sea, western Northwest Pacific Ocean, and their ^239+240Pu activities and ²⁴⁰Pu/²³⁹Pu atom ratios were determined by sector field ICP-MS. The activities of ^239+240Pu ranged from 0.556 ± 0.025 to 0.745 ± 0.023 mBq/g. The atom ratios of ²⁴⁰Pu/²³⁹Pu were almost constant within the whole depth; the average value was 0.227 ± 0.014. This atom ratio was significantly higher than the mean global fallout ratio of 0.18, proving the presence of close-in fallout Pu that originated from the Pacific Proving Ground (PPG). The water masses exchanges between the Kuroshio Current and the Seto Inland Sea brought the PPG source Pu to this area, then Pu was extensively scavenged into sediment particles supplied by the rivers around the bay. The relative contributions of the global fallout Pu and the PPG close-in fallout Pu were evaluated by the two end-member mixing model. The contribution of the PPG close-in fallout was 38?C41% of the total Pu in sediment. The remaining 59?C62% was attributed to direct global fallout and the land-origin Pu transported by the rivers around the Hiroshima Bay.     

Persistent organic pollutants (POPs) at Ross Sea (Antarctica)

The most significant findings on the presence of persistent organic pollutants (POPs) in the marine ecosystem at Ross Sea are presented. Seawater samples were collected in many sampling sites located in a large area of the Ross Sea during various Italian expeditions in Antarctica. Two classes of POPs were considered, namely polychlorobiphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs). The results highlighted the presence of these compounds in seawater samples at a total concentration level of about 50 pg/l for PCBs, and 220 pg/l for PAHs. Moreover, seawater samples showed low to high molecular weight PAHs (LMW/HMW) and phenanthrene to anthracene (PHE/ANT) ratios higher than 1 and 5, respectively, which may suggest the predominance of a petrogenic source (i.e. petroleum product contamination). Results were also obtained on the POP depth profile in the water column at Cape Adere, where two water masses converge and mix, i.e. the Modified Circumpolar Deep Water (MCDW) and the High Salinity Shelf Water (HSSW). According to both the PAH and temperature profiles a two-fold higher PAH and PCB concentration was observed for MCDW samples with respect to HSSW. This result represents the first experimental evidence of the external input of pollutants in this area of the Ross Sea coming from the outer oceanic circulation.     

Distribution of some major and trace elements in Danube Delta lacustrine sediments and soil

Sediment cores collected from lakes Mesteru and Furtuna (eastern part), Sontea channel and soil samples collected from Caraorman bar, all located in the Danube Delta, were analyzed for 42 elements (Ag, Al, As, Be, Na, Mg, P, S, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, As, Se, Br, Rb, Sr, Y, Mo, Ag, Cd, In, Sn, Sb, Cs, Ce, Hf, Hg, Tl. Pb, Bi, Th. U) by instrumental neutron activation analysis (INAA), thick target proton induced X-ray emission (TT-PIXE) and inductively coupled plasma-mass spectrometry (ICP-MS). The INAA and TTPIXE yielded total concentrations whereas the ICP-MS data reflected the fractions soluble in 14M HNO₃. The ICP-MS data exhibited surface enrichment relative to the lower part of the sediment core of Cu, Zn, As, Ag, Cd, In, Sn, Sb, Hg, Tl, Pb, and Bi, most prominently by Cd and Hg. Their vertical distribution in the investigated cores generally reflected the pollution history of recent sediments in Danube delta, showing a steady increase until the end of the 1980s followed by a slow decrease after 1990. The vertical profiles of most remaining elements were characterized by a relatively uniform distribution along the cores. In some cases, the concentrations of As, Cd, Cu, Cr, Mn, Ni and Pb exceeded minimum thresholds of safety, as defined by the Romanian regulations. The elemental composition of the sediment below 20 cm depth (total concentrations) was similar to that of the upper continental crust (UCC) for most elements. Values distinctly higher than UCC were observed for As, Sb (factor ~5) and Cr, Ni, Cu (factor 2 to 3). The nitric acid soluble element concentrations in the soil samples in some cases showed increased values at the surface as compared to 30 cm depth, either due to air pollution or to the action of plants. In no case a large contribution to the topsoil from atmospheric deposition was evident, indicating that the surface contamination of the sediments was mainly by riverine transport. This revised version was published online in July 2006 with corrections to the Cover Date.     

STUDY OF THE INFLUENCE OF HUMIC SUBSTANCES ON THE SORPTION OF RARE EARTH ELEMENTS AT THE KAOLINITE AND BENTONITE SURFACES

The isotherms for sorption of fulvic acid from weathered coal,and the distribution ratios,Rd,of ^169Yb at various concentration of fulvic acid on Na-bentonite and Na-Kaolinite have been measured.Meantime,the dependences of Rd of ^169 Yb on pH values at a constant initial concentration of FA were obtained.It was not found that the parallel relationship between the high affinity of humic substance to the clay and the high uptake of metal which has strong ability to complex with this humic substance.     

Characterization and kinetics analysis of the thermal decomposition of the humic substance from hazelnut husk

A humic substance was obtained from hazelnut husk using an alkali extraction. The chemical and morphological structure of the humic matter was characterized via elemental analysis, Fourier transform infrared spectrometry (FTIR), nuclear magnetic resonance, Brunauer-Emmet-Teller (BET) analysis, scanning electron microscopy (SEM), and thermogravimetric-FTIR (TG-FTIR). In addition, thermal analysis measurements TG analysis-differential thermogravimetry/differential scanning calorimetry (TGA-DTG/DSC) were performed under dynamic air conditions to better determine the origin, physical and chemical structure, and decomposition process of the humic matter. The Kissinger-Akahira-Sunose (KAS) and Flynn-Wall-Ozawa (FWO) methods were used to calculate the kinetic parameters of the high-temperature decomposition process. It was observed that the activation energy values were almost constant at certain conversion and temperature intervals. In addition, the structure of the humic substance at different temperatures was also investigated via FTIR analysis. It was found that the obtained humic substance had a very stable structure and decomposed at a high temperature. The stability of the humic matter can be a useful tool in the environmental quality research of soil.     

Geochemical record of U and Th isotopes in bottom sediments of Lake Kawaguchi at the foot of Mt. Fuji, Central Japan

Sediment cores from Lake Kawaguchi at the foot of Mt. Fuji in Japan were analyzed for U and Th isotopes (²³⁸U, ²³⁴U, ²³²Th, ²³⁰Th and ²²⁸Th) in the light of the linkage to paleoenvironmental changes. These isotopic concentrations and their ratios varied widely with depth of sediment core. A marked disequilibrium (1.1–1.5) higher than the value of 1.0 was observed for ²³⁴U/²³⁸U activity ratios, indicating that U from lake water with high ²³⁴U/²³⁸U ratio (ca. 1.6) was transferred to the bottom sediment by adsorption and/or adhesion onto the settling particles. By using model equations, the U found in the sediment core was separated into lithogenous and autogenous U fractions. These depth profiles were compared with parameters such as organic matter and biogenic-SiO₂ contents and amount of rainfall. Some variations of selected parameters with depth coincided with those of lithogenous or autogenous U. The results obtained suggest that variation in the lithogenous and/or autogenous U in the sediment with depth might be helpful in tracing the geochemical behavior of U and the past environmental changes in the area surrounding Lake Kawaguchi.The authors would like to express their gratitude to Dr. Y. Ohtsuka of Department of Radioecology, Institute for Environmental Sciences and Dr. K. Sasaki of Department of Cultural Properties and Heritage, Kanazawa Gakuin University for sampling of water and rock samples at Lake Kawaguchi.