Elements In Sediment Cores Research Articles

Geospeciation, toxicological evaluation, and hazard assessment of trace elements in superficial and deep sediments.

To evaluate the hazard assessment of dredging and disposal of sediments, an in-depth chemical and toxicological characterization of sediments was carried out in Venice Lagoon. The bioaccessible and mobile concentration of trace elements in superficial and deep sediments (in the Holocene-Pleistocene limit) can deeply affect the quality of the aquatic ecosystem. Geospeciation and total concentration of trace elements in sediment cores were assessed and several toxicological tests were carried out. The indices of contamination (e.g., geochemical accumulation index, Igeo, pollution load index, PLI) and of speciation (individual contamination factor, ICF and global contamination factor, GCF) were evaluated. Factor Analysis (FA) was performed to explore possible significant correlations between toxicity data and sediment chemistry. Results underlined that the total concentration of trace elements cannot adequately assess the hazard, while bioavailability, mobility, and toxicity of trace elements allow a thorough evaluation of the environmental threats. The integration of results from chemical characterization ex ante and toxicity assays will provide for a better sustainable handling and management of sediments.

Evaluation of Sediment-associated Heavy Metal Pollution in Chaohu Lake, Eastern China

Heavy metal pollution in lacustrine sediments is a worldwide environmental issue. In the present study, eight heavy metals including Zn, Pb, Co, Cr, Cd, Mn, As and Cu in sediment cores collected from Chaohu Lake, Eastern China were determined, and potential sources and risks of selected heavy metals were evaluated using multivariate statistical techniques and pollution indices. Results show that all sampling areas were extremely contaminated by Cd, and were not significantly affected by Mn. High accumulation of Zn, Pb and Cu in urban area related sites implies they were generally derived from urban sources including municipal and industrial sewage. Whereas high concentrations of As and Cd, and Co in rural locations possibly suggests agricultural sources. Possible decreasing trends for most elements in the sediment cores indicate the reduction of total input amounts which would be attributed to the increasing operation of wastewater treatment plants in the urban areas. Different intercorrelations between each two elements for four sampling sites reflect the different input sources. Cluster analysis also indicates the residual elements in sediment cores of Chaohu Lake were generally from natural materials for Mn, from urban origins for Cu, Zn and Pb, and from agricultural activities for the remaining elements. The results from both contamination factors and geo-accumulation index (Igeo) suggest sediments were not polluted by Mn, extremely contaminated by Cd, and slightly to moderately impacted by the remaining elements. But all samples were examined with significant metal pollution given their pollution level index values higher than 1.0.

First assessment on trace elements in sediment cores from Namibian coast and pollution sources evaluation

Trace elements (TEs), Rare Earth Elements (REEs) and Pb isotope ratios were determined in six small cores sampled along the Namibian coast and different indices, such as Enrichment Factor, Geo-accumulation Index and Pollution load index, were calculated to evaluate possible metal contamination in the area. Concentrations of Pb, Cu, As and Cd were strongly enhanced at the upper 7 cm of core C5, which is located at Walvis Bay, at the major harbor and urban/industrial center of Namibia, indicating the impact from the recent anthropogenic activities. Principal Component Analysis was applied to the data set indicating possible common sources of the contaminants. Pb stable isotope ratios, combined with the dating of core C5 at Walvis Bay, further confirmed the anthropogenic provenance of Pb sources in the recent sediment deposits, which occurred after 1945, when the anthropogenic activities in the area began to increase. REEs profiles were also determined, showing enrichment in REEs for some of the samples, typical for the minerals present in the area. Ce anomaly was detected in one of the cores but the REEs profile did not reveal anomalies ascribable to anthropogenic influence.

Analysis of Historical Trend of Eutrophication in Lake Nakaumi, Japan, Using Concentrations of Several Index Elements in Sediment Cores

Analysis of Historical Trend of Eutrophication in Lake Nakaumi, Japan, Using Concentrations of Several Index Elements in Sediment Cores

Enrichment of uranium, arsenic, molybdenum, and selenium in sediment cores from boreal lakes adjacent to northern Saskatchewan uranium mines

Assessment of flux rates and concentrations of potentially toxic elements in sediment cores from 5 lakes adjacent to the McClean Lake uranium mines in northern Saskatchewan (impact lakes) compared to results from a set of 5 upwind and distant lakes (reference lakes) clearly indicated enrichment of several elements in lakes close to the mining operations. The flux of uranium to the sediments of the 5 impact lakes was significantly higher post-1960 from the mean pre-1960 background conditions by 1.5 to 23 times. Flux rates of arsenic, molybdenum, and selenium also indicated significant enrichment from background conditions in the majority of the impact lakes. In contrast, large and significant increases in flux only occurred in 1 of the 5 reference lakes for arsenic. The highest levels of enrichment were found in the 3 lakes either in closest proximity to the tailings management facility, waste-rock piles, or downstream from the treated effluent management system. High flux rates and concentrations of elements such as arsenic and vanadium in both the reference lakes and in pre-mining samples of the impact lakes indicated that potentially toxic elements can occur naturally in this region. Sediment core analyses of elemental flux and concentration in both reference lakes and pre-1960 conditions in the impact lakes provided an estimate of natural background conditions. Our data suggest that the McClean Lake mine may be a source for the enrichments of toxic elements in the lakes in close proximity to the mining operations.

Redox conditions in sediments and during sedimentation in the Ontong Java Plateau, west equatorial Pacific

Redox-sensitive elements in sediments, such as manganese (Mn), vanadium (V), molybdenum (Mo), and uranium (U), are promising indicators of past redox conditions during sedimentation and early diagenesis. However, in the Ontong Java Plateau, west equatorial Pacific, there are sparse datasets of redox-sensitive elements in sediment cores. Here, we present a 250 ka record of redox sensitive elements from a 460 cm gravity core at site WP7 (3 degrees 56'S, 156 degrees E, water depth 1 800 m), which was recovered from the southwest Ontong Java Plateau during the 1993 cruise of R/V Science I of the Institute of Oceanology, Chinese Academy of Sciences (IOCAS). Relative to the Post-Archean Australian Shale (PAAS), authigenic Mn, cobalt (Co), nickel (Ni), Mo, V, U, and cadmium (Cd) were found at constantly low levels except when peaks occurred at several depth intervals. Manganese, Co, Ni, and Mo concentrations were elevated at 25-35 cm due to Mn redox cycling. The core was divided into three distinct sections, the top 0-25 cm being oxic, a suboxic section at 25-35 cm and from 35-460 cm which was anoxic. Differential authigenic enrichments of Co, Ni, Mo, V, U, and Cd at the same depth intervals were observed indicating that the enrichments happened during sedimentation or diagenesis and suffered no post settlement redox changes. Therefore, no significant changes in redox conditions during sedimentation must have happened. The water at depth on the Ontong Java Plateau during past 250 ka must have been well oxygenated, possibly resulted from the more or less continuous presence of oxygen-rich deep water like the modern Antarctic Intermediate Water (AAIW) and Antarctic Circumpolar Water (ACW); while it's slightly less oxygenated in glacial intervals, possibly due to ventilation weakening and/or the surface productivity increase.

The concentrations, fluxes, enrichments and chronologies of potential harmful elements in sediment cores from Bohai Bay, North China

To reflect the historical changes, the vertical profiles of concentrations, enrichment factors and burial fluxes of potential harmful elements (PHEs: Ga, Ge, Mo, In, Sn, Sb, Te, Tl, Bi, W and V) were determined in two sediment cores collected from Bohai Bay. Sediment accumulation rates and chronologies were obtained from 210Pb activity-depth profiles. Two sediment accumulation rates in core 2 were observed: a higher rate of 4.78 mm/year before the 1960s and 2.93 mm/year since then. The sediment accumulation rate in core 6 was 2.82 mm/year. The PHE concentrations and burial fluxes exhibited an obvious variation with the depth due to the natural and anthropogenic inputs. Especially, the higher concentrations and burial fluxes of PHEs occurred in the 1960s and 1980s, matching the large runoff and industrial development. Enrichment factors (EFs) of PHEs were computed in order to evaluate their potential sources. Results showed that the EFs of Sb, Te and Bi were higher than 1.5, revealing the anthropogenic inputs; however, the EFs of other PHEs were lower than 1.0, indicating the natural inputs. Moreover, the high EFs of Sb, Te and Bi appeared in the surface or subsurface layers, indicating that the extent of anthropogenic contamination enhanced in recent years. Sequential extraction technique was used to study the ecological risks of PHEs. Results revealed that the ecological risks of Mo, Te and Bi in both cores and Sb and W in core 2 were medium due to their high availability in the exchangeable and carbonate-bound fractions.

Mercury and Other Trace Elements in Sediment Cores from Central Texas Lakes

Metals released during fossil fuel use are important atmospheric pollutants. Mercury and other trace metals can be transferred to an aquatic environment through atmospheric deposition. In the work reported here, a number of sediment cores were retrieved from central Texas lakes in the proximity of a coal-fired power plant in search of local anthropogenic effects. Cores were collected along a transient parallel to the prevailing wind direction (S-SE) in the area. Trace element concentrations in the lignite and in effluents from the power plant showed that some elements remained constant (Al, Cu) throughout the different lignite combustion and power production processes. Some (like Cd and Se) showed an affinity for the smaller particles, whereas others (Hg) showed very low concentrations in all the solid wastes, indicating that they probably escaped with the flue gases. Sediment cores from a lake next to the power plant showed higher trace metal concentration in the upper part of the cores (more recent sediment). For example, there was as much as a tenfold increase in Hg concentration between the core bottom (10 ng/g), where the sediment was approximately 100 years old and the surface (100 ng/g). Cd and Se at surface sediments were also found to be as high as 1.6 and 3.45 microg/g, respectively. The excess metal inventory was higher for the lakes located next to the power plant than for two lakes about 30 km away.

Lead-210 Geochronology and Trace Metal Geochemistry of Sediment Cores from Lake Overstreet and Upper Lake Lafayette, Leon County, Florida

Sedimentation rates and concentrations of major, trace, and rare earth elements in sediment cores from Lake Overstreet and Upper Lake Lafayette in Leon County, Florida were investigated. The constant initial concentration method of 210Pb dating was used to derive accumulation rates of 6.94 mm/yr for the Lake Overstreet core and 5.58 mm/yr for the Upper Lake Lafayette core. Historical profiles of Upper Lake Lafayette for Pb, Zn, V, Cr, Ni, U, Th, and Sc showed two maximum enrichments during 1929 and 1997. These represent two periods: (1) 1929–1983, where enrichment decreased with time, and (2) 1983–1997, where enrichment increased with time. In the Upper Lake Lafayette sediment core, vertical trends in V, Cr, Ni, Pb, Th, and U are similar to rare earth elements, suggesting co-migration and enrichment of these elements during diagenesis. This also may be attributed to their occurrences in heavy minerals. Concentrations of these elements and concentrations of As, Sb, P, and Y are significantly enriched above crustal abundances. The probable sources of these elevated metal concentrations are heavy minerals and phosphate of the Hawthorn Group within the catchment basin. The variations in concentrations of these elements are most likely the result of the input of detrital heavy minerals during different periods. Comparing Upper Lake Lafayette with polluted lakes in Florida indicates that the degrees of enrichment for Al, Fe, P, V, Cr, Ni, Zn, Mn, Ba, and Pb are higher and for Ti, As, and Cu are lower. In contrast, Lake Overstreet is considered a pristine lake in Florida, and the results of the analysis showed that most of the elements identified in their core sediments are present in low concentrations. Wet deposition from the drainage systems of the recharge area is the probable source.

Trace-Element and Major-Element Stratigraphy in Quaternary Sediments from the Arctic Ocean and Implications for Glacial Termination

The distribution patterns of major and trace elements in sediment cores from the Arctic Ocean, specifically the Yermak Plateau and the Nansen Basin, were evaluated as climate and environmental prox ...

Distribution of rare earth elements in sediment cores of Sabine-Neches Estuary

Vertical profiles of several rare earth elements (REEs) were precisely measured in four dated sediment cores from the Sabine-Neches Estuary. From the extensive use of light rare earth elements (LREEs)—enriched zeolites during catalytic cracking process in nearby oil refineries, a significant enrichment of LREEs such as Lanthanum (La) was expected in sediment layers deposited in the estuary in the 1960s and 1970s. The measured concentrations of LREEs, and Fe normalized enrichment factors indicate that sediments are not enriched with light rare earth elements derived from effluents of oil refineries. The lack of strong enrichment of REEs and other trace metals and radionuclides are attributed to the strong binding of these constituents with dissolved organic matter found in high concentrations, and short hydraulic residence time, and/or due to the dilution of these metals by riverine soil particles.

Determination of rare earth elements in sediment cores from Northern Saronikos Gulf, Greece, by instrumental neutron activation analysis

Instrumental Neutron Activation Analysis (INAA) has been applied for the determination of 8 rare earth elements (REE) in sediment cores collected from stations of polluted and unpolluted areas of Northern Saronikos Gulf. The REE determined in cores are: La, Ce, Sm, Eu, Tb, Dy, Yb and Lu. Higher levels of all REE were found in the cores from polluted areas of N. Saronikos Gulf as compared with those from unpolluted areas. Different vertical profiles of REE were found in the cores from two stations of polluted areas which indicate that REE may distinguish pollution sources.

Vertical distribution of various elements in sediment cores from the Japan Sea

Deep-sea sediment cores ranging up to 30,000–80,000 yrs in age were taken from a southern region of the Japan Sea and subjected to analyses for 5 major and 11 trace elements by means of instrumental photon activation analysis with 30 MeV bremsstrahlung. These elements were Ca, Fe, Mg, Na, Ti, Ba, Ce, Co, Cr, Mn, Nb, Ni, Rb, Sr, Y and Zr. Additionally, Al was determined spectrophotometrically. Distribution patterns of these elements with depth in the sediment columns were derived. Enrichments of Ca and Sr by biogenous process were observed; these Ca maxima are well correlated with Mn maxima. Below the Holocene—Pleistocene boundary, continuous transportation of poorly degraded continental debris, which was low in metallic constituents, was noted. A distinct enrichment of the top layer of the sediments in Mn was observed. This is the result of post-depositional upward migration of Mn. Fe, Co and Ni were also enriched in the top layers. In the central part of the basin, the oxidized post-glacial zone appears to be a typical pelagic sediment.