Concentrations Of Elements In Sediments Research Articles

Multivariate statistical “unmixing” of Indian and Pacific Ocean sediment provenance

AbstractThe geochemistry of marine sediment is a massive archive of (paleo)oceanographic information. Accessing that information requires “unmixing” the various influences on marine sediment geochemistry to understand individual sources and marine geochemical processes. Q‐mode factor analysis (QFA) and independent component analysis (ICA) are multivariate statistical techniques that have successfully been applied to large datasets of marine sediment element concentrations to identify the number and composition of marine sediment sources or end‐members. In this study, we apply both techniques to two datasets of marine sediment geochemistry, compare the output, and discuss the advantages of each approach. In both datasets, ICA identified a mixing trend between carbonates and dust, whereas QFA represented the end‐members as two separate factors. In the Pacific and Indian Oceans dataset, both techniques produced three factors or independent components involving rare earth elements, but two of the QFA factors explained a small, almost negligible, amount of the variability of the dataset. Also, QFA identified more aluminosilicate end‐members (dust or volcanic ash) than ICA. In the Indian Ocean Sites 738 and 752 dataset, ICA identified two processes affecting Sr and Ba concentrations as separate independent components, while QFA created a factor representing the covariation of Sr and Ba over intervals of the site's paleoceanographic history. The results of this study exemplify that QFA identifies covariances and finds discrete end‐members contributing to the bulk mass of sediment. ICA works best with non‐Gaussian element distributions and finds geochemical signals and mixing trends that constitute the characteristic structure of the multielemental data.

Assessment of trace and macroelement accumulation in cyprinid juveniles as bioindicators of aquatic pollution: effects of diets and habitat preferences

Juveniles of three cyprinids with various diets and habitat preferences were collected from the Szamos River (Hungary) during a period of pollution in November 2013: the herbivorous, benthic nase (Chondrostoma nasus), the benthivorous, benthic barbel (Barbus barbus), and the omnivorous, pelagic chub (Squalius cephalus). Our study aimed to assess the accumulation of these elements across species with varying diets and habitat preferences, as well as their potential role in biomonitoring efforts. The Ca, K, Mg, Na, Cd, Cr, Cu, Fe, Mn, Pb, Sr, and Zn concentration was analyzed in muscle, gills, and liver using MP-AES. The muscle and gill concentrations of Cr, Cu, Fe, and Zn increased with trophic level. At the same time, several differences were found among the trace element patterns related to habitat preferences. The trace elements, including Cd, Pb, and Zn, which exceeded threshold concentrations in the water, exhibited higher accumulations mainly in the muscle and gills of the pelagic chub. Furthermore, the elevated concentrations of trace elements in sediments (Cr, Cu, Mn) demonstrated higher accumulation in the benthic nase and barbel. Our findings show habitat preference as a key factor in juvenile bioindicator capability, advocating for the simultaneous use of pelagic and benthic juveniles to assess water and sediment pollution status.

BENTHIC MACROINVERTEBRATE COMMUNITY IN TWO AMAZONIAN UPLAND LAKES

Studies of biological communities in Amazonian lakes are limited to floodplains of large rivers. However, the high-altitude lakes of the Serra dos Carajás differ from other lakes in the region due to the high natural concentration of iron and manganese. An important component of this biological community are the macroinvertebrates, some of which are sensitive to environmental and chemical variables. However, little is known about the influence of heavy metal concentrations on this community component in Amazonian lakes. In our study, we observed the importance of variables such as water depth and concentration of chemical elements in sediments on the macroinvertebrate community. Through a redundancy analysis, we found that the depth of the lake affects the number of species and the composition of the benthic macroinvertebrate community. We also found a relative importance of the concentration of manganese in the sediment for the community studied. Our results indicate that the macroinvertebrate community is differentiated in the marginal and central regions of the lake, since the deposition of organic matter and heavy metals in the sediment is different in these two regions of the lake. The relationship found has implications for the management and restoration of upland lakes in the Amazon, helping to preserve this unique ecosystem.

‘Paleofloodscapes’: Application of sediment source fingerprinting to track flood regime change over space and time at the Peace-Athabasca Delta, Canada

Deltas are hydrologically dynamic landscapes where river floodwaters create a mosaic of productive ecosystems that provide important services. The flood regime, however, is vulnerable to upstream anthropogenic activities, climate change and geomorphic processes. Deciphering the roles of multiple potential stressors on flood regime change is critical for developing appropriate adaptive and mitigative strategies but requires knowledge of hydrological variability at broader scales of space and time than is typically available from instrumental and observational records. At the globally recognized Peace-Athabasca Delta (Canada), the timing, magnitude and causes of reduced flooding and drawdown of perched basin water levels remain an intense focus of investigation. Here we employ novel ‘paleofloodscapes’, generated from geospatial interpolation of Bayesian mixing model fingerprinting of sediment elemental concentrations, to quantify variation in the delta's flood regime during the past ~140 years. Results reveal that flooding of the delta began to decline several decades before hydroelectric regulation of Peace River flow, not coincident with it, and the influence of floodwaters from the unregulated Athabasca River has declined more than the regulated Peace River. A key discovery is that widespread flooding of perched basins occurs when ice-jam events on the river(s) coincide with a relatively high water-plane in the delta's open-drainage network. Without knowledge of open-drainage water levels, inferred change to the flood regime of perched basins may be inaccurate when derived solely from analyses of Peace River hydrometric data and climatic records. The paleofloodscapes illustrate that rising sediment delivery caused by a natural river avulsion in 1982 may undermine the intended purpose of a proposed weir installation. The most recent paleofloodscape, developed from lake surface sediment sampling shortly after widespread flooding, demonstrates the value of the approach as a landscape hydrological monitoring tool, and is readily transferrable to other floodplains to track flood regime change.

Trace element of small lake sediments sensitively recorded environmental changes in the watershed: Implications for mining history and urbanization

Lake sediments serve as a sink for trace elements and provide a record of watershed changes resulting from anthropogenic activities and natural processes. In this study, eight trace elements in the sediments of Lake Aha, an urban lake in Guiyang City, Southwest China, were investigated to reveal the effects of historical coal mining and rapid urbanization in the watershed. Results showed that the median contents of measured trace elements in order of Zn (220.00 mg/kg) > Ni (98.16 mg/kg) > Cr (70.26 mg/kg) > Cu (66.20 mg/kg) > As (58.14 mg/kg) > Co (41.66 mg/kg) > Pb (28.33 mg/kg) > Cd (1.39 mg/kg). Except for Cr and Pb, the median concentrations of Cd, As, Zn, Ni, Co, and Cu were 4.64, 2.33, 2.00, 1.92, 1.81, and 1.09 times higher than regional natural background values respectively. Trace element contents in sediments of the center of the lake were significantly higher than in the rest of the sediment cores, resulting from relatively stable hydrodynamic processes in the region. Vertical variation of trace elements indicated that the fluctuations in the intensity of coal mining activities in the tributaries were effectively tracked by variations of trace element levels in the middle layer sediments of the Youyu River and Baiyan River estuaries. The elevated concentrations of Pb in the surface sediments of the Jinzhong River estuary reflected the rapid urbanization in the basin over the past 20 years. PMF analysis demonstrated that As, Cd, and Pb in sediments were from a mixture of natural and urban activities, and Cu, Zn, Ni, and Co originated from coal mining. This study provides important information for comprehending the anthropogenic activities of small-scale lakes and historical environmental changes.

Feasibility Study on Phytoremediation of Potentially Toxic Elements (Cd, Ni and Pb) in Aquatic Environments Using Suaeda maritima Plant Species, a Case Study: Khorkhoran International Wetland, Persian Gulf.

The current study was designed to assess the phytoremediation potential of Suaeda maritima has been assessed for cleanup of contaminated sediments with Cd, Ni and Pb. In so doing, totally, 20 sampling sites were selected in the Khorkhoran International Wetland. The contents of elements in sediments, plant organs and water samples were determined using ICP-OES. The mean contents of Cd, Ni and Pb (mg/kg) in the sediment samples were found to be 0.096, 38.1 and 1.78, respectively. Moreover, the mean levels of Cd, Ni and Pb (mg/kg) in root samples of S. maritime were 0.160, 2.72 and 1.22 respectively; whereas, in leaf samples they were found to be 0.157, 3.34 and 2.23mg/kg, respectively. Furthermore, the mean contents of Cd, Ni and Pb (µg/L) in water samples were 243, 1440 and 3010, respectively. The values of BCF for Cd, BAF for Cd and Pb, and TF for Ni and Pb were higher than 1, which would indicate that S. maritima could possibly be a suitable candidate for the phytostabilization of Cd and the phytoextraction of Ni and Pb.

Assessment of contamination level of watercourses and streambed sediments downstream the Capillitas Mine, Catamarca, Argentina

The present study constrain the degree of contamination by heavy metals and metalloids of streams impacted by mining activities in Capillitas Mine (Catamarca, Argentina), an epithermal precious- and base-metal vein deposit previously mined for copper along with gold and silver; and subsequently for rodhochrosite. Geochemical analyses of water of three streams (Ortíz, Acid and Capillitas) and a small pond depicting a very thin layer of turquoise-colored precipitates in its bottom were performed and the environmental risk factor was calculated. Moreover, the concentrations of potential toxic elements in sediments from the Ortíz and Capillitas streams were determined by ICP-OES and the Index of geoacumulation (Igeo) for As, Cd, Zn, Cu, Mn and Pb was computed.
 According to their major ions concentration the four water samples correspond to calcium SO4 waters. The Acid and Ortíz streams and the turquoise pond show concentrations of Al, Mn, Cd, Zn, Cu, Cr, Ni and Pb that largely exceed the limiting concentrations for protection of aquatic life, as well as for irrigation waters. The Capillitas stream has a lower content of heavy metal but shows concentrations of Mn, Zn, Cu and Pb exceeding the limiting values for protection of aquatic life. 
 According to the obtained Igeo the three streambed sediments from the Ortíz creek are extremely polluted for Cd, Zn and Pb, whereas they range from strongly to extremely polluted for Cu, As and Mn. The sediments from Capillitas creek depict lower contents of metals and metalloids; though it is strongly polluted for Cd, moderately polluted for Cu and unpolluted to moderately polluted for Pb and Zn.

Assessment of trace elements and fluoride originating from phosphogypsum in the sediment of Gulf of Gabes (southeastern Tunisia): what are the potential sources of accumulation and bioavailability?

To assess potential impacts of industrial activities on the pollution status of Gulf of Gabes, twenty sediment and water samples along with phytoplankton enumeration were achieved at different stations with specific features. Comparing trace element concentrations in sediment to applicable SQG standards, we were intrigued by an accumulation of Zn, Cr, Ni, and especially Cd, which exhibited relatively high content compared to these standards. Moreover, trace metal bioavailability was high in front of industrial discharge areas. The chemical speciation pointed out a high affinity of Pb, Zn, Cr, Mn, Ni, Co, and Fe for the residual fraction of the sediment. Bioavailability of trace elements was confirmed in surface sediment by the presence of a potential toxic fraction especially in front of industrial discharge areas. Toxicity assessment performed for the first time in the Gulf of Gabes through SEM and AVS models pointed to a high potential risk near both Ghannouch and Gabes Ports. Finally, the correlations between phytoplankton species and the labile fraction inferred potential phytoplankton bioaccumulation of Zn, Cu, and Cd both in the seawater and in the labile fraction.

Exposure to multiple elements reduces the health of Saccostrea glomerata: An assessment of the Richmond River estuary, NSW, Australia.

This study investigated relationships between Sydney Rock Oyster (SRO) health and element concentrations in sediments and oysters from the Richmond River estuary. Six sites were sampled between November 2019 and May 2020. Multivariate permutational analysis of variance was used to compare oyster health parameters and element concentrations between sites, wet and dry conditions, and in oyster and sediment samples. Statistical analysis revealed significant spatial differences in oyster mortality, condition index, and size. Metal concentrations in oyster flesh significantly differed from metals in sediments. Most metals in sediments were below guideline values, except for Ni at some sites. Mortality, condition index, and weight correlated negatively with individual elements in oyster flesh (P, Zn, Mg, Al, Ni). BEST statistical models included various combinations of metals in sediment and flesh. This study highlights that spatial differences in SRO health tend to be related to site-specific metal compositions in sediment and oysters.

DYNAMICS OF CHEMICALS IN RIVER BOTTOM SEDIMENTS ON THE TERRITORIES IMPACTED BY THE OIL INDUSTRY

Background. Two thirds of all oil reserves of the Russian Federation are concentrated on the territory of Western Siberia. Field work, production and distribution of petroleum products at the oil and gas field are the main reasons for the negative impact on the ecosystems of the northern territories.
 Purpose. The purpose of this study is to evaluate the chemical pollution dynamics of the rivers’ bottom sediments in the Middle Ob region, the region of the Samotlor field.
 Materials and methods. Based on the chemical analysis of the sediment samples, concentrations and total values of the following chemical elements were determined: manganese, copper, nickel, lead, chromium, zinc, iron sulfate ions, chloride ions, petroleum products, mercury. Based on the results of long-term studies of the chemical analysis dynamics of the bottom sediments in the Ob, Agan, and Vakh rivers, a correlation and regression analysis of the studied indicators was carried out.
 Results. The results of the correlation analysis suggest the existence of negative and positive correlations in the studied indicators. Regression analysis of the migration of chemical elements in sediment samples during the study period shows significant fluctuations in the total concentration of chemical elements in sediments, but there is a general tendency to decrease their concentration in sediments.
 Conclusion. Analyzing the ecological state of the studied rivers by the quality of bottom sediments, in general, we can conclude that they are in stable condition. During the study period, there has been a positive dynamics in the concentration of chemical elements in bottom sediments.

A Multiparametric Approach to Unravelling the Geoenvironmental Conditions in Sediments of Bay of Koper (NE Adriatic Sea): Indicators of Benthic Foraminifera and Geochemistry

The Bay of Koper is influenced by agricultural, urban, and port activities, therefore pollution from trace metals is a concern. A total of 20 sediment samples obtained from four 10-cm sediment cores were analyzed. Element concentration in the sediment of the bay was determined spatially and temporally from the recent surface to depth. The results were correlated with the composition and diversity of the benthic foraminiferal assemblages. Major element concentrations indicate natural lithogenic origin (which is also confirmed by mineralogical features). The benthic foraminiferal assemblages in sediment samples, although mainly composed of representatives of the Rotaliida, show moderate to high species diversity and are dominated by the pollution tolerant speciesAmmonia pakinsoniana,Haynesinasp.,Valvulineria bradyanaand the non-keelElphidiumsp. and subordinated byAmmonia tepidaandHaynesina depressula. Canonical correspondence analysis (CCA) on foraminiferal species and trace element concentrations shows a possible control of some potential toxic elements (i.e., Cu, Ni, Pb, Zr, Cr, As) on the diversity and taxonomic composition of foraminiferal assemblages. Nevertheless, foraminiferal diversity and dominance in the bay are related to sediment characteristics such as sediment grain size, and the amount of terrigenous inflow rather than to the element concentrations of sediments. This study evaluated ecological conditions by using the Foram-AMBi and EcoQS indices. The values of the Foram-AMBI index reflect the good to moderate quality of ecological conditions, whereas high to poor ecological statuses were interpreted by calculating EcoQS.

Near-infrared spectroscopy to estimate the chemical element concentration in soils and sediments in a rural catchment

Monitoring the transfer of chemical elements from terrestrial to aquatic environments is essential. To this end, it is necessary to develop fast and low-cost techniques to estimate the concentration of elements in soils and sediments. This study aimed to evaluate multivariate methods and pre-processing techniques to increase the accuracy of estimating the concentration of elements in soils and sediments and to estimate the concentration of elements present in the sediments using calibrated soil models using near infrared spectroscopy (NIR). A total of 316 soil samples and 196 sediment samples were collected in the Guaporé watershed in southern Brazil. These were dried, disaggregated and sieved with a 63 µm sieve size or 230 US mesh standard. Organic carbon was determined by wet oxidation and the total concentration of chemical elements (Al, Ba, Be, Ca, Co, Cr, Cu, Fe, K, La, Li, Mg, Mn, Na, Ni, P, Pb, Sr, Ti, V and Zn) by ICP-OES after microwave-assisted digestion with HCl and HNO3 (3:1). NIR spectra (1000–2500 nm) were recorded for all soil and sediment samples. Multivariate models, for instance partial least square regression (PLSR) and support vector machine (SVM), were tested combined with spectral pre-processing techniques (Detrend, DET; Savitzky-Golay Derivative, SGD; and Standard Normal Variate, SNV) and compared to the raw spectrum (RAW). The SVM model resulted in better predictions for soils, sediments and soils + sediments. In addition, the effects of preprocessing increased the accuracy of the specifications in the order: RAW < SNV < DET = SGD. The best models were obtained by combining the SVM multivariate model with SGD pre-processing. The fit of the models calibrated with soils (R2 = 0.88) and sediments (R2 = 0.89) was superior to the combination of soils and sediments (R2 = 0.85). Prediction of the concentration of elements in sediments through models calibrated with soils had low accuracy, with an average R2 of 0.11 (ranging from 0.00 to 0.46). Therefore, it is necessary to calibrate models separately to estimate the concentration of elements in soils and sediments with greater accuracy. The results showed that it is possible to build accurate spectroscopic models to predict the concentration of elements in soils and sediment samples for all determined elements.

Deep‐Water Formation in the North Pacific During the Late Miocene Global Cooling

AbstractA multiproxy study including organic carbon and bulk nitrogen isotopes along with major and trace element concentrations in sediments from Integrated Ocean Drilling Program (IODP) Sites U1425 and U1430 in the Japan Sea have been conducted in order to trace deep‐water evolution in the Japan Sea and the North Pacific since the late Miocene. The high total organic carbon (TOC) flux, as well as other published geochemical and sedimentary evidence, indicates the occurrence of anoxic deep‐water in the Japan Sea before ∼7.4 Ma. The low‐nitrogen isotope values probably suggest nearly complete denitrification. In contrast, the sharply enhanced biological production but decreased burial of organic matter during ∼7.4–4 Ma, as shown by high enrichment factor of Ba (BaEF) values, together with low TOC flux, highlights enhanced deep‐water oxygenation in the Japan Sea during that time. We suggest that deep‐water formation in the North Pacific ventilated the deep Japan Sea via northern deep seaways before the sea became semi‐closed in the early Pliocene. The synchronously increased equator‐to‐pole temperature gradients driven by late Miocene global cooling may have caused southward shift of mid‐latitude storm tracks, coupled with the weakened East Asian summer monsoon and moisture transport, leading to decreased precipitation in mid‐latitude regions. The potential increases in surface salinity in the North Pacific may have broken the ocean stratification and favored deep‐water formation, and further caused deep‐water ventilation in the Japan Sea.

Spatial and seasonal variation of trace elements contamination in the sediments of a tropical lagoon ecosystem: the Lake Togo-Lagoon of Aného complex (southern Togo)

The Lake Togo-Lagoon of Aneho complex is located in the area of the phosphorite mining which produces different types of waste that are dumped directly into the surrounding environment without treatment. In addition, the contributions of its tributaries after leaching agricultural and urban soils need to be considered. This increases the risk of contamination of the hydrosystem, especially the sediments in trace elements. The objective of this study is to evaluate the level of trace elements contamination and their spatial and seasonal variation in the sediments of the Lake Togo-Lagoon of Aneho complex. The sediment physicochemical parameters were determined in line with French standards. The trace elements were determined using an Atomic Absorption Spectrometer coupled to a hydride and cold vapour generator. The spatial and seasonal variation was assessed using Ordinary Kriging Interpolation method. The average content of trace elements in sediments in mg/kg was as follow: Cd: 0.75, Pb: 13.26, Cr: 50.63, Ni: 36.05, Cu: 10.90, Hg: 0.04, As: 3.88, Zn: 47.38 and Mn: 766.74 in the dry season. In rainy season, the average concentration was: Cd: 0.46, Pb: 9.50, Cr: 27.43, Ni: 21.36, Cu: 9.61, Hg: 0.05, As: 5.23, Zn: 39.21 and Mn: 910.08. These concentrations showed a strong spatial variation. Significant seasonal variations were obtained for conductivity, organic matter as well as for Cd, Pb, Cr, Ni, Hg and As. The sediments were found to be weakly to moderately contaminated and enriched by trace elements with a higher contamination for Cd. The sediments may have low to moderate adverse effects on aquatic living organisms. This trace element contamination is of anthropogenic origin through the phosphorite mining and the agricultural and urban effluents. Therefore, this lagoon ecosystem warrants regular monitoring for better understanding to inform protection of the resource.

Biological Risk Assessment of Heavy Metals in Sediments and Health Risk Assessment in Marine Organisms from Daya Bay, China

The concentrations of heavy metals in sediments and marine organisms in Daya Bay were investigated, and the Monte Carlo method was used to analyze the uncertainty of the results of geo-accumulation characteristics and ecological and health risks. The mean concentrations of metal elements in sediments were in the following order: Zn &gt; Cr &gt; Cu &gt; As &gt; Cd &gt; Hg, while those in marine organisms were Zn &gt; Cu &gt; As &gt; Cr ≈ Cd &gt; Hg. The geo-accumulation index (Igeo) indicated that the primary pollutant was Hg, with 5.46% moderately polluted, and 39.52% for unpolluted to moderately polluted. Potential ecological risks (RI) were between low and high risks, and the contributions of Hg, Cd, and As to ecological risks were 50.85%, 33.92%, and 11.47%, respectively. The total hazard coefficients (THQ) were less than 1, but on the basis of total carcinogenic risks (TCR), the probability of children and adults exceeded the unacceptable risk threshold of 22.27% and 11.19%, respectively. Sensitivity analysis results showed that the concentrations of carcinogenic elements contributed to risk in the order of As &gt; Cd &gt; Cr. Therefore, in order to effectively control heavy metals contamination in Daya Bay, it is necessary to strengthen the management of Hg, Cd, and As emissions.

11000-Year Record of Trace Metals in Sediments off the Southern Shandong Peninsula in the South Yellow Sea

Geochemical background values are the normal concentration of trace metals in the natural environment and sediment cores have been proved to be excellent samples to get these values. The trace metal (Cu, Pb, Zn, Cr, Cd, As, Hg, Ni, Li, and Co) concentration profiles along a sediment core are investigated to get the background values and to assess the depositional processes and contamination levels off the southern Shandong Peninsula, China. All the metals, except As and Hg, had similar concentration profiles with the highest average values during the period of 6 − 3 kyr. The high concentrations of As and Hg occurred before 6ka and during the period of 3 − 0 kyr. The difference in metal concentrations before and after 6 kyr was mainly attributed to the source of core sediments, which are derived from proximal sediment on the Shandong Peninsula before 6 kyr and the mixture of proximal sediment and Yellow River sediment after 6 kyr. The effects of particle size and human activity were mainly contributed to the metal concentrations since 6 kyr. The average concentrations of trace elements in sediments between 6 and 3 kyr were selected as background values. The principal component factor analysis indicate that the metals were from the natural sources throughout the observed depositional period, with the exception of As and Hg, which may had anthropogenic sources for the sediments from the bottom 2 m of the core. Their geoaccumulation indices indicate that the sediments were not contaminated for Cu, Zn, Cr, Cd, Pb, Ni, Li and Co, whereas they were contaminated recently for As and Hg due to the regional civilization and human activities.

Using 206/207Pb isotope ratios to estimate phosphorus sources in historical sediments of a lowland river system

PurposeEngineering and dredging strategies to manage sediment, along with river-scouring, can reveal older sediments. These present a unique opportunity to assess past sources of phosphorus (P) inputs into river sediments. We used the sediment concentrations of P, lead (Pb) and 206/207Pb isotopes to produce ‘first-order’ estimates of the source (diffuse agricultural or sewage treatment) of phosphorus.Materials and methodsSediment cores (n = 30) were collected from the length of the non-tidal River Nene, a lowland river in eastern England. Cores were analysed for sediment elemental concentrations and Pb isotopes. Principal component analysis and linear regression modelling were used to assess the relationships between P, Pb and Pb isotopes. Monte-Carlo simulations and boot-strapping were undertaken to estimate, with 95% confidence intervals, the source of P in these sediments.Results and discussionAnalysis of the relationships between PTotal, PbTotal and 206/207Pb isotope ratios suggested that sediments were deposited largely prior to the phasing out of tetra-ethyl Pb (PbBHT) from petrol. Regression models showed positive correlations between PTotal and PbTotal (R2 = 0.85). Principal component analysis suggested a strong sewage treatment signal for Pb and P enrichment. In the rural upper three water bodies, little sewage treatment work (STW)-derived P was found in the sediment, a consequence of limited STW input and greater sediment transport. In the more urbanised water bodies 4–6, ‘first-order estimates’ of STW P suggest that median concentrations were 30–40% of PTotal.ConclusionsThe strong relationships between Pb and P concentrations in river water provided the opportunity to use 206/207Pb isotope ratios to calculate ‘first-order’ estimates of the proportion of P released from STWs in the historical sediment. Understanding the sources of historical sediment P can be used to assess the success of current sediment management strategies and to base further mitigation measures. Results suggest that whilst much recent sediment P is removed, the legacy sediment remains to contribute P to the water body. Thus, options regarding the practical removal of these sediments and the extent to which this would improve water P status need to be assessed and balanced against options such as further decreasing soil P or STW P stripping.

Assessment of trace element concentrations in sediment and vegetation of mesic and arid African savannahs as indicators of ecosystem health

The savannah biome supports unique biodiversity and provides a multitude of ecosystem services. Defining background concentrations for trace elements in the environment is beneficial for the determination of nutrient deficiencies/hotspots and for the management of pollution. Sediment and corresponding vegetation samples were collected around 48 surface water points in two savannah wildlife areas for assessment and comparison of 20 trace elements using ICP-MS. Site-specific and matrix-specific differences were evident for essential B, Co, Cu, Fe, Mn, Mo, Ni, Se and Zn, potentially toxic As, Cd, Cr, Hg, Pb and V and additional elements Al, Ba, Sb, Sn and Sr analysed. Sediment and vegetation from all sampled locations at both sites contained single or multiple potentially toxic elements at various concentrations. Although the presence of all elements can be linked to underlying geology and geochemistry specific to each site, evidence of anthropogenic cause was also evident at both sites. This paper covers the widest range of trace elements assessed in protected terrestrial wildlife reserves in the South African savannah biome to date and highlights the potential for deleterious consequences of trace element contamination of the environment.

Paleolimnological Assessment of Wildfire‐Derived Atmospheric Deposition of Trace Metal(loid)s and Major Ions to Subarctic Lakes (Northwest Territories, Canada)

AbstractWildfires release terrestrial elements to the atmosphere as aerosols, and these events are becoming more frequent and intense in the Arctic boreal forest as the climate is warming. We quantified the impact of atmospheric deposition of aerosols from local wildfires on metal(loid) fluxes using macroscopic charcoal accumulation rates, historical fire mapping, and element concentrations in 210Pb‐dated lake sediment from five subarctic lakes with small catchments. Lake sediments showed small but significant increases in fluxes (median = 5–10%) for 22 trace metals, metalloids, or major ions following fire events. The impact of wildfire aerosols on element fluxes was mostly due to short‐term (≤2 years) increasing sedimentation rate (6 ± 41% increase), whereas sediment element concentrations were not strongly impacted. Wildfire‐associated deposition to lake sediments was mainly composed of Ca, Al, Fe, Mg, K, Mn, and Na, which are major constituents of ash from burned biomass, but changes in sediment flux were greatest for Sb, As, Ni, Ba, Mn, Mo, and Sr compared to pre‐disturbance conditions. Compared to anthropogenic sources of pollution, wildfire‐associated atmospheric fluxes of metal contaminants to the lakes (e.g., Hg, Pb, As, Sb, and Cd) were low. This study provides quantitative estimates of wildfire impacts on atmospheric geochemical fluxes to subarctic lakes, which can be used for modeling larger‐scale impacts under changing fire regimes.

Geochemical Fractionation and Risk Assessment of Potentially Toxic Elements in Sediments from Kupa River, Croatia

This study investigated the quality of Kupa River sediment using sequential extraction, ecological risk, and contamination indexes (Risk assessment code, Index of geoaccumulation, Enrichment factor, Ecological risk factor, Ecological risk index), determination of magnetic susceptibility of sediments, and statistical methods. The BCR sequential extraction technique was used for evaluating various element-binding forms. Most of the elements were considered to be immobile due to the high availability in the residual fraction. Lead was present mainly in the reducible fraction, while more easily mobile and bioavailable forms were predominant for cadmium and barium. Sediment samples from the river catchment exhibited low ecological risk. The most toxic element, Cd, is the main contributor to the total potentially ecological risk. Increased values of contamination factors have been observed for Zn, Cr, and Ba in some localities. Results of the comparison of element contents in sediments in a 15-year period (2018 vs. 2003) indicated that the situation with toxic element content in sediments along Kupa River improved formost of its course. Unfortunately, on the lower course of the river, the situation has worsened. Using the example of Kupa River sediments, it was shown that the magnetic susceptibility method is excellent indetecting increased values of Cr.