Sediment Quality Guideline Values Research Articles

Equilibrium partitioning approach for metal toxicity assessment in tropical estuarine sediment of Bandon Bay, Thailand

An equilibrium partitioning approach (EqPA) was employed to evaluate the metal toxicity and define sediment quality guidelines (SQGs) for arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), nickel (Ni), lead (Pb), zinc (Zn), and mercury (Hg) in the cockle cultivated areas located in Bandon Bay, Thailand. An assessment of metal toxicity using the [∑SEM]-[AVS] and [∑SEM]-[AVS]/foc models indicated no adverse effect on benthic organisms. The normalized total metal concentrations in this area were below the established SQG values for As, Cd, Cu, Ni, Pb, Zn, and Hg, namely respectively 21.3, 0.8, 84.6, 36.0, 34.6, 440.9 mg/kg dry weight, and 49.3 μg/kg dry weight on sand and calcium carbonate free with 1 % total organic carbon basis, suggesting low metal toxicity. This study provides locality adapted SQG values for supporting sediment quality management specifically in Bandon Bay, potentially serving as a model for other coastal areas.

Trend of PFAS concentrations and prediction of potential risks in Taihu Lake of China by AQUATOX

Per- and polyfluoroalkyl substances (PFAS) are recognized as emerging environmental pollutants due to their high persistence and toxicities to humans and animals. Understanding the temporal trend of PFAS in the environment is important for their pollution control and making appropriate policies. Many studies have reported the PFAS concentrations in Taihu Lake, the third largest lake in China, while their temporal trend during the years was seldom investigated. This study summarizes the PFAS concentrations in the water, sediment and organisms in Taihu Lake from 2009 to 2020 to depict their temporal trends. Meanwhile, the ecological model of AQUATOX was applied to evaluate and predict the potential risks of PFAS from 2012 to 2030. The results showed that the total PFAS concentrations varied but without distinct increase or decrease in both water and sediment during the years, while PFAS concentrations in organisms significantly decreased. The yearly mean concentrations of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) in the water were 21.7–25.4 ng/L and 9.7–26.5 ng/L respectively, lower than the Standards for Drinking Water Quality of China and the suggested water quality criteria to protect the aquatic organisms. In sediment, PFOA and PFOS concentrations were 0.16–0.69 ng/g and 0.15–0.82 ng/g respectively, much lower than the recommended sediment quality guideline values. Based on the AQUATOX prediction, there will be no major threats caused by PFAS to the growth of biota in Taihu Lake in the near future, while the biomass of some species (e.g. carp) will be affected under the perturbation of PFAS. Both field investigation and AQUATOX simulation showed that PFOS concentrations in invertebrates and fish descend steadily, while no remarkable decrease in PFOA concentrations was expected. This study suggests a decreasing ecological risk of PFAS in Taihu Lake, while highlights the necessity of continuous monitoring of PFAS contamination.

Improving toxicity prediction of metal-contaminated sediments by incorporating sediment properties

For the purpose of sediment quality assessment, the prediction of toxicity risk-levels for aquatic organisms based on simple environmental measurements is desirable. One commonly used approach is the comparison of total contaminant concentrations with corresponding water and sediment quality guideline values, serving as a Line of Evidence (LoE) based on chemistry-toxicity effects relationships. However, the accuracy of toxicity predictions can be improved by considering the factors that modify contaminant bioavailability. In this study we used paired chemistry-ecotoxicity data sets for sediments to evaluate the improvement in toxicity risk predictions using bioavailability-modified guidelines. The sediments were predominantly contaminated with metals, and measurements of sediment particle size, total organic carbon (TOC) and acid volatile sulfide (AVS) were used to modify hazard quotients (HQ). To further assess the predictive efficacy of the bioavailability-modified guideline models, sediments with differing contamination levels were tested for toxicity to a benthic amphipod's reproduction. To account for differences between laboratory exposure and field exposure scenarios, where the latter creates greater dilution, both static-renewal and flow-through test procedures were employed, and flow-through resulted in lower dissolved metal concentrations in the overlying waters. We also investigated how lower AVS concentration by oxidation modified the toxicity. This study reaffirmed that consideration of factors that influence contaminant bioavailability improves toxicity risk predictions, however the improvements may be modest. The sediment particle size data had the greatest influence on the modified HQ, indicating that higher percentage of fine particle size (<63 μm) contributed most to a lower predicted toxicity. The comparison of the static-renewal and flow-through test results continue to raise important questions about the relevance of static or static-renewal toxicity test results for risk assessment decisions, as both these test designs may cause unrealistically high contributions of dissolved metals in overlying waters to toxicity. Overall, this study underscores the value of incorporating outcomes from simple and routine sediment analysis (e.g., particle size, TOC, and consideration of AVS) to enhance the predictive efficacy of toxicity risk assessments in the context of sediment quality risk assessment.

Bioaccumulation of estuarine pollutants in leaf oysters (Isognomon ephippium) on the mid-north coast, New South Wales, Australia

Filter feeding bivalves are useful bioindicators for the detection of biologically available pollutants. We investigated trace metals, metalloids, and pesticides in leaf oyster (Isognomon ephippium) soft tissue and shells and compared them to sediment in five estuaries in northern New South Wales, Australia. Concentrations of Pb, Cr, Mn, Ni, Fe and Al were higher in sediments, whereas Zn, Cd, Ag, Hg, Se and As bioaccumulated in the soft tissue. The amount of Cu, Hg and Ni in the sediment from Tweed and Richmond River estuaries exceeded the Australian national sediment quality guideline values. Only one pesticide, atrazine, was detected in leaf oyster soft tissue. Combinations of six elements in the soft tissue were the best predictors of oyster condition index and shell size, whereas sediment contaminants showed weak relationships. Overall, the bioaccumulation of metals and metalloids increases with leaf oyster size and reduces leaf oyster condition, suggesting these large bivalves are useful bioindicators for pollution in estuarine environments.

Geochemical and environmental assessment of potential effects of trace elements in soils, water, and sediments around abandoned mining sites in the northern Iberian Peninsula (NW Spain)

The mineral deposits and traces in the Iberian Peninsula are very numerous and of varied mineralogy. This study aimed to analyze the geochemical and environmental changes detected in soil, water, and sediments around the La Sierre mine, and to determine if contamination persists over time. The concentrations of ten trace elements (As, Co, Cr, Cu, Fe, Mn, Ni, Pb, V, Zn) were measured in 20 soil samples, 10 water samples, and 6 sediment samples, sampling at the most affected points. Soil and sediment samples were analyzed by Inductively Coupled Plasma Mass Spectrometry (ICP-MS) and water samples by Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES). From the Principal Component Analysis (PCA), soil samples SOI-6, 7, and 20 presented high amounts ranging from 14489.86a±7 to 3031.72b ± 1 mg/kg of Co, Cu, Ni, and As, respectively. Water samples WAT-6, 8, and 10 presented high contents of As, Co, Cr, Cu, Fe, Mn, Ni, Pb, V, and Zn, being sample WAT-8 with high values of As, Co, Cu, Fe, and Ni with 48.1 ± 0.82, 368 ± 4, 68.3 ± 0.1, 97.5 ± 1.2, and 152 ± 2 μg/L, respectively, exceeding the regulation given by R.D 314/2016 (Water for human consumption). The sediment samples were compared with the IInterim Sediment Quality Guideline (ISQG) and Probable Effect Level (PEL) values given by the Canadian Sediment Quality Guidelines for the Protection of Aquatic Life. When presenting a high ISQG value, but low PEL, they partially comply with the regulations, which happens with samples SED-1, 2, and 8 for As and SED-5, 6, and 7 for Pb. On the contrary, Cr and Cu do not comply with what is established in samples SED-8 and SED-1 and 8, respectively, whereas, in samples SED-2 and 5, Cu partially complies with the established regulations. The values found for the trace elements present in the abandoned traditional mining area with abundant epithermal deposits prevail over time in soil, water, and sediments.

A Guideline Value for Dioxin-Like Compounds in Marine Sediments.

Sediments to be dredged as part of the installation of a harbor crossing in Sydney, Australia, contained measurable concentrations of dioxin-like compounds. To assess the suitability of these sediments for ocean disposal, a defensible sediment quality guideline value (SQGV) for dioxin-like compounds, expressed as pg toxic equivalent (TEQ)fish /g dry weight, was required. There were deemed to be too many uncertainties associated with a value derived using effects data from field studies. A similar issue was associated with values based on equilibrium partitioning from sediment to pore water, largely associated with the wide range of reported sediment:water partition coefficients. Greater certainty was associated with the use of a tissue residue approach based on equilibrium partitioning between sediment and organisms determined using tissue concentrations in fish, the most sensitive aquatic biota, and biota:sediment accumulation factors. The calculation of an appropriate SQGV used data for dioxin-like compounds in both fish and sediments from Sydney Harbor. A conservative SQGV for dioxin-like compounds of 70 pg TEQ/g dry weight was deemed to be adequately protective of biota that might be exposed to these contaminants in sediments at the ocean spoil ground. The approach is transferable to similar situations internationally. Environ Toxicol Chem 2023;42:257-271. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Toxic elemental abundances in the sediment of the Jamuna River, Bangladesh: pollution status, sources, toxicity, and ecological risks assessment

ABSTRACT In this study, elemental abundances of As, Cd, Cr, Co, Cu, Pb, and Zn in the 30 composite sediment samples from Jamuna River, Bangladesh were measured by atomic absorption spectrophotometer to assess their contamination level, toxicity, and ecological risks in both summer and winter season. In the summer season, mean concentrations of As, Cd, Cr, Co, Cu, Pb, and Zn in sediment samples were 2.82, 1.13, 25.30, 8.63, 22.01, 4.58, and 68.82 mg/kg, respectively. In the winter season, mean concentrations of As, Cd, Cr, Co, Cu, Pb, and Zn were 3.83, 1.48, 43.22, 13.86, 35.63, 8.48, and 100.27 mg/kg, respectively. The mean concentrations of all elements were found lower than the sediment quality guidelines values of probable effect level (PEL), effect range medium (ERM), and toxic effect thresholds (TET) in both seasons. There was a significant variation in elemental concentrations between wet and dry seasons and also between upstream and downstream sites (P < 0.05). Principal component analysis showed Zn, Cr, and Pb; As and Cu; and Cd and Co might have originated from the same geogenic source. The pollution evaluation indices showed consistent outcomes of almost no pollution for As, Cr, Co, Cu, Pb, and Zn, but moderately to strongly polluted for Cd in all seasons. The contamination level of elements follows the decreasing order of Cd > Zn > Cu > As > Co > Cr > Pb for both seasons. The elemental toxicity in the sediments follows the order of Cd > Cr > Zn > As > Cu > Pb, with a very high risk for Cd while a minimal risk for other elements. The ecological threats of the toxic elements were found moderate to very high. Therefore, the findings of our study concluded that the ecological condition of the Jamuna River posed a considerable risk for human health and living organisms.

Metallic mangroves: Sediments and in situ diffusive gradients in thin films (DGTs) reveal Avicennia marina (Forssk.) Vierh. lives with high contamination near a lead‑zinc smelter in South Australia

From 1889, aerial emissions and effluent from a coastal lead‑zinc smelter at Port Pirie, South Australia, have led to the accumulation of lead (Pb), zinc (Zn), arsenic (As), cadmium (Cd) and copper (Cu) in the surrounding marine environment. Despite this, extensive stands of grey mangrove (Avicennia marina) inhabit coastal areas at Port Pirie, right up to the smelter's boundary. To understand the contamination level the mangroves are living in there, elemental concentrations were measured in mangrove sediments, leaves, pneumatophores and fruits at sites 0.30–43.0 km from the smelter. Plant health was assessed via leaf chlorophyll content at four sites with contrasting contamination, as well as in situ labile elemental concentration using diffusive gradients in thin films (DGT). Sites < 1.7 km of the smelter exceeded Australian and New Zealand Environment and Conservation Council (ANZECC) & Agriculture and Resource Management Council of Australia and New Zealand (ARMCANZ) (2000) sediment quality guideline values for As (78.3–191 mg/kg), Cd (5.17–151 mg/kg), Cu (80.7–788 mg/kg), Pb (2,544–14,488 mg/kg) and Zn (281–62,097 mg/kg), while sites further away showed less enrichment above background. Similarly, elevated elemental concentrations in leaves and pneumatophores occurred closer to the smelter (up to 319 mg/kg Pb; 1,033 mg/kg Zn), while fruits had little contamination of non-essential elements (≤ 5.23 mg/kg). Relationship between sediment and leaf elemental concentration was isometric for Pb and anisometric for others. Labile As, Cd, Cu, Pb and Zn exceeded the 95% and 80% level of species protection in marine water by ANZECC & ARMCANZ (2000) near the smelter, but chlorophyll content did not vary significantly among sites (p > 0.05). These results reveal that A. marina tolerate high elemental contamination at Port Pirie, contributing to lesser but still high contamination in plants, warranting further investigation into non-lethal impacts on mangroves or additional biota inhabiting this ecosystem.

The application of sediment quality guidelines and toxicity assessment to identify contaminant hotspots in an urbanised West Australian estuary.

This paper presents a tiered assessment approach that enabled identification, triage, interrogation and confirmation of significantly contaminated areas of an urbanised West Australian estuary. The spatial distribution of organochlorine pesticides (OCPs), polycyclic aromatic hydrocarbons (PAHs) and bioavailable metals was determined in surficial sediments of the Swan-Canning Estuary through broad-scale screening (500 cores, 100 composite samples, 20 locations). The application of sediment quality guideline values (SQGVs) enabled ranking of locations through risk-based scoring and identification of contaminant hotspots. Subsequent targeted ecotoxicological and chemical assessment was undertaken at the highest scoring location in each tributary (80 cores, 16 composite samples, 3 locations, 16 sites). In the Canning tributary, Bull Creek sediments demonstrated the highest metal concentrations and greatest number of SQGVs exceeded. High-level toxicity was experienced in copepods and moderate toxicity in mussels (test sensitivity: copepod>mussel>amphipod). Toxicity-inducing contamination was attributable to two stormwater outfalls and limited to 300 m from points of discharge. In the Swan tributary, Claisebrook sediments demonstrated the highest concentrations of all PAHs, most OCPs and metals and the greatest number of SQGVs exceeded. High-level toxicity was reported in fish and mussels and moderate toxicity in copepods and amphipods (test sensitivity: fish>mussel>amphipod>copepod). Toxicity-inducing contamination included a stretch of estuary >1 km long, and two stormwater outfalls in the area were likely sources. The distribution and nature of PAH contamination suggested an additional source at Claisebrook. This combined chemistry and biological effects dataset provides critical information for the management of planned major development and concomitant estuary-bed disturbance in the coming decade.

Environmental impact of fish farming: assessment of metal contamination and sediment geochemistry at three aquaculture areas from the eastern Aegean coast.

Metal contamination and geochemistry of surface sediments were assessed at three aquaculture sites from the eastern Aegean coast. The chlorophyll degradation products and organic carbon levels were used as indicators of eutrophication status. In Akköy, higher Hg, Pb, and Cd levels were observed around the cages, while maximum concentrations of other elements were determined at stations situated near the Büyük Menderes River estuary. Metal concentrations were less than the central Aegean coast background levels other than Zn, Ni, and Cr in Akköy. Several approximations have been utilized to evaluate potential toxicity of sediments and sediment quality guidelines (SQG) were used to estimate the risks for aquatic life. Ni was the only metal with concentrations exceeding all SQG values, which indicates the highest adverse biological effect in Ildır, Akköy, and occasionally toxic in Güllük. Based on QPEL and QTEL, Ni and Cr were the predominant metal contaminants in all areas. Similarly, Cr and Ni account for the most of the all sediment toxicity in the aquaculture areas according to toxic risk index. It is concluded that sediments around the fish farms are affected by growing input of elements because of aquaculture activity. The levels of chlorophyll degradation products showed oligotrophic and mesotrophic conditions in the three studied aquaculture areas.

Metal(loid) accumulation in the leaves of the grey mangrove (Avicennia marina): Assessment of robust sampling requirements and potential use as a bioindicator

This study assessed the appropriate sampling design required for quantifying variability in metal accumulation in the leaf tissues of A. marina, a dominant mangrove inhabiting Australian estuaries, by applying a hierarchical nested sampling design to sample mangroves at various levels of biological and spatial hierarchies (leaf, branch, tree, site). It was revealed that most variation in metal accumulation occurred among trees and branches, with insignificant variation between sites and among leaves. We also examined the accumulation of metal (loid)s in the leaf tissues collected from six locations across the Georges River estuary in southern Sydney, which differ in metal contamination history. Prospect Creek and Salt Pan Creek were the most contaminated locations, which exceeded sediment quality guideline values for Cu (66.71 ± 2.18 μg/g), Zn (317.14 ± 46.14 μg/g) and Pb (81.02 ± 2.79 μg/g). All metal(loid) concentrations in leaf tissues were much lower than their concentrations in sediment, but essential metals exhibited greater mobility. Out of 10 metal(loid)s, Mn, Co and Pb in leaves showed linear relationships (R2 = 0.28–0.47) with sediment, indicating that mangrove leaves may be used as a bioindicator of environmental loads for these metals.

Sediment spiking and equilibration procedures to achieve partitioning of uranium similar to contamination in tropical wetlands near a mine site

The derivation of sediment quality guideline values (SQGVs) presents significant challenges. Arguably the most important challenge is to conduct toxicity tests using contaminated sediments with physico-chemistry that represents real-world scenarios. We used a novel metal spiking method for an experiment that ultimately aims to derive a uranium SQGV. Two pilot studies were conducted to inform the final spiking design, i.e. percolating a uranyl sulfate solution through natural wetland sediments. An initial pilot study that used extended mixing equilibration phases produced hardened sediments not representative of natural sediments. A subsequent percolation method produced sediment with similar texture to natural sediment and was used as the method for spiking the sediments. The range of total recoverable uranium (TR-U) concentrations achieved was 8–3200 mg/kg. This reflected the concentrations found in natural wetlands and water management ponds found on a uranium mine site and was above natural levels. Dilute-acid extractable uranium (AE-U) concentrations were >80% of total concentrations, indicating that much of the uranium in the spiked sediment was labile and potentially bioavailable. The portion of TR-U extractable as AE-U was similar at the start and end of the 4.5-month field-deployment. Porewater uranium (PW–U) analyses indicated that partition coefficients (Kd) were 2000–20,000 L/kg, and PW-U was greater in post- than pre-field-deployed samples when TR-U was ≤1500 mg/kg, indicating the binding became weaker during the field-deployment period. At higher spiked-U concentrations, the PW-U was lower post-field-deployment. Comparing the physico-chemical data of the spiked sediments with environmental monitoring data from sediments in the vicinity of a uranium mining operation indicated that they were representative of sediments contaminated by mining and that the U-spiked sediments had a clear U concentration gradient. This confirmed the suitability of the spiking procedure for preparing sediments that were suitable for deriving a SQGV for uranium.

Risk assessment of potentially toxic elements in stream sediments around granite quarries, barite mines, and cultivation areas, Southeastern Nigeria.

This study assessed the contamination of streams with potentially toxic elements (PTEs) in sediments around mining, quarrying, and cultivation areas in Akamkpa and environs Southeastern Nigeria. Analysis done using ICP MS technique shows that barium (Ba) and lead (Pb) recorded mean concentrations above their average shale content (ASC) in stream sediments. Chromium (Cr) exceeded Canadian Interim Sediment Quality Guideline (ISQG) and US Environmental Protection Agency (USEPA) screening benchmark value. Pb exceeded Canadian ISQG value but tallies with USEPA benchmark value. Pearson's correlation exhibited significant correlation (p < 0.01) of molybdenum (Mo) with copper (Cu) and Pb; Cu with Pb, vanadium (V), and Ba; V with Cu, Pb, iron (Fe), Ba, and beryllium (Be); and Fe with Be and V. Principal component (PC 1) consists of Pb, Mo, cobalt (Co), Cu, arsenic (As), Cr, V, and nickel (Ni) and showed significant correlation. Geo accumulation index (I-geo) values for Mo, Cu, V, Pb, Zn, Ni, Co, Mn, and Ba fall under unpolluted (0) to moderately polluted (1-2) classes. Maximum enrichment factor (EF) values show extremely high and significant enrichment of Ba and Pb in few locations. Co, Cr, Cu, Mn, and Zn possess maximum EF values classified as moderate enrichment. Ni, Mo, As, and V obtained maximum EF values classified as depleted to minimal enrichment. Modified pollution index (MPI) values showed high PTEs contamination in mostly cultivation locations. Single element potential ecological risk (EiR) mean values trend EiR (As) > EiR (Pb) > EiR (Co) > EiR (Cr) > EiR (Cu) > EiR (V) > EiR (Ni) > EiR (Zn). Comprehensive potential ecological risk (RI) shows medium risk "B" and strong risk "C" levels in few locations. The use of multiple pollution indices such as I-geo, EF, EiR, and RI in pollution assessment indicated similar trend of PTEs contamination of stream sediments. Levels of PTEs contamination are elevated in cultivation areas more than in granite quarrying and mining areas. This study serves as a benchmark for conducting suitable environmental management strategies to scientists in Nigeria and other parts of the world.

Metabarcoding Reveals Changes in Benthic Eukaryote and Prokaryote Community Composition along a Tropical Marine Sediment Nickel Gradient.

The Southeast Asia and Melanesia region has extensive nickel (Ni)-rich lateritic regoliths formed from the tropical weathering of ultramafic rocks. As the global demand for Ni continues to rise, these lateritic regoliths are increasingly being exploited for their economic benefit. Mining of these regoliths contributes to the enrichment of coastal sediments in trace metals, especially Ni. The present study used high-throughput sequencing (metabarcoding) to determine changes in eukaryote (18s v7 recombinant DNA [rDNA] and diatom-specific subregion of the 18s v4 rDNA) and prokaryote (16s v4 rDNA) community compositions along a sediment Ni concentration gradient offshore from a large lateritized ultramafic regolith in New Caledonia (Vavouto Bay). Significant changes in the eukaryote, diatom, and prokaryote community compositions were found along the Ni concentration gradient. These changes correlated most with the dilute-acid extractable concentration of Ni in the sediments, which explained 26, 23, and 19% of the variation for eukaryote, diatom, and prokaryote community compositions, respectively. Univariate analyses showed that there was no consistent change in indices of biodiversity, evenness, or richness. Diatom richness and diversity did, however, decrease as sediment acid extractable-Ni concentrations increased. Threshold indicator taxa analysis was conducted separately for each of the 3 targeted genes to detect changes in taxa whose occurrences decreased or increased along the acid extractable-Ni concentration gradient. Based on these data, 46 mg acid extractable-Ni/kg was determined as a threshold value where sensitive species began to disappear. In the case of the estuarine sediments offshore from lateritized ultramafic regolith in New Caledonia, this is recommended as an interim threshold value until further lines of evidence can contribute to a region-specific Ni sediment quality guideline value. Environ Toxicol Chem 2021;40:1894-1907. © 2021 SETAC.

Chemical speciation of phosphorus in surface sediments from a geological phosphorus-rich watershed, South China

In order to clarify the distribution characteristics and potentially environmental effect of phosphorus (P) chemical speciation in river sediments from a typical geological P-rich (GPR) watershed, South China. Forty-eight sediment samples collected from the Huangbai River watershed, Yichang city, Hubei province. The levels of TP in Huangbai River wathershed were remarkably higher than those in most Chinese lakes, reservoirs, and river. The Ca-P and Res-P were the two dominant species that accounted for 78.7% and 13.3% of TP, respectively. Based on the sediment quality guideline (SQGs) and background values of Chinese soil and sediment, the majority of the mean TP concentrations in surface sediments were higher than their background values. The unique distribution pattern of P species in the Huangbai River watershed depends on local environment conditions and P sources. These findings improve our understanding of the eutrophication and P cycle in the GPR watershed.

Polycyclic aromatic hydrocarbon status in post-hurricane Harvey sediments: Considerations for environmental sampling in the Galveston Bay/Houston Ship Channel region

Hurricane Harvey led to a broad redistribution of sediment throughout Galveston Bay and the Houston Ship Channel (GB/HSC), but the resulting changes in chemical contaminant distributions have yet to be characterized. To address this question, we collected and analyzed post-Harvey sediment for concentrations of the EPA 16 Priority Pollutant polycyclic aromatic hydrocarbon (PAHs), determining the extent to which the spatial distribution and sourcing of contaminants may have changed in contrast to historical surface sediment data (<5 cm) from the National Oceanic Atmospheric Administration (NOAA) available for the years 1996–2011. We found a small, but detectable increase from pre- to post-Harvey in PAH concentrations, with PAH diagnostic sourcing indicating combustion origins. Of the detected PAHs, none exceeded Sediment Quality Guideline values. Overall, we have added to the understanding of PAH spatial trends within the GB/HSC region, and developed a reference PAH baseline to inform future studies.

Speciation and partitioning of uranium in waterbodies near Ranger Uranium Mine

Environmental contextAs a part of the rehabilitation of Ranger Uranium Mine, Northern Australia, closure criteria for water concentrations of uranium and other contaminants in local waterbodies have been developed. Increased concentrations of uranium in the water column can result in an accumulation of uranium in the sediment and be hazardous to benthic organisms. A uranium partitioning relationship was derived to predict sediment uranium concentrations from water column concentrations. AbstractAfter almost four decades of mineral processing, the Ranger Uranium Mine (RUM) is set to cease operations in 2021. Beyond this period, rehabilitation of the Ranger Project Area (RPA) will continue into 2026. As part of the rehabilitation of RUM, water quality guideline values (WQGVs) for U and other metals in local waterbodies have been developed to protect aquatic organisms from the effects of metal toxicity. However, benthic organisms will also be exposed to U as it partitions from the water column to the sediments. This important component of the ecosystem may then be exposed to increased U concentrations through ingestion and adsorption of U from sediments. As increased concentrations of U in the water column can result in an accumulation of U in sediment, a U partitioning relationship was derived to enable prediction of sediment U concentrations when water column concentrations were at the WQGV. In this work, the effect of U counter ions and dissolved organic carbon on uranium speciation was modelled and demonstrated a high affinity for the formation of uranyl-organic complexes. Uranium partitioning was studied using experimental U-spiked sediment data as well as water/sediment data collected from multiple sites on and adjacent to the RPA. Using a Freundlich isotherm, and a water-column U concentration of 2.8µg L−1 (representing the WQGV), the acid-extractable U in sediment was calculated to be 48mg kg−1, i.e. lower than the interim sediment quality guideline value (SQGV) of 94mg kg−1. This offers assurance that a WQGV implementation of 2.8µg L−1 U will not lead to a level of U accumulation in sediment that will impact benthic communities.

Risk assessment for sediment associated heavy metals using sediment quality guidelines modified by sediment properties.

Sediment quality guidelines (SQGs) are a fundamental component of sediment quality assessment framework, frequently used in the first tier of assessment to predict the potential risks of contaminants in sediment. A recognized weakness of SQGs concerns the bioavailability of sediment contaminants, which may vary considerably with different physical-chemical properties. To better evaluate the ecological risks and predict the toxicity of the heavy metals (Cd, Cu, Ni, Pb, Zn) in the sediments of Haihe River of China, the risk quotients derived from total metal concentrations and SQG values were modified using multiple linear regressions with sediment properties, i.e. total organic carbon (TOC), acid-volatile sulfide (AVS), and particle size distribution (PSD). Then, the sediment toxicity was tested with the benthic organisms of chironomids and tubificids, and the relationships between the observed toxicity with the modified risk quotients were investigated. We found that the risk quotient modified with TOC and AVS displayed significantly improved relationship with the toxicity (p<0.001) compared to the original risk quotient without modification (p=0.062-0.074>0.05). Risk assessment indicated that although the heavy metals in the sediments of Haihe River of China are at a relatively low level, potential ecological risks caused by Ni and Zn still exist in some area, especially in the lower reaches along the estuary. The results indicated that the risk quotient and SQG values modified with sediment properties are promising for risk assessment of the metal contaminants in sediments.

Preliminary study on the distribution of metals and persistent organic pollutants (POPs), including perfluoroalkylated acids (PFAS), in the aquatic environment near Morogoro, Tanzania, and the potential health risks for humans

Metals and persistent organic pollutants (POPs), including perfluoroalkylated acids (PFAS), are chemicals with a bioaccumulative potential that are detected in wildlife around the world. Although multiple studies reported the pollution of the aquatic environment with these chemicals, only limited data is present on the environmental pollution of Tanzania's aquatic environment and the possible risks for human health through consumption of contaminated fish or invertebrates. In the present study, we examined the distribution of metals and POPs in fish, invertebrates, sediment and water, collected at two different years at multiple important water reservoirs for domestic and industrial purposes, in the aquatic environment near Morogoro, Tanzania. Furthermore, we assessed the possible risks for human health through consumption of contaminated fish and shrimp.Metal concentrations in the water, sediment, invertebrates and fish appeared to increase in sites downstream from Morogoro city, likely caused by the presence of the city as pollution source. Significant differences in accumulated concentrations of metals and POPs were observed between species, which was hypothesized to be caused by dietary differences. Concentrations of multiple metals exceeded water and sediment quality guidelines values. Only Cu (2.8–17 μg/L) and Zn (<LOQ – 151 μg/L) in water exceeded chronic and acute effect values. Furthermore, PFOS, PBDE and HCB concentrations exceeded biota quality standard values, suggesting an ecological risk caused by these metals and POPs in the aquatic environment around Morogoro.Our results suggest that potential health effects through consumption of contaminated shrimp, and to minor extent fish, are expected. The daily consumption of these proteins (0.016–0.027 kg/capita/day) in Tanzania is similar or higher than the tolerable maximum consumption of shrimp for Cu (<0.02 kg/capita/day), Co (<0.02 kg/capita/day) and PFOS (<0.01 kg/capita/day). The outcome of this study could be used in future studies on metals and POPs in African aquatic ecosystems.

Spatial distribution, fractionation and ecological risk assessment of potentially toxic metals in bottom sediments of the Zarivar freshwater Lake (Northwestern Iran)

Freshwater lakes are one of the most vulnerable ecosystems to environmental contamination. This study was initiated to assess the spatial distribution, fractionation, ecological risk of selected potentially toxic metals (Pb, Zn, Cu, Cr, and Ni) in bottom sediments of the Zarivar lake, the second largest freshwater lake in Iran. The results revealed that Pb, Zn and Cu had the high spatial variability (coefficient of variation >50) across the sampling sites and their maximum concentrations (197.5 for Pb, 198.7 for Zn and 185.6 mg/kg for Cu) were observed in sampling sites from the northern, western and eastern margins of the lake. Cr and Ni with average concentrations of 28.3 and 31.38 mg/kg respectively, exhibited low spatial variability (coefficient of variation <20) and their concentrations did not vary significantly among the sampling sites. Based on the redundancy analysis (RDA), sediment organic matter was strongly correlated with Pb, Zn and Cu while Fe2O3 and Al2O3 showed a positive correlation with Ni and Cr. The calculated average enrichment factor (EF) and geoaccumulation index (Igeo) showed that the contamination level of metals can be arranged in the following order of Pb> Cu > Zn > Cr > Ni. Results from the modified five-step sequential extraction analysis indicated that 40 % of total Pb and Zn were associated with the reducible fraction, 45 % of Cu with the oxidizable fraction and more than 80 % of total Ni and Cr were retrieved from the residual fraction. It was also noticed that Pb, Zn and Cu were more incorporated into the non-residual fractions in the sites with a higher total concentration of these metals, suggesting that both total concentration and fractionation behavior of metals were influenced by their potential sources in the study area. Ecological risk assessment using the potential ecological risk index (PERI) and the modified potential ecological risk index (MPERI) showed that sediments from the eight sampling sites pose a moderate to considerable risk whereas the other sites had low ecological risk level. In comparison to sediment quality guidelines (SQGs), the effects range low (ERL) and probable effect level (PEL) values for Pb, Cu and Zn were exceeded at some sampling sites while Ni and Cr concentrations were found to be below or close to their SQGs values at all the sampling sites. Pb was generally identified as the contaminant of most concern in the study area. Taking into account the results obtained from the fractionation study and the source contribution estimate, it can be inferred that the Pb, Zn and Cu with the average contribution of 79, 54 and 64 % respectively, were mainly derived from anthropogenic sources whereas Ni and Cr with the estimated contribution of 80 and 89 % were predominately from the lithogenic source.