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The article examines the leaching of heavy metals from sediments in various sewer systems, such as stormwater, combined sewer, and sanitary sewer systems. Different types of heavy metals, including nickel, lead, chromium, copper, zinc, and cadmium, were found in varying concentrations in the sediments. The study emphasizes the need for monitoring and identifying sources of heavy metal emissions in sewer systems to prevent potential environmental harm. It also discusses the potential of copper products in reducing the spread of infections, as well as heavy metal pollution, toxicity, and remedial actions in sewage sludge. The text further explores the leaching behavior of major and trace elements from sludge deposits and the human health risks associated with heavy metal concentrations in marine organisms. [Extracted from the article]

Potentially toxic elements (PTEs) re-release from sediment is an essential process in the sediment-water interface (SWI), especially for the influent river estuary as an important accumulation site. In this study, the diffusive gradient in thin films (DGT), high-resolution dialysis (HR-peeper) technique, and BCR sequential extraction were employed to evaluate the release risk of PTEs (As, Cu, Pb, Zn, Cd) in the New Zhuzhao River Estuary of Nansi Lake. Results showed that Cd existed primarily in the non-residual fraction (accounting for 59.87%), and the residual fractions of As, Cu, Pb, and Zn accounted for a greater proportion (12.65 to 33.07%). The mobility of Cd was the highest with a risk assessment code of 33.53% reaching the medium risk category. The resupply capacity calculated by CDGT/CDis showed that As was the largest, with an average value of 0.43, indicating the strongest release capacity of As from the sediment to pore water. Furthermore, the diffusive fluxes using DGT and HR-peeper showed that As possesses a much higher potential to release upward overlying water than other elements. [ABSTRACT FROM AUTHOR]

Seagrass meadows are hotspots of biodiversity with considerable economic and ecological value. The health of seagrass ecosystems is influenced in part by the makeup and stability of their microbiome, but microbiome composition can be sensitive to environmental change such as nutrient availability, elevated temperatures, and reduced pH. The objective of the present study was to characterize the bacterial community of the leaves, bulk samples of roots and rhizomes, and proximal sediment of the seagrass species Cymodocea nodosa along the natural pH gradient of Levante Bay, Vulcano Island, Italy. The bacterial community was determined by characterizing the 16S rRNA amplicon sequencing and analyzing the operational taxonomic unit classification of bacterial DNA within samples. Statistical analyses were used to explore how life-long exposure to different pH/pCO2 conditions may be associated with significant differences in microbial communities, dominant bacterial classes, and microbial diversity within each plant section and sediment. The microbiome of C. nodosa significantly differed among all sample types and site-specific differences were detected within sediment and root/rhizome microbial communities, but not the leaves. These results show that C. nodosa leaves have a consistent microbial community even across a pH range of 8.15 to 6.05. The ability for C. nodosa to regulate and maintain microbial structure may indicate a semblance of resilience within these vital ecosystems under projected changes in environmental conditions such as ocean acidification. [ABSTRACT FROM AUTHOR]

Chemical pollutants present a substantial threat to the survival of the green turtle (Chelonia mydas). In this study, the concentrations of 12 trace elements (TEs) in seawater, sediments, and green turtle forage and eggshells from the Xisha Islands in the South China Sea, along with their patterns of transfer and accumulation, were identified. The results revealed that the median TE concentrations in seawater and sediments were lower than the first-grade limit values of the national standard in China, indicating a low ecological risk. The concentrations (μg·g−1) of TEs in forage ranged from 0.05–0.69, 3.43–14.4, 157–2391, 27.9–124, 2.05–9.39, 0.30–9.78, 2.01–80.50, 0.18–5.76, 0.06–0.98, 2.00–18.4, 0.02–0.24, and 0.01–0.09 for Cr, Mn, Sr, Fe, Ni, Cu, Zn, Se, Cd, As, Pb, and Hg, respectively. Seawater, sediments, turtle forage, and eggshells exhibited different TE profiles, which were driven by Hg, Sr, Cr, and Pb in seawater and sediments; Fe and Ni in sediments; Cd and As in forage; and Zn, Se, and Cu in eggshells. The contents of Cu, Zn, and Se increased slightly with trophic level, indicating that they were transferred through dietary pathways. Although Cd and As appeared to bioaccumulate in green turtle forage, it was not transferred to their eggshells, which may be related to the excretion and metabolism process in the mother's body. Thus, eggshells may be a poor bioindicator for the exposure of female green turtles to these toxic elements. [ABSTRACT FROM AUTHOR]

The Arabian Sea encompasses oxygen minimum zone with denitrifying conditions. For the present study, sediments were collected across three transects off Goa transect (GT), Mangalore transect (MT) and Kochi transect (KT) in contact with water column dissolved oxygen (DO) range of 1.4–118.0 µM. Sediments were investigated for texture, clay mineralogy, total organic carbon (Corg), total nitrogen, CaCO3, δ15N, δ13C, metal content to infer their distribution with changing DO and their use as possible palaeo-proxies. The Corg (0.9–8.6%) is largely marine and δ15N from GT and MT preserves signatures of higher water column denitrification. Al normalised ratios of Cu, Ni, Zn, V and Mo are GT > MT > KT. Nickel could be a productivity proxy for DO <80 µM; Cr, U could be a redox proxy for DO <20 µM; Co and Mn could be a better proxy for DO <80 µM; U/Mo vs. DO could separate sediments with DO less than and >80 µM. We observed that eastern Arabian Sea dataset does not always fall within the defined proxies of the other anoxic basins. The metal concentrations in modern day sediments from the eastern Arabian Sea may be used as a proxy to infer the ancient sediment redox conditions. Highlights: Organic carbon distribution in anoxic sediments. Provenance of sediments. Nitrogen isotopes and geochemistry as palaeo-proxy for anoxic basins. [ABSTRACT FROM AUTHOR]

The trace element of As and Sb have resulted in serious threats to ecological sustainability and human health in the Xijiang River basin, China. The geoaccumulation index (Igeo) results showed the sediment of Xijiang River was heavily contaminated by Sb as well as moderately contaminated by As. The effect of inorganic anions on the released As and Sb from the sediment increases in the following sequence: Cl− < SO42− < CO32− < PO43−. The presence of PO43− and CO32− had the greater effect over As mobility from the sediment compared to Sb. The effect of Ca(II), Al(III), and Mg(II) on the released amount of Sb from the sediment is negligible. Meanwhile, in the case of As, Ca(II) and Mg(II) had small impacts, but the released amount of As increased slightly with an increase of Al(III) concentration. The stability of As and Sb in the sediment was found to be the best at pH 5. The effect of organic compounds (≤ 0.05 mol/L) on the dissolved As percentages from the sediment increased in the following sequence: ethylenediaminetetraacetate (EDTA) < oxalate < citrate, and the effect on Sb release was oxalate < EDTA < citrate at concentrations (≤ 0.025 mol/L). This study provides the basic theoretical basis to manage the mobilization of co-contamination of sediments with As and Sb under the influence of external perturbations. [ABSTRACT FROM AUTHOR]

Purpose: High water-level fluctuations (WLFs) usually lead to the periodic drying and rewetting of littoral sediment, proven to influence the transformation of various sediment contaminants. However, details regarding metal bioavailability variations remain unclear. In this study, oxidation–reduction status transition, metal fraction transformation, and the development of the acid volatile sulfide (AVS) and the simultaneously extracted metals (SEM) were investigated to assess the variations of metal bioavailability in the littoral anoxic sediment during the drying–rewetting process. Methods: A series of sediment cores were collected from the littoral area near the mouth of Nanfei River in Lake Chaohu, China, with half of them exposed to dark conditions with an overlying water cover (the control treatment). The other half was dried through the removal of overlying water and then exposed to air and sunlight (the drying treatment). Every 5 days, three of the dried sediment cores were rewetted for 3 days with lake water collected in situ. Various characteristics were analyzed for both the control and drying sediment cores. The drying and rewetting experiment was carried out for 30 days, and the bioavailability of metals was then evaluated thoroughly through data analyses. Results and discussion: The periodic drying and rewetting process led to the oxidation of the anoxic sediment with a pronounced increase in oxygen penetration depth and redox potential, and a decrease in AVS concentrations in the drying treatment after 15 days of experimentation. Significant increases in the values of the ratio of SEM and AVS, the difference between SEM and AVS, and the organic carbon normalized difference between ΣSEM and AVS were retrieved for the drying treatment after process completion. The increase of metal bioavailability to aquatic organisms was consequently predicted, with the most significant concerns noted regarding Cd and Pb due to their transformation to less firmly bound fractions. Conclusions: The periodic drying and rewetting process could increase the bioavailability of metals in littoral anoxic sediment. Therefore, this process should be given more attention during future management of water level and remediation of littoral sediment in similar areas. [ABSTRACT FROM AUTHOR]

The deposition and release of heavy metals in sediments often lead to their diffusion in lakes, especially for dispersed elements such as cadmium (Cd), which indirectly introduces pollutants into the food chain. The high rate of deposition or release of heavy metals in sediments is a problem to be solved. Southwest China is most famous in the world for the continuous distribution of karst area, for holding the largest area of bare carbonate rocks and for experiencing the strongest karst development in the world. The trace metals in 15 sites of Yelang Lake were determined by diffusive gradients in thin-films (DGT) method. The distribution and release mechanism of Cr, Ni, Cu, Cd, Zn and Pb under high geochemical backgrounds in the karst area of Guizhou Province in Southwest China were discussed. Based on the DGT concentration and pore water analysis, the distribution order of these heavy metal contents is usually upstream (SC), middle (DCB) and downstream (SW) areas of the lake, which increases during the dry season and decreases during the wet season. There was no significant difference in concentration between 0–4 and 4–8 cm depth (p < 0.05). The R values of heavy metals in the dry and wet seasons were highest with cadmium (Cd) and lowest with chromium (Cr) and lead (Pb). The results of the metal geo-accumulation index (Igeo) and the potential ecological risk index are highest on Cd and lowest on Cr. The mean concentrations of Cr, Cd, Zn, Ni (DCB, SW), Pb (SC, DCB) and Cu (SC) are between the corresponding threshold effect level and the probable effect level, and the average potential ecological risk is ranked in descending order of Cd > Pb > Zn > Cu > Ni > Cr. These three areas are at medium risk levels and the potential ecological risks increases from upstream to downstream. The deposition rate of heavy metals in Yelang Lake sediment was higher than the release rate and the ecological risk from heavy metals was relatively low. Since Cd is the main ecological risk factor in the lake, more attention needs to be given to Cd contamination in the Yelang Lake basin of the karst area. [ABSTRACT FROM AUTHOR]

Purpose: We conducted this investigation in order to develop a simple method for the determination of bioavailable vanadium and its speciation within sediments. Materials and methods: The developed method is based on the determination of acid-extractable vanadium, as this fraction is presumably bioavailable, and its subsequent speciation using IC–UV/Vis (ionic chromatography with an ultraviolet-visible detector). A published procedure for vanadium speciation in pore water was further optimized in order to separate V(IV) and V(V) species using column EDTA derivatization on sediment samples. The analytical approach was applied in order to assess acid-extractable vanadium and its speciation within estuary sediments of the Krka River at the Dalmatian coast of Croatia. Results and discussion: The results imply that the majority of vanadium within estuary sediments is in the form of less soluble fraction while the acid-extractable fraction comprises approximately 40% of the total vanadium present. In contrast, open sea sediment (station K4) was completely dominated by the acid-extractable vanadium. The extracted vanadium is in the form of V (IV). Conclusions: Ion-exchange chromatography with an UV/Vis detector is a promising analytical method for vanadium speciation, however, further optimization of the conditions (improvement of the sequential extraction procedure) is needed in order to assess speciation also within other vanadium sedimentary fractions. [ABSTRACT FROM AUTHOR]

We explored the concept of equilibrium passive sampling for methylmercury (MeHg) using the strategy developed for hydrophobic organic chemicals. Passive sampling should allow prediction of the concentration of the chemically labile fraction of MeHg in sediment porewaters based on equilibrium partitioning into the sampler, without modeling diffusion rates through the sampler material. Our goals were to identify sampler materials with the potential to mimic MeHg partitioning into animals and sediments and provide reversible sorption in a time frame appropriate for in situ samplers. Candidate materials tested included a range of polymers embedded with suitable sorbents for MeHg. The most promising were activated carbon (AC) embedded in agarose, thiol–self‐assembled monolayers on mesoporous supports embedded in agarose, and cysteine‐functionalized polyethylene terephthalate, which yielded log sampler–water partition coefficients of 2.8 to 5 for MeHgOH and MeHg complexed with dissolved organic matter (Suwannee River humic acid). Sampler equilibration time in sediments was approximately 1 to 2 wk. Investigation of the MeHg accumulation mechanism by AC embedded in agarose suggested that sampling was kinetically influenced by MeHg interactions with AC particles and not limited by diffusion through the gel for this material. Also, AC exhibited relatively rapid desorption of Hg and MeHg, indicating that this sorbent is capable of reversible, equilibrium measurements. In sediment:water microcosms, porewater concentrations made with isotherm‐calibrated passive samplers agreed within a factor of 2 (unamended sediment) or 4 (AC‐amended sediment) with directly measured concentrations. The present study demonstrates a potential new approach to passive sampling of MeHg. Environ Toxicol Chem 2020;39:323–334. © 2019 SETAC [ABSTRACT FROM AUTHOR]

Purpose: As natural zeolites have been widely used as cost-effective adsorbents for plant nutrients and heavy metals in sediments, it is worthwhile to verify the potential of natural zeolites for mixed-contaminant stabilization including hydrophobic organic contaminants (HOCs). The effectiveness of natural zeolite amendment in sediment on reducing the bioaccumulation of sediment-associated HOCs in V. philippinaram (Cb) was assessed. Then, the role of sediment pore water freely dissolved HOCs (Cfree) in Cb prediction was further identified and modeled. Materials and methods: In this study, a bioavailability-based assessment of the HOC-stabilization efficacy of natural zeolites in maricultural sediments was performed using equilibrium passive sampling. V. philippinaram was adopted as a biological indicator for HOC bioaccumulation. Polydimethylsiloxane (PDMS) was used as a passive sampler for monitoring the concentration of the Cfree. The assumption that Cfree is a central mediator driving the bioaccumulation process of HOCs from the bulk sediment to the exposed organisms was validated by correlating the reductions in Cb and Cfree of the sediments amended with natural zeolites. Subsequently, a model based on this assumption was built and verified for the bioavailability-based assessment of the stabilization efficacy of natural zeolite amendment on sediment-associated HOCs. Results and discussion: The results showed the bioaccumulations of four kinds of HOCs (including polycyclic aromatic hydrocarbons, polybrominated diphenyl ethers, pyrethroids, and organochlorine pesticides) in V. philippinaram were reduced by 7.3–38% after the natural zeolite amendment (10% dry weight in sediments), and the Cfree values measured with PDMS were reduced proportionally. It supported the assumption that Cfree is a central mediator driving the bioaccumulation process of HOCs. Kow of HOCs and two properties of sediment were found to be significantly correlated with the reductions of the Cfree values. Based on these findings, a model to predict the Cb values of PAHs and PBDEs in V. philippinaram was built. The model was then verified by a significant correlation between the predicted and measured values of Cb. Conclusions: The potential of natural zeolites for the stabilization of mixed-contaminants in sediments, including HOCs, was proved as notable reductions of Cb and Cfree of HOCs in the sediments amended by natural zeolite were observed. The results also suggested PDMS is a promising tool for predicting the bioaccumulation of sediment-associated HOCs in V. philippinaram and further for assessing the stabilization efficacy of natural zeolites in maricultural sediments. Modifying natural zeolites to further improve the effectiveness of HOC stabilization is warranted. [ABSTRACT FROM AUTHOR]

Wetlands act as kidneys of land and facilitate remediation of metals and other harmful pollutants through uptake by aquatic macrophytes. The aim of the present study was to investigate metal concentrations in sediments and plants, sources of metal origin, and contamination level in Uchalli Wetland Complex. Sediment samples were collected from 15 randomly selected sites. Metal concentrations (Cd, Pb, Ni, Cu, Zn, Cr, As, Mn) in sediments and macrophytes were determined during summer and winter seasons using the inductively coupled plasma technique. Metal concentrations in sediments during summer and winter seasons were in the order as follows: As > Mn > Zn > Cr > Ni > Cd > Pb > Cu and As > Mn > Zn > Cr > Ni > Pb > Cd >Cu respectively. All analyzed metals were within European Union (EU) limits. In macrophytes, these metals were in the order as follows: Mn > As > Ni > Zn > Cr > Cd > Cu > Pb and As > Mn > Zn > Ni > Cr > Cd > Pb during summer and winter seasons respectively. Contamination degree (Cd) (1.023–5.309) for these lakes showed low contamination during both seasons; mCd values (below 1.5) showed very little contamination degree, while the pollution load index (0.012 to 0.0386) indicated no metal pollution in these lakes. PCA applied on sediment showed that Pb, Zn, Cr, Cu, and Cd had anthropogenic sources of origin. As and Mn were due to natural processes while Ni could be resultant of both anthropogenic and natural sources. PCA on macrophytes showed that Ni, Pb, Cr, Zn, Cu; Cd, As; Mn had anthropogenic, natural, and anthropogenic + natural sources of origin. The study concluded that metal concentrations in sediments were not up to dangerous level. [ABSTRACT FROM AUTHOR]

Evaluations of sediment quality conditions are commonly conducted using whole-sediment chemistry analyses but can be enhanced by evaluating multiple lines of evidence, including measures of the bioavailable forms of contaminants. In particular, porewater chemistry data provide information that is directly relevant for interpreting sediment toxicity data. Various methods for sampling porewater for trace metals and dissolved organic carbon (DOC), which is an important moderator of metal bioavailability, have been employed. The present study compares the peeper, push point, centrifugation, and diffusive gradients in thin films (DGT) methods for the quantification of 6 metals and DOC. The methods were evaluated at low and high concentrations of metals in 3 sediments having different concentrations of total organic carbon and acid volatile sulfide and different particle-size distributions. At low metal concentrations, centrifugation and push point sampling resulted in up to 100 times higher concentrations of metals and DOC in porewater compared with peepers and DGTs. At elevated metal levels, the measured concentrations were in better agreement among the 4 sampling techniques. The results indicate that there can be marked differences among operationally different porewater sampling methods, and it is unclear if there is a definitive best method for sampling metals and DOC in porewater. Environ Toxicol Chem 2017;36:2906-2915. Published 2017 Wiley Periodicals Inc. on behalf of SETAC. This article is a US government work and, as such, is in the public domain in the United States of America. [ABSTRACT FROM AUTHOR]

The influence of epipsammic biofilm developed on riverbed sediment on the sorption, uptake, mobility and transformation of As was studied. Native biofilm was incubated on sediment samples at microcosm level. Once the biofilm had developed, 500 µg L As was spiked in two systems designated BAS and BASP, without P and with equimolar As:P concentration ratio, respectively, and compared with identical control (sterilized) systems (CAS and CASP). The evolution and speciation of arsenic (As) concentrations in the overlying water were followed during two additional weeks. The biofilm enhanced removal of As from the water up to 91 % of its initial concentration, while only ~70 % removal was attained in CAS. Presence of equimolar P concentration enhanced the amount of As removal up to 97 % in BASP, but had no effect in CASP. In the systems with biofilm, As was mostly (~97 %) in As form, whilst As only accounted for ~1 % of total aqueous As. The organic species, monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA), represented 0.6 and 0.7 % of total As, respectively. In contrast, in the systems devoid of biofilm, As accounted for up to 39 % of aqueous As, whereas methylated aqueous species were negligible. The distribution of As in the biofilm showed that ~71 % of the retained As was extracellular, most (>99.5 %) in the form of As. Volatile As forms were only detected in the systems incorporating biofilm. It is concluded that biofilm covering sediments increases As retention, inhibits reduction of As to As and methylates inorganic As, thus playing a key role in the biogeochemistry of As in river environments. [ABSTRACT FROM AUTHOR]

ABSTRACT Passive sampling methods (PSMs) allow the quantification of the freely dissolved concentration ( Cfree) of an organic contaminant even in complex matrices such as sediments. Cfree is directly related to a contaminant's chemical activity, which drives spontaneous processes including diffusive uptake into benthic organisms and exchange with the overlying water column. Consequently, Cfree provides a more relevant dose metric than total sediment concentration. Recent developments in PSMs have significantly improved our ability to reliably measure even very low levels of Cfree. Application of PSMs in sediments is preferably conducted in the equilibrium regime, where freely dissolved concentrations in the sediment are well-linked to the measured concentration in the sampler via analyte-specific partition ratios. The equilibrium condition can then be assured by measuring a time series or a single time point using passive samplers with different surface to volume ratios. Sampling in the kinetic regime is also possible and generally involves the application of performance reference compounds for the calibration. Based on previous research on hydrophobic organic contaminants, it is concluded that Cfree allows a direct assessment of 1) contaminant exchange and equilibrium status between sediment and overlying water, 2) benthic bioaccumulation, and 3) potential toxicity to benthic organisms. Thus, the use of PSMs to measure Cfree provides an improved basis for the mechanistic understanding of fate and transport processes in sediments and has the potential to significantly improve risk assessment and management of contaminated sediments. Integr Environ Assess Manag 2014;10:197-209. © 2014 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals, Inc. on behalf of SETAC. [ABSTRACT FROM AUTHOR]