Sediment Ballet: Unveiling the Dynamics of Metal Bioavailability in Sediments Following Resuspension and Reequilibration.

Assessing the risk of metal-contaminated sediments under disturbed conditions is challenging due to the lack of methods that capture instant changes in metal bioavailability. Existing approaches provide inadequate understandings of the processes regulating metal bioavailability under nonequilibrium conditions. Experiments were conducted to improve our understanding of the metal bioavailability dynamics induced by sediment resuspension and subsequent redeposition (reequilibration).

Spatiotemporal Mapping of the Evolution of Silver Nanoparticles in Living Cells.

Bioaccumulated silver nanoparticles (AgNPs) can undergo transformation and release toxic Ag, which can be further reduced and form secondary AgNPs (AgNPs). However, the intricate interconversions among AgNPs, Ag, and AgNPs remain speculative. Herein, we developed a bioimaging method by coupling the aggregation-induced emission method with the label-free confocal scattering and hyperspectral imaging techniques to quantitatively visualize the biodistribution and biotransformation of AgNPs, AgNPs, and Ag in living cells.

Toxicokinetics and Mussel Watch: Addressing Interspecies Differences for Coastal Cadmium Contamination Assessment.

Bivalves are often employed for biomonitoring contaminants in marine environments; however, in these large-scale programs, unavoidably, using multiple species presents a significant challenge. Interspecies differences in contaminant bioaccumulation can complicate data interpretation, and direct comparisons among species may result in misleading conclusions. Here, we propose a robust framework based on toxicokinetic measurements that accounts for interspecies differences in bioaccumulation.

Turbid Waters and Clearer Standards: Refining Water Quality Criteria for Coastal Environments by Encompassing Metal Bioavailability from Suspended Particles.

Suspended particulate matter (SPM) carries a major fraction of metals in turbid coastal waters, markedly influencing metal bioaccumulation and posing risks to marine life. However, its effects are often overlooked in current water quality criteria for metals, primarily due to challenges in quantifying SPM's contribution. This contribution depends on the SPM concentration, metal distribution coefficients (), and the bioavailability of SPM-bound metals (assimilation efficiency, AE), which can collectively be integrated as a modifying factor (MF).

Enhancing Sediment Bioaccumulation Predictions: Isotopically Modified Bioassay and Biodynamic Modeling for Nickel Assessment.

Quantifying metal bioaccumulation in a sedimentary environment is a valuable line of evidence when evaluating the ecological risks associated with metal-contaminated sediments. However, the precision of bioaccumulation predictions has been hindered by the challenges in accurately modeling metal influx processes. This study focuses on nickel bioaccumulation from sediment and introduces an innovative approach using the isotopically modified bioassay to directly measure nickel assimilation rates in sediment.

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.

Interspecies calibration for biomonitoring metal contamination in coastal waters using oysters and mussels.

Differences in metal bioaccumulation among species make it difficult to compare biomonitoring results obtained using different marine bivalve species. To address this challenge and improve the interpretation of biomonitoring data, we studied the toxicokinetic mechanisms underlying these differences and developed a method to estimate seawater metal concentrations based on metal concentrations in the organisms. We transplanted six common species of oysters and mussels found in Chinese coastal waters into the Jiulong River estuary and monitored metal concentrations in the organisms, water, and suspended particles every three days over a six-week period.

Higher Risks of Copper Toxicity in Turbid Waters: Quantifying the Bioavailability of Particle-Bound Metals to Set Site-Specific Water Quality Criteria.

In coastal waters, particulate metals constitute a substantial fraction of the total metals; however, the prevalent water quality criteria are primarily based on dissolved metals, seemingly neglecting the contribution of particulate metals. Here we developed a method to quantify the toxicity risk of particulate metals, and proposed a way to calculate modifying factors (MFs) for setting site-specific criteria in turbid waters. Specifically, we used a side-by-side experimental design to study copper (Cu) bioaccumulation and toxicity in an estuarine clam, , under the exposure to "dissolved only" and "dissolved + particulate" Cu.

Isotopically Modified Bioassay Bridges the Bioavailability and Toxicity Risk Assessment of Metals in Bedded Sediments.

The application of bioavailability-based risk assessment for the management of contaminated sediments requires new techniques to rapidly and accurately determine metal bioavailability. Here, we designed a multimetal isotopically modified bioassay to directly measure the bioavailability of different metals by tracing the change in their isotopic composition within organisms following sediment exposure. With a 24 h sediment exposure, the bioassay sensed significant bioavailability of nickel and lead within the sediment and determined that cadmium and copper exhibited low bioavailable concentrations and risk profiles.

Application of a Multi-Metal Stable-Isotope-Enriched Bioassay to Assess Changes to Metal Bioavailability in Suspended Sediments.

The direct measurement of particulate contaminant bioavailability is a challenging aspect for the environmental risk assessment of contaminated sites. Here, we demonstrated a multi-metal stable-isotope-enriched bioassay to simultaneously measure the bioavailability of Cd, Cu, and Zn in naturally contaminated sediments following differing periods of resuspension treatment. Freshwater filter-feeding clams were pre-labeled with the isotopes Cd, Cu, and Zn to elevate isotope abundances in their tissues and then exposed to metal-contaminated suspended sediments.

Field to laboratory comparison of metal accumulation on aged microplastics in coastal waters.

The ubiquity of microplastics in the environment has attracted much attention on their risks. Though newly produced plastics were considered inert to aqueous metals, a few studies suggest aged microplastics can accumulate metals. Still, knowledge gap exists on the comparability of metal accumulation in field condition and that acquired in controlled laboratory settings.

Measuring Metal Uptake and Loss in Individual Organisms: A Novel Double Stable Isotope Method and its Application in Explaining Body Size Effects on Cadmium Concentration in Mussels.

Interindividual variabilities in metal bioaccumulation confound our interpretation of the biomonitoring data. Measuring metal toxicokinetics in organism "individuals" may provide insights into the processes underlying the variabilities. Therefore, we developed a double stable isotope method that can simultaneously measure uptake and elimination of metals in individual organisms and thus the distribution of the toxicokinetic parameters.

In Situ DGT Sensing of Bioavailable Metal Fluxes to Improve Toxicity Predictions for Sediments.

An increased risk of adverse biological effects of metals in sediments may be accompanied by high labile metal fluxes as measured by the diffusive gradients in thin films (DGT) technique. To improve the usefulness of the DGT technique for sediment quality risk assessments, we used the simpler and more cost-effective piston DGTs rather than planar DGT probes to measure bioavailable metal fluxes in naturally contaminated sediments with widely varying composition (properties, metals and concentrations) and assessed their prediction of toxicity to amphipod reproduction in a flow-through microcosm. DGT pistons were deployed in sediments under different conditions, both in the field (in situ) and in the laboratory in sediment cores (lab-equilibrated) and in homogenized sediments (lab-homogenized).

Making the Biotic Ligand Model kinetic, easier to develop, and more flexible for deriving water quality criteria.

In aquatic environments, the ecological risks posed by metals are greatly affected by water chemistry, thereby creating challenges for water quality management. Biotic ligand models (BLMs) have become the most widely used tools to interpret and predict water chemistry effects. Traditional BLM development methods require a large number of toxicity tests and organisms, and model predictions are limited to certain toxicity statistics (e.

Contrasting temporal dynamics of dissolved and colloidal trace metals in the Pearl River Estuary.

Metal contamination in the Pearl River Estuary (PRE) is persistent-, yet a comprehensive understanding of distribution and behavior of metals in surface water of this large, multi-source estuary is still lacking. In the present study, water samples from 24 sites spanning the whole estuary during the dry and wet season were collected and fractioned. Trace metal concentrations in samples were then determined following a preconcentration technique using Nobias Chelate-PA1 resin.

Using Zn Isotopic Signatures for Source Identification in a Contaminated Estuary of Southern China.

Zinc isotope ratios in water and suspended particles (SP) were measured in the Pearl River Estuary (PRE), China. Site-to-site δZn values in water varied by approximately 1.3‰ (i.

Bioturbation effects on metal release from contaminated sediments are metal-dependent.

Metal flux measurements inform the mobility, potential bioavailability and risk of toxicity for metals in contaminated sediments and therefore is an important approach for sediment quality assessment. The binding and release of metals that contribute to the net flux is strongly influenced by the presence and behaviors of benthic organisms. Here we studied the effects of bioturbation on the mobility and efflux of metals from multi-metal contaminated sediments that inhabited by oligochaete worms or both worms and bivalves.

Impact of phenol on the performance, kinetics, microbial communities and functional genes of an autotrophic denitrification system.

Nitrate and phenol often co-occur in wastewater because of the complex industrial and agricultural processes, while the impacts of phenol on autotrophic denitrification remain unclear. Here, a sulfur and hydrogen-oxidizing autotrophic denitrification reactor was established, and the effects of different concentrations of phenol on the nitrate removal performance, kinetics, microbial communities, and functional genes were investigated. Increasing concentrations of phenol significantly decreased the denitrification efficiency in the reactor.

Effects of resuspension on the mobility and chemical speciation of zinc in contaminated sediments.

Identifying and quantifying the processes governing the mobilization of metals during resuspension events is key to assessing long-term metals efflux from sediments and associated ecological impacts. We investigated the effects of sediment resuspension on the mobilization and chemical speciation of zinc in two-week-long batch experiments using metal-contaminated sediments from Lake DePue (IL, USA). Measurements of dissolved zinc and sulfate allowed us to characterize the kinetics of metal sulfide dissolution and the resulting net release of zinc to the aqueous phase.

Spatial and temporal variations of bulk and colloidal dissolved organic matter in a large anthropogenically perturbed estuary.

In the present study, we characterized the sources of dissolved organic matter (DOM) and the processes controlling the evolution of DOM in a large anthropogenically perturbed estuary in Southern China. Three-dimensional excitation emission matrices (3D EEMs) revealed that DOM in the estuary was primarily from autochthonous origin although terrestrial sources also contributed to the DOM production. Parallel factor analysis (PARAFAC) of the EEMs dataset indicated that DOM in the estuary was a legacy from the upstream wastewater discharging activities, and estuarine mixing was the primary mechanism responsible for the decreasing concentrations of DOM components.

Interplay between flow and bioturbation enhances metal efflux from low-permeability sediments.

Understanding the interplay effects between processes such as hydrodynamic forcing, sediment resuspension, and bioturbation is key to assessment of contaminated sediments. In the current study, effects of hydrodynamic forcing, sediment resuspension, and bioturbation by the marine polychaete Nereis virens were evaluated both independently and together in a six-month flume experiment. The results show that hydrodynamic forcing without resuspension or worm action slightly enhanced efflux of dissolved Cu to the water column, sediment resuspension released considerable amounts of dissolved Cu, and interactions between hydrodynamics and worm burrowing further enhanced Cu efflux.

An Integrated Experimental and Modeling Approach to Predict Sediment Mixing from Benthic Burrowing Behavior.

Bioturbation is the dominant mode of sediment transport in many aquatic environments and strongly influences both sediment biogeochemistry and contaminant fate. Available bioturbation models rely on highly simplified biodiffusion formulations that inadequately capture the behavior of many benthic organisms. We present a novel experimental and modeling approach that uses time-lapse imagery to directly relate burrow formation to resulting sediment mixing.

Lifetime and dissolution kinetics of zinc oxide nanoparticles in aqueous media.

We have assessed the persistence and lifetime of ZnO nanoparticles (ZnO-NPs) by performing dissolution experiments in three different aqueous media. These experiments were performed at ZnO-NP concentration levels close to the solubility of zincite (∼8 μM or 650 μg l(-1) of ZnO)-a concentration that is orders of magnitude higher than current estimated relevant environmental concentrations. The kinetics were followed by voltammetry, while maintaining the pH at about 7.

Hydrodynamic Forcing Mobilizes Cu in Low-Permeability Estuarine Sediments.

Overlying hydrodynamics play critical roles in controlling surface-porewater exchanges in permeable sediments, but these effects have rarely been characterized in low-permeability sediments. We conducted a series of laboratory experiments to evaluate the effects of varied hydrodynamic conditions on the efflux of metals from low-permeability estuarine sediments. Two Cu-contaminated sediments obtained from the Piscataqua River were subject to controlled levels of hydrodynamic shear in Gust mesocosms, including episodic sediment resuspension.