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Single particle-inductively coupled plasma mass spectrometry (SP-ICP-MS) is a powerful tool for size-characterization of metal-containing nanoparticles (MCNs) at environmentally relevant concentrations, however, coexisting dissolved metal ions greatly interfere with the accuracy of particle size analysis. The purpose of this study is to develop an online technique that couples hollow fiber ultrafiltration (HFUF) with SP-ICP-MS to improve the accuracy and size detection limit of MCNs by removing metal ions from suspensions of MCNs. Through systematic optimization of conditions including the type and concentration of surfactant and complexing agent, carrier pH, and ion cleaning time, HFUF completely removes metal ions but retains the MCNs in suspension. The optimal conditions include using a mixture of 0.05 vol.% FL-70 and 0.5 mmol/L Na

Redox-active quinone and nonquinone moieties represent the electron exchange capacity (EEC) of natural organic matter (NOM), playing an important role in the electron transfer link of microbes and transformation of contaminants/metal minerals. However, the corresponding transformation of quinone/phenol and their respective influence on the EECs during reduction and reoxidation remain poorly characterized. Besides, it is still controversial whether nonquinones donate or accept electrons. Herein, we demonstrated that reoxidation of NOM after reduction can form new phenolic/quinone moieties, thus increasing the EEC. The assessment for the EEC, including the electron-donating capacity (EDC) and electron-accepting capacity (EAC), of nonquinones reflects the contribution of sulfur-containing moieties with considerable EDCs and EACs. In contrast, nitrogen-containing moieties donate negligible electrons even at

A simple and efficient dithizone-functionalized solid-phase extraction (SPE) procedure, online coupled with high-performance liquid chromatography (HPLC)-inductively coupled plasma mass spectrometry, was developed for the first time for enrichment and determination of ultra-trace mercury (Hg) species (inorganic divalent Hg (Hg(II)), methylmercury (CH3Hg(II)) and ethylmercury (C2H5Hg(II)) in cereals and environmental samples. In the proposed method, functionalization of the commercial C18 column with dithizone, enrichment, and elution of the above Hg species can be completed online with the developed SPE device. A simple solution of 2-mercaptoethanol (1% (V/V)) could be used as an eluent for both the SPE and HPLC separation of Hg species, significantly simplifying the method and instrumentation. The online SPE method was optimized by varying dithizone dose, 2-mercaptoethanol concentration, and sample volume. In addition, the effect of pH, coexisting interfering ions, and salt effect on the enrichment was also discussed. Under the optimized conditions, the detection limits of Hg species for 5 mL water sample were 0.15 ng/L for Hg(II), 0.07 ng/L for CH3Hg(II), and 0.04 ng/L for C2H5Hg(II) with recoveries in the range of 85%–100%. The developed dithizone-functionalized C18 SPE column can be reused after a single functionalization, which significantly simplifies the enrichment step. Moreover, the stability of Hg species enriched on the SPE column demonstrated its suitability for field sampling of Hg species for later laboratory analysis. This environment-friendly method offers a robust tool to detect ultra-trace Hg species in cereals and environmental samples.

Deposition of atmospheric mercury (Hg) is the most important Hg source on the high-altitude Himalayas and Tibetan Plateau. Herein, total gaseous Hg (TGM) at an urban and a forest site on the Tibetan Plateau was collected respectively from May 2017 to October 2018, and isotopic compositions were measured to clarify the influences of landforms and monsoons on the transboundary transport of atmospheric Hg to the Tibetan Plateau. The transboundary transported anthropogenic emissions mainly originated over Indo-Gangetic Plain and carried over the Himalayas by convective storms and mid-tropospheric circulation, contributing over 50% to the TGM at the Lhasa urban site, based on the binary mixing model of isotopes. In contrast, during the transport of TGM from South Asia with low altitude, the uptake by evergreen forest in Yarlung Zangbo Grand Canyon largely decreased the TGM level and shifted isotopic compositions in TGM at the Nyingchi forest site, which are located at the high-altitude end of the canyon. Our results provided direct evidence from Hg isotopes to reveal the distinct patterns of transboundary transport to the Tibetan Plateau shaped by landforms and climates, which is critical to fully understand the biogeochemical cycling of Hg in the high-altitude regions.

This study reports a sensitive online method for Hg isotope analysis at ultratrace levels by automated P&T-MC-ICPMS.

Foliar accumulation of atmospheric mercury (Hg), particularly gaseous elemental mercury (Hg(0)), accounts for a significant amount of atmospheric Hg deposition and influences the Hg geochemical cyc...

Redox transformation of mercury (Hg) is critical for Hg exchange at the air-sea interface and it can also affect the methylation of Hg in marine environments. However, the contributions of microalgae and aerobic bacteria in oxic seawater to Hg2+ reduction are largely unknown. Here, we studied the reduction of Hg2+ mediated by microalgae and aerobic bacteria in surface marine water and microalgae cultures under dark and sunlight conditions. The comparable reduction rates of Hg2+ with and without light suggest that dark reduction by biological processes is as important as photochemical reduction in the tested surface marine water and microalgae cultures. The contributions of microalgae, associated free-living aerobic bacteria, and extracellular substances to dark reduction were distinguished and quantified in 7 model microalgae cultures, demonstrating that the associated aerobic bacteria are directly involved in dark Hg2+ reduction. The aerobic bacteria in the microalgae cultures were isolated and a rapid dark reduction of Hg2+ followed by a decrease of Hg0 was observed. The reduction of Hg2+ and re-oxidation of Hg0 were demonstrated in aerobic bacteria Alteromonas spp. using double isotope tracing (199Hg2+ and 201Hg0). These findings highlight the importance of algae-associated aerobic bacteria in Hg transformation in oxic marine water.

Engineered metal-containing nanoparticles (MCNs), which have unique physical and chemical properties, are widely used in various fields such as medicine, pharmaceuticals, and microelectronics as well as in daily supplies. These MCNs are inevitably released into the environment during production and use, thus posing a threat to bacterial communities, animals, plants, and human health. There are also abundant natural MCNs in the environment, which play an important role in the environmental cycle of metals. The shape, size, and surface properties of MCNs have a significant impact on their migration, chemical and physical transformation, and biological intake in the environment. Therefore, the analysis and detection of MCNs in the environment should be aimed not only at quantifying their concentration and chemical composition, but also at determining their shape, particle size, and surface charge. In addition, for the detection of MCNs in the environment, challenges due to their low concentrations and the interference from complex environmental matrices must be overcome. A single detection technique is often insufficient for the analysis and detection of MCNs in a complex environment matrix. Therefore, the development of an effective and reliable online hyphenated technique is urgently needed for the separation and detection of MCNs in the environment. Such online hyphenated techniques should be able to eliminate the interference by complex matrices, improve the particle size detection range, and reduce the element detection limit. The online hyphenation of stationary phase-based separation techniques such as liquid chromatography and gel electrophoresis with inductively coupled plasma-mass spectrometry (ICP-MS) can effectively separate MCNs according to their particle size, with low element detection limits. However, these stationary phase-based separation techniques have a shortcoming of the adsorption of nanoparticles on the stationary phase, which leads to blockage of separation channels and low recoveries of nanoparticles. The online hyphenation of a non-stationary phase separation technique with ICP-MS also shows strong nanoparticle separation ability and low element detection limits, so that the problem of colloid blockage in stationary phase-based separation can be resolved. This method is very promising for the rapid and accurate characterization of the particle size distribution and chemical composition of MCNs. However, it cannot provide information about the nanoparticle number concentration of MCNs and the elemental content of a single MCN. In complex environmental samples, pure MCNs cannot be effectively distinguished from MCNs with environmental corona having different thicknesses or pure MCNs adsorbed on/hetero-agglomerated with inorganic/organic colloids. Online coupling single-particle ICP-MS (SP-ICP-MS), an emerging particle detection technique with non-stationary phase separation, can effectively help overcome the above shortcomings. This method can provide information on the hydrodynamic diameter, metal mass-derived diameter, total number concentration, size-dependent number, and size-dependent mass concentration of MCNs. Therefore, it enables comprehensive characterization of MCNs based on a variety of three-dimensional contour plot chromatograms. This review summarizes the separation mechanisms and applicable detectors for three commonly used non-stationary phase separation techniques: hydrodynamic chromatography (HDC), capillary electrophoresis (CE), and field-flow fractionation (FFF). In addition, it focuses on the characteristics and applications of online-coupling non-stationary phase separation with ICP-MS and SP-ICP-MS. Regarding FFF, this review focuses on the separation techniques that are suitable for online coupling with ICP-MS, such as sedimentation FFF and flow FFF (symmetrical flow FFF, asymmetrical flow FFF, and hollow fiber flow FFF). In addition, the characteristics of the online hyphenation of three non-stationary phase separations, HDC, CE, and flow FFF, with ICP-MS are compared, including the separation mechanism, sample volume, analytical time, detection sensitivity, size range, size resolution, recovery, reproducibility, and capability for ion analysis. Finally, this review proposes the prospects for future development of the online hyphenation of non-stationary phase separation techniques with ICP-MS and SP-ICP-MS.

Due to the increased applications of engineered elemental metal nanoparticles (EMNPs) in recent years, increased attention has been devoted to their release into the environment. EMNPs pose potenti...

The Eastern China Marginal Seas (ECMS) have been facing a variety of environmental problems, including mercury (Hg) pollution. Although several previous studies have been focused on mass balance of Hg in the ECMS, the contribution of Hg transport at the sediment-water interface remains unclear. This study was aimed to access and quantify the importance of sediment-water transport processes in Hg cycling. Significantly positive correlations were observed between Hg concentrations in the overlying and bottom water and the diffusion rates of Hg from sediment to the water. Approximately 2-3 times higher of THg concentrations in the entire water column were observed in a winter cruise with strong waves which was supposed to strengthen the resuspension process. The mass budget of Hg in the ECMS further showed that diffusion and resuspension processes accounted for approximate 46%, 60%, and 16% of total input Hg in the BS, YS, and ECS, respectively. These results suggest that the sediment-water transport processes play an important role in Hg cycling in the ECMS. As an important "pool" of Hg in the ECMS, the transport of Hg at the sediment-water interface may affect the long-term risk assessment of Hg in these systems.

Contact electrification between water and a solid surface is crucial for physicochemical processes at water–solid interfaces. However, the nature of the involved processes remains poorly understood, especially in the initial stage of the interface formation. Here we report that H 2 O 2 is spontaneously produced from the hydroxyl groups on the solid surface when contact occurred. The density of hydroxyl groups affects the H 2 O 2 yield. The participation of hydroxyl groups in H 2 O 2 generation is confirmed by mass spectrometric detection of 18 O in the product of the reaction between 4-carboxyphenylboronic acid and 18 O–labeled H 2 O 2 resulting from 18 O 2 plasma treatment of the surface. We propose a model for H 2 O 2 generation based on recombination of the hydroxyl radicals produced from the surface hydroxyl groups in the water–solid contact process. Our observations show that the spontaneous generation of H 2 O 2 is universal on the surfaces of soil and atmospheric fine particles in a humid environment.

The transformation of mercury (Hg) in the environment plays a vital role in the cycling of Hg and its risk to the ecosystem and human health. Of particular importance are Hg oxidation/reduction and methylation/demethylation processes driven or mediated by the dynamics of light, microorganisms, and organic carbon, among others. Advances in understanding those Hg transformation processes determine our capacity of projecting and mitigating Hg risk. Here, we provide a critical analysis of major knowledge gaps in our understanding of Hg transformation in nature, with perspectives on approaches moving forward. Our analysis focuses on Hg transformation processes in the environment, as well as emerging methodology in exploring these processes. Future avenues for improving the understanding of Hg transformation processes to protect ecosystem and human health are also explored.

Sediment is the primary hotspot for microbial production of toxic and bio-accumulative methylmercury (MeHg). Common remediation strategies such as sediment dredging and capping can be too expensive and cannot degrade MeHg efficiently. Here, we constructed an Escherichia coli strain overexpressing merB gene (DH5α J23106) and assessed the effectiveness of this recombinant strain in degradation of MeHg in culture medium and sediment. DH5α J23106 can efficiently degrade MeHg (with initial concentration from 0.01 to 50 ng/mL) to more than 81.6% in a culture medium under anoxic and oxic conditions. Enriched isotope addition (

Clarifying the sources and fates of atmospheric mercury (Hg) in the Antarctic is crucial to understand the global Hg circulation and its impacts on the fragile ecosystem of the Antarctic. Herein, the annual variations in the isotopic compositions of total gaseous Hg (TGM), with 5-22 days of sampling duration for each sample, were presented for the first time to provide isotopic evidence of the sources and environmental processes of gaseous Hg around the Chinese Great Wall Station (GWS) in the western Antarctic. Different from the Arctic tundra and lower latitude areas in the northern hemisphere, positive δ202Hg (0.58 ± 0.21‰, mean ± 1SD) and negative Δ199Hg (-0.30 ± 0.10‰, mean ± 1SD) in TGM at the GWS indicated little impact from the vegetation-air exchange in the Antarctic. Correlations among TGM Δ199Hg, air temperature, and ozone concentrations suggested that enhanced katabatic wind that transported inland air masses to the continental margin elevated TGM Δ199Hg in the austral winter, while the surrounding marine surface emissions controlled by sea-ice dynamics lowered TGM Δ199Hg in the austral summer. The oxidation of Hg(0) might elevate Δ199Hg in TGM during atmospheric Hg depletion events but have little impact on the seasonal variations of atmospheric Hg isotopes. The presented atmospheric Hg isotopes were essential to identify the transport and transformation of atmospheric Hg and further understand Hg cycling in the Antarctic.

Understanding the presence and dynamics of chemical pollutants in individual cells is fundamentally important for their trafficking, fate, and toxicity in humans. The presence of molecular components (i.e., proteins and mRNA) in individual cells of higher organisms is considered a stochastic event. The characteristics of chemical pollutants, as extrinsic compounds, in subpopulation of human cells on single-cell basis have not been explored yet. Here, we demonstrated the lead (Pb) content in individual mature erythrocytes (m-erythrocytes) of Pb-intoxicated patients, and healthy subjects exhibited a unified pattern in probability distribution (gamma distribution) and dynamics, despite being highly heterogeneous. The Pb content in individual m-erythrocytes decreased with the lifetime of m-erythrocytes. Meanwhile, the distribution and dynamics were found to be highly related to the Pb content in m-erythrocytes and was independent of patients and their status. This is the first study to analyze the distribution pattern of chemical pollutants at a single-cell level in higher organisms. This study sheds light on the molecular mechanism of Pb trafficking and fate in humans and the search for an efficient strategy to improve Pb excretion during Pb treatment.

The Yellow Sea (YS) of China is facing severe mercury (Hg) pollution problems while the concentration of Hg in the sediment is relatively low compared to its high discharge intensity, whose mechanisms are still unclear. Here, we performed batch experiments to investigate the Hg adsorption capacity of the YS sediments. Freundlich isothermal adsorption simulation results showed that the parameters K

Per- and polyfluoroalkyl substances (PFAS) is the emerging contaminants of critical concern. Comprehensive understanding of the transport and fate of PFAS in the vadose-zone, a type of water-unsaturated porous media, is key to determination of the risks of the PFAS contamination in the subsurface and to the development of the effective remediation strategies. PFAS transport in the unsaturated porous media is a complex process. In order to disclose the main factors controlling the PFAS transport in unsaturated porous media, we develop the theoretical model based on the dimensionless governing equations for the transient water flow and PFAS transport. The effects of the dimensionless parameters and numbers on the PFAS transport in 2D unsaturated porous media are uncovered based on the second order accurate finite volume method. We find that the retardation numbers and the dimensionless parameters relevant to the properties of porous media as well as the relation between the surface tension and the PFAS concentration play an important role in the PFAS transport in the unsaturated porous media. The effects of the Péclet numbe, Damköhler numbers, and fraction of instantaneous sorption are not significant, however. These findings provide a better understanding of the PFAS transport in vadose zone.

Mercury (Hg) is a global pollutant of health concern due to formation and bioaccumulation of methylmercury (MeHg) during its biogeochemical cycle. Coastal areas are important regions in the biogeochemical cycling of Hg (Liu et al., 2017), where often-occurring natural and anthropogenic perturbations affect Hg transport and transformation and the associated health risk from Hg. The rapidly growing mariculture associated with the rising global demand for food may have a profound effect on coastal Hg cycling, due to the environmental alterations (e.g., resuspension and sedimentation) caused by maricultural activities (e.g., bottom sowing and harvesting). Through simulating the effect of water scouring, a common harvesting method, this study investigated Hg migration and distribution in particulate and dissolved phases in Laizhou Bay of Bohai Sea, China, where mariculture exists extensively. Particulate total and methyl Hg (PTHg and PMeHg) in water (expressed as ng/L) increased sharply due to the resuspension of sediment, but decreased rapidly after a one-off scouring event. When normalized by particle mass, PTHg and PMeHg (ng/g) in suspended sediment particles were significantly higher than that in the initial sediment, suggesting a higher distribution coefficient and higher affinity to bind Hg in the suspended particles. This may be due to the smaller particle sizes, and higher contents of organic matter and Fe/Mn of suspended sediments compared to the initial sediment. While the concentrations of dissolved THg (DTHg) in water column showed minimum changes or decreased, dissolved MeHg (DMeHg) concentrations increased sharply after the perturbation, due to the possible release of MeHg from porewater and potential Hg methylation during the event. These results provide fundamental information needed for ecological and health risk assessment of Hg in mariculture, and highlights the increased mobility and bioaccumulation of MeHg during anthropogenic perturbations in these areas.

The biogeochemical transformation of gold (Au), i.e. its dissolution and re-precipitation, is critical in supergene transport of Au and formation of Au granules. Besides biogenic reduction, the formation Au granules can also be driven by chemical processes. Previous studies have showed the formation of Au nanoparticles (AuNPs) from ionic Au(III) can be mediated by dissolved organic matter under sunlight. In this letter, we further demonstrated that these AuNPs can further slowly (in years) grow into visible Au granules. Different sized nano-flower and fractal dendrite-like branched gold structures (from tens of nanometres to over 100 μm) were observed in the Au granule sample. This growth of AuNPs into visible Au granules may play a critical role in the supergene mineralization and enrichment of secondary Au and drive the biogeochemical cycle of Au.

Mercurous Hg (Hg(I)) is, from the perspective of chemistry, an inevitable intermediate in Hg(II)/Hg(0) redox, presumably playing a critical role in the environmental transformation of common toxic ...

The ability to assess the responses of cells exposed to nanoparticles at the single cell level will lead to mechanistic understanding of their toxicity and safety. Here, we demonstrated the heterog...

The wide use of silver ions (Ag+) and silver nanoparticles (AgNPs) and their inevitable release into the environment have caused great concern over their environmental and health risks. The understanding of their uptake and accumulation by plants, especially food crops, is important to evaluate their risks. We reported herein the distinct accumulation and translocation characteristics of Ag+ and AgNPs in a rice plant (Oryza sativa L.) at exposure doses of 2, 5, 10, and 20 mg L−1, as well as the critical impact of iron plaque on their assimilation by the plant. As revealed by silver K-edge X-ray absorption near-edge structure (XANES), Ag+ in/on the roots was exclusively transformed into AgCl with Cl− in hydroponic medium. As a result, AgCl maintained Ag+ on the root surface, lowering its bioavailability and translocation (with translocation factors, TFs, from 0.44 × 10−3 to 1.79 × 10−3). On the contrary, AgNPs were assimilated and translocated more effectively (with TFs from 2.44 × 10−3 to 1.23 × 10−2) in comparison to Ag+, although a fraction was transformed into ionic silver species. XANES demonstrated that the iron plaque present on the rice roots could oxidize AgNPs into ionic Ag species, such as AgCl and Ag+–thiol complexes, and increase the uptake and translocation of silver in the rice plant. Compared to iron plaque, dissolved iron was less effective in oxidizing AgNPs. Our findings highlighted the importance of Ag species interconversion and iron plaque in the uptake and translocation of Ag, providing useful data for an improved risk assessment of AgNPs and Ag+ under environmental scenarios.

Polycyclic aromatic hydrocarbons (PAHs) formation from the pyrolysis of waste tires is inevitable because of the complexity of tire formulations and the addition of certain chemicals. In this study, the formation behavior and distribution of PAHs in three-phases were investigated from waste tires under pyrolysis conditions. The influencing factors including the temperature, heating rate, holding time, particle size, catalyzer, and atmosphere, were systematically evaluated. The results showed that PAHs were mainly concentrated in pyrolysis oil (94.59-99.03%), followed by the gas phase (0.96-5.34%), and their content was very low in the solid phase (0.01-0.99%). A higher temperature and slower heating rate lead to partial PAHs decomposition, thus reducing their emissions. The overall formation of PAHs can be inhibited when pyrolyzing coarse-grained tire powder. Furthermore, the PAHs formation mechanisms in waste tires were determined through reaction molecular dynamics, electron paramagnetic resonance, and intermediate products. Tires were mainly decomposed into benzene series, *C