Search Results (17)

The present study focuses on the dynamics of trace metals (TM) in two European rivers, the Mosel and the Meuse. A deterministic description of hydro-sedimentary processes has been performed. The model used to describe pollutant transport and dilution at the watershed scale has been enhanced with the implementation of the MicMod sub-model. The objective of this study is to characterise the dynamics of TM in the water column and bed sediment. A multi-class grain size representation has been developed in MicMod. The dissolved and particulate TM phases have been calculated with specific partitioning coefficients associated with each suspended sediment (SS) class. The processes involved in TM fate have been calibrated in MicMod, including settling velocity, TM releases from the watershed (point and diffuse loads), etc. Following the calibration of the parameters involved in TM transport within the river ecosystem, the main goal is to describe TM dynamics using a pressure–impact relationship model. It was demonstrated that the description of at least one class of fine particles is necessary to obtain an adequate representation of TM concentrations. The focus of this study is low flow periods, which are characterised by the presence of fine particles. The objective is to gain a deeper understanding of the processes that control the transport of TM. This paper establishes consistent pressure–impact relationships between TM loads (urban, industrial, soils) from watersheds and concentrations in rivers. Full article

Ascorbic acid (AH₂) is a commonly used additive in food products. In wheat breadmaking, it is, for example, added to flour for its dough strengthening and bread volume-enhancing effects. While these bread property-enhancing effects are well known, the final chemical fate of AH₂ in breadmaking applications remains nearly undocumented. This study tries to shed light on the chemical fate of AH₂ in wheat breadmaking by investigating the chemical and enzymatic conversion of AH₂ and its reaction products using ¹³C NMR spectroscopy in combination with AH₂ labelled with ¹³C on the C₃ carbon. Following the chemical conversion of AH₂ as function of time, in ultra-pure water, tap water, and wheat flour extracts, in the presence and absence of dissolved O₂ and glutathione (GSH), the specific impact of the presence of trace metal ions, dissolved oxygen and endogenous GSH on the oxidation of AH₂ could be elucidated. Full article

Introduction/Objectives: Since the biological activities and toxicities of ‘foreign’ and/or excess levels of metal ions are predominantly determined by their precise molecular nature, here we have employed high-resolution ¹H NMR analysis to explore the ‘speciation’ of paramagnetic Ni(II) ions in human saliva, a potentially rich source of biomolecular Ni(II)-complexants/chelators. These studies are of relevance to the in vivo corrosion of nickel-containing metal alloy dental prostheses (NiC-MADPs) in addition to the dietary or adverse toxicological intake of Ni(II) ions by humans. Methods: Unstimulated whole-mouth human saliva samples were obtained from n = 12 pre-fasted (≥8 h) healthy participants, and clear whole-mouth salivary supernatants (WMSSs) were obtained from these via centrifugation. Microlitre aliquots of stock aqueous Ni(II) solutions were sequentially titrated into WMSS samples via micropipette. Any possible added concentration-dependent Ni(II)-mediated pH changes therein were experimentally controlled. ¹H NMR spectra were acquired on a JEOL JNM-ECZ600R/S1 spectrometer. Results: Univariate and multivariate (MV) metabolomics and MV clustering analyses were conducted in a sequential stepwise manner in order to follow the differential effects of increasing concentrations of added Ni(II). The results acquired showed that important Ni(II)-responsive biomolecules could be clustered into distinguishable patterns on the basis of added concentration-dependent responses of their resonance intensities and line widths. At low added concentrations (71 µmol/L), low-WMSS-level N-donor amino acids (especially histidine) and amines with relatively high stability constants for this paramagnetic metal ion were the most responsive (severe resonance broadenings were observed). However, at higher Ni(II) concentrations (140–670 µmol/L), weaker carboxylate O-donor ligands such as lactate, formate, succinate, and acetate were featured as major Ni(II) ligands, a consequence of their much higher WMSS concentrations, which were sufficient for them to compete for these higher Ni(II) availabilities. From these experiments, the metabolites most affected were found to be histidine ≈ methylamines > taurine ≈ lactate ≈ succinate > formate > acetate ≈ ethanol ≈ glycine ≈ N-acetylneuraminate, although they predominantly comprised carboxylato oxygen donor ligands/chelators at the higher added Ni(II) levels. Removal of the interfering effects arising from the differential biomolecular compositions of the WMSS samples collected from different participants and those from the effects exerted by a first-order interaction effect substantially enhanced the statistical significance of the differences observed between the added Ni(II) levels. The addition of EDTA to Ni(II)-treated WMSS samples successfully reversed these resonance modifications, an observation confirming the transfer of Ni(II) from the above endogenous complexants to this exogenous chelator to form the highly stable diamagnetic octahedral [Ni(II)-EDTA] complex (K_stab = 1.0 × 10¹⁹ M⁻¹). Conclusions: The results acquired demonstrated the value of linking advanced experimental design and multivariate metabolomics/statistical analysis techniques to ¹H NMR analysis for such speciation studies. These provided valuable molecular information regarding the identities of Ni(II) complexes in human saliva, which is relevant to trace metal ion speciation and toxicology, the in vivo corrosion of NiC-MADPs, and the molecular fate of ingested Ni(II) ions in this biofluid. The carcinogenic potential of these low-molecular-mass Ni(II) complexes is discussed. Full article

Plant-growth-promoting rhizobacteria (PGPR), in addition to their well-known direct effects on plant growth and development, have been reported to be effective in plant abiotic (trace metal, drought, etc.) and biotic (phytopathogens, insects, etc.) stress management. PGPRs are involved in shaping the fate of trace metals in the rhizosphere and plants and thus may also reduce trace metal stress in plants. The aims of our study were to isolate and select indigenous trace-metal-resistant PGP strains and investigate their effects on maize germination and early development. The roles of the two selected strains, Pseudomonas koreensis and Serratia liquefaciens isolated from trace-metal-contaminated soil were investigated to mitigate trace metal stress in 21-day-old Zea mays seedlings. In the present study, 13 bacterial strains were isolated and screened for PGP traits under normal and trace metal stress conditions. The effect of two selected strains was further studied on plant experiments. The germination process, plant growth parameters (length, weight, dry matter content), photosynthetic activity, GPOX activity, trace metal accumulation, and translocation in microbes inoculated Cd (0.5 mM), Zn (1 mM), and Cd + Zn (0.1 + 0.5 mM) treated maize plants was studied. Our results revealed that trace metal toxicity, in terms germination and growth parameters and antioxidant enzyme activity, was enhanced upon inoculation with Pseudomonas koreensis BB2.A.1. Chlorophyll content and accumulation studies showed enhanced results following inoculation with Serratia liquefaciens BB2.1.1. Therefore, both bacterial strains possessed beneficial traits that enabled them to reduce metal toxicity in maize. Full article

Few studies have quantified the complex flux of trace metals from mine tailings to rivers through water erosion, especially in the semi-arid region of North Morocco (Zaida mine) where soil erosion is a severe issue. This study applies (i) methods to understand and estimate the complex flux of trace metals from mine tailings to rivers, using the RUSLE model combined with the concentration of trace metals in the soil and additionally (ii) pollution indices and statistical analyses to assess the sediment contamination by Cd, Cu, Pb, and Zn. Our study revealed that the basin has a low erosion rate, with an average of 9.1 t/ha/yr. Moreover, the soil contamination is particularly high at the north of the mine tailings, as prevailing winds disperse particles across the basin. The assessment of the sediments indicated that Pb is the main contaminant, with concentrations exceeding 200 mg/kg specifically downstream of the tailings. This study also identified high a concentration of trace elements 14 km away from the tailings alongside the Moulouya river, due to the specific hydrological transport patterns in the area. This research contributes to a better understanding of the transport and fate of the trace metals in mining areas. It proposes a replicable method that can be applied in other regions to assess the contamination flows and thereby assist water resource management. Full article

Fe/Mn (hydr)oxides are metallic compounds that exhibit significant redox activity in environmental media and play a pivotal role in geochemical processes, thereby influencing the fate of metals in porous media. The morphology of Fe/Mn (hydr)oxides in natural environments and their interactions with trace metals are significantly influenced by the presence of natural organic matter (NOM). However, there is limited understanding regarding the formation, transport, and stability of Fe/Mn (hydr)oxides in the environment. The present study employed humic acid (HA) as a representative NOM material to investigate the positive influence of HA on the formation of Fe/Mn colloids. However, there remains limited comprehension regarding the formation, transport, and stability of Fe/Mn (hydr)oxides in the natural environment. In this study, we investigated the positive effect of natural organic matter (NOM) on the formation of Fe/Mn colloids using humic acid (HA) as a representative NOM material. We comprehensively characterized the chemical and physical properties of HA–Fe/Mn colloids formed under various environmentally relevant conditions and quantitatively analyzed their subsequent aggregation and stability behaviors. The findings suggest that the molar ratios of C to Fe/Mn (hydr)oxide play a pivotal role in influencing the properties of HA–Fe/Mn colloids. The formation and stability of HA–Fe/Mn colloids exhibit an upward trend with increasing initial molar ratios of C to Fe/Mn. Redox and metal–carboxylic acid complexation reactions between HA and hydrated iron/manganese oxides play a pivotal role in forming colloidal HA–Fe/Mn complexes. Subsequent investigations simulating porous media environments have demonstrated that the colloidal structure resulting from the interaction between HA and Fe/Mn facilitates their migration within surrounding porous media while also enhancing their retention in the surface layers of these media. This study offers novel insights into the formation and stabilization mechanisms of HA–Fe/Mn colloids, which are pivotal for comprehending the behavior of Fe/Mn colloids and the involvement of Fe/Mn (hydr)oxides in geochemical cycling processes within porous media. Full article

The behaviour and fate of trace elements in surface waters are greatly affected by their chemical form in solution, but the aqueous speciation of dissolved trace elements in the North American Great Lakes has received relatively little attention. Here, we present results from geochemical equilibrium modelling with 2021 surface water quality data to examine the spatiotemporal dynamics of trace element speciation in the Great Lakes. The relative abundance of aqueous trace element species appeared consistent with variability in solution chemistry and followed basin-wide trends in pH, alkalinity, salinity, and nutrient levels. The speciation of alkali metals was dominated by free monovalent cations, and that of oxyanion-forming elements by oxoacids, whereas significant fractions (>1%) of other aqueous complexes were also evident for rare earth elements (e.g., Ce and Gd as carbonates), alkaline earth metals (e.g., Sr as sulfates), or transition metals (e.g., Zn as phosphates). Spatially, differences in the relative abundance of aqueous trace element species were <2 orders of magnitude, with the highest variation (~50-fold) occurring for select chloride-complexes, resulting from upstream-to-downstream salinity increases in the basin. Finally, simulations of various future water quality scenarios (e.g., decreasing P levels, increasing temperature and salinity) suggest that the speciation of most trace elements is robust temporally as well. This study demonstrates how considering aqueous speciation may help improve the understanding of trace element dynamics and support water quality management in the Great Lakes. Full article

Adsorption and desorption processes occurring on suspended and bed sediments were studied in two datasets from western Europe watersheds (Meuse and Mosel). Copper and zinc dissolved and total concentrations, total suspended sediment concentrations, mass concentrations, and grain sizes were analyzed. Four classes of mineral particle size were determined. Grain size distribution had to be considered in order to assess the trace metal particulate phase in the water column. The partitioning coefficients of trace metals between the dissolved and particulate phases were calculated. The objective of this study was to improve the description of the processes involved in the transportation and fate of trace metals in river aquatic ecosystems. Useful data for future modelling, management and contamination assessment of river sediments were provided. As it is confirmed by a literature review, the copper and zinc partitioning coefficients calculated in this study are reliable. The knowledge related to copper and zinc (e.g., partitioning coefficients) will allow us to begin investigations into environmental modelling. This modelling will allow us to consider new sorption processes and better describe trace metal and sediment fates as well as pressure–impact relationships. Full article

Zinc oxide (ZnO) particles have been used as dietary supplements because zinc is an essential trace element for humans. Along with the rapid development of nanotechnology, the use of ZnO nanoparticles (NPs) is increasing in the food industry, but their oral toxicity potential still remains to be answered. In this study, the effects of particle size and biological fate of ZnO on acute toxicity, toxicokinetics, and gene expression profiles in the livers were investigated after oral administration of ZnO NPs (N-ZnO), bulk-sized ZnO (B-ZnO) or Zn ions in rats. The plasma concentration-time profiles after a single-dose oral administration of ZnOs differed depending on particle/ionic forms and particle size, showing high absorption of Zn ions, followed by N-ZnO and B-ZnO, although in vivo solubility did not differ from particle size. No significant acute toxicity was found after oral administration of ZnOs for 14 days in rats. However, transcriptomic responses in the livers were differently affected, showing that metabolic process and metal biding were up-regulated by Zn ions and N-ZnO, respectively, which were not pronounced in the liver treated with B-ZnO. These findings will be useful to predict the potential oral toxicity of ZnO NPs and further mechanistic and long-term exposure studies are required to assume their safety. Full article

The rapid expansion of urban impervious surface areas complicates urban-scale heavy metal circulation among various environmental compartments (air, soil, sediment, water, and road dust). Herein, a level III steady-state aquivalence model evaluated the fate of heavy metals in Nanjing, China. Iron was the most abundant heavy metal in all environmental compartments, while cadmium was the rarest. Most simulated concentrations agreed with measured values within three logarithmic residuals. In the simulated heavy metal cycle, industrial emission contributed almost the entire input, whereas sediment burial was the dominant output pathway. The transfer fluxes between bottom sediment and water were the highest. Thereinto, the contribution of sediment resuspension for Fe and Mn was significantly higher than that to the other metal elements, which could partly explain why Fe and Mn are the major blackening ingredients in malodorous black rivers. Road dust was also an important migration destination for heavy metals, accounting for 3–45%, although soil and sediment were the main repositories of heavy metals in the urban environment. The impact of road dust on surface water should not be neglected, with its contribution reaching 4–31%. The wash-off rate constant W for road dust–water process was proved to be consistent with that for film–water and was independent of the type of heavy metals. Sensitivity analysis highlighted the notable background value effect on Fe and Mn. Full article

Roadside ditches play an important role in the quantity and quality of receiving waters. Very little, however, is known about the fate and transport of nutrients and trace metals in roadside ditches, especially their leaching to shallow groundwater. This study sought to document selected water quality constituent levels in infiltrated water (i.e., leachate) in roadside ditches maintained with permanent vegetation. Leachate sampling wells were installed in four roadside ditches, and water samples were collected from the wells following major rainfall events during the years 2016 and 2017. The samples were analyzed for nutrient and metal concentrations. Results indicated that nutrient concentrations in the water samples range from 0.00600 to 0.0107 mg/L for orthophosphate (PO₄–P), 0.00500 to 6.80 mg/L for nitrate (NO₃–N), 0 to 0.007 mg/L for nitrite (NO₂–N), and 0.0100 to 314 mg/L for chloride (Cl⁻). Concentrations of the metals examined varied between 0.0100 and 104 mg/L in water samples. While there was no specific pattern in both nutrient and metal concentrations when roadside ditches maintained with cool season grass were compared to those of warm season grass ditches, results suggest that grass types will likely affect differently uptake of nutrients and metals in the ditches. Full article

Many analytical techniques have limited sensitivity to quantify multi-walled carbon nanotubes (MWCNTs) at environmentally relevant exposure concentrations in wastewaters. We found that trace metals (e.g., Y, Co, Fe) used in MWCNT synthesis correlated with MWCNT concentrations. Because of low background yttrium (Y) concentrations in wastewater, Y was used to track MWCNT removal by wastewater biomass. Transmission electron microscopy (TEM) imaging and dissolution studies indicated that the residual trace metals were strongly embedded within the MWCNTs. For our specific MWCNT, Y concentration in MWCNTs was 76 µg g⁻¹, and single particle mode inductively coupled plasma mass spectrometry (spICP-MS) was shown viable to detect Y-associated MWCNTs. The detection limit of the specific MWCNTs was 0.82 µg L⁻¹ using Y as a surrogate, compared with >100 µg L⁻¹ for other techniques applied for MWCNT quantification in wastewater biomass. MWCNT removal at wastewater treatment plants (WWTPs) was assessed by dosing MWCNTs (100 µg L⁻¹) in water containing a range of biomass concentrations obtained from wastewater return activated sludge (RAS) collected from a local WWTP. Using high volume to surface area reactors (to limit artifacts of MWCNT loss due to adsorption to vessel walls) and adding 5 g L⁻¹ of total suspended solids (TSS) of RAS (3-h mixing) reduced the MWCNT concentrations from 100 µg L⁻¹ to 2 µg L⁻¹. The results provide an environmentally relevant insight into the fate of MWCNTs across their end of life cycle and aid in regulatory permits that require estimates of engineered nanomaterial removal at WWTPs upon accidental release into sewers from manufacturing facilities. Full article

In the environment, a pollutant is rarely present alone, and other contaminants can influence its fate. To investigate the influence of the presence of other pollutants on the sorption of pesticides and trace metals (TM), the adsorption of Aclonifen, alachlor, Cd and Cu onto suspended particulate matter (SPM) was studied. SPM was isolated during the flood event of May 2010 in the Save agricultural watershed of SW France. Adsorption equilibrium was reached after 2 h of contact with SPM for pesticides and 24 h for TM. To simulate natural conditions, the SPM load allowing a maximum adsorption of pollutants was set at 1 g L⁻¹ and the concentration of pollutants at 10 μg L⁻¹. These factors being established, the co-presence experiments showed that most contaminants were influenced by the presence of other pollutant(s) in the water, trace metals to a lesser extent than pesticides. The mutual influence can be either competition for the same adsorption sites or formation of new complexes between pollutants. These phenomena can modify the adsorption capacities of each pollutant. The order of introduction into the aqueous solution also influenced the amount of adsorption of pollutants onto SPM. These results open new perspectives on the fate of pollutants. Full article

The HYDRUS-1D and HYDRUS (2D/3D) computer software packages are widely used finite element models for simulating the one-, and two- or three-dimensional movement of water, heat, and multiple solutes in variably-saturated media, respectively. While the standard HYDRUS models consider only the fate and transport of individual solutes or solutes subject to first-order degradation reactions, several specialized HYDRUS add-on modules can simulate far more complex biogeochemical processes. The objective of this paper is to provide a brief overview of the HYDRUS models and their add-on modules, and to demonstrate possible applications of the software to the subsurface fate and transport of chemicals involved in coal seam gas extraction and water management operations. One application uses the standard HYDRUS model to evaluate the natural soil attenuation potential of hydraulic fracturing chemicals and their transformation products in case of an accidental release. By coupling the processes of retardation, first-order degradation and convective-dispersive transport of the biocide bronopol and its degradation products, we demonstrated how natural attenuation reduces initial concentrations by more than a factor of hundred in the top 5 cm of the soil. A second application uses the UnsatChem module to explore the possible use of coal seam gas produced water for sustainable irrigation. Simulations with different irrigation waters (untreated, amended with surface water, and reverse osmosis treated) provided detailed results regarding chemical indicators of soil and plant health, notably SAR, EC and sodium concentrations. A third application uses the HP1 module to analyze trace metal transport involving cation exchange and surface complexation sorption reactions in a soil leached with coal seam gas produced water following some accidental water release scenario. Results show that the main process responsible for trace metal migration in soil is complexation of naturally present trace metals with inorganic ligands such as (bi)carbonate that enter the soil upon infiltration with alkaline produced water. The examples were selected to show how users can tailor the required model complexity to specific needs, such as for rapid screening or risk assessments of various chemicals nder generic soil conditions, or for more detailed site-specific analyses of actual subsurface pollution problems. Full article

The mobility of selected heavy metals in trace concentrations was investigated in a standard OECD soil irrigated with the effluent of a real municipal wastewater treatment plant. While Cd, Cu and Ni accumulation-migration patterns were mainly influenced by the mobility of colloids generated from soil organic and inorganic matter, Zn mobility was more influenced by the wastewater content of dissolved organic matter and by its salinity. Metal accumulation caused by interaction with colloids resulted in contamination peaks both in different zones of the soil column and in the leaching solution. The release of metals in the leachate was correlated to the contemporary release of silicates from kaolinite and dissolved organic matter, identified through UV absorbance and chemical oxygen demand monitoring. The hypothesized colloidal mobilization was confirmed by spectroscopic studies. The highly heterogeneous complexes of organic and inorganic molecules responsible for metal transport through soil appeared to be structured in highly stable micellar aggregates. Full article