The complexation of heavy metals with dissolved organic matter (DOM) in the environment influences the solubility and mobility of these metals. In this paper, we measured the complexation of Cu, Cd, ...Zn, Ni, and Pb with DOM in the soil solution at pH 3.7−6.1 using a Donnan membrane technique. The results show that the DOM-complexed species is generally more significant for Cu and Pb than for Cd, Zn, and Ni. The ability of two advanced models for ion binding to humic substances, e.g., model VI and NICA-Donnan, in the simulation of metal binding to natural DOM was assessed by comparing the model predictions with the measurements. Using the default parameters of fulvic and humic acid, the predicted concentrations of free metal ions from the solution speciation calculation using the two models are mostly within 1 order of magnitude difference from the measured concentrations, except for Ni and Pb in a few samples. Furthermore, the solid−solution partitioning of the metals was simulated using a multisurface model, in which metal binding to soil organic matter, dissolved organic matter, clay, and iron hydroxides was accounted for using adsorption and cation exchange models (NICA-Donnan, Donnan, DDL, CD-MUSIC). The model estimation of the dissolved concentration of the metals is mostly within 1 order of magnitude difference from those measured except for Ni in some samples and Pb. The solubility of the metals depends mainly on the metal loading over soil sorbents, pH, and the concentration of inorganic ligands and DOM in the soil solution.
Towards a renewed research agenda in ecotoxicology Artigas, Joan; Arts, Gertie; Babut, Marc ...
Environmental pollution (1987),
2012, 2012-Jan, 2012-01-00, 20120101, 2012-01, Letnik:
160, Številka:
1
Journal Article
Recenzirano
New concerns about biodiversity, ecosystem services and human health triggered several new regulations increasing the need for sound ecotoxicological risk assessment. The PEER network aims to share ...its view on the research issues that this challenges. PEER scientists call for an improved biologically relevant exposure assessment. They promote comprehensive effect assessment at several biological levels. Biological traits should be used for Environmental risk assessment (ERA) as promising tools to better understand relationships between structure and functioning of ecosystems. The use of modern high throughput methods could also enhance the amount of data for a better risk assessment. Improved models coping with multiple stressors or biological levels are necessary to answer for a more scientifically based risk assessment. Those methods must be embedded within life cycle analysis or economical models for efficient regulations. Joint research programmes involving humanities with ecological sciences should be developed for a sound risk management.
New regulations and innovative biological tools change the way ecotoxicological risk assessment should be seen. A new research agenda is therefore needed.
A major challenge in nanomaterial environmental risk assessment is to identify whether different manufactured materials need to be assessed individually or if they can be grouped for assessments ...based on selected properties. To date, NPs are grouped on the basis that they are manufactured (
e.g.
, pristine materials), but these are rarely present in the environment as many nanomaterials transform before and after entry into the environment. To assess how transformations change relative hazard and, therefore, the potential for grouping, we assessed the toxicity of silver nanoparticles (NPs) of varying sizes (20, 50 nm) and surface functionalisation (PVP, citrate) in their metallic and sulphidised forms to
Caenorhabditis elegans
in a standard medium lacking organic matter and in extracted soil pore water. The metallic Ag NPs showed only small variations in toxicity, with citrate functionalisation reducing potency and small citrate NPs being least toxic. The toxicity of sulphidised particles was lower than for the pristine forms in all cases, however relative differences among the transformed materials were greater than for the metallic forms. Exposure in soil pore water further reduced toxicity of the citrate, but not PVP functionalised NPs. Overall, transformation reduced citrate functionalised NP toxicity in a size dependent manner, whereas PVP coating preserved similarities across sizes and transformations. Thus despite similar toxicity of the pristine materials, grouping of NPs with a similar coating independent of size appeared only possible for materials with the more persistent PVP surface coating and then only when transformations were first considered.
Pristine and transformed variant nanomaterials were assessed to identify whether chemical speciation changes and ecocorona association affected relatively toxicities and the potential for grouping.
Metal contamination of soils may pose long-term risks to ecosystem health if not properly managed. Future projection of contamination trends, coupled with ecological assessment, is needed to assess ...such risks. This can be achieved by coupling dynamic models of soil metal accumulation and loss with risk assessment on the basis of projected metal levels. In this study, we modeled the long-term dynamics of Cu, Zn, and Cd in agricultural topsoils of a northern Chinese catchment (Guanting reservoir) and related projected metal levels to 2060 to ecological risk. Past metal dynamics were simulated using historical metal inputs from atmospheric deposition, irrigation, fertilizers, and animal manures. Modeling future dynamics was done using scenarios of projected metal input rates. Ecological risk assessment was done using the Potentially Affected Fraction () approach to estimate the combined toxic pressure due to the three metals. Modeled labile soil metals agreed well with measurements from monitoring in 2009 following adjustment of the porewater dissolved organic concentration. Metals were predicted to be largely retained in the topsoil. Projections were sensitive to changes in imposed soil pH, organic matter, and porewater dissolved organic carbon. Modeling suggests that decreases in input rates to between 5% and 7.5% of 2009 levels are required to prevent further accumulation. Computed s suggest zinc makes the greatest contribution to ecological risk. Under the most conservative estimate of , the threshold of potential ecological risk was reached before 2060 in two of the three future input scenarios.
A number of geodisposal concepts for intermediate level radioactive waste involve geological emplacement within cementitious repositories. Such facilities, once rehydrated with groundwater, will ...create high pH environments due to aqueous phase reaction of the cements. This work focuses on the interactions of several important long-lived radionuclide cations with dissolved organic matter (DOM) constituents (humic and fulvic acids) under high pH conditions. We also sought to test the comprehensive speciation model WHAM/Humic Ion Binding Model VII for these specific conditions. Results for Th demonstrate high fractions present as organic complexes at all pH values. Binding of neptunyl to DOM shows a maximum over the pH range expected within an evolving repository. Uranyl exhibits decreasing binding with pH, however, the majority of metal in solution is present as organic complexes under the lower pH conditions investigated (10–10.5). We have updated the WHAM/Model VII binding values for UO22+, and have for the first time added NpO2+ values to the database. These updates now allow application of the model for more complex mixtures across the entire repository pH range. Calculations for three simulated cement interstitial waters (representing different degradation phases) suggest U(VI) and Np(V) are not likely to be significantly bound to DOM under these conditions.
Speciation modelling of uranium (as uranyl) and thorium, in four freshwaters impacted by mining activities, was used to evaluate (i) the influence of the co–contaminants present on the predicted ...speciation, and (ii) the influence of using nine different model/database combinations on the predictions. Generally, co–contaminants were found to have no significant effects on speciation, with the exception of Fe(III) in one system, where formation of hydrous ferric oxide and adsorption of uranyl to its surface impacted the predicted speciation. Model and database choice on the other hand clearly influenced speciation prediction. Complexes with dissolved organic matter, which could be simulated by three of the nine model/database combinations, were predicted to be important in a slightly acidic, soft water. Model prediction of uranyl and thorium speciation needs to take account of database comprehensiveness and cohesiveness, including the capability of the model and database to simulate interactions with dissolved organic matter. Measurement of speciation in natural waters is needed to provide data that may be used to assess and improve model capabilities and to better constrain the type of predictive modelling work presented here.
•Co–contaminants did not largely influence predicted U or Th speciation in freshwaters.•The predicted speciation depended on the model formulation and database.•Speciation modelling should be done with up to date databases.
The Intermediate Dynamic Model for Metals (IDMM) is a model for prediction of the pools of metals (Ni, Cu, Zn, Cd, Pb) in topsoils of catchments resulting from deposition of metals from the ...atmosphere. We used the model to simulate soil metal pools from 1400 onwards in ten UK catchments comprising semi-natural habitats, and compared the results with present day observations of soil metal pools. Generally the model performed well in simulating present day pools, and further improvements were made to simulations of Ni, Cu, Zn and Cd by adjusting the strength of metal adsorption to the soils. Some discrepancies between observation and prediction for Pb appeared to be due either to underestimation of cumulative deposition, or to overestimation of the metal pool under ‘pristine’, pre-industrial conditions. The IDMM provides a potential basis for large scale assessment of metal dynamics in topsoils.
•The Intermediate Dynamic Model for Metals (IDMM) is a new model for long term metal dynamics in semi-natural catchments.•The model describes well current day metal pools in ten semi-natural catchments of the UK.•The IDMM has clear potential for large scale simulation of metal dynamics in soils.
The Intermediate Dynamic Model for Metals predicts the present day pools of Ni, Cu, Zn, Cd and Pb in semi-natural catchment soils of the UK.