Evaluating the arsenic attenuation of soil amended with calcium–magnesium composites of different particle sizes

An attenuation layer composed of ground mixed with stabilising agents can prevent the contamination of the surrounding area when using soils and rocks with geogenic contaminants in embankments. The optimum particle size of the stabilising agent must be selected based on the requirements of the construction site because the mechanical and chemical properties of the attenuation layer are site-specific. However, the relationship between the particle size of the stabilising agent and the attenuation performance of soil–agent mixtures has yet to be fully clarified. This study employs batch sorption tests to evaluate the attenuation of arsenic by a soil mixed with a calcium–magnesium composite with different particle sizes, ranging from powder particles (<0.075 mm in size) to granular particles with diameters between 2.0 and 9.5 mm. Amended soil more effectively attenuates the contaminant than the original soil. In one experiment, a stabilising agent of granular particles (between 2.0 and 9.5 mm) for the amendment increased the soil’s partition coefficient Kd from 14.5 to 22.2 cm³/g, which is more than a 50% improvement in the attenuation. Using a stabilising agent with a smaller particle size for the amendment has a greater impact. Kd increases linearly as the particle size of the stabilising agent decreases down to 0.075 mm. Using the Kd from laboratory tests, simulations with a one-dimensional advection–dispersion equation demonstrate the durability of the attenuation layer. Both the powder and the granular particles show promise as attenuation layer materials

Granular material development applied in an experimental section for civil engineering purposes

In this study, a granular material (GM) derived from wastes generated in waste-to-energy plants was developed. Weathered bottom ash (WBA) and air pollution control (APC) ashes obtained from municipal solid waste incineration (MSWI) were used as raw materials. A mortar (M) with 50 wt. % of APC and 50 wt. % of Ordinary Portland Cement (OPC) CEM-I was prepared. The GM formulation was 20 wt. % M and 80 wt. % WBA. At the laboratory scale, WBA, APC, M, and crushed GM were evaluated by means of dynamic leaching (EN 12457-4) tests, and WBA, M, and crushed GM by percolation column (CEN/TS 16637) tests. The metal(loid)s analyzed were below the non-hazardous limits, regarding the requirement of the metal(loid)s released for waste revalorization. In order to simulate a road subbase real scenario, the crushed GM was tested in an experimental section (10 × 20 × 0.2 m). During a 600-day period, the leachates generated by the percolation of rainwater were collected. This research shows outstanding results regarding the metal(loid)s released for both the 'accumulated' and 'punctual' leachates collected. An accomplishment in the immobilization of metal(loid)s from APC residues was achieved because of the encapsulation effect of the cement. The GM formulation from both MSWI wastes can be considered an environmentally safe procedure for revalorizing APC residues

Stabilization of PFAS contaminated soil with waste-based biochar sorbents

The widespread use of per- and polyfluoroalkyl substances (PFAS) for decades has caused worldwide soil- and groundwater contamination, due to their mobility and persistency. Few existing technologies are suitable for PFAS remediation, hence a great need has arisen for new remediation technologies for PFAS impacted sites. Biochar is a carbonaceous material produced by heating biomass in absence of oxygen and has in recent years increasingly been investigated for PFAS adsorption in both water and soil. In addition to stabilization of contaminants, biochar also contributes to climate change mitigation by locking up carbon from rapidly decomposing biomass, thereby reducing potential emissions of CO2 to the atmosphere. The use of waste as the biomass for biochar production can further contribute to the transition into a more circular economy. In this study, the effects of different waste-based biochars on sorption of PFAS in soil, was investigated through up-flow column percolation tests. A sandy soil with 0.57 ± 0.04% TOC, originating from a former firefighting training facility in the Oslo region was used. The soil was contaminated with aqueous film forming foam (AFFF), containing mainly perfluorooctanesulfonic acid (PFOS), and was packed in columns with 1% (w/w) biochar. The experiment tested 6 different types of biochar, produced from the following 5 feedstocks: clean wood chip pellets (CWC), digested sewage sludge from two different WWTPs (DSS-1 and DSS-2), dewatered raw sewage sludge (DWSS) and waste timber (WT, activated and non-activated). As sludge often is contaminated with e.g., PFAS, handling and disposal can therefore be problematic. Using sludge in the production of biochar, instead of landfilling or incineration, can thus provide a more sustainable solution, as PFAS concentrations have been shown to be significantly reduced after pyrolysis. PFAS analyses were carried out for soil from the columns, for the original soil, and for leachate samples from each column collected at different liquid to solid ratios (L/S). PFOS leaching was reduced in all columns amended with biochar, compared to the control column. The activated WT biochar and the three sewage sludge-based biochars (DSS-1, DSS-2, DWSS) proved to be better sorbents for PFAS originating from the AFFF contaminated soil, than the two non-activated wood-based sorbents (CWC and WT). The leaching of PFOS by biochar amendment was reduced in the following order: aWT (99.9%) > DWSS (98.9 ± 0.24%) > DSS-2 (97.8%) > DSS-1 (91.6%) >> CWC (42.4 ± 5.1%) > WT (33.7%). Distribution coefficients for PFAS sorption to biochar (log Kd, L/kg) showed similar trends and were highest for sorption to the aWT (e.g., log Kd PFOS = 5.09 L/kg). In addition, the four best sorbents also showed reductions of dissolved organic carbon (DOC) concentrations in the leachate. Evaluation of possible DOC-facilitated transport of PFAS in the aqueous phase led to the conclusion of DOC concentrations having a significant effect on PFAS concentrations in the leachate, for PFAS with CF-chains shorter than 8. Stronger PFAS sorption was seen with longer CF-chain lengths. The higher sorption strength of the aWT and the sludge-based biochars, were explained by larger pore diameters (> 0.7 nm) which were able to accommodate the detected PFAS with maximum molecular diameters of 1.02 - 2.2 nm, whereas the majority of the pores in CWC and WT were too small to accommodate PFAS. This is the first ex-situ column study to show that waste/sludge-based biochars can be an effective alternative to e.g. fossil based activated carbon for remediation of PFAS contaminated soil. Furthermore, the application of waste-based sorbents for cleaning of contaminated soil, contributes to circular economy, by utilizing waste fractions as a resource, reducing the content of contaminants in the biochar after pyrolysis, and stabilizing contaminants in soil, in addition to sequestering carbon. A special case of this was the very effective treatment of PFAS contaminated soil by amendment with the DWSS biochar, which was made from sewage sludge contaminated with PFAS originating from the same firefighting training facility as the soil

Study on the migration rules of Sb in antimony ore soil based on HYDRUS-1D

https://egrove.olemiss.edu/aicpa_comm/1198/thumbnail.jp

Future challenges of coastal landfills exacerbated by sea level rise

In England and Wales, there are at least 1700 coastal landfills in the coastal flood plain and at least 60 threatened by erosion, illustrating a global problem. These landfills are a major issue in shoreline management planning (SMP) which aims to manage the risks associated with flooding and coastal erosion. Where landfills exist, "hold the line" (requiring the building or upgrading of artificial defences to maintain the current shoreline) is often selected as the preferred SMP option, although government funding is not available at present. To investigate these issues in detail, three case-study landfills are used to examine the risks of future flooding and erosion together with potential mitigation options. These cases represent a contrasting range of coastal landfill settings. The study includes consideration of sea-level rise and climate change which exacerbates risks of erosion and flooding of landfills. It is fundamental to recognise that the release of solid waste in coastal zones is a problem with a geological timescale and these problems will not go away if ignored. Future erosion and release of solid waste is found to be more of a threat than flooding and leachate release from landfills. However, while leachate release can be assessed, there is presently a lack of methods to assess the risks from the release of solid waste. Hence, a lack of science constrains the design of remediation options

Measurement of the Environmental Impact of Materials

Throughout their life cycles—from production, usage, through to disposal—materials and products interact with the environment (water, soil, and air). At the same time, they are exposed to environmental influences and, through their emissions, have an impact on the environment, people, and health. Accelerated experimental testing processes can be used to predict the long-term environmental consequences of innovative products before these actually enter the environment. We are living in a material world. Building materials, geosynthetics, wooden toys, soil, nanomaterials, composites, wastes and more are research subjects examined by the authors of this book. The interactions of materials with the environment are manifold. Therefore, it is important to assess the environmental impact of these interactions. Some answers to how this task can be achieved are given in this Special Issue

Dynamique des contaminants inorganiques dans les sédiments de dragage (rôle spécifique de la matière organique naturelle)

La gestion au long terme des sédiments de dragage contaminés soulève le problème du devenir des éléments potentiellement toxiques contenus dans ces matrices. Les paramètres physicochimiques influencent la spéciation et la distribution des contaminants sur les différentes phases porteuses organiques ou minérales, ainsi lors de la gestion à terre des sédiments la modification de facteurs tels que l aération, les cycles d humectation/séchage et l activité bactérienne va influencer les paramètres physico-chimiques et donc la spéciation des contaminants. Afin de préciser les mécanismes responsables de la mobilité des éléments potentiellement toxiques et d estimer l acceptabilité environnementale des sédiments de dragage en scénario de valorisation (p. ex. butte paysagère, remblai ou sous couche routière), l étude a été axée sur trois principales étapes :I établir la caractérisation totale des sédiments (granulométrie, minéralogie, teneur en eau, composition de la phase solide, composition de l eau interstitielle) et évaluer selon des procédures normaliséesl influence de facteurs (pH, L/S, température ) sur la lixiviation des éléments et sur les mécanismes géochimiques mpliqués ; II développer un jeu de paramètres d entrée pour le code géochimique ORCHESTRA selon des procédures normalisées (quantification des phases porteuses les plus réactives : argiles, carbonates, oxy-hydroxydes de fer ou d aluminium et matière organique - acide fulviques et humiques) ; III modéliser et prédire les courbes de solubilité des éléments décrites lors des tests normalisés issus de l étape (i) par l intermédiaire du jeu de paramètres d entrée défini dans l étape II. Les tests de lixiviation et la réalisation de modèles sont des approches complémentaires, indispensables pour appréhender et préciser les mécanismes contrôlant la mobilité et la rétention des éléments. Les modélisations des tests de lixiviation dynamique en colonne sont très sensibles aux variations des paramètres d entrée, c est pourquoi les modèles pour les éléments majeurs doivent être le plus adéquats possible. En général, les prédictions pour Al, Ca, Cl, Fe, H2CO3, Mg, Si, SO4, Cu, Cr, MoO4 2- , Pb et Zn ont été proches des données expérimentales, ce qui a indiqué que les processus majoritaires contrôlant la solubilité des éléments ont été pris en compte. Par contre, les prédictions pour Ni et As n ont pas été satisfaisantes, montrant que certains processus de rétention restent encore inconnus et qu ils ne sont pas pris en compte par la base de données MINETEQ2A. Pour mieux décrire le comportement d'As, il semblerait intéressant d intégrer, dans le module NiCA-Donan, la complexation potentielle d'As par la MON.The long-term management of contaminated dredged sediments raises the problem of the fate of the potentially toxic element contained in these matrixes. The physico-chemical parameters influence the speciation and distribution of contaminants between organic or inorganic bearing phases, and the terrestrial management of sediment induces the modification of factors such as oxydation, wetting / drying cycles or bacterial activity that will influence the physico-chemical parameters and thus the contaminant speciation. In order to identify the main mechanisms responsible for the mobility ofpotentially toxic elements and to estimate the environmental acceptability of dredged sediment in valuation scenario (as hill landscape, road fill or undercoat), the study was organized following three main steps I characterizing the sediment (particle size, mineralogy, moisture content, solid phase and pore water composition) and evaluating factors (pH, L / S, temperature ...) that control the leaching of elements, according to standardized procedures, II developing a set of input parameters for the geochemical code ORCHESTRA according to standardized procedures (quantification of the most reactive carrier phases : clays, carbonates, oxyhydroxides of iron or aluminum and organic matter - fulvic and humic acid) III modeling and predicting the solubility curves of the elements described in the standardized tests from step (i) using the set of input parameters defined in step (ii). Leaching tests and implementation models are complementary approaches that are necessary to understand the mechanisms controlling the mobility and retention of elements. Modeling of column dynamic leaching tests is very sensitive to changes in input parameters, so the model for the major elements should be as adequate as possible. The obtained predictions for Al, Ca, Cl, Fe, H2CO3, Mg, Si, SO4 2-, Cu, Cr, MoO4 2-, Pb and Zn were close to the experimental data, which indicates that the main processes controlling the solubility of elements were taken into account. The predictions for Ni and As, however, were not satisfactory, showing that some retention processes are still unknown or were not taken into account by the database MINETEQ2A. A better description of As behavior would require to include inAs complexation by the MON in the module Nica-Donan.TOULON-Bibliotheque electronique (830629901) / SudocSudocFranceF

Reproducibility of up-flow column percolation tests for contaminated soils

<div><p>Up-flow column percolation tests are used at laboratory scale to assess the leaching behavior of hazardous substance from contaminated soils in a specific condition as a function of time. Monitoring the quality of these test results inter or within laboratory is crucial, especially if used for Environment-related legal policy or for routine testing purposes. We tested three different sandy loam type soils (Soils I, II and III) to determine the reproducibility (variability inter laboratory) of test results and to evaluate the difference in the test results within laboratory. Up-flow column percolation tests were performed following the procedure described in the ISO/TS 21268–3. This procedure consists of percolating solution (calcium chloride 1 mM) from bottom to top at a flow rate of 12 mL/h through softly compacted soil contained in a column of 5 cm diameter and 30 ± 5 cm height. Eluate samples were collected at liquid-to-solid ratio of 0.1, 0.2, 0.5, 1, 2, 5 and 10 L/kg and analyzed for quantification of the target elements (Cu, As, Se, Cl, Ca, F, Mg, DOC and B in this research). For Soil I, 17 institutions in Japan joined this validation test. The up-flow column experiments were conducted in duplicate, after 48 h of equilibration time and at a flow rate of 12 mL/h. Column percolation test results from Soils II and III were used to evaluate the difference in test results from the experiments conducted in duplicate in a single laboratory, after 16 h of equilibration time and at a flow rate of 36 mL/h. Overall results showed good reproducibility (expressed in terms of the coefficient of variation, CV, calculated by dividing the standard deviation by the mean), as the CV was lower than 30% in more than 90% of the test results associated with Soil I. Moreover, low variability (expressed in terms of difference between the two test results divided by the mean) was observed in the test results related to Soils II and III, with a variability lower than 30% in more than 88% of the cases for Soil II and in more than 96% of the cases for Soil III. We also discussed the possible factors that affect the reproducibility and variability in the test results from the up-flow column percolation tests. The low variability inter and within laboratory obtained in this research indicates that the ISO/TS 21268–3 can be successfully upgraded to a fully validated ISO standard.</p></div

Reproducibility of up-flow column percolation tests for contaminated soils - Fig 6

<p>Difference in results within laboratory for Se, As, Cu, Mg, F and DOC (a) concentrations and (b) cumulative releases for Soil II; difference in results within laboratory for Se, As, Cu and B (c) concentrations and (d) cumulative releases for Soil III. The “difference between results” and “difference between cumulative results” corresponds to the difference between concentrations and cumulative releases, divided by their mean and expressed in terms of percentage.</p