Speciation of Cu and Zn in bottom ash from solid waste incineration studied by XAS, XRD, and geochemical modelling

Millions of tons of bottom ash (BA) is generated from incineration of industrial and municipal solid waste each year within EU. The magnitude of leaching of metals like Cu and Zn is critical for hazard and risk assessment of these ashes. Although speciation of metals is a key factor to understand and predict metal leaching, speciation of Cu and Zn in BA is not well known. In this study six metal separated and carbonized BA were investigated by a combination of X-ray absorption spectroscopy, X-ray diffraction, leaching/extraction tests, and geochemical modelling. Five of the BA were from grate boilers and one from a fluidized bed incinerator. The aims were to identify similarities in Cu and Zn speciation and to identify main species. The combination of several techniques was necessary to draw conclusions about speciation and displayed coherent results. A similar speciation of Cu and Zn was indicated in the five studied grate boiler ashes although the proportions between species may vary. Copper(II) oxide and Cu metal were the main Cu species in all BA. Zinc(II) oxide and willemite (Zn2SiO4) were identified in grate boiler ashes. The fluidized bed ash contained Zn-Si-minerals and possibly franklinite or gahnite, while the Zn(II) oxide content was low, if any. The results have implications for classification and risk assessment of MIBA. (C) 2020 The Authors. Published by Elsevier Ltd

Mineralogical characterization and speciation of sulfur, zinc and lead in pyrite cinder from Bergvik, Sweden

Roasting of sulfide ores to produce sulfuric acid began on an industrial scale in the middle 1800 ' s and is still used extensively worldwide. The residual, pyrite cinders, have commonly been disposed in the environment where they pose a potential and serious threat to aquatic life. In this project, two profiles in a pyrite cinder deposit in Bergvik, Sweden, have been sampled and a comprehensive mineralogical characterization have been carried out. The objectives were to investigate the composition and morphology of pyrite cinder grains and the speciation of sulfur, Pb and Zn in the solid phase. Scanning electron microscopy showed pyrite cinder grains with a core of the ore minerals pyrite and sphalerite enclosed in layers of iron oxides/hydroxides (mainly hematite). XANES analysis, supported by X-ray diffraction analysis, SEM-EDS and bulk element analysis, showed that content of the residual sulfur in the cinder is mainly sulfides, 55-80%, predominately sphalerite. The remaining mass of sulfur is assumed to be adsorbed or precipitated as secondary sulfate minerals, predominantly associated with the grain surfaces. Calculated saturation indexes indicated barite, anglesite and perhaps aluminite. EXAFS spectroscopy indicated that about half of the Zn was bound to O and half was bound to S. LCF analysis of EXAFS spectra indicated that the main Zn species were sphalerite (40-50%) and franklinite (10-20%). The remaining Zn was associated with iron oxides/hydroxides and Zn minerals like hydrozincite or possibly zinc oxides. SEM-EDS analysis showed Pb precipitate located on both the surface of the grains and in the interior as inclusions. The analytical interpretation indicated anglesite

Large-scale arsenic mobilization from legacy sources in anoxic aquifers: Multiple methods and multi-decadal perspectives

While geogenic arsenic (As) contamination of aquifers have been intensively investigated across the world, the mobilization and transport of As from anthropogenic sources have received less scientific attention, despite emerging evidence of poor performance of widely used risk assessment models. In this study we hypothesize that such poor model performance is largely due to insufficient attention to heterogeneous subsurface properties, including the hydraulic conductivity K and the solid-liquid partition (Kd), as well as neglect of laboratory-to-field scaling effects. Our multi-method investigation includes i) inverse transport modelling, ii) in-situ measurements of As concentrations in paired samples of soil and groundwater, and iii) batch equilibrium experiments combined with (iv) geochemical modelling. As case study we use a unique 20-year series of spatially distributed monitoring data, capturing an expanding As plume in a Chromated Copper Arsenate (CCA)-contaminated anoxic aquifer in southern Sweden. The in-situ results showed a high variability in local Kd values of As (1 to 107 L kg-1), implying that over-reliance of data from only one or few locations can lead to interpretations that are inconsistent with field-scale As transport. However, the geometric mean of the local Kd values (14.4 L kg-1) showed high consistency with the independently estimated field-scale "effective Kd" derived from inverse transport modelling (13.6 L kg-1). This provides empirical evidence for the relevance of using geometric averaging when estimating large-scale "effective Kd" values from local measurements within highly heterogenous, isotropic aquifers. Overall, the considered As plume is prolonged by about 0.7 m year-1, now starting to extend beyond the borders of the industrial source area, a problem likely shared with many of the world's As-polluted sites. In this context, geochemical modelling assessments, as presented here, provided a unique understanding of the processes governing As retention, including local variability in, e.g., Fe/Al-(hydr) oxides contents, redox potential and pH

Combining a Standardized Batch Test with the Biotic Ligand Model to Predict Copper and Zinc Ecotoxicity in Soils

Extraction of soil samples with dilute CaCl2 solution in a routinely performed batch test has potential to be used in site-specific assessment of ecotoxicological risks at metal-contaminated sites. Soil extracts could potentially give a measure of the concentration of bioavailable metals in the soil solution, thereby including effects of soil properties and contaminant "aging." We explored the possibility of using a 0.001 M CaCl2 batch test combined with biotic ligand models (BLMs) for assessment of ecotoxicity in soils. Concentrations of Cu2+ and Zn2+ in soil extracts were linked to responses in ecotoxicity tests (microbial processes, plants, and invertebrates) previously performed on metal-spiked soils. The batch test data for soils were obtained by spiking archived soil materials using the same protocol as in the original studies. Effective concentration values based on free metal concentrations in soil extracts were related to pH by linear regressions. Finally, field-contaminated soils were used to validate model performance. Our results indicate a strong pH-dependent toxicity of the free metal ions in the soil extracts, with R-2 values ranging from 0.54 to 0.93 (median 0.84), among tests and metals. Using pH-adjusted Cu2+ and Zn2+ concentrations in soil extracts, the toxic responses in spiked soils and field-contaminated soils were similar, indicating a potential for the calibrated models to assess toxic effects in field-contaminated soils, accounting for differences in soil properties and effects of contaminant "aging." Consequently, evaluation of a standardized 0.001 M CaCl2 batch test with a simplified BLM can provide the basis for an easy-to-use tool for site-specific risk assessment of metal toxicity to soil organisms. Environ Toxicol Chem 2022;00:1-14. (c) 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC

Metal sorption to ferrihydrite

Phosphorus affects the sorption of many metals and arsenate to iron (hydr)oxides. This may influence the mobility and bioavailability of metals and arsenate. Phosphorus therefore plays an important role in, e.g., determining the ecotoxicological risk of contaminants in soils. The overall aim of this thesis was to improve the understanding of lead(II), copper(II), cadmium(II) and arsenate binding to iron (hydr)oxides. The focus was on how phosphate affects the sorption on ferrihydrite and soils in which ferrihydrite is an important constituent. The effect of phosphate on the sorption of lead(II), copper(II), cadmium(II) and arsenate was determined by batch experiments. X-ray absorption spectroscopy (XAS) was performed to identify the binding mechanisms. Geochemical models were developed based on the XAS results and knowledge about the mineral or soil properties. Phosphate enhanced the sorption of lead(II), copper(II) and cadmium(II) to ferrihydrite. The increased sorption was best explained by the formation of ternary complexes including the ferrihydrite surface, the metal and the phosphate ion. Phosphate competed strongly with arsenate for sorption sites on ferrihydrite. The competition was even stronger on poorly crystalline aluminium hydroxide. Zero-valent iron that is mixed into soil rapidly oxidises to ferrihydrite that can adsorb contaminants. It was shown that the immobilisation of copper and arsenic in soils that had been stabilised by zero-valent iron is long-lasting. Copper immobilisation was most effective at high pH (>6) and at low organic matter content. Competition with phosphate needs to be taken into account when modelling arsenate sorption in soils. Otherwise the latter may be greatly overestimated. Metal sorption to some podzolised soils was investigated in batch experiments. Despite the large influence on metal sorption in the pure ferrihydrite systems the addition of phosphate did not affect lead(II), copper(II) or cadmium(II) sorption to the B and C horizons of podzolised soils. The reasons may be strong metal binding to organic matter combined with a relatively small addition of phosphorus in the experiments. In conclusion this thesis shows that phosphate greatly affects the sorption of lead(II), copper(II), cadmium(II) and arsenate to iron (hydr)oxides. To determine the impact of this effect in more complex matrices such as soils, more research is needed

Bottom ash from incineration of coal, peat and biofuel in roadconstruction - A guide

(1) Projekteringsförutsättningar; (2) Redovisning i bygghandling; (3) Utförande; (4) Drift och underhåll; (5) Återbruk, deponering och överlåtelse; (6) Kvalitetskrav och kontroll; Bilagor: Exempel på utförda objekt: (1) Hudiksvall – bio / RT-rosteraska, botten- och flygaska i transportväg på deponi; (2) Norrtälje – biorosteraska, botten- och flygaska i skogsbilvä

Monitoring natural attenuation of petroleum compounds. Pilot study in Sollentuna, Stockholm

(1) Modellering - överföring till datamodell; (2) Resultat; (3) Prognosticering av föroreningsutbredning i grundvattne

Phosphate effects on cadmium(II) sorption to ferrihydrite

Hypothesis: Phosphate influences the sorption of metals to iron (hydr)oxides. An enhanced formation of inner-sphere complexes on the (hydr)oxide surface can be attributed to electrostatic interactions and/or to changes in metal coordination on the iron (hydr)oxide surface. Phosphate was expected to increase cadmium(II) sorption on ferrihydrite. It should be possible to identify changes in cadmium(II) coordination upon phosphate addition by Extended X-ray absorption fine structure (EXAFS) spectroscopy and implement the identified complexes in a surface complexation model (SCM).Experiments: The effect of phosphate addition on cadmium(II) sorption to ferrihydrite was studied by a series of batch experiments covering the pH range from 4 to 8. EXAFS spectroscopy was performed on ferrihydrite from the batch experiments at the cadmium K edge. The identified surface complexes were incorporated in the Charge distribution multisite complexation (CD-MUSIC) model, and new surface complexation constants were optimized.Findings: Without phosphate addition cadmium(II) formed inner-sphere bidentate complexes on the ferrihydrite surface. With phosphate there was an increased cadmium(II) sorption that could not be explained by electrostatic interactions alone. The enhancement was best explained by the formation of a ternary complex including cadmium(II), phosphate and ferrihydrite surface groups

Molybdenum binding to soil constituents in acid soils

Despite its importance as a trace element, the binding mechanisms of molybdenum in soils are not well known. In this study, we studied the binding of molybdenum onto selected soil samples, and we used X-ray absorption spectroscopy (XAS) to characterize the coordination of molybdenum on three important environmental sorbents: ferrihydrite (Fh), amorphous aluminium hydroxide (Al(OH)(3)) and fulvic acid. The X-ray near-edge structure (XANES) data showed that the added molybdenum(VI) was not reduced, although for the organic samples the coordination shifted from tetrahedral to octahedral. The EXAFS (extended X-ray absorption fine structure) analysis showed that molybdenum(VI) on Fh and Al(OH)(3) was dominated by edge-sharing bidentate complexes with Mo center dot center dot center dot Fe and Mo center dot center dot center dot Al distances of 2.80 and 2.62 angstrom, respectively. For ferrihydrite, there was a minor contribution from a corner-sharing bidentate complex at 3.55 angstrom. Further, geochemical modelling suggested an additional role of an outer-sphere complex at high pH. A sample from a spodic Bs horizon had XANES and EXAFS features similar to those of Mo sorbed to Al(OH)(3), highlighting the importance of Al(OH)(3)-type sorbents in this soil. However, in the studied organic samples molybdenum(VI) was present in a distorted octahedral configuration as an organic complex. The results were used to improve molybdenum binding reaction equilibrium constants in the CD-MUSIC model for ferrihydrite and in the Stockholm Humic Model. Collectively the results show that acid soils may contain sorbents able to bind molybdenum efficiently, and thus prevent its leaching to waters. (C) 2015 Elsevier B.V. All rights reserved

Pålning i förorenade områden. Kunskapssammanställning

Denna rapport sammanfattar den litteratur som hittats men innehåller också allmänna introduktioner till pålning, föroreningar och riskbedömning. Dessa avsnitt vänder sig framförallt till dem som inte arbetar inom respektive område och kan förhoppningsvis underlätta kommunikationen mellan geotekniker, miljötekniker och tillsynsmyndigheter. Mot slutet av rapporten finns också en sammanställning av vad som behövs för att bedöma riskerna med att påla i ett förorenat område samt en diskussion om kunskapsluckor