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

Evidence of the mineral ZnHAsO4 center dot H2O, koritnigite, controlling As(V) and Zn(II) solubility in a multi-contaminated soil

Assessing element speciation and solubility control mechanisms in multi-contaminated soils poses great challenges. In this study, we examined the speciation and mechanisms controlling the solubility of As and Zn in a soil historically contaminated with As, Cu, Cr, and Zn salts used for wood preservation. The leaching behavior of dissolved species, particles, and colloids was studied in an irrigation experiment with intact soil columns. Batch experiments were used to study the solubility of dissolved species as a function of pH (2-8). The speciation of As and Zn in bulk soil and leached particles was studied with microscale X-ray fluorescence (mu-XRF) and extended Xray absorption fine structure (EXAFS) spectroscopy. Chemical speciation and solubility were evaluated by geochemical modelling. mu-XRF of bulk soil and particles showed that As and Zn were correlated in space. Bulkand mu-EXAFS of As and Zn, in combination with calculated ion activity products of possible As-Zn minerals, suggested a koritnigite (ZnHAsO4 center dot H2O) phase controlling the dissolved fraction of As(V) and Zn with an apparent log K-sp of 21.9 +/- 0.46. This phase lowered the solubility of As by almost two orders of magnitude in soil at pH > 5, and could therefore be of great importance at other multi-contaminated sites

The Adsorption of Per- and Polyfluoroalkyl Substances (PFASs) onto Ferrihydrite Is Governed by Surface Charge

An improved quantitative and qualitative understanding of the interaction of per- and polyfluoroalkyl substances (PFASs) and short-range ordered Fe (hydr)oxides is crucial for environmental risk assessment in environments low in natural organic matter. Here, we present data on the pH-dependent sorption behavior of 12 PFASs onto ferrihydrite. The nature of the binding mechanisms was investigated by sulfur K-edge X-ray absorption near-edge structure (XANES) spectroscopy and by phosphate competition experiments. Sulfur K-edge XANES spectroscopy showed that the sulfur atom of the head group of the sulfonated PFASs retained an oxidation state of +V after adsorption. Furthermore, the XANES spectra did not indicate any involvement of inner-sphere surface complexes in the sorption process. Adsorption was inversely related to pH (p < 0.05) for all PFASs (i.e., C-3-C-5 and C-7-C-9 perfluorocarboxylates, C-4, C-6, and C-8 perfluorosulfonates, perfluorooctane sulfonamide, and 6:2 and 8:2 fluorotelomer sulfonates). This was attributed to the pH-dependent charge of the ferrihydrite surface, as reflected in the decrease of surface zeta-potential with increasing pH. The importance of surface charge for PFAS adsorption was further corroborated by the observation that the adsorption of PFASs decreased upon phosphate adsorption in a way that was consistent with the decrease in ferrihydrite zeta-potential. The results show that ferrihydrite can be an important sorbent for PFASs with six or more perfluorinated carbons in acid environments (pH <= 5), particularly when phosphate and other competitors are present in relatively low concentrations

Iron and aluminium speciation in Swedish freshwaters : Implications for geochemical modelling

Speciation governs transport and toxicity of trace metals and is important to monitor in natural waters. Geochemical models that predict speciation are valuable tools for monitoring. They can be used for risk assessments and future scenarios such as termination of liming. However, there are often large uncertainties concerning the speciation of iron and aluminium in the models, due to the complicated chemistry of these metals. Both are important in governing the speciation of other metals, due to (i) their capacity to form minerals onto which metals can adsorb and (ii) their ability to compete for binding sites to natural organic matter (NOM). Aluminium is also potentially toxic and is therefore closely monitored in acidified freshwaters. In this study different phases of iron in Swedish lakes were characterised. This required a good method for preconcentrating the iron colloids. A new method was developed in this thesis that uses an anion-exchange column to isolate the iron colloids prior to characterisation with extended X-ray absorption fine structure (EXAFS) spectroscopy. Iron was present as ferrihydrite in particles but was also strongly monomerically complexed to NOM in two Swedish lakes. Based on the results an internally consistent process-based geochemical equilibrium model was presented for Swedish freshwaters. The model was validated for pH (n = 9 400) and inorganic monomeric aluminium (Ali) (n = 3 400). The model could simulate pH and Ali simultaneously, and be used for scenario modelling. In this thesis, modelling scenarios for decreases and complete termination of liming are presented for the 3 000 limed Swedish lakes. The results suggest that liming can be terminated in 30 % of the Swedish lakes and decreased in many other lakes.QC 20120919</p

Målsjöinventeringen 07/08 - modellering av Ali och pH vid förändrad kalkning

Målet med denna studie är att undersöka vad som händer vid en förändrad kalkning i sjöar, för att se om det går att minska på kalkdosen utan att det innebär en risk för låga pH och höga Ali-halter (monomert oorganiskt aluminium). De viktiga parametrarna pH och Ali har simulerats med en geokemisk jämviktsmodell, dels vid nuvarande uppmätta förhållanden i Målsjöinventeringen 07/08 (ca 3000 sjöar) och dels vid olika scenarier där kalcium- och magnesiumhalterna har minskat. Kalcium- och magnesiumkoncentrationerna har minskats ner till framräknade halter som är en uppskattning av vad de skulle vara i sjöarna utan tillsatt kalk, baserat på kvoten Ca*/Mg* i närliggande okalkade sjöar. För den ursprungliga situationen vid uppmätta förhållanden så hade mindre än 1% av de kalkade sjöarna över 30 μg L-1beräknad halt Ali och uppmätt pH låg på i medeltal 6,8. När istället icke-kalkpåverkade kalcium- och magnesiumkoncentrationer matades in i modellen, blev resultatet att pH minskade till i medeltal 5,7 och Ali ökade till i medeltal 31 μg L-1. Ca 40% av sjöarna fick pH-värden under 5,6 och ca 35% fick Ali-värden över 30 μg L-1. De faktorer som mest styrde vilka sjöar som fick lägst pH var dels hur mycket Ca och Mg-koncentrationerna minskade i förhållande till syraneutraliserande förmåga (ANC) (dvs mängden katjoner till starka baser minus anjoner till starka syror) och dels en geografisk skillnad. Om Ca- och Mg-koncentrationerna minskade med mer än 50% av ANC så minskade pH med mer än 0,4 pH-enheter. Det är alltså en riskfaktor som bör studeras innan avslutad eller minskad kalkning. De län som var mest drabbade av både surt pH och höga Ali-halter var Skånes, Hallands, Västra Götalands, Kronobergs och Örebros län. Där bör följaktligen kalkningen absolut fortsätta. Några län minskade dock väldigt lite i pH och ökade lite i Ali, speciellt Gävleborg och Jämtlands län. I dessa län bör man kunna överväga att minska ner på kalkningen. Om istället kalcium- och magnesiumkoncentrationerna bara minskades motsvarande en halverad kalkning skedde en mycket mindre förändring av pH och Ali. Antalet sjöar med pH under 5,6 blev nu istället 2,5% och 3% hade Ali över 30 μg L-1. Det skulle kunna betyda att för de flesta sjöarna så skulle det gå att minska på kalkningen utan några dramatiska följder. Av sjöarna i denna studie så var de län som var mest drabbade Kronobergs, Örebros och Västra Götalands län, som därmed inte bör minska ner på kalkningen.IKEU-rapport finansierad av Naturvårdsverket.QC 2012021

Role Plays to Facilitate Students' Empathy in Secondary School in English Language Lessons

Mūsdienās empātija ir kļuvusi gandrīz vai ekskluzīva parādība, jo daudzi cilvēki tiecas mērīt savu dzīvi naudas un materiālo vērtību skalā, aizmirstot par tādām pamatvērtībām kā laipnība, labestība, rūpes par citiem cilvēkiem un empātija. Tā kā empātija ir iemācāma, to var iemācīt arī vidusskolas skolēniem un diplomdarba autore uzskatīja, ka lomu spēles varētu būt piemērots veids, kā to izdarīt. Tādēļ diplomdarba mērķis bija izpētīt lomu spēļu izmantošanas iespējas un to nozīmību skolēnu empātijas veicināšanai. Atsevišķa gadījuma pētījums tika veikts ar mērķi noskaidrot, vai un kā piemērotu lomu spēļu izmantošana var veicināt vidusskolēnu empātiju. Tas tika veikts vienā no Jēkabpils vidusskolām, iesaistot 13 skolēnus. Diplomdarba autore izvēlējās 3 lomu spēles, kuras skolēni izspēlēja. Darba autore izmantoja divas datu vākšanas metodes: anketas un novērojumu. Iegūtie dati no skolēnu anketām un diplomdarba autores novērojumiem lomu spēļu laikā parādīja, ka skolēniem patika piedalīties lomu spēlēs un viņi saprata, ka iejusties citu cilvēku vietā nav viegli. Skolēni arī atzina, ka viņi izbaudīja lomu spēles, jo to laikā viņiem bija iespēja bagātināt savu vārdu krājumu, attīstīt runāšanas prasmes un mācību stundas bija aizraujošas un neparastas. Tomēr, skolēni arī atzina, ka viņiem bijis nepietiekams vārdu krājums, lai izteiktu savu viedokli un emocijas. Kopumā, izpētot teorētisko literatūru un veicot pētījumu, diplomdarba autore var secināt, ka skolēniem vajag un var iemācīt empātiju, bet tas prasa vingrināšanos, pacietību un laiku. Izvēloties piemērotas lomu spēles un ievērojot noteiktus to posmus un ieteiktās vadlīnijas to izspēlēšanas procesā, ir iespējams veicināt skolēnu spēju iejusties citu cilvēku vietā un saprast viņu nostāju, domas, vērtības un emocijas.Nowadays empathy has become almost an exclusive thing as many people tend to measure their life only in terms of money and material values, forgetting about such basis as kindness, generosity, care for other people and empathy. As empathy is teachable, it can be taught to secondary school students as well and the author of the Paper considered that role plays could be an appropriate tool used to do that. That is why the aim of the Paper was to explore the possibilities and significance of using role plays to facilitate students’ empathy. The case study was carried out with the aim to find out whether using role plays can facilitate students’ empathy. It was carried out among 13 students in one of Jēkabpils secondary schools. The author of the Paper had chosen three role plays for students to take part in them. The author of the Paper used two data collection methods: questionnaires and observation. The data gained from the students’ questionnaires and the author’s of the Paper observation during the role plays showed that the students liked participating in the role plays and they had learnt that it was not easy to empathize with other people. The students also enjoyed the role plays as they had an opportunity to enrich their vocabulary, develop speaking skills and the lessons were exciting and unusual, however, the students also admitted that they lack vocabulary to express their opinion and feelings. On the whole, having studied the theoretical literature and carried out the research the author of the Paper can conclude that the students should and can be taught empathy, but it requires practice, patience and time. Choosing appropriate role plays and observing certain stages and suggested guidelines in carrying them out facilitate the students’ ability to empathize with other people and understand their position, thoughts, values and feelings

Metal sorption to Spodosol Bs horizons: Organic matter complexes predominate

While metal sorption mechanisms have been studied extensively for soil surface horizons, little information exists for subsoils, for example Spodosol Bs horizons. Here the sorption of cadmium(10, copper(II) and lead(II) to seven Bs horizons from five sites was studied. Extended X-ray absorption fine structure (EXAFS) spectroscopy showed that cadmium(II) and lead(II) were bound as inner-sphere complexes to organic matter. Addition of o-phosphate (to 1 mu mol l(-1)) did not result in any significant enhancement of metal sorption, nor did it influence EXAFS speciation. An assemblage model using the SHM and CD-MUSIC models overestimated metal sorption for six out of seven soil samples. To agree with experimental results, substantial decreases (up to 8-fold) had to be made for the fraction 'active organic matter', f(Hs), while the point-of-zero charge (PZC) of ferrihydrite had to be increased. The largest decreases of f(HS) were found for the soils with the lowest ratio of pyrophosphate-to oxalate-extractable Al (Al-pyp/Al-ox), suggesting that in these soils, humic and fulvic acids were to a large extent inaccessible for metal sorption. The low reactivity of ferrihydrite towards lead(II) can be explained by potential spillover effects from co-existing allophane, but other factors such as ferrihydrite crystallisation could not be ruled out. In conclusion, organic matter was the predominant sorbent for cadmium(II), copper(II) and lead(II). However, for lead(II) the optimised model suggests additional, but minor, contributions from Fe (hydr) oxide surface complexes. These results will be important to correctly model metal sorption in spodic materials

Arsenic adsorption by iron-aluminium hydroxide coated onto macroporous supports: Insights from X-ray absorption spectroscopy and comparison with granular ferric hydroxides.

This paper evaluates the arsenic adsorption characteristics of a macroporous polymer coated with coprecipitated iron-aluminium hydroxides (MHCMP). The MHCMP adsorbent-composite fits best with a pseudo-second order model for As(III) and a pseudo-first order kinetic model for As(V). The MHCMP shows a maximum adsorption capacity of 82.3 and 49.6mgAs/g adsorbent for As(III) and As(V) ions respectively, and adsorption followed the Langmuir model. Extended X-ray absorption fine structure showed that binding of As(III) ions were confirmed to take place on the iron hydroxides coated on the MHCMP, whereas for As(V) ions the binding specificity could not be attributed to one particular metal hydroxide. As(III) formed a bidentate mononuclear complex with Fe sites, whereas As(V) indicated on a bidentate binuclear complex with Al sites or monodentate with Fe sites on the adsorbent. The column experiments were run in a well water spiked with a low concentration of As(III) (100μg/L) and a commercially available adsorbent (GEH(®)102) based on granular iron-hydroxide was used for comparison. It was found that the MHCMP was able to treat 7 times more volume of well water as compared to GEH(®)102, maintaining the threshold concentration of less than 10μgAs/L, indicating that the MHCMP is a superior adsorbent