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MnOx biochars as potential mercury sorbents in the context of global mercury emissions.
No full textWhat role do targeted mercury control technologies play in the context of global anthropogenic mercury emissions reductions and what are the material requirements for a successful mercury sorbent?
Mercury (Hg) pollution is a multi-scalar policy issue. Anthropogenic emissions stem from point sources, but their consequences span the whole globe due to global distribution of the pollutant through the atmosphere, necessitating action across local, global and even temporal scales. To counteract this, the Minamata Convention on Mercury (MCM) aims at reducing levels of `mercury and mercury compounds' in humans and the environment by targeting Hg at different levels of the release cycle, such as trade, use in manufacture, emission sources, and wastes. Against this backdrop, this thesis focusses on different control options for atmospheric Hg emission reduction on a global level, using global scenario modelling, systematic literature review and laboratory studies. Part I of this thesis takes a panoptic view, using global scenario modelling to explore different narratives on future Hg emissions, revolving around a central question:
To what extent are Hg-specific technological interventions necessary to achieve Hg emission reductions globally and where will they be most effective?
Eight different scenarios of energy, climate and clean air policy are considered, all of which influence aspects of Hg emissions. The thesis develops and implements improved modelling representation of Hg removal technologies in the Greenhouse Gas - Air Pollution Interactions and Synergies (GAINS) model. This enables improved representation of Hg-specific control options, as well as co-benefits with traditional air pollutants. Part II is a case study of one such technological solution: a material class with promising Hg sorption and oxidation properties, namely manganese oxide - biochar composites (MnOx-BC). Here, the question is:
Which properties make a MnOx-BC ideal for Hg capture from flue gas - and how can they be achieved through synthesis control?
MnOx-BC material properties are explored using systematic literature review and a laboratory study to underline the relationship between synthesis procedure, biochar feedstock and resulting Mn oxidation state, using X-ray Absorption Near Edge Structure (XANES) to investigate manganese oxidation states. While MnOx-BC sorbents have been studied for Hg capture from coal combustion flue gases, the global modelling shows that this is a sector where much Hg is abated as a co-benefit from particulate matter (PM) and SO2 control. Additionally, the current climate policy and the decarbonisation of the energy system mean that this Hg source will diminish in the future, rendering this emission source less interesting for targeted Hg removal sorbents. Especially the waste sector and manufacturing industries (non-ferrous metals (NFME) and cement) show scope for targeted, further Hg emission removal using novel sorbent technologies in the future, due to their high emission intensity and their continued relevance in a low-carbon, high-population future. The modelling also showed that 17.6% of global Hg emissions could be abated in 2050 compared to 2015 by maximising co-benefits from PM and SO2 control. The most drastic, targeted Hg reduction measures, including a ban on ASGM, would achieve a 79% emission reduction in 2050 relative to 2015, showing that Hg-specific control technologies are crucial to reducing Hg. In terms of material properties, the combination of review and material science established the importance of biochar feedstock and well-controlled synthesis conditions to produce MnOx-BC with optimised porosity, Mn content, Mn distribution and Mn mineralogy. Especially XANES proved to be an excellent method to determine the average Mn oxidation state on the material. This thesis identifies biochars with well-developed macro-and mesoporosity that are impregnated with amorphous Mn(4+) oxides as a promising material. Different synthesis routes using KmNO4 and an oxic calcination step can achieve this
Global scenarios of anthropogenic mercury emissions in GAINS
No full text<p>This dataset contains eight scenarios of<strong> future global mercury emissions</strong> from the base year 2015 to 2050, generated using the GAINS Global model (https://gains.iiasa.ac.at/gains4/GOD/index.login).</p>
<p>File types and abbreviations, as well as scenario descriptions are found in "<strong>2024_ACP_Brocza-etal_Legend.xlsx</strong>" </p>
<p><strong>Types of files:</strong></p>
<table>
<tbody>
<tr>
<td>em_data_hgpaper_*SCEN*</td>
<td>Hg emissions data by year & region, aggregated</td>
</tr>
<tr>
<td>hg_ef_data_hgpaper_*SCEN*</td>
<td>Ranges of emission factors in aggregated regions and sectors</td>
</tr>
<tr>
<td>hg_spec_data_hgpaper_*SCEN*</td>
<td>Speciated Hg emissions in aggregated regions and sectors</td>
</tr>
</tbody>
</table>
<p><strong>Level of detail:</strong></p>
<p>Data are aggregated into 15 regions:</p>
<p>Global, Africa, Asia_Pacific (+ sub-regions China, India, Japan, Southeast_Asia), Central_and_South_America (+ Brazil), Eurasia (+ Russia), Europe (+EU27), Middle_East, North_America (+USA).</p>
<p> </p>
<p>The corresponding manuscript titled "Global scenarios of anthropogenic mercury emissions" has been submitted. </p>
<p> </p>
<p> </p>
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Systematic literature review: Manganese Oxide - biochar composites
No full textSearchable dataset containing metadata on scientific publications describing composites of manganese oxide and biochar (MnOx-BCs).
Further details on the collected data are in the readme file
Tracing mercury transformations in soil using mercury stable isotope analysis
No full textUm das Verhalten von Quecksilber (Hg) in der Umwelt zu verstehen, ist es unumgänglich, seine Speziierung zu kennen, da sich die verschiedenen Spezies stark in ihrer Bioverfügbarkeit und Toxizität unterscheiden. Diese Prozesse in einem natürlichen System zu verstehen, ist oft eine Herausforderung. Da viele der biogeochemischen Prozesse, die in der Umwelt relevant sind, die stabilen Hg-Isotopen charakteristisch fraktionieren, sind Isotopenmessungen an verschiedenen Hg-Pools in einem System eine vielversprechende Möglichkeit, um die Umwandlungsprozesse, die stattgefunden haben, zu verstehen.
Fraktionierungsfaktoren von Hg-Umwandlungsreaktionen wurden hauptsächlich durch Laborexperimente bestimmt - bis jetzt wurde das Konzept des „Process Tracing“ durch Isotopenmessungen noch nicht erfolgreich auf Feldsysteme angewandt. Diese Verknüpfung war das Ziel dieser Arbeit.
An einem durch HgCl2 kontaminierten Standort in Bad Krozingen, Deutschland wurden zwei Rammkernsonden gezogen. Bohrkern K2 stammt aus der am stärksten kontaminierten Zone, wo die HgCl2-Lösung direkt in den Boden eingetragen wurde. K3 war sekundär durch Umlagerung des Erdreichs aufgrund von Bauarbeiten Hg-verseucht. Beide Bohrkerne wurden hinsichtlich ihres Gesamt-Hg-Gehalts analysiert und mithilfe von pyrolytischer Thermodesorption (PTD) charakterisiert. Die am stärksten kontaminierten Proben wurden nach einem optimierten sequentiellen Extraktionsprotokoll (SEP). Hg-Isotope wurden an den Komplettaufschlüssen und den sequentiellen Extrakten gemessen.
Die Ergebnisse von PTD und Gesamtaufschlüssen ergaben sowohl Unterschiede der Bindungsformen von Hg zwischen den beiden Bohrkernen, als auch zwischen den verschiedenen Tiefen. Nur die höchstkontaminierten Proben in K2 (bis zu 802 mg/kg) enthielten Hg(0), und nur die am meisten kontaminierten Proben in K3 (bis zu 100 mg/kg) wiesen Spuren von HgS auf. In beiden Bohrkernen war der Großteil des Hg als Hg(II) an die Matrix gebunden und nicht näher durch PTD bestimmbar.
Über Isotopenmessungen an den extrahierten Pools und Gesamtaufschlüssen konnten nicht nur zwischen Proben und Bohrkernen, sondern auch zwischen den extrahierten Fraktionen Unterschiede festgestellt werden. Die Quellensignatur, die auf Basis einer Literaturrecherche bei -0.45 +/- 0.31 ‰ δ202Hg (2 SD, n=8) angenommen wurde, wurde als Referenz für die gemessenen Werte herangezogen. Während die meistkontaminierten Proben im Kern K2 mit diesem Wert überlappten, zeigten alle Proben aus K3 signifikant schwerere δ202Hg-Werte. Das am stärksten gebundene Hg war in allen Fällen der isotopisch leichteste Pool, das mit 0.5 HNO3 extrahierte Hg in den meisten Fällen schwer relativ zu Gesamtprobe und relativ zur vermuteten Quellensignatur. Der wasserextrahierbare Pool zeigte sich variabel.
Der vorliegende Datensatz demonstriert, dass biogeochemische Prozesse an einem kontaminierten Standort signifikante Hg-Isotopenfraktionierung herbeiführen können. Die beobachtete Fraktionierung stimmt mit Literaturwerten über abiotische Reduktion von Hg und verschiedenen Sorptionsprozessen überein. Die Quantifizierung der verschiedenen Einflüsse auf die Fraktionierung bleibt allerdings der Gegenstand von zukünftigen Untersuchungen.Understanding the speciation of mercury (Hg) in the environment is key to understanding its risk, since mercury species differ drastically in their bioavailability and toxicity. Biogeochemical reactions of Hg have been found to induce Hg stable isotope fractionation between the product and the reactant. Studying stable isotope signatures of different mercury pools thus provides an opportunity to trace the transformations of the contaminant in the soil. While this has been observed both in the field and in the laboratory, few studies have applied these findings to study transformation processes in contaminated field sites, which was the aim of this thesis.
Two soil cores from a HgCl2 contaminated field site in Bad Krozingen, Germany were collected: Core K2 from the source of the contamination and core K3 from the border of the facility, where the contamination is only secondary, from the movement of soil during construction of residential buildings blocks. Both cores were analyzed for their total mercury content and pyrolytic thermo-desorption (PTD) was conducted to characterize its speciation. The highest-contaminated samples were extracted according to a sequential extraction protocol (SEP). Hg stable isotopes were measured on the extracts. The combination of PTD and SEP revealed differences in speciation between the two cores and between different soil depths. Only the most contaminated samples in K2 (up to 802 mg/kg) contained Hg(0), and only the most contaminated samples in K3 (up to 100 mg/kg) contained evidence for HgS. The majority of mercury in both cores was Hg(II), whose exact binding forms could not be determined with the used methods. However, via stable isotope analysis, significant differences in the isotopic signatures of the cores, different depths and different extracted pools could be determined. Assuming the contamination source signature to lie within the average literature value for industrial Hg(0) of -0.45 +/- 0.31 ‰ δ202Hg (2 SD, n=8), the pools of refractory mercury in the most contaminated soil samples in core K2 were within that value, whereas all values in core K3 were significantly heavier, hinting at a more strongly altered mercury pool. Within the most contaminated samples, refractory, tightly bound Hg displayed the lightest signatures, whereas the more labile, 0.5 M HNO3-extractable Hg was significantly heavier. Water-extractable Hg varied widely in its Hg isotopic composition.
This field study demonstrated successfully that biogeochemical transformations induce significant fractionation of Hg stable isotopes, even in a site with only a single source of contamination. The fractionation observed fit well with literature reporting fractionation factors via laboratory experiments, but quantification of the processes remains a project for further study
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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