Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Speciation and bioavailability of chromium and nickel in Swedish freshwater: For improved assessments in life-cycle analysis (LCA)
KTH, School of Chemical Science and Engineering (CHE).
2017 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesisAlternative title
Speciering och biotillgänglighet av krom och nickel i svenska sötvatten (Swedish)
Abstract [en]

Metals are used in every part of our modern society. As population and wealth increases, so does the demand for metals and metal products. This inherently leads to metal emissions, from the process of mining and producing to usage and disposal. Emissions that may possess a threat to human health and the environment. One method to assess possible impacts over the entire chain ‘from cradle to grave’ is life-cycle assessment (LCA). This method is used today by regulatory instances as well as industry to evaluate total environmental impact of a certain product or process. Toxicity impact of chemical emissions is one part of the LCA analysis, calculated as the product of the fate of the chemical, the exposure routes of the chemical and the effect of the exposure. When it comes to metal emissions, evaluating exposure is not trivial, since it depends on the speciation of the metal whether or not an organism will be exposed. In freshwater ecosystems, the sum of all the metal species that are available for biological uptake are referred to as the bioavailable fraction. The speciation pattern, and thus the size of the bioavailable fraction of a metal, is largely dependent on ambient water chemistry, so that regional differences will be observed. Recent improvements in the LCA methodology have incorporated calculations of the bioavailable fraction of metal emissions, as well as regional variability by the use of seven European water types. However, Swedish freshwater is normally softer, with a lower pH and a higher concentration of metals than the European water types. There is therefore a need to evaluate whether the existing system is applicable to Swedish water chemistry, or if there is a need for further implementations.

To this background, the aim of this project has been to evaluate the speciation and bioavailability of chromium and nickel, in a case study of emissions into a freshwater relevant for the Swedish steel industry. Specifically, bioavailability factors (BFs) for the two metals were sought, for implementation in the LCA methodology. To accomplish this, computer modelling using Visual MINTEQ and WHAM has been performed, as well as laboratory experiments. In addition, metal release from slag particles has been investigated.

The results show that the bioavailability of chromium is dominated by the oxidation state of the metal. In the form of Cr(III), it will mainly form insoluble complexes, and the BF is as low as 5·10-5. In the form of Cr(VI) the BF is 0.64. Hence a large amount will be in the largely mobile and bioavailable fraction. This is also the most toxic form of chromium. It is thus very important when assessing chromium emissions to know the oxidation state of the metal. Nickel will mainly be removed from the bioavailable fraction by formation of strong complexes with organic matter. The BF of Ni was established as 0.37 for this case study. Modelling in WHAM gave results in accordance with laboratory results, while Visual MINTEQ seemed to underestimate the BF. Metal content was low in the slag, and the release hardly detectable. However, the results suggest that a large fraction of the released Cr, although low, is in the form of Cr(VI).

Place, publisher, year, edition, pages
2017.
Keyword [en]
Speciation, bioavailability, chromium, nickel, LCA
National Category
Other Chemistry Topics
Identifiers
URN: urn:nbn:se:kth:diva-217362OAI: oai:DiVA.org:kth-217362DiVA, id: diva2:1156069
Available from: 2017-11-10 Created: 2017-11-10 Last updated: 2017-11-10Bibliographically approved

Open Access in DiVA

No full text in DiVA

By organisation
School of Chemical Science and Engineering (CHE)
Other Chemistry Topics

Search outside of DiVA

GoogleGoogle Scholar

urn-nbn

Altmetric score

urn-nbn
Total: 22 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf