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Sorption of PAHs to organic colloids in natural water
2000 (English)Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

Polycyclic aromatic hydrocarbons (PAHs) are a class of compounds that are hazardous both to the environment and the human health. They originate from both natural and anthropogenic sources from where emissions have increased over the last decades. The distribution of these pollutants in the aqueous environment is affected by the presence of organic matter. By sorbing to organic matter, the bioavailability and toxicity of PAHs can be reduced. The sorption ability of natural organic colloids was investigated during the course of an algae bloom in Ekhagen Bay. The interaction is described by the organic carbon normalised colloid-water partitioning coefficient, Kcoc, and it has been derived for pyrene and phenanthrene using both fluorescence quenching technique and a newly developed air-bridge batch method. Cross- flow ultrafiltration was used to isolate and concentrate the colloids. Sorption experiments were conducted at four occasions, twice before the algae bloom started, once in the beginning of the blooming period and once during the peak of the bloom. To describe the organic matter in the bay, the water was analysed for various biogeochemical parameters approximately three times per week. The values of Kcoc varied both depending on the method used and of the development of the algae bloom in Ekhagen. Results from the air-bridge batch method ranged from not measurable to 3.7E+05 ml/gC for pyrene, a value high in comparison to the literature. Kcoc for phenanthrene amounted to 1.2E+04 ml/gC which lay in the ranges reported in the literature. The results suggested that the air-bridge batch method would require sorbents with stronger sorption ability to function satisfactorily. The fluorescence quenching method yielded values comparable to previously reported: between 2.2 and 3.9E+04 ml/gC for pyrene. The results from both methods did indicate a similar trend: the sorption ability of the organic matter seemed to weaken as the algae bloom was approaching. This could be illustrated by the relationship between the Kcoc and the molar absoptivity (e280), a parameter describing the aromaticity of the organic matter. Based on four sorption coefficients obtained during three different stages of the algae bloom, the following relationship was yielded (R2= 0.95): Kcoc = 0.0041 * e280 + 3.7 This suggests that it could be fruitful to further explore whether the single parameter e280 can be used to predict the ability of natural colloids to bind PAHs. The development of such a relationship would simplify estimations of the sorption ability and could subsequently lead to a better understanding of the distribution and thereby the bioavailability and toxicity of hydrophobic pollutants.

Place, publisher, year, edition, pages
Keyword [en]
Technology, geochemistry, pyrene, phenanthrene, PAH, colloids, sorption, natural waters, algae bloom, fluorescence
Keyword [sv]
URN: urn:nbn:se:ltu:diva-43773ISRN: LTU-EX--00/223--SELocal ID: 19b740ba-c4fd-4724-b9e6-b893d71effe5OAI: diva2:1017014
Subject / course
Student thesis, at least 30 credits
Educational program
Environmental Engineering, master's level
Validerat; 20101217 (root)Available from: 2016-10-04 Created: 2016-10-04Bibliographically approved

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