Document Type

Thesis

Degree Name

Master of Science (MSc)

Department

Chemistry

Faculty/School

Faculty of Science

First Advisor

Dirk Wallschläger

Advisor Role

supervisor

Abstract

Methylseleninic acid (MSA(IV)) is an organic form of selenium that has been suggested to be one of the most bioaccumulative forms of selenium in aquatic ecosystems. However, there have been no lab studies that confirm this, which is the reason this study was conducted. Once MSA(IV) and other bioavailable forms of selenium enter aquatic ecosystems, organisms such as algae take up these compounds which then bioaccumulate through the food chain. S. obliquus was exposed to 10 ppb MSA(IV) in 10% Bold’s basal medium (BBM) in a growth chamber to mimic environmental conditions over a 7-day period. Carbon traps and filters were used to monitor selenium concentrations in the air and within algae after microwave digestion. Liquid samples were measured using ion chromatography inductively coupled plasma mass spectrometry (IC-ICP-MS) to monitor selenium speciation. This study found that MSA(IV) is a transient selenium compound that disappears faster from solution in the presence of algae compared to abiotic flasks. In abiotic flasks, photoreduction of MSA(IV) may have occurred, forming an unidentified volatile selenium species. In the presence of algae, MSA(IV) is metabolized to an unknown organic selenium species, which remains in solution. Carbon trap and algal filters produced concentrations below the detection limit due to dilution, meaning in this study the mass balance could not be closed. Overall MSA(IV) is a transient selenium species, transferring approximately 80-99% into the atmosphere in the form of volatile selenium when no algae are present. When algae are present, approximately 10% is transformed into an unknown metabolite which is found in the water, another ~10% is present as other selenium species in the water, and the final ~80% may be present in the algae.

Convocation Year

2026

Convocation Season

Spring

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Included in

Biochemistry Commons

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