Chengyang WangFollow

Date of Award

2018

Document Type

Honors Thesis (Open Access)

Department

Colby College. Environmental Studies Program

Advisor(s)

Christoph Aeppli

Second Advisor

Whitney King

Third Advisor

Denise Bruesewitz

Abstract

Bromoform is a major source of atmospheric bromine. Most bromoform is produced by marine organisms including macroalgae and phytoplankton, using the enzyme bromoperoxidase (BPO). Bromoform can also be a byproduct of industrial processes such as water disinfection. Identifying sources of environmental bromoform is still a challenge. A novel technique of using quadrupole mass spectrometry coupled to a gas chromatography (GCqMS) was developed and optimized for Br isotope analyses. The study shows that GCqMS in single ion monitoring (SIM) mode can measure 81Br with precision of around ±0.7‰ (60pmol bromoform injected). This study aims to investigate stable Br isotopes of bromoform produced from different pathways, including macroalgae (Ascophyllum Nodosum and Fucus Vesculosis) and abiotic bromination with HOBr and phenol. The experimental 81Br results were then used to interpret of bromoform production in the Damariscotta River estuary. The Br isotope signature of bromoform in the Damariscotta River was -0.6±1.8‰ relative to our isotopic standard. That of bromoform produced by A. Nodosum, F. Vesculosis, and the abiotic reaction were 1.8±0.7‰, 2.4±2.6‰, and -1.3±1.2‰, respectively. H2O2 decreased Br isotopic fractionation of bromoform produced by A. Nodosum.

Keywords

Bromoform, bromine, isotope, bromoperoxidase, gas chromatography, mass spectrometry, isotope signature

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