Determination of Trace Elements and Arsenic Species in Freshwater Fish
Creators: Chen, Xiaojian
Publisher: name: University of Alberta Library
Year: 2023

<p>Trace elements are naturally occurring in the environment and important to human health. Elevated concentrations of trace elements present in food could cause adverse health outcomes. Among trace elements, arsenic adversely affects about 200 million people around the world, whose drinking water contains arsenic higher than the World Health Organization guideline level of 10 µg/L. Currently, there is no meaningful guideline for arsenic in food, partly because of the complexity of various arsenic species. Arsenic species in seafood have been studied extensively, but not much research has been done on arsenic speciation in freshwater fish. Determination of arsenic species in freshwater fish is challenging because of lower concentrations of diverse arsenic species. This thesis focuses on the determination of trace elements and arsenic species in 266 freshwater fish collected from eight Alberta water bodies (seven lakes and a storm-water pond). For the determination of trace elements, fish samples were microwave-digested with nitric acid, and the concentrations of trace elements were determined using inductively coupled plasma mass spectrometry (ICP-MS). Fourteen elements, including Al, As, Ba, Cd, Co, Cr, Cu, Mn, Mo, Ni, Se, Tl, V, and Zn, were detectable in fish samples and their concentrations were compared among different fish species, eight water bodies, and multiple years of collection. Six elements, Ag, Be, Pb, Sb, Th, and U, were not detectable in any of the 266 fish samples. For the determination of arsenic species, a methanol-water mixture was used to extract arsenic species from fish filet. High-performance liquid chromatography (HPLC) coupled to the ICP-MS technique was used to achieve separation and quantification of arsenic species. A predominant arsenic species in the 266 fish samples is arsenobetaine (AsB), accounting for 34%-95% of all arsenic species detected in the fish. Dimethylarsinic acid (DMA) and inorganic arsenate (AsV) are the second most commonly detectable arsenic species in freshwater fish samples from Alberta lakes. Monomethylarsonic acid (MMA) was detected in only two fish samples. Five arsenic species, whose chromatographic retention times did not match with any of the available arsenic standards, were also detected. The identity of these five arsenic species remained unknown. Comparisons among the major fish types, including northern pike, lake whitefish, and trout, showed differences in arsenic speciation. Comparisons between two years of fish sample collection from two lakes showed similar concentrations of arsenic species between two years. Comparisons of arsenic speciation results among fish from eight water bodies showed that fish from Cold Lake had approximately 6 times higher total arsenic concentration than fish from other seven water bodies. Most of this difference was attributed to AsB, which was approximately 8 times higher in fish from Cold Lake than fish from other seven water bodies. Future research is needed to understand the reasons for the higher concentrations of AsB and total arsenic in fish of Cold Lake. The results of this thesis research are useful for assessing human exposure to arsenic species and trace elements from fish consumption. </p>