Analysis of Metal Contaminants and Mercury Speciation in Fishes from the Slave and Athabasca Rivers
Date
2019-09-10
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
ORCID
Type
Thesis
Degree Level
Masters
Abstract
The Slave and Athabasca are two connected rivers impacted by a variety of anthropogenic activities such as oil sands extraction, metal mining, pulp mills and agriculture. Concerns have been raised regarding the health of these two rivers especially the Athabasca River which runs through areas of oil sands development. The health of fish in these rivers is one of the primary concerns due to the cultural and economic importance of the fish to local community members. Metal contaminants in fish can have an impact on fish health and can pose a risk to the health of consumers of fish, including humans. This thesis investigates metals in five fish species (burbot, goldeye, northern pike, walleye, and whitefish) from sites along the Slave and Athabasca Rivers during four seasons (summer, fall, winter, and spring). A suite of 25 metals were analyzed by ICP-MS and the majority of the metal concentrations showed little location associated variability nor were they detected at concentrations of concern. One metal, Hg, was detected at concentrations of concern and four metals (As, Se, Tl, and V) demonstrated statistically significant variations in concentrations between sampling sites with greater concentrations in the sites on the lower Slave River compared to the upper Slave River, Athabasca River, and Peace River sites. The concentrations of these metals were not of sufficient magnitude to be of concern to fish or human health, but the trend is of interest due to concerns regarding industrial activities on the Athabasca River. Mean Hg concentrations in fish muscle exceed Health Canada consumption guidelines in 2.6% of fish groups separated by species, location, and season. These concentrations exceeded subsistence advisory Hg guideline concentrations in 47.4% of fish groups. The magnitude of Hg concentrations was not new information as other researchers have found similar concentrations in fish in the region and fish consumption advisories are already in place for the Athabasca River due to Hg concerns. The two species of Hg found in fish are Hg(II) and methylmercury. Methylmercury is the predominant form of Hg in fish and has the potential to biomagnify, increasing concern for fish and human health. A method to analyze for the two Hg species was developed utilizing sodium tetraethylborate derivatization with headspace solid-phased microextraction (SPME) followed by gas chromatography and orbitrap mass spectrometry (GC-Orbitrap MS) analysis. The use of GC-Orbitrap MS allows for the scanning of a wide range of mass/charge (m/z) at high resolution (>200,000). This resolution and scan range were utilized to quantify each Hg species and Hg isotopes. The percent of total Hg represented by methylmercury in a subsample of the fish collected from the Slave and Athabasca Rivers were found to be 82.4% for goldeye, 90.2% in northern pike, 87.2% in walleye, 92.3% in whitefish, and 87.5% in burbot. Isotope patterns of Hg were also determined for these samples though the method was not sensitive enough to detect subtle differences in stable isotope patterns. Mercury concentrations are nearing, and in certain circumstances exceeding, Canadian guidelines. Overall, metal concentrations, with the exception of Hg, in the Slave and Athabasca Rivers do not appear to be at levels of concern for fish or human health at this time. The trend of four metals being greater in the lower Slave River provides an interesting opportunity for further research into metal chemodynamics.
Description
Keywords
Metals, Mercury, Fish, Slave River, Athabasca River
Citation
Degree
Master of Science (M.Sc.)
Department
Toxicology Centre
Program
Toxicology