Summer temporal changes in photoreducible mercury in the lakes of Kejimikujik National Park
LE3 .A278 2016
Bachelor of Science
Environmental & Sustainability Studies
Mercury (Hg) is a global contaminant which can undergo long-range transport in the atmosphere, and be deposited in many remote environments. The methyl mercury form can accumulate in food webs and result in severe adverse effects on organisms. The hypothesis of this research project was that the amount of mercury available for reaction with solar radiation (reduction of divalent mercury (Hg(II)) to elemental mercury(Hg(0))) in surface waters of four lakes in Kejimikujik National Park will significantly change over a summer. This research is significant because the photoreduction of Hg(II) is a mechanism of mercury loss from ecosystems, making less mercury available for methylation and ultimately biomagnification in food webs. Sampling of the four lakes: Big Dam West, Big Dam East, North Cranberry, and Puzzle Lake occurred in May, June, and July, 2015. Water sample analysis for total dissolved mercury (THg), total reducible mercury (Hg(II) red), and dissolved organic carbon (DOC) was conducted in the CARE labs at Acadia University’s K.C. Irving Environmental Science Centre. The percent of Hg(II) red relative to THg was found to decrease significantly in North Cranberry (42%-14% from May to July) and Big Dam East (44%-17% from May to July) between the sampling months. The Hg(II)redto THg in Big Dam West showed a less dramatic decreased between May and July (59%-44%), while Puzzle lake peaked in June and significantly decreased between June and July (14%-29%-20% from May, June, to July, respectively). Factors controlling these variations include DOC oncentration and lake topography. This research provides the first quantitative measurements of photoreducible mercury over a season in surface freshwater lakes, and suggests that photoreduction of Hg(II) to Hg(0) decreases as summer progresses.
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