In the environment, oxidized mercury (Hg) can be converted to more toxic chemical species, such as methylmercury (MeHg), as a result of both abiotic and biotic reactions. Hg and MeHg are present in aquatic ecosystems that flow into the Lake St. Francis region of the St. Lawrence River, but their origin is still being debated. A study of mercury and methylmercury contamination in Lake St. Francis in cooperation with the Raisin Region Conservation Authority (RRCA) is ongoing, in collaboration with the Ontario Ministry of Agriculture, Food, and Rural Affairs (OMAFRA) and the Great Lakes Program. A recent report detailed the experimental results for one portion of the area of concern, the Raisin River. The goal of the present project is to update and expand upon the previous work in order to include other existing and new data for this river and several other watercourses feeding Lake St. Francis. Special attention was paid to the MeHg hotspots in an attempt to link methylation and subsequent mobilization to different types of land use and nutrient profiles compiled from new and existing data.
It was predicted that water draining off wetlands would have higher MeHg concentrations than water from catchments with other land use profiles. Total and methylmercury were expected to be correlated to the concentrations of nitrogen compounds, sulfate, phosphorus, dissolved inorganic carbon (DIC), and especially dissolved organic carbon (DOC). However, wetlands could not be correlated to MeHg as predicted but the area of crop land was correlated positively with the percentage of THg present as MeHg. Forest and impermeable areas were associated with a decrease in mercury. There was no difference in mercury during wet years compared to dry years when compared on an annual basis, but a significant seasonal difference exists between the two categories. MeHg was positively correlated to DOC, NH3, and BOD. THg was positively correlated to BOD, TSS, Escherichia coli, and fecal coliforms. The percentage of THg present as MeHg (%MeHg) was positively correlated to phosphorus. There were also some statistically significant negative correlations. Forest and impermeable area were negatively correlated with the quantity of MeHg, and impermeable area was negatively correlated with %MeHg. Greater predictor strength and more numerous significant correlations are expected under more thorough sampling and more data.
| Identifer | oai:union.ndltd.org:uottawa.ca/oai:ruor.uottawa.ca:10393/28873 |
| Date | January 2010 |
| Creators | Harrison, Sarah |
| Publisher | University of Ottawa (Canada) |
| Source Sets | Université d’Ottawa |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | 104 p. |
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