Hayla E. Evans

Mercury concentrations in wild mink (Mustela vison) and river otters (Lontra canadensis) collected from eastern and Atlantic Canada: relationship to age and parasitism.

Total mercury (Hg) concentrations were measured in the fur, brain and liver of wild mink (Mustela vison) and river otters (Lontra canadensis) collected from eastern and Atlantic Canada. Total Hg concentrations in fur were strongly correlated with levels in the brain and liver. There was no difference in tissue concentrations between male and female mink; however, female otters had significantly higher fur, brain and liver Hg levels than males. Similarly, there was not a significant relationship between Hg concentration and age of mink, whereas in otters, Hg concentrations in all three tissues decreased significantly with age. In both species, only a very small percentage of the variability in Hg concentration was explained by age. After adjusting the data for site-to-site differences in Hg levels, Hg concentrations in the fur of mink infected by the parasite, Dioctophyma renale, were found to be significantly higher than Hg levels in uninfected mink.

The use of Pb/210Pb ratios in lake sediments for estimating atmospheric fallout of stable lead in South-Central Ontario, Canada

The ratio of Pb concentrations (μg g−1) to excess 210Pb (210Pbexc) activities (dpm g−1) in the surface (0–1 cm) sediments of lake cores, together with a knowledge of atmospheric 210Pb fluxes, were used to estimate the atmospheric deposition of stable Pb in south-central Ontario, Canada. Between three and five cores were collected from each of 10 lakes, while in one lake (Red Chalk - Main Basin) a total of 25 cores were obtained. The average atmospheric 210Pbexc flux to the main basin of Red Chalk Lake was calculated to be 1.1 dpm cm−2 year−1, a value which compares favourably with literature estimates of 210Pb deposition for Ontario. The surface Pb/210Pbexc ratios for 61 cores ranged between 1.26 and 3.44 μg dpm−1(average 2.15 ± 0.45 μg dpm−1). Therefore, the predicted atmospheric Pb deposition was 14–38 mg m−2 year−1 (average 24 ± 5.0 mg m−2 year−1). This estimate of stable Pb fallout is similar to those measured by alternate methods and indicates that elemental ratios in lake sediments might be useful for predicting the behaviour of other contaminants in lakes.

Methylmercury accumulation and elimination in mink (Neovison vison) hair and blood: Results of a controlled feeding experiment using stable isotope tracers

Concentrations of metals in hair are used often to develop pharmacokinetic models for both animals and humans. Although data on uptake are available, elimination kinetics are less well understood; stable isotope tracers provide an excellent tool for measuring uptake and elimination kinetics. In the present study, methylmercury concentrations through time were measured in the hair and blood of mink (Neovison vison) during a controlled 60-d feeding experiment. Thirty-four mink were fed a standard fish-based diet for 14 d, at the end of which (day 0), 4 mink were sacrificed to determine baseline methylmercury (MeHg) concentrations. From day 0 to day 10, the remaining mink were fed a diet consisting of the base diet supplemented with 0.513 ± 0.013 µg Me(199) Hg/g and 0.163 ± 0.003 µg Me(201) Hg/g. From day 10 to day 60, mink were fed the base diet supplemented with 0.175 ± 0.024 µg Me(201) Hg/g. Animals were sacrificed periodically to determine accumulation of Me(201) Hg in blood and hair over the entire 60-d period and the elimination of Me(199) Hg over the last 50 d. Hair samples, collected from each mink and cut into 2.0-mm lengths, indicate that both isotopes of MeHg appeared in the hair closest to the skin at approximately day 10, with concentrations in the hair reaching steady state from day 39 onward. The elimination rate of Me(199) Hg from the blood was 0.05/d, and the ratio of MeHg in the hair to blood was 119. A large fraction of MeHg (22% to >100%) was stored in the hair, suggesting that in fur-bearing mammals the hair is a major route of elimination of MeHg from the body.

A comparison of lead and zinc sediment profiles from cores taken by diver and a gravity corer

The zinc and lead concentrations were compared in several pairs of sediment cores obtained with a modified K-B corer and by Scuba diver from Coon Lake, Canada. A slow approach to and penetration of the sediments (ca. 0.1 m s-1) was employed for both coring devices. The modified K-B corer gave similar lead and zinc profiles to the diver cores. The divers observed that the K-B corer caused no disturbance of the surface sediment layers as it approached and entered the sediments. These results suggest that the K-B corer is suitable for use in lake studies requiring short, undisturbed cores from fine-grained sediments.

The effect of core compression on the measurement of zinc concentrations and anthropogenic burdens in lake sediments

An attempt was made to demonstrate the significance of core compression (shortening) by the use of geochemical profiles. In Plastic Lake, Canada, the hypothesis was tested that the measured anthropogenic zinc burdens would differ in the sediments while the measured sediment enrichment factors would be comparable, in shortened and unshortened cores. However, there was no significant difference in either the anthropogenic zinc burdens or the sediment enrichment factors calculated from the shortened and unshortened cores. The fact that the anthropogenic zinc is found, almost exclusively, in the top 10 cm of the sediment in Plastic Lake may explain these results.

Catchment Management in the Industrial Landscape

A catchment can be defined as the area that encompasses a particular aquatic environment (e.g., a lake or a stream) including the land that drains into it. In Sudbury, a catchment can vary from a few hectares of area drained by a small temporary stream to the thousands of square kilometres drained by major rivers in the area.