Robert Flett

Between 1962 and 1969, 10 tonnes of mercury were discharged from a chlor-alkali plant in Dryden, Ontario, to the English–Wabigoon River. Present-day fish mercury concentrations are amongst the highest recorded in Canada. In 2017, the Grassy Narrows Science Team found no evidence of ongoing discharges from the plant site to the river water, even tho...

We investigated whether low-level addition of selenium (Se) could decrease mercury (Hg) in freshwater fish without imposing Se toxicity. Using a regression design, selenite was added to large mesocosms in a lake to achieve target concentrations ≤1.6 μg/L. (198)Hg (spike Hg) was added to mesocosms to determine changes in Hg bioaccumulation. Adding S...

Thousands of fish are sacrificed each year to determine potential human exposure to mercury (Hg) from fish consumption. In this paper, we use lake whitefish Coregonus clupeaformis and northern pike Esox lucius to demonstrate that accurate and reliable measures of fish muscle Hg concentrations can be determined from small samples (100 mg) for CVAAS....

The purpose of this study was to investigate the effect of sewage treatment on total mercury (THg) and methylmercury (MeHg) concentrations in domestic effluents and the contribution of urban sewage treatment facilities to THg and MeHg in rivers. We determined the concentrations of THg and MeHg in unfiltered samples of untreated and treated domestic...

Four terrestrial boreal forest catchments containing different types of wetlands were studied to determine their strength as sources or sinks of methylmercury (MeHg) and total mercury (THg) to downstream ecosystems and to determine if patterns seen in one year were consistent over several years. All catchments were sinks for THg. The wetland type,...

A review of Hg concentrations cited in the literature reveals values in the general sequence: grassland herbs < trees and shrubs < aquatic macrophytes < Sphagnum < mosses < lichens < fungi, excluding those samples collected near point sources of environmental Hg. Samples of vegetation collected from wetland and upland catchments in the Experimental...

Wetlands were found to be important sources of methyl mercury to the boreal forest ecosystem. Yields of methyl mercury were about 26-79 times higher from wetland portions of catchments (1.84-5.55 mg.ha-1.yr-1) than from purely upland areas (0.07 mg.ha-1.yr-1). Mass-balance estimates using methyl mercury inputs in wet deposition and outputs in runof...

Three protocols for the determination of inorganic and organic sulfur fractions were tested for their suitability to estimate total indigenous organic sulfur (Sorg) and35Sorg formed from added35SO42− in sediments of chemically dilute lakes in the ELA. The protocols tested have all been reported in the literature. It was found that two protocols inv...

Fifteen sediment cores from Lake Mcmphremagog showed pronounced peaks of total phos- phorus concentration within the "'"Pb-defined mixed layer, suggesting that P was migrating upward and accumulating near the mud surface. The mobility of P in the sediments was confirmed by the rapid development (5 weeks) of a marked total P maximum in the upper cen...

Acetylene reduction assays in the water columns of several artificially eutrophied lakes in the Experimental Lakes Area revealed that nitrogen fixation by planktonic blue-green algae could supply a significant portion of the nitrogen income to these lakes. In situ ¹⁵ N 2 uptake experiments in one lake indicated that nitrogen fixation was proceeding...

During summer stratification methane-oxidizing bacteria in Lake 227 are confined to a narrow zone within the thcrmoclinc because of their sensitivity to high epilimnctic oxygen concentrations. This oxygen sensitivity is based on the dependence of the oxi- dizers on an oxygen-sensitive nitrogen fixation process. Thus epilimnetic methane oxi- dation...

Previous methods of performing aquatic acetylene-reduction assays are described and several problems associated with them are discussed. A refinement of these older techniques is introduced and problems that it overcomes are also discussed. A depth profile of nitrogen fixation (C2H4 production), obtained by the refined technique, is shown for a fer...

Abstract During summer stratification methane -oxidizing bacteria in Lake 227 are confined to a narrow zone within the thcrmoclinc because of their sensitivity to high epilimnctic oxygen concentrations. This oxygen sensitivity is based on the dependence of the ...

Lake water samples were observed to transform [14-C]ethylene into water-soluble compounds that were undetectable by conventional acetylene reduction assay procedures. Methane oxidizing bacteria, which are known to be common in freshwaters, appeared to be responsible for this activity. As much as 28 percent of added ethylene has been observed to be...

Lake water samples were observed to transform [¹⁴C]ethylene into water-soluble compounds that were undetectable by conventional acetylene reduction assay procedures. Methane oxidizing bacteria, which are known to be common in freshwaters, appeared to be responsible for this activity. As much as 28% of added ethylene has been observed to be transfor...

Thesis (M. Sc.)--University of Manitoba, 1972. Includes bibliographical references (leaves 98-102). Microfilm of typescript.

Thesis (Ph. D.)--University of Manitoba, 1977. Includes bibliographical references (leaves 177-183). Microfiche of typescript.