Methylmercury (MeHg) is the most toxic species of mercury (Hg), and is an important ecosystem contaminant. In wetlands on the Canadian Shield, in NW Ontario, MeHg concentrations in peat and peat porewater ranged from 0.3 to 53 ng $ rm g sp{-1}$ and $<$0.1 to $ rm 7.3 ng l sp{-1},$ respectively. The greatest concentrations of MeHg occurred just below the water table, emphasizing the importance of redox reactions in Hg methylation. Methylmercury partition coefficients between peat and peat porewater ranged from $1.6 times 10 sp3$ to $8.6 times 10 sp5.$ No significant correlations between MeHg and concentrations of $ rm H sp+, NH sb4 sp+, NO sb3 sp-, NO sb2 sp-,$ total dissolved nitrogen (TDN), total dissolved phosphorus (TDP), $ rm SO sb4 sp{2-},$ and dissolved organic carbon (DOC) in the porewater of the wetlands were found. / Following shallow impoundment of a wetland, MeHg concentrations in the upper metre of peat porewater increased from $ rm 0.2 pm 0.2 ng l sp{-1}$ to $ rm 0.8 pm 0.8 ng l sp{-1}.$ Total mercury (T-Hg) and MeHg concentrations were determined in decomposing sedge, spruce needles, and Sphagnum moss, placed in a headwater wetland and the impounded wetland. The amount of T-Hg decreased in all tissues regardless of location. the amount of MeHg increased by as much as an order of magnitude in the tissues placed in the impounded wetland and wet areas (hollows and lawns) of the headwater wetland, but decreased in tissue placed in the dry areas (hummocks) of the headwater wetland. Therefore, it is during anaerobic decomposition of plant material that MeHg is produced in wetlands. / Incubations of peat were performed with addition of Hg, molybdate, $ rm SO sb4 sp{2-}, S sp{2-}, NH sb4NO sb3,$ pyruvate, and upland DOC. Methylmercury production was increased only after addition of $ rm SO sb4 sp{2-}$ and retarded only by $ rm NH sb4NO sb3.$ Although $ rm SO sb4 sp{2-}$ may not be required to methylate Hg, the increased availability of $ rm SO sb4 sp{2-}$ may influence the size and composition of the population of sulfate reducing bacteria in peat, thereby increasing the potential for Hg methylation.

No description available.

<p> An attempt has been made to estimate the abundance of trace and major constituents in the Precambrian surficial rocks in a large part (43,000 square miles) of the Red Lake - Lansdowne House area in northwestern Ontario. The area has an average composition which is close to that of granodiorite, more silicic than most estimates of crustal abundance, close to other estimates for continental shield areas, but possibly deficient in K2O relative to Poldervaart's (1955) estimate. The rocks of this area appear to be low in Be, Ti, V, Cu, Y, Sc and Zr, and high in Sr, relative to crustal abundances based on the proportion of exposed rocks on the surface of the continents (Turekian and Wedepohl, 1961). Analysis of variance techniques have detected significant regional variations of Cr, Mn, Sr and Ba. Significant variation exists between rock types for all trace elements analyzed except Cu.</p> / Thesis / Master of Science (MSc)

Thesis (Ph.D.)--McMaster University, 2003. / Advisors: Ming-ko Woo and Wayne R. Rouse. Includes bibliographical references (p. 97-104). Also available via World Wide Web.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1934. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

No description available.

The effect of lake acidification was evaluated, in the field, in terms of its impact on both the structural and functional composition of the macrozoobenthic community. The littoral macrozoobenthic community and water chemistry of 45 Canadian Shield lakes was sampled. The water chemistry variables sampled included pH, total dissolved calcium, conductivity, and dissolved organic acid (measured as colour). Partial canonical correlation analysis and partial regression analysis were used to identify those components of the macrozoobenthic community that most directly reflected pH variability. This was done by first removing from the data that portion of the variability attributable to total dissolved calcium, conductivity, and dissolved organic acids. In addition, the spatial structure in the data was removed by identifying the geographic coordinates of the sampling sites. / In general, the results presented here are not consistent with previous studies where the response of the macrozoobenthic community was related to pH without consideration of confounding covariables. Snails, leeches, mayflies and crayfish have all been cited for their sensitivity to acidification. The present study found these taxa to reflect, not pH variability, but rather attributes of water hardness. Similar results were found for both total zoobenthic biomass and functional feeding group abundance.

The land of deep water lies in Ontario’s north, atop the boundless rock of the Shield. It holds the secret of an island once blossoming with copper ore. Here primordial elements dance in the ancient landscape and invite us to join them in their awakening. Liquid portals, layered ancient rock and plunging mine shafts unearth a cosmic order born of chaos. Myth, geology and alchemy all fuse together in defining this place. This thesis is a journey to centre of the Shield, through the deep water, rock and voids that encircle it. It is an expedition into the multiplicities of time through the poetic imagination. Here on the bridge to preconsciousness, we are invited in. At the heart lies Copperfields, a mine isolated on an island in Temagami. Once bearing some of the purest copper on Earth, it now sits abandoned amidst fragments of its former glory. The design proposed reclaims these elements and animates them as gateways to the dynamic Shield. In the folds of time, quivering between thought and the preconscious, a fiction rich in meaning and experience is offered up. Let us now embark on our journey to the centre of the Shield.

The land of deep water lies in Ontario’s north, atop the boundless rock of the Shield. It holds the secret of an island once blossoming with copper ore. Here primordial elements dance in the ancient landscape and invite us to join them in their awakening. Liquid portals, layered ancient rock and plunging mine shafts unearth a cosmic order born of chaos. Myth, geology and alchemy all fuse together in defining this place. This thesis is a journey to centre of the Shield, through the deep water, rock and voids that encircle it. It is an expedition into the multiplicities of time through the poetic imagination. Here on the bridge to preconsciousness, we are invited in. At the heart lies Copperfields, a mine isolated on an island in Temagami. Once bearing some of the purest copper on Earth, it now sits abandoned amidst fragments of its former glory. The design proposed reclaims these elements and animates them as gateways to the dynamic Shield. In the folds of time, quivering between thought and the preconscious, a fiction rich in meaning and experience is offered up. Let us now embark on our journey to the centre of the Shield.

A scapolite-hornblende-biotite schist from the Grenville province of the Canadian Shield has been analysed for Tl by an atomic absorption technique with a high sensitivity. K, Rb and some major oxides were determined by wet chemistry. Tl, K/Rb, K/Tl and Tl/Rb were compared to several other rocks and for this report were found to be 432ppb, 429, 4.85x10³ and 88.4x10⁻³ respectively. These values are similar to those quoted for other rocks. / Thesis / Bachelor of Science (BSc)