Human activity has affected metal emissions to the atmosphere on a global scale for several thousand years, resulting in widespread contamination of the environment with toxic heavy metals such as Pb and Hg, thereby threatening both human and environmental health. In recent years ombrotrophic peat bogs have been used to study the changing rates and sources of atmospheric metal deposition, as they receive all their water and nutrients from the atmosphere by dry and wet deposition alone. Cores from such bogs have proved especially useful as archives of atmospheric Pb deposition as Pb is essentially immobile in ombrotrophic peat. The work described in this thesis is primarily concerned with the use of ombrotrophic peat bogs to investigate environmental contamination in Scotland during pre-industrial, industrial and post-industrial (i.e. ca. post-1970 A.D.) times. Cores were collected from ombrotrophic peat bogs at four different geographical locations (Carsegowan Moss, SW; Flanders Moss, W Central; The Red Moss of Balerno, E Central; Turclossie Moss, NE) in Scotland. Air-dried peat samples were dry-ashed and dissolved using microwave-assisted HF IHN03 digestion. Elemental concentrations (e.g. AI, As, Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Ni, P, Pb, S, Sb, Sc, Se, Ti, V, Y, Zn and Zr) and Pb isotope ratios (e.g. 206PbP07Pb) were determined using ICP-OES and ICP-MS as appropriate. For Hg determination, samples were digested with HN03/H2S04 and then analysed by CV AAS. Certified reference materials (e.g. Ombrotrophic Peat (NIMT/UOE/FM001), Canadian Peat (1878 P), Bush Branches and Leaves (DC73349), Peach Leaves (GBW 08501) and Coal (BCR CRM No. 40 and NBS SRM 1635) were used for quality control purposes. The distribution and behaviour of the potentially toxic trace elements (As, Cd, Co, Cr, Cu, Hg, Ni, Sb, Se, V and Zn) and of major elements (Ca, Fe, Mg, Mn, P and S) within the four ombrotrophic peat bogs was investigated and there was strong evidence that Ca, Fe, Mg, Mn, P, S, Se and Zn were mobile in ombrotrophic peat, while As, Cd, Co, Cr, Cu, Hg (at least during industrial and post-industrial periods), Ni, Sb and V, like Pb, were essentially immobile in ombrotrophic peat. Deposition records of conservative lithogenic elements (e.g. concentrations of AI, Sc, Ti, Y and Zr) that occur predominantly in soil dust were also investigated and the chosen conservative elements Sc, Ti and Zr were used in calculations to estimate anthropogenic enrichments of As, Cd, Co, Cr, Cu, Ni, Pb, Sb and V in peat bog profiles. 210Pb- and 14C- dated peat cores were used to reconstruct historical records of atmospheric anthropogenic As, Cd, Co, Cr, Cu, Ni, Pb, Sb and V deposition (since the pre-Roman (i.e. to ca. 380 B.C.)/Roman period) and atmospheric Hg deposition (since the onset of the industrial period) across Scotland. For Pb, on the basis of Pb isotopic composition (e.g. 206PbP Pb), clear indications of contamination during the preRoman/Roman and Mediaeval periods were attributed to the mining and smelting of Pb ores (from Britain and elsewhere in Europe). During the industrial and post-industrial periods, variations in the relative importance of contributions of anthropogenic Pb from different sources were apparent. From ca. the early 17th century A.D. at three of the peat bog sites, the mining and smelting of indigenous Scottish Pb ores, until the early 20th century A.D., were found to be the most important sources of anthropogenic Pb deposition. In contrast, at the most southerly site (Carsegowan Moss), influences from the use of both British Ph ores and imported Australian Ph ores (in more southern parts of Britain) since the late 19th century A.D. were evident. At each of the sites, the increasing importance of Australian-Ph-influenced car-exhaust emissions from the 1930s to late 1990s A.D., along with significant contributions from coal combustion (until the late 1960s A.D.) was evident. For Sb, in general, similarities between the major trends in the concentration profiles of anthropogenic Sb and Ph suggested common sources of these two elements. Perturbations in the anthropogenic Sb/Pb ratios since ca. 1800 A.D., however, were attributed to temporal variations in the relative importance of atmospheric emissions from different sources such as Ph ore mining/smelting, coal combustion and, in recent decades, automobile-related use of compounds of Ph (in leaded petrol) and of Sb (in brake linings). For Hg, in general, during the industrial and post-industrial periods, coal combustion and waste incineration, respectively, were likely to be the most important sources of Hg. For As, clear indications of contamination during the Mediaeval period were probably attributable to the mining and smelting of Ph and Cu ores, and for As, Cd, Co, Cr, Cu, Ni and V, during the industrial and post-industrial periods, a variety of sources (e.g. metallurgical activities, coal and oil combustion, use of phosphate fertilisers and waste incineration) were important to varying extents. Also, in recent years, atmospheric Cu emissions from automobile-related use of compounds of Cu (in motor oil, brake linings and tyres) may have been important. Inter-site and inter-elemental comparison of records of atmospheric metal deposition across Scotland indicated that, in general, atmospheric As, Cr, Hg, Ph and Sb deposition was greatest during the industrial period (between the late 1880s and late 1960s A.D.) and atmospheric Cd, Co, Cu, Ni and V deposition was greatest during the industrial and post-industrial periods (between ca. 1900 and the early 2000s A.D.), although increases in As, Co, Cr, Hg, Ph and Sb deposition were earliest (during the late 19th and early 20th century A.D.) at the most southerly site (Carsegowan Moss). During the industrial and post-industrial periods, levels of As, Ph and Cd contamination were generally highest in the south of Scotland, Cu, Co and Sb in south and central Scotland, and Cr, Ni and V in central Scotland. Overall, the existence of a south to north As, Cd, Co, Cr, Cu, Ni, Ph, Sb and V pollution gradient in Scotland was evident.

No description available.

Vacuum harvested peatlands do not easily regain their hydrological function after peat production therefore restoration is required to create hydrological conditions appropriate for the growth of peat producing fen plant species. Peat extraction at Bic-Saint-Fabien peatland by the block-cut method began in 1946, converted to vacuum harvesting in the early 1970’s and ceased in 2000. After exploitation, about 0.04-1 m of residual minerotrophic sedge peat remained; therefore Bic-Saint-Fabien was restored as a fen. Research occurred in 2008-2011 and restoration began fall 2009 so we have two pre-restoration and two post-restoration study years. Rewetting consisted of blocking active drainage ditches, contouring the peat surface into level terraces to even out elevation differences, and building peat ridges (bunds) to retain runoff. Vegetation was introduced to some recontoured parts of the site by the surface layer transfer method. A straw mulch treatment was applied to minimize evapotranspiration. A water budget was created for the harvested cutover area and an adjacent undisturbed section of Bic-Saint- Fabien for all study years. Data collection for the water budget occurred June 2-August 7 (day of year 153-219). Water table, volumetric soil moisture content and soil-water pressure were also examined to better understand the impact of reconfiguration on the hydrology of the system. A 1-1.5 m thick layer of gyttja (a low permeability, high porosity lake-bed sediment) underlies the residual peat; it was parameterized and assessed to see if it could potentially compress and supply water to the overlying peat when the system is stressed. In 2011, the volumetric moisture content and thickness of gyttja were monitored in the field to estimate the strain placed on the gyttja by seasonal water table variability. Gyttja samples were collected and brought back to the laboratory for parameterization and compressibility tests. A water budget was completed annually for the cutover and undisturbed areas of the peatland. There were no distinguishable differences between study years except that 2008 and 2009 were climatologically wetter. During the water budget period surface and groundwater run-on into the cutover area were negligible making precipitation the principle water input. The dominant water loss from the cutover area was evapotranspiration since runoff was only 2 and 9 mm in 2010 and 2011, respectively. Rewetting did not result in a uniform wetness across the cutover site chiefly due to local differences in peat surface elevation. An interior section of Bic- Saint-Fabien remained saturated for nearly all of 2011; it had mean seasonal water table of +2.8 cm, and volumetric soil moisture content and soil-water pressure, 5 cm below the peat surface were 86% and +4 mbar. At a peripheral section (~100 m away) the values were -14.4 cm, 67% and -13 mbar, respectively. While the interior was generally wetter than the peripheral regions, there were some exceptions, notably near where dams were installed on peripheral drainage ditches. The markedly different spatial patterns of wetness suggests that a uniform prescription regarding vegetation re-establishment in the rewetted section may not be warranted. The bulk density, particle density and porosity of gyttja averaged 0.12 g cm-3 1.57g cm-3 and 92%, in the top 40 cm of the layer. The organic matter content of gyttja decreased with depth from about 70% at a 5 cm depth to 45% at a 45 cm depth. Laboratory compression tests showed 9 and 72% strain at effective stresses of 3.5 and 200 kPa, respectively, demonstrating the potential for releasing water upon compression, which in the field is caused by water table lowering. From day of year 192 to 202 in 2011, when a ~8 cm water level change occurred (effective stress range ~0.8 kPa), the volumetric moisture content and thickness of the top 30 cm of gyttja decreased by 0.4%, and 0.5 cm, respectively, representing 0.1 and 1.7% strain, respectively, as determined from these two different approaches. The compression of gyttja after Bic-Saint-Fabien was rewetted (2011) was small but might have been significant under drier conditions with greater water table variability, such as during the early stages of site drainage when it was being prepared for peat extraction or after peat production ceased. The release of water to the peat layer from the compression of gyttja after peat production finished and before rewetting occurred, might have been an important self-preservation mechanism, eventually making it easier to rewet. Water table drawdown in 2011 produced very small strain rates suggesting gyttja compression in this year had no important role; hence rewetting success was more reliant on other rewetting techniques implemented at this site.

Peats and organic-rich soils are a key part of the global carbon (C) cycle due to their sequestration and storage of atmospheric C as organic matter. Atmospheric deposition as a result of human activities has led to increased inventories of lead (Pb) and mercury (Hg) in UK peats and organic-rich soils. Ombrotrophic peat bogs, which receive all their nutrients and pollutants from the atmosphere, provide a historic record of Pb and Hg deposition within their solid phase. Organic-rich forest soil systems can also act as sinks for anthropogenic Pb but vertical transport of Pb can distort these temporal records. The long-term outlook may, however, be affected by processes which lead to decomposition of organic matter e.g. drying out of peatlands and soils due to climatic change, since these may release Pb into the aqueous phase and volatile Hg to the atmosphere. The associations and speciation of Pb and Hg within peats and organic-rich soils are not well understood but are key to understanding both the potential for release of these pollutants into other environmental compartments and the risks to ecosystems and human health posed by such a release. Investigation of 4 sites in central Scotland showed that, depending on vertical depth, ~40-99% of Pb in ombrotrophic peat was in association with large (0.22 μm – 100 kDa) humic molecules. Near-surface regions where intact plant material had not yet undergone complete humification showed the lowest proportion of Pb-humic association. Historical Pb deposition was retained to similar degrees across each site with recorded inventories to 1986 of 0.340-0.561 g m-2. However, perturbation of the 206Pb/207Pb isotope ratio profile at Glentress forest indicated that limited migration of petrol-sourced Pb may be occurring. Similarly, perturbation of the 210Pb profile at Auchencorth Moss, in addition to discrepancies in the apparent time period in which peak Pb deposition occurred, indicated that Pb may also be subject to migration within this ombrotrophic system. With respect to Hg, between-site differences in speciation were observed. For example, Hg2+ represented < 25% of the total Hg species in the top 10 cm of solid phase ombrotrophic peat but > 50% of the total in forest soil. In contrast, aqueous phase Hg was entirely in the inorganic form across all sites. The occurrence of a solid phase [Hg] peak in layers corresponding to the ~1955 height of coal burning, in addition to the narrow range of peatland Hg inventories to 1950 (2.20-3.23 g m-2) provide evidence that Hg deposition records may be maintained in organic-rich systems to a greater degree than previously assumed. Differences observed in the associations of Pb and the speciation of Hg between the surface vegetation of ombrotrophic bogs and the underlying peat suggests that plants play an integral role in the biogeochemical behavior and sequestration of Pb and Hg in these terrestrial systems.

Thesis (Ph. D.)--Swedish University of Agricultural Sciences, 2000. / Includes bibliographical references.

This research has examined the historical vegetation of two Eastern Otago sites below the regional treeline, with the aim of addressing questions about the distribution and spread of native tussock grasslands prior to human arrival in New Zealand c. 800 yr BP. Pollen and phytolith (plant opaline silicate) proxies have been extracted from peat cores at Swampy Summit and Clarks Junction to provide a record of vegetation spanning the Holocene. Using multiple proxies and two sample sites has allowed for comparisons of the record of vegetation from within sites and between sites. A record of the modern pollen rain was also gathered from localised moss polsters at Swampy Summit in order to reconcile modern pollen assemblages and transport patterns with historical findings. It became clear from the research that the record of vegetation inferred from phytoliths was not analogous to the pollen-based records, which supported the hypothesis that vegetation reconstructions based solely on pollen may be unreliable. Good pollen preservation in the sediments allowed for the identification of over 50 taxa, although only Chionochloid forms were identifiable to a family level in the phytolith records. Poaceae pollen was abundant throughout the Clarks Junction record, suggesting grassland had persisted at this site during the Holocene, while Poaceae pollen at Swampy Summit was minimal and sporadic. Phytoliths at Swampy Summit show grasses have persisted at the site thoughout the Holocene, at times in much greater proportions than the pollen record would suggest, while Chionochloid phytoliths only become common near the top of the record, possibly reflecting increasing dominance of this taxa after human disturbance. In contrast to Swampy Summit, the Clarks Junction phytolith record reflects a more stable presence of grasses throughout the Holocene, with Chionochloid forms present throughout. Phytoliths appear to be a more reliable proxy for local vegetation, with both sites indicating a Holocene presence of grasses below the regional treeline prior to human arrival in New Zealand. In comparison, the pollen record appears to indicate a more regional pattern of vegetation, with the grassland pollen record complicated by pollen dispersal and deposition factors.

No description available.

No description available.

Microscopic charcoal analyses of sediment cores are used widely by palaeoecologists for reconstructing proxy records of past fire activity. Few studies, however, have reconstructed fire histories from UK and Irish moorland environments, a rather surprising situation considering the fact that much of the heather-dominated moorland in the UK and Ireland has been managed and maintained using fire for many centuries, and in some instances millennia. This thesis addresses the main issues regarding the use and applicability of microscopic charcoal analyses in moorland contexts. The literature pertaining to the theory and practical application of microscopic charcoal analyses is comprehensively reviewed, and all aspects of microscopic charcoal analysis, from charcoal production through to the interpretation of sediment charcoal profiles, are discussed and wherever possible related to their applicability in moorland contexts. An investigation of the taphonomy of microscopic charcoal around small moorland fires was conducted in order to provide an appreciation of the processes of charcoal production and the extent of charcoal particle dispersal. The results suggest that small moorland fires produce differential quantities of charcoal particles of different size ranges, smaller particles are produced in significantly greater quantities than progressively larger ones. The majority of charcoal particles produced by small muirburns are deposited locally, within approximately 70-100 m of parent fires, and the wind direction at the time of the fire may be a key factor determining the dispersal of microscopic charcoal particles, the majority being deposited down-wind of fires, few are dispersed laterally or into the wind. A microscopic charcoal quantification technique was developed to reconstruct extended (>50 year) fire histories from moorland soil profiles. A number of fire histories from mor humus-rich moorland soil cores of approximately several centuries duration were reconstructed. Fossil charcoal assemblages produced by in situ fires were distinguished from those produced by nearby ex situ fires on the basis of differences in gross charcoal abundance and charcoal size class distributions. Charcoal assemblages produced by in situ fires are determinable from those produced by ex situ fires because they generally contain a greater total abundance of charcoal particles and higher proportions of medium to large particles. Microscopic charcoal analyses of lake sediment cores from seven UK and Irish moorland catchments were used to reconstruct long-term (>100 year) fire histories. The reconstructed fire histories were used to assess whether changes in fire activity in the catchments may have been responsible for initiating past -episodes of peat erosion, inferred from loss on ignition measurements, and declines in Calluna cover, inferred from pollen analyses, evident at all of the sites. The results suggest that moorland burning may have been an influential factor contributing to the initiation of peat erosion at only one of the seven sites studied. Similarly, fire activity was only significantly related to the loss of Calluna at two of the seven sites studied.

Vacuum harvested peatlands do not easily regain their hydrological function after peat production therefore restoration is required to create hydrological conditions appropriate for the growth of peat producing fen plant species. Peat extraction at Bic-Saint-Fabien peatland by the block-cut method began in 1946, converted to vacuum harvesting in the early 1970’s and ceased in 2000. After exploitation, about 0.04-1 m of residual minerotrophic sedge peat remained; therefore Bic-Saint-Fabien was restored as a fen. Research occurred in 2008-2011 and restoration began fall 2009 so we have two pre-restoration and two post-restoration study years. Rewetting consisted of blocking active drainage ditches, contouring the peat surface into level terraces to even out elevation differences, and building peat ridges (bunds) to retain runoff. Vegetation was introduced to some recontoured parts of the site by the surface layer transfer method. A straw mulch treatment was applied to minimize evapotranspiration. A water budget was created for the harvested cutover area and an adjacent undisturbed section of Bic-Saint- Fabien for all study years. Data collection for the water budget occurred June 2-August 7 (day of year 153-219). Water table, volumetric soil moisture content and soil-water pressure were also examined to better understand the impact of reconfiguration on the hydrology of the system. A 1-1.5 m thick layer of gyttja (a low permeability, high porosity lake-bed sediment) underlies the residual peat; it was parameterized and assessed to see if it could potentially compress and supply water to the overlying peat when the system is stressed. In 2011, the volumetric moisture content and thickness of gyttja were monitored in the field to estimate the strain placed on the gyttja by seasonal water table variability. Gyttja samples were collected and brought back to the laboratory for parameterization and compressibility tests. A water budget was completed annually for the cutover and undisturbed areas of the peatland. There were no distinguishable differences between study years except that 2008 and 2009 were climatologically wetter. During the water budget period surface and groundwater run-on into the cutover area were negligible making precipitation the principle water input. The dominant water loss from the cutover area was evapotranspiration since runoff was only 2 and 9 mm in 2010 and 2011, respectively. Rewetting did not result in a uniform wetness across the cutover site chiefly due to local differences in peat surface elevation. An interior section of Bic- Saint-Fabien remained saturated for nearly all of 2011; it had mean seasonal water table of +2.8 cm, and volumetric soil moisture content and soil-water pressure, 5 cm below the peat surface were 86% and +4 mbar. At a peripheral section (~100 m away) the values were -14.4 cm, 67% and -13 mbar, respectively. While the interior was generally wetter than the peripheral regions, there were some exceptions, notably near where dams were installed on peripheral drainage ditches. The markedly different spatial patterns of wetness suggests that a uniform prescription regarding vegetation re-establishment in the rewetted section may not be warranted. The bulk density, particle density and porosity of gyttja averaged 0.12 g cm-3 1.57g cm-3 and 92%, in the top 40 cm of the layer. The organic matter content of gyttja decreased with depth from about 70% at a 5 cm depth to 45% at a 45 cm depth. Laboratory compression tests showed 9 and 72% strain at effective stresses of 3.5 and 200 kPa, respectively, demonstrating the potential for releasing water upon compression, which in the field is caused by water table lowering. From day of year 192 to 202 in 2011, when a ~8 cm water level change occurred (effective stress range ~0.8 kPa), the volumetric moisture content and thickness of the top 30 cm of gyttja decreased by 0.4%, and 0.5 cm, respectively, representing 0.1 and 1.7% strain, respectively, as determined from these two different approaches. The compression of gyttja after Bic-Saint-Fabien was rewetted (2011) was small but might have been significant under drier conditions with greater water table variability, such as during the early stages of site drainage when it was being prepared for peat extraction or after peat production ceased. The release of water to the peat layer from the compression of gyttja after peat production finished and before rewetting occurred, might have been an important self-preservation mechanism, eventually making it easier to rewet. Water table drawdown in 2011 produced very small strain rates suggesting gyttja compression in this year had no important role; hence rewetting success was more reliant on other rewetting techniques implemented at this site.