Peat Matrix Research Articles

Long-term changes in hydrological pathways in an upland peat catchment—recovery from severe drought?

This study analyses long-term water quality data from an upland peat catchment in order to understand long-term changes in hydrological flowpaths and how they relate to recovery from severe drought and control the release of DOC. The study examined comparative records from rainfall, soil and stream samples over a 9-year period, which included an approximately 1 in 30-year drought 2 years into the period. The study examined single tracers and utilised multivariate statistics to examine changing sources and routes of runoff. The study shows that the severe drought is part of dry period not restricted to a single summer and this extended dry period may give rise to the extent of the chemical changes observed in the stream chemistry. During this period of drought there is no evidence for substantive new flowpaths being generated during the drought, instead the residence time of the water in the upper peat horizon (<10 cm depth) increases and that this increase is reflected in the chemistry of runoff. The soil waters deeper in the peat profile (approx. 50 cm) show increased influence of rainwater compositions and that during drought the residence times at depth increase. There is an offset between the severe drought and maximums in concentrations of Fe, DOC and Al are related to the hydrophobic nature of the peat matrix. The effects of a 30-year drought persisted for no more than 3 years ending with the end of the dry period, and at least the effects of severe drought lasted only a year. The study suggests that in peat catchments summer's are hydrologically independent of the winters and this fact limits the consequences of severe drought.

Simulation of water table level and peat temperatures in boreal peatlands

Hydrology controls the physical, chemical and biological processes in peatlands and hence could be the most important process regulating their function, development and characteristic biogeochemistry. Models describing hydrological processes and soil heat exchange phenomena are an important tool in understanding the peatland biogeochemical cycles of C and N. Presented in this paper is a peat soil climate model that uses weather data, mire site and peat characteristics as input data. The model is related to the heterogeneous peat characteristics (e.g. bulk density, degree of humification, remains of Sphagnum, Carex, Eriophorum and woody tissues), which in turn vary with depth. Evapotranspiration is related to weather parameters and tree stand characteristics. The model simulations were validated against the observed data collected during 1993 and 1994 growing seasons at a fen and bog sites at the Lakkasuo mire complex located in central Finland. The observed and simulated day-to-day variations in water table levels and soil temperatures during both seasons appeared overall to be in phase. As the model lacks the data needed to characterize the peat matrix hysteresis, the model was found lacking in response to wetting and drying cycles. The mean differences between simulated and observed water table levels during 1994 were −0.3 ± 1.3 and −0.5 ± 2.3 cm for the fen and bog sites, respectively. The model was found to be sensitive to mire surface characteristics and evapotranspiration, particularly for the bog site with an unsaturated zone deeper than at the fen. The absolute mean differences between the simulated and measured peat temperatures from 5 to 150 cm were less than 1.0 °C with a maximal standard deviation of 1.6 °C. The model deviations for the upper layers showed larger variations compared to deeper layers, implying a greater accuracy in defining the lower boundary of the thermal regime within the peat column.

Infiltration mechanisms in a herbaceous peat: results of a controlled infiltration experiment/Mécanismes d'infiltration dans une tourbière herbacée: résultats d'une expérience d'infiltration contrôlée

The theoretical spatial distribution of hydraulic head during infiltration is used to interpret the results of infiltration experiments made in the field on a single, isolated, column of herbaceous peat in a flood-plain wetland in central England. Crusts of different hydraulic resistance were applied to the column surface. These regulated the water influx enabling the hydraulic conductivity of the peat to be estimated at between 1 and 19.5 m day-1. It is inferred that, when the hydraulic gradient changes, water may follow different pathways through the peat. Water moves rapidly through macropores in proportion to the applied hydraulic gradient, and infiltrates the peat matrix from the macropore walls. The results indicate the significance of hydraulic conductivity variations with depth, and the importance of precipitation intensity.

Evaluation and optimization of extraction and clean-up methods for the analysis of polycyclic aromatic hydrocarbons in peat samples

The analysis of PAH in peat samples is complicated by the high content of organic matter in peat which affects both extraction efficiency and analytical quality. Therefore, we evaluated the efficiencies of three extraction methods (accelerated solvent extraction (ASE), fluidized bed extraction, ultrasonic extraction) and several clean-up techniques in order to find the best set of methods. ASE proved to be the best extraction method. For clean-up, a procedure using aluminium oxide and silica gel showed the highest efficiency, whereas a method originally developed for soil samples failed to remove the peat matrix satisfactorily. With the optimized extraction and clean-up procedure, 170 samples from Canadian bogs were analysed for PAH. With overall recovery rates between 69 ± 14 and 89 ± 16% and an inaccuracy of ≤20%, the optimized method was a well suitable tool for the analysis of PAH in peat samples.

Analytical procedures for the determination of selected major (Al, Ca, Fe, K, Mg, Na, and Ti) and trace (Li, Mn, Sr, and Zn) elements in peat and plant samples using inductively coupled plasma-optical emission spectrometry

A simple, robust and reliable analytical procedure for the determination of Al, Ca, Fe, K, Li, Mg, Mn, Na, Sr, Ti, and Zn in peat and plant materials by inductively coupled plasma-optical emission spectrometry (ICP-OES) was developed. A microwave heated high pressure autoclave was used to digest powdered sample aliquots (approximately 200 mg) with different acid mixtures including nitric acid (HNO 3), tetrafluoroboric acid (HBF 4) and hydrogen peroxide (H 2O 2). The optimized acid mixture for digestion of plant and peat samples consisted of 3 mL HNO 3 and 0.1 mL HBF 4, in addition to H 2O 2 which was sub-boiled into the PTFE digestion tubes during heating of the autoclave. Using HNO 3 alone, recoveries of Al and Ti were too low by 40 and 160%, respectively, because HNO 3 could not fully liberate the analytes of interest from the silicate fraction of the plant and peat matrix. However, for all other elements (such as Mn, Sr, and Zn), the use of HBF 4 was less critical. The accuracy of the analytical procedure developed was evaluated with peat and plant reference materials of different origin and composition. The ICP-OES instrument was optimized using solutions of plant reference materials considering RF power, nebulizer pressure, auxiliary gas flow and rinse time. Scandium was used as an online internal standard (IS) as it provided accurate results and showed less than 3% drift in sensitivity over time which was lower compared to other potential IS such as Rh (20%) and In (6%). The combination of most sensitive and less sensitive wavelengths allowed to obtain low detection limits and highest possible dynamic range. The achieved procedure detection limits ranged from 0.05 μg g −1 (Li) to 15 μg g −1 (Ca) and allowed a precise quantification of all elements. Comparative X-ray fluorescence spectrometric measurements of solid peat and plant samples generally agreed well with results obtained by digestion/ICP-OES. To overcome interferences caused by Na, K, and Li, a solution of 10 μg g −1 CsCl 2 was successfully used as an ionization buffer. The good agreement between the found and certified concentrations in plant and peat reference materials indicates that the developed analytical procedure is well suited for further studies on the fate of major elements in plant and peat matrices.

Observations of a seasonally shifting thermal optimum in peatland carbon-cycling processes; implications for the global carbon cycle and soil enzyme methodologies

Thermal gradient apparatus has been used to study enzyme activity and carbon cycling in peat collected seasonally from a Northern upland peatland. A thermal optimum was observed in the peat where maximum carbon-cycling enzyme activities (phenol oxidase and β-glucosidase), phenolic compound concentrations, dissolved organic carbon (DOC) concentrations and microbial respiration (CO 2 efflux) were all found in a given season. The thermal optimum for these carbon-cycling processes coincided with the highest ambient soil temperature recorded at the time of peat collection, suggesting microbial acclimation to the external conditions. Under the waterlogged conditions of this experiment, phenol oxidase activites correlated positively with phenolic compounds (winter 0.96, P<0.01; spring 0.92, P<0.001; summer 0.94, P<0.001; autumn 0.88, P<0.001) and β-glucosidase activities with DOC (winter 0.91, P<0.01; spring 0.85, P<0.01; summer 0.92, P<0.001; autumn 0.72, P<0.05). We propose, therefore, that the relative activities of these enzymes is crucial in mobilising DOC from the peat matrix, with implications for carbon exports to the receiving waters (magnitude and molecular weight distribution) and CO 2 efflux to the atmosphere. The pronounced seasonality in carbon processing found here, must be taken into account when modelling carbon flux in and from these systems, if responses to climate change are to be predicted satisfactorily. Furthermore, because the optimum activity of these carbon-cycling enzymes shifted with seasonal changes in temperature, it is essential to perform enzyme assays in soil ecological investigations at field temperatures (rather than standardised temperatures), when information on natural process rates is required.

Linking Belowground Carbon Allocation to Anaerobic CH4 and CO2 Production in a Forested Peatland, New York State

Heterotrophic soil microorganisms rely on carbon (C) allocated belowground in plant production, but belowground C allocation (BCA) by plants is a poorly quantified part of ecosystem C cycling, especially, in peat soil. We applied a C balance approach to quantify BCA in a mixed conifer-red maple (Acer rubrum) forest on deep peat soil. Direct measurements of CH4 and CO2 fluxes across the soil surface (soil respiration), production of fine and small plant roots, and aboveground litterfall were used to estimate respiration by roots, by mycorrhizae and by free-living soil microorganisms. Measurements occurred in two consecutive years. Soil respiration rates averaged 1.2 bm μmol m− 2 s− 1 for CO2 and 0.58 nmol m− 2 s− 1 for CH4 (371 to 403 g C m− 2 year− 1). Carbon in aboveground litter (144 g C m− 2 year− 1) was 84% greater than C in root production (78 g C m− 2 year− 1). Complementary in vitro assays located high rates of anaerobic microbial activity, including methanogenesis, in a dense layer of roots overlying the peat soil and in large-sized fragments within the peat matrix. Large-sized fragments were decomposing roots and aboveground leaf and twig litter, indicating that relatively fresh plant production supported most of the anaerobic microbial activity. Respiration by free-living soil microorganisms in deep peat accounted for, at most, 29 to 38 g C m− 2 year− 1. These data emphasize the close coupling between plant production, ecosystem-level C cycling and soil microbial ecology, which BCA can help reveal.

Connecting methane fluxes to vegetation cover and water table fluctuations at microsite level: A modeling study

The paper presents a process‐based model describing methane flux dynamics in different microsites of boreal peatlands. The simulated fluxes matched well to measurements in all microsites without any parameter adjustment. The model emphasizes the importance of microsite characteristics, water table and vegetation cover for methane fluxes. Water level determines the moisture and oxygen profile in peat matrix and therefore affects methane production and oxidation rates in peat profile. Vascular plants provide methanogenesis with substrates, form a pathway for methane to liberate from peat to the atmosphere and enhance methane oxidation by transporting oxygen to water saturated peat. The model connects methane fluxes to the seasonal photosynthetic cycle of plants at the microsite level and hence dynamically combines the microbial processes in peat to changing environmental factors in the level of peatland ecosystem. Sensitivity analysis of the model reveals the importance of substrate supply to methane fluxes. In addition, the capability of the vascular plants to transport oxygen downwards has a large effect on model outcome. Lack of oxygen and methane keep methane oxidation at a low level in the model simulations, and changes that compensate for these lacks have a remarkable decreasing effect on simulated flux. Dry periods decrease the simulated methane flux considerably, especially if the drought prevails long, threshold for a dramatic decrease lying between 4 and 6 weeks of drought. Increase in air temperature enhances methane flux, especially if the effect of increased temperature on gross primary production is taken into account.

Water budget and surface‐layer water storage in a Sphagnum bog in central Sweden

AbstractA water budget was established for the open, undisturbed bog Stormossen, central Sweden, for the growing seasons of 1996 and 1997 as a part of the NOPEX project. The water budget was complemented with data on the spatial variation of groundwater levels and water contents in different microrelief elements (ridge, hollow and ridge margin). The seasonal (24 May to 4 October) rainfall, evaporation and runoff were 200, 256, and 43 mm in 1996, respectively, and 310, 286 and 74 mm in 1997, giving negative budgets of −99 mm in 1996 and −50 mm in 1997. Approximately 60% of the total budget was caused by storage changes in the upper 40 cm of the bog and 40% by swelling/shrinking in the layers below. This ‘mire breathing’ must be incorporated in future models of mire‐water dynamics. The water content varied diversely among the different microrelief elements, much depending on the properties of moss and peat together with distance to water table. There also was a strong hysteresis in the relationships between groundwater level and measured volumetric water content, depending partly on pore‐throat effects and partly on swelling/shrinking of the peat matrix. A seasonal variation of volumetric water content in a layer beneath water table was found to be larger than what could be justified by compression alone. We think that probable causes could be methane gas expansion together with temperature effects. The main conclusions of this study were: (i) water‐transport and storage characteristics are distinctly different among hummocks, ridges and hollows, (ii) mire wetness cannot be deduced from groundwater levels only, and (iii) an important part of the total water storage was caused by swelling/shrinking of the peat, not by changes in unsaturated water content. Copyright © 2002 John Wiley &amp; Sons, Ltd.

Competitiveness in root colonization by Pseudomonas putida requires the rpoS gene.

The rpoS gene in Pseudomonas putida was essential for plant root colonization under competitive conditions from other microbes. The RpoS- mutant survived less well than the wild-type strain in culture medium, and unlike the wild-type, failed to colonize the roots in a peat matrix containing an established diverse microflora. The RpoS-deficient P. putida isolate was generated by insertion of a glucuronidase-npt cassette into the rpoS gene. The RpoS mutant had dose-dependent increased sensitivity to oxidative stress and produced Mn-superoxide dismutase activity earlier than the parent. While extracts from wild-type P. putida stationary-phase cells contained three isozymes of catalase (CatA, CatB, and CatC), the sigma38-deficient P. putida lacked CatB. These results are consistent with previous findings that CatB is induced in stationary-phase.

Extraction of antimony and arsenic from fresh and freeze-dried plant samples as determined by HG-AAS.

Six extraction media (acetic acid, EDTA, tetrabutylammonium hydroxide, NaOH, MeOH/H2O, acetonitrile/H2O) were tested for their ability to extract antimony (Sb) and arsenic (As) from freeze-dried poplar leaves, pine shoots and spruce shoots, as well as from a peat matrix. Additionally, the extraction efficiency of Sb and As in fresh and freeze-dried elder leaves and poplar leaves was compared. Total concentrations of Sb and As of aliquots (approximately 220 mg) of the freeze-dried samples were analysed by flow injection hydride generation atomic absorption spectrometry (FI-HG-AAS) after open vessel digestion with adequate mixtures of nitric, sulfuric, hydrochloric, and perchloric acid. Three reference materials GBW 07602 Bush Branches and Leaves, GBW 07604 Poplar Leaves, and SRM 1575 Pine Needles were analysed with every batch of samples to ensure the accuracy and precision of the applied analytical procedures. The use of hydrofluoric acid in the digestion mixture leads to distinctly lower As values (down to 40%) than actual concentrations in the investigated plant materials. Extraction efficiencies were generally low and lower for Sb than for As. Solutions of 0.66 mol L(-1) NaOH liberated highest amounts of Sb with approximately 10% for poplar leaves, and approximately 19% each for pine shoots and spruce shoots. Distinctly higher concentrations of As in NaOH extracts of poplar leaves (22%), pine shoots (32%), and spruce shoots (36%) were quantified. Extraction experiments resulted in yields of 7-9% from fresh elder and poplar leaves, respectively, and 8-13% for freeze-dried samples for Sb. The corresponding values for As were 10-35% for the fresh material and 7-37% for the freeze-dried samples.

Subsurface drainage from hummock-covered hillslopes in the Arctic tundra

In the Arctic tundra, subsurface drainage occurs predominantly through the saturated zone within the layer of peat that mantles the hillslopes. In plan view, the peat cover is fragmented into a network of channels due to the presence of mineral earth hummocks. In cross section, the physical and hydraulic properties of the peat vary with depth and the water transmission characteristics (e.g. hydraulic conductivity) of the upper profile differ distinctly from those of the lower. Water flow through the peat is laminar, therefore the friction factor (f) and the Reynolds number (NR) are inversely related. Average values for the coefficient C of the relation f=C/NR, vary from ∼300 near the surface to ∼14,500 at depth. This large difference in C confirms that the larger-diameter soil pores of the living vegetation and lightly decomposed peat near the surface offer much less resistance to water motion than the finer-grained peat deeper in the profile. Also, the variability suggests that subsurface drainage is strongly affected by the position and thickness of the saturated zone within the peat matrix. A first approximation for a model or simulation of the flow regime may consider a peat profile with depth-varying, resistance properties in respect to subsurface flow.

Nitrate Dynamics in Relation to Lithology and Hydrologic Flow Path in a River Riparian Zone

AbstractThe efficiency with which riparian zones remove nitrate (NO−3) from contaminated ground water can vary with landscape setting. This study was conducted to determine the influence of flood plain geometry, lithology, hydrologic flow path, and nitrate transport on mechanisms of nitrate depletion of contaminated ground water. Patterns of NO−3−N, chloride, and dissolved organic carbon (DOC) concentrations and δ15N‐NO−3 and δ18O‐NO−3 values in combination with detailed piezometric head measurements were investigated in a river floodplain connected to a large upland sand aquifer in an agricultural region near Alliston, Ontario, Canada. Ground water discharging to the forested floodplain from the sand aquifer exhibited large spatial variability in NO−3−N concentrations (10–50 mg/L). The transport and depletion of NO−3 was strongly influenced by floodplain geometry and lithology. Little ground water flow occurred through the low‐conductivity matrix of peat in the floodplain. Plumes of NO−3‐rich ground water passed beneath the riparian wetland peat and flowed laterally in a 2‐ to 4‐m‐thick zone of permeable sands across the floodplain to the river. Analyses of the distribution of the NO−3−N concentrations, isotopes, and DOC within the floodplain indicate that denitrification occurred within the sand aquifer near the river where nitrate‐rich ground water interacted with buried channel sediments and surface water recharged from peat to the deeper sands. This study shows that the depth of permeable riparian sediments, ground water flow path, and the location of organic‐rich subsurface deposits may be more important than the width of vegetated strips in influencing the ability of riparian zones to remove nitrate.

Fate of Hydrocarbon Contaminants In Natural Wetlands

Abstract Conventional clean-up approaches to contaminated wetlands are aggressive and expensive, and may harm the wetland ecosystem. Current findings suggest that wetlands may be capable of attenuating contamination through natural processes including sorption, biodegradation, and volatilization. The objective of the study was to conduct a field evaluation of the role of these attenuation mechanisms at four contaminated natural wetlands in Alberta. A second focus of the study was to evaluate contaminant impact on the wetlands vegetation. The results indicate that contaminant attenuation in wetlands are influenced by several parameters, including depth of impact, contaminant composition, presence of peat, flow rates, and seasonal effects. Overall, natural processes appear to be completely attenuating hydrocarbon contamination at two of the four wetlands study sites. At the other two sites, minor concentrations were reaching downgradient receptors. Impact on vegetation was observed at three of the four sites, primarily through mortality of black spruce. The impact on shallow vegetation was generally negligible. Introduction Wetland contamination by hydrocarbons as a result of upstream oil and gas activity is well known, both in Alberta and worldwide. Conventional clean-up approaches (e.g., excavation, trenching, and burning) are aggressive and expensive, and may harm the wetland ecosystem. A more passive, longer term solution may be to focus on containing or removing the source and allow natural processes to remediate the remaining contamination. This approach, known as intrinsic remediation or natural attenuation, has been shown to be effective in various scenarios, from fuel-contaminated groundwater at Air Force Bases to oil spill-impacted shorelines. There has been little investigative work on the subject of intrinsic remediation in hydrocarbon-impacted wetlands. Current findings suggest that wetlands may be capable of retarding and potentially depleting contaminant plumes through natural remediation processes including: sorption, biodegradation, and volatilization. Wetlands are typically water-saturated environments with a high percentage of peat. Peat is an organic-rich material containing partially to highly decomposed plant fibres, roots, and mosses(1). Wetlands containing peat have several unique attributes, which enhance contaminant attenuation in the following ways:Sorption: Sorption may be described as the partitioning of contaminants from the liquid phase to the soil matrix. The peat matrix is highly porous (up to 70%) and has been found to be capable of absorbing up to eight times its weight in oil(2). Peat contains approximately 40% organic carbon by weight. Laboratory testing completed by Tinh et al.(3) indicates that peat's adsorptive capacity is between 30 to 50% of granular activated carbon. Peat is therefore an excellent filter for organic contaminants.Biodegradation: Microorganisms indigenous to the environment are capable of biodegrading most organic contaminants found in petroleum fuels, both aerobically and under anerobic conditions. Due to their high organic content and biodiversity, wetlands exhibit microbial activity exceeding most natural environments(4). The enhanced microbial activity results in greater potential for biodegradation, whereby microbes stimulate the breakdown of organics such as hydrocarbons to form CO2, water, and biomass.Volatilization: Volatilization describes the partitioning of hydrocarbons from the soil phase, dissolved phase, and/or liquid phase into the vapour phase.

Relocation of carbon from decaying litter in drained peat soils

Recent findings have indicated that the carbon density and store in peat soil may increase after drainage for forestry, even if soil respiration has clearly increased. This is caused by the increased organic C flow from tree stands into soil and consequent retention in the peat matrix. Relocation of 14C-activity released from the labelled needle and fine root litter during 4- and 8-month incubation experiments showed that, on average, only 60–80% of the activity lost from litter was emitted to the atmosphere. The proportion retained in the moss layer was from 7 to 14%, in the peat soil from 7 to 18% and in the water percolated through the peat from <1 to 8%. The results thus support the hypothesis that organic C flow may contribute to C storage in drained peat soils.

Chemical dilation and the dual porosity of humified bog peat

Hydrochloric acid and calcium and sodium chloride salt solutions were passed through humified bog peat cores of 1 m length to determine values for the material properties governing solute transport: hydraulic conductivity, effective porosity, and dispersivity. Chloride passed through the bulk peat cores about twice as fast as predicted from chloride breakthrough curves measured by selective-ion probes inserted into the peat 30 cm downgradient from the source. With continued experimentation, chloride dispersion increased. Chloride also passed through the peat up to 12 times slower than predicted by conservative advection. The retardation of the chloride fronts, the faster bulk transport, and the asymmetry of the breakthrough curves all indicate that humified bog peat is a dual porosity medium. Solutes both move preferentially through active macropore spaces and diffuse into dead pore space in the peat matrix. Neither the effective porosity nor the dispersivity of the peat could be precisely determined from the breakthrough curves because the hydraulic conductivity and discharge rates through the peat increased as much as five times when the chloride tracer solutions passed through the cores. In initial experiments, the shapes of the breakthrough curves were generally consistent with dispersivities of the order of centimeters, similar to that observed for granular soils at the same length scale (meters), whereas they `flattened' considerably during later experiments, suggesting dispersivities in the range of tens of centimeters. We hypothesize that the interaction of the chloride tracer solutions with organic-acid functional groups may cause macropores to dilate and micropores to close off.

Molecular biological evidence for the occurrence of uncultured members of the actinomycete line of descent in different environments and geographical locations.

A 16S rDNA based molecular ecological study was performed on a sample taken from a peat bog in Germany. Total DNA was extracted by directly lysing micro-organisms in the peat matrix. The 5' 1400 nucleotides of the bacterial 16S rDNA were amplified using conserved bacterial PCR primers. A clone library was generated by blunt-end cloning and 262 16S rDNA clones were analysed. Of these, 37 were located in the Gram-positive phylum, as determined by hybridization to an oligonucleotide probe specific for Gram-positive bacteria. Analysis of 17 of these clones by sequence analysis and their comparison with published sequences representing all of the main bacterial phyla indicated their membership of the actinomycete line of descent. These peat clones were found to represent three novel lineages, two of which appear to be related to the species Acidimicrobium ferrooxidans, and 'Candidatus Microthrix parvicella'. Clone sequences of the third group are phylogenetically related to Rubrobacter radiotolerans. Comparison with short 16S rDNA clone sequences obtained from DNA isolated from a geothermally heated soil in New Zealand, and from DNA isolated from soil in Australia, Japan and Finland and marine environments from the Atlantic and the Pacific Oceans, suggests that members of these three groups occur in very different environments across the world.

A molecular approach to search for diversity among bacteria in the environment

Molecular 16S rDNA-based techniques were applied to a peat sample from northern Germany in order to investigate the bacterial diversity present and compare the clone sequences with those obtained from similar studies on other terrestrial samples. Genomic DNA was extracted from the peat matrix by a direct lysis procedure. 16S rRNA genes were amplified using PCR primers targeting conserved regions of bacterial 16S rDNA. 16S rDNA fragments were blunt end cloned into a plasmid vector and the resulting clone library of 262 sequences was screened by hybridization with different oligonucleotide probes and sequence analysis of randomly selected clones. The 16S rDNA insert of 76 clones was partially sequenced. Clones identified either by hybridization or by sequence analysis fell into three phyla. As judged by hybridization with a specific oligonucleotide probe, 42% of the clones represented members of the alpha subclass of Proteobacteria. Twenty-five of these clones were selected randomly for sequence analysis; none could be assigned to any of the known genera of this subclass. The second largest clone group comprises 15% of the clones and clusters aroundAcidimicrobium ferrooxidans andRubrobacter radiotolerans, both of which are remotely related to members of the order Actinomycetales. The third major clone cluster (10%) was moderately to remotely related to theAcidobacterium capsulatum phylum. Of the additional clones sequenced, a few could be assigned to other subclasses ofProteobacteria, theVerrucomicrobium phylum and the phylum of spirochetes. Comparison of the results presented here with those from other environments reveals a significant number of common clone clusters. As the vast majority of sequences retrieved from any of the marine and terrestrial samples investigated so far by molecular methods indicate the presence of novel bacterial species it can be assumed that a huge, as yet untapped biotechnological potential is present in the environment.

The Characterization of Water in Peat

AbstractThe functionality and ultimate use of peat are intimately bound up with the way in which absorbed water behaves in the host matrix. Control of the amount of absorbed water, the dynamics of water loss in drying, and the gain of water in rewatering are important determinants in its commercial exploitation. We examined the nature and behavior of water in a range of different Irish peat samples by exploiting the combined capabilities of differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and proton nuclear magnetic resonance (NMR). Up to four different forms of water were detected in heavily hydrated peat: absorbed or tightly bound water, which is non‐freezable and behaves like a glass at low temperatures; two forms of loosely bound water; and bulk water. Increasing temperature across the subambient regime revealed the sequential onset of mobility of the different forms of water. The transitions are well‐defined in terms of both water concentration and the temperature at which motion sets in. Unlike hydrated polymers, NMR estimates of the maximum amounts of bound water at low temperatures depend on overall water content, reflecting the extent to which the peat matrix can restructure and swell when hydrated. The TGA, which maps out the loss of water under controlled conditions of temperature and atmosphere, offers additional evidence on the mechanism of dehydration, indicating that drying on a small scale under laboratory conditions is not grossly impeded by internal barriers. The gratifying consistency between the data from the three experimental techniques used, along with pertinent data in the literature, give additional insights into the role of water in peat.

EFFECTS OF PHYSICAL, CHEMICAL AND BOTANICAL CHARACTERISTICS OF PEAT ON CARBON GAS FLUXES

Peatland ecosystems may contribute about 65% of all natural methane emission to the atmosphere. During May—June 1988, CH4 and CO2 fluxes were measured with the static chamber method at the surface of a basin swamp and at three depths. The daily average fluxes of CH4 and CO2 at the surface of the swamp ranged from 1.146 to 2.178 mmol m−2 d−1 and from 1.966 to 7.242 mmol m+2 d−1 respectively. These amounts of CH4 and CO2 corresponded to 0.02–0.03% of what was released from the 45 to 60-cm depth when exposed to atmospheric pressure. Statistically significant correlations between physical and botanical peat properties and trapped CH4 and CO2 and water flow suggest that outgassing of trapped CH4 and CO2 are closely associated with the peat matrix, peat properties, hydraulic potential, temperature, and concentration gradients.