Characteristics of humic substances in peat of selected peatlands from north-eastern Poland

Abstract

Peat samples collected in six peatlands located in north-eastern Poland were analysed. Two of the investigated psedands were fens, two were transitional bogs and two of them were raised bogs. All peat deposits were investigated in the whole stratigraphic profile, and peat samples were chosen according to the differentiation of peat genus in deposit. pH in water and KCl, degree of decomposition, ash content, carbon content as well as the ratio of humic to falvic acid were evaluated. The highest degree of peat decomposition was found in wood peat (Alneti), and the in moss peat (Bryaleti). The strongest humification was observed in low peat of genus Limno-Phragmitioni (hypnum-moss peat) and Magnocaricioni (sedgeous peat).     

Evaluation of phosphorus mobilization potential in rewetted fens by an improved sequential chemical extraction procedure

After rewetting of peatlands, phosphorus (P) pore‐water concentrations were up to three orders of magnitude greater than under pristine conditions. It was hypothesized that different mobilization processes such as ion‐exchange reactions, biotic/abiotic redox reactions, acidification and ongoing anaerobic decomposition of particulate organic matter by hydrolytic cleavage and fermentation might be responsible. To identify P pools in peat samples of varying degrees of decomposition, we modified and improved a sequential chemical extraction method that allowed conclusions on potential mobilization mechanisms in rewetted peatlands. The results indicated that the earlier drainage of rewetted fens strongly increased the P mobilization potential in the upper decomposed peat layers. Accordingly, the amount of P bound to redox‐sensitive (bicarbonate/dithionite soluble) compounds (BD‐P) was, on average, one order of magnitude greater in decomposed peat of rewetted fens (5.4–14.3 μmol P g^?1 dry matter or DM) than in underlying less‐decomposed peat layers (0.2–1.9 μmol P g^?1 DM) or slightly decomposed peat derived from pristine fens (0.4–2.0 μmol P g^?1 DM). The BD‐P fraction found in the upper very decomposed peat layers appears to be most important for P mobilization in rewetted fens and accounted for 85% of the variability of P mobilization rates. Despite uncertainties regarding P diagenetic processes in peat, as well as the development of microbial decomposition processes, in the long‐term, high pore‐water P concentrations can be expected in rewetted fens for decades to come.     

INFLUENCE OF PEATLANDS ON THE ACIDITY OF LAKES IN NORTHEASTERN ALBERTA,CANADA

About a third of the lakes surveyed in the Birch Mountains Upland of northeastern Alberta, Canada, have pH below 7.0; 25% have alkalinities below 10 mg/L identifying them as acid-sensitive following criteria established by the National Research Council of Canada (1981). Lakes in this region vary greatly as to surface area and depth. Watersheds also vary in area and in amount of peatland cover. Peatlands in the form of peat plateaus and collapse scars, continental bogs, treed and open fens, and shallow organic deposits cover over 50% of some watersheds. Surface water chemistries of these peatlands form three distinct classes: bogs, poor fens and shallow organic deposits. The acidity of certain lakes in this northern area is best explained by effects from high cover ofSphagnum-dominated peatlands in surrounding watersheds. Due to greater flow-through, poor fens appear to be more important than bogs in affecting the acidity of associated lakes.     

Applicability of thermal methods for characterization of peats and plants

Differential thermogravimetric (DTG) and differential thermal analysis (DTA) curves were obtained for some peat materials and peat-forming plants. Four peats were selected on the basis of botanical composition and degree of decomposition. Granulometric fractions and holocellulose preparations from the peats were also analyzed.

The DTG curves showed three main regions of weight loss: the first at 275°–325°C the second at 360°–460°C and the third at 500°–560°C. The first region with a peak at 300°C was by far the most important. It was associated with cellulosic materials which may reflect the degree of decomposition. The size of the 300°C peak could be used for measuring holocellulose in peats, and this might be a valid substitute for chemical means for that measurement, specially in more decomposed peats.

The nature of the 300°C peak did not change significantly with changes in particle size, although the position of the 420°C peak was shisfted toward lower temperatures as particle size decreased. The original features of the peats were generally retained in the separates. Even though the predominance of residues from one species of plants in a particular peat did not greatly influence the shape of the DTG curves, some generalizations concerning the botanical sources of peats were obtained.

In a comparison of DTG and DTA methods, the former appears to provide more useful information on the chemical make-up and on the degree of decomposition of peats.     

Geochemistry and geochemical differentiation on major elements in selected peat bog profiles (south-east of Poland)

Abstract

The geochemical differentiation of major elements in various peat bog profiles from Bieszczady Mountains Region (south-east of Poland) was compared to its botanical origin. Peat cores were taken from ombrotrophic, mesotrophic, and oligotrophic peatlands, which were developed in the stream valley of the River San. Twenty-four various peat samples were analysed for peat genus, degree of peat decomposition, ash content, total nitrogen, and total carbon content of hydrolytic matter as well as content of major elements: Na, K, Mg, Ca. The results show that the botanical composition of peat deposits is no reliable indication of their trophic status. The common feature of investigated Holocene peatlands is their valley localisation on the flood terrace. The specific character of local geommorpho8ogicml and hydrological condition caused that the bottom layer of all investigated bog profiles was made of wood peats (Piceaeti, Pineti, Alneti, and Saliceti peat). The geochemical investigations of stratigraphical profiles confirm that the presented peat bogs showed specific morphological separateness comparing to other raised bogs situated in mountains or lowlands     

ORIGIN AND COMPOSITION OF MINERAL CONSTITUENTS OF FEN PEATS FROM EASTERN POLAND

The main constituents of peat include floral remains (in a various degree of humification), peat humus, and mineral constituents of biotic and non-biotic origin. The organic content is considered to be the main parameter that decides about physical and chemical properties of peat. However, the content and composition of mineral constituents of silted (high-ash) peats may cause differences in chemical and physical properties in comparison to the unsilted (low-ash) peats. Therefore, the identification of mineral content, as well as chemical and mineral composition of inorganic constituents, is essential to predict the properties of silted peats. The aim of this study is to determine the content, composition and the origin of mineral constituents of three fens from the Lubartów Plateau (Eastern Poland).     

Carbon decomposition processes in a peat from the Australian Alps

Carbon dioxide emissions and the mass loss of peat incubated in situ were measured in peat soils in the Australian Alps. The carbon chemistry of incubated peats was characterized using ¹³C nuclear magnetic resonance (NMR). In situ decomposition decreased as a function of increasing alkyl carbon content of the initial organic matter, providing direct evidence of the oft‐cited link between substrate quality and decomposition rates. More mass loss occurred in the bog peat samples than in the dried peat samples. However, at the peat surface, the amount of CO₂ emitted was not significantly different between bog peat and dried peat. Carbon inputs, and therefore the sink or source status, of these peats are yet to be quantified.     

A Comparative Study of the Use of Organic Carbon and Loss on Ignition in Defining Tropical Organic Soil Materials

Organic soils or Histosols or peats as they are commonly referred to, are characterized by the presence of large amounts of organic soil materials (OSM), which is commonly quantified by the Walkley and Black (1934) (WB) method to determine the soil organic matter (SOM) using a correction factor of 1.724. SOM of Histosols is also identified through a combustion (loss on ignition, LOI) or elemental C-analysis (with a carbon-nitrogen-sulfur (CNS) analyzer with combustion and gas density detector). These methods were established using temperate and boreal peat deposits and here we demonstrate that tropical peat deposits require a modified approach. Typical SE-Asian tropical lowland peat pedons from rain forest and oil palm settings were sampled and the material analysed using a CNS analyzer, WB-C and LOI. The ratios for LOI:CNS-C for the 20 samples yielded values between 2.00–3.09 with a mean of 2.50 while the LOI:WB-C ratio yielded values from 1.75 to 2.58 with a mean of 1.94. A comparison of these values for topsoils and subsoils showed mean ratios (LOI:WB-C) of 1.94 and 1.89 for topsoils and subsoils, respectively. The forest samples had higher LOI:WB-C ratios than the subsoils from oil palm settings (1.94 vs 1.84). These values suggest that the standard factor of 1.724 to correct OSM to SOM for tropical soils is untenable. The values to convert CNS and WB-C values of tropical topsoils/subsoils to SOM or LOI should be 2.5 or 1.9, respectively. Our results indicate a significant difference in the soil organic carbon (SOC) of tropical lowland peats depending on the method used.     

Long-term effects of deer browsing and trampling on the vegetation of peatlands

Overabundance of wild ungulates, especially exotic species, is a major threat to several ecosystems worldwide. While the response of forest vegetation to high density of herbivores has been well studied, far less is known about peatland vegetation. In this paper, we assessed the long term impact of white-tailed deer (Odocoileus virginianus) on plant communities of ombrotrophic (bog) and minerotrophic (fen) peatlands in eastern North America. Vegetation of five peatlands that have experienced high deer densities for at least 75 years was compared with that of five peatlands situated at proximity but on deer-free islands. We investigated deer impacts on plant species composition and cover, shrub height and cloudberry (Rubus chamaemorus) fruit/flower production and morphology. In bogs, white-tailed deer had no long-term impact on plant species assemblages, but reduced lichen cover and increased sedges and grasses cover as well as the surface area of bare peat. On the other hand, the floristic composition of fens differed significantly between sites where deer were present or absent. Plant diversity was greater in undisturbed fens than in disturbed fens, especially for shrubs, sedges and liverworts. No detrimental effects of browsing on shrub height were observed. Conversely, deer browsing seemed to have deleterious impacts on cloudberry fruit/flower production as well as on the number of leaves per individual. Overall, our results suggest that white-tailed deer had some important impacts on the vegetation of peatlands that could be harmful for the long-term conservation of peatland plant diversity.     

The nitrogen content of particle size fractions separated from peat and its rate of mineralization during incubation

Particle size fractions, varying from 5 to 0.005 mm, were separated from samples of several peat types using a wet sieving technique. In all types, nitrogen content of fractions increased as particle size decreased, the fine fractions (0.15–0.005 mm) accounting for around 43–64% of the total nitrogen. During incubation, fractions from two blanket peats showed a net release of mineral nitrogen, whereas those from raised bog peats were characterized, for the most part, by net immobilization. Amounts of mineral nitrogen released in fractions from any one peat after 28 days incubation at 30°C did not always correlate with either total nitrogen content or C:N ratio. However, better correlations between mineral nitrogen production and total N were obtained for fractions of similar particle size. The proportion of the total nitrogen that was mineralized tended to be higher in coarse fractions > 0.15 mm, blanket peats giving much higher values than samples from raised bogs. Carbon dioxide release also varied with particle size, being highest in large particles and fibres and least in the size range 0.15–0.5 mm. Smaller particles < 0.15 mm, gave intermediate values that were higher in blanket than in raised bog peat.     

Changes in fatty acid composition with age and environment in different types of peat profiles in Japan

Fatty acid composition of the crude lipid fraction of peat was investigated using several typical peat profiles in Japan. Fatty acid composition varied with the peat layers accumulated in a peat profile since 32,000 years BP. Deposition of long-range transported volcanic ash tephras also affected the composition remarkably due to the acceleration of decomposition. Fatty acid composition differed among high moor, transitional moor, and low moor peat profiles sampled in several locations in Hokkaido, Japan. The difference in the plants involved in the formation of peat was considered to be a very important factor determining the fatty acid composition. For example, arachidic acid was considered to be a good indicator for the presence of reed, while the percentage of stearic acid tended to be high in the high moor peat profiles dominated by sphagnum. As the fatty acids with a longer chain length were more stable than those with a shorter chain length, the percentage of longer fatty acids (C24 and C26) tended to increase and that of shorter fatty acids (CI4 and CI6) to decrease in the lower peat profiles. The drying of peatland also exerted a similar effect on the fatty acid composition.     

Effect of peat type and ph on breakdown of peat using fourier transform infrared spectroscopy

Abstract

Information on breakdown of peats as evidenced by shrinkage during cropping is generally lacking. The objective of this investigation was to study the breakdown of peat of various degrees of decomposition, effect of pH on breakdown and to relate the compositional changes during breakdown using Fourier Transform Infrared Spectroscopy (FTIR). Incubation studies were used in this investigation. Peat with a higher level of decomposition was less susceptible to breakdown. The pH had a major effect on breakdown with high pH leading to increased rate of breakdown. Lignin content of the peats was somewhat related to breakdown of the peats. The breakdown was also strongly correlated to the changes in the ratio of FTIR spectra of the start and to the end of the incubation particularly the 1600/1060 ratio. The 1600 spectra in mostly lignin 1060 spectra are mostly carbohydrate. There was relative enrichment of 1600 spectra in relation 1060 spectra. Other FTIR spectra ratio changes were also significantly correlated with breakdown. The FTIR technique has the potential to predict breakdown of peats.     

FTIR spectroscopy can be used as a screening tool for organic matter quality in regenerating cutover peatlands

Vegetational changes during the restoration of cutover peatlands leave a legacy in terms of the organic matter quality of the newly formed peat. Current efforts to restore peatlands at a large scale therefore require low cost and high throughput techniques to monitor the evolution of organic matter. In this study, we assessed the merits of using Fourier transform infrared (FTIR) spectra to predict the organic matter composition in peat samples at various stages of peatland regeneration from five European countries. Using predictive partial least squares (PLS) analyses, we were able to reconstruct peat C:N ratio and carbohydrate signatures with reasonable accuracy, but not the micromorphological composition of vegetation remains. Despite utilising different size fractions, both carbohydrate (<200 μm fraction) and FTIR (bulk soil) analyses report on the composition of plant cell wall constituents in the peat and therefore essentially reveal the composition of the parent vegetational material. The accuracy of the FTIR-based PLS models for C:N ratios and carbohydrate signatures was adequate to allow for their use as initial screening tools in the evaluation of the present and future organic matter composition of peat during monitoring of restoration efforts.     

Strong negative geochemical anomaly of raised bog peat in the middle taiga zone, Middle Priobye

Peat samples from bogs of the middle taiga zone (Middle Priobye region) represent a strong negative geochemical anomaly of a number of chemical elements compared to peat samples from bogs of the southern taiga of the Middle and Upper Priobye regions. The proximity of mountain systems (the Altai Mountains, the Salair Ridge, and Kuznetskii Alatau) presumably affects peat composition in the southern taiga zone by air transportation of mineral dust. The latter fact enriches peat of raised bogs in certain metals, whilst not reaching the outlying Middle Priobye region.     

Biosorption of macronutrients by Brazilian tropical peats

The objective of this work was to evaluate the adsorption of macronutrients calcium, potassium, magnesium, nitrogen, and phosphorus in two Brazilian tropical peat samples, investigating the effect of pH and determining the kinetics of the adsorption process. Two different Brazilian tropical peat samples were characterized using FTIR, TG, and SEM techniques. Different pH conditions were tested, as well as different mass concentrations of the peats. Differences in the chemical structures of the peat samples directly influenced the adsorptive capacities for the macronutrients. The adsorptive capacity for nitrogen was highest at pH 3, while the best adsorption of calcium and potassium was obtained at pH 6. The best fit to the data was provided by the pseudo-second-order model, which confirmed the rapid adsorption of calcium by both peats.     

Carbon budget of drained peat bogs in Ukrainian Polesie

Methodological aspects of studying the organic carbon budget of drained peat bogs used in agriculture are discussed. Difficulties in the assessment of carbon budget on the basis of measured carbon inflows and outflows are shown. The “soil pool” model of the carbon budget is suggested. It is based on the results of long-term experimental studies of a drained peatland in Ukrainian Polesie. An algorithm for calculating the carbon budget in the aerated part of the peatland—the peat soil proper—is developed with due account for a gradual involvement of the deep peat layers into the zone of soil processes. Data on the loss of dry peat mass and organic carbon per in the course of peat mineralization and surface subsidence are given with due account for the nature of the peatland and the duration of its agricultural use.     

Natural and anthropogenic enrichments of As,Cu, Pb,Sb, and Zn in ombrotrophic versus minerotrophic peat bog profiles,Jura Mountains,Switzerland

Peat cores were taken from two contrasting Sphagnum bogs in the Jura Mountains of Switzerland. At Etang de la Gruyere (EGr), 6.5 m of peat has accumulated during the past 10,000 years. In the first 100 cm of this profile there are several distinct peaks in ash content, but the values are well within the range for typical ombrotrophic Sphagnum bogs. There is also considerable variation in the concentrations of major and trace lithogenic metals (Al, Ti, Sc, Ca, Mg, Rb, and Sr), but most of this is simply a reflection of the natural variations in the amount of mineral matter in the peats. The Ca/Mg molar ratios in the peats at EGr are comparable to or lower than the average rainwater composition in this area, showing that this section of the peat core is ombrotrophic (i.e. rainwater-fed). In other words, the inorganic constituents in the surface peats at EGr were supplied exclusively by atmospheric deposition. This peat core, therefore, is suitable for studying the historical record of atmospheric metal deposition. Arsenic, Cu, Pb, Sb, and Zn are all more abundant in surface and near surface peat layers compared to deeper parts of the profile. Enrichment factors (EFs) for the profile were calculated conservatively by normalizing the metal/Sc ratios of individual peat samples to the average of the five lowest metal/Sc ratios in this part of the core (69–84 cm); these are tentatively assumed to represent pre-Industrial background values. The maximum EFs are approximately 5 times for Cu, 15 times for As, and 30 to 50 times for Pb, Sb, and Zn. At La Tourbière des Genevez (TGe), 1.5 m of peat represents 4,800 years of peat formation. At this site, the ash contents are higher and increase progressively with depth to values which are characteristic of minerotrophic fen peats. The concentration profiles of Al, Ti, Sc, Ca, Mg, Rb, Sr show the same general trend. The Ca/Mg molar ratios of these peats are generally twice the rainwater average, showing that this bog is essentially minerotrophic (ie groundwater-fed). Thus, the inorganic cccstituents in these peats were provided by both atmospheric and hydrospheric processes. Despite this, the Cu, Pb, Sb, and Zn concentrations are generally very similar to those at EGr, especially in the uppermost part of the profile, indicating that recent atmospheric inputs also dominate the supply of these metals to this bog. However, the minimum Pb and Sb concentrations in this profile are approximately five times higher than the corresponding values at EGr. The minerotrophic profile at TGT, therefore, could not by itself be used to calculate rates of atmospheric Pb and Sb deposition because it is impossible to distinguish between atmospheric and hydrospheric metal inputs. At TGe, As concentrations increase continuously with depth, reaching concentrations in the deeper, older peats which are more than 50 times higher than the ‘background’ As values at EGr. At this site the natural supply of As by mineral soil water completely masks the recent, elevated inputs contributed by atmospheric deposition. Thus, the peat core from TGe is also unsuitable for studying atmospheric As deposition.     

Impeded drainage stimulates extracellular phenol oxidase activity in riparian peat cores

Peat drainage, a common land‐use practice in Europe, has been associated with habitat degradation and increased particulate and dissolved carbon release. In the UK, peatland drain blockage has been encouraged in recent years as a management practice to preserve peatland habitats and to reduce fluvial carbon loss and municipal water discoloration. Drain blockage has, however, been found to increase drain‐water dissolved organic carbon (DOC) concentrations and coloration in the short term. In order to investigate the contribution of changes in extracellular phenol oxidase activity to the increase in water coloration following peatland drain blockage, cores collected from a riparian peatland in North Wales were incubated under impeded drainage conditions. Impeded drainage resulted in the stimulation of peat extracellular phenol oxidase activity and heightened soluble phenolic concentrations, suggesting that changes in extracellular phenol oxidase activity may be a key driver of increases in DOC and water coloration following peatland drain blockage. An increase in peat pH with impeded drainage was also observed that may have contributed to the heightened soluble phenolic concentrations – directly (through effects on solubility) and/or indirectly as a driver of the elevated extracellular phenol oxidase activity.     

Nonspecific organic compounds in peat soils of the Subpolar Urals

Specific features of organic matter, molecular composition and distribution of oxygen-containing nonspecific organic compounds (fatty acids, long-chain aliphatic alcohols, and ketones) were revealed in two peat soils on slopes of the Subpolar Urals: the eutrophic peat soil of the spring mire (Hemic Histosols) and the peat soil of a slope mire (Fibric Histosols). Compounds that can serve as molecular markers for some evolutionary stages of peats were determined for this area. Based on the data obtained, the most probable causes of differences in the composition of organic compounds in the peats studied were found to be the following: environmental conditions, water and mineral regime of bog, and differences in the composition of peat-forming plants.     

Contrasting the geochemistry of aluminum among peatlands

Aluminum concentrations were measured in surface waters, pore waters and surface peats of 15 wetlands in south-central Ontario. Wetlands were grouped floristically and chemically as mineralpoor, moderately-poor or mineral-rich fen. Mineral-poor fens were dominated bySphagnum, were low in alkalinity (0.31μeq L^?1) and pH (4.5–6.3). Moderately-poor fens had a mixture of vegetation (Sphagnum, sedges and grasses), mid-alkalinity (23–91μeq L^?1) and pH (5.8–6.4). Mineral-rich fens were dominated by sedges and grasses, had high alkalinity (104–181μeq L^?1) and circumneutral pH (6.2–6.3). Surface water Al concentrations were less in mineral-poor versus moderately-poor and mineral-rich fens (F=32.0; P<0.05). Pore water Al concentrations were lower in 4 of 5 mineral versus the mineral-rich fens (F=92.15; P<0.05). In all but two cases pore water Al (all species <0.2μm) were greater within the fen peats versus the overlying surface waters suggesting that peats could act as a source of Al to the overlying waters. In all wetlands, 70 and 30% of peat Al was recovered by a hydroxylamine hydrochloride/acetic extract (primarily inroganic) and an ammonium hydroxide extract (primarily organic), respectively. Differences in “extractable” Al recovered by the two reagents (i.e., inorganic+organic Al) among the 15 wetlands were independent of wetland type. Distribution coefficients, k _d , were different among the 3 types of wetlands (F=25.0; P<0.05) with theSphagnum dominated mineral-poor fens containing higher values versus the sedge and grass dominated mineral-rich fens. Lower surface and pore water concentrations of Al in mineralpoor versus mineral-rich fens may in part be a result of differences in the degree of minerotrophic influences between the two types of peatlands. As well, the greater binding capacity ofSphagnum peat as indicated by higher k _d 's in the mineral-poor fens, may have contributed to the observed lower pore water and surface water Al concentrations in mineral-poor versus mineral-rich fens. It has been postulated that anthropogenic acidification of peatlands will accelerate the transformation of a mineral-rich fen to that of a mineral-poor fen and ultimately to bog. Changes in Al geochemistry that may ensue as this transition occurs include decreases in pore and surface water Al concentrations with concurrent increases in peat bound Al.