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1.
Blanket‐bog peats, mapped as the Winter Hill and Crowdy associations by the Soil Survey of England and Wales, are an oceanic manifestation of the ombrotrophic ‘raised‐bog’ (Hochmoor) peats that cover large tracts in the boreal zone of the northern hemisphere. This paper examines monthly analyses from 1992 to 1997 of major ions and other variables from an upland blanket bog in southwest England in relation to seasonality, rainfall, and the chemical composition of rainwater. Average ionic composition of surface water (and peat) integrates variable atmospheric solute inputs over the years. The dominant ions in the surface water, Na+ and Cl–, showed only weak seasonality, but divalent cations a stronger seasonal pattern with a summer maximum. Mean pH ranged from c. 4.4 in February to c. 4.2 in August. Changes in concentration of different cations were closely interlinked by cation exchange. The anion deficit, accounted for by anionic groups on the dissolved organic matter, was strongly seasonal with a summer maximum, as was optical absorbance at 320 nm. Nitrate and NH4+ were both at much smaller concentrations than in rain. Nitrate exceeded 1 μmol l?1 only during cold periods in winter, mainly following drought in the summer of 1995; NH4+ reached a few μmol l?1 only in summer. There was evidence of net retention of S by the peat in wet sites and during wet periods, and of net release of SO42– (and acidity) under dry conditions. The 1995 summer drought and ensuing dry year in 1996 had marked and persistent effects on pH, apparent ion deficit (DEF), SO42–, the divalent cations and Fe.  相似文献   

2.
We examined the effect of cation treatments on methanogenic activity and nutrient release from exchange sites in raised bog and fen peats. Treatments consisted of cation chloride solutions (MgCl2, AlCl3 and PbCl2) applied individually. In raised bog peat Al3+ and Pb2+ increased CH4 production. A correlation was found between CH4 production and the amount of micro- and macronutrient cations released by the treatments. In calcareous fen peat, such a stimulation was also found, but there was no correlation between CH4 production and micro and macronutrient release. Direct nutrient and pH effects could not account for these observations. Thus the results support the hypothesis that the methanogenic community in the raised bog is limited by the availability of mineral nutrients and/or inactivity of exo-enzymes, both of which are bound onto exchange sites.  相似文献   

3.
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.  相似文献   

4.
We developed and tested a new method to collect CO2 from the surface to deep layers of a peatland for radiocarbon analysis. The method comprises two components: i) a probe equipped with a hydrophobic filter that allows entry of peat gases by diffusion, whilst simultaneously excluding water, and, ii) a cartridge containing zeolite molecular sieve that traps CO2 passively. We field tested the method by sampling at depths of between 0.25 and 4 m at duplicate sites within a temperate raised peat bog. CO2 was trapped at a depth-dependent rate of between ∼0.2 and 0.8 ml d−1, enabling sufficient CO2 for routine 14C analysis to be collected when left in place for several weeks. The age of peatland CO2 increased with depth from modern to ∼170 BP for samples collected from 0.25 m, to ∼4000 BP at 4 m. The CO2 was younger, but followed a similar trend to the age profile of bulk peat previously reported for the site (Langdon and Barber, 2005). δ13C values of recovered CO2 increased with depth. CO2 collected from the deepest sampling probes was considerably 13C-enriched (up to ∼+9‰) and agreed well with results reported for other peatlands where this phenomenon has been attributed to fermentation processes. CO2 collected from plant-free static chambers at the surface of the mire was slightly 14C-enriched compared to the contemporary atmosphere, suggesting that surface CO2 emissions were predominantly derived from carbon fixed during the post-bomb era. However, consistent trends of enriched 13C and depleted 14C in chamber CO2 between autumn and winter samples were most likely explained by an increased contribution of deep peat CO2 to the surface efflux in winter. The passive sampling technique is readily portable, easy to install and operate, causes minimal site disturbance, and can be reliably used to collect peatland CO2 from a wide range of depths.  相似文献   

5.
Peat forming wetlands are globally important sources of the greenhouse gas CH4. The variability of flux recordings from peatlands is however considerable and the distribution of CH4 below the water table poorly described. Surface peat (0-500 mm below the water table) is responsible for the bulk of emissions and a localised region of intense CH4 concentration may exist within this region but the structure of peat and presence of gas bubbles make the determination of in situ gas distributions problematic. We report on the in situ distribution and concentrations of CH4, CO2 and O2 in surface bog peat cores using Quadrupole Mass Spectrometry and relate this to peat physical structure. Replicate cores collected in spring and autumn from both hollows and hummocks are used (n = 10). CH4 recorded in almost every profile was localised in intense peaks reaching concentrations up to 350 μM at depths where O2 was absent. Each CH4 peak had a coincident CO2 peak with a minimum mean ratio of ∼20:1 (CO2:CH4) and we found more CH4 beneath hollows than hummocks. In statistical comparisons CH4 concentration and distribution differed significantly between profiles for each depth. We demonstrate that variability found within a single core is at least as great as that between cores collected across the bog. The distribution of CH4 was negatively correlated with bulk density and in some cases the location of roots matched those of intense CH4 concentration where bubbles had formed and been trapped. Our comparisons suggest variability in gas distribution is caused by a heterogenous peat structure that controls the movement of gas bubbles and contains localised hotspots of gas production. The small and fine root systems of vascular plants on the peatland surface may cause high levels of methanogenic activity in their vicinity and also represent a physical barrier capable of trapping CH4 bubbles.  相似文献   

6.
Time-dependent uptake of 35S]SO42? from surface water overlying cores of peat occurred by passive diffusion along a concentration gradient set up by SO42? metabolism in the peat. The limiting rate constant of SO42? uptake was related to concentration according to Michaelis-Menten kinetics. In peat cores taken from an area of mire submerged by surface water biologically-mediated uptake began immediately. But in cores taken from an adjacent area where the water table was about 5 cm below the peat surface, SO42? metabolism was slower and developed after a lag of about 2.3–4.0 days. Only about 2.2% of [35S]SO42? taken up by peat cores remained in the water-soluble pool, while about 11% was associated with acid-volatile H2S. Most of the remainder appeared to be incorporated into organic matter. Less than 0.3% was released as H2S into the gas phase. The experimental results are consistent with a flux into the peat of 3.28–7.71 g S m?2yr?1, comparable with 4.76–6.06 g S m?2yr?1 indicated by measurements of S content and age of the peat. The results suggest that uptake and metabolism of dissolved SO42? may be the major route of S incorporation into peat.  相似文献   

7.
A formalized arrangement of morphogenetic types of litter according to the physicochemical parameters provided their significant grouping in three genetic associations. The litter group (highly decomposed + moderately decomposed) is confined to the tall-grass group of bog birch forests. The rhizomatous (roughly decomposed) litter is formed in the sedge-reed grass bog birch forests. The litter group (peaty + peatified + peat) is associated with the bog-herbaceous-moss group of forest types. The genetic associations of the litters (a) reliably characterize the edaphic conditions of bog birch forests and (b)correspond to formation of the peat of certain ecological groups. We found highly informative the acid-base parameters, the exchangeable cations (Ca2+ + Mg2+) and the total potential acidity, which differentiated the genetic associations of litter practically with 100% probability. The expediency of studying litters under groups of forest types rather than under separate types of bog birch forests was demonstrated.  相似文献   

8.
Abundant production of organic matter that decomposes slowly under anaerobic conditions can result in substantial accumulation of soil organic matter in wetlands. Tedious means for estimating production and decomposition of plant material, especially roots, hampers our understanding of organic matter dynamics in such systems. In this paper, I describe a study that amended typical estimates for both production and decomposition of organic matter by measuring net flux of carbon dioxide (CO2) over the peat surface within a conifer swamp, a sedge-dominated marsh, and a bog in the Appalachian Mountain region of West Virginia and western Maryland, USA. The sites are relatively productive, with net primary production (NPP) of 30 to 82.5 mol C m?2 yr?1, but peat deposits are shallow with an average depth of about 1 m. In summer, all three sites showed net CO2 flux from the atmosphere to the peat during the daytime (?20.0 to ?30.5 mmol m?2 d?1), supported by net photosynthesis, which was less than net CO2 flux from the peat into the atmosphere at nighttime (39.2 to 84.5 mmol m?2 d?1), supported by ecosystem respiration. The imbalance between these estimates suggests a net loss of carbon (C) from these ecosystems. The positive net CO2 flux seems to be so high because organic matter decomposition occurs throughout the peat deposit — and as a result concentrations of dissolved inorganic carbon (DIC) in peat pore waters reached 4,000 Μmol L?1 by late November, and concentrations of dissolved organic carbon (DOC) in peat pore waters reached 12,000 Μmol L?1. Comparing different approaches revealed several features of organic matter dynamics: (i) peat accretion in the top 30 cm of the peat deposit results in a C accumulation rate of about 15 mmol m?2 d?1; however, (ii) the entire peat deposit has a negative C balance losing about 20 mmol m?2 d?1.  相似文献   

9.
Historical deposition rates of Hg were determined in 7 ombrotrophic bogs located far from direct sources in Sweden and Norway. The peat bog cores were dated using 210Pb. Based on the dating result 10 to 12 slices from each core were analyzed for Hg. In Southwestern Scandinavia (Rörvik) the deposition rate has increased from about 10 to about 30 μg Hg m?2 yr?1 since the beginning of this century. In Northwestern Norway (Överbygd) the deposition rate has increased from about 10 to about 35 μg Hg m?2 yr?1 since the 1960's. In Southeast Sweden (Aspvreten) the deposition rate decreased since the beginning of this century. There are no significant trends in the historical deposition rates at the two other stations in middle Scandinavia. A comparison between recent Hg deposition rates measured by peat bog analysis, wet precipitation and mosses shows good agreement at all stations except those in Northern Norway were local dry deposition of Hg may be an important source of Hg.  相似文献   

10.
Studies about nitrogen (N) mineralization and nitrification in deep soil layers are rare because N processes are considered to occur mainly in topsoil that hosts active and diverse microbial communities. This study aimed to measure the soil potential net N mineralization (PNM) and nitrification (PNN) down to 4 m depth and to discuss factors controlling their variability. Twenty-one soil cores were collected at the Restinclières agroforestry experimental site, where 14-year-old hybrid walnut trees were intercropped with durum wheat. Soil cores were incubated in the dark in the laboratory at both 6 and 25°C. The soil was a deep calcic fluvisol with a fluctuating water table. It featured a black layer that was very rich in organic matter and permanently water saturated at depths between 3.0 and 4.0 m. The mean soil mineral N content was 3 mg N kg−1 soil in the upper 0.0–0.2 m layer, decreasing until a depth of 2 m and increasing to the maximum value of 25.8 mg N kg−1 soil in the black layer. While nitrate (NO3−) was the dominant form of mineral N (89%) in the upper 0.0–0.2 m layer, its proportion progressively decreased with depth until ammonium (NH4+) became almost the only form of mineral N (97%) in the saturated black layer. Laboratory soil incubation revealed that PNM and PNN occurred at all depths, although the latter remained low at 6°C. The soil nitrate content in the black layer was multiplied by 48 times after 51 days of incubation at 25°C, whereas it was almost inexistent at the sampling date. While the soil total N, the pH and the incubation temperature explained 84% of the variation in PNM, only 29% of the percent nitrification variance was explained by the incubation temperature (Tinc) and the soil C-to-N ratio. These results point out the necessity to consider soil potential net N mineralization and nitrification of deep soil layers to improve model predictions.  相似文献   

11.
The binding of metal to humic substances is problematical. The approaches for studying metal binding to organic matter are briefly reviewed. Ion-selective electrodes (Cu2+ and Pb2+) were used to measure metal complexation by a whole peat and an extracted humic acid (HA) fraction. Scatchard plots and calculation of incremental formation constants were used to obtain values for the binding constants for the metals onto both peat and HA. Both the peat and the humic acid had a larger maximum binding capacity for Pb2+ than for Cu2+ (e.g. at pH = 5 HA gave 0·188 mmol Cu2+ g?1 and 0·564 mmol Pb2+ g?1: peat gave 0·111 mmol Cu2+ g?1 and 0·391 mmol Pb2+ g?1). Overall, the humic acid had a larger metal binding capacity, suggesting that extraction caused conformational or chemical changes. The binding constants (K1) for Cu2+ increased with increasing pH in both peat and humic acid, and were larger in the peat at any given pH (e.g. at pH = 5 HA gave log K1= 2·63, and peat gave log K1= 4·47 for Cu2+). The values for Pb2+ showed little change with pH or between peat and humic acid (e.g. at pH = 5 HA gave log K1= 3·03 and peat gave log K1= 3·00 for Pb2+). In the peat, Cu2+ may be more able to bind in a 2:1 stoichiometric arrangement, resulting in greater stability but smaller binding capacity, whereas Pb2+ binds predominantly in a 1:1 arrangement, with more metal being bound less strongly. Whole peat is considered to be more appropriate than an extracted humic acid fraction for the study of heavy metal binding in organic soils, as this is the material with which metals introduced into an organic soil would interact under natural conditions.  相似文献   

12.
To gain insight into the effects of drying and rewetting events on anaerobic respiration in ombrotrophic peat soils, we investigated bacterial sulfate (SO4) reduction and methane (CH4) production in anaerobic incubations of intact peat microcores from 30 to 40 cm depth of Mer Bleue bog, Ontario/Canada. Concentrations of dissolved SO4, carbon dioxide (CO2), CH4, acetate, and hydrogen (H2) were recorded and net turnover rates calculated from regression. Gross rates of bacterial sulfate reduction were determined by 35SO4 tracer incubation. After incubation, the peat was dried and rewetted, with saturated peat serving as control. CO2 production was initially rapid (up to <360 nmol cm?3 d?1) and slowed towards an endpoint of 2–3 mmol l?1, which was only partly related to thresholds of Gibbs free energies of the involved processes. Acetate rapidly accumulated to levels of 600–800 μmol l?1 and remained constant thereafter. CH4 production (0–2.8 nmol cm?3 d?1) was small and delayed, even after SO4 was depleted, by about 30–40 d. Hydrogenotrophic methanogenesis was endergonic and the process thus likely followed an acetotrophic pathway. Drying and rewetting replenished the SO4 pool, enhanced SO4 reduction rates and suppressed methanogenesis. The overall contribution of net SO4 reduction and methanogenesis to the CO2 production rate was small (0.5–22%) and only enhanced in replicates subjected to drying (35–62%). The major fraction of respiration in the incubated peat cores thus followed yet unidentified pathways.  相似文献   

13.
We studied the consequences of a fire that affected 29 ha of a drained forested raised bog in Tver oblast, Central European Russia. The drainage network consisted of open 1-m-deep ditches with 60 to 160 m ditch spacing. The groundwater level (GWL) varied within the studied drained bog. We used the method of assessing the loss of soil carbon (C) based on the difference between the ash concentration in the burnt peat of the upper layer and underlying unburnt layers. The carbon loss was higher near the drainage ditches than in the sites remote from ditches. The sample median values of carbon loss (kg C/m2) were estimated at 0.37 near the drainage ditches and at 0.22 for the remote sites with a distance of 160 m between ditches. They increased to 2.23 and 0.79 near and far from the drainage ditches for 106 m ditch spacing, and ranged from 1.13 to 2.10 near the drainage ditches and were equal to 0.45 at the remote sites for 60 m ditch spacing. The maximum loss of C was at the bog margin with the 70-cm-deep GWL; the sample median was equal to 2.97 kg C/m2. The results obtained for C loss from the wildfire on the raised bog agree with the estimates obtained by other authors (1.45–4.90 kg C/m2) and confirm the importance of taking such loss into account in the estimates of the carbon budget of peat soils (Histosols).  相似文献   

14.
《Soil biology & biochemistry》2012,44(12):2432-2440
Feedbacks to global warming may cause terrestrial ecosystems to add to anthropogenic CO2 emissions, thus exacerbating climate change. The contribution that soil respiration makes to these terrestrial emissions, particularly from carbon-rich soils such as peatlands, is of significant importance and its response to changing climatic conditions is of considerable debate. We collected intact soil cores from an upland blanket bog situated within the northern Pennines, England, UK and investigated the individual and interactive effects of three primary controls on soil organic matter decomposition: (i) temperature (5, 10 and 15 °C); (ii) moisture (50 and 100% field capacity – FC); and (iii) substrate quality, using increasing depth from the surface (0–10, 10–20 and 20–30 cm) as an analogue for increased recalcitrance of soil organic material. Statistical analysis of the results showed that temperature, moisture and substrate quality all significantly affected rates of peat decomposition. Q10 values indicated that the temperature sensitivity of older/more recalcitrant soil organic matter significantly increased (relative to more labile peat) under reduced soil moisture (50% FC) conditions, but not under 100% FC, suggesting that soil microorganisms decomposing the more recalcitrant soil material preferred more aerated conditions. Radiocarbon analyses revealed that soil decomposers were able to respire older, more recalcitrant soil organic matter and that the source of the material (deduced from the δ13C analyses) subject to decomposition, changed depending on depth in the peat profile.  相似文献   

15.
Isotherms of mono- and polyelement adsorption of Cu2+, Pb2+, and Zn2+ by an ordinary chernozem were described by the Langmuir equation. The values of the adsorption constant k decreased in the range Cu2+ > Pb2+ ≫ Zn2+ for the monoelement adsorption from nitrate and acetate salt solutions, Cu2+ > Pb2+ > Zn2+ for the polyelement adsorption from nitrate solutions, and Pb2+ > Cu2+ ≫ Zn2+ for the polyelement adsorption from acetate solutions. The maximum adsorption (C max, ∞) of individual cations at the polyelement contamination was always lower than at the monoelement contamination because of the mutual competition. At the same time, the values of k for the polyelement adsorption were higher than those for the monoelement adsorption because heavy metals (HMs) interact with most of the specific adsorption centers. It was shown that the ratio between the content of exchangeable cations displaced from the soil exchangeable complex (SEC) into the solution and the content of adsorbed HMs decreased with the increasing concentration of adsorbed HMs. These values could be higher (for Cu2+), equal, or lower than 1 (for Pb2+ and Zn2+). In the former case, this was due to the dissolution of readily soluble salts at low HM concentrations in the SEC. In the latter case, this was related to the adsorption of associated HMs and the formation of new phases localized on the surface of soil particles at high HM concentrations in the SEC.  相似文献   

16.
Feedbacks to global warming may cause terrestrial ecosystems to add to anthropogenic CO2 emissions, thus exacerbating climate change. The contribution that soil respiration makes to these terrestrial emissions, particularly from carbon-rich soils such as peatlands, is of significant importance and its response to changing climatic conditions is of considerable debate. We collected intact soil cores from an upland blanket bog situated within the northern Pennines, England, UK and investigated the individual and interactive effects of three primary controls on soil organic matter decomposition: (i) temperature (5, 10 and 15 °C); (ii) moisture (50 and 100% field capacity – FC); and (iii) substrate quality, using increasing depth from the surface (0–10, 10–20 and 20–30 cm) as an analogue for increased recalcitrance of soil organic material. Statistical analysis of the results showed that temperature, moisture and substrate quality all significantly affected rates of peat decomposition. Q10 values indicated that the temperature sensitivity of older/more recalcitrant soil organic matter significantly increased (relative to more labile peat) under reduced soil moisture (50% FC) conditions, but not under 100% FC, suggesting that soil microorganisms decomposing the more recalcitrant soil material preferred more aerated conditions. Radiocarbon analyses revealed that soil decomposers were able to respire older, more recalcitrant soil organic matter and that the source of the material (deduced from the δ13C analyses) subject to decomposition, changed depending on depth in the peat profile.  相似文献   

17.
The influence of various ecological factors (air and soil temperature, atmospheric pressure, level of peatland waters, and the content of CO2 in the atmosphere) on the emission of CO2 from the surface of a peat deposit of an oligotrophic peatland in the south taiga subzone of West Siberia was studied. On the basis of the investigations, day and seasonal dynamics of the emission of CO2 from the surface of the peat deposit were revealed. A detailed correlation analysis allowed us to describe the dependences of the CO2 flux from the surface of the peat deposit on the environmental parameters at various levels of averaging: hour, day, and month. It was shown that the temperature of the air and surface of the peat deposit have a reliable impact on the emission of CO2 on all time scales. The atmospheric pressure, as a factor that changes relatively slowly, influences the emission of CO2 weakly. The performed studies did not allow us to draw an unambiguous conclusion about the influence of the level of bog waters on the emission of CO2 from the surface of a peat deposit.  相似文献   

18.
Practicable application of red sludge and melanterite (FeSO4) on bog peat soils A new way is shown to dispose the industrial by-products red sludge and melanterite by agricultural application. The ferrous products sorbe the moveable phosphates in the acid bog peat soil, so that they are still available for plants, but will not or only a little be leached. In a field trial the amount of leached phosphorus could be reduced by about 80%. The agricultural use of red sludge and melanterite is thereby at the same time a contribution to reduce the pollution of surface waters.  相似文献   

19.
The effect of Cl?,SO 4 2? , CH3COO?, and NO 3 ? anions on the adsorption of copper, lead, and zinc by an ordinary chernozem has been studied. The effect of the anions on the adsorption of Cu2+, Pb2+, Zn2+ ions is significant but uncertain. It has been shown that the attendant anions affect the shape of the adsorption isotherms, which are described by the Langmuir, Freundlich, or Henri equations. The constants of the adsorption from a nitrate solution calculated from the Langmuir equation (K L) decrease in the following order: Cu2+ > Pb2+ >> Zn2+. The values of the maximum adsorption (C max) decrease in the following order: Cu2+ ≥ Zn2+ > Pb2+ for acetate solutions and in the series Pb2+ > Zn2+ ≥ Cu2+ for nitrate solutions. The values of the Henry constants (K H) calculated for the adsorption of the same cations from chloride solutions decrease in the same order as the values of K L. The CH3COO? anion has the highest effect on the constant values. The NO 3 ? and Cl? anions “switch their places” depending on the attendant cation, but their effect is always lower than that of the acetate anion. The values of C max for copper and zinc are most affected by the CH3COO? anion, and the adsorption of zinc is most affected by the Cl? and NO 3 ? anions. The assessment of the mobility of the adsorbed cations from the extraction with ammonium acetate (pH 4.8) has shown that the content of the desorbed metals is always lower than the content of the adsorbed cations and varies from 0.025 to 83%. According to their mobility, the adsorbed metals form the following order: Zn2+ > Pb2+ > Cu2+. The effect of the attendant anions on the extractability of the adsorbed cations decreases in the following order: chlorides > sulfates > acetates > nitrates.  相似文献   

20.
The influence of some complexing agents of (poly)aminopolycarboxylic acids (diethylenetriaminopentaacetic acid (DTPA), ethylenediaminotetraacetic acid (EDTA), nitrilotriacetic acid (NTA), and iminodiacetic acid (IDA)) on the sorption of Cu2+ by crystal and amorphous (hydr)oxides of Fe(III), Al(III), and Mn(IV) that are widespread mineral components of soils was studied. The obtained results are considered in terms of complex-formation in the solution and on the sorbent’s surface. The effect of the complexing agents on the metal sorption (mobilization/immobilization) is determined by (1) the stability, structure, and sorption capability of compexonates formed in the solution; (2) the acidity, and (3) the nature of the sorbent. The desorption effect on Cu2+ cations was found to change in the following sequence of complexing agents: EDTA > DTPA ? NTA > IDA. The high-dentate complexing agents (EDTA, DTPA) had the greatest impact on ?u2+ cations bound with crystalline (hydr)oxides of Fe, Al, and Mn. The low denticity of the complexing agents (IDA, NTA) and binding of ?u2+ with amorphous sorbents leads to the weakening of desorption. The decrease in acidity promoted the mobilization of the metal under the influence of complexing agents; the increase in acidity caused its immobilization. The growth in the mobility of heavy metals bound with soil (hydr)oxides of Fe, Al, and Mn due to the complexing agents entering the surface and ground water is considered a factor of ecological risk.  相似文献   

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