Peat Column Research Articles

Transport of lead and diesel fuel through a peat soil near Juneau, AK: a pilot study

A set of peat column experiments was used to determine the transport potential of lead (Pb) and diesel range organics (DRO) in palustrine slope wetlands near Juneau, AK. This project is important to southeast Alaskan communities because limited land resources are forcing development of regional wetlands. This study was instigated by concerns that proposed modifications to a nearby rifle range using DRO-contaminated soil posed a potential risk to an anadromous fish-bearing stream 250 m from the site. Three pairs of peat columns were extracted from the rifle range for analysis, one pair along and two pairs across the natural bedding planes of the soil. One column in each pair was spiked with Pb and DRO and the other was used as a control. Approximately 1-year worth of water (171 cm) was passed through each column and leachate was collected at regular intervals. The results showed that substantial DRO transport only occurred along the bedding planes. Leads was surprisingly mobile, both along and across the bedding planes with estimated soil–water partition coefficients several orders of magnitude lower than commonly published values, probably because the peat was heavily Pb-loaded by lead from bullets and because the peat's acidic, organic-rich environment enhanced Pb mobility. The chemical outflow behavior agreed with a simple macropore transport model. These results underscore the need for caution when developing regional wetlands.

Increasing P Retention in the Peat Column Amended with Mineral Soil and Some Rock Phosphates

Peat soils have a very low capacity in retaining P. Mineral soils rich in Fe could be used as ameliorant in increasingthis capacity.The aim of this experiment was to study the use of three rock phosphates and SP-36 on peat amended withmineral soil in increasing P retention. The experiment was conducted in the laboratory of the Centre for Soil and Agroclimate Research and Development, Bogor. P treatments consist of four P fertilizer sources including Morocco rock phosphate,Christmas rock phosphate, Ciamis rock phosphate, and SP-36, and three P level (50, 100 and 200% of P sorption) plus partial and complete control in 2 replications. The experiment conducted in soil column made from PVC pipe 4 inch in diameter. Column was filled with 1 250 g peat cily weight (10.5' C), 250 g of which was amended with mineral soil and each of three rock phosphates or SP-36, and put on as the upper part of the column and incubated for 4 weeks. Leaching was conducted everyday, with 50 cc distilled water for 12 days. Filtrate was collected in 500 cc Erlenmeyer glass, and soluble P was analyzed. After this step peat in the colu~nnw as divided into seven depth that were 0-5, 5-10, 10-20, 20-30, 30-40, 40-50 and 50-60 cm, then P-Bray I was analyzed. The results showed that the applicatiorz of Morocco and Ciamis rock phosphates on peat amended with mineral soil after leaching, resulted in accumulation of P on the upper layers, suggesting that P retention on peat was increased such that P loss could be reduced. Ratio of P content in the soil column at 0-30 cm and 30-60 cm depth for Morocco rock phosphate on the dosages of 50, 100 and 200% of P sorption were 1.54; 1.90; and 2.79, respectively, and that for Ciamis rock phosphate were 1.64; 1.76 and 4.1 I, respectively. The application of Christmas rock phosphate resulted in P accumulation at 30-40 cm depth. Ratio of P content in soil column treated with Christmas rock phosphate at 0-30 cm and 30-60 cm depth on dosages of 50, 100 and 200 % of P sorption were 1..05; 1.11 and 1.38, respectively, suggesting that P was leached to bottom layer. It seems that high Fe in Christmas rock phosphate did not contribute to an increase of P retention. Although the application of SP-36 resulted in P accumulation at the upper layers, P leaching was higher.

Platinum group element abundances in a peat layer associated with the Tunguska event, further evidence for a cosmic origin

We have measured excesses of Pd, Rh, Ru, REE, Co, Sr, and Y in a peat column from the Northern peat bog of the 1908 Tunguska explosion site. Earlier, in this peat column the presence of an Ir anomaly at the event layers (30– 45 cm depth) has been found (Planet Space Sci. 48 (1998) 179). In these layers, Pd, Rh, Ru, Co, Sr, and Y show pronounced anomalies of a factor 4–7 higher than the background value. In the event layers there are also good correlations between the siderophile platinum group elements (Pd, Rh, Ru) and Co, indicators of cosmic material, which imply they might have the same source, i.e. the Tunguska explosive body. The patterns of CI-chondrite-normalized REE in the event layers are much flatter than those in normal peat layers and different from those in the nearby traps. Furthermore, in these layers the patterns of CI-chondrite-normalized PGEs and the element ratios (e.g. C/Pd, C/Rh, and between some siderophile elements) give evidence that the Tunguska explosive body was more likely a comet, although we cannot exclude the possibility that the impactor could be a carbonaceous asteroid. We have estimated the total mass of a solid component of the explosive body up to 10 3–10 6 tons.

Use of hydraulic head to estimate volumetric gas content and ebullition flux in northern peatlands

Hydraulic head was overpressured at middepth in a 4.2‐m thick raised bog in the Glacial Lake Agassiz peatlands of northern Minnesota, and fluctuated in response to atmospheric pressure. Barometric efficiency (BE), determined by calculating ratios of change in hydraulic head to change in atmospheric pressure, ranged from 0.05 to 0.15 during July through November of both 1997 and 1998. The overpressuring and a BE response were caused by free‐phase gas contained primarily in the center of the peat column between two or more semielastic, semiconfining layers of more competent peat. Two methods were used to determine the volume of gas bubbles contained in the peat, one using the degree of overpressuring in the middepth of the peat, and the other relating BE to specific yield of the shallow peat. The volume of gas calculated from the overpressuring method averaged 9%, assuming that the gas was distributed over a 2‐m thick overpressured interval. The volume of gas using the BE method averaged 13%. Temporal changes in overpressuring and in BE indicate that the volume of gaseous‐phase gas also changed with time, most likely because of rapid degassing (ebullition) that allowed sudden loss of gas to the atmosphere. Estimates of gas released during the largest ebullition events ranged from 0.3 to 0.7 mol m−2 d−1. These ebullition events may contribute a significant source of methane and carbon dioxide to the atmosphere that has so far largely gone unmeasured by gas‐flux chambers or tower‐mounted sensors.

Isotopic–geochemical study of nitrogen and carbon in peat from the Tunguska Cosmic Body explosion site

Isotopic–geochemical investigations were carried out on peat samples from the 1908 Tunguska Cosmic Body (TCB) explosion area. We analyzed two peat columns from the Northern peat bog, sampled in 1998, and from the Raketka peat bog, sampled during the 1999 Italian expedition, both located near the epicenter of the TCB explosion area. At the depth of the “catastrophic” layer, formed in 1908, and deeper, one can observe shifts in the isotopic composition of nitrogen (up to Δ 15N = +7.2‰) and carbon (up to Δ 13C = +2‰) and also an increase in the nitrogen concentration compared to those in the normal, upper layers, unaffected by the Tunguska event. One possible explanation for these effects could be the presence of nitrogen and carbon from TCB material and from acid rains, following the TCB explosion, in the “catastrophic” and “precatastrophic” layers of peat. We found that the highest quantity of isotopically heavy nitrogen fell near the explosion epicenter and along the TCB trajectory. It is calculated that 200,000 tons of nitrogen fell over the area of devastated forest, i.e., only about 30% of the value calculated by Rasmussen et al. (1984). This discrepancy is probably caused by part of the nitrogen having dispersed in the Earth’s atmosphere. The isotopic effects observed in the peat agree with the results of previous investigations (Kolesnikov et al., 1998a, 1998b, 1999; Rasmussen et al., 1999) and also with the increased content of iridium and other platinoids found in the corresponding peat layers of other columns (Hou et al., 1998, 2000). These data favor the hypothesis of a cosmochemical origin of the isotopic effects.

Response of Sphagnum fuscum to Nitrogen Deposition: A Case Study of Ombrogenous Peatlands in Alberta, Canada

Peatlands cover about 30% of northeastern Alberta and are ecosystems that are sensitive to nitrogen deposition. In polluted areas of the UK, high atmospheric N deposition (as a component of acid deposition) has been considered among the causes of Sphagnum decline in bogs (ombrogenous peatlands). In relatively unpolluted areas of western Canada and northern Sweden, short-term experimental studies have shown that Sphagnum responds quickly to nutrient loading, with uptake and retention of nitrogen and increased production. Here we examine the response of Sphagnum fuscum to enhanced nitrogen deposition generated during 34 years of oil sands mining through the determination of net primary production (NPP) and nitrogen concentrations in the upper peat column. We chose six continental bogs receiving differing atmospheric nitrogen loads (modeled using a CALPUFF 2D dispersion model). Sphagnum fuscum net primary production (NPP) at the high deposition site (Steepbank—mean of 600 g/m2; median of 486 g/m2) was over three times as high than at five other sites with lower N deposition. Additionally, production of S. fuscum may be influenced to some extent by distance of the moss surface from the water table. Across all sites, peat nitrogen concentrations are highest at the surface, decreasing in the top 3 cm with no significant change with increasing depth. We conclude that elevated N deposition at the Steepbank site has enhanced Sphagnum production. Increased N concentrations are evident only in the top 1-cm of the peat profile. Thus, 34 years after mine startup, increased N-deposition has increased net primary production of Sphagnum fuscum without causing elevated levels of nitrogen in the organic matter profile. A response to N-stress for Sphagnum fuscum is proposed at 14–34 kg ha−1 yr−1. A review of N-deposition values reveals a critical N-deposition value of between 14.8 and 15.7 kg ha−1 yr−1 for NPP of Sphagnum species.

MACROPOROSITY AFFECTS WATER MOVEMENT AND PORE WATER SAMPLING IN PEAT SOILS

The measurement of chemical concentration profiles in pore water is a starting point for the analysis of biogeochemical processes in waterlogged peat soils. Concentration patterns may be obscured when macroporosity causes preferential flow in column experiments and when pore water is retrieved from the peat by suction. To investigate the magnitude of such effects, we used LiBr as a tracer in peat columns at outflow rates of 0, 2–3, and 8 mm d−1. The results were compared with modeled advective-diffusive migration rates. Twenty to fifty percent of the tracer was recovered from depths at which the tracer would have been absent if preferential flow had not occurred. At the high flow rate, the preferential flow was stronger, and the retrieved pore-water was probably in disequilibrium with the matrix. When pore water was retrieved by suction, linear concentration gradients decreased by about 30% through the recovery of water from different depths, and the quality of fitted linear gradients decreased from R2 = 0.99 to R2 = 0.82. When flow rates are low (<3 mm d−1) and pore water concentration values from samplers are aggregated or regressed, the obtained concentration profiles seem to represent the vertical distribution of chemical species reasonably well. The use and interpretation of pore water profiles in peat soils is problematic if flow rates are higher and if vertical gradients are based on individual or few data points that have been obtained by suction samplers.

Nu bli’r der ballade

Nu bli’r der ballade

Development of a biobarrier for the remediation of PCE-contaminated aquifer

The industrial solvent tetrachloroethylene (PCE) is among the most ubiquitous chlorinated compounds found in groundwater contamination. The objective of this study was to develop a biobarrier system, which includes a peat layer to enhance the anaerobic reductive dechlorination of PCE in situ. Peat was used to supply primary substrate (electron donor) continuously. A laboratory-scale column experiment was conducted to evaluate the feasibility of this proposed system or PCE removal. This experiment was performed using a series of continuous-flow glass columns including a soil column, a peat column, followed by two consecutive soil columns. Anaerobic acclimated sludges were inoculated in all three soil columns to provide microbial consortia for PCE biodegradation. Simulated PCE-contaminated groundwater with a flow rate of 0.25 l/day was pumped into this system. Effluent samples from each column were analyzed for PCE and its degradation byproducts (trichloroethylene (TCE), cis-dichloroethylene ( cis-DCE), vinyl chloride (VC), ethylene (ETH), and ethane). Results show that the decrease in PCE concentrations and production of PCE byproducts were observed over a 65-day operating period. Up to 98% of PCE removal efficiency was obtained in this passive system. Results indicate that the continuously released organics from peat column enhanced PCE biotransformation. Thus, the developed biobarrier treatment scheme has the potential to be developed into a cost-effective in situ PCE-remediation technology, and can be utilized as an interim step to aid in system scale-up.

Radiocarbon and stable carbon isotopic evidence for transport and transformation of dissolved organic carbon, dissolved inorganic carbon, and CH4 in a northern Minnesota peatland

To elucidate the roles of hydrology and vegetation in below ground carbon cycling within peatlands, radiocarbon values were obtained for pore water dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), CH4, and peat from the Glacial Lake Agassiz peatland. The major implication of this work is that the rate of microbial respiration within a peat column is greater than the peat decomposition rate. The radiocarbon content of DOC at both bog and fen was enriched relative to solid‐phase peat by ∼150‐300‰ consistent with the advection of recently photosynthesized DOC downward into the peat column. Fen Δ14C values for DIC and CH4 closely track the Δ14C of pore water DOC at depth, indicating that this recent plant production was the predominant substrate for microbial respiration. Aceticlastic methanogenesis apparently dominated the upper third of the peat column (α = 1.05), shifting toward CO2 reduction with depth (1.05 &lt; α &lt; 1.08). Upwelling groundwater contributed as much as 15% of the DIC to the bulk DIC pool at depth in the fen. The similarity of Δ14C values for DIC and CH4 suggests that methanogens utilized DIC from this source as well as DIC produced in situ. Bog Δ14C values for pore water DIC and CH4 differ by ≤ 15‰ at all depths and are depleted in 14C relative to DOC by ∼100‰, suggesting microbial utilization of a mixture of older and modern substrates. CO2 reduction was the primary pathway for methanogenesis at all depths in the bog (α = 1.08), and groundwater influence on bulk DIC was negligible. For both sites, Δ14C−DIC and Δ14C−CH4 are approximately equal at depths where stable isotope data indicate a predominance of CO2 reduction and dissimilar when acetate fermentation is indicated.

87Sr/86Sr as a tracer of groundwater discharge and precipitation recharge in the Glacial Lake Agassiz Peatlands, northern Minnesota

A contrast in the 87Sr/86Sr ratio of atmospherically derived Sr (∼0.710) and Sr from regional bedrock (&gt;0.730) allows quantification of the proportions of precipitation recharge and groundwater discharge into peat columns of bogs and fens in the Glacial Lake Agassiz Peatlands. Two contrasting bog‐fen pairs were studied: the Lost River peatland located over a regional groundwater discharge zone and the Red Lake peatland situated atop a hydrologic divide where recharge is expected to occur. Bog pore waters consist of 90–100% precipitation in the upper 2 m, below which they mix with groundwater. Adjacent fens consist mostly of groundwater, ranging from ∼30% near the surface to ∼100% with depth. At the Red Lake peatland, mixing relations suggest an additional Sr source that may be peat mineralization. Distinct 87Sr/86Sr and [Ca]/[Sr] ratios for groundwater discharging into bog and fen sites are indicative of distinct groundwater sources and are likely indicative of flow paths at two different length scales.

Methane Concentration and Stable Isotope Distribution as Evidence of Rhizospheric Processes: Comparison of a Fen and Bog in the Glacial Lake Agassiz Peatland Complex

This study evaluates relationships between vegetation and stable isotope distribution within a large, northern peat-accumulating wetland. Concentration and δ13C for both porewater and emitted methane were obtained from June–September for two systems characterized by different plant assemblages and hydrologic regimes: a Carex -dominated fen and a Sphagnum -dominated, forested bog crest. Average methane emissions were higher in the fen than at the bog crest across the entire growing season. Fen porewater methane concentrations were maintained at consistently low levels in the upper one-third of the peat column, and emitted methane was substantially13C-depleted (by approx. 6‰) relative to shallow porewater methane, trends which are characteristic of passive plant-mediated transport of rhizospheric methane to the atmosphere. Fen porewater δ13C-CH4values in shallow peat (approx. −59‰) suggest that microbial respiration was primarily driven by acetate fermentation. CO2reduction became more important deeper in the peat column with δ13C-CH4values ranging from approx. −65 to −69‰ between 1 and 2.8m. In contrast to the fen, porewater methane concentrations in the bog were usually at near-maximum levels just below the water table. δ13C values for emitted CH4in the bog were enriched relative to those for shallow porewater CH4by approx. 10‰, indicating that methane was subject to oxidation as it exited from the peat via passive diffusion. Methanogenesis in the peat at the bog crest appears to have been substrate-limited, with porewater δ13C-CH4(approx. −67‰) suggestive of CO2reduction at all depths.

Enhanced bioremediation of trichloroethene contaminated by a biobarrier system

The industrial solvent trichloroethylene (TCE) is among the most ubiquitous chlorinated compounds found in groundwater contamination. The objective of this study was to develop a barrier system, which includes a peat (used as the primary substrates) layer to enhance the aerobic cometabolism of TCE in situ. A laboratory-scale column experiment was conducted to evaluate the feasibility of using this peat biobarrier to remediate aquifers contaminated by TCE. This system was performed using a series of continuous-flow glass columns including a soil column, a peat column, followed by two consecutive soil columns. Activated sludges were inoculated in all three soil columns to provide microbial consortia for TCE cometabolism. Simulated TCE contaminated groundwater with a flow rate of 0.25 L/day was pumped into the system. Effluent samples from each column were analyzed for TCE and its degradation byproducts [cis-dichloroethylene (cis-DCE) and vinyl chloride (VC)]. Average removal efficiency was 96% for TCE over a 60-day operating period. Accumulation of VC was observed due to the depletion of oxygen in the system. Results from this laboratory study reveal that the developed biobarrier treatment scheme would be expected to provide a more cost-effective alternative to remediate chlorinated-solvent contaminated aquifers.

Adsorção de zinco e cádmio em colunas de turfa

The aim of this work was to evaluate the adsorption conditions of zinc and cadmium ions from aqueous solutions using a comercially available peat from Balneario Arroio do Silva, Santa Catarina State, Brazil. Adsorption studies were carried out in column experiments using radiotracers of the studied metals (65Zn and 115Cd). The pH influence and the interference of other ions, such as Na+, Ca2+, Fe3+ and Al3+on the adsorption process were investigated. The results showed that peat columns are able to retain more than 99% of metal ions in solution in a range of pH from 3,7 to 6,5. Ca2+ and Al3+ ions were the main interferent on adsorption of Zn and Cd ions in solution.

The potentialities of SRXRF in studying element migration in swamps of Western Siberia

Data are given on the measurement of multielemental composition of the peat column profile of the eutrophic swamp of Western Siberia at a depth of 8.5 m by the SRXRF method. The results of determination of multielemental composition obtained by SRXRF are compared with the data of measurements performed in the Joint Institute of Nuclear Research by the neutron-activation method.

Simulating vertical flow in large peatlands

Ground-water flow simulations are used to evaluate the importance of three parameters on vertical flow in peatlands: regional slope, permeability of the mineral soil underlying the peat, and peatland topography. Our results indicate that the extent of vertical ground-water flow in peatlands is primarily controlled by mineral soil permeability. Local ground-water flow cells that form under small water-table mounds at bog domes can drive peat pore water into permeable mineral soil. However, when peat forms over low permeability mineral soil, vertical movement of peat pore water becomes negligible and lateral flow of water in the upper portion of the peat column dominates the peatland hydrology. This effect is not due to the low permeability of humified peat layers, as is commonly assumed in many peatland studies. Field data from the Hudson Bay Lowland (Canada) and the Glacial Lake Agassiz peatlands of northern Minnesota confirm the validity of these models. These results are relevant in settings other than peatlands where relief is low and small topographic mounds exist.

Methane stable isotope distribution at a Carex dominated fen in north central Alberta

The methane stable isotope distribution was characterized at a Carex dominated fen in boreal Alberta, Canada, over three growing seasons to examine methane production, oxidation, and transport to the atmosphere; processes which are strongly tied to emergent vegetation and the influence of the rhizosphere (upper 20 cm of peat in this system]. At times when standing floodwater was present, δ13C values of emitted methane averaged −63.6 ± 2.3, −66.3 ± 1.6, and −65.4 ± 1.3‰ for the 1994, 1995, and 1996 seasons, respectively. These emissions were significantly 13C depleted relative to the belowground methane dissolved in rhizospheric pore waters, indicating that gas transport in Carex is dominated by passive diffusion. The rhizosphere was 13CH4 enriched relative to depths below the rhizosphere, consistent with the occurrence of root associated methane oxidation, preferential mobilization of 13CH4, and a relatively greater role of acetate fermentation type methane production. Dual isotope tracers, δ13C and δD, help qualify the role of each of these processes and aid in describing the distribution of production pathways, CO2 reduction, and acetate fermentation. Inverse trends in δ13C‐CH4 and δD‐CH4 depth profiles are consistent with an interpretation suggesting an evolution toward methane production by CO2 reduction with increasing depth. A shift in production mechanisms appears to be the dominate process affecting the stable isotope distribution below 10 cm in the peat column, while oxidation and transport isotope effects are dominant above 10 cm. To test several hypotheses regarding the effects of transport, oxidation, and production on methane isotope distributions, we also present measurements from sites fertilized and sites devegetated (continually clipped) over the 3 year period. Removal of vegetation quickly halted rhizospheric methane oxidation and gas transport while gradually increasing the relative role of CO2 reduction in net methane production as labile substrate was used up. The fertilizer treatment increased above ground biomass and primary productivity but had little effect on the stable isotope distribution. A mass balance calculation indicates that methane emissions are attenuated 0–34% by methane oxidation in the rhizosphere. Results showed little seasonal variability other than during a period when floodwater levels dropped below the peat surface resulting in the13CH4 enrichment of methane emissions.

Fine-scale characteristics of groundwater flow in a peatland

Fine-scale dynamics of groundwater flow were studied in a 1·5 ha peatland in central New York. Measurements of the hydraulic head throughout a detailed network of piezometer clusters revealed spatial and temporal variability in the direction of groundwater flow at a very fine (within a few metres) scale of analysis. Within the small wetland, there were areas of groundwater recharge, discharge and lateral flow. Such patterns of groundwater flow frequently reversed or changed due to fluctuations of only a few centimetres in hydraulic head. Specific conductance, deuterium signatures and calcium concentrations of groundwater corroborated the groundwater flow patterns determined with hydraulic head measurements and illustrated the influence of source water chemistry and evaporation on different layers in the peat column. The control of peat chemistry by such fine-scale groundwater flow may have important implications for plant community composition and diversity in groundwater-fed peatlands. Copyright © 1999 John Wiley & Sons, Ltd.

Finding of probable Tunguska Cosmic Body material:: isotopic anomalies of carbon and hydrogen in peat

Method of a search for traces of Tunguska Cosmic Body (TCB) material using layer-by-layer analysis of the isotopic composition of light elements in peat has been offered. Four peat columns sampled at the explosion epicentre indicated significant carbon and hydrogen isotopic effects in its near catastrophic layers. The shifts, opposite in direction, for carbon (Δ13C reaches +4.3‰) and hydrogen (ΔD reaches −22‰) cannot be attributed to any known terrestrial reasons (fall-out of terrestrial dust and fire soot; emission from the Earth of oil–gas streams; climate changes, humification of peat, and so on). Moreover, the isotopic effects are clearly associated with the area and with the time of the 1908 event. They are absent in the uppermost and the lowest peat layers and also in the control peat columns sampled at the remote places. Since calculated δ13C value for an admixture of carbon (+51–64‰) is very high, these effects may not be explained by contamination of peat with material similar to ordinary chondrites or achondrites, too. Such heavy carbon occurs in the most primitive CI and CM types of carbonaceous chondrites. However, C/Ir ratio in a cosmic admixture is 10,000 times as many as in CI chondrites that points to cometary nature of the TCB. The isotopic effects are in agreement with the increase of the Ir content observed in peat, but, at the same time, small content of Ir points to the low content of dust in the Tunguska comet that sharply differs it from Halleys comet.

Nitrogen Deposition Effects on Carbon Dioxide and Methane Emissions from Temperate Peatland Soils

Northern peatlands are important sources of carbon dioxide and methane emissions to the atmosphere. Increased atmospheric N deposition may have a significant impact on the emission of these greenhouse gases. We studied CO 2 and CH 4 emissions from untreated temperate peat soils from a eutrophic and a mesotrophic fen in a high N deposition area (the Netherlands) and from a mesotrophic fen in a low N deposition area (north-east Poland). In addition, we investigated the effects of N, P and glucose amendments on the emissions of CO 2 and CH 4 from these soils. Nitrogen availability (extractable NH 4 + ) in untreated peat from the high N area was 2.5-7.5 times higher than in the low N area, whereas the pH was 0.9-1.7 units lower. Using 6-week laboratory incubations of peat columns, we found that mean daily CO 2 emission from untreated peat soils from the high N area was lower than that from the low N area. Both linear and multiple regression analysis showed that CO 2 emission was positively related to soil pH (r 2 = 0.64). Additional N supply led to pH reduction and to lower CO 2 emission, especially in the low N peat soils. Thus, increased atmospheric N deposition leads, probably as a result of soil acidification, to lower CO 2 emission. Although glucose amendments resulted in increased CO, and CH 4 emission, we did not find evidence that this was caused by increased mineralization of native peat. Mean daily CH 4 -C emission was about 1-2 orders of magnitude lower than mean daily CO 2 -C emission. In the untreated peat soils from the high N eutrophic site, methane emission was higher than in the high N mesotrophic site and in the low N mesotrophic site. Linear regression analysis showed a positive relation between methane emission and soil fertility variables (r 2 =0.42-0.55), whereas a multiple regression model revealed that methane emission was determined by N-related soil chemistry variables (r 2 = 0.93). Increased nutrient supply initially resulted in higher methane emission from soils of both mesotrophic sites, but there was no effect on the high N eutrophic soil. These results show that increased atmospheric N deposition leads to increased methane emission from low-fertility peat soils. However, the ultimate effect of atmospheric N deposition on trace gas emissions and thereby on global warming is determined by the balance between the ratios of the change in CO 2 -C emission and CH 4 -C emission and the ratio of their global warming potentials (1:21).