A sequential extraction procedure for acid sulfate soils : Partitioning of iron
- Authors: Claff, Salirian , Sullivan, Leigh , Burton, Edward , Bush, Richard
- Date: 2010
- Type: Text , Journal article
- Relation: Geoderma Vol. 155, no. 3-4 (2010), p. 224-230
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- Description: A new sequential extraction scheme for acid sulfate soil materials has been evaluated for iron partitioning in a range of synthetic iron-bearing minerals and natural acid sulfate soil materials. This sequential extraction procedure employs six steps to quantify (1) exchangeable (magnesium chloride extractable), (2) acid (hydrochloric acid) soluble, (3) reactive organic-bound (pyrophosphate extractable), (4) crystalline oxide (citrate buffered dithionite (CBD)) extractable, (5) pyrite-bound (nitric acid extractable) and (6) residual (acid/peroxide digestible) forms of iron. Given its intended use for acid sulfate soil materials that frequently contain pyrite, a primary aim of this new sequential extraction procedure was to differentiate iron bound in pyrite from iron contained in other minerals. The results demonstrated that dissolution of pyrite was effectively isolated in the pyrite-bound extraction step, with dissolution of other iron mineral phases (i.e. akaganeite, ferrihydrite, goethite, hematite, jarosite, magnetite, and schwertmannite) occurring within the other five extraction steps. Following a systematic examination of these synthetic iron mineral phases, the sequential extraction scheme was applied to an acid sulfate soil profile, with detailed data presented for two soil layers: one representative of the sulfidic (unoxidised) conditions, and the other sulfuric (oxidised) conditions. Partitioning data for pyrite-bound iron in the acid sulfate soil profile showed good agreement with that calculated via the independently measured pyrite-bound reduced sulfur. This study indicates that the new sequential extraction procedure is suitable for the assessment of iron partitioning in acid sulfate soil materials. © 2009 Elsevier B.V. All rights reserved.
Effect of sample pretreatment on the fractionation of Fe, Cr, Ni, Cu, Mn, and Zn in acid sulfate soil materials
- Authors: Claff, Salirian , Burton, Edward , Sullivan, Leigh , Bush, Richard
- Date: 2010
- Type: Text , Journal article
- Relation: Geoderma Vol. 159, no. 1-2 (2010), p. 156-164
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- Description: A sequential extraction procedure was applied to acid sulfate soil materials from a soil profile to investigate the effect of sample pretreatment on the geochemical fractionation of selected metals. The samples were prepared for analysis by oven-drying, sieving and grinding the soil, or were examined as collected in field condition. The soil profile encompassed oxidising conditions near the surface, through to reducing conditions at depth. Six metals (Fe, Cr, Ni, Mn, Cu, and Zn) were measured during the sequential extraction procedure, and their fractionation determined in the oxidised and in the reduced zone. Although cumulative totals (the sum of all steps in the sequential extraction procedure) for the metals extracted from both the field condition and dried/ground samples were similar, some significant differences in fractionation within individual extraction steps were observed. Of particular interest was the redistribution of metals from the sulfide-bearing (pyrite-bound) fraction to the more readily available fractions (i.e. labile and acid-soluble), as a result of oven-drying and grinding. The results indicate that when assessing metal fractionation in acid sulfate soil materials, samples should be analysed in field condition in order to avoid the considerable metal fractionation artifacts that are induced by drying and grinding. © 2010 Elsevier B.V.
Contemporary pedogenesis of severely degraded tropical acid sulfate soils after introduction of regular tidal inundation
- Authors: Johnston, Scott , Keene, Annabelle , Bush, Richard , Burton, Edward , Sullivan, Leigh , Smith, Douglas , McElnea, Angus , Martens, Michelle , Wilbraham, Steve
- Date: 2009
- Type: Text , Journal article
- Relation: Geoderma Vol. 149, no. 3-4 (2009), p. 335-346
- Full Text: false
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- Description: Marine tidal inundation was partially restored to a severely degraded tropical acid sulfate soil landscape after having been excluded for over 30 years. The effects on soil acidity and iron-sulfide mineral reformation were investigated by comparing the geochemistry of soils before and after five years of regular tidal inundation. The soil pH increased by 2-3 units and titratable actual acidity (TAA) decreased by ∼ 40-50 μmol H+ g- 1 within former sulfuric horizons. Relict acidity remained at depth (> 1 m) in the underlying sulfidic horizons. δ34S data indicate that tidal inundation caused exchange of marine solutes within former sulfuric horizons, but not within underlying sulfidic material. There was considerable reformation of pyrite within former sulfuric horizons after tidal inundation with reduced inorganic sulfur increasing by ∼ 60 μmol g- 1. Acid-volatile sulfide also accumulated, but mainly near the soil surface (up to 16 μmol g- 1). Reduction of Fe(III) minerals strongly influences the geochemistry of the tidally inundated soils. After tidal inundation the soil pH and Eh closely followed the iron redox couple and there was non-sulfidic solid-phase Fe(II) up to 600 μmol g- 1. There was also substantial diagenetic enrichment of poorly crystalline Fe-oxides near the soil surface following tidal inundation, with reactive Fe spanning 400-1800 μmol g- 1. While the decreases in soil acidity documented here are likely due to a combination of marine alkalinity inputs and reduction of both Fe and SO42-, the relative importance of each process remains to be determined. This study demonstrates that marine tidal inundation can be an effective landscape-scale strategy for ameliorating severe acidity associated with drained acid sulfate soils. © 2008 Elsevier B.V. All rights reserved.
Changes in water quality following tidal inundation of coastal lowland acid sulfate soil landscapes
- Authors: Johnston, Scott , Bush, Richard , Sullivan, Leigh , Burton, Edward , Smith, Douglas , Martens, Michelle , McElnea, Angus , Ahern, Col , Powell, Bernard , Stephens, Luisa , Wilbraham, Steve , Van Heel, Simon
- Date: 2009
- Type: Text , Journal article
- Relation: Estuarine, Coastal and Shelf Science Vol. 81, no. 2 (2009), p. 257-266
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- Description: This study examines the remediation of surface water quality in a severely degraded coastal acid sulfate soil landscape. The remediation strategy consisted of partial restoration of marine tidal exchange within estuarine creeks and incremental tidal inundation of acidified soils, plus strategic liming of drainage waters. Time-series water quality and climatic data collected over 5 years were analysed to assess changes in water quality due to this remediation strategy. A time-weighted rainfall function (TWR) was generated from daily rainfall data to integrate the effects of antecedent rainfall on shallow groundwater levels in a way that was relevant to acid export dynamics. Significant increases in mean pH were evident over time at multiple monitoring sites. Regression analysis at multiple sites revealed a temporal progression of change in significant relationships between mean daily electrical conductivity (EC) vs. mean daily pH, and TWR vs. mean daily pH. These data demonstrate a substantial decrease over time in the magnitude of creek acidification per given quantity of antecedent rainfall. Data also show considerable increase in soil pH (2-3 units) in formerly acidified areas subject to tidal inundation. This coincides with a decrease in soil pe, indicating stronger reducing conditions. These observations suggest a fundamental shift has occurred in sediment geochemistry in favour of proton-consuming reductive processes. Combined, these data highlight the potential effectiveness of marine tidal inundation as a landscape-scale acid sulfate soil remediation strategy. © 2008 Elsevier Ltd. All rights reserved.
Pore water sampling in acid sulfate soils : A new peeper method
- Authors: Johnston, Scott , Burton, Edward , Keene, Annabelle , Bush, Richard , Sullivan, Leigh , Isaacson, Lloyd
- Date: 2009
- Type: Text , Journal article
- Relation: Journal of Environmental Quality Vol. 38, no. 6 (2009), p. 2474-2477
- Full Text: false
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- Description: This study describes the design, deployment, and application of a modified equilibration dialysis device (peeper) optimized for sampling pore waters in acid sulfate soils (ASS). The modified design overcomes the limitations of traditional-style peepers, when sampling firm ASS materials over relatively large depth intervals. The new peeper device uses removable, individual cells of 25 mL volume housed in a 1.5 m long rigid, high-density polyethylene rod. The rigid housing structure allows the device to be inserted directly into relatively firm soils without requiring a supporting frame. The use of removable cells eliminates the need for a large glove-box after peeper retrieval, thus simplifying physical handling. Removable cells are easily maintained in an inert atmosphere during sample processing and the 25-mL sample volume is sufficient for undertaking multiple analyses. A field evaluation of equilibration times indicates that 32 to 38 d of deployment was necessary. Overall, the modified method is simple and effective and well suited to acquisition and processing of redox-sensitive pore water profiles > 1 m deep in acid sulfate soil or any other firm wetland soils. Copyright © 2009 by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America. All rights reserved.
Methane and CO2 emissions from China's hydroelectric reservoirs: a new quantitative synthesis
- Authors: Li, Siyue , Zhang, Quanfa , Bush, Richard , Sullivan, Leigh
- Date: 2015
- Type: Text , Journal article
- Relation: Environmental Science and Pollution Research Vol. 22, no. 7 (2015), p. 5325-5339
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- Description: Controversy surrounds the green credentials of hydroelectricity because of the potentially large emission of greenhouse gases (GHG) from associated reservoirs. However, limited and patchy data particularly for China is constraining the current global assessment of GHG releases from hydroelectric reservoirs. This study provides the first evaluation of the CO
Phytolith occluded carbon and silica variability in wheat cultivars
- Authors: Parr, Jeffrey , Sullivan, Leigh
- Date: 2010
- Type: Text , Journal article
- Relation: Plant and Soil Vol. 342, no. 1-2 (2010), p. 165-171
- Full Text: false
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- Description: Phytolith Occluded Carbon (PhytOC) has recently been demonstrated to be an important long-term terrestrial carbon fraction. The aim of this study was to examine the rates of silica accumulation and carbon bio-sequestered within the silica phytoliths of the leaf and stem material of wheat (Triticum sp.) cultivars. The phytolith content of 53 wheat cultivars sourced from 25 countries around the world and grown on a single trial site was first isolated and the PhytOC content then determined. The data shows that the phytolith occluded carbon content of the wheat cultivars ranged from 0.06% to 0.60% of dry leaf and stem biomass: a range of 1,000%. The data also demonstrates that it is the efficiency by which carbon is encapsulated within silica rather than the quantity of silica accumulated by the plant that is the most important factor in determining the relative PhytOC yields. The potential phytolith carbon bio-sequestration rates in the leaf and stem components of these wheat cultivars ranged up to 0.246 t-e-CO2 ha-1y-1. These phytolith carbon bio-sequestration rates indicate a substantial potential (~50 million t-e-CO2 y-1) exists for increasing the rate of secure carbon bio-sequestration in wheat crops using existing cultivars. © 2010 Springer Science+Business Media B.V.
Carbon bio-sequestration within the phytoliths of economic bamboo species
- Authors: Parr, Jeffrey , Sullivan, Leigh , Chen, Bihua , Ye, Gongfu , Zheng, Weipeng
- Date: 2010
- Type: Text , Journal article
- Relation: Global Change Biology Vol. 16, no. 10 (2010), p. 2661-2667
- Full Text: false
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- Description: The rates of carbon bio-sequestration within silica phytoliths of the leaf litter of 10 economically important bamboo species indicates that (a) there is considerable variation in the content of carbon occluded within the phytoliths (PhytOC) of the leaves between different bamboo species, (b) this variation does not appear to be directly related to the quantity of silica in the plant but rather the efficiency of carbon encapsulation by the silica. The PhytOC content of the species under the experimental conditions ranged from 1.6% to 4% of the leaf silica weight. The potential phytolith carbon bio-sequestration rates in the leaf-litter component for the bamboos ranged up to 0.7 tonnes of carbon dioxide (CO
Comparison of two methods for the isolation of phytolith occluded carbon from plant material
- Authors: Parr, Jeffrey , Sullivan, Leigh
- Date: 2014
- Type: Text , Journal article
- Relation: Plant and Soil Vol. 374, no. 1-2 (2014), p. 45-53
- Full Text: false
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- Description: Background and aims: Phytolith occluded carbon (PhytOC) is of interest for isotope studies, dating of sediments and the capture and storage of carbon. Many methodologies have been used for the isolation of phytoliths from plant material; however, there are wide disparities in the PhytOC contents when determined by different methodologies. In this study we examine the utility of the two main methods used for quantifying PhytOC. Methods: These methods are: (1) a microwave digestion followed by a Walkley-Black digestion, and (2) H2SO4/H2O2. Results: Method (1) produced PhytOC values over 50 times higher than those acquired by method (2). SEM examination indicated that the differences were likely due to shattering of the phytoliths by method (2) allowing consumption by the acid and peroxide of PhytOC. Conclusion: These results indicate that for the samples analysed here: 1] the modified microwave method allowed the total PhytOC to be measured, 2] the H2SO4/H2O2 method allowed the PhytOC within the tightly packed silica matrix to be measured, and 3] the PhytOC retained within the phytolith cavities could possibly be calculated by subtracting 2] from 1]. For the samples analysed here most of the PhytOC resided in the phytolith cavities. © 2013 Springer Science+Business Media Dordrecht.
Improved identification of sulfidic soil materials by a modified incubation method
- Authors: Sullivan, Leigh , Ward, Nicholas , Bush, Richard , Burton, Edward
- Date: 2009
- Type: Text , Journal article
- Relation: Geoderma Vol. 149, no. 1-2 (2009), p. 33-38
- Full Text: false
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- Description: This study examines the acidification behaviour and rate of sulfidic-sulfur oxidation in the incubation method that is currently used in soil taxonomies to identify sulfidic materials, for some clayey textured soil materials. 'Sulfidic' in these taxonomies identifies that a soil material is capable of becoming extremely acidic (i.e. pH < 4) as a result of oxidation of sulfide minerals contained in that soil material. As well as examining incubation slabs of acid sulfate soil materials with the standard 10 mm thickness, the utility of thinner (i.e. 2 mm thick) incubation slabs of these soil materials for identification of sulfidic soil materials was also examined. The clayey soil materials in the 2 mm thick slabs exhibited more rapid sulfidic-sulfur oxidation and acidification and resulted in fewer false-negative sulfidic soil material identifications than did the use of 10 mm thick slabs. However, the rates of sulfidic-sulfur oxidation and sulfide-derived acidification within the slabs (whether 2 mm or 10 mm thick) were not always rapid enough during incubation for the full expression of acidification to be evident within the maximum incubation duration of 8 weeks required by soil classification taxonomies. The results indicate the incubation method for determination of the sulfidic nature of soil materials for soil classification purposes could be improved to reduce the risk of false-negative identification by: i. allowing the use of 2 mm thick slabs, and ii. changing the maximum duration of incubation from 8 weeks to until a stable pH is reached after at least 8 weeks of incubation. © 2008.
Schwertmannite in soil materials : Limits of detection of acidified ammonium oxalate method and differential X-ray diffraction
- Authors: Vithana, Chamindra , Sullivan, Leigh , Bush, Richard , Burton, Edward
- Date: 2015
- Type: Text , Journal article
- Relation: Geoderma Vol. 249-250, no. (2015), p. 51-60
- Full Text: false
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- Description: Schwertmannite is a secondary iron mineral, found in acid mine drainage (AMD) and acid sulfate soils (ASS), that generates acidity when it transforms to stable mineral phases. Acidity liberated during schwertmannite transformation can seriously diminish water quality and soil health. Acidified ammonium oxalate (AAO) extraction in the dark coupled with differential X-ray diffraction (DXRD) analysis is routinely used to identify and to quantify poorly crystalline iron oxide phases such as schwertmannite in AMD environments. However, management of ASS environments is largely impacted due to lack of reliable methods to identify/quantify schwertmannite in soil materials. Our study aimed to evaluate the 15. min AAO extraction method to identify/quantify schwertmannite in soil materials. We extracted soil samples spiked with synthetic and natural schwertmannite (termed as natural organic rich schwertmannitic material) with acidified ammonium oxalate (AAO) for 15. min. We also examined soil samples spiked with schwertmannite through the DXRD analysis under ideal conditions assuming that only schwertmannite would dissolve during the extraction. Our data show that synthetic schwertmannite dissolved partially during the 15. min AAO extraction and as a result the recovered Fe content from schwertmannite-spiked soils was underestimated by ~. 20%. The data also show that soil materials could also influence the recovery of schwertmannite. Fe/S molar ratios of schwertmannite spiked at higher rates (2% and 5%) were closer to the expected ratios. In addition to schwertmannite, goethite and other unidentified minerals in natural organic rich schwertmannitic material also dissolved during the 15. min extraction time. The DXRD analysis data show that schwertmannite in soil materials at contents >. 5% may be identifiable through this approach. Our findings highlight that both the 15. min AAO extraction procedure and the DXRD analysis have limited applicability towards detecting schwertmannite accurately in soil materials. © 2015 Elsevier B.V.
Stability of schwertmannite and jarosite in an acidic landscape : Prolonged field incubation
- Authors: Vithana, Chamindra , Sullivan, Leigh , Burton, Edward , Bush, Richard
- Date: 2015
- Type: Text , Journal article
- Relation: Geoderma Vol. 239, no. (2015), p. 47-57
- Full Text: false
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- Description: Schwertmannite and jarosite are two of the main secondary iron(III) minerals commonly found in acidic, iron and sulfate-rich environments such as acid mine drainage and coastal acid sulfate soils (CASS). Both minerals exert major influence on the water and soil quality in these environments. While there are many studies conducted on the stability of these two minerals under controlled laboratory conditions, the behaviour of schwertmannite and jarosite under field conditions and the factors influencing their behaviour have not been investigated directly. In the present study, we examined the net transformation of introduced schwertmannite and jarosite samples incubated in a typical acidic CASS environment. Pure (synthetic) schwertmannite and jarosite samples were exposed to two main chemical regimes: 1) aerobic-acidic water column and 2) anaerobic-neutral sediment in a CASS environment. Changes in mineralogy, micromorphology, and composition of schwertmannite and jarosite samples were monitored over a period of 12months. Schwertmannite suspended in the water column and buried in sediments transformed to goethite by the end of 12months but more quickly in anoxic, reducing sediments. However, schwertmannite incubated in the acidic water column transformed at a much faster rate than those reported for acidic and aerobic conditions in the laboratory. Jarosite incubated in both the water column and sediments was also transformed to goethite but at a much slower rate than schwertmannite. Dissimilatory microbial reduction and Fe2+-catalysed transformation likely played a major role in accelerating the transformation of both minerals to goethite in sediments. The transformation of both minerals in the water column was sensitive to the hydrological conditions and fluctuations in the water column in relation to antecedent rainfall. In comparison, the sediment's geochemistry was relatively stable and consequently the rate of transformation and dissolution of both schwertmannite and jarosite in this environment was not appreciably affected by variable hydrology. © 2014 Elsevier B.V.
Spatial and temporal changes in estuarine water quality during a post-flood hypoxic event
- Authors: Wong, Vanessa , Johnston, Scott , Bush, Richard , Sullivan, Leigh , Clay, Christina , Burton, Edward , Slavich, Peter
- Date: 2010
- Type: Text , Journal article
- Relation: Estuarine, Coastal and Shelf Science Vol. 87, no. 1 (2010), p. 73-82
- Full Text: false
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- Description: A major fish kill occurred in the Richmond River estuary in January 2008 due to oxygen depletion following extensive overbank flooding. This paper examines spatial and temporal changes in the chemistry of main channel waters, thereby identifying the primary sources of deoxygenating water. Over 40 km of the mid- to lower estuary main channel was deoxygenated within seven days of the flood peak. Hypoxia was confined to downstream of the confluences with mid-estuary backswamp basins and occurred during the later phase of the flood recession. Water chemistry at key locations in the estuary indicated elevated concentrations of redox sensitive species associated with acid sulfate soils (ASS) during the hypoxic period. Peak concentrations of Fe
Seawater causes rapid trace metal mobilisation in coastal lowland acid sulfate soils : Implications of sea level rise for water quality
- Authors: Wong, Vanessa , Johnston, Scott , Burton, Edward , Bush, Richard , Sullivan, Leigh , Slavich, Peter
- Date: 2010
- Type: Text , Journal article
- Relation: Geoderma Vol. 160, no. 2 (2010), p. 252-263
- Full Text: false
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- Description: Coastal floodplains are highly vulnerable to inundation with saline water and the likelihood of inundation will increase with sea level rise. Sediment samples from floodplains containing coastal lowland acid sulfate soils (CLASS) in eastern Australia were subjected to increasing seawater concentration to examine the probable effects of sea level rise on acidity and metal desorption. Ten soils were mixed with synthetic seawater concentrations varying from 0% to 100% at a solid:solution ratio of 1:10 for 4h. There was a slight decrease in pH (≈0.5 units) with increasing seawater concentration following treatment, yet, calculated acidity increased significantly. In most soil treatments, Al was the dominant component of the calculated acidity pool. Al dominated the exchange complex in the CLASS and, correspondingly, was the major metal ion desorbed. In general, concentrations of soluble and exchangeable Al, Fe2+, Ni, Mn and Zn in all soil extracts increased with increasing salinity. Increasing trace metal concentrations with increasing seawater concentration is attributed to the combined effects of exchange processes and acidity. The increasing ionic strength of the seawater treatments displaces trace metals and protons adsorbed on sediments, causing an initial decrease in pH. Hydrolysis of desorbed acidic metal cations can further contribute to acidity and increase mobilisation of trace metals. These findings imply that saline inundation of CLASS environments, even by relatively brackish water may cause rapid, shorter-term water quality changes and a pulse release of acidity due to desorption of acidic metal cations. © 2010 Elsevier B.V.
Abundant stocks and mobilization of elements in boreal acid sulfate soils
- Authors: Yli-Halla, Markku , Virtanen, Seija , Mäkelä, Minna , Simojoki, Asko , Hirvi, Mirva , Innanen, Saila , Mäkelä, Jaakko , Sullivan, Leigh
- Date: 2017
- Type: Text , Journal article
- Relation: Geoderma Vol. 308, no. (2017), p. 333-340
- Full Text: false
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- Description: Large amounts of sulfate and divalent iron (Fe) are released into the pore water of acid sulfate (AS) soils upon oxidation of sulfidic materials. The simultaneously produced acidity dissolves metals from the soil matrix. Reduced horizons of AS soils commonly have a large mineral nitrogen (N) stock in the form of NH4 +-N, which is a potential source of N leaching and gaseous emissions. This study was carried out at three AS soil sites in Finland. Cation composition of pore water was monitored in a monolithic lysimeter experiment. Timothy samples grown in an AS soil were analysed for mineral elements and the soil was investigated for zinc (Zn) distribution in different chemical species at four depths down to 85 cm. The composition of pipestems formed in previous root channels was investigated by SEM, X-ray EDX and XRD. Emissions of CO2 and N2O were measured in an AS field which had a peaty topsoil. Monitoring by closed chambers was carried out at three sites differing in the depth of peat layer (15, 30 and 60 cm). In the sulfuric horizon, large amounts of calcium and magnesium were mobilized. Reflooding stopped the mobilization of those elements but resulted in abundant dissolution of Fe, which became the dominant cation in the pore water. Timothy growing in an AS soil showed only small deviations from the average composition measured in Finland with the exception of Zn that was at the deficiency level. As Zn in the root zone had been dissolved and subsequently leached, it was recovered in easily soluble forms in the subsoil. Pipestem composition indicated accumulation of Fe and formation of a new solid phase probably mostly in the form of schwertmannite even though jarosite was also detected. The annual CO2 emissions from the peaty AS soil were about 6000 kg C ha− 1 but the N2O emissions were relatively small, with a magnitude more typical of mineral rather than organic soils. Thus, large N stock of an AS soil do not necessarily contribute to abundant gaseous N emissions. © 2017 Elsevier B.V.