scholarly journals Greenhouse gas fluxes in a drained peatland forest during spring frost-thaw event

2009 ◽  
Vol 6 (3) ◽  
pp. 6111-6145 ◽  
Author(s):  
M. K. Pihlatie ◽  
R. Kiese ◽  
N. Brüggemann ◽  
K. Butterbach-Bahl ◽  
A.-J. Kieloaho ◽  
...  
Keyword(s):  
Peat Soil ◽  
Flux Measurement ◽  
Good Alternative ◽  
N2o Emission ◽  
Soil Parameters ◽  
N2o Emissions ◽  
N2o Production ◽  
Spring Frost ◽  
Carbon Dioxide Co2 ◽  
Ghg Fluxes

Abstract. Fluxes of greenhouse gases (GHG) carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) were measured during a two month campaign at a drained peatland forest in Finland by the eddy covariance (EC) technique (CO2 and N2O), and automatic and manual chambers (CO2, CH4 and N2O). In addition, GHG concentrations and soil parameters (mineral nitrogen, temperature, moisture content) in the peat profile were measured. The aim of the measurement campaign was to quantify the GHG fluxes before, during and after thawing of the peat soil, a time period with potentially high GHG fluxes, and to compare different flux measurement methods. The forest was a net CO2 sink during the two months and the fluxes of CO2 dominated the GHG exchange. The peat soil was a small sink of atmospheric CH4 but a small source of N2O. Both CH4 oxidation and N2O production took place in the top-soil whereas CH4 was produced in the deeper layers of the peat. During the thawing of the peat distinct peaks in CO2 and N2O emissions were observed. The CO2 peak followed tightly the increase in soil temperature, whereas the N2O peak occurred with an approx. one week delay after soil thawing. CH4 fluxes did not respond to the thawing of the peat soil. The CO2 and N2O emission peaks were not captured by the manual chambers and hence we conclude that automatic chamber measurements or EC are necessary to quantify fluxes during peak emission periods. Sub-canopy EC measurements and chamber-based fluxes of CO2 and N2O were comparable, although the fluxes of N2O measured by EC were close to the detection limit of the EC system. We conclude that if fluxes are high enough, i.e. greater than 5–10 μg N m−2 h−1, the EC method is a good alternative to measure N2O and CO2 fluxes at ecosystem scale, thereby minimizing problems with chamber enclosures and spatial representativeness of the measurements.

scholarly journals Greenhouse gas fluxes in a drained peatland forest during spring frost-thaw event

2010 ◽  
Vol 7 (5) ◽  
pp. 1715-1727 ◽  
Author(s):  
M. K. Pihlatie ◽  
R. Kiese ◽  
N. Brüggemann ◽  
K. Butterbach-Bahl ◽  
A.-J. Kieloaho ◽  
...  
Keyword(s):  
Peat Soil ◽  
Soil Parameters ◽  
High Time Resolution ◽  
N2o Emissions ◽  
Litter Layer ◽  
Freezing And Thawing ◽  
N2o Production ◽  
Spring Frost ◽  
Top Soil ◽  
Ghg Fluxes

Abstract. Fluxes of greenhouse gases (GHG) carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) were measured during a two month campaign at a drained peatland forest in Finland by the eddy covariance (EC) technique (CO2 and N2O), and automatic and manual chambers (CO2, CH4 and N2O). In addition, GHG concentrations and soil parameters (mineral nitrogen, temperature, moisture content) in the peat profile were measured. The aim of the measurement campaign was to quantify the GHG fluxes during freezing and thawing of the top-soil, a time period with potentially high GHG fluxes, and to compare different flux measurement methods. The forest was a net CO2 sink during the two months and the fluxes of CO2 dominated the GHG exchange. The peat soil was a small sink of atmospheric CH4 and a small source of N2O. Both CH4 oxidation and N2O production took place in the top-soil whereas CH4 was produced in the deeper layers of the peat, which were unfrozen throughout the measurement period. During the frost-thaw events of the litter layer distinct peaks in CO2 and N2O emissions were observed. The CO2 peak followed tightly the increase in soil temperature, whereas the N2O peak occurred with a delay after the thawing of the litter layer. CH4 fluxes did not respond to the thawing of the peat soil. The CO2 and N2O emission peaks were not captured by the manual chambers and hence we conclude that high time-resolution measurements with automatic chambers or EC are necessary to quantify fluxes during peak emission periods. Sub-canopy EC measurements and chamber-based fluxes of CO2 and N2O were comparable, although the fluxes of N2O measured by EC were close to the detection limit of the system. We conclude that if fluxes are high enough, i.e. greater than 5–10 μg N m−2 h−1, the EC method is a good alternative to measure N2O and CO2 fluxes at ecosystem scale, thereby minimizing problems with chamber enclosures and spatial representativeness of the measurements.

scholarly journals Nitrous Oxide Emissions in Pineapple Cultivation on a Tropical Peat Soil

2021 ◽  
Vol 13 (9) ◽  
pp. 4928
Author(s):  
Alicia Vanessa Jeffary ◽  
Osumanu Haruna Ahmed ◽  
Roland Kueh Jui Heng ◽  
Liza Nuriati Lim Kim Choo ◽  
Latifah Omar ◽  
...  
Keyword(s):  
Nitrous Oxide ◽  
Soil Temperature ◽  
Peat Soil ◽  
Farming Systems ◽  
N2o Emission ◽  
Nitrous Oxide Emissions ◽  
Natural State ◽  
N2o Emissions ◽  
Wet Season ◽  
Peat Soils

Farming systems on peat soils are novel, considering the complexities of these organic soil. Since peat soils effectively capture greenhouse gases in their natural state, cultivating peat soils with annual or perennial crops such as pineapples necessitates the monitoring of nitrous oxide (N2O) emissions, especially from cultivated peat lands, due to a lack of data on N2O emissions. An on-farm experiment was carried out to determine the movement of N2O in pineapple production on peat soil. Additionally, the experiment was carried out to determine if the peat soil temperature and the N2O emissions were related. The chamber method was used to capture the N2O fluxes daily (for dry and wet seasons) after which gas chromatography was used to determine N2O followed by expressing the emission of this gas in t ha−1 yr−1. The movement of N2O horizontally (832 t N2O ha−1 yr−1) during the dry period was higher than in the wet period (599 t N2O ha−1 yr−1) because of C and N substrate in the peat soil, in addition to the fertilizer used in fertilizing the pineapple plants. The vertical movement of N2O (44 t N2O ha−1 yr−1) was higher in the dry season relative to N2O emission (38 t N2O ha−1 yr−1) during the wet season because of nitrification and denitrification of N fertilizer. The peat soil temperature did not affect the direction (horizontal and vertical) of the N2O emission, suggesting that these factors are not related. Therefore, it can be concluded that N2O movement in peat soils under pineapple cultivation on peat lands occurs horizontally and vertically, regardless of season, and there is a need to ensure minimum tilling of the cultivated peat soils to prevent them from being an N2O source instead of an N2O sink.

scholarly journals Pineapple Residue Ash Reduces Carbon Dioxide and Nitrous Oxide Emissions in Pineapple Cultivation on Tropical Peat Soils at Saratok, Malaysia

2021 ◽  
Vol 13 (3) ◽  
pp. 1014
Author(s):  
Liza Nuriati Lim Kim Choo ◽  
Osumanu Haruna Ahmed ◽  
Nik Muhamad Nik Majid ◽  
Zakry Fitri Abd Aziz
Keyword(s):  
Carbon Dioxide ◽  
Nitrous Oxide ◽  
Peat Soil ◽  
Nitrous Oxide Emissions ◽  
N2o Emissions ◽  
Peat Soils ◽  
Closed Chamber ◽  
Npk Fertilizers ◽  
Npk Fertilizer ◽  
Carbon Dioxide Co2

Burning pineapple residues on peat soils before pineapple replanting raises concerns on hazards of peat fires. A study was conducted to determine whether ash produced from pineapple residues could be used to minimize carbon dioxide (CO2) and nitrous oxide (N2O) emissions in cultivated tropical peatlands. The effects of pineapple residue ash fertilization on CO2 and N2O emissions from a peat soil grown with pineapple were determined using closed chamber method with the following treatments: (i) 25, 50, 70, and 100% of the suggested rate of pineapple residue ash + NPK fertilizer, (ii) NPK fertilizer, and (iii) peat soil only. Soils treated with pineapple residue ash (25%) decreased CO2 and N2O emissions relative to soils without ash due to adsorption of organic compounds, ammonium, and nitrate ions onto the charged surface of ash through hydrogen bonding. The ability of the ash to maintain higher soil pH during pineapple growth primarily contributed to low CO2 and N2O emissions. Co-application of pineapple residue ash and compound NPK fertilizer also improves soil ammonium and nitrate availability, and fruit quality of pineapples. Compound NPK fertilizers can be amended with pineapple residue ash to minimize CO2 and N2O emissions without reducing peat soil and pineapple productivity.

scholarly journals Greenhouse gas flux measurements in a forestry-drained peatland indicate a large carbon sink

2011 ◽  
Vol 8 (11) ◽  
pp. 3203-3218 ◽  
Author(s):  
A. Lohila ◽  
K. Minkkinen ◽  
M. Aurela ◽  
J.-P. Tuovinen ◽  
T. Penttilä ◽  
...  
Keyword(s):  
Carbon Sink ◽  
Accumulation Rate ◽  
Peat Soil ◽  
Net Ecosystem Exchange ◽  
Flux Measurement ◽  
Co2 Exchange ◽  
Co2 Uptake ◽  
Flux Measurements ◽  
Ch4 And N2o ◽  
Carbon Dioxide Co2

Abstract. Drainage for forestry purposes increases the depth of the oxic peat layer and leads to increased growth of shrubs and trees. Concurrently, the production and uptake of the greenhouse gases carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) change: due to the accelerated decomposition of peat in the presence of oxygen, drained peatlands are generally considered to lose peat carbon (C). We measured CO2 exchange with the eddy covariance (EC) method above a drained nutrient-poor peatland forest in southern Finland for 16 months in 2004–2005. The site, classified as a dwarf-shrub pine bog, had been ditched about 35 years earlier. CH4 and N2O fluxes were measured at 2–5-week intervals with the chamber technique. Drainage had resulted in a relatively little change in the water table level, being on average 40 cm below the ground in 2005. The annual net ecosystem exchange was −870 ± 100 g CO2 m−2 yr−1 in the calendar year 2005, indicating net CO2 uptake from the atmosphere. The site was a small sink of CH4 (−0.12 g CH4 m−2 yr−1) and a small source of N2O (0.10 g N2O m−2 yr−1). Photosynthesis was detected throughout the year when the air temperature exceeded −3 °C. As the annual accumulation of C in the above and below ground tree biomass (175 ± 35 g C m−2) was significantly lower than the accumulation observed by the flux measurement (240 ± 30 g C m−2), about 65 g C m−2 yr−1 was likely to have accumulated as organic matter into the peat soil. This is a higher average accumulation rate than previously reported for natural northern peatlands, and the first time C accumulation has been shown by EC measurements to occur in a forestry-drained peatland. Our results suggest that forestry-drainage may significantly increase the CO2 uptake rate of nutrient-poor peatland ecosystems.

Nitrous oxide emission from Australian agricultural lands and mitigation options: a review

Soil Research ◽  
2003 ◽  
Vol 41 (2) ◽  
pp. 165 ◽  
Author(s):  
Ram C. Dalal ◽  
Weijin Wang ◽  
G. Philip Robertson ◽  
William J. Parton
Keyword(s):  
Nitrous Oxide ◽  
Global Warming ◽  
N2o Emission ◽  
Nitrous Oxide Emissions ◽  
N2o Emissions ◽  
Tropical Savannas ◽  
Agricultural Lands ◽  
Mineral N ◽  
N2o Production ◽  
Mitigation Options

Increases in the concentrations of greenhouse gases, carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and halocarbons in the atmosphere due to human activities are associated with global climate change. The concentration of N2O has increased by 16% since 1750. Although atmospheric concentration of N2O is much smaller (314 ppb in 1998) than of CO2 (365 ppm), its global warming potential (cumulative radiative forcing) is 296 times that of the latter in a 100-year time horizon. Currently, it contributes about 6% of the overall global warming effect but its contribution from the agricultural sector is about 16%. Of that, almost 80% of N2O is emitted from Australian agricultural lands, originating from N fertilisers (32%), soil disturbance (38%), and animal waste (30%). Nitrous oxide is primarily produced in soil by the activities of microorganisms during nitrification, and denitrification processes. The ratio of N2O to N2 production depends on oxygen supply or water-filled pore space, decomposable organic carbon, N substrate supply, temperature, and pH and salinity. N2O production from soil is sporadic both in time and space, and therefore, it is a challenge to scale up the measurements of N2O emission from a given location and time to regional and national levels.Estimates of N2O emissions from various agricultural systems vary widely. For example, in flooded rice in the Riverina Plains, N2O emissions ranged from 0.02% to 1.4% of fertiliser N applied, whereas in irrigated sugarcane crops, 15.4% of fertiliser was lost over a 4-day period. Nitrous oxide emissions from fertilised dairy pasture soils in Victoria range from 6 to 11 kg N2O-N/ha, whereas in arable cereal cropping, N2O emissions range from <0.01% to 9.9% of N fertiliser applications. Nitrous oxide emissions from soil nitrite and nitrates resulting from residual fertiliser and legumes are rarely studied but probably exceed those from fertilisers, due to frequent wetting and drying cycles over a longer period and larger area. In ley cropping systems, significant N2O losses could occur, from the accumulation of mainly nitrate-N, following mineralisation of organic N from legume-based pastures. Extensive grazed pastures and rangelands contribute annually about 0.2 kg N/ha as N2O (93 kg/ha per year CO2-equivalent). Tropical savannas probably contribute an order of magnitude more, including that from frequent fires. Unfertilised forestry systems may emit less but the fertilised plantations emit more N2O than the extensive grazed pastures. However, currently there are limited data to quantify N2O losses in systems under ley cropping, tropical savannas, and forestry in Australia. Overall, there is a need to examine the emission factors used in estimating national N2O emissions; for example, 1.25% of fertiliser or animal-excreted N appearing as N2O (IPCC 1996). The primary consideration for mitigating N2O emissions from agricultural lands is to match the supply of mineral N (from fertiliser applications, legume-fixed N, organic matter, or manures) to its spatial and temporal needs by crops/pastures/trees. Thus, when appropriate, mineral N supply should be regulated through slow-release (urease and/or nitrification inhibitors, physical coatings, or high C/N ratio materials) or split fertiliser application. Also, N use could be maximised by balancing other nutrient supplies to plants. Moreover, non-legume cover crops could be used to take up residual mineral N following N-fertilised main crops or mineral N accumulated following legume leys. For manure management, the most effective practice is the early application and immediate incorporation of manure into soil to reduce direct N2O emissions as well as secondary emissions from deposition of ammonia volatilised from manure and urine.Current models such as DNDC and DAYCENT can be used to simulate N2O production from soil after parameterisation with the local data, and appropriate modification and verification against the measured N2O emissions under different management practices.In summary, improved estimates of N2O emission from agricultural lands and mitigation options can be achieved by a directed national research program that is of considerable duration, covers sampling season and climate, and combines different techniques (chamber and micrometeorological) using high precision analytical instruments and simulation modelling, under a range of strategic activities in the agriculture sector.

scholarly journals Impacts of Nitrogen Addition on Nitrous Oxide Emission: Model-Data Comparison

2018 ◽  
Author(s):  
Yujin Zhang ◽  
Minna Ma ◽  
Huajun Fang ◽  
Dahe Qin ◽  
Shulan Cheng ◽  
...  
Keyword(s):  
Nitrous Oxide ◽  
Global Climate ◽  
Pore Space ◽  
Terrestrial Ecosystem ◽  
N2o Emission ◽  
N Deposition ◽  
N2o Emissions ◽  
Emission Model ◽  
N Addition ◽  
N2o Production

Abstract. The contributions of long-lived nitrous oxide (N2O) to the global climate and environment have received increasing attention. Especially, atmospheric nitrogen (N) deposition has substantially increased in recent decades due to extensive use of fossil fuels in industry, which strongly stimulates the N2O emissions of the terrestrial ecosystem. Several models have been developed to simulate N2O emission, but there are still large differences in their N2O emission simulations and responses to atmospheric deposition over global or regional scales. Using observations from N addition experiments in a subtropical forest, this study compared six widely-used N2O models (i.e. DayCENT, DLEM, DNDC, DyN, NOE, and NGAS) to investigate their performances for reproducing N2O emission, and especially the impacts of two types of N additions (i.e. ammonium and nitrate: NH4+ and NO3−, respectively) and two levels (low and high) on N2O emission. In general, the six models reproduced the seasonal variations of N2O emission, but failed to reproduce relatively larger N2O emissions due to NH4+ compared to NO3− additions. Few models indicated larger N2O emission under high N addition levels for both NH4+ and NO3−. Moreover, there were substantial model differences for simulating the ratios of N2O emission from nitrification and denitrification processes due to disagreements in model structures and algorithms. This analysis highlights the need to improve representation of N2O production and diffusion, and the control of soil water-filled pore space on these processes in order to simulate the impacts of N deposition on N2O emission.

scholarly journals Alteration of nitrous oxide emissions from floodplain soils by aggregate size, litter accumulation and plant–soil interactions

2018 ◽  
Vol 15 (22) ◽  
pp. 7043-7057 ◽  
Author(s):  
Martin Ley ◽  
Moritz F. Lehmann ◽  
Pascal A. Niklaus ◽  
Jörg Luster
Keyword(s):  
Nitrous Oxide ◽  
Leaf Litter ◽  
Hot Spots ◽  
Aggregate Size ◽  
N2o Emission ◽  
N2o Emissions ◽  
N2o Production ◽  
Plant Soil ◽  
Floodplain Soils ◽  
Plant Soil Interactions

Abstract. Semi-terrestrial soils such as floodplain soils are considered potential hot spots of nitrous oxide (N2O) emissions. Microhabitats in the soil – such as within and outside of aggregates, in the detritusphere, and/or in the rhizosphere – are considered to promote and preserve specific redox conditions. Yet our understanding of the relative effects of such microhabitats and their interactions on N2O production and consumption in soils is still incomplete. Therefore, we assessed the effect of aggregate size, buried leaf litter, and plant–soil interactions on the occurrence of enhanced N2O emissions under simulated flooding/drying conditions in a mesocosm experiment. We used two model soils with equivalent structure and texture, comprising macroaggregates (4000–250 µm) or microaggregates (<250 µm) from a N-rich floodplain soil. These model soils were planted with basket willow (Salix viminalis L.), mixed with leaf litter or left unamended. After 48 h of flooding, a period of enhanced N2O emissions occurred in all treatments. The unamended model soils with macroaggregates emitted significantly more N2O during this period than those with microaggregates. Litter addition modulated the temporal pattern of the N2O emission, leading to short-term peaks of high N2O fluxes at the beginning of the period of enhanced N2O emission. The presence of S. viminalis strongly suppressed the N2O emission from the macroaggregate model soil, masking any aggregate-size effect. Integration of the flux data with data on soil bulk density, moisture, redox potential and soil solution composition suggest that macroaggregates provided more favourable conditions for spatially coupled nitrification–denitrification, which are particularly conducive to net N2O production. The local increase in organic carbon in the detritusphere appears to first stimulate N2O emissions; but ultimately, respiration of the surplus organic matter shifts the system towards redox conditions where N2O reduction to N2 dominates. Similarly, the low emission rates in the planted soils can be best explained by root exudation of low-molecular-weight organic substances supporting complete denitrification in the anoxic zones, but also by the inhibition of denitrification in the zone, where rhizosphere aeration takes place. Together, our experiments highlight the importance of microhabitat formation in regulating oxygen (O2) content and the completeness of denitrification in soils during drying after saturation. Moreover, they will help to better predict the conditions under which hot spots, and “hot moments”, of enhanced N2O emissions are most likely to occur in hydrologically dynamic soil systems like floodplain soils.

Determining nitrous oxide emissions from subsurface measurements in grazed pasture: A field trial of alternative technology

Soil Research ◽  
2005 ◽  
Vol 43 (6) ◽  
pp. 677 ◽  
Author(s):  
Z. Li ◽  
F. M. Kelliher
Keyword(s):  
N2o Emission ◽  
Gas Diffusion ◽  
Nitrous Oxide Emissions ◽  
Spatial And Temporal Variation ◽  
Measurement Technology ◽  
N2o Emissions ◽  
Emission Measurement ◽  
N2o Production ◽  
Grazed Pasture ◽  
Poorly Drained Soils

Beneath pasture grazed by farmed animals, the soil’s nitrogen (N), oxygen, and temperature regimes can be unevenly distributed in time and space. It is difficult to capture spatial and temporal variation of N2O using conventional emission measurement technology based on gas samples taken in chambers that briefly cover a small area of the soil’s surface. We report the results from field deployment of alternative, non-intrusive N2O emission measurement technology that uses subsurface measurements incorporating the soil processes controlling the net N2O production and gas diffusion rates. During 100 autumn and winter days after dairy cattle urine was applied (650 kg N/ha) to freely and poorly drained pastoral soils near Hamilton, New Zealand (37.8° S, 175.3° E), N2O emissions were determined. The measured values ranged from 0.024 to 1.55 and 0.048 to 3.33 mg N2O-N/m2.h for the freely and poorly drained soils, respectively. Over the 100 days, it was estimated that 0.4 and 1.3% of the applied N was directly emitted to the atmosphere as N2O from the freely and poorly drained soils, respectively.

scholarly journals Greenhouse gas emissions from membrane bioreactors: analysis of a two-year survey on different MBR configurations

2018 ◽  
Vol 78 (4) ◽  
pp. 896-903 ◽  
Author(s):  
Giorgio Mannina ◽  
Kartik Chandran ◽  
Marco Capodici ◽  
Alida Cosenza ◽  
Daniele Di Trapani ◽  
...  
Keyword(s):  
Retention Time ◽  
N2o Emission ◽  
Influential Factors ◽  
Membrane Bioreactors ◽  
N2o Emissions ◽  
Biological Phosphorus Removal ◽  
N2o Production ◽  
Operational Conditions ◽  
Key Factor ◽  
Nitrogen Ratio

Abstract This study aimed at evaluating the nitrous oxide (N2O) emissions from membrane bioreactors (MBRs) for wastewater treatment. The study investigated the N2O emissions considering multiple influential factors over a two-year period: (i) different MBR based process configurations; (ii) wastewater composition (municipal or industrial); (iii) operational conditions (i.e. sludge retention time, carbon-to-nitrogen ratio, C/N, hydraulic retention time); (iv) membrane modules. Among the overall analysed configurations, the highest N2O emission occurred from the aerated reactors. The treatment of industrial wastewater, contaminated with salt and hydrocarbons, provided the highest N2O emission factor (EF): 16% of the influent nitrogen for the denitrification/nitrification-MBR plant. The lowest N2O emission (EF = 0.5% of the influent nitrogen) was obtained in the biological phosphorus removal-moving bed-MBR plant likely due to an improvement in biological performances exerted by the co-presence of both suspended and attached biomass. The influent C/N ratio has been identified as a key factor affecting the N2O production. Indeed, a decrease of the C/N ratio (from 10 to 2) promoted the increase of N2O emissions in both gaseous and dissolved phases, mainly related to a decreased efficiency of the denitrification processes.

scholarly journals Gas chromatography and photoacoustic spectroscopy for the assessment of soil greenhouse gases emissions

2013 ◽  
Vol 43 (2) ◽  
pp. 262-269 ◽  
Author(s):  
Rodrigo da Silveira Nicoloso ◽  
Cimélio Bayer ◽  
Genuir Luis Denega ◽  
Paulo Armando Victória de Oliveira ◽  
Martha Mayumi Higarashi ◽  
...  
Keyword(s):  
Gas Chromatography ◽  
Greenhouse Gases ◽  
Photoacoustic Spectroscopy ◽  
Cropping Systems ◽  
Agricultural Practices ◽  
N2o Emissions ◽  
N2o Fluxes ◽  
Carbon Dioxide Co2 ◽  
Ghg Fluxes

Assessments of soil carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) emissions are critical for determination of the agricultural practices' potential to mitigate global warming. This study evaluated the photoacoustic spectroscopy (PAS) for the assessment of soil greenhouse gases (GHG) fluxes in comparison to the standard gas chromatography (GC) method. Two long-term experiments with different tillage and cropping systems over a Paleudult were evaluated using static chambers. PAS measurements of CO2 and N2O concentrations showed good relationship and linearity (R2=0.98 and 0.94, respectively) with GC results. However, CH4 measurements were significantly affected by air sample moisture which interfered on CH4 detection by PAS. Overestimation of CO2 and N2O concentrations in air samples determined by PAS (14.6 and 18.7%, respectively) were also related to sampling moisture. CO2 and N2O fluxes showed good agreement between methods (R2=0.96 and 0.95, respectively), though PAS overestimated fluxes by 18.6 and 13.6% in relation to GC results, respectively. PAS showed good sensitivity and was able to detect CO2 and N2O fluxes as low as 332mg CO2 m-2 h-1 and 21µg N2O m-2 h-1. PAS analyzer should be detailed calibrated to reduce humidity interference on CO2, CH4 and N2O concentrations measurements avoiding overestimation or erroneous determination of soil GHG fluxes.

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