Advection of NH&amp;lt;sub&amp;gt;3&amp;lt;/sub&amp;gt; over a pasture field and its effect on gradient flux measurements

Loubet, Benjamin; Milford, C.; Hensen, A.; Daemmgen, U.; Erisman, J. W.; Cellier, Pierre; Sutton, Mark A.

doi:10.5194/bg-6-1295-2009

Cited by 39 publications

(37 citation statements)

References 61 publications

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“…For example, the estimation of DFC flux bias was based on an empirical model, and therefore the results are subject to the limitation of the regression models. Application of MM techniques relies on the assumption of a non-divergent vertical flux (Loubet et al, 2009). However, the vertical flux measured at a height may differ from the actual flux at the surface, as a consequence of either horizontal gradients (advection) or changes in storage (changes in concentration with time).…”

Section: Discussionmentioning

confidence: 99%

Mercury vapor air–surface exchange measured by collocated micrometeorological and enclosure methods – Part II: Bias and uncertainty analysis

et al. 2015

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Abstract. Dynamic flux chambers (DFCs) and micrometeorological (MM) methods are extensively deployed for gauging air-surface Hg 0 gas exchange. However, a systematic evaluation of the precision of the contemporary Hg 0 flux quantification methods is not available. In this study, the uncertainty in Hg 0 flux measured by the relaxed eddy accumulation (REA) method, the aerodynamic gradient method (AGM), the modified Bowen ratio (MBR) method, as well as DFC of traditional (TDFC) and novel (NDFC) designs, are assessed using a robust data set from two field intercomparison campaigns.The absolute precision in Hg 0 concentration difference ( C) measurements is estimated at 0.064 ng m −3 for the gradient-based MBR and AGM systems. For the REA system, the parameter is Hg 0 concentration (C) dependent at 0.069 + 0.022C. During the campaigns, 57 and 62 % of the individual vertical gradient measurements are found to be significantly different from 0, while for the REA technique, the percentage of significant observations is lower. For the chambers, non-significant fluxes are confined to a few nighttime periods with varying ambient Hg 0 concentrations. Relative bias for DFC-derived fluxes is estimated to be ∼ ±10, and ∼ 85 % of the flux bias is within ±2 ng m −2 h −1 in absolute terms. The DFC flux bias follows a diurnal cycle, which is largely affected by the forced temperature and irradiation bias in the chambers. Due to contrasting prevailing micrometeorological conditions, the relative uncertainty (median) in turbulent exchange parameters differs by nearly a factor of 2 between the campaigns, while that in C measurement is fairly consistent. The estimated flux uncertainties for the triad of MM techniques are 16-27, 12-23 and 19-31 % (interquartile range) for the AGM, MBR and REA methods, respectively. This study indicates that flux-gradient-based techniques (MBR and AGM) are preferable to REA in quantifying Hg 0 flux over ecosystems with low vegetation height. A limitation of all Hg 0 flux measurement systems investigated is their inability to obtain synchronous samples for the calculation of C. This reduces the precision of flux quantification, particularly in the MM systems under non-stationarity of ambient Hg 0 concentration. For future applications, it is recommended to accomplish C derivation from simultaneous collected samples.

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Section: Discussionmentioning

confidence: 99%

Mercury vapor air–surface exchange measured by collocated micrometeorological and enclosure methods – Part II: Bias and uncertainty analysis

et al. 2015

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“…The application of slurry creates a non-stationary setting where areas of high slurry emissions are surrounded by plots with very small background NH 3 fluxes close to zero. This evokes vertical flux divergence influencing the flux measured at a specific height (Fowler and Duyzer, 1989;Loubet et al, 2009). In order to deduce surface emissions from the EC measurements the flux divergence has to be considered.…”

Section: Field Experimentsmentioning

confidence: 99%

Determination of field scale ammonia emissions for common slurry spreading practice with two independent methods

et al. 2011

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Abstract.At a cropland and a grassland site field scale ammonia (NH 3 ) emissions from slurry application were determined simultaneously by two approaches based on (i) eddy covariance (EC) flux measurements using high temperature Chemical Ionisation Mass Spectrometry (HT-CIMS) and on (ii) backward Lagrangian Stochastic (bLS) dispersion modelling using concentration measurements by three optical open path Fourier Transform Infrared (FTIR) systems. Slurry was spread on the fields in sequential tracks over a period of one to two hours. In order to calculate field emissions, measured EC/HT-CIMS fluxes were combined with flux footprint analysis of individual slurry spreading tracks to parameterise the NH 3 volatilisation with a bi-exponential time dependence. Accordingly, track-resolved concentration footprints for the FTIR measurements were calculated using bLS. A consistency test with concentrations measured by impingers showed very low systematic deviations for the EC/HT-CIMS results (<8 %) but larger deviations for the bLS/FTIR results. For both slurry application events, the period during fertilisation and the subsequent two hours contributed by more than 80 % to the total field emissions. Averaged over the two measurement methods, the cumulated emissions of the first day amounted to 17 ± 3 % loss of applied total ammoniacal nitrogen over the cropland and 16 ± 3 % over the grassland field.

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“…At the global scale emissions of NH x and of nitrogen oxides (NO x ) are comparable, although large uncertainties exist on NH x emissions (Bouwman et al, 1997;Dentener and Crutzen, 1994). Moreover, NH x deposition, along with other reactive nitrogen deposition (NO x , HNO 3 ), leads to eutrophication and induces changes in the biodiversity of terrestrial and aquatic ecosystems (Fangmeier et al, 1994;Krupa, 2003), and may also lead to increased greenhouse gases emissions (such as nitrous oxide N 2 O; Melillo et al, 1989) and to reduced methane oxidation by soils (CH 4 ;MacDonald et al, 1997). There is also a debate as to the extent to which atmospheric nitrogen inputs to forests increase carbon uptake (De Schrijver et al, 2008;de Vries et al, 2008;Magnani et al, 2007).…”

Section: Introductionmentioning

confidence: 99%

Investigating the stomatal, cuticular and soil ammonia fluxes over a growing tritical crop under high acidic loads

et al. 2012

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Abstract. Ammonia concentration and fluxes were measured above a growing triticale field for two months during May and June 2010 at the NitroEurope crop site in Grignon (Fr-Gri) near Paris, France. The measurement campaign started 15 days following a 40 kg N ha −1 application of an ammonium nitrate solution. A new mini-wedd (Wet Effluent Denuder) flow injection analyser with three channels (ROSAA, RObust and Sensitive Ammonia Analyser) was used to measure NH 3 fluxes using the aerodynamic gradient method. The measured ammonia concentrations varied from 0.01 to 39 µg NH 3 m −3 and were largely influenced by advection from the nearby farm. The ammonia fluxes ranged from -560 to 220 ng NH 3 m −2 s −1 and averaged -29 ng NH 3 m −2 s −1 . During some periods the large deposition fluxes could only be explained by a very small surface resistance, which may be partly due to the high concentrations of certain acid gases (HNO 3 and SO 2 ) observed in this suburban area. Ammonia emissions were also observed. The canopy compensation point C c was around 1.5 µg NH 3 m −3 on average. The canopy emission potential c (C c normalised for the temperature response of the Henry equilibrium) decreased over the course of the measurement campaign from c = 2200 to c = 450, the latter value being close to the median stomatal emission potential ( s ) and lower than the median ground emission potential ( g ) for managed ecosystems reported in the literature. The temporal dynamics of the measured NH 3 flux compared well with the Surfatm-NH 3 model using fitted parameters. The subjectivity of the model fitting is discussed based on a sensitivity analysis.

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Advection of NH<sub>3</sub> over a pasture field and its effect on gradient flux measurements

Cited by 39 publications

References 61 publications

Mercury vapor air–surface exchange measured by collocated micrometeorological and enclosure methods – Part II: Bias and uncertainty analysis

Mercury vapor air–surface exchange measured by collocated micrometeorological and enclosure methods – Part II: Bias and uncertainty analysis

Determination of field scale ammonia emissions for common slurry spreading practice with two independent methods

Investigating the stomatal, cuticular and soil ammonia fluxes over a growing tritical crop under high acidic loads

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