Atmospheric ammonia at a moorland site. I: The meteorological control of ambient ammonia concentrations and the influence of local sources

Fléchard, Chris; Fowler, D.

doi:10.1002/qj.49712454705

Cited by 61 publications

(18 citation statements)

References 40 publications

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“…Multiple regression equations (Eqs. 5, 6) were based on previous observations that background NH 3 is dependent on wind speed, temperature and relative humidity (Flechard and Fowler, 1998), but nonetheless error is introduced due to differences between the predicted C b and the actual C b . The mean absolute error (MAE) between the measured and predicted C b for Period 1 and 2 has been applied to offset to the predicted C b time series input into the model to determine the limits (upper and lower) of emission estimates caused by this uncertainty.…”

Section: Uncertainty In Background Concentrationmentioning

confidence: 99%

Ammonia emissions from a grazed field estimated by miniDOAS measurements and inverse dispersion modelling

et al. 2017

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Abstract. Ammonia (NH 3 ) fluxes were estimated from a field being grazed by dairy cattle during spring by applying a backward Lagrangian stochastic model (bLS) model combined with horizontal concentration gradients measured across the field. Continuous concentration measurements at field boundaries were made by open-path miniDOAS (differential optical absorption spectroscopy) instruments while the cattle were present and for 6 subsequent days. The deposition of emitted NH 3 to "clean" patches on the field was also simulated, allowing both "net" and "gross" emission estimates, where the dry deposition velocity (v d ) was predicted by a canopy resistance (R c ) model developed from local NH 3 flux and meteorological measurements. Estimated emissions peaked during grazing and decreased after the cattle had left the field, while control on emissions was observed from covariance with temperature, wind speed and humidity and wetness measurements made on the field, revealing a diurnal emission profile. Large concentration differences were observed between downwind receptors, due to spatially heterogeneous emission patterns. This was likely caused by uneven cattle distribution and a low grazing density, where "hotspots" of emissions would arise as the cattle grouped in certain areas, such as around the water trough. The spatial complexity was accounted for by separating the model source area into sub-sections and optimising individual source area coefficients to measured concentrations. The background concentration was the greatest source of uncertainty, and based on a sensitivity/uncertainty analysis the overall uncertainty associated with derived emission factors from this study is at least 30-40 %.Emission factors can be expressed as 6 ± 2 g NH 3 cow −1 day −1 , or 9 ± 3 % of excreted urine-N emitted as NH 3 , when deposition is not simulated and 7 ± 2 g NH 3 cow −1 day −1 , or 10 ± 3 % of excreted urine-N emitted as NH 3 , when deposition is included in the gross emission model. The results suggest that around 14 ± 4 % of emitted NH 3 was deposited to patches within the field that were not affected by urine or dung.

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Section: Uncertainty In Background Concentrationmentioning

confidence: 99%

Ammonia emissions from a grazed field estimated by miniDOAS measurements and inverse dispersion modelling

et al. 2017

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“…Large wind speeds and unstable conditions reduce R a and thus tend to increase emissions from the canopy (upward fluxes) as well as dry deposition (downward fluxes). However, large wind speeds also increase NH 3 dispersion and thus tend to reduce ambient NH 3 concentration levels close to point sources (Flechard and Fowler, 1998a), such that, although the exchange velocity is higher (higher turbulence, lower R a ), the dry deposition flux may not be greater (Flechard and Fowler, 1998b).…”

Section: Meteorological Controlsmentioning

confidence: 99%

Advances in understanding, models and parameterizations of biosphere-atmosphere ammonia exchange

et al. 2013

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Atmospheric ammonia (NH₃) dominates global emissions of total reactive nitrogen (N_r), while emissions from agricultural production systems contribute about two-thirds of global NH₃ emissions; the remaining third emanates from oceans, natural vegetation, humans, wild animals and biomass burning. On land, NH₃ emitted from the various sources eventually returns to the biosphere by dry deposition to sink areas, predominantly semi-natural vegetation, and by wet and dry deposition as ammonium (NH₄⁺) to all surfaces. However, the land/atmosphere exchange of gaseous NH₃ is in fact bi-directional over unfertilized as well as fertilized ecosystems, with periods and areas of emission and deposition alternating in time (diurnal, seasonal) and space (patchwork landscapes). The exchange is controlled by a range of environmental factors, including meteorology, surface layer turbulence, thermodynamics, air and surface heterogeneous-phase chemistry, canopy geometry, plant development stage, leaf age, organic matter decomposition, soil microbial turnover, and, in agricultural systems, by fertilizer application rate, fertilizer type, soil type, crop type, and agricultural management practices. We review the range of processes controlling NH₃ emission and uptake in the different parts of the soil-canopy-atmosphere continuum, with NH₃ emission potentials defined at the substrate and leaf levels by different [NH₄⁺] / [H⁺] ratios (Γ). Surface/atmosphere exchange models for NH₃ are necessary to compute the temporal and spatial patterns of emissions and deposition at the soil, plant, field, landscape, regional and global scales, in order to assess the multiple environmental impacts of airborne and deposited NH₃ and NH₄⁺. Models of soil/vegetation/atmosphere NH₃ exchange are reviewed from the substrate and leaf scales to the global scale. They range from simple steady-state, "big leaf" canopy resistance models, to dynamic, multi-layer, multi-process, multi-chemical species schemes. Their level of complexity depends on their purpose, the spatial scale at which they are applied, the current level of parameterization, and the availability of the input data they require. State-of-the-art solutions for determining the emission/sink Γ potentials through the soil/canopy system include coupled, interactive chemical transport models (CTM) and soil/ecosystem modelling at the regional scale. However, it remains a matter for debate to what extent realistic options for future regional and global models should be based on process-based mechanistic versus empirical and regression-type models. Further discussion is needed on the extent and timescale by which new approaches can be used, such as integration with ecosystem models and satellite observations

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“…The hollows are depressions up to 30 cm deep and are dominated by blankets of Sphagnum mosses, with various sedges, monocotyledons and other bryophytes also present; the hummocks can be up to 30 cm high, and although Sphagnum mosses are present, there is a larger density of vascular plants with the dominant species being Deschampsia flexuosa, Eriophorum vaginatum and Juncus effusus. Flechard and Fowler (1998) and Dinsmore (2008) have presented more detailed vegetation information for Auchencorth Moss.…”

Section: Study Areamentioning

confidence: 99%

The import and export of organic nitrogen species at a Scottish ombrotrophic peatland

et al. 2016

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Abstract. Dissolved organic nitrogen (DON) contributes significantly to the overall nitrogen budget, but is not routinely measured in precipitation or stream water. In order to investigate the contribution of DON to the deposition and export of N, precipitation, stream and soil water samples were collected from an ombrotrophic peatland and analysed for DON over a 2-year period. In wet-only deposition DON contributed up to 10 % of the total dissolved nitrogen (TDN) and was the most dominant fraction in soil water (99 %) and stream water (75 %). NH + 4 was the most dominate form of N in precipitation, with NO − 3 contributing the least to precipitation, soil water and stream water.Precipitation and stream DON were qualitatively analysed by a two-dimensional gas chromatograph coupled to a nitrogen chemiluminescence detector (GC×GC-NCD) after trapping onto C18 solid phase extraction (SPE) cartridges. Ten unique compounds were detected and five identified as pyrrole, benzonitrile, dodecylamine, N-nitrosodipropylamine and decylamine. Five compounds were present in both precipitation and stream samples: pyrrole, benzonitrile and three unidentified compounds. The SPE-extraction efficiency for DON was very low (11 %), but with improvements DON speciation could become a valuable tool to provide information on its sources and pathways and inform chemical transport models.

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Atmospheric ammonia at a moorland site. I: The meteorological control of ambient ammonia concentrations and the influence of local sources

Cited by 61 publications

References 40 publications

Ammonia emissions from a grazed field estimated by miniDOAS measurements and inverse dispersion modelling

Ammonia emissions from a grazed field estimated by miniDOAS measurements and inverse dispersion modelling

Advances in understanding, models and parameterizations of biosphere-atmosphere ammonia exchange

The import and export of organic nitrogen species at a Scottish ombrotrophic peatland

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