Evaporation from Fractures Exposed at the Land Surface: Impact of Gas-Phase Convection on Salt Accumulation

The influence of gas-particle partitioning and surface-atmosphere exchange on ammonia during BAQS-Met

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-10-21895-2010 ◽

2010 ◽

Vol 10 (9) ◽

pp. 21895-21929 ◽

Cited By ~ 3

Author(s):

R. A. Ellis ◽

J. G. Murphy ◽

M. Z. Markovic ◽

T. C. VandenBoer ◽

P. A. Makar ◽

...

Keyword(s):

Air Quality ◽

Gas Phase ◽

Land Surface ◽

Fine Particulate Matter ◽

Mixing Ratio ◽

Flux Parameterization ◽

Total Ammonia ◽

Regional Air Quality ◽

The Impact ◽

Local Emissions

Abstract. The Border Air Quality and Meteorology study (BAQS-Met) was an intensive field campaign conducted in Southwestern Ontario during the summer of 2007. The focus of BAQS-Met was determining the causes of the formation of ozone and fine particulate matter (PM2.5), and of the regional significance of trans-boundary transport and lake breeze circulations on that formation. Fast (1 Hz) measurements of ammonia were acquired using a Quantum Cascade Laser Tunable Infrared Differential Absorption Spectrometer (QC-TILDAS) at the Harrow supersite. Measurements of PM2.5 ammonium, sulfate and nitrate were made using an Ambient Ion Monitor Ion Chromatograph (AIM-IC) with hourly time resolution.The median mixing ratio of ammonia was 2.5 ppb, with occasional high spikes at night resulting from local emissions. Measurements were used to assess major local emissions of NH3, diurnal profiles and gas-particle partitioning. The measurements were compared with results from A Unified Regional Air-quality Modelling System (AURAMS). While the fraction of total ammonia (NHx≡NH3 + NH4+) observed in the gas phase peaks between 0.1 and 0.8, AURAMS tended to predict fractions of either less than 0.05 or greater than 0.8. The model frequently predicted acidic aerosol, in contrast withobservations whereinNHx always exceeded the observed equivalents of sulfate. One explanation for our observations is that the net flux of ammonia from the land surface to the atmosphere increases when aerosol sulfate is present, effectively buffering the mixing ratio of gas phase ammonia, a process not included in the model. We explore the impact of a bi-directional flux parameterization on the predicted gas-particle partitioning of atmospheric ammonia.

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The influence of gas-particle partitioning and surface-atmosphere exchange on ammonia during BAQS-Met

Atmospheric Chemistry and Physics ◽

10.5194/acp-11-133-2011 ◽

2011 ◽

Vol 11 (1) ◽

pp. 133-145 ◽

Cited By ~ 66

Author(s):

R. A. Ellis ◽

J. G. Murphy ◽

M. Z. Markovic ◽

T. C. VandenBoer ◽

P. A. Makar ◽

...

Keyword(s):

Air Quality ◽

Gas Phase ◽

Land Surface ◽

Fine Particulate Matter ◽

Mixing Ratio ◽

Flux Parameterization ◽

Total Ammonia ◽

Regional Air Quality ◽

Net Flux ◽

Local Emissions

Abstract. The Border Air Quality and Meteorology study (BAQS-Met) was an intensive field campaign conducted in Southwestern Ontario during the summer of 2007. The focus of BAQS-Met was determining the causes of the formation of ozone and fine particulate matter (PM2.5), and of the regional significance of trans-boundary transport and lake breeze circulations on that formation. Fast (1 Hz) measurements of ammonia were acquired using a Quantum Cascade Laser Tunable Infrared Differential Absorption Spectrometer (QC-TILDAS) at the Harrow supersite. Measurements of PM2.5 ammonium, sulfate and nitrate were made using an Ambient Ion Monitor Ion Chromatograph (AIM-IC) with hourly time resolution. The median mixing ratio of ammonia was 2.5 ppb, with occasional high spikes at night resulting from local emissions. Measurements were used to assess major local emissions of NH3, diurnal profiles and gas-particle partitioning. The measurements were compared with results from A Unified Regional Air-quality Modelling System (AURAMS). While the fraction of total ammonia (NHx≡NH3 + NH4+) observed in the gas phase peaks between 0.1 and 0.8, AURAMS tended to predict fractions of either less than 0.05 or greater than 0.8. The model frequently predicted acidic aerosol, in contrast with observations wherein NHx almost always exceeded the observed equivalents of sulfate. One explanation for our observations is that the net flux of ammonia from the land surface to the atmosphere increases when aerosol sulfate is present, effectively buffering the mixing ratio of gas phase ammonia, a process not included in the model. A simple representation of an offline bi-directional flux parameterization using the ISORROPIA thermodynamic model was successful at reducing the population of zero gas fraction points, but not the higher gas fraction points.

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Residual Gas Reactions in the Electron Microscope: I. Qualitative Observations on the Water Gas Reaction

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100101207 ◽

1968 ◽

Vol 26 ◽

pp. 292-293

Author(s):

Richard E. Hartman ◽

Roberta S. Hartman ◽

Peter L. Ramos

Keyword(s):

Electron Beam ◽

Electron Microscope ◽

Gas Phase ◽

Absolute Temperature ◽

Residual Gas ◽

Gas Reactions ◽

Image Position ◽

The Right ◽

Water Gas ◽

Thinning Rate

The action of water and the electron beam on organic specimens in the electron microscope results in the removal of oxidizable material (primarily hydrogen and carbon) by reactions similar to the water gas reaction .which has the form:The energy required to force the reaction to the right is supplied by the interaction of the electron beam with the specimen.The mass of water striking the specimen is given by:where u = gH2O/cm2 sec, PH2O = partial pressure of water in Torr, & T = absolute temperature of the gas phase. If it is assumed that mass is removed from the specimen by a reaction approximated by (1) and that the specimen is uniformly thinned by the reaction, then the thinning rate in A/ min iswhere x = thickness of the specimen in A, t = time in minutes, & E = efficiency (the fraction of the water striking the specimen which reacts with it).

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Integration of Core-Edge Spectroscopy Methods for the Study of Polymers

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010016323x ◽

1996 ◽

Vol 54 ◽

pp. 154-155

Author(s):

E. G. Rightor

Keyword(s):

Excited State ◽

Polymer Blends ◽

Gas Phase ◽

Spatial Resolution ◽

High Spatial Resolution ◽

Electronic States ◽

Core Electron ◽

Bulk Solids ◽

Development Application

Core edge spectroscopy methods are versatile tools for investigating a wide variety of materials. They can be used to probe the electronic states of materials in bulk solids, on surfaces, or in the gas phase. This family of methods involves promoting an inner shell (core) electron to an excited state and recording either the primary excitation or secondary decay of the excited state. The techniques are complimentary and have different strengths and limitations for studying challenging aspects of materials. The need to identify components in polymers or polymer blends at high spatial resolution has driven development, application, and integration of results from several of these methods.

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