Reactive hydrocarbon flux footprints during canopy senescence

Abstract. Formaldehyde (HCHO) is an important intermediate compound in the degradation of volatile organic compounds (VOCs) in the troposphere. Sources of HCHO are largely dominated by its secondary production from VOC oxidation, methane and isoprene being the main precursors in unpolluted areas. As a result of the moderate lifetime of HCHO, its spatial distribution is determined by reactive hydrocarbon emissions. We focus here on Europe and investigate the influence of the different emissions on HCHO tropospheric columns with the CHIMERE chemical transport model in order to interpret the comparisons between SCIAMACHY and simulated HCHO columns. Europe was never specifically studied before for these purposes using satellite observations. The bias between measurements and model is less than 20% on average. The differences are discussed according to the errors on the model and the observations and remaining discrepancies are attributed to a misrepresentation of biogenic emissions. This study requires the characterisation of: (1) the model errors and performances concerning formaldehyde. The errors on the HCHO columns, mainly related to chemistry and mixed emission types, are evaluated to 2×1015 molecule/cm2 and the model performances evaluated using surface measurements are satisfactory (~13%); (2) the observation errors that define the needs in spatial and temporal averaging for meaningful comparisons. Using SCIAMACHY observations as constraint for biogenic isoprene emissions in an inverse modelling scheme reduces their uncertainties by about a factor of two in region of intense emissions. The retrieved correction factors for the isoprene emissions range from a factor of 0.15 (North Africa) to a factor of 2 (Poland, the United Kingdom) depending on the regions.

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Fullerene/Tubule Based Hollow Carbon Nano-Gears

MRS Proceedings ◽

10.1557/proc-349-283 ◽

1994 ◽

Vol 349 ◽

Cited By ~ 12

Author(s):

D.H. Robertson ◽

B.I. Dunlap ◽

D.W. Brenner ◽

J.W. Mintmire ◽

C.T. White

Keyword(s):

Mechanical Properties ◽

Molecular Dynamics ◽

Large Deformations ◽

Hydrocarbon Potential ◽

Angular Velocities ◽

Symmetric Star ◽

Hollow Carbon ◽

Reactive Hydrocarbon

ABSTRACTWe report the design of several symmetric star-shaped closed carbon cages using ball and stick models. Despite the presence of seven- and eight-membered rings, these hollow carbon sprockets—containing less than 500 carbon atoms—are predicted to be more energetically stable than C60. Also, we show that these sprockets can be connected to capped fullerene tubules to form a nanostructure similar to a mechanical gear and shaft. In addition, using molecular dynamics and a reactive hydrocarbon potential, we show that these gears can be turned against each other at high angular velocities without large deformations. These nanogears illustrate some of the possible complex small structures that can be formed by inserting 5-, 7-, and 8-membered rings in an otherwise graphitic network. These nanogears also show surprisingly robust mechanical properties.

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Sources and Time-Variations of Reactive Hydrocarbon Immissions in the Atmosphere of Different Industrial and Rural Areas

International Journal of Environmental & Analytical Chemistry ◽

10.1080/03067317908071168 ◽

1979 ◽

Vol 6 (2) ◽

pp. 145-159 ◽

Cited By ~ 5

Author(s):

J. Nassar ◽

J. Goldbach

Keyword(s):

Rural Areas ◽

Time Variations ◽

Reactive Hydrocarbon

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Simulation of Turbulent Mixing Effects on Essential NOx–O3–Hydrocarbon Photochemistry in Convective Boundary Layer

Applied Sciences ◽

10.3390/app9020357 ◽

2019 ◽

Vol 9 (2) ◽

pp. 357 ◽

Cited By ~ 1

Author(s):

Mi-Sug Kim

Keyword(s):

Boundary Layer ◽

Convective Boundary Layer ◽

Turbulent Mixing ◽

Reaction Rates ◽

Chemical System ◽

Reacting Flow ◽

Convective Boundary ◽

Time Resolved ◽

Eddy Simulation ◽

Reactive Hydrocarbon

The turbulence kinetics model (TKM) describes an overall reaction rate for microscopic mass transfer phenomenon expressed as separation intensity, Is, in a turbulent reacting flow. This study examines the effects of turbulent mixing in the convective boundary layer (CBL) on essential NOx–O3–Hydrocarbon photochemistry containing sources of NO and a surrogate reactive hydrocarbon. The modeling approach applies for all species except OH with an assumption of a photostationary steady state. The TKM results reveal principal findings as follows: (1) effects of turbulence on reaction rates lead to significant segregations throughout most of the CBL in reaction pairs NO + O3, RH + OH and NO + HO2; (2) segregations permit significantly higher concentrations of NO and RH to build up and endure in the CBL than would occur for a non-turbulent atmosphere; (3) turbulent segregation influences limit and shift the ranges of NO and O3 concentrations compared to the non-turbulent case; (4) while there are differences between the TKM results and those for a published Large Eddy simulation (LES) of the same chemical system, there are also strong similarities. Therefore, a future study remains to compare model results to observations if and when appropriately time-resolved measurements of reacting species are obtained.

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