Revising VOC emissions speciation improves the simulation of global background ethane and propane
Matthew J Rowlinson1,2, Mat J Evans1,2, Lucy J Carpenter2
1National Centre for Atmospheric Science, University of York, York, YO10 5DD, UK.
Atmospheric Chemistry and Physics
|October 8, 2024
Summary
Chemical transport models struggle to accurately simulate Non-Methane Volatile Organic Compounds (NMVOCs). Improving emission speciation data significantly reduced the model
Area of Science:
- Atmospheric Chemistry
- Climate Modeling
- Environmental Science
Background:
- Non-Methane Volatile Organic Compounds (NMVOCs) influence atmospheric chemistry, affecting ozone and aerosol formation.
- Accurate simulation of NMVOCs in chemical transport models is crucial for understanding atmospheric processes.
- Previous studies identified significant underestimates in simulated ethane and propane concentrations.
Purpose of the Study:
- To evaluate the GEOS-Chem model's capability in simulating NMVOC concentrations.
- To assess the impact of improved NMVOC emission speciation on model accuracy.
- To resolve long-standing issues in simulating global ethane concentrations.
Main Methods:
- Comparison of model simulations with observational data from NOAA Flask Network and GAW.
- Utilizing the Community Emissions Data System (CEDS) for total NMVOC mass.
- Incorporating regional emission inventories (NEI, NAEI, MEIC) for NMVOC speciation.
Main Results:
- A significant underestimate of simulated ethane (35%) and propane (64%) was confirmed using CEDS.
- Revised speciation data substantially improved ethane simulation (bias reduced from -35% to -4%).
- Propane simulation improved but remained underestimated (bias from -64% to -48%), suggesting a missing source.
Conclusions:
- Improved NMVOC emission speciation resolves the long-term low bias in simulated global ethane.
- While propane simulation is enhanced, a substantial underestimate persists, indicating a need to identify missing sources.
- Changes in NMVOC speciation had minimal impact on tropospheric ozone and OH concentrations.
Related Concept Videos
02:18Conformations of Ethane and Propane
13.7K
In an organic molecule, free rotation about the carbon-carbon single bond results in energetically different conformers of the molecule. Due to this rotation, called the internal rotation, ethane has two major conformations — staggered and eclipsed.
Staggered conformation is a low energy and more stable conformation with the C-H bonds on the front carbon placed at 60°dihedral angles relative to the C-H bonds on the back carbon, leading to a reduced torsional strain. In staggered...
Staggered conformation is a low energy and more stable conformation with the C-H bonds on the front carbon placed at 60°dihedral angles relative to the C-H bonds on the back carbon, leading to a reduced torsional strain. In staggered...
13.7K
02:14Combustion Energy: A Measure of Stability in Alkanes and Cycloalkanes
6.2K
The low reactivity in alkanes can be attributed to the non-polar nature of C–C and C–H σ bonds. Alkanes, therefore, were initially termed as “paraffins,” derived from the Latin words: parum, meaning “too little,” and affinis, meaning “affinity.”
Alkanes undergo combustion in the presence of excess oxygen and high-temperature conditions to give carbon dioxide and water. A combustion reaction is the energy source in natural gas, liquified...
Alkanes undergo combustion in the presence of excess oxygen and high-temperature conditions to give carbon dioxide and water. A combustion reaction is the energy source in natural gas, liquified...
6.2K
02:37Standard Enthalpy of Formation
41.2K
Enthalpy changes are typically tabulated for reactions in which both the reactants and products are at the same conditions. A standard state is a commonly accepted set of conditions used as a reference point for the determination of properties under other different conditions. For chemists, the IUPAC standard state refers to materials under a pressure of 1 bar and solutions at 1 M and does not specify a temperature. Many thermochemical tables list values with a standard state of 1 atm. Because...
41.2K
01:27Inductive Effects on Chemical Shift: Overview
1.1K
The protons in unsubstituted alkanes are strongly shielded with chemical shifts below 1.8 ppm. Methine, methylene, and methyl protons appear at approximately 1.7, 1.2 and 0.7 ppm, while the proton signal from methane appears at 0.23 ppm. An electronegative substituent, such as chlorine, withdraws the electron density from the protons, increasing their chemical shift. Progressive substitution of the hydrogens in methane by chlorine shifts the proton signals increasingly downfield, to 3.05 ppm in...
1.1K
01:29Mass Spectrometry: Branched Alkane Fragmentation
929
This lesson delves into the mass spectrometry of branched alkane fragmentation. Branched alkanes possess secondary or tertiary carbon atoms, which generate relatively stable carbocations if the cleavage occurs at the branching point. The high stability of carbocations drives the instant fragmentation of branched alkanes. Accordingly, the branched alkane's molecular ion peak is very weak or invisible in the mass spectra, especially in comparison to a linear alkane.
929
01:27Benzene to Phenol via Cumene: Hock Process
3.2K
The synthesis of phenol from benzene via cumene and cumene hydroperoxide is called the Hock process. First, a Friedel–Crafts alkylation reaction of benzene with propene gives cumene. Then cumene forms cumene hydroperoxide via a radical chain reaction. In the chain initiation step, the benzylic hydrogen is abstracted to give a benzylic radical. In the chain propagation step, the benzylic radical reacts with an oxygen diradical to form a cumene hydroperoxide radical. The cumene...
3.2K