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We use a continuous 6-year record (1996 - 2001) of GOME satellite measurements of formaldehyde (HCHO) columns over east and south Asia to improve regional emission estimates of reactive nonmethane volatile organic compounds (NMVOCs), including isoprene, alkenes, HCHO, and xylenes. Mean monthly HCHO observations are compared to simulated HCHO columns from the GEOS-Chem chemical transport model using state-of-science, "bottom-up" emission inventories from Streets et al. (2003a) for anthropogenic and biomass burning emissions and Guenther et al. (2006) for biogenic emissions (MEGAN). We find that wintertime GOME observations can diagnose anthropogenic reactive NMVOC emissions from China, leading to an estimate 25% higher than Streets et al. (2003a). We attribute the difference to vehicular emissions. The biomass burning source for east and south Asia is almost 5 times the estimate of Streets et al. (2003a). GOME reveals a large source from agricultural burning in the North China Plain in June missing from current inventories. This source may reflect a recent trend toward in-field burning of crop residues as the need for biofuels diminishes. Biogenic isoprene emission in east and south Asia derived from GOME is 56 ± 30 Tg yr-1, similar to 52 Tg yr-1 from MEGAN. We find, however, that MEGAN underestimates emissions in China and overestimates emissions in the tropics. The higher Chinese biogenic and biomass burning emissions revealed by GOME have important implications for ozone pollution. We find 5 to 20 ppb seasonal increases in surface ozone in GEOS-Chem for central and northern China when using GOME-derived versus bottom-up emissions. Our methodology can be adapted for other regions of the world to provide top-down constraints on NMVOC emissions where multiple emission source types overlap in space and time. Copyright 2007 by the American Geophysical Union.

Quantifying isoprene emissions using satellite observations of the formaldehyde (HCHO) columns is subject to errors involving the column retrieval and the assumed relationship between HCHO columns and isoprene emissions,taken here from the GEOSCHEM chemical transport model. Here we use a 6-year (1996-2001) HCHO column data set from the Global Ozone Monitoring Experiment (GOME) satellite instrument to (1) quantify these errors, (2) evaluate GOME-derived isoprene emissions with in situ flux measurements and a process-based emission inventory (Model of Emissions of Gases and Aerosols from Nature, MEGAN), and (3) investigate the factors driving the seasonal and interannual variability of North American isoprene emissions. The error in the GOME HCHO column retrieval is estimated to be 40%. We use the Master Chemical Mechanism (MCM) to quantify the time-dependent HCHO production from isoprene, α-and β-pinenes, and methylbutenol and show that only emissions of isoprene are detectable by GOME. The time-dependent HCHO yield from isoprene oxidation calculated by MCM is 20-30% larger than in GEOS-CHEM. GOME-derived isoprene fluxes track the observed seasonal variation of in situ measurements at a Michigan forest site with a -30% bias. The seasonal variation of North American isoprene emissions during 2001 inferred from GOME is similar to MEGAN, with GOME emissions typically 25% higher (lower) at the beginning (end) of the growing season. GOME and MEGAN both show a maximum over the southeastern United States, but they differ in the precise location. The observed interannual variability of this maximum is 20-30%, depending on month. The MEGAN isoprene emission dependence on surface air temperature explains 75% of the month-to-month variability in GOME-derived isoprene emissions over the southeastern United States during May-September 1996-2001. Copyright 2006 by the American Geophysical Union.

Classical trajectory simulations of intermolecular collisions were performed for a series of polycyclic aromatic hydrocarbons interacting with the bath gases helium and argon for bath gas temperature from 300 to 2500 K. The phase-space average energy transferred per deactivating collision, ⟨∆Edown⟩, was obtained. The Buckingham pairwise intermolecular potentials were validated against high-level quantum chemistry calculations and used in the simulations. The reactive force-field was used to describe intramolecular potentials. The dependence of ⟨∆Edown⟩ on initial vibrational energy is discussed. A canonical sampling method was compared with a microcanonical sampling method for selecting initial vibrational energy at high bath gas temperatures. Uncertainties introduced by the initial angular momentum distribution were identified. The dependence of the collisional energy transfer parameters on the type of bath gas and the molecular structure of polycyclic aromatic hydrocarbons was examined. [ABSTRACT FROM AUTHOR]

ABSTRACT Incremental ozone impacts or reactivities have been calculated for selected organic compounds using a Master Chemical Mechanism (MCMv3.1) and compared with those calculated elsewhere with the SAPRC-07 chemical mechanism. [...]

The kinetics and H atom yields at both 298 and 195 K were determined for reactions of CN radicals with [C.sub.2][H.sub.2], [C.sub.2][H.sub.4], [C.sub.3][H.sub.6], trans-2-[C.sub.4][H.sub.8] and iso- [C.sub.4][H.sub.8]. The results extended the upper limit of the temperature range of study from 886 to 14010 K and indicate a non-Arrhenius behavior of the rate coefficient.

The kinetics of the reaction of OH [C.sub.2][H.sub.2 are evaluated by using laser flash photolysis at 248 nm to generate OH radicals and laser-induced fluorescence to monitor OH removal. The dependence of the rate coefficients on temperature and on the vibrational quantum number has demonstrated that there is a significant contribution from nonreactive vibrational relaxation in which the potential energy well of the chemical adduct, HO[C.sub.2][H.sub.2] is not significantly sampled.

The various features of the acetone photodissociation mechanism are investigated over the wavelength range 248-330 nm. The temperature, pressure and wavelength dependence of the acetyle yield is presented in the form of Stern-Volmer (SV) plots, which provide evidence for a mechanism involving dissociation from both the first excited singlet and triplet states.

The kinetics of the association reaction OH + SO2 were studied at 2448 nm to generate OH radicals and laser-induced fluorescence to monitor decay under pseudo-first-order conditions, [OH] <

The first direct kinetic measurements on the NS radical are reported. The NS radical was produced from the photolysis of N4S4 at 248nm and detected via laser-induced fluorescence.

Author(s): Alastair C. Lewis (corresponding author) [1, 2]; Nicola Carslaw [1]; Philip J. Marriott [3]; Russel M. Kinghorn [3]; Paul Morrison [3]; Andrew L. Lee [1]; Keith D. Bartle [1]; [...]

The reactions of CH(v=0) and CD(v=0) radicals with H2O and D2O were studied in the temperature range 291 to 723 K. The reactions of CH(v=1) and CD(v=1,2) with H2O and D2O were examined at 293 K. The reactions showed a negative temperature dependence and seem to have no isotope effect. Findings indicate that the reaction does not proceed through direct insertion in the O-H(D) bond, but through the formation of an intermediate complex between CH and H2O, followed by the rearrangement to the overall insertion product, CH2OH.

A new technique for identifying alkylated, oxygenated and nitrated polycyclic aromatic compounds in urban air particulate samples is demonstrated. The method combines high-pressure normal-phase liquid chromatography with a high-resolution gas chromatograph with an ion trap detector mass spectrometer. The new technique was able to identify many substituted polycyclic aromatic compounds.