Isoprene nitrates drive new particle formation in Amazon's upper troposphere.

New particle formation (NPF) in the tropical upper troposphere is a globally important source of atmospheric aerosols. It is known to occur over the Amazon basin, but the nucleation mechanism and chemical precursors have yet to be identified. Here we present comprehensive in situ aircraft measurements showing that extremely low-volatile oxidation products of isoprene, particularly certain organonitrates, drive NPF in the Amazonian upper troposphere.

Extensive field evidence for the release of HONO from the photolysis of nitrate aerosols.

Particulate nitrate ([Formula: see text]) has long been considered a permanent sink for NO (NO and NO), removing a gaseous pollutant that is central to air quality and that influences the global self-cleansing capacity of the atmosphere. Evidence is emerging that photolysis of [Formula: see text] can recycle HONO and NO back to the gas phase with potentially important implications for tropospheric ozone and OH budgets; however, there are substantial discrepancies in "renoxification" photolysis rate constants. Using aircraft and ground-based HONO observations in the remote Atlantic troposphere, we show evidence for renoxification occurring on mixed marine aerosols with an efficiency that increases with relative humidity and decreases with the concentration of [Formula: see text], thus largely reconciling the very large discrepancies in renoxification photolysis rate constants found across multiple laboratory and field studies.

Trichloroacetyl chloride, CClCOCl, as an alternative Cl atom precursor for laboratory use and determination of Cl atom rate coefficients for n-CH[double bond, length as m-dash]CH(CH)CN (x = 3-4).

An investigation of CCl3COCl was conducted with the purpose of using the compound as an alternative Cl atom precursor in laboratory settings. CCl3COCl can be used with or without O2 as a source of Cl atoms and photolysis studies in air and N2 diluent displayed COCl2 and CO as being the major photolysis products. Relative rate studies were performed to determine the Cl atom rate coefficients for reaction with CH3Cl and C2H2 and the results were in agreement with literature values.

Atmospheric Chemistry of Pentafluorophenol: Kinetics and Mechanism of the Reactions of Cl Atoms and OH Radicals.

Fourier transform infrared smog chamber techniques were used to study the kinetics and mechanisms of the reactions of Cl atoms and OH radicals with pentafluorophenol (CFOH) in 700 Torr total pressure of air or N diluent at 296 ± 2 K. Rate constants (OH + CFOH) = (6.88 ± 1.

Quantum Yields and NO Formation from Photolysis of Solid Films of Neonicotinoids.

Neonicotinoids (NN), first introduced in 1991, are found on environmental surfaces where they undergo photolytic degradation. Photolysis studies of thin films of NN were performed using two approaches: (1) transmission FTIR, in which solid films of NN and the gas-phase products were analyzed simultaneously, and (2) attenuated-total-reflectance FTIR combined with transmission FTIR, in which solid films of NN and the gas-phase products were probed in the same experiment but not at the same time. Photolysis quantum yields using broadband irradiation centered at 313 nm were (2.

Atmospheric chemistry of hexa- and penta-fluorobenzene: UV photolysis and kinetics and mechanisms of the reactions of Cl atoms and OH radicals.

Photochemical reactors were used to study the kinetics and mechanisms of reactions of Cl atoms and OH radicals with hexa- and penta-fluorobenzene (C6F6, C6F5H) in 700 Torr total pressure of N2, air, or O2 diluent at 296 ± 2 K. C6F6 and C6F5H undergo ring-opening following 254 nm UV irradiation, but with small quantum yields (φ < 0.03).

Atmospheric Chemistry of n-CH═CH(CH) CN ( x = 0-4): Kinetics and Mechanisms.

Smog chamber/Fourier transform infrared (FTIR) techniques were used to measure the kinetics of the reaction of n-CH═CH(CH) CN ( x = 0-4) with Cl atoms, OH radicals, and O: k(CH═CHCN + Cl) = (1.03 ± 0.13) × 10, k(CH═CHCHCN + Cl) = (2.

Atmospheric Chemistry of (CF)CF-C≡N: A Replacement Compound for the Most Potent Industrial Greenhouse Gas, SF.

FTIR/smog chamber experiments and ab initio quantum calculations were performed to investigate the atmospheric chemistry of (CF)CFCN, a proposed replacement compound for the industrially important sulfur hexafluoride, SF. The present study determined k(Cl + (CF)CFCN) = (2.33 ± 0.

Atmospheric chemistry of Z- and E-CFCH[double bond, length as m-dash]CHCF.

The atmospheric fates of Z- and E-CFCH[double bond, length as m-dash]CHCF have been studied, investigating the kinetics and the products of the reactions of the two compounds with Cl atoms, OH radicals, OD radicals, and O. FTIR smog chamber experiments measured: k(Cl + Z-CFCH[double bond, length as m-dash]CHCF) = (2.59 ± 0.