Heterogeneous reactions between NO3 and N2O5 and diethyl sebacate (DES), glycerol, oleic acid (OA), linoleic acid (LA), and conjugated linoleic acid (CLA) were studied to understand better nighttime aerosol chemistry. The reactive uptake coefficient of NO3 on the liquid alkenoic acids (OA, LA, and CLA) was found to be >0.07, which is higher than previous results for unsaturated organics, including alkenoic acids. This reaction could potentially be an important loss process of particle-phase unsaturated organic compounds in the atmosphere and in laboratory secondary organic aerosol studies. The reactive uptake coefficient of N2O5 on liquid glycerol was also found to be relatively large with a value of (3.2-8.5)x10(-4), suggesting that N2O5 heterogeneous reactions with alcohols may also be atmospherically relevant. For all measurements with OA, CLA, and DES, the reactive uptake coefficients decreased significantly upon freezing. One possible explanation is that the liquid reaction is due to both a surface reaction and a bulk reaction and that the freezing process significantly decreases the importance of any bulk reactions. NO3 reactive uptake coefficients for liquid-phase compounds decreased in magnitude in the order: alkenoic acids>DES>glycerol. This is different compared to previous gas-phase studies and the difference may be due to the large viscosity of glycerol compared to the other organic compounds studied. N2O5 reactive uptake coefficients for liquid-phase compounds decreased in magnitude in the order: glycerol>LA>DES congruent with OA congruent with CLA.

Abstract. Recent atmospheric measurements show that biological particles are a potentially important class of ice nuclei. Types of biological particles that may be good ice nuclei include bacteria, pollen and fungal spores. We studied the ice nucleation properties of water droplets containing fungal spores from the genus Cladosporium, one of the most abundant types of spores found in the atmosphere. For water droplets containing a Cladosporium spore surface area of ∼217 µm 2 (equivalent to ∼5 spores with average diameters of 3.2 µm ), 1% of the droplets froze by −28.5 • C and 10% froze by -30

The carbon kinetic isotope effects (KIEs) of the room-temperature reactions of several light alkanes and ethene with OH radicals were measured in a 30 L PTFE reaction chamber at ambient pressure using gas chromatography coupled with online combustion and isotope ratio mass spectrometry (GCC-IRMS). For simplicity, KIEs are reported in per mil according to (‰) ) (k 12 /k 13 -1) × 1000. The following average KIEs were obtained, (all in ‰) : ethane, 8.57 ( 1.95; propane, 5.46 ( 0.35; n-butane, 5.16 ( 0.67; methylpropane, 8.45 ( 1.49; n-pentane, 2.85 ( 0.79; methylbutane, 2.91 ( 0.43; n-hexane, 2.20 ( 0.07; n-heptane, 1.96 ( 0.26; n-octane, 2.13 ( 0.39; cyclopentane, 1.84 ( 0.13; cyclohexane, 4.46 ( 0.51; methylcyclopentane, 1.77 ( 0.53; ethene, 18.6 ( 2.9. As well, the room-temperature rate constant for the reaction of methylcyclopentane + OH, not previously reported in the literature, was determined using relative rates: (8.6 ( 2.2) × 10 -12 cm 3 molecule -1 s -1 , including the estimated 25% uncertainty in the rate constant for cyclopentane + OH. KIE values for propane, n-butane and n-hexane have been reported previously [J. Geophys. Res. [Atmos.] 2000, 105, 29329]. Our KIE for n-hexane is in agreement with the previous measurement, but our values for propane and n-butane are both higher. The dependence between the KIE and chemical structure is discussed, and a method for estimating unknown carbon KIEs for the reactions of light alkanes with OH radicals is presented. With only one exception, predictions using this method agree within a factor of 2 of the experimental KIE results.

The carbon kinetic isotope effects (KIEs) of the room temperature reactions of benzene and several light alkyl benzenes with OH radicals were studied in a reaction chamber at ambient pressure using gas chromatography coupled with online combustion and isotope ratio mass spectrometry (GCC‐IRMS). The KIEs are reported in per mil according to ɛ (‰) = (KIE − 1) × 1000, where KIE = k12/k13. The following average KIEs were obtained, (all in ‰): benzene 7.53 ± 0.50; toluene 5.95 ± 0.28; ethylbenzene 4.34 ± 0.28; o‐xylene 4.27 ± 0.05, p‐xylene 4.83 ± 0.81; o‐ethyltoluene 4.71 ± 0.12 and 1,2,4‐trimethylbenzene 3.18 ± 0.09. Our KIE value for benzene + OH agrees with the only reported value known to us [Rudolph et al., 2000]. It is shown that measurements of the stable carbon isotope ratios of light aromatic compounds should be extremely useful to study atmospheric processing by the OH radical.