We investigated the reactive uptake of NO3, N2O5, NO2, HNO3, and O3 on three types of solid polycyclic aromatic hydrocarbons (PAHs) using a coated wall flow tube reactor coupled to a chemical ionization mass spectrometer. The PAH surfaces studied were the 4-ring systems pyrene, benz[a]anthracene, and fluoranthene. Reaction of NO3 radicals with all three PAHs was observed to be very fast with the reactive uptake coefficient, gamma, ranging from 0.059 (+0.11/-0.049) for benz[a]anthracene at 273 K to 0.79 (+0.21/-0.67) for pyrene at room temperature. In contrast to the NO3 reactions, reactions of the different PAHs with the other gas-phase species (N2O5, NO2, HNO3, and O3) were at or below the detection limit (gamma

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.

[1] The heterogeneous oxidation of a saturated hydrocarbon monolayer by NO 3 was studied. A flow tube reactor coupled to chemical ionization mass spectrometry was used to determine the reactive uptake coefficient of NO 3 on these surfaces, and X-ray photoelectron spectroscopy (XPS) was used to investigate surface oxidation and to determine if exposure to NO 3 leads to volatilization of the organic substrate. The uptake coefficient of NO 3 by an alkane monolayer is about (8.8 ± 2.5) Â 10 À4 , which may lead to competitive oxidation compared with OH, due to the higher atmospheric abundance of NO 3 under certain conditions. The XPS results are consistent with the formation of 1) C-O groups, 2) ketones or aldehydes, and 3) carboxylic groups. The XPS results also suggest that NO 3 does not rapidly volatilize the organic surface: even under extremely polluted conditions, maximum 10% of the organic layer is volatilized.

There is strong scientific evidence that microbial residues such as amino sugars may be stabilized in soil. However, up to now, no investigation has been carried out to quantify both the amount and timing of such stabilization. This is primarily due to methodological constraints, because it is not possible to differentiate between stabilized (old) and recently produced (new) amino sugars when these biomarkers are conventionally analyzed, e.g. by means of gas chromatography and flame ionization detection. Therefore, the aim of the present study was to test whether compound-specific isotope analysis (delta13C) of amino sugars extracted from soil could be used to differentiate between old and new microbial residues. For this aim a method for the delta13C analysis of individual amino sugars was developed and optimized. First results of delta13C values of glucosamine, galactosamine, mannosamine, and muramic acid in soil samples from two different ecological studies are presented, clearly indicating that discrimination between soil inherent and newly formed amino sugars is possible in stable isotope labeling experiments. Our results further showed that, in the short term (within 1 month), only few amino sugars were built, thus making highly 13C-enriched substrates necessary for the quantification of new amino sugar production and for the determination of amino sugar turnover rates.

Little is known about the delta13C composition of monosaccharides representing the largest carbon reservoir in the biosphere. The main reason for this might be that monosaccharides have to be derivatized prior to gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS) analyses and that a large isotopic correction is necessary for the carbon that has to be added to the original molecule during derivatization, resulting in large uncertainty of the calculated delta13C values of individual monosaccharides. The amount of added derivatization carbon is twice (alditol acetates) or even three times (trimethylsilyl (TMS) derivatives) as high as the amount of the original monosaccharide carbon. In addition, isotope fractionation occurs during acetylation. Therefore, the objectives of this study were (i) to minimize carbon addition during derivatization for GC/C/IRMS measurements of monosaccharides in soil and sediment samples and (ii) to quantify improvements in accuracy and precision of the final results. Minimization of carbon addition was accomplished by derivatization with methylboronic acid (MBA) and TMS thereafter (MBA method). Monosaccharides derivatized with the MBA method instead of TMS reduced the number of added carbon atoms from 2.2-2.7 to 0.3-0.8 per sugar carbon atom. Although the precision of GC/C/IRMS measurements with both methods is comparable (about 0.3 per thousand), delta13C values of an internal standard indicated that the newly developed MBA method is about 2 per thousand more accurate than the TMS method. delta13C comparison between soil samples that differed only slightly in their bulk carbon isotope signature showed that the MBA method is better in proving these small differences on a significant level. Total precision of the whole MBA method including all analytical and calculation steps is better by a factor of almost three than the TMS method.

[1] The reaction of NO 3 with methane soot, hexane soot, and solid pyrene was investigated using a flow tube reactor. The uptake of NO 3 on fresh soot was fast (uptake coefficient >0.1). Based on this result and an assumed density of reactive sites on soot, the time to process or oxidize 90% of a soot surface in the atmosphere would take only approximately five minutes. This suggests that NO 3 chemistry can rapidly oxidize soot surfaces under atmospheric conditions. After exposing soot films to NO 3 for approximately 180 minutes in the laboratory, the uptake reaches a steady-state value. The steady state uptake coefficients (assuming a geometric surface area) were 0.0054 ± 0.0027 and 0.0025 ± 0.0018 for methane and hexane soot, respectively. These numbers are used to show that heterogeneous reactions between NO 3 and soot are not likely a significant sink of gas-phase NO 3 under most atmospheric conditions. The uptake of NO 3 on fresh pyrene surfaces was also fast (uptake coefficient >0.1), and much faster than previously suggested. We argue that under certain atmospheric conditions reactions between NO 3 and surface-bound polycyclic aromatic hydrocarbons (PAHs) may be an important loss process of PAHs in the atmosphere.

[1] The reactions of an alkanethiol and a terminal alkenethiol self-assembled monolayer with NO 3 radicals (in the presence of NO 2 and O 2 ) were studied. For the alkane monolayer, infrared (IR) spectroscopy and time-of-flight secondary ion mass spectrometry (ToF-SIMS) confirmed the formation of organonitrates (RONO 2 ). The observation of organonitrates is in contrast to the recent X-ray photoelectron spectroscopy (XPS) data, which showed very little nitrogen-containing surface species. The identification of organonitrates may help explain why significant volatilization of the organic chain was not observed in recent studies of alkane monolayer oxidation by NO 3 radicals. The reactive uptake coefficient (g) of NO 3 on alkene monolayers determined in our study is higher than the values obtained in a recent study using liquid and solid alkene bulk films. A possible reason for this difference may be the location of the double bond at the interface. Using the g value determined in our studies, we show that under conditions where NO 3 is high the lifetime of an alkene monolayer in the atmosphere may be short (approximately 20 min). XPS, IR, and ToF-SIMS were used to identify surface functional groups after the oxidation of the alkene monolayers by NO 3 . The results are consistent with the formation of C-O, aldehyde/ketone, carboxylic groups, and nitrogen containing species.Citation: Gross, S., and A. K. Bertram (2009), Products and kinetics of the reactions of an alkane monolayer and a terminal alkene monolayer with NO 3 radicals,

Vinyl isobutyl ether is shown to give different types of high polymers depending on the conditions of polymerization.The polymer obtained by rapid polymerization with boron fluoride catalyst is substantially amorphous and rubberlike.A second type of polymer is less rubberlike, comparatively well ordered and gives an x-ray fiber