The reaction of ozone with aqueous sodium bromide particles is investigated with a combination of aerosol chamber experiments, kinetics modeling, and molecular dynamics simulations. The molecular bromine production in the chamber experiments is approximately an order of magnitude greater than that predicted by known chemistry in the gas and bulk aqueous phases with use of a comprehensive computer kinetics model. Molecular dynamics simulations indicate that ozone has significant residence time at the air−solution interface, while making frequent contacts with bromide ions for as long as 50 ps in the surface layer of a 6.1 M NaBr solution. The formation of a complex between ozone and bromide ion, [O3···Br-], which can lead to production of Br2 by reaction at the air−water interface, is therefore feasible. Experimentally observed Br2 is well predicted by including an interface process with a reaction probability of [1.9 ± 0.8] × 10-6 (1 s) as the first step in a surface mechanism to produce additional gas-phase Br2. An estimate of the impact of this interface reaction on bromine formation in the marine boundary layer shows that several ppt of bromine could potentially be produced during the night from this proposed surface chemistry.

Inductively coupled plasmas (ICP) in combination with atomic emission spectrometry (AES) or mass spectrometry (MS) are increasingly supplanting other methods of trace metal analysis (1-3). ICP-AES is ideal for measuring trace metals in a variety of samples because many elements can be measured simultaneously; this is in contrast to atomic absorption, where only one or two elements are typically measured at once and changing the element studied requires changeover of the lamps. ICP has a higher linear dynamic range, lower detection limits for some metals, and shorter analysis time. In addition, some nonmetallic elements such as bromine can be measured by ICP-AES (1-3).The application of ICP in undergraduate experiments to measure trace metals present in core sediments has been described previously by Mabury and coworkers (4). They compared ICP measurements to those using graphite furnace atomic absorption spectroscopy. Page et al. (5) described a physical chemistry experiment to determine the plasma temperature in an ICP.Here we report an experiment in which ICP-AES is used to quantify Zn, Fe, and Cr present in cigarette tobacco, the cigarette filter, and in the ash from burning the cigarette. Tobacco smoke is known to contain a number of toxic metals (6-8) as well as nicotine and polycyclic aromatic hydrocarbons that are harmful to human health (9). Hence, measurement of such metals in tobacco and the associated ash pose a relevant problem for an undergraduate instrumental analysis laboratory. This experiment complements a number of other undergraduate laboratories previously published in this Journal that focus on tobacco and cigarette smoke (10-19). Methods StandardsA stock solution containing As, Se, Sb, Zn, Co, Fe, Cu, and Cr was obtained by diluting 10 mL of an ICP standard (Spex CertiPrep, Inc.) by a factor of 10 with a 0.5% HNO 3 ͞5% HCl mixture (both concentrated TraceMetal

Oxidation of thin films of three solid neonicotinoid pesticides by gas-phase OH radicals yields a variety of products primarily in the surface layers.

While nitro and amino alkenes are common in pharmaceuticals, pesticides, and munitions, their environmental fates are not well known. Ozone is a ubiquitous atmospheric oxidant for alkenes, but the synergistic effects of nitrogen-containing groups on the reactions have not been measured. The kinetics and products of ozonolysis of a series of model compounds with different combinations of these functional groups have been measured in the condensed phase using stopped-flow and mass spectrometry methods. Rate constants span about six orders of magnitude with activation energies ranging from 4.3 to 28.2 kJ mol −1 . Vinyl nitro groups substantially decrease the reactivity, while amino groups have the opposite effect. The site of the initial ozone attack is highly structure dependent, consistent with local ionization energy calculations. The reaction of the neonicotinoid pesticide nitenpyram, which forms toxic N -nitroso compounds, was consistent with model compounds, confirming the utility of model compounds for assessing environmental fates of these emerging contaminants.

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