Leaf surface wax is a source of plant methane formation under UV radiation and in the presence of oxygen.

The terrestrial vegetation is a source of UV radiation-induced aerobic methane (CH4 ) release to the atmosphere. Hitherto pectin, a plant structural component, has been considered as the most likely precursor for this CH4 release. However, most of the leaf pectin is situated below the surface wax layer, and UV transmittance of the cuticle differs among plant species. In some species, the cuticle effectively absorbs and/or reflects UV radiation. Thus, pectin may not necessarily contribute substantially to the UV radiation-induced CH4 emission measured at surface level in all species. Here, we investigated the potential of the leaf surface wax itself as a source of UV radiation-induced leaf aerobic CH4 formation. Isolated leaf surface wax emitted CH4 at substantial rates in response to UV radiation. This discovery has implications for how the phenomenon should be scaled to global levels. In relation to this, we demonstrated that the UV radiation-induced CH4 emission is independent of leaf area index above unity. Further, we observed that the presence of O2 in the atmosphere was necessary for achieving the highest rates of CH4 emission. Methane formation from leaf surface wax is supposedly a two-step process initiated by a photolytic rearrangement reaction of the major component followed by an α-cleavage of the generated ketone.

Investigation of the initial reactions of the Calcote mechanism for soot formation.

The first three reactions of the Calcote mechanism for soot formation, that is, C3H 3 (+) +C2H2→C5H 5 (+) , C5H 5 (+) →C5H 3 (+) H2, and C5H 3 (+) +C2H2→C7H 5 (+) , have been studied based on chemi-ions withdrawn directly from a premixed methane-oxygen flame by supersonic molecular beam sampling. The first reaction is reversible and involves the formation of a specific encounter complex sensitive to pressure and ion kinetic energy. The second reaction appears to require large amounts of internal energy in the C5H 5 (+) ion to proceed. The third reaction is reversible; however, in contrast to the initiating reaction, the C5H 3 (+) ion formed from the [C7H 5 (+) ]* complex exhibits a much lower reactivity. The conclusions are based on ion-molecule reactions as well as collision activation mass spectrometry of isolated chemi-ions. In addition, the product distributions as functions of pressure and ion kinetic energy were studied.

N-Nitrosodiethanolamine revisited.

N-nitrosodiethanolamine is believed to be a weakly carcinogenic chemical, and as it occurs widely--in consumer products for example--it may constitute a significant hazard to humans. However, the chemical evidence concerning the identity, purity and properties of N-nitrosodiethanolamine is incomplete, and this casts some doubt on the basis of the current interest in this substance. In the present paper a purification procedure of synthetic N-nitrosodiethanolamine based on high-performance liquid chromatography is given. Other fractionation procedures such as gas liquid chromatography, ambient pressure column chromatography and distillation are shown to be inadequate. The purity and identity of purified N-nitrosodiethanolamine is established by means of electron impact and field ionization mass spectrometry, including metastable defocusing and collision induced decomposition techniques. Furthermore, 1H and 13C nuclear magnetic resonance and, to a lesser extent, infrared and ultraviolet spectroscopy are used. Deuterium labelled analogues of N-nitrosodiethanolamine and the parent diethanolamine are employed in rationalizing the results obtained.