A new method for using 18O to trace ozone deposition

Isotopically labelled ozone (¹⁸O₃) is an ideal tool to study the deposition of O₃ to plants and soil, but no studies have made use of it due to the technical difficulties in producing isotopically enriched ozone. For ¹⁸O₃ to be used in fumigation experiments, it has to be purified and stored safely prior to fumigations, to ensure that the label is present predominantly in the form of O₃, and to make efficient use of isotopically highly enriched oxygen. We present a simple apparatus that allows for the safe generation, purification, storage, and release of ¹⁸O₃. Following the purification and release of O₃, about half (by volume) of the ¹⁸O is present in the form of O₃. This means that for a given release of ¹⁸O₃ into the fumigation system, a roughly identical volume of ¹⁸O₂ is released. However, the small volume of this concurrent ¹⁸O₂ release (100 nmol mol^?1 in our experiment) results in only a minor shift of the much larger atmospheric oxygen pool, with no detectable consequence for the isotopic enrichment of either soil or plant materials. We demonstrate here the feasibility of using ¹⁸O as an isotopic tracer in O₃ fumigations by exposing dry soil to 100 nmol mol^{?1 18}O₃ for periods ranging from 1 to 11 h. The ¹⁸O tracer accumulation in soil samples is measured using gas chromatography/isotope ratio mass spectrometry (GC/IRMS), and the results show a linear increase in ¹⁸O/¹⁶O isotope ratio over time, with significant differences detectable after 1 h of exposure. The apparatus is adapted for use with fumigation chambers sustaining flow rates of 1 m³ min^?1 for up to 12 h, but simple modifications now allow larger quantities of O₃ to be stored and continuously released (e.g. for use with open‐top chambers or FACE facilities). Copyright © 2009 John Wiley & Sons, Ltd.     

Solitary wave solutions to nonlinear evolution equations in mathematical physics

This paper obtains solitons as well as other solutions to a few nonlinear evolution equations that appear in various areas of mathematical physics. The two analytical integrators that are applied to extract solutions are tan–cot method and functional variable approaches. The soliton solutions can be used in the further study of shallow water waves in (1+1) as well as (2+1) dimensions.