Laser studies of reaction dynamics

Laser and molecular beam techniques allow detailed study of many dynamical properties of single reactive collisions. The chemical scope of these methods is now very wide and includes internal state preparation of reactants, change of collision energies, state detection of products, and thus determination of state-to-state reaction rates. The great impact of laser spectroscopy on knowledge in the field of structure, molecular energy transfer and the mechanism of elementary chemical reactions is illustrated by a few selected examples, including studies in which laser-induced fluorescence (LIF) has been used to to determine the polarization of reaction products     

Fernmeßverfahren

The combination of remote sensing methods like Doppler lidar and FTIR allows remote determination of mass fluxes of gases. Doppler lidar measures the three-dimensional wind vector in the vicinity of diffuse sources, or the velocity of air in a chimney plume if an industrial complex is monitored. FTIR is a multicomponent remote sensing method for gas concentrations. The Fourier transformation of an interferogram of a Michelson interferometer within a FTIR system converts the recorded intensity (function of optical path length) to a spectral signal (function of wavenumber). Both information, velocity and concentration, give the mass fluxes of the tracer (gas). A first test was performed at Munich-Nord power station with FTIR and cw-Doppler lidar. Fluxes of CO₂, CO, NO, and HCl were determined. The results are in good agreement with the fluxes measured byin situ instruments of the power station. The method can be used to control industrial complexes from an outside observation site.     

Effective pollutant emission heights for atmospheric transport modelling based on real-world information

Emission data needed as input for the operation of atmospheric models should not only be spatially and temporally resolved. Another important feature is the effective emission height which significantly influences modelled concentration values. Unfortunately this information, which is especially relevant for large point sources, is usually not available and simple assumptions are often used in atmospheric models. As a contribution to improve knowledge on emission heights this paper provides typical default values for the driving parameters stack height and flue gas temperature, velocity and flow rate for different industrial sources. The results were derived from an analysis of the probably most comprehensive database of real-world stack information existing in Europe based on German industrial data. A bottom-up calculation of effective emission heights applying equations used for Gaussian dispersion models shows significant differences depending on source and air pollutant and compared to approaches currently used for atmospheric transport modelling.     

Heavy metal inputs evolution to an urban hypertrophic coastal lagoon, Rodrigo De Freitas Lagoon, Rio De Janeiro, Brazil

This work discusses the temporal variation of metal concentrations in a hypertrophic coastal lagoon located in the metropolitan area of Rio de Janeiro (Brazil). The lagoon watershed includes one of the mostly densely urbanized areas of the city but without industrial activities. Six sediment cores were collected in the lagoon between May and July 2003 and analyzed for the concentration of metals (Fe, Al, Mn, Zn, Pb, Cu, Cr, and Ni). Typical sedimentation rate was calculated as being 0.75 cm year^???1 and was uniform for at least the past 70 years. Therefore, the alterations in the dynamics of the lagoon caused by changes in its watershed were clearly indicated in sediment cores. The construction of an artificial canal to the sea and the increasing urbanization and soil use changes were the major factors affecting metal accumulation in the lagoon sediments. Metals typical of anthropogenic urban sources (Pb, Zn, and Cu) showed increasing loads following urbanization.