BIOSPHERE DYNAMICS AND CHEMICAL SENSORS

The modern trends of climate modifications and global changes in the b iosphere are connected with 'ozone' and 'greenhouse' problems and with the possible influence on them of hydrogen and different hydrogen-con taining particles (H2O, CH4, OH). The semiconductor metal oxide based sensors allow the measurement of concentrations and fluxes of practica lly all H-containing components of interest. The experimental peculiar ities of obtaining and selectively detecting OH radicals and H atoms a t low pressures and in the presence of other chemically active particl es are discussed. The possibilities of the evaluation of a selective a nd highly sensitive polymer humidity sensor are considered. In additio n, a methane semiconductor sensor is proposed. Its selectivity is base d upon the spatial separation of the sensing element and the porous ca talyst permeable for methane. A differential version of the methane se nsor is proposed, containing two sensitive metal oxide layers active w ith respect to reducing gas detection, one of them being passive with respect to methane detection. The principles of Ricker-noise spectrosc opy are evaluated for the treatment of temporal sequence of the expect ed chemical-sensor signals under atmospheric conditions. Such an analy sis gives the possibility of obtaining information both about the para meters of the non-stationary atmosphere fluxes and the relaxation proc esses in the sensor itself.