Cadmium (Cd) is a hazardous heavy metal whose concentrations have been increasing in Brazilian soils, largely due to mining activities. Eucalyptus species are widely planted in Brazil to produce raw materials, and the confirmation of their phytoremediation potential would link their economic and environmental roles. We examined the Cd-tolerance of Eucaliptus camaldulenses Dehnh and the anatomical and physiological features associated with that capacity. Plants were grown under greenhouse conditions in nutrient solutions with increasing concentrations of Cd (0, 15, 25, 45, 90 µmol m-3). Shoot biomass production was less sensitive to the phytotoxic effects of cadmium than root biomass production due to low Cd transport rates from roots to shoots. Increases in epidermal and endodermal thickness, changes in the vascular conductive elements of the roots, as well as differential nutrient distributions between roots and shoots are features of Cd tolerance in this species. The Cd tolerance of E. camaldulenses and its high biomass production support its potential use in Cd phytoremediation programs.

Microdischarges at moderate to high pressure in argon were investigated. A hole opening diameter of 500 µm direct current (dc) microhollow cathode discharges (MHCD) were characterized by electrical measurements and optical emission spectroscopy (OES) for pressures ranging between 90 and 800 Torr and current from 5 to 20 mA. Current-voltage characteristic curves were obtained as a function of the pressure for this hole diameter. MHCD enables stable dc discharges for molybdenum electrodes material at constant Ar + 2%H2 flow of 0.03 l/min. Optical emission spectroscopy and analysis of the spectral line broadening of plasma line emissions were performed in order to measure gas discharge parameters. Electron number densities were obtained from Hβ Balmer line ( ~ 10(14) cm-3). For the above mentioned discharge conditions, gas temperature was estimated to be 550 - 850 K from OH rotational bands. Excitation temperature was measured based on two lines method (from atomic Mo lines) and from 4p - 4s and 5p - 4s Ar radiative transitions. Hydrogen atom temperature was measured for 800 Torr ( ~ 12000 K).

This work is devoted to the study of the electrical characteristics of microhollow cathode discharges (MHCD) at moderate to high pressure in argon and air for different geometries. High-pressure glow discharges can be operated in MHCD devices with µm electrode spacing. Experiments have been performed to determine the so-called Paschen curves, i.e. the dependence of the breakdown voltage on the product electrode gap and gas pressure. Current-voltage characteristic curves were obtained as a function of the pressure and hole diameter. MHCD enables stable direct current discharges that could be ignited for pressures ranging from 12 to 800 Torr, in a very wide range of current densities and electrodes materials. Evidence of electron field emission was observed for several ranges of gap spacing.