COMPARISON OF VARIOUS APPROACHES TO DETERMINING CO2 FLUXES FROM THE SOIL BY 222Rn CALIBRATED METHOD.

Various approaches of determining CO2 fluxes from the soil based on 222Rn calibrated method were tested. It was shown that the exponential fits of CO2 and 222Rn depth profiles led to uncertainties up to 50% if the depth profiles of CO2 and 222Rn concentration were not measured at sufficient depths. However, CO2 fluxes determined from linear fits of CO2 and 222Rn concentrations in the surface layer of the soil are lower than the fluxes determined from exponential fits, and have lower uncertainties. The comparison of CO2 fluxes derived from 222Rn calibrated methods with directly measured CO2 fluxes showed that the latter are usually on the order of tens of percent higher than the former. CO2 flux from sandy-clay and uncultivated soil was estimated to be on the level of 3.0 mmol m-2 h-1 in the spring and around 7.0 mmol m-2 h-1 in the summer.

Use of threshold-specific energy model for the prediction of effects of smoking and radon exposure on the risk of lung cancer.

Lung cancer is the leading cause of cancer death in both men and women. Smoking causes 80-90% of cases of lung cancer. In this study, an attempt was made to assess the impact of cigarette smoking on the risk of lung cancer by the so-called threshold-specific energy model. This model allows to analyse the biological effects of radon daughter products on the lung tissue, and is based on the assumption that the biological effect (i.e. cell inactivation) will manifest itself after the threshold-specific energy z0 deposited in the sensitive volume of the cell is exceeded. Cigarette smoking causes, among others, an increase in the synthesis of the survivin protein that protects cells from apoptosis and thereby reduces their radiosensitivity. Based on these facts, an attempt was made to estimate the shape of the curves describing the increase in the oncological effect of radiation as a function of daily cigarette consumption.