Seasonal variations of aerosol residence time in the lower atmospheric boundary layer

During a one year period, from Jan. 2002 up to Dec. 2002, approximately 130 air samples were analyzed to determine the atmospheric air activity concentrations of short- and long-lived (222Rn) decay products 214Pb and 210Pb. The samples were taken by using a single-filter technique and gamma-spectrometry was applied to determine the activity concentrations. A seasonal fluctuation in the concentration of 214Pb and 210Pb in surface air was observed. The activity concentrations of both radionuclides were observed to be relatively higher during the winter/autumn season than in spring/summer season. The mean activity concentration of 214Pb and 210Pb within the whole year was found to be 1.4+/-0.27 Bq m(-3) and 1.2+/-0.15 mBq m(-3), respectively. Different 210Pb:214Pb activity ratios during the year varied between 1.78 x 10(-4) and 1.6 x 10(-3) with a mean value of 8.9 x 10(-4) +/- 7.6 x 10(-5). From the ratio between the activity concentrations of the radon decay products 214Pb and 210Pb a mean residence time (MRT) of aerosol particles in the atmosphere of about 10.5+/-0.91 d could be estimated. The seasonal variation pattern shows relatively higher values of MRT in spring/summer season than in winter/autumn season. The MRT data together with relative humidity (RH), air temperature (T) and wind speed (WS), were used for a comprehensive regression analysis of its seasonal variation in the atmospheric air.     

Life cycle assessment of using laser treatment and nanomaterials to produce biogas through anaerobic digestion of slurry

Environment, Development and Sustainability - Recently, laser radiation and nanomaterials have been utilized to improve biogas yield via anaerobic digestion of herd’s manure through...     

A study on natural radiation exposure in different realistic living rooms

In the first part of the paper, the factors affecting 222Rn properties in 25 different realistic living rooms (with low ventilation rates) of different houses in El-Minia City (Upper Egypt) have been studied; they included the activity concentration of 222Rn gas (C(o)), the unattached fraction (f(p)) of 218Po and 214Pb, the unattached potential alpha energy concentration (PAEC) and the equilibrium factor (F). The activity distributions of unattached 218Po and 214Pb as well as for the PAEC were determined. With a dosimetric model calculation [ICRP, 1994b. Human Respiratory Tract Model For Radiological Protection. Pergamon Press, Oxford. ICRP Publication 66] the total deposition fraction of unattached 218Po and 214Pb in human respiratory tract was evaluated to determine the total equivalent dose. An electrostatic precipitation method and a wire screen diffusion battery technique were both employed for the determination of 222Rn gas concentration and its unattached decay products, respectively. The mean activity concentration of 222Rn gas (C(o)) was found to be 110+/-20 Bq m(-3). The mean unattached activity concentrations of 218Po and 214Pb were found to be 0.6 and 0.35 Bq m(-3), respectively. A mean unattached fraction (f(p)) of 0.09+/-0.01 was obtained at a mean aerosol particle concentration (Z) of (2.9+/-0.23) x 10(3)cm(-3). The mean equilibrium factor (F) was determined to be 0.31+/-0.02. The mean PAEC of unattached 218Po and 214Pb was found to be 8.74+/-2.1 Bq m(-3). The activity distributions of 218Po and 214Pb show mean activity median diameters (AMD) of 1.5 and 1.85 nm with mean geometric standard deviations (SD) of 1.33 and 1.45, respectively. The mean activity distribution of the PAEC shows an AMD of 1.65 nm with a geometric standard deviation of 1.25. At a total deposition fraction of about 97% the total equivalent dose to the lung was determined to be about 133 microSv. The second part of this paper deals with a study of natural radionuclide contents of samples collected from the building materials of the rooms under investigations in part one. Analyses were performed in Marinelli beakers with a gamma multichannel analyzer equipped with a NaI(Tl) detector. The samples revealed the presence of the uranium-radium and thorium radioisotopes as well as 40K. Nine gamma-lines of the natural radioisotopes corresponding to 212Pb, 214Pb, 214Bi, 228Ac, 40K and 208Tl were detected and measured. The activity concentrations of 226Ra, 232Th and 40K were determined with mean activity concentrations of 58+/-19, 31+/-11 and 143+/-62 Bq kg(-1), respectively. These activities amount to a radium equivalent (Ra(eq)) of 113 Bq kg(-1) and to a mean value of external hazard index of 0.31.