H. Papaefthymiou

Indoor radon levels and influencing factors in houses of Patras, Greece

Measurements of indoor radon concentrations were performed in 28 low-rise houses and 30 apartments in Patras area from December 1996 to November 1997, using nuclear track detectors. The investigation was focused on the effects of season and floor number, as well as on the existence of a basement in low-rise houses on indoor radon levels. It was found that the differences in mean radon concentrations between adjacent seasons, in a number of 61 selected sampling sites distributed in 28 houses, were statistically significant. As expected, a maximum was found in winter and a minimum in summer. The differences in mean radon concentration on different floors of the same houses were also statistically significant and followed a linear decrease from underground to 2nd floor. In addition, indoor radon concentrations in the ground floor were found to be influenced by the existence or not of a basement. The average annual radon concentration was found to be 41 Bq m(-3) for the houses, 28 Bq m(-3) for the apartments and 38 Bq m(-3) for all the dwellings. These values lead to an average effective dose equivalent of 1.1, 0.7 and 0.9 mSv y(-1), respectively. Residents living on the underground in low-rise houses, during winter, where the average effective dose equivalent is 2.1 mSv y(-1), attain the higher risk.

Natural radioactivity measurements in the city of Ptolemais (Northern Greece)

Specific activities of the natural radionuclides (238)U, (226)Ra, (232)Th and (40)K were measured by means of gamma-ray spectrometry in surface soil samples collected from the city of Ptolemais, which is located near lignite-fired power plants. The mean activity values for (238)U, (226)Ra, (232)Th and (40)K were found to be 42+/-11, 27+/-6, 36+/-5 and 496+/-56 Bq kg(-1), respectively. These values fall within the range of typical world and Greek values for soil. The indoor radon concentration levels, which were also measured in 66 dwellings by means of SSNTD, ranged from 12 to 129 Bq m(-3), with an average value of 36+/-2 Bq m(-3). This value is close to world and Greek average values for indoor radon concentrations. The total effective dose due to outdoor external irradiation of terrestrial origin and to indoor internal irradiation from the short-lived decay products of (222)Rn was estimated to be 1.2 mSv y(-1) for adults, which is lower than the global effective dose due to natural sources of 2.4 mSv y(-1).

Assessment of PM2.5 sources and their corresponding level of uncertainty in a coastal urban area using EPA PMF 5.0 enhanced diagnostics

Datasets that include only the PM elemental composition and no other important constituents such as ions and OC, should be treated carefully when used for source apportionment. This work is demonstrating how a source apportionment study utilizing PMF 5.0 enhanced diagnostic tools can achieve an improved solution with documented levels of uncertainty for such a dataset. The uncertainty of the solution is rarely reported in source apportionment studies or it is reported partially. Reporting the uncertainty of the solution is very important especially in the case of small datasets. PM2.5 samples collected in Patras during the year 2011 were used. The concentrations of 22 elements (Z=11-33) were determined using PIXE. Source apportionment analysis revealed that PM2.5 emission sources were biomass burning (11%), sea salt (8%), shipping emissions (10%), vehicle emissions (33%), mineral dust (2%) and secondary sulfates (33%) while unaccounted mass was 3%. Although Patras city center is located in a very close proximity to the citys harbor, the contribution of shipping originating emissions was never before quantified. As rotational stability is hard to be achieved when a small dataset is used the rotational stability of the solution was thoroughly evaluated. A number of constraints were applied to the solution in order to reduce rotational ambiguity.

Trace metals in lignites and ashes of Greek power plants

In continuation, of an early study of trace metal /TM/ccontent of Greek lignites and power plant ashes, taken to assess mobilization of TM in Greece by the operation of power plants, new data are presented. Both power plant sites in Greece, i. e. /a/ Northern /Ptolemais, Kardia/, and /b/ Southern /Megalopolis/ have been examined for trace metal content in ashes and in locally used lignites. Instrumental neutron activation analysis /INAA/ was used to determine the content of about 30 minor and major elements. The uranium content of southern Greek lignites was found again to be exceptionally high. The new data are correlated with those of our previous investigation.

Determination of water-soluble and insoluble elements in PM2.5 by ICP-MS

The elemental composition of water-soluble and acid-soluble fractions of PM2.5 samples from two different Greek cities (Patras and Megalopolis) was investigated. Patras and Megalopolis represent different environments. Specifically, Patras is an urban environment with proximity to a large port, while Megalopolis is a small city located close to lignite power plants. Both cities can serve as a representative example of European cities with similar characteristics. The concentration of 14 elements (As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Fe, Sr, Ti, V and Zn) was determined in each fraction by ICP-MS. Microwave assisted digestion was used to digest the samples using a mixture of HNO3 and HF. For the determination of the water soluble fraction, water was chosen as the simplest and most universal extraction solvent. For the validation of the extraction procedure, the recoveries were tested on two certified reference materials (NIST SRM 1648 Urban Particulate Matter and NIST 1649a Urban Dust). Results showed that Zn has the highest total concentration (273 and 186 ng/m(3)) and Co the lowest (0.48 and 0.23 ng/m(3)) for Patras and Megalopolis samples, respectively. Nickel with 65% for Patras and As with 49% for Megalopolis displayed the highest solubility, whereas Fe (10%) and Ti (2%) the lowest ones, respectively.

Uranium and other natural radionuclides in the sediments of a Mediterranean fjord-like embayment, Amvrakikos Gulf (Ionian Sea), Greece.

The distribution of the natural radionuclides ((238)U, (232)Th, (226)Ra, (40)K) and the artificial (137)Cs was studied in sediment cores collected from Amvrakikos Gulf, a seasonal anoxic marine basin, using γ-ray spectrometry. The activity of radionuclides, along with the concentrations of Fe and Mn, were also studied in relation to the total organic carbon and the granulometric fractions of the sediments. The results obtained revealed higher (238)U activity concentrations in all the examined sediment samples compared to the world and Greek average values for soil. The high activity values of (238)U are attributed, besides the lattice-held fraction, to phosphate fertilizer inputs in the Gulf via major rivers and/or to alteration processes of phosphate ores located mainly in the drainage basin of the river Louros. The elevated activity values of (40)K could be attributed to the mineralogical composition of the sediments and to phosphate fertilizers containing potassium. Organic matter seems to be a more efficient sorbent for U than clay minerals and amorphous Fe and Mn-oxyhydroxides. Scanning electron microscopy, together with qualitative analysis of some smectites, reveals the occurrence of U, suggesting a limited absorption of U onto clay minerals. The applied BCR sequential extraction procedure revealed that U was found mainly in the refractory phase or associated with organic matter and to a lesser extent as surface-coating oxides, with the exception of one sediment core which is characterized by high content of fresh marine organic matter and presents high percentage of U in the exchangeable fraction.

Natural radioactivity content of granite tiles used in Greece

Measurements of (226)Ra, (232)Th and (40)K activity concentrations in commercial granite tiles imported in Greece were performed using gamma-ray spectrometry. The activity concentration of (226)Ra, (232)Th and (40)K ranged from 1 to 434, 2 to 239 and 71 to 1576 Bq kg(-1), respectively. The calculated activity concentration index (I) values for all granite samples examined were found to be within the EC limit values for superficial and other materials with restricted use.

Oscillatory annealing and temperature effect of neutron irradiated crystalline chemical compounds

Abstract The oscillation component of the isothermal annealing curves of neutron irradiated crystalline tris-ethylenediamine cobalt (III) nitrate, magnesium and potassium chromate, isolated from various isotherms is presented in detailed form and studied kinetically. A temperature effect on the oscillation frequency and amplitude is also demonstrated. The experimental evidence strengthens the postulation for a possible solid state oscillation phenomenon independent of the chemical constitution of the lattice, due to thermodynamical conditions of irreversible processes. The Volterra-Lotka model is used for interpretation of the phenomenon.

Spatial and vertical distribution and risk assessment of natural radionuclides in soils surrounding the lignite-fired power plants in Megalopolis basin, Greece.

Twenty soil profile samples and fourteen surface soil samples collected from the vicinity of the lignite-fired power plants in the Megalopolis basin (Greece) were analysed for their natural radionuclide concentration and (137)Cs, since fossil fuels are associated with naturally occurring radioactive materials and hence with radiological impact. No significant enhancement of surface soil radioactivity levels in the vicinity of lignite-fired plants was observed. A downcore decreasing trend of (137)Cs was observed in a number of cores reflecting its atmospheric origin, whereas the uniform distribution observed in a number of other cores gave information on the mechanical alteration of the soil. The average dose rate value was found to be 63 ± 22 nGy h(-1), while the annual average effective dose from the terrestrial gamma radiation was found to be 0.08 ± 0.03 mSv.

Natural radionuclides content and associated dose rates in fine-grained sediments from Patras-Rion sub-basins, Greece.

The activity concentrations of the natural radionuclides (238)U, (226)Ra, (232)Th and (40)K were measured in soil samples collected from the Patras-Rion sub-basins (Southern Greece) and were found to be 28, 27, 30 and 483 Bq kg(-1), respectively. These values compare well with the average Greek and worldwide values for crustal soil and sedimentary rocks. The mean (226)Ra/(238)U activity ratio was close to 1, implying secular radioactive equilibrium in the uranium series. All soil samples have Ra(eq) values lower than the limit of 370 Bq kg(-1), indicating their safe use in brick production. The average annual terrestrial absorbed dose rate in air was 51±14 nGy h(-1), and the average annual effective dose 0.06±0.02 mSv y(-1), which is consistent with the average worldwide exposure to external terrestrial radiation outdoors (0.07 mSv y(-1)). Non-significant differences between soils with different age and depositional environments were found, which could be attributed to a common source of sediments.