Tripob Bhongsuwan

Airborne radionuclides in mosses collected at different latitudes.

Terrestrial mosses are a promising medium for investigation and monitoring of airborne radionuclide depositions due to their widespread occurrence, ease of sampling, and the possibility of high-resolution gamma spectrometry measurements without preparatory chemical treatment of samples. The overall objective of the present study was to compare (7)Be, (210)Pb and (137)Cs activity concentrations (in Bq/kg) in moss samples collected at two different climate zones: the south of Thailand (7 °N) and in Serbia (∼45 °N) in order to examine deposition of airborne radionuclide in these distant areas. Significant difference of the (210)Pb content (almost a factor of 2) in mosses was observed. The mean value of (7)Be activity in samples from Serbia was almost 40% higher than activity of those collected in Thailand. Level of (137)Cs in Thailand mosses was below the detection limit. It was shown that air transport of water droplets in the area of waterfalls and strong turbulence can deposit U and Th daughter nuclei.

The 7Be profiles in the undisturbed soil used for reference site to estimate the soil erosion

The cosmogenic radionuclide 7Be is increasingly used to obtain information on event-related soil erosion rates within agricultural landscapes. In this study, we select two undisturbed and flat areas to calculate the reference inventory and relaxation mass depth by using 7Be technique to document short-term erosion. Our results showed that the depth distribution of 7Be in undisturbed soil profiles was 1.0 cm in sites S02 and S03; the initial activities were 31.6 and 38.8 Bq.kg-1, respectively. The relaxation mass depths were 5.4 and 7.2 kg.m-2 and the measured reference 7Be inventories were 71 and 110 Bq.m-2 for sites S02 and S03, respectively. The difference values of the relaxation mass depth and the reference inventory of both sites implied that for determining a short term soil erosion using 7Be, the reference site was suggested to be selected as close as possible to the study site.

Measurement of 7Be inventory in the outer Songkhla lagoon, Thailand

The main objective of this study is to estimate the sediment distribution pattern in the outer part of the Songkhla Lagoon, in southern Thailand, by measuring the cosmogenic 7Be in the lake bottom sediment cores. The results indicate that 7Be inventories are larger in the areas where channels collecting water from large subcatchments flow into the lake (mouths of Pak Ro, U-Tapao, Ro-1, and Ro-3 canals). Lower 7Be inventory areas are observed near mouth of channel transporting eroded materials from smaller subcatchments and at the northern tip of Koh Yo island, which is strongly influenced by tidal currents and wind waves which can probably cause sediment re-suspension.

A high natural radiation area in Khao-Than hot spring, Southern Thailand

Natural radioactivity in Khao-Than hot spring area, Surat Thani Province, Thailand was investigated. Gamma dose survey indicated a possible high radiation risk for this area. Rock, soil and hot spring mud samples were collected and analysed by a low background gamma spectrometer. The activity concentrations of (226)Ra, (232)Th and (40)K in samples were 151-139 092 (mean = 13 794), 12-596 (127), 24-616 (215) Bq kg(-1), respectively. X-ray diffraction and Fourier transform infrared spectroscopy indicated that quartz and calcite (CaCO3) are the main constituents in mud samples with varying contents. In conclusion, this study area was reasonably classified as a high natural background radiation area. The source of radium in this area is supposed to be related to the fault fluids enriched in radium that precipitated with calcium in the carbonate terrain and partly absorbed by high cation exchange capacity clays.