Geospatial analysis and assessment of 226Ra, 235U, 232Th, 137Cs, and 40K at Anzali wetland, north of Iran.

Achieving better monitoring and radiation risk assessment is among the main issues in environmental studies. In this regard, natural radioactivity measurements in sediments can provide useful information about the environmental transport mechanism and about the sources of radionuclides. Anzali wetland, as the study area of this research, is located on the southwestern shore of the Caspian Sea with rapidly changing ecosystems. Because of its strategic location, increasing pollution levels, decreasing water table, and increasing sediment discharge from rivers, Anzali wetland has a unique significance in terms of studying its radioactivity from sediment and soil samples. The average 226Ra, 235U, 232Th, 137Cs, and 40K values for 33 sediment and soil samples were 24.66, 3.72, 31.94, 11.66, and 506.38 Bq kg-1, respectively. Variography analyses revealed a spatial structure with minimum/maximum variance equal to 3/8 from 135°/45° azimuth direction. In addition, the fractal geometry indicates values higher than 3.7, 24.5, 30, 25, and 475 Bq kg-1 as anomalous values for 235U, 226Ra, 232Th, 137Cs, and 40K using Kriging estimated data with a search radius of 5000 m, respectively. Compared with the average values published by UNSCEAR (2008) for earth's crust average and compared with the values for the southern areas of Iran (Oman Sea), the estimated average and anomalous data for a pollutant at Anzali wetland do not exceed the reference data. The higher values in the samples of this study could be related to specific environmental problems such as industrial wastewater from about 30 polluted factories transported by 10 major rivers. Agricultural wastes, such as herbicides, pesticides, and fertilizers from rice fields, and being a tourist attraction zone at sea beach are the other most possible pollution sources in the study area.

Assessment of 226Ra, 238U, 232Th, 137Cs and 40K activities from the northern coastline of Oman Sea (water and sediments).

Water and sediment samples were collected from northern coast of Oman Sea covering from Goatr to Hormoz canyon seaport. Water and sediment quality assessment for naturally or anthropogenic radionuclides at Oman Sea as a main strategic golf for trade and transit, is an important issue. Correspondence analysis (CA) by R-mode analysis represents that sigma(T)-temperature-conductivity-O2 parameters are well-correlated with 226Ra, 232Th and 40K. Accordingly Q-mode analysis revealed an indicator samples of ST13W for different radionuclides, ST03W for O2, and simultaneously ST34W-ST21W-ST08W-ST04W for sigma(T) parameters. The CA results overlapped with factor and cluster analysis results that explained 85.8% of total variance of water samples. Descriptive analysis of sediments indicates more significant variation than water samples. The 232Th and 226Ra generally showing that ST13D to ST25D sediments that restricted to Pi Bashk coastline are concentrated from 137Cs and 40K. By comparison with reference-values from Iran and other parts of the world, they are acceptable with respect to environmental and radioisotope hazards.

Evaluation of HPGe detector efficiency for point sources using virtual point detector model.

The concept of a virtual point detector (VPD) has been developed and validated in the past for Ge(Li) and HPGe detectors. In the present research, a new semi-empirical equation involving photon energy and source-virtual point detector distance for the efficiency of point sources by HPGe detectors is introduced , which is based on the VPD model. The calculated efficiencies for both coaxial and off-axis geometries by this equation are in good agreement with experimental data. The estimated uncertainties are less than 4%.