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This work presents the results of 137Cs, 40K, 232Th and 238U concentration (Bq kg−1) values in coastal marine sediments collected from 38 sites along the coastline of the island of Margarita, Venezuela. The purpose was to determine baseline values for these radionuclides in surface marine sediments and to detect if there were any anomalously high concentration values. Only three of the 38 sediments analyzed had measurable values above the detection limit of 0.9 Bq kg−1 for 137Cs and the highest only being 1.4 Bq kg−1. While, the concentration (Bq kg−1) ranges for the primordial radionuclides, 40K, 232Th and 238U were as follows: 12.2–211.7, <1.5–9.8 and <4.4–20.7, respectively. These concentration ranges for the primordial radionuclides can be considered as baseline values for surface marine sediments for areas that are considered not polluted by man or contaminated by nature. Finally, the concentration range of 137Cs can also be employed as baseline values, which only seem to have been the result of the atmospheric testing of nuclear weapons in the past. [ABSTRACT FROM AUTHOR]

As a result of routine soil sampling to determine the 137Cs background activities country-wide in Venezuela, it was decided to further investigate El Mirador (Lookout) area at the base of the Sierra de Lema mountain range. In April 2003 (A), soil samples were collected at eight sites on and around the edge of the diabase outcrop to confirm that this area had anomalously high 137Cs activities. In July 2003 (B), not only soil samples were collected again, but also black mat, palm tree leaves and trunks, fruit bushes leaves and its fruit and fern leaves. The 137Cs content was measured by high resolution gamma-ray spectroscopy by a comparative method with reference materials. The 137Cs activity values range from 16.3 to 30.8 Bq·kg-1 in the soil samples collected in July 2003, 20.7–32.1 Bq·kg−1 for the black mat, 26.3–38.4 Bq·kg−1 for the palm leaves, 16.8–31.2 Bq·kg−1 for the palm trunks and 17.6–27.3 Bq·kg−1 for the fruit bush leaves, while, the 137Cs activity values for the whole fruit were between 23.4 and 30.7 Bq·kg−1; but, the value of the 137Cs activity in the center of the fruit (the edible part) was 51.6 Bq·kg−1, and the value of the 137Cs activity for the fern leaves was 51.8 Bq·kg−1. Thus, most of the 137Cs activity values determined in the soil, black mat and vegetation samples from El Mirador (Lookout) were considered anomalously high with respect to those found near the equator and in other areas of Venezuela. Only the center of the fruit from the Clusia grandiflora bushes and the fern leaves had high activity ratios, about a factor of three and could be considered as biomonitors that concentrate and retain the 137Cs. Finally, these anomalously high 137Cs activities have been attributed not only to the rich organic soils, as sinks, but also due to the affect of the cloud forests. [ABSTRACT FROM AUTHOR]

Radon measurements were performed across two sections of the Avila fault near Caracas, Venezuela. The radon concentrations clearly showed the different tectonic features and lithology at the Tacamahaca and Spanish Trail sites. 214Bi (U-cps) measurements also were related to the lithology. The passive radon method employed laboratory-made dosimeters with LR 115, type 2 celulose nitrate films as detectors. They were buried in the ground at 30 cm depth. While, the active radon method was performed with a Pylon radon measurement system with Lucas cells. The soil gas was also sampled at 30 cm depths, but for only one minute, which was sufficient to fill the 150 cm3 Lucas cells completely. The total radon counts were then separated into those corresponding to 222Rn (radon) and 220Rn (thoron) by a simple computer routine. A comparison of the active and passive methods for the Tacamahaca section over a three-month period showed that both methods could locate precisely the active fault trace. [ABSTRACT FROM AUTHOR]

A simple and rapid technique is presented to determine the relative counts of 214Bi in surface soils to locate active fault traces of the El Pilar Fault in the state of Sucre, Venezuela. The method employes a portable differential gamma-ray spectrometer on site with 300 seconds of measuring time. Three transects across the El Pilar fault of very different geological aspects were studied. One of the advantages of this technique in respect to determining 222Rn in soil-gas is that no soil-gas probes are required to be inserted in the soil and it is not necessary to know the appropriate depth. Finally, it has been suggested that measurements of 1000 seconds would be preferred rather than 300 seconds for future studies even though this would limit the number of measurements to about 20 per day. [ABSTRACT FROM AUTHOR]

The original purpose of this investigation started in 1996 was to study the radiological impact on the local population of the village of Chichiviriche de La Costa. But, soon after the major earthquake (Ms=6.8) in the state of Sucre on July 9, 1997, the objective was changed to study the fluctuation of radon (222Rn) to see if it could be correlated to seismic activity and/or if the amonlous change just before the earthquake can be considered a precusor for it. Measurements of222Rn by simply de-gassing about 250 ml of natural thermal water employing a Pylon AB-5 radiation monitor and counting the radiation after it reached equilibrium were performed. The values for four sampling periods in the first half of 1996 were about 17 Bq/l of222Rn, a month before the earthquake they were less than 15 Bq/l and increased about 70% to 25 Bq/l two days before the seismic event. In about two weeks, they returned to about 18 Bq/l. But, surprisingly, they have gradually increased to about 35 Bq/l, before leveling off at about 27 Bq/l. [ABSTRACT FROM AUTHOR]

The concentrations of40K,226Ra,232Th and137Cs were determined in the upper layers of soils in the central coastal region of Venezuela. The activities of137Cs are higher in the areas where the forest is well developed, oriented towards the wind and at higher elevations. The origin of the137Cs deposition is from water input from the clouds directly in the cloudforest and rainfall from the northeast trade winds. Even though the values of137Cs are much higher in these areas, there is little or no significant increase in the health risk. The natural radioactivity is correlated with the geology in the region except in the area of Urama. The values for the natural radiation background are as follows: for potassium between 1–3%, for radium between 1–3 ppm and for thorium the range was 6–39 ppm. The corresponding amounts of absorbed dose rates in air, the exposure rates and the annual effective dose equivalents are in the following ranges respectively: 11–39 pGy/s, 4–16 uR/h and 0.25–0.86 mSv/y. The annual effective dose equivalents include the contribution of the global average (2.57 mSv/y) of the rest of the natural sources of radiation. Finally, the largest natural radioactivity background, was found near Chichiriviche as a result of the massive granite deposits in this area, but again there is no significant health risk. [ABSTRACT FROM AUTHOR]

The activity of137Cs was determined in mosses and their surrounding soils in three Venezuelan cloud forests. The concentration of137Cs in both the mosses and their respective soils were correlated with elevation (m.a.s.l.). This relationship was the result of the cloud forest effect, no direct deposition by condensation below the base of the clouds and increasing deposition of137Cs with the density of the clouds. The ratio of the activity of137Cs in the mosses to their surrounding soils was in general the same for sites near the top of the mountains, but the ratio at the Altos de pipe location was 3.5 times higher than that of the La Sierra mountain. This was explained by the difference in the water content of the surface and the top soil layer. It was concluded that the137Cs measured in the mosses was from the soil effect rather than new deposition of137Cs in the last three years. [ABSTRACT FROM AUTHOR]

The concentration of137Cs, potassium, thorium and uranium for 6 monitoring sites and 32 other sites at the Venezuelan Institute for Scientific Research (IVIC) were presented, as well as, the estimated air dose and exposure rates for each site. The concentration of137Cs was found to be much higher at many sites at IVIC in respect to the average estimated value of137Cs in Venezuela. But, this was determined to be due to a natural cause, the cloud forest which surrounds the higher elevations. The values of potassium, thorium and uranium were compared to values from other parts of northern Venezuela and were found to agree for sites at similar elevations. They were also shown to be about two to three times higher than global estimates. Thus, the air dose and exposure rates were correspondingly two to three times higher too, but the annual dose from the primordial radionuclides in the soil was estimated to be less than 0.1 mSv, which is considered negligible for health risks. [ABSTRACT FROM AUTHOR]