Hugo Velasco

Universidad Nacional de San Luis · Department of Physics

Under the International Atomic Energy Agency (IAEA) Modelling and Data for Radiological Impact Assessments (MODARIA II) Programme, Working Group 4 activities included collating radionuclide transfer data from Japan following the Fukushima Daiichi Nuclear Power Plant accident and separately collating concentration ratio (CR) data for root uptake of...

In the hilly semi-arid region of central Argentina, where the agricultural frontier expands at the expense of natural ecosystems, soil erosion is one of the most alarming environmental problems. Thus, obtaining knowledge about the dynamics of erosive processes and identifying erosion hotspots constitutes a primary scientific objective. This investi...

In this work we critically assess the soil-to-plant transfer factors (TF) for ¹³⁷Cs and ⁴⁰K in edible fleshy organs of tropical plants that are often components of the human diet. Radionuclide concentrations in soil and plants were obtained from previous investigations developed in Brazil, after the Goiânia radiological accident occurred in 1987. T...

Soil erosion represents a critical socio-economic and environmental hazard for Mexico and the world. Given that soil erosion is a phenomenon influenced by human activities, it is essential to know the level of cultural perspectives on this matter. An instrument with eight scales was applied to 275 university students from a northwestern Mexican cit...

Soil erosion and associated sediment redistribution are key environmental problems in Central Argentina. 14 Specific land uses and management practices, such as intensive grazing and crop cultivation, are 15 considered to be significantly driving and accelerating these processes. This research focuses on the 16 identification of suitable soil trace...

The Chernobyl and Fukushima Dai-ichi Nuclear Power Plant accidents have demonstrated that radiocesium deposited on the ground was one of most important pathway contributions to the air dose rate. Cesium-134 contributes more significantly in the first period of 2-3 y. However, Cs external exposure may remain relevant for decades. The contribution to...

La diversidad biológica en el suelo es amplia y su función ecológica es necesaria para los servicios ecosistémicos que éste provee. Diversas actividades antropogénicas contribuyen a la pérdida de la fertilidad de este recurso y aceleran su erosión. Debido al movimiento del suelo, partículas contaminantes pueden arrastrarse hasta los sitios de depós...

Soil biodiversity is wide and its ecological function is necessary for the ecosystem services it provides. Several anthropogenic activities contribute to the loss of this resource’s fertility and speed up its erosion. As a consequence of ground movement, polluting particles are dragged to sites of deposition (mixtures), generating environmental and...

Soil erosion and associated sediment redistribution are key environmental problems in Central Argentina. Specific land uses and management practices, such as intensive grazing and crop cultivation, are considered significantly driving and accelerating these processes.This research focuses on the identification of suitable soil tracers from hot spot...

This study focuses on the complementary application of two innovative techniques: a) the use of geo-chemical elements as fingerprints to investigate sediment transport and b) to compare the values of 137 Cs soil inventory in an Argentinean site with respect to the local reference value to quantify erosion or sedimentation processes (137 Cs techniqu...

In this work the efficiency calibration curves for a HPGe gamma detector were obtained from soil standards prepared in our laboratory using typical Argentine regional soils. They were made in pot and Petri dish geometries, for different soil granulometries, by using two mixed nuclide reference solutions manufactured by Eckert & Ziegler and provided...

This research focuses on the identification of suitable soil tracers from hot spots of land degradation and sediment fate in an agricultural catchment of central Argentina with erodible loess soils. Using Energy Dispersive X-Ray Fluorescence (EDXRF) for geochemical characterization, element concentrations were used as soil tracers. Tracers were ide...

Cs can be an important environmental contaminant due to fallout from nuclear reactor accidents and atomic weapons testing. Its contribution to the air gamma dose rate at 1 m height above contaminated ground depends on the soil inventory, the migration processes along the soil profile and possible modifications in the spatial distribution. In this p...

Identification of hot spots of land degradation is strongly related with the selection of soil tracers for sediment pathways. This research proposes the complementary and integrated application of two analytical techniques to select the most suitable fingerprint tracers for identifying the main sources of sediments in an agricultural catchment loca...

Large-scale deforestation, intensive land use and unfavourable rainfall conditions are responsible for significant continuous degradation of the Haitian uplands. To develop soil conservation strategies, simple and cost-effective methods are needed to assess rates of soil loss from farmland in Haiti. The fallout radionuclide caesium-137 (137Cs) prov...

We checked the existence of correlations between experimentally determined radon concentration in indoor air and gamma dose rate, in different environments: residences, workplaces in subway stations and radiotherapies, and a gold mine. Except for the mine environment, where a linear correlation (r2 = 0.86) was obtained with statistical significance...

Radon levels in two old mines in San Luis, Argentina, are reported and analyzed. These mines are today used for touristic visitation. Our goal was to assess the potential use of such radioactive noble gas as tracer of geological processes in underground environments. CR-39 nuclear track detectors were used during the winter and summer seasons. The...

Soil-to-plant transfer factors (F v ) are commonly used as a key link to estimate the transference of radionuclides along the human food chain. The use of F v assumes that the radionuclide concentration in plant is linearly related with the radionuclide concentration in soil. However, for different ecosystems and even considering similar soil type...

Beryllium-7 (7Be) is a relatively short-lived radionuclide (half-life 53.3 days) which decays by electron capture either directly to the ground state of 7Li (89.56%) or to an excited state of 7Li (10.44%), which decays to the ground state of 7Li via gamma-ray emission at 477.6 keV. This allows us to easily quantify it by using gamma-ray spectromete...

Concentrations of 137Cs, K and Na in fruits of lemon (Citrus limon B.) and of K and Na in fruits of coconut (Cocos nucifera L.) trees were measured by both gamma spectrometry and neutron activation analysis, with the aim to understand the behaviour of monovalent inorganic cations in tropical plants as well as the plant ability to store these elemen...

There are two naturally occurring radiogenic isotopes of beryllium, (7)Be and (10)Be. These are produced when cosmic radiation interacts with oxygen and nitrogen in the atmosphere. After production, these radionuclides are input to ecosystems through wet and dry deposition. In recent years (7)Be and (10)Be have proved to be powerful tools for study...

In this investigation we evaluate the soil uptake of (137)Cs and (40)K by tropical plants and their consequent translocation to fruits, by calculating the soil-to-fruit transfer factors defined as F(v) = [concentration of radionuclide in fruit (Bq kg(-1) dry mass)/concentration of radionuclide in soil (Bq kg(-1) dry mass in upper 20 cm)]. In order...

Radon levels in two old mines in San Luis, Argentina, are reported and analyzed. The radiation dose and environmental health risk of 222Rn concentrations to both guides and visitors were estimated. CR-39 nuclear track detectors were used for this purpose. The values for the 222Rn concentration at each monitoring site ranged from 0.43 ± 0.04 to 1.48...

Concentrations of K{sup +} and ¹³⁷Cs{sup +} in tissues of the Citrus aurantifolia were measured both by gamma spectrometry and neutron activation analysis, aiming to understand the behavior of monovalent inorganic cations in plants as well as its capability to store these elements. In contrast to K{sup +},Cs{sup +} ions are not essential elemen...

Occupational exposure to respirable crystalline silica and to radiation emitted by natural radionuclides present both in rocks and sands was studied in the Brazilian extractive process and granite product manufacture. Respirable airborne dust samples were collected in working environments, where workers perform different tasks with distinct commerc...

The (7)Be wet deposition has been intensively investigated in a semiarid region at San Luis Province, Argentina. From November 2006 to May 2008, the (7)Be content in rainwater was determined in 58 individual rain events, randomly comprising more than 50% of all individual precipitations at the sampling period. (7)Be activity concentration in rainwa...

Radon and gamma radiation level measurements were carried out inside the La Carolina mine, one of the oldest gold mining camps of southern South America, which is open for touristic visits nowadays. CR-39 track-etch detectors and thermoluminescent dosimeters of natural CaF(2) and LiF TLD-100 were exposed at 14 points along the mine tunnels in order...

There is increasing interest in radiological assessment of discharges of naturally occurring radionuclides into the terrestrial environment. Such assessments require parameter values for the pathways considered in predictive models. An important pathway for human exposure is via ingestion of food crops and animal products. One of the key parameters...

Distribution of 40K and 137Cs in tissues of the Citrus aurantifolia was measured by gamma spectrometry. A simple theoretical model is also proposed to describe the temporal evolution of 40K activity concentration in such tropical woody fruit species. This model exhibits close agreement with the 40K experimental results, in the leaf growing and frui...

In the present paper the contribution to the external gamma dose rate due to 137Cs in soil as a function of time is presented. Sampling sites were selected along the Calabria and Basilicata Regions coastal beaches (southern part of Italy) to assess the external gamma dose rate in air, 1 m above the ground level. A convection-dispersion model, with...

This paper presents a descriptive statistical analysis of radionuclide soil-to-plant transfer factors (Fv) for tropical and subtropical environments. These values were collected from previous databases and standard publications with the objective of contributing to the IAEA Technical Report Series: Handbook of parameter values for the prediction of...

In particular, in 1994 the IAEA published Technical Reports Series No. 364, Handbook of Parameter Values for the Prediction of Radionuclide Transfer in Temperate Environments. Over the years, it has proved to be a valuable reference for radioecologists, modellers and authorities in Member States, and has been quoted in numerous impact assessments....

Caesium uptake by plant roots has been normally associated with the uptake of potassium as the potassium transport systems present in plants have also the capacity to transport caesium. Three grass species (Eragrostis curvula, Cynodon sp and Distichlis spicata) growing in seminatural grassland of central Argentina were selected to study their capab...

In this study, the factors that influence the variability of soil to plant radionuclide transfer factors (TF) in tropical and subtropical environments were statistically analyzed. More than 2,700 TF values were obtained from the literature, and from this four broad soil groups and 13 plant groups were investigated. Additionally, different plant com...

Activity concentrations of 40K, 226Ra and 137Cs have been analyzed in soil and plant samples, collected in permanent grassland in central Argentina. Two near areas (A1 and A2) under field conditions with soil undisturbed at least in the last four decades were selected. For each of the three studied radionuclides we do not find differences in the in...

Beryllium-7 is a natural radionuclide that enters into the ecosystems through wet and dry depositions and has numerous environmental applications in terrestrial and aquatic ecosystems. Atmospheric wet deposition of 7Be was measured in central Argentina. Rain traps were installed (1 m above ground) and individual rain events have been collected. Rai...

Sampling sites, located along the Calabria and Basilicata Regions coastal beaches (south of Italy), were selected to assess the external gamma dose rate in air, 1 m above ground, and to estimate the fraction attributable to the radiocesium and radiopotassium contents along the vertical sand profile. Mean values for the gamma dose rate were: 76±30 n...

Interaction matrices, an expert semi quantitative method to identify multiple interactions among biotic and abiotic components of the ecosystem can be considered as a useful tool to develop conceptual models of the behavior of radionuclides in the environment. This systematic approach facilitates a comprehensible identification of the pathways of t...

A data set of 137Cs and 40K activity values in plant and soil samples, obtained under identical conditions during a four-year period, was analysed in order to determine the temporal trend of the soil-to-plant transfer process. The aggregated transfer factor (Tag) was determined in each sampling site, showing the typical seasonal variations and the...

RSP (Radioecological Software Package) is an interactive support system that simulates the behaviour of radionuclides in semi-natural environments and the consequences on the population in terms of the external exposure. RSP consists of three modules: the first one, soil mobility, simulates the vertical transport of radionuclide in soil using the m...

In the present study we assessed the radiocaesium uptake by plants in order to piece together information on factors affecting the uptake processes, particularly K supply and plant species differences. Vegetation uptake from soil contaminated by the Chernobyl accident was compared at two semi-natural grasslands. The Cs/K discrimination factor (DF),...

To examine the soil-to-plant transfer of 137Cs and 40K, we performed a study based on sampling of natural soil and plants from an alpine pasture site situated in the Giulia Alps, Italy, during July 1997. High 137Cs activity was present in the upper most soil layer, and decreased one order of magnitude at a depth of 10 cm. An opposite gradient was o...

In this paper three transport models are applied to describe the vertical migration process of 137Cs in undisturbed soil. The same experimental data set is used for the calibration of each model. These data were obtained from areas in northeast Italy, where the 137Cs deposition following the Chernobyl accident ranged from 20 to 40 kBq m-2. A diffus...

This paper reports the 90Sr and 137Cs distribution measured in 1987, 1989 and 1990 along a soil profile in a grassland, located in the North of Italy. The vertical distribution of 137Cs in soil due to the Chernobyl accident was used to validate the RABES (RAdionuclides BEhaviour in Soil) model (Velasco et al., 1991).

A mathematical model on the Radionuclide Behaviour in Soil for the study of the migration of radionuclides in undisturbed soil profile has been developed. The model has been calibrated using 134Cs and 137Cs concentrations along soil samples gathered in a natural grassland and beech wood, respectively, located in the Friuli-Venezia Giulia region (no...

En el presente trabajo se calcula la tasa de dosis en aire debida a perfiles de concentración de 137 Cs en suelo en condiciones similares a las medidas experimentalmente en distintos escenarios ambientales. El cálculo se realiza en forma analítica utilizando el método de integración point-kernel. La movilidad vertical en el suelo de la fuente es te...

In this paper, starting from dose rate in air due to gamma emitter radionuclides in soil, changes in dose rate due to source mobility in deep soil are studied. Dose rate is assessed using a Monte Carlo simulation (DAGES code) at a 1 m height above ground for an arbitrary distribution of the contaminant in soil. The radionuclides vertical mobility i...

Vertical migration of 137 Cs global fallout was studied in soils from Argentina. The sampling area is located in natural and semi-natural grassland in San Luis Province (33º 40' S, 65º 23' W), and is positioned within Instituto Nacional de Tecnología Agropecuaria (INTA) of Argentina. To obtain the 137 Cs transport parameters from observed activity-...