Radioactive Soil Characterization of State of Sao Paulo-Brazil

Goro Hiromoto, PhD, Instituto de Pesquisas Energeticas e Nucleares, Av. Prof. Lineu Prestes 2242, Sao Paulo, SP, CEP 05508-000, Brasil, Tel: 55 11 3816-9234, Fax: 55 11 3816-9240, Email: hiromoto@ipen.br
Ana Claudia Peres, MSc, Instituto de Pesquisas Energeticas e Nucleares, Av. Prof. Lineu Prestes 2242, Sao Paulo, SP, CEP 05508-000, Brasil, Tel: 55 11 3816-9287, Fax: 55 11 3816-9206, Email: acperes@ipen.br
Maria Helena Taddei, MSc, Comissao Nacional de Energia Nuclear, Laboratorio de Poços de Caldas, Rod. Andrade-Poços de Caldas km 13, Poços de Caldas, MG, CEP 37701-970, Brasil, Tel: 55 35 3722-4010, Fax: 55 35 3722-3622, Email: mhtaddei@cnen.gov.br
Marcio Roberto Soares, PhD, Universidade Federal de Sao Carlos, Centro de Ciencias Agrarias, Rod. Anhanguera km174, Araras, SP, CEP 13600-970, Brasil, Tel: 55 19 3543-2616, Fax: 55 19 3543-2616, Email: mrsoares@cca.ufscar.br  
Luís Reynaldo Ferracciú Alleoni, PhD, Universidade de São Paulo/Escola Superior de Agricultura Luiz de Queiroz, Av. Pádua Dias, 11, Piracicaba, SP, CEP 13418-900, Brasil, Tel: 55 19 3429-4171, Fax: 55 19 3434-5354, Email: lrfalleo@esalq.usp.br.

For the proper management of the soil and groundwater quality, background levels of toxic element in such ecossystems should be known. The aim of this study is to determine quality reference values for radioactive contents in representative soils of São Paulo State – Brazil.

Thirty samples were collected and activity concentration of U-nat, Th-nat, Ra-228, Ra-226, Pb-210, Po-210, Cs-137 and K-40 were evaluated and corrrelated with soil mineralogical characteristics. The type and local of the soil collected were chosen according to their representativity and spatial distribution in the State geological formation, as well as taking into account the nearness from large urban areas. The samples were measured by passive gamma spectrometry and sequencial chemical extraction followed by alpha spectrometry. Results showed a wide variation on background levels for natural radionuclides of the uranium and thorium series and very low concentration of Cs-137 due to the radioactive fallout precipitation.

Understanding the Spatial Distribution of Soil Contaminants:  A Technique for Evaluating Anthropogenic and Geomorphic Disturbances using Fallout Plutonium

Michael E. Ketterer, Ph.D., Department of Chemistry and Biochemistry, Northern Arizona University, 20 South Beaver St., Flagstaff, Arizona, 86011, Tel: 928-523-7055, Fax: 928-523-8111, Email: Michael.ketterer@nau.edu
Amanda D. Astorga, Department of Chemistry and Biochemistry, Northern Arizona University, 20 South Beaver St., Flagstaff, Arizona, 86011, Tel: 602-432-7879, Fax: 928-523-8111, Email: ada29@nau.edu
Paul T. Gremillion, Ph.D., Civil & Environmental Engineering Department, Northern Arizona University, 69 McConnell Drive, Flagstaff, Arizona 86011, Tel: 928-523-5382, Fax: 928-523-2300, Email: paul.gremillion@nau.edu

Studies of soil surface contaminants frequently evaluate the spatial pattern of pollutants.  This information is needed for understanding sources, prediction, interpolation, and determining pollutant quantities. Geostatistical procedures assume the contaminant concentration is a regionalized variable, exhibiting a range defined by a semivariogram.  Geostatistics frequently fails; the presence of many anomalous “disturbed” samples produces a large “nugget effect”.

Both anthropogenic and geomorphic processes re-distribute soil and contaminants in the surface environment.  Human factors include cultivation, replacement of soil with “fill”, and grading of sites for construction and development.  Geomorphic processes consist of sheet and rill erosion, and aeolian transport.  These factors are omnipresent; there is no way in advance, other than using subjective field observations, to evaluate “disturbance”.  Locations that are “disturbed” are unlikely to contain complete inventories of a pollutant; hence “disturbed” locations cannot fit a spatial pattern reflecting the original deposition of the contaminant.  Interpretation of the spatial distribution becomes complex or impossible.

We present an approach to evaluate the degree of disturbance of surface soils based upon measurements of plutonium activities.  Plutonium was deposited globally on the Earth’s surface from 1950’s-1960’s nuclear weapons tests, and is mainly present in the top 30 cm of the soil profile.  The deposition inventory (^239+240Pu, Bq/m²) is a locally uniform value and a predictable function of latitude and precipitation.  Anthropogenic or geomorphic re-distribution of soils alter the original Pu inventory and depth distribution; hence Pu measurements can be used to evaluate the degree of soil “disturbance” in the past 50 years.  Rapid determination of ^239+240Pu in large numbers of samples is economically feasible using ICPMS.

We present the basis for the technique and examples of its use in studying contaminants deposited from non-ferrous metal smelters in arid areas.  These settings are severely affected by human and geomorphic processes; incorporating ^239+240Pu information improves interpretations of the spatial patterns of contaminants.

Indoor Radon: Short- and Long-Term Influence of Prolonged Precipitation

Douglas Mose, George Mushrush, and George Siaway, Chemistry Department, George Mason University, Fairfax, VA 22030, Tel: 703-273-2282, Email: dje42@aol.com

For long-term radon measurements, home occupants are allowed by USEPA recommendations to open windows. Although the partial vacuum caused by rising warm air in a home is diminished when windows are open, rainfall still increases indoor radon concentrations. Our studies have shown that a significant rainfall (more than 1/4" in one event) increases radon until the rain stops and evaporation begins. More importantly, we found that a season of above-average rainfall produces above-average radon concentrations, even if a measurement is taken during a non-rainfall interval. This seasonal effect can result in measurements that are atypical for a home.    

Studying Natural Radioactivity of River Water, Armenia  

Armen K. Saghatelyan, Doctor of sciences, Director of the Center for Ecological-Noosphere Studies of the National Academy of Sciences of the Republic of Armenia, 68 Abovian Str., Yerevan 375025, Armenia, Tel: (+374-10)569 331, Fax: (+374-10)580 254, Email: ecocentr@sci.am
Anna G. Nalbandyan, Ph.D., Laboratory of Radioecology, the Center for Ecological-Noosphere Studies of the National Academy of Sciences of the Republic of Armenia, 68 Abovian Str., Yerevan 375025, Armenia, Tel: (+374-91)500 731, Fax: (+374-10)580 254, Email: annag9@yahoo.com
Armen A. Stepanyan, Ph.D., Central Analytical Laboratory, the Center for Ecological-Noosphere Studies of the National Academy of Sciences of the Republic of Armenia, 68 Abovian Str., Yerevan 375025, Armenia, Tel: (+374-91)424 860, Fax: (+374-10)580 254, Email: h_armenian@hotmail.com

The level of natural radioactivity of river water directly depends on chemical composition of riverbed forming rocks and soils. Basically, such a level is conditioned by radioactive isotope ⁴⁰K - a constant constituent of total K in naturally occurring set of isotopes that makes 0,0118% of it.

The goal of this research is analyzing natural river water radioactivity through total K-based recalculation of ⁴⁰K ratio and justification of compatibility of measurement results. The research is being performed in the frame of an ongoing NATO SfP project “South Caucasus River Monitoring” (http://www.kura-araks-natosfp.org). Chemical analyses of total K were initiated in 2004 and 2005, and radiometric measurements have just been launched.

Established are two basic tendencies for seasonal variations in river water radioactivity: 1. decrease (spring flood) - peak (summer) - decrease (fall), 2. decrease (spring flood) – steady increase from summer to the end of fall.     

The following results were obtained for annual variations of total K (measured) and ⁴⁰K (recalculated): in 2004 and 2005, respectively, total K was changing 1 to 10 mg/L and 0.9 to 11.8 mg/L, whereas ⁴⁰K calculations were 0.03 to 0.30 Bq/L and 0.03 to 0.35 Bq/L. Gamma-spectrometric measurements of ⁴⁰K in some samples collected in winter 2006 varied 0.07 to 0.25 Bq/L. Thus, collation of preliminary results for winter periods 2004-2006 allows establishing some 15% difference between recalculated and measured data.

The research is still in progress and more data will have been obtained on a monthly basis by the end of 2006.

Determination of Screening Level for Soil Radioactive Contamination

Ana Claudia Peres, MSc. Instituto de Pesquisas Energeticas e Nucleares, Av. Prof. Lineu Prestes 2242, Sao Paulo, SP, CEP 05508-000, Brasil, Tel: 55 11 3816-9287, Fax: 55 11 3816-9206. E-mail: acperes@ipen.br
Goro Hiromoto, PhD, Instituto de Pesquisas Energeticas e Nucleares, Av. Prof. Lineu Prestes 2242, Sao Paulo, SP, CEP 05508-000, Brasil, Tel: 55 11 3816-9234, Fax: 55 11 3816-9240. E-mail: hiromoto@ipen.br

At the present, decision about clean-up of sites contaminated with radioactive elements has been addressed case-by-case, since there is no general guidance or recommendation to deal with in our country, at early phases of the problem identification. For chemicals, CETESB - the governmental organization in charge of preventing and controlling environmental pollution in São Paulo State - has established quality reference, prevention and intervention values, as the first step in order to implement a remediation policy based on human health risk assessment. The aim of this study is to develop a methodology for the establishment of target values for radioactive soil contamination, as far as possible consistent and compatible with the approach adopted by CETESB for sites contaminated with chemicals.

The following steps has been addressed in this study: conceptual scenario and model development; codification of the equations in an electronic spreadsheet; choosing of proper input values; derivation of the prevention and intervention levels for selected radionuclides using Monte Carlo approach. The mathematical model developed was mainly based on the equations used by U.S. Environmental Protection Agency and National Council on Radiation Protection and Measurements for soil screening purposes.

Results are presented for selected natural and man-made radioactive elements.

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