Abnormal high natural radium concentration in surface waters

Unexpected high 228Ra concentrations, up to 2 Bq 1(-1), were found in waters of a coastal lagoon close to a monazite sand separation plant. Due to their use as process waters in this plant, the initial supposition was a contamination related to its operation. However, it was concluded that these abnormal radium concentrations had a natural origin, springs at the lagoon head area with high 228Ra and 226Ra concentrations. The strong relationship among radium and light rare-earth elements (LREEs), the observed 228Ra/226Ra activity ratio and the rare-earth element pattern in the spring waters suggested that monazite is the main source of nuclides for water, indicating the disturbance of monazite chemical stability by the combined effects of low pH and high salinity. Both factors combined allow relatively low mobility of thorium, but, on the other hand, a relatively high mobility of radium and LREEs.     

Daily ingestion of 232Th, 238U, 226Ra, 228Ra and 210Pb in vegetables by inhabitants of Rio de Janeiro City

The concentrations of the naturally occurring radionuclides 232Th, 238U, 210Pb, 226Ra and 238Ra were determined in the vegetables (leafy vegetables, fruit, root, bean and rice) and derived products (sugar, coffee, manioc flour, wheat flour, corn flour and pasta) consumed most by the adult inhabitants of Rio de Janeiro City. A total of 88 samples from 26 different vegetables and derived products were analyzed. The highest contribution to radionuclide intake arises from bean, wheat flour, manioc flour, carrot, rice, tomato and potato consumption. The estimated daily intakes due to the consumption of vegetables and derived products are 1.9 mBq of 232Th (0.47 microg), 2.0 mBq of 238U (0.17 microg), 19 mBq of 236Ra, 26 mBq of 210Pb and 47 mBq of 228Ra. The estimated annual effective dose due to the ingestion of vegetables and their derived products with the long-lived natural radionuclides is 14.5 microSv. Taking into account literature data for water and milk from Rio de Janeiro the dose value increases to 29 microSv, with vegetables and derived products responsible for 50% of the dose and water for 48%. 210Pb (62%) and 228Ra (24%) were found to be the main sources for internal irradiation.     

Can Hediste diversicolor (Nereidae, Polychaete) be considered a good candidate in evaluating PAH contamination? A multimarker approach

The aim of this study was to develop a preliminary characterization of the biological responses of Hediste diversicolor to polycyclic aromatic hydrocarbons (PAHs) under controlled laboratory conditions. In order to test the effects of PAH exposure, a battery of biomarkers was applied to the polychaetes by exposing them to sublethal concentrations of benzo[a]pyrene (0.1 and 0.5 mg L⁻¹) for 10 d under laboratory conditions. The battery of biomarkers tested included oxidative stress biomarkers (glutathione content, enzymatic activities of catalase, glutathione S-transferases, glutathione reductase, glutathione peroxidases), total oxyradical scavenging capacity (TOSC) toward peroxyl and hydroxyl radicals and activity of acyl CoA oxidase (AOX) as a marker of peroxisome proliferation measured in the entire body; lipofuscin and neutral lipid accumulations and levels of Ca²⁺-ATPase activity analyzed in the intestinal epithelium; lysosomal membrane stability and genotoxic effects measured as DNA strand breaks and frequency of micronuclei in coelomocytes. Chemical analyses were also carried out to verify the polychaete’s benzo[a]pyrene (B[a]P) bioaccumulation levels after the exposure period. The results obtained indicate that B[a]P caused significant changes in most of the parameters measured in H. diversicolor. Biological responses to the organic compound were particularly significant for the biomarkers measured in the intestinal epithelium and in coelomocytes, emphasizing that these tissues were more affected during our experimental conditions. Considering the key trophic role of this benthic species in estuarine and coastal ecosystems, this study confirmed that H. diversicolor is an appropriate bioindicator of organic contamination.     

Radium and uranium levels in vegetables grown using different farming management systems

Vegetables grown with phosphate fertilizer (conventional management), with bovine manure fertilization (organic management) and in a mineral nutrient solution (hydroponic) were analyzed and the concentrations of ²³⁸U, ²²⁶Ra and ²²⁸Ra in lettuce, carrots, and beans were compared. Lettuce from hydroponic farming system showed the lowest concentration of radionuclides 0.51 for ²²⁶Ra, 0.55 for ²²⁸Ra and 0.24 for ²³⁸U (Bq kg⁻¹ dry). Vegetables from organically and conventionally grown farming systems showed no differences in the concentration of radium and uranium. Relationships between uranium content in plants and exchangeable Ca and Mg in soil were found, whereas Ra in vegetables was inversely correlated to the cation exchange capacity of soil, leading to the assumption that by supplying carbonate and cations to soil, liming may cause an increase of U and a decrease of radium uptake by plants. The soil to plant transfer varied from 10⁻⁴ to 10⁻² for ²³⁸U and from 10⁻² to 10⁻¹ for ²²⁸Ra.     

WATER QUALITY MODEL CALIBRATION: A COMPARISON OF INPUT AND OUTPUT ERROR CRITERIA1

ABSTRACT: A common framework for the analysis of water resources systems is the input-parameter-output representation. The system, described by its parameters, is driven by inputs and responds with outputs. To calibrate (estimate the parameters) models of these systems requires data on both inputs and outputs, both of which are subject to random errors. When one is uncertain as to whether the predominant source of error is associated with inputs or outputs, uncertainty also exists as to the correct specification of a calibration criterion. This paper develops and analyzes two alternative least squares criteria for calibrating a numerical water quality model. The first criterion assumes that errors are associated with inputs while the second assumes output errors. Statistical properties of the resulting estimators are examined under conditions of pure input or output error and mixed error conditions from a theoretical perspective and then using simulated results from a series of Monte Carlo experiments.     

The reproductive cycle of the Thecosomatous pteropod Limacina retroversa in the western South Atlantic

The reproductive cycle of Limacina retroversa in the Argentine Sea was studied by gonadal analysis. Samples were collected in 1978–1979. The relation between gonadal maturity and size is dependent on the season and the geographical area. Evidence of in situ reproduction was found at the beginning of spring and at the end of summer, indicating that the life cycle in the area consists of two generations per year. In accordance with the season of birth, both generations develop different strategies. Individuals born in spring mature early and reproduce before the end of summer. The offspring born in summer survive the cold season without reaching sexual maturity and reproduce in the following spring.