M. A. Bacchi

Ni-Cr Alloy as Neutron Flux Monitor: Composition and Homogeneity Assessment by NAA

A Ni-Cr alloy was chosen as an in-house reference material for neutron flux measurement due to the well-known physical constants of the nuclides or interest and its low cost. The quantification of the Cr and Ni content was performed by neutron activation analysis (NAA), using certified reference materials from NIST as comparators. The concertrations and standard combined uncertainties were 19.32 ± 0.07 % for Cr and 80.2 ± 1.1 % for Ni, and the material is very homogeneous for Cr and moderate homogeneous for Ni.

Brazilian Experience on k0 Standardized Neutron Activation Analysis

After more than ten years working with multicomparator instrumental neutron activation analysis, mainly applied to the characterization of environmental samples, the Radioisotopes Laboratory (CENA/USP) started changing gradually to the k0-method in 1997. The main activities developed, as well as some of the results obtained, are presented here. Even though there is much more work to be done, the good quality of the results and the possibility of elemental determinations without the co-irradiation of standards may lead to the definitive adoption of the k0-method in a near future.

Seleção de epífitas acumuladoras de elementos químicos na Mata Atlântica

Epiphytes are efficient indicators of atmospheric pollution because of their direct uptake of chemical elements from atmosphere. Leaves from eleven species of bromeliads and one species of orchid were collected in the Parque Estadual Carlos Botelho, SP, for determination of sixteen chemical elements. The selection of the best biomonitor species was based on the diversity and accumulation of chemical elements in the leaves. With an average accumulation index of 0.7, Canistropsis billbergioides has potential to be used as a biomonitor of chemical elements in the Atlantic Forest.

A new monitor for routine thermal and epithermal neutron fluence rate monitoring in k0 INAA

The Zr-Au set for monitoring the thermal and epithermal neutron fluence rate and the epithermal spectrum parameter alpha is not always practicable for routine application of INAA in well-thermalized facilities. An alternative set consisting of Cr, Au and Mo provides values for the thermal neutron fluence rate, f and alpha that are not significantly different from those found via the Zr-Au method and the Cd-covered Zr-method. The IRMM standard SMELS-II was analyzed using the (Au-Cr-Mo) monitor and a good agreement was obtained.

RARE EARTH ELEMENTS IN CITRUS PRODUCTION SYSTEMS

This work focuses on the determination of rare earth elements (REE) in citrus ecosystem using instrumental neutron activation analysis (INAA) and inductively coupled plasma mass spectrometry (ICP-MS). A comprehensive sampling was carried out in two organic and two conventional farms in the vicinity of Borborema city, São Paulo State, Brazil. The concentrations of lanthanum (La) in leaves were similar to those found in the soil with soil-to-plant transfer factors ranging from 0.65 to 1.05. The amount of REE decreased sequentially in the compartments soil, leaf, peel, pulp, seed and juice. Citrus plants can be considered accumulators of REE.

Pathway of rare-earth elements in a Brazilian forestry fragment

The Mata de Santa Genebra is a fragment of semi-deciduous tropical forest located in an urban area of Sao Paulo State, Brazil. Potential sources of rare-earth elements (REE), such as oil refinery, agricultural activities and high-traffic roads, are situated close to this region. In this study, the central portion of the fragment dominated by Pachystroma longifolium and Esenbeckia leiocarpa was evaluated for the distribution of La, Ce, Nd, Sm, Eu, Tb and Yb in the soil, leaf and litter sub-compartments applying instrumental neutron activation analysis (INAA). Leaf/soil concentration ratios (CR) of P. longifolium were higher than those obtained for E. leiocarpa by a factor of 20. Considering leaf/litter concentration ratios, no retranslocation of these elements was noticed for both species before litterfall. Accumulation of REE and typical distribution patterns were observed for the plant sub-compartments. The high La content may be attributed to preferential uptake by these plants or to external atmospheric sources.

Amazon estuary — assessment of trace elements in seabed sediments

The interactive processes operating on the continental shelf adjacent to the river mouth control the amount and the characteristics of the Amazon discharge reaching the Atlantic Ocean. In this study, the distribution of trace elemental concentrations, with emphasis to the rare-earth elements, in sediment cores collected at several stations from the Amazon continental shelf during the falling water period was investigated by instrumental neutron activation analysis. Cores from the terrigenous and blue water zones have relatively uniform REE concentrations throughout the profile. Cerium anomalies for samples of the upper section of the eight stations are consistently positive and of high values (normally >2). Similar variation in the elemental concentration ratios between the seabed sediments and Amazon River suspended sediments was seen for stations located in the biogenic and blue water zones, with an enrichment for Ce, Sm, Fe, Th, and Sc and a depletion for the La, Eu, Tb, Yb, Co, Cr, Cs, Hf, Ta, and Zn. The shale-normalized REE patterns from shelf sediments are enriched in LREE relative to HREE, with enrichment factors varying from 1.5 for stations near the river mouth (terrigenous zone) to 1.9 for stations located far in the blue water zone. Published data for the Amazon River suspended sediment agree remarkably well with this observation of LREE-enrichment.

Neutron activation analysis for assessing chemical composition of dry dog foods

Brazil holds the second largest population of domestic dogs in the world, with 33 million dogs, only behind the United States. The annual consumption of dog food in the country is 1.75 million tons, corresponding to the World’s sixth in trade turnover. Dog food is supposed to be a complete and balanced diet, formulated with high quality ingredients. All nutrients and minerals required for an adequate nutrition of dogs are added to the formulation to ensure longevity and welfare. In this context, the present study aimed at assessing the chemical composition of dry dog foods commercialized in Brazil. Thirty-four samples were acquired in the local market of Piracicaba and analyzed by instrumental neutron activation analysis (INAA) to determine the elements As, Br, Ca, Co, Cr, Cs, Fe, K, La, Na, Rb, Sb, Sc, Se, U, and Zn. In general, the concentrations of Ca, Fe, K, Na, and Zn complied with the values required by the Association of American Feed Control Officials (AAFCO). To evaluate the safety of dog food commercialized in Brazil, further investigation is necessary to better understand the presence of toxic elements found in this study, i.e. Sb and U. INAA was useful for the screening analysis of different types and brands of dry dog foods for the determination of both essential and toxic elements.

Arsenic and Chromium in Brazilian Agricultural Supplies

Arsenic (As) and chromium (Cr) contents were measured in agricultural supplies used at different farms in São Paulo State, Brazil. The highest mass fractions of As were found in thermophosphates, reaching levels of 4 mg/kg. The highest mass fractions of Cr (21 g/kg) were found in calcium magnesium silicate, while the thermophosphates also presented high values reaching approximately 1 g/kg. The levels of As were within Brazilian guidelines, but the values of Cr in thermophosphates exceeded the levels permitted in Brazil. The As content in fertilizers may be considered safe (<5 mg/kg) in terms of environmental pollution. However, the Cr content in calcium magnesium silicate following continuous use may constitute a significant problem in Brazil due to potentially increasing levels of this metal in soils.

Informational Asymmetry in the Brazilian Orange Juice Market

Certification, labeling, standardization, traceability, and origin seals take part of a context where the information plays a key role for the guarantee of food safety. However, the available information about food quality attributes is frequently imperfect to consumers, producers, and industry. In the agri-food chain, the consumer is the actor with the lowest degree of information. The main qualitative-quantitative variables of the juice characteristics from different production systems were confronted with an analysis of the consumer perception, in order to clarify the main questions related to the quality of different types of orange juice. The research (185 questionnaires) carried out with consumers of orange juice in the campus “Luiz de Queiroz,” University of São Paulo, Piracicaba, São Paulo state, Brazil, showed that the majority of consumers consider that the information on the labels is not clear. Moreover, about 70% of the interviewed participants did not know the difference between orange juice and nectar. The main reason for consumption of orange juice was the flavor and the main reason for buying a specific brand was the price. The results suggest that the orange juice industries practice an opportunistic attitude, taking advantage of the fact that the consumer is unaware of the legal definition of nectar, different types of orange juices, and information on the labels of different orange juices and nectars.