Iron Quadrangle, Brazil: Elemental concentration determined by k 0 -instrumental neutron activation analysis Part II: Kale samples

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1 Journal of Radioanalytical and Nuclear Chemistry, Vol. 270, No.1 (2006) Iron Quadrangle, Brazil: Elemental concentration determined by k 0 -instrumental neutron activation analysis Part II: Kale samples M. A. B. C. Menezes, 1 * + H. E. L. Palmieri, 1 ** L. V. Leonel, 1 ** H. A. Nalini Jr., 2 R. Jaimovi 3 1 Nuclear Technology Development Center, Brazilian Commission for Nuclear Energy, CDTN/CNEN, Caixa Postal 941, Belo Horizonte, Brazil * Division for Reactor and Irradiation, Laboratory for Neutron Activation Analysis ** Division for Chemistry and Radiochemistry 2 Federal University of Ouro Preto, Geological Department, Ouro Preto, Brazil 3 Department of Environmental Sciences, Jožef Stefan Institute, Ljubljana, Slovenia (Received April 6, 2006) The objective of this study was to evaluate the influence of mining activity on elemental concentrations in kale grown around a mining area. Two sites studied are in the Iron Quadrangle, Minas Gerais, Brazil, considered one of the richest mineral-bearing regions in the world. One site is near mineral exploration activity and the other is an ecological area. A comparator site outside the Iron Quadrangle was also analyzed. This work focused on the determination of the elemental concentrations in kale applying the k 0 -instrumental neutron activation analysis. As the Brazilian legislation specifies values for soil only, the results for kale were compared to the literature values and it was found that the vegetable does not present any health risks. Introduction The Iron Quadrangle, 1 5 a region located in the Brazilian Minas Gerais State, is rich in mineral occurrences and it is well known for its exploration of iron and gold ores. Associated with the exploration and processing of the ores, several metals are discharged into the environment. The mineral exploration and correlated activities are the main sources of metal contamination in soil, waterways, river sediment and fish. As a step towards evaluating the potential health risk caused by contamination by the mining industry, measurements were carried out to determine elemental concentrations in matrices associated with the food chain. The importance of this study was to reveal the health risks to the population living around the mining areas and growing vegetables for their own use, based only on the elemental concentrations determined. In another study it was verified if mining activity had contaminated the soil in the vegetable gardens. This study has been summarized in a separate paper, 6 where details concerning the sites studied, soil sampling and preparation are given. Completing the assessment, the here presented work applies to kale, verifying if this vegetable suffered from the impact of the pollutants from the soil. Place of the study Inside the Iron Quadrangle, the site selected with mineral exploration activity is called Honório Bicalho (HB) in the district of Nova Lima. This small village is located between a closed gold mine one of the Morro Velho mines and the Das Velhas River. Two other sites were sampled for comparison. One was the Ecological Park of Tripuí (PT) that presents no mineral occurrence of economical interest, and the other site is not inserted in the Iron Quadrangle and does not present any mining activity, region of Barreiro (B). The vegetable chosen to be evaluated was kale, very common in vegetable gardens and in typical food, served almost everyday. Experimental Sampling and sample preparation The kale samples were collected from ten points in each vegetable garden and mixed to compose one sample representative from each vegetable garden and season, totalizing six samples. The kale leaves were washed with deionized water and sliced in small pieces manually. The samples were frozen and then lyophilized. Application of k 0 -instrumental neutron activation analysis The k 0 -instrumental neutron activation method 7 9 was applied for kale, to determine the elemental concentration in the samples. The irradiation was performed in the TRIGA Mark I IPR-R1 reactor located at the Nuclear Technology Development Centre (CDTN) of the Nuclear Energy National Commission (CNEN), at 100 kw, under a thermal flux of n. cm 2. s menezes@cdtn.br /USD Akadémiai Kiadó, Budapest 2006 Akadémiai Kiadó, Budapest Springer, Dordrecht

2 The irradiation was in the carrousel, IC-40. The samples were irradiated simultaneously accompanied by a neutron flux monitor Al Au (0.1%) IRMM-530RA foil cut into discs (diameter of 5 mm, thickness 0.1 mm). Each sample was weighed in a polyethylene vial suitable for irradiation. The mass of the kale analyzed was around 300 mg. To assure the effectiveness of the k 0 - standardization, the reference material GBW Poplar Leaves, 10 was analyzed too. To determine the elements produced radionuclides with short half-lives, the irradiation time was 5 minutes, and 8 hours for medium and long-lived radionuclides. The gamma-spectroscopy was carried out after suitable decay and it was performed by an HPGe detector with 15% relative efficiency. For the spectra analysis and peak area evaluation, the HyperLab program 11,12 was used. The software package KAYZERO/SOLCOI 13 was applied to calculate the elemental concentrations. Results and discussion Table 1 shows the results of the experimental and certified values for the reference material. The results for the kale samples are shown in Table 2 in fresh weight. Unfortunately, it was not possible sampling the kale from Barreiro during the wet season due to plagues. Table 2 also gives the values for the certified reference material Bowen s Kale, 14 which is generally considered to have the best consensus data for elemental concentrations. Except for the elements whose detection limits determined in the CDTN are higher than the concentrations reported for Bowen s Kale, the elemental concentrations for the samples studied are compatible with the literature values. Arsenic is the only element for which higher concentration was found compared to the Bowen s Kale, two kale samples from HB had As levels three times as high. Brazilian environmental legislation and literature The Brazilian Council for Environment (Conselho Nacional do Meio Ambiente CONAMA) has proposed a law concerning the soil quality preservation and contaminated areas management: Proposal of Resolution version No. 11/09/03, Guidelines and Procedures Concerning Soil Quality and the Management of Contaminated Areas (Proposta de resolução versão 11/09/03, Brazil, 2003). However, the Brazilian legislation foresees concentration limits only for some elements in soil. The proposed Resolution established specific values: prevention and intervention values. The former refers to a possible change in the natural quality of the soil and the latter reflects a contamination level. It means that a concentration of any chemical element or parameter is higher than this value, indicates potential health-related risks. Table 3 shows the prevention values in general, the intervention values for exposure in residential areas and the values determined in soil samples. Table 3 also shows the values suggested by the literature 15 for edible plants as well as the results for kale samples. The results are compared to the literature, because the Brazilian legislation, law No. 685 (27th August, 1998), published by Sanitary Brazilian Agency of the Health Ministry (Vigilância Sanitária do Ministério da Saúde, Brazil, 1998), does not specify a maximum elemental concentration allowed for vegetables. Table 1. Elemental concentration (in mg. kg 1 ) in certified reference material GBW Element (GSV-3, Poplar Leaves) Experimental value Certified value Ag <0.6 (0.013) As 0.4 ± ± 0.06 Au < NR Ba <30 26 ± 2 Br 7.2 ± ± 1.1 Ca ± ± 700 Cd < ± 0.05 Ce 0.5 ± ± 0.05 Co 0.60 ± ± 0.03 Cr < ± 0.05 Cs < ± Cu < ± 0.5 Dy <1 (0.036) Eu ± ± Fe 308 ± ± 11 Ga <0.3 NR Hf <0.1 (0.026) Hg < ± Ho <0.2 NR K ± ± 400 La 0.28 ± ± 0.01 Mn 48 ± 2 45 ± 2 Mo < ± 0.01 Na 214 ± ± 10 Nd <5 (0.22) Rb 8 ± ± 0.6 Sb < ± Sc 0.10 ± ± Se < ± 0.01 Sm ± ± Sr 173 ± ± 5 Ta <0.1 NR Tb <0.0 NR Th < ± U <2 (0.028) V <0.9 (0.64) W <0.4 NR Yb < ± Zn 51 ± 3 37 ± 1 NR: Not reported. Non-certified information values in brackets. 118

3 Table 2. Elemental concentration (in fresh weight, mg. kg 1 ) in kale Element Dry season Wet season Bowen s Kale B kale 1 HB kale 2 HB kale 3 PT kale 4 Ag <1 <1 <1 <1 NR As < ± ± 0.02 < Au <0.05 <0.05 <0.05 < Ba <10 <10 <10 <10 NR Br 1.9 ± ± ± ± Ca <3000 <3000 < ± Cd <20 <20 <20 < Ce <1 <1 <1 <1 NR Cl 3117 ± ± ± ± Co <0.1 <0.1 <0.1 < Cr <1 <1 <1 < Cs <0.1 <0.1 <0.1 < Dy <1 <1 <1 <1 NR Eu <0.1 <0.1 <0.1 <0.1 NR Fe <30 <30 <30 35 ± Ga <0.4 <0.4 <0.4 <0.4 NR Hf <0.1 <0.1 <0.1 <0.1 NR Hg <0.1 <0.1 <0.1 <0.1 NR K 5397 ± ± ± ± La <0.05 <0.05 <0.05 < Mn 2.4 ± ± 2 5 ± 1 8 ± Mo <2 <2 <2 < Na 118 ± ± ± 6 10 ± Nd <5 <5 <5 <5 NR Rb <0.5 < ± 1 5 ± Sb <0.02 <0.02 <0.02 < Sc <0.001 <0.001 <0.001 < Se <1 <1 <1 <1 NR Sm <0.03 <0.03 <0.03 <0.03 NR Sr <20 <20 <20 <20 NR Ta <0.001 <0.001 <0.001 <0.001 NR Tb <0.01 <0.01 <0.01 <0.01 NR Th <0.01 <0.01 <0.01 <0.01 NR U <0.1 <0.1 <0.1 <0.1 NR V <1 <1 <1 < W <1 <1 <1 < Yb <0.05 <0.05 <0.05 <0.05 NR Zn 3.6 ± ± ± ± B kale: Kale sample from Barreiro. HB kale: Kale sample from Honório Bicalho. TP kale: Sample from Park of Tripuí. NR: Not reported. For kale, the literature reports only values considered normal for As, Cd, Hg and Sb in edible plants. Even for Cd, with a high detection limit, the results for kale sampled in both sites are compatible with those suggested in the literature. Conclusions The k 0 -instrumental neutron activation analysis, was suitable to determine several elements in the soil and in the biomaterial, kale. It was not necessary to apply any dissolution procedure, which is an important characteristic of this technique, avoiding possible contamination and loss of sample. Solubilization is a sine qua non condition of other techniques such as atomic absorption spectrophotometry or ICP-MS. The high detection limits for some elements are due to current work conditions, which were not optimized for them. In the future, by increasing the reactor power, offering a higher thermal neutron flux, and by improving the detection efficiency, the method will surely be more suitable for such elements. The results obtained in reference materials were in good agreement with the certified values, which illustrates the good accuracy of the technique. The results for kale samples are compatible with the values reported in the literature for the Bowen s Kale certified reference material. 119

4 120 M. A. B. C. MENEZES et al.: IRON QUADRANGLE, BRAZIL: ELEMENTAL CONCENTRATION, PART II

5 Concerning the quality level of the soil according to the Brazilian Legislation, except for those elements whose detection limit are high, the PT soil is considered a reference soil, as the elemental concentration is lower than the prevention values. This result is compatible for an ecological region. Considering the Brazilian proposal for environmental legislation CONAMA only barium (B sample) and arsenic (B, dry season, and HB, dry and wet season, samples) presented higher concentration than the intervention value for residential exposure. According to the quality level, these soils are contaminated. However, it is not possible to affirm the contamination, because of possible natural mineral occurrence. Concerning the biomaterial kale, the concentrations found for these elements are consistent with the existing literature values. This cannot be confirmed for Cd because of the high detection limit. For arsenic, the samples from Honório Bicalho (dry and wet season) presented higher values than those of Bowen s Kale, however, they are within the range of the normal values for edible plants. It is important to emphasise that even growing in a type of soil, which is not a reference soil, the vegetable does not present any health risks. This study was a first assessment of these regions just to give an insight into concentrations of elements in the soil and a vegetable. Further samplings will give more results, better reflecting the quality level of the soil and its impact on other vegetables. * This work was partially supported by the International Atomic Energy Agency under Grant BRA project. References 1. J. MATSCHULLAT, R. P. BORBA, E. DESCHAMPS, B. R. FIGUEIREDO, T. GABRIO, M. SCHWENK, Appl. Geochem., 115 (2000) E. DESCHAMPS, V. CIMINELLI, F. LANGE, J. MATSCHULLAT, B. RAUE, H. SCHMIDT, J. Soils Sediments, 2 (2002) H. S. PIMENTEL, J. C. LENA, H. A. NALINI Jr., Environ. Geol., 43 (2003) L. V. CRUZ, M. Sc. Thesis, Universidade Federal de Ouro Preto, Ouro Preto, Brazil, M. A. B. C. MENEZES, H. E. L. PALMIERI, L. LEONEL, H. A. NALINI Jr., M. E. DESCHAMPS, R. JAIMOVI, Report on the First Research Co-Ordination Meeting, NAHRES-75, International Atomic Energy Agency, Vienna, M. A. B. C. MENEZES, H. E. L. PALMIERI, L. LEONEL, H. A. NALINI Jr., R. JAIMOVI, J. Radioanal. Nucl. Chem., 270 (2006) F. DE CORTE, The k 0 -Standardisation Method; a Move to the Optimisation of Neutron Activation Analysis, Ryksuniversiteit Gent, Gent, B. SMODIŠ, R. JAIMOVI, P. STEGNAR, S, JOVANOVI, J. Radioanal. Nucl. Chem., 160 (1992) M. A. B. C. MENEZES, C. V. S. SABINO, M. B. FRANCO, G. F. KASTNER, E. H. MONTOYA ROSSI, J. Radioanal. Nucl. Chem., 257 (2003) National Research Centre for CRM, Institute of Geophysical and Geochemical Exploration Components, GBW 07604, Langfang, China, A. SIMONITS, J. OSTOR, S. KALVIN, B. FAZEKAS, J. Radioanal. Nucl. Chem., 257 (2003) HYPERLAB-PC V5.0, User s Manual, Institute of Isotopes, Budapest, F. DE CORTE, R. VAN SLUIJS, A. SIMONITS, J. KUCERA, B. SMODIŠ, A. R. BYRNE, A. DE WISPELARE, D. BOSSUS, J. FRANA, Z. HORAK, R. JAIMOVI, Appl. Radiation Isotopes, 55 (2001) S. A. KATZ, J. Radioanal. Nucl. Chem., 251 (2002) J. E. FERGUSSON, The Heavy Elements: Chemistry, Environmental Impact and Health Effects, Pergamon, Oxford,