HEAVY METAL ANALYSIS IN GROUNDWATER SAMPLES BY SR-TXRF

Transcription

1 2005 International Nuclear Atlantic Conference - INAC 2005 Santos, SP, Brazil, August 28 to September 2, 2005 ASSOCIAÇÃO BASILEIA DE ENEGIA NUCLEA - ABEN ISBN: HEAVY METAL ANALYSIS IN GOUNDWATE SAMPLES BY S-TXF Silvana Moreira 1, Maria Ficaris 1, Ana Elisa S. de Vives 2, Orghêda L. A. D. Zucchi 3, Virgílio F. Nascimento Filho 4 1 Depto. de ecursos Hídricos Faculdade de Engenharia Civil, Arquitetura e Urbanismo (FEC) Universidade Estadual de Campinas (UNICAMP) Avenida Albert Einstein, Caixa Postal Campinas, SP silvana@fec.unicamp.br 2 Faculdade de Engenharia, Arquitetura e Urbanismo (FEAU) Universidade Metodista de Piracicaba (UNIMEP) odovia Santa Bárbara D Oeste/Iracemápolis, km Santa Bárbara D Oeste, SP aesvives@unimep.br 3 Faculdade de Ciências Farmacêuticas de ibeirão Preto (FCFP) Universidade de São Paulo (USP) Avenida do Café, s/n ibeirão Preto, SP olzucchi@fcfrp.usp.br 4 Lab. Instrumentação Nuclear - Centro de Energia Nuclear na Agricultura (CENA) Universidade de São Paulo (USP) Avenida Centenário, Caixa Postal Piracicaba, SP ABSTACT In order to obtain information about levels of heavy metals in groundwater, analysis were carried out on samples from monitoring and supplying wells located in Campinas, São Paulo State, Southeastern Brazil. The analytical technique used was Synchrotron adiation Total eflection X-ay Fluorescence (S-TXF) and all the measurements were performed at Synchrotron Light Source Laboratory, using a white beam and a Si(Li) detector in total reflection condition. The determined elements were Al, Cr, Mn, Fe, Ni, Cu, Zn, Ba and Pb. The results were compared with the maximum allowed values (MPV) established by the Brazilian Health Department. The detection limits obtained varying from 0.10 up to 8 µg.l -1 were in agreement with the values presented by others analytical techniques. 1. INTODUCTION The number of wells in Brazil is every time larger, in spite of not disposing of the exact amount, it is considered that approximately 10,000 wells for supplying are perforated per year in the country 1. In the São Paulo State, in 2001, they were sent 4 thousand of grants, which 2 thousand were licenses of well perforations 2. Only in the São Paulo State are 308 municipal districts totally provisioned by underground waters 3 ; due to this scenery, it is possible to have the vision of the great importance of this resource in the economic, social and health areas.

2 The pollutants, in a general way, reach the superficial waters directly, the ones which if auto debug with relative facility, mainly when the pollutants cited are degraded bio-chemically, but the underground waters, although more protected, are vulnerable to the polluted charges that reach them for infiltration, through the land. The inadequate disposition of urban and industrial solid residues in the soil increases the possibility of contamination of the underground water resource; wells bad built, wells abandoned without appropriate cover are also examples of pollution causes, that can be aggravated by resulting problems of the industrialization and of the uncontrolled urbanization, for the development of predatory agricultural activities and the intensive use of modern chemical input. The aim of this paper is to use the S-TXF for the quantitative analysis of underground water samples with the purpose of verifying the presence of heavy metals. The results were compared with the values limits established (Decree December 29, 2000) of the Brazilian Health Ministry Instrumentation 2. MATEIALS AND METHODS All the measurements were accomplished in X-ray Fluorescence beamline at the Synchrotron Light Source Laboratory, in Campinas, SP, South-east Brazil. For the sample excitation a white beam (polychromatic) of synchrotron radiation under total reflection geometry was used and a Si(Li) semiconductor detector (165 ev at 5.9 kev) for detection Samples: Collection, Treatment and Preparation For the sampling of the monitoring wells it is necessary to purge the water of the wells and to wait for approximately 1 day until collect the underground water sample, in agreement with NB and the Guides for sampling and preservation of water samples 6. The collections of the supplying wells were performed in Campinas and region around, São Paulo State. In this case, the collection was made through the opening of existent faucet in the exit of the well, being been the careful of verifying before if the well was in operation, case was, the collection was made soon after, otherwise, it let to slip water of 15 to 20 minutes so that the water stagnated could be removed. After the collection, the samples were acidified and maintained in refrigeration for posterior analyses. In the sample preparation 1 ml of each sample was taken, being added 100 µl of Ga solution (concentration of ng.ml -1 ), used as internal standard, to follow a 5 µl was putted on the Perspex sample disks for posterior evaporation under infrared lamp 7, and after analyzed for 100 s Quantitative Analysis and Detection Limits The concentration of the element of interest was calculated using the equation:

3 C i I I i p = (1) p C S where: C i and C p = concentrations of the element i and the internal standard; S = relative sensitivity (in relation to the element used as internal standard); I i and I P = intensities of the characteristic X-rays and the internal standard. The detection limits DL i for each element i is directly related with the background intensity I i (BG), in agreement with the equation 8 : DL where t = measuring time, in seconds. I ( BG) C i P i = 3 (2) t I PS 3. ESULTS AND DISCUSSION 3.1. System Calibration and Detection Limits For the system calibration were prepared ten standard solutions containing Ga as internal standard, five for each series K and L. The standards were irradiated by 100 s and the obtained spectra were fitted with the use of the software Quantitative X-ay Analysis. The experimental sensitivity for each element contained in the standard solutions was determined and so the sensitivity curves were fitting (equations 3 and 4) for elements of interest, including those for which standards are not available. K Series: S = exp ( Z = Z Z 3 ) (3) L Series: S = exp ( Z Z Z ) (4) 2 = Using the equations 3 and 4 with the data of the background intensities, the detection limits were calculated for a 100 s measuring time and extrapolated for 1000 s (Table 1). Table 1. Detection Limits (µg.l -1 ) for 1000 s counting time. Element Al Si S Cl K Ca Ti Cr Mn DL Element Fe Ni Cu Zn Ga Br Sr Ba Pb DL

4 3.2. esults for Groundwater Analysis of Landfill Pirelli Tables 2 and 3 show the results of the analysis performed in groundwater samples of Pirelli landfill collected in March and June, 2003, respectively, in rainy and dry seasons. Table 2. Metal concentrations in groundwater samples of landfill Pirelli, Campinas. Samples collected in March, Sample Al Cr Mn Fe Ni Cu Zn Ba Pb Samples collected in March, P P < P P57 < P PM PM MPV* *MPV Maximum Permissive Value (Decree 1469 of Brazilian Health Ministry). Table 3. Metal concentrations in groundwater samples of landfill Pirelli, Campinas. Samples collected in June, Sample Al Cr Mn Fe Ni Cu Zn Ba Pb P P53 < P54 < P < < P56 < <1.85 P57 < < P58 < PM4 < <1.85 MPV* Chromium not reached the maximum permissive value (VMP), but was present in almost wells, except for P55 sample. Lead was present in all wells in the first sampling (March) and it was detected in 6 of 8 wells analysed in the second sampling (June), with concentrations above the maximum permissive value. Moreover Ba was detected in 2 wells with levels upper to the VMP in the first sampling, and in three wells in the second sampling. All wells present copper element, but the contents were smaller than the maximum established by the legislation.

5 In the second sampling, Al was detected just in 2 of 8 monitoring wells, and its concentration in P50 well ( mg.l -1 ) was very higher than the values determined before. Elements as Ni, Zn, Cu, Mn and Fe were present in all wells analysed in the two sampling. In relation to Ni element just in one well in the first sampling, its concentration was above the VMP, but for the second sampling its concentrations were smaller than the VMP in all wells analysed esults of Supplying wells from Campinas State University (UNICAMP) Table 4 presents the concentrations of the elements determined by the S-TXF analysis in groundwater samples of the supplying wells from UNICAMP, collected in April Table 4. Metal concentrations of supplying wells from UNICAMP. Samples collected in April Sample Cr Mn Fe Ni Cu Zn Ba Pb P P P P MPV* The elements detected with values above the maximum permissive value were Cr (2 wells) and Pb (1 well). In all wells were determined Pb, but just in one of them was surpass the established limit, while in the other three wells, the values were very clear to the permissive Wells from Metropolitan region of Campinas (MC) The Table 5 presents the minimum, maximum and the average of the concentrations in groundwater samples of the supplying wells from Metropolitan egion of Campinas, collected in April and May 2003 (number of samples collected = 64). Table 5. Metal concentrations in groundwater samples of supplying wells collected from Metropolitan region of Campinas. Al Cr Mn Fe Ni Cu Zn Ba Pb Minimum Maximum Average MPV CONCLUSIONS Using the S-TXF was possible carry out the quantitative analysis in groundwater samples in order to verify the presence of heavy metals and to compare the obtained results with the

6 maximum permissive values established by the Brazilian Health Ministry (Decree 1469). The detection limits obtained (from 0.10 up to 8 µg.l-1) are in agreement with the values cited by others analytical techniques. In the landfill Pirelli was detected some elements with contents above the maximum permissive values for elements that represent risks to the health as Ba and Pb, what was expected for a landfill that received during many years several kinds of residues without control. In the supplying wells, in the case of UNICAMP, elements as Cr (237 µg.l -1 ) and Pb (13 µg.l -1 ) were not expected, so becomes necessary the monitoring of these wells to verify if these elements will be continued to be detected with values above allowed. In the Metropolitan area of Campinas, elements not expected, like Cr and Pb, were detected. In 15 wells were observed values above the permissive for Pb, and its presence were frequent in the analysed wells, indicating the necessity to continue to monitoring these wells. ACKNOWLEDGMENTS This study had technical support from National Synchrotron Light Laboratory (LNLS) under research proposal D09B - XF 1503 and EFEENCES 1. EBOUÇAS, A. C. Groundwater in Brazil. Episods, 11, 209, (2000). 2. DAEE. Águas Subterrâneas em São Paulo. 1, São Paulo (2003). 3. CETESB. elatório de Qualidade das Águas Subterrâneas do Estado de São Paulo (2001). 4. ANVISA. Portaria 1469 (Dec 29, 2000). html (2000). 5. ABNT. NB 13895: Construção de Poços de Monitoramento e Amostragem. São Paulo, (1987). 6. CETESB. Guia de Coleta e Preservação de Amostras de água. São Paulo,150p., (1988). 7. MOEIA, S.; VIEIA, C. B.; COAUCCI FILHO, B.; STEFANUTTI,.; JESUS, E. F. O. - Study of the metals absorption in culture corn irrigated with domestic sewage by S-TXF. Instrumentation Science & Technology, 33, 73-85, (2005). 8. LADISICH, W.; IEDE,.; WOBAUSCHEK, P; AIGINGE, H. Total reflection X- ray fluorescence analysis with monoenergetic excitation using rotating anode X-ray tubes. Nuclear Instruments and Methods in Physics esearch, 330A, , (1993).