species arboreal as a bioindicator of the environmental pollution: analysis by sr-txrf

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Nuclear Instruments and Methods in Physics Research A 579 (2007) 494–498

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Species arboreal as a bioindicator of the environmental pollution:Analysis by SR-TXRF

Ana Elisa Sirito de Vivesa,�, Silvana Moreirab, Sandra Maria Boscolo Brienzac,Jean Gabriel S. Medeirosd, Mario Tomazello Filhod, Orgheda Luiza Araujo

Domingues Zucchie, Virgilio Franco do Nascimento Filhof, Regina Cely Barrosog

aMethodist University of Piracicaba, Rodovia Iracemapolis/Santa Barbara, km 01, Santa Barbara D’Oeste 13450-000, SP, BrazilbState University of Campinas, Cidade Universitaria ‘‘Zeferino Vaz’’, Campinas 13083-970, SP, BrazilcMethodist University of Piracicaba, Rodovia do Ac-ucar, Km 156, Piracicaba 13400-911, SP, Brazil

dUniversity of Sao Paulo, Av. Padua Dias, 11 Piracicaba 13418-900, SP, BrazileUniversity of Sao Paulo, Av. dos Bandeirantes, 390 Ribeirao Preto 14040-901, SP, Brazil

fUniversity of Sao Paulo, Av. Centenario, 303 Piracicaba 13400-970, SP, BrazilgState University of Rio de Janeiro, Rua Sao Francisco Xavier, 524 Rio de Janeiro 20550-900, RJ, Brazil

Available online 10 April 2007

Abstract

This paper aims to study the environmental pollution in the tree development, in order to evaluate its use as bioindicator in urban

and countrysides. The sample collection was carried out in Piracicaba city, Sao Paulo State, that presents high level of environmental

contamination in water, soil and air, due to industrial activities, vehicle combustion, sugar-cane leaves burning in the harvesting, etc.

The species Caesalpinia peltophoroides (‘‘Sibipiruna’’) was selected because it is often used in urban arborization. Synchrotron radiation

X-ray fluorescence technique (SR-TXRF) was employed to identify and quantify the elements and metals of nutritional and toxicological

importance in the wood samples. The analysis was performed in the Brazilian Synchrotron Light Source Laboratory, using a white

beam for excitation and an Si(Li) detector for X-ray detection. In several samples were quantified P, K, Ca, Ti, Fe, Sr, Ba and Pb

elements.

r 2007 Elsevier B.V. All rights reserved.

PACS: 07.85.Qe; 78.70.En; 07.88.+y

Keywords: Heavy metals; Environmental contamination; Tree rings; Total reflection X-ray fluorescence analysis

1. Introduction

Urbanization and industrialization have introducedvarious harmful substances into the atmosphere. Airpollution is offensive and can be a genuine health hazardto human beings as well as to vegetation and manyhorticultural plants.

Environmental pollution is one of the main causes of lifedeteriorating and several plants have been used as bioindi-

e front matter r 2007 Elsevier B.V. All rights reserved.

ma.2007.04.109

ing author.

ess: [email protected] (A.E.S. de Vives).

cators: lichens, agricultural crops, ornamental plants andsome species of trees.In temperate regions, trees usually produce one

growth ring every year and it is possible to determinethe ring’s age accurately. Trace metals are depositedin the rings and accumulated in the wood. Some authorshave showed a correlation between environmentalpollution and the metal concentrations in the growthrings [1].This study has the purpose to determine the elemental

concentrations in the ring trees of Caesalpinia peltophor-

oides (‘‘Sibipiruna’’) used as a bioindicator of theenvironmental pollution. This species was chosen due

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ARTICLE IN PRESSA.E.S. de Vives et al. / Nuclear Instruments and Methods in Physics Research A 579 (2007) 494–498 495

to its prevalent use as urban forestation in the areastudied.

2. Theoretical

2.1. System calibration and quantitative analysis

Multielemental standards solutions, in different concen-trations, containing Al, Si, K, Ca, Ti, Cr, Fe, Ni, Zn, Ga,Se, Sr and Mo for K series and Mo, Cd, Ba, Sb, Pt, Tl andPb for L series were prepared by an adequate dilution ofstock solutions. Gallium was added as internal standard inall standard solutions and samples [2].

For TXRF, it is not necessary to correct the matrixeffect, and the fluorescent intensity of the element i isdirectly proportional to its concentration.

Ri ¼ SR � Ci (1)

where Ci is the concentration of element i in thesample (mgmL�1), SR the relative sensitivity for elementi (non-dimensional) and Ri the relative counting(mgmL�1).

Table 1

Confidence interval (CI) of average concentrations (m) for the elements

present in Caesalpinia peltophoroides (‘‘Sibipiruna’’) samples

Period (years) Concentration (mg g�1)

P K Ca

1971–1973 1031753 26545755 8602784

1974–1976 1849751 275437131 9630760

1977–1979 1396763 293787259 10074743

1980–1982 911718 18731759 6414727

1983–1985 545766 20495715 5483745

1986–1988 857754 20914782 6823769

1989–1991 1114794 26690788 960778

1992–1994 11377132 13889710 7768710

1995–1997 1808730 4134739 9098734

1998–2000 3206774 3774766 19241777

2001–2003 1015716 2922726 7800735

MDL 13.4 2.6 1.4

CI ¼ m7t s (confidence interval at po0.05).

3. Experimental

3.1. Samples: preparation and measurement

Wood samples of C. peltophoroides (‘‘Sibipiruna’’) werecollected in Piracicaba city, Sao Paulo State, SoutheastBrazil. The samples were removed of species 34-yearsold from an avenue with high vehicular traffic. Thesamples were obtained through the method, classified asnon-destructive which consists of the retreat of woodcylinders by introduction of a Pressler probe in the trunk ofthe trees [3]. After the polish of the sheets, the annualgrowth rings were identified. Each sample corresponds to a3-year growth interval. The samples were crushedand so 100mg of dried material was submitted to thedigestion procedure (nitric acid/hydrogen peroxide).The final volume of the acid digestion was completedto 25mL with non-ionized and non-mineralized water.In 1mL of the extracts, 100 mL Ga (102.5 mgmL�1) wasadded as internal standard. Afterwards, 5 mL of thismixture was transferred onto Perspex support and soevaporated with infrared lamp producing a thin film on thecarrier surface.

The synchrotron radiation X-ray fluorescence technique(SR-TXRF) analysis was carried out in the X-rayFluorescence Beamline at the Brazilian Synchrotron LightSource Laboratory, located in Campinas city, Sao PauloState, Brazil. The standards and wood samples weremeasured for 100 s employing a white beam (2–24 keV),2mm width and 1mm height, operating under totalreflection conditions. The X-ray detection was performedby an Si (Li) detector (165 eV, 5.9 keV, FWH).

4. Results and discussion

4.1. Calibration of the system

The fluorescent intensities were obtained from fitting thespectra with Quantitative X-ray Analysis System (QXAS)[2]. Experimental relative sensitivities were calculated for K(Eq. (2)) and L series (Eq. (3)):

SR ¼ expð�15:313þ 0:786Z � 0:003179Z2

� 2:0585� 10�4Z3Þ

R2 ¼ 0:998 (2)

SR ¼ expð�16:733� 1:338Z � 0:02667Z2

� 1:5923� 10�4Z3Þ

R2 ¼ 0:988. (3)

4.2. Quantitative analysis of wood samples

After the system calibration was possible to determine P,K, Ca, Ti, Fe, Sr, Ba and Pb in wood samples (Tables 1–3)and also the minimum detection limits (MDLs) for thesame elements. The detection limits (MDLs) were obtainedbased on the background spectrum for each element ofinterest [2].

4.3. TXRF validation procedure

In order to check the accuracy of the procedure used forquantitative analysis, two standard reference materialswere analysed, and the calculated data compared with thecertified values [4].The first standard reference material for ICP/AAS called

Contract Required Detection Limits Standard (Sigma41,401-8) was prepared by addition of 500 mL standard

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Table 3


present in Caesalpinia peltophoroide (‘‘Sibipiruna’’) samples


Ba Pb

1971–1973 11.7172.33 46.5476.44

1974–1976 22.3073.72 32.5374.90

1977–1979 10.8770.47 31.5071.94

1980–1982 15.7771.96 29.0972.50

1983–1985 7.1872.35 30.6870.50

1986–1988 o1.27 23.4572.64

1989–1991 136.8275.35 15.9074.68

1992–1994 3.4470.57 17.2872.80

1995–1997 13.9471.03 9.8970.93

1998–2000 18.7771.41 13.7070.680

2001–2003 5.0771.06 14.5170.56

MDL 1.27 1.07


Fig. 1. P, K and Ca distributions in function of sampling years for

Caesalpinia peltophoroides measured by SR-TXRF.

Fig. 2. Concentration ratio for K and Ca in Caesalpinia peltophoroides

measured by SR-TXRF.

Fig. 3. Concentration ratio for K and P in Caesalpinia peltophoroides


Table 2


present in Caesalpinia peltophoroide (‘‘Sibipiruna’’) samples


Ti Fe Sr

1971–1973 4.3570.91 o0.15 39.1675.28

1974–1976 10.3970.29 69.4771.33 47.2973.24

1977–1979 3.9071.78 o0.15 40.7170.91

1980–1982 6.3671.19 40.9172.61 29.4473.46

1983–1985 5.2971.25 10.0970.60 18.1771.09

1986–1988 o0.39 o0.15 23.4771.64

1989–1991 15.2670.76 o0.15 44.5170.48

1992–1994 o0.39 o0.15 31.5870.24

1995–1997 o0.39 o0.15 23.4972.49

1998–2000 5.8570.30 o0.15 59.4274.86

2001–2003 1.0670.04 18.3570.82 28.3171.37

MDL 0.39 0.15 1.42


A.E.S. de Vives et al. / Nuclear Instruments and Methods in Physics Research A 579 (2007) 494–498496

solution with 100 mL Ga (102.5 mgmL�1) and 1mLdeionized water. For the preparation of the standardDrinking Water Pollutants (Aldrich), 500 mL standard and50 mL Ga (102.5 mgmL�1) were mixed.

The relative standard deviations (RSDs) between mea-sured and certified values for Cr, Mn, Co, Ni, Cu, Zn, As,Se, Ba and Pb elements were lower than 10% for all theelements.

The main mineral elements are P, K and Ca and theseasonally variations for these elements are often reported[5]. The distribution patterns for K showed a decreasetowards the bark (Fig. 1) indicating a trend of smallmobile.

The K/Ca concentration ratios showed a maximum for1983–1985 period followed by a decrease towards the bark(Fig. 2) and the same trend was observed for K/P ratios

(Fig. 3). The K/Ca ratios obtained in this study agree withthe values reported by Vives et al. [6].The Ca/Sr ratio has been found to be constant in the

period of this study (Fig. 4) and the maximum values forboth the elements were observed in the 1998–2000 period.

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Fig. 4. Concentration ratio for Ca and Sr in Caesalpinia peltophoroides


Fig. 5. Pb distribution in function of sampling years for Caesalpinia

peltophoroides measured by SR-TXRF.

Fig. 6. Concentration ratio for Pb and Ca in Caesalpinia peltophoroides


A.E.S. de Vives et al. / Nuclear Instruments and Methods in Physics Research A 579 (2007) 494–498 497

This agrees with previous results where Ca/Sr ratio hasbeen found constant in a tree [7].

The metals Ti and Fe were not registered in all woodsamples and the results do not show a regular tendency.

For Ti, the highest values were found between 1989 and1991 and for Fe between 1974 and 1976.The Ba, Sr and Ca elements are divalent cations and in

the nature they have the same behaviour. For Ca/Ba andSr/Ba, the maximum ratios have been found in the1986–1988 period followed by a decrease in 1989–1991and again an increase in the ratios for 1992–1994 period.Levels higher than 30 mg g�1 of Pb are considered

excessive or toxic and 43 mg g�1 is the threshold valueindicating death of trees, and normal concentrations inplants are less than 10 mg g�1 [8]. However, Pb concentra-tions found in this study varied from 9.89 to 46.54 mg g�1.The threshold value was observed between 1971 and 1973and toxic levels occurred between 1974 and 1979. Leadpattern distribution showed a decrease towards the bark(Fig. 5) but the concentrations remain high. Lead pollutionis caused by industrial emissions, and on a large scale iscaused by vehicular emissions from motors using lead asadditive in gasoline. In the Brazilian legislation, theaddition of Pb as additive in gasoline was prohibited from1990.The maximum values for the Pb/Ca ratios were found in

the 1971–1973 and 1983–1985 periods. From 1985 can beobserved a decreasing trend as can be visualized in theFig. 6, and Martin et al. [9] observed the same trend.

5. Conclusions

This study indicated the usefulness of C. peltophoroides

(‘‘Sibipiruna’’) species as bioindicator of environmentalpollution. The nutrient ratios can be used in order to makea temporal distribution of some elements, like P, K, Ca, Srand Ba.For Pb was observed a decrease towards the bark,

indicating a reduction in air pollutants in the last years,mainly after 1990 when its use as additive in gasoline wasprohibited.

Acknowledgements

This study had financial support from Research Fund ofMethodist University of Piracicaba and technical supportfrom Brazilian Synchrotron Light Source Laboratory(under research proposal D09B–XRF–2866).

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species arboreal as a bioindicator of the environmental pollution: analysis by sr-txrf

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