IDENTIFICATION OF AIR POLLUTION ELEMENTS IN LICHENS

IDENTIFICATION OF AIR POLLUTION ELEMENTS IN LICHENS USED AS BIOINDICATORS, BY THE XRF AND AAS METHODS* GABRIEL STATE1, ION V. POPESCU2,3,4, ANCA GHEBOIANU3, CRISTIANA RADULESCU3, IOANA DULAMA3, IULIAN BANCUTA3, RALUCA STIRBESCU5 1

National College “Ienăchiţă Văcărescu” Târgovişte, Romania, [email protected] 2 Academy of Romanian Scientists 54 Bucharest 05009, Romania 3 Valahia University of Târgovişte, Romania 4 National Institute of Physics and Nuclear Engineering, Bucharest-Magurele, Romania 5 Doctoral School of Physics, Faculty of Physics, University of Bucharest Received September 14, 2009

The aim of this work was the monitoring of the air quality in the Târgovişte town and its surroundings by using of the lichens as biomonitors. The methods used were Energy Dispersive X-Ray Fluorescence (EDXRF) and Atomic Absorption Spectroscopy (AAS). The measurements were performed in the laboratories of the Faculty of Sciences and Arts from Valahia University of Târgovişte. We have studied the presence of heavy metals such as Cd, Co, Cr, Cu, Fe, Pb and Zn. The EDXRF method has been used mainly as a qualitative analysis, the precise determination of concentrations of the elements being done by the AAS method. Since samples have been also taken from places less exposed to the pollution factors, the study allowed the comparative analysis of air quality between high and low polluted areas. Key words: Lichen, AAS, EDXRF, air pollution.

1. INTRODUCTION

The presented study is referring to a problem of great national and international importance, which is represented by the air quality control. In particular, we have chosen Târgovişte and the places around it, for the evaluation of air pollution with heavy metals resulted from the social-economical activities such as: the production of steel, stainless steel, energy in power stations, the oil exploitations and traffic. We have chosen the lichens as biomonitors to accomplish our study. There have been some advantages of their using [1–4]: slowly growing, insignificant change of their morphology, long life during the year, higher area contact with atmosphere, * Paper presented at the 10th International Balkan Workshop on Applied Physics, July 6–8, 2009, Constanţa, Romania.

Rom. Journ. Phys., Vol. 56, Nos. 1–2, P. 240–249, Bucharest, 2011

2

Identification of air pollution elements

241

etc. These are the reasons for which they have been used in many air quality studies. The lichen species collected in our work were: Xanthoria Parietina (in most of the cases), Parmelia Furfuracea and Peltigera Canina. Taking into consideration the fact that these species of lichens have different absorption properties for the air pollutants, we tried to collect samples of one species from all places; in some of the cases, when this was not possible, we made the necessary corrections, taking into account the absorption properties of each element for every species [1]. The element concentrations from lichen samples were determined by Energy Dispersive x-ray Fluorescence (EDXRF)[5] and Atomic Absorption Spectroscopy (AAS) [6, 7] methods. Moreover, in order to achieve the elemental analysis with a high sensitivity and precision for the environmental samples, there can be used the Neutron Activation Analysis (NAA) [8], Chlorophyll Fluorescence(CF) [9] Electron Spectroscopy (ES) [10,11], Particle Induced X Ray Emission (PIXE) [12–14], Total Dissolved Solids(TDS) [15] and Inductively Coupled Plasma – Atomic Emission Spectroscopy (ICP-AES) [7, 13]. The results to be presented in this work were obtained from samples collected in the interval 16th–28th April 2009. The trees for the lichen sampling were chosen from the areas with different pollution levels: some were collected near the economical units which produce gaseous pollutants, others were taken near the roads which had different traffic values and the others were also collected from the forest, far away from any sources of pollution (Fig. 1). Thus we can have the possibility to make a comparative analysis between heavy metal air pollution in those places. For each sample we recorded the following characteristics: the moment of sampling, the day, the name of the place and the GPS coordinates. 2. SAMPLE PREPARATION

The samples were first washed with water then dried for 2 hours at 60ºC. After that, a quantity of about 5g of every sample was powdered and put in clean testing chambers covered with 2.5 µm Fluxana TF-125-345 Mylar thin film to be studied by the EDXRF method. The data acquisition time was set to 30 min. For AAS testing we used the same samples that had been used for EDXRF. Therefore we put a quantity of about 0.3 g from each sample in teflon cylinders and then we added 2 ml of nitric acid (HNO3) and 3 ml of hydrogenperoxide (H2O2). The cylinders were heated in a microwave oven with the following temperature program: raising to 145ºC in 10 min and maintaining it for 5 min; raising to 180ºC in 5 min and maintaining it for 10 min; cooling to 100ºC in 1 min and maintaining it for 10 min. The digested sample was then filtered and filled to 50 ml with deionized water.

242

Gabriel State et al.

3

Fig. 1. The places of lichens sampling from Târgoviste and localities around it (the map was exported from Google Earth).

3. INSTRUMENTS

The x-ray fluorescence analysis was done by the Elvax EDXRF spectrometer which has the energy resolution of 165 eV at 5.9 keV (55Fe isotope).The software of the instrument provides the qualitative and quantitative analysis of the samples by quadratic stepwise multiple regressions. The GBC Avanta AAS with flame and GBC Avanta Ultra Z with graphite furnace spectrometers were used for atomic absorption analysis. They can detect concentrations of ppm order, respectively of ppb order from each sample. The instruments came with specialized software for calibration and for providing the results with associated errors. For the preparation of the samples we used a Berghof SpeedWave MWS2 microwave oven pressure digestion installation.

4


243

4. RESULTS AND DISCUSSION

Figs. 2–8 evidences the concentrations obtained by AAS or EDXRF methods for Cd, Co, Cr, Cu, Fe, Pb and Zn from places referred by its GPS coordinates. In each graph the maximal and the minimal concentration as well as the ratio between them is included. We have chosen this way of interpreting the results because the allowed maximal concentration isn’t published. An Index of Air Pollution (IAP) or an modified Index of Air Pollution (mIAP) [16–18] can be determined, after collecting a large number of samples; we have not been able to do this due to the small number of trees on which the lichens grow, especially in Targoviste. Graphs were made using Microsoft Excel 2007 [19]. Studying the obtained results it can see that near steel and stainless steel factories from Targoviste, respectively the power plant from Doicesti, the values of the element concentrations c are maximal, exceeding the minimal ones from 11.9 times (for Cd) to 31.2 times (for Zn). The minimal values correspond to the samples collected at distances greater than 15 km of Targoviste or Doicesti, deep in the forest (Table 1). Table 1 The extreme values of the element concentrations and the sampling places Element c(ppm) Cd Co Cr Cu Fe Pb Zn

Place c(ppm) Place c(ppm) Place c(ppm) Place c(ppm) Place c(ppm) Place c(ppm) Place

Minimal value (ppm)

Error (ppm)

0.1 0.005 Between Cobia and Dragodana, inside the forest 0.13 0.03 Dragodana, inside the forest 5.08 0.6 Dragodana, inside the forest 2.66 0.14 Between Cobia and Dragodana, inside the forest 412 28 Ungureni, inside the forest 5.00 0.45 Cobia, inside the forest 5 0.22 Between Cobia and Dragodana, inside the forest

Maximal value Error (ppm) Max/Min (ppm) 1.19 0.05 11.90 Steel factories Targoviste 2.61 0.62 Steel factories Targoviste 64.47 7.73 Doicesti power plant 34.08 2.3 Steel factories Targoviste 6071 473 Steel factories Targoviste 75 7 Steel factories Targoviste 156 7.02 Steel factories Targoviste

19.92 12.69 12.81 14.73 15.01 31.20

The heavy metal air pollution in the two of residential areas that were the subject of this study is presented in Table 2, where we calculated the ratio between the local values of elements concentrations and their minimum values that were

244


5

listed in Table 1. National College “Ienachita Vacarescu” of Targoviste is located about 2 km from the industrial area, in the other side of the town; Vacaresti is a locality situated at 8 km from the steel factories. It can see that in these places the heavy metals concentrations from air exceed the minimum values from the areas less polluted from 1.66 to 14.26 times. Table 2 The ratios between elements concentrations from two of residential areas and the minimum ones listed in Table 1 Element/Place Cd (max/min) Co (max/min) Cr (max/min) Cu (max/min) Fe (max/min) Pb (max/min) Zn (max/min)

National College “Ienachita Vacarescu” 1.66 6.58 4.63 6 3.01 3.28 14.26

Fig. 2. Concentrations of cadmium (Cd).

Vacaresti 1.67 2.75 2.21 5.86 2.26 2.77 8.36

6


Fig. 3. Concentrations of cobalt (Co).

Fig. 4. Concentrations of chromium (Cr).

245

246


Fig. 5. Concentrations of copper (Cu).

Fig. 6. Concentrations of iron (Fe).

7

8


247

Fig. 7. Concentrations of lead (Pb).

Fig. 8. Concentrations of zinc (Zn).

4. CONCLUSIONS

The EDXRF as a multi-elemental analysis method, allows the qualitative analysis of elements with Z>13 in lichen samples; if element concentrations are greater than 10 ppm, the EDXRF method also provides a good quantitative analysis.

248


9

The AAS, as a single element analysis method provides a much more precise quantitative analysis of every element than EDXRF; contrary to EDXRF, which is nondestructive and fast, the AAS is destructive and slower. By using these two methods, an accurate quantitative assessment of the level of environmental pollution in a given area can be obtained. For our study, these two methods allowed us to identify the heavy metals as pollutants of the air, with concentrations that are much higher in industrial zones than in the ones placed in less polluted places, highlighting the need for further studies of the other air pollutants, and their possible presence in water and soil. REFERENCES 1. J.E. Sloof and B.Th. Wolterbeek, Interspecies comparison of lichens as biomonitors of traceelement air pollution, Interfaculty Reactor Institute, Delft University of Technology, December 1991. 2. S.F. Heller-Zeisler, R. Zeisler, E. Zeiller, R.M. Parr, Z. Radecki, K.I. Burns, P.De Regge, Report on the intercomparison run for the determination of trace and minor elements in lichen material, International Atomic Energy Agency, Vienna, Austria, June 1999. 3. Quality Assurance Handbook for Air Pollution Measurement Systems Volume II: Part 1: Ambient Air Quality Monitoring Program Quality System Development, august 1998. 4. http://www.lichens.ie/. 5. V. Ghisa, I.V. Popescu, M. Belc, A. Ene, Study of Some Roman Brooches Discovered at Tomis Constanta, by X-Ray Fluorescence Technique, Romanian Journal of Physics 53 (3–4), 557–562, ISSN 1221–146x, 2008. 6. G. Dima, I.V. Popescu, C.Stihi, C. Oros, S. Dinu, Laur Manea, Gh. Vlaicu, Fe, Mn and Zn concentration determination from Ialomita river by atomic absorbtion spectroscopy, Rom. Journ. Phys. 51 , No 5–6, 633–638, 2008. 7. I.V. Popescu, C. Stihi, Gh.V. Cimpoca, G. Dima, Gh. Vlaicu, A. Gheboianu, I. Bancuta, V. Ghisa, G. State, Environmental samples analysis by atomic absorption spectrometry (AAS) and inductively coupled plasma-optical emission spectroscopy (ICP-AES), Romanian Journal of Physics, vol. 54 , No. 7–8, p. 741–746, 2009. 8. A. Ene, I.V. Popescu, V. Ghisa, Study of Transfer Efficiencies of Minor Elements during Steelmaking by Neutron Activation Technique, Romanian Reports in Physics 61(1), 165–171, ISSN 1221–1451, 2009. 9. S. Apostol, C.Stihi, C.Oros, The use of the chlorophyll fluorescence for estimation of photosynthetic electron transport flow in water stressed pea plants, Journal of Optoelectronics and Advanced Materials, 9,9 p. 2912–2925, 2007. 10. V. Andrei, R. Cristescu, Gh. Vlaicu, E. Andrei, C. Oros, C. Stihi, G. Dima, S. Dinu, Electron spectroscopy studies of the diamond like carbon thin films, Journal of Optoelectronics and Advanced Materials, 9,7, p. 2288–2290, 2007. 11. V. Andrei, E. Andrei, Gh. Vlaicu, C. Stihi, G. Dima, C. Oros, S. Dinu, Chemical binding and structure of carbonic thin films with advanced properties studied by electron spectroscopy, Journal of Optoelectronics and Advanced Materials, 9,7, p. 2295, 2007. 12. C. Stihi, I.V. Popescu, G. Busuioc, T. Badica, A. Olariu, G. Dima, Particle Induced X-Ray Emission (PIXE) analysis of Basella Alba L leaves, Journal of Radioanalytical and Nuclear Chemistry, Vol. 246, No 2 (2000), 445–447.

10


249

13. C. Stihi, A. Bancuta, I.V. Popescu, M. Virgolici, Gh.V. Cimpoca, M. Gugiu, Gh. Vlaicu, Air pollution studies using PIXE and ICP-AES methods, IoP Journal of Physics: Conference Series 41 (2006), 565–568. 14. I.V. Popescu, A. Ene, C. Stihi, A. Bancuta, G. Dima, T. Badica, V. Ghisa, Analytical applications of particle-induced X-ray emission (PIXE), Six International Conference of the Balkan Physical Union Book Series: AIP Conference Proceedings, vol. 899, p: 538, 2007. 15. C. Stihi, I.V. Popescu, S. Apostol, Gh. Vlaicu, Water quality monitoring using Total Dissolved Solids measurements, Revista de Chimie, 58, nr. 12, p. 1335–1336, 2007. 16. F. Leblanc, J. De Sloover, Relation between industrialization and the distribution and growth of epiphytic lichens and mosses in Montreal, Canadian Journal of Botany48 (8): 1485–1496, 1970. 17. S.D. Zelenko, S.Y. Kondratyuk, The lichens of Darnitsa forest park (Kiev), Ukrayinskyi Botanichnyi Zhurnal 51, 104–16, 1994. 18. L. Dymytrova, Epiphytic lichens and bryophytes as indicators of air pollution in Kyiv city (Ukraine), Folia Cryptog. Estonica, Fasc. 46: 33–44, 2009. 19. www.microsoft.com, the official website of Microsoft.

IDENTIFICATION OF AIR POLLUTION ELEMENTS IN LICHENS

Recommend Documents