Asbestos pollution levels in river water measured by proton-induced X-ray emission (PIXE) techniques

Environmental Pollution (Series B) 5 (1983) 83-90

Asbestos Pollution Levels in River Water Measured by Proton-induced X-ray Emission (PIXE) Techniques S. Monaro, S. Landsberger,* R. Lecomtet & P. Paradis Laboratoire de Physique Nucleaire, Universit+ de Montr6al, Montr6al, Qu6bec, H3C 3J7, Canada

& G. Desaulniers & A. P'an Depart6ment de M6dicine du Travail et d'Hygi6ne du Milieu Faeult6 de M6dicine, Universit6 de Montr6al, Montr+al, Qu6bec, H3C 3J7, Canada

ABSTRACT We have used proton-induced X-ray emission ( P1XE) techniques to assess the asbestos pollution of the B~cancour river in QuObec. The asbestos pollution levels at twelve different sites along the river have been determined from the measured magnesium concentrations. The results clearly show that in the mining areas the asbestos pollution is high and that it decreases after the lakes located downstream. Furthermore, it has been shown that the meteorological conditions play a large rdle in the spread and variation of the pollution levels in river water.

INTRODUCTION

It is well known that about I0 6 asbestos fibres per litre are present in natural waters. This fibre concentration is probably coming from the soil erosion produced by natural causes and thus it may be considered as * Present address: National Research Council, Division of Physics, X-Rays and Nuclear Radiations, Ottawa K IA OR6, Canada. 5" Present address: D6partement de M6decine Nucl~aire et Radiobiologie, Centre Hospitalier Universitaire de Sherbrooke, Sherbrooke, Qu+bec, J1H 5N4, Canada. 83 Environ. Pollut. Ser. B. 0143-148X/83/0005-0083/$03.00 ~-5'Applied Science Publishers Ltd, England, 1983. Printed in Great Britain

84

S. Monaro, S. Landsberger, R. Lecomte, P. Paradis, G. Desaulniers, A. P'an

normal. However, much larger asbestos fibre concentrations (as high as 10 ~1 fibres litre-~) have been detected and measured in lakes, rivers and much of the drinking water of Canada and the United States (Cunningham & Pontefract, 1971 ; Durham & Pang, 1975, 1976; McMillan et al., 1977; Schmitt et al., 1977). Clearly these asbestos pollution levels could entail harmful effects upon the exposed population. The biological and environmental impact of the asbestos pollution in water has so far received very little attention and the few existing studies give contradictory results (McMillan et al., 1977). This unfortunate situation is probably caused by a lack of systematic data over the wide period of time (20 or 30 years) embracing the initial exposure and the possible appearance of biological effects in the affected subjects. Such data exist in the case of asbestos pollution in air and have allowed accurate predictions concerning the dangers related to breathing asbestos fibres (Selikoff, 1969; Hodges, 1973). Similar data are clearly needed for asbestos pollution in water in order to gauge its long-range impact upon the population. In the present work we wish to show how asbestos pollution levels in river water can be assessed via PIXE methods. The feasibility of these methods has been already proven and reported elsewhere (Desaulniers et al., 1979; Monaro et al., 1981).

EXPERIMENTAL PROCEDURES Water samples have been collected from the B6cancour river in Qu6bec. This river drains the water from the mining areas of Thetford Mines and Black Lake; it is highly exposed to the runoffwaters coming from mining wastes and tailings located on the river's edges. The samples were collected from twelve locations placed upstream and downstream from the tailing dumps in order to compare data from exposed and unexposed pollution sites. The total distance covered was approximately 180km. From each of the 5 litre collected samples, two samples of 250 ml were simultaneously filtered through GS-type Millipore filters. The various pairs of filters with their retained residues were then dried and prepared for the TEM (Transmission Electron Microscope) and PIXE (ProtonInduced X-Ray Emission) experiments respectively, in order to compare the results obtained by both methods. The filter prepared for the PIXE measurements was placed whole in a

Asbestos pollution measurements in river water

85

beaker and ashed at low temperature (200 °C) to destroy both the organic matrix of the sample and the filter. The ashes .were then dissolved in 1 ml of H N O 3 (2y) and doped with 300ppm of Co used as an internal standard. The targets were prepared by placing 200 pl of this solution on a 0.1 pm Nuclepore filter and drying under vacuum. The targets were bombarded with a 1"6 MeV proton beam obtained from the Universit6 de Montr6al Tandem Van de Graaff accelerator. The sample X-ray yields (asbestos and its non-fibrous counterpart serpentine are composed essentially of silicon and magnesium as 3MgO.2SiO.2H20 plus a few heavier trace elements) were measured with the targets placed at 45 ° to the incident beam, using a Si(Li) detector having a 160eV resolution at an energy of 5.9 keV. The X-ray spectra were automatically recorded and analysed on-line by a 3100 CDC computer using methods and techniques developed in this laboratory (Barrette et al., 1976; Lecomte et al., 1978, 1981).

RESULTS

Reproducibility In order to check the reproducibility of the sample preparation procedures and the PIXE analysis, nine different water samples collected the same day at the same sampling site have been prepared independently to study the variation of the trace element concentrations. The results of these measurements are presented in Table 1 which shows that the elements detected in the water samples can be divided into two classes. The first group contains elements whose concentration is determined within a 4 ~o-7 ~o standard deviation (Mg, A1, Si, K, Ti, Ca, Mn and Fe) and in this group one can find several important suspended particles. The elements of the second group have, instead, a standard deviation of 12 ~ 19 ~o (Na, P, S, CI, Cr) and with the exception of Cr do not belong to the asbestos fibres.

Water pollution studies in the B~cancour river Concentration vs time. In Fig. 1, the average concentration of Mg

determined from all the twelve sites is plotted versus the sampling time. The error bars represent the standard error on the mean value. It can be

86

S. Monaro, S. Landsberger, R. Lecomte, P. Paradis, G. Desaulniers, A. Fan TABLE 1 Results on the Reproducibility of the Measured Concentrations for Nine Samples Collected the Same Day at the Same Sampling Site 7 Element

Concentration (mg litre- 1)

Standard deviation (rag litre- ~)

Standard deviation (%)

Na Mg

0.778 1.204 2.574 6.399 0.171 0.068 0.067 0.601 0.164 0.075 0.007 0.179 1.140

0.099 0.060 0.162 0.420 0.028 0.013 0.007 0.038 0.007 0.005 0.002 0.007 0.048

13 5 6 7 16 19 12 6 5 6 17 4 4

AI Si P S CI K Ca

Ti Cr Mn Fe

observed that there are smooth variations from sampling to sampling, with the exception of sampling no. 5. This increase can probably be explained in terms of meteorological factors. In fact, the weather was either sunny or cloudy during all samplings except for sampling no. 5, which was characterised by heavy rains before and during the collection day. A similar trend has also been noted for all the other trace elements. This may suggest the presence of some erosion process. C o n c e n t r a t i o n vs site. Excluding sampling no. 5, the average Mg concentrations at each sampling site are shown in Fig. 2 (bottom curve). It can be seen that the concentration increases sharply in the mining area and drops rapidly after the lakes area. This decrease of the Mg concentration could indicate the existence of a sedimentation process of the suspended matter. The upper curve represents the Mg concentration calculated for sampling no. 5. The two curves show a similar pattern. However, the Mg concentration is about twice as high as that determined in normal weather, with the exception of site no. 40, where it increases by four times. The fact that the high pollution level at site no. 40 drops very fast suggests

87

Asbestos pollution measurements in river water

Mg

400

I

I

I

I

I

I

i

2

4

6

8

10

12

14

TIME(WEEKS)

Fig. 1. Average concentration values of Mg determined from all twelve collection sites and measured for each different sampling which was carried out every two weeks.

that the particles coming from the erosion of the tailings may also sediment very fast due to their larger size and weight. Correlation between elements and fibres. To investigate the eventual pattern between the elemental concentration fluctuations and the number of asbestos fibres present in the river water, the counterparts of the samples analysed with PIXE were studied with the TEM techniques. The elemental concentrations determined from the PIXE analysis at the twelve sites and for all the samplings have been correlated with each other and with the number of fibres measured by the TEM procedures. The final MQ 2400 :::~:

20O0

•

Mining area Town

• Lake 1600 IZO0 8O0 400 I0

50

;~5

95

5()

IO0

7'5

I00

IJO Site

I;~5

I~)00ist(Jnce (kin)

Fig. 2. Mg concentration values determined along the B+cancour river. The upper curve represents the Mg concentrations calculated from sampling no. 5. The bottom curve represents the average values calculated from all the other samplings.

88

S. Monaro, S. Landsberger, R. Lecomte, P. Paradis, G. Desaulniers, A. P'an

TABLE 2 Pearson Correlation Coefficients (r) Between the Elemental Concentrations and the Number of Fibres per litre Na

Mg AI

Si

P

S

CI

K

Ca

77

Cr

Mn

Fe Fibres

Nal.00 0.58 0.56 0.58 0.27-0.11 0.23 0.51 0.27 0.50 0.45 0-62 0.65 0.29 Mg 1-00 0.66 0.77 0.53 0 . 2 1 0 . 5 1 0.68 0.58 0.64 0.39 0.59 0.78 0.70 AI 1.00 0.93 0.01 - 0 . 1 3 0.09 0.99 0.50 0.98 0-62 0 . 8 1 0.93 0.15 Si 1.00 0.29 0.05 0.22 0.95 0.68 0.94 0 . 6 1 0.73 0.89 0.34 P 1.00 0.37 0.57 0.07 0.65 0.02 0.22 0.10 0.23 0.72 S 1'00-0.02 -0"04 0.41 - 0 . 0 7 -0"24 - 0 ' 2 4 -0"13 0.26 Cl 1.00 0'09 0"22 0 - 1 1 0 " 2 9 0'16 0"25 0"55 K 1"00 0"57 0 " 9 9 0 " 6 3 0.78 0.91 0.19 Ca 1.00 0-53 0 " 3 5 0'38 0-56 0"48 Ti 1.00 0 " 6 4 0.74 0"88 0'15 Cr 1.00 0.54 0.63 0.02 Mn 1.00 0.88 0-26 Fe 1.00 0.31 Fibres 1.00

results are shown in Table 2. It is found that magnesium is the element that is mostly related to the number of fibres (r = 0.70). This is expected since Mg is a major component of asbestos. The correlations for P and C1 are not considered very meaningful since the elements are not present in the asbestos fibres (Giauque et al., 1977). f/! i0 Io ee

0.498

•

0.373 0.249 O. 124

250

500

750 (lug/I)

IOOO

1250

< C > Mg

Fig. 3. Relationship established between the Mg concentrations measured by the PIXE technique and the number of fibres per litre if/l) determined by the TEM method (see text).

Asbestos pollution measurements in riz'er water

89

For clarity, the strong relationship between Mg and the number of fibres per litre is also shown in Fig. 3. The deviation of a few points from the best regression line is partly owing to the large variations encountered in the determination of the number of fibres per litre with the TEM counting procedure. Variations of the order of 600 ~ have often been measured with this procedure.

CONCLUSIONS This work has shown that PIXE analysis is very valid in detecting asbestos pollution in river water. The asbestos pollution levels have been correlated to the measured magnesium concentrations at each of the twelve sampling sites. The data clearly show that the pollution is high in the mining area and it sharply decreases downstream. The results are supported by parallel measurements carried out with the usual TEM techniques. Furthermore, it appears that the asbestos pollution levels are affected by the meteorological conditions. Thus in order to chart correctly the asbestos pollution in river water, the sampling procedures must be performed at uniform meteorological conditions.

ACKNOWLEDGEMENT The work reported in this paper was supported by the Natural Sciences and Engineering Research Council of Canada.

REFERENCES Barrette, M., Lamoureux, G., Lebel, E., Lecomte, R., Paradis, P. & Monaro, S. (1976). Trace element analysis of freeze-dried blood serum by proton and alpha-induced X-rays. Nucl. Instr. and Meth., 134, 189-96. Cunningham, H. M. & Pontefract, R. (1971). Asbestos fibres in beverages and drinking water. Nature, Lond., 232, 332-3. Desaulniers, G., P'an, A., Lecomte, R., Paradis, P., Landsberger, S. and Monaro, S. (1979). On the use of the PIXE method to determine river water pollution in asbestos mining areas. Int. J. Appl. Radiat. and Isotop., 30, 261-2.

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Durham, R. W. & Pang, T. (1975). Asbestos fibers in Lake Superior, Water Quality Parameters. Am. Soc. Test. & Mater., Spec. Tech. Rep., 573, 5-13. Durham, R. W. & Pang, T. (1976). Asbestiform fiber levels in Lakes Superior and Huron. Environment Canada, Inland Waters Directorate, Canada Centre for Inland Waters, Burlington, Ontario, Scientific Series, No. 67, Minister of Supply and Services Canada. Catalog No. EN36-502/67. Giauque, R. D., Garrett, R. B. & Goda, L. Y. (1977). Energy dispersive X-ray fluorescence spectrometry for determination of twenty-six trace and two major elements in geochemical specimens. Analyt. Chem., 49, 62-7. Hodges, L. (1973)..Environmental pollution. New York, Holt, Rinehart and Winston. Lecomte, R., Landsberger, S., Paradis, P., Monaro, S. & Desaulniers, G. (1981). X-Ray Spectrosc., 10, 113-16. Lecomte, R., Paradis, P., Monaro, S., Barrette, M., Lamoureux, G. & M+nard, H. A. (1978). Automatic data acquisition and on-line analysis of trace element concentration in serum samples. Nucl. Instr. & Meth., 150, 289-99. McMillan, L. M., Stout, R. C. & Willey, B. F. (1977). Asbestos in raw and treated water: an electron microscopy study. Environ. Sci. & Technol., 11,390-4. Monaro, S., Lecomte, R., Paradis, P., Landsberger, S. & Desaulniers, G. (1981). Asbestos pollution assessment in river water by PIXE methods. Nucl. Instr. & Meth., 181,239-41. Schmitt, R. P., Lindsten, D. & Shannon, T. F. Decontaminating Lake Superior of asbestos fibers. Environ. Sci. & Technol., 11,462-5. Selikoff, I. J. (1969). Asbestos. Environment, 11, 3-13.