J Radioanal Nucl Chem (2010) 283:465–470 DOI 10.1007/s10967-009-0438-3
Water quality assessment of Toledo River and determination of metal concentrations by using SR-TXRF technique F. R. Espinoza-Quin˜ones • S. M. Pala´cio • A. N. Mo´denes • N. Szymanski C. E. Zacarkim • D. C. Zenatti • M. M. T. Fornari • M. A. Rizzutto • M. H. Tabacniks • N. Added • Alexander D. Kroumov
•
Received: 28 July 2009 / Published online: 30 December 2009 Ó Akade´miai Kiado´, Budapest, Hungary 2009
Abstract The region of Toledo River, Parana´, Brazil is characterized by intense anthropogenic activities. Hence, metal concentrations and physical–chemical parameters of Toledo River water were determined in order to complete an environmental evaluation catalog. Samples were collected monthly during one year period at seven different sites from the source down the river mouth, physical– chemical variables were analyzed, and major metallic ions were measured. Metal analysis was performed by using the synchrotron radiation total reflection X-ray fluorescence technique. A statistical analysis was applied to evaluate the reliability of experimental data. The analysis of obtained results have shown that a strong correlation between physical–chemical parameters existed among sites 1 and 7, suggesting that organic pollutants were mainly responsible for decreasing the Toledo River water quality.
F. R. Espinoza-Quin˜ones (&) S. M. Pala´cio A. N. Mo´denes N. Szymanski C. E. Zacarkim D. C. Zenatti M. M. T. Fornari Postgraduate Program of Chemical Engineering, NBQ, West Parana´ State University, rua da Faculdade 645, Toledo, Parana´ 85903-000, Brazil e-mail:
[email protected] M. A. Rizzutto M. H. Tabacniks N. Added Institute of Physics, University of Sa˜o Paulo, ua do Mata˜o s/n., R 187, University city, Sa˜o Paulo 05508-900, Brazil A. D. Kroumov Center of Applied Energy Research and Biosystem Agricultural Engineering, University of Kentucky, 212 C.E. Barnhart Building, Lexington, KY 40546-0276, USA
Keywords Trace elements SR-TXRF technique Physical–chemical parameters Environmental monitoring
Introduction In natural aquatic ecosystems, the organic and inorganic chemical pollutions are of worldwide concern. Increasing human land occupation and industrial pollutions of river water, especially in developing countries, has made the river water quality evaluation a crucially important matter in recent years. Many efforts have been directed toward making qualitative and quantitative decisions based on the monitoring water quality data and interpretation of results [1]. Studies have demonstrated the declining water quality was correlated with the increasing agricultural development at catchments scale [2, 3]. The activities originated from the use of agricultural and urban lands have contributed for an increasing of organic and inorganic pollutants and suspended particulate matter, among others [4–6]. Due to the rapid dilution of effluents, a monitoring of the pollutants have become a challenging and thus requires sensitive analytical techniques, intensive sampling programs and long collection time [7]. In the last decade, the total reflection X-ray fluorescence with synchrotron radiation (SR-TXRF) became a highly useful multi-element technique for a determination of trace elements in environmental samples [8–16]. It should be noted that in the past, no relatively comprehensive research on water quality in the mentioned river has been performed. Hence, the main objective of this study was to monitor the levels of trace elements in the samples of Toledo River water by using the SR-TXRF technique as well as to
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determine the physical–chemical parameters values and their possible correlations.
Materials and methods Sampling sites The Toledo River hydrographic basin is located in the southern region of Brazil in the western part of Parana´ State. This region is situated between 24°460 and 24°450 S latitudes and 53°340 and 53°460 W longitudes, respectively and drains an area of approximately 97 km2 (approximately 30 km long). The river has been polluted by untreated urban wastewaters, as well as by the run-offs from farms and agricultural lands, and discharges from tannery industries or other industrial sources. Seven sampling sites were installed along the river stream to identify potential pollution sources. A sample collection protocol was set up for monthly collection of water samples and for measuring heavy metal concentrations and physical– chemical parameters. A map of the area under investigation with a localization of the sampling sites is shown in Fig. 1. Analytical procedure Water samples were collected monthly during one year between December 2003 and November 2004. One liter of water approximately from the middle of the water stream was sampled with a polypropylene vessel. All the samples (in sites from 1 to7) were collected during one day. The physical–chemical analyses of aliquots of the representative samples included: pH, electrical conductivity,
turbidity, ammonium-nitrogen (NH4?–N), nitrate-nitrogen (NO3-–N), nitrite-nitrogen (NO2-–N), fecal and total coliforms, dissolved oxygen (DO), biochemical oxygen demand (BOD5), total ortho-phosphate (PO43-), suspended solids (SS). Standard methods [17] were adapted for all physical–chemical measurements. Standard stock solution (11.6 g L-1) of yttrium was quantitatively prepared by dissolving a 50-g Merck package Y(NO3)3:6H2O in Ultra Pure Milli-Q water. The solution was stored in an acid-washed volumetric flask. Multi elements stock solutions have been also prepared from mono-elements standard solutions of some light (K, Cr, Mn, Fe, Cu, Zn, Ga, Br, Sr, and Y) and heavy (Mo, Ag, Cd, Sb, Cs, Ba, Sm, Dy, and Pb) elements, mixed in different concentrations, in order to cover an energy wide region of K and L X-ray series, and to obtain sensitivity curves from the synchrotron radiation reflection X-ray fluorescence technique. Milli-Q water was used throughout the multi-standard material preparation. A 10-lL aliquot of yttrium stock solution was added to 10 mL of each sample. An aliquot of 5 lL was pipetted on 3 mm thick acrylic disks, and left to dry at ambient temperature in a clean box. In each sample batch, procedural blanks were included. The detections limits were set up as three times value of the procedural blanks standard deviation. SR-TXRF measurements The SR-TXRF measurements were carried out by using a polychromatic X-ray beam, with beam energy from 2 up to 23 keV from the D09-XRF beam-line of the Brazilian Light Synchrotron Laboratory. Each reflector disk containing the
Fig. 1 Map of the Toledo River hydrological basin showing the location of the seven sampling sites
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Water quality assessment and determination of metal concentrations
467
Table 1 Mean annual value of physical–chemical and biological parameters of Toledo River water samples taken from seven collection sites BELa
Parameters
Site 1
Site 2
Site 3
Site 4
Site 5
Site 6
Site 7
Total coli-forms (103 MPN/100 mL)
5
2.20
8.8
7.2
13.8
236
166
190
Fecal coli-forms (103 MPN/100 mL)
1
0.06
3.6
2.9
3.0
27.5
84
103
NH4?–N (mg l-1)
0.02
0.13
0.20
0.17
0.13
0.80
9.06
9.20
(mg l )
10
0.41
1.18
1.15
1.40
1.72
2.65
3.12
(mg l-1)
1
0.02
0.02
0.03
0.04
0.05
0.22
0.83
DO (mg l-1)
5
8.47
9.16
8.65
8.63
8.72
7.42
7.36
BOD5 (mg l-1)
5
1.72
2.16
1.5
2.22
3.04
6.4
11.14
PO43- (mg l-1)
0.025
0.006
0.02
0.03
0.03
0.06
0.91
0.84
pH
6–9
6.55
6.41
6.66
6.66
6.82
7.10
7.30
SS (mg l-1)
50
4
12
13
16
24
85
71
Turbidity (NTU)
100
4.2
13.3
23.2
24.9
29.8
31.4
36.2
NO3-–N NO2-–N
a
-1
Brazilian Environmental Legislation of river water of class II. 2
evaporation-residual sample was put in an X-ray total reflection position and the acquisition time was set up at 300 s. A Si(Li) detector, with 160 eV FWHM@Mn-Ka line, surrounded by tantalum collimators and placed at 90o to the incident beam, was used for X-Ray detection. The SR-TXRF measurements were performed in air. The X-ray spectra were analyzed by using the AXIL software [18]. Background-subtracted Ka (K, Cr, Mn, Fe, Cu, Zn, Ga, Br, Sr, and Y) or La (Sr, Mo, Ag, Cd, Sb, Cs, Ba, Sm, Dy, and Pb) peak areas were used to determine the relative sensitivity yields of the SR-TXRF spectrometer and to calculate the samples elements concentrations. Statistical analysis Fit test Goodness was employed in order to test the samples null hypothesis based on an error normal distribution, by using the Kolmogorov–Smirnov method [19]. Parametrical statistical methods were applied because of the null hypothesis acceptance. Relations between physical–chemical parameters and elements concentration values were analyzed by an application of Spearman’s correlation coefficient (non-parametric measure of correlation). All statistical analyses were carried out at 95% (p = 0.05) confidence interval.
Results and discussion Physical–chemical parameters The annual monitoring results of eleven physical–chemical parameters values are summarized in Table 1. The null hypothesis for Kolmogorov–Smirnov test was that the data error was normally distributed. In order to explore monitor trends for both planning and day-to-day management of
surface water quality for the public, the river pollution index (see Table 2) was applied to assess the river water quality through DO, BOD5, SS, and NO3-–N values. In addition, a strong positive and significant Spearman’s correlation coefficient was found between the most physical–chemical parameters (total and fecal coli-forms, NH4?–N, NO3-–N, NO2-–N, PO43-, pH, and suspended solids) values at seven collection sites in Toledo river (see Table 3), while no statistically significant correlation coefficient was found between physical–chemical and elements concentration values. The fact has shown that the main source of pollutions in Toledo River could be addressed to an organic origin. Comparing the collection sites (see Table 1), the values of these indicators increased systematically along the river course, reaching the maximum values at the last collection site where the influence of the Toledo city activities (municipal wastewater treatment plant, industrial and untreated domestic wastewaters) onto the river water quality is more evident. The analysis of the samples have shown that all physical–chemical parameters values at the collection site 1 were below the maximum limits recommended by the Brazilian Environmental Legislation (BEL) for river water of class II [20]. Hence, the domestic wastewater treatment, agricultural and aquiculture activities were under control. Analysis of the samples taken from sites 2 to 4 has shown that these parameters values slightly increased above the recommended limits where agricultural plantations and agglomeration of farm with piggery breeding were settled in, contributing mainly with the increase of organic pollutants in the river ecosystem. Near the site 4 a river water treatment plant for drinking water was installed. Between site 4 and 5 the untreated wastewaters of Toledo city are released into the river, resulting in a high increase of the amount of total and fecal coli-forms according to recommended limits by the BEL. Upstream the site 6, treated
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F. R. Espinoza-Quin˜ones et al.
468 Table 2 The classification ranks defined by using the river pollution index (RPI) Items/ranks
Good
Slightly polluted
Moderately polluted
Heavily polluted
DO (mg l-1)
Above 6.5
4.6–6.5
2.0–4.5
Under 2.0
BOD5 (mg l-1)
Under 3.0
3.0–4.9
5.0–15
Above 15
NH4?–N (mg l-1)
Under 0.5
0.5–0.99
1.0–3.0
Above 3.0
SS (mg l-1)
Under 20
20–49
50–100
Above 100
Table 3 Spearman correlation coefficients between the physical–chemical and biological parameter values of water samples at seven collection sites inside the Toledo River T. coli-forms T. coli-forms F. coli-forms NH4?–N
F. coli-forms
NH4?–N
NO3-–N
NO2-–N
0.857
0.739
0.893
0.829
0.937
DO
PO43-
pH
SS
Turbidity
0.793
0.757
0.821
0.857
0.964
0.847
0.847
0.775
0.857
0.893
0.847
0.773
0.809
0.755
0.775
0.811
NO3-–N NO2-–N
0.937
0.901
0.865
0.929
0.964
0.945
0.982
0.955
0.991
0.927
0.991
0.955
0.919
0.955
DO PO43pH SS
0.964
food processing originated-industrial effluent is released into the Toledo River. In sites 5 and 6, the river water quality could be classified as moderately polluted according to the river pollution index (see Table 2). At the site 7 which is located after the municipal wastewater treatment plant, the river water could be classified as strongly polluted.
Elements concentrations Based on the strong X-ray Ka peak intensity of known element concentrations in multi element standard samples, the relative-to-gallium sensitivity values were determined for both X-ray K and L series of the SR-TXRF spectrometer and were fitted (see Fig. 2) by applying an exponential-type function (see Eqs. 1, 2). A set of good correlation coefficients and v2 values for both sensitivity curves were obtained. SK ðZ Þ ¼ 0:0166 exp 17:572 þ 1:559 Z 0:0258 Z 2 ; r 2 ¼ 0:9981 ð1Þ SL ðZ Þ ¼ 18:398 exp 20:277 þ 0:446 Z 0:0031 Z 2 ; ð2Þ r2 ¼ 0:9894 where, SK and SL -represent the relative-to-ytrium fluorescent sensitivity for light and heavy elements, respectively, Z is the atomic number.
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Fig. 2 Experimental and fitted relative-to-Yttrium sensitivities for K and L series for SR-TXRF
The following elements of interest K, Ca, Ti, Cr, Mn, Fe, Cu, Zn, Sr and Ba, and Y, as internal standard were mainly identified by their strong X-ray Ka and La lines. The X-ray energy region of light elements such as Al, P and S, among others, was identified as a non accessible region by the configuration of SR-TXRF spectrometer. In addition, some elements were not possible to identify because of their low concentrations in river waters samples
Water quality assessment and determination of metal concentrations
469
Table 4 Annual mean value of elements concentrations of Toledo river water samples taken from seven collection sites BELa (mg l-1)
Element
Elements concentration at collection site (mg l-1) Site 1
Site 2
Site 3
Site 4
Site 5
Site 6
Site 7
K
1.348
3.387
3.388
3.852
5.033
26.016
27.445
Ca
10.645
15.214
16.380
19.482
25.582
44.264
44.634
Ti
0.266
0.296
0.404
0.416
0.798
0.614
1.173
Cr
0.050
0.024
0.024
0.026
0.026
0.034
0.031
0.033
Mn
0.500
0.091
0.062
0.068
0.073
0.116
0.140
0.192
Fe
5.000
2.716
2.911
3.553
3.690
6.093
5.648
8.875
Cu Zn
0.013 5.000
0.014 0.124
0.024 0.090
0.032 0.096
0.037 0.151
0.027 0.136
0.032 0.140
0.100 0.155
0.059
0.080
0.074
0.088
0.093
0.152
0.140
0.079
0.055
0.069
0.072
0.135
0.108
0.167
Sr Ba a
1.000
Brazilian Environmental Legislation of river water of class II. 2
and the strong X-ray peak interference caused by the main elements in it. All Ytrium-relative-to element concentrations in river water samples were calculated by using Eq. 3. The values of the mean, standard deviation and range element concentrations of the samples from the river waters at each site are summarized in Table 4. Ci ðZ Þ ¼
IZi CY I Y Si ð Z Þ
ð3Þ
where, Ii -represents the Ka or La X-ray line fluorescent intensity of the element; Ci stands for the element concentration in the sample; CY is the ytrium concentration (internal standard). In Table 4, it can be observed that K, Ca and Fe concentrations profiles have a similar pattern of increase comparing them with the physical–chemical parameters (total and fecal coli-forms, NH3–N, BOD5, PO4 and SS) when downstream from site 1 to 7. After the site 5, where food processing based-industrial effluents are released into the river, an increase of K and Ca concentrations was observed. The fact can be interpreted with a presence of K and Ca elements connected with anthropogenic activities. Thus, the bad river water quality is mainly due to the contribution of organic pollutants originated from the Toledo city.
Conclusions The goal of this work was considered as a first attempt to identify inorganic and organic pollutants of the Toledo River. The main physical–chemical parameters having huge impact on the river water quality were summarized as follows: total and fecal coli-forms, ammonia nitrogen, BOD5, orto-phosphate, and suspended solids. Analysis of
the samples has shown that mentioned parameters values were above the limits recommended by the Brazilian Environmental Legislation. Between sites 6 and 7, a major portion of the pollutants can be addressed to the food processing based-industrial and municipal wastewater treatment plant effluents. The only high increase of K and Ca concentration values were monitored at sites of the Toledo city. The analysis of the obtained results has shown that the water samples taken from the river were moderately and heavily polluted; hence the improved techniques for industrial and municipal wastewater treatment have to be set up in order to prevent further environmental changes. Acknowledgements We are grateful to the Brazilian Light Synchrotron Laboratory (LNLS) for the partial financial support of this study (project #1624).
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