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Study of seleniferous soils using instrumental neutron activation analysis
Applied Radiation and Isotopes 69 (2011) 818–821
Contents lists available at ScienceDirect
Applied Radiation and Isotopes journal homepage: www.elsevier.com/locate/apradiso
Study of seleniferous soils using instrumental neutron activation analysis Alok Srivastava a,n, G.S. Bains a, R. Acharya b, A.V.R. Reddy c a b c
Department of Chemistry, Panjab University, Chandigarh 160014, India Radiochemistry Division, Bhabha Atomic Research Centre, Mumbai 400085, India Analytical Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400085, India
a r t i c l e i n f o
a b s t r a c t
Article history: Received 18 June 2010 Received in revised form 19 January 2011 Accepted 20 January 2011 Available online 3 February 2011
Soil samples from the seleniferous region of Punjab State in India were analyzed by instrumental neutron activation analysis (INAA) using reactor neutrons and high resolution g-ray spectrometry. Samples were collected from three different depths namely surface, root and geological bed zones. Concentrations of 15 elements including selenium and arsenic were determined by relative method. For comparison purposes, soil samples collected from a non-seleniferous region were also analyzed. & 2011 Elsevier Ltd. All rights reserved.
Keywords: Seleniferous soil INAA g-Ray spectrometry Selenium Arsenic Toxicity
1. Introduction Selenium (Se) is an essential trace element but when present at elevated concentrations in the local environment can be quite toxic. The safe limit recommended by World Health Organization (WHO) for soil and water are less than 1 mg kg 1 (ppm) and 10 mg L 1 (ppb), respectively. The range between selenium toxicity and deficiency is rather narrow. The problems related to selenium toxicity were documented as early as twelfth century by Marco Polo while traveling through China as the disease mentioned by him had symptoms of selenium toxicity in livestock. Excess of selenium can lead to problems like alkali disease, cracked hoofs and horns in animals besides giddiness, lassitude, diarrohea, nervousness, mental depression, garlic odor to breath, hair and nail loss and deformity in humans (Willett et al., 1983). Arsenic (As) on the other hand is not an essential trace element but could be quite toxic due to its pro-oxidant nature. It is a known human carcinogen, a teratogen and a suspected cardiovascular toxin. Arsenicosis is characterized by melanosis, keratosis and cancers of the skin, lungs, liver and bladder. The severe human exposure to arsenic is geographically found in the plains of Ganga and Brahmaputra where many of the indigenous population are exposed to higher As levels in drinking water that exceed the WHO recommended limit of 10 ppb. The element
n
Correspondence author. Tel.: + 91 172 2534424; fax: + 91 172 2545074. E-mail address: [email protected] (A. Srivastava).
0969-8043/$ - see front matter & 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.apradiso.2011.01.027
which can counteract the toxicity of the pro-oxidant arsenic is selenium (Schrauzer, 1981) as it is a strong anti-oxidant. It has been suggested by Spallholz et al. (2004) that selenium used as nutritional supplement can reduce the toxic effects of arsenic to a considerable extent. Selenium is found in high concentrations across the globe from plains of America, the prairie provinces of Canada, Soviet Union and China (Cranston, 1985; Losi and Frankenberger, 1997; Tan et al., 2002). The Nawanshahr–Hoshiarpur region of Punjab in India lying between 311 to 311 150 North Latitude and 761 to 761 150 East Longitude has also been reported to have elevated levels of selenium (Bhatnagar, 2001; Srivastava et al., 2002, 2006; Dhillon and Dhillon, 2003; Sharma et al., 2009). It is still not clear how this region became so rich in selenium. Dhillon and Dhillon (1991) hypothesized that the reason for elevated levels could perhaps be due to the additional selenium deposition from leaching of previously existing seleniferous deposits by seasonal rivulets, which come from the higher reaches of Siwalik Hills and drain into this region. They were the first to make an attempt to estimate the concentration of selenium in soil and biota using the conventional colorimetric method. Srivastava et al. (2002) later extended the work using instrumental neutron activation analysis (INAA) technique. Recently, Sharma et al. (2009) used INAA for determination of concentration of selenium in soil and crop products from seleniferous region of Punjab state, India. INAA has been used by Acharya et al. (2009) for determination of arsenic in water samples and by Nyarku et al. (2010) for studying arsenic in gold ore. INAA is an established simultaneous
A. Srivastava et al. / Applied Radiation and Isotopes 69 (2011) 818–821
multi-element measurement technique and has been employed in diverse fields such as geological, biological, biogeochemical, environmental, medical and cosomological origin (Davis et al., 1982; Frontasyeva and Steinnes, 1995; Luten et al., 1977; Morrison and Potter, 1972; Stone et al., 1988). The use of high flux research reactor and high resolution gamma spectrometer with high efficiency high purity germanium (HPGe) detector coupled to a multi-channel analyzer makes this method highly sensitive for simultaneous determination of many elements (Balaji et al., 2000; Moens and Dams, 1995; Muramatsu et al., 1989). It is further observed that between arsenic and selenium, INAA is more sensitive to arsenic than selenium due to favorable nuclear properties of arsenic like isotopic abundance, half life of 76 As (26.3 h) and the gamma-ray abundance of 559 keV (DeCorate and Simonits, 1989). The objective of the present work is to determine the concentration of different elements with special emphasis on selenium and arsenic to understand their toxicity potential as well as to examine the issue of their deposition. In view of this, soil samples from three different depths of three different places of seleniferous region of Punjab State, India, were analyzed by INAA. In addition, two surface soil samples from the non-seleniferous region of Singbhum, Jharkhand, were also analyzed by INAA.
2. Experimental The soil samples used for the study in the present work were collected using the standard auger method. The location for sampling was selected on the basis of findings published in earlier work by Srivastava et al. (2002). Fig. 1 shows the map of the region from where the sample collection was undertaken. The samples from Barwa, Jainpur and Nazarpur were collected from three different depths viz. surface zone (0–10 cm), root zone (20–40 cm) and geological bed (80–120 cm).
819
The soil samples in powder form weighing about 100 mg each were wrapped in thin aluminum foil separately. The reference materials SL-1 (comparator standard) and SL-3 (control) obtained from IAEA were also packed in a similar way. The individual packets were then wrapped in a large aluminum foil and placed in an aluminum container, which was sent to CIRUS reactor of Bhabha Atomic Research Centre (BARC), Mumbai, for irradiation. The size of the comparator as well as the sample was kept small to minimize the neutron self shielding and gamma-ray attenuation effects. The irradiations were carried out for 6 h with a neutron flux of the order of 1013 cm 2 s 1. After a cooling period of two days, the samples were transferred to a fresh aluminum foil to avoid blank activity due to aluminum. Then the individual packets were mounted on standard Perspex plates. The gamma activity of the activation products was assayed using a 40% relative efficiency HPGe detector coupled to a PC based 8k channel analyzer with a reproducible sample to detector geometry at about 5 cm from the face of the detector. The detector system had a resolution of 1.9 keV at 1332 keV of 60Co. The samples were counted for 1000 to 10,000 s after cooling samples for periods ranging between 2 and 15 days. The gamma rays of 264 keV (75Se) and 559 keV (76As) were used in the present work as there are no spectral interference of the gamma rays of both the activation products (DeCorate and Simonits, 1989). 2.1. Calculations The peak areas were determined using peak fit software PHAST, developed at BARC. The relative method of INAA was employed for calculating the concentrations of the elements of interest using the following relation: mx ¼ mstd cpsx =cpsstd
ð1Þ
where mx is the mass of the element of interest, mstd is the mass of the element in the reference standard, cpsx and cpsstd are the decay corrected count rates (counts per second, cps) of activation product of interest in the sample and the reference standard, respectively. The mx is converted to concentration (mg/kg) by dividing with the sample mass.
3. Results and Discussion
Fig. 1. Map of Punjab showing the Hoshiarpur and Nawanshahr districts from where samples were collected.
The concentrations of 14 elements including Na, K, Fe, Cr, As and rare earth elements (REEs) were determined in reference material from IAEA namely RM SL-3 and the results are shown in Table 1. Selenium concentration was determined in IAEA RM SL-1 using elemental standard of Se, since RM SL-3 does not have certified/information concentration value of Se. The deviations with respect to certified concentration values were found to be within 76%. Table 1 also contains 3s detection limits of all elements in the present experimental conditions for a representative soil sample. The results on the concentration level of 15 elements determined in the present work from three different depths namely surface (S), root zone (R) and geological bed (G) are shown in Table 2 for three locations namely Jainpur (J), Barwa (B) and Nazarpur (NZ). The uncertainties quoted are standard deviations obtained from four replicate sample analysis. The concentration profiles of the above mentioned 15 elements were determined at surface level 0–10 cm depth, root zone level 20–40 cm and at a depth ranging between 80 and 120 cm, which for all practical purposes could be considered as geological zone where the effect of uptake due to phyto-accumulation is minimal. In other words the concentrations could be taken as a representative of the normal geological distribution. It is observed from Table 2 that in general the concentrations of most of the
820
A. Srivastava et al. / Applied Radiation and Isotopes 69 (2011) 818–821
elements studied in the present work increased considerably with the increase in depth. The decrease in the concentration observed in some cases especially in the region between the surface and root zone could be attributed to the phenomenon of phytoaccumulation. This aspect comes out very clearly in the case of selenium in the samples of Jainpur and Barwa. Sharma et al. (2009) in their study on phyto-accumulation have shown that the farmers in Jainpur and Barwa region are known to grow maize, mustard, wheat and rice which are very good phyto-accumulators of selenium. In other cases one observes that there is not a big difference on the contrary there is a slight increase. These are the elements which could normally be present in fertilizers and perhaps pesticides used by farmers of this region. The region where the study was carried out has been reported to be seleniferous. This comes out very clearly from the data obtained in the present work. It is further observed that besides Se concentration values, the concentrations of all elements except for Cr (59–124 mg kg 1) are in the expected value range for such type of soil samples. For comparison purpose, INAA study was extended to non-seleniferous surface soil from Singbhum in Jharkhand State, which lies between 221 030 and 221 440 North Latitude and 861 100 and 861 120 East Longitude. This region is known to be rich in iron ore and low grade gold reserves. The soil samples from the above stated region were collected and studied under experimental conditions similar to that of samples
Table 1 Results of elemental concentrations (mg kg 1) of elements present in IAEA RM SL-3 and detection limits (mg kg 1) in a representative soil sample. Element
This work
Certified (info) value
Detection limit
Na K Br La Sm U As Ce Cr Co Fe Rb Zn Th Sea
6787 7 358 8985 7 352 5.8 7 0.4 21.7 7 1.7 3.6 7 0.1 2.42 7 0.21 3.35 7 0.25 43.3 7 1.5 34.8 7 2.3 4.12 7 1.7 111257 450 37.2 7 2.1 29.7 7 1.5 7.2 7 0.3 2.83 7 0.17
6690 7343 8740 7786 5.6 70.6 22.5 7 0.9 3.8 70.3 2.30 70.23 3.20 70.19 45.4 7 1.8 (32.69) (3.89) (10930) 38.8 7 1.9 (30.1) 7.02 70.50 (2.9)
0.5 4.0 0.35 0.05 0.005 0.05 0.02 0.1 0.06 0.03 3.4 0.1 0.08 0.1 0.3
( )—information value. a
from the seleniferous region of Punjab. The data related to concentration level of 11 elements are shown in Table 3 along with a representative data from a sample taken from Jainpur, a seleniferous region. The samples from Singbhum region did reflect the expected pattern thereby authenticating the methodology used in the present work. During the above stated authentication study a very interesting observation was made. The samples from the non-seleniferous zone were found to have low Cr concentrations and high concentrations of Au, Fe and As. A similar arsenic rich region has been reported in southern Tuscany region of Italy (Baroni et al., 2004). There are reports of arsenic toxicity in the neighboring region comprising of West Bengal and Bangladesh so it should not come as a surprise if one observes arsenic in this region too (Boylan and Spallholz, 2009; Jacobs et al., 1970). It would be interesting to carry out study on arsenic in the water bodies of Singbhum region of Jharkhand since the level of arsenic in the soil is rather high (35 and 45 mg kg 1). This study would help in establishing toxicity effect due to arsenic, which is known to be a class 1 carcinogen in normal populace residing in that region. The present study further showed that the concentration of arsenic in soil in the seleniferous pockets of Punjab ranged from 4 to 11 mg kg 1, which is lower than that observed in Bangladesh. In an US-AID study carried out recently by Shah et al. (2009) in Bangladesh it was observed that in more than half of the top soil the concentration of arsenic was more than 10 mg kg-1. Recently, Hundal et al. (2009) have identified a region in Punjab where they found that ground water had arsenic level much higher than 10 mg kg 1: the recommended limit set by US
Table 3 Concentration of elements in mg kg 1 (ppm) from surface soil samples in two soil samples from non-seleniferous (NS) region and one from seleniferous (S) region. Element
Sample 1 (NS)
Sample 2 (NS)
Sample (S)
Chromium Scandium Samarium Lanthanum Sodium Potassium Gold Cobalt Iron Arsenic Selenium
1.12 7 0.02 21.9 7 0.6 3.6 70.1 21.5 7 0.6 6232 7 93 195967 353 1.7 70.1 6.7 70.9 68053 7 5716 34.8 7 2.1 o 0.3
1.00 70.05 24.8 7 1.2 3.5 7 0.2 17.3 7 1.4 5421 7 38 14896 7521 1.3 7 0.1 8.7 7 1.8 69095 7 14372 46.0 7 4.1 o0.3
72.1 7 2.7 12.8 7 0.10 6.9 70.2 43.0 70.6 5202 7 36 133217 719 o 0.05 15.1 7 0.6 367317 367 6.5 70.3 17.7 7 0.6
IAEA RM SL-1.
Table 2 Concentration of elements from Jainpur (J), Barwa (B) and Nazarpur (NZ) at different depths namely surface (S), root zone (R) and geological bed (G) in mg kg 1 (ppm). Element
J (S)
J (R)
J (G)
B (S)
B (R)
B (G)
NZ (S)
NZ (R)
NZ (G)
Chromium Scandium Samarium Lanthanum Sodium Potassium Cobalt Iron Zinc Arsenic Selenium Rubidium Uranium Thorium Bromine
72.1 7 27 12.8 7 0.1 6.9 7 0.2 43.07 0.6 5202 7 36 133217 719 15.1 7 0.6 367317 367 136 7 5 6.5 7 0.3 17.7 7 0.6 1507 16 3.017 0.05 17.1 7 0.3 3.3 7 0.2
82.2 7 3.3 13.3 7 0.1 5.47 0.1 31.7 7 0.4 2107 7 23 4783 7 550 15.4 7 1.2 38400 7 730 97.9 7 5.4 4.77 0.3 3.77 0.3 175.6 7 17.6 3.97 0.1 16.9 7 0.5 2.97 0.2
93.6 7 7.6 14.5 7 0.1 6.2 7 0.1 35.7 7 0.6 1683 7 22 3297 7 824 14.7 7 1.2 401007 3082 99. 97 8.9 5.4 7 0.3 4.9 7 1.1 222.8 7 16.7 4. 17 0.2 19.3 7 0.7 7.1 7 0.7
93.7 7 6.0 19.4 7 0.2 9.1 7 0.2 62.4 7 0.8 6090 7 49 13100 7 995 24.3 7 1.4 54500 7 1145 173 7 10 5.4 7 0.4 12.5 7 0.9 229.320.9 4.07 0.2 21.3 7 0.7 4.8 7 0.4
109.4 7 8.4 19.6 7 0.1 7.2 7 0.2 47.7 7 0.5 3340 7 33 9590 7 786 22.5 7 1.2 56200 7 1124 133 7 7 8.5 7 0.5 3.1 7 0.6 184.9 7 15.5 3.7 7 0.3 19.1 7 0.8 5.3 7 0.4
178.6 710.1 26.8 70.3 10.3 70.1 66.5 70.5 3790 731 13090 7602 27.4 71.1 76300 71068 175 78 10.5 70.3 4.1 71.2 248.9 724.2 4.9 70.4 26.4 70.5 7.7 70.7
59.4 72.4 9.0 70.1 5.0 70.2 29.3 70.3 2610 718 6840 7616 10.4 70.6 25300 7543 76.3 73.1 4.6 70.2 7.0 70.4 95.9 73.4 2.1 70.1 11.4 70.4 3.1 70.2
75.4 7 3.5 10.27 0.1 5.77 0.1 34.1 7 0.3 2730 7 19 70207 575 12.4 7 0.7 29100 7 601 74.6 7 3.7 5.87 0.2 3.07 0.3 122.4 7 5.9 3.57 0.3 13.9 7 0.3 4.87 0.4
124.0 7 6.6 16.2 7 0.2 8.5 7 0.1 50.2 7 0.7 3550 7 32 7920 7 988 17.4 7 1.3 45100 7 1082 108 7 7 9.4 7 0.4 3.0 7 0.3 181.7 7 12.9 7.9 7 0.5 18.9 7 0.6 9.8 7 0.7
A. Srivastava et al. / Applied Radiation and Isotopes 69 (2011) 818–821
Protection Agency and World Health Organization. In the light of the above stated observations it would be interesting to carry out further study of arsenic in soil and water in Punjab as well as the newly identified Singbhum region of Jharkhand in Eastern India.
4. Conclusions In conclusion it can be stated that the present work has been successful in demonstrating the power of instrumental neutron activation analysis in obtaining detailed elemental concentration of different elements in soil samples. The data generated in this work has lead to useful input information for carrying out further biogeochemical studies besides identification of new areas in the Indian States of Punjab and Jharkhand, which require further study to mitigate the toxicity problems arising due to selenium and arsenic.
Acknowledgements The authors are thankful to Ms. Neetu Sharma, Ms. Pragati Sharma and Ms. P. Aggarwal for their assistance with the counting and preparation of some of the initial samples besides Dr. C.R. Suri of Institute for Microbial Technology, Chandigarh, who helped us with the procurement of soil samples from Singbhum. We are thankful to UGC-DAE CSR for providing financial support for the project under contract number CSR/CD/MUM/CRS-M-129/07/2837. The authors are also thankful to Dr. V.K. Manchanda, Head Radiochemistry Division and Dr. P.K. Pujari of Radiochemistry Division of BARC, for their support. We would also like to thank Mr. Amol D. Shinde and K.K. Swain of the Analytical Chemistry Division of BARC, for their valuable help. One of us (AS) would like to thank Alexander von Humboldt Foundation, Bonn, Germany, for providing summer fellowship to work in Aachen University of Applied Sciences, Juelich, Germany, where major part of the manuscript was prepared. References Acharya, R., Nair, A.G.C., Reddy, A.V.R., 2009. Instrumental and speciation neutron activation analysis for arsenic in water samples. J. Radioanal. Nucl. Chem. 81, 279–283. Balaji, T., Acharya, R.N., Nair, A.G.C., Reddy, A.V.R., Rao, K.S., Naidu, G.R.K., Manohar, S.B., 2000. Multielement analysis in cereals and pulses by k0 instrumental neutron activation analysis. Sci. Total Environ. 253, 75–79. Baroni, F., Boscagli, A., Di Lella, L.A., Protano, G., Riccobono, F., 2004. Arsenic in soil and vegetation of contaminated areas in southern Tuscany (Italy). J. Geochem. Explor. 81, 1–14. Bhatnagar, S., 2001. Study of drinking water quality of Nawanshahr region. Department of Chemistry, M.Sc. Dissertation, Panjab University, Chandigarh. Boylan, M., Spallholz, J.E., 2009. In: Srivastava, Alok, Roy, Ipsita (Eds.), Bionanogeo Sciences: The Future Challenge. Ane Books, New Delhi.
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Cranston, D.A., 1985. Canadian Minerals Year Book 1983–1984: Review and Outlook, Catalogue No. M 38-5/33E, Mineral Resources Branch, Energy, Mines and Resources Canada, Ottawa. Davis, A.M., Tanaka, T., Grossman, L., Lee, T., Wasserburg, G.J., 1982. Chemical composition of HAL, an isotopically-ususal allende, inclusion. Geochim. Cosmochim. Acta 46, 1627–1651. DeCorate, F., Simonits, A., 1989. K0-measurements and related nuclear data compilation for (n,g) reactor neutron activation analysis. J. Radioanal. Nucl. Chem. 133, 43–130. Dhillon, K.S., Dhillon, S.K., 1991. Selenium toxicity in soil, plants and animals in some parts of Punjab, India. Int. J. Environ. Stud. 37, 15–24. Dhillon, K.S., Dhillon, S.K., 2003. Quality of underground water and its contribution towards selenium enrichment of soil-plant system for a seleniferous region of northwest India. J. Hydrol. 5 (272), 120–130. Frontasyeva, M.V., Steinnes, E., 1995. Epithermal neutron activation analysis of mosses used to monitor heavy metal deposition around an iron smelter complex. Analyst 120, 1437–1440. Hundal, H.S., Singh, K., Singh, D., 2009. Arsenic content in ground and canal waters of Punjab, north–west India. Environ. Monit. Assess. 154, 393–400. Jacobs, L.W., Syers, J.K., Keeney, D.R., 1970. Arsenic sorption by soil. Soil Sci. Soc. Am. J. 34, 750–754. Losi, M.E., Frankenberger, W.T., 1997. Bioremediation of selenium in soil and water. Soil 162, 692–702. Luten, J., Das, H., De Ligny, C., 1977. The determination of bromine and iodine in environmental water samples by thermal neutron activation and isotope exchange. J. Radioanal. Nucl. Chem. 6 (35), 147–155. Moens, L., Dams, R., 1995. A comparison between two methods for trace and ultratrace element analysis. J. Radioanal. Nucl. Chem. 192, 29–38. Morrison, G.H., Potter, N.M., 1972. Multielement neutrin activation analysis of biological material using chemical group separations and high-resolution gamma spectrometry. Anal. Chem., 839–8427.4, 839–842. Muramatsu, Y., Cortes Toro, E., Parr, R.M., 1989. Nuclear-related analytical techniques: literature retrieval from INIS database. J. Radioanal. Nucl. Chem. 133, 249–257. Nyarku, M., Nyarku, B.J.B., Serfor-Armah, Y., Osae, S., 2010. Investigating concentration distributions of arsenic, gold and antimony in grain-size fractions of gold ore using instrumental neutron activation analysis. Appl. Radiat. Isot. 68, 378–383. Schrauzer, G.N., 1981. In: Spallholz, J.E., Martin, J.L., Ganther, H.E. (Eds.), Selenium in Biology and Medicine. AVI, Westport, Connecticut, USA. Shah, M.A.L., Jahiruddin, M., Rahman, M.S., Ghani, M.A., 2009. Proceedings of Workshop on Arsenic in Water–Soil–Crop Systems. BRRI Publication. Sharma, N., Prakash, R., Srivastava, A., Sadana, U., Acharya, R., Prakash, N., et al., 2009. Profile of selenium in soil and crops in seleniferous area of Punjab, India by neutron activation analysis. J. Radioanal. Nucl. Chem. 281, 59–62. Spallholz, J.E., Boylan, M., Rhaman, M.M., 2004. Environmental hypothesis: is poor dietary selenium intake an underlying factor for arsenicosis and cancer in Bangladesh and West Bengal, India? Sci. Total Environ. 323, 21–32. Srivastava, A., Bhatnagar, S., Kumar, A., Kumar, S., Sadana, U.S., Spallholz, J.E., 2006. In: Proceedings of Eighth International Conference on Selenium in Biology and Medicine, University of Wisconsin, Madison (USA). Srivastava, A., Kumar, A., Singh, M., Singla, M., Scindia, Y., Nair, A.G.C, 2002. Multielement analysis of soil from the north-western region of India by neutron activation analysis using the single comparator method with special reference to selenium toxicity. J. Radioanal. Nucl. Chem. 254, 645–648. Stone, S.F., Zeisler, R., Koster, B.J., 1988. Neutron activation analysis of major, minor, and trace elements in marine sediments. Trans. Am. Nucl. Soc. 56, 228–229. Tan, Ja, Zhu, W, Wang, W., Li, R., Hou, S., Wang, D., 2002. Selenium in soil and endemic diseases in China. Sci. Total Environ. 284, 227–235. Willett, W., Morris, J.S., Pressel, S., Taylor, J.O., Polk, B.F., Stampfer, M.J., 1983. Prediagnostic serum selenium and risk of cancer. Lancet 322, 130–134.
Contents lists available at ScienceDirect
Applied Radiation and Isotopes journal homepage: www.elsevier.com/locate/apradiso
Study of seleniferous soils using instrumental neutron activation analysis Alok Srivastava a,n, G.S. Bains a, R. Acharya b, A.V.R. Reddy c a b c
Department of Chemistry, Panjab University, Chandigarh 160014, India Radiochemistry Division, Bhabha Atomic Research Centre, Mumbai 400085, India Analytical Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400085, India
a r t i c l e i n f o
a b s t r a c t
Article history: Received 18 June 2010 Received in revised form 19 January 2011 Accepted 20 January 2011 Available online 3 February 2011
Soil samples from the seleniferous region of Punjab State in India were analyzed by instrumental neutron activation analysis (INAA) using reactor neutrons and high resolution g-ray spectrometry. Samples were collected from three different depths namely surface, root and geological bed zones. Concentrations of 15 elements including selenium and arsenic were determined by relative method. For comparison purposes, soil samples collected from a non-seleniferous region were also analyzed. & 2011 Elsevier Ltd. All rights reserved.
Keywords: Seleniferous soil INAA g-Ray spectrometry Selenium Arsenic Toxicity
1. Introduction Selenium (Se) is an essential trace element but when present at elevated concentrations in the local environment can be quite toxic. The safe limit recommended by World Health Organization (WHO) for soil and water are less than 1 mg kg 1 (ppm) and 10 mg L 1 (ppb), respectively. The range between selenium toxicity and deficiency is rather narrow. The problems related to selenium toxicity were documented as early as twelfth century by Marco Polo while traveling through China as the disease mentioned by him had symptoms of selenium toxicity in livestock. Excess of selenium can lead to problems like alkali disease, cracked hoofs and horns in animals besides giddiness, lassitude, diarrohea, nervousness, mental depression, garlic odor to breath, hair and nail loss and deformity in humans (Willett et al., 1983). Arsenic (As) on the other hand is not an essential trace element but could be quite toxic due to its pro-oxidant nature. It is a known human carcinogen, a teratogen and a suspected cardiovascular toxin. Arsenicosis is characterized by melanosis, keratosis and cancers of the skin, lungs, liver and bladder. The severe human exposure to arsenic is geographically found in the plains of Ganga and Brahmaputra where many of the indigenous population are exposed to higher As levels in drinking water that exceed the WHO recommended limit of 10 ppb. The element
n
Correspondence author. Tel.: + 91 172 2534424; fax: + 91 172 2545074. E-mail address: [email protected] (A. Srivastava).
0969-8043/$ - see front matter & 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.apradiso.2011.01.027
which can counteract the toxicity of the pro-oxidant arsenic is selenium (Schrauzer, 1981) as it is a strong anti-oxidant. It has been suggested by Spallholz et al. (2004) that selenium used as nutritional supplement can reduce the toxic effects of arsenic to a considerable extent. Selenium is found in high concentrations across the globe from plains of America, the prairie provinces of Canada, Soviet Union and China (Cranston, 1985; Losi and Frankenberger, 1997; Tan et al., 2002). The Nawanshahr–Hoshiarpur region of Punjab in India lying between 311 to 311 150 North Latitude and 761 to 761 150 East Longitude has also been reported to have elevated levels of selenium (Bhatnagar, 2001; Srivastava et al., 2002, 2006; Dhillon and Dhillon, 2003; Sharma et al., 2009). It is still not clear how this region became so rich in selenium. Dhillon and Dhillon (1991) hypothesized that the reason for elevated levels could perhaps be due to the additional selenium deposition from leaching of previously existing seleniferous deposits by seasonal rivulets, which come from the higher reaches of Siwalik Hills and drain into this region. They were the first to make an attempt to estimate the concentration of selenium in soil and biota using the conventional colorimetric method. Srivastava et al. (2002) later extended the work using instrumental neutron activation analysis (INAA) technique. Recently, Sharma et al. (2009) used INAA for determination of concentration of selenium in soil and crop products from seleniferous region of Punjab state, India. INAA has been used by Acharya et al. (2009) for determination of arsenic in water samples and by Nyarku et al. (2010) for studying arsenic in gold ore. INAA is an established simultaneous
A. Srivastava et al. / Applied Radiation and Isotopes 69 (2011) 818–821
multi-element measurement technique and has been employed in diverse fields such as geological, biological, biogeochemical, environmental, medical and cosomological origin (Davis et al., 1982; Frontasyeva and Steinnes, 1995; Luten et al., 1977; Morrison and Potter, 1972; Stone et al., 1988). The use of high flux research reactor and high resolution gamma spectrometer with high efficiency high purity germanium (HPGe) detector coupled to a multi-channel analyzer makes this method highly sensitive for simultaneous determination of many elements (Balaji et al., 2000; Moens and Dams, 1995; Muramatsu et al., 1989). It is further observed that between arsenic and selenium, INAA is more sensitive to arsenic than selenium due to favorable nuclear properties of arsenic like isotopic abundance, half life of 76 As (26.3 h) and the gamma-ray abundance of 559 keV (DeCorate and Simonits, 1989). The objective of the present work is to determine the concentration of different elements with special emphasis on selenium and arsenic to understand their toxicity potential as well as to examine the issue of their deposition. In view of this, soil samples from three different depths of three different places of seleniferous region of Punjab State, India, were analyzed by INAA. In addition, two surface soil samples from the non-seleniferous region of Singbhum, Jharkhand, were also analyzed by INAA.
2. Experimental The soil samples used for the study in the present work were collected using the standard auger method. The location for sampling was selected on the basis of findings published in earlier work by Srivastava et al. (2002). Fig. 1 shows the map of the region from where the sample collection was undertaken. The samples from Barwa, Jainpur and Nazarpur were collected from three different depths viz. surface zone (0–10 cm), root zone (20–40 cm) and geological bed (80–120 cm).
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The soil samples in powder form weighing about 100 mg each were wrapped in thin aluminum foil separately. The reference materials SL-1 (comparator standard) and SL-3 (control) obtained from IAEA were also packed in a similar way. The individual packets were then wrapped in a large aluminum foil and placed in an aluminum container, which was sent to CIRUS reactor of Bhabha Atomic Research Centre (BARC), Mumbai, for irradiation. The size of the comparator as well as the sample was kept small to minimize the neutron self shielding and gamma-ray attenuation effects. The irradiations were carried out for 6 h with a neutron flux of the order of 1013 cm 2 s 1. After a cooling period of two days, the samples were transferred to a fresh aluminum foil to avoid blank activity due to aluminum. Then the individual packets were mounted on standard Perspex plates. The gamma activity of the activation products was assayed using a 40% relative efficiency HPGe detector coupled to a PC based 8k channel analyzer with a reproducible sample to detector geometry at about 5 cm from the face of the detector. The detector system had a resolution of 1.9 keV at 1332 keV of 60Co. The samples were counted for 1000 to 10,000 s after cooling samples for periods ranging between 2 and 15 days. The gamma rays of 264 keV (75Se) and 559 keV (76As) were used in the present work as there are no spectral interference of the gamma rays of both the activation products (DeCorate and Simonits, 1989). 2.1. Calculations The peak areas were determined using peak fit software PHAST, developed at BARC. The relative method of INAA was employed for calculating the concentrations of the elements of interest using the following relation: mx ¼ mstd cpsx =cpsstd
ð1Þ
where mx is the mass of the element of interest, mstd is the mass of the element in the reference standard, cpsx and cpsstd are the decay corrected count rates (counts per second, cps) of activation product of interest in the sample and the reference standard, respectively. The mx is converted to concentration (mg/kg) by dividing with the sample mass.
3. Results and Discussion
Fig. 1. Map of Punjab showing the Hoshiarpur and Nawanshahr districts from where samples were collected.
The concentrations of 14 elements including Na, K, Fe, Cr, As and rare earth elements (REEs) were determined in reference material from IAEA namely RM SL-3 and the results are shown in Table 1. Selenium concentration was determined in IAEA RM SL-1 using elemental standard of Se, since RM SL-3 does not have certified/information concentration value of Se. The deviations with respect to certified concentration values were found to be within 76%. Table 1 also contains 3s detection limits of all elements in the present experimental conditions for a representative soil sample. The results on the concentration level of 15 elements determined in the present work from three different depths namely surface (S), root zone (R) and geological bed (G) are shown in Table 2 for three locations namely Jainpur (J), Barwa (B) and Nazarpur (NZ). The uncertainties quoted are standard deviations obtained from four replicate sample analysis. The concentration profiles of the above mentioned 15 elements were determined at surface level 0–10 cm depth, root zone level 20–40 cm and at a depth ranging between 80 and 120 cm, which for all practical purposes could be considered as geological zone where the effect of uptake due to phyto-accumulation is minimal. In other words the concentrations could be taken as a representative of the normal geological distribution. It is observed from Table 2 that in general the concentrations of most of the
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elements studied in the present work increased considerably with the increase in depth. The decrease in the concentration observed in some cases especially in the region between the surface and root zone could be attributed to the phenomenon of phytoaccumulation. This aspect comes out very clearly in the case of selenium in the samples of Jainpur and Barwa. Sharma et al. (2009) in their study on phyto-accumulation have shown that the farmers in Jainpur and Barwa region are known to grow maize, mustard, wheat and rice which are very good phyto-accumulators of selenium. In other cases one observes that there is not a big difference on the contrary there is a slight increase. These are the elements which could normally be present in fertilizers and perhaps pesticides used by farmers of this region. The region where the study was carried out has been reported to be seleniferous. This comes out very clearly from the data obtained in the present work. It is further observed that besides Se concentration values, the concentrations of all elements except for Cr (59–124 mg kg 1) are in the expected value range for such type of soil samples. For comparison purpose, INAA study was extended to non-seleniferous surface soil from Singbhum in Jharkhand State, which lies between 221 030 and 221 440 North Latitude and 861 100 and 861 120 East Longitude. This region is known to be rich in iron ore and low grade gold reserves. The soil samples from the above stated region were collected and studied under experimental conditions similar to that of samples
Table 1 Results of elemental concentrations (mg kg 1) of elements present in IAEA RM SL-3 and detection limits (mg kg 1) in a representative soil sample. Element
This work
Certified (info) value
Detection limit
Na K Br La Sm U As Ce Cr Co Fe Rb Zn Th Sea
6787 7 358 8985 7 352 5.8 7 0.4 21.7 7 1.7 3.6 7 0.1 2.42 7 0.21 3.35 7 0.25 43.3 7 1.5 34.8 7 2.3 4.12 7 1.7 111257 450 37.2 7 2.1 29.7 7 1.5 7.2 7 0.3 2.83 7 0.17
6690 7343 8740 7786 5.6 70.6 22.5 7 0.9 3.8 70.3 2.30 70.23 3.20 70.19 45.4 7 1.8 (32.69) (3.89) (10930) 38.8 7 1.9 (30.1) 7.02 70.50 (2.9)
0.5 4.0 0.35 0.05 0.005 0.05 0.02 0.1 0.06 0.03 3.4 0.1 0.08 0.1 0.3
( )—information value. a
from the seleniferous region of Punjab. The data related to concentration level of 11 elements are shown in Table 3 along with a representative data from a sample taken from Jainpur, a seleniferous region. The samples from Singbhum region did reflect the expected pattern thereby authenticating the methodology used in the present work. During the above stated authentication study a very interesting observation was made. The samples from the non-seleniferous zone were found to have low Cr concentrations and high concentrations of Au, Fe and As. A similar arsenic rich region has been reported in southern Tuscany region of Italy (Baroni et al., 2004). There are reports of arsenic toxicity in the neighboring region comprising of West Bengal and Bangladesh so it should not come as a surprise if one observes arsenic in this region too (Boylan and Spallholz, 2009; Jacobs et al., 1970). It would be interesting to carry out study on arsenic in the water bodies of Singbhum region of Jharkhand since the level of arsenic in the soil is rather high (35 and 45 mg kg 1). This study would help in establishing toxicity effect due to arsenic, which is known to be a class 1 carcinogen in normal populace residing in that region. The present study further showed that the concentration of arsenic in soil in the seleniferous pockets of Punjab ranged from 4 to 11 mg kg 1, which is lower than that observed in Bangladesh. In an US-AID study carried out recently by Shah et al. (2009) in Bangladesh it was observed that in more than half of the top soil the concentration of arsenic was more than 10 mg kg-1. Recently, Hundal et al. (2009) have identified a region in Punjab where they found that ground water had arsenic level much higher than 10 mg kg 1: the recommended limit set by US
Table 3 Concentration of elements in mg kg 1 (ppm) from surface soil samples in two soil samples from non-seleniferous (NS) region and one from seleniferous (S) region. Element
Sample 1 (NS)
Sample 2 (NS)
Sample (S)
Chromium Scandium Samarium Lanthanum Sodium Potassium Gold Cobalt Iron Arsenic Selenium
1.12 7 0.02 21.9 7 0.6 3.6 70.1 21.5 7 0.6 6232 7 93 195967 353 1.7 70.1 6.7 70.9 68053 7 5716 34.8 7 2.1 o 0.3
1.00 70.05 24.8 7 1.2 3.5 7 0.2 17.3 7 1.4 5421 7 38 14896 7521 1.3 7 0.1 8.7 7 1.8 69095 7 14372 46.0 7 4.1 o0.3
72.1 7 2.7 12.8 7 0.10 6.9 70.2 43.0 70.6 5202 7 36 133217 719 o 0.05 15.1 7 0.6 367317 367 6.5 70.3 17.7 7 0.6
IAEA RM SL-1.
Table 2 Concentration of elements from Jainpur (J), Barwa (B) and Nazarpur (NZ) at different depths namely surface (S), root zone (R) and geological bed (G) in mg kg 1 (ppm). Element
J (S)
J (R)
J (G)
B (S)
B (R)
B (G)
NZ (S)
NZ (R)
NZ (G)
Chromium Scandium Samarium Lanthanum Sodium Potassium Cobalt Iron Zinc Arsenic Selenium Rubidium Uranium Thorium Bromine
72.1 7 27 12.8 7 0.1 6.9 7 0.2 43.07 0.6 5202 7 36 133217 719 15.1 7 0.6 367317 367 136 7 5 6.5 7 0.3 17.7 7 0.6 1507 16 3.017 0.05 17.1 7 0.3 3.3 7 0.2
82.2 7 3.3 13.3 7 0.1 5.47 0.1 31.7 7 0.4 2107 7 23 4783 7 550 15.4 7 1.2 38400 7 730 97.9 7 5.4 4.77 0.3 3.77 0.3 175.6 7 17.6 3.97 0.1 16.9 7 0.5 2.97 0.2
93.6 7 7.6 14.5 7 0.1 6.2 7 0.1 35.7 7 0.6 1683 7 22 3297 7 824 14.7 7 1.2 401007 3082 99. 97 8.9 5.4 7 0.3 4.9 7 1.1 222.8 7 16.7 4. 17 0.2 19.3 7 0.7 7.1 7 0.7
93.7 7 6.0 19.4 7 0.2 9.1 7 0.2 62.4 7 0.8 6090 7 49 13100 7 995 24.3 7 1.4 54500 7 1145 173 7 10 5.4 7 0.4 12.5 7 0.9 229.320.9 4.07 0.2 21.3 7 0.7 4.8 7 0.4
109.4 7 8.4 19.6 7 0.1 7.2 7 0.2 47.7 7 0.5 3340 7 33 9590 7 786 22.5 7 1.2 56200 7 1124 133 7 7 8.5 7 0.5 3.1 7 0.6 184.9 7 15.5 3.7 7 0.3 19.1 7 0.8 5.3 7 0.4
178.6 710.1 26.8 70.3 10.3 70.1 66.5 70.5 3790 731 13090 7602 27.4 71.1 76300 71068 175 78 10.5 70.3 4.1 71.2 248.9 724.2 4.9 70.4 26.4 70.5 7.7 70.7
59.4 72.4 9.0 70.1 5.0 70.2 29.3 70.3 2610 718 6840 7616 10.4 70.6 25300 7543 76.3 73.1 4.6 70.2 7.0 70.4 95.9 73.4 2.1 70.1 11.4 70.4 3.1 70.2
75.4 7 3.5 10.27 0.1 5.77 0.1 34.1 7 0.3 2730 7 19 70207 575 12.4 7 0.7 29100 7 601 74.6 7 3.7 5.87 0.2 3.07 0.3 122.4 7 5.9 3.57 0.3 13.9 7 0.3 4.87 0.4
124.0 7 6.6 16.2 7 0.2 8.5 7 0.1 50.2 7 0.7 3550 7 32 7920 7 988 17.4 7 1.3 45100 7 1082 108 7 7 9.4 7 0.4 3.0 7 0.3 181.7 7 12.9 7.9 7 0.5 18.9 7 0.6 9.8 7 0.7
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Protection Agency and World Health Organization. In the light of the above stated observations it would be interesting to carry out further study of arsenic in soil and water in Punjab as well as the newly identified Singbhum region of Jharkhand in Eastern India.
4. Conclusions In conclusion it can be stated that the present work has been successful in demonstrating the power of instrumental neutron activation analysis in obtaining detailed elemental concentration of different elements in soil samples. The data generated in this work has lead to useful input information for carrying out further biogeochemical studies besides identification of new areas in the Indian States of Punjab and Jharkhand, which require further study to mitigate the toxicity problems arising due to selenium and arsenic.
Acknowledgements The authors are thankful to Ms. Neetu Sharma, Ms. Pragati Sharma and Ms. P. Aggarwal for their assistance with the counting and preparation of some of the initial samples besides Dr. C.R. Suri of Institute for Microbial Technology, Chandigarh, who helped us with the procurement of soil samples from Singbhum. We are thankful to UGC-DAE CSR for providing financial support for the project under contract number CSR/CD/MUM/CRS-M-129/07/2837. The authors are also thankful to Dr. V.K. Manchanda, Head Radiochemistry Division and Dr. P.K. Pujari of Radiochemistry Division of BARC, for their support. We would also like to thank Mr. Amol D. Shinde and K.K. Swain of the Analytical Chemistry Division of BARC, for their valuable help. One of us (AS) would like to thank Alexander von Humboldt Foundation, Bonn, Germany, for providing summer fellowship to work in Aachen University of Applied Sciences, Juelich, Germany, where major part of the manuscript was prepared. References Acharya, R., Nair, A.G.C., Reddy, A.V.R., 2009. Instrumental and speciation neutron activation analysis for arsenic in water samples. J. Radioanal. Nucl. Chem. 81, 279–283. Balaji, T., Acharya, R.N., Nair, A.G.C., Reddy, A.V.R., Rao, K.S., Naidu, G.R.K., Manohar, S.B., 2000. Multielement analysis in cereals and pulses by k0 instrumental neutron activation analysis. Sci. Total Environ. 253, 75–79. Baroni, F., Boscagli, A., Di Lella, L.A., Protano, G., Riccobono, F., 2004. Arsenic in soil and vegetation of contaminated areas in southern Tuscany (Italy). J. Geochem. Explor. 81, 1–14. Bhatnagar, S., 2001. Study of drinking water quality of Nawanshahr region. Department of Chemistry, M.Sc. Dissertation, Panjab University, Chandigarh. Boylan, M., Spallholz, J.E., 2009. In: Srivastava, Alok, Roy, Ipsita (Eds.), Bionanogeo Sciences: The Future Challenge. Ane Books, New Delhi.
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