Indian Journal of Geo-Marine Sciences Vol. 43(3), March 2014, pp. 323-328
OPINION ARTICLE
Distribution of copper in the coastal waters of Kalpakkam and comment on "Distribution of heavy metals in the vicinity of a nuclear power plant, east coast of India: with emphasis on copper concentration and primary productivity" published in Indian Journal of Marine Sciences (2010), Volume 39 (Issue 2) by Rajamohan et al. (2010) K K Satpathy*& S Biswas 1
Environment & Safety Division, Radiological Safety & Environmental Group, Electronics Instrumentation & Radiological Safety Group, Indira Gandhi Centre for Atomic Research, Kalpakkam, Tamil Nadu 603 102, India *[E-Mail:
[email protected]]
An article by Rajamohan et al.1 published in IJMS reported the distribution of heavy metals (Fe, Cu, Cd and Hg) in the coastal waters of Kalpakkam, east coast of India. Although, the paper reported the distribution of above heavy metals, however, the main focus was on Cu. The paper (Rajamohan et al.1) concluded that concentration of Cu was very small compared to earlier published data. The earlier published data from the same locality were rejected by Rajamohan et al.1 based on statistical comparison using reference values reported from a laboratory involved in coastal water monitoring programme (Iyer2). Incidentally, one among the rejected data belonged to one of the present authors. In view of this, we decided to analyse Cu in the Kalpakkam coastal water samples collected recently (Padhi et al.3) and the results are discussed along with Rajamohan et al.1 paper. Before proceeding further, it is important to mention here that, one among the primary lessons learnt from statistics is that, comparisons must be made only of things that are similar in nature. Chalk can't be compared to cheese. But when it is done sometimes, it is necessary to drive home the contrast between the two in substance, texture and taste. It is more serious when odious scientific comparisons are made and conclusions are drawn. The purpose of this article is to open up a debate on the methodology, discussion and conclusion reported by Rajamohan et al.1 within the ambit of analytical chemistry, defination of dissolved metal, total dissolved metal, acid leachable plus dissolved metal and literatures cited by them. A dialectical perusal of the above article concluded that it lacks technical clarity in both
the purpose and interpretation of the associated work. The present paper has focused on the following points: 1) The procedure adopted by Selvaraj4, Satpathy et al.5 and Rajamohan et al.1 for heavy metal estimation and 2) Discussion on the reference data used by Rajamohan et al.1 for comparing with earlier data In any scientific investigation involving natural water bodies/ecosystems, it is equally important to mention the year and month of sample collection in order to co-relate the results with environmental parameters. Incidentally, there was no mention of sample collection period by Rajamohan et al.1. This was all the more necessary when results were compared and reported on a temporal scale. For example, quality of water samples collected from Kalpakkam coast during February-May (post NE monsoon/summer period) would be entirely different from that during October-January (NE monsoon period). The coastal water sample collected during post NE monsoon period at Kalpakkam has a signature of southern oceanic water and the sample collected during NE monsoon period has a signature of water coming from north influenced by massive riverine discharge. As it is known, during October to January, the NE monsoon is active at Kalpakkam and almost (average 770 mm) 60-65% of the annual rainfall is received during this period, affecting the coastal water characteristics significantly. Remarkably, Rajamohan et al.1 reported in their paper that the
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maximum rainfall received during a year at Kalpakkam ranged from 270-310 mm which did not match with the rainfall data available during the last 45 years (1968-2012). In addition, rainfall data provided in their
Table 2 (the average maximum rainfall varies from 200-300 mm) also did not corroborate with available data. The rainfall data for Kalpakkam during the period 1968-2012 is given in Table 1. It shows that
Table 1−Rainfall data (1968-2013)
1968 1969 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012
Post-Monsoon (February-May)
Pre-Monsoon (June - September)
Monsoon (October-January)
Total Year Rainfall
31.1 117.5 55.2 116.5 89.3 0 33.4 0 1.3 13.4 28.1 64.1 14.7 40.2 0.4 0 222.3 2.7 40.4 39.6 20.7 85.5 303.8 23.5 2.5 12.2 9.2 271.6 130.5 36.7 50.1 224.6 247.8 76.7 24 17 169.4 146 52.7 69 213 35 63 33 8
253.4 238.2 793.1 322.6 383.2 579 382.2 445.2 500.2 384.1 700.9 278.8 343.3 533.2 341.5 708.2 510.9 665.7 150.2 230.4 473.8 289.1 271 569.7 300.3 406.3 445.8 588.4 656.3 388.3 542.7 277.6 424.1 478.2 288.7 392.2 243.5 307 251.9 660.5 135 463 512 364 375
283.6 1317.3 1134.4 791.3 833.5 557.2 251.4 776.6 1382.5 1293.7 1194.3 854.6 776.2 407.1 365.3 837.9 730.1 1475.9 620.6 818.7 589.9 752.2 828.4 878 732 1040.3 1170.6 336.6 931.2 1200.1 1132.8 947.8 399.2 706.1 658.5 592 753.1 1429.8 748.4 413 300 760 810 640.5 941
568.1 1673 1982.7 1230.4 1306 1136.2 667 1221.8 1884 1691.2 1923.3 1197.5 1134.2 980.5 707.2 1546.1 1463.3 2144.3 811.2 1088.7 1084.4 1126.8 1403.2 1471.2 1034.8 1458.8 1625.6 1196.6 1718 1625.1 1725.6 1450 1071.1 1261 971.2 1001.2 1166 1882.8 1053 1142.5 648 1258 1385 1037.5 1324
OPINION ARTICLE
the rainfall varied from 568.1 to 2144.3 mm having the highest in the year 1985. The average annual rainfall received during the last 45 years is 1243 mm. Even rainfall received during NE monsoon period (October-January) during the last 45 years varied from 283.6 to 1475.9 mm. Therefore, information on rainfall data reported by Rajamohan et al.1 was ambiguous and misleading. A sample collected during monsoon period can't be compared with that of another collected during summer/post-monsoon period. Selvaraj4 had sampled during pre-monsoon (September, 1995) and post-monsoon (April, 1996) period and to compare with Selvaraj4 values, Satpathy et al.5 sampled during post-monsoon (March, 2006) period to maintain same parity for temporal comparison. The role of sampling period (period of the year) has been lucidly exemplified by Ouseph6 wherein he has reported dissolved Cu concentration of 0.8, 10.0 and 8.0 µg l-1 for monsoon, post-monsoon and pre-monsoon period respectively, indicating more than one order of magnitude variation among the three seasons. Thus, the report emphasized the need to notify the sampling period in order to understand the seasonal impact and draw meaningful conclusion while comparing with other reported values. Likewise, when one compares and discusses results with that of others, one need to follow the same procedure, otherwise comparison would be odious. Rajamohan et al.1 reported (their Table 3) total dissolved Cu values from various studies of Selvaraj4, Satpathy et al.5 and Iyer2 for comparison. In order to understand with clarity, it is necessary to look at the defination of each of the terminology used by the above authors. As per APHA7: Dissolved metal: Those constituents (metals) of an unacidified sample that pass through 0.45 µm membrane filter and estimated; Suspended metal: Those constituents (metals) of an unacidified sample that are retained by a 0.45 µm membrane filter and estimated; Total metal: The concentration of metals determined on an unfiltered sample after vigorous digestion, or the sum of the concentrations of metals in both dissolved and suspended fractions; Dissolved and Acid leachable metal (Acidextractable metal): The concentration of metal in an unfiltered sample treated with dilute mineral acid. Selvaraj4 had reported dissolved plus acid leachable (samples were acidified without filtration)
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portion of metals in his paper. To compare with Selvaraj4 values, Satpathy et al.5 followed the same procedure (samples were acidified without filtration) and reported dissolved plus acid leachable Cu content in Kalpakkam coastal water. Rajamohan et al.1 used unfiltered samples which were stored at 4 °C until analysis. There was no mention of acidification of the samples, which implied that the procedure undertaken by them was different from that of Selvaraj4 as well as Satpathy et al.5. In this context, it is essential to mention here that unfiltered samples with considerable amounts of particulate matter (coastal water generally has) should not be acidified or kept frozen because of the risk of desorption of trace metals or of rupture of the planktonic cell membranes (Grasshoff et al.8) leading to values which does not represent dissolved metal. From the available information from Rajamohan et al.1 paper, the heavy metal values reported do not fall strictly into any of the standard category. In addition, without indicating the sample collection period, it was not appropriate for them (Rajamohan et al.1) to compare their values with that of Selvaraj4 as well as with Satpathy et al.5. Data reported by Satpathy et al.5 pertained to dissolved plus acid leachable Cu content during the post-monsoon period, in order to compare that fraction of Cu as reported by Selvaraj4. Any comparison with others data needs quid pro quo protocol and as evident it was not followed by Rajamohan et al.1. The period (March, 2006) during which Satpathy et al.5 sampled coincided with posttsunami period and this coast was severely affected by December 2004 tsunami. It has been observed from our data, that the suspended matter content during post-tsunami period was significantly higher than the pre-tsunami period (Satpathy et al.9). Investigation on metal content during post-tsunami period is reported to be higher than that of pre-tsunami period (Prasath and Khan10) which was attributed due to the impact of tsunami that caused large scale SW inundation and the receding tidal waves carried debris, anthropogenic wastes, adjacent terrestrial parts and domestic disposal from the lands into the sea. Therefore, the period during which Satpathy et al.5 carried out investigation had relatively high suspended matter and dissolved Cu, an impact of tsunami, both contributed simultaneously to the elevated Cu content as dissolved plus acid leachable. Notwithstanding the above inconsistencies, the values reported by Rajamohan et al.1 contradicted
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their earlier report. Rangarajan and Narasimhan11 had reported dissolved (filtered) Cu content in seawater samples from Kalpakkam coast with and without acidification. They (Rangarajan and Narasimhan11) observed that Cu concentrations in filtered acidified samples (~ 1.9-5.0 µg/l) were more than that in the filtered unacidified samples (~ 0.3-1.3 µg/l). A comparison of Cu content estimated under different conditions reported by various authors from east coast of India is given in Table 2, essentially to illustrate that drawing conclusion, by comparing data from various sources without following similar scientific protocol does not make any sense. On comparison of Cu concentration reported during 1987 (Rangarajan and Narasimhan11, samples collected in 1987) and reported during 2010 (Rajamohan et al.1, sample collection year and period not known), it is concluded that values of Rajamohan et al.1) (unfiltered values 1.3-4.6 µg/l) were less than that of Rangarajan and Narasimhan11 (filtered and acidified) which was
sampled more than two decades ago. Recently, Padhi et al.3 analyzed samples collected during February 2010 to January 2011 from Kalpakkam coastal water and their dissolved (filtered and then acidified) Cu concentration ranged from 3.5-4.95 µg/l (Table 2). Considering the role of suspended particulate matter (SPM) in dissolved plus acid leachable Cu content, it is pertinent to discuss the contribution of SPM content in acid leachable fraction of heavy metal. The SPM content in the Kalpakkam coastal water during the period 2006 ranged from 21.7-49.3 mg/l. It is reported that (Ouseph6) around 80-90% of trace metal get leached from the SPM by treatment with acid, leading to considerable increase in dissolved + acid leachable metal as compared to only dissolved metal. In this context, the result of Kuppusamy and Giridhar12 who reported dissolved Cu content in the coastal waters of Mahabalipuram, a tourist spot, 15 km north of Kalpakkam coast is worth discussing here. Their dissolved Cu concentration ranged from 3.68-36.7 µg/l
Table 2Copper concentrations recorded from various studies in and around Kalpakkam Reference Location
Period of sample collection
Year of Procedure (Estimated Publication Component)
1
Kalpakkam coastal water
NA
2010
Unfiltered samples stored at 4 0C
2
Indian coastal water
NA
1999
Samples acidified
3
MAPS Jetty, Kalpakkam Waters of innershelf region (up to a water depth of 52 m) off Kalpakkam coast
February, 2010 - January, 2011 a) Pre-monsoon (September, 1995)
2013
Filtered samples acidified Samples acidified
4
1999
Values (µg/l)
Remark
Abstract: 0.05 - 5.1 Table 3: 1.3 - 4.6 Table 4: 2.0 - 2.2 0.5 - 0.8
Does not fall under any category Dissolved plus acid leachable metal Dissolved metal
3.5 - 4.95 a) Pre-monsoon: 72 - 2565
Dissolved plus acid leachable metal
b) Post-monsoon (April, 1996)
b) Post-monsoon: 64 - 2029 34 - 49
5
Kalpakkam coastal water
March, 2006
2006
Unfiltered samples acidified
11
MAPS Jetty, Kalpakkam
March- June, 1987 (Weekly)
1987
a) Filtered samples acidified
a) ~ 1.9 - 5.0
b) Filtered samples unacidified a) Samples filtered
b) ~ 0.3 - 1.3
12
Mahabalipuram coast
May, September & December, 1999
2004
b) Samples filtered, SPM collected & digested NA: Not Available
a) 3.68 - 36.7
b) 27.91 - 119.20
Dissolved plus acid leachable metal a) Dissolved metal
b) Dissolved metal a) Dissolved metal b) Suspended metal
OPINION ARTICLE
Table IIIConcentration of heavy metals in the Indian Coastal waters (Iyer2) Elements
Concentration range (µg/l)
Cd Cr Cu Fe Mn Pb Zn
0.1-0.4 0.5-1.0 0.5-0.8 0.8-1.7 1.0-2.0 0.6-1.1 2.8-3.9
Table IVValues of dissolved copper (µg/l) from tables in Rajamohan et al.1 Table Rajamohan et al.1 Table 3
1.39 ± 0.15 2.12 ± 0.23 2.24 ± 0.12 3.90 ± 0.34 2.10 ± 0.40 2.40 ± 0.43 4.50 ± 0.97
Table 4 Table 7
2.0 - 2.2 1.21 ± 1.53 2.66 ± 1.11
Iyer 2
Rao et al. 15 Remarks
2.11 ± 0.4 2.18 ± 0.4 2.12 ± 0.4 2.10 ± 0.3 2.20 ± 0.5 2.11 ± 0.4 2.15 ± 0.4
22 33 19 23 The values 25 mismatch 22 with one 43 another although 35 source is 24 same 20 0.7 - 5.0 16 - 170 2.14 ± 0.04 26.65 ± 7.76
while the particulate bound Cu content ranged from 27.91-119.20 µg/g. Munksgaard and Parry13 has reported that the Cu concentration in unfiltered coastal seawater was about 240% more as compared to filtered seawater whereas in offshore water which has relatively low SPM content, Cu content was about 100% more in unfiltered sample as compared to filtered sample. Thus, the quantity of suspended matter content present in the water sample would influence significantly the amount of acid leachable plus dissolved or total metal content available in the sample. It is also reported that not only the quantity of SPM but also the size of SPM matters; as the size of the SPM increases, its contribution towards metal content decreases (Singhal et al.14). As mentioned earlier suspended matter content is also a function of season. Perusal of literature indicated that unfiltered sample when acidified, the metal concentration is significantly higher than the filtered sample. Interestingly, Rajamohan et al.1 has also expressed similar opinion in their paper, however, their procedure conform to none (dissolved or dissolved plus acid leachable or total dissolved). They reported
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total dissolved Cu which appeared to be a misnomer as far as their procedural protocol was concerned (unfiltered samples without any acidification was used). Copper data from C-MARS (Iyer2) used by Rajamohan et al.1 formed the basis of statistical acceptance and rejection of others reported Cu values. Rajamohan et al.1 (page 186, 1st column, line 20) reported that the mean of the Cu concentration as reported by Iyer2 was 2.14 µg/l. A perusal of the above cited literature (Iyer2) revealed Cu concentration ranged from 0.5-0.8 µg/l (values reported by Iyer2 is reproduced in Table 3 here). However, values reported by Rajamohan et al.1 were not only different from Iyer2 quoted value but also differed with their own in different tables such as in Table 3 (2.10-2.20 µg/l), Table 4 (0.7-5.0 µg/l) and Table 7 (2.14 µg/l) which is reported in our Table 4. In fact, there is a total mismatch of data including other metals reported by Iyer2 and those cited by Rajamohan et al.1. It is much beyond our comprehension about the source of the values presented in the column V of Table 3 and Table 4 by Rajamohan et al.1 as these values were not reported by Iyer2. Moreover, column V of Table 3 and Table 4 reported by Rajamohan et al.1 should have been the same since the source of cited reference is same (Iyer2). Therefore, the conclusion made (page 188, line 24) by Rajamohan et al.1 that Cu values reported by them were in agreement with Iyer2 was acceptable or not acceptable is axiomatic. Conveniently, Rajamohan et al.1 did not compare their other metal content with that of Iyer2 which did not give credence to their result. In conclusion, the present letter is intended to emphasize the need for maintaining uniformity in the sample collection period, procedure, proper use of cited literature before attempting any comparison with others data to make it scientifically tenable. Moreover, it is also aimed to raise awareness for the benefit of the scientific community to avoid such mistake as above in future. Reference 1 Rajamohan, R., Rao, T.S., Anupkumar, B., Sahayam, A.C., Krishna, M.V.B., Venugopalan, V.P., Narasimhan, S.V., Distribution of heavy metals in the vicinity of a nuclear power plant, east coast of India: with emphasis on copper concentration and primary productivity, Indian Journal of Marine Sciences, 39 (2) (2010) 182-191. 2 Iyer, C.S.P., Analytical techniques for marine pollution
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3
4
5
6
7
8
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monitoring, (Proceedings of the 8th National symposium on Environment, Indira Gandhi Centre for Atomic Research, Kalpakkam, India), 1999, pp. 1-3. Padhi, R.K., Biswas, S., Mohanty, A.K., Prabhu, R.K., Satpathy, K.K., Nayak, L., Temporal distribution of dissolved trace metal in the coastal waters of southwestern Bay of Bengal, India, Water Environment Research, 85 (8) (2013) 696-705. Selvaraj, K., Total dissolvable copper and mercury concentrations in innershelf waters, off Kalpakkam, Bay of Bengal, Current Science, 77(4) (1999) 494-497. Satpathy, K.K., Natesan, U., Kalaivani, S., Mohanty, A.K., Rajan, M., Raj, B., Total dissolved copper concentrations in coastal waters of Kalpakkam, Current Science, 91 (8) (2006) 1008-1010. Ouseph, P.P., Dissolved and particulate trace metals in the Cochin estuary, Marine Pollution Bulletin, 24 (4) (1992) 186-192. American Public health Association (APHA), Standard methods for the estimation of water and wastewater, 17th Edition, (APHA, Washington, DC.) 1989, pp. 3-1-3-163. Grasshoff, K., Ehrhardt, M., Kremling, K., Methods of seawater analysis, (Verlag Chemie, Weinheim) 1983, pp. 189246. Satpathy, K.K., Mohanty, A.K., Natesan, U., Prasad, M.V.R., Sarkar, S.K., Seasonal variation in physicochemical properties of coastal waters of Kalpakkam, east coast of India with special emphasis on nutrients, Environmental Monitoring and
Assessment, 164 (2010) 153-171. 10 Prasath, P.M.D., Khan, T.H., Impact of tsunami on the heavy metal accumulation in water, sediments and fish at Poompuhar coast, southeast coast of India, E-Journal of Chemistry, 5 (1) (2008) 16-22. 11 Rangarajan, S., Narasimhan, S.V., Monitoring of heavy metals in Kalpakkam coastal waters by voltammetric method, (Proceedings of the International seminar on instrumental methods of electroanalytical techniques, Mysore (Nov. 26-28., 1987)), 1987, pp. 109-119. 12 Kuppusamy, M.R., Giridhar, V.V., Trace metal speciation in environmental aquatic samples of Palar river, Mahabalipuram and its adjoining coast, Bulletin of Electrochemistry, 20 (3) (2004) 119-124. 13 Munksgaard, N.C., Parry, D.L., Trace metals, arsenic and lead isotopes in dissolved and particulate phases of North Australian coastal and estuarine seawater, Marine Chemistry, 75 (2001) 165-184. 14 Singhal, R.K., Preetha, J., Karpe, R., Tirumalesh, K., Kumar, S.C., Hegde, A.G., The use of ultra filtration in trace metal speciation studies in sea water, Environment International, 32 (2006) 224-228. 15 Rao, I.N., Krupanidhi, G., Kumari, R.R., Heavy metal pollution in the Visakhapatnam harbour waters, east coast of India (Bay of Bengal), Indian Journal of Environmental Protection, 21 (2001) 825-830.
