Assessment of trace element accumulation in surface ...

Marine Pollution Bulletin xxx (2016) xxx–xxx

Contents lists available at ScienceDirect

Marine Pollution Bulletin journal homepage: www.elsevier.com/locate/marpolbul

Baseline

Assessment of trace element accumulation in surface sediments off Chennai coast after a major flood event V. Gopal a, S. Krishnakumar b,⁎, T. Simon Peter c, S. Nethaji d, K. Suresh Kumar b, M. Jayaprakash d, N.S. Magesh a a

Department of Geology, Anna University, Guindy Campus, Chennai, 600 025, India Department of Geology, University of Madras, Guindy Campus, Chennai, 600 025, India Centre for GeoTechnology, Manonmaniam Sundaranar University, Tirunelveli 62701, India d Department of Applied Geology, University of Madras, Guindy Campus, Chennai 600 025, India b c

a r t i c l e

i n f o

Article history: Received 28 July 2016 Received in revised form 27 September 2016 Accepted 5 October 2016 Available online xxxx Keywords: Trace element concentration Major flood events Surface sediments Chennai coast Urban runoff Metal accumulation indexes

a b s t r a c t The present study was conducted to assess the trace element concentration in marine surface sediments after major flood event of Chennai metropolis, India. Thirty surface samples were collected from off Chennai coast. Trace elements, organic matter, CaCO3, sand-silt-clay and C/N ratios were studied to understand the accumulation dynamics on sediments. The elemental concentration, calcium carbonate and OM distribution suggest that they are derived from urban runoff and transported through Adyar and Cooum Rivers. The enrichment factor reveals that the sediments are enriched by Pb, Cu, Zn, Cr, Co, Ni followed by Fe. The observed Igeo value shows that the samples are contaminated by Pb, Cu and Zn. The elemental concentration of the surface sediments is low when compared to other coastal region except Pb. The elevated level of Pb in the surface sediments is probably due to migration of contaminated urban soil from industrial and transportation sectors into marine environment. © 2016 Published by Elsevier Ltd.

The allogenic sediments deposited in estuarine and coastal environments are becoming increasingly polluted with minor metals due to urban and industrial development in coastal regions. Hence, understanding the sources of pollution in offshore aquatic systems is important to monitor environmental degradation. Anthropogenic sources like discharge of industrial effluents and sewage dumping contribute significantly to pollution and sediments become the ultimate sink (Magesh et al., 2011; Kasilingam et al., 2016). In this connection, flood is one of the natural disasters, contribute the allogenic polluted sediments to the marine environment. The 2015 South Indian floods resulted from heavy rainfall generated by the annual northeast monsoon in November–December 2015. They affected the Coromandel Coastal region of the South Indian states like Tamil Nadu and Andhra Pradesh, and the union territory of Puducherry specifically Chennai city. The flooding has been attributed to the 2014–16 El Niño events. The abnormal raining event set off the flood and it was intensified due to unregulated urban planning, illegal construction and improper design and maintenance of drainage systems. Chennai is metropolitan city, situated at 13° 04′ N 80° 17′ E on the southeast coast of India and in the northeast corner of Tamil Nadu

⁎ Corresponding author. E-mail addresses: [email protected] (V. Gopal), [email protected] (S. Krishnakumar), [email protected] (T. Simon Peter), [email protected] (S. Nethaji), [email protected] (K. Suresh Kumar), [email protected] (M. Jayaprakash), [email protected] (N.S. Magesh).

http://dx.doi.org/10.1016/j.marpolbul.2016.10.019 0025-326X/© 2016 Published by Elsevier Ltd.

(Fig. 1). It is located on a flat coastal plain with an average elevation of 6 m. The geology of Chennai comprises mostly of clay, shale and sandstone. The average annual rainfall is about 1400 mm and it receives rainfall mostly by north-east monsoons, from September to December. The two ephemeral streams running through the study area namely Cooum River in the central region and the Adyar River in the southern region. These two rivers are heavily polluted with effluents and trash from domestic and commercial sources. Many researches carried out numerous works on trace elemental concentration in tsunamigenic sediments, drought, flooding in urban areas, tsunami event including short term and long-term impact on biological system, (Ranjan et al., 2008, Srinivasalu et al., 2010, Reza Modarres et al., 2016, Diakakis et al., 2016, Carla Morri et al., 2015, Hussain et al., 2010). However, the metal accumulation dynamics in the sediments off Chennai coast after the major flood event is not reported so far and it is the first ever report of its kind. Therefore, the present study was focused on the elemental concentration and C/N ratio on marine sediments off Chennai coastal region after major flood event. Thirty marine surface sediment samples were collected using van veen grab sampler between Adyar and Cooum River mouth in a gridded pattern. The sampling locations were fixed using a hand held GPS (Garmin-eTrex). The collected samples were properly numbered and transferred to laboratory for further analysis. The sediment samples were dried at 60 °C in hot air oven and dried samples were pulverized for elemental analysis. Calcium carbonate (CaCO3) and trace element analysis was performed as suggested by Loring and Rantala (1992).

2

V. Gopal et al. / Marine Pollution Bulletin xxx (2016) xxx–xxx

Fig. 1. Location of the study area.

Organic matter was determined by exothermic heating and oxidation with potassium dichromate and concentrated H2SO4. The excess amount of dichromate titrated with 0.5 N ferrous ammonium sulfate solution (Gaudette et al., 1974). The pulverized samples (b2 mm) were used for estimating the carbon and nitrogen using a CHNS analyzer (TOC-5000 A auto analyzer Shimadzu, Japan) at the department of Applied Geology, University of Madras, Chennai. For digestion, 0.5 g of the sediment sample was placed in a Teflon bomb and 1 ml of aqua regia (AR grade HNO3: HCl; 1:3 v/v) was added, followed by 6 ml HF. The sealed bomb was kept in boiling water bath (2 h and 30 min). After the bomb was removed from the water bath, the contents were added to 5.6 g of boric acid crystals in a 100 ml polypropylene, standard flask. The flask was made up to a volume of 100 ml with double distilled water. The digested solution was analyzed for selected trace elements (Fe, Mn, Cu, Cr, Co, Ni, Pb, Zn and Cd) using Atomic Absorption Spectrophotometer (Perkin Elmer, AA-200) at Department of Applied Geology, University of Madras, Chennai. The detection limit of the analyzed

elements was 0.01 ppm for Fe, Mn, Cr, Cu, Ni, Cd, Zn and 0.05 ppm for Pb. The certified standard reference material (MESS-2) was used to ensure the accuracy of the analysis with a recovery percent value ranging between 91.7 and 105.7% (Table 1). Table 1 Comparison of MESS 2 certified values for total trace elements. Elements

Fe Cr Mn Ni Cu Zn Cd Pb

MESS 2 Obtained value

Certified value

% recovered

4.25 104.1 322.6 45.3 33.2 153 0.22 22.3

4.34 105 324 46.9 33.9 159 0.24 21.1

97.93 99.14 99.57 96.59 97.94 96.23 91.67 105.69

V. Gopal et al. / Marine Pollution Bulletin xxx (2016) xxx–xxx

The concentration of the elements and sand-silt-clay percentage, calcium carbonate and organic matter were given in Table 2 and shown in Figs. 2, 3 & 4. The textural characteristics of the sediments indicate that all the sample locations are composed of sand followed by silt and clay. The long-shore drift and sediment transport had contributed the sand and silt particles in the off shores. However, the discharge points of the river mouth were noticed with high clay content, which is transported from the terrestrial sources. The two main rivers Cooum and Adyar contributes clay to the marine environment which is far low when compared with natural recycling of sand and silt in the off shore. The availability of fine fractions in nearby the river mouth may be due to supply of fine grain sediments from the urban region. Further the availability of elevated sand fractions in the sediments probably due to removal of clay fractions due to inflow of flood water. The enrichment of OM and C/N ratio is chiefly controlled by the availability of fine fractions in the sediments (Fig. 2). According to Kendall et al. (2001), the molar C/N of soils generally ranges from 8 to 15 which are due to well degraded organic matter originating from vascular plants. Similarly, the C/N of the sedimentary organic matter of marine origin in shelves and slope region ranges from 6 to 14 (Tyson, 1995). Similar observations were noticed from studied surface sediment samples, which reveal that they may be derived from same origin (from 6.18 to 8.83, with an average of 7.38%). The OM and CaCO3 ranges from 0.12 to 16.34% and 0.5 to 12.5%. The spatial diagram for trace elements, calcium carbonate and OM distribution clearly suggest that they are derived from river discharge and later transported to the offshore by long shore sediment drift. The low concentration of elements in the inner part of the study region also supported the above findings. The high concentration of CaCO3 content is due to buried calcareous debris by recent sediments supplied by flood event or removal of calcareous matter from near shore sediments due to fast inflow of rainwater through the river mouth. The concentration of Fe and Mn ranges from 8319 to 30,434 μg/g and 149 to 1042 μg/g respectively. The low concentration of Fe and Mn is noticed in the middle part of the study area. The supply of Fe and Mn into the marine environment is chiefly from riverine input and the middle part does not have any

3

river source to supply Fe and Mn. Similar observations were reported by earlier workers (Jonathan et al., 2004; Krishnakumar et al., 2015). The spatial map of Fe and Mn shows few elevated locations probably due to local variations followed by influence of riverine input. The concentration of the element rages from 2.2 to 151.3 μg/g for Ni, 37.2 to 599.9 μg/g for Cu, 2.9 to 3935.5 μg/g for Pb, 48.2 to 267.1 μg/g for Zn, 8.5 to 853.2 μg/g for Cr, 4.7 to 67.9 μg/g for Co. The concentration of trace elements near by the coast and nearby the confluence point of the river suggest that the trace elements are chiefly derived from human induced factors such as industrial activities, urban transportation and draining of untreated sewage into the river channels during flood event. The results also suggest that the contaminants transported along the coast by long shore drift currents. The local elevation of the elemental concentration is controlled by textural characteristics, availability of carrier phase parameters such as OM and CaCO3 content. The elemental concentration of the other coastal region sediments and mean crustal average value is higher than the studied surface sediments except Pb (Table 3). The maximum concentration of Pb in the surface sediments is probably due to transportation of lead contaminated urban soil from Chennai metropolis (Krishna and Govil, 2008; Jonathan et al., 2010). The possible source of lead in the urban areas is application of leaded petrol and untreated sewage effluents from industries. Geo-accumulation index (Igeo) was suggested in order to assess the metal concentration of sediments by comparing present elemental concentrations with pre-industrial levels. The present calculation enables the assessment of contamination by comparing the present and crustal average value of elemental concentrations (Muller, 1979). The Igeo can be calculated by using the following formula: Igeo ¼ Log2

Cn 1:5  Bn

ð1Þ

where, ‘Cn’ is the measured concentration of the examined metal ‘n’ in the sediments and ‘Bn’ is the geochemical background concentration of the metal ‘n’ of crustal average (Taylor and Mclennan, 1995).

Table 2 Trace elements concentration, Fe, Mn (in μg/g), Sand-Silt-clay ratio, CaCO3, OM, C/N ratio (in %) and textural descriptions of the surface sediments of Bay of Bengal, Tamil Nadu, India. S. no

Fe

Mn

Cr

Cu

Pb

Zn

Co

Ni

Sand

Silt

Clay

CaCO3

OM

C/N

Texture description

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

18,099 23,196 17,961 18,632 12,711 19,898 20,040 16,789 17,281 23,135 12,442 28,070 10,479 10,101 8403 16,135 11,843 11,487 10,486 28,067 10,079 10,000 8758 9392 9260 8319 30,434 9373 9898 10,208

560 658 641 694 412 777 819 565 564 1042 382 673 460 244 199 514 410 336 287 558 149 231 214 209 219 177 623 201 238 319

283.2 382.5 268.6 248.7 153.1 285.5 268.6 234 222.8 301.9 123 733.3 301.7 78.4 41 157.9 65.3 57.9 58.5 566.1 16.7 43.5 33.4 33.3 37.1 8.5 853.2 43.4 42.9 57.9

197.3 254.6 158.9 103.6 98.4 71.4 69 97.4 63.2 54.4 69.4 228.8 210 79.6 52.3 58.5 57 48.9 51.3 599.9 55.7 64.7 59.3 47.6 47.8 37.2 300.7 64.7 45.6 47.5

26.5 47.4 27.1 60.9 30.1 50.5 40 38.2 35.5 40.6 3935.5 3261 113.9 131.4 432.8 48.2 150.1 82 26 783.6 205.5 16.7 34.1 2.9 22.3 6.5 61.3 11.7 10.9 17.2

154 211.3 186.4 143 106.4 99.7 107.4 135.1 101 103.3 79.6 223.6 256.6 83.5 64.7 75.5 66.4 56.5 57.5 267.1 64.8 69.6 62.7 48.2 140.8 52.1 260 212.1 116.8 111.6

41.3 52.6 38 38.5 23 40.7 40.4 52.4 37.1 39.8 13.3 67.5 56.6 10.2 10.6 22.6 17.6 11.8 11.8 56.4 6.1 7.1 4.7 7.2 7.4 5 67.9 7.1 11.9 13.2

69.6 113.5 66.5 58.4 42.4 56.5 59.8 76.7 59 56.8 55.9 151.3 150 29.1 24 36.4 29.9 18.4 15.7 149.7 6.9 8.7 4.2 8.7 7.8 3 148.7 2.2 10.5 16.4

80.12 38.85 86.53 98.99 99.72 99.10 99.21 99.50 89.61 98.66 98.88 27.27 33.38 91.04 99.82 76.70 96.55 96.37 97.36 18.61 97.11 97.09 98.79 98.21 97.94 97.60 21.35 97.33 95.79 96.40

1.35 3.37 0.89 0 0 0 0 0 0.81 0 0 6.85 4.92 0.49 0 1.79 0 0 0 7.38 0 0 0 0 0 0 10.29 0 0.049 0

18.53 57.78 12.58 1.01 0.28 0.90 0.79 0.50 9.58 1.34 1.12 65.89 61.70 8.47 0.18 21.51 3.45 3.63 2.64 74.01 2.89 2.91 1.21 1.79 2.06 2.40 68.36 2.67 4.16 3.60

4.5 6.5 4 3 7.5 2.5 2 3.5 3 2.5 2.5 4.5 3 2.5 4.5 2 6.5 2 5.5 3.5 4.5 0.5 3 3.5 6 5.5 4.5 6 5.5 12.5

0.25 2.21 0.37 0.25 0.25 0.25 0.37 0.37 0.12 0.25 0.25 9.95 10.20 0.61 0.25 1.23 0.25 0.61 0.12 16.34 0.12 0.12 1.11 0.25 0.37 0.25 14.25 0.12 0.37 0.49

7.13 7.65 6.18 7.66 7.43 7.32 7.35 7.37 7.35 7.35 7.35 8.14 8.57 7.42 7.34 7.60 7.50 7.48 7.56 8.83 7.33 7.34 7.34 7.30 6.43 6.36 6.35 7.79 6.48 8.03

Very fine sand Very coarse silt Fine sand Fine sand Medium sand Fine sand Fine sand Fine sand Very fine sand Fine sand Medium sand Coarse silt Very coarse silt Coarse sand Coarse sand Very fine sand Medium sand Medium Sand Medium sand Coarse silt Coarse sand Coarse sand Coarse sand Coarse sand Coarse sand Coarse sand Coarse silt Coarse sand Coarse sand Medium sand

4

V. Gopal et al. / Marine Pollution Bulletin xxx (2016) xxx–xxx

Fig. 2. Spatial distribution diagram of sand, silt, clay, CaCO3, OM and C/N ratio.

Concentrations of geochemical background are multiplied every time by 1.5 in order to allow content fluctuations of a given substance in the environment as well as the influence of very small anthropogenic effects. The Igeo based sediment quality was classified based on values as follows. The Igeo class ranging from 0 - unpolluted, 0 to 1 unpolluted to moderately polluted, 1 to 2 moderately polluted, 2 to 3 moderately polluted to strongly polluted, 3 to 4 strongly polluted, 4 to 5 strongly polluted to extremely polluted, and N5 extremely polluted. The mean Geoaccumulation index of the elements in the surface sediment is − 2.61 for Fe, − 1.87 for Mn, − 0.39 for Cr, 0.04 for Cu, 1.60 for Pb, 0.04 for Zn, − 0.93 for Co and −1.93 for Ni. The observed Igeo value shows that the samples are contaminated by Pb, Cu and Zn. Other elements such as Fe, Mn, Cr, Co and Ni are derived from geogenic origin (Table 4).

Enrichment factor value (EF) was calculated for each metals commonly by dividing normalizing metal (Al) by the background concentration ratio of the sediments and dividing of normalizing metal (Al) by the background ratio of the crust (Jonathan et al., 2004). ðMetal=AlÞsample ðMetal=AlÞBackground

ð2Þ

EF value normalizes the measured elemental content with respect to a sample reference elements like Fe or Al (Ravichandran et al., 1995). Deely and Fergusson (1994) proposed Fe can be used as normalizing element to calculate the enrichment factor. Iron usually has a relatively high natural concentration and it is not enriched from human induced

V. Gopal et al. / Marine Pollution Bulletin xxx (2016) xxx–xxx

Fig. 3. Spatial distribution diagram of Fe, Mn, Cr and Cu of the surface sediments.

5

6

V. Gopal et al. / Marine Pollution Bulletin xxx (2016) xxx–xxx

Fig. 4. Spatial distribution diagram of Pb, Zn, Co and Ni of the surface sediments.

V. Gopal et al. / Marine Pollution Bulletin xxx (2016) xxx–xxx

7

Table 3 comparison of trace elemental concentration with other coastal regions of India, crustal average and sediments derived from natural disaster events (Tsunami). Study area

Fe

Mn

Cu

Pb

Cd

Ni

Cr

Zn

References

Chennai coast, Southeast coast of India Tsunamigenic sediments, Pichavaram mangroves SE coast of India Palk Strait, South east coast of India Surface sediments, Gulf of Mannar Surface sediments, Tuticorin Coast Crustal Average

15,032.5 24,998 55,680.3 1 2600 28,717 44,900

445.8 801 661.4 305 330 700

113.2 132.3 69.1 57 52 55

325 143.8 19.52 16 42 12.5

DNA 34.74 0.4 0.16 6 0.2

51.2 252.1 27.9 24 30 75

200.1 617 302.3 177 15 100

123.9 106 244.2 73 247 70

Present study Ranjan et al., 2008 Kasilingam et al., 2016 Jonathan et al., 2004 Magesh et al., 2013 Taylor, 1964

DNA - Data not available, All the elemental concentration in μg/g.

the contamination degree of the environment (Hakanson, 1980). The concentration levels may be classified based on their intensities on a scale ranging from 1 to 6 ((0 = none, 1 = none to medium, 2 = moderate, 3 = moderately to strong, 4 = strongly polluted, 5 = strong to very strong, 6 = very strong), Muller, 1969)). According to Angulo (1996), PLI can give an estimate of metal contamination status and the necessary action that should be taken. The PLI can be calculated by the following formula:

sources in marine sediments (Niencheski et al., 1994; Ramasamy et al., 2015). The enrichment factor was classified as follows: 0 to 1 background concentration, 1 to 2 minimal enrichment, 2 to 5 moderate enrichment, 5 to 20 significant enrichment, 20 to 40 very rich enrichment, and N40 extremely high enrichment. EF values are N10 considered to be non-crustal source. The mean enrichment of the trace elements are 1.72 for Mn, 6.09 for Cr, 7.14 for Cu, 9.76 for Pb, 6.94 for Zn, 3.70 for Co, 2.26 for Ni. The surface sediments of the study area is enriched by following elements such as Pb, Cu, Zn, Cr, Co, Ni and Fe (Table 4). The pollution level of the surface sediments was calculated as suggested by Tomlinson et al., 1980 in order to identify the pollution, which permits a comparison of pollution levels between the sites at different period. Initially, the contamination factor was calculated for pollution load index using following equation. CFmetal ¼

C metal Cbackground

PLI ¼ ðCF1 CF2  CF3  ……:  CFn Þ1=n

ð4Þ

The pollution load index ranges from 0.22 to 3.86 (Fig. 5). The elemental contamination of the surface sediments suggest that northern and southern part of the study area is contaminated by trace elements due riverine input which transports untreated sewage into marine environment. Pearson correlation coefficient (r) was applied to calculate the relationship between metal concentration, sand-silt-clay, CaCO3 and OM. The significant positive correlation (p b 0.01) was observed in clay, OM, Fe, Cr, Cu, Zn, Co and Ni (Table 5). Factor analysis was performed to identify the probable sources of metal pollutants in the study area (Prasanna et al., 2012; Kalpana et al., 2016). The cumulative percentage of variance explained contribute to 87.23% in which PC1 contributes

ð3Þ

Here, ‘CF’ is the ratio obtained by dividing the concentration of each element in the sediments by the baseline or background value (average crustal value). The ‘CF’ is the single element contamination index, the sum of contamination factors for all elements examined represents

Table 4 Enrichment factor (EF) and Geoaccumulation index (Igeo) of the elements of surface sediments, Bay of Bengal, Chennai. S. no

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 Mean

Enrichment factor (EF)

Geoaccumulation index (Igeo)

Mn

Cr

Cu

Pb

Zn

Co

Ni

Fe

Mn

Cr

Cu

Pb

Zn

Co

Ni

1.83 1.68 2.12 2.21 1.92 2.31 2.42 1.99 1.93 2.67 1.82 1.42 2.60 1.43 1.40 1.89 2.05 1.73 1.62 1.18 0.88 1.37 1.45 1.32 1.40 1.26 1.21 1.27 1.42 1.85 1.72

8.81 9.28 8.42 7.51 6.78 8.08 7.55 7.85 7.26 7.35 5.57 14.71 16.21 4.37 2.75 5.51 3.10 2.84 3.14 11.36 0.93 2.45 2.15 2.00 2.26 0.58 15.78 2.61 2.44 3.19 6.09

11.16 11.24 9.06 5.69 7.92 3.67 3.52 5.94 3.74 2.41 5.71 8.34 20.51 8.07 6.37 3.71 4.93 4.36 5.01 21.88 5.66 6.62 6.93 5.19 5.28 4.58 10.11 7.07 4.72 4.76 7.14

6.59 9.20 6.80 14.72 10.67 11.43 8.99 10.25 9.25 7.90 1424.65 523.25 48.96 58.59 231.98 13.45 57.08 32.15 11.17 125.75 91.83 7.52 17.54 1.39 10.85 3.52 9.07 5.62 4.96 7.59 92.76

6.84 7.33 8.35 6.17 6.73 4.03 4.31 6.47 4.70 3.59 5.15 6.41 19.69 6.65 6.19 3.76 4.51 3.96 4.41 7.65 5.17 5.60 5.76 4.13 12.23 5.04 6.87 18.20 9.49 8.79 6.94

5.14 5.11 4.76 4.65 4.07 4.61 4.54 7.03 4.83 3.87 2.41 5.42 12.16 2.27 2.84 3.15 3.35 2.31 2.53 4.53 1.36 1.60 1.21 1.73 1.80 1.35 5.02 1.71 2.71 2.91 3.70

2.89 3.67 2.78 2.35 2.50 2.13 2.24 3.43 2.56 1.84 3.37 4.05 10.75 2.16 2.14 1.69 1.90 1.20 1.12 4.00 0.51 0.65 0.36 0.70 0.63 0.27 3.67 0.18 0.80 1.21 2.26

−2.22 −1.86 −2.23 −2.18 −2.73 −2.09 −2.08 −2.33 −2.29 −1.87 −2.76 −1.59 −3.01 −3.06 −3.33 −2.39 −2.83 −2.88 −3.01 −1.59 −3.07 −3.08 −3.27 −3.17 −3.19 −3.34 −1.47 −3.17 −3.09 −3.05 −2.61

−1.35 −1.11 −1.15 −1.04 −1.79 −0.87 −0.80 −1.33 −1.34 −0.45 −1.90 −1.08 −1.63 −2.55 −2.84 −1.47 −1.80 −2.08 −2.31 −1.35 −3.26 −2.62 −2.74 −2.77 −2.70 −3.01 −1.19 −2.83 −2.58 −2.16 −1.87

0.92 1.35 0.84 0.73 0.03 0.93 0.84 0.64 0.57 1.01 −0.29 2.29 1.01 −0.94 −1.87 0.07 −1.20 −1.37 −1.36 1.92 −3.17 −1.79 −2.17 −2.17 −2.02 −4.14 2.51 −1.79 −1.81 −1.37 −0.39

1.26 1.63 0.95 0.33 0.25 −0.21 −0.26 0.24 −0.38 −0.60 −0.25 1.47 1.35 −0.05 −0.66 −0.50 −0.53 −0.75 −0.69 2.86 −0.57 −0.35 −0.48 −0.79 −0.79 −1.15 1.87 −0.35 −0.86 −0.80 0.04

0.50 1.34 0.53 1.70 0.68 1.43 1.09 1.03 0.92 1.11 7.71 7.44 2.60 2.81 4.53 1.36 3.00 2.13 0.47 5.39 3.45 −0.17 0.86 −2.69 0.25 −1.53 1.71 −0.68 −0.78 −0.12 1.60

0.55 1.01 0.83 0.45 0.02 −0.07 0.03 0.36 −0.06 −0.02 −0.40 1.09 1.29 −0.33 −0.70 −0.48 −0.66 −0.89 −0.87 1.35 −0.70 −0.59 −0.74 −1.12 0.42 −1.01 1.31 1.01 0.15 0.09 0.04

0.14 0.49 0.02 0.04 −0.71 0.12 0.11 0.48 −0.02 0.09 −1.50 0.85 0.59 −1.88 −1.82 −0.73 −1.09 −1.67 −1.67 0.59 −2.62 −2.40 −3.00 −2.38 −2.34 −2.91 0.86 −2.40 −1.66 −1.51 −0.93

−0.69 0.01 −0.76 −0.95 −1.41 −0.99 −0.91 −0.55 −0.93 −0.99 −1.01 0.43 0.42 −1.95 −2.23 −1.63 −1.91 −2.61 −2.84 0.41 −4.03 −3.69 −4.74 −3.69 −3.85 −5.23 0.40 −5.68 −3.42 −2.78 −1.93

8

V. Gopal et al. / Marine Pollution Bulletin xxx (2016) xxx–xxx

Fig. 5. Spatial distribution map of the Pollution Load Index (PLI) of the surface sediments.

Table 5 Bivariate Pearson correlations of metal concentration of surface sediments. Parameters

Sand

Silt

Clay

Sand Silt Clay CaCO3 OM Fe Mn Cr Cu Pb Zn Co Ni

1.000 −0.959⁎⁎ −1.000⁎⁎ 0.007 −0.916⁎⁎ −0.680⁎⁎

1.000 0.950⁎⁎ −0.028 0.950⁎⁎ 0.720⁎⁎

1.000 −0.005 0.908⁎⁎ 0.672⁎⁎

−0.313 −0.832⁎⁎ −0.856⁎⁎

0.310 0.887⁎⁎ 0.821⁎⁎

0.311 0.821⁎⁎ 0.856⁎⁎

−0.247 −0.818⁎⁎ −0.747⁎⁎ −0.883⁎⁎

0.250 0.786⁎⁎ 0.739⁎⁎ 0.856⁎⁎

0.246 0.817⁎⁎ 0.744⁎⁎ 0.882⁎⁎

⁎⁎ Correlation is significant at the 0.01 level (2-tailed). ⁎ Correlation is significant at the 0.05 level (2-tailed).

CaCO3

1.000 −0.055 −0.162 −0.246 −0.108 −0.029 −0.112 0.116 −0.133 −0.126

OM

Fe

1.000 0.626⁎⁎ 0.237 0.799⁎⁎ 0.863⁎⁎

1.000 0.813⁎⁎ 0.932⁎⁎ 0.695⁎⁎

0.250 0.763⁎⁎ 0.668⁎⁎ 0.820⁎⁎

0.225 0.635⁎⁎ 0.880⁎⁎ 0.810⁎⁎

Mn

Cr

Cu

Pb

Zn

Co

Ni

1.000 0.665⁎⁎ 0.330 0.075 0.394⁎ 0.783⁎⁎ 0.618⁎⁎

1.000 0.750⁎⁎ 0.293 0.766⁎⁎ 0.915⁎⁎ 0.913⁎⁎

1.000 0.178 0.784⁎⁎ 0.688⁎⁎ 0.806⁎⁎

1.000 0.127 0.167 0.326

1.000 0.762⁎⁎ 0.817⁎⁎

1.000 0.942⁎⁎

1.000

V. Gopal et al. / Marine Pollution Bulletin xxx (2016) xxx–xxx

9

References

Table 6 Extracted factor loadings of the rotated component matrix. Parameters

PC1

PC2

PC3

Sand Silt Clay CaCO3 OM Fe Mn Cr Cu Pb Zn Co Ni Eigen values % of variance Cumulative %

−0.96 0.94 0.95 0.17 0.94 0.56 0.13 0.76 0.87 0.28 0.83 0.63 0.81 7.09 54.53 54.53

−0.20 0.22 0.19 −0.34 0.13 0.76 0.96 0.59 0.24 −0.11 0.30 0.73 0.51 3.06 23.53 78.05

−0.07 0.10 0.07 −0.67 0.12 0.12 0.07 0.14 0.02 0.78 −0.15 0.04 0.17 1.19 9.18 87.23

Extraction method – principal component analysis; rotation – varimax with Kaiser normalization.

54.53% followed by 23.53% for PC2 and 9.18% for PC3 (Table 6). The rotated space of the principal component plot reveals that all the parameters are grouped under component 1 except sand (Fig. 6). The association of the elements with clay, OM and CaCO3 clearly suggest that the elements are moving together and chiefly controlled by these three parameters. Lead is categorized as a separate group under component 1 and its probable source is associated with transportation sector, thermal power plants, and urban sewage. Such sources could have contaminated the urban soil and due to urban runoff triggered by major flood event, these contaminants were carried into marine environment. The trace element concentration in marine surface sediments was investigated after major flood event of Chennai metropolis, India. The elemental concentration, calcium carbonate and OM distribution of the sediments suggest that they are derived from urban runoff, transported through Adyar and Cooum Rivers and confluence into the marine environment. The enrichment factor revels that the sediments are enriched by Pb, Cu, Zn, Cr, Co, Ni followed by Fe. The Igeo value shows that the sediments are contaminated by Pb, Cu and Zn. The elemental concentration of the surface sediments is low when compared to other coastal region except Pb. The analytical results and statistical data reveal that the elevated level of Pb is probably due to migration of contaminated urban soil into marine environment.

Fig. 6. Rotated space principal component plot of elements of surface sediments in rotated space.

Angulo, E., 1996. The Tomlinson pollution load index applied to heavy metal ‘MusselWatch’ data: a useful index to assess coastal pollution. Sci. Total Environ. 187, 19–56. Deely, J.M., Fergusson, J.E., 1994. Heavy metal and organic matter concentration and distributions in dated sediments of a small estuary adjacent to a small urban area. Sci. Total Environ. 153, 97–111. Diakakis, M., Deligiannakis, G., Pallikarakis, A., Skordoulis, M., 2016. Factors controlling the spatial distribution of flash flooding in the complex environment of a metropolitan urban area.The case of Athens 2013 flash flood event. Int. J. Disaster Risk Reduct. 18, 171–180. Gaudette, H.E., Flight, W.R., Toner, L., Folger, D.W., 1974. An inexpensive titration method for the determination of organic carbon in recent sediments. J. Sediment. Petrol. 44, 249–253. Hakanson, L., 1980. An ecological risk index for aquatic pollution control. A sedimentological approach. Water Res. 14, 975–1001. Hussain, S.M., Mohan, S.P., Jonathan, M.P., 2010. Ostracoda as an aid in identifying 2004 tsunami sediments: a report from SE coast of India. Nat. Hazards 55, 513–522. Jonathan, M.P., Jayaprakash, M., Srinivasalu, S., Roy, P.D., Thangadurai, N., Muthuraj, S., 2010. Evaluation of acid leachable trace metals in soils around a five centuries old mining district in Hidalgo, Central Mexico. Water Air Soil Pollut. 205, 227–236. Jonathan, M.P., Rammohan, V., Srinivasalu, S., 2004. Geochemical variations of major and trace elements in recent sediments, off the Gulf of Mannar, the southeast coast of India. Environ. Earth Sci. 45, 466–480. Kalpana, G., Shanmugasundharam, A., Nethaji, S., Viswam, Arya, Kalaivanan, R., Gopal, V., Jayaprakash, M., 2016. Evaluation of total trace metal (TTMs) enrichment from estuarine sediments of Uppanar, southeast coast of India. Arab. J. Geosci. 9, 34. Kasilingam, K., Suresh Gandhi, M., Krishnakumar, S., Magesh, N.S., 2016. Trace element concentration in surface sediments of Palk Strait, south east coast of Tamil Nadu, India. Mar. Pollut. Bull. 111 (1–2), 500–508. Kendall, C., Silva, S.R., Kelly, V.J., 2001. Carbon and nitrogen isotopic compositions of particulate organic matter in four large river systems across the United States. Hydrol. Process. 15, 1301–1346. Krishna, A.K., Govil, P.K., 2008. Assessment of heavy metal contamination in soils around Manali industrial area, Chennai, southern India. Environ. Geol. 54, 1465–1472. Krishnakumar, S., Ramasamy, S., Magesh, N.S., Chandrasekar, N., Simon Peter, T., 2015. Metal concentrations in the growth bands of Porites sp.: a baseline record on the history of marine pollution in the Gulf of Mannar, India. Mar. Pollut. Bull. 101, 409–416. Loring, D.H., Rantala, R.T.T., 1992. Manual for the geochemical analyses of marine sediments and suspended particulate matter. Earth Sci. Rev. 32, 235–283. Magesh, N.S., Chandrasekar, N., Krishna Kumar, S., Glory, M., 2013. Trace element contamination in the estuarine sediments along Tuticorin coast – Gulf of Mannar, southeast coast of India. Mar. Pollut. Bull. 73, 355–361. Magesh, N.S., Chandrasekar, N., VethaRoy, D., 2011. Spatial analysis of trace element contamination in sediments of Tamiraparani Estuary, Southeast Coast of India. Estuar. Coast. Shelf Sci. 92, 618–628. Modarres, R., Sarhadi, A., Burn, D., 2016. Changes of extreme drought and flood events in Iran. Glob. Planet. Chang. Doi http://dx.doi.org/10.1016/j.gloplacha.2016.07.008. Morri, C., Montefalcone, M., Lasagna, R., Gatti, G., Rovere, A., Parravicini, V., Baldelli, G., Colantoni, P., Bianchi, C.N., 2015. Through bleaching and tsunami: coral reef recovery in the Maldives. Mar. Pollut. Bull. 98 (1–2), 188–200. Muller, G., 1969. Index of geoaccumulation in sediments of the Rhine river. J. Geol. 108–118. Muller, G., 1979. Schwermetalle in den sediments des Rheins-Veranderungen seitt 1971. Umaschan 79, 778–783. Niencheski, L.F., Windom, H.L., Smith, R., 1994. Distribution of particulate trace metal in Patos Lagoon estuary (Brazil). Mar. Pollut. Bull. 28, 96–102. Prasanna, M.V., Praveena, S.M., Chidambaram, S., Nagarajan, R., Elayaraja, A., 2012. Evaluation of water quality pollution indices for heavy metal contamination monitoring: a case study from Curtin Lake, Miri City, East Malaysia. Environ. Earth Sci. 67 (7), 1987–2001. Ramasamy, S., Krishna Kumar, S., Stephen Pitchaimani, V., Parthasarathy, P., Ramachandran, A.A., 2015. Assessment of trace element accumulation in core sediments, Bay of Bengal, South east coast of India. J. Applied Geochem. 17 (3), 342–351. Ranjan, R.K., Ramanathan, A.L., Singh, G., 2008. Evaluation of geochemical impact of tsunami on Pichavaram mangrove ecosystem, southeast coast of India. Environ. Geol. 55, 687–697. Ravichandran, M., Baskaran, M., Satschi, P.H., Bianchi, T.S., 1995. History of trace metal pollution in Sabine-Neches estuary, Beaumount, Texas. Environ. Sci. Technol 29 (6), 1495-150. Srinivasalu, S., Jonathan, M.P., Thangadurai, N., Ram-Mohan, V., 2010. A study on pre- and post-tsunami shallow deposits off SE coast of India from the 2004 Indian Ocean tsunami: a geochemical approach. Nat. Hazards 52, 391–401. Taylor, S.R., 1964. Abundance of chemical elements in the continental crust: a new table. Geochim. Cosmochim. Acta 28, 1273–1285. Taylor, S.R., Mclennan, S.M., 1995. The geochemical evolution of the continental crust. Rev. Geophys. 33, 241–265. Tomlinson, D.L., Wilson, J.G., Harris, C.R., Jeffrey, D.W., 1980. Problems in the assessment of heavy metal levels in estuaries and the formation of a pollution index. Helgol. Mar. Res. 33 (1–4), 566–575. Tyson, R.V., 1995. Sedimentary Organic Matter. Chapman and Hall, London.