Environ Monit Assess (2015) 187:469 DOI 10.1007/s10661-015-4531-5

Bimonthly variability of persistent organochlorines in plastic pellets from four beaches in Mumbai coast, India H. B. Jayasiri & C. S. Purushothaman & A. Vennila

Received: 4 July 2014 / Accepted: 12 April 2015 # Springer International Publishing Switzerland 2015

Abstract Organochlorines (OCs) such as polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) were analysed in plastic pellets collected from four beaches of Mumbai coast bimonthly from May 2011 to March 2012. A total of 72 pools of pellets were extracted and analysed by gas chromatograph equipped with a Ni63 electron capture detector (ECD). The median concentrations of seven ΣPCBs and 16 ΣOCPs were 37.08 and 104.90 ng g−1 (n=72), respectively. PCB-28 was recorded at the highest concentration with a mean of 17.58±2.77 ng g−1 among the seven PCBs studied, followed by PCB-52 and PCB101. Bimonthly variation was significant for ΣPCBs. The ΣPCB concentration in November was at par with that of September and was significantly higher than those of the other months (p<0.05) with an increasing trend during the monsoon period. Among the OCPs, γ-HCH recorded the highest concentration with a mean of 33.88±5.97 ng g−1 followed by heptachlor and αHCH. The ΣOCPs and ΣHCHs are not significantly varied among the months and sites. However, significant variation was observed for ΣDDTs among the months and sites (p<0.05). The significantly higher H. B. Jayasiri (*) National Aquatic Resources, Research and Development Agency, National Institute of Oceanography and Marine Sciences, Crow Island, Colombo 15, Sri Lanka e-mail: [email protected] C. S. Purushothaman : A. Vennila Aquatic Environment and Health Management Division, Central Institute of Fisheries Education, Panch Marg, Versova, Mumbai 400 061, India

concentration of ΣDDT (46.55±12.23 ng g−1) was found in January than in the other months while it was intermediate in November. The study confirmed that plastic pellets are a trap for various cyclodine compounds in addition to PCB, HCH and DDT. Further, pellets can be used to study the temporal variability for a range of organic micropollutants. Keywords Polychlorinated biphenyls . Organochlorine pesticides . Cyclodine compounds . Mumbai . Plastic pellets . Monsoon

Introduction Organochlorines (OCs) such as polychlorinatedbiphenyls (PCBs) and organochlorine pesticides (OCPs) represent an important group of persistent organic pollutants (POPs) that have caused worldwide concern as toxic environmental contaminants (Wu et al. 1999). These compounds are characterized by low water solubility, high lipid solubility and low degradability, and have the ability to bioaccumulate and biomagnify (Anon 1995; Anon 2010). PCBs are found in industrial chemicals and as by-products of manufacturing processes and waste incineration. There are increasing concerns over the dispersion of POPs in the global environment and their impact upon wildlife (Jeminez 1997; Jones and de Voogt 1999). As a party to the Stockholm Convention, India is legally obligated to abide by the objectives of the treaty and is encouraged to support research on POPs.

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Plastics are synthetic organic polymers and resistant to degradation in the environment. Such debris is composed of fragments of manufactured plastic products (user plastic) and pre-production plastic pellets (industrial pellets, virgin pellets, plastic resin beads or nurdles) that are shipped from manufacturing plants to plastic processing factories to be melted and moulded into consumer products (USEPA 1992). Many plastics are less dense than water and float at the sea surface microlayer (SML), where hydrophobic compounds are rich (Wurl and Obbard 2004) making SML both a sink and a source for a range of pollutants including chlorinated hydrocarbons. The SML is highly contaminated in many urban and industrialized areas of the world, resulting in severe ecotoxicological impacts, which may lead to drastic effects on the marine food web and to fishery recruitment in coastal waters (Wurl and Obbard 2004). Thus, SML plays an important role in the fate of POPs in aqueous ecosystems (Southwood et al. 1999). The microplastics have high potential to sorb organic pollutants from SML due to the high surface area (Thompson et al. 2004) and the hydrophobic nature (Karapanagioti and Klontza 2008). These hydrophobic substances can be readily ingested by invertebrates at the base of the food web (Thompson et al. 2004). Thus, the microplastic particles (less than 5 mm in size) are potentially dangerous to marine species due to the risk of magnification over the food chain (Endo et al. 2005). However, once plastic debris reaches the ocean, the floating component is dispersed in various ways and strands on beaches all over the world affecting the marine environment. Thus, plastics, particularly microplastics, can be used as passive samplers for monitoring pollution in coastal waters (Mato et al. 2001). Plastics constitute the majority of marine litter worldwide (Derraik 2002), and there have been many investigations carried out on marine plastics. As plastic production and usage continue to increase, particularly in the economically developing countries, the environmental implications of plastic disposal should be carefully considered to avoid unintentional release, magnification, and transport of contaminants (Thompson et al. 2009a, b). Plastic resin pellets and fragments of plastic resulting from breakdown of larger objects are known sources and sinks of xenoestrogens and POPs in marine and freshwater environments (Mato et al. 2001; Moore et al. 2005). Different plastics and resins have widely varying properties with respect to contaminant adsorption and desorption

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(Teuten et al. 2009). Adsorbed hydrophobic chemicals such as PCBs and OCPs onto microplastics pose a high environmental risk to marine organisms. However, the chemical aspects of plastics have not been addressed consistently (Frias et al. 2010). Though, Carpenter et al. (1972) first detected PCBs in polystyrene spherules collected from Niantic Bay in the USA and suggested that PCBs are adsorbed on to the plastic from the surrounding seawater, no supporting evidence was provided. After a 30-year break, Mato et al. (2001) carried out a series of systematic studies on toxic chemicals in marine plastics and revealed the existence of various organic micropollutants (i.e. PCBs, DDE and nonylphenol) in the stranded plastic resin pellets collected on beaches, and also detected PCBs in polypropylene pellets from the Japanese coasts. The resin pellets in industrialized areas contain larger quantities of PCBs than those in a remote site, suggesting that contaminant concentrations in resin pellets are determined by the pollution levels in the surrounding environment. Due to the ubiquitous occurrence on world beaches, and their ease of collection and shipment, plastic resin pellets are used by International Pellet Watch (IPW) as passive samplers. IPW is a volunteer-based global monitoring programme designed to monitor the pollution status of the oceans and to understand the risks associated with the chemicals in marine plastics. IPW has drawn global pollution maps of POPs and identified hot spots (Ogata et al. 2009; Karapanagioti et al. 2011). Endo et al. (2005) and Ogata et al. (2009) examined the concentrations of PCBs in beached resin pellets to reveal the variability between individual particles and the differences among the beaches in Tokyo, Japan. They reported that the sporadic high concentrations of PCBs in pellets from remote islands could be the dominant route of exposure to the contaminants at remote sites. Yellowing is an indication of environmental residence time of the pellets (Endo et al. 2005). Therefore, yellowing polyethylene pellets are most suitable for the monitoring of POPs. Smith (2008) also suggested that the degree of staining of pellet is an indicator of the length of time the pellet has been in the sea and hence, its length of exposure to pollutants. Karapanagioti and Klontza (2008) conducted an experiment with eroded plastic pellets and provided an insight of the sorptive behaviour of the pellets and the organic compounds used. The concentrations of hydrophobic contaminants adsorbed on plastics show distinct spatial variations reflecting global pollution patterns. The concentrations

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of PCBs are higher in the coasts of USA, Japan and the west European countries, whereas these are minimal in tropical Asia (Ogata et al. 2009). Most of the research on the chemical aspects of marine plastics has been carried out in developed countries such as Japan, Greece, Portugal, USA, etc. (Mato et al. 2001; Endo et al. 2005; Rios et al. 2007; Frias et al. 2010, 2011; Karapanagioti et al. 2010, 2011). Further, many studies of OCs were concerned with PCB, HCH and DDT but not on other chlorinated compounds such as cyclodienes. Most of the studies of POPs on plastics attempted to explain the spatial variation. However, Ryan et al. (2012) found that the concentrations of the three groups of POPs (PCBs, DDTs and HCHs) analysed from pellets have decreased at all the three sites sampled, suggesting that the quantities in South African coastal waters have decreased over the last two decades. Their results have supported the value of routine sampling of polyethylene pellets to monitor the changes in environmental burdens of POPs in coastal waters. The present study aimed to evaluate the bimonthly variability of persistent OCs in beached plastic pellets collected from Mumbai coast during a 1-year period.

Methods and materials Study area Mumbai (18° 55' N, 72° 54' E) is the most populous (~12.5 million) metropolitan city on the west coast of India and the capital of the State of Maharashtra. The State of Maharashtra accounts for a 653-km long coastline with 17 % sandy beaches, many of them are lying within the Mumbai city (Kumar et al. 2006). The increase in urbanization and industrialization has led to an increase in marine discharges. The city generates 2.2× 106 m3 day−1 of domestic sewage, out of which, about 2.0×106 m3 day−1 (largely untreated) enters the marine waters including creeks and bays (Zingde 1999). Tides, currents and waves bring these pollutants to the beaches. Mumbai has a great diversity of industries in the metropolitan region. About 8 % of the industries in the country are located upstream around Mumbai. A variety of industries, including refineries and petrochemical complexes from this area, release their effluents, largely untreated, into the sea. There are a number of ports wherein the ship and cargo handling activities contribute

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to marine pollution. This has resulted in the degradation of the coastal water quality and the contamination of adjoining beaches and seafronts (Kumar et al. 2006). The tidal range at Mumbai coast reaches a maximum value of about 5 m during spring tide (Unnikrishnan et al. 1999). Moreover, the seasonally reversing monsoon winds over the Northern Indian Ocean force a seasonally reversing circulation in the upper ocean (Shankar et al. 2002). Industrial effluents and domestic sewage from the highly developed metropolitan area of the city enter the shelf in the region. Furthermore, the area has considerable economic importance. Out of the nine beaches located in Mumbai coast, four beaches namely Aksa, Versova, Juhu and Mahim, which show wide geographical coverage, and degree of beach usage for recreation and tourism activities, were selected for the study (Fig. 1). Mumbai weather experiences very little seasonal variation due to the moderating effect of the Arabian Sea. However, it can be categorized into four seasons: summer, winter, monsoon and the withdrawal season. December to February is the winter season, March to May is summer, June to September experiences monsoon and October to December is the withdrawal season (http://www.mapsofindia.com/ mumbai/mumbai-weather.html). Mumbai receives most of the rain during the monsoon season and accounts for a total rainfall of about 1800 mm in a year. The Arabian Sea becomes rough and turbulent with high-rising waves during the monsoon season.

Sampling The field surveys were carried out on a bimonthly basis from May 2011 to March 2012 to cover all the seasons in Aksa, Versova, Juhu and Dadar beaches. Sampling was carried out just after the high tide. Tide predictions were obtained from online admiralty charts (UKHO Easy Tide) for Bandra tide station which is located just north to Dadar beach. The plastic pellets were picked up one by one from the sand surface using solvent-rinsed stainless tweezers or by hand along the high tide line. Around 100 pellets were collected from each beach (Endo et al. 2005) at each site. Samples were stored in amber-coloured glass vials and transported to the laboratory. Pellets were kept in desiccators to remove moisture and stored in pre-baked amber glass vials at 4 °C till the chemical analysis was performed (Hirai et al. 2011).

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Environ Monit Assess (2015) 187:469

Fig. 1 Map showing the sampling sites in Mumbai coast

Analysis of POPs in plastic pellets The POPs in the plastic samples were analyzed according to the method described by Ogata et al. (2009). Among the pellets, yellowing ones were selected by the naked eye for chemical analysis. The coloured or pigmented pellets were excluded from the analysis (Endo et al. 2005). The pellets were pooled in triplicate with each pool consisting of ten pellets at each site. Each pool (sample) was weighed and introduced into a 30-ml amber vial. Approximately 15 ml of n-Hexane (chromatography grade, Merck) was added and shaken well, and the vial was kept in dark at room temperature for 72 h for extraction. The n-Hexane solution was then transferred with a glass pipette into an amber vial. The extraction was repeated using fresh solvent. These sequential extracts were combined and concentrated by rotary evaporator (Superfit, India) up to approximately 0.5 ml and introduced on to a fully activated silica gel

column (18 cm×0.5 cm i.d.; 100–200 mesh silica gel from Merck). The column was conditioned using n-Hexane. Then, the sample extract was added to the column using a combusted disposable pasture pipette. The vial was rinsed three times with 2 ml hexane, and the rinsate was added to the column using the same disposable pipette for the sample and rinsate transfer. Another 3 ml hexane was added, and the first fraction of 5 ml hexane was eluted and discarded. The second fraction, containing PCBs and 4,4’-DDE, aldrin and heptachlor, was eluted with another 30 ml hexane. The third fraction, containing other pesticides and PAHs, was eluted with 20 ml hexane/dichloromethane (DCM) (3:1 v/v). The second and third fractions were evaporated to ~1.0 ml by the rotary evaporator and transferred into 2.0-ml amber vials and further concentrated to 0.5 ml by purified gentle N2 stream (98 %) and sealed in an amber vial until analyzed using gas chromatograph (GC).

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The second and third fractions of concentrated extracts were analysed for PCBs and OC pesticides using a GC (14B, Shimadzu, Japan) equipped with a Ni63 electron capture detector (ECD). The fused silica capillary column was BP-1 from Restek, USA (30 m length× 0.25 mm i.d., 0.25-μm film thickness of stationary phase). The oven temperature programme was 80 °C for 1 min to 155 °C at the rate of 15 °C min−1 and increased by 5 °C min−1 to 290 °C, and held for 15 min. The detector make up gas was nitrogen at a flow rate of 30 ml min−1. The detector and injector temperatures were 300 and 280 °C, respectively. The injected volume was 1 μl and the total run time was 48 min. Data acquisition and analysis were achieved by the use of the GC Solution software supplied by Shimadzu, Japan. Analytes were identified and quantified by external standards method for PCBs and OCPs. A certified solution (10 ng μl −1 ) of standard PCB mix (seven compounds; PCB-28, 52, 101,138, 153, 180, 209) was purchased from Sigma-Aldrich (Germany), and the pesticide mix standard (2000 ppm) solution (16 compounds) was purchased from Supelco (USA); the studied OCPs are HCH isomers (α, β, γ, δ), 4,4'-DDT and its metabolites (4,4'-DDE, 4,4'-DDD) and cyclodienes (aldrin, dieldrin, endosulfan I(α), endosulfan II(β), endosulfan sulfate, endrin, endrin aldehyde, heptahlor and heptachlor epoxide-B). Statistical analysis All statistical comparisons were performed using SPSS software (Version 16). The analysis of variance was carried out for the effect of month, beach and their interactions at the significance level of p<0.05 for the ΣPCBs and ΣOCPs. For significant effects, the mean separation was carried out by Duncan grouping at p= 0.05. Principal component analysis (PCA) was performed for PCBs in plastic pellets to examine the underlying relationships between the variables.

Results Of the pellets collected for OC analysis, the diameter of 50 randomly selected pellets averaged 4.30±0.11 mm (range=2–5 mm), while subsequent gravimetric analysis

revealed an average pellet mass of 23.0±1.0 mg (range=10–55 mg). Polychlorinated biphenyls (PCBs) In the 72 pools of plastic pellets analysed, the concentration of ΣPCBs varied widely from undetectable levels to 210.34 ng g−1 with a median of 37.08 ng g−1. PCB was found in 70 analytical pools (97 %). PCB-28 was recorded at the highest concentration with a mean of 17.58±2.77 ng g−1 among the seven PCBs studied followed by PCB-52 and PCB-101 (Fig. 2). PCB-209 was not reported in any of the samples analysed. PCB-28 was found as the most dominant PCB congener with 72 % of frequency of detection among the seven PCBs followed by PCB-52 (66 %). In general, the frequency of detection and ΣPCB concentration decreased with the increasing IUPAC number of PCBs except PCB-153. The highest median of ΣPCB concentration of 204.34 ng g−1 was observed in Versova beach followed by Dadar beach (167.51 ng g−1) in November (after the monsoon season). The lowest median concentration of ΣPCB was found in Juhu beach in March (Table 1). Two-way ANOVA showed significant difference for ΣPCBs among the months (Table 2). No significant difference was found for ΣPCBs among the beaches and the interaction of beaches and months. The mean ΣPCBs concentration in November was at par with that of September and was significantly higher than those of the other months with increasing trend during the monsoon period (Fig. 3). PCA extracted two components with eigenvalues greater than 1, which accounted for 67.46 % of the total variance. PCB-101, PCB-138, PCB-153 and PCB-180 were tightly associated in the Component 1 which 25

20 Concentraon (ng g-1)

Sample analysis by GC-ECD for PCBs and OCPs

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15

10

5

0 PCB-28

PCB-52

PCB-101 PCB-138 PCB-153 PCB-180 PCB-209

Fig. 2 Mean concentration (±SE) of PCBs in plastic pellets (n=72)

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Table 1 Median concentration (ng g−1) for different groups of organochlorines in plastic pellets (n=3) ΣPCBs Aksa May

Versova

28.28

Juhu

24.15

47.48

Dadar 101.07

July

23.63

55.11

31.32

25.72

September

65.31

81.51

81.11

43.48

November

46.73

204.34

61.25

167.51

January

17.87

17.97

19.92

22.58

March

10.09

8.12

0.42

21.08 36.26

ΣHCHs May

69.21

29.02

29.34

July

54.83

51.69

43.42

25.65

September

15.30

139.81

35.67

38.31

November

21.58

223.01

47.33

87.34

January

40.24

21.44

44.45

24.67

March

251.41

42.56

38.21

12.35

ΣOCPs May

189.58

172.40

166.55

158.01

July

56.93

216.20

197.79

29.55

September

55.02

474.19

70.61

74.89

November

64.89

351.21

98.04

137.23

January

162.58

97.25

131.25

777.15

March

300.23

73.12

98.63

39.69

ΣDDTs May

0.30

July

1.50

8,29

33.31

7.74

9.92

12.11

3.90

September

7.71

6.20

10.12

7.88

November

23.52

63.08

7.82

37.36

January

13.36

12.59

30.02

110.46

10.92

5.60

20.04

20.15 62.30

March

ΣCyclodienes May

85.51

97.98

94.73

July

8.93

183.91

32.30

2.74

16.02

356.51

22.74

19.85

September November

19.79

65.12

25.10

65.12

January

67.61

52.24

35.53

614.23

March

41.34

bdl

40.37

6.38

bdl below detection limit

accounted for 47.52 % of the total variance, while PCB28 and PCB-52 were explained by the Component 2, which accounted for 19.95 % of the total variance. This suggests that the tri- and tetra- chlorinated compounds are tightly bound to the Factor 2 while others (penta-, hexa- and hepta- chlorinated compounds) are bound to the Factor 1 (Fig. 4). All of the PCBs showed good

correlations with the respective extracted component (Table 3). The lower chlorinated compounds (tri- and tetra- PCBs) predominated over higher chlorinated compounds with 74 % (Fig. 5) of the total PCB concentration in the pellets. Organochlorine pesticides The concentrations of ΣOCPs ranged from 12.89 to 1446.41 ng g−1 with a median of 104.90 ng g−1. γHCH recorded the highest concentration in beach plastic pellets in Mumbai coast with a mean of 33.88 ± 5.97 ng g−1 followed by heptachlor and α-HCH. The β-HCH recorded (Fig. 6) the lowest concentration (2.4±0.61 ng g−1). The 4, 4'-DDT and γ-HCH were observed as the most dominant OCPs among the 16 OCPs studied with 80.56 % frequency of detection. However, OCPs such as 4, 4'-DDE, δ-HCH, α-HCH and 4, 4'-DDD were found to have more than 50 % frequency of detection. Endosulfan sulfate and endrin reported the lowest frequency of detection among the 72 samples. The average ratio of the sum of DDE and DDD to DDT was 1.56 (n=72). As the ratio exceeds one, the degradation products predominated over the parent DDT. The mean concentrations of DDT, HCH and cylodiene compounds were 21.90±3.06, 72.86± 26.37 and 104.03±22.39 ng g−1, respectively (Table 4). The highest median concentration of ΣOCP (474.19 ng g −1 ) was found in Versova beach in September followed by Dadar beach (777.15 ng g−1) in January. The highest median HCH concentration of 223.01 ng g−1 was observed in Versova beach in September, while the highest median of DDT concentration (110.46 ng g−1) was in Dadar beach in January. The highest median concentration of cyclodiene (614.23 ng g −1 ) was in Dadar beach in January (Table 1). Two-way ANOVA revealed that the ΣOCPs and ΣHCHs did not vary significantly among the months and beaches. However, the interaction of months and beaches was observed for ΣOCPs. Significant variation was observed for ΣDDTs among the months, beaches and their interactions (Table 2). The significantly higher concentration of ΣDDT (46.55±12.23 ng g−1) was found in January than in the other months while November was intermediate (Fig. 7). The ΣDDTs in pellets collected from Dadar beach was at par with that of Juhu beach and was significantly higher than that of the other beaches with an increasing trend from north to

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Table 2 Results of two-way ANOVA for distribution of organochlorines in plastic pellets Source

ΣPCBs

df

ΣOCPs

MS

F

ΣHCHs

MS

F

MS

ΣDDTs

ΣCyclodienes

F

MS

F

MS

F

Month

5

12957

7.4*

26630

0.6

6113

0.6

2602

9.0*

37077

1.4

Beach

3

1124

0.6

81652

1.9

15755

1.6

1695

5.8*

37099

1.5

Month*Beach

15

3212

1.8

146477

3.4*

15539

1.6

1050

3.6*

75846

3.2

Error

48

1761

*

43570

9685

290

23934

Significant difference at p=0.05

south along the coast (Table 4). The HCH isomers and cyclodiene compounds accounted for 42 and 36 % of total OCPs, respectively (Fig. 8).

Discussion Contamination of polychlorinated biphenyls in plastic pellets A large variability of ΣPCB concentration among the 72 analytical pools was found (below detection limit to 210.34 ng g−1) in pellets collected from Mumbai beaches as the individual pellets might have different residence times in sea water and different pathways (i.e., exposure to different concentrations of PCBs). This variability has been discussed by Endo et al. (2005). Most of the workers have given attention to evaluate the spatial variation on POPs in plastic pellets, particularly on a large scale. However, Ryan et al. (2012) analysed the pellets from 1984 to 2008 at three South African beaches and reported the long-term decrease of POPs. The concentrations of hydrophobic contaminants 120 c

ΣPCBs (ng g-1)

100 bc

80 60

ab ab

40 a

a

20 0 May

Jul

Sep

Nov

Jan

Mar

Fig. 3 Bimonthly variation of ΣPCBs in plastic pellets (n=12); different letters within each month represent significant difference at p=0.05

adsorbed on to plastics have shown distinct spatial variations reflecting global pollution patterns (Ogata et al. 2009; Teuten et al. 2009). This indicates that the pellets can be used to study the variability in regional scale rather than small scale with the different levels of pollution. However, the geomorphology of the area (i.e., bays, estuaries and semi-enclosed seas) with different point-sources of pollutants may provide the small-scale spatial variability of POPs. Though plastic pellets were not separated to polypropylene (PP) and polyethylene (PE) in this study, higher concentrations of PCBs have been reported in PE pellets than PP pellets (Endo et al. 2005; Teuten et al. 2009). Ogata et al. (2009) plotted the median concentrations of Σ13PCBs of five pools on a global map and indicated 43 ng g−1 Σ13PCBs for Mumbai. It is in agreement with the present study as values are in the same order of magnitude. The median PCB concentration of this study can be more representative as 72 pools were analysed for four beaches. Further, median PCB concentration was higher than the global background pollution level (<10 ng g−1) (Heskett et al. 2012) which is typical of many developing country samples (Ogata et al. 2009). The recycling of electronic waste and poor management of ship-breaking activities are suggested as potential sources of PCBs in India (Zhang et al. 2008). The largest ship-scrapping yard in the world is located in Alang (Gujarat) in the west coast of India. PCB-209 is rare in environmental samples (McFarland and Clarke 1989; Rajendran et al. 2005), particularly in the developing countries. Thus, it was not detected in any of the samples. PCB-28 was the most prevalent and highly concentrated PCB congener among the seven PCBs studied. It may be the most commonly used PCB congener in industrial application in India. However, conclusion cannot be made by studying just seven PCBs. Rios et al. (2007) found PCBs 52, 101, 118 and

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Fig. 4 Component plot in rotated space for PCBs in plastic pellets

170 as the most common PCBs among the 36 PCBs studied. Their study is closely consistent with the present study with the prevalence of PCB-52 which is the second most dominant one followed by PCB-101. In contrast to the present study, PCB-138 has been detected at the highest concentrations in the PCB profile of the beaches in Greece (Karapanagioti et al. 2011). However, different workers have used PCB mixtures with different congener profiles. Thus, a comparison might yield wrong interpretations. Frias et al. (2010) reported the four-time higher concentration of PCB congener 26 than the other congeners. Temporal variation of ΣPCB was significant with an increasing trend during the monsoon period. The chemical contaminants might have been flushed out by high

Table 3 Significant factor loadings (italic marked) for PCBs in plastic pellets

freshwater discharge to the coastal environment including organic contaminants during monsoon resulting in significantly high PCB concentration in November just after the monsoon. The study sites selected for the present investigation are within 50 km along the coastline. Thus, spatial variation cannot be significant for most of the POP groups due to mixing. Endo et al. (2005) suggested that considering the mobility of floating resin pellets, concentrations in pellets should be taken as an estimate for a relatively large area rather than for the point where the pellets were sampled. Further, the recent activities linked to the major developments in Mumbai also may explain the local increases in PCBs through the re-suspension of sediment during construction and dredging. The most significant input for POPs is atmospheric deposition. During monsoon, the prevailing winds may pick up chemical molecules, dust and other particles contaminated with pesticides and industrial chemicals,

Rotated component matrix PCBs

1 PCB-28

5-7 chlorinated PCBs 26%

Component 2 0.072

0.630

PCB-52

0.034

0.855

PCB-101

0.818

0.025

PCB-138

0.904

0.013

PCB-153

0.909

0.019

PCB-180

0.730

0.260

Variance (%)

47.52

Total variance (%)

67.47

19.95

3-4 chlorinated PCBs 74%

Fig. 5 Overall, relative compositions of lower chlorinated (triand tetra-) and higher chlorinated (penta-, hexa- and hepta-) compounds in plastic pellets (n=72)

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50 45 40 35 30 25 20 15 10 5 0

400 TOCPs

Concentraon (ng g-1)

Concentraon (ng g-1)

Environ Monit Assess (2015) 187:469

350

THCHs

300

TDDTs TCyclodines

250 200 150 100

c

50

a

a

a May

Fig. 6 Mean concentration (±SE) of OCPs in plastic pellets (n=72)

and carry these out to the sea. Here, a number of processes such as dry and wet deposition, air-sea gas exchange and aerosol will cause them to settle on the sea surface. Odabasi et al. (2008) showed that PCB input is dominated by dry deposition in the Izmir Bay, Aegean Sea. The atmospheric input of PCBs accounts for more than 90 % of the total in the western Mediterranean (Tolosa et al. 1997). Precipitation is a key factor in contaminant transport. Rain and snow scavenge aerosols and gases from the atmosphere and deposit them at the Earth’s surface (MacDonald et al. 2000). Storm water, treated sewage water and industrial waste all contribute POPs when discharged directly into the ocean. The effluents, largely untreated, of many industries located in Mumbai might be discharged into the marine environment through point-sources (Zingde 1999). From many disparate sources, POPs tend to settle and concentrate into the surface skin of the sea known as the SML. Hirai et al. (2011) found high PCB concentrations in plastic fragments in urban beaches than those in remote beaches and the open ocean. The pellets collected from Tokyo Bay and Osaka Bay, which are surrounded by the

Jul

Sep

a

b

0 Nov

Jan

Mar

Fig. 7 Bimonthly variation of ΣOCPs, ΣHCHs, ΣDDTs and ΣCyclodienes in plastic pellets (n=12; the values with different letters vary significantly at p=0.05 among months in terms of ΣDDTs)

most industrialized areas in Japan, have been found to harbour high concentrations of PCBs (Endo et al. 2005). Karapanagioti et al. (2011) found high concentrations of PCBs in very enclosed seas of Saronikos and Patrasgulfs in Greece. Maharashtra is the most industrialised state of India with 23.66 % of the total value added to the raw materials through manufacture in the factory sector followed by Gujarat (12.64 %). Further, the oldest and largest dumping ground is located in Gorai, Mumbai. Mumbai situated on the coast generates 7500 million tonnes of solid waste including electronic equipment, computers, servers, mobile phones, biomedical waste, hazardous waste, and construction and demolition debris per day, and dumps these in the nearby creeks (Sahu 2007). There are about 40,000 small- and large- scale industrial units in the city, 523 of them in the chemicals sector, 531 in textiles and nine deal with pesticides. The estimated quantity of industrial effluent is about 240 million litres per day in Greater Mumbai (Anon 2009). Also, there are no known natural sources of PCBs. Thus, the coastal environment might receive large quantities of

Table 4 Concentration of organochlorines (mean±SE) in plastic pellets from four beaches (n=18) Beach

Organochlorines ΣPCBs

ΣHCHs

ΣDDTs

ΣCyclodienes

ΣOCPs

Aksa

45.75±9.78

68.81±20.54

10.79±3.27a

85.43±34.21

165.04±49.36

Versova

83.71±20.91

113.95±41.45

18.60±5.11ab

149.18±47.57

281.73±79.59

Juhu

47.30±10.13

52.41±8.95

24.39±4.20bc

49.22±10.20

126.03±13.89

c

Dadar

63.37±12.61

50.23±12.67

33.82±9.22

132.23±66.89

197.27±30.21

Mean

54.92±6.27

71.35±12.32

21.90±3.06

104.02±22.39

197.27±30.21

Values within the column with different superscripts vary significantly (p<0.05)

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Contamination of organochlorine pesticides in plastic pellets

Cyclodines 36%

HCHs 42%

DDTs 22%

Fig. 8 Overall relative compositions of DDTs, HCHs and cyclodienes (n=72)

organic contaminants from industrial sources of Mumbai. PCBs have been used as coolants and lubricants in transformers, capacitors and other electrical equipment because they do not burn easily and are good insulators. The beaches where the study was carried out are in the highly urbanized area of the city. Thus, the high concentration of POPs, particularly PCBs, can be expected. In landfills, plastics are exposed to an extraction solvent in the form of acidic leachates with high ionic strength and neutral or alkaline leachates containing high-molecular weight organic compounds. Thus, landfill leachates can be an important source of POPs in India. The PCA revealed that the four PCBs of penta-, hexa- and hepta- chlorinated compounds which had high positive loadings of Component 1 might have mostly originated from identical sources such as industrial mixtures. The sources of tri- and tetra- chlorinated compounds, which are common and highly concentrated, might have a different source. Tri- and tetra- chlorinated congeners had greater relative abundance in all the beaches. This congener pattern is similar to those observed for plastic fragments (Hirai et al. 2011) and water samples (Sobek and Gustafsson 2004; Gioia et al. 2008) in the open ocean. PCBs are atmospherically transported and, therefore, volatile (lower chlorinated) congeners are selectively transported to the open ocean (Gioia et al. 2008). Thus, atmospheric transport could be the source of lower chlorinated congeners, particularly during the monsoon. Rios et al. (2007) also reported the predominance of lower-chlorinated congeners in the plastic fragment samples from the Central Pacific Gyre. The occurrence of mainly man-made OCs in regions far away from industrialised and densely populated areas indicates that atmospheric transport is an important route to disperse these compounds.

India is now the second largest manufacturer of pesticides in Asia after China and ranks twelfth globally. There has been a steady growth in the production of technical grade pesticides in India, from 5000 t in 1958 to 102,240 t in 1998 (Mathur 1999). This high usage and production may affect the concentration of OCPs in the coastal environment off Mumbai. Sixteen OCPs were evaluated in plastic pellets in the study. Though many workers evaluated POPs in plastics, they have only reported the HCHs and DDTs among OCPs. The present study also confirmed that cyclodiene is an important group among the OCPs. The most common OCPs were 4,4'-DDT and γ-HCH (lindane). Sarkar and Gupta (1987) reported the distribution of different OCs in coastal water as follows: γHCH >aldrin >4,4’-DDE > deildrin> 4,4’-DDT > 4,4’DDD. The mean concentrations of these compounds were found in the order γ-HCH>deildrin>aldrin> 4,4’-DDE>4,4’-DDT>4,4’-DDD for the plastic pellets collected from beaches as these compounds are believed to be adsorbed from sea water. India was by far the largest producer (6344×103 kg) and consumer (3188×103 kg) of DDT in 2007 (van den Berg 2008). Therefore, DDT concentration in soil, water and sediment can be high in India, particularly in Mumbai region, due to its huge population density. Thus, the reported mean ΣDDT concentration in this study was high compared to the median value reported by Ogata et al. (2009). However, the DDT reported for Chennai by Ogata et al. (2009) is higher than the values for Mumbai in this study. The ΣDDT concentration significantly varied among the months showing the highest value in January. Extensive quantities of DDT are used after the monsoon to control mosquitoes as also freshwater discharge to the coastal marine environment is high during this season, which might increase the DDT concentration in coastal waters off Mumbai and, in turn, in plastic pellets. Spatially, significantly high DDT concentration in pellets of Dadar indicates high concentration of DDT in Mahim Bay. The Mahim Creek which enters the Mahim Bay receives the overflow of Vihar and Powai lakes during monsoon via the Mithi River (85 m3 s−1 during August) and the system resembles an effluent drain affecting pollution in the bay. The Mithi River and the Mahim Creek are known to be highly polluted water

Environ Monit Assess (2015) 187:469

bodies receiving large volumes of sewage and industrial effluents and have been investigated in the past (Zingde and Desai 1981; Zingde and Sabnis 1994). Thane Creek, which receives waste water from the heavily industrialized Thane-Belapur belt, Chembur, Colaba and Thane, enters the coastal environment (Zingde and Govindan 2000) south of Dadar. Therefore, the coastal geomorphology, effluent discharge, current pattern and water exchange in the bay might have contributed largely to the high contamination by organic pollutants (i.e., OCPs) in pellets collected from Dadar. The long-shore currents and net sediment transport along the coast towards the south (Kumar et al. 2006), particularly during the southwest monsoon, might have resulted in the high pollution level in Dadar compared to the other study sites. Thus, γ-HCH was found at the highest concentration and was reported as one of the most dominant OCP compounds in plastic pellets. Ogata et al. (2009) reported that DDT concentrations in the tropical Asian countries are comparable to those in Japan and Europe. They observed that DDT has still been used in some locations in tropical Asian countries to kill mosquitoes (Nhan et al. 1998; van den Berg 2008) which potentially harbour malarial parasites. The lower concentration of DDT in the Aksa and Versova beaches than that of the other two beaches may be due to the low usage of DDT for mosquito control as the human population density is lower than that of Juhu and Dadar region. The predominance of degradation products (DDD and DDE) over DDT suggests the legacy pollution of DDT or fast degradation and biotransformation in the tropical environment. Among the degradation products, DDE was generally dominant over DDD. This is reasonable because the plastics float on the sea surface where conditions favour aerobic conversion of DDT to DDE. However, Ogata et al. (2009) reported that the predominance of DDT at Ocean Beach, San Francisco, could be due to washed-out DDT as run-off stored in soil and/or agricultural lands since the application of the compound is not a current practice in the USA. Hirai et al. (2011) also reported the legacy pollution of DDTs in some locations in Japan where degradation products of DDT are dominant. The median concentrations of ΣDDTs have ranged from 0.7 to 4.1 ng g−1 in remote beaches (Heskett et al. 2012). But they found the dominance of DDT over the degradation products and suggested current usage of DDT on the islands and/or spillage of stored DDT.

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High ΣDDT levels can be explained by the current application of DDT for malaria control in India. This could probably also be due to DDT being introduced into the environment as a pesticide that was applied over agriculture fields. The agricultural application was banned in most areas and now, it is mostly the environmental redistribution of legacy pollution that is occurring. The median concentration of ΣHCHs was high in the pellets of Mumbai beaches compared to most of the countries (Ogata et al. 2009). The ΣHCH concentration was higher than that of ΣDDT concentration which suggests that high quantities of HCHs are still used in India. Sarkar and Gupta (1987) and Rajendran et al. (2005) reported that HCH concentration is greater than that of DDT in sea water. However, many authors reported higher levels of DDTs than HCHs in pellets (Ogata et al. 2009; Karapanagioti et al. 2011). The coastal ocean off Mumbai might have mixed up the ΣOCPs and ΣHCHs by physical processes, and there may not be a significant difference among the months and beaches. Among the four isomers of HCHs, the γ isomer was predominant in the pellets in agreement with Heskett et al. (2012) in St. Helena beach, supporting lindane as the primary source of HCHs. The present study reports much higher concentrations of the two groups of OCPs compared to the background levels of DDTs (<4 ng g−1) and HCHs (<2 ng g−1) in pellets as reported by Heskett et al. (2012). The mean concentrations of heptachlor, EndosulfanI(α), dieldrin and aldrin were above 15 ng g−1 suggesting the high usage of these pesticides for agriculture in India, particularly in the western part.

Conclusions Based on the analysis of plastic pellet samples from Mumbai coast, the mean concentrations PCBs, HCHs, DDTs and cyclodienes indicate the pollution status of the coastal waters. Temporal variations of some OCs were related to the monsoonal impact. The study revealed that there is no significant difference among the studied beaches as they are located in a relatively small area. The study confirmed that the plastic pellets are a trap for various cyclodiene compounds in addition to PCB, HCH and DDT. Further, pellets can be used to study the temporal variability for a range of organic micropollutants.

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Acknowledgments This study was a part of the Ph. D. research of the first author. Thus, he acknowledges the Sri Lanka Council of Agricultural Research Policy and National Aquatic Resources Research Development Agency, Sri Lanka, for the financial and administrative arrangements to carry out the work at the Central Institute of Fisheries Education, Mumbai, India. The Director, CIFE, India, is greatly acknowledged for the facilities provided during the study.

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