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Microplastic presence in commercial marine sea salts: A baseline study along Tuticorin Coastal salt pan stations, Gulf of Mannar, South India
Marine Pollution Bulletin 150 (2020) 110675
Contents lists available at ScienceDirect
Marine Pollution Bulletin journal homepage: www.elsevier.com/locate/marpolbul
Baseline
Microplastic presence in commercial marine sea salts: A baseline study along Tuticorin Coastal salt pan stations, Gulf of Mannar, South India
T
S. Selvama, A. Manishaa,b, S. Venkatramananc,d,∗, S.Y. Chunge, C.R. Paramasivamf, C. Singarajag a
Department of Geology, V.O. Chidambaram College, Tuticorin, Tamil Nadu, India Affiliated to Manonmaniam Sundaranar University (Registration No: 18212232062029), Abishekapatti, Tirunelveli-12, Tamil Nadu, India c Department for Management of Science and Technology Development, Ton Duc Thang University, Ho Chi Minh City, Viet Nam d Faculty of Applied Sciences, Ton Duc Thang University, Ho Chi Minh City, Viet Nam e Department of Earth and Environmental Sciences, Pukyong National University, Nam-gu, Busan, South Korea f Department of Remote Sensing, Bharathidasan University, Tiruchirappalli, Tamil Nadu, India g Department of Geology, Presidency College, Chennai, Tamil Nadu, India b
ARTICLE INFO
ABSTRACT
Keywords: Microplastic Sea salts μ-FT-IR Tuticorin salt pans Gulf of mannar India
The present baseline research infers that the salts present in the sea may contain microplastics (MPs), as the seawater is contaminated due to a number of anthropogenic activities. Herein, 25 types of sea salt samples were collected from salt pans located in the Tuticorin coastal region. The MPs present in the samples were separated and identified by various methods such as handpicking, visual classification, and micro-Fourier transform infrared spectroscopy (μ-FT-IR) and atomic force microscopy (AFM). The MPs that measured less than 100 μm formed the major part of the salts, accounting to 60% of the MPs among the total pollutants. The MPs that were found in abundance in the sea salts were polypropylene, followed by polyethylene, nylon, and cellulose. This study was conducted in salt pan areas and demarcated the percentage of MPs present in sea salts. Table salt, which is a prime edible commodity, was found to be contaminated with MPs through polluted seawater, which poses a threat to public health.
Since the past two decades, humans have been disposing plastic waste in seas and rivers, consequently causing coastline, seabed, and surface water pollution. According to experts’ speculation, microplastics (MPs) are inevitably present everywhere in the environment and enter into the food chain through the salt that is used in our diet. The first peer-reviewed article on MP pollution in the Earth was published more than 47 years ago (Buchanan, 1971; Ainley et al., 1990). MPs are plastic pieces or fragments of size less than 5 mm that have been originated not only in oceanic environments but also in freshwater sediments. The common manufacturing process of sea salt is conducted in evaporation ponds, wherein saltwater is strenuously dried by exposure to wind and sunlight. The salt crystallizes from the concentrated thick brine; subsequently, these crystallized salts are further set in a settling pond settle through the accumulation under the control method. Before packing the salt in containers of various sizes for different uses and applications, properties enhanced and chemical substances involved for the separation of salts. Rock salt is the product of production, and it should further be refined on the basis of its purpose of use. (Aho et al., 1980; Soylak and Yilmaz, 2006). The World Health
∗
Organization (WHO, 2012) have recommended salt intake of 6 grams per day for adults. However, the daily salt intake is 8–11 grams per day in Europe and 9 grams per day in most countries worldwide (Ng and Obbard, 2006; Fendall et al., 2009; Mozaffarian et al.,. 2014; Zhao et al., 2014; Bouwmeester et al., 2015; Koelmans et al., 2015; Arunkumar et al., 2016; Veerasingam et al., 2016), but salt consumption in Turkey is 14.5–18.5 grams per day, which is appreciably higher than the worldwide and Europe averages (Erdem et al., 2010; Erkoyun et al., 2016). Table salt contains an abundance of contaminants, which is augmented by this top abundance of natural substances. A number of studies conducted worldwide have reported the abuse of MPs in Turkish seas (Aytan et al., 2016; Gundogdu and Cevik, 2017). Aytan et al. (2016) reported that the boilerplate MP content in November was 1.4 ± 1.2 × 103 particles/m−3 and that in February was 0.7 ± 0.5 × 103 particles/m−3 in the Black Sea coast of Turkey. Yang et al. (2015) observed that the amount of MPs found was 7–681 items/ kg in sediments due to the leaching of salts from Chinese bazaar. Table 1 presents the details of polymer types in the MPs found in sea salts worldwide.
Corresponding author. Department for Management of Science and Technology Development, Ton Duc Thang University, Ho Chi Minh City, Viet Nam. E-mail address: [email protected] (S. Venkatramanan).
https://doi.org/10.1016/j.marpolbul.2019.110675 Received 15 June 2019; Received in revised form 9 October 2019; Accepted 17 October 2019 Available online 24 October 2019 0025-326X/ © 2019 Elsevier Ltd. All rights reserved.
Marine Pollution Bulletin 150 (2020) 110675
S. Selvam, et al.
Table 1 Polymer type of microplastics compare to world sea salt. Plastic type
Table 2 Types, colours, sizes and polymer identification of plastic items.
Sea salt (%)
Polyethylene (PE) Polyethylene terephthlate (PET) Polyurethane (PU) Polypropylene (PP) Polymethyl-methacrylate (PMMA) Polyamide-6 (PA-6) Polyvinylchloride (PVC) polyester (PES) poly(1-butene) (PB) PE and PP copolymer (PE−PP) Polymerized, oxidized material(POM) Polyalkene (PAK) Polyacrylonitrile (PAN) Poly methyl acrylate (PMA) Ethylene vinyl acetate (EVA) Poly(vinyl acetate:ethylene) 3:1 Cellophane (CP) Cellulose (CL) Nylon (NY) Unidentified particles
China (Sedat Gündoğdu, 2018)
Spain (Maria et al., 2017)
Present Study (Tuticorin, India)
12.5% 18.8%
3.3% 81.3%
41.5% —
25.0% 18.8% —
6.7% —
— 22.7% —
12.5% 12.5% 13.6 9.1 0
— — — — —
— — — — —
2.3
—
—
0 2.3 2.3 — 2.3
— — — — —
— — — — —
18.2 — — 3.8
— — — 1.2
— 11.2% 8.7% 11.2%
Identification Category
Capricious
Percentage
Types of plastic
Fragment Fibre Sheet White Blue Green Colourless Small microplastic (< 2 mm) Large microplastic (2–5 mm) Mesoplastic (> 5 mm) Polyethylene Polypropylene Cellulose Nylon Unidentified Particles
55% 42% 3% 45% 17% 13% 25% 100% 0 0 41.5% 22.7% 11.2% 8.7% 11.2%
Colours of plastic
Sizes of plastic Polymer identification of plastic
In India, nearly 24 million tonnes of raw salt are produced in a year, out of which 20% is exported mainly to China, Japan, Indonesia, and the United States (Reddy et al., 2006; Krishnakumar et al., 2017). The major salt-manufacturing states in India are Gujarat, Tamil Nadu, Rajasthan, Maharashtra, Andhra Pradesh, Orissa, and West Bengal according to their production scale. In India, Tuticorin (Tamil Nadu) is the second leading producer of salt with an average estimated production of 25 lakh tonnes of salt every year (Sedat Gundogdu, 2018; Maria et al., 2017). Of the total area, 25,000 acres of land are covered under salt pans, and small-scale manufacturing is carried out on 10,000 acres of land. Thus far, there are no detailed studies conducted in India
Fig. 1. Location map of the study area along with sampling points at Tuticorin, Gulf of Mannar, South India.
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Marine Pollution Bulletin 150 (2020) 110675
S. Selvam, et al.
Fig. 2. Microplastic polymers and micro-Fourier transform infrared spectroscopy peaks in salt pans of Tuticorin.
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Marine Pollution Bulletin 150 (2020) 110675
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on the impact of MPs present in sea salt on human health. The main objective of the present study is to highlight the MP contamination in sea salts currently produced in the Tuticorin salt pans, Tamil Nadu, India. In India, sea salts that are produced in chief salt-manufacturing centers in Tuticorin are exported to China, Japan, and across regions in India. Herein, 25 salt samples were collected from different salt pans that were selected on the basis of their quality in August 2018. Fig. 1 shows the study area containing the sampling sites. Each sample was collected to a weight of 1.5 kg in a standard packet. In the Tuticorin region, the salt manufacturing process involves pumping of seawater into evaporation ponds of many levels, which are extended to several acres of land. This seawater is left to crystallize under controlled methods to obtain fine-quality sodium chloride. Further, the density of the brine is observed with utmost care to maintain the salinity and transparency of the salt. Exposure of the seawater to wind without moisture and strong sunlight quickens the formation of salt crystals by increasing the evaporation rate. Afterwards, the salt undergoes different size of manufacturing processes before being packed in containers on the basis of the purpose and value-added usage. For instance, rock salt is one such product from salt pan that is easily contaminated by MPs through the aerial route as well as through the resource material itself. MP extraction was done using the method explained in many studies (Cole et al., 2013; Dubaish and Liebezeit, 2013; Harrison et al., 2014; Yang et al., 2015; Duis and Coors, 2016; Karami et al., 2017a). A portion of the sample, 250 g of salt collected from each amalgamation, was taken in 1-L jars, and 100 ml of H2O2 (approximately 30%) was added to the sample to oxidize the amoebic materials if present. Then, 1-L jars were aligned into an incubator at a temperature of 65 °C and 85 revolutions per minute (rpm) acceleration for 24 h. Subsequently, these samples were stored at specific temperatures for 48 h. After that, add 800 ml salty solution poured into each bottle to dissolves alkali. These bottles were stored for 24 h at a specified temperature. Once, the clearing action was completed, the afloat present was clarified, it and formed a 47 mm 0.2 μm artificial nitrate film to add 10–14 ml of 5 M NaI and was placed in antiseptic Petri dishes (density = 1.6 g/ml) as mentioned in Karami et al. (2017b). The sample was centrifuged to ensure the complete separation of MPs. The particles that settled at the bottom after centrifugation were transferred into Petri dishes for further examination under a microscope. A binocular stereo zoom microscope was used to assess the type
and quantity of MPs in a quadrant counted through visual classification. Random selection of leftover particles was done to confirm the presence of MPs using a micro-Fourier transform infrared spectrometer (μ-FT-IR) (Thermo Fisher Scientific; NICOLAT iS5 KBr window iD1 model). The photographs of the MPs were displayed in abstracted plates. The MP type as a pie chart was generated using Microsoft Excel, version 2012. The locations for sample collection were chosen on the basis of the accessibility of nearby salt pans along the coastal environment. The type of various MPs particles were analyzed by μ-FT-IR. However, μ-FTIR is not the only method that defines the acceptable level of MPs. Various types of MPs were identified, including nylon (NY), cellulose (CL), polyethylene (PE), and polypropylene (PP), and some MPs or nonplastic particles were unidentified (Fig. 2). An elevated level of MP waste was found in Tuticorin city sea salt sample (No. 16–21) in this study. Sea salts crystallized in the Tuticorin city sample contain a high level of MPs as compared to that in other area salts, which is an expected outcome (Table 2). Because of the lack of previous reports on MPs as a contaminant in Tuticorin city, there is no possibility of comparison. The results show the low level of MPs particles through the intake of the salts, which warrants insignificant health impacts. Auta et al. (2017) and Law and Thompson (2014) have stated that rivers, overflow from drainage systems, wastewater treatment plants, currents, and tidal waves form the most indispensable ground for MP contamination in marine bodies. Perhaps, these MPs are a meticulous hazard to organisms because of their miniature size and absorption of persistent organic contaminants. These MPs, containing adsorbed metals and chemicals, are eventually ingested by organisms through seafood. The μ-FT-IR results of the characterization of MPs are shown in Fig. 2. The 98% spectrum was identified based on the μ-FT-IR results. The contaminated sea salts were found to have common microplastics such as polyethylene, polypropylene, cellulose, and nylon (Table 1). Domestic waste materials were found to be the main source of polyethylene and polypropylene contaminants. Every day, large volumes of polyethylene covers in the form of tea covers, milk covers, cooking covers, shop covers, medicine covers, and bust plastic materials are left abandoned due to lack of proper garbage disposal (Fig. 3). Polyethylene is the most common element found in packaging material and floaters that are used during fishing practices. Recently, MPs were also recorded from Arctic sea ice, fish, sea birds and sea salts in highly contaminated surface waters. Until now, only a limited number of global surveys have been conducted on the quantity and distribution of MPs in marine sea
Fig. 3. Microplastic polymers deposited along the Gulf of Mannar coast through buckle channels.
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Fig. 4. Pie chart showing the distribution of microplastic polymers, expressed in percentage.
salts (Soylak and Yilmaz, 2006; Van Cauwenberghe et al., 2013; Jambeck et al., 2015; Mason et al., 2017; Schirinzi et al., 2017). Nylon and cellulose are also observed in sea salts, as fiber, net webbing, and textiles. nylon chiefly accounts as a pollutant in the coast through the use of fishing nets and nylon ropes. Moreover, Cellulose sponge clothes waste was derived from textile industries around the salt pan stations. The much higher MPs contents in sea salts were identified in the Tuticorin city area, as the people in that region dumped plastic waste into marine bodies through the buckle channel (Fig. 3). The type of MPs present in representative sampling sites is shown in Fig. 4 (Patters and Bratton, 2016). Disintegration definitely affects MP features and differs on account of the accustomed ecology system. Hence, the present study lays concrete abasement for presence of plastics in freshwater environments, where water turbulence, wind velocity, concrete chafe, and freeze-thaw cycles play a basic role in the abrasion of MPs (Duis and Coors, 2016). Patterns of abrasion, such as pits, fractures, flakes, and adhering particles, were empiric in the AFM images of the MPs advised actuality (Fig. 5). Hence, it is axiomatic that MPs in Tuticorin accomplished abrasion at various levels. In addition to the antecedent, the circadian acclimated artificial items are sources of MPs. Accordingly, Fig. 5 clearly shows the AFM images. The present study suggested that
accumulation rates of MPs widely affected by urban activities, shore and coastal uses, wind and ocean currents. Seawater contamination refers to the presence of abundant contaminants that associate with sea salts, including plasticizers such as benzyl butyl phthalate and 2-ethylhexyl. Plastic usage is the fundamental source for these contaminants. Nevertheless, plastics adsorbs effluents from the seawater and intrude into the sea products. Consequently, abyssal MPs in sea salts might pose a threat to human health through food consumption. In conclusion, it is highly recommended to forbid and control MP abuse in sea salts, particularly in Tuticorin, Tamil Nadu, in India. The sea salts produced from the seawater columns of salt pans of the study area are intended to possess MPs, and this is affirmed through this research. This research would serve as the basis for reporting and alerting the society about the growing MP contamination in sea salts. Declaration of competing interest The authors declare that there is no conflict of interests regarding the publication of this paper.
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Fig. 5. AFM image of microplastics in sea salt from the Tuticorin region showing four types of plastics on the plastic surface.
S. Selvam, et al.
Marine Pollution Bulletin 150 (2020) 110675
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Marine Pollution Bulletin 150 (2020) 110675
S. Selvam, et al.
Acknowledgments
Harrison, J.P., Schratzberger, M., Sapp, M., Osborn, M.A., 2014. Rapid bacterial colonization of low-density polyethylene microplastics in coastal sediment microcosms. BMC Microbiol. 14, 232–247. Jambeck, J.R., Geyer, R., Wilcox, C., Siegler, T.R., Perryman, M., Andrady, A., Narayan, R., Law, K.L., 2015. Plastic waste inputs from land into the ocean. Science 347, 768–771. Karami, A., Golieskardi, A., Choo, C.K., Larat, V., Galloway, T.S., Salamatinia, B., 2017a. The presence of microplastics in commercial salts from different countries. Sci. Rep. 7 (46173), 1–9. Karami, A., Golieskardi, A., Choo, C.K., Romano, N., Ho, Y.B., Salamatinia, B., 2017b. Ahigh-performance protocol for extraction of microplastics in fish. Sci. Total Environ. 578, 485–494. Krishnakumar, S., Ramasamy, S., Simon Peter, T., Godson, Prince S., Chandrasekar, N., Magesh, N.S., 2017. Geospatial risk assessment and trace element concentration inreef associated sediments, northern part of Gulf of Mannar Biosphere Reserve, Southeast coast of India. Mar. Pollut. Bull. 125 (1–2), 522–529. Koelmans, A.A., Besseling, E., Shim, W.J., 2015. Nanoplastics in the aquatic environment. Critical review. In: Bergmann, M., Gutov, L., Klages, M. (Eds.), Marine Anthropogenic Litter. Springer, Berlin, pp. 325–343. Law, K.L., Thompson, R.C., 2014. Microplastic in the seas. Science 345, 144–145. Mason, S., Kammin, L., Eriksen, M., Aleid, G., Box, C., Williamson, N., 2017. Pelagic plastic pollution within the surface waters of Lake Michigan, USA. J. Gt. Lakes Res. 753–759. Iñiguez, Maria E., Conesa, Juan A., Andres, F., 2017. Microplastics in Spanish table. Salt Scientific Reports 7, 8620. https://doi.org/10.1038/s41598-017-09128-x. Mozaffarian, D., Fahimi, S., Singh, G.M., Micha, R., Khatibzadeh, S., Engell, R.E., Lim, S., Danaei, G., Ezzati, M., Powles, J., 2014. Global sodium consumption and death from cardiovascular causes. N. Engl. J. Med. 371, 624–634. Ng, K.L., Obbard, J.P., 2006. Prevalence of microplastics in Singapore's coastal marine environment. Mar. Pollut. Bull. 52, 761–767. Patters, C.A., Bratton, S.P., 2016. Urbanization is a major influence on microplastic ingestion by sunfish in the BrazosRiver Basin, Central Texas, USA. Environ. Pollut. 210, 380–387. Reddy, M.S., Basha, S., Adimurthy, S., Ramachandraiah, G., 2006. Description of the small plastics fragments in marine sediments along the Alang-Sosiya ship-breaking yard, India. Estuar. Coast Shelf Sci. 68, 656–660. Schirinzi, G.F., Perez-Pomeda, I., Sanchis, J., Rossini, C., Farre, M., Barcelo, D., 2017. Cytotoxic effects of commonly used nanomaterials and microplastics on cerebral and epithelial cells. Environ. Res. 67, 579–587. Sedat, Gundogdu, 2018. Contamination of table salts from Turkey withmicroplastics. Food Addit. Contam. A. https://doi.org/10.1080/19440049.2018.1447694. Soylak, M., Yilmaz, S., 2006. Heavy metal levels in sediment samples from Lake Palas, Kayseri-Turkey. Fresenius Environ. Bull. 15, 340–344. Van Cauwenberghe, L., Vanreusel, A., Mees, J., Janssen, C.R., 2013. Microplastic pollution in deep-sea sediments. Environ. Pollut. 182, 495–499. Veerasingam, S., Mugilarasan, M., Venkatachalapathy, R., Vethamony, P., 2016. Influence of 2015 flood on the distribution and occurrence of microplastic pellets along the Chennai coast, India. Mar. Pollut. Bull. 109, 196–204. World Health Organization (WHO), 2012. Guidelines for Drinking Water Quality Recommendation. pp. 1–6 Geneva. Yang, D.Q., Shi, H.H., Li, L., Li, J.N., Jabeen, K., Kolandhasamy, P., 2015. Microplastic pollution in table salts from China. Environ. Sci. Technol. 49, 13622–13627. Zhao, S., Zhu, L., Wang, T., Li, D., 2014. Suspended microplastics in the surface water of the Yangtze Estuary System, China: first observations on occurrence, distribution. Mar. Pollut. Bull. 86, 562–568.
The first author Dr. S. Selvam gratefully acknowledge the financial support of Department of Science and Technology – SERB- ECR (Ref. No. F.ECR/2018/001749). The authors are also grateful to Shri A.P.C.V. Chockalingam, Secretary, and Dr. C.Veerabahu, Principal, V.O.C College, Tuticorin, for their support to carry out the study. We would like to acknowledge the invaluable support of the reviewers and editor whose comments helped to improve the quality of the manuscript. References Ainley, D.G., Spear, L.B., Ribic, C.A., 1990. The incidence of plastic in the diets of pelagic seabirds in the eastern equatorial Pacific region. In: Shomura, R.S., Codfrey, M.L. (Eds.), Proceedings of the Second International Conference on Marine Debris. US Department of Commerce, Honolulu, pp. 653. Aho, K., Harmsen, P., Hatano, S., Marquardsen, J., Smirnov, V.E., Strasser, T., 1980. Cerebrovascular disease in the community, results of a WHO collaborative study. Bull. World Health Organ. 58 (1), 113–130. Arunkumar, A., Sivakumar, R., Sai Rutwik Reddy, Y., Bhagya Raja, M.V., Nishanth, T., Revanth, V., 2016. Preliminary study on marine debris pollution along Marina beach, Chennai, India. Reg. Stud. Mar. Sci. 5, 35–40. Auta, H.S., Emenike, C.U., Fauziah, S.H., 2017. Distribution and importance of microplastics in the marine environment: a review of the sources, fate, effects, and potential solutions. Environ. Int. 102, 165–176. Aytan, U., Valente, A., Senturk, Y., Usta, R., Esensoy Sahin, F.B., Mazlum, R.E., Agirbas, E., 2016. First evaluation of neustonic microplastics in Black Sea waters. Mar. Environ. Res. 119, 22–30. Buchanan, J.B., 1971. Pollution by synthetic fibres. Mar. Pollut. Bull. 23, 88–99. Bouwmeester, H., Hollman, P.C., Peters, R.J., 2015. Potential health impact of environmentally released micro-and nanoplastics in the human food production chain: experiences from nanotoxicology. ES T (Environ. Sci. Technol.) 49, 8932–8947. Cole, M., Lindeque, P., Fileman, E., Halsband, C., Goodhead, R., Moger, J., Galloway, T.S., 2013. Microplastic ingestion by zooplankton. Environ. Sci. Technol. 47, 6646–6655. Dubaish, F., Liebezeit, G., 2013. Suspended microplastics and black carbon particles in the Jade system, southern North Sea. Water Air Soil Pollut. 224, 1352. Duis, K., Coors, A., 2016. Microplastics in the aquatic and terrestrial environment: sources (with a specific focus on personal care products), fate and effects. Environ. Sci. Eur. 28 (2), 1–25. Erdem, Y., Arici, M., Altun, B., Turgan, C., Sindel, S., Erbay, B., Derici, U., Karatan, O., Hasanoglu, E., Caglar, S., 2010. The relationship between hypertension and salt intake in Turkish population: SALTURK study. Blood Press. 19, 313–318. Erkoyun, E., Sozmen, K., Bennett, K., Unal, B., Boshuizen, H.C., 2016. Predicting the health impact of lowering salt consumption in Turkey using the DYNAMO health impact assessment tool. Public Health 140, 228–234. Fendall, L.S., Sewell, M.A., 2009. Contributing to marine pollution by washing your face: microplastics in facial cleansers. Mar. Pollut. Bull. 58, 1225–1228. Gündoğdu, S., Çevik, C., 2017. Micro-and mesoplastics in northeast levantine coast of Turkey: the preliminary results from surface samples. Mar. Pollut. Bull. 118, 341–347.
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Contents lists available at ScienceDirect
Marine Pollution Bulletin journal homepage: www.elsevier.com/locate/marpolbul
Baseline
Microplastic presence in commercial marine sea salts: A baseline study along Tuticorin Coastal salt pan stations, Gulf of Mannar, South India
T
S. Selvama, A. Manishaa,b, S. Venkatramananc,d,∗, S.Y. Chunge, C.R. Paramasivamf, C. Singarajag a
Department of Geology, V.O. Chidambaram College, Tuticorin, Tamil Nadu, India Affiliated to Manonmaniam Sundaranar University (Registration No: 18212232062029), Abishekapatti, Tirunelveli-12, Tamil Nadu, India c Department for Management of Science and Technology Development, Ton Duc Thang University, Ho Chi Minh City, Viet Nam d Faculty of Applied Sciences, Ton Duc Thang University, Ho Chi Minh City, Viet Nam e Department of Earth and Environmental Sciences, Pukyong National University, Nam-gu, Busan, South Korea f Department of Remote Sensing, Bharathidasan University, Tiruchirappalli, Tamil Nadu, India g Department of Geology, Presidency College, Chennai, Tamil Nadu, India b
ARTICLE INFO
ABSTRACT
Keywords: Microplastic Sea salts μ-FT-IR Tuticorin salt pans Gulf of mannar India
The present baseline research infers that the salts present in the sea may contain microplastics (MPs), as the seawater is contaminated due to a number of anthropogenic activities. Herein, 25 types of sea salt samples were collected from salt pans located in the Tuticorin coastal region. The MPs present in the samples were separated and identified by various methods such as handpicking, visual classification, and micro-Fourier transform infrared spectroscopy (μ-FT-IR) and atomic force microscopy (AFM). The MPs that measured less than 100 μm formed the major part of the salts, accounting to 60% of the MPs among the total pollutants. The MPs that were found in abundance in the sea salts were polypropylene, followed by polyethylene, nylon, and cellulose. This study was conducted in salt pan areas and demarcated the percentage of MPs present in sea salts. Table salt, which is a prime edible commodity, was found to be contaminated with MPs through polluted seawater, which poses a threat to public health.
Since the past two decades, humans have been disposing plastic waste in seas and rivers, consequently causing coastline, seabed, and surface water pollution. According to experts’ speculation, microplastics (MPs) are inevitably present everywhere in the environment and enter into the food chain through the salt that is used in our diet. The first peer-reviewed article on MP pollution in the Earth was published more than 47 years ago (Buchanan, 1971; Ainley et al., 1990). MPs are plastic pieces or fragments of size less than 5 mm that have been originated not only in oceanic environments but also in freshwater sediments. The common manufacturing process of sea salt is conducted in evaporation ponds, wherein saltwater is strenuously dried by exposure to wind and sunlight. The salt crystallizes from the concentrated thick brine; subsequently, these crystallized salts are further set in a settling pond settle through the accumulation under the control method. Before packing the salt in containers of various sizes for different uses and applications, properties enhanced and chemical substances involved for the separation of salts. Rock salt is the product of production, and it should further be refined on the basis of its purpose of use. (Aho et al., 1980; Soylak and Yilmaz, 2006). The World Health
∗
Organization (WHO, 2012) have recommended salt intake of 6 grams per day for adults. However, the daily salt intake is 8–11 grams per day in Europe and 9 grams per day in most countries worldwide (Ng and Obbard, 2006; Fendall et al., 2009; Mozaffarian et al.,. 2014; Zhao et al., 2014; Bouwmeester et al., 2015; Koelmans et al., 2015; Arunkumar et al., 2016; Veerasingam et al., 2016), but salt consumption in Turkey is 14.5–18.5 grams per day, which is appreciably higher than the worldwide and Europe averages (Erdem et al., 2010; Erkoyun et al., 2016). Table salt contains an abundance of contaminants, which is augmented by this top abundance of natural substances. A number of studies conducted worldwide have reported the abuse of MPs in Turkish seas (Aytan et al., 2016; Gundogdu and Cevik, 2017). Aytan et al. (2016) reported that the boilerplate MP content in November was 1.4 ± 1.2 × 103 particles/m−3 and that in February was 0.7 ± 0.5 × 103 particles/m−3 in the Black Sea coast of Turkey. Yang et al. (2015) observed that the amount of MPs found was 7–681 items/ kg in sediments due to the leaching of salts from Chinese bazaar. Table 1 presents the details of polymer types in the MPs found in sea salts worldwide.
Corresponding author. Department for Management of Science and Technology Development, Ton Duc Thang University, Ho Chi Minh City, Viet Nam. E-mail address: [email protected] (S. Venkatramanan).
https://doi.org/10.1016/j.marpolbul.2019.110675 Received 15 June 2019; Received in revised form 9 October 2019; Accepted 17 October 2019 Available online 24 October 2019 0025-326X/ © 2019 Elsevier Ltd. All rights reserved.
Marine Pollution Bulletin 150 (2020) 110675
S. Selvam, et al.
Table 1 Polymer type of microplastics compare to world sea salt. Plastic type
Table 2 Types, colours, sizes and polymer identification of plastic items.
Sea salt (%)
Polyethylene (PE) Polyethylene terephthlate (PET) Polyurethane (PU) Polypropylene (PP) Polymethyl-methacrylate (PMMA) Polyamide-6 (PA-6) Polyvinylchloride (PVC) polyester (PES) poly(1-butene) (PB) PE and PP copolymer (PE−PP) Polymerized, oxidized material(POM) Polyalkene (PAK) Polyacrylonitrile (PAN) Poly methyl acrylate (PMA) Ethylene vinyl acetate (EVA) Poly(vinyl acetate:ethylene) 3:1 Cellophane (CP) Cellulose (CL) Nylon (NY) Unidentified particles
China (Sedat Gündoğdu, 2018)
Spain (Maria et al., 2017)
Present Study (Tuticorin, India)
12.5% 18.8%
3.3% 81.3%
41.5% —
25.0% 18.8% —
6.7% —
— 22.7% —
12.5% 12.5% 13.6 9.1 0
— — — — —
— — — — —
2.3
—
—
0 2.3 2.3 — 2.3
— — — — —
— — — — —
18.2 — — 3.8
— — — 1.2
— 11.2% 8.7% 11.2%
Identification Category
Capricious
Percentage
Types of plastic
Fragment Fibre Sheet White Blue Green Colourless Small microplastic (< 2 mm) Large microplastic (2–5 mm) Mesoplastic (> 5 mm) Polyethylene Polypropylene Cellulose Nylon Unidentified Particles
55% 42% 3% 45% 17% 13% 25% 100% 0 0 41.5% 22.7% 11.2% 8.7% 11.2%
Colours of plastic
Sizes of plastic Polymer identification of plastic
In India, nearly 24 million tonnes of raw salt are produced in a year, out of which 20% is exported mainly to China, Japan, Indonesia, and the United States (Reddy et al., 2006; Krishnakumar et al., 2017). The major salt-manufacturing states in India are Gujarat, Tamil Nadu, Rajasthan, Maharashtra, Andhra Pradesh, Orissa, and West Bengal according to their production scale. In India, Tuticorin (Tamil Nadu) is the second leading producer of salt with an average estimated production of 25 lakh tonnes of salt every year (Sedat Gundogdu, 2018; Maria et al., 2017). Of the total area, 25,000 acres of land are covered under salt pans, and small-scale manufacturing is carried out on 10,000 acres of land. Thus far, there are no detailed studies conducted in India
Fig. 1. Location map of the study area along with sampling points at Tuticorin, Gulf of Mannar, South India.
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Fig. 2. Microplastic polymers and micro-Fourier transform infrared spectroscopy peaks in salt pans of Tuticorin.
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on the impact of MPs present in sea salt on human health. The main objective of the present study is to highlight the MP contamination in sea salts currently produced in the Tuticorin salt pans, Tamil Nadu, India. In India, sea salts that are produced in chief salt-manufacturing centers in Tuticorin are exported to China, Japan, and across regions in India. Herein, 25 salt samples were collected from different salt pans that were selected on the basis of their quality in August 2018. Fig. 1 shows the study area containing the sampling sites. Each sample was collected to a weight of 1.5 kg in a standard packet. In the Tuticorin region, the salt manufacturing process involves pumping of seawater into evaporation ponds of many levels, which are extended to several acres of land. This seawater is left to crystallize under controlled methods to obtain fine-quality sodium chloride. Further, the density of the brine is observed with utmost care to maintain the salinity and transparency of the salt. Exposure of the seawater to wind without moisture and strong sunlight quickens the formation of salt crystals by increasing the evaporation rate. Afterwards, the salt undergoes different size of manufacturing processes before being packed in containers on the basis of the purpose and value-added usage. For instance, rock salt is one such product from salt pan that is easily contaminated by MPs through the aerial route as well as through the resource material itself. MP extraction was done using the method explained in many studies (Cole et al., 2013; Dubaish and Liebezeit, 2013; Harrison et al., 2014; Yang et al., 2015; Duis and Coors, 2016; Karami et al., 2017a). A portion of the sample, 250 g of salt collected from each amalgamation, was taken in 1-L jars, and 100 ml of H2O2 (approximately 30%) was added to the sample to oxidize the amoebic materials if present. Then, 1-L jars were aligned into an incubator at a temperature of 65 °C and 85 revolutions per minute (rpm) acceleration for 24 h. Subsequently, these samples were stored at specific temperatures for 48 h. After that, add 800 ml salty solution poured into each bottle to dissolves alkali. These bottles were stored for 24 h at a specified temperature. Once, the clearing action was completed, the afloat present was clarified, it and formed a 47 mm 0.2 μm artificial nitrate film to add 10–14 ml of 5 M NaI and was placed in antiseptic Petri dishes (density = 1.6 g/ml) as mentioned in Karami et al. (2017b). The sample was centrifuged to ensure the complete separation of MPs. The particles that settled at the bottom after centrifugation were transferred into Petri dishes for further examination under a microscope. A binocular stereo zoom microscope was used to assess the type
and quantity of MPs in a quadrant counted through visual classification. Random selection of leftover particles was done to confirm the presence of MPs using a micro-Fourier transform infrared spectrometer (μ-FT-IR) (Thermo Fisher Scientific; NICOLAT iS5 KBr window iD1 model). The photographs of the MPs were displayed in abstracted plates. The MP type as a pie chart was generated using Microsoft Excel, version 2012. The locations for sample collection were chosen on the basis of the accessibility of nearby salt pans along the coastal environment. The type of various MPs particles were analyzed by μ-FT-IR. However, μ-FTIR is not the only method that defines the acceptable level of MPs. Various types of MPs were identified, including nylon (NY), cellulose (CL), polyethylene (PE), and polypropylene (PP), and some MPs or nonplastic particles were unidentified (Fig. 2). An elevated level of MP waste was found in Tuticorin city sea salt sample (No. 16–21) in this study. Sea salts crystallized in the Tuticorin city sample contain a high level of MPs as compared to that in other area salts, which is an expected outcome (Table 2). Because of the lack of previous reports on MPs as a contaminant in Tuticorin city, there is no possibility of comparison. The results show the low level of MPs particles through the intake of the salts, which warrants insignificant health impacts. Auta et al. (2017) and Law and Thompson (2014) have stated that rivers, overflow from drainage systems, wastewater treatment plants, currents, and tidal waves form the most indispensable ground for MP contamination in marine bodies. Perhaps, these MPs are a meticulous hazard to organisms because of their miniature size and absorption of persistent organic contaminants. These MPs, containing adsorbed metals and chemicals, are eventually ingested by organisms through seafood. The μ-FT-IR results of the characterization of MPs are shown in Fig. 2. The 98% spectrum was identified based on the μ-FT-IR results. The contaminated sea salts were found to have common microplastics such as polyethylene, polypropylene, cellulose, and nylon (Table 1). Domestic waste materials were found to be the main source of polyethylene and polypropylene contaminants. Every day, large volumes of polyethylene covers in the form of tea covers, milk covers, cooking covers, shop covers, medicine covers, and bust plastic materials are left abandoned due to lack of proper garbage disposal (Fig. 3). Polyethylene is the most common element found in packaging material and floaters that are used during fishing practices. Recently, MPs were also recorded from Arctic sea ice, fish, sea birds and sea salts in highly contaminated surface waters. Until now, only a limited number of global surveys have been conducted on the quantity and distribution of MPs in marine sea
Fig. 3. Microplastic polymers deposited along the Gulf of Mannar coast through buckle channels.
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Fig. 4. Pie chart showing the distribution of microplastic polymers, expressed in percentage.
salts (Soylak and Yilmaz, 2006; Van Cauwenberghe et al., 2013; Jambeck et al., 2015; Mason et al., 2017; Schirinzi et al., 2017). Nylon and cellulose are also observed in sea salts, as fiber, net webbing, and textiles. nylon chiefly accounts as a pollutant in the coast through the use of fishing nets and nylon ropes. Moreover, Cellulose sponge clothes waste was derived from textile industries around the salt pan stations. The much higher MPs contents in sea salts were identified in the Tuticorin city area, as the people in that region dumped plastic waste into marine bodies through the buckle channel (Fig. 3). The type of MPs present in representative sampling sites is shown in Fig. 4 (Patters and Bratton, 2016). Disintegration definitely affects MP features and differs on account of the accustomed ecology system. Hence, the present study lays concrete abasement for presence of plastics in freshwater environments, where water turbulence, wind velocity, concrete chafe, and freeze-thaw cycles play a basic role in the abrasion of MPs (Duis and Coors, 2016). Patterns of abrasion, such as pits, fractures, flakes, and adhering particles, were empiric in the AFM images of the MPs advised actuality (Fig. 5). Hence, it is axiomatic that MPs in Tuticorin accomplished abrasion at various levels. In addition to the antecedent, the circadian acclimated artificial items are sources of MPs. Accordingly, Fig. 5 clearly shows the AFM images. The present study suggested that
accumulation rates of MPs widely affected by urban activities, shore and coastal uses, wind and ocean currents. Seawater contamination refers to the presence of abundant contaminants that associate with sea salts, including plasticizers such as benzyl butyl phthalate and 2-ethylhexyl. Plastic usage is the fundamental source for these contaminants. Nevertheless, plastics adsorbs effluents from the seawater and intrude into the sea products. Consequently, abyssal MPs in sea salts might pose a threat to human health through food consumption. In conclusion, it is highly recommended to forbid and control MP abuse in sea salts, particularly in Tuticorin, Tamil Nadu, in India. The sea salts produced from the seawater columns of salt pans of the study area are intended to possess MPs, and this is affirmed through this research. This research would serve as the basis for reporting and alerting the society about the growing MP contamination in sea salts. Declaration of competing interest The authors declare that there is no conflict of interests regarding the publication of this paper.
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Fig. 5. AFM image of microplastics in sea salt from the Tuticorin region showing four types of plastics on the plastic surface.
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Acknowledgments
Harrison, J.P., Schratzberger, M., Sapp, M., Osborn, M.A., 2014. Rapid bacterial colonization of low-density polyethylene microplastics in coastal sediment microcosms. BMC Microbiol. 14, 232–247. Jambeck, J.R., Geyer, R., Wilcox, C., Siegler, T.R., Perryman, M., Andrady, A., Narayan, R., Law, K.L., 2015. Plastic waste inputs from land into the ocean. Science 347, 768–771. Karami, A., Golieskardi, A., Choo, C.K., Larat, V., Galloway, T.S., Salamatinia, B., 2017a. The presence of microplastics in commercial salts from different countries. Sci. Rep. 7 (46173), 1–9. Karami, A., Golieskardi, A., Choo, C.K., Romano, N., Ho, Y.B., Salamatinia, B., 2017b. Ahigh-performance protocol for extraction of microplastics in fish. Sci. Total Environ. 578, 485–494. Krishnakumar, S., Ramasamy, S., Simon Peter, T., Godson, Prince S., Chandrasekar, N., Magesh, N.S., 2017. Geospatial risk assessment and trace element concentration inreef associated sediments, northern part of Gulf of Mannar Biosphere Reserve, Southeast coast of India. Mar. Pollut. Bull. 125 (1–2), 522–529. Koelmans, A.A., Besseling, E., Shim, W.J., 2015. Nanoplastics in the aquatic environment. Critical review. In: Bergmann, M., Gutov, L., Klages, M. (Eds.), Marine Anthropogenic Litter. Springer, Berlin, pp. 325–343. Law, K.L., Thompson, R.C., 2014. Microplastic in the seas. Science 345, 144–145. Mason, S., Kammin, L., Eriksen, M., Aleid, G., Box, C., Williamson, N., 2017. Pelagic plastic pollution within the surface waters of Lake Michigan, USA. J. Gt. Lakes Res. 753–759. Iñiguez, Maria E., Conesa, Juan A., Andres, F., 2017. Microplastics in Spanish table. Salt Scientific Reports 7, 8620. https://doi.org/10.1038/s41598-017-09128-x. Mozaffarian, D., Fahimi, S., Singh, G.M., Micha, R., Khatibzadeh, S., Engell, R.E., Lim, S., Danaei, G., Ezzati, M., Powles, J., 2014. Global sodium consumption and death from cardiovascular causes. N. Engl. J. Med. 371, 624–634. Ng, K.L., Obbard, J.P., 2006. Prevalence of microplastics in Singapore's coastal marine environment. Mar. Pollut. Bull. 52, 761–767. Patters, C.A., Bratton, S.P., 2016. Urbanization is a major influence on microplastic ingestion by sunfish in the BrazosRiver Basin, Central Texas, USA. Environ. Pollut. 210, 380–387. Reddy, M.S., Basha, S., Adimurthy, S., Ramachandraiah, G., 2006. Description of the small plastics fragments in marine sediments along the Alang-Sosiya ship-breaking yard, India. Estuar. Coast Shelf Sci. 68, 656–660. Schirinzi, G.F., Perez-Pomeda, I., Sanchis, J., Rossini, C., Farre, M., Barcelo, D., 2017. Cytotoxic effects of commonly used nanomaterials and microplastics on cerebral and epithelial cells. Environ. Res. 67, 579–587. Sedat, Gundogdu, 2018. Contamination of table salts from Turkey withmicroplastics. Food Addit. Contam. A. https://doi.org/10.1080/19440049.2018.1447694. Soylak, M., Yilmaz, S., 2006. Heavy metal levels in sediment samples from Lake Palas, Kayseri-Turkey. Fresenius Environ. Bull. 15, 340–344. Van Cauwenberghe, L., Vanreusel, A., Mees, J., Janssen, C.R., 2013. Microplastic pollution in deep-sea sediments. Environ. Pollut. 182, 495–499. Veerasingam, S., Mugilarasan, M., Venkatachalapathy, R., Vethamony, P., 2016. Influence of 2015 flood on the distribution and occurrence of microplastic pellets along the Chennai coast, India. Mar. Pollut. Bull. 109, 196–204. World Health Organization (WHO), 2012. Guidelines for Drinking Water Quality Recommendation. pp. 1–6 Geneva. Yang, D.Q., Shi, H.H., Li, L., Li, J.N., Jabeen, K., Kolandhasamy, P., 2015. Microplastic pollution in table salts from China. Environ. Sci. Technol. 49, 13622–13627. Zhao, S., Zhu, L., Wang, T., Li, D., 2014. Suspended microplastics in the surface water of the Yangtze Estuary System, China: first observations on occurrence, distribution. Mar. Pollut. Bull. 86, 562–568.
The first author Dr. S. Selvam gratefully acknowledge the financial support of Department of Science and Technology – SERB- ECR (Ref. No. F.ECR/2018/001749). The authors are also grateful to Shri A.P.C.V. Chockalingam, Secretary, and Dr. C.Veerabahu, Principal, V.O.C College, Tuticorin, for their support to carry out the study. We would like to acknowledge the invaluable support of the reviewers and editor whose comments helped to improve the quality of the manuscript. References Ainley, D.G., Spear, L.B., Ribic, C.A., 1990. The incidence of plastic in the diets of pelagic seabirds in the eastern equatorial Pacific region. In: Shomura, R.S., Codfrey, M.L. (Eds.), Proceedings of the Second International Conference on Marine Debris. US Department of Commerce, Honolulu, pp. 653. Aho, K., Harmsen, P., Hatano, S., Marquardsen, J., Smirnov, V.E., Strasser, T., 1980. Cerebrovascular disease in the community, results of a WHO collaborative study. Bull. World Health Organ. 58 (1), 113–130. Arunkumar, A., Sivakumar, R., Sai Rutwik Reddy, Y., Bhagya Raja, M.V., Nishanth, T., Revanth, V., 2016. Preliminary study on marine debris pollution along Marina beach, Chennai, India. Reg. Stud. Mar. Sci. 5, 35–40. Auta, H.S., Emenike, C.U., Fauziah, S.H., 2017. Distribution and importance of microplastics in the marine environment: a review of the sources, fate, effects, and potential solutions. Environ. Int. 102, 165–176. Aytan, U., Valente, A., Senturk, Y., Usta, R., Esensoy Sahin, F.B., Mazlum, R.E., Agirbas, E., 2016. First evaluation of neustonic microplastics in Black Sea waters. Mar. Environ. Res. 119, 22–30. Buchanan, J.B., 1971. Pollution by synthetic fibres. Mar. Pollut. Bull. 23, 88–99. Bouwmeester, H., Hollman, P.C., Peters, R.J., 2015. Potential health impact of environmentally released micro-and nanoplastics in the human food production chain: experiences from nanotoxicology. ES T (Environ. Sci. Technol.) 49, 8932–8947. Cole, M., Lindeque, P., Fileman, E., Halsband, C., Goodhead, R., Moger, J., Galloway, T.S., 2013. Microplastic ingestion by zooplankton. Environ. Sci. Technol. 47, 6646–6655. Dubaish, F., Liebezeit, G., 2013. Suspended microplastics and black carbon particles in the Jade system, southern North Sea. Water Air Soil Pollut. 224, 1352. Duis, K., Coors, A., 2016. Microplastics in the aquatic and terrestrial environment: sources (with a specific focus on personal care products), fate and effects. Environ. Sci. Eur. 28 (2), 1–25. Erdem, Y., Arici, M., Altun, B., Turgan, C., Sindel, S., Erbay, B., Derici, U., Karatan, O., Hasanoglu, E., Caglar, S., 2010. The relationship between hypertension and salt intake in Turkish population: SALTURK study. Blood Press. 19, 313–318. Erkoyun, E., Sozmen, K., Bennett, K., Unal, B., Boshuizen, H.C., 2016. Predicting the health impact of lowering salt consumption in Turkey using the DYNAMO health impact assessment tool. Public Health 140, 228–234. Fendall, L.S., Sewell, M.A., 2009. Contributing to marine pollution by washing your face: microplastics in facial cleansers. Mar. Pollut. Bull. 58, 1225–1228. Gündoğdu, S., Çevik, C., 2017. Micro-and mesoplastics in northeast levantine coast of Turkey: the preliminary results from surface samples. Mar. Pollut. Bull. 118, 341–347.
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