Environmental Pollution 204 (2015) 117e123
Contents lists available at ScienceDirect
Environmental Pollution journal homepage: www.elsevier.com/locate/envpol
Accumulation of floating microplastics behind the Three Gorges Dam Kai Zhang a, d, Wen Gong b, Jizhong Lv c, Xiong Xiong a, Chenxi Wu a, * a
State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China School of Earth Sciences, China University of Geosciences, Wuhan 430074, China c Department of Criminal Investigation, Hubei Public Security Bureau, Wuhan 430070, China d Graduate University Chinese Academy of Sciences, Beijing 100039, China b
a r t i c l e i n f o
a b s t r a c t
Article history: Received 14 January 2015 Received in revised form 24 March 2015 Accepted 26 April 2015 Available online
We investigated the occurrence and distribution of microplastics in surface water from the Three Gorges Reservoir. Nine samples were collected via trawl sampling with a 112 mm mesh net. The abundances of microplastics were from 3407.7 103 to 13,617.5 103 items per square kilometer in the main stream of the Yangtze River and from 192.5 103 to 11,889.7 103 items per square kilometer in the estuarine areas of four tributaries. The abundance of microplastics in the main stream of the Yangtze River generally increased as moving closer to the Three Gorges Dam. The microplastics are made exclusively of polyethylene (PE), polypropylene (PP), and polystyrene (PS). Together with microplastics, high abundance of coal/fly ash was also observed in the surface water samples. Comparing with previously reported data, microplastics in the TGR were approximately one to three orders of magnitudes greater, suggesting reservoirs as potential hot spot for microplastic pollution. © 2015 Elsevier Ltd. All rights reserved.
Keywords: Microplastics Reservoir Dam Distribution Accumulation
1. Introduction Plastics are probably the most versatile synthetic materials invented by human. Due to the unique properties, such as lightweight, strength, durability, corrosion-resistance, and electrical insulation, plastics are widely used (Thompson et al., 2009). Nearly all products used in our daily life contain plastics. In the last 50 years, annual world production of plastics increased drastically. In 2012, 280 million tons of plastics were produced globally with less than a half got disposed in landfills or recycled while the rest may still be in use or otherwise be discarded into the environment (Rochman et al., 2013). In the environment, larger plastic items can slowly breakdown into small pieces via physical, chemical and biological processes (O'Brine and Thompson, 2010; Singh and Sharma, 2008). Plastic debris 1.0 g mL 1) were also observed (Sadri and Thompson, 2014), likely due to a higher water velocity and a mix of fresh water with sea water. In the TGR, the water flow is
K. Zhang et al. / Environmental Pollution 204 (2015) 117e123
119
Fig. 1. Geographic location, sampling sites, and the abundance of microplastics from each site.
relatively slow, and plastics with a density >1.0 g mL 1 might settle to the bottom during their transport in the water. A large number of particles with a spherical shape were also observed floating in the water in samples from all sites. Those particles have a glassy surface, are about 200 mm in size, and can reflect light when examine under the stereomicroscope, which makes them distinguishable from microplastics. Those particles
were identified as aluminum silicate as suggested by their elemental compositions obtained using an Energy Dispersive Spectroscopy on a Scanning Electron Microscopy (SEM/EDS) (Fig. 2). As suggested by Eriksen et al. (2013a), those particles were probably coal ash or coal fly ash, which are generated during the combustion of coal related products. Due to their high abundance (more abundance than microplastics) and floating in the water,
Table 1 Distance from the dam, towing distance, microplastic abundance, and proportion of each plastic type for the sampling sites and the watershed area of the tributaries. Sample ID Main stream CJ01 CJ02 CJ03 CJ04 CJ05 Tributary QG YS TZ XX a
Distance from the dam (km)
Towing distance (m)
Watershed areaa (km2)
Microplastic abundance (103 counts km
41.5 34.8 23.5 13.4 6.1
400 410 390 400 400
e e e e e
45.0 39.9 32.1 31.1
400 400 400 390
523.0 193.7 248.0 3095.0
Huang et al. (2006).
2
)
PE (%)
PP (%)
PS (%)
4680.0 12,087.8 3407.7 8535.0 13,617.5
36.79 37.52 39.31 40.87 37.43
63.21 62.44 47.97 58.66 62.28
0.00 0.04 12.7 0.47 0.29
797.5 192.5 2350.0 11,889.7
45.38 40.1 50.29 57.12
54.62 56.0 47.90 42.14
0.00 3.90 1.81 0.73
120
K. Zhang et al. / Environmental Pollution 204 (2015) 117e123
Fig. 2. SEM image of the spherical shape particles (A and B), Elemental analysis using the SEM/EDS showing it to be aluminum silicate (C).
coal/fly ash might also pose potential risks to the aquatic organisms living within the area. 3.2. Shapes and size distribution of microplastics Typical examples of microplastics collected from the TGR are
presented in Fig. 3. The microplastics were classified into sheet, line, foam, and fragment according to their morphology. Different from the results from the Great Lakes (Eriksen et al., 2013a), microbeads were not observed in this work. Microbeads are used in many consumer facial cleansers and have been identified as potential sources for microplastics (Fendall and Sewell, 2009). This
Fig. 3. Typical examples of microplastics observed in the TGR (A), sheets (B), lines (C), foams (D), fragments (E).
K. Zhang et al. / Environmental Pollution 204 (2015) 117e123
121
Fig. 4. Size distribution of microplastics observed in the TGR (Sampling sites are ordered in decreasing distance from the dam).
may suggest that microbeads facial cleansers are less frequently used in the TGR region comparing to well-developed regions. Microplastics in TGR are most likely from the degradation of daily used plastic products. Microplastics with a flexible sheet shape are most likely from the breakdown of plastic bags or packing materials. Lines are probably pieces of fishing lines or ropes from local shipping and fishery activities. Whereas foam and other irregular shape fragments can origin from packaging materials and plastic containers. Microplastics were classified into four categories according to their size: 112e300 mm, 300e500 mm, 500 mme1.6 mm, and 1.6e5 mm. Microplastics between 500 mm and 1.6 mm were the most abundant from most sites, accounting for 30e57% of the total microplastics (Fig. 4). Many previous research investigated the size distribution of microplastics (Browne et al., 2010; Eriksen et al., 2013a; Sadri and Thompson, 2014; Zhao et al., 2014). Unfortunately, direct comparison was impossible as different size categories were used by different researchers. However, the distribution of plastic debris generally skews towards medium and small sizes, probably because the degradation of one large plastic
debris can generate several pieces of small fragments. Whereas smaller microplastics may be less persistent than the larger ones due to a larger surface area. Therefore, the size distribution of microplastics depends on both their generation and degradation rates. The fate and behavior of different size microplastics need to be further investigated. The shapes of microplastics from different size categories were presented in Fig. 5. Lines were larger than 500 mm, foams were larger than 1.6 mm, whereas fragment and sheet were found in all size categories. This pattern may be related to their origins. Foams were all cells from the disintegration of Styrofoam based on their shapes and FT-IR spectra. Styrofoam is made from closed-cell extruded polystyrene foam and extensively used in thermal insulation and craft applications. Only observed in 1.6e5 mm category suggesting that the further degradation of individual cell of extruded polystyrene foam is difficult. 3.3. Comparison with data from other areas The abundance of microplastics from the TGR was compared with the data from other areas worldwide (Table 2). The average
Fig. 5. Composition of microplastics of different morphology in each size classification category (Sampling sites are ordered in decreasing distance from the dam).
122
K. Zhang et al. / Environmental Pollution 204 (2015) 117e123
Table 2 Comparison of microplastic abundance in the surface water samples from the Three Gorges Reservoir with data from other areas. Study area
Size class (mm)
Microplastic abundance (103 counts km Range
North Atlantic Subtropical Gyre North Western Mediterranean Sea South Pacific Subtropical Gyre Lake Superior Lake Huron Lake Erie Lake Hovsgol, Mongolia North Shore Channel, Chicago
>0.333 0.333e5.0 >0.333 >0.333 >0.333 >0.333 >0.333 >0.333
Estuary rivers in the Chesapeake Bay Three Gorges Reservoir
0.333e5.0 0.112e5.0
e 5.5e297.9 3407.7e13,617.5 192.5e11,889.7
4. Conclusions High abundance of microplastics were observed in samples collected from the TGR. The types of microplastics were identified to be PE, PP, and PS. The abundance of microplastics showed an increasing trend as moving towards the dam. Tributaries contributed significant amount of microplastics to the main stream, and the abundance of microplastics found in the tributary estuaries might be related to the human activities within the river watershed. The morphology of the microplastics suggests their origin from the degradation of plastic products and the size distribution showed the dominance of medium size microplastics. Compared to other marine and freshwater habitats, the abundance of microplastics was one to three orders of magnitudes higher in the TGR but comparable to those observed from sites under heavy human influence. Our work for the first time demonstrates that reservoirs can potentially be important areas for the accumulation of microplastics. Additional works are needed to understand the fate and behavior and to assess the ecological risks of microplastics in reservoirs. Acknowledgment This work was funded by National Critical Project for Science and Technology on Water Pollution Prevention and Control (2012ZX07104-002-005, 2012ZX07101-007-002) and State Key Laboratory of Freshwater Ecology and Biotechnology (2014FBZ03). Dr. Chenxi Wu thanks the support from the Youth Innovation Promotion Association of the Chinese Academy of Sciences.
)
References
Mean
0e580 0e892 0e396.3 1.3e12.6 0e6.5 4.7e446.3 1.0e44.4
abundance of microplastics from the TGR is one to three orders of magnitudes higher than those observed from other areas, except samples from the North Shore Channel site downstream a wastewater treatment plant (WWTP) in Chicago (McCormick et al., 2014). Effluent from WWTPs was found to be an important point source of microplastics (Browne et al., 2011; Dubaish and Liebezeit, 2013). But in the TGR, microplastics are more likely from nonpoint source and are carried to the reservoirs by surface runoff as most areas within the Three Gorges region are underdeveloped. For small towns, no WWTP is currently available and the recycle and disposal of garbage are not well managed. More importantly, large amount of microplastics and large plastic debris were transported to the TGR from upstream and got accumulated behind the dam as floating microplastics cannot pass the dam. Microplastics can be generated from large plastics on land and then be transported to rivers, or be produced after large plastics are transported to the rivers. The degradation of plastics and formation of microplastics in both terrestrial and freshwater environments need to be further characterized.
2
e 116 26.9 5.4 2.8 105.5 20.3 730.3 (upstream) 6698.3 (downstream) e 8465.6 (mainstream) 3807.4 (tributary)
Law et al., 2010 Collignon et al., 2012 Eriksen et al., 2013a Eriksen et al., 2013b Eriksen et al., 2013b Eriksen et al., 2013b Free et al., 2014 McCormick et al., 2014 Yonkos et al., 2014 This work
References Browne, M.A., Crump, P., Niven, S.J., Teuten, E., Tonkin, A., Galloway, T., Thompson, R., 2011. Accumulation of microplastic on shorelines woldwide: sources and sinks. Environ. Sci. Technol. 45, 9175e9179. Browne, M.A., Galloway, T.S., Thompson, R.C., 2010. Spatial patterns of plastic debris along estuarine shorelines. Environ. Sci. Technol. 44, 3404e3409. Carpenter, E.J., Smith, K.L., 1972. Plastics on the Sargasso Sea surface. Science 175, 1240e1241. Collignon, A., Hecq, J.-H., Glagani, F., Voisin, P., Collard, F., Goffart, A., 2012. Neustonic microplastic and zooplankton in the North Western Mediterranean Sea. Mar. Pollut. Bull. 64, 861e864. Dekiff, J.H., Remy, D., Klasmeier, J., Fries, E., 2014. Occurrence and spatial distribution of microplastics in sediments from Norderney. Environ. Pollut. 186, 248e256. Dubaish, F., Liebezeit, G., 2013. Suspended microplastics and black carbon particles in the Jade System, Southern North Sea. Water Air Soil Pollut. 224, 1e8. Eriksen, M., Mason, S., Wilson, S., Box, C., Zellers, A., Edwards, W., Farley, H., Amato, S., 2013a. Microplastic pollution in the surface waters of the Laurentian Great Lakes. Mar. Pollut. Bull. 77, 177e182. Eriksen, M., Maximenko, N., Thiel, M., Cummins, A., Lattin, G., Wilson, S., Hafner, J., Zellers, A., Rifman, S., 2013b. Plastic pollution in the South Pacific Subtropical Gyre. Mar. Pollut. Bull. 68, 71e76. Fendall, L.S., Sewell, M.A., 2009. Contributing to marine pollution by washing your face: microplastics in facial cleansers. Mar. Pollut. Bull. 58, 1225e1228. Foekema, E.M., De Gruijter, C., Mergia, M.T., van Franeker, J.A., Murk, A.J., Koelmans, A.A., 2013. Plastic in North Sea fish. Environ. Sci. Technol. 47, 8818e8824. Free, C.M., Jensen, O.P., Mason, S.A., Eriksen, M., Williamson, N.J., Boldgiv, B., 2014. High-levels of microplastic pollution in a large, remote, Mountain Lake. Mar. Pollut. Bull. 85, 156e163. Gasperi, J., Dris, R., Bonin, T., Rocher, V., Tassin, B., 2014. Assessment of floating plastic debris in surface water along the Seine River. Environ. Pollut. 195, 163e166. Hidalgo-Ruz, V., Gutow, L., Thompson, R.C., Thiel, M., 2012. Microplastics in the marine environment: a review of the methods used for identification and quantification. Environ. Sci. Technol. 46, 3060e3075. Huang, Z., Li, Y., Chen, Y., Li, J., Xin, Z., Ye, M., Li, J., Lv, P., Li, C., Zhou, X., 2006. Water Quality Protection and Water Environmental Carrying Capacity Calculation for Three Gorges Reservoir. In: Series of Ecological and Environmental Protection for Three Gorges Project. China Water Power Press. Ivar do Sul, J.A., Costa, M.F., 2014. The present and future of microplastic pollution in the marine environment. Environ. Pollut. 185, 352e364. t-Ferguson, S., Maximenko, N.A., Proskurowski, G., Peacock, E.E., Law, K.L., More Hafner, J., Reddy, C.M., 2010. Plastic accumulation in the North Atlantic Subtropical Gyre. Science 329, 1185e1188. McCormick, A., Hoellein, T.J., Mason, S.A., Schluep, J., Kelly, J.J., 2014. Microplastic is an abundant and distinct microbial habitat in an urban river. Environ. Sci. Technol. 48, 11863e11871. Ning, P., Zhang, Z., 2010. On formation and features of floating garbage on water surface in Three Gorges area. J. Chongqing Three Gorges Univ. 26, 1e4. O'Brine, T., Thompson, R.C., 2010. Degradation of plastic carrier bags in the marine environment. Mar. Pollut. Bull. 60, 2279e2283. Rech, S., Macaya-Caquilp an, V., Pantoja, J.F., Rivadeneira, M.M., Jofre Madariaga, D., Thiel, M., 2014. Rivers as a source of marine litter e a study from the SE Pacific. Mar. Pollut. Bull. 82, 66e75. Rochman, C.M., Browne, M.A., Halpern, B.S., Hentschel, B.T., Hoh, E., Karapanagioti, H.K., Rios-Mendoza, L.M., Takada, H., Teh, S., Thompson, R.C., 2013. Policy: classify plastic waste as hazardous. Nature 494, 169e171. Sadri, S.S., Thompson, R.C., 2014. On the quantity and composition of floating plastic debris entering and leaving the Tamar Estuary, Southwest England. Mar. Pollut. Bull. 81, 55e60. €l€ Seta a, O., Fleming-Lehtinen, V., Lehtiniemi, M., 2014. Ingestion and transfer of
K. Zhang et al. / Environmental Pollution 204 (2015) 117e123 microplastics in the planktonic food web. Environ. Pollut. 185, 77e83. Singh, B., Sharma, N., 2008. Mechanistic implications of plastic degradation. Polym. Degrad. Stab. 93, 561e584. Thompson, R.C., Moore, C.J., vom Saal, F.S., Swan, S.H., 2009. Plastics, the environment and human health: current consensus and future trends. Philos. Trans. R. Soc. B Biol. Sci. 364, 2153e2166. Thompson, R.C., Olsen, Y., Mitchell, R.P., Davis, A., Rowland, S.J., John, A.W.G., McGonigle, D., Russell, A.E., 2004. Lost at sea: where is all the plastic? Science 304, 838. Van Cauwenberghe, L., Vanreusel, A., Mees, J., Janssen, C.R., 2013. Microplastic pollution in deep-sea sediments. Environ. Pollut. 182, 495e499. € hler, A., 2012. Uptake and effects of microvon Moos, N., Burkhardt-Holm, P., Ko plastics on cells and tissue of the Blue Mussel Mytilus edulis L. after an experimental exposure. Environ. Sci. Technol. 46, 11327e11335. ~ oz, D., Brennholt, N., Bourrain, X., Buchinger, S., Wagner, M., Scherer, C., Alvarez-Mun Fries, E., Grosbois, C., Klasmeier, J., Marti, T., Rodriguez-Mozaz, S., Urbatzka, R.,
123
Vethaak, A., Winther-Nielsen, M., Reifferscheid, G., 2014. Microplastics in freshwater ecosystems: what we know and what we need to know. Environ. Sci. Eur. 26, 1e9. Woodall, L.C., Sanchez-Vidal, A., Canals, M., Paterson, G.L.J., Coppock, R., Sleight, V., Calafat, A., Rogers, A.D., Narayanaswamy, B.E., Thompson, R.C., 2014. The deep sea is a major sink for microplastic debris. R. Soc. Open Sci. 1, 140317. Yonkos, L.T., Friedel, E.A., Perez-Reyes, A.C., Ghosal, S., Arthur, C.D., 2014. Microplastics in four estuarine rivers in the Chesapeake Bay, U.S.A. Environ. Sci. Technol. 48, 14195e14202. Zbyszewski, M., Corcoran, P.L., Hockin, A., 2014. Comparison of the distribution and degradation of plastic debris along shorelines of the Great Lakes, North America. J. Gt. Lakes. Res. 40, 288e299. Zhao, S.Y., Zhu, L.X., Wang, T., Li, D.J., 2014. Suspended microplastics in the surface water of the Yangtze Estuary System, China: first observations on occurrence, distribution. Mar. Pollut. Bull. 86, 562e568.
Contents lists available at ScienceDirect
Environmental Pollution journal homepage: www.elsevier.com/locate/envpol
Accumulation of floating microplastics behind the Three Gorges Dam Kai Zhang a, d, Wen Gong b, Jizhong Lv c, Xiong Xiong a, Chenxi Wu a, * a
State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China School of Earth Sciences, China University of Geosciences, Wuhan 430074, China c Department of Criminal Investigation, Hubei Public Security Bureau, Wuhan 430070, China d Graduate University Chinese Academy of Sciences, Beijing 100039, China b
a r t i c l e i n f o
a b s t r a c t
Article history: Received 14 January 2015 Received in revised form 24 March 2015 Accepted 26 April 2015 Available online
We investigated the occurrence and distribution of microplastics in surface water from the Three Gorges Reservoir. Nine samples were collected via trawl sampling with a 112 mm mesh net. The abundances of microplastics were from 3407.7 103 to 13,617.5 103 items per square kilometer in the main stream of the Yangtze River and from 192.5 103 to 11,889.7 103 items per square kilometer in the estuarine areas of four tributaries. The abundance of microplastics in the main stream of the Yangtze River generally increased as moving closer to the Three Gorges Dam. The microplastics are made exclusively of polyethylene (PE), polypropylene (PP), and polystyrene (PS). Together with microplastics, high abundance of coal/fly ash was also observed in the surface water samples. Comparing with previously reported data, microplastics in the TGR were approximately one to three orders of magnitudes greater, suggesting reservoirs as potential hot spot for microplastic pollution. © 2015 Elsevier Ltd. All rights reserved.
Keywords: Microplastics Reservoir Dam Distribution Accumulation
1. Introduction Plastics are probably the most versatile synthetic materials invented by human. Due to the unique properties, such as lightweight, strength, durability, corrosion-resistance, and electrical insulation, plastics are widely used (Thompson et al., 2009). Nearly all products used in our daily life contain plastics. In the last 50 years, annual world production of plastics increased drastically. In 2012, 280 million tons of plastics were produced globally with less than a half got disposed in landfills or recycled while the rest may still be in use or otherwise be discarded into the environment (Rochman et al., 2013). In the environment, larger plastic items can slowly breakdown into small pieces via physical, chemical and biological processes (O'Brine and Thompson, 2010; Singh and Sharma, 2008). Plastic debris 1.0 g mL 1) were also observed (Sadri and Thompson, 2014), likely due to a higher water velocity and a mix of fresh water with sea water. In the TGR, the water flow is
K. Zhang et al. / Environmental Pollution 204 (2015) 117e123
119
Fig. 1. Geographic location, sampling sites, and the abundance of microplastics from each site.
relatively slow, and plastics with a density >1.0 g mL 1 might settle to the bottom during their transport in the water. A large number of particles with a spherical shape were also observed floating in the water in samples from all sites. Those particles have a glassy surface, are about 200 mm in size, and can reflect light when examine under the stereomicroscope, which makes them distinguishable from microplastics. Those particles
were identified as aluminum silicate as suggested by their elemental compositions obtained using an Energy Dispersive Spectroscopy on a Scanning Electron Microscopy (SEM/EDS) (Fig. 2). As suggested by Eriksen et al. (2013a), those particles were probably coal ash or coal fly ash, which are generated during the combustion of coal related products. Due to their high abundance (more abundance than microplastics) and floating in the water,
Table 1 Distance from the dam, towing distance, microplastic abundance, and proportion of each plastic type for the sampling sites and the watershed area of the tributaries. Sample ID Main stream CJ01 CJ02 CJ03 CJ04 CJ05 Tributary QG YS TZ XX a
Distance from the dam (km)
Towing distance (m)
Watershed areaa (km2)
Microplastic abundance (103 counts km
41.5 34.8 23.5 13.4 6.1
400 410 390 400 400
e e e e e
45.0 39.9 32.1 31.1
400 400 400 390
523.0 193.7 248.0 3095.0
Huang et al. (2006).
2
)
PE (%)
PP (%)
PS (%)
4680.0 12,087.8 3407.7 8535.0 13,617.5
36.79 37.52 39.31 40.87 37.43
63.21 62.44 47.97 58.66 62.28
0.00 0.04 12.7 0.47 0.29
797.5 192.5 2350.0 11,889.7
45.38 40.1 50.29 57.12
54.62 56.0 47.90 42.14
0.00 3.90 1.81 0.73
120
K. Zhang et al. / Environmental Pollution 204 (2015) 117e123
Fig. 2. SEM image of the spherical shape particles (A and B), Elemental analysis using the SEM/EDS showing it to be aluminum silicate (C).
coal/fly ash might also pose potential risks to the aquatic organisms living within the area. 3.2. Shapes and size distribution of microplastics Typical examples of microplastics collected from the TGR are
presented in Fig. 3. The microplastics were classified into sheet, line, foam, and fragment according to their morphology. Different from the results from the Great Lakes (Eriksen et al., 2013a), microbeads were not observed in this work. Microbeads are used in many consumer facial cleansers and have been identified as potential sources for microplastics (Fendall and Sewell, 2009). This
Fig. 3. Typical examples of microplastics observed in the TGR (A), sheets (B), lines (C), foams (D), fragments (E).
K. Zhang et al. / Environmental Pollution 204 (2015) 117e123
121
Fig. 4. Size distribution of microplastics observed in the TGR (Sampling sites are ordered in decreasing distance from the dam).
may suggest that microbeads facial cleansers are less frequently used in the TGR region comparing to well-developed regions. Microplastics in TGR are most likely from the degradation of daily used plastic products. Microplastics with a flexible sheet shape are most likely from the breakdown of plastic bags or packing materials. Lines are probably pieces of fishing lines or ropes from local shipping and fishery activities. Whereas foam and other irregular shape fragments can origin from packaging materials and plastic containers. Microplastics were classified into four categories according to their size: 112e300 mm, 300e500 mm, 500 mme1.6 mm, and 1.6e5 mm. Microplastics between 500 mm and 1.6 mm were the most abundant from most sites, accounting for 30e57% of the total microplastics (Fig. 4). Many previous research investigated the size distribution of microplastics (Browne et al., 2010; Eriksen et al., 2013a; Sadri and Thompson, 2014; Zhao et al., 2014). Unfortunately, direct comparison was impossible as different size categories were used by different researchers. However, the distribution of plastic debris generally skews towards medium and small sizes, probably because the degradation of one large plastic
debris can generate several pieces of small fragments. Whereas smaller microplastics may be less persistent than the larger ones due to a larger surface area. Therefore, the size distribution of microplastics depends on both their generation and degradation rates. The fate and behavior of different size microplastics need to be further investigated. The shapes of microplastics from different size categories were presented in Fig. 5. Lines were larger than 500 mm, foams were larger than 1.6 mm, whereas fragment and sheet were found in all size categories. This pattern may be related to their origins. Foams were all cells from the disintegration of Styrofoam based on their shapes and FT-IR spectra. Styrofoam is made from closed-cell extruded polystyrene foam and extensively used in thermal insulation and craft applications. Only observed in 1.6e5 mm category suggesting that the further degradation of individual cell of extruded polystyrene foam is difficult. 3.3. Comparison with data from other areas The abundance of microplastics from the TGR was compared with the data from other areas worldwide (Table 2). The average
Fig. 5. Composition of microplastics of different morphology in each size classification category (Sampling sites are ordered in decreasing distance from the dam).
122
K. Zhang et al. / Environmental Pollution 204 (2015) 117e123
Table 2 Comparison of microplastic abundance in the surface water samples from the Three Gorges Reservoir with data from other areas. Study area
Size class (mm)
Microplastic abundance (103 counts km Range
North Atlantic Subtropical Gyre North Western Mediterranean Sea South Pacific Subtropical Gyre Lake Superior Lake Huron Lake Erie Lake Hovsgol, Mongolia North Shore Channel, Chicago
>0.333 0.333e5.0 >0.333 >0.333 >0.333 >0.333 >0.333 >0.333
Estuary rivers in the Chesapeake Bay Three Gorges Reservoir
0.333e5.0 0.112e5.0
e 5.5e297.9 3407.7e13,617.5 192.5e11,889.7
4. Conclusions High abundance of microplastics were observed in samples collected from the TGR. The types of microplastics were identified to be PE, PP, and PS. The abundance of microplastics showed an increasing trend as moving towards the dam. Tributaries contributed significant amount of microplastics to the main stream, and the abundance of microplastics found in the tributary estuaries might be related to the human activities within the river watershed. The morphology of the microplastics suggests their origin from the degradation of plastic products and the size distribution showed the dominance of medium size microplastics. Compared to other marine and freshwater habitats, the abundance of microplastics was one to three orders of magnitudes higher in the TGR but comparable to those observed from sites under heavy human influence. Our work for the first time demonstrates that reservoirs can potentially be important areas for the accumulation of microplastics. Additional works are needed to understand the fate and behavior and to assess the ecological risks of microplastics in reservoirs. Acknowledgment This work was funded by National Critical Project for Science and Technology on Water Pollution Prevention and Control (2012ZX07104-002-005, 2012ZX07101-007-002) and State Key Laboratory of Freshwater Ecology and Biotechnology (2014FBZ03). Dr. Chenxi Wu thanks the support from the Youth Innovation Promotion Association of the Chinese Academy of Sciences.
)
References
Mean
0e580 0e892 0e396.3 1.3e12.6 0e6.5 4.7e446.3 1.0e44.4
abundance of microplastics from the TGR is one to three orders of magnitudes higher than those observed from other areas, except samples from the North Shore Channel site downstream a wastewater treatment plant (WWTP) in Chicago (McCormick et al., 2014). Effluent from WWTPs was found to be an important point source of microplastics (Browne et al., 2011; Dubaish and Liebezeit, 2013). But in the TGR, microplastics are more likely from nonpoint source and are carried to the reservoirs by surface runoff as most areas within the Three Gorges region are underdeveloped. For small towns, no WWTP is currently available and the recycle and disposal of garbage are not well managed. More importantly, large amount of microplastics and large plastic debris were transported to the TGR from upstream and got accumulated behind the dam as floating microplastics cannot pass the dam. Microplastics can be generated from large plastics on land and then be transported to rivers, or be produced after large plastics are transported to the rivers. The degradation of plastics and formation of microplastics in both terrestrial and freshwater environments need to be further characterized.
2
e 116 26.9 5.4 2.8 105.5 20.3 730.3 (upstream) 6698.3 (downstream) e 8465.6 (mainstream) 3807.4 (tributary)
Law et al., 2010 Collignon et al., 2012 Eriksen et al., 2013a Eriksen et al., 2013b Eriksen et al., 2013b Eriksen et al., 2013b Free et al., 2014 McCormick et al., 2014 Yonkos et al., 2014 This work
References Browne, M.A., Crump, P., Niven, S.J., Teuten, E., Tonkin, A., Galloway, T., Thompson, R., 2011. Accumulation of microplastic on shorelines woldwide: sources and sinks. Environ. Sci. Technol. 45, 9175e9179. Browne, M.A., Galloway, T.S., Thompson, R.C., 2010. Spatial patterns of plastic debris along estuarine shorelines. Environ. Sci. Technol. 44, 3404e3409. Carpenter, E.J., Smith, K.L., 1972. Plastics on the Sargasso Sea surface. Science 175, 1240e1241. Collignon, A., Hecq, J.-H., Glagani, F., Voisin, P., Collard, F., Goffart, A., 2012. Neustonic microplastic and zooplankton in the North Western Mediterranean Sea. Mar. Pollut. Bull. 64, 861e864. Dekiff, J.H., Remy, D., Klasmeier, J., Fries, E., 2014. Occurrence and spatial distribution of microplastics in sediments from Norderney. Environ. Pollut. 186, 248e256. Dubaish, F., Liebezeit, G., 2013. Suspended microplastics and black carbon particles in the Jade System, Southern North Sea. Water Air Soil Pollut. 224, 1e8. Eriksen, M., Mason, S., Wilson, S., Box, C., Zellers, A., Edwards, W., Farley, H., Amato, S., 2013a. Microplastic pollution in the surface waters of the Laurentian Great Lakes. Mar. Pollut. Bull. 77, 177e182. Eriksen, M., Maximenko, N., Thiel, M., Cummins, A., Lattin, G., Wilson, S., Hafner, J., Zellers, A., Rifman, S., 2013b. Plastic pollution in the South Pacific Subtropical Gyre. Mar. Pollut. Bull. 68, 71e76. Fendall, L.S., Sewell, M.A., 2009. Contributing to marine pollution by washing your face: microplastics in facial cleansers. Mar. Pollut. Bull. 58, 1225e1228. Foekema, E.M., De Gruijter, C., Mergia, M.T., van Franeker, J.A., Murk, A.J., Koelmans, A.A., 2013. Plastic in North Sea fish. Environ. Sci. Technol. 47, 8818e8824. Free, C.M., Jensen, O.P., Mason, S.A., Eriksen, M., Williamson, N.J., Boldgiv, B., 2014. High-levels of microplastic pollution in a large, remote, Mountain Lake. Mar. Pollut. Bull. 85, 156e163. Gasperi, J., Dris, R., Bonin, T., Rocher, V., Tassin, B., 2014. Assessment of floating plastic debris in surface water along the Seine River. Environ. Pollut. 195, 163e166. Hidalgo-Ruz, V., Gutow, L., Thompson, R.C., Thiel, M., 2012. Microplastics in the marine environment: a review of the methods used for identification and quantification. Environ. Sci. Technol. 46, 3060e3075. Huang, Z., Li, Y., Chen, Y., Li, J., Xin, Z., Ye, M., Li, J., Lv, P., Li, C., Zhou, X., 2006. Water Quality Protection and Water Environmental Carrying Capacity Calculation for Three Gorges Reservoir. In: Series of Ecological and Environmental Protection for Three Gorges Project. China Water Power Press. Ivar do Sul, J.A., Costa, M.F., 2014. The present and future of microplastic pollution in the marine environment. Environ. Pollut. 185, 352e364. t-Ferguson, S., Maximenko, N.A., Proskurowski, G., Peacock, E.E., Law, K.L., More Hafner, J., Reddy, C.M., 2010. Plastic accumulation in the North Atlantic Subtropical Gyre. Science 329, 1185e1188. McCormick, A., Hoellein, T.J., Mason, S.A., Schluep, J., Kelly, J.J., 2014. Microplastic is an abundant and distinct microbial habitat in an urban river. Environ. Sci. Technol. 48, 11863e11871. Ning, P., Zhang, Z., 2010. On formation and features of floating garbage on water surface in Three Gorges area. J. Chongqing Three Gorges Univ. 26, 1e4. O'Brine, T., Thompson, R.C., 2010. Degradation of plastic carrier bags in the marine environment. Mar. Pollut. Bull. 60, 2279e2283. Rech, S., Macaya-Caquilp an, V., Pantoja, J.F., Rivadeneira, M.M., Jofre Madariaga, D., Thiel, M., 2014. Rivers as a source of marine litter e a study from the SE Pacific. Mar. Pollut. Bull. 82, 66e75. Rochman, C.M., Browne, M.A., Halpern, B.S., Hentschel, B.T., Hoh, E., Karapanagioti, H.K., Rios-Mendoza, L.M., Takada, H., Teh, S., Thompson, R.C., 2013. Policy: classify plastic waste as hazardous. Nature 494, 169e171. Sadri, S.S., Thompson, R.C., 2014. On the quantity and composition of floating plastic debris entering and leaving the Tamar Estuary, Southwest England. Mar. Pollut. Bull. 81, 55e60. €l€ Seta a, O., Fleming-Lehtinen, V., Lehtiniemi, M., 2014. Ingestion and transfer of
K. Zhang et al. / Environmental Pollution 204 (2015) 117e123 microplastics in the planktonic food web. Environ. Pollut. 185, 77e83. Singh, B., Sharma, N., 2008. Mechanistic implications of plastic degradation. Polym. Degrad. Stab. 93, 561e584. Thompson, R.C., Moore, C.J., vom Saal, F.S., Swan, S.H., 2009. Plastics, the environment and human health: current consensus and future trends. Philos. Trans. R. Soc. B Biol. Sci. 364, 2153e2166. Thompson, R.C., Olsen, Y., Mitchell, R.P., Davis, A., Rowland, S.J., John, A.W.G., McGonigle, D., Russell, A.E., 2004. Lost at sea: where is all the plastic? Science 304, 838. Van Cauwenberghe, L., Vanreusel, A., Mees, J., Janssen, C.R., 2013. Microplastic pollution in deep-sea sediments. Environ. Pollut. 182, 495e499. € hler, A., 2012. Uptake and effects of microvon Moos, N., Burkhardt-Holm, P., Ko plastics on cells and tissue of the Blue Mussel Mytilus edulis L. after an experimental exposure. Environ. Sci. Technol. 46, 11327e11335. ~ oz, D., Brennholt, N., Bourrain, X., Buchinger, S., Wagner, M., Scherer, C., Alvarez-Mun Fries, E., Grosbois, C., Klasmeier, J., Marti, T., Rodriguez-Mozaz, S., Urbatzka, R.,
123
Vethaak, A., Winther-Nielsen, M., Reifferscheid, G., 2014. Microplastics in freshwater ecosystems: what we know and what we need to know. Environ. Sci. Eur. 26, 1e9. Woodall, L.C., Sanchez-Vidal, A., Canals, M., Paterson, G.L.J., Coppock, R., Sleight, V., Calafat, A., Rogers, A.D., Narayanaswamy, B.E., Thompson, R.C., 2014. The deep sea is a major sink for microplastic debris. R. Soc. Open Sci. 1, 140317. Yonkos, L.T., Friedel, E.A., Perez-Reyes, A.C., Ghosal, S., Arthur, C.D., 2014. Microplastics in four estuarine rivers in the Chesapeake Bay, U.S.A. Environ. Sci. Technol. 48, 14195e14202. Zbyszewski, M., Corcoran, P.L., Hockin, A., 2014. Comparison of the distribution and degradation of plastic debris along shorelines of the Great Lakes, North America. J. Gt. Lakes. Res. 40, 288e299. Zhao, S.Y., Zhu, L.X., Wang, T., Li, D.J., 2014. Suspended microplastics in the surface water of the Yangtze Estuary System, China: first observations on occurrence, distribution. Mar. Pollut. Bull. 86, 562e568.
