Microplastics Pollution on Soft Shores in Hong Kong

This document is downloaded from Outstanding Academic Papers by Students

(OAPS), Run Run Shaw Library, City University of Hong Kong.

Title Microplastics pollution on soft shores in Hong Kong

Author(s) Ng, Wing Yi (伍詠怡)

Ng, W. Y. (2016). Microplastics pollution on soft shores in Hong Kong Citation (Outstanding Academic Papers by Students (OAPS), City University of Hong Kong).

Issue Date 2016

URL http://dspace.cityu.edu.hk/handle/2031/85

This work is protected by copyright. Reproduction or distribution of Rights the work in any format is prohibited without written permission of the copyright owner. Access is unrestricted.

CITY UNIVERSITY OF HONG KONG Department of Biology and Chemistry

BSc (Hons) in Environmental Science and Management Project Report

Microplastics Pollution on Soft Shores in Hong Kong

NG Wing Yi

October 2016

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This document is downloaded from Outstanding Academic Papers by Students (OAPS), Run Run Shaw Library, City University of Hong Kong Table of content

1. Abstract ...... 5 2. Introduction ...... 6 2.1 Background of Microplastics Pollution...... 6 2.1.1 History of Microplastics ...... 6 2.1.2 Sources of Microplastics ...... 7 2.1.3 Microplastics Pollution in Hong Kong ...... 8 2.2 Previous Researches on Microplastics Pollution ...... 9 2.2.1 Previous Researches in Foreign Countries ...... 9 2.2.2 Previous Researches in Hong Kong ...... 10 2.3 Aims and Hypotheses ...... 11 3. Sampling and Analytical Assessment of Microplastics ...... 13 3.1 Collection Site ...... 13 3.2 Sediment Sampling ...... 15 3.3 Extraction of Microplastics from Sediment Samples ...... 17 3.3.1 Heavy Liquid for Density Separation ...... 17 3.3.2 Preparation of Zinc Chloride Solution ...... 18 3.3.4 Organic Matter Digestion ...... 19 3.4 Identification of Microplastics ...... 22 3.4.1 Microscopic Examination ...... 22 3.4.2 Fourier-transform infrared (FTIR) Spectroscopy ...... 23 3.5 Particle Size ...... 25 3.6 Total Organic Carbon (TOC) Analysis ...... 26 4. Results ...... 28 4.1 Microplastics Abundance ...... 28 4.2 Composition of Microplastics ...... 30 4.3 Chemical Nature of Microplastics ...... 35 4.4 Particle Size and Total Organic Carbon ...... 40 5. Discussion...... 42 5.1 Comparison of Microplastics Pollution between Western and Eastern Shores . 42 5.3 Comparisons with Previous Studies ...... 50 5.3.1 Comparisons with Local Beach Surveys of Microplastic Pollution ...... 50 5.3.2 Comparisons with Other Countries of Microplastics Pollution ...... 52 5.4 Errors, Limitation and Improvements...... 55 6. Conclusion ...... 58 7. Acknowledgement ...... 59 8. References ...... 60

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This document is downloaded from Outstanding Academic Papers by Students (OAPS), Run Run Shaw Library, City University of Hong Kong 9. List of Figures ...... 74 10. List of Tables ...... 76 11. Appendix ...... 77 11.1 Microplastics Data Sheet ...... 77

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This document is downloaded from Outstanding Academic Papers by Students (OAPS), Run Run Shaw Library, City University of Hong Kong 1. Abstract

Microplastics (< 5 mm) in sediments from eastern waters and western waters in Hong Kong

were investigated to evaluate the significance of the Pearl River in microplastic pollution.

Sediments and microplastics were collected from four sandy beaches in Hong Kong. They

were Luk Keng Tsuen (LKT) and Sha Lo Wan (SLW) in the western part of Hong Kong in

close proximity to the Pearl River estuary and Sha Tsui (ST) and To Tei Wan (TTW) in the

eastern waters. Microplastics were extracted from sediments by density separation using zinc

chloride solution (d > 1.6 g cm−3). 47.8 ± 12.1 particles per kilogram in ST, 5.0 ± 1.3 particles

per kilogram in TTW, 29.0 ± 17.7 particles per kilogram in LKT and 8.5 ± 0.5 particles per

kilogram in SLW were found under an optical microscope, respectively.

These microplastics were identified by attenuated total reflectance Fourier-transform infrared

(ATR-FTIR) spectroscopy. Polyethylene, nylon66, polyester (alkyd resin), polystyrene,

polypropylene and poly (methyl methacrylate) were characterized to be major types of the

microplastics. Results reported herein showed that the amount of microplastics at ST were

significantly higher than at TTW and SLW. The results also indicated that instead of the Pearl

River, local sources, which were mainly from various anthropogenic activities, were the major

contributors of microplastics pollution. The results, however should interpret with caution due

to limited number of sampling sites. A more comprehensive study involving more beaches is

recommended if time is allowed.

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This document is downloaded from Outstanding Academic Papers by Students (OAPS), Run Run Shaw Library, City University of Hong Kong 2. Introduction

2.1 Background of Microplastics Pollution

2.1.1 History of Microplastics

For the last century, plastics have been an indispensable element for innovation and have

contributed to the development and progress of the world. Being a lightweight, durable, strong

and excellent thermal and electrical insulator, plastics are ideally suited for a variety of

applications. In fact, the worldwide production of plastic has increased from 1.5 million tons

in 1950 to 311 million tons in 2014 (PlasticsEurope, 2015). The extensive use of plastic has

caused a dramatic increase in the plastic waste which becomes a global environmental issue.

Ingestion of plastics by birds (Cadee, 2002; Mallory, 2008) and turtles (Bugoni & Krause, 2001;

Tomas and Guitart, 2002; Mascarenhas ., 2004) is extensively recorded worldwide and more

than 40% of marine bird species are found to ingest plastics (Rios & Moore, 2007). A particular

concern in recent years is the occurrence of plastic debris which cannot be seen by naked eyes

known as microplastics in the oceans. At present, the definition of microplastics is still under

debate. In 2008, the National Oceanographic and Atmospheric Agency (NOAA) of the US

established a broader working definition to include all plastic particles less than 5mm in

diameter (NOAA, 2008). The larger plastics (1 ‒ 5 mm) are called mesoplastics whereas those

between 1 µm – 1 mm are known as nanoplastics. The most common plastics that can be found

in the environment include Polyethylene (PE), Polypropylene (PP), Polystyrene (PS), Poly

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This document is downloaded from Outstanding Academic Papers by Students (OAPS), Run Run Shaw Library, City University of Hong Kong (ethylene terephthalate) (PET) and Poly (vinyl chloride) (PVC) (Dris et al., 2015).

2.1.2 Sources of Microplastics

Microplastics are originated from a wide variety of sources and can simply be classified into

primary and secondary sources. The primary sources refer to the direct discharge of small

plastics like pellets or powders while the secondary sources mean the fragmentation or

degradation of large plastics resulted from UV radiation, mechanical abrasion, biological

degradation and disintegration (Fig.1) (Andrady, 2011; Cole et al., 2011; Hidalgo-Ruz et al.,

2012). One of the common primary sources of microplastics is the plastic particles which are

also known as microbeads used as abrasive in cosmetic or personal care products. Since these

particles are too small, the waste treatment plants are not able to remove them effectively and

hence they are discharged and accumulating in the ocean (Zitko & Hanlon, 1991; Gregory,

1996). About 20% of the ocean microplastics came from fishing industry. Nowadays plastic

gears used by global fishing fleets are mostly made of PE, PP and nylon (Watson et al., 2006).

However, some of the gears are lost or discarded at sea during use and hence increased the

marine plastic debris. The aquaculture also contributes to the majority of plastic debris in the

oceans (Hinojosa & Thiel, 2009). Another source that cannot be ignored is the atmospheric

inputs i.e. plastic fragments which are transported by wind (Dris et al., 2015). Other marine-

based sources including extensive fishing, recreational and maritime uses of the ocean increase

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This document is downloaded from Outstanding Academic Papers by Students (OAPS), Run Run Shaw Library, City University of Hong Kong the influx of plastics debris into the oceans (Ribic et al., 2010).

2.1.3 Microplastics Pollution in Hong Kong

In fact, Hong Kong is facing the same environmental threat which comes from local and

extraneous pollutions. The amount of plastic wastes generated in Hong Kong has increased

from 1709 tons in 2006 to 2015 tons in 2014. The most common plastic wastes are plastic bags,

polystyrene dining wares and food packaging (HKEPD, 2015). They could be some of the local

sources of microplastic pollution because these wastes can be dumped into the ocean directly

and indirectly. The microplastics then are produced by mechanical, microbial or UV

degradation and transported by wind. Microplastics may also come from the Pearl River Delta

(PRD) where nine densely populated cities are located. They are Guangzhou, Foshan,

Zhongshan, Zhuhai, Dongguan, Shenzhen, Huizhou, Jiangmen and Zhaoqing. The total

population of these 9 cities is about 60 million. The PRD becomes a potential contributor of

plastics wastes in Hong Kong due to the mismanagement of dumping sites in China such as

illegal landfill. In July 2016, a large amount of trash was found in Hong Kong beaches and

most of them were from mainland. It is believed that the trash was come from the Pearl River

in mid-June due to severe rain storms and floods in provinces along the river. Owing to the

prevalent southwest wind, the trash which was supposed to end up in the South China Sea was

blown onto Hong Kong shores. (Horwitz, 2016).

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This document is downloaded from Outstanding Academic Papers by Students (OAPS), Run Run Shaw Library, City University of Hong Kong 2.2 Previous Researches on Microplastics Pollution

2.2.1 Previous Researches in Foreign Countries

A number of studies have revealed that microplastics pollution has become a global issue. The

first report of microplastics contamination in 2004 indicated that the breakdown of large

plastics debris result in the accumulation of smaller fragments but the impacts on marine

organisms were still unknown at that time (Thompson et al., 2004). This report had drawn the

attention of the scientific community. In the next few years, microplastics pollution was

reported on a global scale from the poles to equator (Barnes et al., 2009; Browne et al., 2011;

Hidalgo-Ruz et al., 2012) and microplastics were found in various habitats including the ocean

surface waters (Law et al. 2010; Collignon et al., 2012; Goldstein et al. 2012; Ivar do Sul et

al., 2013), the deep sea (Van Cauwenberghe et al., 2013; Woodall et al., 2014) , estuaries (Sadri

& Thompson 2014), freshwater shorelines (Imhof et al., 2013), subtidal sediments (Browne et

al., 2011) and lakes (Eriksen et al., 2013). Another report has shown that the Arctic Sea ice has

been contaminated by high concentration of microplastics which will be released back to open

water due to global warming (Obbard ., 2014).

Apart from contaminating marine and freshwater environments, polystyrene microbeads have

toxic effects at tissue, cellular and molecular levels in marine mussels (Pont et al., 2016). Some

studies have reviewed the physical impacts of microplastics on marine organisms. The

bioavailability of microplastics depends on size, density, color and abundance and they are non-

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This document is downloaded from Outstanding Academic Papers by Students (OAPS), Run Run Shaw Library, City University of Hong Kong biodegradable. After ingestion, microplastics would accumulate in the body of zooplankton

and fish and result in bioaccumulation and bio-magnification (Wright et al., 2013).

Since microplastic pollution is an emerging global environmental issue, there is still no

standard method for extracting microplastics from sediments and animals. The most commonly

used method is density separation (Hidalgo-Ruz et al., 2012) which depends on the density of

concentrated salt solution to separate sediment from microplastics. Another method was using

the principle of elutriation for sediments (Claessens ., 2013; Zhu, 2015; Kedzierski ., 2016).

Elutriation was a process that using an upward stream of gas or liquid to separates lighter

particles from heavier ones and a PVC column was usually used for microplastics separation

(Claessens ., 2013). However, the set-up of this method could be very complicated and there

was potential contamination by PVC. Due to these reasons, using concentrated salt solution for

microplastics separation was still commonly used.

2.2.2 Previous Researches in Hong Kong

Very few studies have reported on the microplastics pollution in Hong Kong. One study

suggested that Hong Kong has a great potential to become a hotspot of microplastic pollution

due to its geographical location (Fok et al., 2015). The study has investigated seven simplified

water control zones which included 25 beaches. The result has shown that some factors could

influence the microplastics concentration. For example, the frequency of beach maintenance

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This document is downloaded from Outstanding Academic Papers by Students (OAPS), Run Run Shaw Library, City University of Hong Kong and the prevailing wind direction. It has also indicated that the abundance of microplastics in

the west coast was much greater than that of the east coast, suggesting that the Pearl River

plays a critical role in discharging microplastics to Hong Kong.

Other researches have focused on the microbeads which often found in personal care and

cosmetic products (PCCPs) (Chang, 2015; Napper ., 2015; Cheung & Fok, 2016). In Hong

Kong, Cheung and Fok (2016) estimated that there were 342.2 billion microbeads with size

around 0.3 to 1 mm were discharged to the sea from untreated sewage or wastewater treatment

plants. Nowadays, the plastic microbeads are in widespread use in personal care products.

Unfortunately, they cannot be removed by preliminary wastewater treatment plant. The study

has suggested that legislative actions are required to restrict the release of microplastics due to

its unknown effects and persistence in the environment.

2.3 Aims and Hypotheses

The aim of this study is to compare the microplastic pollution on four selected sandy shores in

western and eastern waters of Hong Kong. Since Hong Kong is vulnerable to microplastic

pollution from the Pearl River, two sandy shores which are in close proximity to the Pearl River

estuary were sampled while the other two shores in the eastern waters as the controls. It is

hypothesized that shores located in western waters are more polluted by microplastics than

those in the eastern waters.

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This document is downloaded from Outstanding Academic Papers by Students (OAPS), Run Run Shaw Library, City University of Hong Kong This study was supported by a study conducted by Cheung and Fok (2015). Their result showed

that the microplastics abundance in western coast of Hong Kong waters was greater than that

in eastern coast. However, there were several limitations in their study. First, they used sea

water to extract the microplastics but the sea water densities were varied in these two regions.

The western area was close to Pearl River, the water salinity was lower than the eastern area

which the coastal areas were connected to South China Sea. In order words, the sea water

densities in eastern and western waters were not the same. Therefore, there was inconsistency

during microplastics extraction. Second, their research underestimated the microplastics

pollution in Hong Kong because some of the microplastics with higher density such as

polyvinyl chloride (PVC) (d = 1.16-1.30 g cm−3) could not be extracted by sea water (d = 1.02

g cm−3).

In order to have a comprehensive analysis, zinc chloride solution was used in density separation.

This could ensure the heavier microplastics were also extracted.

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This document is downloaded from Outstanding Academic Papers by Students (OAPS), Run Run Shaw Library, City University of Hong Kong 3. Sampling and Analytical Assessment of Microplastics

3.1 Collection Site

Sediments and microplastics were collected from four sandy beaches in Hong Kong, namely

Sha Lo Wan (SLW), Luk Keng Village or Luk Keng Tsuen (LKT), To Tei Wan (TTW), and Sha

Tsui (ST). SLW and LKT are located in the western area of Hong Kong which are closed to the

Pearl River while TTW and ST are located in the eastern part of Hong Kong.

As shown in Figure 1, SLW (22.291486, 113.901947) is located in the northwest of Lantau

Island and on the south of Hong Kong International Airport. LKT (22.333389, 114.023036) is

located at the Yam O peninsula on Lantau Island. TTW (22.227946, 114.234445) is a squatter

village on Hong Kong Island and lies to the west of Shek O, Hong Kong Island. ST

(22.359637,114.265488) is a sheltered beach located at Pak Sha Wan, Sai Kung.

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This document is downloaded from Outstanding Academic Papers by Students (OAPS), Run Run Shaw Library, City University of Hong Kong Fig 1. Map showing the collection sites.

(Retrieved from Google Map)

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This document is downloaded from Outstanding Academic Papers by Students (OAPS), Run Run Shaw Library, City University of Hong Kong 3.2 Sediment Sampling

To prevent contamination, the sampling tools (e.g. stainless steel shovel and cotton bags) used

were non-plastic. The sediments were collected at the strandline between June and August 2016.

A 30 m long transect line was set up along the strandline and three sediments samples were

collected (Fig. 2). Three quadrats with an area of 50 cm × 50 cm each were randomly placed

along the transect line. Each quadrat was divided equally into four squares and sediments were

collected from two of them to a depth of 3 cm (Fig. 3). For the analysis of particle size

distribution and total organic content, three more samples were randomly collected along the

same transect line. All samples were transported to the laboratory immediately and air dried at

room temperature.

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This document is downloaded from Outstanding Academic Papers by Students (OAPS), Run Run Shaw Library, City University of Hong Kong Fig 2. A 30 m transect line was set up

Fig 3. Two quadrats were randomly selected.

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This document is downloaded from Outstanding Academic Papers by Students (OAPS), Run Run Shaw Library, City University of Hong Kong 3.3 Extraction of Microplastics from Sediment Samples

3.3.1 Heavy Liquid for Density Separation

Microplastics were extracted by density separation. The densities of common consumer-plastic

ranged from 0.8 to 1.4 g cm−3 which included heavier polymers such as PET and PVC. In order

to extract the microplastics from sediments, heavy liquid such as high density saturated salt

solutions could be employed for floating of microplastics on the surface of the solution

(Bergmann et al., 2015). Saturated sodium chloride solution with a density of about 1.2 g cm−3

was often used in the extraction of microplastics (Thompson et al., 2004; Ng & Obbard, 2006;

Browne et al., 2010; Browne et al., 2011; Claessens et al., 2011). However, microplastics with

a density that higher than the sodium chloride solution (i.e. microplastic density ≧ 1.2 g cm−3)

could not be extracted. More importantly, these types of high density polymer (e.g. PVC, d =

1.4 g cm−3) were produced in huge quantities (PlasticsEurope, 2015) and commonly found in

the aquatic environment (Andrady & Neal, 2009; Andrady, 2011; Brandon et al., 2016).

Therefore, density of heavy liquid itself should be taken into consideration. In fact sodium

chloride solution could be replaced by zinc chloride solution (d = 1.5 – 1.7 g cm−3) (Imhof et

al., 2012; Liebezeit & Dubaish, 2012), sodium iodine solution (d = 1.8 g cm−3) (Nuelle et al.,

2014) or lithium metatungstate (d = 1.6 g cm−3 ) (Sullivan & Callender, 2015). Considering the

cost, zinc chloride would be the best choice among them.

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This document is downloaded from Outstanding Academic Papers by Students (OAPS), Run Run Shaw Library, City University of Hong Kong 3.3.2 Preparation of Zinc Chloride Solution

Ultrapure water (18.2 MΩ·cm, Millipore) was used throughout the experiment. 400 g of zinc

chloride (purity ≧98%)) was dissolved in 300 mL water. 4 g of critic acid (purity ≧99.5%)

was added to promote solubility. The solution was sonicated for 20 min to ensure that it was

saturated. The solution was subsequently filtered under vacuum to remove any remaining

precipitates. This procedure yielded a heavy zinc chloride solution that possessed a density >

1.6 g cm−3. After the density separation process, every batch of zinc chloride was recovered for

further reuse.

3.3.3 Density Separation

In this study, microplastics were defined as < 5 mm. Therefore, 2000 g of dried sediment from

one sample was weighted and sieved over a 5 mm mesh in order to remove larger particles.

The fraction greater than 5 mm was sorted and discarded in this study. After sieving, the

microplastics were extracted through density separation in zinc chloride solution in a 5 L glass

bottle. The sediments with zinc chloride solution were stirred for five minutes to ensure the

sediments in the lower part could be immersed in the solution. After it was homogenized, the

container was covered by aluminum foil to prevent contamination and the sediment was

allowed to settle overnight. The particles with lower density than the zinc chloride solution

were floated on the solution surface and collected by following procedure. A glass tube was

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This document is downloaded from Outstanding Academic Papers by Students (OAPS), Run Run Shaw Library, City University of Hong Kong inserted in the filtering flask which connected to a vacuum pump so that reduced pressure was

generated in the flask. The glass tube was placed on the surface of the zinc chloride solution

and the floating materials were then transferred into the filtering flask. These materials were

subsequently collected on a filter paper (Whatman, pore size = 11 µm) using the Nalgene

filtration system. They were washed by 10 mL water to remove excess zinc chloride. Any

visible material > 5 mm in any dimension was removed by metal forceps. To investigate the

potential contamination during the experimental process, a procedure control was set up. 500

mL zinc chloride solution was prepared in a 600 mL beaker and the same procedure for density

separation was carried out (without sediment). This control allowed the determination of

airborne contamination from the atmosphere. Any particles collected on a filter paper were

examined later.

3.3.4 Organic Matter Digestion

The extracted materials left on the filter paper were transferred into a glass bottle and treated

with 10 mL 30% hydrogen peroxide (purity ≥ 99.9%). The glass bottle was sealed by a metal

cap to prevent decomposition of hydrogen peroxide. The glass bottle was placed at room

temperature for 72 hours to allow completion of digestion.

After treated with hydrogen peroxide, the materials were collected again on a filter paper and

rinsed by 10 mL water to remove hydrogen peroxide. It was noted that there were some

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This document is downloaded from Outstanding Academic Papers by Students (OAPS), Run Run Shaw Library, City University of Hong Kong remaining substances that apparently not to be plastics (e.g. wood chips, charcoal, and shell).

They were therefore carefully distinguished by either naked eye or examined under a

microscope. The materials remained on the filter paper were then transferred carefully to a

glass petri dish and dried in oven at 80°C for 24 hours (Fig. 4).

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This document is downloaded from Outstanding Academic Papers by Students (OAPS), Run Run Shaw Library, City University of Hong Kong Fig 4. The materials remained on the filter paper and the procedural control after oven-dried for 24 hours.

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This document is downloaded from Outstanding Academic Papers by Students (OAPS), Run Run Shaw Library, City University of Hong Kong 3.4 Identification of Microplastics

3.4.1 Microscopic Examination

The dried filter papers containing suspicious microplastics were inspected under an optical

microscope. Some selection criteria were established following Norén (2007) to lower the

probability of misidentification. The criteria were: (1) the cellular or organic structure should

be invisible in the plastic or fiber, (2) the entire fibers should be equally thick, (3) particles

should display a clear and homogeneous color if they are colored and, (4) particles are not

shinny. According to Marine & Environmental Research Institute (2015), the general

characteristics that are used for stereomicroscopic identification are shape and color (Appendix

I).

The microplastics on each filter were weighted (to the nearest 0.001 g), counted, classified and

collected into a small glass bottle for further characterization by FTIR spectroscopy. Some

particles could not be classified even under the highest magnification available (4×). They may

be algae, salt crystals, sand, animal parts and shell. Thus they were classified as potential

microplastics and collected in a separate glass bottle. In some cases, a large area of filter paper

was covered by aggregated debris loads and salt piles that increased the difficulty of

identification. They were removed aside carefully by forceps so that some of the microplastics

would not be neglected. Moreover, it should be noted that some microplastics would adhere to

the surface of debris, so that they need to be carefully examined.

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This document is downloaded from Outstanding Academic Papers by Students (OAPS), Run Run Shaw Library, City University of Hong Kong The abovementioned procedural control (section 3.2.3) was also inspected by stereomicroscopy.

The number of particles in the control was counted.

3.4.2 Fourier-transform infrared (FTIR) Spectroscopy

FTIR spectroscopy provides accurate identification of plastics polymer particles based on their

unique IR spectra (Thompson et al., 2004). Most of the common plastics presents characteristic

stretching bonds in both functional group regions (1500 - 1400 cm-1) and the fingerprint region

(400 - 1500 cm-1). By assessing their highly specific and distinct peak position of the particles,

the microplastics can be recognized.

The microplastics and potential microplastics obtained in section 3.3.1 were analyzed for their

chemical nature through ATR-FTIR spectroscopy (Thermo Scientific Nicolet iS50 with ATR

accessory (ZnSe)) with 8 co-added scans with a spectral resolution of 16 cm−1. The percentage

of reflectance was obtained as an IR spectrum and compared to the polymer library (Hummel

Polymer Library). The match factor greater than or equal to 70 was set to be confirmation for

corresponding polymer. However, the size of particle smaller than 0.1 mm could not be

chemically characterized due to the weak signal. The procedural protocols for the entire

microplastics analysis are summarized in Figure 5.

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This document is downloaded from Outstanding Academic Papers by Students (OAPS), Run Run Shaw Library, City University of Hong Kong Sediment sampling (3.2)

Air Dry

Density separation (3.3.3)

Floating solids Settled solids Used zinc chloride solution

Treated with Discarded hydrogen Recovered Peroxide (3.3.4)

Microscopic Exam FTIR Spectroscopy (3.4.1) (3.4.2)

Fig 5. Flow diagram for the analysis of microplastics. The number in the brackets refers to the number of this section.

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This document is downloaded from Outstanding Academic Papers by Students (OAPS), Run Run Shaw Library, City University of Hong Kong 3.5 Particle Size

The particle size distribution is important because it is used to predict some important physical

and chemical properties such as solubility, flowability and surface reaction (Retsch, 2009).

These properties could be factors that affect the microplastic distribution. The particle sizes of

four sandy shores were analyzed by dry sieving to determine the particle size range.

Six dry and clean 250-ml beakers were weighed to the nearest 0.001g. 200g of oven-dried

sediment was weighed and transferred to a stack of sieves. The sizes of the sieves were 2 mm,

1 mm, 500 µm, 250 µm, 125 µm and 63 µm. The sieves having larger pore sizes were placed

above the ones having smaller pore sizes, i.e., 2 mm sieve was on the top and 63 µm was on

the bottom. The sediment was poured into a stack of sieves and a brush was used to sweep the

particles for 5 minutes. After sweeping, the top sieve was removed from the stack without

losing any of the retained material. There were some materials stuck in the openings and they

were removed by using brush. The retained material continued to pass through the remaining

sieves. The materials which stayed on each of the sieves were transferred to a beaker and

weighed.

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This document is downloaded from Outstanding Academic Papers by Students (OAPS), Run Run Shaw Library, City University of Hong Kong 3.6 Total Organic Carbon (TOC) Analysis

All the oven-dried sediments from four different sandy shores were grind into fine powder

separately using mortar and pestle. Then the fine powders were screened over a 5 mm mesh.

After sieving, 0.5 g ± 0.05g of powders were weighed and transferred to a 250 mL dry, clean

conical flask. Three replicates were conducted for each sandy shore. Reagents required in this

analysis were: 0.167 M potassium dichromate, 0.5 M ferrous sulphate solution, concentrated

sulphuric acid, orthophosphoric acid, indicator solution and sulphuric acid with silver sulphate

solution.

Before analyzing the sample, standardization of ferrous sulphate solution was required. First,

5 ml of potassium dichromate solution was pipetted into a 250 ml conical flask. Then 10 ml of

concentrated sulphuric acid was added and the mixture was swirled thoroughly and allowed to

cool for 30 minutes in a fume hood. After that, 100 ml of double distilled deionized water was

added to the mixture followed by 5 ml of orthophosphoric acid and 0.5 ml of indicator. Next,

the mixture was titrated with ferrous sulphate solution from a burette with swirling and the

initial volume of ferrous sulphate solution was recorded. When the color of the solution was

changed from blue to green, an extra 0.25 ml of potassium dichromate solution was added and

the color was reversed to blue. Ferrous solution then was added drop by drop with continued

swirling until the color of the solution was changed from blue to green. The total volume of

ferrous sulphate used was recorded. Three replicates were carried out for standardization of

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This document is downloaded from Outstanding Academic Papers by Students (OAPS), Run Run Shaw Library, City University of Hong Kong ferrous sulphate solution. Analysis of organic matter was the same as standardization of ferrous

sulphate solution except that 10 ml sulphuric acid with silver sulphate was added after adding

5 ml of potassium dichromate solution into the conical flask instead of 10 ml concentrated

sulphuric acid.

3.7 Statistical Analysis

All statistical analyses were conducted with SigmaPlot, Windows Version 12.5. Differences in

the abundance of various types of microplastics such as pellet, fragment and line among four

sandy shores were analyzed using one-way analysis of variance (ANOVA) after normality

checked by Shapiro-Wilk test was passed. If significant differences were found among

treatment groups, pairwise multiple comparison procedures (Tukey method) at a significance

level of p≦0.05 were conducted.

Differences in fiber abundance among sites were analyzed by Kruskal-Wallis One Way

Analysis of Variance on Ranks as the homogeneity of variances determined by Brown-

Forsythe’s test failed. Tukey test was used for pairwise comparisons between the four sites.

Mann-Whitney Rank Sum Test was used to examine whether the particle size and total organic

carbon among four sites were significantly different

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This document is downloaded from Outstanding Academic Papers by Students (OAPS), Run Run Shaw Library, City University of Hong Kong 4. Results 4.1 Microplastics Abundance

The abundance of microplastics from the four sites and procedure controls are shown in Figure

6 and Table 1. The microplastic abundance at ST was significantly higher than that at TTW (F

= 10.285, p = 0.005) and SLW (F = 10.285, p = 0.009). In contrast, no significant difference

was observed between ST and LKT (F = 9.756, p = 0.218). In ST and LKT, the average

microplastic found was 47.8 ± 12.1 particles per kilogram and 29.0 ± 17.7 particles per

kilogram, respectively while the average abundance at TTW and SLW was 5.0 ± 1.3 particles

per kilogram and 8.5 ± 0.5 particles per kilogram, respectively.

The microplastics found in the procedure controls indicated that there was airborne

contamination (Table 1).

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This document is downloaded from Outstanding Academic Papers by Students (OAPS), Run Run Shaw Library, City University of Hong Kong ST: Sha Tsui TTW: To Tei Wan LKT:Luk Keng Tsuen SLW: Sha Lo Wan

Fig 6. Number of microplastics per kilogram sediments (mean ± S.D.) in four different sites

(n=3).

Sites ST TTW SLW LKT

Mean/500 mL ZnCl2 6.7 2.7 4.3 3.7

SD 4.0 2.1 1.5 2.1

Table 1. Number of microplastic per 500 mL of zinc chloride solution obtained from each of the procedure control (mean± S.D.).

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This document is downloaded from Outstanding Academic Papers by Students (OAPS), Run Run Shaw Library, City University of Hong Kong 4.2 Composition of Microplastics

Various shapes of microplastics were identified under a microscope. They were pellets, fibers,

fragments or lines and other shapes (Fig. 7).

Fragments were the most commonly found microplastics at all the sites especially ST and LKT

(Fig. 8). Pairwise multiple comparison procedures showed that there was significant difference

between ST and TTW (F = 6.081, p = 0.032) but not for other sites.

Moreover, significant inter-site difference of fibers was observed (H = 8.201, p = 0.042) among

4 sites (Fig. 9). Most of the fibers were found in ST while very few were found in LKT. When

comparing the mean number of fibers of these two sites, there were statistically significant

difference between ST and LKT (H = 8.201, p = 0.028).

Majority of lines were found at ST and LKT (Fig. 10). The mean number of lines found at these

sites were significant indistinguishable although lines found at ST was higher than the other

sites (F = 1.340, p = 0.328).

Pellets were the least common microplastics obtained from all the sites (Fig. 11) and no inter-

site differences in the number of pellets were found (F = 0.510, p = 0.686).

Particles of various colors were found with blue, green, white and transparent being the most

common.

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This document is downloaded from Outstanding Academic Papers by Students (OAPS), Run Run Shaw Library, City University of Hong Kong (a) (b)

Fig 7. Common type of microplastics found in the sediments: (a) Pellet; (b) fiber; (c) fragment; (d) Line

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This document is downloaded from Outstanding Academic Papers by Students (OAPS), Run Run Shaw Library, City University of Hong Kong ST: Sha Tsui TTW: To Tei Wan LKT: Luk Keng Tsuen SLW: Sha Lo Wan

Figure 8. Number of fragments per kilogram of sediments (mean ± S.D.) in four different sites

(n=3).

ST: Sha Tsui TTW: To Tei Wan LKT: Luk Keng Tsuen SLW: Sha Lo Wan

Figure 9. Number of fibers per kilogram of sediments in four different sites (n=3).

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This document is downloaded from Outstanding Academic Papers by Students (OAPS), Run Run Shaw Library, City University of Hong Kong ST: Sha Tsui TTW: To Tei Wan LKT: Luk Keng Tsuen SLW: Sha Lo Wan

Fig 10. Number of lines per kilogram of sediments (mean ± S.D.) in four different sites (n = 3).

ST: Sha Tsui TTW: To Tei Wan LKT: Luk Keng Tsuen SLW: Sha Lo Wan

Fig 11. Number of pellets per kilogram sediments (mean ± S.D.) in four different sites (n = 3).

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This document is downloaded from Outstanding Academic Papers by Students (OAPS), Run Run Shaw Library, City University of Hong Kong ST: Sha Tsui TTW: To Tei Wan LKT: Luk Keng Tsuen SLW: Sha Lo Wan

Fig 12 Number of microplastics with other shapes per kilogram of sediments (mean ± S.D.) in four different sites (n = 3).

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The microplastics found at ST, LKT and SLW were characterized by ATR-FTIR respectively

and there were no plastics for characterization in TTW. Majority of the microplastics were

identified as polyethylene (PE) and nylon66 at ST, polyester (alkyd resin) at LKT, polystyrene

(PS) and polyethylene (PE) at SLW. Also, a small proportion of polypropylene (PP) was found

at PSW and LKT, and poly (methyl methacrylate) (PMMA) at PSW (Fig. 13).

For ST, PE accounted for 35.2% of the 54 pieces of microplastics analyzed. The second largest

proportion was nylon 66 with 27.8%. The proportions of polyester (alkyd resin) (13.0%) and

PS (11.1%) were similar. Polymers accounted for less than 10% included 5.6% for PE, 3.7%

for PVC and ~1.6% for PMMA (Fig. 14).

For LKT, 21 pieces of microplastic were analyzed with 71.4% being polyester (alkyd resin),

and 9.5% each for nylon 66 and PP. The proportions of PE and PS were the same with 4.76%

each (Fig. 15).

Only three types of plastic were found at SLW with seven pieces of microplastic being studied.

The largest proportion was PS (57.1%) while the second largest one was PE (28.6%). The

remaining proportion was nylon 66 (14.3%) (Fig. 16)

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This document is downloaded from Outstanding Academic Papers by Students (OAPS), Run Run Shaw Library, City University of Hong Kong a) b) c)

100 Sample 1 - LKT Sample 2 - LKT 100 Sample 3 - LKT 95 100

95 85 95

75 90 90 Polystyrene Polyamide 6.6 (nylon 66) Polypropylene Match: 73.31 Match: 79.23 Match: 86.64 100 100

75 75

% Reflectance

50 25

25 25 0 0 0 3750 3000 2250 1500 750 3750 3000 2250 1500 750 3750 3000 2250 1500 750 1 1 1 Wavenumber (cm ) Wavenumber (cm ) Wavenumber (cm )

Fig 13a. The compositions of microplastics in sediments from the four sites. (a). PS at LKT with 73.31 match values; (b) Nylon 66 at LKT with 77.04 match values; (c) PP at LKT with 86.64 match values;

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100 Sample 6 - PSW 100.0 Sample 4 - LKT Sample 5 - LKT 100

90 97.5 95

95.0 90 70

Polyester (alkyd resin) Poly(methyl methacrylate) (PMMA - acrylic) Polyethlyene (low density) Match: 77.04 100 Match: 76.10 Match: 84.80 100 100

90 75 75 % Reflectance % Reflectance % Reflectance 80 50 50 70 25 60 25

0 50 3750 3000 2250 1500 750 3750 3000 2250 1500 750 3750 3000 2250 1500 750 Wavenumber (cm1) Wavenumber (cm1) Wavenumber (cm1)

Fig 13b. The compositions of microplastics in sediments from the four sites. (d) Polyester at LKT with 77.04 match values; (e) PMMA at LKT with 76.10 match values and (f) LDPE at PSW with 84.80 match values.

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This document is downloaded from Outstanding Academic Papers by Students (OAPS), Run Run Shaw Library, City University of Hong Kong PS: Polystyrene PP: Polypropylene PE: Polyethylene PVC: Poly (vinyl chloride) PMMA: poly (methyl methacrylate)

PVC PMMA 4% PP 2% 6%

Polyester(Alkyd resin) 13%

PE 36%

Nylon66 28%

PS 11%

Fig 14. Composition of microplastics at ST.

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PP 9%

PE PS 5% Nylon66 5% 10%

Fig 15. Composition of microplastics at LKT.

PS: Polystyrene Nylon 66 PE: Polyethylene 14% PE 29%

PS 57%

Fig 16. Composition of microplastics at SLW.

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This document is downloaded from Outstanding Academic Papers by Students (OAPS), Run Run Shaw Library, City University of Hong Kong 4.4 Particle Size and Total Organic Carbon

The particle size of the four sites was analyzed by dividing them into eastern area and southern

area and no statistical significant difference of particle size was found between east and west

(p = 0.667). The median particle size at ST was the largest (mostly over 2 mm) and was much

greater than the other three sites. The particle size at LKT was the smallest (Fig. 17).

For TOC, the percentage of carbon was the highest at ST, followed by SLW and LKT. TTW

has the lowest amount of carbon (Fig. 18). However, their differences were statistically

indistinguishable as tested by Mann-Whitney Rank Sum Test.

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This document is downloaded from Outstanding Academic Papers by Students (OAPS), Run Run Shaw Library, City University of Hong Kong

) Ф Phi (

Fig 17. Particle sizes at the four sites.

Fig 18. The percentage of total organic carbon at the four sites.

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This document is downloaded from Outstanding Academic Papers by Students (OAPS), Run Run Shaw Library, City University of Hong Kong 5. Discussion

5.1 Comparison of Microplastics Pollution between Western and Eastern Shores

This study revealed inter-site differences in microplastic abundance with ST being the most

polluted site but no regional difference between western and eastern shores was found. The

results are not in line with the hypothesis that the western shores were more polluted than the

eastern ones because of input from the Pearl River. The possible reason was the discharge of

microplastics from local sources. The location of ST is close to recreational areas such as Trio

Beach and the sea activity center. There is also an institute on the beach which organizes various

activities like canoeing and sailing. Therefore, these areas have high human activities which

would be possible pollution sources at ST. Similar results were reported upon by Stolte . (2015)

in which sediment samples were collected in Warnemünde, Germany during the peak month

vacation season in July when the microplastics abundance was the highest (532 fragments per

kg dry weight sediment). Another study has shown that less microplastics was found in the

mangroves with a lower level of human activities while those mangrove sites near to

recreational areas and fish farms like Changi were found to have the highest concentration of

microplastics (Nor &Obbard, 2014). Therefore, it is believed that localized pollution is a more

important source of microplastics.

Although human activity (e.g., littering) does not cause the generation of microplastic instantly,

the in situ weathering of mesoplastics and plastic debris on beaches may contribute to

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This document is downloaded from Outstanding Academic Papers by Students (OAPS), Run Run Shaw Library, City University of Hong Kong microplastics pollution (Gregory & Andrady , 2003). The specific heat capacity of sand (664

J/kg) is relatively low compared to the sea, so plastic debris on the beach is exposed to very

high temperature. Under this condition, the light-initiated oxidative degradation is speeded up

(Andrady, 2011). Consequently, the mesoplastics is broken down into microplastics and left on

the beach.

ST had the highest concentration of microplastics which may be due to physical abrasion

through wave action on mesoplastics and plastic debris on the beach (Colton et al., 1974;

Gregory, 1978; Andrady, 2003; Thompson et al., 2004). The median sediment particle size at

ST was larger than that at other sites and the wave action was also stronger. It is believed that

larger wave action may suggest a greater physical abrasive effect on mesoplastics that promotes

fragmentation.

The microplastics found at LKT and SLW was greater than those at TTW. The possible reason

may be the plastic debris came from the Pearl River. In mid-June, many provinces along the

Pearl River such as Guangdong, Guangxi, Hunan and Jiangxi had experienced severe rain

storm and flood (Knott & Wright, 2016). The heavy rainfall and flood caused much trash

entered the sea and reached Hong Kong by southwest monsoon wind and the sea currents (EPD,

2015). Based on visual observation, many refuses were found during sediment sampling at

LKT and some of them had Simplified Chinese on the package (Fig. 19). Also, there was high

concentration of microplastics found in the south of China (Peng ., 2015). Some of the studied

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This document is downloaded from Outstanding Academic Papers by Students (OAPS), Run Run Shaw Library, City University of Hong Kong sites were close to Hong Kong such as Haikou. These indicated that the microplastics pollution

was very serious in China and affects Hong Kong.

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This document is downloaded from Outstanding Academic Papers by Students (OAPS), Run Run Shaw Library, City University of Hong Kong Fig 19. Refuse with simplified Chinese was found at LKT.

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This document is downloaded from Outstanding Academic Papers by Students (OAPS), Run Run Shaw Library, City University of Hong Kong 5.2 Potential Sources

The majority types of microplastic were found to be fragments, fibers, lines and pellets.

Fragments were normally found in irregular shape with various colors. They mainly came from

continuous chemical, physical and photochemical fragmentation of larger plastic debris and

deposited on the beach (Ng & Obbard, 2006; Costa et al., 2009). As mentioned in Section 5.1,

human activities contribute to microplastics pollution. Thus high amount of microplastic

fragments found at ST and LKT may be due to plastics being thrown directly to the sea during

seaside and recreational activities or improper disposal of plastic wastes on beaches. Besides,

ST is adjacent to Pak Sha Wan Pier where many vessels were anchored (Fig. 20) and there is

an indigenous village at LKT. As a result, fragments may be lost from these vessels and

anthropogenic activities near the shores.

The major source of fibers is from clothing through washing of textiles (Browne et al., 2011;

Dris et al., 2015). The most common way of laundering is by washing machines and therefore

it becomes the main way by which the fibers are released into our environment. The fibers from

fabrics are lost through pilling. Pilling refers to forming of fibers balls that stand proud on the

surface of the fabric results from the entwining of the fabric surface during wearing or washing

(Hussain et al., 2008). Then entangled masses of fibers were formed and may be pulled away

from fabric during laundering or wearing. As a result, microplastics fibers are formed and

released to the environment. By collecting wastewater from domestic washing machines,

Browne et at. (2011) estimated that a single garment could produce over 1900 fibers in one 46

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This document is downloaded from Outstanding Academic Papers by Students (OAPS), Run Run Shaw Library, City University of Hong Kong wash. Moreover, wastewater treatment plants are unable to remove microplastics effectively

(Zitko & Hanlon, 1991; Gregory, 1996). It is believed that textiles are the major sources of

microplastic fibers.

Lines, usually identified as fishing lines under microscopic examination, were found at ST,

LKT and SLW. They may originate from the fish culture zones. The fisheries in Hong Kong

mainly consist of three aspects: capture fisheries, mariculture and pond fish culture (AFCD,

2012). There are 26 fish culture zones with some of them being very close to ST and LKT

(AFCD, 2012). For ST, there are three fish culture zones nearby, namely Kai Lung Wan, Kau

Sai and Ma Nam Wat while Ma Wan is the only fish culture zone that is close to LKT (Fig. 21).

This may explain the source of lines and why ST had a greater number of lines than the other

sites.

Plastic pellets with shape of a disk were usually the raw material for manufacturing of other

plastics goods through molding (Mato ., 2001). They are transported via trucks, trains and cargo

containers on ships (Plastic Free Seas, 2013). The pellets could be released to the sea

unintentionally during transportation or manufacture. Once they were released, surface run-off,

stream, or river waters would carry the pellets to the ocean or introduced directly to the sea. In

fact, Hong Kong is at high risk of this plastic pellets pollution. One of the reasons was a huge

plastics demand and production in China. The consumption was over 60 million tons in 2012

and 26% of the world production of plastic in 2014 was from China which is the largest

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This document is downloaded from Outstanding Academic Papers by Students (OAPS), Run Run Shaw Library, City University of Hong Kong producer in the world (Jiangling & Yao, 2013; PlasticEurope, 2015). In fact, Hong Kong

experienced pellet pollution in 2012 caused by Typhoon Vicente (Williams, 2012). The plastic

resin pellets from six shipping containers owned by a Chinese shipping company were lost

during the typhoon. This led to an astounding number of plastic resin pellets discharged to

Hong Kong waters and only ~60% of them were recovered (Man, 2012).

In 2015 Hong Kong had over 94.9 million tons of transshipment cargo, while these cargoes

were mainly supplied by and destined in China (HKTDC, 2016). This meant the sea transport

between Hong Kong and China was very busy. However, over 300 marine accidents happened

within Hong Kong waters in 2015 (Marine Department, 2016). Based on the high demand of

plastics in China and busy sea transport between the two places, China could be one of the

major sources of microplastics in Hong Kong waters.

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This document is downloaded from Outstanding Academic Papers by Students (OAPS), Run Run Shaw Library, City University of Hong Kong Fig 20. Many ships are anchored at Pak Sha Wan Pier.

Fig 21. Twenty six fish culture zones in Hong Kong. The number indicates different fish culture zones located in Hong Kong. Retrieved from AFCD website: http://www.afcd.gov.hk/misc/download/annualreport2012/eng/appendix-08.html

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This document is downloaded from Outstanding Academic Papers by Students (OAPS), Run Run Shaw Library, City University of Hong Kong 5.3 Comparisons with Previous Studies

5.3.1 Comparisons with Local Beach Surveys of Microplastic Pollution

This study adopted a beach survey to reveal the spatial variation of microplastics in sediments of

Hong Kong. Cheung et al. (2015) conducted a beach survey to determine if the Pearl River is a

vital pollution source in Hong Kong. They found that the microplastics found on the west coast

were more abundant than on the east coast, confirming the significant of the Pearl River as a source

of plastic debris. However, these results did not match the findings of my study which did not reveal

regional differences between eastern and western shores. Probably localized pollution is a larger

contributor at some of my study sites. According to Section 5.2, it is believed that a large proportion

of microplastics in this study, such as fibers, was originated from land that could also be found in

Hong Kong. Meanwhile the types of microplastics in Cheung et al.’s study were mainly expanded

polystyrene, followed by fragments and pellets although the samples were not analyzed by FTIR.

In contrast, fragments and fibers were found to be the most abundant in this study and all the

microplastics found were confirmed by FTIR.

Another study has focused on microbeads found in Hong Kong coastal waters (Cheung & Fok,

2016). Plastic microbeads are commonly used in personal care and cosmetic products (PCCPs) for

a scrubbing agent such as toothpaste and facial cleanser (Leslie, 2004). Although the microbeads

used in PCCPs were identified as a pollutant in the past two decades (Gregory, 1996), it did not

raise too much attention. Cheung et al. (2016) estimated that around 340 billion microbeads are

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This document is downloaded from Outstanding Academic Papers by Students (OAPS), Run Run Shaw Library, City University of Hong Kong emitted to Hong Kong waters through sewage effluent. No microbeads, however, were found in

my study. A possible explanation was that some of the microplastics obtained in this study were

suspected to be microbeads. After UV degradation, wave action or other physical abrasion, the

spherical shape was changed into irregular shapes (Isobe, 2016). The most prevalent plastics that

used for microbeads were PE, PMMA, nylon, PET and PP (Plastic Free Seas, 2013). Based on the

FTIR results, these types of plastics were mostly found in the samples. So it is believed that some

of the microplastics obtained might be microbeads. Another possible reason was that some

microbeads made from plastics with higher density (e.g. PMMA (d = 1.18 g cm−3), PET (d = 1.34-

1.39 g cm−3) compared with sea water density (d = 1.02 g cm−3) (UNEP, 2015). Consequently, the

heavier microbeads may sink to the bottom of the sea so that they could not reach the beaches.

Despite the fact that no microbeads were observed in this study, their pollution threats should not

be underestimated. In Hong Kong, there were over fifty products containing microbeads (Plastic

Soup Foundation & North Sea Foundation, 2016). Most of them are readily available in the

consumer market. This showed that the personal care and cosmetic products used in our daily life

could incessantly contribute to microbeads pollution.

The previous study found that microbeads may potentially become a vector in transporting

persistent organic pollutants (POPs) (Napper et al., 2015). POPs, which either occur naturally (e.g.

volcanoes) or are synthesized, are widely used as pesticides and other industrial chemicals (EPD,

2016). They are highly toxic and persistent in the environment for decades which allow them to

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This document is downloaded from Outstanding Academic Papers by Students (OAPS), Run Run Shaw Library, City University of Hong Kong travel a long distance and give rise to global pollution. Importantly, POPs can accumulate in fatty

tissue in organisms, causing bioaccumulation or bio-magnification via food chain. Once the

microplastics carrying POPs are ingested by marine organisms, the POPs would accumulate inside

their bodies and eventually threaten the ecosystem and human health.

5.3.2 Comparisons with Other Countries of Microplastics Pollution

It was difficult to compare the concentration of microplastics with other countries because there

was no consistent microplastic size classification and the sampling method varied from one study

to another. For example, McDermind and McMullen (2004) defined microplastic as sizes of plastics

between 1-15 mm and 2 mm sieve was used in collecting them.

Nevertheless, the abundance of microplastics and majority of microplastics identified were similar.

More examples can be found in Table 2. Generally, microplastics abundance was from 1429 to

2330 per kilogram dry sediment (Table 2) (Vianello et al., 2013; Qiu et al., 2015; Ballent et al.,

2016).

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This document is downloaded from Outstanding Academic Papers by Students (OAPS), Run Run Shaw Library, City University of Hong Kong Country Site Abundance Microplastics Major plastic Reference /Region (number of particles/ kg dry size (mm) sediment)

Hong Kong 4 beaches 5.0 - 47.8 <5mm Polyester This study (alkyd resin),PP,PE

Italy 2 beaches 672 - 880 0.03 - 0.5 PP,PE Vianello ,. (2013)

Canada 5 beaches along the shore of 20 - 470 <2 PE,PS Ballent ,. (2016) Lake Ontario China Beibu Gulf & Coastline of 5014 - 8714 <5 HDPE,PET,PE,PS Qiu ,. (2015) China Sea

Table 2. Comparison of microplastic abundance (number of microplastics / kg dry sediment).

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This document is downloaded from Outstanding Academic Papers by Students (OAPS), Run Run Shaw Library, City University of Hong Kong PE, PP and PS were the most widespread microplastics found in previous studies

(Vianello et al., 2013; Qiu et al., 2015; Ballent et al., 2016). PE was produced for

manufacturing bottles, plastic bags, fishing line and film for food packaging while PP

was usually made into folders, food packaging, hinged caps and straws (PlasticEurope,

2015). Due to low cost and durable characteristic, PS was commonly used in plastics

boxes and cups for fresh food transportation and take-away food (PlasticEurope, 2015).

PVC, PMMA and nylon were also found in some studies (Ballent et al., 2016; Castillo

et al., 2016). PVC was plastics with good mechanical properties and excellent chemical

resistance therefore it is used for ship tanks, fuel storage tanks and sewage pipes (The

European Council of Vinyl Manufacturers, 2015). PMMA is used for lighting including

exterior and interior lighting in the automotive industry due to its high light

transmission and resistance to UV light and weathering (PlasticsEurope, 2012). Nylon

was synthetic fiber with great resistance to heat and friction (Antron, 2013). They were

found in the samples possibly related to loss from paint coatings from ship tanks and

fuel storage tanks and from land through sewage effluent (Othmer, 1997; Riyaz & Desai,

2013; Chen et al., 2015).

An interesting finding in this study was that the amount of alkyd resin (polyester) at

LKT was much more than other plastics such as PE and PP. This was consistent with

the study of Kang et al. (2015) although in other studies only a small amount of alkyd

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This document is downloaded from Outstanding Academic Papers by Students (OAPS), Run Run Shaw Library, City University of Hong Kong resin was (Frias et al., 2014; Castillo et al., 2016;). Alkyd resin is cheap and has good

weathering properties so it is an excellent choice of protective coating includes marine

coating automotive refinishing primers (Polymer Properties Database, 2015). The

sources of alkyd resin at LKT probably were paint for ships and vessels. The mechanical

fragmentation and degradation such as wave motion suggested that the paint was lost

to the ocean and carried by currents (Frias et al., 2014).

5.4 Errors, Limitation and Improvements

There were three errors and three limitations in this study. First of all, after being dried

at room temperature, the plastics became more brittle and further fragmentation was

noticed during the extraction process. Therefore, extra care should be taken to handle

microplastics. For example, direct stirring was not recommended, instead, mechanical

shaker should be more appropriate.

Secondly, misidentification of microplastics may occur when the sample contained

more natural materials (e.g. diatom, pine needles and salt crystals) since their shape,

size and morphology were similar to those of microplastics. If the suspicious particles

could not be identified by direct observation, FTIR analysis would be performed.

However, FTIR could not always identify substances because there was a “size limit”

(i.e. samples were too small to be detected, the size limit reported here was ca. 0.1 mm)

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This document is downloaded from Outstanding Academic Papers by Students (OAPS), Run Run Shaw Library, City University of Hong Kong for particles to be detected. Therefore, the guideline for identification of microplastics

should be strictly followed which reported in MERI (2015) to minimize the error.

At last, there was airborne contamination in this study. This contamination was

recurrent in microplastics research (Davison & Asch, 2011; Foekema et al., 2013;

Cauwenberghe & Janssen, 2014). This contamination can be minimized in several ways.

Firstly, the filters used in density separation (Section 3.2.3) should be covered with an

aluminum foil except during microscopic observation. Secondly, the filters should be

stored in glass petri dishes so that the possible contamination by plastic petri dishes is

reduced. Thirdly, lab coat with natural fiber or cotton should be worn at all time instead

of polyester-type that could avoid synthetic materials entering into the samples.

For the limitations of the study, as the sediments were dried at room temperature, it was

hard to define to what extent the sediment was completely dry. Some water content

might remain in the sediment and led to reduction in density of zinc chloride solution.

To improve this limitation, the samples should be freeze-dried or oven-dried. If allowed,

freeze-dried samples should be used because some microplastics may be decomposed

at high temperature. Therefore, if oven-dry is necessary, a lower temperature and longer

time for drying should be used.

Moreover, there were only four sites from two regions (east and west) and two replicates

for each site were used to investigate the extent of microplastics pollution by the Pearl

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This document is downloaded from Outstanding Academic Papers by Students (OAPS), Run Run Shaw Library, City University of Hong Kong River input. The sample size is insufficient because the distribution of plastics is site

specific and depends on ocean current, monsoon wind, flooding, and sampling and

processing methods used (Chubarenko et al., 2016; Veerasingam et al., 2016). More

sampling sites located in both eastern and western areas are recommended for future

studies. Sea surveys are also necessary because the results can help understand the

oceanic transportation of microplastics.

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This document is downloaded from Outstanding Academic Papers by Students (OAPS), Run Run Shaw Library, City University of Hong Kong 6. Conclusion

Microplastics pollution is a growing problem of increasing concern. This study

illustrated ST located in the eastern area of Hong Kong had the highest abundance of

microplastics among four sites while TTW had the lowest abundance of microplastics.

Most of the microplastics found were fragments, fibers, pellets and lines. This study

also revealed major types of microplastics found were alkyd resin, PE, PP and PS which

were usually found in local consumer products. Based on the number of microplastics

found in western shores were not more than the eastern ones, it suggested that the major

source of microplastics pollutions should not only include influx from the Pearl River.

The local sources also contributed to microplastics pollution in Hong Kong. Secondary

microplastics and primary microplastics were produced from various local activities.

The results, however should interpret with caution due to limited number of sampling

sites. A more comprehensive study involving more beaches is recommended if time is

allowed.

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This document is downloaded from Outstanding Academic Papers by Students (OAPS), Run Run Shaw Library, City University of Hong Kong 7. Acknowledgement

I would like to express my greatest gratitude to my supervisor, Dr SG Cheung, to

provide me with the precious opportunity to work on this Final Year Project. He is a

generous and patient supervisor who has provided me with plenty of inspiring advices

and guidance, especially when I was confused. Also, I would like to thank Miss Xiaoyu

Xu for helping and supporting me in these few months. I also would like to show my

deepest appreciation to following research and research assistants for providing helpful

support during my experimental work: Michael Lo, Billy Kwan, Vincent.

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This document is downloaded from Outstanding Academic Papers by Students (OAPS), Run Run Shaw Library, City University of Hong Kong 8. References

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Bulletin, 62, 1596-1605.

Arthur, C., Baker, J., & Bamford, H. (2009). Proceedings of the International Research

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Browne, M. A., Crump, P., Niven, S. J., Teuten, E., Tonkin, A., Galloway, T. S., et al.

(2011). Accumulation of microplastic on shorelines woldwide: Sources and sinks.

Environmental Science and Technology, 45, 9175–9179.

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This document is downloaded from Outstanding Academic Papers by Students (OAPS), Run Run Shaw Library, City University of Hong Kong

Browne, M. A., Galloway, T. S., & Thompson, R. C. (2010). Spatial Patterns of Plastic

Debris along Estuarine Shorelines. Environmental Science & Technology Environ. Sci.

Technol., 44(9), 3404-3409.

Bugoni, L., Krause, L., & Petry, M. V. (2001). Marine Debris and Human Impacts on

Sea Turtles in Southern Brazil. Marine Pollution Bulletin, 42(12), 1330-1334.

Cadée, G. C. (2002). Seabirds and floating plastic debris. Marine Pollution Bulletin,

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Castillo, A. B., Maslamani, I. A., & Obbard, J. P. (2016). Prevalence of microplastics

in the marine waters of Qatar. Marine Pollution Bulletin, 111, 260-267.

Cauwenberghe, L. V., & Janssen, C. R. (2014). Microplastics in bivalves cultured for

human consumption. Environmental Pollution, 193, 65-70.

Cauwenberghe, L. V., Vanreusel, A., Mees, J., & Janssen, C. R. (2013). Microplastic

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This document is downloaded from Outstanding Academic Papers by Students (OAPS), Run Run Shaw Library, City University of Hong Kong 9. List of Figures

Figure 1. Map showing the collection sites ------14

Figure 2. A 30 m transect line was set up. ------16

Figure 3. Two quadrats were randomly selected ------16

Figure 4. The materials remained on the filter paper and the procedural control after oven-dried for 24 hours ------21

Figure 5. Flow diagram for the analysis of microplastics. The number in the brackets refers to the number of this section ------24

Figure 6. Number of microplastics per kilogram of sediments (mean ± S.D.) in four different sites (n = 3) ------29

Figure 7. Common type of microplastics found in the sediments: (a) Pellet; (b) fibers; (c) fragment; (d) Line------31

Figure 8. Number of fragments per kilogram of sediments (mean ± S.D.) in four different sites (n = 3) ------32

Figure 9. Number of fibers per kilogram of sediments in four different sites (n = 3) ------32

Figure 10. Number of lines per kilogram of sediments (mean ± S.D.) in four different sites (n = 3) ------33

Figure 11. Number of pellets per kilogram of sediments (mean ± S.D.) in four different sites (n = 3) ------33

Figure 12. Number of microplastics with other shapes per kilogram of sediments (mean ± S.D.) in four different sites (n = 3) ------34

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This document is downloaded from Outstanding Academic Papers by Students (OAPS), Run Run Shaw Library, City University of Hong Kong Figure 13. The compositions of microplastics in sediments from the four sites. (a). PS at LKT with 73.31 match values; (b) Nylon 66 at LKT with 77.04 match values; (c) PP at LKT with 86.64 match values; (d) Polyester at LKT with 77.04 match values; (e) PMMA at LKT with 76.10 match values and (f) LDPE at PSW with 84.80 match values------36-37

Figure 14. Composition of microplastics at ST. ------38

Figure 15. Composition of microplastics at LKT ------39

Figure 16. Composition of microplastics at SLW ------39

Figure 17. Particle sizes at the four sites ------41

Figure 18. The percentage of total organic carbon at the four sites ------41

Figure 19. Refuse with simplified Chinese was found at LKT------45

Figure 20. Many ships are anchored at Pak Sha Wan Pier------49

Figure 21. Twenty six fish culture zones in Hong Kong. The number indicates different fish culture zones located in Hong Kong------49

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Table 1 Number of microplastic per 500 mL of zinc chloride solution Obtained from each of the procedure control (mean ± S.D.) ------29

Table 2.Comparison of microplastic abundance (number of microplastics / kg dry sediment). ------52

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This document is downloaded from Outstanding Academic Papers by Students (OAPS), Run Run Shaw Library, City University of Hong Kong 11. Appendix

11.1 Microplastics Data Sheet

Blue Red Transparent White Black Green Other colors Total per Pieces/Kg Potential plastic filter Pellet

Fiber

Fragment

Line

Other shape Total

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