Luận văn thạc sĩ Quản lý tài nguyên và môi trường: Assessment of microplastic pollution in dry and wet atmospheric fallouts in Ho Chi Minh city, Vietnam

INTRODUCTION

Necessity of the research

Nowadays, plastic pollution is an emerging concern worldwide According to the statistic report, plastic production is continually increasing, with 299 million metric tons produced in 2013 and estimations of 33 billion tons for 2050 (Rochman et al., 2014) Number of plastic wastes (consisting of in-use plastics) entering the oceans was calculated for 2010 at 4 –12 million tons per year (Jamback et al., 2015)

In 2015, there were more than 407 million tons of plastic was produced, followed by

302 million tons of plastic pieces (around three-quarters) were discharged into the ocean (Gayer et al., 2017) Recently, scientists from Netherland reported that about 1.15 to 2.41 million tones of plastic debris were released into the ocean daily Besides, authors firstly pointed out the temporal change of marine plastic emission, with over

74 % of plastic items were distributed into ocean in rainy season (Lebreton et al., 2017) The presence of plastic wastes caused a dramatic change of the nature of solid wastes in human society, especially in developing countries where plastic products are often mismanaged or abandoned in illegal dumping sites (Stanton et al., 2019)

As a result, these plastic particles are scattered throughout the oceans and are found along the coastal zones, in seabed sediments, beach sands, or floating on water surface and even in frozen ice in Arctic and Antarctic regions as well as accumulating in continental aquatic systems, consisting of lakes, canals and rivers (Barnes et al., 2009)

The existence of plastics in the aquatic system poses challenges on the world’s environment The 2030 Agenda for Sustainable Development and its Sustainable Development Goals dedicated several necessary goals that are relevant to this issue (e.g SDG 11, SDG 12, SDG 14), especially the Target 14.1 which states: “By 2025, prevent and significantly reduce marine pollution of all kinds, in particular from land- based activities, including marine debris and nutrient pollution” Under the impacts from many factors such as mechanical processes, oxidation, and biodegradation, microplastics (MiPs), plastic particles that less than 5 mm in size (Arthur, 2009) are formed and can last thousands of years in the environment due to their chemical stability and durability MiPs are considered as a new pollutant that is of great concern

Truong Tran Nguyen Sang Page 2 by the world due to deleterious effects on the survival and reproduction of aquatic organisms through ingestion and accumulation (Ma et al., 2019) as well as affect human health through seafood or salt ingestion and inhalation of airborne MiPs (Prata et al., 2018)

Recently, global studies have shown the distribution and harmful effects of MiPs on marine environments such as seas (Zhu et al., 2019; Zhao et al., 2018; Thompson et al., 2004), freshwater lakes (Rios mendoza & Balcer, 2019; Eerkes- Medrano et al., 2015), rivers (McCormick et al., 2014; Moore et al 2008), and terrestrial environments (Jambeck et al., 2015) In Vietnam, Lahens et al (2018) also reported that the concentrations of MiPs in the water of HCMC’s canals and Saigon river varied from 270 to 518×10 3 fibers/m 3 and from 7 to 223 fragments/m 3 (Lahens et al., 2018)

While the presence of plastic debris in the marine environment is widely documented, their sources, dynamic and fate in rivers and estuaries remain poorly understood and largely undocumented (Gasperi et al., 2018; Dris et al., 2015b) Among the sources of MiPs, urban inputs such as wastewater treatment plant effluents are increasingly studied while the atmospheric compartment is mostly neglected, though the fact that plastic debris can escape as wind-blown debris was previously reported, leading to human exposure and the potential for subsequent health risks (Gasperi et al., 2018)

HCMC is the most dynamic area as a social, cultural and economic center of Vietnam, where services, exchange of goods and traffic in this area have been expanded for a long time which drives economic growth, followed by a dramatic increase of air pollution In a recent study on the relationship between air pollution and human health in HCMC, over 90% of children less than 5 years old were infected by respiratory disease (Ho, 2017) The presence of MiPs in atmospheric fallout have become an environmental and social challenge due to their ability to spread (i) toxic additives added during plastics production or (ii) organic and inorganic contaminants adhering on MiP surface to the aquatic environment More seriously, these small particles can accumulate in human’s body during the inhalation, then enter the nose and mouth and cause lung diseases (Gasperi et al., 2018)

Truong Tran Nguyen Sang Page 3

Therefore, it is urgent to conduct a survey on MiPs contamination in atmosphere in terms of human health risk The lack of data on sources and fate of plastic contamination in rivers and estuaries in developing countries makes HCMC, the economic capital of Vietnam and one of the most dynamic developing cities from South East Asia, an adapted pilot study site to study MiPs in the atmospheric fallout.

Research objective

The objective of the study is to characterize MiPs pollution in the dry and wet atmospheric fallout in HCMC.

Study area

Dry and wet atmospheric fallout samples were collected from three following sites: 1) Urban area (on the roof of CARE building, University of Technology, district 10);

2) Suburbs area (house of local people in Cu Chi district);

Research content

To obtain the research objective, a one year monitoring on the occurrence of MiPs in dry and wet atmospheric fallout was conducted in three different areas of HCMC (urban zone, countryside, landfill) in order to:

- Determine the presence of MiPs (fragments and fibers) in the dry and wet atmospheric fallouts in HCMC,

- Characterize (i) their physical characteristics such as type, size, shape and (ii) chemical composition, and

- Investigate temporal variation of atmospheric MiPs concentration through the year, respectively related to the surrounding environment.

Methodology and research Techniques

Microplastic pollution has become one of global environmental issues in recent decades At present, studies on MiPs mainly based on the investigation of concentration of these small particles in the environment In this study, a long-term monitoring (in 12 months) was conducted at three sampling sites (urban, sub-urban area and a landfill) for preliminarily assessing the concentration of MiPs in the

Truong Tran Nguyen Sang Page 4 atmosphere in HCMC Experiments were set up in 4 main steps: (i) sampling, (ii) sample treatment, (iii) sample filtration and (iv) visual observation using the stereoscope As a results, the presence of MiPs as well as their characteristics (shape, size, color) in HCMC was illustrated and in comparison with that of different areas in the world

Methods used in implementing the research are as follow:

- Theory analysis and synthesis: a literature review on definition, characteristics, sources and impacts of MiPs on the environment, organisms and human health was necessary for understanding the research field The summary on situation of relative studies will clarify the research gaps at the present, as a result the research objective become more impressive Besides, methods for collecting and treating samples used in previous studies can be applied with adaptation for the current study, allowing more objective comparisons

- Sampling and laboratory treatment: this technique is important in experimental researches Results of these studies were mostly based on the data from collection and sample analysis at the laboratory Practical monitoring data will provide the current sate of the area studied, describe more realistically environmental conditions affecting to the research subject Therefore, discussions and comparisons become more objective and convincible

- Data analysis: results from sampling and laboratory analysis was firstly showed in raw data and difficult for describing research results Data analysis methods, using analytical and statistical tools for arranging, re-formatting, performing data on tables and charts are necessary to clarify the results and key findings of the study.

Scientific and practical value of the research

This study will thus i) be the first one in this scientific topic to be leaded in Vietnam, ii) will be the first one conducted in a developing country where the waste and plastic waste management differed strongly from developed country (so far no

Truong Tran Nguyen Sang Page 5 papers dealing in developing country were published, and iii) will bring new knowledge on the MiPs in the atmospheric environment

Data on composition, nature, and distribution of MiPs in the atmosphere will raise awareness of residents on microplastic pollution and be helpful for the Department of Natural Resources and Environment, as well as the Ministry of Natural Resources and Environment in making plastic waste management solutions and propose measures to prevent, control and minimize plastic pollution on rivers and canals.

LITERATURE REVIEW

Situation of plastic pollution in the world and Vietnam

In original, plastic was defined as "malleable" or "flexible" material used widely for manufacturing most of industrial products (Moore, 2008) Due to their numerous properties such as resistance, lightweight, durability and low cost, plastic items have been used worldwide in households, schools, hospitals and factories, leading to the global annual production of plastic polymers has grown tremendously from 1.7 in 1950 to 350 million tons in 2015 (Gayer et al., 2017) and are forecasted to double by 2025, and triple by 2050 (Plastic Europe, 2016) (Figure 2.1) Nowadays, plastic is a common material used in place of glass, metal, wood, leather, fabric, etc to produce daily items, such as raincoats, water pipes, household items and industrial products owing to advantage characteristics as durable, light, cheap, hard to break and colorful At present, the most widely used type of plastic are Polyethylene (PE), Polypropylene (PP), Polystyrene (PS) and Polyethylene terephthalate (PET), more than 90% of plastic products all over the world are made up these types (Andrady and Neal, 2009)

Figure 2.1 The increase of global plastic production, measured in tones per year, from

1950 through to 2015 (Gayer et al., 2017) For decades, the production and consuming of plastic products produce a large number of plastic wastes, leading to a dramatic nature change of solid wastes in human society More seriously, as a results of poor waste management and low

Truong Tran Nguyen Sang Page 7 recycling rate (as can be seen in Figure 2.2, from 1980 to 2015, only 55 percent of global plastic waste was discarded, the remaining was incinerated and recycled, accounted for 25% and 20%, respectively) (Geyer et al., 2017; Ritchie & Roser, 2018), significant number of plastic wastes was found on worldwide centennial environment and finally entered and persisted in marine ecosystems through natural impacts as river runoff and atmospheric transport, beach littering and human activities as shipping and fishing According to data on global estimates from Jamback et al (2015) along with plastic waste generation rates, coastal population sizes and waste management practices by conutry, Ritchie and Roser (2018) calculated and described pathway by which plastic enters the world’s oceans, as a result the amount of plastic in surface waters was estimated ranging from 10,000 to 100,000 tons per year (Figure 2.3)

Figure 2.2 Estimated historic trends in global plastic disposal method (from 1980 to 2015)

Figure 2.3 Route of plastic items enters the world’s oceans (Ritchie and Roser, 2018)

The fate of plastic debris in marine aquatic systems has become a major worldwide environmental concern in term of adverse consequences to marine life and potentially human health

The 2030 Agenda for Sustainable Development and its Sustainable Development Goals dedicated several goals that are relevant to this issue (e.g SDG

11, SDG 12, SDG 14), especially the Target 14.1 which states: “By 2025, prevent and significantly reduce marine pollution of all kinds, in particular from land-based activities, including marine debris and nutrient pollution” In 2015, the United Nation Environmental Assembly (UNEA), adopted the Resolution 1/6 on ‘Marine plastic debris and microplastics’ which stated to focus on the “identification of the key sources of marine plastic debris and microplastics” and on taking into account the

“specification of areas especially in need of more research, including key impacts on the environment and on human health” (UNEP, 2016) The UNEP (United Nation for Environmental Protection) report on ‘global lessons and research to inspire action and guide policy change’ (UNEP, 2016) emphasized as key messages that “The

‘leakage’ of plastics into the ocean can occur at all stages of the production-use- disposal cycle, especially due to inadequate wastewater and solid waste collection and management, but the amount of marine plastic is so far poorly quantified”

Being considered as the dominant input of plastic debris to oceans, role of centennial rivers and estuaries on their emissions to the ocean is now recognized Lebreton et al (2017) reported that there are 1.15 to 2.41 million tones of plastic enter

Truong Tran Nguyen Sang Page 9 the oceans from global rivers system annually, most of them mostly located in Asia (accounted for 86%), Africa, South and central America and Europe (as showed in figure 2.4) However, these estimations are mainly based on solid waste data and hydrological information of rivers More insitu plastic assessment need to be conducted in rivers for better understanding, and the effects of factors such as population density, levels of urbanization and industrialization by region, rainfall rates and the presence of weirs and dams also play a significant role in littering river plastic into the ocean and need to be widely considered (Lebreton et al., 2017)

Figure 2.4 Global plastic input to the oceans by region, 2015 (Lebreton et al., 2017)

In Vietnam, plastic industry is a global sector that has grown rapidly in the recent years with an annual growth rate of 16 - 18% More than 80% of this production, which mostly are consumer products and packaging, is localized in the South of Vietnam, near Ho Chi Minh City – the economic capital of the country Unfortunately, the almost absence of treatment of domestic (i.e 10%) and industrial wastewaters and the weaknesses of solid waste management have pushed Vietnam to be among the main contributors of plastic waste to rivers and oceans (Jambeck et al, 2015; Lahens et al., 2018) According to statistic data from Bliss Saigon (2016), in

Ho Chi Minh City, there are 250,000 tones of plastic wastes were generated each year, but only 19.2 % of them was transferred to landfills, the rest are either recycled or released directly into the environment, leading to soil and water pollution On the

Truong Tran Nguyen Sang Page 10 other side, the informal waste recycling, leading to an increase in air and water pollution is also an important sector in Vietnam.

Overview on microplastic pollution

2.2.1 Definition and properties of Microplastic

In 1972, the world first recognized small pieces of plastic in water environments when a large number of small plastic particles (plasticles) were found floating on the surface of the Sargassco Sea (Carpenter and Smith, 1972) At that time, these small pieces of plastic were simply called "plastic particles" Until a publication in 2004, the new "MiPs" term was introduced by Thompson (2004) For distinguishing small plastic samples (about 50 μm in size) collected from beaches and sediments in Plymouth, UK from larger plastic debris such as fishing nets, plastic bottles, plastic bags, etc, scientists used the term "MiPs" In 2009, Arthur suggested that MiPs also include pieces less than 5 mm, which are lightweight, resistant, durable and easy to ubiquitous in the aquatic environment, such as ocean, river, estuary, lake, and even rainwater (Arthur, 2009) Nowadays, the term of “MiPs”, plastic particles of less than 5 mm in size was commonly used in all current studies In 2015, GESAMP proposed provided a more scientifically rigorous definition of microplastic pieces base on comparing the size corellation between microplastic particles and other organisms (GESAMP, 2015)

Figure 2.5 Size range of plastic debris in comparison with living materials (GESAMP,

2.2.2 Sources of microplastics generation into the environment

MiPs were first discovered and reported in the 1970s (Carpenter and Smith, 1972) Later, global studies have shown their harmful effects on marine environments, aquatic animals and the ability to affect human health due to MiPs absorption through the food chain Microplastics particles are made up of particles that differ in size, specific density, chemical composition, and shape (Duis and Coors, 2016) They originate from the so-called primary sources, which are the manufactured products (pellets, cosmetic products) and the so-called secondary sources that are the fragments and fibers produced from breakdown of larger macroplastic debris under environmental conditions (Table 2.1) (Auta et al., 2017)

Primary MiPs are microscopic particles based on their small size (Auta et al., 2017) Their sources include intermediate sources of plastic products such as raw plastic material (nurdles and pellets); wastes released from the maintenance and breakdown of plastic products and by-products during the industrial production They

Truong Tran Nguyen Sang Page 12 include plastic particles used in facial cleansers, tooth paste, resin pellets and cosmetics like bath gels, scrubs, peelings (Cole et al., 2011), eye shadow, deodorant, blush powders, make up foundation, mascara, shaving cream, baby products, bubble bath lotions, hair coloring, nail polish, insect repellents and sunscreen (Costa et al., 2010) Primary microplastics are usually released into rivers through domestic and industrial wastewaters and finally enter to oceans

Secondary MiPs are larger pieces of plastic fragmented from plastic materials in marine and terrestrial environments (Norwegian Environment Agency, 2015) This type is mainly released due to the decomposition process under solar radiation (UV rays), which leads to the breakdown of chemical bonds in the polymer matrix because of the oxidation In addition, weather processes also affect the formation of these fragments such as current, wind or by laundry process of synthetic textiles (Figure 2.6) (Barnes et al., 2009; Wagner et al., 2014)

Table 2.1 Overview of sources of two types of MiPs (Duis and Coors, 2016)

- Specific cosmetic products containing MiPs as defoliants/abrasives;

- Specific medical applications (e.g dentist tooth polish);

- Drilling ﬂuids for oil and gas exploration;

- Pre‑production plastics, production scrap, plastic granulate: accidental losses, run‑oﬀ from processing facilities

- General littering, dumping of plastic waste

- Losses of waste during waste collection, from landfill sites and recycling facilities

- Losses of plastic materials during natural disasters

- Synthetic polymer particles used to improve soil quality and as composting additive

- Abrasion/release of fibers from synthetic textiles

- Release of fires from hygiene products

- Paints based on synthetic polymers (ship paints, other protective paints, house paint, road paint): abrasion during use and paint removal, spills, illegal

- Abrasion from other plastic materials (e.g household plastics)

Both MiPs types (primary and secondary) exist in marine ecosystems at high concentrations It has been estimated that about 245 tonnes of MiPs are discharged into aquatic environment each year (Morris, 2015) and higher proportion of source of microplastic pollution in oceans was found for secondary ones (Eriksen et al., 2013; Hidalgo-Ruz et al., 2012) With properties like plastic, durable, difficult to decompose in the environment, MiPs causes many consequences such as marine species consuming them and MiPs entering the food chain or spreading pollutants are absorbed on the surface of plastic (Fossi et al., 2016)

Figure 2.6 Formation and accumulation of microplastic particles

Moreover, because of their small size and low density, MiPs can transfer easily from contenial environment to oceans under wind movement (Allen et al., 2019; Rezaei et al., 2019) Chen et al (2019) also suggested that through precipitation to land and sea, atmospheric microplastics should be considered as a key source of microplastics in the coastal and oceanic environments As the correlation of MiPs distribution in the atmosphere, terrestrial and aquatic ecosystems, Chen at al (2019) pointed out the dynamic cycle of MiPs among these compartments (as showded in Figure 2.7)

Figure 2.7 Potential MiPs sources and pathways (Liuet al., 2019)

2.2.3 Formation and factors affecting to the abundance of atmospheric MiPs

Synthetic textiles, erosion of synthetic rubber tires, and city dust are thought to be the most important sources of atmospheric MiPs (Rezaei et al., 2019; Boucher and Friot, 2017; Dris et al., 2017; Dris et al., 2016) Other sources of airborne MiPs may include plastic fragments and fibers from clothes and house furnitures (Dris et al.,

2016, 2017), waste incineration, landfills (Dris et al., 2016), industrial emissions, particles released from traffic (Dris et al., 2015) Moreover, textile fiber processing industry, with their annual growth approximately 6.6% over the last decade, may contribute a part of fine plastic fibers (1-5 mm in length) to the atmosphere (Cesa et al., 2017) Indeed, synthetic clothing is thought to be the main source of airborne MiPs (Dris et al., 2016), in both indoor and outdoor environment Furthermore, the industrial chopping or grinding of synthetic material can result in the formation of these fine particles

For fate of atmospheric microplastics in the environment, Rezaei et al (2019) pointed out that wind erosion as a driver for transport of light density microplastics Besides, other factors as rainfall, population densities, local environments and human activities also effect on the concentration and deposition of MiPs in the atmosphere Study on factors effecting to the abundance of airbone MiPs, Allen et al (2019) demonstrated the possitive correlation between rainfall and snowfall and MiP deposition in the Pyrenees mountains (Allen et al., 2019) In term of effect of wind movement on distribution of MiPs in the atmosphere, recent studies found that wind direction also showed strong correlation with the concentrations of airborne MiPs

(Abbasi et al., 2019; Klein and Fischer, 2019; Liu et al., 2019b) In particular, the change of wind direction from west to sound will increase concentration of MiPs in the atmosphere (Klein and Fischer, 2019) and higher concentration of airborne MiPs was found at downwind sites (Browne et al., 2010)

In term of the effect of population density on concentration of airborne MiPs, Dris et al (2016) found higher concentration of atmospheric MiPs in sampling sites with dense surrounding population For studies conducted in different countries, correlation between polution density and concentration of MiPs was also indicated

In particular, concentration of airborne MiPs found in Shanghai was higher than in Paris, as a results of more dense population (nearly twice) (Dris et al., 2016; Liu et al., 2019a) Potential explanations were also proposed base on the generation of more domestic atmospheric in more populous cities through human activities Having said that, custom of people in Shanghai also contribute significant of MiPs to the atmosphere In particular, people living in Shanghai usually dry their clothes, bed sheets, pillows, and blankets on balconies or lines (Liu et al., 2019) As a result, during the sunlight exposure, UV irradiation would easily promote the breakdown and degradation of the synthetic textiles into microfibers (Song et al., 2017) In addition, the local environment, such as altitude and geographical environment, also effect to the abundance of atmospheric MiPs Liu et al (2019) identified that concentration of airborne MiPs decrease when altitudes increase (Liu et al., 2019) Dris et al (2017) firstly investigate on the different between abundance of airborne MiPs in both indoor and outdoor environment Authors found higher concentration of airborne MiPs in outdoor atmosphere as a result of air renovation in outdoor environments In other words, indoor dust samples contain higher concentration than that of outdoor dust samples, which might contribute to the higher abundance of microplastics indoors Besides, different potential sources from furniture, textile products, building materials, living habits also increase concentration of MiPs in households (Dris et al., 2017) For example, the use of carpets or traditional cleaning methods in rooms substantially contribute to the abundance of atmospheric microplastic in comparion with modern furniture as vacuum cleaner Klein and

Fischer (2019) suggested that rivers can play important role in reducing the spread of MiPs, as a result of slowing down the wind movement

2.2.4 The harmful effects of MiPs pollution on the environment, organisms and humans

Once in the environment, MiPs could induce deleterious effects on the survival and reproduction of aquatic organisms through ingestion and accumulation (Sussarellu et al., 2016) They can also affect human health through seafood or salt ingestion and inhalation of airborne MiPs (Prata, 2018) a) Bioaccumulation of MiPs on aquatic organisms

The effects of microplastics (MP) on aquatic organisms are currently the subject of intense research with a lot of relative publications Many studies was conducted in diversity of aquatic pieces in field or at laboratory (as showed in Figure 2.8)

Figure 2.8 Studies were defined according the number of individuals per groups of organisms (De et al., 2018)

2.2.4 The harmful effects of MiPs pollution on the environment,

General research situation on Microplastic pollution in the world

Environmental scientists started investigating marine microplastics in the early 2000s Today, a wealth of studies demonstrates that MiPs have ubiquitously permeated the aquatic environtment

In marine systems, Pan et al (2019) found large amount of microplastics in surface water of Northwestern Pacific Ocean High concentration of microplastic particles, ranging from 4.38 x 10 4 to 1.46 x 10 6 items km -2 was also recorded in Arabian Bay (Abayomi et al., 2017) Besides, microplastics was also found in marine sediment, known as the final destination of microplastics in marine environments (Woodall et al., 2014) Recently, Chinese scientists measured 155 and 142 items kg -

1 (dry weight) in the offshore sediments collected at the Yellow Sea and East China Sea, respectively (Zhang et al., 2018)

Microplastics have been also widely detected in freshwater systems from Asia, Europe, North America, and Africa (Shen et all., 2019) Abundace of microplastics at concentration of 0.028 particles.m -3 was found in the surface water collected from Tamar Estuary (England) (Sadri and Thompson, 2014) Higher concentration of microplastics was also observed from surface samples taken from Asian countries There were 2,425 to 7,050; 293 to 7,924 and even 172,000 to 419,000 microplastic.m -

3 observed from surface samples collected at areas: (i) eight urban lakes in Changsha (China) (Yin et al., 2019), (ii) Pearl and Nakdong River in South Korea (Lin et al., 2018; Eo et al., 2019) and (iii) Saigon river in Vietnam (Lahens et al., 2018), respectively In addition, freshwater sediments have been also widely used as media for studies on microplastic pollution (Cozar et al., 2014) At present, Shen et al (2019) summarized a large number of studies on accumulation of microplastics in freshwater sediments, there were 19 related studies was conducted around the world since 2012 (Shen et al., 2019)

The presence of microplastics was also found in the effluents of wastewater treatment plants (WWTPs), which was considered as a potential source of microplastics in aquatic environments In particular, average concentraion of 0.05 items (fibers or fragments).l -1 of treated wastewater was found from samples collected in 17 different WWTPs in the USA (Mason et al., 2016) Ziajahromi et al (2017) and Gundogdu et al (2018) also reported similar concentrations of microplastics in treated wastewater samples collected at WWTPs in Astralia and Turkey, at 10 7 and 1.2 x 10 6 particles.l -1 , respectively In developing countries, related studies has not been concerned In term of drinking water, few works was also conducted For instance, 0.7 microplastics m -3 was found in drinking water sample collected from a drinking water treatment plant in Germany (Mintenig et al., 2019)

Microplastic particles was also found accumualting in both marine and freshwater organisms (plaktonic organisms, invertebrates or vertebrates) (Ribeiro et al., 2019) Cole et al (2013) demonstrated microplastic in size under 30.6 àm can be easily uptaken by Acartia clausi, while Oyster larvae of all ages can ingest 0.16 to 7.3 àm microplastics (Cole and Galloway, 2015) Recently, impacts of microplastics on growth and health of hermatypic corals was conducted by Reichert et al (2019)

Authors predicted that corals from Indo-Pacific are in risk of being exposured by microplastic at concentration of 200 particles.l -1 (Reichert et al., 2019) b) In other environments and atmospheric fallouts

All over the world, studies on presence of microplastics are conducted in many regions and for various research objects Recent studies demonstrated the occurrence of microplastics in framland soil (Zhang et al., 2019) and alpine glacier (Ambrosini et at, 2019) Group of scientists from Canada and Switzerland also pointed out the existence of 8 to 41 MiPs in a liter of melted ice collected from Baltic Sea (Geilfus et al., 2019)

While the number of research on marine MiPs is more advanced, there are immense gaps of knowledge regarding continental MiPs (Dris et al., 2016), especially their dynamic and fate in rivers and oceans remain poorly understood and largely undocumented (Dris et al., 2015), especially the lack of research on the presence and accumualtion of microplastic in atmospheric compartment, which was considered as main factor which complemented the concentration of microplastics into the aquatic environment (Dris et al., 2016, Cai et al., 2018) Allen et al (2019) also pointed out that microplastic can be transported through the atmosphere at a distance of over 95km (Allen et al., 2019)

To date, only nine international publications which have demonstrated the presence of MiPs in the atmospheric compartment (Dris et al., 2015; Dris et al., 2016; Dris et al., 2017; Zhou et al., 2017; Cai et al., 2018; Allen et al., 2019; Liu et al., 2019; Klein and Fischer, 2019 and Abbasi et al., 2019) Other studies mainly investigated effect of airbone MiPs on human health (Gasperi et al., 2018; Prata et al 2018; Peng et al., 2017) These studies mostly used two common sampling methods for collecting airborne microplastics In particular, atmospheric fallouts will be directly collectted through a funnel and into a glass bottle or collected more complexly by air pumping Samples taken by both methods then was filtered, MiP particles was retained on filters, the quantity of MiPs then was mearsured by visual observation, using the stereoscope

Dris et al (2015) investigated the microplastic pollution at school zone (Paris-Est Cre1teil University, 11 km for from centre of Paris) Average concentration of

118 microplastics.m -2 d -1 was dound during 3-months monitoring, from Februray 26 to May 22, 2014 (Dris et al., 2015) In this first study on the existence of MiPs in atmospheric fallouts, results was roughly presented in terms of concentraion of MiPs and shape classification

Dris et al (2016) evaluated the presence of fibrous MPs in total atmospheric fallout (including dry and wet deposition) at one urban site and one suburban site in the Paris Megacity Total atmospheric fallout was collected continuously on the roofs of buildings Based on a 1-year and a 6-month monitoring period on each site concentration of atmospheric fallout of between 2 and 355 fibers/m 2 /day was indicated (Dris et al., 2016) In this study, FTIR analysis for identifying chemical composition of microplastic item was firstly applied The results showed that half of detected fibers was in natural source

Difference from other studies, concentration of fibers in both indoor and outdoor environments was firstly investigated by Dris et al (2017) Authors conducted sampling in three different indoor sites (two private apartments and one office) and one out door site As a result, 190-670 of fibers was found in settled dust in indoor environments, with concentration ranged form 1,586 to 11,130 fibers m -

2.d -1 Among fiber types natural fibers made up 67% of the analyzed fibers in indoor environments, similar to results was reported in marine and continental studies dealing with microplastics

In Yantai city (Shangdong province located in East China), Zhou et al (2017) reported that deposition flux of atmospheric microplastics attained a maximum of 1.46×10 5 n/(m 2 a), consitsing of 1.38×10 5 n/(m 2 a) of fibers, followed by 6.29×10 3 , 7.65×10 2 and 2.45×10 2 n/(m 2 a) of the fragments, films and foams, respectively Cai et al (2018) conducted the survey on characteristics of MiPs in the atmospheric fallout from Dongguan city, China As a resluts, MiPs of three different polymers, i.e., PE, PP, and PS, were identified Diverse shapes of MiPs including fiber, foam, fragment, and film were also clarified, with the dominance of fiber form The concentrations of non-fibrous MiPs and fibers ranged from 175 to 313 particles/m 2 /day in the atmospheric fallout (Cai et al., 2018) Besides, surface charactersitics of microplastics was also illustrated

Short-term evaluation on source and risk assesment of atmospheric microplastic was also conducted in Shanghai, China Authors found 0 – 4 items.m -3 of air at the sampling site Moreover, mornophological such as: shape, color, size range and chemical composition of sespected microplastics, was fisrtly identified (Liu et al., 2019) The difference of concentration of MiPs by height of sampling area also investigated in this study As a result, the lowest concentration was observed at the sampling site near the sea, while in contennial area, the average concentrations of MiPs recorded at 1.7m above the ground in the city were higher than the concentrations recorded at 80 m above the ground However, these conclusions need to be clarified in next studies in the future

Most recently published relative article performed the atmospheric transport and deposition of microplastics in a remote area of the Pyreness mountains The concentration of 249 fragments, 73 films and 44 fibers per square meter was found, coressponding to the average of 365 items.m -2 d -1 , same as concentration of microplastic found in Paris (Allen et al., 2019)

Concentration of 275 microplastics.m -2 d -1 was observed in atmospheric fallout collectted in Hamburg metropolitant area in the north of Germany during the sampling period from December 2017 to February 2018 (Klein and Fischer, 2019)

In Asaluyeh County (Iran), the number of microfibers was found ranging from approximately 0.3 to 1.1 per a cubic meter of air (Abbasi et al., 2019)

The existence of MiPs in the atmosphere is assumed to be the result of wind- blowing of MiPs from the ground surface, especially from the landfills before or even after burying and from the waste incinerators (Cai et al., 2018) Numerous studies assumed that 80% of the plastic pollution found in the marine environment originates from a terrestrial origin (Andrady and Neal, 2009), but the dynamics of the continental inputs into the marine environments are poorly documented Similarly, knowledge on the sources, fate and transfer of MiPs in continental environments are extremely limited Special attention should be paid to the sources of MiPs in urban areas, atmospheric and effluent from wastewater treatment plant

Moreover, within the studies conducted to date only performed preliminary the atmospheric micropastic contamination in high income countries (Figure 2.9)

Chapter Summary

As documented by the numerous publications above, plastic and microplastic pollution need to be considered as one of the most intensely discussed issues in environmental science and in the society, along with other five big problems, listed as: (i) air pollution and climate change, (ii) deforestation, (iii) soil degradation, (iv) overpopulation and (v) species extinction

Environmental scientists have been investigating on microplastic pollution in term of distribution, change of concentration by region, geographically and

Truong Tran Nguyen Sang Page 25 temporally and in diversity of areas studied as: aquatic environment (oceans, seas, centennial rivers, lakes and cannels), organisms, beach sand, ice, farmland soil, and even in the atmosphere Besides, research aim to characterizing physical (shape, size, color) and chemical composition (surface structure, synthetic or natural) was also conducted More especially, in recent years, some studies have shown that microplastics can be also ubiquitous in the atmosphere Beside the main source of airborne MiPs form synthetic textiles, the degradation and fragmentation of plastic products, waste incineration, industrial and traffic emissions, and dust re-suspension also may increase the concentration of airborne microplastics Under impact of wind movement, MiPs can transport through the atmosphere over a long distance, and present ubiquitously worldwide, even in remote mountain catchments and polar regions Besides, human activities and weather conditions, such as rainfall, snowfall and wind, have been confirmed to affect the abundance and deposition of airborne microplastics The inhalation or ingestion of microplastics along with hazardous chemical and microorganisms from their surface might increase the risks to human health

While relative studies are being conducted in high income countries, the lack of relative research in developing countries was indicated This study firstly investigated on the presence of MiPs in the atmosphere in HCMC, one of big cities in developing countries The methods for sampling, sample treatment and MiP identification were based on techniques proposed in previous relative studies Next chapters will provide more information on research methods as sampling, samples treatment, data analysis as well as results found in this study.

MATERIALS AND METHODS

Study area

Dry and wet atmospheric fallout samples were collected from three sites in HCMC:

- Site S1 in urban area, on the roof of building (located in a school zone), in district 10

- Site S2 in sub-urban area (household in Cu Chi District),

- and Site S3 in Phuoc Hiep landfill

At site S1, sampling device was placed on the roof top of a building, in a school zone, which was at the height of 10 m above the ground This site was surrounded by other buildings, opposite to a construction site and polluted by dense traffic avenue The Site S2 was located in a household in a sub-urban area of Ho Chi Minh City, the sampling device was installed at the sampling height of 2 m above the ground Site S3 was a landfill, sampling device was placed on the ground, surrounded by a lot of trees, high density of traffic (Figure 3.1)

Figure 3.1 Sampling sites with geographic distances

Sample collection was conducted during 12 months Dry and wet atmospheric fallouts were taken twice a month, from June 15 th 2018 to May 25 th 2019 There were

72 samples collected during the dry season (from November to April) and the rainy season (from May to October) with a sampling duration of 3 or 4 days for each sample The collection of samples was carried out on the same day at all sites in order to allow comparison No interruption of the sampling occurred during the whole monitoring period, providing a full view of the annual variability of the atmospheric fallout It would be more insightful if at least duplicate could be sampled at one sampling sites However, time effort and costs were not be afforded by this study Therefore, for each sampling sites, only one sample was collected at a time.

Sampling and pre-treatment

So far, there have been only 09 publications on MiPs in atmospheric fallout: 04 in France (Dris et al., 2016; Dris et al., 2015; Dris et al., 2017; Allen et al.,2019), 01 in Germany, 01 in Iran (Abbasi et al., 2019) and 03 in China (Zhou et al., 2017; Cai et al, 2018; Liu et al., 2019) It was important to compare the results from this study to previous available results for investigating any difference on atmospheric microplastic pollution in different regions around the world

According to tested results for trial samples taken and analyzed, direct dust sampling method by pumping and filtrating through filters and impinges usually used in common atmospheric environmental surveys was not effective and appropriate for MiPs analysis due to the existence of many unexpected particles Therefore, the designed sampling device was inspired by the devices described by Dris et al (2015) and Cai et al (2018), and consisted of a 250 mm diameter glass funnel placed on a

10 litters glass bottle to collect rain water and air dust falling into the funnel area (surface of 0.049m 2 ) and into the bottle (Figure 3.2) The same sampling device was installed at different heights at three sampling sites

The sampling techniques were described as follow:

For dry atmospheric fallout samples (collected during dry days, i.e absence of rain): dry fallouts were collected by cleaning the funnel with 350mL of miliQ water in order to collect all dry dust settled in the glass bottle Then, these bottles were moved to CARE lab and stored in the fridge at 4 o C

Figure 3.2 Sampling device for dry and wet atmospheric fallouts

For wet atmospheric fallout samples: all fallouts (from dust and rainwater) were collected together in a 2L glass cylinder The volume of collected rain water was recorded for considering the correlation between the rainfall and concentration of atmospheric MiPs After the volume measurement, the wet samples were also stored in glass bottles and kept in the fridge at 4 o C

During the sampling process, the funnel and the bottle were rinsed three times with miliQ water in order to recover all microplastics that might be adhering into its walls

The Protocol for the sample treatment was adapted from Lahens et al (2018) and aims to (i) provide filters which are easy to observe under stereomicroscope and (ii) minimize chemical cost during treatment process The process is described hereafter and in Figure 3.3:

Step 1: sieving with a 1 mm sieve and primary filtration

After measuring the volume of water, the samples were firstly sieved through a 1-mm sieve using milliQ water to remove the big pieces of organic particles present in the samples At the same time, if there were long anthropogenic fibers (more than

1 mm in size), those fibers were isolated and kept in a separate filter for stereomicroscopic observation

After sieving, if the total volume of water was less than 350ml, the sample was directly stored in a glass bottle and kept at room temperature If the total volume of water was exceeded 350 mL, the bottle was put 24H in the fridge for particles settlement Then, the supernatant which may retain low density plastic was filtrated

Truong Tran Nguyen Sang Page 29 until the sample volume is about 350 mL and the settled particles would be stored in a glass bottle and kept at room temperature

Step 2: density separation with NaCl solution (density = 1.18 g/cm 3 )

For both dry and wet samples, density separation using sodium chloride solution (NaCl Merck®), prepared at density of 1.18 ± 0.02 g.cm -3 was performed in the reparatory funnel, the used volume of NaCl solution is equal to the volume of samples After separation step, the supernatant was stored in a closed bottle for next steps

For 350 mL of each sample, 1 g SDS (Sodium Dodecyl Sulphate, Merck®) was added into the sample Agitation was gently done to make sure SDS was thoroughly diluted, then sample bottle was kept in the laboratory oven at 50 o C for 24 hours

Step 4: Addition of Biozyms SE and F (1mL for each), 48 h, 40 o C

After 24 hours of SDS addition, 1 mL of biozym SE (protease and amylase, Spinnrad®) and 1mL of biozym F (lipase, Spinnrad®) were added into the sample using an Eppendorf pippette After agitation, the samples were kept in the laboratory oven at 40 o C for 48 hours

15 mL of H2O2 (Hydrogen Pyroxide, Merck®) was added to the sample After agitation, the sample was also kept in the laboratory oven at 40 o C for 48 hours

After chemical extraction described as above, the pre-treated samples were filtrated through several GF/A filters (1.6 àm porosity, Whatmanđ), using a glass filtration unit Afterward, all the filters were kept in petri dishes for further stereomicroscopic observation and FTIR analysis

Visual observation and FTIR analysis

The particles on the filters were then observed using a stereomicroscopic S6D integrating a MC170 camera and LAS software (Figure 3.4) for determination of physical characteristics (quantity, shape, size, color)

Figure 3.4 Stereomicroscopic S6D integrated with a MC170 camera

Each filter was read from left to right, then move down one row, and then read from right to left until total particles on filters was examined This method aimed to ensure items were not double counted

The MiP identification was based on rules proposed by Hidalgo –Ruz et al (2012) and Dris et al (2015) for limiting the over-estimation on the number of fragments and fibers on each filter MiP particles was distinguished with other materials (algae, salt crystals and sand, dust, animals, animal parts and shells, phytoplankton, zooplankton, etc by following rules: (i) fibers have to be equally thick through their entire length, (ii) fibers don’t have cellular or organic structures inside and (iii) MiP particles should exhibit clear and homogeneous color throughout (Hidalgo –Ruz et al., 2012) All particles with described characteristic above and had size from 100àm to 5,000àm were acquired and then images were saved in the computer LAS software then was used for counting the quantity as well as characterizing their size and color In term of shape, this study concentrated on distribution and characteristics of fibers and fragments

 For fibrous particles: size was mostly measured in length, the minimum size was 100àm

 For fragment particles: size was measure in surface area

 Color was distinguished based on basic color for both fibers and fragments.

Data analysis

For each analyzed image by LAS software, an excel file consisting of information on sizes and color of MiP particles was exported Then, all excel files corresponding to one sample were synthetized Collected data were illustrated under charts using Microsoft excel 2018 software MiP fallouts were expressed as a concentration of items per square meter per day The formula was used for calculating concentration of MiPs was:

- Q: number of MiPs observed in each sample (items)

Chapter summary

This chapter described the methods for sampling and treating the samples in the laboratory Besides, information on sampling device, chemicals used, and techniques for visual observation were also performed in detail The results illustrated in next chapters will answer the following questions:

• Are MiPs (fragments and fibers) present in the dry and wet atmospheric fallouts of HCMC, Vietnam?

• What are their type, size range, shape and color?

• Do the MiP concentrations vary temporally and spatially?

THE OCCURANCE OF MICROPLASTIC IN DRY AND WET

The occurrence of microplastic in atmospheric fallout of Ho Chi Minh City

4.1.1 Number of microplastics found in the sampling sites

During a one-year monitoring, microplastic fibers and/or fragments were found in all samples collected at the three sampling sites (nr) (in both urban and sub-urban areas) There were totally 1,724, 613 and 2,454 microplastic observed respectively at District 10, Cu Chi district and Phuoc Hiep landfill In particular, the number of MiPs found in district 10 (site 1) ranged from 28 to 187 per sample (mean 71.8 ± SD 38.1) Large quantity of total MiPs, ranging from 51 to 179 items (mean 102.3 ± SD 30) was also observed in samples collected from site 3 (Phuoc Hiep landfill), which was similar to abundance of MiPs found in Doulgas fir forest (located in the North of Germany), there were 109.4 ± 19.2 of MiPs observed during three months sampling period in that site (Klein and Fischer, 2019) For samples collected from site 2 (Cu Chi district), there were 10 to 62 of MiP particle found (mean 25.5 ±

SD 12.4) The results were shown in Table 4.1 and Figure 4.1

Table 4.1 Number of microplastic fibers and fragments found at three sampling sites

Sampling site Total number Median Shape in %

Figure 4.1 Abundance of micropastic particle found per sample at three sampling sites

(from 15 th June, 2018 to 25 th May, 2019)

4.1.2 Shape of microplastics found at the three sampling sites

In term of shape of MiPs found, this study mainly detected the accumulation of fibers and fragments in atmospheric fallout in HCMC with the dominance of fibers recorded, corresponding to 4,545 (or 92%) fibers and 400 fragments (or 8%) while fragments accounted for 95 % of total MiPs (fibers and fragments) found in Hamburg metropolitan area (Klein and Fisher et al., 2019) Other studies also performed the presence of fibers and fragments as main shape of MiPs in other areas Besides, microplastic film and foam was also found in Dongguan and Yantai cities (China), occupied 3% and fewer 1% of total MiPs observed, respectively (Cai et al., 2018; Zhou et al., 2017), a few amount of microplastic granule and spherule was also observed in the atmosphere of Shanghai and Asaluyeh (Liu et al., 2019; Abbasi et al., 2019)

As showed in table 4.1, the number of fibers found at all sampling sites predominated over the number of fragments, respectively 94%, 95% and 95 % of total microplastics, at S1, S2 and S3 (Figure 4.3).There were totally 1,619, 584 and 2,342 fibers observed at S1 (district 10), S2 (Cu Chi district) and S3 (Phuoc Hiep landfill), and respectively 259, 59, 112 of fragments detected at those three sites

This observation is similar to the results reported by Dris et al (2015), who found that more than 90% of the total atmospheric microplastic taken from the

District 10 Cu Chi district Phuoc Hiep landfill

Mi cr oplas ti c part icl es per sm aple

Urban site Sub-urban site

Truong Tran Nguyen Sang Page 35 rooftop of Paris-Est Créteil University, which was 11 km far from center of Paris, was fibers (Dris et al., 2015) Cai et al (2018) also reported same result for the samples collected in Doungguan City, China (Cai et al., 2018) Zhou et al (2017) also found that 95% of MiPs found in Yantai City was fibers of different colors (white, black, red and transparent), other types as fargments, films and foams were also obsreved in lower proportion, at 4%, 1% and fewer than 1%, respectively

In more details, the number of fibers found at district 10 fluctuated from 26 items (for sample collected on Nov 25, 2018) to 184 items (for sample collected on Mar 15, 2019), corresponding to the proportion of 83.6 % to 98.4 %, in comparison with smaller percentage, ranging from 1.6 to 16.4 % of found fragments Fibers and fragments were found in all samples (n$) collected at this site (Figure 4.2a)

For samples collected at S2 (Cu Chi district) and S3 (Phuoc Hiep landfill), differences were recorded In Cu Chi district, the presence of fragments was only found in 13 samples over 24 samples collected, no fragments was detected in April, May and November The largest number of fibers found in this sampling site was 62 items, about 3 times less than figure recorded at S1, as showed in Fig 4.2b In Phuoc Hiep landfill, 51 to 165 fibers were measured in all samples (n$), while fragments were only found in 10 samples (Figure 4.2c) We note that the two samples collected in May, 2018, occupied 55 % of total fragments found in all samples No significant difference on concentration of fragments during sampling time found in S1 and S2

Figure 4.2 Percentage of total microplastic fibers and fragments found in all samples at a) S1, b) S2 and c) S3 a) District 10 b) Cu Chi district c) Phuoc Hiep landfill

Figure 4.3 Percentage of total microplastic fibers and fragments found in all samples of each sampling site The presence of the fibers in the atmosphere might mainly be derived from textiles, including clothes, carpets, sofas and chairs (Dris et al., 2016; Gasperi et al.,

2018), while fragments might be generated form the breakdown of larger plastic products, such as packing material, plastic containers and cleaning products (Wang et al., 2018; Yuan et al., 2019) For other types as films and foams, Di et al (2019)

Truong Tran Nguyen Sang Page 38 suggested degradation of plastic bags or polystyrene packing bags under weather condition and ultraviolet radiation.

Concentrations of MiPs at the three sampling sites

From the number of MiP fibers and fragments observed in each sample, knowing the sampling surface was 0.049m 2 and the sampling duration, we calculated the concentration of MiP in items.m - ².d -1

Table 4.2 Concentration of microplastic fibers and fragments found at three sampling sites

The average concentration of MiPs (both fibers and fragments) observed in urban area (District 10) was of 402 ± 209 items m -2 d -1 (as showed in Table 4.2), roughly 4 times more than the concentrations measured in the urban area of Paris, (110 ± 96 items m -2 d -1 , Dris et al., 2016), 10 times more than ones observed in Dongguan City, China, (36 ±7 items m -2 d -1 , Cai et al., 2018) and around 2 times more than mean concentrations of MiPs observed in three urban sites of Hamburg City, Germany (214.6 items m -2 d -1 , Klein and Fischer, 2019) We note that those studies applied different methodology with direct filtration only (Dris et al., 2016; Klein and Fischer, 2019) or direct filtration and drying filters at 50 o C in 48 hours before storing

Truong Tran Nguyen Sang Page 39 them in petri dishes (Cai et al., 2018) We suggest that the difference of methodology used in studies might lead to difference on results observed Simple protocols (filtration without any extraction steps using chemicals) was used in previous studies could not remove unexpected particles in the samples, leading to the accumulation of high concentration of particles, consisting of MiPs, organic and inorganic compounds, zooplankton or algae on the filters after filtration step As results, the identification of MiPs on filters might become extremely difficult and overestimation or underestimation can easily take place

Besides, the difference of limit size considered in studies might also explain for this difference In this study, we considered fibers and fragments in minimum size of 100 àm, while previous studies observed MiPs in smaller size, 63 àm (Abbasi et al., 2019), 50 àm (Dris et al., 2016; Dris et al., 2017, Zhou et al., 2017) or even 23 àm (Liu et al., 2019) In other words, studies consider MiPs in smaller size might observe larger concentration of MiPs and comparison become more difficult In addition, the difference on method of calculation the concentration of MiPs also lead to the difficulty in comparing results found in different areas In this study, concentration of MiPs in the atmospheric was calculated as items.m -2 d -1 , which was similar to the unit used in studies of Dris et al (2015), Dris et al (2017), Zhou et al., (2017), Cai et al (2018), Klein and Fischer (2019) and Allen et al (2019), while, Dris et al (2017), Liu et al (2019) and Abbasi et al (2019) evaluate the presence of MiPs in a cubic meter of air

The Figure 4.4 performed the temporal variation of concentrations of fibers and fragments found at S1 The concentration of fibers fluctuated from 163 to 937 items.m -2 d -1 , with an average concentration of 393,6 items.m -2 d -1 , roughly 15 times more than the average of fragments concentrations estimated at 25,3 items.m -2 d -1 , which fluctuated from 5 to 61,1 items.m -2 d -1

Figure 4.4 Concentration of microplastic fibers and fragments found in District 10

High concentration of MiPs found in Distrtict 10 may come from the use of textiles, daily local activities such as directly hanging clothes under UV light, city dust, car smoke, building construction, which was similar to sources demonstrated in previous studies

4.2.2 Site 2: sub-urban area (Cu Chi district)

As can be seen in table 2, in the sub – urban site (Cu Chi district), there were

141 ± 64 items m -2 d -1 of MiPs recorded in average, which was about 3 times more than concentration of microplastic particles observed in sub-urban area of Paris, at 53 ± 38 items m -2 d -1 (Dris et al., 2016).However, one other study conducted in a remote mountain catchment (French Pyreness) found larger concentration of MiPs, around

365 items found daily per 1 m 3 of air (Allen et al., 2019)

The Figure 4.5 performed the temporal variation of concentrations of fibers and fragments measured at S2 The concentration of fibers fluctuated from 50.9 to 315.8 items.m -2 d -1 , with an average concentration of 140.1 items.m -2 d -1 , roughly 19 times more than the average of fragments concentrations estimated at 7.5 items.m -2 d -

1, which fluctuated from 0 to 67.9 items.m -2 d -1

Figure 4.5 Concentration of microplastic fibers and fragments at Cu Chi district

Similar to accumulation sources of MiPs described at D10, in Cu Chi District, MiPs are also generated from point and non-point sources Main point sources need to be considered including breakdown of plastics from buildings/households, kitchen smoke from households Other non-point sources can also distribute asignificant quantity of MiPs into the atmosphere there as: city dust, car smoke, hanging clothes, burning illegal grabages or breakdown of house furnitures

The MiP concentration in samples taken at Phuoc Hiep landfill was also recorded with average concentration of 551 ± 139 items m -2 d -1 , high concentration of MiPs was found in all samples collected from this site (n$), ranging from 346.3 to 845.4 items m -2 d -1 This study firstly conducted the monitoring in a landfill, which was considered as one of main sources for formation and transport of atmospheric MiPs into the environment (Cai et al., 2019) In particular, 86 % of total solid wastes in HCMC was landfilled at two major landfills (Phuoc Hiep and Da Phuoc), consisting of 3,794 tons of plastic monthly (Verma et al., 2016) Because Phuoc Hiep landfill was closed 5 years ago, the sampling device was installed 10m far from the weight station of the landfill, which was surrounded by trees for investigating the influence of the degradation of plastic waste under UV light and weather conditions on surrounding environment The concentration of MiPs found was similar to results

Truong Tran Nguyen Sang Page 42 reported by Klein and Fischer et al (2019) In the forested area of Harburg Hills in the south of Harburg (Germany), concentration of atmospheric MiPs found was 331.4, 512 and 343.1 items m -2 d -1 at oak forest, Dougkas fir forest and open field, respectively, with an average of 395.5 items m -2 d -1 We suggest that, the degradation of plastic waste in landfill was one of the main sources of MiPs in the atmosphere Besides, the number of MiPs attaching on leaves might the potential source of MiPs entering to air environment

As showed in figure 4.6, the concentration of fibers found in this landfill was also higher than that of fragments, fluctuated from 346.3 to 840.3 items.m -2 d -1 , with an average concentration of 566 items.m -2 d -1 , roughly 19.5 times more than the average of fragments concentrations estimated at 29 items.m -2 d -1 , which fluctuated from 0 to 251.3 items.m -2 d -1 (Table 4.2)

Figure 4.6 Concentration of microplastic fibers and fragments at Phuoc Hiep landfill

Point and non-point sources of MiPs found in Phuoc Hiep landfill is minor different from other sites MiPs in this site mainly may come from degradation of plastic wastes, car smoke Besides, a lagre number of MiPs accumulate onto leaf surface can distribute MiPs into the ground by rain or wind

Spatial variation of microplastic concentration in atmospheric fallout

Microplastic concentration in atmospheric fallout at different areas was different In this study, the highest and lowest concentrations of microplastic particles were found in site S3 (Phuoc Hiep landfill) and S2 (household in Cu Chi District), respectively S3 was located in a landfill which concentrates a large number of plastic wastes and high traffic density with a lot of trucks coming in and out everyday S2 was located in household from sub-urban area of Ho Chi Minh City, where population density was low Moderate concentration of MiP was observed in S1, which was located in a university zone at urban area of HCMC with dense population and 20m far from a construction site and was much closer to that of S3

Figure 4.7 Concentration of atmospheric MiPs at each sampling site

Different concentrations of MiPs found at three sampling sites (as showed in Figure 4.7) might come from the difference on population density at these sites In particular, average concentration of atmospheric MiPs found in site 1 (District 10) was 402 ± 209 items.m -2 d -1 , nearly 3 times more than that of S2 (Cu Chi District), as a result of higher population density at 41,000 people.km -2 in District 10, comparing to that of 1,000 people.km -2 in Cu Chi district We note that, construction site was also one of main sources of MiPs in S1 Although plastics are not always visible in construction sites, they are used in a wide and growing range of applications, including insulation, piping, window frames and interior design, under impact of

District 10 Cu Chi District Phuoc Hiep landfill C oncent rat ion of Mi P s (i tem s.m - 2 d -1 )

Truong Tran Nguyen Sang Page 44 weather conditions, these large plastics fragment into MiPs, followed by the distribution of these small particles in surrounding areas

The average concentration of microplastics observed in the three sites in HCMC was 380 ± 231 items m -2 d -1 , 3 times and 10 times larger than in Paris and Dongguan City, big cities in developed countries (Dris et al., 2016; Cai et al., 2018) Similar concentration, at 365 ± 69 items m -2 d -1 was found in Shanghai (Liu et al., 2019) The higher concentrations observed in HCMC than in other cites as Paris, Dongguan, Hamburg, although the fact that these cities had higher population density than in HCMC HCMC has population of 8.5 million people, 3 times and 1.5 times less than that of Shanghai and Paris, respectively As a result, population density might not the factor directly affect to the accumulation of MiPs in the atmosphere, the difference might originate from the different levels in plastic waste management

To be honest, pollution concentration of MiPs at different areas, which was featured by differences on density of population, local activities, weather conditions (light intensity, wind rate, concentration of dusty, rainfall) was found different However, due to the lack of statistic data on above factors in this study as well as limitation on research time, correlation between concentration of microplastic particles and those factors are still not declared in this study

P re ci pit at ion in m l it em s m -2 d -1 precipitation in ml concentration of microplastics a)

Figure 4.8 Concentration of MiPs compared to volume of rain water (ml) at each sampling site a) site 1, b) site 2 and c) site 3 Figure 4.8 showed that no strong correlation between concentration of MiPs and volume of rainwater was found, similar to results reported by Klein and Fischer (2019) However, higher concentration of microplastic particles was observed in dry samples (precipitation = 0 ml) The highest concentrations of atmospheric MiPs was found in dry samples at three sampling locations, corresponding to 954.2, 315.8 and 937.1 items m -2 d -1 , respectively.

Temporal variation of microplastic concentration

The concentration of MiPs fragments and fibers observed fluctuated during the sampling time, particularly larger numbers of items were found during dry days,

P re ci pit at ion in m l it ems m -2 d -1 precipitation in ml concentration of microplastics b)

P re ci pit at ion in m l it em s m -2 d -1 precipitation in ml concentration of microplastics c)

Truong Tran Nguyen Sang Page 46 saying that there was a decrease in microplastic accumulation in atmospheric fallout at Phuoc Hiep landfill in rainy days which may be due to the impact of high rainfall in terms of limiting air pollutants concentration (Kwak et al., 2016)

The variation of microplastic concentration was different at three sampling sites, but highest concentrations of MiPs was found in the early months at all sites The monthly average concentration of atmospheric MiPs at three sampling sites was calculated base on the total number of MiPs found during 7 days of sampling and illustrated in Figure 4.10 In particular, highest concentrations of total MiPs were 952.4, 315.8 and 814.9 items m -2 d -1 was found on February, March and April at S1, S2 and S3, while lowest values were observed in May, June and October, corresponding to concentration of 211.35, 62.8 and 412.35 items m -2 d -1 , respectively

As results, concentration of MiPs in the atmospheric varied temporally In general, the variation was different at different areas The variation trend was illustrated most clearly in site 2 (Cu Chi district) In S1 (district 10) and S3 (Phuoc Hiep landfill), the concentration of atmospheric MiPs might be affected by surrounding environments In other worlds, plants in S3 and buildings in S1, the difference on density of population monthly at two sites can explain for this fluctuation Besides, the dramatic increase in concentration of MiPs at S1 in May might come from the decrease in number of students during summer holiday Concentration of MiPs found in the atmospheric of Phuoc Hiep landfill might be effected by the shedding Under impact of wind-blow, leaves fall into the sampling device and input a part of MiPs in the samples, as explained by Klein and Fischer (2019), air pollutants can attach on leaf area instead of reaching the ground

Figure 4.9 Monthly Concentration of microplastic (items m -2 d -1 ) at the three sampling sites

The difference on microplastic concentration observed from three sampling sites was considered to be mainly related to the population density and local activities at each location (Cai et al., 2018) Besides, the volume of rainwater on sampling time was also recorded and different at three sampling sites for evaluating any correlation between the concentration of microplastic particles and volume of collected rainwater Similar to results reported by Dris et al (2016), no significant correlation was highlighted (Figure 4.10)

Figure 4.10 Concentration of atmospheric microplastics on site S1, S2, S3 in parallel with daily rainfall (volume of rainwater) 0

N ovem be r D ec em b er Ja nuar y Febr uar y Ma rc h A pr il Ma y Jun e Jul y A ugus t Sept em be r O ct ober

Cu Chi district Phuoc Hiep landfill

V ol ume of rai nw at er ( L )

Cu ChiPhuoc Hiep landfillVolume of rainwater - S1Volume of rainwater - S2Volume of rainwater - S3

Table 4.3 summarized existing research on MiPs in the atmosphere in the world

To date, knowledge of atmospheric MiPs remains limited Only few studies have examined the occurrence of MiPs in the atmosphere Previous studies were mostly conducted in few studies and regions and only reported on the abundance and simple characteristics as shape, size, color and nature of MiPs in the atmosphere First results demonstrated that airborne MiPs was found in all regions studied (both high and low countries, urban and rural/remote areas) and accumulate differently as a result of the difference on population density, living standard, economic development and specially the level of plastic waste management between regions and countries However, the difference in methods of collecting and treating samples as well as considering different minimum sizes, also leading to difficulty in comparing

The current study firstly investigates the long-term monitoring at three different areas in a developing country As a result, the occurrence of MiPs was found in the HCMC and varied temporally and spatially.

Chapter summary

The occurrence of microplastics in atmospheric fallouts in Ho Chi Minh City was illustrated in this chapter High concentration of fibers and fragments was recorded and in comparing to other relative studies In addition, information on shape, temporal and spatial variation of microplastics concentration in atmospheric was also described Results on size range, color and chemical composition of atmospheric found at sampling sites are performed and detail discussed in the next chapter, may partly help to explain the origins of the MiPs, i.e natural or anthropogenic, in further analyses for microplastic contamination assessment

Table 4.3 Concentration of microplastics in different areas

Sampling area Methods for sampling and samples treatment

Concentration (items.m -2 d -1 ) References Paris Urban area Directly filtration 100 29 -280 Dris et al., 2015

Paris Urban, sub- urban Directly filtration 50 2 - 355 Dris et al., 2016

Paris Urban area Density separation + filtration 50 0.9 n.m -3 Dris et al., 2017

Yantai Urban area Chemical extraction + filtration 50 400 n.m -2 d -1 Zhou et al., 2017

Directly filtration + drying filter under 50 o C in 48hrs

Pyrenees Remote area Chemical extraction + filtration 50 365 ± 69 Allen et al., 2019

Klein and Fischer et al.,

Chemical extraction + filtration - 1 n/m 3 Abbasi et al.,

HCMC Urban, sub- urban, landfill

PHYSICAL CHARACTERISTICS OF MICROPLASTIC IN

Size of fibers and fragments measured at the sampling sites

Concerning the size of MiPs found in District 10, most of the fibers and fragments were in the small size range (Figure 5.1) As can be seen in Figure 5.1 a, the smaller fibers, ranging from 100 – 1,100 μm in length were predominant with nearly 75% total fibers counted while longer fibers (larger than 1,100 μm in length) were relatively rare However, results reported by Dris et al (2015) were in contrast For samples collected on the rooftop of Paris-Est Creteil University, authors found that 50 % fibers were longer than 1,000àm (Dris et al., 2015)

Among fibers found at S1- District 10, ones in length of 300-500 àm occupied highest proportion, at 23.9 % of total fibers This result was similar to length distribution of fibers shown by Dris et al (2016), authors found 23 % of fibers in the 400-600 àm size range in total detected fibers Cai et al (2018) also reported the highest percentage, about 28% of fibers in length size of 200-700 àm for samples collected in Dongguan City (Cai et al., 2018) For samples collected from remote mountains in Paris, Allen et al (2019) primarily found the highest portion of small fibers, with lengths of 100 – 200 àm and 200 – 300 àm Aditionally, Dris et al (2017) observed largest number of fiber in lengths ranging from 50 – 450 μm in samples collected from indoor and outdoor sampling sites at Paris

In term of the longest fibers observed, this study found fiber in length of 5,00 àm, similar to result of Dris et al (2016), Dris et al (2017), Liu et al (2019) and Klein & Fischer (2019), while fibers up to 4,300 àm long were identified as longest ones found in Dongguan City (China) (Cai et al., 2018) Base on results reported by Dris et al (2017), the length of the fibers in indoor air was always less than 3,250 μm and the longest fiber detected in outdoor air was 1,650 μm In remote area, Allen et al (2019) found the longest fiber in 2,600 àm long among fibers observed from samples collected in Pyreness Mountains

In this site, the fragments were also predominated by smallest surface areas There were 27 and 30 fragments in the surface area range of 1,000 – 10,000 àm 2 and 10,000 – 20,000 àm 2 , respectively, occupied 57 % of total number of fragments observed for all dry and rainy days in District 10 (Figure 5.1b)

Figure 5.1 Cumulative percentage of a) length of microplastic fibers (m); b) area of microplastic fragments (m 2 ) in District 10

Figure 5.2 Cumulative percentage of a) length of microplastic fibers (m); b) area of microplastic fragments (m 2 ) in Cu Chi District Figure 5.2 showed the cumulative percentage in range size of fibers and fragments found in atmospheric fallout in Cu Chi district In contrast with highest

C umul at ive perc ent age (% )

Truong Tran Nguyen Sang Page 52 proportions of small fragments measured in S1, most of fragments found in S2 were in largest surface area There were 9 fragments larger than 80,000 àm 2 in surface area, corresponding to 31% of the total found in this site However, fibers in length size under 1,100 àm was also predominant ones in all of items found, accounted for

Figure 5.3 Cumulative percentage of a) length of microplastic fibers (m); b) area of microplastic fragments (m 2 ) in Phuoc Hiep landfill Similar to fibers found in S1 and S2, most of fibers observed from samples collected in Phuoc Hiep landfill was also under 1,100 àm in length (about 71%) For fragments found in this site, nearly 50% of them were in the smallest surface area (1,000-10,000 m 2 )

C umul at ive perc ent age (% )

Figure 5.4 Cumulative percentage of a) length of microplastic fibers (m); b) area of microplastic fragments (m 2 ) in three sampling sites The difference of size range proportion of fibers and fragments was observed at the three sampling sites As can be seen in Figure 5.4a, most of fibers found at three sampling sites were in length of 300 - 500 àm, representing 24%, 19% and 25%, respectively However, for fragments, the predominant surface area range in D10 was 10,000 – 20,000 range size, counted for 29%, whereas fragments of smallest and highest range area (1,000 - 10,000 m 2 and larger than 80,000m 2 ), occupied 50% and 31% of MiPs found in Cu Chi district and Phuoc Hiep landfill, respectively (figure 5.4b)

Cu Chi Phuoc Hiep landfill

Length of microplastic fibers (mm)

Cu ChiPhuoc Hiep landfill

Color distribution of fibers and fragments found at three sampling sites 54

Figure 5.5 Total microplastics with colors found in the atmospheric fallout collected in sampling sites a) S1, b) S2 and c) S3

In term of color, the blue MiPs was the most dominant for both fibers and fragments (Figure 5.5) Blue microplastics accounted for 66%, 58% and 63 % of total fibrous items observed in S1, S2 and S3, respectively Other colors were in different orders at each sampling sites In district 10 and Phuoc Hiep landfill, transparent ones was the second popular ones, occupied 10% and 24 %, respectively, while violet items made up 20%, ranked 2 nd place in total microplastic particles observed in Cu Chi District Other items in pink, green, white were also found in all samples, but the

Blue Transparent Pink Green Violet White a)

Transparent Pink Green Violet White b)

Transparent Pink Green Violet White c)

Truong Tran Nguyen Sang Page 55 different on proportion was not significant Color distribution of MiPs observed from different areas was different Liu et al (2019) found blue and black items comprised the majority of MiPs, accounted for 37% and 33% of the total MiPs found around the science building of East China Normal University, respectively, while white- transparent items occupied 66 % of MiPs found in street dust of Asaluyeh city (Iran) (Abbasi et al., 2019) These studies mainly characterized color distribution of total MiPs, consisting of fibers, fragments and granules found, no data on distribution proportion of each type was highlighted The current study first time pointed out the color distribution of each type of microplastics observed from atmospheric fallouts (in term of fibers and fragments) in a long-term monitoring Other previous studies mostly concentrated on the concentration, size range (Dris et al., 2015), even surface characteristics or chemical compositions of microplastics (Cai et al., 2018, Kai et al., 2019)

White Violet Green Pink Transparent Blue a)

Figure 5.6 Percentage of fibers in colors found in the atmospheric fallout collected in sampling sites a) S1, b) S2, c) S3 For fibers, blue ones was found in all samples collected (nr) and made up from 63% to 80%, 40 % to 71 % and 50 % to 94% for sample collected at District 10,

Cu Chi district and Phuoc Hiep landfill, respectively Fibers in other colors (transparent, pink, white, violet and green) were also found at different cumulative proportion for each sample In other words, the variety of color and cumulative

Sampling time white violet Green Pink Transparent Blue b)

Sampling time white violetGreenPinkTransparentBlue c)

Truong Tran Nguyen Sang Page 57 proportion of fibers was found different in different sample collected at three sampling sites

Fibers observed from samples collected in Shanghai were identified in more color than in this study In particular, few MiPs in brown, yellow and grey was also found in the school zone of East China Normal University, accounted for 7%, 3.5 % under 1%, respectively (Liu et al., 2019), comparing to the highest percentages of blue and black ones, presenting 37% and 33%, respectively

White green Pink Transparent Blue a)

Sampling time whiteGreenPinkTransparentBlue b)

Figure 5.7 Percentage of fibers in colors found in the atmospheric fallout collected in sampling sites a) S1, b) S2, c) S3 For fragments, the percentage of MiP fragments in terms of colors were more variable in comparison to that of MiP fibers and different at three sampling sites

In S1, fragments were found in blue, white, transparent, pink and green Proportion of blue fragments fluctuated from 29% to 100%, average at 70%, occupied most of fragments found in this site Other colors in decreasing order were white (0 to 66%), transparent (0 to 43%), pink (0 to 33%) and green (0 to 17%) (As showed in Figure 5.7a) Figure 5.7c performed that in S3 blue fragments were also predominant ones, accounted for highest percentage, at 60 %, followed by transparent ones (35%) Same amount of fragments in pink, black and white also observed, each of them occupied nearly 2% of total fragments observed in this site As can be seen in figure 5.7b, blue fragments presented in all samples observed with fragments in site 2 However, among fragments found in this site, white ones were the predominant There are 13 white fragments detected from S2, occupied 45 % of total fragments found Besides, 4 items (or 13.8%) and 1 item (or 3.4%) of transparent and pink fragments also found from this site, respectively There were no green fragments found in S2

Sampling time white black Pink Transparent Blue c)

Most plastic products are coloured by directly adding color masterbatches into the main polymer for creating an more attractive appearance despite the high risk of becoming less sustainable of polymer In particular, color masterbatch, which is in form of pellets (granules), is usually mixed with other materials such as plastic fillers or additives in the production of plastic products (Wong et al., 1997)

Plastics can be colored in many different ways The coloring of plastics uses either pigments or dyes Pigments are organic or inorganic solid particles that are not soluble in polymers Organic pigments provide transparent color and have smaller average particle size with lower thermal stability than inorganics Organic pigment compounds include quinacridones (red) and phthalocyanines white inorganic ones include titanium dioxide (white), carbon black and metal oxides Inorganic pigments provide opaque color and posses high thermal stability However, they do not typically have as bright a color as organic pigments (Wong et al., 1997)

Dyes are organic liquids that are soluble in the plastic and then are dispersed, losing their crystal or particulate structure Dyes are generally used for brighting, clearing and transparenting colors because of their insignificant effect on light transmission through the colored plastic The selection of color, pigments or dyes used in a given application will be determined by the basic structure of the polymer

In recent years, the color respect of microplastics, especial its impacts on the ingestion preferences are studied as an indicator reflecting their potential toxicity.In particular, the lighter colored microplastics are claimed to having lower molecular weight of PAH, and darker microplastics contain higher weight PAH (Fisher et al., 2017) In other words, black microplastics tended to adsorb more chemicals, such as PCBs and PAHs than the white ones (Antunes et al., 2013) As a result, the organisms might occumulate enriched polutants throughout the circulatory system, tissues and organs due to ingestion along with the microplastics (Frias et al., 2013)

Besides, color of MiPs can make them look like marine plankton or grasses, which are daily food for aquatic organisms For instance, 80% of the amberstripe scads in a previous study was found ingesting mainly blue polyethylene fragments, which presented similar morphology in color and size with their blue copepod prey (Ory et a., 2017) Mostly dark colors of MiPs, especially green microplastic fibers,

Truong Tran Nguyen Sang Page 60 which resembled marine plankton, were found in the digestive systems of flathead grey mullet Mugil cephalus (Cheung et al., 2018) The white, clear and blue MiPs, were the most common colors of the microplastics ingested by the planktivorous fishes in the North Pacific central gyre due to the resemblance to their food source

Additionally, the color could reflect the degree of being weathered of the MiPs The affinity between the microplastic surfaces and contaminants is affected, and the loss of the pollutants on the surface of the MiPs during weathering results in a low degree of adsorption The direct relationship between color and pollutant enrichment is a significant discovery in toxicological research The clear mechanisms from the aspects of the chemical composition and how the microplastics with different colors behaved in the aquatic environment should be studied in the future

Moreover, considering the ingestion preference of the organisms and the predictable variation of the contaminant enrichment, monitoring of the MiP color spectrum could be beneficial to the preliminary assessment of MiP toxicity for organisms with different feeding preferences (Hiu et al., 2020)

Tiêu đề	Assessment of Microplastic Pollution in Dry and Wet Atmospheric Fallouts in Ho Chi Minh City, Vietnam
Tác giả	Trương Trần Nguyễn Sang
Người hướng dẫn	TS. Kiều Lê Thủy Chung, TS. Emilie Strady
Trường học	University of Technology
Chuyên ngành	Environmental and Natural Resources Management
Thể loại	Master Thesis
Năm xuất bản	2020
Thành phố	Ho Chi Minh City

Định dạng
Số trang	110
Dung lượng	3,18 MB