Consistent transport of terrestrial microplastics to the ocean through

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Characterization of Natural and Affected Environments

Consistent transport of terrestrial microplastics to the ocean through atmosphere Kai Liu, Tianning Wu, Xiaohui Wang, Zhangyu Song, Changxing Zong, Nian Wei, and Daoji Li Environ. Sci. Technol., Just Accepted Manuscript • DOI: 10.1021/acs.est.9b03427 • Publication Date (Web): 13 Aug 2019 Downloaded from pubs.acs.org on August 13, 2019

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Environmental Science & Technology

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Consistent transport of terrestrial microplastics

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to the ocean through atmosphere

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Kai Liu a, Tianning Wu a, Xiaohui Wang a, Zhangyu Song a, Changxing Zong a, Nian

4

Wei a, Daoji Li a,

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a: State Key Laboratory of Estuarine and Coastal Research, East China Normal

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University, 500 Dongchuan Road, Shanghai 200062, China

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Abstract: Although atmospheric transport and deposition could be an important

8

pathway of terrestrial pollutants to the ocean, a few information concerning the

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presence and distribution of these suspended atmospheric microplastics in marine air is

10

available. We investigated, for the first time, the occurrence and distribution of

11

suspended atmospheric microplastics (SAMPs) in the west Pacific Ocean. In this study,

12

the spatial distribution, morphological appearance, and chemical composition of

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suspended atmospheric microplastics were studied through continuous sampling during

14

a cruise. SAMPs abundance ranged from 0 to 1.37 n/m3, the median of 0.01 n/m3. Fiber,

15

fragment, and granule SAMPs quantitively constituted 60%, 31%, and 8% of all MPs,

16

respectively. Interestingly, plastic microbeads with numerical proportion of 5% were

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also observed. A high suspended atmospheric microplastics abundance was found in

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the coastal area (0.13±0.24 n/m3), while there was less amount detected in the pelagic

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area (0.01±0.01 n/m3). The amount of suspended atmospheric microplastics collected

 Corresponding Author: Daoji Li. e-mail: [email protected]

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ACS Paragon Plus Environment


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during the daytime (0.45 ± 0.46 n/m3) was twice the amount collected at night (0.22 ±

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0.19 n/m3), on average. Our observations provide field-based evidence that suspended

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atmospheric microplastics are an important source of microplastics pollution in the

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ocean, especially the pollution caused by textile microfibers.

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Keywords: Atmosphere; suspended atmospheric microplastics; distribution; west

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Pacific Ocean

26 27

TOC ART

28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 2


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Introduction

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It is well known that microplastic (MPs) pollution is ubiquitous in the marine

49

environment1-3, and its potential ecological risk is a global concern4. Due to their small

50

size and affinity for persistent organic pollutants5, MPs cause physical and/or

51

physiological damage of the biota exposed to a high dose6-7.

52

The pathway and quantitive analysis of MPs transport from the terrestrial source to

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ocean has been a major challenge, considering the complex and multiple factors from

54

human activities and environment. Traditionally, riverine input8 and coastal discharge9

55

are considered major sources of marine plastic pollution. Recently, several studies

56

suggested that atmospheric MPs could be the potential source for marine MPs

57

pollution10-11. However, atmospheric transport as potential pathway for inland MPs to

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the ocean has been rarely investigated and are poorly understood. A recent study

59

revealed that atmospheric MPs was both detected in the urban and suburban area10. The

60

transportation of SAMPs may be influenced by the roles of atmospheric circulation and

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atmospheric dynamic12. However, most of the research was performed in central urban

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cities13 or coastal areas11, which only revealed the MPs migration in a terrestrial

63

environment. The presence, distribution, and composition of MPs within marine

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atmosphere are still relatively unknown. Therefore, we sampled sea air during a cruise

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in the west Pacific Ocean. It is hoped that this research would provide a better

66

understanding of the transport of terrestrial MPs to the ocean.

67 68

Material and methods

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Study area and sampling

3



70

The distribution of suspended atmospheric microplastics (SAMPs) was investigated

71

in the west Pacific Ocean from November 24, 2018 to January 3, 2019, when the winter

72

monsoon prevailed in the studied area. Sampling was continuously conducted

73

throughout the cruise (Fig.1-a, SI-1). In order to avoid the contamination from the ship,

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it headed either forward or sideways against the wind throughout the cruise.

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As described by Liu et al 11, we used the same technique for SAMPs sampling. In

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brief, the samples of SAMPs were conducted as following procedures. Atmospheric

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samples were collected using a KB-120F type intelligent middle flow total suspended

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particulate sampler (Jinshida, Qingdao, China) with an intake flow rate of 100 ± 0.10

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L/min. Three instruments were set horizontally on the top of the ship at intervals of 1.70

80

m (horizontally)(Fig.1-b). The weather conditions were continuously recorded by a

81

portable meteorological station (Kestrel 5500L, USA) every 20 min. Whatman GF/A

82

glass microfiber filters (1.60 μm pore size, 90 mm diameter) were used during the

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sampling procedure. All of the apparatus was calibrated prior to use. Sampling was

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conducted in triplicate every 4-24 h, depending on the weather conditions (i.e., if there

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was rain). Once the sampling was finished, filter in the instrument was carefully

86

removed and transferred to pre-cleaned sampling cassettes with stainless-steel

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tweezers. Unfortunately, malfunction of the three sampling devices occurred on

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December 1-2 and December 18-20, 2018, because of the rain, resulting in missing

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samples during that period. There was also a malfunction of two of the sampling

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devices, so there were no replicated samples after December 20, 2018. Overall, there

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were 89 samples (filters) collected during this cruise (ab=38; bc=30; cd=21)

92 93 94

SAMPs sample identification In the laboratory, all of suspected microplastics on the filters were photographed and 4


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marked under a stereomicroscope (Leica M165 FC, Germany) with a Leica DFC 450C

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camera on the top.

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A Micro-Fourier Transform Infrared Spectrometer (Thermo Nicolet iN10, USA) with

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an internal mercury cadmium telluride (MCT) detector was used to identify the

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presence of the marked substance14. In present work, all of the marked substance was

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identified. The micro-FTIR spectra were obtained under the transmission mode.

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Calibration to the ambient carbon dioxide and water vapor levels was conducted to

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correct the background interference before analysis. Background signal was obtained

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by scanning the other part of diamond window in the pressure pool and then used to

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automatically calibrate the background interfere during the SAMPs identification.

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The spectra were then analyzed using the OMNIC 9 software package and evaluated

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using the OMNIC spectra library. Samples with matching values > 60% were

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considered plastic materials.

108 109

Source and transport modelling of the SAMPs

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The Hybrid Single Particles Lagrangian Integrated Trajectory (HYSPLIT) model in

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the backward direction has been widely applied to identify the origin of air masses15. It

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could be used for the source identification of fine particulate matters16-17 and

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successfully adopted for verifying the potential source of SAMPs in the remote area18.

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During the modeling, the number of days that was used to calculate the trajectory

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frequencies was set to 48 h. The level adopted for the reversion was 10 m due to the

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approximate sampling height (9.42 m). Meteorological data from GDAS (Global Data

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Assimilation System) was used to simulate the transport of SAMPs.

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Parameters used in the modelling were based on the reference16-17 but higher duration

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period in current study was chosen because of possibly longer transport distance 5



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ascribed to the relative lower density (0.01-1.7 g/cm3) of the common plastic matrix19.

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Source points for the backward trajectory were 122.89°E, 30.85° N (ab), 131.88°E,

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30.37°N (bc); cd: 144.80°E, 16.93°N (cd).

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Weight estimation of the SAMPs

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For better interpretation of the terrestrial input of SAMPs to the ocean, rough

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estimation of the mass weight of the SAMPs was conducted. The weight of the SAMPs

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could be roughly estimated according to the methods by Liu et al11. The total weight of

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the SAMPs was roughly estimated using the following formula:

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𝑀𝑆𝐴𝑀𝑃𝑠 = 𝐴𝛿𝑚𝛿𝜌𝛿ℎ∑0𝑆𝛿,

129

where MSAMPs, 𝑚𝛿, and Sδ represent the total weight (g) of the SAMPs, mass of a single

130

piece of the SAMPs, and sampling area (m2), respectively; 𝐴𝛿 and 𝜌𝛿 represent the

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mean abundance (n/m3) and density (g/cm3) of the SAMPs with specific polymer

132

compositions, respectively. h was the constant value of 9.42 m, the sampling height

133

above sea level.

𝑛

⑴

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Fibrous and fragmented MPs are most abundant both in terrestrial20 and marine

135

environment21. Therefore, we roughly calculated the mass of these two kinds of

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SAMPs. The fibrous SAMPs were generally seen as cylinders, while the fragmented

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SAMPs were deemed cuboid11. The mass of a single piece of fibrous SAMP was

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computed with the following formula:

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𝑚𝛿 = 𝜋𝑟2𝛿𝐿𝛿,

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where rδ and Lδ indicate the transect length and size (along its longest dimension),

141

respectively, of the SAMP. The mass of a single piece of fragmented SAMP was

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calculated with the following formula:

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𝑚𝛿 = 𝑧𝛿𝐿2𝛿,

⑵

⑶

6


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where Zδ and Lδ are the thickness and size (along its longest dimension) of the

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fragmented SAMP.

146 147

Quality assurance and quality control

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All the filters, stainless tweezers, and glass vessels were wrapped with aluminum foil

149

and heated at 450°C overnight before usage. The sample cassettes were totally

150

submerged in the acid media (HCl: H2O, volume ratio 1:10) overnight and then washed

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by distilled water (resistivity: 9.5 MΩ·cm, 25°C) until they reached neutrality. Finally,

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these cassettes were thoroughly rinsed with Milli-Q water (resistivity: 18.2 MΩ·cm,

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25°C) 5-7 times and air-dried in an SW-CJ-1FB type ultra-clean worktable (Sujing,

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Shaoxing) with a vertical wind (0.6 m/s).

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All of the solutions used in this study were filtrated with a 1.6 μm pore size GF/A

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glass microfiber membrane (N0 1820-047, Whatman, UK) prior to use. The

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identification process of the SAMPs were performed in an ultra-clean stainless-steel

158

room (researchers used an air shower before entering), and cotton and nitrile gloves

159

were worn to prevent external contamination during the sampling and analysis

160

procedure.

161 162

Statistical analyses

163

Data analysis was performed using the SPSS 23.0 software. Normality of dataset was

164

tested with Shapiro-Wilk’s test. If SAMPs was not normally distributed, nonparametric

165

tests (Kruskal-Wallis test) was conducted to determine the difference of spatial and

166

temporal distribution of SAMPs. Statistical significance and extreme difference were

167

represented with *=P＜0.05 and **=P＜0.01, respectively.

7



168

The sizes (along its longest dimension) of collected MPs were measured using the

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Image J software (version 1.51j8). Fig.1 was produced with Ocean Data View (Schlitzer,

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2018) and the other graphs were generated by Origin Pro 2017.

171 172

Results and discussion

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Distribution pattern

174

For the first time, we demonstrated the presence of MPs in sea air and their spatial

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distribution from the coastal area to the open ocean. In this study, 26 filters were free

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of SAMPs contamination and 88% of these samples were from the bc and cd areas.

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Overall, SAMPs abundance ranged from 0 to 1.37 n/m3, with the median of 0.01 n/m3

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(Shapiro-Wilk test, P=0.00 ＜ 0.01). Similar to previous study11, heterogenous

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distribution of atmospheric MPs was also found within the replicate collected samples

180

(coefficient of variation: 0-173%). A high SAMPs abundance was found in the coastal

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area (0.13 ± 0.24 n/m3) (ab), while the minimum (no particles were identified) was

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detected in the pelagic area (bc and cd region) (Fig.2-a). Generally, the abundance of

183

the SAMPs tended to decrease and then reach the plateau as the distance away from the

184

continent increased.

185

Based on the occurrence (depositional and suspended) of SAMPs, detailed

186

comparison of the atmospheric MPs among studies was illustrated in Table.1. Overall,

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a higher SAMPs abundance was observed within urban cities, and low abundance with

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apparently lower values was generally found in the coastal area or the pelagic

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environment.

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Significant difference (Kruskal-Wallis test, 2=36.69, df=2, P=0.00 ＜ 0.01) was

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spatially found among the sampling area (ab, bc and cd), implying the nonconservative

192

behavior of SAMPs. Although higher median abundance (0.27 n/m3) was observed 8


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during the daytime, compared with data collected at night (0.22 n/m3) (Fig.2-b), no

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apparent variation was statistically found between samples collected from daytime and

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night period (Kruskal-Wallis test, 2=0.92, df=1, P=0.34 ＞ 0.05). Relative lower

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abundance of SAMPs at night could possibly have resulted from the SAMPs settlement

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caused by the high relative humidity at night, especially on the sea. Liu et al11 found a

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negative relationship between the relative humidity and SAMPs abundance during their

199

investigation. Higher value of relative humidity at night could potentially contribute to

200

the settlement of the SAMPs in present study. Therefore, this period could be crucial

201

for the SAMPs entering the seawater from the sea-air interface. Based on our

202

observation, it was roughly speculated that 52% of SAMPs during the daytime could

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possibly deposit and dispersed in the marine aquatic environment.

204 205

Morphological features

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Fiber, fragment, and granule SAMPs were observed, which constituted 60%, 31%,

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and 8% of all MPs by quantity, respectively. Surprisingly, the rest of the SAMPs were

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plastic microbeads (N=10), which presence in the sea air is firstly reported. Plastic

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microfibers and fragments were observed during the whole cruise, while no trace of

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microbeads was found in the samples from the cd (pelagic) area. Generally, the SAMPs

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shape composition becomes less diverse as the distance away from the coastline

212

increases. In terms of the temporal SAMPs shape composition, the total number of

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SAMPs decreased at night, of which the numerical proportion of fibrous SAMPs

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decreased the most (12%) (Fig.2-b). It was roughly speculated that plastic microfibers

215

are more easily subjected to settlement, which could possibly indicate a close

216

relationship with the fibers’ density and size.

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The size distributions of SAMPs of every shape are shown in Fig. 1S. The size of the

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SAMPs was 16.14-2,086.69 μm, with the average of 318.53 μm. Overall, the size of

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the SAMPs in our research tended to be smaller than those observed in other studies

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(Table 1). Therefore, it speculated that relatively small sized SAMPs could be easily

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transported to the pelagic environment, and their migration to more remote areas is

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likely driven by the wind18.

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The fibrous SAMPs had the highest mean and variation size, while the microbeads

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were the smallest in terms of the average size (Fig.3-a). The overall size order was as

225

follows: fiber (474.81±416.14 μm) > fragment (142.16±98.92 μm) > granule

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(93.65±32.96 μm) > microbead (39.09±21.70 μm). The temporal variation of the

227

SAMPs size is shown in Fig.3-b. The size of the SAMPs varied from 16.14 μm to

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1,785.31 μm during the day and 35.62 μm to 2,086.09 μm at night. Relative higher size

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was found during the daytime (391.79±378.44 μm) than at night (307.72±413.22 μm)

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on average. The absence of large SAMPs could possibly be attributed to the

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atmospheric deposition to the ocean surface during the night. Small sized SAMPs could

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be easily spread to more remote areas by the wind.

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Polymer composition

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We observed 201 particles of SAMPs in this study and identified 14 polymer types

235

(PET:

polyethylene

terephthalate,

EP:

epoxy

resin,

236

polypropylene, PS: polystyrene, PE: polyethylene, PVC: polyvinyl chloride, Phe:

237

phenoxy resin, ALK: alkyd resin, RY: rayon, PMA: poly(N-methyl acrylamide), PA:

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polyamide, PVA: poly (vinyl acetate), PAN: polyacrylonitrile, and PP: polypropylene)

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through spectral analysis (Table 1S in the supporting information). PET, EP, and PE-

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PP SAMPs comprised 57%, 10%, and 6% of the verified MP particles, respectively.

241

Meanwhile, 190 pieces of cellulose were verified during the spectrum analysis and 10


PE-PP:

polyethylene-

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constitute 24% of all observed particles by quantity. A detailed comparison with the

243

results of other studies is illustrated in Table 1.

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An exceptionally high percentage of PET was observed in the sea air (54%). The

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spatial and temporal variation of the SAMPs chemical composition is shown in Fig.3-

246

a and Fig.3-b, respectively. PET SAMPs were the most common particles found in the

247

studied area and comprised the major part of total SAMPs in every sampled area.

248

Statistical analysis revealed that there was no significant difference of the polymer

249

compositions among these three regions (Kruskal-Wallis test, 2=0.89, df=2, P=0.64＞

250

0.05) and no apparent temporal variation of major polymer components of the SAMPs

251

was found (Kruskal-Wallis test, 2=0.08, df=1, P=0.77＞0.05).

252

Drastically small amount of PET SAMPs in the bc area could possibly be due to

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complex joint action of significant distance away from the emission source and

254

environmental factors. SAMPs collected in bc area could potentially derived from

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textile source of remote region and transport would be independent of the

256

precipitation27. Though the total number of isolated SAMPs decreased by quantity, the

257

numerical ratio of the PET SAMPs was higher in the cd region, where there are a few

258

islands with inhabitants. A higher relative content of PE-PP was observed in the bc and

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cd areas (pelagic area) compared with the ab area (coastal area). The SAMPs with a

260

low density and small size could possibly have been transported farther out. Another

261

explanation might be that the fine SAMPs with a lower density originated from the

262

deposition of atmospheric MPs at higher altitudes18.

263

Interesting temporal variations of the polymer composition of SAMPs were found

264

(Fig.3-b). The proportion of PET and PE-PP decreased at night compared with the

265

results from the daytime, which was speculated to have a close relationship with its

266

physic-chemical property (density and hydroscopicity) and environmental factors 11



267

(pollution source and humidity). The EP polymer made up about four times the number

268

of SAMPs collected at night than collected during the day. RY and PVC were not

269

observed in the sample collected during the night, which was possibly influenced by

270

the density of the materials. Overall, the spatial and temporal variation of the SAMPs

271

may be mainly affected by the combination of the polymer density and relative

272

humidity from the surroundings.

273

Sources and weight estimations of SAMPs

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Sources of SAMPs may be complex and hard to trace, but their physical appearance

275

(Fig. 4) and chemical compositions can be used to tentatively explore their origin. The

276

primary sources of colorful fiber-shaped SAMPs probably originated from textile

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materials. The highest quantitative proportion of the PET microfiber probably

278

originated from the abrasion or breakdown of clothes fabricated with synthetic fibers.

279

PE-PP fragments with a black color and irregular shape could have resulted from the

280

incomplete combustion of plastic debris in the terrestrial environment. Once it was

281

released into the air through a chimney, the fragments may have been transported to

282

remote areas through the wind, with some of the fragments entering the marine

283

ecosystem11.

284

In the present study, there were 14 pieces of EP SAMPs with granule and microbead

285

shapes. Based on their spherical appearance and black color, these fragments may have

286

been the product of a thermal reaction. Considering their small size (85.69±55.83 μm,

287

on average) and low density, we speculated that the SAMPs with the EP component

288

mainly originated from the atmospheric deposition at a higher altitude18. This

289

speculation is consistent with the findings by Allen et al18. During the investigation of

290

Pyrenees mountainous catchment (few human activities), higher numerical proportion

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of smaller sized atmospheric MPs ( ＜125 μm) was found at 1,425 m above the sea

292

level.

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The general emission source and transport of SAMPs were roughly inferred using the

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monthly wind field (Fig. 2S). The SAMPs in area ab could have resulted from Korean

295

and northeastern Chinese emissions. It was speculated that Japan could be a source of

296

the SAMPs found in the bc area. For the southeast part of the sampling area (cd), a

297

potential source of these synthetic particles could be the adjacent Mariana Islands. This

298

previous conclusion was explicitly confirmed by further backward trajectory analysis

299

of HYSPLIT model. General emission and dispersion pattern of the SAMPs pollution

300

for each area (ab, bc, and cd) could be traced (Fig.3S).

301

Due to the prevalence (91% of the total SAMPs) of the fibrous and fragmented

302

SAMPs, the total weight of the SAMPs was approximated by the sum of the SAMPs in

303

the studied area. Based on the previous equation ⑴, the total weight of the SAMPs

304

input from the adjacent continent was estimated. The rough estimation of the SAMPs

305

weight was found using the above formulas (Table 2S). Based on our preliminary

306

modeling, there were 101 kg SAMPs within the top 9.42 m of sea air from November

307

to December 2018. Assuming all of these SAMPs were spread from the nearby

308

continent, there are about 1.21 metric tons of SAMPs entering the marine ecosystem

309

within the studied area annually. Based on the temporal (day and night) variation of the

310

present study, there are 0.63 tons of atmospheric MPs deposition through the air-sea

311

interface at night. In the event of rain, more SAMPs will probably enter the seawater.

312

The pathway and quantitive analysis of MPs transport from the terrestrial region to

313

marine environment has been a major challenge. Although considerable amount of

314

these pollutant in the ocean was ascribed to the riverine and coastal discharge 8-9 through

315

modelling, MPs could potentially and consistently contribute to the marine MPs 13



316

pollution through atmosphere. In present study, for the first time, we provide the field-

317

based evidence testifying the prevalence and distribution of MPs in the sea air. Invisible

318

but not negligible amount of SAMPs was observed during the cruise of the west Pacific

319

Ocean, ranging from 0 n/m3 to 1.37 n/m3. Our observation implied SAMPs could be

320

another vital source for the marine MPs pollution, especially for the smaller sized MPs.

321

Through atmospheric circulation, these atmospheric MPs could be possibly transported

322

to the polar region. Based on our preliminary estimation, 1.21 metric tons of SAMPs

323

from the terrigenous source would be annually transported to the marine environment,

324

leading to the further unexpected ecological consequence. Our study is aimed to provide

325

the baseline for the better understanding the bio-geo-chemical cycles of MPs on earth.

326

Associated content

327

Supporting information

328

Normalized size distribution of fibrous, fragment, granule and microbead SAMPs

329

observed in the study (Fig.1S). Polymer types of identified SAMPs in the study

330

(Table.1S). Monthly wind field at 10 m height (a: November; b: December) during the

331

cruise in the study (Fig.2S). 48 hours backward trajectory of SAMPs in the study

332

(Fig.3S). Total weight of SAMPs collected in the present study (Table.2S). Detail

333

information of the atmospheric samples and physic-chemical property of observed

334

SAMPs (SI-1, a separate excel file).

335

Author information

336

Corresponding Author

337

Tel: +86 (21)-62231085

338

ORCID

339

Kai Liu: 0000-0003-3555-4567

340

Notes

E-mail: [email protected]

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The authors declare no competing financial interest

342 343

Acknowledgments

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This research was financially supported by the National Key Research and

345

Development Program (2016YFC1402205), the National Natural Science Fund of

346

China (41676190), and the ECNU Academic Innovation Promotion Program for

347

Excellent Doctoral Students (YBNLTS2019-007). We would like to thank Zheng Hui

348

and Wu Jianbao from the Rainbow Fish Company for their sampling assistance. We

349

also offer our sincere gratitude to the NOAA Air Resources Laboratory for the

350

provision of the HYSPLIT transport and dispersion model (http://www.ready.noaa.gov)

351

used in this study.

352

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Robbens, J; Paul-Pont, I; Soudant, P; Huvet, A. Oyster reproduction is affected by

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annual input into the sea from China. Acta. Oceanol. Sin, 2018, 37(11), 26-39.

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10. Dris, R.; Gasperi, J.; Saad, M.; Mirande, C.; Tassin, B. Synthetic fibers in

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atmospheric fallout: a source of microplastics in the environment?. Mar. Pollut. Bull,

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waters: the first reported values of particles in surface and sub-surface samples. Sci.

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the Changjiang Estuary, China. Environ. Pollut. 2017, 225, 283-290.

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transport emissions on the elemental composition of PM10-2.5 and PM2.5 in Beirut.

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27. Stanton, T.; Johnson, M.; Nathanail, P.; MacNaughtan, W.; Gomes, R. L.

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Freshwater and airborne textile fibre populations are dominated by ‘natural’, not

430

microplastic, fibres. Sci. Total. Environ, 2019, 666, 377-389.

431 432 433 434

Figure and table list

435

Fig. 1 Geo-location of the sampling track (a) and sampling device used in the study

436

(b) The red dotted line and black dots indicate the cruise track and beginning or ending

437

points of the SAMPs sampling, respectively (more information in SI-1). The division

438

of the sampling areas (ab, bc, and cd) was based on the general distance from the

439

coastline, representing the nearshore (ab), pelagic (bc) and remote (cd) region.

18


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440

Fig.2 Spatial (c) and temporal (d) distribution of SAMPs abundance. In Fig.1-d,

441

day and night SAMPs were collected on November 24 and 25, 2018, before the

442

departure of the ship. The pie charts show the corresponding shape composition of

443

every sample area or period. Extreme significant difference (P=0.000) was found

444

between the SAMPs abundance from ab and other regions (bc and cd). No apparent

445

difference of SAMPs abundance was spatially found between bc and cd area.

446

Fig.3 Spatial (a, c) and temporal (b, d) variation of SAMPs morphological

447

appearance (shape and size) and polymer compositions. In the Fig.3-a and Fig.3-c,

448

the spatial variation of the SAMPs size and polymers was illustrated, respectively; In

449

the Fig.3-b and Fig.3-d, the temporal distribution of the SAMPs size and chemical

450

composition was demonstrated, respectively

451

Fig. 4 Photos of typical SAMPs sampled from the atmosphere in the study. a, b:

452

fibers; c, d: fragments; e: granule; and f: microbead

453

Table 1 Physicochemical characteristics of atmospheric microplastics among

454

studies.

455 456 457 458 459 460 461 462 463 19



464 465 466 467 468 469 470 471

Figure 1

472 473 474

a

b

475 476

ab

477 478 479 480

bc

481 482 cd

483 484 485 486 487 488 20


Page 20 of 25

Page 21 of 25


489 490 491 492 493 494 495 496

Figure 2

497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 21



Page 22 of 25

514 515 516 517 518 519 520 521

Figure 3

522 523 524

a

b

c

d

525 526 527 528 529 530 531 532 533 534 535 536 537 538 22


Page 23 of 25


539 540 541 542 543 544 545 546 547

Figure 4

548 549 550 551 552

a

b

c

d

e

f

553 554 555 556 557 558 559 560 561 562 563 23



564 565 566 567 568 569 570

Table 1

24


Page 24 of 25

Page 25 of 25


571 572 573 574

Studied Area Paris (urban city)13 Paris (urban and suburban area)10 Paris (urban)23

575 576 577 578 579 580 581

Dongguan (coastal city)24 Yantai (coastal city)17 Pyrenees mountains (remote mountain)18

Sample State Depositional Depositional Depositional Depositional Depositional

MPs Abundance 0.29×102-2.80×102 n/(m2·d) 0.02×102-3.55×102 n/(m2·d) 1.59×103-1.11×104 n/(m2·d) 1.75×102-3.13×102 n/(m2·d) 1.30×103-1.10×104 n/(m2·d)

Physical and Chemical Characterization of MPs Size (mm) Color1

Shape

Polymer Types2

Fiber

0.10-5

N/A

N/A

Fiber

0.05-0.60

N/A

PET, PA, PU

Fiber

0.05-3.25

N/A

PA, PE, PP

N/A

Black, blue, pink, red, white, yellow

PE, PP, PS

0.05-1

Black, red, transparent, white

PET, PE, PVC, PS

Fiber, foam, film, fragment Fiber, foam, film, fragment

Depositional

365±69 n/(m2·d)

Fiber, fragment, film

0-3

N/A

PET, PE, PP, PVC, PS

Asaluyeh county, Iran (coastal city)26

Suspended

0.30-1.10 n/m3; 1.00 n/m3 (average)

Fiber, fragment

0-5

Black, blue, green, grey, orange, pink, red, transparent, white, yellow

N/A

Shanghai (coastal city)11

Suspended

0-4.18 n/m3; 1.42±1.42 n/m3 (average)

Fiber, fragment, granule

0.02-9.55

Black, blue, brown, green, grey, red, transparent, yellow

PET, PE, PES, PAN, PMA, EVA, EP, ALK

Suspended

0-1.37 n/m3; 0.06±0.16 n/m3 (average)

0.02-2

Black, blue, brown, green, grey, orange, pink, purple, red, transparent, white, yellow

PET, PE, PE-PP, PES, ALK, EP, PA, PAN, Phe, PMA, PP, PS, PVA, PVC

582 West Pacific Ocean (open ocean) (present study)

Fiber, fragment, granule, microbead

1 N/A stands for “not reported.” 2 PET: polyethylene terephthalate; PE: polyethylene; PE-PP: polyethylene-polypropylene; PP: polypropylene; PES: polyester; PAN: polyacrylonitrile; PMA: poly (N-methyl acrylamide); EP: epoxy resin; ALK: alkyd resin; Phe: phenoxy resin; PVA: poly(vinyl acetate); PS: polystyrene; PVC: poly (vinyl chloride); PA: polyamide; and Phe: phenoxy resin

25


Consistent transport of terrestrial microplastics to the ocean through

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