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Article

Concentrations of Airborne Microplastics during the Dry Season at Five Locations in Bangkok Metropolitan Region, Thailand

by
Danuwas Sarathana
and
Ekbordin Winijkul
*
Environmental Engineering and Management, Asian Institute of Technology, Pathum Thani 12120, Thailand
*
Author to whom correspondence should be addressed.
Atmosphere 2023, 14(1), 28; https://doi.org/10.3390/atmos14010028
Submission received: 26 November 2022 / Revised: 17 December 2022 / Accepted: 20 December 2022 / Published: 24 December 2022
(This article belongs to the Section Air Quality)
Browse Figures
Versions Notes

Abstract

:
Information on airborne microplastics (AMPs) in Thailand is still not available. This study monitored and identified AMPs in Bangkok Metropolitan Region (BMR), Thailand. A high-volume air sampler was used to collect AMPs at five different locations in BMR. These five locations are university, roadside, urban park, dumpsite, and industrial estate. The results showed that AMPs concentration was averaged at 333.42 ± 142.99 per cubic meter (n/m3). The concentration of AMPs at the dumpsite was much higher than the concentration in the other areas. The relationship between AMPs and total suspended particles (TSP) was highly dependent on the locations and sources of microplastics nearby. Higher AMP with higher TSP were found at the university, dumpsite, and industrial estate. On the other hand, lower AMP with higher TSP were found at the roadside and urban park. Regarding the shape of the AMPs, the majority (97.22%) of the AMPs were in fragment form while only 2.78% were in fiber form. Polyethylene (PE) in the fragments and cellophane in the fibers were the major polymer types which were present in all locations.

Graphical Abstract

1. Introduction

The production of plastics around the world has grown significantly in the past six decades, reaching 368 million tons in 2019 [1]. Due to its advantages, which are light weight, tolerant to degradation, and being inexpensive, it is widely used for many purposes globally [2]. Moreover, its production was predicted to nearly triple in the next 40 years [3]. According to information from the United Nations Globally Harmonized System, more than half of the plastics associated with monomer, additives, and chemical by-products are dangerous and can cause negative effects to the environment [4].
Accumulation of small plastic particles in the environment is increased by improper waste disposal and slow degradation processes. The size of plastic wastes can be changed by degradation processes in the environment and classified into five size ranges, which consist of larger than 500 mm (megaplastics), 50–500 mm (macroplastics), 5–50 mm (mesoplastics), 1–5 mm (microplastics), and smaller than 1 μm (nanoplastics) [5]. Recently, many researchers have focused on microplastics as a global emerging environmental problem because they are ubiquitous and persistent in the environment. In addition, microplastics have a potential to cause negative effects on human health and the environment [6]. Microplastics can be classified as primary and secondary microplastics based on their origin. Primary microplastics are distributed into the environment directly, such as microbeads in personal care and resin pellets [7]. Secondary microplastics are released from the large fragments of plastics under the degradation processes of biological, chemical, mechanical, and/or photo-oxidative interactions [8]. Several shapes of microplastics can be identified in the environment, such as fragments, foams, fibers, shafts, and flakes. The fate and degradation of microplastics can be dictated by both their size and shape [9].
The presence of microplastics has been widely reported in many environmental compartments, such as marine and fresh water [10,11], and the terrestrial system [12]. Unfortunately, there is still limited research on microplastics in the atmosphere [13]. Airborne microplastics (AMPs) should be considered as a big issue in human health because the AMPs constitute a part of atmospheric particulate matter [14] and can enter the human body and lungs during breathing [15]. Many studies reported that plastic fibers and particles have been found in human lungs [16,17,18], lymph nodes [19,20], and even in the bloodstream [21]. Moreover, several types of AMPs, such as polypropylene (PP), polyethylene terephthalate (PET), polystyrene (PS), and resin were detected in human lung tissue [22]. Although there is not enough evidence on the toxicity of microplastics in human health, it was reported that microplastics from inhalation and ingestion can be a major causes of lung inflammation [6].
In recent years, the number of reports on microplastic monitoring in the air have increased, and several methods to monitor AMPs have been developed. Most of the studies examine AMPs based on passive measurements, but the information of AMPs concentration that derived from active sampling methods are still sparse [23]. Apart from different collection methods, separating microplastics from other contaminants in the samples, especially particulate matter which have similar size to microplastics, is difficult. This study used an active sampling method to collect and examine AMP abundance and identify polymer types at five different locations in the Bangkok Metropolitan Region (BMR), which has rapid urbanization and plays an important role in plastic production [24,25]. Thus, this study is the first to provide the current situation of airborne microplastics in Thailand.

2. Materials and Methods

2.1. Sampling Sites

This study was focused on monitoring AMP in the BMR, which is an urban agglomeration of Bangkok city and five surrounding provinces, namely, Pathum Thani, Nonthaburi, Nakhon Pathom, Samut Sakhon, and Samut Prakan. The total area of the BMR is around 7762 square kilometers with the population density of 1400 inhabitants per square kilometer [26]. Five sampling locations were selected based on the areas with different types of land use and sources of microplastics. These five sampling locations are located in three provinces in the BMR, namely, Bangkok, Pathum Thani, and Samut Prakan. The map of the BMR and the sampling locations in this study are presented in Figure 1.
The first location was the Asian Institute of Technology (AIT), which represents activities at a university campus (location A: 13°45’31.4″ N 100°37’05.4″ E). The second and third locations were roadside (location B: 13°45’22.7″ N 100°37’07.9″ E) and an urban park (location C: 13°45’22.7″ N 100°37’07.9″ E) in front of Ramkhamheang University. These two locations are in a high traffic area (with tire abrasion as potential microplastic source) on the same road. While Ramkhamheang University’s roadside was selected as an area with high traffic with no tree, the Ramkhamheang University’s park was selected to study the level of AMPs in the park. Several studies have reported that different tree species have different impacts on capturing pollutants in the air [27,28]. However, the effect of different types of trees in filtering airborne microplastics has not been investigated in this study. The next location was a garbage dumpsite (location D: 14°08’28.3″ N 100°40’26.5″ E) where AMPs are possibly from the process of the refuse-derived fuel (RDF) production from plastics wastes. Lastly, an industrial estate (location E: 13°33’04.9″ N 100°40’04.4″ E) was selected to represent microplastic levels in an industrial area. The criteria of site selection are provided in Table 1.
Figure 1A–E shows the five sampling locations in this study. Information about each location is provided as follows:
  • University: The high-volume air sampler was placed in an open space with limited human activities nearby.
  • Roadside: The high-volume air sampler was placed around 200 m from a heavy traffic road.
  • Urban park: The high-volume air sampler was placed around 200 m from a heavy traffic road and inside an urban park with many trees.
  • Dumpsite: The high-volume air sampler was placed 50 m away from the RDF processing building where cutting and shredding of plastic wastes to different sizes for RDF production were conducted.
  • Industrial estate: The high-volume air sampler was placed at an industrial estate’s office which is far away from the factories.

2.2. Sampling Methods

Airborne microplastics (AMPs) were collected by the active sampling method using a high-volume air sampler (TE-5170, Tisch Environmental, Inc., Ohio) that is widely used for sampling total suspended particles. For filter paper selection, previous studies [15,29,30,31,32,33,34] used filter papers with the pore sizes ranging from 0.7 to 3.0 μm with no report of AMPs with size less than 10 μm due to the limitation of the current identification methods. For this study we selected a quartz filter with a pore size of 2.2 μm and smooth surface to make it easy to count the number of AMPs. The high-volume air sampler was operated at the flow rate of 75 m3/h. Air samples were continuously filtrated for 24 h during weekdays (Monday to Friday) and weekends (Saturday and Sunday). The filter papers were weighed before and after the sampling using a 4-digit balance (NewClassic Balance-ML2014, Switzerland) for measuring total suspended particulate (TSP). Temperature (°C), relative humidity (%), wind speed (m/s), and wind direction were collected from the Thai Meteorological Department. The samples were collected for 7 days at each location for five locations with a total of 35 samples. The sampling period was three months during the dry season from December 2021 to February 2022.

2.3. Quantification and Identification of AMPs

The Nile red staining method was successfully applied to identify AMPs in previous studies due to it being inexpensive and having the ability to identify microplastics easily [15,29,30,35,36,37]. This method dyes the samples for ease of counting the number of microplastics because Nile red makes the hydrophobic surface of plastics fluorescent when observing through fluorescence microscopes. The collected sample on a quarter of the filter was dyed with Nile red solution in this study. Nile red solution was prepared by mixing Nile red (C26H18N2O2 ultrapure) with chloroform (CHCl3) in a volumetric flask before transferring to a brown glass bottle for storage. One milliliter of Nile red solution was dropped on the filters in two sequences of 0.5 mL each. Then, the stained filter was dried for 24 h at room temperature under laboratory fume hood [38]. The colored filter was put in the covered Petri dish to avoid loss of colored particles and post-collection contamination from AMPs in laboratory room before examining by fluorescence stereomicroscope.
Then, the colored particles from the Nile red staining method were enumerated under a fluorescence stereomicroscope (Olympus SZX16) at 80× to 100× magnification under UV light, and the Olympus cellSens Standard 1.18 software was used to record and measure the lengths of colored particles. According to the Air Quality Guidelines for Europe, the shapes of microplastics can be classified based on their morphology. Fibers were defined by the fraction of length to diameter equal to or more than 3:1 [39] while other particles are fragments. The sizes of AMPs was classified as 2.2–2.5 μm, 2.5–10 μm, 10–100 μm, 100–300 μm, 300–1000 μm, and 1000–5000 μm based on the longest dimension of the microplastic.
The samples from all locations were analyzed by Fourier transform infrared spectrometer (FTIR) to identify the polymer types of the microplastics, such as polyethylene terephthalate (PET), high density polyethylene (HDPE), low density polyethylene (LDPE), polyvinyl chloride (PVC), polypropylene (PP), and polystyrene (PS). FTIR provides the infrared absorption spectra of substances. The results of this analysis were done based on the absorption bands.

2.4. Contamination Control

The quartz filter was wrapped with aluminum foil and put in a desiccator both before and after use. The filter screen and collecting area of the high-volume air sampler were cleaned with alcohol and dry cotton cloth before use. After the sample was collected, the filter was placed on an aluminum tray and covered with aluminum foil to avoid contamination of microplastics in the air after sampling. To prevent contamination during laboratory processing, cotton lab coats and single-use glass nitrile gloves were worn during all laboratory procedures. All glassware and materials were thoroughly washed by Milli-Q water three times before use and covered with aluminum foil after cleaning. Moreover, all samples were processed in a laminar flow hood. A field blank filter was used during the whole sampling process without air passing through the filter and laboratory processes were performed with the same laboratory protocols as the actual sample. No microplastic was found on the field blank filters in this study.

3. Results

3.1. Number Concentration of AMPs at Five Sampling Locations

The concentrations of AMPs at five locations were averaged at 333.42 ± 142.99 per cubic meter (n/m3). The concentration was found as dumpsite > roadside > urban park > industrial estate > university (Figure 2). The highest AMPs number concentration was at the dumpsite with 581.90 ± 28.39 n/m3. At the dumpsite, the high-volume air sampler was put close to the source of AMPs from the RDF processing of plastic wastes. The AMPs concentration at the roadside (349.53 ± 18.53 n/m3) was similar to that at the urban park (312.45 ± 50.43 n/m3) since these two locations are on the same road, one without trees and one inside the park surrounded by trees. At the industrial estate, the abundance of AMPs was 221.48 ± 31.58 n/m3, which was significantly lower than the concentration at the dumpsite, roadside, and urban park. At the university, the lowest concentration (201.72 ± 15.58 n/m3) was observed among the five sampling locations.
In terms of concentration of AMPs in different land-use types (residential, roadside, and industry), the concentration of AMPs in the industrial area (dumpsite) was much higher than that in the residential area (university) and roadside. However, samples collected inside the industrial estate showed low concentration (almost comparable to the concentration at the university) since the samplers were placed far away from the factories.

3.2. Shapes of AMPs

Microplastic fiber was the microplastic with a ratio of length-to-diameter ≥3:1 [39] while the other particles were classified as fragments in this study. Figure 3 shows fragment and fiber shapes of microplastics with Nile red staining under fluorescence stereomicroscope.
In this study, fragments were the dominant shape of AMPs in all locations in the BMR as shown in Figure 4, ranging from 94.29% to 99.11% of the total number of AMPs in the samples at different locations. With all samples in this study, fragments accounted for 97.22% while fibers accounted for 2.78% of the total number of AMPs in all samples (Figure 4f).

3.3. Sizes of AMPs

The size of AMPs was detected in five locations in the BMR ranging from 2.35 to 196.65 μm for fragments, and 72.89 to 3586.14 μm for fibers. The AMPs size in all locations showed the highest percentage in the range of 10–100 μm (51.94%), followed by 2.5–10 μm (27.09%), 2.2–2.5 μm (19.89%), 100–300 μm (0.65%), 300–1000 μm (0.34%), and 1000–5000 μm (0.10%) as presented in Figure 5. The size distribution of microplastics in different size ranges in all sampling sites was similar. More than 98% of AMPs, which constituted the majority, had sizes less than 100 μm. AMPs with sizes larger than 100 μm were present mostly in the university (3.06%) and dumpsite (1.00%) locations where the sources of AMPs were possibly from washing and drying clothes and RDF processing within the areas.

3.4. Polymer Types of AMPs

In this study, samples at each location were selected for FTIR analysis to identify the polymer types of AMPs. Due to the limitation of FTIR spectrometer, only microplastics with sizes larger than 20 μm were analyzed under FTIR. The most common polymers found in this study were polyethylene (PE), polyurethane (PU), polypropylene (PP), polystyrene (PS), and cellophane.
Three types of polymers were found at the university, which were PE, PP, and cellophane. For the roadside and urban park, PE, PU, and cellophane were detected. The highest variety of polymer types were found at the dumpsite, i.e., PP, PU, PE, PS, and cellophane. At the industrial estate, PP, PE, and cellophane were detected, similar to what were found at the university.

4. Discussion

Microplastics are increasingly a concern as a pollutant that can affect human health and the environment. Although the abundance of microplastics was ubiquitously studied in the aquatic and terrestrial environment [10,12], microplastics in an atmospheric environment has limited number of studies. Based on our review of current literature on AMPs in an outdoor environment (Table 2), there is a large variation in AMPs concentration, ranging from <1 to 2019 n/m3. Concentration of AMPs, which was found in the cities, tended to be higher than the values in the open ocean and open sea where no nearby source of microplastics are found. In this study, the 24 h concentration of AMPs from five locations in the BMR was averaged as 333.42 ± 142.99 n/m3, which is at the same level of what was found in the big cities in China (282 ± 127 n/m3) [29,30]. The concentration collected at the roadside by Kaya et al. [15] in Sakarya, Turkey (2019 n/m3), was much higher than the roadside (349.53 ± 18.53 n/m3) and the urban park (312.45 ± 50.43 n/m3) in this study, while a much lower concentration of AMPs was detected in some high traffic areas in Brazil, ranging from 14.02 to 15.90 n/m3. Moreover, at the urban park surrounded by many trees, the concentration of AMPs was slightly lower than that from the roadside when both areas have high traffic volume (both sampling locations were located at the same main road). Similarly, Liao et al. [30] found that the concentration of AMPs in the park was slightly lower than the concentration in the residential areas. However, in this study, the differences in the concentrations between both locations were not significant. Moreover, the sampling at these two locations did not happen at the same time. Thus, the lower concentration may also come from the variation in microplastic concentration between the two weeks of the sampling.
At the industrial areas in this study (dumpsite and industrial estate), the concentration of AMPs at the industrial estate was much lower than the concentration at the dumpsite. Although there are many plastic production industries in the industrial estate, the sampling location at the industrial estate is far from those sources. Therefore, the concentration of AMPs at the industrial estate should represent ambient airborne microplastic concentration that is far away from the sources, similar to the samples collected at the university.
In terms of AMP concentration during weekdays and weekends, the concentration of AMPs during weekdays was higher than the concentration during weekends, especially in the areas near the potential sources of AMPs (roadside, urban park, and dumpsite) as shown in Figure 6. The reason should be the reduction of activities releasing AMPs during weekends. For example, number of vehicles on the road was reduced and the RDF process was stopped during weekends. On the other hand, the concentration of AMPs in some areas (university and industrial estate) where the sampling locations were far away from the sources of AMPs showed that the AMPs concentration during weekdays was slightly higher than that during weekends by only 2%.
Although microplastics are one component of total particulate matter in the air, information about the relationship between AMPs and total suspended particles (TSP) is still limited. The results of TSP concentration and AMPs concentration for 35 samples at five sampling locations in this study are shown in Figure 7. Because of the limitation of and enumerating AMPs as number per cubic meter (n/m3) which was different for the unit of TSP, namely, microgram per cubic meter (μg/m3), the compositions of AMPs in TSP fraction are difficult to estimate. However, from Figure 7, it can be interpreted that the correlations between TSP and AMPs are highly dependent on the location. At the dumpsite, university, and industrial estate, a positive relationship (the higher the TSP, the lower the AMP) between AMP and TSP was found. A negative relationship (the higher the TSP, the lower the AMP) between AMP and TSP was found at the roadside and urban park. When considering all samples in this study, there is no relationship between AMP and TSP in the BMR. This finding is similar to the results of monitoring AMPs in five big cities in China where AMPs had no mutual relationship with PM10 and PM2.5 [29]. In addition, the sources of AMPs and TSPs may be different. TSPs can be released from several sources, such as road dust, industry, power plants, and domestic burning [40], while the main sources releasing AMPs can be plastic litter from human activities, which were physically and chemically degraded before suspension in the air [23].
Metrological parameters (relative humidity, temperature, and wind speed and direction) with 24 h concentration of AMPs are summarized in Table S1 (Supplemental Materials). For the correlation between AMPs and meteorological parameters, Pearson correlation (r) was used. There was a weak correlation between concentration of microplastics and wind parameters (speed and direction) at all locations (r < ±0.38), except the roadside. At the roadside, r = −0.77 between AMPs and average wind speed, meaning high concentration was found with lower wind speed. However, there was no relationship between main wind direction and AMPs. For AMPS and humidity, there were some relationships with r = −0.97 at the industrial estate and r = 0.83 at the roadside. For temperature and AMPs, r = 0.86 and r = −0.81 were found at the roadside and university, respectively. Thus, more samples and in situ meteorological parameters are needed to study the effects of metrological parameters on the concentration of AMPs.
Generally, morphology of AMPs can be classified into various shapes, such as fiber, fragment, film, and sphere. Since the microplastics in this study were collected from the atmosphere, most particle sizes were smaller than 100 μm, leading to difficulties in identifying film and sphere morphologies. Moreover, all samples were stained with Nile red solution, which made all particles fluorescent including film. As a result, film morphologies were difficult to observe in this study. Thus, two forms of AMPs can be identified, namely, fragment and fiber. Some studies, such as Ding et al. [32], can identify more shapes of AMPs (fragment, fiber, granule, foam, and film) by using stereomicroscopy. The results in this study showed that the main shape was fragment, which accounted for 97.22% of the detected microplastics. Similarly, fragment was found with the same proportion in six megacities of China [29,30]. In contrast, some studies, such as in the northwestern South China Sea, West Pacific Ocean, showed that AMPs were predominantly presented as fibers [32,33].
As for the size of AMPs, there is still lack of data for AMPs with sizes less than 10 μm because of the challenges of an analysis method. Zhu et al. [29] and Liao et al. [30] reported that the most abundant size range was microplastics of less than 100 μm, which was similar to what we found in this study. However, some studies found that the most abundant size was larger than 100 μm with fibers as the majority of AMPs [32,33,34]. This study also showed that AMPs in fragment form were dominant in the size range less than 100 μm, and most fiber was found in the microplastics with size larger than 100 μm as shown in Figure 8.
For the polymer types, PE, PU, PP, PS, and cellophane were detected not only in this study, but also in other studies (Table 2). PE, which was found in every sampling site, was the dominant polymer type for AMPs in the fragment form while cellophane was the major type of AMPs in the fiber form. This finding was similar to the study in Surabaya, Indonesia, where cellophane was detected in AMPs in the fiber form [34]. The polymer types of AMPs can be directly linked to the sources of AMPs. For example, more types of AMPs were found at the dumpsite than other locations in this study because all types of wastes were collected in this area for producing RDF, leading to several types of AMPs being generated during RDF production processes (sorting and shredding processes). However, due to the limitation of FTIR, it cannot detect particles smaller than <20 μm. Therefore, other analytical techniques, such as micro-FTIR, micro-Raman, and pyrolysis-GCMS, should be applied to identify the AMPs in the inhalable size range.

5. Conclusions

Our study reports the first evidence of airborne microplastics in Thailand. The concentration of AMPs was studied at five locations, namely, university, roadside, urban park, dumpsite, and industrial estate, to provide the situation of AMPs during the dry season. The concentration of AMPs was 333.42 ± 142.99 n/m3 and ranged from 201.72 to 581.90 n/m3 at the five locations in this study. Concentration of AMPs was found to be dumpsite > roadside > urban park > industrial estate > university. The concentration was higher when the samples were collected close to the sources of microplastics (RDF processing at the dumpsite and traffic at the roadside and urban park), and the concentration was lower when the samples were collected far from the sources (representing ambient concentration at the industrial estate and university). Moreover, this study found that weekday AMPs levels were higher than the weekend AMPs levels, especially at the dumpsite, roadside, and urban park where source activities were less during the weekend. The results in this study provide the current situation of AMPs, which can be used for further studies to better manage airborne microplastics in Thailand.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/atmos14010028/s1, Table S1: Detail airborne microplastic monitoring results and meteorological parameters.

Author Contributions

Conceptualization, E.W.; methodology, E.W.; formal analysis, D.S.; investigation, D.S.; data curation, D.S.; writing—original draft preparation, D.S.; writing—review and editing, E.W.; visualization, D.S.; supervision, E.W. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

All data are reported in the present manuscript.

Acknowledgments

Authors would like to thank Tatchai Pussayanavin and Faculty of Science, Ramkhamhaeng University, Thailand, for the fluorescence stereomicroscope (Olympus SZX16).

Conflicts of Interest

The authors declare no conflict of interest.

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Figure 1. (a) Map of the BMR and location of sampling sites, (b) sampling device at each location: (A) university; (B) roadside; (C) urban park; (D) dumpsite; (E) industrial estate.
Figure 1. (a) Map of the BMR and location of sampling sites, (b) sampling device at each location: (A) university; (B) roadside; (C) urban park; (D) dumpsite; (E) industrial estate.
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Figure 2. Concentration (mean ± S.D.) of AMPs at five locations in the BMR.
Figure 2. Concentration (mean ± S.D.) of AMPs at five locations in the BMR.
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Figure 3. Shapes of Nile red staining plastic particles under fluorescence stereomicroscope. (a) Fragment; (b) fiber.
Figure 3. Shapes of Nile red staining plastic particles under fluorescence stereomicroscope. (a) Fragment; (b) fiber.
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Figure 4. Percent of AMPs in different shapes. (a) University; (b) roadside; (c) urban park; (d) dumpsite; (e) industrial estate; (f) all locations.
Figure 4. Percent of AMPs in different shapes. (a) University; (b) roadside; (c) urban park; (d) dumpsite; (e) industrial estate; (f) all locations.
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Figure 5. Size distribution for AMPs in five locations in the BMR.
Figure 5. Size distribution for AMPs in five locations in the BMR.
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Figure 6. Concentration (mean ± S.D.) of AMPs at five locations during weekdays and weekends.
Figure 6. Concentration (mean ± S.D.) of AMPs at five locations during weekdays and weekends.
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Figure 7. Relationship of AMPs concentration and TSP concentration across the five sampling sites in the BMR.
Figure 7. Relationship of AMPs concentration and TSP concentration across the five sampling sites in the BMR.
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Figure 8. Percent of fragments and fibers in different size ranges of AMPs found in the BMR.
Figure 8. Percent of fragments and fibers in different size ranges of AMPs found in the BMR.
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Table
Table 1. The criteria of site selection in this study.
Table 1. The criteria of site selection in this study.
CriteriaUniversityRoadsideUrban ParkDumpsiteIndustrial Estate
Land use typeResidential areaRoadsideRoadsideIndustrial areaIndustrial area
Source of AMPs nearbyNoYesYesYesNo
Types of trees in 50 × 50 m2 with the high-volume air sampler in the centerNoNoCoconut trees, deciduous trees, palm trees, bushes, etc.NoNo
Table
Table 2. Comparison of number concentration and characteristics of AMPs with previous studies.
Table 2. Comparison of number concentration and characteristics of AMPs with previous studies.
Study AreaEnvironmentNumber Concentration (n/m3)Abundance SizeShapesPolymer TypesReference
Sao Paulo, BrazilOutdoor14.02–15.90Not AvailableNot AvailablePolyester: 80.40%,
other: 19.60%		[15]
5 megacities, ChinaOutdoor282 ± 127<30 μm: 61.60%,
30–100 μm: 33.10%,
100–300 μm: 4.70%,
300–100 μm: 0.50%,
>1000 μm: 0.03%		Fragments: 88.20%,
Fibers: 11.80%		PE, PS, PVC, PA, PP, PET[29]
Wenzhou, ChinaOutdoor189 ± 85<30 μm: 65.10%,
30–100 μm: 29.40%		Fragments: 94.20%,
Fibers: 5.80%		PE, PS, polyester[30]
Sakarya, TurkeyOutdoor2019Not AvailableFragments, FibersPA, PU, PE, polyester (PES)[31]
The northwestern South China SeaOutdoor0.04 ± 0.02<200 μm: 28%,
200–500 μm: 24%,
500–1000 μm: 26%,
>2000 μm: 4%		Fibers: 65%,
Fragments: 20%,
Granules: 8%,
Foam: 4%,
Film: 3%		Polyester: 29%,
rayon: 19%,
PP: 15%,
PE: 13%,
PS: 10%,
PA: 8%,
phenoxy resin: 6%		[32]
West Pacific OceanOutdoor0–1.37<500 μm: >50%Fiber: 60%
Fragment: 31%		PET: 57%
PE: 10%		[33]
Surabaya, IndonesiaOutdoor55.93–174.97<1500 μm: 48%FiberCellophane, PE, PET[34]
5 locations in BMR, ThailandOutdoor333.42 ± 142.992.2–2.5 μm: 19.89%,
2.5–10 μm: 27.09%,
10–100 μm: 51.94%,
100–300 μm: 0.65%,
300–1000 μm: 0.34%,
1000–5000 μm: 0.10%		Fragments: 97.22%,
Fibers: 2.78%		PE, PU, PP, PS, cellophaneThis study
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Sarathana, D.; Winijkul, E. Concentrations of Airborne Microplastics during the Dry Season at Five Locations in Bangkok Metropolitan Region, Thailand. Atmosphere 2023, 14, 28. https://doi.org/10.3390/atmos14010028

AMA Style

Sarathana D, Winijkul E. Concentrations of Airborne Microplastics during the Dry Season at Five Locations in Bangkok Metropolitan Region, Thailand. Atmosphere. 2023; 14(1):28. https://doi.org/10.3390/atmos14010028

Chicago/Turabian Style

Sarathana, Danuwas, and Ekbordin Winijkul. 2023. "Concentrations of Airborne Microplastics during the Dry Season at Five Locations in Bangkok Metropolitan Region, Thailand" Atmosphere 14, no. 1: 28. https://doi.org/10.3390/atmos14010028

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