Atmospheric microplastic transport and deposition to urban and pristine tropical locations in Southeast Asia

Atmospheric microplastics deposition in a central Indian city: Distribution, characteristics and seasonal variations

Atmospheric microplastics (AMPs) transport and deposition in urban areas contribute to microplastics pollution. The present study investigates AMPs deposition, characteristics, potential sources, and the influence of meteorological factors in a central Indian city. AMPs were collected over three land-use types, viz. institutional, commercial, and industrial areas, during four seasons: summer, monsoon, autumn, and winter. The deposition flux of microplastics ranged from 212.53 ± 52.32 to 543.25 ± 71.23 particles/m2/day. The AMPs were predominantly fibres (87.84 %), followed by films (5.43 %), with particle size <1000 μm contributed 43.67 %. The predominant polymer types identified were polyethylene terephthalate (PET, 37.39 %), nylon (20.49 %), and polypropylene (PP, 10.27 %). Higher deposition fluxes were recorded in summer, with 491.06 ± 73.37 particles/m2/day. Correlation analysis revealed a negative correlation between rainfall and AMPs deposition, suggesting a potential cleaning role of rainfall. The estimated annual deposition flux of AMPs in Nagpur city was 3.22 × 1013 particles. Higher AMPs deposition was attributed to plastic waste littering, industrial emissions, and textiles. The estimated mean annual inhalation exposures of AMPs of size 50-250 μm for children and adults were 7375.84 ± 1312.89 and 3738.17 ± 665.39 MPs/kg-bw/year, respectively. The findings of this study contribute to understanding the fate of AMPs and its implications for human exposure. The findings underscore the importance of reducing and managing plastic waste.

Evaluating the role of urban green infrastructure in combating traffic-related microplastic pollution

As cities grapple with the invisible threat of airborne microplastics (MPs), non-exhaust emissions, especially traffic-related MPs, contribute significantly to urban air pollution. While emission regulations have reduced exhaust pollutants, non-exhaust sources remain a significant challenge. Urban green infrastructure (UGI), valued for aesthetic and ecological functions, remains underexplored for MP mitigation. This study assesses the role of a Thuja occidentalis hedge in Kaunas, Lithuania, as a natural barrier against traffic-related MPs. Over a four-month seasonal campaign, passive deposition sampling was conducted at four distances from the street, with additional sampling in the hedge's absence for an experimental-control comparison. Optical microscopy revealed distinct size and shape distributions, while μ-FTIR spectroscopy confirmed dominant polymer compositions: PE (69.05 %) in spring, PIR (35.96 %) in winter, and ACRs (28.52 %) in summer. The highest average fragment concentration occurred in spring (98.25 %), while fibers peaked in winter (12.75 %). Black was dominant year-round, with the highest average in spring (55.35 %), followed by white in winter (42.16 %) and brown in spring (26.98 %). MPs in the 50-100 μm range were most abundant, reaching 55.26 % in spring. A similar trend appeared in vertical MP distribution. The most pronounced difference was noticed at (+1 m) behind the hedge, where MP concentration was 4.59 particles cm-2 day-1, significantly lower than 9.2 particles cm-2 day-1 in the control. The hedge showed peak removal efficiencies in summer (64.5 % total MPs, 64.3 % fragments, 71.4 % fibers). The 50-100 μm range exhibited the highest efficiency, averaging 67.25 % with a seasonal high of 94.24 % in spring. Strong Mantel (rm) and Pearson's (r) correlations of very small MPs (<20 μm) at -1 m suggest a significant influence from tire wear, brake wear, and road dust resuspension. This study highlights Thuja hedge as an active defender against MP pollution, advocating for its strategic integration into urban design to enhance public health protection.

Microplastic proliferation in Malaysia's waterways: bridging knowledge gaps for environmental health

Microplastic (MP) pollution is an imperative environmental concern in Malaysia, distinguished by its insidious nature and enduring detrimental impacts. The nation grapples with challenges such as intensified industrial activities, inadequate plastic waste management, and insufficient law enforcement. There is an urgent need to address Malaysian waterways to mitigate this "Silent Killer" that compromises the food chain, with approximately 50% of MP ingestion attributed to fish, averaging 502.3 mg per individual daily. This review critically evaluates both primary and secondary sources of MP pollution within Malaysia's aquatic ecosystems, categorizing them into three distinct groups: (1) terrestrial sources, (2) aquatic sources, and (3) atmospheric sources. The regulatory frameworks and socioeconomic determinants, including the escalation of vehicle usage and industrial operations, inform these classifications. The research compilation utilized scientific databases, academic conferences, and sector-specific reports. The study underscores the paucity of information regarding MP pollution. It highlights the necessity for comprehensive investigations employing standardized methodologies and primary data collection, encompassing seafood samples, small streams, drainage systems, and sludge analysis. Additionally, secondary data sources, such as air samples from industrial precincts and aquatic environments, are essential for assessing MP. Raising public awareness about post-consumer plastic waste management and oil disposal in restaurants and workshops is crucial. Robust legal frameworks must be enacted and enforced across the nation, extending beyond urban locales, with stringent enforcement and standardized data gathering being vital for formulating effective strategies to reduce plastic waste and foster a safer ecological environment.

Microplastics in the Amur tiger's habitat: Occurrence, characteristics, and risk assessment

Microplastics (MPs) are emerging environmental pollutants that pose a significant threat to wildlife within forest ecosystems. However, the quantity and types of MPs in wildlife forest habitats remain unclear. This study is the first to assess the distribution of MPs in the Amur tiger habitat of northeast China. Our results showed that MPs were detected in soil, water, atmosphere, forage plants, and ungulate and top predator feces within the forest ecosystem, respectively. The average diameter of all detected MPs was 44.99 ± 34.80μm. The predominant polymers found in the samples were polyamide, polyvinyl chloride, and polyurethane. Certain sample types shared similar MP polymer type distributions, indicating potential links in their sources and transfer pathways. Consequently, these findings provide some new insights on the new pollution problem in Amur tiger forest habitats and prompt us to consider how to control and manage the MPs pollution sources in the tiger conservation.

Atmospheric Microplastic Pollution in Textile Industrial Areas: Source, Composition, and Health Risk Assessment

Microplastics (MPs) have been increasingly recognized as a pervasive environmental pollutant, with their presence extending to the atmosphere in urban, suburban, and even remote locations. Despite this, the precise sources of atmospheric microplastics remain elusive. Our study focuses on elucidating the contribution of textile industries to atmospheric microplastic pollution by investigating the atmospheric fallout within and around textile industrial areas. Samples of suspended MPs were collected over seven days from indoor and outdoor locations in six textile industries at Dhaka city, Bangladesh. Through examination using fluorescent microscopy and Fourier transform infrared (FTIR) spectroscopy, we identified transparent and black microplastics, predominantly synthetic textile fibres with lengths ranging from 20 to 180 μm. Chemical analysis revealed polymers such as polyester, nylon, regenerated cellulose, and natural fibres among the observed microplastics. Deposition rates inside the textile factory ranged from 109.0 × 103 to 245.3 × 103 MPs/m2/day, while those outside ranged from 19.3 × 103 to 72.7 × 103 MPs/m2/day, indicating a significant contribution of textile operations to atmospheric microplastic contamination. Furthermore, we calculated the exposure of textile workers to microplastics through inhalation and ingestion, with average rates of 8.7 ± 4.3 mg/kg-Bw/year and 97.9 ± 17.5 mg/kg-Bw/year, respectively. These findings emphasize the substantial health risks faced by textile workers due to microplastic exposure. In conclusion, our study provides compelling evidence implicating the textile factory as a noteworthy source of atmospheric microplastic pollution. It is crucial to address this issue in order to reduce environmental contamination and protect the health of those employed in textile production plants.

Microplastics contamination in natural sea turtle nests at Redang Island, Malaysia

This study presents the first evidence of microplastics in natural sea turtle nests at Chagar Hutang Turtle Sanctuary (CHTS) on Redang Island, a crucial habitat for green turtles. Microplastics were detected in all studied turtle nests (0-70 cm depth), with a total abundance of 12,270 microplastic items per kg dry weight of sand. Fibers (80.7 %) were the most prevalent shape, primarily black (37.9 %), with a high proportion of small-sized particles (<300-1000 μm), indicating prolonged accumulation and environmental degradation. These microplastics, primarily polyethylene terephthalate (PET) and polyethylene (PE), are likely from fishing nets, food packaging, and textiles. Despite the sanctuary's remote location, it is heavily impacted by microplastics carried by tides and wind, raising concerns about their potential effects on turtle egg incubation. The findings offer critical insights into the impact of microplastics on turtle habitats and underscore the urgent need for conservation efforts to protect green sea turtles in Malaysia.

Influence of meteorological conditions on atmospheric microplastic transport and deposition

Atmospheric microplastics are of great concern because of their potential impact on the environment and human health. Although several studies have shown the presence of large quantities of microplastics in the air, questions about the transport and deposition of microplastics in the atmosphere remain unanswered. Based on these shortcomings, this review provides a comprehensive overview of the influence of meteorological conditions on atmospheric microplastic fate. Dry and wet deposition are the main removal mechanisms for atmospheric microplastic. Furthermore, by exploring how wind facilitates the long-range transport of microplastics between terrestrial and marine ecosystems, establishing a global microplastic cycle. Besides, this review also examines the effects of other meteorological conditions on atmospheric microplastic transport. Characteristics of current atmospheric microplastic models are summarized, particularly with respect to the consideration of meteorological conditions. Finally, we propose future research directions and mitigation measures for atmospheric microplastic pollution, which are necessary for mitigating atmospheric microplastic pollution and protecting ecosystems and human health.

Potential source contribution function coupled with mass spectrometry detection to identify source of atmospheric polyethylene terephthalate

Source identification of atmospheric microplastics (MPs) is crucial for the development of mitigation policies. Compared with wind directions or backward trajectories of air masses, the potential source contribution function (PSCF) analysis identifies more comprehensive sources of atmospheric particles. However, conducting PSCF analysis requires hourly pollutant concentration data, which cannot be met by the atmospheric MPs abundance obtained through commonly used methods. In this study, total suspended particles (TSP) samples were collected hourly and the concentrations of atmospheric polyethylene terephthalate (PET) were detected using a liquid chromatography-tandem mass spectrometry. Atmospheric concentrations of PET MPs were 112.9 ± 39.04 ng/m³ (average ± SD). Based on the hourly backward trajectories of air masses and the varied PET concentrations at the sampling site, potential sources of atmospheric PET were identified by PSCF analysis. The backward trajectory-based method indicates that atmospheric PET of the target site in this study primarily originates from dry farmlands. In comparison, both the residential areas and the dry farmlands were identified by PSCF as major sources of atmospheric PET at the receptor site. In contrast, both the backward-trajectory based method and PSCF analysis indicate that TSP mainly originates from the dry farmlands near the sampling site. This indicates that atmospheric PET in urban areas may have different sources from those of TSP, and PSCF is a suitable method for identifying sources of atmospheric PET.

Spatial and seasonal variations of atmospheric microplastics in high and low population density areas at the intersection of tropical and subtropical regions

There is limited information regarding spatial and seasonal variations of atmospheric microplastics (MPs) and factors influencing MPs at the intersection of tropical and subtropical regions. A one-year study was conducted at sites in a high-population-density village (HPDV) and a low-population-density village (LPDV) in Taiwan to investigate the characteristics and influencing factors of airborne MPs. The predominant shapes, sizes, and polymer compositions of MPs were fragments, 3 to 25 and 26-50 μm, and polyamide at both sites. Seasonal variation in MP morphologies was not significant. Average MP concentrations were 2.20 ± 2.97 particles/m3 and 1.92 ± 2.35 particles/m3 at the HPDV and LPDV sites, respectively, and did not differ significantly. Higher concentrations and smaller sizes of MPs were found during the summer at both sites, while the predominant wind direction was southerly or southwesterly. In samples with temperatures exceeding 25 °C, the temperature was positively associated with MP concentrations at both the HPDV and LPDV sites. These results reflect that temperature influences the variations in the concentrations and sizes of MPs at our study site. Future research should consider the adverse risks of MP inhalation during the hot season. Moreover, when sites with different population densities and levels of human activity are closed, MP concentrations will not differ significantly between these areas since airflow can transport these particles from high-population-density areas into low-population-density areas in a short time.

Assessing the external atmospheric input of microplastics: Two strategies based on polymer composition and aging characteristics

Microplastics (MPs) can be transported over long distances in the environment, hence, distinguishing between MPs generated locally and those introduced from external sources is necessary for regional MP pollution management. In this study, MPs pollution in the dust of Siziwang banner (Sizi), a sparsely populated area on the Mongolian Plateau, and Hohhot, a city with large populations, was observed. The high proportion of small MPs in Sizi (<25 μm), combined with the fact that most air masses reaching the area have undergone long-distance transport, supports the presence of external input through atmosphere. Based on the significantly different composition distributions and surface characteristics of the small sized MPs in Sizi and Hohhot, a composition-based Bray-Curtis similarity index (Comp-BCs) and a carbonyl index-based BCs index (CI-BCs) were established. Contributions of the external MPs input to small MPs in Sizi were estimated as 23-36 %, indicating that the role of atmospheric input on MPs pollution in sparsely populated areas should not be overlooked.

Sources, environmental fate, and impacts of microplastic contamination in agricultural soils: A comprehensive review

The pervasive presence of microplastics has emerged as a pressing global environmental concern, posing threats to food security and human health upon infiltrating agricultural soils. These microplastics primarily originate from agricultural activities, including fertilizer inputs, compost-based soil remediation, irrigation, and atmospheric deposition. Their remarkable durability and resistance to biodegradation contribute to their persistent presence in the environment. Microplastics within agricultural soils have prompted concerns regarding their potential impacts on agricultural practices. Functioning as significant pollutants and carriers of microcontaminants within agricultural ecosystems, microplastics and their accompanying contaminants represent ongoing challenges. Within these soil ecosystems, the fate and transportation of microplastics can detrimentally affect plant growth, microbial communities, and, subsequently, human health via the food chain. Specifically, microplastics interact with soil factors, impacting soil health and functionality. Their high adsorption capacity for hazardous microcontaminants exacerbates soil contamination, leading to increased adverse effects on organisms and human health. Due to their tiny size, microplastic debris is easily ingested by soil organisms and can transfer through the food chain, causing physiological and/or mechanical damage. Additionally, microplastics can affect plant growth and have the potential to accumulate and be transported within plants. Efforts to mitigate these impacts are crucial to safeguarding agricultural sustainability and environmental health. Future research should delve into the long-term impacts of environmental aging processes on microplastic debris within agricultural soil ecosystems from various sources, primarily focusing on food security and human beings.

Microplastics in the atmospheric of the eastern coast of China: different function areas reflecting various sources and transport

Suspended atmospheric microplastics (SAMPs) display varying occurrence characteristics on different underlying surfaces in urban areas. This study investigated the occurrence characteristics, source apportionment, and transportation patterns of SAMPs in two typical underlying surfaces: the downtown area (Site T) and the industrial area (Site C) of a coastal city in China. In the spring of 2023, a total of 32 types comprising 1325 SAMPs were detected. The average MP abundances were found to be 3.74 ± 2.86 n/m3 in Site T and 2.67 ± 1.68 n/m3 in Site C. In Site T, SAMPs attributed to living source constituted 78.05%, while industry was the main source in Site C with a proportion reaching 42.89%, consistent with the functional zoning of the underlying surface. Furthermore, HYSPLIT analysis revealed that there was no significant difference between these two sites in long-distance horizontal transport affected by external airflow regardless of altitude; conversely, PCA indicated a notable correlation between vertical velocity and both abundance and species diversity. According to the hourly average wind speeds, the maximum transmission distance was computed as 350 km for updraft and the minimum transmission distances was as low as 32 m for downdraft. Subsequently, the coincidence between the source proportion of SAMPs on random day and meteorological parameters confirmed the synergistic impact on SAMPs transport influenced by functional zoning, geographic environment, and vertical velocity.

Centennial Records of Microplastics in Lake Cores in Huguangyan Maar Lake, China

Microplastic records from lake cores can reconstruct the plastic pollution history. However, the associations between anthropogenic activities and microplastic accumulation are not well understood. Huguangyan Maar Lake (HML) is a deep-enclosed lake without inlets and outlets, where the sedimentary environment is ideal for preserving a stable and historical microplastic record. Microplastic (size: 10-500 μm) characteristics in the HML core were identified using the Laser Direct Infrared Imaging system. The earliest detectable microplastics appeared unit in 1955 (1.1 items g-1). The microplastic abundance ranged from n.d. to 615.2 items g-1 in 1955-2019 with an average of 134.9 items g-1. The abundance declined slightly during the 1970s and then increased rapidly after China's Reform and Opening Up in 1978. Sixteen polymer types were detectable, with polyethylene and polypropylene dominating, accounting for 23.5 and 23.3% of the total abundance, and the size at 10-100 μm accounted for 80%. Socioeconomic factors dominated the microplastic accumulation based on the random forest modeling, and the contributions of GDP per capita, plastic-related industry yield, and total crop yield were, respectively, 13.9, 35.1, and 9.3% between 1955-2019. The total crop yield contribution further increased by 1.7% after 1978. Coarse sediment particles increased with soil erosion exacerbated microplastics discharging into the sediment.

Probabilistic Estimation of Airborne Micro- and Nanoplastic Intake in Humans

Little research exists on the magnitude, variability, and uncertainty of human exposure to airborne micro- and nanoplastics (AMNPs), despite their critical role in human exposure to MNPs. We probabilistically estimate the global intake of AMNPs through three main pathways: indoor inhalation, outdoor inhalation, and ingestion during indoor meals, for both children and adults. The median inhalation of AMPs is 1,207.7 (90% CI, 42.5-8.48 × 104) and 1,354.7 (90% CI, 47.4-9.55 × 104) N/capita/day for children and adults, respectively. The annual intake of AMPs is 13.18 mg/capita/a for children and 19.10 mg/capita/a for adults, which is approximately one-fifth and one-third of the mass of a standard stamp, assuming a consistent daily intake of medians. The majority of AMP number intake occurs through inhalation, while the ingestion of deposited AMPs during meals contributes the most in terms of mass. Furthermore, the median ANP intake through outdoor inhalation is 9,638.1 N/day (8.23 × 10-6 μg/d) and 5,410.6 N/day (4.62 × 10-6 μg/d) for children and adults, respectively, compared to 5.30 × 105 N/day (5.79 × 10-4 μg/d) and 6.00 × 105 N/day (6.55 × 10-4 μg/d) via indoor inhalation. Considering the increased toxicity of smaller MNPs, the significant number of ANPs inhaled warrants great attention. Collaborative efforts are imperative to further elucidate and combat the current MPN risks.

Anthropogenic and environmental factors partly co-determine the level, composition and temporal variation of beach debris

The accumulation of human-derived waste on our coasts is an escalating phenomenon, yet the relative importance and potential interactions among its main drivers are not fully understood. We used citizen-science standardized collections to investigate how anthropogenic and environmental factors influence the level, composition, and temporal variation of beach debris. An average of 58 kg and 803 items/100 m, dominated by single-use items of land (rather than sea) origin, were collected in the 881 beaches sampled. Interactions between anthropogenic and environmental factors (e.g., human use × beach substrate) were the strongest predictors of beach debris, accounting for 34% of the variance explained in its amount and composition. Beach debris showed a highly stochastic temporal variation (adjusted R2 = 0.05), partly determined by interactions between different local and landscape anthropogenic pressures. Our results show that both environmental and anthropogenic factors (at the local and landscape scale) co-determine the level and composition of beach debris. We emphasize the potential of citizen-science to inform environmental policy, showing that land-originated single-use items dominate beach debris, and the importance of considering their multiple anthropogenic and environmental drivers to improve our low predictive power regarding their spatio-temporal distribution.

Microplastics are ubiquitous and increasing in soil of a sprawling urban area, Phoenix (Arizona)

Microplastics are environmental contaminants that have been extensively studied in marine and aquatic environments; terrestrial ecosystems, where most microplastics originate and have the potential to accumulate, typically receive less attention. This study aims to investigate the spatial and temporal soil concentrations of microplastics in a large desert metropolitan area, the Central Arizona-Phoenix Long-Term Ecological Research (CAP-LTER) area. Soil samples from the Ecological Survey of Central Arizona (ESCA) surveys (2005 and 2015) were leveraged to study spatial distributions and the temporal change of microplastic abundances. The temporal soil microplastics data were supplemented by microplastics deposition fluxes in a central location within the area (Tempe, AZ) for a period of one year (Oct 5th, 2020 to Sept 22nd, 2021). Samples were processed and microplastics were counted under an optical microscope to obtain quantitative information of their distribution in soil. Results for the spatial variation of the microplastic abundances in soil samples in Phoenix and the surrounding areas of the Sonoran Desert from 2015 depict microplastics as ubiquitous and abundant in soils (122 to 1299 microplastics/kg) with no clear trends between different locations. Microplastics deposition fluxes show substantial deposition in the local area (71 to 389 microplastics/m2/day with an average deposition flux of 178 microplastics/m2/day) but the role of resuspension and redistribution by dust storms to deposition may contribute to the unclear spatial trends. Comparison between the 2005 and 2015 surveys show a systematic increase in the abundance of microplastics and a decrease in microplastics size. Micro-Raman spectroscopy identified a variety of plastics including PE, PS, PVC, PA, PES and PP. However, a majority of microplastics remained chemically unidentifiable. Polyethylene was present in 75 % of the sampling sites and was the most abundant polymer on average in all soil samples.

Robinia pseudoacacia L. (Black Locust) Leaflets as Biomonitors of Airborne Microplastics

Here we investigate the suitability of Robinia pseudoacacia L. (black locust) leaflets as a novel biomonitor of airborne microplastics (MPs) including tyre wear particles (TWPs). Leaflets were collected from rural roadside locations (ROs, n = 5) and urban parks (UPs, n = 5) in Siena, Italy. MPs were removed by washing, identified by stereomicroscope, and analysed for polymer type by Fourier transform infrared spectroscopy. Daily MP deposition was estimated from leaf area. The mass magnetic susceptibility and the bioaccumulation of traffic-related potentially toxic elements (PTEs) were also analysed. The total number of MPs at ROs was significantly higher at 2962, dominated by TWPs, compared with 193 in UPs, where TWPs were not found. In contrast, total microfibres were significantly higher in UPs compared with ROs (185 vs. 86). Daily MP deposition was estimated to range from 4.2 to 5.1 MPs/m2/d across UPs and 29.9-457.6 MPs/m2/d across ROs. The polymer types at ROs were dominated by rubber (80%) from TWPs, followed by 15% polyamide (PA) and 5% polysulfone (PES), while in UPs the proportion of PES (44%) was higher than PA (22%) and polyacrylonitrile (11%). The mean mass magnetic susceptibility, a proxy of the bioaccumulation of traffic-related metallic particles, was higher at ROs (0.62 ± 0.01 10-8 m3/kg) than at UPs (-0.50 ± 0.03 10-8 m3/kg). The content of PTEs was similar across sites, except for significantly higher concentrations of Sb, a tracer of vehicle brake wear, at ROs (0.308 ± 0.008 µg/g) compared with UPs (0.054 ± 0.006 µg/g). Our results suggest that the waxy leaflets and easy determination of surface area make Robinia an effective biomonitor for airborne MPs including TWPs.