Profiling the Vertical Transport of Microplastics in the West Pacific Ocean and the East Indian Ocean with a Novel in Situ Filtration Technique.

A new technique involving large-volume (10 m3) samples of seawater was used to determine the abundance of microplastics (MPs) in the water column in the West Pacific Ocean and the East Indian Ocean. Compared to the conventional sampling methods based on smaller volumes of water, the new data yielded abundance values for the deep-water column that were at least 1-2 orders of magnitude lower. The data suggested that limited bulk volumes currently used for surface sampling are insufficient to obtain accurate estimates of MP abundance in deep water. Size distribution data indicated that the lateral movement of MPs into the water column contributed to their movement from the surface to the bottom. This study provides a reliable dataset for the water column to enable a better understanding of the transport and fate of plastic contamination in the deep-ocean ecosystem.

Consistent Transport of Terrestrial Microplastics to the Ocean through Atmosphere.

Although atmospheric transport and deposition could be an important pathway of terrestrial pollutants to the ocean, little information concerning the presence and distribution of these suspended atmospheric microplastics in marine air is available. We investigated, for the first time, the occurrence and distribution of suspended atmospheric microplastics (SAMPs) in the west Pacific Ocean. In this study, the spatial distribution, morphological appearance, and chemical composition of suspended atmospheric microplastics were studied through continuous sampling during a cruise. SAMPs abundance ranged from 0 to 1.37 n/m3, the median of 0.01 n/m3. Fiber, fragment, and granule SAMPs quantitively constituted 60%, 31%, and 8% of all MPs, respectively. Interestingly, plastic microbeads with numerical proportion of 5% were also observed. A high suspended atmospheric microplastics abundance was found in the coastal area (0.13 ± 0.24 n/m3), while there was less amount detected in the pelagic area (0.01 ± 0.01 n/m3). The amount of suspended atmospheric microplastics collected during the daytime (0.45 ± 0.46 n/m3) was twice the amount collected at night (0.22 ± 0.19 n/m3), on average. Our observations provide field-based evidence that suspended atmospheric microplastics are an important source of microplastics pollution in the ocean, especially the pollution caused by textile microfibers.

Enhanced impacts evaluation of Typhoon Sinlaku (2020) on atmospheric microplastics in South China Sea during the East Asian Summer Monsoon.

Atmospheric transport is an important pathway through which microplastics (MPs) are widely exchanged between marine and terrestrial environments. However, the impacts of frequent extreme weather events, such as typhoons, on atmospheric MPs is poorly understood. To address this issue, we collected suspended atmospheric MPs (SAMPs) and rainfall samples in the South China Sea during Typhoon Sinlaku (2020). Our results revealed a higher abundance of suspended MPs (1.05 ± 0.55 n/100 m3) during the typhoon than in the pre-typhoon period (0.59 ± 0.48 n/100 m3). Nine polymer types were identified by micro-FTIR, among which the dominant were polyethylene terephthalate (PET, 62.82%) and polypropylene (PP, 19.23%). Moreover, rainfall appeared more inclined to remove larger sizes, more colors and more polymer types of MPs from the atmosphere. The trajectory source-receptor plot indicated that the typhoon significantly changed the pathway of MP transport in the atmosphere, including the direction and distance. To our knowledge, this is the first study to elucidate the impact of typhoons on atmospheric MP transportation. Our results indicate that airborne MPs may pose unexpected ecological risks to marine and coastal ecosystems due to their increased abundance from more distant sources, resulting from typhoon events.

Exponential decrease of airborne microplastics: From megacity to open ocean.

Atmospheric transport has been recognized as an important route for microplastics (MPs) entering the ocean since the early 2019s, yet little data of their distribution patterns in marine air are currently available. In this study, we conducted continuous measurements of atmospheric MPs in the marine boundary layer across the western Pacific Ocean. Results suggested that synthetic MPs comprised 25.89 % of all identified particles, with the most being cotton and cellulose (51.68 %). Research revealed that atmospheric synthetic microfibers (22.54 %) are higher than the proportion of the surface oceanic synthetic microfibers (8.20 %) in the recent study. Further, the size of airborne MP fibers over open ocean is probably not the limiting factor during long-range transport. The mean abundance of atmospheric MPs over the western Pacific Ocean during sampling period was 0.841 ± 0.698 items/100 m3. Regression analysis revealed an exponential relationship between average MP abundance and average longitude of sampled stations, and the average abundance of airborne MPs in coastal megacity is three orders of magnitude higher than that in sampled marine air of western Pacific. This study provides a better understanding on the impact of atmospheric transport of MPs within the global plastic cycle.

Pelagic microplastics in surface water of the Eastern Indian Ocean during monsoon transition period: Abundance, distribution, and characteristics.

Microplastics (MPs) have been documented in almost all marine environments, including coastal regions, the open ocean, and the deep sea. However, relatively little knowledge was available about MP pollution in the open ocean, especially the Indian Ocean. We conducted field observations at 36 stations in the Eastern Indian Ocean (EIO), using a typical manta trawl with a mesh size of 330 µm for surface water sampling. Ours is the first study to obtained comprehensive and comparable baseline data about MPs in the EIO, including abundance, spatial distribution and characteristics. Abundance of MPs in the EIO varied from 0.01 items m-2 to 4.53 items m-2, with an average concentration of 0.34 ± 0.80 item m-2. The mean concentration of MPs in the Bay of Bengal (BoB) was 2.04 ± 2.26 items m-2 and 0.16 ± 0.17 items m-2 in the open ocean of the EIO. These results illustrate the high spatial heterogeneity of MPs distribution. Micro-FTIR analysis of polymer composition showed that the vast majority of MPs consisted of polypropylene (PP, 51.11%) and polyethylene (PE, 20.07%). Our data show that MP pollution in the EIO, whether in the epeiric sea or the open ocean, is among the highest of the world's oceans. The BoB is likely to become a MP hotspot due to the vast input of land-based plastics and the presence of multiscale recirculation gyres. These results are absolutely thought provoking: The EIO needs more attention on MPs.

To what extent are we really free from airborne microplastics?

Quality assurance and quality control (QA&QC) procedures are vital for ensuring data reliability, but little is known about the use of such procedures in reducing airborne microplastic (MP) contamination. To address this issue, we tried to determine the efficiency of two common methods (washing and ashing experimental glassware) for removing airborne MPs and identified airborne contamination during MP analytical procedure. The results showed the removal efficiencies of washing and ashing were an average of 88%-98% and 100%, respectively, indicating that both methods could eliminate most of the spiked airborne MPs with no significant difference noted between the two methods. Although rigorous measures were taken to prevent contamination from ambient air, trace amounts of airborne MPs were still detected, which is an issue that has not been adequately investigated in previous studies. All of the procedural contaminants detected in this study were fibrous. Approximately 88% of these fibers were cotton-like (cotton, cellulose, and cellophane) fibers, and 13% of them were plastic. Surprisingly, cotton-like fibers and MPs had a similar size distribution, suggesting that they may have undergone a similar weathering process. In the end, to cope with inevitable airborne contamination, several measures were proposed for further research. Such measures will provide the necessary methodological assistance for accurate quantification of MP pollution in the field.

Global inventory of atmospheric fibrous microplastics input into the ocean: An implication from the indoor origin.

Atmospheric transport could be a significant pathway for inland microplastics (MPs, with size＜5 mm) to the ocean in addition to catchment runoff and coastal discharge. However, atmospheric input of MPs to the ocean is rarely quantified. To address this issue, transport of atmospheric MPs from source to sink was studied in the Asia-Pacific region during nine cruises from October 2018 to September 2019. Both deposited atmospheric MPs (DAMPs) and suspended atmospheric MPs (SAMPs) were collected, ranging from 23.04 n/(m2·d) to 67.54 n/(m2·d), and 0 to 1.37 n/m3, respectively. Size composition revealed that atmospheric deposition of MPs originating in terrestrial regions seems inadequate and insufficient to quantify the atmospheric input to the ocean. In addition, combined with aerodynamic modelling, for the first time, we estimated that 7.64-33.76 t of fibrous atmospheric MPs was globally generated in 2018, which is 3 % and 31 % of riverine input MPs of The Yangtze River and The Pearl River in terms of mid-point mass, respectively. The increasing load of ingestible plastics from sea air could have a far-reaching impact on marine ecosystem.

A novel method enabling the accurate quantification of microplastics in the water column of deep ocean.

Little information concerning microplastic (MP) pollution in the deep ocean is currently available, and a huge gap exists between sampling methodology and obtaining an authentic dataset. Verified sampling methodology is a fundamental step in the accurate determination of MP pollution in the pelagic environment, of which sample volume is a crucial factor. To address this methodological challenge, in situ filtration technology, a novel sampling method for microplastics in the water column, was proposed and investigated. On 27 April 2019, we took the East China Sea as a typical example in order to determine the relationship between sample volume and MP abundance. Analysis indicated that the filtrated volume has an impact on MP quantification and significant exponential regression between the sample volume and MPs was observed. This investigation indicated that a small volume sample could easily lead to MP overestimation, with at least 8 m3 water required to obtain reliable data.