Search

• Airborne particulate matter was collected from urban and industrial sites in Ahvaz. • Microplastics (MPs) were isolated from samples and characterised by established techniques. • All MPs were fibrous and the dominant polymers were PET, nylon and polypropylene. • Concentrations of MPs (< 0.017 m−3) exhibited no clear temporal trends or inter-site differences. • Sample characteristics and trajectory modelling suggest both local and long-range sources. Airborne particulate matter (PM) with an aerodynamic size cutoff of 10 µm (PM10) has been collected using a high volume air sampler at two locations (urban and residential) in the city of Ahvaz, Iran, for sixteen 24-hour periods over four months (late summer to early winter). Microplastics (MPs) in the PM were isolated after sample digestion and were subsequently characterised by established techniques. All MPs sampled (n = 322) were of a fibrous nature, with polyethylene terephthalate, nylon and polypropylene being the dominant polymers and consistent with textiles and fabrics as the principal source. Despite a distinct seasonality (temperature and wind) over the study period, the abundance, size and colour of the fibres exhibited no clear temporal trend, and no clear differences were observed between the two sites. Concentrations of MPs ranged from none detected to about 0.017/m3 (median = 0.0065/m3) and are at the low end of ranges reported in the recent literature for various urban and remote locations. While some MPs may have a local origin, the weathering of other MPs and their acquisition of extraneous geosolids and salts suggests that long-range transport is also important. Back-trajectory calculations indicate that regional sources are mainly to the north and west of Ahvaz, but a southerly, maritime source is also possible in late autumn. Although concentrations of MPs in the atmosphere are well below those encountered in indoor air, further studies are required to elucidate their potential ecological impacts. [Display omitted] [ABSTRACT FROM AUTHOR]

Highlights: Microplastics (MPs) and microrubbers (MRs) determined in lichens and mosses around Shiraz. In lichens, MPs mainly thin fibres up to 1 MP g -1 ; MRs were < 0.1 MP g -1 . In mosses, abundances were similar but with a greater fraction of larger, non-fibrous particles. Larger MPs and MRs decreased in abundance with distance and elevation from Shiraz. Around Shiraz, the common moss, Grimmia critina, would be the most suitable biomonitor. Lichens and mosses have been employed as biomonitors of atmospheric particulate pollutants, like metals and industrial solids, for many decades. Here, we evaluated the potential of nine species of crustose and foliose lichens and a widely distributed moss (Grimmia critina) to act as biomonitors of airborne microplastics (MPs) and microrubbers (MRs). About 200 lichens and 40 mosses were sampled across different altitudinal transects in the vicinity of Shiraz City, southwest Iran, and MPs and MRs were quantified and characterised after sample peroxidation. In most species of lichen, MP and MR abundance overall was < 1 g -1 and < 0.1 g -1 , respectively, and the majority of plastics were fibres of < 10 µm in diameter and < 1000 µm in length. Respective weight normalised abundances of MPs and MRs were similar in G. critina, but there were greater proportions of both larger (> 1000 µm) and non-fibrous particles among the MPs. In both lichens and moss, there was a greater number of larger MPs and MRs at locations closest to and at the same elevation as Shiraz than at more distant and elevated locations, suggesting an inverse relationship between particle size and distance travelled. Among the lichens, members of the genus Acarospora, with their areolated form, appeared to act as the most suitable biomonitors for MPs and MRs. Overall, however, the wide distribution of the moss, G. crinita, and its ability to intercept and accumulate a broader range of sizes and shapes of MPs and MRs make this species a better choice, at least in the type of environment studied., (© 2024. The Author(s), under exclusive licence to Springer Nature B.V.)

Although airborne urban particles are a concern for air quality and human health, little information exists on the levels and characteristics of microplastics (MPs) and microrubbers (MRs) in this setting. In the present study, MPs and MRs are quantified and characterised in road dusts and accumulations captured passively (and up to elevations of 177 cm above road level) in the steps of utility poles at 18 locations throughout the city of Shiraz, southwest Iran. Dust accumulation rates were greatest at road level (median = 45 g m−2 month−1) and declined with elevation (median = 2.0 g m−2 month−1 at 177 cm). The accumulation rates and concentrations (per g of dust) of MPs and MRs were more variable between locations but accumulation declined with elevation for both particle types and MR concentration (up to ∼27,000 MR g−1) was always greater than corresponding MP concentration (up to ∼3300 MP g−1). Increasing elevation was also accompanied by an increasing proportion of fine (≤100 μm) and fibrous particles, and in particular for MPs. Fractionation in the quantities and characteristics with elevation above road level are attributed to the extent of resuspension of MPs and MRs from the road surface by wind and passing traffic, with aerodynamic considerations predicting the greatest and most widespread resuspension of fibrous MPs. The fractionation of MPs and MRs with elevation above road level also results in different exposures for adults and children. [Display omitted] • Microplastics (MPs) and microrubbers (MRs) measured in Shiraz urban dusts. • MP/MR concentrations spatially variable but declined with height (<2 m) from road level. • Proportion of finer and fibrous particles increased with elevation. • Observations attributed to resuspension from road surface by wind and traffic. • Different MP/MR exposures are predicted for adults and children. [ABSTRACT FROM AUTHOR]

• Microplastic (MP) concentrations in Shiraz groundwater range from 0.1 to 1.3 MP L−1. • The majority of MPs were fibres but fragments and films were also present. • The main polymers were polystyrene, polyethylene and polyethylene terephthalate. • Land use, hydrology and geology determine MP distribution. • Hydrological considerations suggest residence times between years and decades. Despite the significance of groundwater to the hydrological cycle and as a source of potable water, very little information exists on microplastics (MPs) in this environment. In the present study, MPs have been determined in ten well samples obtained from an alluvial aquifer in a semi-arid region (Shiraz, Iran) following filtration, digestion and inspection under a binocular microscope. A total of 96 MPs were identified, and concentrations ranged from 0.1 to 1.3 MP L−1 (mean and median = 0.48 and 0.43 MP L−1, respectively) and exhibited a complex distribution across the area that reflected differences in land use and local hydrology and geology. The majority of MPs (about 70%) were fibres of ≤ 500 μm in length, but fragments and films were present at some sites, and the dominant polymers were polystyrene, polyethylene and polyethylene terephthalate. Coupling meteorological and water table monitoring data from the regional water organization and published information on aquifer hydrology, we estimate a lag time from precipitation to water table intrusion of between one and five months and groundwater velocity flows of between 0.01 and 0.07 m d−1. Although the extent of retardation of MPs within the pores of groundwater is unknown, by considering empirical data and theoretical predictions on particle flow through porous media in the literature we surmise that MP residence times in the aquifer are likely to range from years to decades, thereby impeding any clear means of source identification. Nevertheless, and more generally, the consumption of potable groundwater may make to a contribution to MP exposure through ingestion. [ABSTRACT FROM AUTHOR]

Samples of fresh snow (n = 34) have been collected from 29 locations in various urban and remote regions of northern Iran following a period of sustained snowfall and the thawed contents examined for microplastics (MPs) according to established techniques. MP concentrations ranged from undetected to 86 MP L -1 (mean and median concentrations ~20 MP and 12 MP L -1 , respectively) and there was no significant difference in MP concentration between sample location type or between different depths of snow (or time of deposition) sampled at selected sites. Fibres were the dominant shape of MP and μ-Raman spectroscopy of selected samples revealed a variety of polymer types, with nylon most abundant. Scanning electron microscopy coupled with energy-dispersive X-ray analysis showed that some MPs were smooth and unweathered while others were more irregular and exhibited significant photo-oxidative and mechanical weathering as well as contamination by extraneous geogenic particles. These characteristics reflect the importance of both local and distal sources to the heterogeneous pool of MPs in precipitated snow. The mean and median concentrations of MPs in the snow samples were not dissimilar to the published mean and median concentrations for MPs in rainfall collected from an elevated location in southwest Iran. However, compared with rainfall, MPs in snow appear to be larger and more diverse in their shape and composition (and include rubber particulates), possibly because of the greater size but lower terminal velocities of snowflakes relative to raindrops. Snowfall represents a significant means by which MPs are scavenged from the atmosphere and transferred to soil and surface waters that warrants further attention., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)