Characteristics of unorganized emissions of microplastics from road fugitive dust in urban mining bases

Examining magnetic susceptibility as a proxy for microplastic pollution in granulometric fractions of road dust: A case study in Warsaw, Poland

The main objective was to assess the contamination of road dust (RD) with microplastics (MPs) and plasticizers and to investigate whether magnetic susceptibility (χ) can indicate MP pollution. The study employed laser direct infrared (LDIR) imaging with a quantum cascade laser (QCL), magnetic susceptibility measurement using the MFK1-FA Kappabridge, and gas chromatography-mass spectrometry (GC-MS). RD collected in Warsaw was divided into the fractions: 0.8 mm (1-0.8 mm), 0.6 mm (0.8-0.6 mm), 0.4 mm (0.6-0.4 mm), 0.2 mm (0.4-0.2 mm), and <0.2 mm. MP analysis revealed materials such as polypropylene and rubber, with the highest number of MPs (51,660 particles) in the <0.2 mm. RD was analyzed for bisphenol A and phthalic acid esters, with the highest concentrations of DEHP and DBP in the <0.2 mm fraction. χ were highest in the fraction <0.2. Strong correlations were found between χ and DEHP (0.78), DBP (0.96), and BPA (0.89) for WAW2 and between χ and MPs (0.97) for WAW4. Strong correlations were also observed for the 0.2 mm and <0.2 mm fractions between χ and DBP. The main conclusion is that χ strongly correlates with DEHP and DBP in the <0.2 mm fraction and with MPs in the 0.2 mm fraction. This study is novel due to the limited research on using χ as a screening method for MP pollution, making it a promising, cost-effective tool for pollution monitoring. The results could support the development of simplified monitoring tools, helping to assess human exposure risks and improve environmental management strategies.

Occurrence, Emission, and Transport of Tire and Road Wear Particles across Four Environmental Compartments along Ring Road Networks in Beijing

Tire and road wear particles (TRWPs) are an appreciable source of microplastics (MPs); however, knowledge of their large-scale occurrence and mass flux based on robust sampling and quantification is limited. Herein, the first city-wide survey of TRWPs across environmental compartments (road dust, snowbank, water, and sediment from rivers and lakes) along four ring roads (beltways) in Beijing was performed. TRWP concentrations (n = 74) were quantified using bonded-sulfur as a marker to reveal the city-wide spatial distributions and adopted to establish a framework estimating TRWP emission factors (EFs) and mass flux from generation to remote atmospheric, terrestrial, and aquatic transport. The TRWP concentrations were 0.46 × 104-3.55 × 104 μg/g (road dust), 0.65-46.18 mg/L (water), 0.28 × 104-1.79 × 104 μg/g (sediment), and 9.46-19.12 mg/L (snowbank) and were highly related to nearby traffic conditions. Based on total EFs (34.4-288.5 mg/vKT) and airborne EFs (6.2-17.2 mg/vKT) calculated from the preceding concentrations, the TRWP emissions in Beijing were determined as 1.28 × 104 t/a. Among them, 61.3% was eventually disposed of in landfills owing to frequent road sweeping and high runoff treatment efficiency and 18.1% was stranded on the roadside; nevertheless, 11.9% escaped to freshwater systems and 5.7 and 3.0% airborne transported to remote land and ocean, respectively. This study provides new insights into the emissions and fate of TRWPs.

Sandstorms contribute to the atmospheric microplastic pollution: Transport and accumulation from degraded lands to a megacity

Surface dust from degraded lands is a major global aerosol source, mobilized by meteorological events like sandstorms. Microplastics (MPs) in dust can be enriched in the atmosphere and transported over long distances to sensitive regions during sandstorms. This study was conducted in a megacity frequently impacted by sandstorms in spring, exploring the influx, characteristics, enrichment mechanism, and transport pathway of sandstorm-derived MPs. The deposition rate of these MPs reached 1823.65 ± 892.53 items·m-2·d-1, predominantly consisting of low-density polymers and those mainly used in synthetic fiber, with an average size of 60.75 µm. Compared to MPs in annual atmospheric deposition, these MPs were smaller and contained a higher proportion of potentially harmful polymers. These factors could increase exposure risks for residents from sandstorm-derived MPs, along with distinct meteorological and ecological effects. Backward trajectory analysis suggested the observed sandstorms originated from the Mongolian Plateau, over 1000 km away. Comparisons of MPs from surface-collected dust on the Mongolian Plateau with sandstorms-delivered MPs revealed the transport was determined by MP shape, size, and density. This study highlights the critical role of sandstorms in the MP atmospheric cycling, emphasizing the extensive impacts of MPs and the need for coordinated mitigation efforts across regions.

Review on the relationship between microplastics and heavy metals in freshwater near mining areas

Microplastics (MPs), degraded from plastic wastes, have drawn significant attention worldwide due to its prevalence and rapid transition. Contamination of freshwater with MPs has become an emerging global issue. Heavy metals (HMs), a prominent global pollutant, also garnered much attention due to their potential interaction with MPs, presenting a multifaceted environmental threat. The primary source of HM contamination in freshwater has been identified as mining sites. Additionally, the increasing use of plastic materials within mining areas raises concerns about MP release into the surrounding freshwater environments. Recent studies only provide information on the contamination of HMs status with MPs. However, studies on the mechanism responsible for MPs contamination from both external and internal sources of freshwater MPs and HMs are limited. The knowledge gaps in the deposition and fate of MPs in various mining situations and the possibility of combined impacts of heavy metals and MPs in the ecosystem raise ecological concerns. Here, we review the origins of MPs and HM pollution within mining sites and explore the potential combined detrimental impacts on plants and animal life. We found out that polystyrene (PS) and polyethylene (PE) have higher adsorption affinity to heavy metals, and the mingle toxic consequence of the MPs and HM can depend on the MP surface properties, pH, and salinity of the neighboring water solution. The Langmuir and Freundlich isotherm models enable the efficient design of adsorption systems. The Langmuir model describes single-layer adsorption at homogeneous sites, while the Freundlich model addresses multilayer adsorption on heterogeneous surfaces. The crucial mechanism of adsorption and desorption that underlies the occurrence of both MPs and heavy metals is a decisive matter in this issue.

Occurrence and distribution of microplastics in freshwater aquaculture area with different culture modes in Yangtze River Delta of China

There are multiple sources of microplastic contamination in freshwater aquaculture areas, such as water inputs, use of plastic farming tools and weathering of discarded plastics, leading to microplastic contamination of aquaculture environments, but microplastics in freshwater aquaculture areas are still limited. In our study, we investigated the distribution of microplastics (MPs) in the aquaculture water, sediments and crabs during the growth cycle of crabs with different culture modes. The results show that from May to October, MPs in surface water first increased and then decreased, which is related to water evaporation and river water recharge caused by local hot and sunny weather. The concentration of microplastics in surface water reached a maximum of 9.25 items/L in September and 0.34 items/g-dry weight in sediment in June. The MPs in the sediments, although relatively stable, fluctuated due to river water replenishment. The number of detected MPs in male crabs was higher than that in female crabs, 17.96 ± 6.23 and 16.71 ± 4.45 items/individual, respectively. Crabs of different sexes were not selective for the color of MPs. The abundance of microplastics in different tissues of river crabs was in the order of foregut > hindgut > gill > hepatopancreas, whereas they were not detected in muscles. There were microplastic uptake and excretion behaviors during the growth culture cycle of river crabs. The microplastic amount was higher in the early stage and then showed a dynamic change of decreasing and then increasing. The number of MPs was higher in culture modes with different sex ratios, especially in male-dominated culture modes, which may be related to the more frequent activities of male crabs when the male ratio is high. This study provides useful information to understand the accumulation of microplastics in cultured hairy crabs and the source sinks and transportation of microplastics in artificial freshwater aquaculture in China.

Tire and road wear particles in the aquatic organisms - A review of source, properties, exposure routes, and biological effects

With the continuous development of the modern social economy, rubber has been widely used in our daily life. Tire and road wear particles (TRWPs) are generated by friction between tires and the road surface during the processes of driving, acceleration, and braking. TRWPs can be divided into three main components according to their source: tire tread, brake wear, and road wear. Due to urban runoff, TRWPs flow with rainwater into the aquatic environment and influence the surrounding aquatic organisms. As an emerging contaminant, TRWPs with the characteristics of small particles and strong toxicity have been given more attention recently. Here, we summarized the existing knowledge of the physical and chemical properties of TRWPs, the pathways of TRWPs into the water body, and the exposure routes of TRWPs. Furthermore, we introduced the biological effects of TRWPs involved in size, concentration, and shape, as well as key toxic compounds involved in heavy metals, polycyclic aromatic hydrocarbons (PAHs), N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD), and benzothiazole on aquatic organisms, and attempted to find the relevant factors influencing the toxic effects of TRWPs. In the context of existing policies that ignore pollution from TRWPs emissions in the aquatic environment, we also proposed measures to mitigate the impact of TRWPs in the future, as well as an outlook for TRWPs research.

An explicit review and proposal of an integrated framework system to mitigate the baffling complexities induced by road dust-associated contaminants

Road dust-associated contaminants (RD-AC) are gradually becoming a much thornier problem, as their monotonous correlations render them carcinogenic, mutagenic, and teratogenic. While many studies have examined the harmful effects of road dust on both humans and the environment, few studies have considered the co-exposure risk and gradient outcomes given the spatial extent of RD-AC. In this spirit, this paper presents in-depth elucidation into the baffling complexities induced by both major and emerging contaminants of road dust through a panorama-to-profile up-to-date review of diverse studies unified by the goal of advancing innovative methods to mitigate these contaminants. The paper thoroughly explores the correlations between RD-AC and provides insights to understand their potential in dispersing saprotrophic microorganisms. It also explores emerging challenges and proposes a novel integrated framework system aimed at thermally inactivating viruses and other pathogenic micro-organisms commingled with RD-AC. The main findings are: (i) the co-exposure risk of both major and emerging contaminants add another layer of complexity, highlighting the need for more holistic framework strategies, given the geospatial morphology of these contaminants; (ii) road dust contaminants show great potential for extended prevalence and severity of viral particles pollution; (iii) increasing trend of environmentally persistent free radicals (EPFRs) in road dust, with studies conducted solely in China thus far; and (iv) substantial hurdle exists in acquiring data concerning acute procedural distress and long-term co-exposure risk to RD-ACs. Given the baffling complexities of RD-ACs, co-exposure risk and the need for innovative mitigation strategies, the study underscore the significance of establishing robust systems for deep road dust contaminants control and future research efforts while recognizing the interconnectivity within the contaminants associated with road dust.

Tire plastic and road-wear particles on Yujing Expressway in the restoration area of Mu Us Sandy Land: Occurrence characteristics and ecological risk screening

Tire plastic and road-wear particles (TPR-WP) are a current research priority as one of the main environmental sources of microplastics. We selected a unique land use type - desert restoration area, collected soil and dust samples from the Yujing Expressway and its service areas, and analyzed TPR-WP abundance, type, size and morphology by laser direct infrared (LDIR). The abundance of TPR-WP in expressway dust (14,446.87 ± 10,234.24 n/kg) was higher than that in soil (7500 ± 3253.64 n/kg). Random forest model showed that the source of TPR-WP was highly correlated with economic factors and natural climate. Overall, the proportion of small and medium-sized TPR-WP in dust was higher than soil, more than half of the TPR-WP in dust were in 20 - 50 µm range. The proportion of small particle size TPR-WP increased with the rise of elevation. The pollution load index suggested that the survey region was generally at level I risk zone, while the ecological risk index indicated that the pollution level of expressway was III and IV, and the service area was IV. In general, the study was of great significance for clarifying the distribution and risk of TPR-WP in soil and dust of expressways and service areas.

Uptake, transport and accumulation of micro- and nano-plastics in terrestrial plants and health risk associated with their transfer to food chain - A mini review

Waste plastics enter the environment (water, soil, and atmosphere) and degrade into micro- and nano-plastics (MNPs) through physical, chemical, or biological processes. MNPs are ubiquitous in the environment and inevitably interact with terrestrial plants. Terrestrial plants have become important potential sinks, and subsequently, the sources of MNPs. At present, many studies have reported the effects of MNPs on plant physiology, biochemistry, and their phototoxicity. However, the source, detection method, and the absorption process of MNPs in terrestrial plants have not been systematically studied. In order to better understand the continuous process of MNPs entering terrestrial plants, this review introduces the sources and analysis methods of MNPs in terrestrial plants. The uptake pathways of MNPs in terrestrial plants and their influencing factors were systematically summarized. Meanwhile, the transport pathways and the accumulation of MNPs in different plant organs (roots, stems, leaves, calyxes, and fruits) were explored. Finally, the transfer of MNPs through food chains to humans and their health risks were discussed. The aim of this work is to provide significant theoretical knowledge to understand the uptake, transport, and accumulation of MNPs in terrestrial plants and the potential health risks associated with their transfer to humans through food chain.

Quantification of microplastic by particle size down to 1.1 μm in surface road dust in an urban city, Japan

The impact of microplastics (MPs, plastic particles ≤5 mm) on ecosystems is of great concern. Road surfaces represent a significant source of MPs where plastic fragments are physically and chemically reduced to MPs. However, the literature lacks information on fragmentation tendencies below 11 μm. This study aimed to characterize the occurrence of MPs in road dust in different size fractions down to 1.1 μm. Road dust was collected at five sites near a major road in Kusatsu city, Japan, and partitioned by size into 13 fractions (1.1-850 μm). The coarser fractions accounted for a greater proportion of the dust. The percentage of organic matter, determined by loss on ignition, increased as the fractions became finer. Pyrolysis-gas chromatography-mass spectrometry was used to quantify 12 types of polymers in each fraction. The dust was found to contain nine types of MP, namely, polyethylene (PE), polypropylene (PP), polyvinylchloride (PVC), polystyrene (PS), styrene/butadiene rubber (SBR), acrylonitrile/butadiene/styrene resin (ABS), polycarbonate (PC), polymethylmethacrylate (PMMA), and polyamide 66 (PA66). The total MP concentration in road dust particles by particle size fraction (concentrationf) began to increase from the 125-250 μm fraction and remained elevated in finer fractions down to 1.1 μm, indicating that MPs in the road dust micronized to at least 1.1 μm. However, for individual polymer types, the tendency for concentrationf to increase or decrease with particle size fraction varied: the concentrationf of some polymers, such as PE and PVC, remained elevated in fractions down to 1.1 μm; the concentrationf of SBR, a rubber-MP, showed a stable or decreasing trend in fractions of 7.0-11 μm and finer. Particles of PE, PVC, and some other plastics might become increasingly finer, even down to 1.1 μm. Further research is needed to understand the comminution limits of these polymers under pertinent environmental conditions.

Influence of vehicle and pavement characteristics on dust resuspension from soil pavement of open-pit mine

It is essential to explore the distribution characteristics of dust concentration distribution near the surface of soil pavement in open-pit mines to develop effective dust control measures. Therefore, in this study, the dust resuspension process of soil pavement was analyzed by building the dust resuspension experimental system of open-pit mine, and the change rules of dust concentration under different factors were investigated. The results showed that under the action of wheel rolling, the dust moved around the wheel along the vertical direction, and the diffusion trajectory in the horizontal direction was approximately parabolic. After re-suspension of the open-pit mine soil pavement, the area of high dust concentration behind the wheel is roughly triangular. The relationship between the average dust concentration (Total dust, Respirable dust and PM2.5) and the vehicle speed and weight were fit to a power function, while the relationship with silt content and water content were quadratic. Vehicle speed and water content had significant effect on the total dust, respirable dust (RESP) and PM2.5 average concentration, while vehicle weight and silt content had little effect on the respirable dust and PM2.5 average concentration. When the water content of mine soil pavement reached 3 %, the average dust concentration could be reduced to <10 mg/m³, and the vehicle speed should be reduced as much as possible under the mine production permitting conditions.

Occurrence and distribution characteristics of aged microplastics in the surface water, sediment, and crabs of the aquaculture pond in the Yangtze River Delta of China

The artificial breeding of freshwater crabs in China has become the main source, accounting for 45.69 % of the total output in 2020. However, microplastics widely exist in ponds due to the addition of meals, and the aging and breakage of plastic tools, and people know little about the occurrence of microplastics in the environment and the tissues of crabs during the cultivation of crabs in ponds. In this study, the abundance and characteristics of microplastics in ponds and crabs were studied finely, and the types of microplastics produced by meals and tools and the aging degree of microplastics in different media were studied in a typical aquaculture experimental base in the Yangtze Estuary of China. After we digested all the samples, there were microplastics in the water, sediment, and inedible part of crabs and crab meals, mainly in fiber shape, with a particle size of 100~300μm, and they have a certain degree of aging. The abundance of microplastics in surface water ranges from 4.4 to 10.8 items/L, and that in sediment ranges from 28.6 to 54.3 items/100 g·dry weight sediments. The average abundance of microplastics in crabs was 23.9 ± 15.9 items/individual. The content of microplastics in crabs' intestinal tissue was the highest, followed by gills and hepatopancreas. At the same time, the microplastics found in crabs were positively correlated with crab body weight and negatively correlated with hepatopancreas index. The results show that in the process of artificial breeding pond feeding, microplastics will be released from the process of meals dissolving in water, and fall off due to wear and tear during the use of tools. Microplastics found in the water, sediments and the tissues of crabs were all aged. Humans have a risk of ingesting microplastics when they eat the tissues of nonedible parts of crabs.

Characteristics of microplastics and the role for complex pollution in e-waste recycling base of Shanghai, China

Plastics used in electric and electronic products cover a wide range, and contain many additives, such as brominated flame retardant and so on. These compounds and microplastics may be released into environment when the electric and electronic products are obsoleted and recycled. This study explores the characteristics of microplastics and the complex pollutions in a formal e-waste recycling base in Shanghai, China. The maximum abundance of microplastics is observed in dust samples of the recycling base and the average abundance is 44277 ± 69032p/50 g. 103 kinds of polymers are identified, including 4 kinds of packaging plastics, 32 kinds of engineering plastics, 18 kinds of rubber, and 49 kinds of other polymers. It is found that microplastics show weak adsorption effect for heavy metals. However, microplastics are important carrier of ∑₈PBDEs released during the whole recycling processes, and BDE-209 account for more than 50 % of PBDEs in microplastics. It is estimated that the microplastics load inside the e-waste recycling base was 4.01 tons based on the measured statistics. This study will provide theoretical basis for further understanding the potential pollution of microplastics and upgrading the corresponding control measures.