What is hiding below the surface - MPs including TWP in an urban lake

Microplastics in lakes: Distribution patterns and influencing factors

As a kind of new pollutants, microplastics (MPs) have aroused public concern due to their widespread presence and potential ecological risks. Lakes, as crucial freshwater ecosystems and important water resources, are particularly vulnerable to MPs pollution. While MPs are known to be unevenly distributed within lakes, their distribution patterns and influencing factors have not been thoroughly understood. This review analyzes 84 field studies across 64 lakes worldwide to elucidate MPs distribution patterns and their driving mechanisms. Analysis reveals that MPs abundance is typically highest near areas of intense human activity and major water inflows, though hydrodynamics and wind conditions also influence spatial patterns. MPs characteristics (shape, size, color, polymer type) show distinct distribution patterns influenced by source types, transport mechanisms, and degradation processes. While surface water MPs concentrations vary seasonally due to precipitation, wind, and human activities, sediment cores indicate increasing MPs abundance in recent deposits. Integration of water and sediment sampling reveals that MPs characteristics affect their vertical distribution, with denser particles prone to sedimentation. This review identifies key knowledge gaps, including limited data on vertical distributions and temporal variations, and emphasizes the need for standardized methods and quantitative analysis of driving factors. These reviewed findings provide a foundation for understanding MPs fate in lake ecosystems and improving risk assessment capabilities, offering valuable insights for future surveys on MPs.

Tire wear particles in aquatic environments: From biota to ecosystem impacts

Tire wear particles (TWPs), mainly generated through friction between tires and road surfaces, represent a major source of traffic-related microplastic pollution, posing threats to biota and ecosystem functions. These particles are a complex mixture of toxic compounds, including heavy metals (e.g., zinc) and organic compounds (e.g., 6-PPD), and their diverse leachates exacerbate their ecological impacts. This review collates current knowledge on the occurrence of TWPs and their leachates in aquatic systems, emphasizing their toxicological effects on species and cascading ecological consequences at the community and ecosystem levels. TWP concentrations in aquatic environments span several orders of magnitude, ranging from 10-5 to 104 mg/L in water via pyrolysis-GC/MS. TWPs and their leachates induce oxidative stress, DNA damage, and alter immune responses of aquatic biota, while disrupting feeding behavior, reproduction, and survival. At the ecosystem level, TWPs and their leachates cause shifts in species composition, reduce biodiversity, and alter trophic interactions, destabilizing natural food web dynamics through selective pressure that promotes tolerant taxa and triggers cascading ecological effects. Their presence significantly influences carbon and nitrogen cycling, with environmentally relevant concentrations could promote primary producers, while higher concentrations inhibit photosynthetic nitrogen-fixing biota, disrupt microbial communities, and impair processes such as denitrification and carbon mineralization. Their toxicological and ecological impacts are likely to be intensified by global environmental change, highlighting the need for long-term studies under realistic environmental conditions to better understand underlying mechanisms and develop effective mitigation strategies.

Microplastics and tyre wear particles in urban runoff from different urban surfaces

Urban runoff is an important conveyor of microplastics (MPs) and tyre wear particles (TWP) to receiving waters. However, knowledge of contributions by surfaces within land use type/activities is currently limited. To address this knowledge gap, runoff samples were collected simultaneously during three rainfall events in October and November 2020 at three locations in Luleå, Sweden, with different urban surfaces (parking lot, road and roof). The occurrence of MPs (by number and estimated mass) and TWP (mass) were determined using μ-FTIR and Pyr-GC/MS, respectively. MPs and TWP were found at all sites in all events, with large variations between events and sites. The highest concentrations of MPs (number) and TWP were found in road runoff followed by parking lot runoff and roof runoff. The mass concentrations of MPs did not follow the same pattern and were generally highest at the parking lot, highlighting the importance of reporting data as both mass and particle numbers to derive a complete overview of MPs and TWP behaviour. Polypropylene, polyethylene, and polyester accounted, on average, for 99 % of MP polymers (by mass and number) at all sites with common sources, including traffic (vehicle wear and tear) and littering. MPs in the <75 μm fraction contributed >50 % of the total number of MPs in parking lot runoff, >58 % in roof runoff and > 90 % in road runoff.

Spotlight on the long-term effects of micro/nanoplastics exposure on Spirulina platensis: Algal cells, extracellular polymeric substances, and phycocyanin

Spirulina platensis (SP) provides humans with proteins and natural pigments. The effects of micro/nanoplastics (MNPs) on SP are of great interest. We focused on the effects of high concentrations (100-300 mg/L) of polystyrene MNPs on SP for 50 days. MNPs caused growth retardation, a decrease in peak concentration of algal cells, the emergence of surface cracks and pores, and stimulated the secretion of extracellular polymeric substances that promoted heterogeneous aggregation of SP. During the first 35 days, there were significant differences between the exposure groups in the phycocyanin concentration, yield and purity and the ratio of phycocyanin to phycobiliprotein, with the higher MNPs concentration resulting in lower values, whereas on day 50 there were no statistically significant differences in any of these metrics between the control or exposure groups. This study enriches the knowledge about the long-term effects of MNPs on SP for microalgae culture and food industry.

Composition and concentrations of microplastics including tyre wear particles in stormwater retention pond sediments

Stormwater is recognised as a vector for microplastics (MPs), including tyre wear particles (TWPs) from land-based sources to receiving waterbodies. Before reaching the waterbodies, the stormwater may be treated. In this study, sediments from six treatment facilities (five retention ponds and a subsurface sedimentation tank) were analysed to understand MP occurrence, concentrations, sizes, polymer types and distribution between inlet and outlet. The concentrations of MPs showed large variations between and within different facilities with MP concentrations of 1,440-72,209 items/kg (analysed by μFTIR) corresponding to 120-2,950 μg/kg and TWP concentrations from

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Key Words

• FTIR imaging
• MP
• TWP
• pyrolysis–GC–MS
• stormwater management
• urban runoff

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MESH Headings

• Microplastics/analysis
• Geologic Sediments/chemistry
• Water Pollutants, Chemical/analysis
• Ponds
• Environmental Monitoring
• Rain/chemistry
• Particle Size

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Grants

• 2016-05176 VINNOVA
• 2022-03092 VINNOVA
• R092 Interreg
• Svenskt Vatten

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Affiliation(s)

Lisa Öborn Department of Civil, Environmental and Natural Resources Engineering, Luleå University of Technology, SE-971 87 Luleå, Sweden; Environment and Health Administration, City of Stockholm, Fleminggatan 4, Box 8136, Stockholm SE-104 20, Sweden
Heléne Österlund Department of Civil, Environmental and Natural Resources Engineering, Luleå University of Technology, SE-971 87 Luleå, Sweden E-mail:
Claudia Lorenz Division of Civil and Environmental Engineering, Department of the Built Environment, Aalborg University, Thomas Manns Vej 23 Aalborg Øst, 9220 Denmark; Department of Science and Environment, Roskilde University, Universitetsvej 1, Roskilde 4000, Denmark
Alvise Vianello Division of Civil and Environmental Engineering, Department of the Built Environment, Aalborg University, Thomas Manns Vej 23 Aalborg Øst, 9220 Denmark
Jeanette Lykkemark Division of Civil and Environmental Engineering, Department of the Built Environment, Aalborg University, Thomas Manns Vej 23 Aalborg Øst, 9220 Denmark
Jes Vollertsen Division of Civil and Environmental Engineering, Department of the Built Environment, Aalborg University, Thomas Manns Vej 23 Aalborg Øst, 9220 Denmark
Maria Viklander Department of Civil, Environmental and Natural Resources Engineering, Luleå University of Technology, SE-971 87 Luleå, Sweden

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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.

Treating wastewater for microplastics to a level on par with nearby marine waters

Retention of microplastics (MPs) at the third largest wastewater treatment plant (WWTP) in Sweden was investigated. The plant is one of the most modern and advanced of its kind, with rapid sand filter for tertiary treatment in combination with mechanical, biological, and chemical treatment. It achieved a significantly high treatment efficiency, which brought the MP concentration in its discharge on par with concentrations measured in marine waters of the same region. This novel data shows that properly designed modern WWTPs can reduce the MP content of sewage down to background levels measured in the receiving aquatic environment. Opposite to current understanding of the retention of MP by WWTPs, a modern and well-designed WWTP does not have to be a significant point source for MP. MPs were quantified at all major treatment steps, including digester inlet and outlet sludge. MPs sized 10-500 µm were analyzed by a focal plane array based micro-Fourier transform infrared (FPA-µFTIR) microscopy, a hyperspectral imaging technique, while MPs above 500 µm were analyzed by Attenuated Total Reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy. Mass was estimated from the hyperspectral images for MPs <500 µm and from microscope images >500 µm. The overall treatment efficiency was in terms of MP counts 99.98 %, with a daily input of 6.42 × 1010 and output of 1.04 × 107 particles. The mass removal efficiency was 99.99 %. The mechanical part of the treatment, the pre-treatment, and primary stages, reduced both the MP counts and mass by approximately 71 %. The combined biological treatment, secondary settling, and final polishing with rapid sand filtration removed nearly all the remaining 29 %. MPs became successively smaller as they passed the different treatment steps. The digester inlet received 1.04 × 1011 MPs daily, while it discharged 9.96 × 1010 MPs, causing a small but not significant decrease in MP counts, with a corresponding MP mass reduction of 9.56 %.

Snow dumping station - A considerable source of tyre wear, microplastics, and heavy metal pollution

Snow dumping stations can be a hotspots for pollutants to water resources. However, little is known about the amount of microplastics including tyre wear particles transported this way. This study investigated microplastics and metals in snow from four snow dumping stations in Riga, Latvia, a remote site (Gauja National Park), and a roof top in Riga. Microplastics other than tyre wear particles were identified with Attenuated Total Reflection Fourier Transform Infrared (ATR-FTIR) (>500 µm) and focal plane array based micro-Fourier Transform Infrared (FPA-µFTIR) imaging (10-500 µm), tyre wear particles by Pyrolysis Gas Chromatography-Mass Spectroscopy (Py-GC-MS), and total metals by Inductively Coupled Plasma with Optical Emission Spectroscopy (ICP-OES). Microplastics detected by FTIR were quantified by particle counts and their mass estimated, while tyre wear particles were quantified by mass. The concentrations varied substantially, with the highest levels in the urban areas. Microplastic concentrations measured by FTIR ranged between 26 and 2549 counts L-1 of melted snow with a corresponding estimated mass of 19-573 µg/L. Tyre wear particles were not detected at the two reference sites, while other sites held 44-3026 µg/L. Metal concentrations varied several orders of magnitude with for example sodium in the range 0.45-819.54 mg/L and cadmium in the range 0.05-0.94 µg/L. Correlating microplastic measured by FTIR to metal content showed a weak to moderate correlation. Tyre wear particles, however, correlated strongly to many of the metals. The study showed that snow can hold considerable amounts of these pollutants, which upon melting and release of the meltwater to the aquatic environment could impact receiving waters.