Effects of near-bed turbulence on microplastics fate and transport in streams

Integration of ecological restoration and landscape aesthetics: Mechanisms of microplastic retention by optimization of aquatic plants landscape design in urban constructed wetlands - A case study of the living water park in Chengdu

Microplastic (MP) pollution is prevalent in urban water environments, with increasing evidence of its negative environmental impacts. This study examines the role and mechanisms of aquatic plant landscapes in the ecological remediation of MP (0.05-5 mm) in urban constructed wetland parks, using the Living Water Park in Chengdu as a case study. Over a period of two years, a systematic investigation of MP characteristics, abundance and distribution in the water environment as well as aquatic plant landscapes in the park. Sampling was carried out for the three stages of the Fuhe River before, during and after its flow through the park, and for the water bodies at each step of the water purification system within the Living Water Park, and a total of 66 samples of freshwater microplastics (MPs)were collected at 8 preliminary and 25 official sampling sites selected. MPs were observed in all samples, with higher abundance found in more close-to-natural areas, such as ecological wetlands and streams. Aquatic plants play a crucial role in MP remediation through adsorption, uptake (Mp ≤ 5 μm) and accumulation. A positive correlation was found between MP abundance, aquatic plant species diversity, and public landscape evaluation. More diverse and layered wetland plant configurations exhibited better MP remediation capabilities. The study suggests specific aquatic plant species and combinations for optimal MP remediation, emphasizing the importance and feasibility of aquatic plant landscapes in urban constructed wetland parks. The findings highlight the potential of urban constructed wetland parks for MP remediation and provide important doi:ces for their long-term development and landscape design, proposing strategies from plant combination optimization to integrated landscape design and maintenance.

Impact of Fenton aging on the incipient motion of microplastic particles in open-channel flow

Upon entering the environment, Microplastics (MPs) experience aging processes that modify their properties and integrity. Previous methods for predicting the incipient motion of MPs have been validated using pristine plastics, which do not account for the effects of aging. This can lead to uncertainties in both quantification and characterization. This study investigates the effect of aging on the incipient motion of MPs with different bed roughness (smooth and rough beds) and MP properties (e.g., grain sizes and densities) in an open-channel flow. Five types of MPs were subjected to four different degrees of aging using the Fenton reagent, and their incipient velocities were tested on beds with two distinct roughness. The results suggest that the incipient velocity of MPs increases linearly with aging. However, this increase is not uniform across different particles and bed roughness. Upon comparing various commonly employed sediment incipient velocity equations, experimental results are in agreement with Ruijin Zhang's equation as the most precise. The parameters in Ruijin Zhang's equation are modified to enhance its applicability for predicting the incipient velocity of aged MPs. This study provides novel insights into the incipient motion of aged MPs in an open-channel flow, highlighting the intricate interaction between aged MP characteristics and bed roughness.

Hotspots lurking underwater: Insights into the contamination characteristics, environmental fates and impacts on biogeochemical cycling of microplastics in freshwater sediments

The widespread presence of microplastics (MPs) in aquatic environments has become a significant concern, with freshwater sediments acting as terminal sinks, rapidly picking up these emerging anthropogenic particles. However, the accumulation, transport, degradation and biochemical impacts of MPs in freshwater sediments remain unresolved issues compared to other environmental compartments. Therefore, this paper systematically revealed the spatial distribution and characterization information of MPs in freshwater (rivers, lakes, and estuaries) sediments, in which small-size (<1 mm), fibers, transparent, polyethylene (PE), and polypropylene (PP) predominate, and the average abundance of MPs in river sediments displayed significant heterogeneity compared to other matrices. Next, the transport kinetics and drivers of MPs in sediments are summarized, MPs transport is controlled by the particle diversity and surrounding environmental variability, leading to different migration behaviors and transport efficiencies. Also emphasized the spatio-temporal evolution of MPs degradation processes and biodegradation mechanisms in sediments, different microorganisms can depolymerize high molecular weight polymers into low molecular weight biodegradation by-products via secreting hydrolytic enzymes or redox enzymes. Finally, discussed the ecological impacts of MPs on microbial-nutrient coupling in sediments, MPs can interfere with the ecological balance of microbially mediated nutrient cycling by altering community networks and structures, enzyme activities, and nutrient-related functional gene expressions. This work aims to elucidate the plasticity characteristics, fate processes, and potential ecological impact mechanisms of MPs in freshwater sediments, facilitating a better understanding of environmental risks of MPs in freshwater sediments.

Vertical distribution of microplastic along the main gate of Indonesian Throughflow pathways

Even though Pacific - Indian Ocean exchange [Indonesian Throughflow (ITF)] has been measured for the last three decades, the measurements of microplastic in the region is very limited. This study was the initial investigation of the vertical distribution of microplastic in the deep-sea areas across the ITF Pathway. Niskin water samples were utilized to obtain the samples from a water column in a range of 5 to 2450 m. A total of 924 microplastic particles with an average abundance of 1.062 ± 0.646. n/L were found in the water column. Our findings indicate that water temperature and water density are the most significant factors correlated to the microplastic concentration. This study will be the first report discussing the distribution of microplastics in the deep-sea water column that could be highly significant in determining the fate and transport of microplastic within Indonesian waters that exits into the Indian Ocean.