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• MPs were mainly fibrous, blue and in 20–500 μm in industrial mariculture. • Long operating time led to higher MP concentration in RAS. • Occurrence and distribution of MPs was analyzed in long & short operated RAS. • Microfilter removed MP in film, granule, fragment and those > 1000 μm efficiently. • PMF model was used to analyze the source of MP based on the polymer type. Industrial mariculture, a vital means of providing high quality protein to humans, is a potential source of microplastics (MPs) which have recently received increasing attention. This study investigated the occurrence and distribution of microplastics in feed, source water and recirculating aquaculture system (RAS) with long & short operating times as well as in fish from typical industrial mariculture farms in China. Results showed that microplastics occurred in all samples with the average concentration of 3.53 ± 1.39 particles/g, 0.70 ± 0.17 particles/L, 1.53 ± 0.21 particles/L and 2.21 ± 0.62 particles/individual for feed, source water, RAS and fish, respectively. Microplastics were mainly fiber in shape, blue in color and 20–500 μm in size. Compared with short operated RAS, long operating time led to higher microplastic concentration in RAS, especially that of microplastic in 20–500 μm, granular and blue. Regardless of short or long operating time, microplastics in RAS mainly gathered in culture tank, tank before microfilter and fixed-bed biological filter, and the microfilter removed efficiently the microplastic with the shape of film, granule, fragment as well as those with size > 1000 μm. As for the polymer types, polyamide (PA, 71.9 %) and polyethylene terephthalate (PET, 65.7 %) dominated in feed and source water, respectively, which may be the reason for the high proportion of PA (38.8 % and 26.4 %) and PET (31.8 % and 30.2 %) in RAS and fish. In addition, polypropylene (PP) was also detected in RAS (18.7 %) and fish (22.6 %), indicating that other plastic facilities such as PP brush carrier also made a contribution. Positive matrix factorization (PMF) model revealed three sources of MP in RAS, namely plastic facilities, industrial sewage and plastic packaging products. Our results provided a theoretical basis for the management of MP in RAS. [Display omitted] [ABSTRACT FROM AUTHOR]

• Scavenging efficiency of rainfall for airborne MPs extended a period after the rain. • Contributions of airborne MPs to rivers could not be ignored. • Intercepting masses by trees only offset those loading into rivers. • Sparse and lowrise buildings are sensitive areas for airborne MPs. The issue of airborne microplastics (AMPs) pollution is receiving increasing attention, but effective solutions are still limited. In this study, AMPs were collected in pairs from an open space and under a tree (Ficus virens) in the suburb of Chengdu, southwest China, to investigate the current pollution status. The meteorological factors and underlying surface types were analyzed to investigate whether these factors could influence and mitigate the pollution of AMPs. The results showed that the fibrous AMPs accounted for the vast majority and the dominant polymers were polypropylene-polyethylene (PP-PE) and polypropylene (PP), with an average deposition flux of AMPs of 192 n/m2/d (22.41 µg/m2/d). Rainfall was found to have the prolonged scavenging efficiency for AMPs, which could extend to 8 to 48 hours after the end of rainfall, and this is a new insight into the relationship with meteorological factors. Interactions between the key underlying surface types and AMPs were also studied. The representative tree species (Ficus virens) had a low interception rate of 6.25% for AMPs and retained mainly small-sized AMPs and more fibers. The masses of AMPs loaded into Chengdu rivers could reach 1149 kg annually, with the unit mass load of 13.6 kg/km2 in urban rivers and 8.2 kg/km2 in suburban rivers. The masses intercepted by trees and bushes throughout the city only offset the masses loading in rivers, and open or sparse buildings were found to be sensitive areas for AMPs, which indicated the urgent need to control and mitigate the pollution of AMPs, especially in these sensitive areas. This work comprehensively analyzed the AMPs pollution from various perspectives and attempted to find ways to mitigate this pollution. [Display omitted] [ABSTRACT FROM AUTHOR]

Climate change and increasing eutrophication are expected to increase the release of autochthonous organic matter (OM) to sediments, where most contaminants are transformed or mineralized in freshwater lakes. This study sought to evaluate how cyanobacteria- and macrophyte-derived OM (COM and MOM) affected the microbial attenuation of 17α-ethinylestradiol (EE2) in the sediment from eutrophic Lake Taihu in China. In two months of water-sediment microcosm experiments, the input of COM and MOM both promoted EE2 degradation more strongly than humic acids, and the degradation efficiency was significantly and positively correlated with the cometabolism of increasing organic carbon in sediments (P < 0.001). The enhanced degradation was explained by responses of indigenous bacterial community to OM amendment as a priming effect. The immediate breakdown of biodegradable components such as proteinaceous substances in COM and MOM remarkably augmented the metabolic activity of bacteria in terms of the stimulated activity of extracellular enzymes including fluorescein diacetate and dehydrogenase, as well as the elevated production of proteins and polysaccharides in extracellular polymeric substances. In the meantime, the bacterial community composition was reshaped toward a more eutrophic state, leading to the clear upregulation of metabolic function genes of organic carbon and xenobiotics. Correlation-based network analysis further determined the strong facilitative coordination between the community members and the compositional variability of OM in the cometabolism. These results suggest that cyanobacterial blooms-dominated zones are potential hotspot areas for steroid estrogen attenuation, a finding of significance for the control and management of complex pollution in freshwater lakes. Image 1 • Input of autochthonous OM enhanced microbial degradation of EE2 in lake sediments. • EE2 degradation was positively related to cometabolism of degradable OM components. • Autochthonous OM increased bacterial metabolic enzyme activity and EPS secretion. • Facilitative interactions among microbes were promoted by proteinaceous substances. • Autochthonous OM upregulated xenobiotic metabolic function genes of bacterial group. [ABSTRACT FROM AUTHOR]