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Microplastics pollution in nearshore marine environment has become increasingly prominent and has received widespread attention. As a major leisure and entertainment place in coastal cities, bathing beaches not only provide an environment for microplastics to enter the ocean, but also provide a place for the retention of microplastics. In this paper, the distribution, composition and seasonal variation of microplastics in seawater and sediments of six bathing beaches along the coast of Qingdao were studied. The results showed that the average abundance of microplastics in the sediments of the Qingdao bathing beach was 91.11 ± 26.76 items/m2 (13.77 ± 4.39 items/kg) in the winter and 147.78 ± 34.80 items/m2 (21.98 ± 5.97 items/kg) in the summer. The microplastic abundance in the seawater in the summer (average: 567.50 ± 101.06 items/m3) was significantly higher than that in the winter (average: 326.11 ± 49.03 items/m3, p 0.05). To an extent, it can reflect the correlation between the abundance of microplastics and human recreational activities. The microplastics detected at the bathing beaches were mainly lines (80.5%) and fragments (7.9%) with a size range of 100 to 1000 μm. Rayon (41.8%) and polyethylene terephthalate (PET, 16.9%) were the main polymer types. The microplastic characteristics showed significant seasonal differences, more diversity in summer than in winter. These results emphasized that the distribution and movement of microplastics in bathing beaches were affected by seasons, human activities and coastal currents.

Microplastics in bivalves have caused widespread concern due to their potential health risk to humans. In this study, microplastics in the digestive systems of four locally cultured bivalve species (scallop Chlamys farreri, mussel Mytilus galloprovincialis, oyster Crassostrea gigas, and clam Ruditapes philippinarum) in Qingdao, China, were analyzed and detected in 233 out of 290 bivalve samples (80%) over four seasons. The microplastic abundance in four species of bivalves ranged between 0.5 and 3.3 items/individual or 0.3 and 20.1 items/g wet weight digestive system, with significant species-specific and region-specific differences but no season-specific differences. Microfiber was the most predominant shape of all microplastics found. Eighteen types of polymer with diameters between 7 and 5000 μm were identified by μ-FT-IR (505 of 587 suspected items identified as microplastics) with polyvinyl chloride (PVC) and rayon being the most abundant ones. Bivalves collected in summer contained more larger-sized microplastics. R. philippinarum accumulated more smaller-sized microplastics and showed different microplastic features compared with the other three species of bivalves. By comparing and analyzing the microplastic polymer types between each bivalve species and the ambient environment, microplastic in clam can best reflect the variability of microplastic polymer types in sediment among different areas. Mussels can reflect the variability of microplastic polymer types in water to an extent. Therefore, clam and mussel are recommended to serve as bioindicators for microplastic pollution in the sediment and water, respectively. The occurrence of microplastics pollution in bivalves worldwide is wide, and bivalves can act as the transporter of microplastics to humans. Our results suggest that bivalves have an important role as environmental bioindicators and the pollution of microplastics in bivalves needs attention.

Microplastics, as an emerging pollutant, are widely spread in the oceans. The sampling method is the most basic and important factor affecting the reported microplastic abundance data. Three sampling methods, most commonly used for microplastic collection, including direct filtration with 0.45 μm pore size membrane, 20 μm sieve pre-concentration followed by 0.45 μm filtration and Manta trawling with a 150 μm mesh size net were studied. The results showed that there were orders of magnitude difference in abundance of microplastic across the three methods with 0.45 μm direct filtration yielding 1600.0–4000.0 items/m3, 20 μm sieve pre-concentration yielding 10.0–50.0 items/m3, and 150 μm trawl net yielding 0.13–0.24 items/m3. The polymer types of microplastic collected by the three methods were similar, but polymer proportions were different. PES and rayon dominated in the samples collected by direct filtration and sieve pre-concentration. PES and PP accounted for a higher proportion in the trawling samples. The abundance and polymer types of microplastics had a clear correlation between direct filtration and sieve pre-concentration (p

In this study, the interaction of emerging pollutant polyvinyl chloride microplastics (PVC MPs) and human serum albumin (HSA) was investigated by fluorescence spectroscopy, UV–visible (UV–vis) absorption spectroscopy, circular dichroism (CD), and Fourier transform infrared (FT-IR) spectroscopy under simulated physiological conditions. Fluorescence results showed that PVC MPs (about 5000 nm in size) can effectively quench the intrinsic fluorescence of HSA through static quenching owing to the formation of HSA-PVC complex. The binding constants (Ka) between PVC and HSA at different temperatures were calculated as 4.97 × 103 M−1, 3.46 × 103 M−1 and 2.51 × 103 M−1, respectively. The number of binding sites was 1.26. The enthalpy change (ΔH), entropy change (ΔS) and free energy change (ΔG) were calculated to be −59.27 kJ·mol−1, 70.76 J·mol−1 K−1 and − 80.35 kJ·mol−1, respectively, indicating that the interaction of PVC with HSA was mainly driven by electrostatic forces. Moreover, results of UV–vis, FT-IR and CD further demonstrated that the microenvironment and secondary structure of HSA were changed a lot induced by PVC, leading to a decrease in α-helix. This work not only provides an insight into the intermolecular interaction between PVC and HSA, but also elucidates the potential biological toxicity of MPs at a molecular level.

Phosphorus (P) speciation, burial, and transformation are poorly constrained under low-oxygen conditions. Sequential chemical extraction techniques, in-situ incubation, and laboratory incubation were employed to explore P cycling in the low-oxygen area of coastal Rushan. The study determined that the total P concentrations in the coastal area of Rushan Bay were higher than those of other China shelf seas, and largely affected by anthropogenic activities. The phosphate (DRP) fluxes in the study area calculated using an incubation method (0–1960 μmol m − 2 day − 1 ) and measured based on pore water gradients (1.5–50.4 μmol m − 2 day − 1 ) were both highly correlated with oxygen conditions. Sediment incubations showed that DRP diffusion from the sediment mainly originates from Fe–P and Auth-P dissolution and that Org-P recycling contributed only a small portion of the total released P pool. The benthic phosphate flux can be 60 times higher under low bottom-water oxygen levels of 63–150 μmol L − 1 than under oxygen levels exceeding 150 μmol L − 1 in the study area. The P accumulation rates and burial efficiencies in this study area ranged from 16.5–33.3 μmol cm − 2 year − 1 and 81.1–83.4%, respectively, and were regulated by the oxygen level and diffusive DRP flux. This study indicates that low oxygen levels between 63 and 150 μmol significantly govern P transformation and preservation in the sediment and P pools in the water column.