Severe microplastic pollution from anthropogenic activities in coastal zones presents an imminent risk to marine ecosystems. In this study, abundant microplastics (15–12,852 items kg−1) with sizes ranging between 0.16 and 5.0 mm were extracted from 17 sediment samples collected in sandy beaches and mangrove wetlands of the Qinzhou Bay, Guangxi Province, Southwest China. Three types of microplastics (i.e. polystyrene, polypropylene, and polyethylene) were identified with Fourier transform infrared (FTIR) spectroscopy analysis. These detected microplastics were characterized by different colors (white, transparent, yellow, green, red, and blue) and shapes (fragment, fiber, and sphere). Microplastics were concentrated on supratidal beaches and wetlands outside of mangrove, and less abundant on intertidal beaches and inside of mangrove wetlands. Meanwhile, high microplastic concentrations were observed near mollusk farms. The spatial distribution and chemical speciation indicated that microplastics were derived from disintegration of large plastic debris (e.g., Styrofoam buoys used to support mollusk rafts) abandoned by aquaculture industry. Further, coastal vegetation (e.g. mangrove) could trap microplastic particles.

The Gulf of Pozzuoli includes the former second largest Italian steelworks of Bagnoli. The REE, Y, Th and Sc pollution in sediments of the Gulf of Pozzuoli was determined. Ce, La, Nd and Pr had the highest percentage distribution of rare earth elements normalized respect to chondrite with 31.19, 28.35, 19.51 and 8.41% individually. It was observed a marked enrichment of these elements, from west to the east from 26.39 to 111.04 mg/kg and from onshore to offshore from 31.67 to 217.74 mg/kg. The output of the principal component analysis revealed that the REE were mainly of anthropic origin being clearly linked to that of PAHs, metals and organic matter. This, together with their distribution patterns, highlighted the role of the former Bagnoli metallurgical plant in the pollution of the gulf.

A two-dimensional model was used to reconstruct scenarios related to the mass fish death phenomenon that occurred along the Central Coast of Vietnam. First, a Weather Research Forecasting model was used to simulate the wind field during April 2016, and was then used as an input to the two-dimensional (2D) model. Second, the calibration of the 2D model showed high conformity in both the phases and amplitude between the simulated and observed water levels. The simulation results of two scenarios, S1 and S2, were highly recommended for explaining the mass fish death phenomenon that occurred along the coast from Ha Tinh Province to Thua Thien-Hue Province. The calculated results of water quality data combined with the toxic concentration measured in fish will ultimately enable the simulation of the delimiting pollution zones and will facilitate response solutions when a similar phenomenon occurs in the future.

We investigated the aragonite saturation state (Ωarag) during all four seasons in a coastal region of southern Korea that receives considerable freshwater input. The surface Ωarag values were higher during productive seasons with enhanced freshwater influences, likely due to an increased net removal of dissolved inorganic carbon (DIC) from the water column (i.e., biological control). In addition, during the productive seasons, enhancement of Ωarag was observed with decreasing salinity within a linear mixing zone present between river-influenced surface and saltier bottom waters. DIC appeared to be effectively sequestered from the warmer, less salty surface water by downward flux of organic matter, but not significantly affected by the relatively DIC-rich, cooler and saltier bottom waters under strong stratification conditions during these seasons (i.e., physical control). Low phytoplankton productivity and seasonal breakdown of the stratification caused reduced saturation in other seasons and made the study area a weak sink for atmospheric CO2.

Identification of contamination in estuarine ecosystems that are impacted by anthropogenic pressures, such as the Seine estuary, is difficult to determine without considering the role environmental variation plays on the end points selected. Currently, there is interest in identifying methods in which the influence of confounding factors can be described and accounted for. In this context, the aim of this study was to define a baseline assessment criteria (BAC) for enzymatic biomarkers in ragworms (Hediste diversicolor) collected in a reference site (Authie). The model took into consideration the weight, temperature and salinity of the site. Values collected in the Seine estuary were analyzed with the model to determine if differences between the sites could potentially be due to contamination or were explained by environmental variation. In general, biomarker responses from the Seine estuary fell within the range of BAC, suggesting that environmental variation could explain some of the results.

Sulfur and iron are abundant and have close, complex interactions with the biogeochemical cycle of arsenic (As) in mangrove ecosystems. A hydroponic experiment was conducted to investigate the influences of variable SO42− and Fe2+ supplies on radial oxygen loss (ROL), iron plaque formation and As translocation in Avicennia marina upon exposure to As(III). The results indicate that A. marina is an As-tolerant plant, the application of iron and sulfur not only showed positive growth effects but also induced much higher amounts of ROL-induced iron plaque formation on root surfaces. The presence of iron plaque remarkably improved the proportion of As sequestration near this area but consequently reduced the proportion of As translocation in root. Therefore, it is concluded that iron plaque may act as a barrier for protection against As, and iron and sulfur play important roles in controlling the growth and translocation of As in A. marina seedlings.

Microlitter (0.5–5mm) concentrations in water column (depth range from 0 to 217.5m) of the main Baltic Proper basins are reported. In total, 95 water samples collected in 6 research cruises in 2015–2016 in the Bornholm, Gdansk, and Gotland basins were analysed. Water from 10- and 30-litre Niskin bathometers was filtered through the 174μm filters, and the filtrate was examined under optical microscope (40×). The bulk mean concentration was 0.40±0.58 items per litre, with fibres making 77% of them. Other types of particles are the paint flakes (19%) and fragments (4%); no microbeads or pellets. The highest concentrations are found in the near-bottom samples from the coastal zone (2.2–2.7 items per litre max) and from near-surface waters (0.5m) in the Bornholm basin (5 samples, 1.6–2.5 items per litre). Distribution of particles over depths, types, and geographical regions is presented.

The 240Pu/239Pu atom ratio and 239+240Pu activity of seawater in the East China Sea (ECS) was measured in order to examine the Pu sources and elaborate Pu scavenging process. High 240Pu/239Pu atom ratios (0.187–0.243, average = 0.221 ± 0.017) in the surface water and water column were observed during 2011, implying of non-global fallout Pu sources. The distribution of 240Pu/239Pu atom ratio in the ECS was in agreement with the introduction pathway of the Kuroshio, showing a decreasing trend away from the outer shelf. An even higher 240Pu/239Pu atom ratios (0.243–0.263, average = 0.253 ± 0.007) were observed in the Kuroshio, indicating the non-global fallout Pu signal from the Pacific Proving Grounds (PPG). Using a two end-member mixing model, the Pu source from the PPG contribution was calculated to be 36 ± 9% in the ECS seawater. The 239+240Pu activities of surface seawater were in the range of 2.00–2.95 mBq m−3 in the ECS. The spatial distribution of 239+240Pu activity in the surface seawater showed an increasing trend from the outer shelf to the nearshore. Moreover, 239+240Pu inventory of water column at the station DH23 in the ECS was calculated to be ~0.29 Bq m−2, which was 1–3 orders of magnitude lower than the estimates of sediment cores in the ECS shelf (9–407 Bq m−2). Such differences were determined by the high degree Pu scavenging efficiency in the ECS and high Pu input carried by terrestrial sediments from the Yangtze River. Finally, both 240Pu/239Pu atom ratios and 239+240Pu activities were identical before and after the Fukushima nuclear accident (FNA), suggesting that the impact of the FNA on the ECS was negligible.

Microplastics are small plastic particles, globally distributed throughout the oceans. To properly study them, all the methodologies for their sampling, extraction, and measurement should be standardized. For heterogeneous samples containing sediments, animal tissues and zooplankton, several procedures have been described. However, definitive methodologies for samples, rich in algae and plant material, have not yet been developed. The aim of this study was to find the best extraction protocol for vegetal-rich samples by comparing the efficacies of five previously described digestion methods, and a novel density separation method. A protocol using 96% ethanol for density separation was better than the five digestion methods tested, even better than using H2O2 digestion. As it was the most efficient, simple, safe and inexpensive method for isolating microplastics from vegetal rich samples, we recommend it as a standard separation method.

Microplastics that are contained in household dust, personal care products, and other factors, are discharged into sewage treatment facilities (STF). While these microplastics are treated at the STF with a high treatment efficiency through settling, precipitation, filtering, and other treatments, considering the large amount of effluent, large quantities of microplastics are still discharged into marine environments. In this study, biological STF using the anaerobic-anoxic-aerobic (A2O), sequence batch reactor (SBR), and the Media processes were investigated to confirm the efficiency of these treatments and the associated amounts of microplastics released for each process. The three investigated processes were found to have treatment efficiencies of about 98% or more. However, due to the large amount of effluent, more than four billion pieces of microplastic were released each year in each facility. Thus, even though biological STF show high treatment efficiencies, substantially large amounts of microplastics are still released into the marine environment.