Consequences of anthropogenic activities and beach dynamics on vertical distribution of microplastics in the mid-intertidal sediments of Donghai Island, China.

Microplastic accumulation and resulting degradation are significant threats to the coastal ecosystems around the world. Baseline information on microplastics and their sources is of great importance for a permanent waste management system. The present study focused on the vertical distribution and characteristics of microplastics in the mid-intertidal zone of Donghai Island, China. At eight locations, sediment samples were collected from surface to a depth of 30 cm at intervals of 5 cm. Overall, we found five different polymer types, and vertical distributions of microplastics varied ranging from 0 to 200 particles/kg, with the mean value of 32.92±41.35 particles/kg. Sediment samples collected from all stations contained microplastics with high contribution of fibres. Intruded microplastic materials recorded in sediment samples at a depth of 30 cm demonstrate that microplastics may be present at depths greater than 30 cm. Scanning electron microscopy-energy dispersive X-ray (SEM-EDAX) analysis revealed presence of common elements in the microplastics surface (silicon, aluminium, magnesium, copper, and calcium). Based on the observations and results from this study, we suggest implementing a robust microplastic removal management program in Donghai Island to avoid serious microplastic intrusion effects on benthos and environmental contamination.

Impact of intensive mariculture activities on microplastic pollution in a typical semi-enclosed bay: Zhanjiang Bay.

Microplastic (MP) was investigated in Zhanjiang Bay, a semi-enclosed bay in south China and famous for considerable mariculture industry, to evaluate whether mariculture activities accelerated MP pollution. The MP abundances ranged from 0 to 2.65 n/m3 (number/m3), showing seasonal variances with higher levels in May and September and lower levels in January. In the inner part of the bay, a significantly high MP abundance and predominance of foam were found during the oyster breeding period, and pollution sources were prone to be single and extensive. This suggested that MPs were strongly influenced by the intensive plastic products for oyster culturing, especially during breeding. Moreover, plastic cages used for culturing were the main source of MPs in the central part of the bay. By conducting statistical analysis for eight representative bays, the economic growth, social development, agriculture structure, and aquaculture development were supposed to influence the local MP pollution level.

Microplastics in the western Pacific and South China Sea: Spatial variations reveal the impact of Kuroshio intrusion.

Surface currents play an essential role in the worldwide distribution of microplastics in the coastal seas and open oceans. As a branch of the western boundary currents (WBCs), Kuroshio changes seawater properties and pollutant levels of the South China Sea (SCS) during its intrusion process. To study the impact of Kuroshio intrusion on microplastics, we conducted field observations on surface water from the western Pacific (WP) and SCS. Microplastic abundances in the surface water of WP (0.02-0.10 particles m-3) were generally lower than those in the SCS (0.05-0.26 particles m-3). Fragments and granules dominated their apparent characteristics, and showed spatial classifications in different areas. The abundance of fragment, granule and foam showed a similar unimodal trend, as they peaked when the Kuroshio fraction was 0.1, implying the effect of Kuroshio intrusion was a combination of the dilution and biogeochemical influence. The polymer types of microplastics, dominated by polypropylene (PP), polyethylene (PE), polyester (PES), polymethacrylate (PMA) and phenoxy resin (PR), showed complicated compositions in the northern SCS, and Kuroshio intrusion was not the dominant influencing factor. Further study is needed to discover the comprehensive effect of Kuroshio intrusion on the fate of microplastics and is expected for the whole WBC system.

[Distribution Characteristics and Ecological Risk Assessment of Organochlorine Pesticides in Sediments of Zhanjiang Bay].

Sixteen surface sediment samples were collected from the estuary of the Suixi river to the mouth of Zhanjiang Bay and then analyzed for organochlorine pesticides (OCPs) by GC-MS to investigate their distribution and ecological risk. The results showed that the concentrations of OCPs in the sediments ranged from nd to 189.52 ng·g-1 (mean 32.17 ng·g-1), including HCHs (mean 5.81 ng·g-1) and DDTs (mean 26.90 ng·g-1). The distribution characteristics showed that the highest OCPs concentrations were found in the estuary and the main shipping lane areas, and the concentration in the nearshore area was higher than that offshore. Source analysis indicated that the HCHs mainly originated from agricultural applications, while no industrial input was observed. Some "hot-spots" areas occurred in harbors and shipping channels, likely as a result of the presence of paint flakes. Additionally, the concentrations of DDTs were found to be higher than the limits of Chinese Marine sediment quality criteria, and p,p'-DDT was the main type of DDT, presenting inevitable adverse biological effects and high ecological risk. Compared with other bays in China, the concentrations of OCPs in this study were in the upper-median pollution level, especially in harbors and boat maintenance facility areas. High OCPs inputs may occur, and thereby represent a certain ecological risk in Zhanjiang Bay.