Impacts of terrestrial input on the distribution characteristics of microplastics in the East China Sea characterized by chromophoric dissolved organic matter (CDOM) analysis.

Large quantities of microplastics are found in the East China Sea (ECS), however, the impacts of complicated terrestrial input on the distribution characteristics of microplastics have not been studied. Hence, we aimed to characterize the microplastic distribution in the ECS combined with the fluorescence characteristics of chromophoric dissolved organic matter (CDOM), a sensitive technique to trace terrestrial substances in seawater. The average microplastic abundance in the surface seawater of ECS was 34.73 ± 4.05 items/m3 and sites in the north ECS had a higher microplastic abundance (55.90 ± 2.47 items/m3) than those in the southern region (11.22 ± 4.01 items/m3), due to its proximity to the Yangtze River estuary and Hangzhou Bay. Polyethylene (PE, 44.2 %) was the most abundant microplastic type in the northern region, whereas polyethylene terephthalate (PET, 28.4 %) had a higher proportion in the south ECS. Besides, sites in the north ECS had a higher diversity index of microplastics, suggesting various sources of microplastic pollution. Interestingly, a stronger correlation with the diversity index was found for protein-like component C3 (R2 = 0.56) in northern regions compared to fulvic-like component C1 (R2 = 0.32) and humic-like component C2 (R2 = 0.28), suggesting the significant impact of anthropogenic discharge. Moreover, no correlation between fluorescence components and microplastic diversity index was found in the south ECS, indicating that CDOM can reflect the impact range of terrestrial input on the distribution characteristics of microplastics. This research might be useful in assessing and reducing the impact of terrestrial input on the distribution characteristics of microplastics in the ECS.

Effects of different treatment processes in four municipal wastewater treatment plants on the transport and fate of microplastics.

The behavior of microplastics in wastewater treatment plants has been investigated, but specific effects of treatment process on microplastics' fate are still unclear due to varied analysis methods and regional differences. In this study, four wastewater treatment plants in Ningbo of southeastern China with different treatment processes were selected to investigate transport and fate of microplastics. Based on number of microplastic particles, fibers and fragments were the main microplastics types in wastewater, while synthetic cellulose represented the largest fraction. The dominance of fibers (76.7%-90.0%) and small particle sizes (<2.0 mm, 62.5%-81.5%) in effluents suggested that they escaped easily from the wastewater treatment plants. The abundance of microplastics particles decreased from 78.0 ± 2.9 items/L in influent to 6.0 ± 2.8 items/L in effluent for anaerobic-anoxic-oxic process, 100.0 ± 3.1 items/L to 4.3 ± 3.4 items/L for sequencing batch reactor activated sludge process, 105.0 ± 5.3 items/L to 3.5 ± 2.6 items/L for cyclic activated sludge technology, 65.0 ± 4.3 items/L to 3.0 ± 1.6 items/L for oxidation ditch process. The microplastics removal capacity of primary and secondary treatment processes for four wastewater treatment plants ranged from 83.7% to 96.3%. Application of different tertiary treatment processes (coagulation/flocculation, membrane related technology and disinfection) enhanced microplastics removal to achieve overall removal rate of 92.3%-96.7%. The removed microplastics from the wastewater treatment plants were mainly transferred to sludge (226.1 ± 95.7-896.0 ± 144.0 items/g dry weight). The biological treatment unit played an important role in microplastics removal with rates varying between 86.9%-95.2%, while tertiary treatment reduced daily microplastics emission 1.4 × 108-2.3 × 108 items/day. This study suggests that proper selection of wastewater treatment unit could significantly reduce the emission number of microplastics, which supports an efficient control strategy of microplastics in wastewater treatment plants.

How biofilms affect the uptake and fate of hydrophobic organic compounds (HOCs) in microplastic: Insights from an In situ study of Xiangshan Bay, China.

Microplastic (MP) has been identified as an emerging vector that transports hydrophobic organic compounds (HOCs) across aquatic environments due to its hydrophobic surfaces and small size. However, it is also recognized that environmental factors affect MP's chemical vector effects and that attached biofilms could play a major role, although the specific mechanisms remain unclear. To explore this issue, an in situ experiment was conducted at Xiangshan Bay of southeastern China, and dynamics of HOCs (i.e., polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs)) and bacterial communities related to the model MP (i.e., PE fibers) were analyzed and compared. Through bacterial characterizations including the 16S rRNA approach, higher summer temperatures (31.4 ± 1.07 °C) were found to promote colonizing bacterial assemblages with larger biomasses, higher activity and more degrading bacteria than winter temperatures (13.3 ± 2.49 °C). Consequently, some sorbed pollutants underwent significant decline in the summer, and this decline was particularly the case for PAHs with low (2-3 rings) and median (4 rings) molecular weights such as phenanthrene (59.4 ± 1.6%), chrysene (70.6 ± 4.2%), fluoranthene (77.1 ± 13.3%) and benz[a]anthracene (71.5 ± 11.0%). In our winter test, however, most pollutants underwent a consistent increase throughout the 8-week exposure period. Moreover, more biorefractory pollutants including PCBs and high molecular weight (5-6 rings) PAHs accumulated regardless of bacterial characteristics. Two putative PAH-degrading bacteria appeared with high relative abundances during the summer test, i.e., family Rhodobacteraceae (18.6 ± 0.5%) and genus Sphingomicrobium (22.4 ± 3.6%), associated with drastic decreases in low (45.2 ± 0.4%) and median (66.0 ± 2.5%) molecular weight PAHs, respectively. Bacterial degradation effects of biofilms on PAHs are also supported by the correlative dynamics of salicylic acid, an important degradation intermediate of PAHs. The results of this study indicate that MP's HOC vector effects are essentially determined by interactions between attached pollutants and microbial assemblages, which are further related to bacterial activity and pollutant features. Further studies of biofilm effects on MP toxicity and on the metabolic pathways of MP-attached HOCs are required.

Microplastics and associated PAHs in surface water from the Feilaixia Reservoir in the Beijiang River, China.

Microplastics have been a prevalent and persistent contamination problem in the global aquatic environment. In particular, microplastics that can adsorb persistent organic pollutants (POPs) and therefore transfer these POPs to organisms in the aquatic environment have received much attention. In this study, an investigation of microplastics in the surface water of the Feilaixia Reservoir (Guangdong Province, China), which is an important part of people's daily lives in Guangdong Province was carried out, mainly focusing on the characteristics and spatial distribution of microplastics, as well as microplastics and their adsorded PAHs in the surface water of the Feilaixia Reservoir were investigated. The average abundance of microplastics in the surface water of the Feilaixia Reservoir was 0.56 ±â€¯0.45 items/m3. Six kinds of polymers, including polyethylene (PE), polypropylene (PP), polystyrene (PS), expanded polystyrene (EPS), polyvinyl chloride (PVC) and polyethylene terephthalate (PET), were identified, among which PP (52.31%) and PE (27.39%) were the major compositions. Four shapes of microplastics, i.e., foams, films, fragments and fibers were found, and films (37.78%) being the main shape. The most common typical size of the plastic particles ranged from 0.6 to 2 mm (41.36%). The total concentration of the sixteen PAHs carried on the EPS, PE and PP microplastics ranged from 282.4 to 427.3 ng/g; chrysene, benzo [ghi] perylene, and phenanthrene were abundant in the samples, at concentrations of 39.5-89.6 ng/g, 34.6-56.8 ng/g and 25.6-45.6 ng/g, respectively. Based on the ratios of the PAH isomers (Flut/Py < 1 and Phe/Ant >10), it was speculated that the source of the PAHs may be derived from the imperfect combustion of fossil fuels.

Assessment of microplastics derived from mariculture in Xiangshan Bay, China.

Mariculture activities including enclosure, raft and cage cultures employ a variety of plastic gear such as fishing nets, buoyant material and net cages. The plastic gear poses a potential source of microplastics to the coastal environment, but relevant data on the impacts of mariculture are still limited. To this end, a semi-enclosed narrow bay (i.e., Xiangshan Bay, China) with a long-term mariculture history was investigated to assess how mariculture activities affect microplastics in seawater and sediment. The results indicated that mariculture-derived microplastics accounted for approximately 55.7% and 36.8% of the microplastics in seawater and sediment, respectively. The average microplastic abundances of seawater and sediment were 8.9 ±â€¯4.7 (mean ±â€¯SD, n = 18) items/m3 seawater and 1739 ±â€¯2153 (n = 18) items/kg sediment, respectively. The types of mariculture-derived microplastics included polyethylene (PE) foam, PE nets, PE film, polypropylene (PP) rope, polystyrene (PS) foam and rubber. PE foam had the highest proportion (38.6%) in the seawater samples. High usage rates and the porous structure of PE foam led to the high abundance. The average microplastic sizes of seawater and sediment are 1.54 ±â€¯1.53 mm and 1.33 ±â€¯1.69 mm, respectively. The spatial variations in the abundance and size of microplastics implied that the mariculture-derived microplastics in Xiangshan Bay were transported along the Bay to the open sea. The results of this study indicate that mariculture activity can be a significant source of microplastics. Further research is required to investigate how the high microplastic abundance in mariculture zone affects marine organisms, especially cultured seafood.

Occurrence of microplastics in the beach sand of the Chinese inner sea: the Bohai Sea.

The occurrence of microplastics in the beach sand of the Bohai Sea was investigated for the first time. The Bohai Sea is the largest Chinese inner sea and its coastal region is one of the most densely urbanized and industrialized zones of China. Samples from three costal sites (i.e., Bijianshan, Xingcheng and Dongdaihe) were collected, quantified and identified for microplastic analysis. Effects of sample depth and tourism activity were investigated. Surface samples (2 cm) contained higher microplastic concentrations than deep samples (20 cm). Samples from the bathing beach exhibited higher microplastic concentrations than the non-bathing beach, suggesting the direct contribution of microplastics from tourism activity. Of eight types of microplastics that were found, PEVA (polyethylene vinyl acetate), LDPE (light density polyethylene) and PS (polystyrene) were the largest in abundances. Moreover, the non-plastic items from samples were analyzed and results revealed that the majority abundance of the observed non-plastics were viscose cellulose fibers. Further studies are required to evaluate the environmental hazards of microplastics, especially as they may "act as a contaminant transporter" to the Bohai Sea ecosystem.

Occurrence of microplastics in the coastal marine environment: First observation on sediment of China.

Microplastics in sediments from the Beibu Gulf and the coastline of China Sea were investigated to evaluate the occurrence and abundance of microplastics in China for the first time. Microplastics (<5mm) were taken from sediments by a flotation method. The number of microplastics was counted by a fluorescence microscope, an instrument that is rarely used in the detection of microplastics in sediments. This instrument led to results that were satisfactory. Compared with other sampled areas, microplastics were found in massive concentrations in China. Four types of microplastics, HDPE, PET, PE and PS, were identified. The results will provide useful background information for further investigations.