The destiny of microplastics in one typical petrochemical wastewater treatment plant

Vertical transfer of microplastics in nearshore water by cultured filter-feeding oysters

Microplastics (MPs) are widely distributed in the sea, but the vertical transfer of MPs by marine organisms in coastal area is still poorly understood. In this study, we used laser direct infrared (LDIR) spectroscopy to determine the number and characteristics of MPs deposited by cultured oyster Crassostrea gigas and further compared the differences between MPs of natural deposit and biodeposit in field environments. The amounts of MPs found in the biodeposit of cultured oysters were 3.54 times greater than that in the natural deposition. The polymer types of biodeposit MPs also differed from those of natural deposition. It was estimated that a single oyster can deposit 15.88 MPs per day, which is a figure much higher than the initial results, and hotspots of MPs deposition may be formed within the oyster aquaculture area. We used generalized linear mixed model (GLMM) to further infer the sources of MPs in sediments and found that distance to shore, cultured zone and urban center were important predictors of MPs abundance in sediments of aquaculture area. The above results suggest that cultured bivalves have an important capacity for MPs biodeposition and will further change the vertical distribution pattern of MPs in coastal environments.

Identification and quantification of microplastics in salts by complementary approaches using pyrolysis-gas chromatography/quadrupole-time of flight mass spectrometry (Py-GC/QTOFMS) and laser direct infrared (LDIR) chemical imaging analysis

Microplastics (MPs) and nanoplastics (NPs) have been suspected as contaminants in various foodstuffs, including salts, all over the world. Regarding the different sizes and polymer types, the mass concentrations of actual plastic particles in salt are not very clear. The purpose of this study is to develop a scalable method for qualitative and quantitative analysis of MPs and NPs by using Pyrolysis Gas Chromatography Quadrupole-Time of Flight mass spectrometry (Py-GC/QTOFMS) to detect their mass concentrations in salt samples. The targeted and suspected lists of polymers in salts were compiled based on the combined results of the high-resolution mass spectrometry (HRMS) full scanning with auxiliary MS dataset and the laser direct infrared (LDIR) chemical imaging analysis. The seven targeted MPs with polymer standards, i.e., polyvinyl chloride (PVC), polymethyl methacrylate (PMMA), polypropylene (PP), polystyrene (PS), polyethylene (PE), polyethylene terephthalate (PET), and polycarbonate (PC), were first subjected to a full MS scanning mode of the Py-GC/QTOFMS analysis. Subsequently, the parental masses of their pyrolysis compounds were used as the seeds to generate the related daughter masses. This process established both retention time and mass-pairs matching for the target MS/MS mode for enabling the identification and quantification of the particles. The suspected MPs with a matching degree >0.65 in the LDIR list were explored either by the full scan MS. Only PVC was identified, and PET was suspected. The Py-GC/QTOFMS result is complementary and comparable to the LDIR detection with the matching degree >0.85. We identified that PVC and PET (suspected) can be measured in both commercial and bulk sea salts, and their concentrations in sea salts are much higher than in rock salts, implying heavy contamination of the seawater.

Comparison of phthalate esters (PAEs) in freshwater and marine food webs: Occurrence, bioaccumulation, and trophodynamics

Phthalate esters (PAEs) have received widespread attentions due to their ubiquity in various kinds of matrices and potential biotoxicity. This study systematically compared the concentrations, bioaccumulation, trophodynamics and health risk of PAEs in 25 species (n = 225) collected from a marine (Bohai Bay, BHB) and freshwater environment (Songhua River, SHR), China. Results showed that di-(2-ethylhexyl) phthalate and di-n-butyl phthalate were the predominant PAEs in the organisms from the two aquatic environments. The total concentrations of 6 PAEs in algae and fish from SHR were significantly higher than those from BHB. Two food webs were constructed in BHB and SHR based on the abundance of 15N in the organisms. All the PAEs except dimethyl phthalate exhibited trophic dilution with the trophic magnification factors less than 1. Moreover, an obvious biodilution of PAEs was observed in marine food web compared to freshwater food web. A low health risk of PAEs was found in organisms from both BHB and SHR. However, di-(2-ethylhexyl) phthalate exhibited a potential carcinogenic risk by consumption of some benthos in BHB and fish in SHR. This study provides a valuable perspective for understanding the trophodynamics and health risk of PAEs in marine and freshwater environments.

Risk assessment of microplastic exposure: A case study near a refinery factory at the central coast of Vietnam

The goal of this study was to identify the presence of microplastics on the beach near a refinery in the central coast of Vietnam. In this study, 11 sampling sites were selected within a length of 300 m of the beach. The results showed that microplastics were presented in all collected samples with an average concentration of 1582 ± 660 MPs/kg. Fibers were the predominant shape of microplastics found in the samples, which accounted for 57.11 %, while the rest were classified as fragments. The average size of microplastics varied greatly around 83.1 ± 74.3 μm with the vast majority having a size smaller than 50 μm (41.84 %). A total of 11 polymers of microplastics were detected from collected samples, Polyethylene Terephthalate was the main polymer with 46.43 %. The pollution load index of microplastics was 3.15 showing that refinery activities could expose microplastic to the environment.