Evaluating the fate of hexabromocyclododecanes in the coastal environment: Fugacity analysis using field data

Inventorization and ecological risk assessment of tetrabromobisphenol A and hexabromocyclododecane in sediments from Guangdong coastal area of South China Sea

Brominated flame retardants (BFRs) exhibit excellent flame retardant properties and are widely used in various industries. Among the common BFRs, tetrabromobisphenol A (TBBPA) and hexabromocyclododecane (HBCDs) pose substantial ecological and human health risks due to their extensive application and long-range transport. This study established 131 sample collection sites along the coast of the South China Sea (SCS) in Guangdong Province to assess the concentration, distribution, inventory, and ecological risk of TBBPA and HBCDs in surface sediments. The concentrations of TBBPA in SCS sediments ranged from < limit of detection (LOD) to 80 μg/kg dry weight (dw), and those of HBCDs from < LOD to 18 μg/kg dw. The diastereoisomers of HBCDs (α-, β-, and γ-HBCD) in the sediment samples accounted for 36 %, 13 %, and 51 %, respectively. Human activities, particularly those associated with nearby electronic waste disassembly and textile and garment industries, considerably influenced the dispersion of TBBPA and HBCDs. The inventories of TBBPA and HBCDs in Guangdong Province's SCS were estimated to be 3.2 × 105 kg and 7.2 × 104 kg, respectively. The average risk quotient values ranged from <0.01 to 0.016, indicating a low to negligible environmental risk. This study provides deeper insights into the distribution and scientific significance of HBCDs and TBBPA in SCS sediment samples, elucidates the current state of BFR contamination, and offers recommendations for future research on environmental safety and human health in the region.

Distribution characteristics and migration trends of hexabromocyclododecanes between seawater-sediment system in different seasons of fishing grounds along the Yellow sea and East China sea coasts

Pollutants in the ecological environment of fishery seawater are harmful to the survival and reproduction of aquatic organisms. Hexabromocyclododecanes (HBCDs) were 42.9% detected within ND-48.89 ng/L in 177 seawater samples and 30.7% within ND-1.07 ng/g dw in 88 sediment samples of the fisheries in the Yellow Sea and East China Sea, respectively. γ-HBCD accounted for 65% of seawater and 89% of sediment samples. HBCDs in seawater in winter (ND-48.89 ng/L) were significantly higher than in summer (ND-4.99 ng/L), possibly because the re-suspension caused by winds and waves could re-migrate HBCDs from the sediment to the seawater in winter. However, seasonal differences of HBCDs in sediment were not significant. The fugacities indicated HBCDs' migrating trend from seawater to sediment due to their hydrophobic nature. There is almost no terrestrial input of HBCDs from the Yangtze and Yellow Rivers, and currently used fishery materials in marine may compose long-lasting sources of HBCDs.

Expanded polystyrene buoys as an important source of hexabromocyclododecanes for aquatic ecosystem: Evidence from field exposure with different substrates

The production and use of hexabromocyclododecanes (HBCDs) have been strictly limited due to their persistence, toxicity and bioaccumulation. However, the release of HBCDs from related products and wastes would continue for a long time, which may cause many environmental problems. In this study, we investigated the occurrence and distribution of HBCDs and microplastics (MPs) in aquatic organisms inhabiting different substrates. HBCDs were measurable in the seawater, sediment, expanded polystyrene (EPS) substrates and organism samples. Mostly, the concentrations of HBCDs in organisms inhabiting EPS buoys were significantly higher than those of the same species inhabiting other substrates. Meanwhile, the diastereomeric ratio (α/γ) of HBCDs in organisms inhabiting EPS buoys was closer to that in EPS buoys. The fugacity values of HBCDs in EPS buoys were much higher than those in other media, implying that HBCDs can be transferred from EPS buoys to other media. Additionally, MPs derived from EPS buoys would be mistaken as food and ingested by aquatic organisms. The transfer of HBCDs from EPS buoys to aquatic organisms can be achieved by aqueous and dietary exposures. In combination, the contribution of MP ingestion to HBCDs for aquatic organisms should be very limited. These results supported EPS buoys as an important source of HBCDs for the aquatic ecosystem. To effectively control HBCDs pollution, it is necessary to discontinue or reduce the use of EPS buoys.

Plastic debris as a mobile source of additive chemicals in marine environments: In-situ evidence

Plastic debris can act as a source of hazardous chemicals in the ocean, but the significance of its role in the environment is not yet known. To address this question, a comprehensive field study of highly contaminated and non-contaminated islands was conducted. Comparison of the plastic additive hexabromocyclododecanes and ubiquitous contaminants polychlorinated biphenyls in marine invertebrates showed that the load of stranded plastics plays a significant role in the bioaccumulation of plastic additives in the marine debris-contaminated island. Fugacity analysis indicates that net flow of hexabromocyclododecanes occurred from plastics to environmental reservoirs. Additionally, significantly higher levels of antioxidants, 2,4-di-tert-butylphenol and butylated hydroxytoluene, was found in the marine invertebrates inhabiting the marine debris-contaminated island than those inhabiting the marine debris-noncontaminated island, but ultraviolet stabilizers did not show the regional difference. This study provides the first field evidence that the movement of plastic debris in the ocean drives the dispersal of plastic additives to pristine waters.

Occurrence and distribution of organophosphate flame retardants in seawater and sediment from coastal areas of the East China and Yellow Seas

Organophosphates (OPEs) are manmade organic pollutants that are widely used as flame retardants, plasticizers, and antifoaming and hydraulic agents. In this study, seven OPEs in seawater and sediment from the Yellow Sea and East China Sea were determined to study the distribution and diffusion behavior, and to evaluate the environmental risks. The ΣOPEs in the seawater and sediments ranged from below the method detection limit (<MDL) to 497.40 ng/L and from < MDL to 66.50 ng/g dw, respectively. Tri-n-butyl phosphate (TnBP), tris-(1, 3-Dichloro-2-Propyl) phosphate (TDCPP), and tri-meta-cresyl phosphate (TmCP) were the dominant OPEs in the seawater and sediments. OPEs were mainly distributed in coastal areas and the South Yellow Sea, indicating that they are mainly affected by land-based pollution and ocean currents. Fugacity analysis shows that tri-para-cresyl phosphate (TpCP) was in a state of equilibrium, while TDCPP, TnBP, and TmCP other OPEs tended to diffuse from sediment to water. The diffusion behavior of OPEs is mainly affected by their chemical properties. Hazard quotient (HQ) values of TmCP and TpCP in sediment samples were >1.0, indicating high ecological risks to aquatic organisms.

Equilibrium leaching of selected ultraviolet stabilizers from plastic products

Despite the importance of (micro)plastics in the release of plastic additives, the leaching mechanism of organic plastic additives from various plastic materials is poorly understood. In this study, the equilibrium leaching of five highly hydrophobic ultraviolet (UV) stabilizers (UV326, UV327, UV328, UV329, and UV531) from three plastics (low-density polyethylene (LDPE), polyethylene terephthalate (PET), and polystyrene (PS)), was investigated employing acetonitrile-water cosolvent systems. Their extrapolated water solubilities were in the 0.15-0.54 μg L^-1 range, limiting their transport as "dissolved" in water and (micro)plastics are likely those particulate carriers. The equilibrium leaching of UV stabilizers from plastics was better explained by the Flory-Huggins model incorporating the nonideal behavior caused by the size disparity between UV stabilizers and polymer materials and their compatibility. Specifically, leaching of UV stabilizers from LDPE showed a positive deviation from Raoult's law, whereas slight negative deviations were observed in PET and PS. In addition, the equilibrium concentration of the benzotriazoles in LDPE increased linearly with the volume fraction up to only 0.4%. These observations could be explained by the unfavorable interactions of UV stabilizers with polyethylene, indicating that polymer type should be also important when evaluating the fate of hydrophobic additives. Because equilibrium distribution of additives between (micro)plastics and water is crucial for evaluating the fate and transport of hydrophobic plastic additives, further studies on the leaching equilibrium of various additives from different plastic materials are necessary.

Estimating the Bioaccumulation Potential of Hydrophobic Ultraviolet Stabilizers Using Experimental Partitioning Properties

Although hydrophobic ultraviolet (UV) stabilizers are an emerging environmental concern because of their widespread occurrence, persistence, and bioaccumulation potential, experimental values of their partitioning properties required for risk assessment are scarce. In this study, n-octanol-water partition (Kow) and lipid-water partition constants (Klipw), which are key parameters for environmental risk assessment, were experimentally determined for five selected hydrophobic UV stabilizers (UV326, UV327, UV328, UV329, and UV531) based on third-phase partitioning among polydimethylsiloxane (PDMS), water, and n-octanol/lipid. The partition constants between PDMS and water (KPDMSw), obtained using the dynamic permeation method were used to derive Kow and Klipw. The obtained log Kow and log Klipw values were in the ranges of 7.08-7.94 and 7.50-8.34, respectively, indicating that the UV stabilizers exhibited a high bioaccumulation potential in aquatic environments. The experimental Kow and Klipw values obtained in this study provide valuable information for the evaluation of the fate, distribution, bioavailability, and toxicity of the UV stabilizers in aquatic environments.