Bisphenol analogues in water and sediment from the Beibu Gulf, South China Sea: Occurrence, partitioning and risk assessment

Bisphenol analogues (BPs) have gained increasing attention in recent years due to their ubiquitousness in the environment, potential endocrine disrupting properties and ecological impacts. However, very little information is available on the occurrence, partitioning and ecological risks of BPs in marine environments. In the present study, six BPs were investigated in surface water and sediment samples from the Beibu Gulf, South China Sea. Results showed that bisphenol A (BPA) was the predominant BP in both water and sediment samples with levels ranging from 5.26 to 12.04 ng/L in water and 0.56 to 5.22 ng/g dw in sediment samples, followed by bisphenol AF (BPAF: 0.44-0.60 ng/L in water and 0.08-0.66 ng/g dw in sediment samples, respectively) and bisphenol S (BPS: 0.07-0.63 ng/L in water and not detected (ND) to 0.19 ng/g dw in sediment samples, respectively). There is no significant spatial difference of BPs levels between riverine sediment samples and coastal sediment samples. Compared with other studies, the concentrations of BPs from the Beibu Gulf were relatively low. The mean log-transformed sediment-seawater partitioning coefficients (log K_oc) ranged from 4.4 (DHBP) to 5.2 (BPAF) and the log K_oc values for all the target BPs were generally higher than those reported in freshwater environments. The present study firstly reported the field-based log K_oc values for BPB (mean: 4.5) and DHBP (mean: 4.4). The estimated risk quotient (RQ) and 17β-estradiol (E2) equivalent quotient (EEQ) values indicated that the ecological and human health impacts were negligible associated with target BPs. The present study provided reliable and detailed data for completely evaluating contamination level and environmental behaviors of BPs in the Beibu Gulf.

Insights into the effects of salinity on the sorption and desorption of legacy and emerging per-and polyfluoroalkyl substances (PFASs) on marine sediments

Per-and polyfluoroalkyl substances (PFASs) have attracted extensive attention since this century due to their wide distribution, persistence, bioaccumulation/biomagnification potential, and (eco)toxicity. In the present study, we investigated the sorption kinetics, sorption isotherms and desorption behaviors of legacy and emerging PFASs with different chain lengths and functional end groups onto marine sediments at four different salinities (0, 10, 20, and 30 practical salinity units (psu)). Results revealed that the sorption of PFASs onto sediment can be well described by the pseudo-second-order kinetic model. PFASs sorption was influenced by both compound-specific and solution-specific parameters. The distribution coefficient (K_d) for PFASs were increased with the increase of perfluorocarbon chain length and salinity, suggesting that hydrophobic and electrostatic interactions were involved in the adsorption process. 6:2 FTSA showed the lowest adsorption among PFASs with eight carbon atoms (6:2 FTSA, PFOA and PFOS). The increase of perfluorocarbon chain length of PFASs and salinity would result in the decrease of desorption rate of PFASs from sediment. In addition, PFCAs were desorbed more easily from the sediment than the PFSAs with the same perfluorocarbon chain length at all salinity groups. The present study demonstrated that salinity can apparently influence the fate of PFASs in aquatic environment and provided valuable data for modeling the fate of PFASs in real environment.

Occurrence, source apportionment and risk assessment of antibiotics in water and sediment from the subtropical Beibu Gulf, South China

The widespread use of antibiotics has raised global concerns, but scarce information on antibiotics in the subtropical marine environment is available. In the present study, seawater and sediment samples were collected to investigate the occurrence, spatial distribution, source, and ecological risks of 22 antibiotics in the Beibu Gulf. The total concentrations of target antibiotics (∑antibiotics) were in the range of 1.74 ng/L to 23.83 ng/L for seawater and 1.33 ng/g to 8.55 ng/g dry weight (dw) for sediment. Spatially, a decreasing trend of antibiotic levels from coast to offshore area was observed, with relatively high levels at the sites close to the Qinzhou Bay and Qiongzhou Strait. Sulfamethoxazole (SMX), trimethoprim (TMP), and norfloxacin (NOX) were predominant in seawater, while NOX, enoxacin (ENX), and enrofloxacin (ENR) were the most abundant antibiotics in sediment. In general, the sediment-water partitioning coefficients (K_d) were positively correlated with log molecular weight (MW). Salinity, particle size, and pH of water were predicted to be vital factors influencing the partition of sulfadiazine (SDZ), CIX, and ENR (p < 0.05). Livestock and aquaculture were identified as dominant sources of antibiotics in the Beibu Gulf based on PCA-MLR and Unmix model. Risk assessment revealed that SMX, CIX could pose medium risks to algae in the Beibu Gulf. Overall, our results provided paramount insights into understanding the fate and transport behaviors of antibiotics in the subtropical marine environment.

Distribution, partitioning behavior and potential source of legacy and alternative per- and polyfluoroalkyl substances (PFASs) in water and sediments from a subtropical Gulf, South China Sea

Legacy per- and polyfluoroalkyl acids (PFASs) have received global concern over the scientific and public community since this century. However, the information on alternative PFASs pollution in the marine environment, especially in the subtropical marine environment is extremely limited. This study investigated the occurrence, partitioning, potential sources, and ecological risks of PFASs, including perfluoroalkane sulfonic acids (PFSAs), perfluoroalkyl carboxylic acids (PFCAs), and alternative PFASs, in surface water and sediments from the subtropical Beibu Gulf, South China. Concentrations of total PFASs (∑PFASs) were in the range of 0.98-2.64 ng/L in water and 0.19-0.66 ng/g (dry weight, dw) in sediment, respectively. Perfluorooctanoic acid (PFOA) was the most abundant PFAS in water, while PFASs in sediment were dominated by perfluorooctanesulfonic acid (PFOS) and PFOA. Among investigated environmental parameters (total organic carbon (TOC), grain size, water pH, sediment pH, and salinity), TOC and salinity were the dominant factors influencing the sediment-water distribution coefficient (K_d) of PFOA, perfluorodecanoic acid (PFDA), and perfluorononanoic acid (PFNA). Log K_d and log soil organic carbon-water distribution coefficient (K_oc) both increase with increasing carbon chain length of PFASs. Significantly positive correlations between PFOS and perfluorohexanoic acid (PFHxA) (p < 0.05), PFOA and perfluoro-1-butane-sulfonamide (FBSA) were observed, suggesting that these PFASs might have similar sources and transport routes. Preliminary environmental risk assessment showed that PFOA and PFOS would not pose risks to the marine aquatic environment. This is the first comprehensive survey of legacy and alternative PFASs in a subtropical area of the Beibu Gulf, which provides significant data and scientific basis to better understand the fate of PFASs and pollution control management.

Legacy and alternative per- and polyfluoroalkyl substances in a subtropical marine food web from the Beibu Gulf, South China: Fate, trophic transfer and health risk assessment

The usage of alternative per- and polyfluoroalkyl substances (PFASs) has been increasing due to the restriction and elimination of legacy PFASs. However, there is limited knowledge on bioaccumulation and trophic magnification of alternative PFASs, especially in subtropical ecosystems. In the present study, we performed a comprehensive survey to investigate the occurrence, bioaccumulation and trophic magnification of legacy and alternative PFASs in subtropical marine food webs in the Beibu Gulf, South China. Results showed that perfluorobutanoic acid (PFBA) and perfluorooctanoic acid (PFOA) were the predominant PFASs in water phase, while perfluorooctane sufonate (PFOS) contributed most to the sum of target PFASs in sediments and marine organisms. Of the investigated PFASs, PFOS and 6:2 chlorinated polyfluoroalkyl ether sulfonic acids (F-53B) exhibited the highest bioaccumulation factor with values > 5000, qualifying as very bioaccumulative chemicals. There was a significant positive correlation between log BSAF and the carbon chain length of perfluoroalkyl carboxylic acids (PFCAs). Trophic magnification (TMF) was observed for PFOS and F-53B, while the remaining PFASs were biodiluted through the present food web. The hazard ratios for PFOS and PFOA in all organisms were far less than unity, suggesting overall low PFAS risks for humans through consumption of marine organisms.

Antibiotics in a subtropical food web from the Beibu Gulf, South China: Occurrence, bioaccumulation and trophic transfer

Antibiotics are of particular concern because of their ubiquity in aquatic environment and long-term adverse effects on aquatic organisms and humans. However, there is no information about the bioaccumulation and trophic magnification of antibiotics in subtropical environments. In this study, we determined the concentrations of 22 antibiotics to investigate their occurrence, bioaccumulation and trophic magnification in a subtropical food web from the Beibu Gulf. The total concentrations of target antibiotics ranged from 52.94-77.76 ng/L in seawater, 9.69-15.43 ng/g dry weight (dw) in sediment, and 0.68-4.75 ng/g wet weight (ww) in marine organisms, respectively. Macrolides were the predominant antibiotics in water, while fluoroquinolones were more abundant in sediment and biota samples. The total concentrations of target antibiotics in examined marine taxa descended in the order: crustacean > cephalopod > fish, with antibiotic profiles displaying distinct difference among taxa. Log BAFs (bioaccumulation factor) for antibiotics in all organisms ranged from -0.50 for erythromycin-H₂O (ETM-H₂O) to 2.82 for sulfamonomethoxine (SMM). Significantly negative correlation was observed between the log D_ow and log BAF values (p < .05), indicating that log D_ow is a good predictor of antibiotics bioaccumulation potential in marine organisms. The trophic magnification factors (TMFs) for sulfadiazine (SDZ) and enoxacin (ENX) were greater than unity, suggesting the trophic magnification of these chemicals through the food web. In contrast, enrofloxacin (ENR), ciprofloxacin (CIX), ofloxacin (OFX), norfloxacin (NOX), ETM-H₂O and trimethoprim (TMP) were biodiluted in the food web from the Beibu Gulf. This study provides substantial information on the fate and trophic transfer of antibiotics in a subtropical marine ecosystem.