•∑7PBDEs and BDE-209 showed sharp increase since the 1990s.•Increasing human activities were responsible for these increases.•Core analysis indicated debromination of highly brominated congeners.•TOC-dependent deposition of PBDEs.•Marine organic matter drove PBDE deposition in sediment.The Southern Yellow Sea (SYS) is an important reservoir of anthropogenic organic contaminants, such as polybrominated diphenyl ethers (PBDEs). To reconstruct the historical records of PBDEs and examine their relationships with the human activities and organic matters, a210Pb-dated sediment core was collected from the central mud area in the SYS. The concentrations of tri-to hepta-BDEs (∑7PBDEs) and BDE-209 ranged from 9.8 to 99.8 pg g−1 d.w. and from 12.1 to 855.4 pg g−1 d.w., respectively, both displaying the increasing trends from the bottom to the surface. More importantly, there was a faster increase for PBDEs since the 1990s, especially for BDE-209, which responded well with the rapid economic growth, and the increases of urbanization and industrialization in the local areas of the SYS. The analogously vertical patterns and significant relationships between PBDEs and total organic carbon (TOC) implied the TOC-dependent deposition of PBDEs in the core. Furthermore, multiple biomarker-based proxies of terrestrial organic matter (TOM) and marine organic matter (MOM) were introduced to systematically investigate the different effects of TOM and MOM on PBDE deposition in the SYS. The similarly down-core profiles and significant correlations were found between PBDEs and the MOM proxies (sum of rassicasterol, dinosterol and C37 alkenones (∑A + B + D) and marine TOC) as well as the branched and isoprenoid tetraether (BIT), but not for TOM proxies (∑C27+C29+C31 n-alkanes, terrestrial and marine biomarker ratio (TMBR) and terrestrial TOC), indicating that MOM was an important factor driving PBDE deposition in the sediment core from the SYS.

•East Asian Winter Monsoon-driven “hydrodynamic sorting effect” is a major control on lignin proxies.•Lignin can be adopted as a reliable proxy for paleoclimate evolution.•Century-scale changes in the East Asian Winter Monsoon are broadly correlated with “Bond cycles”.•ENSO is a dominant factor for multi-thousand-year variation of biomarkers.The varying intensity of the East Asian Winter Monsoon (EAWM) governs the strength of the counter-clockwise surface circulation of the South Yellow Sea and the redistribution of sediment and terrestrial organic material that had accumulated on the shallow shelf during the summer season into the central part of that basin. We compiled a time series spanning about 6.3 ka of terrestrial lignin proxies from sediment core N02 from Central Yellow Sea Mud that has well-preserved high-resolution sedimentary records (24 yr/cm average spacing). The “hydrodynamic sorting effect” driven by century-scale climate variation in the strength of the EAWM exerts the main underlying control on the variation of lignin proxies in marginal sea sediments, rather than paleovegetation variability in provenance region driven by the East Asian Summer Monsoon (EASM). Our lignin proxies data imply that North Atlantic climate forcing recorded by ice-rafted debris (“Bond cycles”) played a critical role in generating EAWM variability on these centennial timescales during the Holocene. These variations of lignin records are superimposed on general multi-thousand-year trends that appear to mirror the relative frequency and intensity of the El Niño Southern Oscillation (ENSO). Our results indicate that lignin can be adopted as an additional reliable proxy for paleoclimate evolution, at least in South Yellow Sea area.Download high-res image (164KB)Download full-size image

•Effects of TOM and MOM on DP deposition were first explored by multi-biomarkers.•Hydrodynamic forcing and atmospheric deposition were responsible for DP in the SYS.•MOM was the predominant contributor in controlling DP deposition to sediments in the SYS.•Competition may occur between TOM and MOM for DP adsorption.As an emerging halogenated organic contaminant, Dechlorane Plus (DP) was scarcely reported in marine environments, especially in China. In this work, 35 surface sediments and a sediment core were collected across the Southern Yellow Sea (SYS) to comprehensively explore the spatio-temporal distribution and possible migration pathway of DP. DP concentrations ranged from 14.3 to 245.5 pg/g dry weight in the surface sediments, displaying a seaward increasing trend with the high levels in the central mud zone. This spatial distribution pattern was ascribed to that fine particles with the elevated DP levels were preferentially transported to the central mud zone under hydrodynamic forcing and/or via long-range atmospheric transportation and deposition. DP concentrations in sediment core gradually increased from the mid-1950s to present, which corresponded well with the historical production and usage of DP, as well as the economic development in China. Significantly positive correlation between DP and total organic carbon (TOC) in both surface sediments and sediment core indicated TOC-dependent natural deposition of DP in the SYS. We used multiple biomarkers, for the first time, to explore the potential effects of terrestrial and marine organic matters (TOM and MOM) on DP deposition. The results showed that competition may occur between TOM and MOM for DP adsorption, and MOM was the predominant contributor in controlling DP deposition in the marine sediments from the SYS.Download high-res image (254KB)Download full-size image

•Hydrodynamic sorting dominated variations of lignin records in offshore area.•Lignin records in CYSM can well reflect paleoclimate changes during the Holocene.•ENSO dominated the long-term trends of biomarkers in the SYS during the Holocene.•EAWM dominated the variations of biomarkers on shorter time scale.•Paleoclimate in SYS was controlled by both regional and global climatic factors.Sediment core A02 collected from the central Yellow Sea mud (CYSM) was analyzed for various lignin parameters to provide evidence for the paleoclimate changes in the southern Yellow Sea (SYS) area during the Holocene. The results showed that the variations of various lignin parameters were dominated by the hydrodynamic sorting process driven by climate factors, and in turn lignin records can well reflect paleoclimate changes during the Holocene. The paleovegetation of the Yellow River basin was dominated by nonwoody angiosperms, and the terrestrial organic matter in core A02 was highly degraded and mainly came from peat and surface soils. Compared with climate records in previous studies, we found that terrestrial organic matter indicator Ʃ8, marine organic matter indicator P phenols and vegetation parameters S/V, C/V ratios had the similar variation trends with the El Niño-Southern Oscillation (ENSO) on the millennial time scale and correlated well with the Bond events (0 to 6) and the East Asian Winter Monsoon (EAWM) on the multidecadal to centennial time scale. ENSO events dominated the long-term trends of the biomarkers in the SYS during the Holocene while EAWM for the shorter time scale. Lignin records of core A02 responded not only to the regional climatic factors such as the EAWM but also to the global climatic factors such as Bond events and ENSO. In addition to the global cold climate events, it also recorded other regional cold events (at around 3.7 cal. kyr B.P., 6.5 cal. kyr B.P. and 7.0 cal. kyr B.P.) and coincided well with previous related records in the East Asian. These proved that the paleoclimate in SYS area was controlled by both regional and global climatic factors.

•The photodegradation of NP was studied by Suntest-CPS+ photo simulator.•The degradation reaction of NP obeyed pseudo-first-order kinetics.•NO3− could accelerate the photodegradation of NP by a factor of more than 3.•The strong synergy between NO3− and HCO3− resulted in NP removal of 95% in only 30 min.•Fe3+ contributed little to the interaction in the combination with NO3− and HCO3−.A Suntest-CPS+ sunlight simulator was used to investigate the direct and indirect photolysis of nonylphenol (NP) exposing to simulated sunlight in aqueous solution. The degradation reaction of NP obeyed a pseudo-first-order kinetics. Based on the pseudo-first-order rate constant (k) obtained from experimental data, the half-life of NP was calculated under different conditions, which ranged from 0.41 to 2.39 h. The affecting factors (NO3−, Fe3+ and HCO3−), especially their interactions on NP photodegradation, were systematically studied for the first time in the present study. The results showed that NO3− significantly influenced the photodegradation of NP and had a degradation ceiling. NO3− and HCO3− exhibited a synergistic effect on the photodegradation of NP and this interaction was very strong, which showed an abnormal phenomenon in dynamics, whereas the influence of Fe3+/HCO3− was slight on the photodegradation of NP. In addition, Fe3+ contributed little to the interaction in combining with other ions (NO3− and HCO3−). The light-absorbing ions (NO3− and Fe3+) with low concentration could inhibit the photolysis of NP only at the beginning of degradation process, indicating that the competition for energy and photons between NP molecule and light-absorbing ions is stronger than the photosensitizing effect at the initial stage. But this effect diminished with prolonged irradiation. Additionally, it was proved that the formation of free radicals during the photodegradation reaction was not the rate-determining step in NP indirect photodegradation. Meanwhile, compared with HO, CO3− had a higher oxidation rate on NP degradation, attributed to the generation of the more stable transition state between NP and CO3− during the degradation process.

The relationship between the chemical structure and biodegradation activity (− logt1/2) of 17 polycyclic aromatic hydrocarbons (PAHs) was studied using density functional theory (DFT) and stepwise multiple linear regression analysis (SMLR) methods. The equilibrium geometries and vibration frequency have been investigated at B3LYP/6-31 + G(d,p) level. One high correlation coefficient was found between the wagging vibration frequency (Freq) of the whole molecule and − logt1/2, which is resulted by the special structural characteristic with a big conjugated system. By means of regression analysis, the main factors influencing biodegradation activity were screened, and the equations of quantitative structure–activity relationship (QSAR) were established. The evaluation of the developed QSAR showed that the relationships are significant and the model had good predictive ability. The QSAR model showed that the biodegradation activity was closely related to molecular structure: the chemical bond strength of benzene ring played an important role in biodegradation process; In addition, low molecular weight PAHs are more degradable than the high molecular weight compounds.Highlights► The equilibrium geometries and vibration frequency have been investigated. ► The main factors influencing biodegradation activity were screened. ► The equations of quantitative structure-activity relationship were established. ► The QSAR model has good robustness and predictive ability.

•PCB and PBDE levels showed decreasing gradient from coastal areas to outer sea.•PCBs came from local human activities, surface runoff and atmospheric deposition.•PBDEs mainly originated from commercial Penta-, Octa- and Deca-BDEs in BS.•Penta- and deca-BDE homologs were major contributors of ecological risks in BS.Polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) were analyzed to assess the environmental quality in the surface sediments from Bohai Sea (BS), China. Concentrations of ∑37PCBs, ∑7PBDEs and BDE-209 were 0.157–1.699, 0.100–0.479 and 0.464–6.438 ng/g (dry weight), respectively. All of these concentrations decreased generally from the coastal areas towards the outer sea, indicating intensive influences of anthropogenic activities. Principal component analysis (PCA) coupled with multiple linear regression (MLR) revealed that 82.1% of the PCBs in BS came from direct discharge of local anthropogenic activities, 16.3% from surface runoff of contaminated soils and 1.6% from atmospheric deposition. PBDEs were mainly derived from the usage and dismantling of products containing commercial Penta-, Octa- and Deca-BDEs. According to sediment quality guidelines (SQGs), the ecological risks of PCBs could be negligible, and penta- and deca-BDE homologs might be the major contributors of ecological risks in the BS sediments.

•Transfer of PAHs from sediment to mollusk, shrimp and crab in BS was predicted.•Petroleum and emission are the key contributing to both PAHs and the related TEQ.•95th percentile CR and non-CR values suggested no potential health risk in BS.Assessing the health risk of PAHs in sediments was quite difficult because sediment occurred in sea floor, and it was very hard to contact with them directly for humans. This study was attempted to reveal the relationship between concentrations of PAHs in surface sediments and health risk of seafood consumers. The transfer (bioaccumulation) of PAHs from surface sediment into benthic organisms was predicted. Source contributions to PAHs and related toxicity and health risks (from intake of PAHs-contaminated benthic organisms) were studied based on PMF model and Monte Carlo simulation, respectively. Total concentrations of PAHs (TPAHs) ranged from 149.40 to 1211.97 ng g− 1 in sediments of Bohai Sea (BS), China. Petroleum and vehicular emission, coal combustion and coke oven constituted 40.0%, 32.2% and 27.8% of PAHs, respectively, but contributed 53.0%, 22.8% and 24.2% of toxicity posed by PAHs in sediment. For children, teens and adults, the 95th percentile carcinogenic and non-carcinogenic risks were below the threshold values of 10− 6 and 1.0, respectively, suggesting no potential health risk. Sensitivity analysis suggested that exposure duration (ED) and PAH concentrations (CS) were the two most sensitive parameters in risk assessment. The results provided a method to evaluate the quality of sediments and the potential health risk related to PAHs in marine sediments.

•Coal combustion, vehicle emission and coke oven are key PAH sources in BS and NPYS.•Combined biological toxicity of PAHs is lower than that of the individual PAHs.•TEQcarcs suggest potentially low carcinogenicity of PAHs exposure in BS and NPYS.Sources and ecological risk of sixteen priority PAHs in surface sediments from Bohai Sea (BS) and northern part of the Yellow Sea (NPYS) were investigated. The total concentrations of PAHs varied in ranges 149.24–1211.81 and 148.28–907.47 ng/g for BS and NPYS, respectively. Principal component analysis-multiple linear regression (PCA–MLR) suggested that coal combustion, vehicular emission and coke oven could be the primary PAH contributors, accounting for 56.6%, 29.2% and 14.2% of PAH concentrations, respectively. Analysis with sediment quality guidelines (SQGs) indicated that acenaphthylene, fluorene, phenanthrene, fluoranthene, pyrene and dibenzo(a,h)anthracene may occasionally cause adverse biological effects in some stations. Organic carbon (OC)-normalized analysis and mean effects range-median quotient (M-ERM-Q) suggested that the combined ecological risk of PAHs was generally low. The toxic equivalent concentrations of carcinogenic PAHs were 12.87–64.6 ng/g-BaPeq and 5.95–68.80 ng/g-BaPeq in BS and NPYS, respectively, suggesting low carcinogenic risk for both BS and NPYS.