Minggang Cai

Polybrominated Diphenyl Ethers vs Alternate Brominated Flame Retardants and Dechloranes from East Asia to the Arctic

Marine boundary layer air and seawater samples taken during a polar expedition cruise from East China Sea to the Arctic were analyzed in order to compare the occurrence, distribution, and fate of the banned polybrominated diphenyl ethers (PBDEs) with their brominated alternatives as well as the chlorinated Dechloranes. The sum of PBDEs (∑(10)PBDEs) in the atmosphere ranged from 0.07 to 8.1 pg m(-3) with BDE-209 being the dominating congener and from not detected (n.d.) to 0.6 pg L(-1) in seawater. Alternate brominated flame retardants (BFRs), especially hexabromobenzene (HBB), (2,3-dibromopropyl-2,4,6-tribromophenyl ether (DPTE), pentabromotoluene (PBT), 2-ethylhexyl 2,3,4,5-tetrabromobenzoate (EHTBB), bis-(2-ethylhexyl)-tetrabromophthalate (TBPH), were detected in higher concentrations than PBDEs, even in the high Arctic (0.6 to 15.4 pg m(-3) for sum of alternate BFRs), indicating the change of PBDEs toward alternate BFRs in the environmental predominance. In addition, Dechlorane Plus (DP) as well as Dechlorane 602, 603, and 604 were detected both in the atmosphere and in seawater. The highest concentrations as well as the highest compound variability were observed in East Asian samples suggesting the Asian continent as source of these compounds in the marine environment. The air-seawater exchange indicates strong deposition, especially of alternate BFRs, as well as dry particle-bound deposition of BDE-209 into the ocean.

Occurrence of Perfluoroalkyl Compounds in Surface Waters from the North Pacific to the Arctic Ocean

Perfluoroalkyl compounds (PFCs) were determined in 22 surface water samples (39-76°N) and three sea ice core and snow samples (77-87°N) collected from North Pacific to the Arctic Ocean during the fourth Chinese Arctic Expedition in 2010. Geographically, the average concentration of ∑PFC in surface water samples were 560 ± 170 pg L(-1) for the Northwest Pacific Ocean, 500 ± 170 pg L(-1) for the Arctic Ocean, and 340 ± 130 pg L(-1) for the Bering Sea, respectively. The perfluoroalkyl carboxylates (PFCAs) were the dominant PFC class in the water samples, however, the spatial pattern of PFCs varied. The C(5), C(7) and C(8) PFCAs (i.e., perfluoropentanoate (PFPA), perfluoroheptanoate (PFHpA), and perfluorooctanoate (PFOA)) were the dominant PFCs in the Northwest Pacific Ocean while in the Bering Sea the PFPA dominated. The changing in the pattern and concentrations in Pacific Ocean indicate that the PFCs in surface water were influenced by sources from the East-Asian (such as Japan and China) and North American coast, and dilution effect during their transport to the Arctic. The presence of PFCs in the snow and ice core samples indicates an atmospheric deposition of PFCs in the Arctic. The elevated PFC concentration in the Arctic Ocean shows that the ice melting had an impact on the PFC levels and distribution. In addition, the C(4) and C(5) PFCAs (i.e., perfluorobutanoate (PFBA), PFPA) became the dominant PFCs in the Arctic Ocean indicating that PFBA is a marker for sea ice melting as the source of exposure.

Spatial distribution of per- and polyfluoroalkyl compounds in coastal waters from the East to South China Sea

The spatial distribution of per- and polyfluoroalkyl compounds (PFCs) were investigated in coastal waters collected onboard research vessel Snow Dragon from the East to South China Sea in 2010. All samples were prepared by solid-phase extraction and analyzed using high performance liquid chromatography/negative electrospray ionization-tandem mass spectrometry (HPLC/(-)ESI-MS/MS). Concentrations of 9 PFCs, including C(4) and C(8) (PFBS, PFOS) perfluoroalkyl sulfonate (PFSAs), C(5)-C(9) and C(13) (PFPA, PFHxA, PFHpA, PFOA, PFNA, PFTriDA) perfluoroalkyl carboxylates (PFCAs), and N-ethyl perfluorooctane sulfonamide (EtFOSA) were quantified. The ΣPFC concentrations ranged from 133 pg/L to 3320 pg/L, with PFOA (37.5-1541 pg/L), PFBS (23.0-941 pg/L) and PFHpA (0-422 pg/L) as dominant compounds. Concentrations of PFCs were greater in coastal waters along Shanghai, Ningbo, Taizhou, Xiamen and along coastal cities of the Guangdong province compared to less populated areas along the east Chinese coast. Additionally, the comparison with other seawater PFC measurements showed lower levels in this study.

Ultra trace analysis of 17 organochlorine pesticides in water samples from the Arctic based on the combination of solid-phase extraction and headspace solid-phase microextraction-gas chromatography-electron-capture detector

Solid-phase extraction (SPE) was combined with headspace solid-phase microextraction (HS-SPME) for the highly effective enrichment of 17 ultra trace organochlorine pesticides in water samples. The target compounds were successfully transferred from water samples to a gas chromatography capillary column by means of four consecutive steps, namely SPE, solvent conversion, HS-SPME, and thermal desorption of the SPME fiber. Parameters, including elution volume and breakthrough volume in the SPE step, temperature in the solvent conversion step, and fiber type, ionic strength, extraction temperature, extraction time, and pH in the SPME step were optimized to improve the performance of the method through either single factor comparative experiment or the orthogonal experimental design approach. After optimization, the method gave high sensitivity with a method detection limit ranging from 0.0018 to 0.027 ng L(-1), good repeatability with a relative standard deviation less than 20% (n=4) and acceptable recovery with a value mostly exceeding 60%. External standard calibration was employed for the quantification, and a wide linear range (from 0.0010 to 60 ng mL(-1)) with R(2) values ranging from 0.9988 to 0.9999 were observed. In the end, the method was successfully applied to the Arctic samples, and the results showed that, among all the organochlorine pesticides, hexachlorocyclohexanes (HCHs) were the most predominant in the Arctic surface water body with sum of their concentrations ranging from 0.262 to 3.156 ng L(-1).

Polyfluorinated compounds in the atmosphere along a cruise pathway from the Japan Sea to the Arctic Ocean

Neutral polyfluorinated alkyl substances (PFASs) were measured in high-volume air samples collected on board the research vessel Snow Dragon during the 4th Chinese National Arctic Expedition from the Japan Sea to the Arctic Ocean in 2010. Four volatile and semi-volatile PFASs (fluorotelomer alcohols (FTOHs), fluorotelomer acids (FTAs), perfluoroalkyl sulfonamides (FASAs), and sulfonamidoethanols (FASEs)) were analyzed respectively in the gas and particle phases. FTOHs were the dominant PFASs in the gas phase (61-358pgm(-3)), followed by FTAs (5.2-47.9pgm(-3)), FASEs (1.9-15.0pgm(-3)), and FASAs (0.5-2.1pgm(-3)). In the particle phase, the dominant PFAS class was FTOHs (1.0-9.9pgm(-3)). The particle-associated fraction followed the general trend of FASEs>FASAs>FTOHs. Compared with other atmospheric PFAS measurements, the ranges of concentrations of ∑FTOH in this study were similar to those reported from Toronto, north America (urban), the northeast Atlantic Ocean, and northern Germany. Significant correlations between FASEs in the gas phase and ambient air temperature indicate that cold surfaces such as sea-ice, snowpack, and surface seawater influence atmospheric FASEs.

Occurrence of polychlorinated biphenyls (PCBs) together with sediment properties in the surface sediments of the Bering Sea, Chukchi Sea and Canada Basin

The spatial distribution and potential source of polychlorinated biphenyls (PCBs) in surface sediments from Bering Sea, Chukchi Sea, and Canada Basin and the relationship between PCBs and sedimentary properties including grain size, water content, loss on ignition, total organic carbon, and black carbon were explored. ΣPCBs (the sum of the detected PCB congeners) concentrations fluctuated in the study area, ranging from 22-150, 60-640 and 24-600 pg g(-1) dry weight for the Bering Sea, Chukchi Sea, and Canada Basin. A similar homologue pattern was observed at different locations, with tri-chlorinated PCBs being the dominant homologue, implying that the PCBs came mainly from the atmospheric transportation and deposition and ocean current transportation. No apparent co-relationships between PCB concentrations and sediment properties were obtained, indicating that the distribution of PCBs was not only controlled by their source, but also by the multi-factors such as atmospheric transport and depositing, mixing, partitioning and sorption in the water column and sediments.

Content and distribution of trace metals in surface sediments from the northern Bering Sea, Chukchi Sea and adjacent Arctic areas

Concentrations of trace metals (Zn, Cr, Cu, V, Cd and Pb), total organic carbon (TOC), black carbon (BC) and their granulometry were examined in 25 surface sediment samples from the northern Bering Sea, Chukchi Sea and adjacent areas. Trace metal concentrations in the sediments varied from 21.06-168.21 mg kg(-1) for Zn, 8.91-46.94 mg kg(-1) for Cr, 2.69-49.39 mg kg(-1) for Cu, 32.46-185.54 mg kg(-1) for V, 0.09-0.92 mg kg(-1) for Cd, and 0.95-15.25 mg kg(-1) for Pb. The geoaccumulation index (Igeo) indicated that trace metal contamination (Zn and Cd) existed in some stations of the study area. The distribution of grain size plays an important role in influencing the distribution of trace metals (Zn, Cr, Cu, V, and Pb) in sediments from the Chukchi Sea and adjacent areas.

Fate of Polycyclic Aromatic Hydrocarbons in Seawater from the Western Pacific to the Southern Ocean (17.5°N to 69.2°S) and Their Inventories on the Antarctic Shelf

Semivolatile organic compounds such as polycyclic aromatic hydrocarbons (PAHs) have the potential to reach pristine environments through long-range transport. To investigate the long-range transport of the PAHs and their fate in Antarctic seawater, dissolved PAHs in the surface waters from the western Pacific to the Southern Ocean (17.5°N to 69.2°S), as well as down to 3500 m PAH profiles in Prydz Bay and the adjacent Southern Ocean, were observed during the 27th Chinese National Antarctic Research Expedition in 2010. The concentrations of Σ9PAH in the surface seawater ranged from not detected (ND) to 21 ng L(-1), with a mean of 4.3 ng L(-1); and three-ring PAHs were the most abundant compounds. Samples close to the Australian mainland displayed the highest levels across the cruise. PAHs originated mainly from pyrogenic sources, such as grass, wood, and coal combustion. Vertical profiles of PAHs in Prydz Bay showed a maximum at a depth of 50 m and less variance with depth. In general, we inferred that the water masses as well as the phytoplankton were possible influencing factors on PAH surface-enrichment depth-depletion distribution. Inventory estimation highlighted the contribution of intermediate and deep seawater on storing PAHs in seawater from Prydz Bay, and suggested that climate change rarely shows the rapid release of the PAHs currently stored in the major reservoirs (intermediate and deep seawater).

Bioaccumulation and biomagnification of halogenated organic pollutants in mangrove biota from the Pearl River Estuary, South China.

Four biota species were collected from mangrove ecosystems of the Pearl River Estuary to investigate the bioaccumulation and biomagnification of polychlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethane (DDT), polybrominated diphenyl ethers (PBDEs), dechlorane plus (DP), and decabromodiphenyl ethane (DBDPE). Concentrations of ΣPCBs, ΣDDTs, ΣPBDEs, DP, DBDPE and anti-Cl11-DP (the dechlorination product of anti-DP) in mangrove biota ranged from 32.1-466, 153-3819, 3.88-59.8, 0.18-6.88, not detected (nd)-30.6 and nd-2.65 ng/g lipid weight, respectively. Daggertooth pike conger (Muraenesox cinereus) had higher concentrations of contaminants than the other three biota species. Significant positive relationship between anti-Cl11-DP and anti-DP levels was observed in mangrove biota. DDTs were the predominant HOPs in all biota species, followed by PCBs and PBDEs. All the target compounds exhibited biomagnification, with biomagnification factors greater than 1 in the studied feeding relationships. Food web magnification was found for ΣPCBs, ΣDDTs, ΣPBDEs and DP, with trophic magnification factors of 2.76, 2.61, 2.20 and 2.31, respectively.

Lost but can't be neglected: Huge quantities of small microplastics hide in the South China Sea

Large quantities of microplastics with small particle sizes were found in the South China Sea (SCS). The abundances of microplastics in seawater were 0.045±0.093and 2569±1770particles/m3 according to the bongo net and pumping sampling methods, respectively. Smaller-size fractions (size<0.3mm) contributed 92% of the number of microplastics to the total load. Continental slope is the largest reservoir of microplastics with an inventory of 295tons. 21 polymer types were found in the samples using the micro Fourier Transform Infrared Spectroscopy (FTIR), among which alkyds (22.5%) and polycaprolactone (PCL) (20.9%) accounted for almost half of the total polymer content. Lighter plastics would not only concentrate upon the coastal area, being more likely to drift further into open seas with ocean currents. The distribution characteristics showed that it was mainly controlled by terrestrial input of the Pearl River. This study, as the first report from SCS on microplastics in water for its distribution and influence factors, provided impetus for further research on the transportation fate and the behavior of this emerging pollutant from coastal zone to the open oceans.