Duohong Chen

Pollution characterization and diurnal variation of PBDEs in the atmosphere of an E-waste dismantling region.

Diurnal air samples were collected from the E-waste dismantling region Guiyu and the underwear industry region Chendian. This was the first report to present the diurnal variation of PBDEs in the atmosphere. The average concentrations of 11 PBDE congeners were 11,742 pgm(-3) in the daytime, and 4830 pgm(-3) at night in Guiyu, while the concentrations were lower in Chendian with 376 pgm(-3) in the daytime, and 237 pgm(-3) at night. BDE-209 accounted for 22% and 31.3% of the total PBDEs in Guiyu and Chendian, respectively. The diurnal variation trends of BDE-47, -99, -153, -183, and -209 were also analyzed in detail in the two regions.

Source Apportionment Using Radiocarbon and Organic Tracers for PM2.5 Carbonaceous Aerosols in Guangzhou, South China: Contrasting Local- and Regional-Scale Haze Events

We conducted a source apportionment and investigated the atmospheric behavior of carbonaceous aerosols during hazy and normal days using radiocarbon ((14)C) and biomass burning/secondary organic aerosol (SOA) tracers during winter in Guangzhou, China. Haze episodes were formed either abruptly by local emissions or through the accumulation of particles transported from other areas. The average contributions of fossil carbon to elemental carbon (EC), water-insoluble organic carbon, and water-soluble organic carbon were 71 ± 10%, 40 ± 6% and 33 ± 3%, respectively. High contributions of fossil carbon to EC (80-90%) were observed for haze samples that were substantially impacted by local emissions, as were the highest (lowest) ratios for NO3(-)/SO4(2-) (OC/EC), which indicates that these particles mainly came from local vehicle exhaust. Low contributions of fossil carbon to EC (60-70%) were found for haze particles impacted by regional transport. Secondary organic carbon (SOC) calculated using SOA tracers accounts for only ∼ 20% of the SOC estimated by (14)C, which is probably because some important volatile organic carbons are not taken into account in the SOA tracer calculation method and because of the large discrepancy in ambient conditions between the atmosphere and smog chambers. A total of 33 ± 11% of the SOC was of fossil origin, a portion of which could be influenced by humidity.

Phase partitioning, concentration variation and risk assessment of polybrominated diphenyl ethers (PBDEs) in the atmosphere of an e-waste recycling site

The daytime and nighttime air samples were collected from an e-waste recycling site in Guiyu (GY) and its upwind and downwind direction sites in Chendian (CD) and Gurao (GR), respectively, during September and December 2005 to determine the phase partitioning, seasonal and diurnal variation of polybrominated diphenyl ethers (PBDEs). The three sites showed similar congener compositions with BDEs-28, -47, -99, -207 and -209 as the dominant congeners. The gas phase contribution ranged from 42.1% ± 17.1% of the total PBDEs in summer to 9.0% ± 8.6% in winter. Partitioning of PBDEs between gas and particulate phases was well correlated with the subcooled liquid vapor pressure (P(L)(0)) for all samples. Both Junge-Pankow adsorption model and K(OA)-based absorption model fitted well the PBDEs data in winter but overestimated the sorption of PBDEs in summer. The mean atmospheric concentrations of BDEs-47 (2748 pg m(-3) in summer and 6146 pg m(-3) in winter) and -99 (1656 pg m(-3) in summer and 4911 pg m(-3) in winter) in GY were much higher than those from other places around the world. Additionally, the time series of PBDEs in GY demonstrated a pronounced diurnal variation pattern, but not CD and GR, where PBDEs appeared partly associated with regional accumulation. Source characterization from local emissions may be the major factor controlling the diurnal variation of PBDEs in GY air. The risk assessment showed that the total daily intakes of BDE-99 in GY was 9.0-34.9 ng kg(-1)-bwd(-1), which is higher than the maximal allowed intake level (0.26 ng kg(-1)-bwd(-1)) with factors of 35-135, indicating possible health risk for GY residents with exposure to PBDEs.

Source apportionment of PM2.5 at urban and suburban areas of the Pearl River Delta region, south China - With emphasis on ship emissions

Daily PM2.5 samples were collected at an urban site in Guangzhou in 2014 and at a suburban site in Zhuhai in 2014-2015. Samples were subject to chemical analysis for various chemical components including organic carbon (OC), element carbon (EC), major water-soluble inorganic ions, and trace elements. The annual average PM2.5 mass concentration was 48±22μgm-3and 45±25μgm-3 in Guangzhou and Zhuhai, respectively, with the highest seasonal average concentration in winter and the lowest in summer at both sites. Regional transport of pollutants accompanied with different air mass origins arriving at the two sites and pollution sources in between the two cities caused larger seasonal variations in Zhuhai (>a factor of 3.5) than in Guangzhou (<a factor of 2.0). Positive matrix factorization (PMF) analysis identified six and five major source factors for PM2.5 in Guangzhou and Zhuhai, respectively. Ship emissions, a source factor previously ignored in making emission control policies in the Pearl River Delta region of south China, were among the top contributors to PM2.5 at both sites, accounting for >17% of PM2.5 mass concentrations.

Organosulfates from Pinene and Isoprene over the Pearl River Delta, South China: Seasonal Variation and Implication in Formation Mechanisms

Biogenic organosulfates (OSs) are important markers of secondary organic aerosol (SOA) formation involving cross reactions of biogenic precursors (terpenoids) with anthropogenic pollutants. Until now, there has been rare information about biogenic OSs in the air of highly polluted areas. In this study, fine particle (PM2.5) samples were separately collected in daytime and nighttime from summer to fall 2010 at a site in the central Pearl River Delta (PRD), South China. Pinene-derived nitrooxy-organosulfates (pNOSs) and isoprene-derived OSs (iOSs) were quantified using a liquid chromatograph (LC) coupled with a tandem mass spectrometer (MS/MS) operated in negative electrospray ionization (ESI) mode. The pNOSs with MW 295 exhibited higher levels in fall (151 ± 86.9 ng m(-3)) than summer (52.4 ± 34.0 ng m(-3)), probably owing to the elevated levels of NOx and sulfate in fall when air masses mainly passed through city clusters in the PRD and biomass burning was enhanced. In contrast to observations elsewhere where higher levels occurred at nighttime, pNOS levels in the PRD were higher during the daytime in both seasons, indicating that pNOS formation was likely driven by photochemistry over the PRD. This conclusion is supported by several lines of evidence: the specific pNOS which could be formed through both daytime photochemistry and nighttime NO3 chemistry exhibited no day-night variation in abundance relative to other pNOS isomers; the production of the hydroxynitrate that is the key precursor for this specific pNOS was found to be significant through photochemistry but negligible through NO3 chemistry based on the mechanisms in the Master Chemical Mechanism (MCM). For iOSs, 2-methyltetrol sulfate ester which could be formed from isoprene-derived epoxydiols (IEPOX) under low-NOx conditions showed low concentrations (below the detection limit to 2.09 ng m(-3)), largely due to the depression of IEPOX formation by the high NOx levels over the PRD.

Effect of telophase enucleation on bovine somatic nuclear transfer.

Telophase enucleation has been proven to be an efficient method for preparing recipient cytoplasts in bovine embryonic nuclear transfer (2, 11). This research was designed to study in vitro development of bovine oocytes containing transferred somatic cell nuclei, reconstructed by using enucleated in vitro-matured oocytes 32 h of age at telophase II stage as recipient cytoplasts, compared with those 24 h of age at metaphase II stage. Two protocols for donor cell injection were adopted, i.e., subzonal injection (SUZI) and intracytoplasmic injection (ICI). Bovine oviduct epithelial cells (BOECs) and bovine cumulus cells (BCCs) from an adult cow were used as nuclear donors for these experiments. In SUZI groups, the fusion rate of donor cells, both BOECs and BCCs, with MII enucleated oocytes were higher than those with TII enucleated oocytes (54% vs. 41% and 53% vs. 39%, respectively; P<0.05), but the development rates to morula plus blastocyst stage in MII groups were lower than those in TII groups (22% vs. 39% and 21% vs. 41%, respectively; P<0.05). In ICI groups, about 26% of enucleated MII oocytes injected with BOECs or BCCs cleaved and only small parts of them developed to blastocyst stage (4% and 3%, respectively; P>0.05). When BOECs or BCCs were intracytoplasmically injected into oocytes enucleated at TII stage, no blastocyst was formed in either donor cell group and no cleavage occurred in BOEC group. Our data demonstrated that telophase enucleation is beneficial to early embryo development when bovine somatic nuclei are transferred by subzonal injection. However, it is harmful when donor cells are directly injected into the cytoplast of the enucleated oocytes.

Polymorphisms of GSTT1 and GSTM1 and increased micronucleus frequencies in peripheral blood lymphocytes in residents at an e-waste dismantling site in China

In the present study, we investigated whether genetic polymorphisms of metabolic enzymes in an exposed population were associated with genotoxic effects of the pollutants from e-waste in 58 subjects (the exposed) resided in a typical e-waste recycling site and 80 subjects (the controls) from a village away from the recycling site. Effects of genetic polymorphisms of glutathione S-transferases (GSTs) (GSTT1 and GSTM1) on the frequency of micronucleated binucleated cells (MNed BNC) in peripheral blood lymphocytes were evaluated. GSTM1 and GSTT1 were typed using PCR-restriction fragment length polymorphism methods. Cytogenetic alterations were evaluated using the cytokinesis-block micronucleus assay. The MNed BNC frequency was significantly higher in the exposed group (median: 4.0‰, IQR: 2.0–7.0‰) than in the control group (median: 1.0‰, IQR: 0.0–2.0‰, P < 0.01 for both comparisons); sera GST activities were also higher in the exposed subjects with either non-null GSTT1 (mean ± SD: 20.27 ± 6.43) or non-null GSTM1 (mean ± SD: 19.71 ± 4.89) than in the controls (mean ± SD: 18.79 ± 4.91 and 19.34 ± 6.42, respectively, P < 0.05 for both). Although the increased MNed BNC frequencies among the exposed group may be associated with the co-exposure of various chemical pollutants in the environment, there was no statistical evidence of an association between GSTs genotypes and frequencies of micronuclei in the study population. Because this study size was small, the mechanism of genotoxic effects caused by exposure to e-waste needs to be further validated in larger studies.

Physical and observable characteristics of cloud‐to‐ground lightning over the Pearl River Delta region of South China

Cloud-to-ground (CG) lightning characteristic parameters deduced from the lightning location system (LLS) for five differing microenvironmental areas relative to megacity, city, municipal town, hilly suburban area, and mountainous rural area conditions were examined in our 2009–2011 Pearl River Delta (PRD) study. Our LLS data analysis showed that there were high variation of lightning characteristics and phenomenal changes among these areas. As a supplement to the usual study of physical characteristics, an observation-based methodology had been developed to study the lightning behavior, while the respective thunderstorms were traversing through these observation areas. Special features and phenomenal changes related to the lightning characteristic parameters, such as observable lightning stroke days (OLSDs) and observable lightning stroke frequency and density for an OLSD, were also addressed. Microenvironmental variation due to change in topography, degree of urbanization, urban effect, and thunderstorm strength was found to affect the spatial distribution of lightning stroke and the severity of lightning activities over the observation areas. This approach increases our understanding of lightning in subtropical China. It also tells us more about the behavior of lightning while the thunderstorm traverses through an observation area. This information is lacking in previous studies.

In situ detection of the chemistry of individual fog droplet residues in the Pearl River Delta region, China

We use a single-particle aerosol mass spectrometer (SPAMS) coupled with a ground-based counterflow virtual impactor (GCVI) to measure the chemical compositions of individual submicron fog droplet residues. This is the first report of single-particle mass spectrometry measurements of fog droplet residual particles at ground level in an urban area. We show that most of the fog droplet residues were composed of elemental carbon (EC) (67.7%), followed by K-rich (19.2%) and mineral dust/metal (12.3%) particles. The predominance of EC-containing particles demonstrated that these particles could be effective fog nuclei and highlights the important influence of anthropogenic emissions on regional climate system. Compared with interstitial and ambient aerosols, nitrate was enhanced, sulfate was depressed, and ammonium- and organics-containing particles were hardly found in the fog droplet residues during fog events, suggesting that dust and metal particles containing nitrate may be preferentially activated and that ammonium and organics may not play important roles in fog formation in Guangzhou. We also present direct observational evidence that trimethylamine (TMA) and hydroxymethanesulfonate (HMS) are not found within fog droplet residues, although we previously observed enhanced gas-to-particle partitioning of these compounds by fog processing. Additionally, higher fraction or intensities of [K]+, [Fe]+ and [SiO3]- were found in fog droplet residues than in ambient and interstitial particles.

Maturation of the reconstructed oocytes by germinal vesicle transfer in rabbits and mice.

The present study was designed to evaluate the feasibility of germinal vesicle (GV) transfer in rabbits and mice. The GV oocytes were collected from ovaries and cultured in 20 microg/mL 3-isobutyl-1-methylxanthin (IBMX) in TCM199 medium, which caused oocytes to shrink, enlarging the perivitelline space to facilitate the GV removal and transfer. Pairs of GV-cytoplast complexes were fused with electric pulses, and the fused, reconstructed oocytes were cultured in TCM199 for 24 h. Results are as follows: 1) The exposure time of rabbit GV oocytes to IBMX medium affected the success of GV removal. For oocytes cultured for 2 and 3 h in IBMX medium, removed rates were 56% and 44, respectively, significantly higher (P < 0.05) than removal rates of GV oocytes cultured for 1 and 4 h (27% and 27%, respectively); 2) There was no significant difference (P > 0.1) in fusion and maturation rates of rabbit reconstructed oocytes collected at 72 and 84 h after initiation of FSH injection to donors; 3) eCG in the maturation media improved development of rabbit-to-rabbit GV transferred oocytes but had no positive effect on mouse-to-rabbit GV transferred oocytes; 4) When mouse GV-karyoplasts were injected into enucleated rabbit oocytes, fusion rates of GV-karyoplasts measuring 40- to 50-microm and 80- to 90-microm in diameters obtained were 84% and 93%, respectively. The rates were significantly higher (P < 0.05) than fusion rates after transferring GV-karyoplasts measuring 30- to 35-microm in diameter (63%). The maturation rate (89%) of reconstructed oocytes composed of 80- to 90-microm mouse GV-karyoplasts and rabbit GV-enucleated cytoplasts was higher than that seen for oocytes composed of 40- to 50-microm (77%, P<0.05) or 30- to 35-microm (59%, P<0.01) mouse karyoplasts. Thirty-five of the 63 (56%) mature mouse-to-rabbit reconstructed oocytes had the normal complement of 20 chromosomes.