Mai Bixian

Polycyclic aromatic hydrocarbons in sediments from the Pearl river and estuary, China : spatial and temporal distribution and sources

Abstract Polycyclic aromatic hydrocarbons (PAHs) were measured in surface sediments and dated core sediments from the Pearl river and estuary, China, to investigate the spatial and temporal variability of anthropogenic pollutants. The sediments from the sampling stations at the Guangzhou channel have the highest concentrations of PAHs, owing to contributions from the large amount of urban/industrial discharges from the city of Guangzhou. The significant decrease of PAHs concentrations in sediments from the Shiziyang channel is mainly attributed to the increasing degradation and desorption of low molecular weight PAHs and alkyl PAHs, and the dilution by less contaminated water and particles from the East river. The PAH contaminants were concentrated on the western side in the Lingding bay of the Pearl river estuary because of the hydrodynamic and sedimentation conditions. Based on the characteristics of the parent compound distributions (PCDs) and the alkyl homologue distributions (AHDs) of PAHs, the potential source of PAHs in sediments from each sampling station was identified. Results indicated that the pyrogenic (combustion) source, characterized by the abundance of parent PAHs, were predominant in the heavily contaminated station (ZB01) near the aging industrial area, and the petrogenic (petroleum- derived) PAHs were more abundant in the stations (ZB02, ZB03) adjacent to the petrochemical plant and shipping harbor. Sediments from Lingding bay show variable distributions of PAH composition and variety in the proportion of combustion and petrogenic sources for the PAHs in different stations. Perylene, a naturally derived PAH, was found to be highly abundant in less contaminated stations. Analysis of the dated sediments (210Pb) indicates that higher PAH concentrations occurred in the sediments deposited after 1980, and higher fluxes of PAHs discharged to the Pearl river are found after 1990.

Synthesis, characterization and photocatalytic property of nano-sized Zn2SnO4

Nano-sized Zn2SnO4 materials have been synthesized using the coprecipitation method. The synthetic conditions and the calcination behaviors of nano-sized Zn2SnO4 materials have been studied. The nano-sized Zn2SnO4 materials have been characterized with X-ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetry and differential thermal analysis (TG-DTA) and specific surface area. As a result, the kinetic grain growth equation for nano-sized Zn2SnO4 can be expressed as D4.78 = 9.12 × 1023t exp(−40.6 × 103/T), with an activation energy for grain growth of Q = 337.9 KJ/mol. The nano-sized Zn2SnO4 materials have been used as photocatalysts to decompose benzene in water solution. The results show that Zn2SnO4 can photocatalytically decompose benzene, and the photocatalytic capacity for Zn2SnO4 relates to the grain size, which is discussed in terms of the surface effect and the quantum size effect.

Advances in the study of current-use non-PBDE brominated flame retardants and dechlorane plus in the environment and humans

The fate of the high production volume, currently in use, and not regulated non-polybrominated diphenyl ether (PBDE) flame retardants, such as tetrabromobisphenol A (TBBPA), hexabromocyclododecane (HBCD) and dechlorane plus (DP), and the alternative flame retardants of PBDE, such as BTBPE and DBDPE, in the environment has attracted increasing attention and aroused concern due to the increasing regulation and phasing-out of PBDEs. This paper reviews the distribution, bioaccumulation, human exposure and environmental behavior of those non-PBDE flame retardants in various environmental compartments. The data gaps and needs for future research are discussed.