Photocatalytic degradation of dissolved organic matter in landfill leachate by heterostructural ZnO-rGO composite catalysts.

The dissolved organic matter (DOM) in landfill pollutes not only the landfill and surroundings, but also the environment far away from the landfill by infiltrating into the soil and/or flowing on the ground surface. Developing an efficient photocatalyst to degrade DOM is an interesting topic. Herein, the catalysts composed of ZnO and reduced graphene oxide (ZnO-rGO) with different morphologies were fabricated with a two-step hydrothermal method. The phase composite and microstructure were analyzed, and the degradation efficiency of the DOM under ultraviolet light was investigated. Three kinds of ZnO-rGO composite catalysts with different morphologies were successfully synthesized, and rGO was coated on the ZnO surface to form heterostructural composite catalysts. The catalyst powders have similar Raman and FT-IR spectra, but have different specific surface areas and band gaps. The degradation efficiency of DOM by ZnO-rGO composites is higher than that of pure ZnO powder. Compared to pure ZnO, ZnO-rGO composite catalysts contain more oxygen vacancies and a narrower band gap, and the heterostructure is beneficial for accelerating electron separation, inhibiting electron recombination.

Synthesis and characterization of TiO2/ZnO heterostructural composite for ultraviolet photocatalytic degrading DOM in landfill leachate.

In order to investigate the photocatalytic degradation of dissolved organic matter (DOM) in landfill leachate, TiO2/ZnO heterostructural composite powders were fabricated combining with hydrothermal synthesis and solid-state reaction method. The prepared TiO2/ZnO composite powders consist of anatase TiO2 nanoparticles distributing on the surface of wurtzite ZnO particles. The optical band gap of TiO2/ZnO powder is less than that of pure ZnO or TiO2 powder. TiO2/ZnO catalyzers show high ultraviolet-degradation efficiency for methylene blue and dissolved organic matter. The degradation rate of TiO2/ZnO powder for fulvic acid-like substances in landfill leachate is 2.99 times that of pure ZnO powder, and is 1.30 times that of pure TiO2 powder. The degradation of fulvic acid-like substances by TiO2/ZnO photocatalyst reduced some molecular weight of benzene ring structure substances in leachate. The effective separation of electron and hole in heterostructural TiO2/ZnO photocatalyst is the main reason for its high photocatalytic degradation efficiency of DOM in landfill leachate.

[Canonical correspondence analysis between phytoplankton community and environmental factors in macrophtic lakes of the middle and lower reaches of Yangtze River].

The phytoplankton communities in 4 macrophtic lakes (Longgan Lake, Liangzi Lake, Futou Lake and Baoan Lake) in Middle-Lower Yangtze Plain were investigated in September 2011, and 7 phylum and 231 species of phytoplankton were detected in the waters. The results indicated that phytoplankton was mainly composed of Cyanophyta, Bacillariophyta and Chlorophyta. The four lakes were mesotrophic. And the main phytoplankton was Phormidium foveolarum, Synedra ulna, Phormidium tenu and Tribonema minus. The relationships between the distribution of phytoplankton and environmental factors in each sampling site were studies by canonical correspondence analysis. The results demonstrated that pH and Total phosphorus are the key factors for the distribution of phytoplankton communities in 4 typical macrophtic lakes in Middle-Lower Yangtze Plain.

[Speciation and vertical distribution of heavy metals in sediments of Baiyangdian Lake].

In order to find out the heavy metal concentrations and their potential ecological risks on sediments in Baiyangdian Lake, 0-14 cm surface sediments had been collected by the no-disturbance-gravity sampler at seven representative sampling points of Baiyangdian Lake. Optimized BCR sequential extraction procedure was used to carry out the analysis of heavy metal forms in the surface sediments. The heavy metal contents of different forms and in different depths were determined. The relationship between different forms of heavy metal and total organic carbon (TOC) in the sediments was analyzed. The geo-accumulation index (Igeo) was employed to evaluate the extent of heavy metal contamination. The results demonstrated that Co, Fe, Mn, Pb, Zn were mainly in residual form, acid soluble form, Fe-Mn oxide and organic matter bound forms respectively. The tendency of organic bound form of heavy metals and TOC of sediments was greater than the others. The concentration of Co, Pb, Zn decreased with the increase of sediment depth, with the maximal concentration was between 0-2 cm, while the concentration of Mn was the minimal between 6-8 cm and the maximal was at 14 cm. Baiyangdian sediments were not contaminated as a whole by Co, Mn, apart from medium pollution in the entrance of the Fuhe River. The other regions were lightly polluted by Zn and Pb.