Lakes play an important role in socioeconomic development and ecological balance in China, but their water quality has deteriorated
considerably in recent decades. In this study, we investigated the spatial–temporal variations of eutrophication parameters
(secchi depth, total nitrogen, total phosphorus, chemical oxygen demand, chlorophyll-a, trophic level index, and trophic state index) and their relationships with lake morphology, watershed land use, and socioeconomic
factors in the Yunnan Plateau lakes. 相似文献
Two sediment matrices with different characteristics were amended with chars from different sources for bioaccumulation assay with filter-feeding Chironomus plumosus larvae. Chars greatly decreased porewater concentrations of PAHs (Ciw) measured using polyethylene devices in sediments. In organic rich sediment matrix-based systems where suspended char particles were absent, PAH concentrations in larvae (CiB) were significantly correlated with Ciw, and there was no difference in water-based bioaccumulation factors (BAFs) between different treatments, suggesting that water absorption was the main contaminant uptake route for larvae. In organic poor sediment matrix-based systems where suspended char particles were present, poor Pearson correlation between CiB and Ciw was found, but there was a significant linear increase of BAF values with char contents, which indicated that ingestion of suspended char particles could also be important for PAH bioaccumulation. Therefore, we need to rethink of the effectiveness and risks for the application of black carbon to sediment/soil remediation. 相似文献
An intensive sampling of aerosol particles from ground level and 100 m was conducted during a strong pollution episode during the winter in Xi'an, China. Concentrations of water-soluble inorganic ions, carbonaceous compounds, and trace elements were determined to compare the composition of particulate matter (PM) at the two heights. PM mass concentrations were high at both stations: PM10 (PM with aerodynamic diameter < or =10 microm) exceeded the China National Air Quality Standard Class II value on three occasions, and PM2.5 (PM with aerodynamic diameter < or =2.5 microm) exceeded the daily U.S. National Ambient Air Quality Standard more than 10 times. The PM10 organic carbon (OC) and elemental carbon (EC) were slightly lower at the ground than at 100 m, both in terms of concentration and percentage of total mass, but OC and EC in PM2.5 exhibited the opposite pattern. Major ionic species, such as sulfate and nitrate, showed vertical variations similar to the carbonaceous aerosols. High sulfate concentrations indicated that coal combustion dominated the PM mass both at the ground and 100 m. Correlations between K+ and OC and EC at 100 m imply a strong influence from suburban biomass burning, whereas coal combustion and motor vehicle exhaust had a greater influence on the ground PM. Stable atmospheric conditions apparently led to the accumulation of PM, especially at 100 m, and these conditions contributed to the similarities in PM at the two elevations. Low coefficient of divergence (CD) values reflect the similarities in the composition of the aerosol between sites, but higher CDs for fine particles compared with coarse ones were consistent with the differences in emission sources between the ground and 100 m. 相似文献
Nitrogen-doped titanium dioxide (TiO2) and Fe–N-codoped TiO2 layers on fly ash cenospheres (FAC) as floating photocatalyst were successfully prepared through sol–gel method. Photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), ultraviolet (UV)–Vis diffuse reflectance spectroscopy (DRS), and nitrogen adsorption analyses for Brunauer–Emmett–Teller (BET) specific surface area. Photocatalytic efficiency of the prepared catalyst was evaluated through using the decomposition of Rhodamine B (RhB) as a model compound under visible light irradiation. Photocatalytic activity and kinetics of catalyst under visible light were detected in details from different Fe/Ti mole ratios by detecting photodegradation of RhB. Experimental results show that when the calcination temperature was 550 °C, the dosage of FAC was 3.0 g, and the mole ratio of Fe/Ti was 0.71 %; the synthesized Fe–N-TiO2/FAC photocatalyst presented as anatase phase and that N and Fe ions were doped into TiO2 lattice. The material’s specific surface area was 34.027 m2/g, and UV–Vis diffuse reflectance spectroscopy shows that the edge of the photon absorption has been red shifted up to 400–500 nm. Fe–N-codoped titanium dioxide on FAC had excellent photocatalytic activity during the process of photodegradation of RhB under visible light irradiation.