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
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.
As a global pollutant, high levels of mercury (Hg) have been found in remote ecosystem due to the long range atmospheric transport. In this study, a total of 60 fish samples were collected from four rivers across the Tibetan Plateau to study the accumulation of Hg in remote and high-altitude aquatic environment. The total Hg (THg) and methylmercury (MeHg) in fish muscles ranged from 11 to 2097 ng/g dry weight (dw) (average: 819 ng/g dw) and from 14 to 1960 ng/g dw (average: 756 ng/g dw), respectively. Significantly positive linear relationships were observed between the THg (r = 0.591, p < 0.01, n = 36) and MeHg concentrations (r = 0.473, p < 0.01, n = 36) with the trophic level of fish from Lhasa River, suggesting trophic transfer and biomagnification of Hg in this aquatic ecosystem. Moreover, the THg levels in fish had significantly positive correlations with the length (r = 0.316, p < 0.05, n = 60) and weight (r = 0.271, p < 0.05, n = 60) of fish. The high levels of Hg were attributed to the slow growth and long lifespan of the fish under this sterile and cold environment. Risk assessment revealed that the consumption of Oxygymnocypris stewartii, Schizothorax macropogon, Schizothorax waltoni, Schizopygopsis younghusbandi and Schizothorax o'connori would lead to a high exposure to MeHg. 相似文献
Gangba sheep are known for having typical sensory characteristics attributed to free range conditions and grazing on wild plants. The genuine Gangba mutton was selected as the experimental group, and the commercial Tibetan mutton was selected as the control group, the nutritive composition of basic chemical components, amino acids and fatty acids in mutton were investigated to correlate its unique meat quality and eating satisfaction. The results showed that fatty acids were significantly higher (P<0.05) in Gangba mutton than in commercial mutton, and the higher content of flavoring amino acids (glutamic acid and aspartame) were primarily responsible for the taste attributes umami of meat juices. Moreover, the trace elements analysis in mutton and grazing factors (forage, water source and soil) were conducted, to explain the source of essential trace elements in mutton. The concentrations of essential trace elements show that the Gangba mutton was a valuable source for highly available Cu and Zn in human nutrition, and well managed with few detected of toxicity metal. The concentrations of essential trace elements in mutton are closely related to the trace elements in environmental grazing factors. In conclusion, the congenital grazing conditions (a highly mineralized water resource, natural forages and clean soils) were shown to contribute to the unique meat characteristics of Gangba sheep. 相似文献
The seasonal variations and spatial distributions of 4-tert-octylphenol (OP), 4-nonylphenol (NP) and bisphenol A (BPA) in surface waters, suspended solids and surface sediments in the Huangpu River and its tributaries (Suzhou River and Yunzao Brook) were firstly investigated. The mean concentrations of OP, NP and BPA in the three rivers were 10.59, 120.96 and 22.93 ng L?1 in surface waters, 199.87, 2,300.87 and 84.11 ng g?1 in suspended solids and 9.49, 119.44 and 7.13 ng g?1 dry weight in surface sediments, respectively. The concentrations of NP and OP were higher in summer than in winter in the suspended solids and surface sediments, while the reverse was true in surface waters. Similarly, the levels of BPA were lower in summer than in winter in surface sediments, while the opposite was true in surface waters and suspended solids. These seasonal variations might be attributed to temperature and stream flows. High levels of OP, NP and BPA were found in surrounding river intersections, residential and industrial areas. Their concentrations decreased gradually with increasing distance from those areas, while the lowest levels were measured in near less urbanized and agricultural areas. These phenomena might indicate that the stream current and pollutant source were the major factors that affect the spatial distributions of OP, NP and BPA in the three rivers. Ecological risk assessment indicated that NP was the only one of the three pollutants with the potential to influence local aquatic organisms. The results of this study provide scientific support for control of these pollutants. 相似文献