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691.
Airborne concentrations of PAH in the vicinity of the source region with open‐air burning of metal scraps were measured between February, 1992 and November, 1993. The activity of open‐air burning decreased significantly since 1993 due to prohibition regulation. Both gaseous phase and particle‐bound PAH were measured at five sampling sites, which included one reference sampling site far away from the source region. Both values of gaseous and particle‐bound PAH concentrations, which were measured in the vicinity of source region, decreased clearly during the two years monitoring period. It shows that the uncontrolled open‐air burning of metal scraps was a significant emission source of airborne PAH in the study area. The profiles of various species of PAH were also compared. A large decrease in benzo(a)pyrene was observed in the source region. 相似文献
692.
Removal of nitrogen and phosphorus from textile wastewater by soilless culture of Lolium multiflorum
A technique of soilless culture for removal of total nitrogen (TN) and total phosphorus (TP) from textile wastewater using Lolium multiflorum was conducted in this research. The TN concentration decreased from 50.72 mg/L to 24.64–27.89 mg/L and TP decreased from 6.9 mg/L to 3.7–4.1 mg/L in the experimental tank with the size of 4.7 m x 1.2 m x 0.75 m. The results suggested that L. multiflorum could absorb a large amount of N and P elements from the wastewater. This technique of soilless culture has many advantages such as simple equipment, low cost, easy operation, low energy consumption, convenient management and flexible disposition. 相似文献
693.
污染场地河道底泥浸出液对斑马鱼胚胎的毒性效应 总被引:2,自引:0,他引:2
为了评价某污染场地河道底泥对水生生物的毒性效应及其潜在生态风险,以斑马鱼(Brachydanio rerio)为受试生物,进行了河道底泥浸出液对斑马鱼胚胎的发育毒性实验。结果表明,5种底泥浸出液(A1、A2、A3、A4、A5)对斑马鱼胚胎的发育均有毒性效应,浸出液对斑马鱼胚胎的死亡率存在一定的剂量-效应关系,随着浸出液体积分数的增加,死亡率显著上升。浸出液对胚胎孵化抑制作用明显,随着浸出液体积分数的增加,孵化率显著下降。且能引起斑马鱼胚胎多种中毒症状,如水肿,鱼体弯曲,发育不全等异常现象,表明该段河道底泥存在潜在的生态风险。因此,在后期的污染场地河道整治中,需对河道底泥进行挖掘清理和无害化处理。 相似文献
694.
Effects of riparian land use on water quality and fish communities in the headwater stream of the Taizi River in China 总被引:1,自引:0,他引:1
Sen DING Yuan ZHANG Bin LIU Weijing KONG Wei MENG 《Frontiers of Environmental Science & Engineering》2013,7(5):699-708
Riparian land use remains one of the most significant impacts on stream ecosystems. This study focuses on the relationship between stream ecosystems and riparian land use in headwater regions. Four riparian land types including forest, grassland, farmland, and residential land were examined to reveal the correlation between stream water and fish communities in headwater streams of the Taizi River in north-eastern China. Four land types along riparian of 3 km in length were evaluated at 25, 50, 100, 200 and 500 m widths, respectively. Generally, the results found a significant relationship between riparian land uses and stream water quality. Grassland was positively correlated with water quality parameters (conductivity and total dissolved solids) at scales from 100 to 500 m riparian width. Farmland and residential land was negatively correlated with water quality parameters at scales from 25 to 500 m and from 50 to 200 m riparian widths, respectively. Although the riparian forest is important for maintaining habitat diversity and fish communities, the results found that only fish communities were significantly correlated with the proportion of riparian farmland. Farmland had a positive correlation with individual fish abundance within a riparian corridor of 25 to 50 m, but a negative correlation with fish diversity metrics from 25 to 100 m. This study indicates that effective riparian management can improve water quality and fish communities in headwater streams. 相似文献
695.
696.
Optimization of process parameters for mature landfill leachate pretreatment using MAP precipitation
Wei LI Xiaowen DING Min LIU Yuewen GUO Lei LIU 《Frontiers of Environmental Science & Engineering》2012,6(6):892-900
Chemical precipitation is a useful technology as a pretreatment to treat mature landfill leachate with high concentrations of ammonium-nitrogen (N H 4 + - N ) and refractory organic compounds. Orthogonal experiments and factorial experiments were carried out to determine the optimal conditions enhancing the magnesium ammonium phosphate (MAP) precipitation process, and the experimental results demonstrated that the removal rate of N H 4 + - N was more than 85% when MgO and NaH2PO4·2H2O were applied as external sources of magnesium and phosphorous under the optimal conditions that molar ratio n(Mg)∶n(N)∶n(P) = 1.4∶1∶0.8, reaction time 60 min, original pH of leachate and settling time 30 min. In the precipitation process, pH could be maintained at the optimal range of 8–9.5 because MgO could release hydroxide ions to consume hydrogen ions. Calcium ions and carbonate ions existed in the leachate could affect the precipitation process, which resulted in the decrease of N H 4 + - N removal efficiency. The residues of MAP sediments decomposed by heating under alkaline conditions can be reused as the sources of phosphorous and magnesium for the removal of high concentrations of N H 4 + - N , and up to 90% of ammonium could be released under molar ratio of n[OH]∶n[MAP] = 2.5∶1, heating temperature 90°C and heating time 2h. 相似文献
697.
698.
699.
Study on tri-axial creep experiment and constitutive relation of different rock salt 总被引:2,自引:0,他引:2
To evaluate the effect of the long-term operation of a salt cavern in a given construction on rock deformation and its stability, tri-axial creep tests to the glauberite, anhydrite, and argillaceous rock salt are conducted, from which the creep curves as well as exponential functions of strain rate during the steady creep stage and creep constitutive equations of different rock salt in the experimental process derived are obtained. The study results show that: (i) Under the same deviatoric stress, the strain rate of argillaceous rock salt is lower than the glauberite and anhydrite, and the difference becomes larger with the increase of the deviatoric stress; (ii) The creep constitutive equations of different kinds of rock salt are in good agreement with the Burgers model, besides which the respective characteristics of these two creep models are compared. The change of creep parameters also illustrates the discrepancy of rock salt. The researching results can provide some references for long-term stability analysis of gas storage in salt caverns. 相似文献
700.