黄河兰州市区段水质污染的监测与防治

通过对黄河兰州市区段2007年水质进行监测,评价分析了黄河兰州段水体的污染现状、污染变化及其特征,结果表明黄河兰州市区段水质存在着不同程度的污染。对造成水质污染的原因、污染危害及防治对策进行了讨论,提出了相应的污染防治对策。     

垃圾焚烧飞灰熔融过程中重金属分离效果影响因素研究

采用重庆同兴垃圾焚烧发电厂产生的焚烧飞灰,在感应炉上进行熔融处理实验研究,探讨了熔融温度、熔融时间、碱度等因素对熔融过程中重金属分离效果的影响.结果表明,重金属的挥发率按其熔沸点高低区分明显,Pb、Zn和Cd的挥发率较高,分别为80%、60%和95%左右;Cr、Mn的挥发率均低于10%.随着熔融时间、熔融温度和碱度的增加,Pb、Zn、Cd、Mn、Cr的挥发率变化趋势不明显;铁浴熔融方式可进一步促进Zn、Pb、Hg的挥发,有利于Cr、Cu从熔渣中分离出来,与生铁形成合金.对熔渣的浸出毒性测试结果表明,重金属元素的浸出毒性均可达标(GB5085.3-1996).     

Degradation and detoxification of microcystin-LR in drinking water by sequential use of UV and ozone

Microcystins (MCs) produced by cyanobacteria are strong hepatotoxins and classified as possible carcinogens.MCs pose a considerable threat to human health through tainted drinking and surface waters.Herein filtrated water from a waterworks in Harbin,China,was spiked with microcystin-LR (MC-LR) extracted from a toxic scum of microcystis aeruginosa,and the spiked sample waters were treated using UV irradiation with consequent ozonation process (UV/O3),compared with ozonation at a dose range commonly applied in water treatment plants,UV irradiation at 254 nm and UV irradiation combined with ozonation (UV+O3),respectively.The remaining of toxins were analyzed using high-performance liquid chromatography and also determined using a protein phosphatase type 2A inhibition assay,which was utilized to evaluate the reduction in toxicity.Results indicated that in comparison to other three processes (O3,UV,and UV+O3),UV/O 3 process could effectively decrease both the concentration and toxicity of MC-LR at 100 μg/L level after 5 min UV irradiation with consequent 5 min ozonation at 0.2 mg/L (below 1 μg/L),while 0.5 mg/L ozone dose was required for the level below 0.1 μg/L.The addition of an UV treatment step to the existing treatment train may induce significant transformation of micropollutants and breaks down the natural organic matters into moieties unfavorable for ozone decomposition,stabilizing the ozone residual.These findings suggested that sequential use of UV and ozone may be a suitable method for the removal of these potentially hazardous microcystins from drinking water.     

Iron-doped Mn-Ce/TiO2 catalyst for low temperature selective catalytic reduction of NO with NH3

The catalysts of iron-doped Mn-Ce/TiO 2(Fe-Mn-Ce/TiO 2) prepared by sol-gel method were investigated for low temperature selective catalytic reduction(SCR) of NO with NH 3.It was found that the NO conversion over Fe-Mn-Ce/TiO 2 was obviously improved after iron doping compared with that over Mn-Ce/TiO 2.Fe-Mn-Ce/TiO 2 with the molar ratio of Fe/Ti = 0.1 exhibited the highest activity.The results showed that 96.8% NO conversion was obtained over Fe(0.1)-Mn-Ce/TiO 2 at 180°C at a space velocity of 50,000 hr 1.Fe-Mn-Ce/TiO 2 exhibited much higher resistance to H 2 O and SO 2 than that of Mn-Ce/TiO 2.The properties of the catalysts were characterized using X-ray diffraction(XRD),N 2 adsorption,temperature programmed desorption(NH 3-TPD and NOx-TPD),and Xray photoelectron spectroscopy(XPS) techniques.BET,NH3-TPD and NOx-TPD results showed that the specific surface area and NH3 and NOx adsorption capacity of the catalysts increased with iron doping.It was known from XPS analysis that iron valence state on the surface of the catalysts were in Fe3+ state.The doping of iron enhanced the dispersion and oxidation state of Mn and Ce on the surface of the catalysts.The oxygen concentrations on the surface of the catalysts were found to increase after iron doping.Fe-Mn-Ce/TiO2 represented a promising catalyst for low temperature SCR of NO with NH3 in the presence of H2 O and SO2.     

Metal chlorides loaded on activated carbon to capture elemental mercury

Activated carbon (AC) was considered to be an effective sorbent to control mercury in combustion systems. However, its capture capacity was low and it required a high carbon-to-mercury mass ratio. AC loaded with catalyst showed a high elemental mercury (Hg0) capture capacity due to large surface area of AC and high oxidization ability of catalyst. In this study, several metal chlorides and metal oxides were used to promote the sorption capacity of AC. As a result, metal chlorides were better than metal oxides loaded on AC to remove gaseous mercury. X-ray diffractometer (XRD), thermogravimetric analyzer (TGA) and specific surface area by Brunauer- Emmett-Teller method (BET) analysis showed the main mechanisms: first, AC had an enormous surface area for loading enough MClx; second, Cl and MxOy were generated during pyrogenation of MClx; finally, there were lots of active elements such as Cl and MxOy which could react with elemental mercury and convert it to mercury oxide and mercury chloride. The HgO and HgCl2 might be released from AC’s porous structure by thermo regeneration. A catalytic chemisorption mechanism predominates the sorption process of elemental mercury. As Co and Mn were valence variable metal elements, their catalytic effect on Hg0 oxidization may accelerate both oxidation and halogenation of Hg0. The sorbents loaded with metal chlorides possessed a synergistic function of catalytic effect of valence variable metal and chlorine oxidation.     

When signal meets noise: immunity of the frog ear to interference

Sound stimulates the tympanic membrane (TM) of anuran amphibians through multiple, poorly understood pathways. It is conceivable that interactions between the internal and external inputs to the TM contribute to the nonlinear effects that noise is known to produce at higher levels of the auditory pathway. To explore this issue, we conducted measurements of TM vibration in response to tones in the presence of noise in the frog Eupsophus calcaratus. Laser vibrometry revealed that the power spectra (n = 16) of the TM velocity in response to pure tones at a constant level of 80 dB sound-pressure level (SPL) had a maximum centered at an average frequency of 2,344 Hz (range 1,700–2,990 Hz) and a maximum velocity of 61.1 dB re 1 μm/s (range 42.9–66.6 dB re 1 μm/s). These TM-vibration velocity response profiles in the presence of increasing levels of 4-kHz band-pass noise were unaltered up to noise levels of 90 dB SPL. For the relatively low spectral densities of the noise used, the TM remains in its linear range. Such vibration patterns facilitate the detection of tonal signals in noise at the tympanic membrane and may underlie the remarkable vocal responsiveness maintained by males of E. calcaratus under noise interference.     

基于灰色综合评价的通航安全角度下吴淞口建闸方案优选

将层次分析法与灰色关联分析法相结合,评价吴淞口挡潮闸3个备选方案对通航安全的影响。首先通过专家调查法,并对相关资料进行综合分析,确定吴淞口水闸建设工程方案通航安全影响评价指标,然后运用层次分析法计算各指标权重,最后利用灰色关联分析建立灰色评价模型,得到关联序,定量分析各方案在通航安全影响方面的优劣,得出最优方案,为吴淞口建闸方案的确定提供依据。     

Evaluation of noise environments during daily activities of university students

Noise conditions specifically in areas inside university facilities and its impact on the quality of life of university students are topics that have received little attention. This paper presents a study of the noise conditions in which university students of various institutions in Madrid, Spain, carry out their daily studies. A representative number of measurements was carried out using noise dosemeters and dataloggers in order to evaluate the levels of noise, noise dose and exposure to noise during school periods and extracurricular activities. The results were compared with the recommendations given by current environmental noise regulations. This paper was complemented with a survey to get to know how students perceive the exposure to noise in university environments.     

How do children learn to cross the street? The process of pedestrian safety training

Objective: Pedestrian injuries are a leading cause of child death and may be reduced by training children to cross streets more safely. Such training is most effective when children receive repeated practice at the complex cognitive–perceptual task of judging moving traffic and selecting safe crossing gaps, but there is limited data on how much practice is required for children to reach adult levels of functioning. Using existing data, we examined how children's pedestrian skills changed over the course of 6 pedestrian safety training sessions, each composed of 45 crossings within a virtual pedestrian environment.

Methods: As part of a randomized controlled trial on pedestrian safety training, 59 children ages 7–8 crossed the street within a semi-immersive virtual pedestrian environment 270 times over a 3-week period (6 sessions of 45 crossings each). Feedback was provided after each crossing, and traffic speed and density were advanced as children's skill improved. Postintervention pedestrian behavior was assessed a week later in the virtual environment and compared to adult behavior with identical traffic patterns.

Results: Over the course of training, children entered traffic gaps more quickly and chose tighter gaps to cross within; their crossing efficiency appeared to increase. By the end of training, some aspects of children's pedestrian behavior was comparable to adult behavior but other aspects were not, indicating that the training was worthwhile but insufficient for most children to achieve adult levels of functioning.

Conclusions: Repeated practice in a simulated pedestrian environment helps children learn aspects of safe and efficient pedestrian behavior. Six twice-weekly training sessions of 45 crossings each were insufficient for children to reach adult pedestrian functioning, however, and future research should continue to study the trajectory and quantity of child pedestrian safety training needed for children to become competent pedestrians.