城市轨道交通噪声的声源特性研究进展

分析了城市轨道交通噪声的主要类型、基本特性、传播规律及其影响因素;综述了国内外城市轨道交通噪声的预测及测量分析技术的研究成果,并对其进行了总结比较,阐述了各种方法的特点、主要成就和局限;最后探讨了城市轨道交通噪声领域今后的研究方向和发展趋势,为解决城市轨道交通发展中的噪声问题提供了参考.     

城市铁路噪声环境影响及防治对策

以即将建设的某工程为例,分析了城市铁路噪声对环境的影响,并提出了相应的防治对策。     

铁路噪声预测模式的监测验证与误差分析

为了验证列车通过的等效声级、等效时间及预测模式的正确性,选择了一个开阔的场所,在距离铁路外轨中心线30 m处采用两种不同的方式记录列车通过时的源强及持续时间,然后利用监测值预测60 m处的1h等效连续A声级,并与60 m处的1h等效连续A声级监测值进行对比.结果表明,列车经过身边到离开时的持续时间作为等效时间,经过身边时的最大噪声级作为源强,所得到的预测值与监测值的误差范围在-0.3～0.9 dB(A),方差为0.229,离散度较小,预测值与监测值较吻合,可用于指导设计与规划工作.同时,在分析误差产生原因的基础上,提出了提高预测准确性的建议.     

Impact of roadside noise barriers on particle size distributions and pollutants concentrations near freeways

Increasing epidemiological evidence has established an association between a host of adverse health effects and exposure to ambient particulate matter (PM) and co-pollutants, especially those emitted from motor vehicles. Although PM and their co-pollutants dispersion profiles near the open freeway have been extensively characterized by means of both experimental measurements and numerical simulations in recent years, such investigations near freeways with roadside barriers have not been well documented in the literature. A few previous studies suggested that the presence of roadside structures, such as noise barriers and vegetation, may impact the decay of pollutant concentrations downwind of the freeway by limiting the initial dispersion of traffic emissions and increasing their vertical mixing due to the upward deflection of airflow. Since the noise barriers are now common roadside features of the freeways, particularly those running through populated urban areas, it is pertinent to investigate the impact of their presence on the particles and co-pollutants concentrations in areas adjacent to busy roadways. This study investigated two highly trafficked freeways (I-710 and I-5) in Southern California, with two sampling sites for each freeway, one with and the other without the roadside noise barriers. Particle size distributions and co-pollutants concentrations were measured in the immediate proximity of freeways and at different distances downwind of the freeways. The results showed the formation of a “concentration deficit” zone in the immediate vicinity of the freeway with the presence of roadside noise barrier, followed by a surge of pollutant concentrations further downwind at 80–100 m away from freeway. The particle and co-pollutants concentrations reach background levels at farther distances of 250–400 m compared to 150–200 m at the sites without roadside noise barriers.     

Characteristics analysis of near-field and far-field aerodynamic noise around high-speed railway bridge

Environmental Science and Pollution Research - The aerodynamic noise around the high-speed railway bridge is studied by the train-bridge-flow field numerical model and theory analysis. With the...     

Tracer studies to characterize the effects of roadside noise barriers on near-road pollutant dispersion under varying atmospheric stability conditions

A roadway toxics dispersion study was conducted at the Idaho National Laboratory (INL) to document the effects on concentrations of roadway emissions behind a roadside sound barrier in various conditions of atmospheric stability. The homogeneous fetch of the INL, controlled emission source, lack of other manmade or natural flow obstructions, and absence of vehicle-generated turbulence reduced the ambiguities in interpretation of the data. Roadway emissions were simulated by the release of an atmospheric tracer (SF₆) from two 54 m long line sources, one for an experiment with a 90 m long noise barrier and one for a control experiment without a barrier. Simultaneous near-surface tracer concentration measurements were made with bag samplers on identical sampling grids downwind from the line sources. An array of six 3-d sonic anemometers was employed to measure the barrier-induced turbulence. Key findings of the study are: (1) the areal extent of higher concentrations and the absolute magnitudes of the concentrations both increased as atmospheric stability increased; (2) a concentration deficit developed in the wake zone of the barrier with respect to concentrations at the same relative locations on the control experiment at all atmospheric stabilities; (3) lateral dispersion was significantly greater on the barrier grid than the non-barrier grid; and (4) the barrier tended to trap high concentrations near the “roadway” (i.e. upwind of the barrier) in low wind speed conditions, especially in stable conditions.     

Predictions of long-term performance of granular iron permeable reactive barriers: field-scale evaluation

Long-term performance is a key consideration for the granular iron permeable reactive barrier (PRB) technology because the economic benefit relies on sustainable operation for substantial periods of time. However, predictions on the long-term performance have been limited mainly because of the lack of reliable modeling tools. This study evaluated the predictive capability of a recently-developed reactive transport model at two field-scale PRBs, both having relatively high concentrations of dissolved carbonate in the native groundwater. The first site, with 8 years of available monitoring data, was a funnel-and-gate installation, with a low groundwater velocity through the gate (about 0.12 m d(-1)). The loss in iron reactivity caused by secondary mineral precipitation was small, maintaining relatively high removal rates for chlorinated organics. The simulated concentrations for most constituents in the groundwater were within the range of the monitoring data. The second site, with monitoring data available for 5 years, was a continuous wall PRB, designed for a groundwater velocity of 0.9 m d(-1). A comparison of measured and simulated aqueous concentrations suggested that the average groundwater velocity through the PRB could be lower than the design value by a factor of two or more. The distribution and amounts of carbonate minerals measured in core samples supported the decreased groundwater velocity used in the simulation. The generally good agreement between the simulated and measured aqueous and solid-phase data suggest that the model could be an effective tool for predicting long-term performance of granular iron PRBs, particularly in groundwater with high concentrations of carbonate.     

Effects of initial iron corrosion rate on long-term performance of iron permeable reactive barriers: Column experiments and numerical simulation

Column experiments and numerical simulation were conducted to test the hypothesis that iron material having a high corrosion rate is not beneficial for the long-term performance of iron permeable reactive barriers (PRBs) because of faster passivation of iron and greater porosity loss close to the influent face of the PRBs. Four iron materials (Connelly, Gotthart-Maier, Peerless, and ISPAT) were used for the column experiments, and the changes in reactivity toward cis-dichloroethene (cis-DCE) degradation in the presence of dissolved CaCO₃ were evaluated. The experimental results showed that the difference in distribution of the accumulated precipitates, resulting from differences in iron corrosion rate, caused a difference in the migration rate of the cis-DCE profiles and a significant difference in the pattern of passivation, indicating a faster passivation in the region close to the influent end for the material having a higher corrosion rate. For the numerical simulation, the accumulation of secondary minerals and reactivity loss of iron were coupled using an empirically-derived relationship that was incorporated into a multi-component reactive transport model. The simulation results provided a reasonable representation of the evolution of iron reactivity toward cis-DCE treatment and the changes in geochemical conditions for each material, consistent with the observed data. The simulations for long-term performance were also conducted to further test the hypothesis and predict the differences in performance over a period of 40 years under typical groundwater conditions. The predictions showed that the cases of higher iron corrosion rates had earlier cis-DCE breakthrough and more reduction in porosity starting from near the influent face, due to more accumulation of carbonate minerals in that region. Therefore, both the experimental and simulation results appear to support the hypothesis and suggest that reactivity changes of iron materials resulting from evolution of geochemical conditions should be considered in the design of iron PRBs.     

300 MW燃煤锅炉机组超细颗粒聚并器的实验研究

为了解决燃煤锅炉烟气中超细颗粒难以脱除的问题,基于流体动力学原理设计了一种超细颗粒聚并器,并在300 MW燃煤锅炉机组电除尘器的前置烟道中进行了实验研究。结果表明,聚并器内部存在超细颗粒之间以及超细颗粒与大颗粒之间的相互聚集行为,从而使超细颗粒数量显著减少。例如,对于粒径在2.65和10.48 μm以下的颗粒,其体积比例在聚并器出口分别减少了56.7%和62.3%,在电除尘器出口的粉尘浓度减少了26.34 mg/Nm3,这表明,基于流体动力学原理的聚并器对超细颗粒的聚并作用明显,具有良好的应用前景。     

The effect of combined loading on the behavior of micropiled rafts installed with inclined condition

One of the major disadvantages of micropiles is their low lateral stiffness and flexural rigidity due to the small diameter. This limitation can be handled in current practice, by installing the micropile with inclined condition or providing a steel casing. Additional steel casings will increase the lateral load capacity of micropiles but increase the project cost as well. Thus, inclination of micropile which is relatively simple and cheap is recommended. In this paper, a comprehensive numerical analysis is conducted on the behavior of micropiled rafts installed with inclined condition under combined vertical and lateral loading. A FEM calibrated against full-scale axial and lateral field tests is used to conduct the analysis. The soil profile is soft clay soil underlain by a layer of dense sand. The study investigates the impact of several parameters which are as follows: magnitude of vertical loading, reinforcement type, inclination angle of micropiles, and number of inclined micropiles. The study reveals that increasing vertical loads causes continuous decrease in the lateral load capacity of micropiled rafts. When all micropiles installed are inclined, the positively inclined micropiles carry 79–86% of the total lateral load carried by micropiles, whereas the negatively inclined ones carry 14–21%. Inclined micropiles offer greater lateral load sharing ratio (α_h) than that of vertical ones, largest at θ = 45°. The effect of micropile reinforcement on improving the lateral performance is low compared to the effect of micropile inclination angle.

     

Impact of insecticides on the American robin (Turdus migratorius) in a suburban environment

The purpose of this study was to examine the effects of diazinon and acephate applications to ornamental trees on the breeding behaviour and productivity of the American robin and to measure the effect of repeated chlorpyrifos spraying on robin productivity. No cases of adult or juvenile mortality were recorded, and nestling production was not affected. Plasma cholinesterase (ChE) activity in females exposed to diazinon or acephate was significantly lower than that in controls. However, there were no pronounced changes in parental care. The absence of a significant impact on behaviour despite the marked change in plasma ChE levels may have been due to one of several factors, i.e. (1) the insecticide had not reached the brain 18 to 24 h after spraying, and (2) exposure was insufficient to produce behavioural changes. The use of diazinon and acephate on ornamental trees should not be harmful to robins. There was a negative correlation between nest productivity and the number of lawns surrounding the nest treated with chlorpyrifos once or more in the preceding 2 years. The decline in earthworm numbers and their reduced biomass due to repeated chlorpyrifos use may account for the lower productivity recorded during the nesting season.     

道路路障对街道峡谷内污染物扩散的影响

采用数值模拟,研究不同风向角α (α=0°、45°、90°)及道路屏障位置(中间单路障和两侧双路障)对街道峡谷内机动车尾气污染物扩散的影响。数值模拟采用标准 k-ε 湍流模型且Sct选择0.3时,计算结果与风洞实验结果较好吻合。结果表明,2种路障布置方式可有效降低人行道内污染物浓度,特别是,当α=45°时,污染物浓度最多可降低46.23%。同时,风向角α对街道峡谷内污染物扩散影响较大。当 α=90°时,空气流通不良使得污染程度最为严重,且污染集中在背风侧近地面。单路障比双路障布置对污染物扩散影响更大,前者使污染物主要集中在街道中心背风侧,其他位置浓度明显降低;双路障时仅在一定范围内改善人行道内空气品质,但对街道整体污染物分布影响不大。     

饮食业后堂噪声综合控制技术研究

分析了饮食业后堂噪声的频率特性,采取隔声、吸声、消声控制技术和防油雾措施,并独创设计了一种排油烟通风复合消声器,解决了同时排油烟和降噪的难题,得出了饮食业后堂噪声综合控制的有效工艺。经2年的实际应用证明,降噪能力强,可满足60dB(A)的区域环境标准的要求,效果稳定,是一项值得推广的技术。特别是排油烟通风复合消声器、通风消声窗及“声闸”的设计参数,可在同类噪声控制中推广应用。     

Impact of ambient temperature on hospital admissions for respiratory diseases in suburban rural villages in northwest China

Environmental Science and Pollution Research - Extreme temperature is strongly associated with human health, but few studies are available for the effects of extreme temperatures on respiratory...     

Effects of suburban land use on phosphorus fractions and speciation in the Upper Peruque Creek, Eastern Missouri

This field study was conducted to explore the spatial and seasonal changes in total phosphorus and fraction distribution in relation to land uses. Water samples were collected biweekly at four sampling locations, which represented different potential phosphorus sources along the Upper Peruque Creek in Eastern Missouri. Total phosphorus concentrations of > 0.8 mg/L appeared sporadically at site 2, downstream of a small community, with an average of 0.82 +/- 0.14 mg/L in fall. Particulate phosphorus accounted for approximately 80% of total phosphorus at all sampling sites, except for site 2, where approximately 50 to 75% of dissolved phosphorus was often observed. Approximately 71 and 85% of total phosphorus in the sediment was in the form of iron (III) phosphate at the headwaters and downstream sites, respectively; 29 and 15% was in the form of phytic acid at the two sites. Land uses affect the total phosphorus concentration and alternate phosphorus fraction and speciation in the creek.     

Impacts of pavement types on in-vehicle noise and human health

Noise is a major source of pollution that can affect the human physiology and living environment. According to the World Health Organization (WHO), an exposure for longer than 24 hours to noise levels above 70 dB(A) may damage human hearing sensitivity, induce adverse health effects, and cause anxiety to residents nearby roadways. Pavement type with different roughness is one of the associated sources that may contribute to in-vehicle noise. Most previous studies have focused on the impact of pavement type on the surrounding acoustic environment of roadways, and given little attention to in-vehicle noise levels. This paper explores the impacts of different pavement types on in-vehicle noise levels and the associated adverse health effects. An old concrete pavement and a pavement with a thin asphalt overlay were chosen as the test beds. The in-vehicle noise caused by the asphalt and concrete pavements were measured, as well as the drivers’ corresponding heart rates and reported riding comfort. Results show that the overall in-vehicle sound levels are higher than 70 dB(A) even at midnight. The newly overlaid asphalt pavement reduced in-vehicle noise at a driving speed of 96.5 km/hr by approximately 6 dB(A). Further, on the concrete pavement with higher roughness, driver heart rates were significantly higher than on the asphalt pavement. Drivers reported feeling more comfortable when driving on asphalt than on concrete pavement. Further tests on more drivers with different demographic characteristics, along highways with complicated configurations, and an examination of more factors contributing to in-vehicle noise are recommended, in addition to measuring additional physical symptoms of both drivers and passengers.Implications: While there have been many previous noise-related studies, few have addressed in-vehicle noise. Most studies have focused on the noise that residents have complained about, such as neighborhood traffic noise. As yet, there have been no complaints by drivers that their own in-vehicle noise is too loud. Nevertheless, it is a fact that in-vehicle noise can also result in adverse health effects if it exceeds 85 dB(A). Results of this study show that in-vehicle noise was strongly associated with pavement type and roughness; also, driver heart rate patterns presented statistically significant differences on different types of pavement with different roughness.     

卡拉OK扰民噪声治理的研究

分析了卡拉OK扰民噪声的特点 ,通过现场实验和实测 ,研究了不同装修结构对房间隔声、隔振效果的影响     

The impact of sewage irrigation on the uptake of mercury in corn plants (Zea mays) from suburban Beijing

The impact of sewage irrigation on the uptake and translocation of mercury (Hg) in corn plants (Zea mays) was investigated. Corn plants were harvested the same day from two nearby fields in suburban Beijing, one irrigated historically with sewage effluent, and one irrigated solely with groundwater. Hg content was analyzed in the soil, roots and stems, while percent moisture and soil organic content were analyzed in the soil samples. The concentration of Hg in the soil and roots, and the soil organic content were not significantly different between the two fields, despite the historic practice of sewage irrigation. Hg content in roots was positively correlated with soil Hg concentration (r=0.95, n=6). The transfer coefficients between roots and stems were significantly higher in the control site (control: 2.06, sewage-irrigated: 0.44, p<0.05), indicating that the barrier effect of the roots was not consistent between the two fields.     

政府环境绩效评估中隐性绩效初探

政府环境绩效存在滞后现象,根据绩效在时间轴上的分布,提出显性绩效和隐性绩效,并定义这2类绩效.依据行为科学中的期望理论提出,在进行绩效评估时把隐性绩效考虑其中.提高目标价值估计,或通过创造条件,提高目标实现的概率,都能激发出领导者对环境保护、生态建设更高的积极性.     

电吸附设备工作过程的研究

研究了电压、流量及重碳酸盐碱度对电吸附设备除盐的影响,同时对高碱度水的酸化吹脱作为预处理进行了研究。实验结果表明,电吸附设备的最佳工作电压为1.4 V,最佳工作流量为1.5 m³/h。在进水碱度为170～500 mg/L时,HCO^-₃的脱附率为64%～83%。研究还发现,酸化吹脱是高碱度水的有效预处理方法,避免了HCO^-₃在电极内的积累。