水体中几种无机离子对硝酸根敏化甲芬那酸光降解影响研究

以中压汞灯为光源,研究环境浓度范围内硝酸根对甲芬那酸(MEF)光降解的影响机制.结果表明,甲芬那酸在不同浓度硝酸根溶液中的光解反应符合准一级动力学规律,其降解速率常数随硝酸根离子浓度增大而增大,当硝酸根离子浓度由0增至1 mmol·L-1时其速率常数由0.00627 min-1增至0.0232 min-1;以异丙醇为分子探针检测到羟基自由基存在于MEF光解过程中;光解过程中产生亚硝酸根,其浓度随着反应的进行而不断增大;碱性水环境对硝酸根敏化甲芬那酸的光解反应有利;碳酸盐、氯离子、三价铁对硝酸根敏化甲芬那酸光解产生抑制作用.采用UPLC/MS/MS对硝酸根敏化MEF光降解产物进行鉴定,并提出3条可能的光解路径.毒性研究表明,在硝酸根敏化甲芬那酸光降解过程中,生成了具有较甲芬那酸而言更高风险的中间产物.     

Photochemical oxidation and dispersion of gaseous sulfur compounds from natural and anthropogenic sources around a coastal location

The photochemical oxidation and dispersion of reduced sulfur compounds (RSCs: H₂S, CH₃SH, DMS, CS₂, and DMDS) emitted from anthropogenic (A) and natural (N) sources were evaluated based on a numerical modeling approach. The anthropogenic emission concentrations of RSCs were measured from several sampling sites at the Donghae landfill (D-LF) (i.e., source type A) in South Korea during a series of field campaigns (May through December 2004). The emissions of natural RSCs in a coastal study area near the D-LF (i.e., source type N) were estimated from sea surface DMS concentrations and transfer velocity during the same study period. These emission data were then used as input to the CALPUFF dispersion model, revised with 34 chemical reactions for RSCs. A significant fraction of sulfur dioxide (SO₂) was produced photochemically during the summer (about 34% of total SO₂ concentrations) followed by fall (21%), spring (15%), and winter (5%). Photochemical production of SO₂ was dominated by H₂S (about 55% of total contributions) and DMS (24%). The largest impact of RSCs from source type A on SO₂ concentrations occurred around the D-LF during summer. The total SO₂ concentrations produced from source type N around the D-LF during the summer (a mean SO₂ concentration of 7.4 ppbv) were significantly higher than those (≤0.3 ppbv) during the other seasons. This may be because of the high RSC and SO₂ emissions and their photochemistry along with the wind convergence.     

建筑基坑(槽)土方坍塌的成因及预防措施

国内近年来在建筑施工中经常发生土方坍塌事故，给人民生命财产造成了巨大损失。为此我们必须认真分析事故原因，总结经验教训，采取有效改进措施，才能防止类似事故重复发生。     

Ag/Ag2SO3 plasmonic catalysts with high activity and stability for CO2 reduction with water vapor under visible light

Environmental Science and Pollution Research - The conversion of CO2 into useful raw materials for fuels and chemicals by solar energy is described using a plasmonic photocatalyst comprised of Ag...     

基于时差收敛算法的声发射源定位方法研究

本文针对传统基于时差的声发射定位方法精度及稳定性不足且易受检测环境影响的问题,提出了一种基于收敛算法的声发射源定位方法,经过循环迭代不断优化声发射信号的到达时刻计算方式,使得定位计算重构的定位源稳定收敛在近似同一区域,从而提高声发射源的定位准确度。     

Optimization of the food waste water incineration with respect to CO and NO<Subscript>x</Subscript> emission characteristics

The incineration of food waste water in conjunction with the domestic waste is getting attention as a food waste water treatment method, due to its low treatment cost and high efficiency. Many studies verified that the ammonia in the food waste water served as a reducing agent to suppress the generation of NO_x when the food waste water was injected and incinerated. However, they have not revealed the correlation between the change in the concentration of the CO and NO_x by the influence of the solid matters contained in the food waste water on the incineration of the wastes. The purpose of this study is to determine the optimum amount of the food waste water injected through four nozzles in the primary and secondary incineration chambers and to assess the correlation between the concentration of CO and NO_x in accordance with the food waste water injection in each chamber of the incinerator. For the study, four food waste water injection nozzles were installed; two (A and B) at the top of the primary incineration chamber and the other two (C and D) in the secondary incineration chamber. The correlation between the change in the concentration of CO and NO_x was studied adjusting the amount of the food waste water injected through the nozzles. From the result, Case II showed the concentration of CO and NO_x as 1.8–10 and 14–26 ppm, respectively, while Case I showed that of CO and NO_x as 15–30 and 9–18 ppm, respectively. Those levels are well below the Korean emission criteria, 50 ppm for CO and 80 ppm for NO_x. Based on the results, it is evident there is a certain trade-off between emission of CO and NO_x, and Case II which has relatively low concentration of CO is easier and cheaper to control.     

Ecological and economic impacts of green roofs and permeable pavements at the city level: the case of Corvallis,Oregon

A city's spatial footprint is covered by extensive impervious building roofs and paved surfaces, which contribute to greater storm-water runoff, more surface pollutants, and less carbon sequestration, hence, worse ecosystem services. This research conducts an empirical study on the ecological and economic impacts of a citywide adoption of green roofs and permeable pavements in Corvallis, OR. The effects on ecosystem services of using green roofs and pervious pavements for a low impact development are modelled using Integrated Value of Ecosystem Services Trade-offs and compared to those from the City's current conventional development without green roofs and pervious pavements. The differences are analysed for ecological impact by storm-water yield, storm-water purification, and carbon sequestration and economic impact by a cost-benefit comparison. The results indicate that low impact development, especially intensive green roofs on commercial/industrial buildings and permeable pavements for parking lots, plays a significant role, even with a higher initial implementation cost, for long-term urban sustainability.     

中国社会保险缴费对就业的挤出效应

近年来我国社会保险制度快速发展,社会保险缴费不断增长,其对劳动力市场上的影响也逐渐凸显,表现之一是我国的就业增长相对于劳动人口的增长显得非常缓慢。梳理国内外相关文献发现,社会保险缴费会对就业产生挤出效应。本文在理论上讨论了社会保险缴费产生就业效应的作用机制,并通过2004-2010年的省级面板数据分析,发现我国社会保险缴费的快速增长对就业有挤出效应。在其他条件不变的情况下,社会保险缴费率每增加1%,平均来说会导致总就业水平减少0.153%,城镇就业水平减少0.06%。分区域的研究表明,社会保险缴费对我国的高收入地区和中等收入地区的就业都有显著的挤出效应,但是对低收入地区的就业影响不明显。本文的政策含义是要注意社会保险缴费的快速上涨可能会对就业产生不利影响,应该减轻企业和个人的社保负担。     

Possible particulate nitrite formation and its atmospheric implications inferred from the observations in Seoul,Korea

Simultaneous measurements of gaseous species and fine-mode, particulate inorganic components were performed at the University of Seoul, Seoul in Korea. In the simultaneous measurements, a certain level of nitrous acid (HONO) was observed in the gas-phase, indicating possible heterogeneous HONO production on the surface of the ambient aerosols. On the other hand, high particulate nitrite (NO^2?) concentrations of 1.41(±2.26) μg/m³ were also measured, which sometimes reached 18.54 μg/m³. In contrast, low HONO-to-NO₂ ratios of 0.007(±0.006) were observed in Seoul. This indicates that a significant fraction of HONO is dissolved in atmospheric aerosols. Around the Seoul site, sufficient alkalinity may have been provided to the atmospheric aerosols from the excessive presence of NH₃ in the gas-phase. Due to the alkaline particulate conditions (defined in this study as a particle pH >～3.29), the HONO molecules produced at the surface of the atmospheric aerosols appeared to have been converted into particulate nitrite, thereby preventing their further participation in the atmospheric O₃/NO_y/HO_x photochemical cycles. It was estimated that a minimum average of 65% of HONO was captured by alkaline, anthropogenic, urban particles in the Seoul measurements.