西北工业城市冬季PM2.5污染特征及理化性质

为研究西北工业城市冬季PM_2.5污染特征及理化性质,以甘肃省白银市为例,采用单颗粒气溶胶质谱等相关仪器,开展实时在线PM_2.5化学组分观测,与兰州市同期进行对比分析.结果表明,观测期间白银市PM_2.5浓度（44.89 μg·m^-3）显著低于同期兰州市（70.69 μg·m^-3）,但含重金属颗粒物占比（7.84%）明显高于兰州市（2.92%）,化学组分复杂,PM_2.5以较大粒径颗粒物贡献为主;白银含Cu、Pb和Zn颗粒物粒径分布范围较宽,其中含Cu和Zn颗粒物数量、颗粒物混合比多大于兰州市;主要污染源为汽车尾气30.91%和二次无机源13.00%,机动车尾气贡献均高于其他对比城市;2020年1月4日发生的污染过程主要由汽车尾气和二次无机源贡献增加引起,加之前期气象扩散条件较差.白银冬季PM_2.5污染治理应以汽车尾气和二次无机源减排为主,同时加强大气重金属污染管控.     

储罐冷却材料喷涂装置的设计与优化

针对火灾情况下油罐区的保护问题,设计了一种储罐冷却材料喷涂装置。装置通过“动”、“静”结构结合的设计方案,满足了对高吸水性聚合物冷却材料的混配溶胀与喷涂要求。利用FLUENT软件对新型旋流静态混合器的分析结果表明,新型旋流静态混合器切向速度大,径向混合能力和湍流扩散能力强,有利于实现良好的混合效果。     

Seasonal differences in sources and formation processes of PM2.5 nitrate in an urban environment of North China

Nitrate (NO₃⁻) has been the dominant ion of secondary inorganic aerosols (SIAs) in PM_2.5 in North China. Tracking the formation mechanisms and sources of particulate nitrate are vital to mitigate air pollution. In this study, PM_2.5 samples in winter (January 2020) and in summer (June 2020) were collected in Jiaozuo, China, and water-soluble ions and (δ¹⁵N, δ¹⁸O)-NO₃⁻ were analyzed. The results showed that the increase of NO₃⁻ concentrations was the most remarkable with increasing PM_2.5 pollution level. δ¹⁸O-NO₃⁻ values for winter samples (82.7‰ to 103.9‰) were close to calculated δ¹⁸O-HNO₃ (103‰ ± 0.8‰) values by N₂O₅ pathway, while δ¹⁸O-NO₃⁻ values (67.8‰ to 85.7‰) for summer samples were close to calculated δ¹⁸O-HNO₃ values (61‰ ± 0.8‰) by OH oxidation pathway, suggesting that PM_2.5 nitrate is largely from N₂O₅ pathway in winter, while is largely from OH pathway in summer. Averaged fractional contributions of P_N2O5+H2O were 70% and 39% in winter and summer sampling periods, respectively, those of P_OH were 30% and 61%, respectively. Higher δ¹⁵N-NO₃⁻ values for winter samples (3.0‰ to 14.4‰) than those for summer samples (-3.7‰ to 8.6‰) might be due to more contributions from coal combustion in winter. Coal combustion (31% ± 9%, 25% ± 9% in winter and summer, respectively) and biomass burning (30% ± 12%, 36% ± 12% in winter and summer, respectively) were the main sources using Bayesian mixing model. These results provided clear evidence of particulate nitrate formation and sources under different PM_2.5 levels, and aided in reducing atmospheric nitrate in urban environments.     

扬水造流技术控藻机制研究

围绕扬水造流技术的两个关键控藻参数Vmix(水体垂直混合速率)和Emix:Eu(混合深度与真光层深度之比),分别在实验室和现场围隔中开展模拟实验探讨藻类的时空分布.结果表明,实验开始20h后藻类垂直分布趋向动态平衡,Vmix31.08cm/min时2h内藻类未出现浮聚现象,Vmix31.35cm/min则能够长期(320h)遏制表面水华;根据20h平衡分布变异系数对光照和混合组合条件下的控藻效果进行了分类.藻类生消实验显示衰亡速率常数K与Emix:Eu呈正相关(R2=0.85,P<0.05,n=5),表明增大Emix:Eu在一定程度上有利于促进藻类衰亡.现场围隔实验结果表明,Emix:Eu对藻类生长消亡的显著影响,并认为在自然条件下,扬水造流技术要发挥控藻效用,Emix:Eu必须33:1.     

三峡水库香溪河库湾夏季蓝藻水华成因研究

为探讨香溪河夏季蓝藻水华发生过程及主要影响因素,于2010年7月19日~8月30日在蓝藻水华暴发区域开展持续监测,并对水华过程进行分析.结果表明,水华持续25d,自7月23日暴发,8月16日逐渐消退,藻密度最高达到108.03′106cells/L,优势藻种为鱼腥藻(Anabaena);自身悬浮机制、固氮机制、能够产生藻毒素抑制其他藻类生长,是鱼腥藻成为优势藻种的主要原因;充足的营养物质、显著的水体分层是水华暴发的必要条件,水华期间蓝藻对硝氮利用显著;在具备充足的营养盐的稳定水体中,水温持续升高、混合层与真光层比值的降低是诱发蓝藻水华的关键因子,并且在混合层与真光层比值为0.5时对蓝藻增殖影响最大.     

深层搅拌法(浆液法)在东深供水工程软基处理中的应用

通过东深供水工程AIIII标段深层搅拌法处理软基的施工实践,总结深层搅拌法对于软土地基的施工工艺、质量控制手段、质量检查方法及其适用范围。     

WATER QUALITY STRATIFICATION IN SHALLOW WASTEWATER STABILIZATION PONDS1

ABSTRACT: The physical limnology of three modern wastewater stabilization ponds serving a small community in Minnesota was investigated over a 1-year period (July 1989 - October 1990). Water temperatures and associated meteorological parameters were recorded continuously; underwater light, dissolved oxygen, pH, and Secchi depth were measured intermittently (about weekly). Measurements of nutrients and planktonic species were made by other investigators. Water quality stratification dynamics were studied by analyzing variations of water temperature, dissolved oxygen, and pH distributions with time and over depth. Intermittent stratification and mixing of the shallow waste stabilization ponds (1–2 m deep) were documented and related to weather. The strong response of the ponds to seasonal and daily weather variations was observed. Three types of pond stratification conditions have been identified: (1) completely mixed during consecutive day and night, (2) stratified during the day and well-mixed during the night, and (3) continuously stratified during day and night. A diurnal cycle of stratification dynamics was first noticed in late April and persisted through summer and into fall. Differences in light attenuation and hence temperature stratification and DO distribution between pond 1 (primary), pond 2 (second primary) and pond 3 (secondary) in the wastewater treatment system were documented and related to different waste loading conditions. Temperature stratification affects chemical, microbial, and planktonic processes in the ponds. Results presented in this paper can be used to provide guidance for water quality sampling in monitoring of pond performance. Information on true mixing conditions is also needed to gain better understanding of important factors affecting pond operation, and for process simulations and reactor modeling of waste stabilization ponds.     

PRECISE WATER VELOCITY MEASUREMENTS USING PHOTOGRAMMETRIC TECHNIQUES1

ABSTRACT Necessary input parameters for studying mixing zone characteristics of thermal plumes are horizontal surface and subsurface water velocities. Using time lapse aerial photography and analytical photogrammetric techniques, movements of drogues in an effluent plume were traced. From these traces accurate velocity vectors were obtained. Photographic coordinates of drogue images were measured using a glass scale. From the photo coordinates and the results of a ground control survey, an analytical solution was made for positions of drogues in the water at known intervals of time. Drogue positions were mapped for selected exposures thereby providing a visual display of velocity vectors in the study area. A rigorous error analysis was performed to determine the validity of the computed results.     

FIELD MEASUREMENT OF FLOW VELOCITIES,SUSPENDED SOLIDS CONCENTRATIONS,AND TEMPERATURES IN LAKE OKEECHOBEE1

ABSTRACT: This paper presents a field investigation of collecting hydrodynamic and sediment data in Lake Okeechobee with analyses examining mechanisms affecting sediment resuspension in the lake. Lake Okeechobee is a large subtropical lake located in south central Florida. Three‐dimensional flow velocities, suspended solids concentrations (SSC), and temperatures at four locations were measured from January 18 to March 5, 2000. Analyses of these data indicate that wind is the dominant factor in driving flow velocities and therefore transporting suspended solids. Wind direction also affects the SSC, especially in the north central and west littoral areas of the lake. The surface and bottom velocity components frequently flow in opposite directions, forming a stratification of the water column and preventing suspended solids from settling out. This retention of SSC in the water column may have a strong impact on the water quality of Lake Okeechobee. This study provides valuable storm event data and mechanism analyses, which will improve our understanding of the transport of suspended solids, thermal exchanges, and flow patterns within Lake Okeechobee.     

微量试样破碎仪与降噪防尘结构设计

实验室实验使用的试样，一般都是20-30g的微量。实验前必须对试样进行破碎预处理。由于目前没有满足要求的处理设备。实验人员仍使用传统的手工破碎方法。浪费了时间和精力。介绍一种微量试样破碎处理仪器，既满足实验室微量试样的破碎，还解决了轻质毛发类样品的破碎问题。破碎机构的降噪防尘设计，解决了粉尘和噪音污染的问题，并能在破碎时改善物质的堆积状态。有效地提高了破碎效率。