How Green is Too Green? Public Opinion of What Constitutes Undesirable Algae Levels in Streams1

Abstract: A public opinion survey was carried out in Montana to ascertain if the public identifies a level of benthic (bottom‐attached) river and stream algae that is undesirable for recreation. The survey had two parts; an On‐River survey and a By‐Mail survey. The On‐River survey was conducted via 44 trips randomly scheduled throughout the state during which recreators were interviewed in‐person at the stream. Selection of stream segments and survey dates/times was based on known, statewide recreational use patterns. By‐Mail survey forms were sent to 2,000 individuals randomly selected from Montana’s Centralized Voter File (CVF) available from the Montana Secretary of State. The CVF was current through 2004 and represented over 85% of the state’s eligible voting population. In both surveys, eight randomly ordered photographs depicting varying levels of stream benthic algae were presented, and participants were asked if the algae level shown was desirable or undesirable for recreation. Survey form design, selection of photographs, and pretesting followed acceptable protocols that limited unintentional bias through survey execution. There were 433 returned forms (389 complete) for the By‐Mail survey, while the On‐River survey documented 563 interviews. In both surveys, as benthic algal chlorophyll a (Chl a) levels increased, desirability for recreation decreased. (Other measures of benthic algae biomass are presented as well.) For the public majority, mean benthic Chl a levels ≥200 mg/m² were determined to be undesirable for recreation, whereas mean levels ≤150 mg Chl a/m² were found to be desirable. Error rates were within the survey’s statistical design criteria (≤5%). The largest potential error source was nonresponse in the By‐Mail survey; however, the population represented by nonrespondents would have to exhibit profoundly different perceptions of river and stream algae to meaningfully alter the results. Results support earlier work in the literature suggesting 150 mg Chl a/m² represents a benthic algae nuisance threshold.     

高压水射流清洗油井结垢管安全生产问题讨论

针对目前油田开发生产中出现的油井管存在结垢日益严重、清洗难度大、污染环境、影响油水井安全生产等问题,理论与实际结合,提出了利用高压水射流清洗结垢管技术。给出了结垢管安全清洗的工艺流程及清洗装置,并阐明射流清洗的工作原理、结构特点、技术标准、检验方法、安全保护措施等,同时进行了高压旋转喷头的设计和其他技术参数的优选。通过胜利油田孤东采油厂结垢管现场高压水射流安全清洗,证实该技术具有良好的经济效益和社会效益,保证结垢管的安全使用和油水井的安全生产。     

船舶螺旋桨射流对湘江河床底泥扰动影响分析

船舶航行时螺旋桨产生的射流会对河道水流产生扰动,这种扰动是否能引起河床底泥的再悬浮需要更深入的论证分析。通过对比分析螺旋桨射流发展规律的研究成果,以湘江典型河段为研究对象,结合实船测量结果和此段河流地质资料,探讨了螺旋桨射流对湘江长株潭段河床底泥扰动的影响,并对此段河床底泥起动和悬浮条件进行了理论分析。结果表明:在周围环境流速较低的条件下,螺旋桨射流初始速度、河床水深及泥沙粒径是决定泥沙是否运动的主要因素。湘江长株潭河段已基本库区化,大部分河道平均水深远大于航道的标准水深2.8 m,河床泥沙平均粒径大于0.87 mm,其中细颗粒泥沙很少,由于螺旋桨射流断面平均流速小于泥沙起动流速,悬浮指标计算值远大于4,因此可以判断船舶正常航行在该段河流时底泥难以起动和再悬浮。     

城镇化下平原水系变化及河网连通性影响研究

针对平原区城镇化背景下水系减少及连通受阻等下垫面变化引起的洪涝加剧问题,综合考虑水系结构和水力特性等因素,建立满足行洪排涝需求的平原水系连通度量方法,并以浙东沿海平原河网区为例,分析了城镇化下平原水系特征变化及其对河网连通度的影响。结果表明:1近20a来研究区水系数量和结构复杂性均存在不同程度的衰减,河网密度和水面率分别减少20%和30%左右,水系尤其是低等级河道的减少导致河网结构趋于骨干化;2河网连通度受水面率等数量特征和水系空间连接结构的共同影响,在水系数量持续减少情况下,整个河网连通度呈现先减少后增加的趋势,说明了骨干河道工程对水系空间结构特征的优化,可缓解水系减弱对河网连通的负面效应;3建立的河网连通度方法合理反映了水系数量和结构变化下的河网连通度演变规律,以及水系变化下区域排涝能力的空间差异特征,具有操作性强特点。     

Hot,Salty Water: A Confluence of Issues in Managing Stormwater Runoff for Urban Streams

Research increasingly highlights cause and effect relationships between urbanization and stream conditions are complex and highly variable across physical and biological regions. Research also demonstrates stormwater runoff is a key causal agent in altering stream conditions in urban settings. More specifically, thermal pollution and high salt levels are two consequences of urbanization and subsequent runoff. This study describes a demonstration model populated with data from a high gradient headwaters stream. The model was designed to explain surface water‐groundwater dynamics related to salinity and thermal pollution. Modeled scenarios show long‐term additive impacts from salt application and suggest reducing flow rates, as stormwater management practices are typically designed to do, have the potential to greatly reduce salt concentrations and simultaneously reduce thermal pollution. This demonstration model offers planners and managers reason to be confident that stormwater management efforts can have positive impacts.     

Detention Outlet Retrofit Improves the Functionality of Existing Detention Basins by Reducing Erosive Flows in Receiving Channels

By discharging excess stormwater at rates that more frequently exceed the critical flow for stream erosion, conventional detention basins often contribute to increased channel instability in urban and suburban systems that can be detrimental to aquatic habitat and water quality, as well as adjacent property and infrastructure. However, these ubiquitous assets, valued at approximately $600,000 per km² in a representative suburban watershed, are ideal candidates to aid in reversing such cycles of channel degradation because improving their functionality would not necessarily require property acquisition or heavy construction. The objective of this research was to develop a simple, cost‐effective device that could be installed in detention basin outlets to reduce the erosive power of the relatively frequent storm events (~ < two‐year recurrence) and provide a passive bypass to maintain flood control performance during infrequent storms (such as the 100‐year recurrence). Results from a pilot installation show that the Detain H₂O device reduced the cumulative sediment transport capacity of the preretrofit condition by greater than 40%, and contributed to reduced flashiness and prolonged baseflows in receiving streams. When scaling the strategy across a watershed, these results suggest that potential gains in water quality and stream channel stability could be achieved at costs that are orders of magnitude less than comparable benefits from newly constructed stormwater control measures.     

燃煤锅炉机组电改袋工程成功案例分析

以宝钢电厂3#机组电改全袋工程为例,论述了该成功工程的特点,介绍了袋式除尘器及滤料的比选过程、结构型式和设计参数,总结了除尘系统所具有的技术特色和投运后所取得的效果,该案例对袋式除尘器在电站锅炉的推广应用具有参考意义。     

Eichhornia crassipes capability to remove naphthalene from wastewater in the absence of bacteria

The aim of the current study was to investigate the potential of an aquatic plant, the water hyacinth (Eichhornia crassipes) devoid rhizospheric bacteria, to reduce naphthalene (a polyaromatic hydrocarbon) present in wastewater and wetlands.The capability of sterile water hyacinth plants to remove naphthalene from water and wastewater was studied in batch systems. Water hyacinths enhance the removal of pollutants through their consumption as nutrients and also through microbial activity of their rhizospheric bacteria.Experimental kinetics of naphthalene removal by water hyacinth coupled with natural rhizospheric bacteria was 100% after 9 d. Plants, decoupled of rhizospheric bacteria, reduced naphthalene concentration up to 45% during 7 d. Additionally, naphthalene uptake by water hyacinth revealed a biphasic behavior: a rapid first phase completed after 2.5 h, and a second, considerably slower rate, phase (2.5-225 h). In conclusion, water hyacinth devoid rhizospheric bacteria reduced significantly naphthalene concentration in water, revealing a considerable plant contribution in the biodegradation process of this pollutant.     

脉冲袋式除尘器过滤风速的确定

过滤风速的选择是设计布袋除尘器的关键。本文在对工程应用中的脉冲袋式除尘器相关参数测定后,采用数学拟合法,得出了过滤风速与烟粉尘粒径的对数成正比、与废气含尘浓度和废气温度成反比的数学关系,并建立了具体的数学模型。     

大气压等离子体射流对水中铜绿微囊藻的灭活作用

以铜绿微囊藻为研究对象,将空气源大气压等离子体射流(APPJ)引入到液相,构建新型的大气压等离子体射流液相反应体系,考察了不同APPJ处理方式对铜绿微囊藻的灭活效率,观察了放电处理的藻细胞形态,分析了培养基p H的变化和液相产生的主要活性物质(H2O2和O3)对藻灭活的作用,并探讨了APPJ灭活铜绿微囊藻的作用机理。研究结果表明,当电压为7 k V,空气气体流速为4 L/min,藻液吸光度约为0.200,铜绿微囊藻的灭活率达到99.16%;处理后的藻发生细胞变形和破裂;处理后的藻液中产生H2O2和O3等活性物质,同时产生大量的NO-3和NO-2离子,导致液相p H迅速下降。通过考察主要活性物质(H2O2和O3)及藻液p H因素发现,单一因素灭活效果不佳,主要活性物质(H2O2和O3)和p H的组合因素是APPJ灭活水中铜绿微囊藻的主要原因。