两种生态净化措施对水源水库光学环境的影响

为了评估生态净化措施对水体光学环境的影响,以上海金泽水库为例,在微纳米曝气复氧和水生植物净化两种生态净化措施前后布设采样点进行了光学衰减系数（水体光合辐照度（PAR）衰减系数）、真光层深度和透明度及相关水质指标的监测和分析.结果表明：水生植物净化和曝气复氧净化措施有利于水体光学环境的改善,经微纳米曝气后,水体透明度增大20%~25%,真光层深度增大2.2%~14.8%,光学衰减系数降低0.4%~4.4%;经水生植物净化后,水体透明度增大20%~29.4%,真光层深度增大6%~20%,光学衰减系数降低17.3%~20.5%.逐步回归结果表明不同生态净化措施的光学环境改善机制不同,微纳米曝气主要通过叶绿素、溶解性有机物、温度、溶解氧影响水体光学环境,水生植物净化主要通过浊度影响水体光学环境.冬季,两种生态净化措施对总氮和溶解性有机物均没有改善效果.     

垂向湍流扩散和光耦合对下沉藻增长的影响——基于内陆混浊湖泊(太湖)分析

在假设温度恒定、弱化营养盐限制作用的条件下,利用太湖背景漫射衰减系数、日变化太阳辐射等数据,通过下沉藻生长与水环境相结合的耦合模型,模拟下沉藻增长过程中垂向湍流扩散和光之间的耦合.结果表明：在相对清洁水体中（背景漫射衰减系数小于1.1/m）,下沉藻类无需垂向湍流扩散均可维持增长;混浊水体中（背景漫射衰减系数介于1.1~3.0/m）下沉藻类增长需垂向湍流扩散维持,且最低垂向湍流扩散值随背景漫射衰减系数增大而增大,二者间存在指数函数关系;最低垂向湍流扩散（D）、水深（z）与藻类下沉速度（v）间的佩克莱数应位于0.38~13.89,否则垂向湍流扩散对比其他因素（藻类沉降和光衰减）,对水柱中下沉藻类的增长的作用甚小;当背景漫射衰减系数大于3.0/m,水柱平均光能可能难以满足藻类增长,藻类持续消亡.该研究有助于厘清气候变化背景下水生生态系统中的浮游植物种群演替机制.     

典型农药污染场地地下水中苯系物监控自然衰减研究

通过对某农药污染场地地下水中苯系物（BTEX）4年的长期监测数据进行分析,识别了该场地地下水中BTEX浓度的空间分布规律,并研究了场地地下水中BTEX的自然衰减规律.结果表明,地下水BTEX污染程度较重,浓度为0.001~180.52 mg·L^-1,平均浓度为13.30 mg·L^-1;BTEX浓度和污染羽面积随时间出现波动式变化,但整体仍呈逐渐减小的趋势,表明地下水中BTEX发生了自然衰减;地下水中氧化还原电位（ORP）与BTEX浓度呈显著负相关,说明研究区中BTEX高浓度区域在发生生物降解;研究区BTEX的衰减速率较小,半衰期较长,说明该场地单纯依靠监控自然衰减的修复时间将较长,需要与化学刺激等其他主动修复技术相结合以提高自然衰减效率.     

氯代烃污染场地生物自然衰减修复研究进展

随着监测自然衰减技术的不断发展和日趋成熟,其在氯代烃污染场地修复领域中的应用越来越广泛和深入。本文在简要回顾监测自然衰减技术来源和发展的基础上,围绕主导氯代烃去除的生物自然衰减过程,综合探究了影响监测自然衰减效率的污染物、生物和环境因素,概述了评估氯代烃污染场地自然衰减能力的实地监测和数值模拟手段,并基于室内模拟实验和场地实际应用现状,分析了其与强化衰减技术联合应用的发展趋势。今后需要在复合污染体系的自然衰减特征、生物降解调控机理研究、数值模拟及同位素分析等手段的应用等方面进一步深入研究,以期为氯代烃污染场地的绿色修复提供参考。     

基于多主体建模的安全注意力衰减模型研究

为预防由安全注意力衰减引起的虚假安全问题,构建员工安全注意力衰减模型。采用多主体建模法并基于Netlogo仿真平台,分析个体因素、管理因素和环境因素对员工安全注意力水平的影响。试验结果表明:在环境因素和管理因素确定的情况下,员工安全注意力水平主要受熟悉程度和安全意识的影响。同时员工安全注意力水平对管理者的危机意识有反馈作用。安全信号强度、频率、员工对安全信息的期待和任务难度以及管理者的监督有效性,均影响员工安全注意力水平。在企业安全管理的具体实施过程中,企业应该考虑如何有效控制上述调节因素并提高员工安全注意力水平。     

护听器声衰减值的3种测试方法

关于护听器声衰减能力的评价,目前有好几种方法都有大量文献充分地论证。本文介绍了3种标准化的评价方法：真耳听阈衰减法（Real～ear attenuation at threshold,PEAT）,真耳内置麦克风（Microphone in real ear,MIRE）,和声学仿真测量装置（Acoustical test fixture,ATF）方法。讨论了评价护听器声衰减能力,这3种方法各自的优缺点和适用范围。REAT方法是评价护听器声衰减值最准确的方法之一,目前被国际标准普遍采用。     

杭州西湖水体光学状况及影响因子分析

2004年10月8日在杭州西湖6个不同湖区共布设10个采样点进行水下光场的测定,并采集水样分析悬浮物、叶绿素a、有色可溶性有机物（CDOM）浓度。结果表明,3类主要光衰减物质总悬浮物、叶绿素a和DOC的浓度分别为3.68~42.76 mg/L、4.64~85.95 μg/L、5.19~9.22 mg/L;CDOM在440 nm波长处吸收系数为0.30~1.46 m-1;PAR衰减系数在1.13~6.04 m-1间变化,均值为4.00±1.69 m-1;对应的真光层深度为0.76~4.08 m,均值为1.54±1.11 m;仅南湖和茅家埠两个湖区真光层深度大于水深,其他湖区由于水深远大于真光层深度,在现有的光照条件和水位下要恢复沉水植物困难较大。对PAR衰减系数、真光层深度、透明度等表观光学参数与主要水色因子进行相关分析发现,水体中浮游藻类和有机颗粒物对西湖水体光学性质影响最大。     

IMPACT ASSESSMENT MODEL FOR CLEAR WATER FISHES EXPOSED TO EXCESSIVELY CLOUDY WATER1

ABSTRACT: A new type of empirical model described here enables real time assessment of impacts caused by excessive water cloudiness as a function of (a) reduced visual clarity (excessive cloudiness) and (b) duration of exposure to cloudy conditions, in fisheries or fish life stages adapted to life in clear water ecosystems. This model takes the familiar form used in earlier suspended sediment dose effect models where z is severity of ill effect (SEV), x is duration of exposure (h), y is black disk sighting range (y BD, m)—a measure of water clarity, a is the intercept, and b and c are slope coefficients. As calibrated in this study the model is Severity of ill effect is ranked on a 15‐step scale that ranges from 0 to 14, where zero represents nil effect and 14 represents 100 percent mortality. This model, based on peer consultation and limited meta analysis of peer reviewed reports, accomplishes the following: (a) identifies the threshold of the onset of ill effects among clear water fishes; (b) postulates the rate at which serious ill effects are likely to escalate as a function of reduced visual clarity and persistence; (c) provides a context (the “visual clarity” matrix, with its cell coordinates) to share and compare information about impacts as a function of visual clarity “climate” (d) demonstrates changes in predator prey interactions at exposures greater than and less than the threshold of direct ill effects; (e) calibrates trout reactive distance (cm) as function of water clarity in the form where y represents reactive distance (cm) and x represents visual clarity (black disk sighting range, cm), and where a and b are intercept and slope respectively, such that (f) identifies black disk sighting range, in meters, and its reciprocal, beam attenuation, as preferred monitoring variables; and (g) provides two additional optical quality variables (Secchi disk extinction distance and turbidity) which, suitably calibrated as they have been in this study, expand the range of monitoring options in situations in which the preferred technology—beam attenuation equipment or black disk sighting equipment—is unavailable or impractical to use. This new model demonstrates the efficacy of peer collaboration and defines new research horizons for its refinement.     

Computer-aided modeling of the protective effect of explosion relief vents in tunnel structures

This paper aims at contributing to the efficient design of explosion protection systems against confined explosions. The issue addressed concerns the quantitative estimation of the protective effect of explosion relief vents in the case of confined explosions inside tunnels. A series of virtual experiments performed by computer simulation, revealed how the number of vents, their diameter, as well as the angle between the vents and the tunnel, influences the blast wave attenuation. The computational study was performed considering a complicated large-scale tunnel configuration with branches on its half portion. The purpose was the calculation of the attenuation effect due to the presence of vents by comparing the total explosion-specific impulse developing at antidiametric positions inside the tunnel. Simulations were carried out via a three-dimensional numerical model built in the computational fluid dynamics code CFX 5.7.1, which has been validated in previous papers against experimental overpressure histories data demonstrating reasonable performance. Computer results showed that the use of branch vents provides an effective method for shock wave attenuation following an explosion, whereas their statistical elaboration revealed that the attenuation is mainly affected by the number of vents and their diameter. In contrast, the angle between the side vents and the main tunnel appeared to slightly affect the pressure wave weakening. Eventually, the quantitative influence of the above parameters was effectively illustrated in functional diagrams, so that the total attenuation effect may be promptly estimated, if the design variables are known. In addition, two statistical models with reasonable fitting to the calculated data are proposed, which express the attenuation effect as a dependent variable of the design variables including their interactions.     

河水-地下水交互带内砷及金属的自然衰减过程

在简单介绍污染物自然衰减作用定义的基础上,重点分析了河水-地下水交互带内As和以矿山废水为来源的金属污染物的自然衰减行为:主要包括吸附作用,氧化还原作用,生物转化作用等。其中详细介绍了金属Fe、Al的氢氧化物/氧化物对As化合物和其他金属如Cd、Cu和Zn等的吸附作用;Ca2+、Fe2+、磷酸盐、重碳酸盐等阴阳离子和天然有机质对吸附作用的影响;金属微生物氧化还原作用以及微生物作用下As(V)与As(III)的相互转化过程。研究发现,阳离子可以增强金属的吸附作用,阴离子主要是参与竞争吸附;天然有机质对金属吸附过程的抑制作用阻碍金属的固定;交互带内氧化还原条件的变化可以引起一系列的氧化还原反应;微生物催化还原不利于As的自然衰减。最后指出目前河水-地下水交互带内金属污染物衰减过程研究存在的问题以及今后的发展方向。