Wall losses of oxygenated volatile organic compounds from oxidation of toluene: Effects of chamber volume and relative humidity

Vapor wall losses can affect the yields of secondary organic aerosol. The effects of surface-to-volume (S/V) ratio and relative humidity (RH) on the vapor-wall interactions were investigated in this study. The oxygenated volatile organic compounds (OVOCs) were generated from toluene-H₂O₂ irradiations. The average gas to wall loss rate constant (k_gw) of OVOCs in a 400 L reactor (S/V = 7.5 m⁻¹) is 2.47 (2.41 under humid conditions) times higher than that in a 5000 L reactor (S/V = 3.6 m⁻¹) under dry conditions. In contrast, the average desorption rate constant (k_wg) of OVOCs in 400 L reactor is only 1.37 (1.20 under humid conditions) times higher than that in 5000 L reactor under dry conditions. It shows that increasing the S/V ratio can promote the wall losses of OVOCs. By contrast, the RH effect on k_gw is not prominent. The average k_gw value under humid conditions is almost the same as under dry conditions in the 400 L (5000 L) reactor. However, increasing RH can decrease the desorption rates. The average k_wg value under dry conditions is 1.45 (1.27) times higher than that under humid conditions in the 400 L (5000 L) reactor. The high RH can increase the partitioning equilibrium timescales and enhance the wall losses of OVOCs.     

外绝缘用液体硅橡胶的自然老化因素研究

近年来,液体硅橡胶(Liquid Silicone Rubber,LSR)已经在外绝缘领域得到了较为广泛的应用,但是目前对其耐老化性能的研究还不够深入。尤其是在中国南方地区使用时,高温、高湿环境更容易导致液体硅橡胶的老化。在许多地区都观察到了电流、电压互感器的液体硅橡胶绝缘外套的龟裂、老化现象,对设备的安全运行产生了影响。本文设计并实施了在光照、高温、高湿、电晕等老化因素作用下的液体硅橡胶人工老化试验,并对老化试验后的样品进行了硬度、力学性能、憎水性、光泽度以及SEM、FTIR等微观性能试验和分析。认为在光照作用下,高温、高湿环境对液体硅橡胶具有加速老化作用,表现为硬度上升、憎水性下降、光泽度下降,并且在表面出现细微裂纹。     

Introduction: General versus specific measures and the special case of core self‐evaluations

This paper introduces a Journal of Organizational Behavior point/counterpoint exchange (this issue) that focuses on the appropriate level of aggregation primarily in the assessment of personality in general and core self‐evaluations (CSE) in particular. Gilad Chen reviews arguments for and against the higher‐order construct of CSE, offering a number of recommendations for strengthening it. Timothy Judge and John Kammeyer‐Mueller offer a defense of CSE, and then extend the discussion to the measurement of other constructs beyond the personality domain. Together these two papers provide important insights about the appropriate level of aggregation of individual measures, and situations in which higher‐order versus lower‐order measures might be preferred. Copyright © 2011 John Wiley & Sons, Ltd.     

Energy metabolism and growth of Monoporeia affinis Lindstr. in the Northern Lake Krivoe (Karelia)

The physiological method for estimating production based on the relationship between growth and energy metabolism has been used for calculating model growth curves for the amphipod Monoporeia affinis and comparing them with the results of field studies. Calculations demonstrated that the physiological growth curves fit the results of field observations best under certain conditions which have zoological sense: the growth curve should reflect the actual maximum body size of an animal in the given population, the duration of the life cycle, and the time required for reaching the reproductive size.     

能见度与PM2.5浓度关系及其分布特征

利用相对湿度、能见度和PM_(2.5)质量浓度观测数据,针对不同相对湿度下,建立了消光系数与PM_(2.5)质量浓度之间线性关系,并分析了相关关系的全国分布特征.结果表明,我国中东部大部分地区在一定相对湿度区间内均可建立线性相关关系,而且相关性较好,相对湿度40%～90%区间内的平均相关系数高于0. 75,其中北京相关系数高达0. 9.北京、长三角和四川等地的PM_(2.5)单位质量消光效率在同等相对湿度下明显大于其他地区.不同地区湿度对能见度影响程度不同,北京等地在相对湿度大于90%时相对湿度对能见度作用大于PM_(2.5),而广州在相对湿度大于80%时相对湿度的作用明显增强.利用能见度反算北京地区PM_(2.5)浓度可知,1980～1996年,PM_(2.5)浓度年际变化不大,受采暖方式影响冬季PM_(2.5)浓度显著较高; 1997～2009年呈现缓慢下降趋势; 2010～2012年呈现上升趋势. 1980年以来,全国的PM_(2.5)浓度整体呈上升的趋势,尤其是华北地区,PM_(2.5)浓度始终高于全国其他地区.     

气象因素对香港地区臭氧污染的影响

基于2000~2015年香港地区的臭氧监测数据和气象数据,分析了香港的臭氧污染特征及气象因素对臭氧污染的影响.结果表明:(1)香港地区臭氧浓度呈现明显的季节变化特征,其中秋季春季冬季夏季,臭氧超标日集中在夏季和秋季,超标日发生在冬季和春季的情形极少.(2)2000~2015年香港臭氧日最大8h平均浓度(MDA8)年均浓度呈增长趋势,平均增长速率为0.77μg·(m3·a)-1,臭氧MDA8第90百分位数浓度同样呈增长趋势,增长速率为1.49μg·(m3·a)-1.(3)较高的气温是香港地区臭氧污染发生的必要条件,气温越高越容易导致更高浓度的臭氧污染.(4)绝大多数情况下,臭氧浓度与相对湿度间呈负相关关系,相对湿度越高,香港地区的臭氧MDA8平均浓度及第90百分位数浓度均会降低.(5)当香港发生臭氧污染时,盛行风往往从偏北风或偏东风转为偏西风.随着风速的增大,臭氧平均浓度变化不大,但是臭氧第90百分位数浓度会明显降低.(6)降水和云量是影响臭氧浓度的重要因素,连续多日的无雨或少雨天气是臭氧污染事件发生的必要条件,而随着云量的增加,臭氧平均浓度和第90百分位数浓度会持续降低.(7)在太阳总辐射量≤20 MJ·m-2或日照时长≤10 h的情况下,臭氧浓度与太阳辐射及日照时长呈正相关关系.然而,在太阳辐射强烈的情况下(太阳总辐射量 20 MJ·m-2或日照时长 10 h),随着太阳辐射增强或日照时长的增加地面臭氧浓度反而降低,这是因为太阳辐射强烈的情况常出现在雨后天晴的背景下,并盛行来自海洋的偏南风,使得臭氧污染不易形成.(8)香港臭氧超标日的出现往往伴随着一系列气象条件的共同改变,包括晴天少雨、辐射增强、边界层高度增加、相对湿度降低、风速变小以及气温升高等气象特征,污染结束则伴随着相反的气象变化.     

北京地区大气温湿廓线对气溶胶垂直分布的影响

目的分析北京地区大气温湿廓线对气溶胶垂直分布的影响。方法利用北京地区2017年9月至2018年8月每日两次(08时和20时)的气象探空、地面PM_(2.5)浓度和气溶胶激光雷达消光系数资料,分析不同污染条件下大气温湿廓线与气溶胶消光系数廓线的关系。结果地面PM_(2.5)浓度和210m气溶胶消光系数的相关系数达到0.77。春季、秋季和冬季污染条件下的近地面消光系数约是清洁条件下的5倍,夏季污染条件下的近地面消光系数约是清洁条件下的3倍。相比清洁条件下,污染条件下各季节的大气温度垂直递减率偏小,并且低层大气相对湿度偏大。结论大气温度廓线代表大气层结稳定性,影响气溶胶的扩散高度,而相对湿度廓线与气溶胶吸湿增长密切相关,两者对气溶胶消光系数的垂直分布都有重要影响。     

太阳跟踪聚光高加速老化试验系统特性研究

目的对自主研制的基于"冷光"反射镜户外高加速光老化系统特性展开研究。方法利用大气环境条件监测技术获得系统样机关键性能数据。结果"冷光"反射镜在295～700 nm波长范围内的反射率达到90%以上,增强了系统样机在该波长范围内的反射太阳光谱,在310nm波段处获得约3.5倍太阳直射辐照强度。聚光太阳辐照分布均匀,靶板处平均辐照强度最大可达0.655 W/(m2·nm),标准偏差为2.6%。白天样品表面温度不超过直接暴露样品表面温度10℃,样品周围空气湿度与大气相对湿度接近,并可通过喷淋系统控制样品周围空气的相对湿度,以模拟多种自然气候环境。结论经过对比系统太阳光谱、辐照强度及温湿度等特性数据,系统增强了紫外辐照强度,并有效控制了试验样品的温度和湿度,可为系统自然加速试验老化机理及相关性研究提供数据支持。     

西南喀斯特流域枯季地下水电导率特征及水-岩作用分析

受特殊水文地质条件影响,西南喀斯特流域水动力过程与物质循环过程复杂,利用单一水文信息分析该地区水动力过程具有较大难度。地下水电导率受喀斯特水文地质条件影响显著,可以综合反映区域水动力条件与岩性特征。论文选取贵州普定县后寨河流域为研究区,通过野外调查及地下水电导率原位测定,结合流域地形、岩性及落水洞、岩溶泉等岩溶地貌空间分布规律,分析了喀斯特流域枯季地下水电导率空间分布及其受水-岩特征的影响。结果表明,山丘区地下水电导率较低,主要由于喀斯特山区是岩溶裂隙/管道网络发育的强径流区,水-岩接触时间较短。随高程降低,地下水电导率呈现增加趋势,表明地下水流速度减缓,水-岩接触时间变长。地下水电导率受岩性特征影响显著,石灰岩区水-岩作用强烈,易形成较高电导率地下水,平均电导率650 μS/cm,白云岩区水-岩作用减弱,地下水电导率降低,平均值523 μS/cm。     

Combined application of conservative transport modelling and compound-specific carbon isotope analyses to assess in situ attenuation of benzene, toluene, and o-xylene

In recent years, compound specific isotope analyses (CSIA) have developed into one of the most powerful tools for the quantification of in situ biodegradation of organic contaminants. In this approach, the calculation of the extent of biodegradation of organic contaminants in aquifers is usually based on the Rayleigh equation, and thus neglects physical transport processes such as dispersion that contribute to contaminant dilution in aquifers. Here we combine compound specific isotope analyses with a conservative transport model to study the attenuation of aromatic hydrocarbons at a former gasworks site. The conservative transport model was first used to simulate concentration reductions caused by dilution at wells downgradient of a BTEX source. In a second step, the diluted concentrations, together with the available stable carbon isotope ratios and carbon fractionation factors for benzene, toluene and o-xylene were applied in the Rayleigh equation to quantify the degree of biodegradation at each of those wells. At the investigated site, where other attenuation processes such as sorption and volatilisation were proven to be negligible, the combined approach is recommended for benzene, which represents a compound for which the effect of biodegradation is comparable to or less than the effect of dilution. As demonstrated for toluene and o-xylene, the application of the Rayleigh equation alone is sufficient if dilution can be proved to be insignificant in comparison to biodegradation. The analysis also suggests that the source width and the position of the observation wells relative to the plume center line are significantly related to the degree of dilution.