河流型硅藻水华研究进展

通过对硅藻水华发生机制相关文献的研究分析,对硅藻水华发生机制做了一般性探讨,并重点关注了河流型水华的发生机制的独特点。河流水华种类主要为中心硅藻纲,静水生态系统水华种类除中心硅藻纲还包括部分羽纹硅藻纲种类。河流水华硅藻种类对营养盐浓度、温度和光照等环境因子具有一定的适应范围。与静水生态系统相比,河流硅藻水华受气象和水文等物理指标的影响更为明显。河流硅藻水华中常具有时滞现象,其中由气象和水文因素引起的时滞现象最为明显。目前河流硅藻水华的防治仍然以上游水库下泄稀释为主,但是这种方法会造成一定的水资源浪费。河流水华硅藻的生理属性、硅藻水华对生态系统的影响、节水与抑制水华的统筹以及其他控制水华的方法都是未来河流硅藻水华研究的重点。     

Specific features of seedage in Norway spruce (Picea abies karst.) in the northern Moscow region

Climatic characteristics of the northern Moscow region and the periodicity of seedage in Norway spruce were analyzed retrospectively. The relationship between the intensity of seedage and weather conditions in the period before seedage was revealed.     

反渗透膜处理维生素C凝结水的最优工艺条件

针对维生素C生产工艺中产生的凝结水产量大、处理成本高、存储运输困难和营养物质含量偏低等问题，采用反渗透技术对VC凝结水进行处理。实验建立小试规模反渗透膜处理装置，采用无量纲化多元回归分析方法，分析了操作条件指标与渗透水评价指标两套指标体系之间的关系，定量评价了各个操作条件指标对渗透水评价指标的整体影响程度，并在此基础上研究了最佳操作条件的工艺参数。结果表明：建立的无量纲化多元回归分析方法切实有效，在正交实验设计水平范围内，压力、pH和回流比均是多目标系统的影响因子，操作条件指标对渗透水评价指标的整体影响程度大小顺序为：压力〉pH〉回流比〉温度，且各自影响程度所占比例分别为43．02％、29．01％、25．07％和2．89％。各个操作因子对多指标系统的影响是独立的。在只考虑系统收益而不考虑膜污染的情况下，最佳操作条件分别为：温度r=30．65，压力P=1．5MPa，回流比r=0．78，pH=7．475。     

植被混凝土无侧限抗压强度的室内试验初探

通过对植被混凝土室内试验结果的归纳和分析,研究了水泥掺入比、龄期和浸水条件对植被混凝土无侧限抗压强度的影响。     

Wet weather impact on trihalomethane formation potential in tributaries to drinking water reservoirs

During rain storm events, land surface runoff and resuspension of bottom sediments cause an increase in Trihalomethane (THM) precursors in rivers. These precursors, when chlorinated at water treatment facilities will lead to the formation of THMs and hence impact drinking water resources. In order to evaluate the wet weather impact on the potential formation of THMs, river samples were collected before, during and after three rain storms ranging from 15.2 to 24.9 mm precipitation. The samples were tested for THM formation potential and other indicators including UV254 absorbance, turbidity and volatile suspended solid (VSS). Average levels of THMs increased from 61 μg/l during dry weather to 131 μg/l during wet weather, and then went back to 81 μg/l after rain ended. Wet weather values of THM are well above the maximum contaminant level (MCL) 80 μg/l, set by EPA for drinking water. THM indicators also exhibited similar trends. Average levels increased from 0.6 to 1.8 abs; 2.6 to 6 ntu; and 7.5 to 15 mg/l respectively for UV254, turbidity and VSS. A positive correlation was observed between THM formation and THM indicators. The t-test of significance (p-value) was less than 0.05 for all indicators, and R values ranged from 0.85 to 0.92 between THMs and the indicators, and 0.72 to 0.9 among indicators themselves.     

Plant and Soil System Responses to Ozone After 3 Years in a Lysimeter Study with Juvenile Beech (Fagus sylvatica L.)

A lysimeter study was performed to monitor effects of elevated ozone on juvenile trees of Fagus sylvatica L. as well as on the plant–soil system. During a fumigation period over almost three growing seasons, parameters related to plant growth, phenological development and physiology as well as soil functions were studied. The data analyses identified elevated ozone to delay leaf phenology at early and to accelerate it at late developmental stages, to reduce growth, some leaf nutrients (Ca, K) as well as some soluble phenolics (hydroxycinnamic acid derivatives, total flavonol glycosides). No or very weak ozone effects were found in mobile carbon pools of leaves (starch, sucrose), and other phenolic compounds (flavans). Altered gene expression related to stress and carbon cycling corresponded well with findings from leaf phenology and chemical composition analyses indicating earlier senescence and oxidative stress in leaves under elevated ozone. Conversely in the soil system, no effects of ozone were detected on soil enzyme activities, rates of litter degradation and lysimeter water balances. Despite the fact that the three reported years 2003–2005 were climatically very contrasting including a hot and dry as well as an extremely wet summer, and also mild as well as cold winters, the influence of ozone on a number of plant parameters is remarkably consistent, further underlining the phytotoxic potential of elevated tropospheric ozone levels.     

Determination of explosion limits – Criterion for ignition under non-atmospheric conditions

Many industrial processes are run at non-atmospheric conditions (elevated temperatures and pressures, other oxidizers than air). To judge whether and if yes to what extent explosive gas(vapor)/air mixtures will occur or may be generated during malfunction it is necessary to know the safety characteristic data at the respective conditions. Safety characteristic data like explosion limits, are depending on pressure, temperature and the oxidizer. Most of the determination methods are standardized for ambient conditions. In order to obtain determination methods for non-atmospheric conditions, particularly for higher initial pressures, reliable ignition criteria were investigated. Ignition tests at the explosion limits were carried out for mixtures of methane, propane, n-butane, n-hexane, hydrogen, ammonia and acetone in air at initial pressures up to 20 bar. The tests have been evaluated according to different ignition criteria: visual flame propagation, temperature and pressure rising. It could be shown that flame propagation and occasionally self-sustained combustion for several seconds occurred together with remarkable temperature rise, although the pressure rise was below 3%. The results showed that the combination of a pressure rise criterion of 2% and a temperature rise criterion of 100 K seems to be a suitable ignition criterion for the determination of explosion limits and limiting oxidizer concentration at higher initial pressures and elevated temperatures. The tests were carried out within the framework of a R&D project founded by the German Ministry of Economics and Technology.     

Development and Operational Testing of a Super‐Ensemble Artificial Intelligence Flood‐Forecast Model for a Pacific Northwest River

Coastal catchments in British Columbia, Canada, experience a complex mixture of rainfall‐ and snowmelt‐driven contributions to flood events. Few operational flood‐forecast models are available in the region. Here, we integrated a number of proven technologies in a novel way to produce a super‐ensemble forecast system for the Englishman River, a flood‐prone stream on Vancouver Island. This three‐day‐ahead modeling system utilizes up to 42 numerical weather prediction model outputs from the North American Ensemble Forecast System, combined with six artificial neural network‐based streamflow models representing various slightly different system conceptualizations, all of which were trained exclusively on historical high‐flow data. As such, the system combines relatively low model development times and costs with the generation of fully probabilistic forecasts reflecting uncertainty in the simulation of both atmospheric and terrestrial hydrologic dynamics. Results from operational testing by British Columbia's flood forecasting agency during the 2013‐2014 storm season suggest that the prediction system is operationally useful and robust.     

不同天气型下武汉城市圈PM2.5污染及大气层结特征分析

利用2015—2019年PM_2.5和气象要素观测资料、NCEP和ERA5再分析资料,分析不同天气型下武汉城市圈PM_2.5区域污染时空分布、天气尺度环流和大气层结特征.结果表明,城市圈污染以武汉为中心,多为轻度-中度污染,西部重于东部.造成武汉城市圈区域污染增长的天气形势包括4类,分别为冷高压底前部型、高压后部型、均压场型和低压倒槽型.4类污染天气型均有较低的混合层高度和地表通风系数,且边界层 存在弱下沉运动和逆温,抑制污染垂直扩散.但气象要素影响PM_2.5污染的机理各异：冷高压底前部型主要为大气压梯度引导偏北大风带来 污染物远程输送,边界层冷平流导致低温、锋面逆温和浅薄高湿层（65%~80%）,强输入性污染配合吸湿性累积增长造成严重污染,逆温厚度对PM_2.5增幅作用明显;低压倒槽型东南风输入污染弱,但高温、低压引起气流辐合导致本地污染汇积,边界层暖平流带来平流逆温和深厚湿层（1000~750 hPa）,逆温层底高偏低、厚度偏厚,促进污染物在近地面吸湿增长;高压后部和均压场型均为浅薄湿层（1000~975 hPa）、湿度中等（56%~75%）,污染物吸湿增长相对较弱,高压后部型主要为偏东风短程输入污染为主;均压场型则为小风静稳天气,多晴空辐射逆温,逆温 强度大,大气扩散能力差,污染主要为弱北风的输入和本地累积.     

2021年中国北方首次沙尘天气的多源遥感分析

利用多源遥感数据和NCEP再分析资料,从沙尘源区的地理环境和气候特征出发,对2021年中国北方首次沙尘天气事件每日的大气环流形势以及沙尘的水平,垂直分布特征进行深入的研究分析.结果表明:源区内异常增温,降水稀少的气候背景下致使大面积裸露松散的土壤含水量较低,为大范围,高强度沙尘天气的形成提供了物质基础;频繁活动的冷空气,是沙尘天气爆发的动力因子.沙尘在强风中沿东南方向向下游地区输送和扩散,中国西北,华北,黄淮,江淮,江汉地区和江南北部等地先后受到沙尘天气的影响,空气质量迅速恶化,首要污染物为PM₁₀.此外,沙尘气溶胶东移也波及朝鲜半岛,日本等下游地区.在输送过程中,内陆地区沙尘主要分布在1~6km,而下游地区的沙尘则集中分布在2km高度附近,粒径较大的沙尘出现在近地表的频率较高,较小的颗粒主要分布在对流层中下层.