Comparison of Numerical Street Dispersion Models with Results from Wind Tunnel and Field Measurements

Numerical dispersion models developed and validated in different European countries were applied to data sets from wind tunnel and field measurements. The comparison includes the Danish Operational Street Pollution Model (OSPM) and the microscale flow and dispersion model MISKAM. The latter is recommended for application in built-up areas in the draft of the new German guideline VDI 3782/8. In a first step the models were applied to simplified street configurations. Different parameters as length and height of adjacent buildings and the angle of the incoming flow were varied. The results were compared to recent wind tunnel measurements. In a second step the models were applied to two extensively investigated field data sets from Jagtvej, Copenhagen and G ttinger Straße, Hannover. Intensified and more transparent and accessible validation procedures would be helpful for the thorough user.     

环境空气质量指数计算方法与分级方案比较

环境空气质量指数(AQI)广泛应用于各国环境空气质量评价体系之中,旨在为公众提供简单明了的空气质量信息和健康指引。通过对不同国家和地区空气质量指数的名称、计算方法、分级方案进行深入分析和比较,系统分析了各种空气质量指数的优缺点,并针对我国当前的空气质量指数体系存在的问题提出了相应的改进建议。     

基于水体交换模拟的白洋淀围堤围埝拆除方案比选

白洋淀是华北平原最大的浅水湖泊,因水产养殖等社会经济活动需要,淀内高密度建设围堤围埝,不利于水体交换,影响了水体环境和生态功能.基于MIKE 21软件,构建了白洋淀二维水动力模拟模型,选取水力滞留时间、滞水区面积比、流线分布均匀度等指标,提出了水体交换能力综合改善率计算方法,模拟了基准与低、中、高3种围堤围埝拆除强度情景的水体交换能力变化,进行了方案比选.结果表明,与基准情景相比,3种拆除强度情景下,流线分布均匀度均有增加,滞水区面积比分别减少6.17%、9.04%、9.24%,水力滞留时间分别缩短约1、2、3 d,水体交换能力综合改善率分别为34.37%、42.84%、47.25%,3种拆除情景对水体交换能力提升均有明显效果.本研究可为湖泊阻水构筑物拆除方案比选提供技术方法,为湖泊水体交换能力提升、水生态修复提供技术依据.     

A comparison of four process-based models and a statistical regression model to predict growth of Eucalyptus globulus plantations

In forest management and ecological research, consideration of the impacts and risks of climate change or management optimisation is complex. Computer models have long been applied as tools for these tasks. Process-based forest growth models claim to overcome the limitations of empirical statistical models, but the capacity of different process-based models and modelling approaches have rarely been compared directly. This study evaluates stepwise multiple regression models in comparison to four process-based modelling approaches (3-PG, 3-PG+, CABALA and Forest-DNDC) for greenfield predictions of Eucalyptus globulus plantation growth from 2 to 8 years after planting throughout southern Australia.     

一类拟线性抛物型偏微分方程的解

建立了一类拟线性抛物性方程初边值问题的比较原理,从而利用单调方法证明了具有齐次Dirichlet边值条件的拟线性抛物型偏微分方程解的存在唯一性;同时也运用第一特征函数构造上、下解的方法讨论具体的拟线性抛物型方程解的爆破现象．参9．     

大气光化学烟雾反应机理比较(Ⅱ)HOx和光化学氧化产物的比较

在相同初和排放条件下,对四种应用较广的光化学烟雾反应机理（GB4－99RADM2,RACM,SAPPRC99）进行了6组方案的比较,比较物种包括：（1）OHHO2自由基,（2）H2O2,HNOE,PAN,甲醛和有机硝酸酯光学产物,（3）甲苯和SO2,（4）NOy,NOa,由于各机理对VOCs,自由基及含氮化合物处理的不同,导致了模拟结果存在较大差异,我们用模式模拟这些物种时,应特别注意要理不同而带来的模拟结果差异。     

二氧化碳排放的国际比较及对我国低碳经济发展的启示

首先分析了我国二氧化碳排放的基本情况,指出当前二氧化碳排放增长率虽然有所下降,但环境形势依然严峻。然后从国家碳排放总量、人均CO2排放量、单位GDP二氧化碳排放量、国家累积碳排放和人均累积碳排放几个方面对我国二氧化碳排放水平与国际水平进行了比较,并结合节能减排目标对我国低碳经济的发展提出了相关建议。     

Effects of previous sublethal pulse to ammonium nitrate on mortality and total length on Epidalea calamita larvae

Ammonium nitrate is one of the most widespread contaminants related with the viability of natural amphibian populations. In this study we have evaluated in terms of mortality and total length the effects that a previous sublethal pulse to ammonium nitrate generates in Epidalea calamita. Experiments were divided in two phases. In the first one, tadpoles were exposed to two different treatments, with and without a low ammonium nitrate concentration (22 mg NH₄NO₃ L⁻¹). The second phase consisted in static toxicity experiments from both origin treatments with five different nominal concentrations (0, 22, 45, 90 and 180 mg NH₄NO₃ L⁻¹). Results showed that tadpoles that had experienced a previous sublethal exposure showed a negative effect on survival (57% of reduction in the LC₅₀ value) and total length, throughout an increase in their sensitivity. These results could help us to understand the situation of amphibian populations inhabiting aquatic ecosystems exposed to discontinuous and variable pulses of pollutants.     

膜基材对动态膜生物反应器性能的影响研究

选用5种滤布作为动态膜生物反应器(DMBR)的膜基材在相同操作条件下进行对比实验,考察反应器运行周期、反冲洗前后过滤压力、膜通量的恢复情况,分析DMBR进出水水质.结果表明,应用DMBR处理模拟生活污水,其中孔径为24μm的涤纶短纤滤布组成的DMBR对COD、氨氮和总氮的去除率分别为90%、80%和48%以上;运行周期...     

Measured and modelled tritium concentrations in freshwater Barnes mussels (Elliptio complanata) exposed to an abrupt increase in ambient tritium levels

To improve understanding of environmental tritium behaviour, the International Atomic Energy Agency (IAEA) included a Tritium and C-14 Working Group (WG) in its EMRAS (Environmental Modelling for Radiation Safety) program. One scenario considered by the WG involved the prediction of time-dependent tritium concentrations in freshwater mussels that were subjected to an abrupt increase in ambient tritium levels. The experimental data used in the scenario were obtained from a study in which freshwater Barnes mussels (Elliptio complanata) were transplanted from an area with background tritium concentrations to a small Canadian Shield lake that contains elevated tritium. The mussels were then sampled over 88 days, and concentrations of free-water tritium (HTO) and organically-bound tritium (OBT) were measured in the soft tissues to follow the build-up of tritium in the mussels over time.The HTO concentration in the mussels reached steady state with the concentration in lake water within one or two hours. Most models predicted a longer time (up to a few days) to equilibrium. All models under-predicted the OBT concentration in the mussels one hour after transplantation, but over-predicted the rate of OBT formation over the next 24 h. Subsequent dynamics were not well modelled, although all participants predicted OBT concentrations that were within a factor of three of the observation at the end of the study period. The concentration at the final time point was over-predicted by all but one of the models. The relatively low observed concentration at this time was likely due to the loss of OBT by mussels during reproduction.