系统动力学方法在城市生活垃圾产生系统的应用

准确预测城市生活垃圾产生量是构建与运行生活垃圾管理系统的首要条件. 我国大部分城市生活垃圾的历史统计数据稀缺,传统预测方法往往难以得到要求精度的预测结果. 在系统地分析生活垃圾产生量影响因素及因素间互动关系的基础上,建立了基于VENSIM软件的系统动力学模型,并将该模型应用于深圳市城市生活垃圾产生系统. 结果表明:运用系统动力学方法可以较好地进行城市生活垃圾产生量预测,解决了数据稀缺条件下城市生活垃圾产生量的精确预测问题,为处理处置工艺的选择和规模的确定提供了数据支撑,同时可以在垃圾产生量预测的基础上进行不同政策下系统的行为模拟.      

Vegetation restoration dynamics in the forest-steppe system of the middle Volga region

The current dynamics of ecosystems of the forest-steppe system is most adequately described via determining the probable trajectories of changes in its elements in a simple Markov chain. The obtained data have made it possible to determine the direction of succession and draw its scheme. Theoretically possible series of community development are presented. The succession of community restoration from the spread of shrubs over steppificated fallow lands to the formation of low forests of European bird cherry has been analyzed. The restoration cycle of ecosystem dynamics is described by eight age stages.     

Modelling Seasonal Dynamics from Temporal Variation in Agricultural Practices in the UK Ammonia Emission Inventory

Most ammonia (NH₃) emission inventories have been calculated on an annual basis and do not take into account the seasonal variability of emissions that occur as a consequence of climate and agricultural practices that change throughout the year. When used as input to atmospheric transport models to simulate concentration fields, these models therefore fail to capture seasonal variations in ammonia concentration and dry and wet deposition. In this study, seasonal NH₃ emissions from agriculture were modelled on a monthly basis for the year 2000, by incorporating temporal aspects of farming practice. These monthly emissions were then spatially distributed using the AENEID model (Atmospheric Emissions for National Environmental Impacts Determination). The monthly model took the temporal variation in the magnitude of the ammonia emissions, as well as the fine scale (1-km) spatial variation of those temporal changes into account to provide improved outputs at 5-km resolution. The resulting NH₃ emission maps showed a strong seasonal emission pattern, with the highest emissions during springtime (March and April) and the lowest emissions during summer (May to July). This emission pattern was mainly influenced by whether cattle were outside grazing or housed and by the application of manures and fertilizers to the land. When the modelled emissions were compared with measured NH₃ concentrations, the comparison suggested that the modelled emission trend corresponds fairly well with the seasonal trend in the measurements. The remaining discrepancies point to the need to develop functional parametrisations of the interactions with climatic seasonal variation.     

Patch dynamics based on Prisoner's Dilemma game: superiority of golden rule

There has been much literature on ecological model of Prisoner's Dilemma (PD) game. This game illustrates that cooperation can evolve in situations where individuals tend to look after themselves. In order to explain some behaviors of altruism in animal societies, the strategy All Cooperate (AC), often called the Golden Rule, is more appropriate than other strategies. However, very little is known about the superiority of AC. In the present article, we study patch dynamics based on non-iterated PD game, applying two different methods: island and lattice models. Each patch is assumed to be either vacant or composed of a population of AC or All Defect (AD), where AD means a selfish strategy. Both models exhibit a phase transition between a phase where both AC and AD survive, and a phase where AD is extinct. The latter phase means that AC beats AD completely. In the case of lattice model, the extinction of AD easily occurs and the abundance of AC takes a larger value, compared with the island model. Our models can be also extended to general iterated PD game; we describe the reason why AC can outperform any other strategy.     

Engineering-geological hazards and management in the Mountain Crimea coastal zone

The main engineering-geological hazards and their factors of the Mountain Crimea coastal region are considered. A characteristic shore line site of Cape Kikineiz and its neighboring coastal area near the Katsiveli settlement has been studied in more detail. The important characteristic of the site is a high diversity of geological conditions with numerous manifestations of dangerous engineering-geological processes: shore and hydrological network abrasion, loss of slopes and rocks stability, etc. These processes have intensified during the last decades under the influence of natural and man-induced factors. The results of preliminary study of geo-environmental situation of the area are presented. The program for further research and possible recommendations for rational coastal hazard management and area ecological state improvement are outlined.     

南京市大气气溶胶中二元羧酸昼夜变化研究

2002年3月14-19日在南京大学校园内进行了为期1周的采样,用以研究大气气溶胶PM_2.5中的低分子量(C₂～C₁₀)二元羧酸的昼夜变化规律.结果表明,南京市大气气溶胶中二元羧酸的夜间质量浓度(平均为460ng/m3)普遍高于相应的白天质量浓度(平均为350 ng/m3).草酸是含量最高的二元羧酸,其次是丁二酸与丙二酸,这3种二元羧酸占所检测到的水溶性有机酸总量的89%.由C3/C4(ρ(丙二酸)/ρ(丁二酸))(平均为1.00)可以判断采样期间气溶胶中有机酸主要来源于大气的光化学氧化反应,从C6/C9(ρ(己二酸)/ρ(壬二酸))(平均为0.88)可以认为生物源是有机酸的一个重要来源.      

Study on convection and dispersion characteristics of dense gases in urban environment considering trees

Although several studies on the dispersion of heavy toxic gas released from ruptured tanks on vehicles during transportation have considered complex terrain such as urban buildings, the influence of trees on the flow field in urban areas during gas dispersion tends to be ignored. In this study, a Computational Fluid Dynamics (CFD) model was proposed to investigate the characteristics of gas release and dispersion from loaded vehicle in the urban environment. In this model, the tree crown was treated as a porous medium, and the influence of drag due to the crown was incorporated into the model by a momentum source term through a user-defined function. In this study, the dynamic characteristics of chlorine (Cl₂) dispersion under the conditions of building distribution, tree species and porosities were comprehensively analysed, to cover the influence of urban complexity, leaf density, and tree planting configuration. The results show that compared with flat terrain, the presence of urban buildings will prolong the dense gas retention time and increase the dangerous distance. It is found that the horizontal dispersion distance can increase by 63% and the isosurface of 25 ppm hazardous gas can increase by 130% with the introduction of buildings. Compared with the terrain with only buildings, the introduction of arbors or shrubs can result in a 147% or 359% increase in the maximum concentration. Also, trees will prolong the dispersion duration. It is also found that the higher the porosity, the less the wind blocking effect, and the weaker the ability of capturing gas. The wind field affected by arbores and shrubs are different in height, and arbores capture more Cl₂. Planting short shrubs around buildings can effectively reduce the spread of harmful gases.     

Effects of surrounding land use and water depth on seagrass dynamics relative to a catastrophic algal bloom

Seagrasses are the foundation of many coastal ecosystems and are in global decline because of anthropogenic impacts. For the Indian River Lagoon (Florida, U.S.A.), we developed competing multistate statistical models to quantify how environmental factors (surrounding land use, water depth, and time [year]) influenced the variability of seagrass state dynamics from 2003 to 2014 while accounting for time‐specific detection probabilities that quantified our ability to determine seagrass state at particular locations and times. We classified seagrass states (presence or absence) at 764 points with geographic information system maps for years when seagrass maps were available and with aerial photographs when seagrass maps were not available. We used 4 categories (all conservation, mostly conservation, mostly urban, urban) to describe surrounding land use within sections of lagoonal waters, usually demarcated by land features that constricted these waters. The best models predicted that surrounding land use, depth, and year would affect transition and detection probabilities. Sections of the lagoon bordered by urban areas had the least stable seagrass beds and lowest detection probabilities, especially after a catastrophic seagrass die‐off linked to an algal bloom. Sections of the lagoon bordered by conservation lands had the most stable seagrass beds, which supports watershed conservation efforts. Our results show that a multistate approach can empirically estimate state‐transition probabilities as functions of environmental factors while accounting for state‐dependent differences in seagrass detection probabilities as part of the overall statistical inference procedure.