示踪技术用于气体泄漏扩散模拟的多元线性回归分析

采用江苏工业学院油气储运安全综合实验模型平台,利用示踪技术(以CO2为示踪剂),模拟了有害气体瞬时泄漏扩散的整个过程.并结合多元线性回归分析的基本方法,定量分析了气体泄漏扩散过程,建立了多元线性回归模型,初步确定了泄漏气体浓度与相关物理量的变化关系,在此基础上得到了2个定量评价指标:确定性系数R=0.991,相关系数r=0.995.研究表明,在实验室建立的试验模型能较好地反映现实情况,模型仿真度较高,数据拟合效果较好.研究可为评价模型的相似性提供理论参考,对有害气体泄漏扩散事故应急救援、实施有效的现场控制,具有一定的科学参考价值.     

A framework for allocating conservation resources among multiple threats and actions

Land managers decide how to allocate resources among multiple threats that can be addressed through multiple possible actions. Additionally, these actions vary in feasibility, effectiveness, and cost. We sought to provide a way to optimize resource allocation to address multiple threats when multiple management options are available, including mutually exclusive options. Formulating the decision as a combinatorial optimization problem, our framework takes as inputs the expected impact and cost of each threat for each action (including do nothing) and for each overall budget identifies the optimal action to take for each threat. We compared the optimal solution to an easy to calculate greedy algorithm approximation and a variety of plausible ranking schemes. We applied the framework to management of multiple introduced plant species in Australian alpine areas. We developed a model of invasion to predict the expected impact in 50 years for each species-action combination that accounted for each species’ current invasion state (absent, localized, widespread); arrival probability; spread rate; impact, if present, of each species; and management effectiveness of each species-action combination. We found that the recommended action for a threat changed with budget; there was no single optimal management action for each species; and considering more than one candidate action can substantially increase the management plan's overall efficiency. The approximate solution (solution ranked by marginal cost-effectiveness) performed well when the budget matched the cost of the prioritized actions, indicating that this approach would be effective if the budget was set as part of the prioritization process. The ranking schemes varied in performance, and achieving a close to optimal solution was not guaranteed. Global sensitivity analysis revealed a threat's expected impact and, to a lesser extent, management effectiveness were the most influential parameters, emphasizing the need to focus research and monitoring efforts on their quantification.     

以氢气为主要成分的其他可燃气体对低浓度甲烷爆炸特性的影响

为研究矿井火区中一氧化碳(CO)、氢气(H_2)、乙烯(C_2H_4)和乙烷(C_2H_6)等其他可燃气体对甲烷(CH_4)爆炸特性的影响,利用可视球形气体爆炸系统开展了多元可燃气体爆炸压力特性试验,观察并分析了峰值爆炸压力、最大爆炸压力上升速率及其相应时间。通过高速摄影系统拍摄了视窗范围内爆炸火焰传播图像,基于边缘检测方法确定了火焰前锋位置,继而得到最大火焰传播速度。分析了以氢气为主要成分的其他可燃气体对低浓度CH_4-空气混合物压力特性和火焰传播行为的影响。结果表明,多元可燃气体的存在增加了低浓度CH_4-空气混合物的爆炸危险性。随混合气体体积分数增加,低浓度CH_4-空气混合物的峰值爆炸压力、最大爆炸压力上升速率和最大火焰传播速度非线性增加;此外,到达峰值爆炸压力、最大爆炸压力上升速率的时间显著缩短。     

不同孔径排放钻孔有效影响半径的时空响应

针对矿井在施工排放钻孔局部防突措施时,已知排放时间,如何确定排放钻孔孔径和钻孔间距这一难题,提出一种钻屑量和钻屑瓦斯解吸指标现场测试法,结合数值模拟计算,确定不同孔径排放钻孔有效排放半径随时间的变化规律。研究结果表明:同一孔径排放钻孔,随着排放时间的增加,有效排放半径呈幂指数增大;不同孔径排放钻孔,随着排放钻孔直径的增加,有效排放半径呈幂指数增大。研究结论对矿井选取合适的排放钻孔孔径及布置参数具有指导意义。     

一种赤腹松鼠种群数量的估计方法

赤腹松鼠剥食树皮的行为对林木危害严重,根据野外长期的观察和研究发现,赤腹松鼠在剥落树皮上遗留下来的上门齿齿印间距具有个体差异,可以用作个体识别的依据.对2003年监测样地内赤腹松鼠在剥落树皮上的齿印间距测量记录,并统计分析以估计赤腹松鼠的个体数量.结果表明:种群数量与危害率的相关系数为0.876,P=0.01,表现出很强的正相关关系;显示在较小面积内,该方法可以用来估计赤腹松鼠的个体数量.同时对该方法的基本条件和局限进行了讨论.图2表4参10     

Accounting for the Mesoscale Effects on the Air Pollution in Some Cases of Large Sulfur Pollution in Bulgaria or Northern Greece

The objective of the present work is to demonstrate the influence of the meso-scale dynamic phenomena on the larger scale air pollution characteristics. A limited set of episodes with very large sulphur pollution in Bulgaria or Northern Greece is chosen for the study. A 3D quasi-hydrostatic model of the meso-scale dynamics, based on the Businesque approximation (the formulation of Guthman) is used for the purpose. Some numerical experiments for the Balkan Peninsula are carried out under different background (synoptic) conditions. The simulated flow systems outline the main topography effects, typical for the region, such as slope winds, channelling of the air flows or blocking effects. Numerical simulations of the air pollution transport are also carried out, with and without accounting for the meso-scale deformations of the wind field. The comparison of the air pollution characteristics, obtained in both the cases demonstrates that the underlying surface heterogeneity in some of the synoptic situations may have influence not only on the detailed air pollution field in the region, but also on some larger scale pollution characteristics – the total pollution quantity in the air above the countries, the mean surface concentration, the pollution fluxes trough the country boundaries, dry and wet deposition.     

川西亚高山白桦林小气候的时空动态特征

对川西亚高山白桦林(海拔2 540 m)内太阳辐射、空气温湿度以及土壤5 cm和15 cm层温度等进行了连续的定位观测.结果表明:1)林冠下的太阳辐射日进程与林冠上的不同,但辐射强度随着太阳高度角的变化而变化;林冠下太阳辐射日总量不仅受林冠上辐射日总量的影响,也受森林群落生长季节的影响;春、夏和秋季,林冠下平均辐射日总量分别占林冠上平均辐射日总量的53.1%、39.4%和55.8%.2)夏季,白天空气温度高于土壤温度,而夜间则相反;空气温度和土壤温度的日极端温度出现的时间不同步,空气温度对太阳辐射强度的敏感性比土壤温度的敏感性高.3)春季,土壤表层>4℃的积温高于空气和土壤底层>4℃的积温;夏季,>4℃的积温由高到低的次序为:林冠下空气>土壤5 cm层>土壤15 cm层,而秋季的比较结果与之相反;空气日平均温度与土壤日平均温度有显著的线性关系(P<0.001).4)林冠下的空气相对湿度(RH)比林冠上的高,林冠下的空气RH日变幅和季节性变幅比林冠上的小.图7表1参19     

Chemical defense: incorporation of diet-derived pyrrolizidine alkaloid into the integumental scales of a moth (<Emphasis Type="Italic">Utetheisa ornatrix</Emphasis>)

Summary. Evidence is presented that pyrrolizidine alkaloid acquired by Utetheisa ornatrix (Lepidoptera, Arctiidae) as a larva from Crotalaria foodplants is incorporated in part into the scales of the adult. A single forewing of a male or female moth may contain in the order of 6 to 13 g monocrotaline in its scale cover or about 1 to 2% of the moths systemic monocrotaline content. Based on estimates of the number of scales per forewing, the monocrotaline content of individual scales is calculated to be in the order of 0.1 and 0.2 ng monocrotaline per male and female scale, respectively. This amounts to concentrations of about 1 and 3%, values roughly at a par with the average systemic concentration (0.5-0.6%) previously determined for monocrotaline in Utetheisa. It is argued that the presence of pyrrolizidine alkaloid in the moths scale coating could account for the promptness with which adult Utetheisa are rejected by spiders. It is suggested further that chemical impregnation of scales with substances deterrent to predators may be more widespread among insects than generally assumed.     

MODELING OF NONPOINT SOURCE POLLUTION OF NITROGEN AT THE WATERSHED SCALE1

ABSTRACT: The Watershed Nutrient Transport and Transformation (NTT-Watershed) model is a physically based, energy-driven, multiple land use, distributed model that is capable of simulating water and nutrient transport in a watershed. The topographic features and subsurface properties of the watershed are refined into uniform, homogeneous square grids. The vertical discretization includes vegetation, overland flow, soil water redistribution and groundwater zones. The chemical submodel simulates the nitrogen dynamics in terrestrial and aquatic systems. Three chemical state variables are considered (NO₃^-_-, NH₄⁺, and Org-N). The NTT-Watershed model was used to simulate the fate and transport of nitrogen in the Muddy Brook watershed in Connecticut. The model was shown to be capable of capturing the hydrologic and portions of the nitrogen dynamics in the watershed. Watershed planners could use this model in developing strategies of best management practices that could result in maximizing the reductions of nitrogen export from a watershed.     

Bacterial community structure analyses to assess pollution of water and sediments in the Lake Shkodra/Skadar, Balkan Peninsula

- Goal, Scope, Background. Lake Skadar is the largest lake in Balkan Peninsula, located on the Montenegro-Albanian border. The unique features of the lake and wide range of endemic and rare or endangered plant and animal species resulted in the classification of the Skadar as a wetland site of international significance. In spite of its importance the Lake is influenced by inflowing waters from river Morača and other regional rivers contaminated by the industry, municipal and agricultural activities in the area. Therefore, the Lake has been subject of various physical, chemical, biological and toxicological examinations. However, community-level analyses are most relevant to assess the effect of stressors on aquatic ecosystems. In the present study bacterial community structure among differently polluted sites of the lake was compared by genetic fingerprinting technique. Methods Water and sediment samples were collected from five differently polluted sampling sites on the Lake Skadar in spring and autumn of the same year. The bacterial community structure in the samples was characterized and compared by temporal temperature gel electrophoresis (TTGE) analysis of polymerase chain reaction-amplified bacterial 16S rRNA genes. Results and Discussion The TTGE analysis resulted in many distinguishable and reproducible band patterns, allowing reliable comparison of bacterial communities among sampling sites. Results on the bacterial community structure revealed that three of the selected locations can be considered as sites that have not shown any pollution degradation determined by our method, due to similar structure of bacterial community in the sediment samples. On the other hand, significant shifts in bacterial community structure in the mouth of the river Morača and Plavnica were shown. Since the results coincide with some of the bioassays and chemical analysis performed previously, the changes in bacterial community structure are explained as an effect of antropogenic pollution on the lake ecosystem by waters of river Morača and stream Plavnica. Conclusion The TTGE has proven to be an efficient and reliable method to monitor bacterial dynamics and community shifts in aquatic environment, especially in the sediments. Within the variety of environmental quality assessments the use of TTGE analyses of bacterial community is strongly recommended, particularly as an initial investigation. However, in any conclusion on the state of the environment, the TTGE results should be combined to some other biological, chemical and hydrological data. Recommendation and Outlook Since prokaryotes are a crucial group of organisms in the biosphere, the ecosystem function studies are largely based on bacterial communities. Therefore, bacterial community structure analysis should be a part of an integrated weight of evidence approach in pollution assessment. In case of Triad approach, consisting of chemical analyses, bioassays, and community studies in the field, the TTGE bacterial community structure analyses should be placed in the later Triad leg. In comparison to other community studies, based on various biotic indices, the TTGE bacterial community analysis has proven to be very sensitive, reliable and less time consuming.