武汉市主要绿化树种滞尘效应研究

本实验对武汉市城区主干道主要绿化树种的滞尘效应与叶表面结构进行了研究。结果表明：（1）同一尘源条件下,不同树种的滞尘能力差异显著。乔木中悬铃木滞尘能力较高,可达6.9345 g/m²;小乔木中紫薇和紫叶李是滞尘能力较高的树种,滞尘能力分别为1.9543 g/m²和1.8790 g/m²;灌木中红花檵木和杜鹃等有较强的滞尘能力,分别可达4.0373 g/m²和3.8875 g/m²;（2）利用扫描电镜观察叶表面结构发现：叶表具毛被、褶皱、较深的不规则网格等特征的树种滞尘能力较高,叶表平滑或叶表网格结构规则且较浅时滞尘能力较低;（3）同一树种在不同的尘源条件下滞尘能力差异显著,空气中颗粒物浓度越高,滞尘能力也越大。以车流量近似模拟尘源条件表明,滞尘能力与车流量呈正相关。     

内蒙古沙尘气溶胶浓度及其输送特性——朱日和春季情形的个例研究

利用WPS宽范围粒径谱仪对朱日和春季0.01～10μm的沙尘气溶胶观测资料,以及20m梯度塔气象要素资料,对沙尘天气日和非沙尘天气日的气溶胶浓度、谱分布以及输送特性进行了个例研究.结果表明:沙尘气溶胶浓度有明显的日变化特征,不同粒径段粒子的变化特征有所不同;沙尘气溶胶浓度在沙尘天气和非沙尘天气存在较大差别,粒径越大,这种差别越明显;气象要素对沙尘气溶胶浓度的分布有较大的影响,风速、气温、相对湿度与不同粒径段粒子的相关性不同;沙尘暴过程对不同粒径段粒子的输送特性不同,不同粒径段对应的输送距离和输送量有较大差别.     

Leaching from granular cement-based materials during infiltration/wetting coupled with freezing and thawing

Many secondary materials are being considered for use as substitutes for natural aggregates in highway applications due to their suitable engineering and economic properties. During the design life of the application, recycled materials are exposed to freeze/thaw cycles and other aging processes such as carbonation, coupled with intermittent infiltration/wetting by precipitation events. In such scenarios, leaching of material constituents is a primary pathway for environmental impact. This paper presents results of the effect of freezing and thawing on the leaching behavior of major and minor constituents from a laboratory formulated granular cement-based material. Scenarios considered included water percolating through the material (flow-through) and run-off (flow-around), both important leaching pathways in highway environments. The effect of moisture content at the time of freezing, number of freeze/thaw (F/T) cycles, and material size reduction were investigated. F/T exposure and subsequent infiltration/wetting resulted in consolidation and self-cementing of the granular cement-based material. For the flow-around scenario, F/T exposure resulted in a reduction in constituent release with time and increasing F/T cycles. For the flow-through scenario, moisture content at the time of freezing was an important parameter and an increase in the release was initially observed due to preferential flow/cracks and/or constituent redistribution prior to a decrease that resulted from self-cementing during further thawing and percolation.     

A dynamic hydrological Monte Carlo simulation model to inform decision-making at Lake Toolibin,Western Australia

Lake Toolibin, an ephemeral lake in the agricultural zone of Western Australia, is under threat from secondary salinity due to land clearance throughout the catchment. The lake is extensively covered with native vegetation and is a Ramsar listed wetland, being one of the few remaining significant migratory bird habitats in the region. Currently, inflow with salinity greater than 1000 mg/L TDS is diverted from the lake in an effort to protect sensitive lakebed vegetation. However, this conservative threshold compromises the frequency and extent of lake inundation, which is essential for bird breeding. It is speculated that relaxing the threshold to 5000 mg/L may pose negligible additional risk to the condition of lakebed vegetation. To characterise the magnitude of improvement in the provision of bird breeding habitat that might be generated by relaxing the threshold, a dynamic water and salt balance model of the lake was developed and implemented using Monte Carlo simulation. Results from best estimate model inputs indicate that relaxation of the threshold increases the likelihood of satisfying habitat requirements by a factor of 9.7. A second-order Monte Carlo analysis incorporating incertitude generated plausible bounds of [2.6, 37.5] around the best estimate for the relative likelihood of satisfying habitat requirements. Parameter-specific sensitivity analyses suggest the availability of habitat is most sensitive to pan evaporation, lower than expected inflow volume, and higher than expected inflow salt concentration. The characterisation of uncertainty associated with environmental variation and incertitude allows managers to make informed risk-weighted decisions.     

Analysis of Damaging Hydrogeological Events: The Case of the Calabria Region (Southern Italy)

A period of bad weather conditions due to prolonged intense rainfall and strong winds can trigger landslides, floods, secondary floods (accumulation of rain on surfaces with low permeability), and sea storms, causing damage to humans and infrastructure. As a whole, these periods of bad weather and triggered phenomena can be defined as damaging hydrogeological events (DHEs). We define a methodological approach based on seven simple indexes to analyze such events. The indexes describe the return period (T) and trend of rainfall, the extent of hit areas, and the level of damages; they can be considered attributes of georeferenced features and analyzed with GIS techniques. We tested our method in an Italian region frequently hit by DHEs. In a period of 10 years, 747 damaging phenomena (landslides, 43%; floods, 38%) and 94 DHEs have been classified. The road network and housing areas are the most frequently damaged elements, threatened by all types of damaging phenomena. T classes are almost in accordance with the level of damage. These results can be used to outline warning levels for civil protection purposes, to forecast the areas most likely to be hit and the potential ensuing damage, to disseminate information concerning vulnerable areas, and to increase people’s awareness of risk.     

中小锅炉爆炸事故规律分析与研究

为研究中小型锅炉爆炸事故的规律,对中小型锅炉爆炸案例进行调查和分析,并进行了缺水再进水试验和炉胆失稳模拟试验。研究认为,爆炸主要原因是缺水和超压,缺水造成材料性能下降明显,进水汽化造成锅内压力骤升,并给出了立式锅炉爆炸机理。从锅炉结构、水容积、安全附件等方面的爆炸事故因素考虑,对3种中小型锅炉进行安全性分析,并提出了事故预防措施。     

浅析低瓦斯煤矿瓦斯防治安全评价

笔者结合煤矿安全评价工作的经验,通过运用预先危险分析对低瓦斯煤矿瓦斯防治进行分析,得出瓦斯爆炸是最严重的瓦斯事故。进而通过对瓦斯爆炸的事故树分析,得出了导致瓦斯爆炸的27个基本事件。应用事故树分析中的最小割集、最小径集和结构重要度,对瓦斯爆炸进行了研究。结果表明,瓦斯爆炸不发生所必须的最低限度的基本事件集合即最小径集有6个,其中严格控制瓦斯浓度,杜绝一切火源,是预防煤矿瓦斯爆炸的最重要途径。从源头上防止瓦斯爆炸的发生,提高我国煤矿安全生产水平。     

锅炉烟尘测试中锅炉负荷率的计算方法探讨

GB5468 -91规定 ,锅炉烟尘测试时 ,必须对锅炉的运行负荷进行测试 ,而实际监测过程中 ,许多锅炉房不具备测试的计量条件 ,为了解决这一问题 ,文章提出利用烟气量和空气过剩系数计算锅炉负荷率。在实际监测工作中 ,该方法方便、易于操作 ,所得结果和标准规定方法所得结果有很好的一致性     

拉萨市环境空气质量与气象特征分析

分析了拉萨市环境空气质量及其拉萨市的地理位置、地形地貌和气候特征的关系。研究结果表明 ,自然沙尘是拉萨市环境空气质量的主要自然源。月降尘量与降水、大风等有明显的相关关系。加快拉萨地区生态环境建设 ,增加植被覆盖率 ,减少沙源是改善拉萨市环境空气质量的关键     

Assessment of groundwater contamination by nitrate leaching from intensive vegetable cultivation using geographical information system

This study employed the Geographical Information System (GIS) technology to investigate nitrate contamination of groundwater by agrochemical fertilizers in the Kakamigahara Heights, Gifu Prefecture, central Japan. Thematic information and chemical data of groundwater from the Heights were analyzed in a GIS environment to study the extent and variation of nitrate contamination and to establish spatial relationships with responsible land use types. The high and correlated concentrations of Ca(2+), Mg(2+), SO(4)(2-), and NO(3)(-) reflected the polluted nature of the unconfined highly permeable Kakamigahara aquifer. Ninety percent of the water samples showed nitrate concentrations above the human affected value (3 mg/l NO(3)(-)), while more than 30% have exceeded the maximum acceptable level (44 mg/l NO(3)(-)) according to Japan regulations. The spatial analyses indicated that groundwater contamination by nitrate is closely associated with one specific land use class, the "vegetable fields". The nitrate concentration of groundwater under vegetable fields was significantly higher than that under urban land or paddy fields. Most of the unacceptable nitrate levels were encountered in boreholes assigned to "vegetable fields" but a few were also found in boreholes allotted to "urban" class. Therefore, the vegetable fields were considered the principal source of nitrate contamination of groundwater in the Kakamigahara. However, contamination from urban sources is also possible.