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81.
在明、清两代,皇宫曾有过几次毁灭性的火灾,每次都给老百姓带来了沉重的负担。  相似文献   
82.
秋冬季节降水偏少.风干物燥,加上秋冬季农事野外生产生活用火多,稍有不慎就会引发森林火灾。因此,必须加强火源管理.做好森林防火.  相似文献   
83.
Providing an accurate estimate of the dry component of N deposition to low N background, semi-natural habitats, such as bogs and upland moors dominated by Calluna vulgaris is difficult, but essential to relate nitrogen deposition to effects in these communities. To quantify the effects of NH3 inputs to moorland vegetation growing on a bog at a field scale, a field release NH3 fumigation system was established at Whim Moss (Scottish Borders) in 2002. Gaseous NH3 from a line source was released along of a 60 m transect, when meteorological conditions (wind speed >2.5 m s?1 and wind direction in the sector 180–215°) were met, thereby providing a profile of decreasing NH3 concentration with distance from the source. In a complementary study, using a NH3 flux chamber system, the relationships between NH3 concentrations and cuticular resistances were quantified for a range of NH3 concentrations and micrometeorological conditions for moorland vegetation. Cuticular resistances increased with NH3 concentration from 11 s m?1 at 3.0 μg m?3 to 30 s m?1 at 30 μg m?3. The NH3 concentration data and the concentration-dependent canopy resistance are used to calculate NH3 deposition taking into account leaf surface wetness. The implications of using an NH3 concentration-dependent cuticular resistance and the importance for refining critical loads are discussed.  相似文献   
84.
企业可持续发展评价指标体系的选定原则及构建框架   总被引:3,自引:0,他引:3  
为了制定企业可持续发展的战略决策,须制定可持续发展的指标体系,并依据这一体系对数据和资料进行收集、整理和分析,从而确定可靠而有效的政策方针。文中论述了可持续发展指标体系的定义、选定标准、原则和可持续发展的评价指标体系,提出了压力-状态-响应框架模型以及不同层次的指标体系框架。该指标体系分为总体层、系统层、状态层、变量层和要素层五个等级。对于持续发展的表征指标及对目前发展的可持续性评估,还需要长时间和切合实际的探讨。  相似文献   
85.
For (134/137)Cs, and many other soil contaminants, research into transfer to plants has focused on particular crops and phytoremediation candidates, producing uptake data for a small proportion of all plant taxa. Despite the significance of differences in uptake between plant taxa, the capacity of soil-to-plant transfer models to predict them is currently confined to those taxa for which data exist, there being no method to predict uptake by other taxa. We used residual maximum likelihood (REML) analysis on data from experiments (including 89 plant taxa from China plus 32 phytoremediation candidates) together with data from the literature, to construct a database of relative (134/137)Cs concentrations in 273 plant taxa. The REML (134/137)Cs concentrations in plants are not normally distributed but significantly clustered. Analysis of variance (ANOVA), coded with a recent ordinal phylogeny for flowering plants, showed that plant taxa do not behave independently for (134/137)Cs concentration because 42 and 15% of inter-taxa differences are associated with phylogeny above the species and ordinal level, respectively. In general, Eudicots, and especially the Caryophyllales, Asterales, and Brassicales, have high (134/137)Cs concentrations, while the Fabales and Magnoliids, in particular Poales, have low (134/137)Cs concentrations. Plants of the stress-tolerant ruderal (S-R) growth strategy sensu Grime have, in general, high concentrations of Cs, while those of the competitive (C) and generalist (C-S-R) strategies have low concentrations, although these effects are less pronounced than those of phylogeny. Plant phylogeny and growth strategy might thus be used to predict a significant portion of inter-taxa differences in plant uptake of (134/137)Cs.  相似文献   
86.
Negatively charged carboxymethylated polyethersulfone (CMPES) and positively charged quaternized polyethersulfone (QAPES) ultrafiltration (UF) membranes were prepared by bulk chemical modification and non-solvent induced phase separation method. The effects of PES membrane interfacial electrokinetic property on the bovine serum albumin (BSA) membrane fouling behavior were studied with the aid of the membrane-modified colloidal atomic force microscopy (AFM) probe. Electrokinetic test results indicated that the streaming potential (ΔE) of QAPES membrane was not consistent with its expected IEC value, however, within the pH range of 3–10, the ζ potentials of two charged-modified PES membranes were more stable than the unmodified membrane. When pH value was 3, 4.7 or 9, the interaction behavior between charged PES membrane and BSA showed that there was significant linear correlation between the jump distance r 0 of membrane-BSA adhesion force (F/R) and the ζ potential absolute value. Charged modification significantly reduced the adhesion of PES membrane-BSA, and the adhesion data was good linear correlated with the flux decline rate in BSA filtration process, especially reflected in the CMPES membrane. The above experimental facts proved that the charged membrane interfacial electric double layer structure and its electrokinetic property had strong ties with the protein membrane fouling behavior.
  相似文献   
87.
2006~2008年,对长江中游的一个浅水湖泊--肖四海进行了水质和水生植被研究,并结合历史资料分析了肖四海1987~2008年不同渔业发展阶段的水环境特征。研究结果表明:1987~2008年期间,该湖营养状况经历了中营养→富营养→中营养→富营养→中营养的变化过程,沉水植被经历了消亡→恢复→旺盛→衰退的演替过程,这种变化主要受不同阶段的渔业方式的影响。草食性鱼类和河蟹的过量放养、化肥的大量使用以及饵料的大量投放等不合理的渔业方式导致了水生植被的消亡和水体的富营养化,而合理的渔业方式不会对水体环境产生消极影响,并据此提出了长江中下游湖泊渔业可持续发展的建议  相似文献   
88.
Assessment of groundwater quality plays a significant role in the utilization of the scarce water resources globally and especially in arid regions. The increasing abstraction together with man-made contamination and seawater intrusion have strongly affected groundwater quality in the Arabia Peninsula, exemplified by the investigation given here from the United Arab Emirates, where the groundwater is seldom reviewed and assessed. In the aim of assessing current groundwater quality, we here present a comparison of chemical data linked to aquifers types. The results reveal that most of the investigated groundwater is not suitable for drinking, household, and agricultural purposes following the WHO permissible limits. Aquifer composition and climate have vital control on the water quality, with the carbonate aquifers contain the least potable water compared to the ophiolites and Quaternary clastics. Seawater intrusion along coastal regions has deteriorated the water quality and the phenomenon may become more intensive with future warming climate and rising sea level.  相似文献   
89.
Three important groups of semi-volatile organic compounds (SVOCs), polycyclic aromatic hydrocarbons (PAHs), organic chlorinated pesticides (OCPs) and phthalate esters (PAEs), were produced by various human activities and entered the water body. In this study, the pollution profiles of three species including 16 PAHs, 20 OCPs and 15 PAEs in water along the Beijiang River, China were investigated. The concentrations of Σ16PAHs in the dissolved and particulate phases were obtained as 69–1.5 × 102 ng L?1 and 2.3 × 103–8.6 × 104 ng g?1, respectively. The levels of Σ20OCPs were 23–66 ng L?1 (dissolved phase) and 19–1.7 × 103 ng g?1 (particulate phase). Nevertheless, higher levels of PAEs were found both in the dissolved and particulate phases due to abuse use of plastic products. Furthermore, non-cancer and cancer risks caused by these SVOCs through the ingestion absorption and dermal absorption were also assessed. There was no non-cancer risk existed through two kinds of exposure of them at current levels, whereas certain cancer risk existed through dermal absorption of PAHs in the particulate phase in some sampling sites. The results will show scientific insights into the evaluation of the status of combined pollution in river basins, and the determination of strategies for incident control and pollutant remediation.  相似文献   
90.
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