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排序方式: 共有897条查询结果,搜索用时 15 毫秒
521.
Jia Liu Yunshan Ge Xin Wang Lijun Hao Jianwei Tan Zihang Peng Chuanzhen Zhang Huiming Gong Ying Huang 《环境科学学报(英文版)》2017,29(7):238-248
In this study, the particle size-resolved distribution from a China-3 certificated light-duty diesel vehicle was measured by using a portable emission measurement system (PEMS). In order to examine the influences of vehicle specific power (VSP) and high-altitude operation, measurements were conducted at 8 constant speeds, which ranged from 10 to 80 km/hr at 10 km/hr intervals, and two different high altitudes, namely 2200 and 3200 m. The results demonstrated that the numbers of particles in all size ranges decreased significantly as VSP increased when the test vehicle was running at lower speeds (< 20 km/hr), while at a moderate speed (between 30 and 60 km/hr), the particle number was statistically insensitive to increase VSP. Under high-speed cruising conditions, the numbers of ultrafine particles and PM2.5 were insensitive to changes in VSP, but the numbers of nanoparticles and PM10 surged considerably. An increase in the operational altitude of the test vehicle resulted in increased particle number emissions at low and high driving speeds; however, particle numbers obtained at moderate speeds decreased as altitude rose. When the test vehicle was running at moderate speeds, particle numbers measured at the two altitudes were very close, except for comparatively higher number concentrations of nanoparticles measured at 2200 m. 相似文献
522.
在现有的各种回收处理高浓度含酚废水的方法中,溶剂萃取法最为有效.但现有常用脱酚萃取剂分别存在着萃取效能低等诸多缺点,萃残液中一般尚存有几十至几百mg·l-1的酚类,本文提出了协同-络合萃取法,并按该法原理研制了HC-1—HC-4四类新型协同-络合萃取剂.其中HC-3和HC-4对苯酚稀溶液的萃取平衡常数分别为KHC-30=612.4和KHC-40=483.7,单级萃取可将两组中高浓度的含酚废水中酚浓度降至10mg·l-1以厂,脱酚率99%.该法为一步脱酚达标提供了可能性. 相似文献
523.
Ge Wang Huijin Zhang Saixing Zeng Xiaohua Meng Han Lin 《Corporate Social Responsibility and Environmental Management》2023,30(1):28-52
Although widely explored in many studies, how and why combined top management team (TMT) and corporate characteristics affect environmental information disclosures (EID) are still lacking clarity. This study uses both fuzzy-set qualitative comparative analysis and necessary condition analysis to reconcile the inconclusive results concerning the configurational effects of these characteristics on EID and to validate the robustness. From a sample of listed construction engineering corporates during the 2014–2018 period, the high EID level is associated with several complex configurations that contain the core characteristics such as corporate ownership and size, whereas the low EID level is related to the configurations including TMT salary and corporate profitability. The findings support the four tenets of equifinality, asymmetry, complexity, and causal asymmetry in complexity theory. Our results capture the complex non-linear effects of TMT and corporate characteristics and shed new light on environmental disclosure management for corporate sustainable development. 相似文献
524.
525.
Fre´de´rique Barbier Fre´de´ric Plassard Ge´rard Duc Michelle Petit-Ramel 《Chemistry and Ecology》2013,29(3-4):177-186
In order to prevent contamination of subsoil and groundwater by leachates containing heavy metals, montmorillonite linings are used on landfill bottoms. It is therefore important to understand ion uptake by this clay. In this study we have performed percolation of lead(II) and cadmium(II) through columns filled firstly with a technical bentonite and then with a reference bentonite. Elution curves provide an evaluation of metals retention. After the percolation step, columns are cut and metal ions are extracted to evaluate influence of side effects and soil depth on metal uptake. Moreover retentions of lead(II) and cadmium(II) are compared. 相似文献
526.
甲硫醚和甲硫醇作为硫化氢进入人体之后的主要代谢产物,具有一定的标识作用. 针对血液中甲硫醚和甲硫醇的检验进行研究,建立了顶空气相色谱检验方法. 实验采用对含硫化合物具有高灵敏度的火焰光度检测器(FPD),同时发现向0.5 mL血样中加入0.15 g氯化钠可使检出效率得到提升. 本方法血中甲硫醚的标准曲线范围为0.01—2.00 μg·mL−1,相关系数(R2)为0.997,检出限为0.003 μg·mL−1,定量限为0.01 μg·mL−1. 虽然甲硫醇由于自身沸点太低,不适合对其进行定量分析,但对其进行定性检测,也可为硫化氢中毒提供一定的依据. 本研究建立的方法可直接应用于血液中微量甲硫醚和甲硫醇的检测,从而为硫化氢中毒案件的检验鉴定提供依据. 相似文献
527.
轮作休耕是保障黑土区耕地资源可持续利用的重要手段。科学合理确定粮食作物轮作休耕的耕地利用规模及空间分布,对实现黑土区耕地修养生息、提升地力和平衡粮食供求结构具有重要意义。以东北典型黑土区——克山县、拜泉县和依安县为研究区,运用作物种植空间适宜性评价模型、多目标优化(MOP)模型和智能体土地布局优化配置(AgentLA)模型,基于地块尺度构建耕地轮作和休耕布局,适度调整轮作休耕规模及分布。结果发现:(1)研究区主要作物种植适宜性高值和低值区存在明显空间差异。玉米和大豆种植适宜性高值区交汇于依安县北部和克山县西部,是玉米—大豆轮作优势区域。主要作物种植适宜性低值区交汇于依安县南部和拜泉县西南部,是休耕的重点区域。(2)基于种植结构优化的轮作规模实现了大豆种植比例增加和玉米种植比例减少,缓解了目前玉米阶段性供大于求、大豆供给不足的现实矛盾。通过设定多种粮食供求情景确定休耕规模有利于灵活应对粮食市场变动。(3)兼顾耕地空间适宜性和集聚性的轮作休耕布局有利于充分利用耕地资源禀赋比较优势、发展规模化经营,对提高耕地利用效率具有重要作用。研究通过科学重构黑土区耕地轮作和休耕空间布局,实现了耕地空间适宜性、空间集聚性、种植结构合理性和粮食供求稳定性的同步提升,为实现黑土区耕地资源合理可持续利用和粮食安全提供政策参考。 相似文献
528.
造纸黑液木质素用于制备人造板胶粘剂的研究 总被引:3,自引:0,他引:3
分别采用硫酸、硝酸和盐酸从造纸黑液中提取木质素,以此替代部分苯酚.制备改性人造板用酚醛树脂胶粘剂,并测定其固体含量、动力黏度(40℃)、游离甲醛含量和胶合强度等性能;考察了3种酸析木质素掺入量、催化剂(氧氧化钠)加入量和苯酚与甲醛摩尔比(简称酚醛比)对木质素酚醛树脂胶粘剂性能的影响.结果表明,当硫酸、硝酸木质素掺入量为苯酚用量的20%(质量分数,下同)时,获得的胶粘剂性能较好;以硝酸木质素掺入量为苯酚用量的20%为例,当氢氧化钠加入量为苯酚用量的0.6%(质量分数)、酚醛比为1.0:1.5时.制备的硝酸木质素酚醛树脂胶粘剂胶合性能较好.用木质素替代部分苯酚,不仅可以降低产品成本,而且减少了苯酚的用量,更环保. 相似文献
529.
530.
As part of a comprehensive environmental management system, many countries establish emission control targets for mass emissions of a pollutant. Such targets are often the key objective of an environmental policy, such as an emission trading program. In China, however, it is more than just an objective of one particular policy; it has become a concept that has influenced many national environmental policies and activities. The objective of this article is to review the implementation of the total emission control policy in the past 10 years and explore emerging issues in its implementation. The article has three sections: a summary of the implementation experience, issues with the design and implementation of the policy, and policy recommendations. 相似文献