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241.
242.
废旧轮胎橡胶颗粒与砂土组成的橡胶颗粒土相比于纯砂而言,具有密度轻、弹性变形能力强、耗能大、剪切模量低等特点,可广泛应用于边坡、挡土墙和路基回填、桥台跳车治理以及建筑隔震减振等工程领域。通过共振柱试验,重点对比研究了橡胶含量、粒径及围压对混合土动剪切模量和等效阻尼比的影响规律。结果表明,小应变范围内,在围压和粒径相同时,随橡胶含量的增加,橡胶土动剪切模量减小,阻尼比增大,动剪模量比衰退变缓;含量和粒径相同时,围压增大,动剪模量增大,动剪模量比衰退变缓,阻尼比减小。在大应变幅值下,橡胶含量较低时,随着围压增大,动剪模量比衰退明显加快;而当橡胶含量较高时,围压对其影响与小应变范围相同;而围压与橡胶含量相同时,不同橡胶粒径的模量与阻尼比曲线非常接近。橡胶土的动剪模量与阻尼比主要受橡胶含量与固结围压影响,而粒径影响可忽略不计。 相似文献
243.
244.
广东沿海地区是我国经济发达地区,同时也是受地质灾害威胁严重的地区.据相关资料显示,截止2003年底,广东省近10年间发生较大规模的地质灾害330起,造成直接死亡778人,直接经济损失27亿元.因此,地质灾害的治理显得尤为迫切,如何在减灾过程中避免事故的发生成为一个重要的课题.以东山岭为例就沿海地区滑坡治理过程中的安全控制过程及方法进行分析探讨. 相似文献
245.
Batch sorption and column breakthrough studies were conducted to investigate the potential of layered double hydroxides (LDHs) to remove bacteriophage MS2 from contaminated waters. All four of the LDHs evaluated in this study had very high retention capacities for MS2. Sorption results showed that MS2 could be completely removed from 5.2 x 10(2) plaque-forming units (pfu)/mL solution by Mg-Al LDH 2 (i.e., 2:1 Mg to Al ratio LDH), with the highest sorption capacity observed in this study of 1.51 x 10(10) pfu/g. Attachment of MS2 to LDHs was a rapid process and reached quasi-equilibrium after a 1-h reaction time. Within the pH range studied (pH 4-9), Mg-Al LDH 2 showed high sorption potential for MS2 at all pH values but sorption decreased slightly with increasing solution pH. Background solution anions influenced virus sorption, with SO4(2-) and HPO4(2-) decreasing sorption significantly whereas the presence of NO3- had little effect on the attachment of MS2 to Mg-Al LDH 2. The addition of another virus (phiX174) only caused a slight decrease in the retention of MS2 by Mg-Al LDH 2, suggesting that there was insignificant competitive sorption between MS2 and phiX174 on LDH surfaces. Results from column experiments indicate that there was no MS2 breakthrough from columns packed with Mg-Al LDH 2-coated sand, suggesting complete MS2 retention at the virus concentration tested. The high mass recovery by beef extract solution revealed that the removal of viruses by the LDH was due to sorption of MS2 to LDH surfaces, rather than inactivation. 相似文献
246.
Xiaoliang Lu Qianlai Zhuang 《Mitigation and Adaptation Strategies for Global Change》2010,15(5):467-487
The Midwest of the United States includes 12 states and accounts for about a quarter of the total United State land area.
In recent years, there is an increasing interest in knowing the biomass potential and carbon balance over this region for
the past and the future. In this study, we use the Terrestrial Ecosystem Model (TEM) to evaluate these quantities in the region
from 1948 to 2099. We first parameterize the model with field data of major crops, including corn (Zea mays), soybean (Glycine max), and wheat (Triticum spp); then the model is applied to the region for the historical period (1948–2000). Next, we evaluate the simulated forestry
biomass with forest inventory data, the agricultural net primary production (NPP) with agricultural statistics data, and the
regional NPP with a satellite-based product at the regional scale. Our results show that the simulated annual NPP for the
Midwest increased by 1.75% per year and the whole Midwest terrestrial ecosystem acted as a carbon sink during 1948–2005. During
the 21st century, vegetation and soil carbon fluxes and pools show an increase trend with a great inter-annual variability.
The ecosystems serve as a carbon sink under future climate scenarios. NPP in the Midwest will increase and net ecosystem production
(NEP) will also increase and show an even larger interannual variability. This study provides the information of the biomass
and NEP at a state- level in the Midwest, which will be valuable for the region stakeholders to better manage their land for
the purpose of increasing carbon sequestration on the one hand and meeting the increasing demand of biomass on the other. 相似文献
247.
城市河流沉积物镉污染的潜在生态风险评价——以重庆市清水溪为例 总被引:1,自引:0,他引:1
针对目前河流污染问题的严重性,采用Hakanson潜在生态风险指数法,通过分析清水溪流域18个采样点沉积物中典型重金属污染物镉的含量,定量确定了清水溪沉积物中重金属镉的污染程度和潜在生态风险程度。结果表明:清水溪流域镉污染非常严重,上游比下游污染严重,而且在新桥到高滩岩段受到重金属镉的高强度污染,对周围环境存在着极高的镉生态风险。在清水溪干流采样点沉积物中镉的质量浓度范围在0.38~1.48mg·kg^-1之间,平均值0.85mg·kg^-1,各支流沉积物中镉的质量浓度范围为0.51~1.08mg·kg^-1。对于清水溪各支流镉的污染程度与潜在生态风险程度由高到低的排序为杨家沟〉金竹沟〉芭蕉沟〉关井沟〉石碾盘沟。 相似文献
248.
Qianlai Zhuang Tonglin Zhang Jingfeng Xiao Tianxiang Luo 《Mitigation and Adaptation Strategies for Global Change》2009,14(1):85-99
Net primary production (NPP) of terrestrial ecosystems provides food, fiber, construction materials, and energy to humans.
Its demand is likely to increase substantially in this century due to rising population and biofuel uses. Assessing national
forest NPP is of importance to best use forest resources in China. To date, most estimates of NPP are based on process-based
ecosystem modeling, forestry inventory, and satellite observations. There are little efforts in using spatial statistical
approaches while large datasets of in-situ observed NPP are available for Chinese forest ecosystems. Here we use the surveyed
forest NPP and ecological data at 1,266 sites, the data of satellite forest coverage, and the information of climate and topography
to estimate Chinese forest NPP and their associated uncertainties with two geospatial statistical approaches. We estimate
that the Chinese forest and woodland ecosystems have total NPP of 1,325 ± 102 and 1,258 ± 186 Tg C year−1 in 1.57 million km2 forests with a regression method and a kriging method, respectively. These estimates are higher than the satellite-based
estimate of 1,034 Tg C year−1 and almost double the estimate of 778 Tg C year−1 using a process-based terrestrial ecosystem model. Cross-validation suggests that the estimates with the kriging method are
more accurate. Our developed geospatial statistical models could be alternative tools to provide national-level NPP estimates
to better use Chinese forest resources. 相似文献
249.
Analysis of bacterial community in bulking sludge using culture-dependent and -independent approaches 总被引:1,自引:0,他引:1
Decai Jin Ping Wang Zhihui Bai Xinxin Wang Hong Peng Rong Qi Zhisheng Yu Guoqiang Zhuang 《环境科学学报(英文版)》2011,23(11):1880-1887
Combination of 16S rRNA gene clone library and cultivation for assessing of bacterial diversity of the microflora in bulking sludge was evaluated in the study. 相似文献
250.
本文作者主要研究了腐殖酸对聚乙烯吡咯烷酮包覆的纳米银颗粒(polyvinylpyrrolidone-coated AgNPs)毒性的影响,受试生物涵盖了水生系统不同的营养级别,包括藻类(Raphidocelis subcapitata)、水蚤类(Chydorus sphaericus)以及淡水鱼类(Danio rerio)。结果显示,腐殖酸可降低AgNPs对本研究中所有水生生物的毒性,并具有明显的剂量效应关系。原因为:1)腐殖酸使AgNPs表面带有更多负电荷,这阻碍了AgNPs与藻细胞的接触,使毒性降低;2)腐殖酸抑制了AgNPs中Ag+的溶出,而本研究显示自由Ag+的毒性高于团聚的纳米银颗粒。
精选自Zhuang Wang, Joris T.K. Quik, Lan Song, Evert-Jan Van Den Brandhof, Marja Wouterse and Willie J.G.M. Peijnenburg. Humic substances alleviate the aquatic toxicity of polyvinylpyrrolidone-coated silver nanoparticles to organisms of different trophic levels. Environmental Toxicology and Chemistry: Volume 34, Issue 6, pages 1239–1245, June 2015.
DOI: 10.1002/etc.2936
详情请见http://onlinelibrary.wiley.com/doi/10.1002/etc.2936/full 相似文献