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排序方式: 共有80条查询结果,搜索用时 15 毫秒
1.
根据国家科技攻关研究的结果,论证了长江中下游地区地下水中Zn元素的背景特征的形成及其分布规律与地下水的含水介质成分、有机质含量、氧化还原环境、地下水迳流条件和地下水酸碱度之间的关系。 相似文献
2.
在贵阳乌当断层南北两侧 ,下石炭统九架炉组、祥摆组和旧司组的分布和沉积特征存在明显的变化。九架炉组基本分布于乌当断层北西侧 ,祥摆组由北向南的沉积环境向浅海相呈有规律的变化 ,旧司组则仅在乌当断层南侧分布。这些地层的分布规律、沉积环境的变化说明了乌当断层为黔中隆起南侧边缘断层 ,且该断层自早古生代形成后 ,为一多期次活动断层。 相似文献
3.
The comprehensive control efficiency for the formation potentials(FPs) of a range of regulated and unregulated halogenated disinfection by-products(DBPs)(including carbonaceous DBPs(C-DBPs), nitrogenous DBPs(N-DBPs), and iodinated DBPs(I-DBPs)) with the multiple drinking water treatment processes, including pre-ozonation, conventional treatment(coagulation–sedimentation, pre-sand filtration), ozone-biological activated carbon(O_3-BAC) advanced treatment, and post-sand filtration, was investigated. The potential toxic risks of DBPs by combing their FPs and toxicity values were also evaluated.The results showed that the multiple drinking water treatment processes had superior performance in removing organic/inorganic precursors and reducing the formation of a range of halogenated DBPs. Therein, ozonation significantly removed bromide and iodide,and thus reduced the formation of brominated and iodinated DBPs. The removal of organic carbon and nitrogen precursors by the conventional treatment processes was substantially improved by O_3-BAC advanced treatment, and thus prevented the formation of chlorinated C-DBPs and N-DBPs. However, BAC filtration leads to the increased formation of brominated C-DBPs and N-DBPs due to the increase of bromide/DOC and bromide/DON.After the whole multiple treatment processes, the rank order for integrated toxic risk values caused by these halogenated DBPs was haloacetonitriles(HANs)》haloacetamides(HAMs) haloacetic acids(HAAs) trihalomethanes(THMs) halonitromethanes(HNMs) 》I-DBPs(I-HAMs and I-THMs). I-DBPs failed to cause high integrated toxic risk because of their very low FPs. The significant higher integrated toxic risk value caused by HANs than other halogenated DBPs cannot be ignored. 相似文献
4.
Although Asia is thought to have played a critical role in the radiation of artiodactyls, the fossil record of stem selenodonts
(“dichobunoids”) remains dramatically poor in tropical Asian regions. In this study, we report a new dichobunid genus and
species Cadutherium kyaukmagyii and a new basal ruminant genus and species Irrawadymeryx pondaungi, from the late Middle Eocene Pondaung Formation, Central Myanmar. Although the scarcity of the present material prevents
any attempts to investigate the phylogenetic relationships of Cadutherium with contemporaneous forms from other Holarctic landmasses, this new form shed new light on the diversity of these small
rabbit-like ungulates during a key period of their evolutionary history. Reexamination of the small-bodied artiodactyls from
Pondaung leads us to propose new identifications of certain published specimens and, in turn, to investigate the temporal
and geographic distribution of taxa recognized in the Pondaung Formation. Although fragmentary, these potential new taxa reveal
an unsuspected diversity of small forms among artiodactyls of Pondaung. This addition to the Eocene record of dichobunoids
and early ruminants provides further insight in the diversity of dental patterns among small artiodactyls from the Pondaung
Formation and attests to the antiquity of these groups in Southeast Asia. 相似文献
5.
TiO2 nanomaterial is promising with its high potential and outstanding performance in photocatalytic environmental applications, such as CO2 conversion, water treatment, and air quality control. For many of these applications, the particle size, crystal structure and phase, porosity, and surface area influence the activity of TiO2 dramatically. TiO2 nanomaterials with special structures and morphologies, such as nanospheres, nanowires, nanotubes, nanorods, and nanoflowers are thus synthesized due to their desired characteristics. With an emphasis on the different morphologies of TiO2 and the influence factors in the synthesis, this review summarizes fourteen TiO2 preparation methods, such as the sol-gel method, solvothermal method, and reverse micelle method. The TiO2 formation mechanisms, the advantages and disadvantages of the preparation methods, and the photocatalytic environmental application examples are proposed as well. 相似文献
6.
以该实验的观测资料为基础,通过数据分析表明,对大连星海地区OH自由基消耗的主要环境VOCs组分是烯烃类物质,对O3生成潜势贡献最高的环境VOCs组分是芳香烃类物质;综合LiOH及OFP值评价,识别影响大连星海地区O3生成的关键环境VOCs反应活性物种为丙烯、甲苯、间对二甲苯等物质。 相似文献
7.
Knowledge of the factors that influence the diffusion of contaminants, such as the diffusivity and the connected porosity, is crucial to modeling the long-term fate and transport of contaminants in subsurface systems with small or negligible advective flow, such as in fractured crystalline rock. Fractured rock is naturally heterogeneous, and hence, understanding the diffusivity of a molecule through this material (or the formation factor of the medium) becomes a complex problem, with critical concerns about the scale of laboratory measurements and about the spatial variability of these measurements relative to the scale needed for fate and transport modeling. This study employed both electrical and tracer-based laboratory methods to investigate the effects of scale and pore system connectivity on the diffusivity for volcanic matrix rock derived from the study site, a former underground nuclear test site at Amchitka Island, Alaska. The results of these investigations indicate a relatively well-connected pore system with scale effects generally limited to approximately 6 cm lengths and well-correlated to observed heterogeneous features. An important conclusion resulting from this study, however, is that there is a potential for the estimated diffusivity to be misrepresented by an order of magnitude if multiple samples or longer sample lengths are not used. Given the relatively large number of measurements resulting from these investigations, an analysis of the probability density function (PDF) of the diffusivity was possible. The PDF of the diffusivity was shown to generally follow a normal distribution for individual geologic layers. However, when all of the geologic layers are considered together, the distribution of the subsurface as a whole was shown to follow a lognormal distribution due to the order of magnitude differences amongst the layers. An understanding of these distributions is essential for future stochastic modeling efforts. 相似文献
8.
Saif Ud din R.P. Oskui Maurice B. Dusseault A.N. Al Ghadban 《Journal of environmental management》2009,91(1):186-194
Waste generation and accumulating quantities of oil field waste are a matter of environmental concern. This study proposes the Slurry Fracture Injection (SFI) technique as an alternative waste disposal method. The slurried solids injection waste disposal method is environmentally secure and permanent, leaving no future liabilities that must be risk-evaluated or priced. An entire waste stream comprising ground solids and waste water can be injected into deep and hydraulically secure target strata with no contamination of potable water-bearing formations or formations outside the target zone that may contain resources (gas and oil). The slurry injection method can be used to clean and reclaim landfills, oil pits and granular waste dumps. This article proposes a two-tier screening method for evaluating the feasibility of this technique and the identification of suitable target zones. A stringent environmental and process control monitoring program should complement the planning and operational period to ensure environmental protection, waste containment, and regulatory HSE compliance. 相似文献
9.
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