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排序方式: 共有390条查询结果,搜索用时 15 毫秒
161.
介绍了一种用于气溶胶生成机制研究的流管反应器(Jiao-FTR,J-FTR)的设计及表征.借助计算流体力学(CFD)模拟和实验测定,表征了不同进气结构和实验条件下反应器内流场的发展及稳定,移动进气管的喷射效应以及气体和颗粒物在反应器内的平均停留时间.结果表明,预混合段进气方式,主流流量,移动进气管结构及注入流量对J-FTR的流场发展以及气体和颗粒物的停留时间具有较大影响;J-FTR的预混合进气段具有使主流快速过渡为层流的优势,在对称进气条件下,当主流流量不超过8L/min,气流在进入主反应段之前可发展为稳定的层流;当移动进气管使用大内径的直管或径面十字型结构时,可以有效减小或避免移动进气管的喷射效应.以上结果不仅可为使用J-FTR开展大气化学和气溶胶生成机制研究提供重要的实验指导,也可为其他研究者设计FTR,进行流管实验提供借鉴. 相似文献
162.
鄱阳湖流域人为氮磷输入演变及湖泊水环境响应 总被引:5,自引:0,他引:5
人类活动导致的氮磷营养盐富集是我国湖泊富营养化问题形成的重要驱动力.鄱阳湖是我国最大的淡水湖泊,随着流域经济社会的迅速发展,湖体营养盐水平上升,降低了鄱阳湖及长江中下游地区的水环境质量.然而,人类对鄱阳湖流域氮磷输入的影响程度尚不明确,湖体氮磷浓度与流域人为氮磷输入的关系也缺乏定量研究.因此,本研究基于人为净氮输入模型(NANI)、人为净磷输入模型(NAPI)和多元统计回归模型,评估了鄱阳湖流域1949—2013年人类活动导致的氮磷输入量,构建了人为氮磷输入与湖泊氮磷浓度的响应模型.结果表明,研究期内鄱阳湖流域的人为净氮输入和人为净磷输入分别增长6倍和15倍,化肥施用是20世纪80年代以来的主要增长因子;鄱阳湖氮磷浓度与流域人为氮磷输入显著相关,根据多元回归模型的可决系数,NANI可解释88%的湖体TN浓度变化,NAPI和湖泊平均水位可解释64%的TP浓度变化.提高氮磷的循环利用率同时维持湖泊生态水位对于降低鄱阳湖富营养化水平具有重要意义. 相似文献
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165.
Limit values (LVs) are legal concentration limits for constituents, residues and contaminants in consumer products or for
emissions from production processes into environmental compartments. They are a traditional regulatory aid to manage chemicals
in human environments. To make them proactive, LVs should become enforced by means of a transparent and informed decision
process whose starting point is the Basic Rule of Environmental Hygiene, BREH:Avoid useless exposure as far as possible, minimize useful exposure in a reasonable manner, and prevent that exposure which
is dangerous. The BREH calls upon minimizing exposure not only according toon site risk potentials and acceptance, but also tooff site avoidability and acceptability. 相似文献
166.
Swapan Khanra Claudio Minero Valter Maurino Ezio Pelizzetti Binay K. Dutta Davide Vione 《Environmental Chemistry Letters》2008,6(1):29-34
Here we show that the photolysis of FeCl2+ upon UV irradiation of Fe(III) at pH 0.5, yielding Cl• and then Cl2−•, upon further reaction with Cl−, induces phenol degradation. The photolysis of FeCl2+ can be highlighted and studied as the huge interference by FeOH2+ can be avoided under such conditions. Our data allowed the assessment of a photolysis quantum yield for FeCl2+ of 5.8 × 10−4 under UVA irradiation, much lower compared to the literature value of 0.5. The discrepancy can be explained if the photolysis
process is efficient but photoformed Fe2+ and Cl• undergo recombination inside the solvent cage. 相似文献
167.
The primary aim of the study was to analyse the non-steady state of filtration for selected electrostatic filter materials designed for use in respiratory protective devices. The obtained results showed that the filtration process in electrostatic filters was dependent in the main on the following factors: type of the filter material, electrostatic field strength of the material, and the charge of the aerosol.To a lesser degree the filtration process depended on the sign of the charge and the relative humidity of the air. A significant correlation was found between the increase in the penetration and the decrease in breathing resistance while the filter was being loaded.The effect of resuspension (tearing off and re-deposition of dust agglomerates inside the filter) on the filtration process very significant. It was also observed that under certain conditions electrostatic filter materials lost their protection properties. 相似文献
168.
Caitlin D. Kuempel Vivitskaia J. D. Tulloch Alyssa L. Giffin B. Alexander Simmons Valerie Hagger Carol Phua Ove Hoegh-Guldberg 《Conservation biology》2022,36(3):e13856
Conserving coral reefs is critical for maintaining marine biodiversity, protecting coastlines, and supporting livelihoods in many coastal communities. Climate change threatens coral reefs globally, but researchers have identified a portfolio of coral reefs (bioclimatic units [BCUs]) that are relatively less exposed to climate impacts and strongly connected to other coral reef systems. These reefs provide a proactive opportunity to secure a long-term future for coral reefs under climate change. To help guide local management efforts, we quantified marine cumulative human impact (CHI) from climate, marine, and land pressures (2013 and from 2008 to 2013) in BCUs and across countries tasked with BCU management. Additionally, we created a management index based on common management measures and policies for each pressure source (climate, marine, and land) to identify a country's intent and commitment to effectively manage these pressures. Twenty-two countries (79%) had increases in CHI from 2008 to 2013. Climate change pressures had the highest proportional contribution to CHI across all reefs and in all but one country (Singapore), but 18 BCUs (35%) and nine countries containing BCUs (32%) had relatively high land and marine impacts. There was a significant positive relationship between climate impact and the climate management index across countries (R2 = 0.43, p = 0.02), potentially signifying that countries with greater climate impacts are more committed to managing them. However, this trend was driven by climate management intent in Fiji and Bangladesh. Our results can be used to guide future fine-scale analyses, national policies, and local management decisions, and our management indices reveal areas where management components can be improved. Cost-effectively managing local pressures (e.g., fishing and nutrients) in BCUs is essential for building a climate-ready future that benefits coral reefs and people. 相似文献
169.
贵州省务川汞矿区土法炼汞过程中汞释放量的估算 总被引:12,自引:0,他引:12
通过对酸性水溶液、含Fe3+水溶液、含Fe2+水溶液、细菌菌液和细菌培养基水溶液脱除二氧化硫的实验,探讨了微生物液相氧化二氧化硫的途径.以液相中SO42-浓度考察了Fe3+浓度、Fe2+浓度、进口SO2浓度以及温度对脱硫成酸的影响.微生物脱硫有2种机制:一是直接氧化作用,即氧化亚铁硫杆菌(Thiobacillus ferrooxidans)将S(IV)氧化成S(VI);二是间接催化氧化,氧化亚铁硫杆菌在酸性条件下具有快速氧化Fe2+成Fe3+,增强Fe3+对SO2的液相催化氧化能力,研究表明微生物脱硫以间接催化氧化为主.在浓度0~1.2g/L之间,Fe3+和Fe2+浓度越高,脱硫效果越好,氧化亚铁硫杆菌表现出对Fe3+/Fe2+体系氧化SO2的强化效果.入口SO2浓度越高,细菌脱硫效率越低,但液相中SO42-浓度随进口SO2浓度增加变化不大.温度对微生物脱硫影响较大,最佳脱硫温度为30~40℃. 相似文献
170.
Tendencies in plant cover synanthropization depending on the pattern and intensity of anthropogenic impacts on natural complexes have been revealed in specially protected areas of different classes (a nature reserve and a nature park). 相似文献