An estimation of present and projected diesel particle evolution over Chigago

The impact of a potential increase in vehicular diesel emissions on atmospheric particle concentrations and size distributions in a large urban area (Chigago) is investigated numerically, for idealized meteorological conditions. Results indicate that the projected increase in diesel emissions would affect mainly the concentrations of particles with diameters smaller than 1 μm; larger particles would not be affected significantly. The particle concentrations in the accumulation mode (diameter near 0.2 μm) would be increased by about a factor of ten, while the concentration of particles of the Aitken nuclei mode (diameter near 0.02 μm) would be reduced significantly. The area in which the annual average air quality particulate standard is exceeded is quite small for the reference case based on emissions in 1983, but would increase to cover almost the entire urban area for the projected increase in diesel emissions in 2000.     

Aerosol particles in the developing world; a comparison between New Delhi in India and Beijing in China

In developing countries, aerosol particles damage the health of hundreds of millions of people. Migration from the country side to megacities increases emissions and exposure to particles. Some countries have started to limit emissions based on particulate mass, but this may increase particle number concentrations. In this study we discuss some earlier measurements carried out in the developing world and compare results from one-week measurement campaigns concerning the particle number size distribution and PM₁₀ mass concentrations in New Delhi, India and Beijing, China. Our results show that submicron particle concentrations are high in both places. The average PM₁₀ concentration was 360 μg/m³ in New Delhi and 120 μg/m³ in Beijing. The corresponding total particle number concentrations in the size range 3–800 nm were 63 000 cm^?3 and 35 000 cm^?3. Number and mass concentrations and their characteristics showed significantly different behaviour between these two locations, which stresses the importance of long-term simultaneous measurements of both quantities in different types of megacities.     

芜湖市区驾校微环境地表灰尘中汞的分布特征及影响因素

为了解驾校不同微环境地表灰尘中Hg的污染情况,使用测汞仪(Hydra II C)测定了芜湖市区26个驾校全粒径和细粒径灰尘样品中Hg的含量,并进行了统计分析。结果表明:芜湖市区驾校地表全粒径和细粒径灰尘中Hg的平均含量分别为49.36,59.97 ng/g,均低于芜湖市土壤背景值,且全粒径与细粒径灰尘中Hg含量存在极显著性差异(P0.01)。对于全粒径灰尘,驾校不同微环境地表灰尘Hg含量呈现出:倒车入库S弯侧方位停车直角转弯坡道定点,细粒径灰尘则表现出:倒车入库S弯侧方位停车坡道定点直角转弯,两者呈现出相似的规律,其中倒车入库、S弯和侧方位停车3个项目细粒径灰尘Hg含量显著高于直角转弯和坡道定点项目(P0.05),倒车入库项目全粒径灰尘Hg含量显著高于坡道定点项目(P0.05)。通过对驾校地表灰尘Hg的影响因素分析,室内驾校全粒径和细粒径灰尘中Hg的平均含量均高于室外驾校,燃气驾校不同微环境地表灰尘Hg的平均含量均高于燃油驾校,且燃油和燃气驾校全粒径地表灰尘Hg含量呈现显著性差异(P0.05);相关性分析发现,对于全粒径与细粒径灰尘,S弯、倒车入库和侧方位停车项目灰尘Hg含量均与教练车密度呈极显著相关,芜湖市区驾校地表灰尘Hg的含量受汽车尾气排放的影响。驾校汽车尾气排放及燃油泄露等导致的Hg污染不容小觑,且存在累积性,教练常年在驾校工作,其健康受到一定威胁,驾校Hg污染需加以重视。     

DOC与POC耦合柴油机燃用调合生物柴油颗粒物的排放特性

在一台高压共轨柴油机上进行燃用调合生物柴油(B0、B10和B20)台架试验,利用MOUDI颗粒分级采样系统和气相色谱-质谱联用仪(GC-MS)分别研究氧化催化器(diesel oxidation catalyst,DOC)结合颗粒氧化催化器(particle oxidation catalyst,POC)对颗粒物的粒径质量浓度分布和可溶性有机组分(SOF)的影响。结果表明:随着生物柴油的掺混比增加,各粒径范围的排气颗粒物质量浓度均下降,质量浓度峰值均在0.18~0.32μm;颗粒物SOF中脂类、酸类质量分数增加,烷烃类、芳香烃、酚类物质质量分数减少;B0和B20的碳原子数质量分数均呈现近似以C16为峰值的正态分布。加装DOC+POC后,3种燃料颗粒物的质量浓度均降低,聚集态颗粒的质量浓度转化率高于粗颗粒态,其中B20聚集态转化率最高,为58.36%;随着生物柴油的掺混比增加,DOC+POC对SOF的转化率增大,其中B20颗粒中SOF转化率达65.15%;DOC+POC对脂类和酸类物质净化作用明显,加装DOC+POC后,B20脂类和酸类物质的质量分数降幅分别为55.45%和43.27%;DOC+POC对B20颗粒物中SOF的C12~C18氧化作用明显。     

不同掺混比例生物柴油的非常规污染物排放特性

为了实现柴油机的清洁燃烧,需要系统研究非常规污染物的生成机理与排放特性。根据羰基类、芳香烃类物质的理化性质特点,提出了柴油机非常规污染物高效快速的测量方法,采用不同掺混比例的生物柴油进行了柴油机台架试验,探讨了不同燃料、不同工况下柴油机非常规污染物的排放特性。结果表明,二硝基苯腙采样结合高效液相色谱技术,可以实现柴油机排气中15种羰基类污染物的快速准确测定,活性炭吸附结合气相色谱-质谱联用技术可以实现芳香烃污染物的定性定量分析;中、低负荷时,生物柴油掺混比例对柴油机总羰基排放的影响不大,随着负荷的增加,BD50（生物柴油和市售0#柴油按体积比1:1配制的调合油）和BD0（纯柴油）的总羰基排放呈升高趋势,BD100（以地沟油为原料的生物柴油）的总羰基排放有所降低;BD0的单环芳香烃最大排放浓度最高,3种燃料的气相多环芳香烃排放在低负荷和高负荷工况点存在"双峰"特征,三环菲约占所有环数多环芳香烃总量的44%,燃用生物柴油可降低柴油机约32%的多环芳香烃排放。该研究为柴油机非常规污染物的排放控制提供了参考。     

重型柴油机颗粒物分布规律的试验研究

为了同时控制车用重型柴油机的颗粒物排放质量和数目,该文对稳态工况及瞬态工况下柴油机排放颗粒物分布规律进行了试验研究。试验结果表明:在稳态工况下,随着负荷的增加或者转速的提高,积聚态及核态颗粒物数目浓度、中位直径(count median diameter,CMD)、表面积和质量均呈现增大趋势,且峰值向大粒径方向偏移。在本研究中,稳态工况全工况总颗粒物数目浓度为1.5×10~6~4.5×10~6个/cm~3,积聚态颗粒物数目浓度为2×10~6~1×10~7个/cm~3,而核态颗粒物数目浓度为1×10~7~3×10~7个/cm~3,在总颗粒物数目浓度中占比为65%~96%。全工况当量比均小于0.7,在中低转速,当量比对颗粒物分布影响较为明显,在高转速尤其是大负荷条件下,当量比的影响减弱。在瞬态工况下,颗粒物数目浓度出现了与颗粒物质量类似的排放尖峰现象,浓度峰值达到2×108~7×108个/cm~3,比其对应的稳态工况出现的浓度峰值高出1个数量级。而且排放尖峰现象中,积聚态颗粒物数目浓度占主要部分,其峰值浓度比稳态工况要高出2个数量级,此时排放尖峰现象中核态颗粒物数目浓度也出现明显增长。排放尖峰现象对应的粒径主要集中在积聚态颗粒物的50~200 nm范围和核态颗粒物的6~8 nm及20~50 nm范围。这主要是因为当量比在瞬态过程出现了超过临界当量比0.8的情况。研究结果对重型柴油机颗粒物排放控制以及生成机理有重要指导意义,并可为排放后处理器的匹配计算提供数据支持。     

Source Apportionment of the Atmospheric Aerosol in Lahore, Pakistan

Samples of airborne particulate matter (PM_2.5) were collected at a site in Lahore, Pakistan from November 2005 to January 2006. A total of 129 samples were collected using an Andersen Reference Ambient Air Sampler 2.5-400 sampler and analyzed for major ions, trace metals, and organic and elemental carbon concentrations. The data set was then analyzed by positive matrix factorization (PMF) to identify the possible sources of the atmospheric PM collected in this urban area. Six factors reproduced the PM_2.5 sample compositions with meaningful physical interpretation of the resolved factors. The sources included secondary PM, diesel emissions, biomass burning, coal combustion, two-stroke vehicle exhaust, and industrial sources. Diesel and two-stroke vehicles contributed about 36%, biomass burning about 15%, and coal combustion sources around 13% of the PM_2.5 mass. Nearly two thirds of the PM_2.5 mass is carbonaceous material. Secondary particles contributed about 30% of PM_2.5 mass. The conditional probability function (CPF) was then used to help identify likely locations of the sources present in this area. CPF analysis point to the east and northeast, which are directions of urban and industrial areas located across the border near Amritsar, India as the most probable source for high PM_2.5 concentration from diesel and two-stroke vehicles exhaust in Lahore. Analysis of those days within three different ranges of PM_2.5 concentration shows that most of the measured high PM_2.5 mass concentrations were driven by diesel and two-stroke vehicle emissions including the associated primary sulfate. The use of the potential source contribution function (PSCF) to find the source locations of regionally transported particles is inapplicable in situations when high PM_2.5 concentrations are dominated by local sources and local meteorology.     

Identification of Fine Particle Sources in Mid-Atlantic US Area

The U.S. Environmental Protection Agency (EPA) designated 20 urban areas including major cities located in mid-Atlantic US area as being in non-attainment of the new national ambient air quality standards for PM_2.5 (particulate matter ≤2.5 μm in aerodynamic diameter). To support the development of effective State Implementation Plans for PM_2.5 in the non-attainment area, 24-h integrated Speciation Trends Networks data collected in the mid-Atlantic US urban area were analyzed through the application of the positive matrix factorization (PMF). A total of 117 to 235 samples and 27 to 29 chemical species collected at the four monitoring sites between 2001 and 2003 were analyzed and six to nine sources were identified. Secondary particles provided the highest contributions to PM_2.5 mass concentrations (38–50% for secondary sulfate; 9–18% for secondary nitrate). Potential source contribution function analyses show the potential source areas and pathways of secondary particles contributing to this region, especially the regional influences of the biogenic as well as anthropogenic secondary particles. Motor vehicle emissions contributed 21–33% to the PM_2.5 mass concentration. In four sites in southern New Jersey and Delaware, gasoline vehicle and diesel emissions were tentatively separated by different abundances of organic and elemental carbons. The compositional profiles for gasoline vehicle and diesel emissions are similar across this area. In addition, other combustion sources, aged sea salt, and intercontinental dust storms were identified.     

柴油-航空煤油宽馏程混合燃料对柴油机燃烧与排放的影响

为了研究柴油-航空煤油宽馏程混合燃料对柴油机燃烧与排放的影响,按照中国3号航空煤油(rocket propellant 3,RP3)的掺混比(体积比)分别为20%、40%与60%与国VI柴油进行混合,配制3种具有不同理化特性的柴油-RP3宽馏程混合燃料(D80K20、D60K40与D40K60),并通过台架试验,研究了最大扭矩转速2700 r/min所对应的100%、50%与10%负荷工况(分别记为A、B、C工况)下,D100、D80K20、D60K40和D40K60对柴油机缸内工作过程、排放、颗粒物浓度与粒径分布的影响规律。结果表明,3种工况下,与D100相比,RP3掺混比增加到60%时,缸内最大压力的变化范围小于0.2 MPa,预混燃烧放热率峰值增大13.21~27.43 J/°CA,滞燃期延长2.19~2.53°CA,燃烧持续期缩短1.73~1.91°CA,预混燃烧累积放热百分比增加4.66%~5.28%,缸内最高温度的上升幅度小于35 K,与放热率峰值和最大燃烧压力相对应的曲轴转角后移1.67~2.23°CA,有效热效率上升0.15%~0.46%。柴油-RP3宽馏程混合燃料能够显著降低柴油机碳烟排放,并且降低效果随着柴油机负荷的增加和RP3掺混比的增大更加明显,但对NOX排放没有明显的影响,与D100相比,柴油机在3种工况下燃用D40K60时的碳烟排放分别降低53.6%、44.1%、35%,NOX排放的上升幅度均小于2%,核态颗粒物数量浓度上升12.5%~90.6%,积聚态颗粒物数量浓度、颗粒物总数量浓度、颗粒物表面积浓度和总质量浓度分别降低20.1%~45.8%、14.2%~42.1%、32.5%~41.6%、28.5%~38.8%,且积聚态颗粒物的粒径朝小粒径方向移动。试验结果表明,柴油-RP3宽馏程混合燃料对柴油机燃烧与排放有重要的影响,能明显改善柴油机碳烟与NOX排放之间的trade-off关系,并且在降低柴油机颗粒物总数量浓度、总质量浓度以及表面积浓度方面具有较为显著的效果,有利于降低柴油机DFP载体上的颗粒物堆积、延长DFP再生周期。     

甲醇-调合生物柴油燃烧及排放微粒粒径分布特性试验

为了探究调合生物柴油掺烧甲醇对柴油机燃烧特性及微粒粒径分布的影响,该文利用燃烧分析仪及EEPS 3090型微粒粒径测试系统研究了柴油机燃用甲醇-调合生物柴油微乳化燃料的燃烧过程及微粒数量浓度分布特性。试验结果表明,与燃用调合生物柴油相比,柴油机掺烧甲醇后缸内燃烧压力、压力升高率以及放热率曲线均后移,压力升高率峰值及放热率峰值均增加;当柴油机处于低负荷时,排气中的微粒粒径均处于6~22 nm之间,呈现核态;在高负荷时,微粒粒径处于6~275 nm之间,主要呈现积聚态,且数量浓度呈单峰正态分布。随着甲醇添加比例的增加,核态微粒比例上升,积聚态微粒比例下降,且排气中微粒的总数下降。研究结果为甲醇-生物柴油混合燃料的燃烧及微粒排放控制提供了参考。     

Polycyclic Aromatic Hydrocarbons and their Molecular Diagnostic Ratios in Airborne Particles (PM10) Collected in Rio de Janeiro, Brazil

Atmospheric polycyclic aromatic hydrocarbons (PAHs) were determined in particulate matter (PM10) collected in a suburban area with industrial and vehicular emissions in the Metropolitan Area of Rio de Janeiro City (Brazil). A total of 22 samples were collected between March and August 2005 by means of a high volume PM10 sampler. The particulate matter contained in the filters was extracted ultrasonically with dichloromethane. The extracts were later analyzed by gas chromatography coupled to a mass spectrometer (GC/MS). The individual concentrations of PAHs ranged between the detection limit and 0.386 ng m^?3. The PAHs concentrations observed in this study were towards the lowest end of the range of values reported for other European locations and also lower than values obtained for South America. PAHs concentrations and molecular ratios showed that light cars seem to be the main contributors to PM10 emissions, but diesel vehicles are clearly minor emission sources and industrial contributions should not be disregarded until more data are obtained.     

纳米CeO2催化剂对柴油机碳烟颗粒和NO降低效果

为采取后处理技术同时控制柴油机颗粒(PM)和一氧化氮(NO)排放,该研究采用沉淀法制备了3组纳米二氧化铈(CeO_2)催化剂,通过X射线衍射(XRD)法、BET法测比表面积与孔径、氢气程序升温还原法(H2-TPR)对其性能进行表征,并利用碳烟起燃温度和峰值温度以及NO向N_2的转化率分别对催化剂进行活性评价。试验结果表明:3组制备的CeO_2催化剂平均粒径依次为7、12和20 nm,明显小于商业级CeO_2;自制CeO_2相较于商业级CeO_2具有较大的比表面积,且比表面积越大催化活性越高;自制的CeO_2有3个较明显的H2还原峰,依次对应表面吸附氧、表面晶格氧以及体相晶格氧;CeO_2对碳烟颗粒催化氧化的效率由高到低依次为20、12和7 nm,这3组CeO_2催化剂较未添加催化剂时起燃温度依次降低了124,109,93℃,峰值温度依次降低了185,104,102℃;CeO_2对NO转化率最高可以达到70%,且温度窗口比较宽。研究结果对CeO_2在排放后处理领域的应用具有指导意义。     

Monitoring of Submicron Particulate Matter Concentrations in the Air of Turin City, Italy. Influence of Traffic-limitations

Several studies have shown the association between ambient particulate matter (PM) and adverse health effects, thus highlighting the need to limit the anthropogenic sources of PM, especially motor vehicle emissions. PM exposure is commonly monitored as mass concentration of PM10 or PM2.5, although increasing toxicity with decreasing aerodynamic diameter has been reported. In the present study an analysis was performed of the concentration and size distribution of airborne PM fractions collected at street level in the city center of Turin, Italy, to verify the usefulness of “ecological” days with traffic limitations. PM levels were determined daily at five different outdoor sites, from Thursday to Tuesday for 7 weeks (five with “ecological” Sunday, two with normal traffic density). Air sampling was performed using a six-channel laser particle counter to determine the number of particles (n°/l) in six size ranges between 0.3 and 10 μm. Climatic conditions and indoor PM levels were also monitored. The PM size distribution was constant for all the samples tested, with the 90% of the particles smaller than 0.5 μm, suggesting that measurements for count are needed in addition to the traditional ones based on the mass. The total number of particles was highly variable comparing days or weeks of monitoring, but much less among the sites of air sampling. The restriction of motor vehicle circulation has not determined any significant effect on PM levels and, in the winter period, PM0.5 peak concentrations were measured also on the ecological days.     

柴油机燃烧甲醇/生物柴油尾气颗粒物热解特性分析

采集了甲醇/生物柴油(5%、10%、15%)混合燃料在柴油机燃烧的尾气颗粒。采用热重分析仪和切线法、Flynn-Wall-Ozawa(FWO)热解动力学方法,研究颗粒挥发及氧化规律,分析了颗粒热解特征温度和活化能。结果表明:随着甲醇掺混量的增加,颗粒中H_2O的质量分数由2.6%增加到3.5%,可溶有机物(soluble organic fraction,SOF)质量分数由26.1%增加到32.5%,SOF的质量变化速率增大,对应的峰值温度后移;在O_2氛围中,SOF挥发阶段与在N2氛围中的表现基本一致,但质量变化速率明显增大;碳烟(soot)质量减小,由70.3%减少到63.8%,soot质量变化率峰值增大;SOF析出温度变化较小,soot起始燃烧温度明显降低,由488℃降低到458℃,SOF起始燃烧温度与燃尽温度均有所降低,颗粒的热解总反应时间缩短;颗粒的热解反应活化能由140.3 k J/mol降低117.3 k J/mol,颗粒的热解性能增强,颗粒更易被氧化。研究结果可为甲醇/生物柴油燃烧颗粒的处理及柴油机颗粒捕集器(diesel particulate filter,DPF)再生提供依据。     

Urban-Scale Seasonal and Spatial Variability of Ultrafine Particle Number Concentrations

In epidemiological studies, ultrafine particle (UFP) data from a single monitoring site are generally used as a measure of population exposure potentially resulting in exposure misclassification. From August 2009 to October 2010, 1-week campaigns were conducted during each season. The temporal and spatial variations of UFP number size distributions were investigated at 12 monitoring sites distributed across a 9?×?9?km urban area in Rochester, New York using a Fast Mobility Particle Sizer^TM spectrometer. The overall average number concentrations of 5.6- to 560-nm particles in summer, winter, spring, and fall were 9,025, 10,939, 4,955, and 14,485?cm^?3, respectively. Coefficients of divergence and correlation coefficients were calculated between site pairs to assess the spatial heterogeneity in the particle number size distributions. Moderate spatial divergence and uniform temporal variation were found for the chosen sites. Elevated UFP number concentrations were observed near highways, off-road diesel engines, and residential wood combustion sources, indicating significant contributions to the UFP exposure of people living adjacent to these sources. Our results suggest that one stationary monitoring site may not represent the actual human UFP exposure over a whole urban area.     

农用柴油机的DPF再生条件与排放性能智能多目标优化

为提升农用柴油机的DPF再生性能、排放和燃油经济性,提出了基于增强循环训练的智能多目标优化方法。通过BP神经网络构建了DPF再生条件预测模型,并提出AMSO算法提高预测精度。基于NSGA-III对多个控制参数进行优化,并通过稳态和WHTC瞬态循环试验验证。结果表明：在稳态试验验证中,优化后DPF入口和出口温度平均增加了6.10%和2.90%,O₂浓度增加了18.86%,同时,NO_x、烟度和BSFC的平均降低分别为10.72%、11.48%和0.24%,确保了DPF的高效安全再生。在瞬态测试验证中,DOC入口温度、DPF入口温度和O₂浓度明显改善,分别增加了31.00%、2.60%和0.50%,同时,NO_x和烟度排放分别降低了10.40%和0.80%,燃油消耗减少了3.5%。证明了提出的优化方法解决了农用柴油机DPF再生与排放优化问题,为柴油机再生模式下控制参数优化提供指导。     

Heavy Metals and Polycyclic Aromatic Hydrocarbons (PAHs) in a Rural Community Leewards of a Waste Incineration Plant

In a rural community (Stephanskirchen, Southern Germany) near a waste incineration plant 7 soils, sewage sludge, waste incineration residues, the gutter sediment of a family home, and mosses were sampled to determine the total concentrations of Cd, Pb, Zn and 20 PAHs. Representative samples were used to measure NH₄NO₃- and EDTA-extractable Cd, Pb, and Zn as well as 20 PAHs in particle size separates (clay, silt, fine and coarse sand). Sites near the main road, hill top, and forested sites contain up to 1.24 mg Cd, 888 mg Pb, and 279 mg Zn per kg. The heavy metal concentrations of the sewage sludge, the gutter sediment, and especially the waste incineration residues are extremely high (up to 57 mg Cd, 3300 mg Pb, and 5700 mg Zn per kg). The extractability of Pb and Zn with NH₄NO₃ is low (< 5%), that with EDTA is high (up to 71.2% of total Cd, 82.5% of total Pb, and 47.2% of total Zn). The sum concentrations of PAHs range between 0.4 and 470 mg kg^?1. The silt has the highest PAH concentrations of the particle size separates. High saturation of organic matter with PAHs in the sand indicates high recent PAH deposition. Selected ratios of single PAHs reveal diesel and gasoline exhausts as main sources for PAH. Principal component and cluster analysis show that the pollutant pattern depends on the C_org concentration and on the time passed since deposition. There is no significant influence of the waste incineration emissions on the heavy metal and PAH concentrations.     

高原缺氧环境下生物质燃料对柴油机性能和排放的影响

为了研究不同类别的含氧生物质燃料在高原缺氧环境下对发动机性能和排放的影响,在一台卧式双缸柴油机上分别燃用柴油、乙醇柴油E10(含10%体积分数的乙醇和90%体积分数的柴油)及生物柴油-乙醇-柴油B10E10(含10%体积分数的生物柴油,10%体积分数的乙醇和80%体积分数的柴油)3种燃料进行了对比试验。试验结果表明,在不对柴油机做任何调整的情况下,分别燃用E10和B10E10 2种含氧生物质混合燃料后,柴油机动力性下降,外特性转矩平均下降幅度分别达到4.24%和5.49%;当量燃油消耗率基本低于柴油,经济性有所改善。燃用含氧生物质燃料后,柴油机的经济性变化情况除了与燃料本身的属性相关,还与转速和负荷相关。燃用E10混合燃料后,柴油机的一氧化碳(CO)排放在低负荷时高于柴油,高负荷时低于柴油;碳氢化合物(HC)排放高于柴油水平,升高幅度范围达4.9%~27.4%;氮氧化物(NOX)排放在低负荷时低于柴油,高负荷时趋于柴油水平。燃用B10E10混合燃料后,一氧化碳(CO)和碳氢化合物(HC)排放在低负荷时都趋于柴油水平,高负荷时都低于柴油水平;氮氧化物(NOX)排放在低负荷时低于柴油,高负荷时高于柴油水平。柴油机在燃用E10和B10E10 2种混合燃料后,碳烟排放均低于柴油水平。柴油机燃用B10E10混合燃料后的碳氢化合物(HC)排放,碳烟排放以及低负荷时的一氧化碳(CO)排放均低于E10,氮氧化物(NOX)排放基本高于E10。与E10燃料相比,B10E10混合燃料在柴油机的一氧化碳(CO)和碳氢化合物(HC)以及碳烟排放方面具有更好的改善效果;但是动力性下降幅度较大,氮氧化物(NOX)排放增加。该研究可为含氧生物质燃料在高原缺氧地区的应用提供参考。     

粒径对冻融过程中加氮灌溉土壤N2O排放的影响

通过室内模拟的方法,研究了冻融过程潮土两种粒径（1 cm和0.25 mm）在加氮灌溉条件下N2O的排放通量,并且分析比较了3种氮素形态（铵态氮、硝态氮和酰胺态氮）和3种浓度（40、200和800 mg/L）对土壤N2O的排放通量的影响。结果表明：冻结前,除硝态氮浓度在大于200 mg/L时,细土N2O排放通量小于粗粒径土壤,其他氮素形态和浓度得到相反结果;冻结过程细土达到N2O稳定排放通量的时间要早于粗粒径土壤;融化后细土比粗粒径土壤早出现N2O排放峰,并且该峰值总体比粗粒径土壤小;随氮素浓度增加,粗粒径土壤3种氮素形态平均N2O累积排放量分别比细粒径土壤多45.46%、7.81%和46.87%。建议土壤在加氮灌溉时应尽量避免施加硝态氮肥,铵态氮肥的施用应尽量考虑降低浓度,并建议在灌溉越冬水且土壤冻结后耙碎大土块以减少N2O排放。     

废气再循技术对正丁醇/柴油燃烧颗粒结构及分形特征的影响

为深入了解添加含氧燃料和废气再循环技术(exhaust gas recirculation,EGR)共同作用对颗粒结构及分形特征的影响,运用颗粒分级采样装置采集了EGR率分别为0、10%、20%时,柴油机燃用正丁醇质量百分比为10%的正丁醇/柴油混合燃料(N10)的燃烧颗粒(N10EGR0、N10EGR10%、N10EGR20%),通过电镜试验和图像处理技术,开展了不同EGR率对正丁醇/柴油燃烧颗粒的影响研究,分析了颗粒群的微观结构、平均粒径、分形维数,基本碳粒子的层面间距、微晶尺寸等物理结构参数的变化规律,结果表明,N10EGR0、N10EGR10%、N10EGR20%燃烧颗粒群整体呈现团簇状结构,颗粒粒径范围主要集中在30~70 nm之间,呈正态单峰分布;随着EGR率的增加,粒径范围向大粒径方向移动,平均粒径逐渐增大,N10EGR20%与N10EGR0相比,平均粒径增大约为19%;计盒维数逐渐减小,表明颗粒间的团簇程度逐渐减弱。不同EGR条件下的基本碳粒子结构相似,呈指纹状球形碳层结构,随EGR率的增加,基本碳粒子的内核碳层排列无序性和外壳石墨晶体结构无规则性增强,平均层面间距和弯曲度逐渐增大,微晶尺寸逐渐减小。该研究为含氧燃料与EGR共同作用对颗粒的形成机理以及降低柴油机颗粒排放的措施提供理论参考。