有机气溶胶对中国境内云凝结核数量的贡献研究

根据κ-K?hler理论, 利用2006年中国境内气溶胶浓度的数值模拟结果, 计算总体气溶胶活化为云凝结核的数浓度, 并评估有机气溶胶对云凝结核数量的贡献。中国境内云凝结核数浓度总体呈东部高西部低的分布, 这与东部受到更多人为源排放影响、气溶胶浓度高有关。假设气溶胶各类化学组分彼此外混合, 则各季节云凝结核数浓度为0.9×10³~1.2×10³ cm^-3, 有机气溶胶对云凝结核数量贡献全年平均为30%。假设气溶胶中有机组分彼此内混合并与其他组分外混合, 则各季节云凝结核数浓度为0.9×10³~1.1×10³cm^-3, 有机气溶胶对云凝结核数量的贡献全年平均28%。尽管有机气溶胶对云凝结核数量的年平均贡献相差不大, 但夏季和冬季的贡献有较大差异, 原因在于夏季有更多的二次有机气溶胶生成, 而冬季更多的是一次有机气溶胶排放。因此, 有机气溶胶是中国云凝结核的重要来源, 并且有机气溶胶的混合状态对云凝结核数量有很大的影响。     

云凝结核数浓度观测影响因子的实验室研究

气溶胶的云滴活化能力影响云的微物理特性, 还表征气溶胶吸湿性的强弱。活化气溶胶(即云凝结核, Cloud Condensation Nuclei, CCN)的观测研究中的重要方法是CCN计数器(CCN Counter, CCNC)的应用。针对CCNC观测的影响因子进行了实验室研究。实验结果表明, CCNC所处的气压和设置的流量会对过饱和比产生等比例的影响, 而进气温度可能导致非线性的影响。实验中发现当气压差超过300 hPa时, CCNC气压调节装置会导致气溶胶的损失, 且损失的比例随着压差的增大而增大。在气溶胶浓度超过10000个/cm³、过饱和比低于0.2%时, 会出现对CCN数浓度的低估, 可能是由于水汽消耗导致CCN无法全部活化而不能被CCNC观测。研究结果及给出的建议对CCN的观测有指导意义, 同时有利于CCN数据的质量控制和分析工作。     

天津郊区夏季气溶胶谱分布特征观测研究

2009年7月11日到8月14日, 在天津市武清区对粒径在0.02~1.00 μm范围内的气溶胶粒子谱分布进行了连续观测。在对气溶胶谱分布资料进行详细统计分析和参数化的基础上, 研究了其日变化规律及其与风速、风向等气象条件的关系。在该粒径范围内, 气溶胶粒子数浓度的平均值为1.7×10⁴cm^-3, 体积浓度的平均值为59 μm³/cm³。气溶胶的数浓度和谱分布具有明显的日变化规律, 粒子数浓度在道路交通的早晚高峰期间和午后太阳辐射最强的时间段出现峰值, 这与道路上机动车的排放和光化学反应中的气?粒转化过程密切相关。局地风速和风向对气溶胶浓度有显著影响。总体而言, 粒子浓度的高值均出现在低风速条件下, 与风向没有明显的依赖关系, 这说明本地源排放是粒子的重要来源。粒子浓度随着风速增加而降低, 且在盛行南风时出现相对高值, 这说明当地受到来自南部较污染地区输送的影响。     

Size distribution and element composition of dust aerosol in Chinese Otindag Sandland

Dust aerosol is one important component of atmos-pheric aerosols, and plays important roles in the Earth’s climate system and the biogeochemical cycle. Large amounts of dust aerosols produced from windblown soils and deserts are emitted annually into the atmosphere and transported over long distance to downwind land and ocean areas[1]. The deserts and desertification soils in northern China are important sources of East Asia dust aerosols. It is estimated that 800 Mt of dust aerosols emit-t…     

土壤质地组分及含水量对小麦禾谷胞囊线虫病发生的影响

在室内条件下研究了5种土壤质地组分和6种土壤含水量对小麦禾谷胞囊线虫病发生的影响.结果表明,纯黏土最不适合小麦胞囊线虫病的发生.在供试的5个土壤质地组分处理中,纯黏土的病情指数最低,其次为黏土∶细沙=3∶1的处理,两个处理病情指数均在25以下;黏土∶细沙=1∶3的处理病情指数最高,其次为纯细沙和黏土∶细沙=1∶1的处理,这3个处理病情指数均在60以上;病株率调查结果表明,纯黏土与黏土∶细沙=3∶1处理病株率较低,均低于70%,黏土∶细沙=1∶3处理、黏土∶细沙=1∶1处理和纯细沙处理的病株率均大于85%,黏土∶细沙=1∶3处理的病株率达到100%,显著高于黏土∶细沙=3∶1处理和黏土处理.研究发现,土壤含水量过高或过低均不适合该病害的发生,在供试的6个土壤含水量处理中,土壤含水体积分数29.74%的处理和4.68%的处理病情指数均低于60;含水体积分数12.78%,14.25%,6.93%处理的病情指数为75～85;含水体积分数9.61%的处理病情指数最高,为88.73,最适于小麦胞囊线虫病的发生.     

厦漳泉地区气溶胶污染特征及影响因素分析

利用卫星Terra和Aqua上搭载的中分辨率成像光谱仪（moderate resolution imaging spectratiometer,MODIS）的气溶胶产品,研究福建省厦漳泉地区气溶胶污染特征和影响因素,并对比了3市气溶胶质量浓度的差异。研究结果表明2002—2017年厦漳泉地区气溶胶质量浓度的变化趋势可以分为三个阶段:一是在2002—2007年呈现平缓的增长;二是在2008—2011年没有明显的变化;三是在2012年之后,气溶胶质量浓度开始出现明显的下降趋势。在16年的时间里,区域平均气溶胶质量浓度减少了5.1 μg/cm2(约为23.10%),说明厦漳泉地区空气质量有较明显的改善。在气溶胶质量浓度较高的厦门市,2012年出现最大值（45.0 μg/cm2）,之后逐渐下降,到2017年（平均值为37.6 μg/cm2）约下降了16.34%。厦漳泉地区气溶胶质量浓度呈现明显的季节变化,最大值出现在4月;5月开始出现较大的下降;秋末冬初出现最低值;12月区域平均值为(18.4±5.2) μg/cm2,但是时间上的波动达到最大,同时空间异质性也很明显。厦漳泉地区气溶胶质量浓度的空间分布异质性明显,在10~85 μg/cm2之间变化。气溶胶质量浓度高值区主要出现在沿海的泉州市、厦门市和漳州市的城区,三个城区的高值分别为85,75,65 μg/cm2,高值区年际间波动较小;而低值区由于受到其他区域的影响,年际间波动较大。     

在特定环境中气溶胶组分光学特性的分析

基于Mie散射的OPAC软件包,分析了在激光雷达探测气溶胶时的3种特定环境(大陆洁净、大陆污染、海上污染)下各种气溶胶组分对光学特性(消光系数、散射系数、吸收系数、激光雷达比)的影响,对比了在550、1 000 nm这2个波长下的变化规律.研究结果表明:在550、1 000 nm这2个波长下不同环境中气溶胶组分的消光系数、散射系数随水滴数浓度的增加均呈线性递增,大陆洁净型和大陆污染型气溶胶环境的吸收系数变化均比较缓慢.在海上污染型气溶胶环境中,当气溶胶组分为积聚模态海盐和粗模态海盐时,水滴数浓度的变化率为0,这表明在这2种气溶胶组分环境下,吸收系数不随水滴数浓度的变化而变化; 激光雷达比受雷达波长和气溶胶环境组分2个因素的影响,该值在大陆污染型气溶胶环境下的变化最为明显,在水溶性和非水溶性组分下大幅递减,而在煤烟组分下大幅递增.     

基于OPAC的典型环境中气溶胶组分的光学特性分析

利用基于Mie散射理论的云和气溶胶粒子的光学特性软件(OPAC)在不同激光雷达探测波段对一般大陆(典型气溶胶组分:水溶性、不溶性和烟尘气溶胶)、沙漠(典型气溶胶组分:水溶性、核模态矿物、积聚模态矿物和粗模态矿物气溶胶)和洁净海洋(典型气溶胶组分:水溶性、积聚模态海盐和粗模态海盐)3种环境下的气溶胶光学参数(散射系数、光学厚度和激光雷达比)进行了仿真研究,分析了各环境中光学参数随气溶胶组分数浓度的变化规律以及各组分对光学特性的影响.结果表明消光系数和光学厚度在不同激光波段、不同环境下均随组分数浓度线性递增,在上述环境中对消光系数和光学厚度影响最大的组分依次为水溶性气溶胶、积聚模态矿物气溶胶和积聚模态海盐气溶胶.激光雷达比变化规律十分复杂,受探测波长及气溶胶组分的双重影响,一般大陆环境中非水溶性气溶胶在2个波段上的影响占主导地位;沙漠环境中,不同波段上积聚模态矿物气溶胶对激光雷达比的影响最大;洁净海洋环境中,积聚模态海盐气溶胶对激光雷达比的影响最强.     

曲轴箱窜气对柴油机尾气微粒排放影响

针对一台2.0 L柴油机搭建了试验台架,通过控制曲轴箱窜气直接排入大气或是引入进气系统,采用尾气粒径谱仪对两种情况相应的尾气微粒数量浓度进行测量,分析比较试验结果来研究曲轴箱窜气对内燃机微粒排放的影响。结果表明:曲轴箱窜气引入进气主要影响柴油机尾气中核模态微粒及100 nm以下集聚态微粒的粒径数量浓度分布,主要表现在高峰峰值的增加和新峰值区域的形成。另一方面,曲轴箱窜气引入进气使柴油机各工况下尾气微粒总数量浓度增加,中、大窜气量工况微粒绝对数量增加明显,增幅分别为44.2%和38.5%。     

垃圾渗滤液处理系统中微生物群落结构变化研究

采用基于PCR的变性梯度凝胶电泳(PCR-DGGE) 和 real-time PCR 方法, 分析了深圳市某垃圾渗滤液处理系统中总细菌和硝化细菌的生物量及群落结构变化, 探究生物量与水质变化间的关系及环境因素对微生物群落结构的影响。结果表明, 该垃圾渗滤液处理系统具有很好的氨氮和总有机碳(TOC) 去除效果, 总去除率分别为 99.9% 和 91.4% 。在垃圾渗滤液处理系统中, 总细菌、氨氧化菌(AOB) 、亚硝酸盐氧化菌(NOB) 的生物量与 TOC 及氨氮浓度没有显著相关性(p > 0. 05); 溶解氧不影响AOB 生物量, 但明显影响NOB 生物量。微生物群落结构及多维尺度(DMS) 分析表明:在该废水处理系统中, DO浓度对总细菌和 NOB 微生物群落结构有重要影响; 而氨氮浓度是影响 AOB 群落结构的关键因素。     

Modern pollen-vegetation relationship based on discriminant analysis across an altitudinal transect on Gongga Mountain, eastern Tibetan Plateau

Quantitative relationship between modern pollen assemblage and altitudinal vegetation belt is crucial for the reconstruction of paleovegetation in the mountain regions.Modern pollen analysis on 70 topsoil samples was conducted across an altitudinal transect(1100-4500 m) on the eastern slope of Gongga Mountain in the eastern Tibetan Plateau with an elevation interval of 50 m.Distributions of major pollen types along the transect indicated a weak correlation between Pinus pollen and the elevation.Distributions of Picea and Abies pollen(percentage sum of 2%-8%) could fairly indicate the elevation range of 2700-3700 m,as well as the subalpine dark coniferous forest and the timberline in the region.High percentage intervals of alpine types of Ericaceae,Cupressaceae and Cyperaceae were correlated to the high-elevation regions(3700-4500 m) dominated by alpine shrub meadow and alpine meadow.Seven altitudinal vegetation belts on the eastern slope of Gongga Mountain were well defined by discriminant analysis conducted on the modern pollen assemblages,as reflected by high values of probability of modern analog.Most of the modern pollen assemblages(88.5%) were typical for the vegetation types at their sampling locations.Thus,the relationship between the modern pollen assemblages and vegetation across the altitudinal transect based on discriminant analysis can be applied to the quantitative reconstruction of paleovegetation changes in the mountain regions of the eastern Tibetan Plateau.     

Evaluation of the effect of air pollution control during the Beijing 2008 Olympic Games using Lidar data

To examine the effect of pollution control measures on Beijing air quality during the 2008 Olympic Games, this paper analyzes the variation of aerosol extinction coefficient observed with a Dual-wavelength Polarized Lidar in Beijing during the Olympic Games. The results show that (1) during the Beijing Olympic Games, the aerosol extinction coefficient decreased to about 42.3% in the surface layer (below 250 m) compared with that in 2007 under almost the same meteorological conditions, indicating the effecti...     

Characteristics of clouds,precipitation, and latent heat in midlatitude frontal system mixed with dust storm from GPM satellite observations and WRF simulations

A heavy dust storm originating in Mongolia and Inner Mongolia traveled to Northeast China and met a midlatitude frontal system on May 3, 2017. The potential ice nuclei (IN) effects of mineral dust aerosols on the vertical structure of clouds, precipitation, and latent heat (LH) were studied using Global Precipitation Mission (GPM) satellite observations and Weather Research and Forecasting (WRF) model simulations. The WRF simulations correctly captured the main features of the system, and the surface rain rate distribution was positively correlated with data retrieved from the GPM Microwave Imager. Moreover, the correlation coefficient increased from 0.31 to 0.54 with increasing moving average window size. The WRF-simulated rainfall vertical profiles are generally comparable to the GPM Dual-Frequency Precipitation Radar (DPR) observations, particularly in low layers. The joint probability distribution functions of the rain rate at different altitudes from the WRF simulation and GPM observations show high positive correlation coefficients of ~0.80, indicating that the assumptions regarding the raindrop size distribution in the WRF model and DPR retrieval were consistent. Atmospheric circulation analysis and aerosol optical depth observations from the Himawari-8 satellite indicated that the dust storm entered only a narrow strip of the northwest edge of the frontal precipitation system. The WRF simulations showed that in carefully selected areas of heavy dust, dust can enhance the heterogeneous ice nucleation process and increase the cloud ice, snowfall, high-altitude precipitation rate, and LH rate in the upper layers. This effect is significant at temperatures of ?15 °C to ?38 °C and requires dust number concentrations exceeding 106 m?3. It is important to accurately classify the dusty region in this type of case study. In the selected vertical cross section, the WRF-simulated and DPR-retrieved LH have comparable vertical shapes and amplitudes. Both results reflect the structure of the tilted frontal surface, with positive LH above it and negative LH below it. The simulated area-averaged LH profiles show positive heating in the entire column, which is a convective-dominated region, and this feature is not significantly affected by dust. DPR-based LH profiles show stratiform-dominated or convective-dominated shapes, depending on the DPR retrieval product.     

Geochemical characteristics and zones of surface snow on east Antarctic Ice Sheet

The surface-snow geochemical characteristics are discussed on the East Antarctic Ice Sheet, depending on the stable isotopes ratios of oxygen and hydrogen, concentration of impurities (soluble-ions and insoluble micro-particle) in surface snow collected on the ice sheet. The purpose is to study geochemical zones on the East Antarctic Ice Sheet and to research sources and transportation route of the water vapor and the impurities in surface snow. It has been found that the ratio coefficients, as S1, d1 in the equation δD =S1δ^18O d1, are changed near the elevation 2000 m on the ice sheet. The weight ratio of Cl^-/Na^ at the area below the elevation of 2000 m is close to the ratio in the sea salt; but it is about 2 times that of the sea salt, at the inland area up to the elevation of 2000 m. The concentrations of non-sea-salt Ca^2 ion (nssCa^2 ) and fine-particle increase at the interior up to the elevation 2000 m. At the region below the elevation of 2000 m, the impurity concentration is decreasing with the elevation increasing. Near coastal region, the surface snow has a high concentration of impurity, where the elevation is below 800 m. Combining the translating processes of water.vapor and impurities, it suggests that the region up to the elevation 2000 m is affected by large-scale circulation with longitude-direction, and that water-vapor and impurities in surface snow come from long sources. The region below the elevation 2000 m is affected by some strong cyclones acting at peripheral region of the ice sheet, and the sources of water and impurities could be at high latitude sea and coast. The area below elevation 800 m is affected by local coastal cyclones.     

Detection of methane plumes in the water column of Losatchev hydrothermal vent field, Mid-Atlantic Ridse

During DY105-17 cruise onboard the PJV ＂Da Yang Yi Hao＂ in 2005, methane concentrations in the water column above Logachev hydrothermal vent field were measured by applying stripping/trapping-gas chromatographic （GC） and the distinct methane plumes were detected. Results show that the background methane concentration within the Logachev area is from 1.05 nmol/L to 1.68 nmol/L, significantly higher than the background level of the Atlantic abyssal plain of 0.4-0.5 nmol/L, suggesting that hydrothermal venting is a major source of dissolved methane to the ocean. The highest anomalies of methane concentrations in the water column range from 7.14 nmol/L to 113.9 nmol/L and occur just at 180-500 m above the seafloor. The distribution of methane concentration and the structural characteristics of hydrothermal plumes are strongly influenced by the supply of underlying hydrothermal fluids, the mixing process of ocean bottom currents and the microbial oxidation. Furthermore, the differences in distribution of methane plume between the station MAR-CTD3 and the other stations indicate a probable unknown hydrothermal vent site nearby. There occurs high concentration of methane along with temperature and nephelometry anomalies, which strongly confirms that the subtle measurement of methane concentration in water column is one of the effective ways to locate active sites of hydrothermal venting.     

Aerosol flotation of low-grade refractory molybdenum ores

The characteristics of aerosol flotation, which include the effect of the concentration and particle size of kerosene aerosol on the molybdenum (Mo) flotation index and the effect of kerosene aerosol dosing method on the kerosene dosage and flotation time, were studied in the flotation of low-grade refractory molybdenum ores using kerosene aerosol. The results revealed that the particle size and concentration of kerosene aerosol had little effect on the Mo grade but had significant effect on the Mo recovery. A smaller particle size and a lower concentration of kerosene aerosol were beneficial to the Mo aerosol flotation. For the received Mo ore samples, the optimized particle size of kerosene aerosol was 0.3-2 μm and the optimized aerosol concentration was 14 mg/L. The compressed air atomizer had a more uniform distribution of aerosol particles than the ultrasonic atomizer, and the aerosol concentration was controlled easily, so the compressed air atomizer was more suitable for the research of aerosol flotation. Compared with conventional flotation in which kerosene was directly added into the ore pulp, the flotation time was reduced by ~30%, and the dosage was decreased by ~20% in aerosol flotation, while the Mo flotation index was similar.     

一种基于虚拟传感的双通道主动降噪方法

在主动噪声控制系统中,有效降噪范围受通道数量的影响很大,传统方式主要是通过增加系统通道数量来扩大有效降噪范围(3 dB以上),成本较高,且对计算能力要求极高.为实现在不增加通道数、误差传感器及扬声器数量的情况下,扩大有效降噪范围,使用了一种基于虚拟误差传感的方法,在FxLMS双通道主动噪声控制系统中研究虚拟传感器设置的位置与有效降噪范围的关系.结果表明:在虚拟传感器设置为不同位置时,有效降噪范围由12 cm增加到26 cm.     

Analysis of variation trends and causes of aerosol optical depth in Shaanxi Province using MODIS data

The temporal and spatial variations and causes of aerosol optical depth （AOD） in Shaanxi Province were investigated based on the Moderate Resolution Imaging Spectroradiometer （MODIS） derived aerosol data for the period of March 2000-February 2012. The results showed that the distribution of aerosol was largely affected by topography and local economic activities. Heavy aero- sol loading and increasing tendency in AOD was observed in Guanzhong, Hanzhong and Ankang basin, while a reverse tendency was revealed in most other regions. The spatial distribution of aerosol Angstrom wavelength exponent was predominantly related to vegetation coverage in Shaanxi. Airborne dust from ground is an important source of coarse mode aerosols. Vegetation im- provement indicated by an increase in normalized difference vegetation index （NDVI） and a reduction in dust weather led to a gradual decrease in coarse mode AOD to the north of Qinling Mountains in Shaanxi, while anthropogenic activities led to an in- crease in fine mode AOD in other areas except those covered by forests. The main aerosol type gradually shifted to the urban industrial type in Shaanxi.     

基于内容流行度的移动CCN缓存策略研究

近年来,为了适应互联网应用由发送者驱动的端到端通信模式向接收者驱动的海量内容获取模式的转变,并从网络体系架构层面提供对可扩展和高效内容获取的原生支持,研究界近年来提出以内容为中心的新型网络(content-centric networking,CCN)体系架构,它能够高效地支持未来互联网上的内容分发.随着移动用户数量的不断增加,未来移动用户也将访问CCN网络,针对内容中心网络中的用户移动性问题,提出了一种基于内容流行度的移动性缓存策略.该策略考虑用户移动性,利用半马尔科夫模型对用户移动性进行建模,同时采用多元线性回归模型对内客流行度进行预测,结合用户移动性与原有内容流行度提出一种移动性缓存策略.仿真实验表明,移动性的加入会对内容的流行度产生较大的影响,该策略能有效地提升缓存命中率.     

含烃废水中硫化物生物氧化的影响因素

采用填充聚氨酯(FPUFS)载体的上流式生物氧化反应器处理含烃废水中的硫化物,考察了曝气量、水力停留时间(HRT)、进水硫化物浓度、pH值和进水石油烃浓度对硫化物生物氧化的影响。结果表明,在曝气量为300mL/min,HRT为90min,进水硫化物浓度<300mg/L,pH值为6.1～7.8的条件下,硫化物去除率在80%以上。在试验考察的石油烃浓度范围内,反应器对总有机碳(TOC)没有明显的去除效果,石油烃对硫化物去除率的影响不超过5%,但硫酸根转化率随石油烃浓度的增加显著下降。