四川盆地一次当地排放和沙尘输送双重影响的区域空气重污染过程研究

针对四川盆地大气污染及其成因的特殊性,本文使用四川盆地18个城市的大气污染监测和气象观测数据以及NCEP1°×1再分析资料,对2017年12月19日～2018年1月3日四川盆地由当地过量排放和外来沙尘输送双重影响的区域性大气污染过程进行分析。结果表明：2017年12月19～28日四川盆地环流场配置不利大气污染物扩散,垂直温度层结稳定,在当地污染源持续排放下污染物浓度缓慢上升,此阶段为静稳型大气污染。之后29日冷空气过程打破前期不利污染物扩散的环流场及垂直温度层结,导致气态污染物下降明显,但伴随冷空气活动的外来沙尘使PM10浓度迅速增大,使四川盆地部分城市出现沙尘型重污染;特别是广元地区受沙尘直接影响最严重,PM10浓度是原来的4.5倍;成都市虽没有通过沙尘天气的表观判断,但对颗粒物离子浓度和化学组分都有显著影响;因此,当时PM10和CO浓度24h比值变化受沙尘输送和天气条件共同影响,在不同时段和地区都存在明显差异,初步揭示出由静稳型大气污染向沙尘型污染转换阶段的内在变化特征,具有重要科学价值。     

塔克拉玛干沙漠与撒哈拉沙漠沙尘气溶胶光学特性对比研究

基于2007—2021年CALIPSO和MODIS主、被动卫星遥感探测数据,对塔克拉玛干沙漠和撒哈拉沙漠的气溶胶光学特性时空分布特征进行探究及对比分析。结果表明：（1）两大沙漠的沙尘气溶胶对总气溶胶的贡献率最大,气溶胶类型季节变化的相对单一性反映了塔克拉玛干沙漠和撒哈拉沙漠地区存在沙漠沙尘排放对总气溶胶成分的显著影响;（2）塔克拉玛干沙漠气溶胶光学厚度AOD的峰值出现在春季（春季>夏季>秋季>冬季）,而撒哈拉沙漠AOD的峰值出现在夏季（夏季>春季>秋季>冬季）;（3）撒哈拉沙漠总气溶胶抬升高度与塔克拉玛干沙漠相近,但近地面层消光系数明显小于塔克拉玛干沙漠;塔克拉玛干沙漠的消光系数平均值在所有季节中均大于撒哈拉沙漠,故塔克拉玛干沙漠的沙尘气溶胶AOD比撒哈拉沙漠的大;相比沙漠沙尘气溶胶,塔克拉玛干沙漠和撒哈拉沙漠都无明显的污染沙尘和抬升烟活动。上述研究结果揭示了两大沙漠源区沙尘气溶胶光学特性的观测事实与利用大气气溶胶时空变化特征反映区域气候变化的可能性。     

沙尘暴天气的成因及其天气形势分析

对我国北方及我省沙尘暴天气发生的机制及其相应的天气形势进行了分析,揭示了沙尘暴天气发生、发展的规律以及在具体预报中的着眼点。     

生物活性元素Fe来源及其溶解度影响因素研究综述

具有生物活性的元素Fe被认为限制了海洋生物生产力,其在海洋生态系统中的生物地球化学循环对全球碳循环起到调节作用,全球40％～50％的海洋因“高叶绿素低营养盐”(HNLC)“缺Fe”而初级生产力较低.然而,关于生物活性元素Fe的研究不仅涉及海洋科学,还与大气科学、环境科学、地球科学等学科紧密联系.近些年,围绕生物活性元素“Fe”开展的研究不仅是地球科学领域的前沿问题,还是海洋学家与环境学家共同关注的热点问题.目前,尽管对于生物活性元素Fe的研究已取得很大的进展,但模型、室内实验及野外观测之间仍存在很大的挑战与不确定性.系统地总结了生物活性元素Fe最重要的自然来源方式,详细介绍了影响生物活性元素Fe溶解度的主要因素,最后,对将来的工作提出建议,为我国未来开展类似的研究提供参考.     

辽东永宁组(群)沉积特征

通过对永宁组沉积序列、沉积特征、沉积环境等研究认为永宁盆地基本保持了原始面貌,为一东高西低的箕形盆地,物源分别由东西侧注入。永宁组沉积前,辽东古陆可能还存在同辽西杨庄组、雾迷山组相当的层位。永宁组主要为河流－冲积扇沉积体系,其中又包含有泥石流、颗粒流、片流、主河道、分枝河道等相体。永宁组是多个扇体相叠加而成的产物,每个大的砾岩层均可代表一次大的洪水事件     

浑善达克沙地起沙率和起沙量的估计

利用起沙通量模式和地面起尘半经验方案,估算了浑善达克沙地春季地表的临界起沙风速及沙尘天气期间的起沙通量,以及地面尘排放总量及其平均年增长率。计算结果表明,浑善达克沙地2001年春季地表临界起沙风速为5.61 m.s-1,沙尘天气期间平均起沙通量为4.40×10-7g.cm-2.s-1;1999年该沙区起尘量约占我国北方起尘总量的2.4%,春季起尘占全年的57%;1986年和1999年起沙总量分别为3.73×105t.a-1和4.87×105t.a-1,其平均年增长率为2.07%。     

In situ observation of penetration process in silica aerogel: Deceleration mechanism of hard spherical projectiles

A large number of cometary dust particles were captured with low-density silica aerogels by NASA’s Stardust Mission. Knowledge of the details of the capture mechanism of hypervelocity particles in silica aerogel is needed in order to correctly derive the original particle features from impact tracks. However, the mechanism has not been fully understood yet. We shot hard spherical projectiles of several different materials into silica aerogel of density 60 mg cm⁻³ and observed their penetration processes using an image converter or a high-speed video camera. In order to observe the deceleration of projectiles clearly, we carried out impact experiments at two velocity ranges; ∼4 km s⁻¹ and ∼200 m s⁻¹. From the movies we took, it was indicated that the projectiles were decelerated by hydrodynamic force which was proportional to v² (v: projectile velocity) during the faster penetration process (∼4 km s⁻¹) and they were merely overcoming the aerogel crushing strength during the slower penetration process (∼200 m s⁻¹). We applied these deceleration mechanisms for whole capture process to calculate the track length. Our model well explains the track length in the experimental data set by Burchell et al. (Burchell, M.J., Creighton, J.A., Cole, M.J., Mann, J., Kearsley, A.T. [2001]. Meteorit. Planet. Sci. 36, 209-221).     

Electrical stress and strain in lunar regolith simulants

Experiments to entrain dust with electrostatic and fluid-dynamic forces result in particulate clouds of aggregates rather than individual dust grains. This is explained within the framework of Griffith-flaw theory regarding the comminution/breakage of weak solids. Physical and electrical inhomogeneities in powders are equivalent to microcracks in solids insofar as they facilitate failure at stress risers. Electrical charging of powders induces bulk sample stresses similar to mechanical stresses experienced by strong solids, depending on the nature of the charging. A powder mass therefore “breaks” into clumps rather than separating into individual dust particles. This contrasts with the expectation that electrical forces on the Moon will eject a submicron population of dust from the regolith into the exosphere. A lunar regolith will contain physical and electrostatic inhomogeneities similar to those in most charged powders.     

R-band light curve of Comet 9P/Tempel 1 during the Deep Impact event

We present high-speed CCD photometry of Comet 9P/Tempel 1 during the Deep Impact event on 2005 July 4 UT. Approximately 2 h and 50 min of R-band data were acquired at Mount Laguna Observatory with a temporal resolution of 5.5 s. The flux increased by 9% in the first minute after impact. This was followed by a more gradual two-part linear rise, with a change in slope at 9.2 min post-impact, at which time the rate of brightening increased from ∼ to ∼. An analysis of the light curve obtained with the guide camera on the United Kingdom Infrared Telescope and yields very similar results. These findings are mildly in disagreement with the 3-part linear rise found by Fernández et al. (2007) in that we do not find any evidence for a change at 4 min post-impact. We interpret the linear rise phase as due to solar illumination of the edge of an expanding optically thick dust ejecta plume. After approximately 20 min, the light curves begin to flatten out, perhaps coincident with the start of the transition to becoming optically thin. In the large apertures (>10^″) the light curve continues to gradually rise until the end of the observations. In smaller apertures, the light curves reach a peak at approximately 50 min, then decrease back towards the pre-impact flux level. The drop in flux in the smaller apertures may be caused by the ejecta expanding beyond the edge of the photometric aperture, and if so, we can use this timescale to infer an expansion velocity of ∼, consistent with previous published estimates.     

利用多通道MODIS遥感资料反演沙尘气溶胶尺度分布的个例试验

为了利用水面进行大气气溶胶粒子尺度分布的反演,需要水体光谱反射率资料;本文利用水库上空MODIS观测的表观反射率资料来订正出实际的水体光谱反射率。假设在干旱的春季水库水面反射率变化不大,用订正的水库水面光谱反射率平均值进行大气气溶胶尺度分布的反演。从两天个例研究来看,利用多通道MODIS资料可以反演出大气气溶胶粒子的尺度变化。结合天气分析2002年4月11日水库上空气溶胶光学厚度增加、粒子变粗,是由于上游区域的沙尘在高空强西北气流引导下到达本地区。