Vertical structures of PM10 and PM 2.5 and their dynamical character in low atmosphere in Beijing urban areas

The vertical structures and their dynamical character of PM2.5 and PM10 over Beijing urban areas are revealed using the 1 min mean continuous mass concentration data of PM2.5 and PM10 at 8, 100, and 320 m heights of the meteorological observation tower of 325 m at Institute of Atmospheric Physics, Chinese Academy of Sciences (IAP CAS tower hereafter) on 10―26 August, 2003, as well as the daily mean mass concentration data of PM2.5 and PM10 and the continuous data of CO and NO2 at 8, 100 (low layer), 200 (middle layer), and 320 m (high layer) heights, in combination with the same period meteorological field observation data of the meteorological tower. The vertical distributions of aerosols observed on IAP CAS tower in Beijing can be roughly divided into two patterns: gradually and rapidly decreasing patterns, I.e. The vertical distribution of aerosols in calm weather or on pollution day belongs to the gradually decreasing pattern, while one on clean day or weak cold air day belongs to the rapidly decreasing pattern. The vertical distributive characters of aerosols were closely related with the dynamical/thermal structure and turbulence character of the atmosphere boundary layer. On the clean day, the low layer PM2.5 and PM10 concentrations were close to those at 8 m height, while the concentrations rapidly decreased at the high layer, and their values were only one half of those at 8 m, especially, the concentration of PM2.5 dropped even more. On the clean day, there existed stronger turbulence below 150 m, aerosols were well mixed, but blocked by the more stronger inversion layer aloft, and meanwhile, at various heights, especially in the high layer, the horizontal wind speed was larger, resulting in the rapid decrease of aerosol concentration, I.e. Resulting in the obvious vertical difference of aerosol concentrations between the low and high layers. On the pollution day, the concentrations of PM2.5 and PM10 at the low, middle, and high layers dropped successively by, on average, about 10% for each layer in comparison with those at 8 m height. On pollution days, in company with the low wind speed, there existed two shallow inversion layers in the boundary layer, but aerosols might be, to some extent, mixed below the inversion layer, therefore, on the pollution day the concentrations of PM2.5 and PM10 dropped with height slowly; and the observational results also show that the concentrations at 320 m height were obviously high under SW and SE winds, but at other heights, the concentrations were not correlated with wind directions. The computational results of footprint analysis suggest that this was due to the fact that the 320 m height was impacted by the pollutants transfer of southerly flow from the southern peripheral heavier polluted areas, such as Baoding, and Shijiazhuang of Hebei Province, Tianjin, and Shandong Province, etc., while the low layer was only affected by Beijing's local pollution source. The computational results of power spectra and periods preliminarily reveal that under the condition of calm weather, the periods of PM10 concentration at various heights of the tower were on the order of minutes, while in cases of larger wind speed, the concentrations of PM2.5 and PM10 at 320 m height not only had the short periods of minute-order, but also the longer periods of hour order. Consistent with the conclusion previously drawn by Ding et al., that air pollutants at different heights and at different sites in Beijing had the character of "in-phase" variation, was also observed for the diurnal variation and mean diurnal variation of PM2.5 and PM10 at various heights of the tower in this experiment, again confirming the "in-phase" temporal/spatial distributive character of air pollutants in the urban canopy of Beijing. The gentle double-peak character of the mean diurnal variation of PM2.5 and PM10 was closely related with the evident/similar diurnal variation of turbulent momentum fluxes, sensible heat fluxes, and turbulent kinetic energy at various heights in the urban canopy. Besides, under the condition of calm weather, the concentration of PM2.5 and PM10 declined with height slowly, it was 90% of 8 m concentration at the low layer, a little lesser than 90% at the middle layer, and 80% at the high layer, respectively. Under the condition of weak cold air weather, the concentration remarkably dropped with height, it was 70% of 8 m concentration at the low layer, and 20%―30% at the middle and high layers, especially the concentration of PM2.5 was even lower.     

Uncertainty analysis of CO_2 flux components in subtropical evergreen coniferous plantation

We present an uncertainty analysis of ecological process parameters and CO2 flux components (Reco, NEE and gross ecosystem exchange (GEE)) derived from 3 years’ continuous eddy covariance meas-urements of CO2 fluxes at subtropical evergreen coniferous plantation, Qianyanzhou of ChinaFlux. Daily-differencing approach was used to analyze the random error of CO2 fluxes measurements and bootstrapping method was used to quantify the uncertainties of three CO2 flux components. In addition, we evaluated different ...     

日本虎斑猛水蚤在抑食金球藻中存活、发育和繁殖的实验研究

抑食金球藻(Aureococus anophagefferens)可以形成褐潮, 并对贝类、浮游动物等多种生物均能造成不利影响。为进一步探究抑食金球藻对浮游动物的影响, 本文以日本虎斑猛水蚤(Tigriopus japonicus)为实验生物, 研究抑食金球藻对日本虎斑猛水蚤摄食、存活、生长发育以及繁殖的影响。日本虎斑猛水蚤具有易于在实验室培养、生长周期短、雌雄异体等优点, 是海洋毒性污染物检测的模式生物。实验利用高效液相色谱分析方法, 在日本虎斑猛水蚤体内色素中检测到了抑食金球藻的特征色素19’-丁酰氧基岩藻黄素(But-fuco), 表明日本虎斑猛水蚤能够摄食抑食金球藻。当微藻生物量(相对碳含量)分别同为0.7 μg/mL和7.2 μg/mL时, 在抑食金球藻中无节幼体发育至桡足幼体及成体的存活率均高于以青岛大扁藻为饵料的对照组, 但无显著差异, 并且在前者中无节幼体的发育时间显著低于后者, 12 d内雌体的产卵次数与产卵量显著高于后者。结果表明, 日本虎斑猛水蚤在抑食金球藻中能进行正常的生命活动, 并且是首次报导的一种能够在抑食金球藻中正常摄食、生存、生长发育和繁殖的浮游动物。因此, 当褐潮发生时, 由于贝类幼体等生物会受到显著的不利影响, 日本虎斑猛水蚤等抗性较强的生物可能会成为优势种, 从而会影响浮游动物群落结构的组成, 进而可能会使整个海洋生态系统发生变化。本研究有助于全面了解褐潮对海洋生态系统的影响。     

台阶式沉井等效墩宽计算方法探究

桥梁工程中存在形状各异的桥墩,在研究不同截面桥墩的局部冲刷特性时,桥墩尺寸的定量描述非常重要。以台阶式沉井结构为研究对象,梳理并分析了国内外相关等效桥墩宽度计算方法,发现各类公式本质上为计算不同条件下的桥墩平均阻水宽度。开展了台阶式沉井局部冲刷试验研究,基于试验数据对比分析了各类等效墩宽计算方法的计算结果,发现Melville和Raudkivi的等效墩宽计算公式能够较好地估算考虑动床条件下台阶式沉井的平均阻水宽度;进一步收集了国内外193组台阶式沉井类结构的局部冲刷试验数据,数据集统计分析结果显示Melville和Randkivi的等效墩宽计算公式能够较为准确且保守地量化大多数台阶式沉井类结构的截面非均匀性;最后基于数据集冲深墩宽比统计结果对该公式近似方法的合理性进行了讨论。     

多连通域浮式平台波浪载荷水池模型试验研究

大型多连通域浮式平台的典型代表是大型海上旅游浮式综合体,依据概念设计,开展大型多连通域浮式平台的波浪载荷水池模型试验研究,试验对不同海况下4种典型多连通域浮式平台方案进行波浪载荷测量,包括剖面的垂向弯矩、水平弯矩和扭矩等,通过观察试验现象和分析测量数据,获得了不同方案大型多连通域浮式平台的波浪载荷特性。试验结果表明：由于平台质量大、振动阻尼大,所以高频载荷成分小;平台在自由状态下载荷值基本都小于平台只释放垂荡状态载荷值;在方案四高波高状态下,平台波浪载荷的高频成分包含了波浪的非线性、约束柱与平台之间的耦合、平台自身的高频振动等。研究成果可为大型海上旅游浮式综合体的结构设计提供设计载荷输入,支撑平台的强度校核评估。     

The Ulva prolifera genome reveals the mechanism of green tides

The genome of green microalgae has rarely been reported. Ulva prolifera is a green microalga that has received much attention. Despite research articles about U...     

内蒙古典型草原和草甸草原相对花粉产量重估

相对花粉产量（RPP）是利用地层花粉数据定量重建古植被的重要参数,但目前估算的不同地区同一植物类型的RPP多存在差异。为了解植被盖度计算方法对花粉产量的影响,本项研究利用卫星影像数字化重新计算了内蒙古锡林郭勒典型草原和乌拉盖草甸草原采样点周边100 m以外的植被数据,利用ERV模型重新估算了主要花粉类型的RPP,并运用景观重建算法（LRA）进行了检验。锡林郭勒典型草原ERV模型分析显示,ERV子模型1结合1/d距离加权法与植被-花粉数据拟合度最高,得到的相关花粉源范围（RSAP）为1470 m;以蒿属为参照种（RPP=1±0）,各科属RPP依次为藜科（0.53±0.03）、十字花科（0.17±0.01）、唐松草属（0.14±0.02）、菊科（0.09±0.01）、莎草科（0.08±0.006）、委陵菜属（0.07±0.01）、禾本科（0.050±0.003）。乌拉盖草甸草原ERV模型分析显示,ERV子模型1结合Prentice距离加权法与植被-花粉数据拟合度最高,得到的RSAP为770 m;以蒿属为参照种（RPP=1±0）,各科属RPP依次为藜科（5.85±0.58）、蓼科（5.27±0.37）、石竹科（5.15±0.47）、莎草科（4.16±0.13）、菊科（1.63±0.09）、百合科（0.49±0.08）、唇形科（0.38±0.06）、禾本科（0.200±0.004）。重估的RSAP和RPP均与首次估算时存在差异,表明植被盖度计算方法确实会影响RSAP和RPP。景观重建算法对RPP检验结果表明,卫星影像数字化估算的RPP重建的植被盖度与实际植被的相关性更高。

     

现代黄河三角洲YRD-1401孔MIS 5以来沉积层序及其古环境意义

近年来渤海地区晚更新世以来沉积环境演化和地层划分存在争议。本文对现代黄河三角洲东南海岸带YRD-1401孔岩芯（长81.00 m）沉积物进行综合研究,旨在建立该孔晚更新世以来地层的沉积相序列和时间标尺,为解决地层划分争议提供新的证据。根据AMS ¹⁴C和光释光测年结果,并考虑到YRD-1401孔底部地层光释光年代的不精确性,本文主要研究YRD-1401孔MIS 5以来的沉积演化史。综合分析YRD-1401孔沉积地层的岩性特征和底栖有孔虫组合变化,结合测年结果,该孔可划分为6个沉积单元（从下往上DU 6~DU 1）：最底部的DU 6（51.35~81.00 m）为受潮流影响的河流沉积（其形成时间有待进一步研究）,DU 5（37.64~51.35 m）为MIS 5潮坪-近岸浅海沉积,DU 4（30.71~37.64 m）为MIS 3早期的潮坪沉积,DU 3（23.50~30.71 m）为MIS 3晚期至全新世早期形成的河流沉积,DU 2（14.22~23.50 m）为全新世早期（约10 cal.ka B.P.）至1855年形成的滨岸沼泽-滨岸浅水-近岸浅海~前三角洲沉积-海洋改造层,DU 1（0~14.22 m）为1855年以来发育的现代黄河三角洲沉积。晚更新世以来该孔有3个海相层（自下而上分别是DU 5、DU 4和DU 2）,分别形成于MIS 5、MIS 3早期和全新世,表明晚更新世以来全球海平面变化是其主要控制因素。研究区MIS 4的沉积地层出现缺失。渤海沿岸地区多个钻孔地层的对比表明,区域性的差异构造沉降、沉积物供给和地层完整性等因素也是影响研究区晚更新世以来沉积地层发育的重要因素。

     

新疆及邻区Pn速度层析成像

利用新疆及邻区2万多条Pn射线的走时资料,采用层析成像的方法反演该地区上地幔顶部的Pn速度结构.主要结果是:①新疆地区平均h速度为.2km/s,高于中国大陆地区的平均值(.0km/s),速度变化量从-0.3km/s到0.2km/s.②准噶尔盆地是明显的高Pn速度区,高速区与地貌形状吻合较好,最大值达.4km/s;塔里木盆地整体上呈现高速异常二者都可能与盆地是稳定地块、构造活动和变形较弱有关.③在盆地与山脉的交接带即主要的构造活动带,存在较低的Pn速度,可达7.9km/s.④塔里木南缘中部存在一显著的低速区,可能与岩浆活动和构造活动较强有关.⑤上地幔顶部波速各向异性整体上盆地中心较弱,边缘地带较强.新疆南部波速的各向异性可能是因印度板块对欧亚大陆的碰撞使地幔物质向北蠕动的结果.