综合物探方法在不稳定斜坡地质灾害勘察中的应用研究

不稳定斜坡体地形复杂、坡度大,表层土、石混杂,下部岩石裂隙发育,探测难度大,缺乏有效的物探手段精确圈定不稳定斜坡体的分布位置及空间赋存状态。用超高密度电法和微动探测相结合,推断了不稳定斜坡的范围及空间赋存状态。工程实地勘查表明,综合物探方法具有较高的可靠性,为地质灾害的治理打下了良好的基础。     

Mercury cycling during acid rain recovery at the forested Lesní potok catchment,Czech Republic

From 2011 to 2019, mercury (Hg) stores and fluxes were studied in the small forested catchment Lesní potok (LES) in the central Czech Republic using the watershed mass balance approach together with internal measurements. Mean input fluxes of Hg via open bulk deposition, beech throughfall and spruce throughfall during the periodwere 2.9, 3.9 and 7.6 μg m⁻² year⁻¹, respectively. These values were considerably lower than corresponding deposition Hg fluxes reported in the early years of the 21st century from catchments in Germany. Current bulk precipitation inputs at unimpacted Czech mountainous sites were lower than those in Germany. The largest Hg inputs to the catchment were via litterfall, averaging 22.6 and 17.8 μg m⁻² year⁻¹ for beech and spruce stands. The average Hg input, based on the sum of mean litterfall and throughfall deposition, was 23.0 μg m⁻² year⁻¹, compared to the estimated Hg output in runoff of 0.5 μg m⁻² year⁻¹, which is low compared to other reported values. Thus, only ~2% of Hg input is exported in stream runoff. Stream water Hg was only weakly related to dissolved organic carbon (DOC) but both concentrations were positively correlated with water temperature. The estimated total soil Hg pool averaged 47.5 mg m⁻², only 4% of which was in the O-horizon. Thus Hg in the O-horizon pool represents 72 years of deposition at the current input flux and 3800 years of export at the current runoff flux. Age-dating by ¹⁴C suggested that organic soil contains Hg from recent deposition, while mineral soil at 40–80 cm depth contained 4400-year old carbon, suggesting the soil had accumulated atmospheric Hg inputs through millennia to reach the highest soil Hg pool of the soil profile. These findings suggest that industrial era intensification of the Hg cycle is superimposed on a slower-paced Hg cycle during most of the Holocene.     

天津市人口郊区化特征及其动力因素

基于"五普""六普"街道、乡镇数据,运用GIS及人口密度模型分析天津市人口郊区化的时空演变特征,并根据2005—2015年各区县数据,剖析其动力因素。结果表明:天津市中心区繁荣与郊区化并存,属于市中心发展型郊区化;天津已形成多中心格局,副中心人口聚集效应日益显著;人口郊区化伴随就业岗位的郊区化,但人口和产业存在空间分异现象;土地、住房制度改革及郊区经济发展加快了人口郊区化进程,公共服务的集中延缓了人口向郊区迁移,滨海新区发展、交通与通信网络的现代化为人口向郊区的迁移创造了条件。提出进一步推进城市组团式发展、推动产业结构与布局调整及以公共服务引导人口流动等措施实现中心城区人口向郊区有序分流。     

干涸尾闾湖盆区泥漠地表磨蚀释尘特征

沙粒的表面磨蚀效应是地表产尘、释尘的重要机制,针对干湖盆泥漠地表开展磨蚀释尘实验研究,对理解干湖盆地表风蚀过程及盐碱尘暴形成机理具有重要意义。对采自西居延海干涸湖盆泥漠地表土样进行室内磨蚀模拟实验,研究了不同粒级（细、中、粗）沙粒不同落沙角度（30°,45°,60°）的磨蚀效应。结果表明：（1）泥漠地表磨蚀实验中能够产生明显释尘效应的沙粒粒级阈值为中沙（0.25 mm<M_d<0.50 mm）;（2）磨蚀粒径粒级相同时,磨蚀角度会对泥漠地表磨蚀释尘速率产生影响,磨蚀量的角度排序为60°>30°>45°,但同一粒级3种角度下的磨蚀释尘率差异不显著。（3）磨蚀角度为45°时,计算了泥漠地表的质量磨蚀率与能量磨蚀率,其中中沙为0.04 g·kg^-1、0.43 g·J^-1,粗沙为0.08 g·kg^-1、0.74 g·J^-1,极粗沙为0.26 g·kg^-1、2.54 g·J^-1;在磨蚀沙粒粒级倍增而磨蚀角度不变情况下,泥漠地表磨蚀释尘率与能量磨蚀率未发生正比例线性增长变化。     

微塑料添加对小麦苗期生长及干物质分配的影响

土壤环境中微塑料污染已成为全球关注的环境问题。关于微塑料对于植物生长的直接影响和由于土壤理化性状改变的间接影响研究已逐步开展,但针对小麦的研究鲜见报道。试验选择两个旱地小麦品种(甘春27和禾尚头)作为研究对象,选取高密度聚乙烯作为微塑料添加,设置3种质量浓度(0、1、4 g·kg^-1)开展盆栽试验,对不同微塑料组合处理下小麦的出苗率、株高、全株生物量和地上/地下干物质分配进行了分析。结果表明：(1)微塑料添加对两个品种出苗率没有影响。(2)禾尚头在添加1 g·kg^-1微塑料时比添加0、4 g·kg^-1时全株生物量分别高46.7%、8.5%,甘春27在添加1 g·kg^-1微塑料时比添加0、4 g·kg^-1时全株生物量分别高28.7%、17.2%;甘春27整体比禾尚头在3种浓度处理下全株生物量分别高24.9%、9.6%、1.5%。(3)不同试验处理条件下,甘春27将更多的干物质分配在地上植株的构建,其在地下(根系)和地上(茎叶)部分的分配比例整体小于禾尚头。整体上,适度微塑料添加可...     

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高层大气密度的午夜极大值特征分析与建模

利用CHAMP (CHAllenging Minisatellite Payload)、GRACE-A (Gravity Recovery and Climate Experiment-A)、SWARM-C (The Earth''s Magnetic Field and Environment Explorers-C)等3颗极轨卫星的资料, 研究360—480km高层大气密度在低纬度区域的午夜极大值(Midnight Density Maximum, MDM)现象. MDM一般出现在23:00- 02:00 LT (Local Time)之间,峰值位置在低纬度15°以内,谷值位置在中纬度35°-45°附近,整体略偏向南半球,振幅约为平均密度的26%.随着高度增大以及太阳辐射水平的增强,MDM振幅呈减小趋势;冬至和夏至日附近的季节效应会减弱MDM振幅,在春秋分日的振幅最大.用3个主流大气模型DTM2000 (Drag Temperature Model 2000), NRLMSISE00 (US Naval Research Laboratory, Mass Spectrom-eter and Incoherent Scatter radar)和JB2008 (Jacchia- Bowman 2008 model)对MDM进行模拟,JB2008没有刻画出MDM现象;另两个模型低估了MDM效应,在360km和480km两个高度DTM2000模型的振幅仅为观测的46%和53%, NRLMSISE00模型仅为观测的33%和26%;模型没有准确刻画出MDM与高度、辐射水平和季节的关系.联合3颗卫星的资料,研究了-种基于地理纬度的6阶勒让德多项式,同时融合地方时和高度因素的经验函数,在振幅和相位上可以较好地刻画MDM特征,相关系数达到0.923,可为大气密度模型的修正提供借鉴,服务于低轨道航天器高精度轨道预报.     

Estimation of crowd density from UAVs images based on corner detection procedures and clustering analysis

With rapid developments in platforms and sensors technology in terms of digital cameras and video recordings, crowd monitoring has taken a considerable attentions in many disciplines such as psychology, sociology, engineering, and computer vision. This is due to the fact that, monitoring of the crowd is necessary to enhance safety and controllable movements to minimize the risk particularly in highly crowded incidents (e.g. sports). One of the platforms that have been extensively employed in crowd monitoring is unmanned aerial vehicles (UAVs), because UAVs have the capability to acquiring fast, low costs, high-resolution and real-time images over crowd areas. In addition, geo-referenced images can also be provided through integration of on-board positioning sensors (e.g. GPS/IMU) with vision sensors (digital cameras and laser scanner). In this paper, a new testing procedure based on feature from accelerated segment test (FAST) algorithms is introduced to detect the crowd features from UAV images taken from different camera orientations and positions. The proposed test started with converting a circle of 16 pixels surrounding the center pixel into a vector and sorting it in ascending/descending order. A single pixel which takes the ranking number 9 (for FAST-9) or 12 (for FAST-12) was then compared with the center pixel. Accuracy assessment in terms of completeness and correctness was used to assess the performance of the new testing procedure before and after filtering the crowd features. The results show that the proposed algorithms are able to extract crowd features from different UAV images. Overall, the values of Completeness range from 55 to 70 % whereas the range of correctness values was 91 to 94 %.     

基于新型探测资料对西安一次弱降水预报失误的原因分析

利用微波辐射计、激光测风雷达、多普勒雷达、相控阵雷达等新型探测资料、地面加密观测资料、ERA5再分析及多模式数值预报结果对2022年4月24日西安城区一次弱降水预报出现明显失误的原因进行分析,结果表明：(1)全球数值预报模式和中尺度数值预报模式对本次过程西安城区均报有明显降水,主要原因为模式对低层相对湿度预报明显偏大;(2)多种新型探测数据分析认为近地层湿度条件较差及中层的绝对水汽含量低,中层的干暖空气不利于成云致雨,垂直上升运动不强,且由于低层非常干燥,使水滴在下沉过程中蒸发,从而无法形成雨滴下落,这些原因共同造成西安城区无降水,低层相对湿度预报偏大是造成这次西安城区降水预报失误的主要原因之一;(3)造成西安城区近地层湿度条件差的原因是城市干热岛效应和低层干暖平流输送,且降水云团翻越秦岭后其湿空气绝热下沉至城区后出现增温降湿,使得城区形成较为深厚的干层,即使有雨滴在下落过程中也会造成更强的蒸发,这也是城区没有降水的重要原因之一;(4)预报员主观预报订正出现空报主要是源于对边界层水汽、抬升条件等关键降水要素缺乏订正能力,且对大城市的干热岛效应和秦岭山区地形影响研究不足。     

大型海藻孔石莼抑制浮游微藻生长的原因初探--种群密度及磷浓度的作用

本文以磷浓度和种群密度为变量 ,以亚心形扁藻为浮游微藻代表 ,采用实验生态学手段研究了大型海藻孔石莼与浮游微藻 (亚心形扁藻 )间的竞争。结果显示 ,不论营养盐浓度如何 ,高密度的孔石莼皆能显著抑制浮游微藻的生长。分析显示 ,高密度的孔石莼压制浮游微藻生长的原因 ,不是由于对氮、磷等营养盐的竞争所致 ,而可能是其他原因所致。