基于多参数指标的长江口滨岸多环芳烃来源辨析

在长江口滨岸及临近排污口、滨岸河流、城市中心城区采集悬浮颗粒物、表层沉积物、街道灰尘等样品, 分别利用GC-MS 和GC-C-IRMS 定量分析了不同环境介质中的多环芳烃 (PAHs) 与有机单体化合物稳定碳同位素(δ¹³C), 开展了基于PAH 环数、分子量特征比值和有机单体化合物稳定碳同位素组成等参数指标的长江口滨岸悬浮颗粒物与表层沉积物中PAHs 源解析研究。研究结果显示, 长江口滨岸悬浮颗粒物与表层沉积物中的PAH 化合物主要以3~4 环为主, 与吴淞排污口、石洞口污水处理厂、黄浦江、滨岸小河流以及上海中心城区等潜在来源区域不同环境介质中的PAHs 组成特征相似, 主要来源于汽油、柴油、煤炭和木材的不完全燃烧以及石油残余物的混合。其中, 木材和煤炭不完全燃烧形成的PAHs 以及石油残余物, 枯季经过滨岸河流及排污口直接输入, 洪季则为城市街道灰尘被暴雨冲刷, 随地表 径流最终汇入河口; 汽车排放(汽油、柴油不完全燃烧) 产生的PAHs 主要富集在城市交通区和商业区的街道灰尘中, 枯季借助区域盛行风迁移至河口区, 洪季则主要通过暴雨径流冲刷进入河口。     

地磁场能量在地球内部的分布及其长期变化

用国际参考地磁场模型(IGRF)分析了地磁场能量在地球内部的分布及其长期变化.结果表明,从1900年到2005年,地核以外地磁场总能量由6.818×1018J减少到6.594×1018J,减小了3.3%,地表以外地磁场总能量由8.658×101J减小到.63×101J,减小了11.4%.分析地球内部不同圈层地磁场能量的变化表明,地壳(A层)、上地幔(B层)、转换带(C层)、下地幔D′层的地磁场总能量在减小,但是下地幔"层的地磁场总能量却在快速增加.磁能密度随时间的变化更清楚地显示出磁能增加和减小的分界面在r=3840km处.上述结果表明,地核和地表以外地磁场总能量在趋势性减小的同时,也在进行重新分配.进一步分析表明,下地幔D"层磁能快速增长,主要是由高阶磁多极子的增强引起的.在地磁场倒转前,偶极矩减小而多极性相对增强在能量分布上的表现就是磁能向下地幔底部(特别是D"层)集中.     

Characterization of hydraulic suitability of Chinese sturgeon (Acipenser sinensis) spawning habitat in the Yangtze River

Hydrodynamic flow fields affect the ecological processes such as the water diversity and the distribution of organisms. Understanding the hydrodynamic and ecological processes is critical for the restoration and protection of especially fragile ecological habitats in river systems. This study uses turbulent flow to characterize the ecological behaviour of Chinese Sturgeon (Acipenser sinensis) in the Yangtze River. The Delft3D‐Flow model, which is first validated with field‐measured data, is used to simulate the flow field within spawning habitats of Chinese Sturgeon, downstream of Gezhouba Dam. The model‐simulated turbulent kinetic energy (TKE) and its distribution pattern are then used to characterize the hydraulic environment of the fish's spawning habitat. For the spawning habitat, downstream of Gezhouba Dam, the lower limit of TKE for the Chinese Sturgeon egg mass field is 0.025 m²/s², which occurs at a velocity less than 1.7 m/s. Chinese Sturgeon prefers habitats with TKE range of 0.010 ~ 0.015 m²/s² for resting. This suggests that discharge regimes provide the basis for ecological regulation of the Three Gorges Reservoir and the scientific reference for river management. Copyright © 2011 John Wiley & Sons, Ltd.     

A STUDY ON TYPHOON MOVEMENT PART Ⅲ:EFFECT OF THE HORIZONTAL MOMENTUM EXCHANGE BETWEEN TYPHOONS AND ENVIRONMENT

Two semi-asymmetric flow patterns of typhoons are chosen to qualitatively determine the effect of exchange of horizontal momentum between inflow and outflow layers and the environment on the motion of typhoons. The results show that only the asymmetric flow component (residual after azimuthal mean flow has been removed) could cause a net momentum input into or output from a typhoon and therefore contribute to the changes in speed and direction of the typhoon movement. A typhoon with major inflow and/or outflow channels on its right (left) side would tend to accelerate and turn left (decelerate and turn right); On the other hand, a typhoon with major inflow and/or outflow channels in the rear (front) semicircle would tend to accelerate and turn right (decelerate and turn left).     

Dynamics and relationships of Ca, Mg, Fe in litter, soil fauna and soil in Pinus koraiensis-broadleaf mixed forest

The Liangshui Natural Reserve in Heilongjiang Province of China was selected as the study area. The authors collected the samples of forest litter （Tilia amurensis, Fraxinus mandshurica, Pinus koraiensis, Acer mono, Betula costata, and mixed litter）, soil in humus horizon （0--5cm） and soil horizon （5-20cm）, and soil macrofauna （Oligochaeta, Geophiloporpha and Juliformia） from 2001 to 2002. The role of soil macrofauna in the material cycle was analyzed through comparing the macro-element contents among various parts of the subsystems and using enrichment index （El）. The results indicate that dynamic changes of various litters are very complicated. The contents of Fe in each kind of litter increase firstly, and then decrease in the study period. The changes of macro-element contents are greater in the broad-leaf litter than in the coniferous litter, and the mixed litter is in the middle level, but the differences among them are not significant. The contents of Mg and Fe in humus are higher than those in soil, but the contents of Ca in soil are higher than that in humus. The dynamic changes of macro-element contents in soil and soil fauna are not consistent with those in litter. The diplopod presented obvious enrichment of Ca and Mg （E1〉1）, but it does not significantly enrich Fe. Earthworm has a stronger enrichment ability of Fe than diplopod and scolopendra, but E1〈1. Soil fauna can make great influences on the material cycle of the subsystems.     

基于现代大地测量手段的青藏高原南缘地壳形变分析

基于2003~2013年GRACE卫星重力、GPS和绝对重力数据对青藏高原南缘地壳形变进行探讨分析。结果表明,拉萨测站1999~2015年垂向隆升速率为1.5 mm/a,显示出拉萨测站持续隆升的特点。结合南加州综合网络构建的远程连续GPS参考站,另外选择TPLJ、CHLM、JMSM测站数据进行分析。GPS结果表明,4个测站2003~2013年平均隆升速率为2.3±0.11 mm/a,GRACE垂向位移时间序列显示4个测站2003~2013年除季节性变化外也具有轻微上升趋势,平均速率为0.35 mm/a。联合绝对重力资料在考虑诸多因素(地壳隆升、侵蚀、GIA等)后得到拉萨测站近年重力变化约为-0.97 μGal/a,青藏高原拉萨测站地下地壳底部增厚速率约为4.4 cm/a,揭示了青藏高原南部地区的地壳形变特征--地壳隆升与底部增厚。     

基于卷积神经网络的ICESat-2光子点云去噪分类

ICESat-2（Ice, Cloud, and land Elevation Satellite-2）是美国NASA（National Aeronautics and Space Administration）在2018年发射的激光测高卫星,其上搭载的激光测高系统ATLAS（Advanced Topographic Laser Altimeter System）采用微脉冲多波束光子计数激光雷达系统,因其低能耗、高探测灵敏度、高重复频率的特性极大改善了沿轨采样密度,但也使获取的数据中包含大量的噪声,如何有效实现光子点云去噪分类成为后续应用的关键,也是当前研究的热点和难点,为此本文提出一种基于卷积神经网络的光子点云去噪和分类算法。首先将光子点云按照沿轨和高程方向划分格网,去除明显的噪声光子,并将每个粗信号光子点栅格化为影像;然后基于少量样本构建的卷积神经网络分类模型实现光子点云精去噪和分类;最后利用机载激光雷达数据进行验证,并与ATL08产品的去噪分类结果进行对比。结果表明,对于裸地和森林区域,卷积神经网络算法均能有效去除噪声光子,特别对于森林区域,可同时实现去噪和分类;其中,裸地区域地表计算的R²和RMSE分别为1.0和0.72 m,森林区域地表和树冠计算的R²分别为1.0和0.70, RMSE分别为1.11 m和4.99 m。本文利用深度学习算法实现光子点云去噪分类,在裸地和森林区域均取得了较好的结果,为后续光子点云数据处理提供了参考。     

基于空间面板计量模型的雾霾对中国城市旅游流影响的空间效应

以中国342个市域单元为研究对象,借助双变量LISA模型、空间面板杜宾模型等方法,探究了1998-2016年雾霾与中国城市旅游流的空间关联特征,分析了雾霾对旅游流的影响及其空间溢出效应。结果表明,在中国雾霾PM_2.5与城市旅游流有东高西低的分布特点,在胡焕庸线两侧的空间分布呈现出与地形和城市发展等因素的空间耦合性;雾霾与城市旅游流（含国内和入境旅游流）均表现出显著的空间集聚和空间依赖特征,雾霾污染对旅游流产生明显的影响并形成相应的空间效应;雾霾对旅游流的抑制区域在不断扩大,H-L型城市数量的增加、L-H型集聚区的片状扩张和华北、华中地区的L-H型集聚的“空心化”现象均表明旅游流具有低雾霾指向性;雾霾污染与旅游流的倒“U”型曲线关系表明经典的EKC假说对中国城市旅游流同样适用,且雾霾污染的显著负向影响主要存在于入境旅游方面;雾霾和旅游流均具有明显的正向空间溢出效应,将雾霾治理同经济发展、对外联系、旅游开发、生态保护和交通建设等因素结合起来进行综合治理,才能为旅游发展创造美好的环境,实现国际、国内旅游健康、协调、可持续的高质量发展。     

经济层面和技术层面的碳减排研究

相关资料和事实表明,全球气候发生了很大的变化。二氧化碳是温室效应中最重要的温室气体,碳减排工作是缓解温室效应的一项重要措施,为当前科学研究热点之一。本文主要从经济和技术两个方面,较为系统和全面地介绍了当前碳减排方面的研究进展。经济层面的研究,包括数量化模型、碳税机制和碳减排附加效应几个方面。专业技术方面的研究,包括对碳行为的源汇和贮量的计算研究、碳循环研究、以及减少碳排放的工业技术的运用等。文章还简要提出了中国在碳减排研究方面应采取的几点措施。     

The complex nonlinear systems with fractal as well as chaotic dynamics of annual runoff processes in the three headwaters of the Tarim River

This paper attempted to identify fractal and chaotic characteristics of the annual runoff processes in headwaters of the Tarim River. Methods of fractal analyses were used to explore several aspects of the temporal changes from 1957 to 2002. The main findings are as follows: (1) The annual runoff processes of the three headwaters of the Tarim River are complex nonlinear systems with fractal as well as chaotic dynamics. (2) The correlation dimensions of attractor derived from the time series of the annual runoff for the Hotan, Yarkand and Aksu rivers are all greater than 3.0 and non-integral, implying that all three rivers are chaotic dynamical systems that are sensitive to initial conditions, and the dynamic modeling of their annual runoff process requires at least four independent variables. (3) The time series of annual runoff in each river presents a long-term correlation characteristic. The Hurst exponent for the period of 1989 to 2002 suggests that we may expect to see an increasing trend in the annual runoff of the Aksu and Yarkand rivers in the years after 2002, but a decreasing tendency for the Hotan River in the same period.