Study of statistically correcting model CMAQ-MOS for forecasting regional air quality

Based on analysis of the air pollution observational data at 8 observation sites in Beijing including outer suburbs during the period from September 2004 to March 2005, this paper reveals synchronal and in-phase characteristics in the spatial and temporal variation of air pollutants on a city-proper scale at deferent sites; describes seasonal differences of the pollutant emission influence between the heating and non-heating periods, also significantly local differences of the pollutant emission influence between the urban district and outer suburbs, i.e. the spatial and temporal distribution of air pollutant is closely related with that of the pollutant emission intensity. This study shows that due to complexity of the spatial and temporal distribution of pollution emission sources, the new generation Community Multi-scale Air Quality (CMAQ) model developed by the EPA of USA produced forecasts, as other models did, with a systematic error of significantly lower than observations, albeit the model has better capability than previous models had in predicting the spatial distribution and variation tendency of multi-sort pollutants. The reason might be that the CMAQ adopts average amount of pollutant emission inventory, so that the model is difficult to objectively and finely describe the distribution and variation of pollution emission sources intensity on different spatial and temporal scales in the areas, in which the pollution is to be forecast. In order to correct the systematic prediction error resulting from the average pollutant emission inventory in CMAQ, this study proposes a new way of combining dynamics and statistics and establishes a statistically correcting model CMAQ-MOS for forecasts of regional air quality by utilizing the relationship of CMAQ outputs with corresponding observations, and tests the forecast capability. The investigation of experiments presents that CMAQ-MOS reduces the systematic errors of CMAQ because of the uncertainty of pollution emission inventory and improves the forecast level of air quality. Also this work employed a way of combining point and area forecasting, i.e. taking the products of CMAQ for a center site to forecast air pollution for other sites in vicinity with the scheme of model products "reanalysis" and average over the "area".     

Chemical forms of heavy metal contaminants in sediments of Miyun reservoir

The chemical forms, spatial distribution and sources of As, Hg, Cd, Pb and Zn in sediments of the Miyun reservoir were studied. The results of sequential extraction demonstrate that most of As, Pb and Zn were bound to the residual fraction, Hg was associated with the sulfide fraction while Cd was associated with the carbonate fraction and the residual fraction. On the vertical profiles the concentrations of the heavy metals in total and each fractions mostly decreased with increasing depths in sediments, suggesting that the heavy metals input from the upstream watershed increases yearly. Summation of the residual fraction, the sulfide fraction and the carbonate fraction accounts for 60.03%―85.60% of the total heavy metal contents in the sediments, which represent the geochemical background values of the elements and relate closely to soil erosion. Results of the main factor analysis show that most sediments of the reservoir come from the upstream soil erosion, the point source pollution and domestic waste. Moreover, the microbial activities taking place on the sediment-water interface are also one of the major factors to cause the increasing content of the organic matter fraction and the iron-manganese oxide fraction. Environmental change of the reservoir water could make the removability of the heavy metals increase, leading to the increase of their concentrations in pore water in sediments, and imperiling water quality of the reservoir.     

Analysis of the environmental sensitivities of a typical dynamic epikarst system at the Nongla monitoring site, Guangxi, China

Nongla, a typical karst dynamic system (KDS) monitoring site, is located at Nongla Village, Mashan County, Guangxi, China. The data from a Greenspan CTDP300 multichannel data logger indicates that the KDS is highly sensitive to environmental changes. Multi-day and diurnal physico-chemical composition of epikarst spring water is quite different under different climatic conditions. During a day with no rainfall, water temperature and air temperature have similar variations. Electrical conductivity (EC) has good positive correlation with pH value and water temperature. During rainstorms, the physico-chemical composition of the spring water is initially strongly effected by dilution, pH and EC drop rapidly. However, half to one hour later, EC returns to normal and the CO₂ effects will be the dominant physical effect. This is due to the high fissure rates and high permeability in the epikarst zone. Dilution effects were observed during the entire rainstorm event,whereas, it only acts during the earliest period of light rain. Therefore, it is necessary to examine the water–rock–CO₂ combination as a whole system to explain the hydrochemical behavior of epikarst processes.     

基于高通量测序的表层水体纤毛虫多样性评估方法比较与优化

基于扩增子的高通量测序技术广泛应用于微型生物多样性的研究, 不同的测序手段和数据分析流程, 影响着微型生物多样性与群落结构的分析结果。本研究以易于形态鉴定的砂壳纤毛虫作为研究对象, 比较DNA测序、RNA测序和形态学方法检获的多样性和物种组成等, 探究序列分析流程中关键步骤: 嵌合体处理、可操作分类单元分析方法选择、合并相似分类单元以及去除稀有类群等对多样性结果的影响。研究结果显示无论基于DNA还是RNA的分子手段与形态学方法检获的主要物种基本一致, 与DNA测序相比, RNA测序检获的物种数少, 但差异不显著。基于97%以上相似度聚类和单核苷酸变异所得群落结构相似, 无显著差异; 且所有分析方法都能在一定程度上反映出自然界中不同类群的相对丰度。相较于单核苷酸变异和其他相似度阈值, 99%相似度下聚类所得多样性更为接近形态学结果。去除嵌合体和稀有类群(去除阈值: DNA测序0.05%; RNA测序0.07%), 可明显改善分子多样性虚高的问题。本研究为纤毛虫等真核微生物的分子多样性研究提供了科学的数据分析流程, 对未来真核微生物多样性研究具有指导意义。     

长江漫滩区深大异形基坑施工对紧邻特大型桥梁影响及变形控制研究

随着地下空间资源的开发利用,越来越多深基坑呈现出开挖深、规模大、形状不规则等特点,其支护结构设计复杂,施工难度大,具有明显的空间效应。本文以南京地铁某基坑工程为例,分析基坑施工对邻近桥梁的影响。其场区位于长江下游漫滩相二元结构地层分布地段,上部软土层厚度大,下部承压含水层地下水位高、水量丰富,地质条件复杂,该基坑为典型的深大异形基坑,距离某大桥的双曲拱引桥仅为7. 2 m,由于之前桥梁已遭受其他地下工程施工产生的较大变形,所以后续工程对其影响变形控制要求极高。为此,该车站基坑支护结构设计基于地下空间实际功能采用设置分隔墙分区开挖及MJS超深工法墙综合变形控制方案。本文通过有限元数值模拟计算,开展复杂环境下基坑开挖引起的围护结构及桥梁桩基的变形预测分析,计算结果显示,该深大狭长异形基坑开挖对邻近桥梁沉降变形影响显著,通过设置分隔墙分区开挖及MJS工法墙进行变形控制,能够较好地控制基坑的空间效应,减少“长边效应”、“异形效应”等对桥梁沉降变形的影响。通过现场基坑开挖过程实际监测结果,验证这一综合变形控制方案的可行性。该研究成果对于类似复杂地质条件下深大狭长异形基坑的支护及施工设计具有很好的借鉴意义。     

沙南凹陷古近系中深层砂岩储层特征与岩性油气藏勘探

渤海湾盆地沙南凹陷陡坡带古近系沙河街组二段发育辫状河三角洲相砂岩储集层,该储层受构造位置、埋藏速率、古地温变化、断裂作用的影响,在不同构造区特别是中深层,其物性具有明显的差异性。笔者等利用钻井、测井、地震及分析化验等资料,对中深层砂岩储层沉积相、成岩作用及孔隙演化特征进行研究,提出优质储层的主控因素及演化规律。结果表明,研究区中深层砂岩以岩屑长石砂岩为主,孔隙以粒间溶孔、粒内溶孔为主,储层存在中孔中渗型、中孔低渗型、低孔低渗型和低孔特低渗型4类,且以中孔低渗型为主。储层孔隙总体比较发育,储层整体表现为中等孔隙度、中等渗透率,储层物性较好。对区内优质储层发育的控制因素进行研究表明,富含石英、长石的物源区母岩是区内优质储层发育的物质基础,三角洲分流河道沉积相是优质储层发育的主要沉积相类型,成岩晚期方解石胶结物经过强溶蚀作用是优质储层发育的关键因素。对中深层优质储层时空演化规律分析表明,沙南凹陷南次洼曹妃甸14- e构造区发育辫状河三角洲相砂体,且这些砂体都位于有效烃源岩内,油气运聚条件优越,所以岩性油气藏勘潜力较大。已钻井也证明了区内厚油层的存在,说明该区是沙南凹陷岩性油气藏勘探最有利场所。     

基于A- CGAN的深反射地震数据随机噪声压制方法研究

基于深度学习的地震数据噪声压制方法是当前地震数据去噪处理的重要方向。深度学习方法突破了传统滤波处理的局限,在对常规地震数据的噪声压制中表现出效率高、信噪分离效果好的特点。但针对深部弱有效反射数据,当前的深度学习方法特征提取能力有限,难以取得较好的去噪效果。笔者等结合深反射地震数据特点,针对当前深度学习噪声压制方法在特征提取及对数据集依赖上的局限,提出了基于注意力循环生成对抗网络(Attention Cycle- Consistent Generative Adversarial Networks,A- CGAN)的深反射地震数据随机噪声压制方法。借助循环一致生成对抗网络(Cycle- Consistent Generative Adversarial Networks,Cycle- GAN)的域映射思想,降低对数据集的要求。为了构建适用于深反射地震数据的去噪网络,从3个方面对Cycle- GAN进行改进：在Cycle- GAN的生成器（去噪器）中加入残差结构和注意力机制,用于加深网络深度和提高其特征提取能力;在Cycle- GAN的鉴别器中使用块判决,提高鉴别精度和准确度;在损失函数部分加入感知一致性损失函数,提升网络模型恢复纹理细节信息的能力。通过合成地震数据和实际深反射地震数据测试,验证了优化算法的有效性,体现了良好的应用价值。     

闽北东坑火山盆地白垩纪火山—侵入杂岩的岩石成因与金成矿

火山岩和侵入岩是许多浅成低温热液型金矿床成矿物质和流体的重要来源。中生代时期华南陆块经历了强烈的岩浆—热液活动,在中国东南沿海地区形成了大量的火山—侵入杂岩和浅成低温热液金矿。本文选取该区研究程度较低的闽北政和县东坑火山盆地为研究对象,利用岩相学、年代学、全岩地球化学、Sr—Nd—Hf同位素等方法,来探讨该火山盆地中火山岩和侵入岩的成因联系、岩浆演化过程以及它们与盆地内同时期金矿的关系。东坑火山盆地由多种岩性的火山岩和空间上与其密切共生的浅成侵入相花岗斑岩、石英二长斑岩,以及携带暗色微粒包体的花岗岩脉组成。LA- ICP- MS锆石U- Pb定年显示,东坑的火山岩和侵入岩均形成于白垩纪（101. 0±0. 9~97. 3±1. 2 Ma）,其全岩Sr—Nd同位素组成较均一\[n（87Sr）/ n（86Sr）\]i=0. 7085~0. 7104;εNd(t)= -8. 83~ -7. 34,但锆石Hf同位素组成变化范围较大εHf(t)= -14. 0~3. 3。岩石地球化学特征显示,该盆地火山—侵入杂岩为富碱、富钾的准铝—弱过铝质岩石,这些岩石具有连续线性变化的主量元素特征、右倾的稀土配分曲线、弱至中等的Eu负异常（Eu/Eu* =0. 19~0. 83）、较高的氧逸度（lgfO2=-17. 44~-4. 18）以及大离子亲石元素Rb、K、Pb富集,高场强元素Nb、Ta、Ti亏损的特征。综合年代学及岩石地球化学特征,认为东坑火山盆地中的火山—侵入杂岩是在古太平洋板块俯冲后撤的伸展构造背景下,幔源岩浆上涌促使地壳源岩发生重新熔融并与之混合,不断演化,最终侵位于地壳浅表的产物。岩浆的源区组成、结晶分异和高氧逸度条件等共同造就了该盆地及周围同时期金的成矿。     

Effect of the Initial Vortex Structure on Intensity Change During Eyewall Replacement Cycle of Tropical Cyclones: A Numerical Study

This study investigates the effect of the initial tropical cyclone (TC) vortex structure on the intensity change during the eyewall replacement cycle (ERC) of TCs based on two idealized simulations using the Weather Research and Forecasting (WRF) model. Results show that an initially smaller TC with weaker outer winds experienced a much more drastic intensity change during the ERC than an initially larger TC with stronger outer winds. It is found that an initially larger TC vortex with stronger outer winds favored the development of more active spiral rainbands outside the outer eyewall, which slowed down the contraction and intensification of the outer eyewall and thus prolonged the duration of the concentric eyewall and slow intensity evolution. In contrast, the initially smaller TC with weaker outer winds corresponded to higher inertial stability in the inner core and weaker inertial stability but stronger filamentation outside the outer eyewall. These led to stronger boundary layer inflow, stronger updraft and convection in the outer eyewall, and suppressed convective activity outside the outer eyewall. These resulted in the rapid weakening during the formation of the outer eyewall, followed by a rapid re-intensification of the TC during the ERC. Our study demonstrates that accurate in- itialization of the TC structure in numerical models is crucial for predicting changes in TC intensity during the ERC. Additionally, monitoring the activity of spiral rainbands outside the outer eyewall can help to improve short-term intensity forecasts for TCs experiencing ERCs.     

Evaluating the effect of input variables on quantifying the spatial distribution of croaker Johnius belangerii in Haizhou Bay,China

A habitat model has been widely used to manage marine species and analyze relationship between species distribution and environmental factors. The predictive sk...