Spatial variability of E. coli in an urban salt-wedge estuary

This study investigated the spatial variability of a common faecal indicator organism, Escherichia coli, in an urban salt-wedge estuary in Melbourne, Australia. Data were collected through comprehensive depth profiling in the water column at four sites and included measurements of temperature, salinity, pH, dissolved oxygen, turbidity, and E. coli concentrations. Vertical variability of E. coli was closely related to the salt-wedge dynamics; in the presence of a salt-wedge, there was a significant decrease in E. coli concentrations with depth. Transverse variability was low and was most likely dwarfed by the analytical uncertainties of E. coli measurements. Longitudinal variability was also low, potentially reflecting minimal die-off, settling, and additional inputs entering along the estuary. These results were supported by a simple mixing model that predicted E. coli concentrations based on salinity measurements. Additionally, an assessment of a sentinel monitoring station suggested routine monitoring locations may produce conservative estimates of E. coli concentrations in stratified estuaries.     

耦合气溶胶气候模式FGOALS-f3-L模拟青藏高原地区气溶胶特性

基于新耦合气溶胶气候模式FGOALS-f3-L模拟分析了2002-2011年青藏高原地区气溶胶时空分布特征.结果表明:青藏高原地区,沙尘,硫酸盐,碳质气溶胶(包括黑碳,有机碳和混合碳)地表质量浓度分别占比为53.6％,32.2％,14.2％;在拉萨站点,模拟的气溶胶地表质量浓度被低估,尤其是黑碳和有机碳气溶胶;模拟的气...     

Mineralogical evidence for multiple dust sources in an early Triassic loessite

Loessite present in a borehole into the Smith Bank Formation (early Triassic age, Central North Sea) differentiates five coeval source terranes for aerosol dust, three long-distance sources and two local sources. All were active immediately following the end Permian mass extinction. Long-distance sources are sedimentary, basic magmatic and acid–intermediate volcanic. Although predominantly silt-sized and dominated by quartz with subordinate feldspars, muscovite and illite, evidence of basic and acid–intermediate magmatic/volcanic sources are pervasive. Baddeleyite is diagnostic of basic magmatism, an origin supported by enrichment of plagioclase relative to potassium feldspar. Deduction of acid–intermediate volcanism comes from the collective occurrence of irregular geometry quartz, volcanic shards, Ti-mineralization, euhedral biotite, sanidine, the co-occurrence of apatite and zircon, and the common occurrence of a tosuditic clay mineral. The tosuditic phase occurs as an unusual diagenetic dioctahedral chlorite/smectite formed at low temperature (<45°C), during very shallow burial by the decomposition of unstable rhyo-dacitic and andesitic grains in alkaline pore water from an adjacent lake that yielded pore fluids with a high Al : Si ratio. The Siberian Traps large igneous province is the likely source terrane for the magmatic and volcanic silt. Locally sourced clay pellets and kaolinite booklets formed from aeolian erosion of an adjacent, periodically desiccated lake-floor and a kaolinitic regolith, respectively. Inference of a prolonged harsh, arid climate leaves no evidence of any periods of sustained humidity or climatic fluctuation, such as pedogenesis. The association between the end Permian mass extinction, emplacement and aeolian erosion of the Siberian Traps large igneous province, and location of the Smith Bank Formation in a large lacustrine endorheic basin, combine to preserve a record of prolonged harsh climate in the early Triassic.     

南京市气溶胶PM2.5一次来源解析

在南京大学鼓楼校区（市区）和南京信息工程大学（郊区）校园,分季采集PM2.5及其主要排放源的颗粒样品,在南京大学现代分析测试中心用X-荧光分析法分析样品中的化学元素,应用化学元素平衡法（CMB）计算了各主要源对PM2.5的贡献。结果表明对市区扬尘和建筑尘是PM2．5最主要的贡献源,贡献率合计约70％;燃煤尘和冶炼尘仅为约15％。对郊区扬尘和煤烟尘是PM2．5的最主要贡献源,平均贡献率分别为50％和22．4％,建筑尘的平均贡献率为8．3％,冶炼尘的贡献小于8％。这些结果可为治理气溶胶细颗粒源提供决策依据。     

平流层臭氧对人类活动排放氯化物及氮氧化物的非线性响应

利用本文所建立的平流层下部臭氧异相光化学系统,研究硫酸气溶胶表面积浓度以及氯化物和氮氧化物的排放强度对系统状态的影响.光化系统由19种分别来自氧族、氢族、氮族、氯族和碳族的化学成分组成.研究结果指出,仅就气溶胶而言,它不是一个重要的决定光化系统行为的因子.然而,当它与奇氯ClOx或奇氮NOx的外源共同影响系统时,通过复杂的非线性光化学过程,它将使系统的行为发生重大变化.可以看到,在某些确定的参数范围内,系统存在多平衡态解,并构成一个“折叠"突变流型.     

Multi-temporal RADARSAT-2 polarimetric SAR for maize mapping supported by segmentations from high-resolution optical image

Due to its ability to penetrate the cloud, Synthetic Aperture Radar (SAR) has been a great resource for crop mapping. Previous research has verified the applicability of SAR imagery in object-oriented crop classification, however, speckle noise limits the generation of optimal segmentation. This paper proposed an innovative SAR-based maize mapping method supported by optical image, Gaofen-1 PMS, based segmentation, named as parcel-based SAR classification assisted by optical imagery-based segmentation (os-PSC). Polarimetric decomposition was applied to extract polarimetric parameters from multi-temporal RADARSAT-2 data. One Gaofen-1 image was then used for parcel extraction, which was the basic unit for SAR image analysis. The final step was a multi-step classification for final maize mapping including: the potential maize mask extraction, pure/mixed maize parcel division and an integrated maize map production. Results showed that the overall accuracy of the os-PSC method was 89.1%, higher than those of pixel-level classification and SAR-based segmentation methods. The comparison between optical- and SAR-based segmentation demonstrated that optical-based segmentation would be better at representing maize field boundaries than the SAR-based segmentation. Moreover, the parcel- and pixel-level integrated classification will be suitable for many agricultural systems with small landownership where inter-cropping is common. Through integrating advantages of the SAR and optical data, os-PSC shows promising potentials for crop mapping.     

利用地震台阵识别中深源远震sP和pP震相确定震源深度

震源深度是目前最难确定的震源参数之一,基于密集的近台观测数据可以准确确定近震震源深度,但对远震的震源深度无法较好地约束。远震反射波震相sP和pP包含用于确定震源深度的有效信息,理论上可以对远震的震源深度进行有效约束。将国内测震台站中台间距远小于震中距的区域台站作为台阵,通过互相关、震相对齐、波形叠加聚束等处理,可以提升sP和pP深度震相的信噪比。利用IASP91全球模型,根据震相走时差得到较为准确的震源深度。本文计算了2017—2020年M≥6.0的64个国外远震的震源深度。通过与GCMT、GFZ、USGS等机构给出的结果相比,验证了此方法得到的震源深度的可靠性。通过讨论破裂持续时间对pP震相识别的影响,得到此方法在矩震级6.0～8.5时,在不同深度上有较好的适用性。     

利用接收函数探讨新疆几次中强地震的地壳孕育深度

在分析2009～2012年新疆地区的远震P波接收函数过程中,发现部分台站的接收函数中存在清晰且能量较强的壳内间断面转换波。本文分别利用接收函数中的壳内间断面和莫霍面转换波,联合接收函数H-κ叠加方法和时间窗滑动方法,分析了2009～2012年新疆6次中强地震震中周围的7个地震台站下方的地壳和上地壳(壳内间断面上方地壳)介质泊松比在地震前后随时间的动态变化情况。结果显示:乌苏、于田和独山子3个地震台站的地壳介质泊松比在对应的3次中强地震前后出现了较为明显且持续的下降过程,下降幅度大于均值误差,变化形态特征呈"V"字型(乌苏台呈双"V"字型),地震发生在"V"字形成的尾端,但其上地壳介质泊松比在地震前后没有出现明显低值异常变化;其他4个地震台站下方的地壳和上地壳介质泊松比在地震前后没有观测到明显低值异常。根据观测结果,推测3次中强地震前后地壳介质泊松比出现低值异常主要源于中下地壳,地壳孕育深度位于中下地壳。     

大步长波场深度延拓的理论

波场延拓是地震偏移成像的基础. 快速进行目标区波场延拓对石油勘探中急需发展的深部地震勘探和无组合海量地震数据的成像有重要意义. 在目标区成像中,目前已有的波场延拓方法,包括基于走时计算的Dix方法和射线追踪方法,以及基于小步长波场递推的方法,在适应复杂介质、计算精度和计算效率的某一方面还不能完全满足实际需要. 本文提出一种基于“算子相位”李代数积分的快速计算延拓算子的方法,称为大步长波场延拓方法. 在该方法中,指向目标区的波场延拓算子象征的复相位被表示成波数的线性组合. 线性组合的系数是层速度函数及其导数的深度积分,计算和存储较为方便. 波场延拓算子通过相移算子加校正的方法,利用快速Fourier变换在空间域和波数域予以实现. 利用动力学等价关系导出了便于计算的表达式. 本文比较了算子主象征函数用一步法展开和用两步法展开的精度,从而说明大步长方法的精度要高于递推方法. 在横向和纵向线性变化介质中,将大步长方法的脉冲响应与递推法做了比较,说明大步长延拓算子的走时精度主要取决于相移因子中的横向变速校正项;且在各种近似下,大步长算子发生的频散都非常小.     

中国近海大气气溶胶的时间和地理分布特征

通过对中国近海10个航次气溶胶观测资料的统计分析得出:(1)从黄海、东海至日本以南海域气溶胶中地壳元素年平均浓度明显减小,在春季尘暴多发期间地壳元素浓度离到岸距离接指数规律递减.污染元素气溶胶浓度分布与陆源排放量和离岸距离有一定关系.(2)海上陆源气溶胶浓度的季节分布为:春季最大,秋冬次之,夏季最小.受日本排放源的影响,日本以南海域污染元素浓度最大值出现在冬季.(3)Se元素浓度与海洋源密切相关.海盐元素从黄海、东海至日本以南海域浓度逐渐增加,主要受周围海况影响,与风速呈现一定程度的正相关.影响近海气溶胶浓度的主要因素有陆源气溶胶排放量、降水分布和大尺度天气形势.