Chloride source delineation in an urban-agricultural watershed: Deicing agents versus agricultural contributions     

Andrew Oberhelman  Eric W. Peterson 《水文研究》2020,34(20):4017-4029

Analyses (n = 525) of chloride (Cl⁻), bromide (Br⁻), nitrate as nitrogen (NO₃-N), sodium (Na⁺), calcium (Ca²⁺) and potassium (K⁺) in stream water, tile-drain water and groundwater were conducted in an urban-agricultural watershed (10% urban/impervious, 87% agriculture) to explore potential differences in the signature of Cl⁻ originating from an urban source as compared with an agricultural source. Only during winter recharge events did measured Cl⁻ concentrations exceed the 230 mg/L chronic threshold. At base flow, nearly all surface water and tile water samples had Cl⁻ concentrations above the calculated background threshold of 18 mg/L. Mann–Whitney U tests revealed ratios of Cl⁻ to Br⁻ (p = .045), to NO₃-N (p < .0001), to Ca²⁺ (p < .0001), and to Na⁺ (p < .0001) to be significantly different between urban and agricultural waters. While Cl⁻ ratios indicate that road salt was the dominant source of Cl⁻ in the watershed, potassium chloride fertilizer contributed as an important secondary source. Deicing in watersheds where urban land use is minimal had a profound impact on Cl⁻ dynamics; however, agricultural practices contributed Cl⁻ year-round, elevating stream base flow Cl⁻ concentrations above the background level.  相似文献   

基于深度学习的目标检测定位系统设计与实现     

王俊强  李建胜  程相博  杨戬峰 《测绘与空间地理信息》2020,(1):133-136,144

针对传统遥感影像目标检测方法效率不高,并且无有效手段对检测信息进行管理利用的问题,提出了在B/S构架下基于深度学习的目标检测及定位方法。通过集成深度学习框架、WebGIS以及数据库,实现了集遥感影像目标检测、展示及管理于一体的目标检测定位系统,满足多用户基于前端浏览器的并发目标检测需求。利用网格划分策略,实现了基于前端的大区域范围的目标快速检测。基于某机场飞机目标及某城市区域运动场目标检测结果表明:本文设计的目标检测定位系统能够在前端实现目标快速检测定位,具有较高检测精度,并可有效管理检测信息,为深度学习循环再利用提供数据支撑。  相似文献   

Researching and Teaching the Anthropocene     

Kenneth R. Young 《Geographical review》2019,109(2):258-264

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再探温跃层有孔虫B/Ca与温度和[CO₃^2-]的依赖性及其在24 ka以来热带西太平洋次表层碳酸盐系统重建中的应用     

郭景腾  李铁刚  熊志方  仇晓华  常凤鸣 《海洋学报(英文版)》2019,38(9):71-86

The B/Ca ratio of planktonic foraminifer shells has been used as a proxy for reconstructing past ocean carbonate chemistry. However, recent studies have revealed significant uncertainties associated with this proxy, such as whether seawater temperature or [ CO_3~(2-)] is the dominant control on the partition coefficient(K_D) of planktonic foraminiferal B/Ca. To address these uncertainties and thus improve our understanding of the planktonic foraminiferal B/Ca proxy, we analysed B/Ca ratios in the tests of Neogloboquadrina dutertrei(300–355 μm) and Pulleniatina obliquiloculata(355–400 μm) in surface sediment samples from the tropical western Pacific and South China Sea. The relationship between these B/Ca ratios and bottom water calcite saturation states(Δ[ CO_3~(2-)]) is weak, thus suggesting only a small dissolution effect on the B/Ca of the two species. The correlation coefficients(R~2) between the B/Ca ratios of N. dutertrei and P. obliquiloculata and environmental parameters(e.g., temperature, salinity, phosphate, DIC and ALK) in the tropical western Pacific and South China Sea are not high enough to justify using B/Ca ratios as a palaeoenvironmental proxy in the study areas. The significant correlation between K_D values of N. dutertrei and P. obliquiloculata and carbonate system parameters(e.g.,[ CO_3~(2-)], DIC, ALK, pH and [ HCO_3~-]) in the study area reflect chemical links between the K_D denominator and these variables. Based on our surface sediment calibration, an empirical relationship between the K_D of N.dutertrei and temperature is proposed in the tropical western Pacific. We also generated a record of B/Ca ratios in N. dutertrei(300–355 μm) from Core MD06-3052 in the tropical western Pacific over the past 24 ka to evaluate the application of the revised B/Ca proxy method. Based on the reconstructed empirical relationship for B/Ca and subsurface seawater ALK, we estimated subsurface seawater carbonate system parameters in the tropical western Pacific since 24 ka. In general, the estimated subsurface seawater pH and [ CO_3~(2-)] show an increase with time, and the record of subsurface seawater pCO_2 shows a decrease with time, in the tropical western Pacific over the past 24 ka. The consistent trends in subsurface seawater pCO_2 and opal flux during deglaciation may imply that the reported increase in subsurface water pCO_2 in the study area was promoted by enhanced upwelling in the Southern Ocean.  相似文献   

A stochastic method for the prediction of icebreaker bow extreme stresses     

《Applied Ocean Research》2019

It is well established that the ship-ice interaction process is quite complex and associated ice loads on the icebreaker hull is a stochastic process. Obviously, novel accurate statistical methods and models should be developed and applied to estimate extreme bow stresses.This paper studies icebreaker bow stresses based on measured distribution of ice thickness in the Arctic Ocean on the way to and from the North Pole. Since the vessel route was carefully selected searching for easier ice conditions, the Arctic Ocean crossing was not a straight linear but a meandering path. Thus, the specific ship route data was biased with respect to general ice statistics in the region, but true with respect to the route specific ice data encountered by a ship navigating in that region. Therefore the route specific ice thickness data is directly needed for ship design and navigation analysis. It is assumed that captains are competent and knowledgeable, and therefore will select a route that provides the most favourable ice conditions.This paper contributes to study of the newest Chinese self-designed polar icebreaker, serving the purpose of enhancing icebreaker operational reliability. Finite Element Method software package ANSYS/LS-DYNA has been employed to simulate bow stress pattern for a particular icebreaker operating in the Arctic Ocean. Extreme bow stresses were estimated using Naess-Gaidai method. The latter is a first application of Naess-Gaidai method to a distribution with lower bound. Thus this paper aims at introducing an efficient method of estimating route-specific icebreaker extreme bow stresses.  相似文献   

Reservoir architecture and heterogeneity distribution in floodplain sandstones: Key features in outcrop,core and wireline logs     

Luis Miguel Yeste  Augusto N. Varela  César Viseras  Neil D. Mcdougall  Fernando García-García 《Sedimentology》2020,67(7):3355-3388

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机载WIDAS数据的Landsat卫星反照率初步验证   总被引：1，自引：1，他引：0  

何丹丹  焦子锑  董亚冬  张小宁  丁安心  尹思阳  崔磊  常雅轩 《遥感学报》2019,23(1):53-61

随着精细化监测的需求,中高空间分辨率的地表反照率产品逐渐成为气候模型的主要输入。目前,中高空间分辨率反照率产品的验证主要基于地表站点的通量塔观测数据,区域机载飞行数据的验证依然相对较少。因此,本文基于区域机载数据验证Landsat反照率产品。针对内蒙古自治区根河森林试验区所获取的机载红外广角双模式成像仪(WIDAS)多角度反射率数据,应用BRDF原型反演算法估算其反照率,分析了应用机载数据验证中高空间分辨率反照率产品的潜力。2016年内蒙古根河森林试验区机载WIDAS飞行多角度观测的可用多角度范围为25°,以前的研究表明BRDF原型反照率反演算法表现出对小观测角度的反照率反演结果的鲁棒性。因此,机载WIDAS反照率在一定程度可用于星载反照率的验证。首先,基于核驱动模型和各向异性平整指数(AFX)提取了试验区4种MODIS二向性反射分布函数(BRDF)原型;然后,将其作为先验知识应用到根河森林WIDAS机载数据的反照率反演中;最后,用WIDAS反照率和单个地面通量塔观测的反照率对Landsat卫星数据的反照率进行初步验证。验证结果表明Landsat反照率与WIDAS反照率结果较为一致,但略有低估,总体均方根误差(RMSE)约为0.02,偏差为0.0057。在多角度观测范围较小时,BRDF原型的反照率反演算法可为星载地表反照率的验证提供了一种有效的验证手段。  相似文献   

A 560–440 ka tephra record from the Mercure Basin,southern Italy: volcanological and tephrostratigraphic implications          下载免费PDF全文

BIAGIO GIACCIO  PAOLO GALLI  EDOARDO PERONACE  ILENIA ARIENZO  SEBASTIEN NOMADE  GIAN PAOLO CAVINATO  MARCO MANCINI  PAOLO MESSINA  GIANLUCA SOTTILI 《第四纪科学杂志》2014,29(3):232-248

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Modelling the internal stress field in argillaceous rocks under humidification/desiccation     

L.L. Wang  A. Pouya  M. Bornert  B. Halphen 《国际地质力学数值与分析法杂志》2014,38(16):1664-1682

This paper deals with analytical and numerical modelling of the internal stress generated in argillaceous rocks during humidification/desiccation processes, which is an essential issue for damage study. This local stress field arises from two mechanisms: (i) complex interactions between free swelling/shrinking clay matrix and non‐strained inclusions of carbonate and quartz and (ii) a self‐restraint effect induced by the moisture gradient during the transient moisture exchange process. The inclusion–matrix interaction is investigated in different cases. Firstly, the analytical solution of the stress around a cylindrical inclusion embedded in an infinite swelling matrix is derived: The inclusion would suffer tension (compression) under humidification (desiccation), and the resulting cracking patterns are discussed. Then, the problem of two inclusions with different distances in an infinite swelling matrix is considered, and it is shown that the local stress around an inclusion will be perturbed and amplified by neighbouring inclusions. Finally, an inclusion outcropping at the free surface of a swelling matrix is modelled as to investigate the effect of free surface: The inclusion–matrix interface undergoes shear stresses of which the maximum is found at the free surface. In addition to the inclusion–matrix interaction, the self‐restraint effect is investigated: The induced stress is maximal at the beginning of humidification/desiccation processes and vanishes gradually with time. The quantity of the self‐restraint stress is strongly controlled by the hydric loading rate. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

哈尔滨市地下水中29种抗生素分布特征研究   总被引：1，自引：1，他引：0  

马健生  王卓  张泽宇  刘强  李丽君 《岩矿测试》2021,(6):944-953

当前对抗生素滥用监管及其研究正在加强,近年来中国主要水域中抗生素均有不同程度的检出,地表水及地下水中抗生素的污染状况持续受到关注。因进入环境中的抗生素种类繁多、结构复杂,一般实验室难以实现同时分析多种类抗生素。本文在哈尔滨市共采集地下水样品26组,采样范围包括人口密集、工业生产、农畜业等生活生产地区。利用超高效液相色谱-三重四极杆串联质谱联用技术分析了样品中的磺胺类、喹诺酮类、大环内酯类、β-内酰胺类、四环素类、林可酰胺类等6大类共29种典型抗生素含量,研究了哈尔滨市地下水中典型抗生素的检出及分布状况。结果表明：①哈尔滨市地下水中6大类典型抗生素均有不同程度检出,其中以磺胺类、喹诺酮类、大环内酯类、四环素类为主,检出率分别为61.5%、46.2%、42.3%、38.5%;②哈尔滨市地下水检出的抗生素含量范围在0.02～612ng/L之间,其中磺胺噻唑、磺胺嘧啶、林可霉素检出的最高浓度超过100ng/L,相比于国内外部分地区（如中国北京、天津,西班牙巴塞罗那）喹诺酮类整体含量偏低;③检出抗生素含量较高的采样点位主要分布在城市的中部、南部和东部地区,这些区域也是该市人口相对密集区,且附近普遍分布有制药厂、家禽牲畜养殖厂、城市排污口等。由此揭示了哈尔滨市城市地下水中抗生素分布特征受人类生产生活活动影响且具有明显的相关性。  相似文献