Multi‐element analysis of sea water from Sepetiba Bay,Brazil, by total reflection x‐ray fluorescence spectrometry using synchrotron radiation

Trace elements in the surface waters of Sepetiba Bay were studied by total reflection x‐ray fluorescence spectrometry using synchrotron radiation (SRTXRF). The bay is located in the south of Rio de Janeiro State, Brazil. The water samples were collected at 21 sampling stations, prepared in order to preconcentrate the metallic elements with ammonium pyrrolidinedithiocarbamate and to remove the salt matrix. Samples were spiked with an internal standard (Se) and the precipitated dithiocarbamates of trace elements were separated by filtration through a Millipore filter, then transferred to a Perspex reflector and digested with HNO₃ for SRTXRF measurement. Elemental concentrations of Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo and Pb were determined and a comparison was made between the results obtained and the values given in the literature for sea water. Copyright © 2005 John Wiley & Sons, Ltd.     

海南岛沿岸海域水体漫衰减系数光谱分析及LiDAR测深能力估算

机载激光雷达测深是近年来蓬勃发展的主动式水深测量方法,能够快速精准地获取近岸水深和水下地形,特别是对于浅海、岛礁等船只无法达到的区域具有显著优势。而机载激光雷达系统的测深能力主要受到水体浑浊度的影响。激光测深实验中对实验区域的水体浑浊度研究将有助于实验方案的设计。以中国海南岛沿岸海域为例,研究了该海域水体浑浊度和机载激光雷达测深系统CZMIL(coastal zone mapping and imaging LiDAR)测深能力之间的关系,建立了运用水体漫衰减系数估算机载激光雷达测深系统测深能力的算法。首先分析并确定了实验区域的漫衰减系数K_d(490)反演算法;其次,运用该区域实测光学数据建立了漫衰减系数K_d(490)和K_d(532)之间的数值关系;接着总结了K_d(532)和CZMIL系统最大测深值之间的关系;最后运用MODIS数据合成了海南岛沿岸海域在CZMIL系统海道测量模式下的测深能力空间分布图,重点分析了海口和陵水附近海域的最大可测水深分布情况。为海南岛沿岸海域开展激光测深实验提供了参考和依据。     

Low-frequency sound absorption and attenuation in marine medium

Original experimental data are analyzed on the low-frequency sound attenuation in the Mediterranean, Black, and Baltic Seas, Sea of Japan, and the north-western region of the Pacific Ocean. In these regions, waters significantly differ in their temperatures and salinities. The analysis is aimed at obtaining an expression for calculating the low-frequency absorption coefficient in sea water. The analysis uses the previously published data on the measured (by the temperature discontinuity method) low-frequency relaxation times associated with boron present in sea water. The dependence of the absorption on the pH value (which was revealed in the 1970s) and the experimental data on sound absorption at frequencies higher than 5–10 kHz are also taken into account. As a result of the analysis based on the assumption that low-frequency relaxation takes place, an expression is proposed that relates the low-frequency absorption to the temperature, salinity, and pH value and equally well describes the experimental frequency dependences of attenuation for the four regions at hand (except for the Baltic Sea). Increased attenuation coefficients are noticed for shallow seas and deep-water regions where waters are influenced by intense currents, strait zones, and zones of mixing waters of different origin, i.e., for the ocean areas where, in addition to the attenuation, sound scattering by inhomogeneities of the marine medium and sound energy leakage into the sea floor are significant.     

Landsat-8的舟山近岸海域总悬浮物遥感反演与时空变异研究

总悬浮物(TSM)是海洋水质和水环境评价的主要参数之一。舟山海域位于杭州湾边缘,泥沙含量多,总悬浮物长期处于高浓度状态,其分布与动态变化对近岸水质、水循环以及该区域的渔业、旅游业都有较大影响。Landsat-8卫星影像作为一种应用广泛、空间分辨率高、便于获取的光学信息,可以为舟山海域的TSM观测提供有力的技术手段。利用舟山近岸海域实测TSM吸收系数a_p(440)和水面光谱,开发了基于Landsat-8反演TSM的最优模型,发现基于近红外和蓝色波段比B5/B2的S-函数和线性函数模型反演精度较好,相对于线性模型,S-函数具有更强的鲁棒性,该模型形式为a_p=3.72/(0.009+e-5.249B5/B2),克服了常用函数模型（如线性、对数、指数函数）应用于实际卫星影像时出现光谱幅度范围受限的困难。海岸带内陆复杂水体水色遥感的另一难点是大气校正,以往的研究往往只采用某种大气校正模型,但该模型不一定适合研究水域,从而使得校正结果并不一定是最优的。在本研究中,验证比较了FLAASH,6S和ACOLITE三种大气校正方法面向Landsat-8水色反演的校正结果,发现ACOLITE方法获取的光谱形状最准确,误差最小,特别在蓝色波段,明显好于FLAASH和6S方法。将最优模型应用于舟山近岸海域2013到2018年的10幅Landsat-8图像。实测数据和反演结果显示：舟山近岸海域的TSM吸收系数a_p(440)的变化范围在1.64～417.04 m-1,均值118.47 m-1,TSM吸收占水体总吸收的90%以上,该海域实测的水面光谱形状呈现典型的河口海岸带复杂浑浊水体的光谱特征,很多光谱曲线具有双峰特征,遥感反射率幅值较大,特别是红色、近红外波段,由于受河口高浓度TSM的影响,遥感反射率高于远海较清洁的海水;衢山、洋山、宁波等近岸区域的TSM浓度明显高于东极、嵊泗等远海区域,随河口羽化区呈现由高到低的梯度变化,在近岸区域分布复杂,外海区域分布较为均匀。在时间分布上具有冬季浓度远高于夏季的特点,其中12月最高,最大值为413.32 m-1,8月最低,最小值为3.69 m-1,5月、10月期间也有TSM的局部峰值。这些TSM时空变异特征表明舟山海域悬浮物的分布和变化一方面受地形、海流、潮汐、季风、台风等自然环境因素的影响,另一方面也受如海运、港口建设、海岛旅游等人类活动的较大影响。     

Shallow ambient noise variability due to distant shipping noise and tide

Study and characterization of distant shipping component of ambient noise in shallow water aid in design of passive surveillance algorithms and effective signature analysis of marine vessels. This letter presents the work carried out on real ambient noise recording in very shallow water condition close to a commercial port with heavy shipping activity to study and characterize the distant shipping noise component for variations due to tide. Ambient noise recording was carried out by a bottom mounted sensor at 30 m depth at regular interval for a period of over one month and the spectrum in the band 10–1.6 kHz was characterized for its diurnal spectral variation. The study concluded that the distant shipping noise component due to heavy small vessel activity in the nearby port resulted in up to 35 dB variation in the shallow water ambient noise in coastal areas that may have serious implication on passive surveillance algorithms performance in the vicinity if adequately not addressed. This is the first such effort in ambient noise measurement and characterization in the extremely shallow water channel condition prevalent in the tropical waters off the west coast of India.     

Environmental behavior of actinides

Since the plutonium concentration in ocean waters is quite low, most of the plutonium deposited in marine waters has been sorbed onto plants and sediments. Actinides in natural waters usually are not in a state of thermodynamic equilibrium for long time periods as their solubility and migration behavior is strongly related to the form in which the nuclides are introduced initially into the aquatic system for long time periods. Their solubility depends on pH (hydrolysis), E _H (oxidation state), reaction with complexants (e.g., carbonate, phosphate, humic acid, etc.), sorption to surfaces of minerals and/or colloids, etc. The primary variable is the oxidation state of the actinide cation. Actinides can be present in more than one oxidation state which complicates modeling actinide environmental behavior.Np(V)O₂ ⁺ and Pu(V)O₂ ⁺ are weakly complexing and resistant to hydrolysis and subsequent precipitation, but both can undergo reduction to the IV oxidation state. The solubility of NpO₂ ⁺ can be as high as 10^?4M, while that of PuO₂ ⁺ is more limited as the very low solubility of Pu(OH)₄ promotes reduction to Pu(IV). The solubility of hexavalent UO₂ ²⁺ in sea water is limited by hydrolysis, but has a relatively high concentration due to carbonate complexation. Americium(III) hydroxocarbonate, Am(CO₃)(OH), is the limiting species for the solubility of Am(III) in sea water. Thorium has a very low solubility due to the formation of Th(OH)₄.     

Environmental behavior of actinides

Since the plutonium concentration in ocean waters is quite low, most of the plutonium deposited in marine waters has been sorbed onto plants and sediments. Actinides in natural waters usually are not in a state of thermodynamic equilibrium for long time periods as their solubility and migration behavior is strongly related to the form in which the nuclides are introduced initially into the aquatic system for long time periods. Their solubility depends on pH (hydrolysis), E _H (oxidation state), reaction with complexants (e.g., carbonate, phosphate, humic acid, etc.), sorption to surfaces of minerals and/or colloids, etc. The primary variable is the oxidation state of the actinide cation. Actinides can be present in more than one oxidation state which complicates modeling actinide environmental behavior. Np(V)O ₂ ⁺ and Pu(V)O ₂ ⁺ are weakly complexing and resistant to hydrolysis and subsequent precipitation, but both can undergo reduction to the IV oxidation state. The solubility of NpO ₂ ⁺ can be as high as 10⁻⁴M, while that of PuO ₂ ⁺ is more limited as the very low solubility of Pu(OH)₄ promotes reduction to Pu(IV). The solubility of hexavalent UO ₂ ²⁺ in sea water is limited by hydrolysis, but has a relatively high concentration due to carbonate complexation. Americium(III) hydroxocarbonate, Am(CO₃)(OH), is the limiting species for the solubility of Am(III) in sea water. Thorium has a very low solubility due to the formation of Th(OH)₄.     

Contributions of the different water sources to the Elqui river runoff (northern Chile) evaluated by H/O isotopes

We present the results of an isotope (2H and 18O) and hydrogeochemical study in order to constrain the origin, recharge, and evolution of the surface and groundwater in the arid Andean realm of the Elqui watershed. The results of 2H and18O analyses of water samples obtained during our summer and winter campaigns indicate a generally meteoric origin of the river and spring waters of the watershed. The isotope signature of water of the Elqui river and its tributaries as well as that of groundwater in the coastal region fits the 2H-18O relation of delta2H =7.61delta18O+6.1. A relatively fast discharge and a quasi-closed catchment area can be asserted for water along the river flow path. The tributaries from the more arid coastal area, north of the Elqui river, differ in their isotopic signature due to evaporation and hydrochemically due to interactions with the strongly altered and fractured volcanic rocks of the basement. In the Andean zone, the18O-enriched hydrothermal spring of Ba?os del Toro exhibits the influence of water-rock interaction processes. The chemistry of the river water changes from sulphate- to chloride-rich along the river course from the high Andean mountains to the coast. The sulphate-rich character of these Andean waters reflects their passage through sulphide-rich rock massifs that were subjected to strong oxidation processes in the near superficial environment. This sulphate signature is enforced by past and present mining of precious metal epithermal deposits (e.g. those of El Indio-Tambo Au-Cu-As district), in which mineralised zones were developed during a series of Miocene magmatic-hydrothermal episodes in the Andean realm. Owing to the proximity of the lower Elqui river waters and its tributaries to the Pacific coast, the chloride character may be induced by agricultural and marine (sea spray, fog) sources. Generally, the main source of the Elqui river water is mainly attributed to surface runoff and less to contributions from the basement fractured aquifer.     

Behavior of the warm ocean water at the south coast of Kyushu

The warm ocean water filaments are emanated periodically in winter from the meandering Kuroshio Current at the East China Sea. They bring the intermittent warm ocean water intrusion into the Kagoshima Bay well known as ‘Kyucho’ phenomenon. From the satellite SST images, the warm water intrusion is also observed at the Fukiage Seashore. In addition to the warm water intrusions, the cold-water mass at the Osumi Strait is observed. In this study, the numerical analysis is performed to understand these phenomena. A density current is calculated by a multi-leveled finite difference method (FDM). Then, particle trajectories are calculated by the Lagrangian particle tracking method by using the previous current result. Particles are dealt with as passive tracers to be a model of plankton and hyponeuston (i.e. larva, eggs or seeds) of an open sea. Calculated results of the warm water mass show similar features of the SST images, i.e. the warm water intrusions into the bay and the cold-water mass generation. The warm water intrusion occurs when it reaches the mouth of the bay or the edge of the coast. The cold-water mass is concerned with a horizontal vortex shed from the edge of the cape. The cold-water mass is produced in a stagnation region by a horizontal vortex rather than upwelling from the deep ocean. The particle trajectories have a tendency to pile up in the bay and a stagnation region behind of the peninsula. These results supply the fundamental knowledge that contributes to biological problems at the south of Kyushu in winter adequately.     

Experimental Study of Laminar Convective Heat Transfer and Pressure Drop of Cuprous Oxide/Water Nanofluid Inside a Circular Tube

Laminar convective heat transfer enhancement of cuprous oxide (Cu₂O)/water nanofluid flowing through a circular tube was investigated experimentally in the present work. A continuous closed loop was designed to measure heat transfer coefficients and pressure drop associated with the flow of Cu₂O/water nanofluid over a wide range of laminar flow conditions. Comparison of the nanofluid experimental results with those of pure water have shown significant enhancement for heat transfer coefficients. On average, a 10% increase in heat transfer coefficient was observed with 16% penalty in pressure drop.     

Exploring Quantum Physics through Hands-On Projects,by D. Prutchi and S.R. Prutchi

In the last decade there have been extensive advances in the use of sonar systems for the mapping of the sea floor. Different sediment types can now be delineated and displayed in analogue form for subsequent mapping and analysis.

Earlier restrictions on operating depth have been overcome, and acoustic sensors in the side-scan sonar mode can now be used from ships at normal hydrographic survey speeds over the whole Continental Shelf.

Research effort at the University of Bath has led to the development of systems which are now widely used for cable survey problems, and for studying the transport of sediment in coastal waters. The geophysical use of these new techniques is still only at an early stage. With the greatly increased interest now in marine problems and in undersea technology, one may look forward to considerable development in this field of applied physics.     

Evaporation and heat exchanges between the sea and the atmosphere in the Gulf of Trieste during 1988

Summary Daily mean values of meteo-oceanographic parameters are used to compute evaporation and heat fluxes between the sea and the atmosphere in the Gulf of Trieste during 1988. Incoming solar radiation, long-wave radiation, latent and sensible heat fluxes are considered in the total heat budget. The contribution of the single parameters entering each formula is examined and a comparison between the results from different evaporative formulae is performed. The total heat budget for the year considered gives a net loss of energy of 21 W/m² which must be supplied by the heat transported by marine currents. The balance is positive for the sea surface from April to July, negative for the remaining period. Long-wave radiation accounts for the 45% of the total heat loss, latent heat for 53% and sensible heat for 2%. Computed annual mean evaporation is 1058 mm, with high peaks of more than 15 mm/day during strong Bora wind events. Evaporation slightly prevails on precipitation giving a net water loss of 30 cm. A comparison with what is found in the literature shows these results representative of the entire North Adriatic Sea. They confirm that this basin represents a sink of heat whose role in the general Mediterranean circulation consists in trasforming surface warmer waters coming from South in denser ones.     

The lidar investigation of the upper water layer fluorescence spectra of the Baltic Sea

Marine water in coastal areas and open zone of the Baltic Sea is characterized by complex biophysical structure caused by mixing of different water masses and high human impact. Our lidar investigation of the Baltic upper seawater layer allows obtaining, in real-time and without disturbing the aquatic medium, the continuous fluorescence spectra of seawater in visible range of light. These spectra provide the information about concentration of Chlorophyll a (Chl a) and humus-type (HS) of colour dissolved organic matter (CDOM) as well as allow distinguishing coastal and open-sea waters.     

Effects of closed immersion filtered water flow velocity on the ablation threshold of bisphenol A polycarbonate during excimer laser machining

A closed flowing thick film filtered water immersion technique ensures a controlled geometry for both the optical interfaces of the flowing liquid film and allows repeatable control of flow-rate during machining. This has the action of preventing splashing, ensures repeatable machining conditions and allows control of liquid flow velocity. To investigate the impact of this technique on ablation threshold, bisphenol A polycarbonate samples have been machined using KrF excimer laser radiation passing through a medium of filtered water flowing at a number of flow velocities, that are controllable by modifying the liquid flow-rates. An average decrease in ablation threshold of 7.5% when using turbulent flow velocity regime closed thick film filtered water immersed ablation, compared to ablation using a similar beam in ambient air; however, the use of laminar flow velocities resulted in negligible differences between closed flowing thick film filtered water immersion and ambient air. Plotting the recorded threshold fluence achieved with varying flow velocity showed that an optimum flow velocity of 3.00 m/s existed which yielded a minimum ablation threshold of 112 mJ/cm². This is attributed to the distortion of the ablation plume effected by the flowing immersion fluid changing the ablation mechanism: at laminar flow velocities Bremsstrahlung attenuation decreases etch rate, at excessive flow velocities the plume is completely destroyed, removing the effect of plume etching. Laminar flow velocity regime ablation is limited by slow removal of debris causing a non-linear etch rate over ‘n’ pulses which is a result of debris produced by one pulse remaining suspended over the feature for the next pulse. The impact of closed thick film filtered water immersed ablation is dependant upon beam fluence: high fluence beams achieved greater etch efficiency at high flow velocities as the effect of Bremsstrahlung attenuation is removed by the action of the fluid on the plume; low fluences loose efficiency as the beam makes proportionally large fluence losses at it passes through the chamber window and immersion medium.     

Flow encoded NMR spectroscopy for quantification of metabolite flow in intact plants

An NMR flow quantification technique applicable to metabolite flow in plants is presented. It combines flow sensitive magnetization preparation with slice selective spectroscopy. Flow encoded NMR spectroscopy is described to quantify, for the first time, flow velocities of metabolites in plants non-invasively. Flow sensitivity is introduced by magnetization preparation based on a stimulated echo experiment, prior to slice selective spectroscopy. For flow quantification eight different flow-weighted spectra are collected. With this flow preparation very slow flow velocities down to 0.1mm/s can be detected and small amounts of flowing metabolites can be observed despite the large background signal of stationary and flowing water. Important sequence optimization steps include appropriate choice of experimental parameters used for flow encoding as well as complete balancing of eddy currents from the flow encoding gradients. The method was validated in phantom experiments and applied in vivo. Examples of quantitative flow measurements of water and metabolites in phantoms and plants are provided to demonstrate the reliability and the performance of flow encoded spectroscopy.     

Trouble-shooting deployment and recovery options for various stationary passive acoustic monitoring devices in both shallow- and deep-water applications

Deployment of any type of measuring device into the ocean, whether to shallow or deeper depths, is accompanied by the hope that this equipment and associated data will be recovered. The ocean is harsh on gear. Salt water corrodes. Currents, tides, surge, storms, and winds collaborate to increase the severity of the conditions that monitoring devices will endure. All ocean-related research has encountered the situations described in this paper. In collating the details of various deployment and recovery scenarios related to stationary passive acoustic monitoring use in the ocean, it is the intent of this paper to share trouble-shooting successes and failures to guide future work with this gear to monitor marine mammal, fish, and ambient (biologic and anthropogenic) sounds in the ocean-in both coastal and open waters.     

中国近海黄色物质吸收光谱特征分析

黄色物质是中国近海水体光学特性的重要影响因素。基于在中国近海海洋光学调查中获取的908个站位的黄色物质吸收系数数据,对黄色物质440nm吸收系数(ag(440))进行了分析,研究表明:(1)在封闭或半封闭海湾以及河口海域的ag(440)较其它海域明显偏大。(2)ag(440)占水体440nm总吸收系数(at(440))的百分比值分布特点与ag(440)的分布特点呈相反的趋势,即ag(440)越大,其对水体总吸收的贡献越小。     

Circulation and heat exchanges of the Northern Adriatic in the winter season 1992/93

Summary The sea currents, temperature and conductivity were measured continuously at two stations and two depths of the eastern part of the Northern Adriatic during the winter season 1992/93. Meteorological elements were measured simultaneously at the two nearest meteorological stations on the Croatian coast (Rovinj, Pula). The sea level was also measured in that period at Rovinj. One severe bora storm was observed in the period of measurements. Qualitative good agreement between observed currents and velocities of the earlier developed models for the response of the Northern Adriatic to the bora and sirocco wind forcing has been shown. The sea currents on the Rovinj-Po transect are of the opposite direction to the bora wind because of tis spatial heterogeneity. The sea level observed at Rovinj station rose during the bora blows and it was much higher than what expected in the developed models. The response time of the currents to the bora forcing is computed by using correlation function between currents and wind. The heat exchanges on the sea-atmosphere surface are calculated. The correlation between same wind components and between total heat exchanges for two different stations was made. The sea temperature evolution calculated from meteorological data agrees well with what observed, especially for the Pula station. At the end of the measurement period the new dense water (σ_t=29.3 kg m⁻) was observed. We dedicate this article to the memory of colleague Antonio Michelato. D. Morožin is not employed at the Institute R. Boŝković.     

Effect of the size on the aggregation and sedimentation of graphene oxide in seawaters with different salinities

Graphene oxide (GO) with different sizes is inevitably released into the water environment during its production, use, and disposal. Aggregation and sedimentation would occur when GO entered into the water with high ionic strength. However, the environmental behavior and fate of GO in the coastal water are not well known. Therefore, in the present study, the aggregation and sedimentation of GO nanosheets with different sizes in seawater with different salinities were investigated. GO nanosheets with different sizes were prepared by the ultrasonic pulverization. Compared to original GO, the ultrasonically pulverized GO was more stably dispersed in deionized water. In artificial seawater, the aggregation–sedimentation process became more intense with increasing GO concentration and salinity. With the decrease of the GO nanosheet size, the aggregation–sedimentation rate increased, while the critical aggregation and sedimentation salinity decreased. As GO could deposit in wide coastal waters, which might cause potential ecological risks to marine benthic organisms, its environmental behavior, fate, and ecological risks in the coastal water should be further investigated.     

A comparison of numerical and analytical radiative-transfer solutions for plane albedo of natural waters

Several numerical and analytical solutions of the radiative transfer equation (RTE) were compared for plane albedo in a problem of solar light reflection by sea water. The study incorporated the simplest case—a semi-infinite one-dimensional plane—parallel absorbing and scattering homogeneous layer illuminated by a monodirectional light beam. Inelastic processes (such as Raman scattering and fluorescence), polarization and air-water surface refraction-reflection effects, were not considered. Algorithms were based on the invariant imbedding method and two different variants of the discrete ordinate method (DOM). Calculations were performed using parameters across all possible ranges (single-scattering albedo ω₀ and refracted solar zenith angle θ₁), but with a special emphasis on natural waters. All computations were made for two scattering phase functions, which included an almost isotropic Rayleigh phase function and strongly anisotropic double-peaked Fournier-Forand-Mobley phase function. Models were validated using quasi-single-scattering (QSSA) and exponential approximations, which represent the extreme cases of ω₀→0 and ω₀→1, respectively. All methods yielded relative differences within 1.8% for modeled natural waters. An analysis of plane albedo behavior resulted in the development of a new extended QSSA approximation, which when applied in conjunction with the extended Hapke approximation developed earlier, resulted in a maximum relative error of 2.7%. The study results demonstrated that for practical applications, the estimation of inherent optical properties from observed reflectance can best be achieved using an extended Hapke approximation.