Rare anthropogenic and natural particles suspended in deep ocean waters

Four hundred membrane filters from the Atlantic and Pacific deep waters have been scanned for coloured and opaque particles by a method integrating the light and the scanning electron microscopes, the electron microprobe and the micro-X-ray diffraction camera. About 40 different types of particles have been found. A tentative classification of the particles and of their morphological and chemical varieties is presented, according to their anthropogenic or natural origins. From this point of view, the particles fall into five groups: (1) particle species exclusively produced by man's activities (like brass, cobalt aluminate); (2) particles exclusively produced by natural processes (like amphibole, ilmenite); (3) particles rarely produced by natural processes, but massively so by man (like metallic copper, chromium oxide); (4) a large group of particles massively produced by nature and by man (like magnetite spherules, malachite); (5) a very small group of particles whose origin could not be attributed at present. Very few entirely new compounds from the point of view of continental mineralogy have been encountered.     

大气悬浮颗粒物粒谱分析研究

本文对大气悬浮颗粒物的测量是利用半导体激光器,通过镜片组形成双光斑,当颗粒物经过双光斑时发生散射,由雪崩二极管检测散射光形成双峰信号,双峰间距即为待测粒子通过双光斑时的飞行时间,利用飞行时间可得到相应的粒径大小. 大量的实验表明空气中的粒谱呈正态高斯分布,这点与理论分析结果相一致.     

Eddy formation in the bays of Kamchatka and fluxes to the open ocean

Ocean Dynamics - The Eastern Kamchatka Current (EKC) is the western boundary current of the North Pacific subpolar gyre. Southeast of the Kamchatka Peninsula lies a large anticyclonic eddy, the...     

Chemical and isotopic study of extraterrestrial particles from the ocean floor

We report chemical, mineralogic and Rb-Sr data on deep-sea spherules and on particles from an Antarctic Ocean core in which an excess Ir content has been identified.⁸⁷Sr/⁸⁶Sr compositions in the deep-sea spherules are determined to 1–2‰ and are in the range 0.730–0.757. The⁸⁷Sr/⁸⁶Sr compositions and the Sr concentrations are in the range observed for the majority of chondritic meteorites.⁸⁴Sr/⁸⁸Sr ratios are normal to within 1%. Extreme depletion of Rb relative to the chondritic abundance is found in the deep-sea spherules. These data support the inference based on chemical composition and mineralogy that the deep-sea spherules are produced by the ablation or heating of meteoroids in the Earth's atmosphere with substantial loss of Rb by volatilization. Most terrestrial sources for the deep-sea spherules can be excluded, based on the chemical composition and on the Sr isotopic composition. The results on vesicular, Ir-rich particles from the Antarctic Ocean core give⁸⁷Sr/⁸⁶Sr in the range 0.703–0.705 and within the range observed for ocean island basalts but significantly above mid-ocean ridge basalts (MORB). A crystalline basaltic particle from this core shows non-radiogenic⁸⁷Sr/⁸⁶Sr= 0.701 ± 0.001, in the range observed for MORB and basaltic achondrites. The Sr data on the vesicular particles do not provide positive support for an extraterrestrial provenance for these materials. The basaltic particles cannot reasonably be the primary source of the high Ir concentration and some other lithic component remains to be identified.     

藻源性湖泛水体显黑颗粒的元素形态分析与鉴定

湖泛现象是我国超富营养化浅水湖泊面临的最严峻环境问题之一,水体发黑、发臭是湖泛水体最显著和基本的物理特征.针对太湖湖泛显黑颗粒缺乏从元素形态直接给出证据的问题,针对室内模拟藻体和沉积物存在下形成的湖泛水体,采用多种图谱分析技术,对厌氧截留分离的显黑颗粒物质及其化学组成和元素形态进行了分析鉴定.扫描电镜-X射线能谱分析与荧光光谱分析表明:湖泛水体显黑颗粒物质以藻类残体和悬浮沉积物颗粒物为主,其组成元素以C、O、Si为主;与未发生湖泛的对照样相比,湖泛水体显黑颗粒物样品中具有更高的Fe、S含量.X射线光电子能谱Fe、S微区分析进一步表明:湖泛显黑颗粒物样品中Fe主要以Fe(Ⅱ)的形式存在、S则以还原态S2-的形式赋存,两者具有共同化合成Fe S的充要条件.因此,缺氧厌氧条件下,湖泛水体的显黑物质组成是Fe S,它可由水体中Fe2+和ΣS2-通过化学共沉淀形成,并主要通过吸附于悬浮颗粒物之上而使得整个水柱呈现黑色,指示湖泛的暴发过程和维持状态.     

A simple model of seasonal open ocean convection

 Aspects of open ocean deep convection variability are explored with a two-box model. In order to place the model in a region of parameter space relevant to the real ocean, it is fitted to observational data from the Labrador Sea. A systematic fit to OWS Bravo data allows us to determine the model parameters and to locate the position of the Labrador Sea on a stability diagram. The model suggests that the Labrador Sea is in a bistable regime where winter convection can be either “on” or “off ”, with both these possibilities being stable climate states. When shifting the surface buoyancy forcing slightly to warmer or fresher conditions, the only steady solution is one without winter convection.  We then introduce short-term variability by adding a noise term to the surface temperature forcing, turning the box model into a stochastic climate model. The surface forcing anomalies generated in this way induce jumps between the two model states. These state transitions occur on the interannual to decadal time scale. Changing the average surface forcing towards more buoyant conditions lowers the frequency of convection. However, convection becomes more frequent with stronger variability in the surface forcing. As part of the natural variability, there is a non-negligible probability for decadal interruptions of convection. The results highlight the role of surface forcing variability for the persistence of convection in the ocean.     

A simple model of seasonal open ocean convection

 A simple tutorial model of open-ocean deep convection is presented, based on the seminal box model of Welander. The model is extended to include prognostic variables of the deep box. An approximate analytical solution is found and discussed for a surface forcing which includes a seasonal cycle. The model helps to illustrate, e.g., the basic balances at work in determining the duration of the winter convection season or the rate dependence of the response of convection to surface warming.     

Hydrogen isotopes in palmitic and stearic acids in suspended particles from the Changjiang River Estuary

Hydrogen isotopes in lipid biomarkers can trace past changes in the hydrologic cycle. Recent studies have revealed the potential of hydrogen isotopes in microalgal lipids for quantitatively reconstructing water δ~2H(δD) values and salinity. In this study we collected suspended particles along a salinity gradient from the Changjiang River Estuary(CRE), and measured δD values in fatty acids in these particles. The results indicated that δD values of water were correlated highly with salinity from the CRE, in agreement with the results from other estuaries. δD values in palmitic acid and stearic acid had a positive correlation with δD values of water from the CRE. Nevertheless, in the CRE, hydrogen isotope fractionation in fatty acids relative to water increased as salinity increased, opposite the trend in hydrogen isotope fractionation with salinity found in microalgal culture and field studies. We attribute the increase in hydrogen isotope fractionation as salinity increased to light availability, which was likely lower in the particle rich mixing zone at the end of the estuary, and potentially as well to multiple sources of fatty acids in the CRE.     

Theoretical/numerical model for the transport of non-uniform suspended sediment in open channels

In this paper, we address the transport of multi-disperse suspended sediment mixtures in open channels, via the use of the two-fluid model. To that end, we extend previously developed frameworks for the dilute and non-dilute transport of suspended sediment. Within the scope of the Reynolds-averaged Navier-Stokes (RANS) equations, these modeling frameworks comprise mass and momentum equations for both phases (water and sediment). Here, we calculate the distribution of total volumetric concentration of sediment using two approaches: (1) by considering the mixture as represented by a single size; we call this approach Partial two-fluid model for uniform sediments (PTFMU); and (2) by combining the volumetric concentration of the sediment corresponding to several particle size classes; we call this approach Partial two-fluid model for non-uniform sediments (PTFMNU). In the second approach, we propose a methodology for the computation of the overall velocity of the disperse phase as a function of the velocities of each size class. k-ε type closures to account for the turbulence in the carrier phase (water) are applied. We also consider the coupling between the two phases through the drag force. Velocities of the carrier and disperse phases, and concentrations for each sediment class size are numerically solved by integrating the differential equations over control volumes. In order to validate our models, we compare numerical results to experimental data of Einstein and Chien [H.A. Einstein, N. Chien, Effects of heavy sediment concentration near the bed on velocity and sediment distribution, MRD sediment series report, University of California, Berkley, 1955] and Taggart et al. [W.C. Taggart, C.A. Yermoli, S. Montes, A. Ippen, Effects of sediment size and gradation on concentration profiles for turbulent flow, Massachusetts Institute of Technology, 1972]. Results of mean velocity of the carrier phase are in close agreement with the experimental data. For the prediction of sediment concentrations, we observe that there is a difference in the results using the two approaches mentioned above. We additionally obtain values of the Schmidt number needed to improve the agreement between predictions of the distribution of suspended sediment and the experimental data, and discuss the effect of sediment size and increasing sediment concentration on the values of the Schmidt number.     

Organic micropollutants in marine plastics debris from the open ocean and remote and urban beaches

To understand the spatial variation in concentrations and compositions of organic micropollutants in marine plastic debris and their sources, we analyzed plastic fragments (∼10 mm) from the open ocean and from remote and urban beaches. Polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), dichloro-diphenyl-trichloroethane and its metabolites (DDTs), polybrominated diphenyl ethers (PBDEs), alkylphenols and bisphenol A were detected in the fragments at concentrations from 1 to 10,000 ng/g. Concentrations showed large piece-to-piece variability. Hydrophobic organic compounds such as PCBs and PAHs were sorbed from seawater to the plastic fragments. PCBs are most probably derived from legacy pollution. PAHs showed a petrogenic signature, suggesting the sorption of PAHs from oil slicks. Nonylphenol, bisphenol A, and PBDEs came mainly from additives and were detected at high concentrations in some fragments both from remote and urban beaches and the open ocean.     

Coccolith chemistry reveals secular variations in the global ocean carbon cycle?

The mismatch between the 100 and 400 k.y. components of Pleistocene climate and the relative power of those terms from the eccentricity of the Earth's orbit remains a challenge to the Milankovitch hypothesis. Coccolithophores have the potential to respond to parameters of orbital forcing other than insolation, and, as a critical component of the ocean carbon cycle, can act to modify the climate response. The first direct comparison of coccolith fraction Sr/Ca, alkenone abundance and automated coccolithophore counts, shows that CF Sr/Ca is largely driven by changing production of bloom species, with unusually high Sr/Ca ratios. The periods of high CF Sr/Ca and high bloom production mark periods of high global coccolithophore production, which correlate inversely with the low amplitude 100 and higher amplitude 400 k.y. eccentricity orbital frequency. ∼ 400 k.y. cycles of coccolithophore bloom production correspond to periods of enhanced carbonate accumulation in some parts of the ocean, deep ocean dissolution in others, positive shifts in global ocean δ¹³C, and acmes of Gephyrocapsa caribbeanica and Emiliania huxleyi. The link between production of coccolithophore blooms and eccentricity may be due to orbital control of silica leakage from the Southern Ocean, to the orbitally defined inverse correlation between insolation and growing season length and the asymptotic growth response to these parameters, or to changes in nutrient input from weathering. During the Pleistocene, the eccentricity induced coccolithophore acmes have no apparent influence on atmospheric carbon dioxide (pCO₂) due to the shift towards small bloom coccolithophores, or to coupling with increased diatom productivity, or the ballast effect of the calcium carbonate rain, such that Pleistocene climate has no significant variance at the largest amplitude eccentricity forcing of 400 k.y. Coccolithophores and their influence on the carbon cycle may act as a filter between the incident orbital forcing and resultant climate.     

Has the amount of tar on the open ocean changed in the past decade?

Quantitative surveys of beach tar on Bermuda during 1978–1979 are compared with similar surveys in 1971–1972. A 15% increase in the mean, while not significantly different from previously observed levels, is significantly higher than the reported 27% decrease due to improvements in tanker operations.     

自然水体中悬浮物对反硝化影响的研究进展

悬浮物在自然水体（池塘、河流、湖泊等）中普遍存在,相较于上覆水,是微生物更为倾向的附着载体。相较于沉积物,更易获取硝酸盐,是水体反硝化发生的热点微区。悬浮物在水体中经历一系列碰撞、絮凝、溶解、离子交换、吸附解吸等物理化学过程,从而会引起颗粒物粒径、营养盐浓度等发生变化;悬浮物的沉降和再悬浮过程也会引起上覆水和沉积物之间的物质交换,并在好氧缺氧过渡过程中对氮转化造成影响,从而直接或者间接影响水体反硝化速率。本文概括了国内外关于悬浮物影响水体反硝化的研究进展和热点,总结了不同浓度、粒径、组成和种类的悬浮物对反硝化作用的影响,从溶解氧、功能微生物、无机氮、有机碳等环境因素重点归纳了悬浮物影响反硝化的过程,比较和分析了悬浮物反硝化的测定方法。结合当前悬浮物反硝化研究现状,建议未来可以从新兴污染物悬浮物、机理模型、测定方法等方面展开深入研究。     

Experimental investigation of suspended particles transport in porous medium under variable temperatures

This paper presents a study on suspended particle transport in porous medium with the aid of a sand layer transportation–deposition testing system to determine the kinetic characteristics of particles in porous medium under variable temperatures. Quartz sand and quartz powder were chosen as the porous medium and particle in the tests, respectively. Four size compositions and two operational modes, that is, temperature reduction mode (changing from 18°C to 5°C) and temperature increment mode (changing from 18°C to 35°C), were adopted. The turbidity and concentration of quartz powder were measured under various conditions. We observed a high temperature‐independent correlation between them. Breakthrough curves under different conditions were analysed using this testing system. The results showed that changes in temperature affected the particle transport process to some extent, and the degree of influence was closely related to the time moment of the temperature change onset. Moreover, we found a hysteresis phenomenon in the breakthrough curve under both temperature reduction and increment conditions. The results also indicated that the temperature effect was particularly significant for smaller particles. The typical curves to represent particle transport process under variable temperatures were put forward according to the results. To explain the test results, four factors, that is, water viscosity, adsorption effect, double layer force, and particle kinetic energy, were considered and categorized as promotion or constraining factors.     

Quantifying the suspended sediment discharge to the ocean from the Markham River,Papua New Guinea

The Markham River is a small river draining a tropical mountain range with altitudes between 1000 and 3000 m and discharges directly into a submarine canyon, the head of which is at 30 m depth and reaches depths of 500 m only 4 km from the shore. As such, the Markham discharge system serves as a possible analogue for rivers discharging onto margins during low stands of sea-level. Located in a tectonically active area and with high rainfall, sediment supply is high and episodic and is sometimes related to catastrophic mountain landslides. The river has an estimated sediment load of 12 Mt yr⁻¹. Occasionally, high energy flows are generated at the river mouth which is evident from the channel morphology and sediment distribution. Profiles of salinity and suspended sediment concentrations (SSC) show that sediment is dispersed via a plume with components at both the surface, intermediate depth along isopycnal surfaces and near the sea bed. The dispersal pattern of the surface freshwater plume is largely determined by the buoyancy force. The surface plume is very thin with salinity gradients 15 ppt m⁻¹ while a Richardson number greater than unity suggested that the mixing zone is highly stratified. Estimates of the horizontal sediment flux gradient of the surface plume along the estuary axis suggest that about 80% of the sediment discharged is lost from the plume within a distance of 2 km from the river mouth. Particle fall velocities estimated from the vertical flux indicate values less than those of flocculated material. Layers of sediment with SSCs between 500 and 1000 mg l⁻¹ were observed at intermediate depths and near the seabed during periods of both high and intermediate discharge. The mass of sediment in a SSC layer at intermediate depths between 150 and 250 m within the canyon channel was estimated to be equivalent to an average of 2 to 3 days of Markham sediment discharge. SSCs near the seabed of between 250 and 750 mg l⁻¹ suggest that layers of significantly elevated density exist near the seabed, moving under the influence of gravity down steep seabed slopes of the Markham canyon.     

Beginning of the new solar cycle (cycle 24) in the large-scale open solar magnetic field

It is proposed to determined minimums of the 11-year solar cycles based on a minimal flux of the large-scale open solar magnetic field. The minimal fluxes before the finished cycle 23 (Carrington rotation CR 1904) and the started cycle 24 (CR 2054, April 2007) were equal to 1.8 × 10²² and 1.2 × 10²² μs, respectively. The long-term tendency toward an approach to a deep minimum of solar activity is confirmed. On the assumption that magnetic flux variations from minimums to maximums are proportional to each other, the anticipated value of the maximal Wolf number during cycle 24 is estimated as W _max = 80.     

The effect of temperature on the seepage transport of suspended particles in a porous medium

The main purpose of this study is to experimentally investigate the effect of temperature on the seepage transport of suspended particles (SP) with a median diameter of 10–47 μm in a porous medium for various seepage velocities. The results show that the rise of temperature accelerates the irregular movements of SPs in the porous medium and reduces their migration velocity. As a result, the pore volume corresponding to the peak value of the breakthrough curves is apparently delayed, and the peak value in the effluent is decreased. The migration velocity of SPs decreases with increasing particle size, regardless of the Darcy velocity and temperature. The longitudinal dispersivity of SPs decreases slightly with increasing temperature and then remains almost unchanged. Larger particles experience more irregular movements induced by the limit of pore size, which leads to a larger dispersivity. The deposition coefficient increases with increasing temperature, especially in the case of a high seepage velocity, and then tends to be stable. The deposition coefficient for large‐sized particles is higher than that for small‐sized particles, which can be attributed to the restriction of large‐sized particles by the narrow pores in the porous medium. The recovery rate decreases slightly with the increase of temperature until a critical value is reached, beyond which it remains almost unchanged. In summary, temperature is a significant factor affecting the transport and deposition of SPs in the porous medium, and the transport parameters such as particle velocity, dispersivity, and deposition coefficient.     

Tidal variation of total suspended solids over the Yangtze Bank based on the geostationary ocean color imager

Hourly mapping by a Geostationary Ocean Color Imager was used to reveal the spatial pattern and tidal variation of total suspended solids(TSS) over the Yangtze Bank in the Yellow and East China Seas during the winter. The TSS form a tongueshaped structure, which decreases further offshore in a stepwise manner. The stepwise change is separated by two fronts of TSS,which are located near the 20-m and 50-m isobaths. The tidal variation of TSS concentration during the study period is evident and can be divided into three stages: decay, maintenance, and growth. Compared with the relatively stationary TSS during the maintenance stage, drastic changes exist during the decay and growth stages. In terms of tide-induced mixing, the dynamic analysis shows that both the topography and the tidal currents play an important role in the spatio-temporal variation of TSS during the tidal period. In particular, spatial distribution is primarily determined by the topography, whereas the temporal variations in tidal scale are determined by the tidal currents.