Seasonal variations of dimethylsulfide (DMS) and dim-ethylsulfoniopropionate (DMSP) in the sea-surface microlayer and subsurface water of Jiaozhou Bay and its adjacent area

The distributions of DMS and its precursor dimethylsulfoniopropionate, in both dissolved （DMSPd） and particulate fractions （DMSPp） were determined in the sea-surface microlayer and corresponding subsurface water of the Jiaozhou Bay, China and its adjacent area in May and August 2006. The concentrations of all these components showed a clear seasonal variation, with higher concen- trations occurring in summer. This can be mainly attributed to the higher phytoplankton biomass observed in summer. Simultaneously, the enrichment extents of DMSPd and DMSPp in the mi- crolayer also exhibited seasonal changes, with higher values in spring and lower ones in summer. Higher water temperature and stronger radiant intensity in summer can enhance their solubility and photochemical reaction in the microlayer water, reducing their enrichment factors （the ratio of concentration in the microlayer to that in the corresponding subsurface water）. A statistically significant relationship was found between the microlayer and subsurface water concentrations of DMS, DMSP and chlorophyll a, demonstrating that the biogenic materials in the microlayer come primarily from the underlying water. Moreover, our data show that the concentrations of DMSPp and DMS were significantly correlated with the levels of chlorophyll a, indicating that phytoplankton biomass might play an important role in controlling the distributions of biogenic sulfurs in the study area. The ratios of DMS/chlorophyll a and DMSPpchlorophyll a varied little from spring to summer, suggesting that there was no obvious change in the proportion of DMSP producers in the phytoplankton community. The mean sea-to-air flux of DMS from the study area was estimated to be 5.70 μmol/（m^2·d）, which highlights the effects of human impacts on DMS emission.

Preliminary study on the distribution of nutrients, organic matter, trace metals in sea surface microlayer in Xiamen Bay and Jiulong Estuary

The enrichment of nutrients (Noa-, Noa-, PO43-), suspended particles, organic matter (POC, PON,DOC) , and trace metals (Cu, Ni, Cd) was determined in the sea surface microlayer of Xiamen Bay and Jiulong Estuary. The mean enrichment factors ([Xi]microlayer/[Xi ]15cm in depth) mostly ranged between 1 . 0 and 2. 0. The dissolved forms were the major forms of the components measured, the enrichment of dissolved organic matter and suspended particles could lead to the changes in the total amount and speciation of nutrients and trace metals. No correlation was observed between sample concentrations, speciation, enrichment factors and sample locations. However, some evidence shows that these parameters are correlated with sea state, indicating the complexity and dynamic nature of the sea surface microlayer.

Numerical Simulation of Residual Stress during Microlayer Composite Material Processing by EBPVD Technique

The preparation technology of microlayer composite material by the electron beam physical vapor deposition (EBPVD) technique was briefly introduced. Taking the advantage of the large-scale commercial softvare of finite element analysis, areasonable physical model was built up during the deposition processing and the distribution of residual stress was analyzedbetween substrate and deposition layer or among deposition layers. The results show that: with the increasing substrate preheating temperature, the interlaminar shear stress increases but the axial residual stress decreases. The probability of curlingup after de-bonding tends to enhance as the thickness of deposition film increases.

Surface microlayer enrichment of volatile organic compounds and semi-volatile organic compounds in drinking water source

Enrichment of volatile organic compounds(VOC) and semi-volatility organic compounds(SVOC) in surface microlayer(SM) of three drinking water sources were studied. The enrichment factor( EF s) were 0.67 to 13.37 and 0.16 to 136, respectively. The results showed some VOC and most SVOC could enrich in SM. Some EF s of SVOC was quite high. Suspension and temperature could affect EF s of SVOC, slim wind and water movement do not destroy enrichment of organic in SM.

Comparison of the Water Quality between the Surface Microlayer and Subsurface Water in Typical Water Bodies in Sichuan

Investigation and assessment of water quality status in the surface microlayer (SML) and subsurface water (SSW) in several kinds of typical water bodies in Sichuan were carried out from May to June 2010.The results showed that N, P were enriched to some extent at SML in Xichi pool, Funan River and Longquan reservoir, which made concentrations of the indexes such as total nitrogen (TN), total phosphorus (TP), chemical oxygen demand (COD)of SML be much higher than those of SSW (P<0.05), and the exceeding rates were up to 100%. The contents of TN,TP,COD of SML and SSW in Xichi pool, and Funan River exceeded III even Ⅳlevel of water quality standard, while these indexes in Longquan reservoir were lower than Ⅲ or Ⅱlevel of water quality standard. Though Chl. a mass concentration at SML and SSW in Funan River was prominently lower than those in Xichi pool and Longquan reservoir, according to the eutrophic evaluation standard, the water bodies of SML and SSW in Funan River and Xichi pool were in middle eutrophication, the highest index of eutrophication (E value) was up to 66.78, while there was light entuophic in Longquan reservoir, and there had obvious difference with E value and COD, TP, TN (P<0.05). This research shows that the water quality of Longquan reservoir is generally well. While Funan River is a middle eutrophication, and its pollution is more serious than Xichi pool, the two waters belong to national III even IV level, and SML has the capability of enrichment to the pollutants such as N, P.

Accumulation of Gel Particles in the Sea-Surface Microlayer during an Experimental Study with the Diatom <i>Thalassiosira</i><i>weissflogii</i>

Since the early 80’s, the sea-surface microlayer (SML) has been hypothesized as being a gelatinous film. Recent studies have confirmed this characteristic, which confers properties that mediate mass and energy fluxes between ocean and atmosphere, including the emission of primary organic aerosols from marine systems. We investigated SML thickness and composition in five replicate indoor experiments between September and December 2010. During each experiment, the SML and underlying seawater were sampled from four seawater tanks: one served as control, and three were inoculated with Thalassiosira weissflogii grown in chemostats at 180, 380 and 780 ppm pCO2. We examined organic material enrichment factors in each tank, paying particular attention to gel particles accumulation such as polysaccharidic Transparent Exopolymer Particles (TEP) and the proteinaceous Coomassie Stainable Particles (CSP). While previous studies have observed carbohydrates and TEP enrichment in the microlayer, little is yet known about proteinaceous gel particles in the SML. Our experiments show that CSP dominate the gelatinous composition of the SML. We believe that the enrichment in CSP points to the importance of bacterial activity in the microlayer. Bacteria may play a pivotal role in mediating processes at the air-sea interface thanks to their exudates and protein content that can be released through cell disruption.

DETERMINATION OF APPARENT SAMPLING THICKNESS OF SEA SURFACE MICROLAYER

In situ and laboratory studies of sea -surface microlayer microlayer sampling methods using glass plate , rotating drum , screen and funnel samplers were conducted . For glass plate and rotating drum samplers, surface microlayer samples of different thickness were collected by controlling their withdrawal rate and rotating rate. The relationships between pH, surface tension, the concentration of dissolved trace metals Cu and Pb, phophate , particulate mattersand sampling thickness were carefully investigated . It was shown that physicochemical and biological properties obviously at the sampling thickness of about 50 um, which is consistent with the mean thickness of the boundary film in the models of gas exchangee across the sea surface . It is proposed that the apparent sampling thickness of the surface microlayer should be less than 40 μm The factors affecting affecting the sampling thickness are discussed , and the feasibility and applicable conditions for different sampling methods are evaluated .

Microlayered Composite Materials on Basis of Copper, Refractory, Rare-Earth Metals, and Carbon for Electrical Contacts and Electrodes

A technology for obtaining microlayered composite materials of Cu-Zr-Y-Mo, Cu-Zr-Y-Cr, Cu-Zr-Y-W and Cu-Zr-Y-C systems by means of high-speed electron-beam evaporation-condensation, structure, electrical, and mechanical properties at ambient and elevated temperatures is developed.

Comparison of the water quality of the surface microlayer and subsurface water in the Guangzhou segment of the Pearl River, China

The water quality in the surface microlayer （SML） and subsurface water （SSW） in the Guangzhou segment of Pearl River, a eutrophic urban river section in China, were ana- lyzed. The spatial and temporal dynamics of nutrient concentrations, heavy metals and bac- teria were examined from two sampling sites in monthly samples throughout 2010. The mean concentrations of total nitrogen, ammonia, nitrate and nitrite were higher than 7.0 mg/L, 3.1 mg/L, 1.1 mg/L and 0.3 mg/L, while total phosphorus and orthophosphate were 0.5 mg/L and 0.1 mg/L, respectively. These results indicated that the water quality was rich in minerals and eutrophic. The mean concentrations of Mn and Fe were higher than 0.013 mg/L; and Ni, Cr and Pb were higher than 0.001 mg/L. The mean concentrations were in the order of Mn 〉Fe 〉 Ni 〉 Pb 〉 Cr. The concentrations of heavy metals in the Guangzhou segment were lower than the limit of the surface water quality standards in China and the World Health Organization （WHO）, but higher than the median values in the world＇s freshwater. The density of bacteria ranged from 3.30×10^5 to 5.23×10^6 cells/mL, and the amount of cultivable heterotrophic bac-teria ranged from 1.30×10^3 to 1.89×10^6 cfu/mL. Fecal coliform levels were beyond the V class of China water quality standard. The SML was enriched in nutrients, heavy metals and bac- teria, with the maximum enrichment factor of 3.84 for nutrients, 8.00 for heavy metals, and 3.04 for bacteria, suggesting that the water quality of the SML of the Guangzhou segment of the Pearl River was more serious than in the SSW.

Orientation of LDPE Crystals from Microscale to Nanoscale via Microlayer or Nanolayer Coextrusion

Abstract The microlayer or nanolayer coextrusion of hundreds or thousands of alternating low density polyethylene （LDPE）/polystyrene （PS） microlayers or nanolayers were used to study the orientation of LDPE crystals in the confined quasi-two-dimensional or two-dimensional space. The clear and continuous layer structures from microscale to nanoscale can be found in SEM images. The morphology evolution of LDPE crystals in the confined microlayer or nanolayer can he varied from 3D spherulites, 2D spherulites, stacked edge-on lamellar, to single edge-on lamellar. Due to the orientation of the LDPE crystals, the tensile strength of the films increases obviously when the layer thickness reduces to nanoscale. The 2D small angle X-ray scattering （SAXS） patterns can reflect the average degree of orientation of LDPE in the confined layers. The stacking of LDPE lamellae is suppressed in interlamination and oppositely in parallel to the extrusion direction. The specific orientation function f can be calculated from the patterns. The infrared dichroism further confirms the mutation of the orientation of LDPE crystals from microscale to nanoscale in the confined space.

An Improved Treatment on the Apparent Contact Angle of a Single-Bubble in Consideration of Microlayer for Simulations of Nucleate Pool Boiling

Numerical simulation of single-bubble growth behavior during nucleate pool boiling was developed based on the volume of fluid method considering the thin liquid layer under the bubble(microlayer).However,the experimental values of apparent contact angle(the small region connecting the microlayer and bulk liquid)are crucial for the simulations.Reliance on experimental results limited the further application of such numerical method.In this study,a new method calculating the force balance,used to determine the interface shape near the apparent contact angle,was proposed instead of using the experimental values of the apparent contact angle.As a result,the good agreement was shown between the simulation results obtained based on the new and previous numerical methods.The simulation results were also in consistent with the experimental results.It can be concluded that the single-bubble behavior,including the heat transfer characteristics,during nucleate pool boiling can be simulated based on the proposed method.

Heat Transfer in the Microlayer Under a Bubble During Nucleate Boiling

Many studies have shown that a very thin liquid microlayer forms under vapor bubbles during nucleate boiling. The heat transfer from the surface to the bubble is then significantly affected by this mi- crolayer and the curved region leading into the microlayer. Various models have been developed to predict the microlayer shape and the heat transfer along the curved interfacial region, but they tend to have incon- sistent boundary conditions or unrealistic results. This paper presents a theoretical model to predict the mi- crolayer thickness and the heat transfer rates for a variety of conditions. The results show how the wall su- perheat, the Hamaker constant, the bubble radius, and the accommodation coefficient at the interface affect the evaporation heat transfer rates and the microlayer shape for a large range of conditions for water and FC 72. The microlayer results are then shown to compare well with predictions made by solving the Na- vier-Stokes equations in the microlayer.

Biogeochemical cycles of selenium in Antarctic water

Both vertical and horizontal profiles of total dissolved selenium,dissolved organic and inorganic selenium,including Se(IV)and Se(VI),as well as particulate selenium in seawater were obtained on a basis of newly developed separation technique form Antarctic Ocean,where the prodiction of deep waters occurs.The results exhibited that the concentrations of Se(IV) and Se(VI) were elevated and the total concentration in the surface of the high latitude waters (1. 31 nmol/L) was above those at lower latitudes (1.09 nmol/L) and also that previously reported from the Southern Ocean(1.18 nmol/L,Suzuki,1987).Preliminary investigation using specifically designed microlayer-sampler,that was first employed to identify the main biogeochemical proeesses,revealed Antarctic Ocean being functioning as a potential source as selenium in sea-air exchange. The mean life time of the selenium,detected as Se(IV) in deep water, was also estimated rather shorter than the residence time of the water mass, based on the samples collected from the cruise of China's Sixth Scientific Expedition.

Response of Phytoneuston Community to Organic Nitrogen and Phosphorus Revealed by HPLC-Pigments Method

The sea surface microlayer(SML)is the thin boundary layer between the ocean and the atmosphere.Phytoplankton community in the SML is known as phytoneuston and has a different community structure and biomass from the phytoplankton of the underlying bulk water.In this study,water samples were collected from the SML of Daya Bay in southern China in September,October,and December of 2013.Algal growth potential(AGP)tests were conducted by adding different forms of nitrogen(N),phosphorus(P)and silicate(Si).Phytoneuston grew well with both inorganic and organic nutrients,and showed comparable community structure after nutrient addition.A total of 16 pigments were analyzed in the SML samples collected from Daya Bay in this study.Phytopigments were dominated by the cyanobacteria-diagnostic pigment(zeaxanthin,Zea)in September and October,and by diatom-diagnostic pigment(fucoxanthin,Fuco)in December.The concentrations and proportions of Fuco increased greatly after the nutrient addition,and the concentrations and proportions of Zea decreased accordingly.Additionally,the diatom pigment index(DiatDP)increased after nutrient addition,and the prokaryotic pigment index(ProkDP)conversely decreased.The results suggested that massive occurrences of Zea and cyanobacteria are important characteristics of phytoneuston structure in Daya Bay especially in warm seasons,and nutrient addition especially Si addition promoted the growth of diatoms.

Phylotype resolved spatial variation and association patterns of planktonic Thaumarchaeota in eastern Chinese marginal seas

The majority of marine ammonia oxidizers belong to Thaumarchaeota,a phylum of Archaea,which is distributed throughout the water column.Marine surface waters contain distinct thaumarchaeotal phylotypes compared to the deeper ocean,but spatial dynamics of the surface-associated lineages are largely unsolved.This study of 120 seawater samples from the eastern Chinese marginal seas identifed contrasting distribution and association patterns among thaumarchaeotal phylotypes across diferent dimensions.Horizontally,Nitrosopumilus-like and Nitrosopelagicus-like phylotypes dominated the surface water(3 m)of the Yellow Sea(YS)and East China Sea(ECS),respectively,along with increased abundance of total free-living Thaumarchaeota in ECS.Similar compositional changes were observed in the surface microlayer.The spatial heterogeneity of particle-attached Thaumarchaeota was less clear in surface microlayers than in surface waters.Vertically,the Nitrosopelagicus-like phylotype increased in abundance from surface to 90 m in ECS,which led to an increase in the proportion of Thaumarchaeota relative to total prokaryotes.This occurred mainly in the free-living fraction.These results indicate a clear size-fractionated niche partitioning,which is more pronounced at lower depths than in the surface water/surface microlayer.In addition,associations of Thaumarchaeota with other microbial taxa varied between phylotypes and size fractions.Our results show that a phylotype-resolved and size-fractionated spatial heterogeneity of the thaumarchaeotal community is present in surface oceanic waters and a vertical variation of the Nitrosopelagicus-like phylotype is present in shallow shelf waters.

Bioptical microcycles of laminated speleothems from China and their chronological significance

Interfaces of microlayers, in most stalagmites from China, consist of opaque and organic materials. Observed with microscope, the interfaces seem dark under transmitted light and luminiferous under reflected fluorescent light. Stalagmites in which the two optical characters are unified spatially would be most suitable for cross-dating use, and can play an important role in the study on speleochronology and speleoclimatology.

Alkaline phosphatase activity in the phosphorus-limited southern Chinese coastal waters

Three fractions of alkaline phosphatase activity(APA),including phytoplankton APA(phyto-APA),bacterial APA(bact-APA),and free-APA,were examined in the sea surface microlayer(SML)and the subsurface water(SSW)from Daya Bay,Guishan Island,and Guanghai Bay of southern China.Relationships between APA and environmental parameters were analyzed.The growth of phytoplankton was significantly limited by dissolved inorganic phosphorus(DIP)in the three sea areas,especially in Daya Bay.TotalAPA ranged between 1.41 and 35.26 nmol/L/hr,and the highest value was found in Daya Bay.The increased APA in Daya Bay was the result of the increase of phytoplankton biomass and the response of phytoplankton to P limitation.Phyto-APA was the main contributor in Daya Bay,while phyto-and free-APA co-dominated in Guishan Island and Guanghai Bay.Bact-,phyto-,and total-APA showed a significant inverse power function relationship with DIP,and 0.2μmol/L was the threshold for DIP on particulates and totalAPA.Pearson correlation analysis suggested that DIP limitation together with high N levels enhanced APA.High water temperature and freshwater input accelerated APA as well.Principal component analysis clearly separated samples from the three sea areas,as well as from the SML and the SSW,which indicated the differences in environmental parameters and APA levels.Our results highlight the influence of phosphorus limitation and environmental parameters on APA.

Calculation of sea-to-air flux of substances

DIMETHYL sulfide （DMS） is a principal volatile organic sulphur compound in seawater. Once released to the atmosphere, DMS is rapidly oxidized to non-sea-salt sulfate (NSS-SO42-) and thus participates in the climate change and the acid rain formation. Therefore, widespread attention has been paid to DMS. So far, there are few reported studies regarding the

A thermal-hydrodynamic coupling method for simulating the interplay between bubble departure and wall temperature variation in nucleate boiling

A thermal-hydrodynamic coupling model is used to investigate the interplay between the wall temperature distribution and the bubble departure during the nucleate boiling process.The boiling process is modeled as the combination of three subprocesses:the transient heat conduction process in the solid heater,the evaporation of the microlayer underneath the bubble,and the bubble dynamics in the two-phase bulk fluid region.The moving bubble interface is captured by the volume of fluid method in the OpenFOAM framework.The proposed model is validated against the experimental results of the boiling process of the water on an Indium Tin Oxide heater.The predicted results agree well with related measurements in the literature.Following the validation,the effects of the boiling heat flux on the bubble departure period are examined.The results show that the bubble departure period decreases with the increase of the applied heat flux.High heat flux will cause irregularity in the departure periods for successive bubbles due to the influence of the wake flow evoked by the rising bubble.Furthermore,the influence of the bubble contact angle on the boiling heat-transfer performance is investigated.It is confirmed that the bubble departure diameter increases with the increase of the contact angle,meanwhile,the average wall temperature decreases with the increase of the contact angle.

HYDRODYNAMIC RESISTANCE EFFECT OF FLUID LAYER BETWEEN TWO IMMERSED APPROACHING PARTICLES

A three-dimensional direct simulation of an immersed solid particle approaching another particle, or a flat wall, is conducted to investigate the mechanics of hydrodynamic impact of immersed particles. The simulation method is based on a modified immersed boundary method using a fixed grid system. When the particle separation distance becomes smaller than grid spacing, to account for the hydrodynamic resistance effect of liquid layer between particles near contact, a microlayer model is developed to allow determination of the pressure profile within the micro-layer without neglecting the inertial force of the layer flow. The pressure force is then taken into account in equation of particle motion. Comparisons of the simulation results with the experimental results reported in the literature are shown to substantiate the model presented in this study. The simulations reveal the complex three-dimensional flow field of the liquid and the motion of the approaching particle. The fluid pressure in the gap caused by the unsteady motion of the particle is significantly increased when the separation distance of particles is less than about one-tenth diameters of particle. Therefore the velocity of approaching particle starts to decrease due to the hydrodynamic resistance force at this position.