Showing papers on "Deposition (chemistry) published in 2004"

Impact of nitrogen deposition on the species richness of grasslands

Abstract: A transect of 68 acid grasslands across Great Britain, covering the lower range of ambient annual nitrogen deposition in the industrialized world (5 to 35 kg Nha–1 year–1), indicates that long-term, chronic nitrogen deposition has significantly reduced plant species richness. Species richness declines as a linear function of the rate of inorganic nitrogen deposition, with a reduction of one species per 4-m2 quadrat for every 2.5 kg Nha–1 year–1 of chronic nitrogen deposition. Species adapted to infertile conditions are systematically reduced at high nitrogen deposition. At the mean chronic nitrogen deposition rate of central Europe (17 kg Nha–1 year–1), there is a 23% species reduction compared with grasslands receiving the lowest levels of nitrogen deposition.

Layer by Layer Buildup of Polysaccharide Films: Physical Chemistry and Cellular Adhesion Aspects

Abstract: The formation ofpolysaccharide films based on the alternate deposition of chitosan (CHI) and hyaluronan (HA) was investigated by several techniques. The multilayer buildup takes place in two stages: during the first stage, the surface is covered by isolated islets that grow and coalesce as the construction goes on. After several deposition steps, a continuous film is formed and the second stage of the buildup process takes place. The whole process is characterized by an exponential increase of the mass and thickness of the film with the number of deposition steps. This exponential growth mechanism is related to the ability of the polycation to diffuse "in" and "out" of the whole film at each deposition step. Using confocal laser microscopy and fluorescently labeled CHI, we show that such a diffusion behavior, already observed with poly(L-lysine) as a polycation, is also found with CHI, a polycation presenting a large persistence length. We also analyze the effect of the molecular weight (MW) of the diffusing polyelectrolyte (CHI) on the buildup process and observe a faster growth for low MW chitosan. The influence of the salt concentration during buildup is also investigated. Whereas the CHI/HA films grow rapidly at high salt concentration (0.15 M NaCl) with the formation of a uniform film after only a few deposition steps, it is very difficult to build the film at 10(-4) M NaCl. In this latter case, the deposited mass increases linearly with the number of deposition steps and the first deposition stage, where the surface is covered by islets, lasts at least up to 50 bilayer deposition steps. However, even at these low salt concentrations and in the islet configuration, CHI chains seem to diffuse in and out of the CHI/HA complexes. The linear mass increase of the film with the number of deposition steps despite the CHI diffusion is explained by a partial redissolution of the CHI/HA complexes forming the film during different steps of the buildup process. Finally, the uniform films built at high salt concentrations were also found to be chondrocyte resistant and, more interestingly, bacterial resistant. Therefore, the (CHI/HA) films may be used as an antimicrobial coating.

Nitrogen deposition modifies soil carbon storage through changes in microbial enzymatic activity

Abstract: Atmospheric nitrogen (N) deposition derived from fossil-fuel combustion, land clearing, and biomass burning is occurring over large geographical regions on nearly every continent. Greater ecosystem N availability can result in greater aboveground carbon (C) sequestration, but little is understood as to how soil C storage could be altered by N deposition. High concentrations of inorganic N accelerate the degradation of easily decom- posable litter and slow the decomposition of recalcitrant litter containing large amounts of lignin. This pattern has been attributed to stimulation or repression of different sets of microbial extracellular enzymes. We hypothesized that soil C cycling in forest ecosystems with markedly different litter chemistry and decomposition rates would respond to anthro- pogenic N deposition in a manner consistent with the biochemical composition of the dominant vegetation. Specifically, oak-dominated ecosystems with low litter quality should gain soil C, and sugar maple ecosystems with high litter quality should lose soil C in response to high levels of N deposition (80 kg N-ha-1-yr-1). Consistent with this hypothesis, we observed over a three-year period a significant loss of soil C (20%) from a sugar maple- dominated ecosystem and a significant gain (10%) in soil C in an oak-dominated ecosystem, a result that appears to be mediated by the regulation of the microbial extracellular enzyme phenol oxidase. Elevated N deposition resulted in changes in soil carbon that were ecosystem specific and resulted from the divergent regulatory control of microbial extracellular en- zymes by soil N availability.

CO oxidation on Aun/TiO2 catalysts produced by size-selected cluster deposition.

Abstract: Planar model catalysts were prepared by deposition of size-selected gold clusters containing up to seven atoms on rutile TiO2 (110). Molecular oxygen is observed to bind inefficiently to the surface, probably at oxygen vacancies, and some oxygen also appears to bind to the gold clusters. Stable CO binding is observed atop gold for catalysts prepared by Au and Au2 deposition, but not for larger Aun. CO oxidation activity is strongly dependent on cluster size, with Au7-prepared samples >50 times more reactive than samples prepared by Au or Au2 deposition

Mud and Mudstones: Introduction and Overview

Abstract: Overview.- Production of Mud and Silt.- Transport and Deposition.- Role of Oxygen.- Muddy Depositional Systems.- Burial.- Provenance of Mudstones.- Muddy Basins.- Practicalities.

Effects of Nitrogen Deposition on Insect Herbivory: Implications for Community and Ecosystem Processes

Abstract: The deposition of anthropogenically fixed nitrogen (N) from the atmosphere onto land and plant surfaces has strong influences on terrestrial ecosystem processes. Although recent research has expanded our understanding of how N deposition affects ecosystems directly, less attention has been directed toward the investigation of how N deposition may affect ecosystems indirectly by modifying interactions among organisms. Empirical evidence suggests that there are several mechanisms by which N deposition may affect interactions between plants and insect herbivores. The most likely mechanisms are deposition-induced shifts in the quality and availability of host plant tissues. We discuss the effects of N deposition on host plant chemistry, production, and phenology, and we review the evidence for the effects of N deposition on insect herbivores at the individual, population, and community levels. In general, N deposition has positive effects on individual insect performance, probably due to deposition-induced improvements in host plant chemistry. These improvements include increased N and decreased carbon-based defensive compound concentrations. The evidence to date suggests that N deposition may also have a positive effect on insect populations. These effects may have considerable ecological, as well as economic consequences if the rates of herbivory on economically important timber species continue to increase. Deposition-induced changes in plant–herbivore relationships may affect community and ecosystem processes. However, we predict that the larger-scale consequences of interactions between N deposition and herbivory will vary based on site-specific factors. In addition, interactions between N deposition and other global-scale changes may lead to nonadditive effects on patterns of herbivory.

Microbial community response to nitrogen deposition in northern forest ecosystems

Abstract: The productivity of temperate forests is often limited by soil N availability, suggesting that elevated atmospheric N deposition could increase ecosystem C storage. However, the magnitude of this increase is dependent on rates of soil organic matter formation as well as rates of plant production. Nonetheless, we have a limited understanding of the potential for atmospheric N deposition to alter microbial activity in soil, and hence rates of soil organic matter formation. Because high levels of inorganic N suppress lignin oxidation by white rot basidiomycetes and generally enhance cellulose hydrolysis, we hypothesized that atmospheric N deposition would alter microbial decomposition in a manner that was consistent with changes in enzyme activity and shift decomposition from fungi to less efficient bacteria. To test our idea, we experimentally manipulated atmospheric N deposition (0, 30 and 80 kg NO3−-N) in three northern temperate forests (black oak/white oak (BOWO), sugar maple/red oak (SMRO), and sugar maple/basswood (SMBW)). After one year, we measured the activity of ligninolytic and cellulolytic soil enzymes, and traced the fate of lignin and cellulose breakdown products (13C-vanillin, catechol and cellobiose). In the BOWO ecosystem, the highest level of N deposition tended to reduce phenol oxidase activity (131±13 versus 104±5 μmol h−1 g−1) and peroxidase activity (210±26 versus 190±21 μmol h−1 g−1) and it reduced 13C-vanillin and 13C-catechol degradation and the incorporation of 13C into fungal phospholipids (p<0.05). Conversely, in the SMRO and SMBW ecosystems, N deposition tended to increase phenol oxidase and peroxidase activities and increased vanillin and catechol degradation and the incorporation of isotope into fungal phospholipids (p<0.05). We observed no effect of experimental N deposition on the degradation of 13C-cellulose, although cellulase activity showed a small and marginally significant increase (p<0.10). The ecosystem-specific response of microbial activity and soil C cycling to experimental N addition indicates that accurate prediction of soil C storage requires a better understanding of the physiological response of microbial communities to atmospheric N deposition.

Apparent decreases in colloid deposition rate coefficients with distance of transport under unfavorable deposition conditions: a general phenomenon.

Abstract: The transport of polystyrene microspheres was examined in packed glass beads under a variety of environmentally relevant ionic strength and flow conditions. The observed profiles of numbers of retained microspheres versus distance from the column entrance were much steeper than expected based on a constant rate coefficient of deposition acrossthe length of the column, indicating apparent decreases in deposition rate coefficients with transport distance. Deviation in the profile from log-linear decreases with distance was greatest under highly unfavorable conditions (low ionic strength), relatively reduced under mildly unfavorable conditions (high ionic strength), and was eliminated under favorable conditions. The generality of apparent decreases in deposition rate coefficients with distance of transport among microspheres, bacteria, and viruses leads to the conclusion that such effects reflect processes that are fundamental to filtration under unfavorable conditions. Numerical simulations of experiments that were performed under unfavorable conditions utilized a log-normal distribution of deposition rate coefficients among the colloid population in orderto simulate the effluent curves and retained profiles simultaneously. It is shown that while straining could be a significant contributor to the steep retained profiles at low ionic strength, where overall retention is low, distribution in interaction potentials among the population was a viable mechanism that can yield apparent decreases in deposition rate coefficients with distance of transport.

Sulfur pollution suppression of the wetland methane source in the 20th and 21st centuries

Abstract: deposition, within the range of global acid deposition. We apply a model of this relationship to demonstrate the potential effect of changes in global sulfate deposition from 1960 to 2080 on both northern peatland and global wetland CH4 emissions. We estimate that sulfur pollution may currently counteract climate-induced growth in the wetland source, reducing CH4 emissions by 15 Tg or 8% smaller than it would be in the absence of global acid deposition. Our findings suggest that by 2030 sulfur pollution may be sufficient to reduce CH4 emissions by 26 Tg or 15% of the total wetland source, a proportion as large as other components of the CH4 budget that have until now received far greater attention. We conclude that documented increases in atmospheric CH4 concen- tration since the late 19th century are likely due to factors other than the global warming of wetlands.

Nitrogen deposition and increased carbon accumulation in ombrotrophic peatlands in eastern Canada

Abstract: [1] Recent and long-term accumulation rates of carbon (C), using 210Pb- and 14C-dating, were examined in 23 ombrotrophic peatlands in eastern Canada, where average 1990–1996 atmospheric wet nitrogen (N) deposition ranged from 0.3 to 0.8 g N m−2 yr−1. The average recent rate of C accumulation (RERCA) over the past 150 years was 73 ± 17 (SD) g C m−2 yr−1, ranging from 40 to 117 g C m−2 yr−1. The difference in RERCA between hummocks (78 g C m−2 yr−1) and hollows (65 g C m−2 yr−1) was significant. Increased RERCA over the past 50 years was found in hummocks and hollows in regions of higher N deposition and related to both elevated N deposition and growing degree-days above +5°C. There was a statistically significant positive relationship between N deposition alone and present-day C accumulation in both hummocks and hollows (R2 = 0.28 and 0.38, respectively). Recent N accumulation was significantly larger in high N deposition regions. The total average aboveground vegetation biomass of hollows and hummocks did not differ significantly with N deposition. However, a significantly larger vascular plant leaf biomass was found in both hollows and hummocks of the high N deposition class than in the low N deposition class (>0.6 and <0.4 g m−2 yr−1, respectively). The average long-term apparent rate of C accumulation (LORCA) at 15 sites was 19 ± 8 (SD) g C m−2 yr−1, with no significant difference due to age of peat inception, latitude, or continentality.

Characterization of iron oxide thin films

Abstract: Iron oxide thin films were grown with gas-phase deposition on a glass substrate in order to study the effects of the deposition temperature and time on the film properties. Characterization of the samples was performed using x-ray photoelectron spectroscopy, x-ray diffraction, and atomic force microscopy. It was observed that the film deposited at 350°C consisted of γ-Fe2O3 whereas films produced at temperatures between 400°C and 500°C could be identified as α-Fe2O3. Increasing the deposition temperature resulted in an increase of the grain size at temperatures between 350°C and 450°C. When the deposition time was decreased, a part of the iron ions were observed to be in the divalent state. Copyright © 2004 John Wiley & Sons, Ltd.

Monitoring nitrogen deposition in throughfall using ion exchange resin columns: a field test in the San Bernardino Mountains.

Abstract: Conventional throughfall collection methods are labor intensive and analytically expensive to implement at broad scales. This study was conducted to test an alternative approach requiring infrequent sample collection and a greatly reduced number of chemical analyses. The major objective of the study was to determine the feasibility of using ion exchange resin (IER) to measure N deposition in throughfall with field deployment periods of 3 to 12 mo. Nitrogen deposition measurements in bulk throughfall collected under pine (Pinus sp.) canopies and in forest clearings were compared between co-located conventional throughfall solution collectors and IER throughfall collectors using mixed bed IER columns. Deposition data were collected for 1 yr at a high deposition site (Camp Paivika, CP) and a relatively low one (Barton Flats, BF) in the San Bernardino Mountains in southern California: Annual throughfall deposition values (kg ha -1 of NH 4 -N + NO 3 -N) under large ponderosa pine trees (Pinus ponderosa Laws.) were 145.8 and 143.9 at CP and 17.0 and 15.0 at BF according to the IER and conventional methods, respectively. Analogous values for bulk deposition in forest clearings were 15.6 and 12.3 at CP and 4.0 and 3.3 at BF. It was concluded that the IER collectors can be used for routine monitoring of deposition in throughfall and bulk deposition, provided that field blanks are used to account for background levels of N in the IER columns, which at times are slightly elevated, possibly from slow release of amine groups from the anion exchange resin during field exposures.

Deposition of anatase on the surface of activated carbon

Abstract: As part of a program looking into utilization of activated carbon prepared from waste material, titanium dioxide was deposited on the surface of active carbon (AC). This will be used in future work as potential photo-catalyst for treatment of chlorinated phenols in aqueous medium. Three different techniques were used: chemical vapour deposition (CVD), direct air-hydrolysis (DAH) and high-temperature impregnation (HTI) techniques. The total TiO2 deposited and amount crystallized into anatase TiO2 by each technique is estimated. The pre-sonication was found useful in introducing part of the hydrolysis step within the small pores. The effect of each deposition procedure on surface area, porosity and thermal stability of the sample was studied by nitrogen adsorption, mercury intrusion, methylene blue (MB) adsorption and thermal gravimetric analysis. Surface texture of the potential catalysts was studied by electron microscopic techniques. Results showed that different procedures gave different yields of total and anatase TiO2. On the other hand, there was significant reduction, which may be due to TiO2 deposition, in porosity and surface area. The reduction in MB adsorption was proportional to anatase TiO2 but not to the total TiO2 deposited. Chemical vapour deposition gave more anatase TiO2 than the direct air-hydrolysis technique, which is thought to form the deposit within the micro-meso pores, and caused more porosity-surface area reduction. It is thought that TiO2 particles inside the pores have more opportunity to crystallize into the anatase form. The deposited layer of TiO2 apparently catalyzed slight weight loss at low temperatures but generally gave more thermal stability for the support. Non-activated carbon (C) was used and its thermal stability, porosity and surface area were not affected by TiO2 deposition. The deposition, in non-activated carbon, is thought to occur on external surface, which may be due to absence of large micropores.

Nitrogen deposition and plant species interact to influence soil carbon stabilization

Abstract: Anthropogenic nitrogen (N) deposition effects on soil organic carbon (C) decomposition remain controversial, while the role of plant species composition in mediating effects of N deposition on soil organic C decomposition and long-term soil C sequestration is virtually unknown. Here we provide evidence from a 5-year grassland field experiment in Minnesota that under elevated atmospheric CO2 concentration (560 ppm), plant species determine whether N deposition inhibits the decomposition of soil organic matter via inter-specific variation in root lignin concentration. Plant species producing lignin-rich litter increased stabilization of soil C older than 5 years, but only in combination with elevated N inputs (4 g m )2 year )1 ). Our results suggest that N deposition will increase soil C sequestration in those ecosystems where vegetation composition and/or elevated atmospheric CO2 cause high litter lignin inputs to soils.

Asphaltene Deposition on Metallic Surfaces

Abstract: The potential for asphaltene deposition in wellbores and flowlines is a major concern during design of oil production and transportation facilities, especially in deep‐water environments. Understanding the processes that control asphaltene deposition, especially the relationship between precipitation and deposition, can help to reduce the risk and cost. Stainless steel capillary tubes were used to study the influences of factors including temperature, degree of asphaltene instability, and precipitant molar volume on asphaltene deposition from mixtures of stock‐tank oils and n‐alkanes. Temperature varied from 20°C to 60°C. Pressure drop across the capillary tube was used to estimate the amount and distribution of deposit formation. Existing asphaltic particles in stock‐tank oil samples did not create deposits. Below the wax appearance temperature, intermittent pressure spikes indicated deposition of wax. Above the wax appearance temperature, deposition occurred gradually from near‐onset mixtures c...

Deposition and mobilization of clay colloids in unsaturated porous media

Abstract: [1] We report results on the effects of porewater pH and transients in porewater flow on the deposition and mobilization of colloid-sized clay particles within unsaturated sand columns. The deposition rates of illite under steady-flow conditions were essentially independent of pH, while the deposition rates of kaolinite nearly doubled as the pH decreased from 7.4 to 4.6. Mobilization of kaolinite colloids was slow or negligible under steady-flow conditions; however, transients in porewater flow induced rapid colloid release. A model that accounts for rate-limited deposition reactions and that links colloid mobilization to variations in moisture content and porewater velocity describes the effluent colloid concentrations measured during the steady-flow and transient-flow stages of the column experiments. On the basis of these results we infer that the effects of pH on clay-colloid deposition depend on the mineralogy of the clay colloids and that perturbations in flow are critical in mobilizing clay colloids within the vadose zone.

Effect of body size on breathing pattern and fine-particle deposition in children.

Abstract: Interchild variability in breathing patterns may contribute to variability in fine particle lung deposition and morbidity in children associated with those particles. Fractional deposition (DF) of ...

Kinetics of electrophoretic deposition for nanocrystalline zinc oxide coatings

Abstract: An integrated process combining the preparation of ZnO nanoparticles and the formation of ZnO coatings using electrophoretic deposition (EPD) is reported The work focuses on the deposition kinetics of nanocrystalline ZnO coatings on copper electrodes during EPD by direct measurement of the thickness of the deposited layer The experimental results show that the EPD process is a powerful route to fabricate uniform coatings with desired thickness and excellent surface smoothness, which might be attributed to small particle size and narrow size distribution On the other hand, the deposition kinetics changes with applied voltage and deposition time The deposition thickness increases with increasing applied voltage and deposition time In a short deposition time, the deviation of deposition rate between the theoretical and experimental values is caused by voltage drops during deposition, and the discrepancy increases with the applied voltage Moreover, the increasing voltage drop and depletion of the suspension lead to decreasing current and lower deposition rate after longer deposition time The critical transition time of deposition kinetics is found to exponentially decrease with increasing applied voltage

Role of Ionic Depletion in Deposition during Electrophoretic Deposition

Abstract: A model is developed for deposition during the electrophoretic deposition (EPD) process. It suggests that ions that move with the charged particles in suspension are depleted at the depositing electrode, locally changing the pH toward the isoelectric point (pH lep ) to give coagulation. The variation of zeta (ζ) potential is modeled via chemical-equilibrium and surface-adsorption isotherms. The model successfully fits the experimental data for Al 2 O 3 particles in ethanol when the Freundlich surface-adsorption isotherm is assumed. Calculations predict the co-ion concentration gradient as a function of location within the suspension, and the deposition time and its role in the coagulation process during EPD.

Annual variations in pollen deposition and meteorological conditions on the fell Aakenustunturi in northern Finland: Potential for using fossil pollen as a climate proxy

Abstract: Annual variation in meteorological parameters (7 years) and pollen deposition (6 years) for 4 sites on a transect across an altitudinal timberline on Aakenus, a fell in northern Finland were monitored, in order to see how pollen production, as reflected by pollen deposition (grains cm year), is related to climate conditions. Wind direction and wind speed before and after estimated flowering time were determined. These indicated that, within the forest and at the physiognomic forest line, pollen deposition is primarily from plants growing within the forested area on the fell and that the contribution of windblown pollen from further south is minimal. Pollen deposition can, therefore, be taken as equivalent to pollen production. Simple linear correlation coefficients between pollen deposition and one-month and two-week mean temperature, effective temperature sums and cumulative effective temperature sums for the current and previous summers were calculated. For Pinus sylvestris the quantity of pollen deposi...

Fluxes of nitrogen oxides over a temperate deciduous forest

Abstract: [1] Eddy covariance flux measurements of NO, NO2, and O3 were obtained above the mixed deciduous canopy at Harvard Forest in central Massachusetts from April to November 2000. Net deposition of NOx was observed throughout the measurement period, with average velocity of ∼0.2 cm s−1. At night, NO2 is deposited at a rate that depends nonlinearly on NO2 concentration and cannot be explained by N2O5 hydrolysis, suggesting HONO formation by heterogeneous disproportionation of NO2. During the day, photochemically driven NOx fluxes conform to the predicted behavior based on gradients of light and eddy diffusivity through the canopy, with residual net flux attributable to both stomatal and nonstomatal processes. The results were consistent with a compensation point for NO2 near 1.5 nmol mol−1. These results were confirmed by independent evidence from NO, NO2, and O3 profiles acquired at the site over several years. If the rate of NOx deposition observed at this site in April through November continues during the winter, it would have a larger potential impact on tropospheric chemistry because mixing depths are shallow and chemical NOx oxidation is slow during winter; the impact at night is important for the same reasons. The results contradict widely used parameterizations of NO2 deposition that both overestimate stomatal uptake and do not allow for surface uptake when stomates are closed.

Uptake of methanol to the North Atlantic Ocean surface

Abstract: An anticorrelation between atmospheric methanol (CH3OH) concentrations and wind speed and a positive correlation between dimethylsulphide (DMS) concentrations and wind speed have been observed at the coastal air monitoring site of Mace Head in Ireland, during a period of cyclonic activity in which the averaged surface wind speed changed substantially as a low-pressure system evolved over the northeast Atlantic. These observations suggest a net air-to-sea flux of CH3OH. This conclusion is supported by the good agreement between the wind speed dependencies of the measured gas concentrations and theoretical predictions using wind-induced turbulent gas transfer velocities of DMS and CH3OH calculated from a resistance model, embedded in a photochemical box model. For a wind speed of 8 m s−1, an ocean deposition rate of methanol of between 0.02 and 0.33 cm s−1 is calculated, with a best estimate of 0.09 cm s−1, in good agreement with deposition rates used in global models and derived from atmospheric budgets. The large uncertainty in the calculated deposition rates is due almost entirely to the uncertainty in the degree of saturation of methanol in the surface ocean, highlighting the critical requirement for measurements of methanol in seawater. Owing to the dependence on wind speed, the deposition rates calculated showed substantial range and the calculated contribution of ocean deposition to total loss of CH3OH (ocean uptake and gas phase OH oxidation) varied from approximately 20% to 60%.

Plasma enhanced chemical vapour deposition of hydrogenated amorphous silicon at atmospheric pressure

Abstract: Amorphous hydrogenated silicon films were grown using an atmospheric pressure helium and hydrogen plasma with silane added downstream of the source. A maximum deposition rate of 120±12 A min−1 was recorded at a substrate temperature of 450°C, 6.3 Torr H2, 0.3 Torr SiH4, 778 Torr He, 32.8 W cm−3, and an electrode-to-substrate spacing of 6.0 mm. The deposition rate increased rapidly with the silane and hydrogen partial pressures, up to 0.1 and 7.0 Torr, respectively, then remained constant thereafter. By contrast, the deposition rate decreased exponentially as the electrode-to-substrate distance was increased from 5.0 to 10.5 mm. The total hydrogen content of the films ranged from 2.5 to 8.0± 1.0 at%. These results together with a model of the plasma chemistry indicate that H atoms and SiH3 radicals play an important role in the deposition process.

Power deposition outside the divertor in ASDEX Upgrade

Abstract: The heat deposition outside the divertor region in ASDEX Upgrade was measured using thermography and Langmuir probes, as well as thermometry and cooling water calorimetry for a type-I ELMy H-mode discharge with low density ( ). The total deposited energy to non-divertor components was found to be below 8% of the total plasma energy throughput. The main part of this energy is deposited onto the low field side limiters. The radial heat flux deposition profile measured with an infrared camera at the protection limiter is the radial continuation of the heat flux profile measured in the lower outer divertor mapped to the mid-plane. Twenty-five per cent of the plasma energy loss by ELMs is detected at non-divertor components. The large area of the central column is loaded with about 10% and the ion cyclotron resonance heating and protection limiters with 15%. The ELM contribution to the non-divertor energy deposition is about 60% of the total non-divertor load. A systematic investigation of ELM energy deposition outside the divertor as a function of plasma and edge parameters is in progress.

Adhesion kinetics of viable Cryptosporidium parvum oocysts to quartz surfaces

Abstract: The transport and deposition (adhesion) kinetics of viable Cryptosporidium parvum oocysts onto ultrapure quartz surfaces in a radial stagnation point flow system were investigated. Utilizing an optical microscope and an image-capturing device enabled real time observation of oocyst deposition behavior onto the quartz surface in solutions containing either monovalent (KCl) or divalent (CaCl2) salts. Results showed a significantly lower oocyst deposition rate in the presence of a monovalent salt compared to a divalent salt. With a monovalent salt, oocyst deposition rates and corresponding attachment efficiencies were relatively low, even at high KCl concentrations where Derjaguin−Landau−Verwey−Overbeek (DLVO) theory predicts the absence of an electrostatic energy barrier. On the other hand, in the presence of a divalent salt, oocyst deposition rates increased continuously as the salt concentration was increased over the entire range of ionic strengths investigated. The unusually low deposition rate in a mon...