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Flooding and channel characteristics control the occurrence, spatial extent, and depth of streambed disturbance. This research quantifies the frequency and depth of streambed disturbance in a small, coastal salmon-spawning stream resulting from 249 floods. Bed disturbance was documented by monitoring the three-dimensional positions of gravel tracers and producing cellular maps within a geographic information system (GIS). The most active areas make up about 1% of the streambed. Undisturbed areas constitute between 31 and 53% of the bed. Maximum disturbance depths exceed 20 cm in more than half of the active bed. Logistic regression equations based on two bed characteristics correctly describe disturbance frequency and depth over most of the bed. Results provide insight into the active zone of bedload transport, correspond with expectations of partial sediment transport, and document potential refugia that persist over many life cycles of the stream community. Copyright © 2017 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

A tracer test was conducted to aid in the investigation of water movement and solute transport at a crude-oil spill site near Bemidji, Minnesota. Time of travel was measured using breakthrough curves for rhodamine WT and bromide tracers moving from the soil surface through oil-contaminated and oil-free unsaturated zones to the saturated zone. Results indicate that the rates of tracer movement were similar in the oil-free unsaturated and saturated zones compared to the oily zones. These results are somewhat surprising given the oil contamination in the unsaturated and saturated zones. Rhodamine tracer breakthrough in the unsaturated and saturated zones in general was delayed in comparison to bromide tracer breakthrough. Peak tracer concentrations for the lysimeters and wells in the oily zone were much greater than at the corresponding depths in the oil-free zone. Water and tracer movement in the oily zone was complicated by soil hydrophobicity and decreased oil saturations toward the periphery of the oil. Preferential flow resulted in reduced tracer interaction with the soil, adsorption, and dispersion and faster tracer movement in the oily zone than expected. Tracers were freely transported through the oily zone to the water table. Recharge calculations support the idea that the oil does not substantially affect recharge in the oily zone. This is an important result indicating that previous model-based assumptions of decreased recharge beneath the oil were incorrect. Results have important implications for modeling the fate and transport of dissolved contaminants at hydrocarbon spill sites. [ABSTRACT FROM AUTHOR]

Irrigation, while being an important anthropogenic factor affecting the local to regional water cycle, is not typically represented in regional climate models. An irrigation scheme is incorporated into the Noah land surface scheme of the Weather Research and Forecasting (WRF) Model that has a calibrated convective parameterization and a tracer package is used to tag and track water vapor. To assess the impact of irrigation over the California Central Valley (CCV) on the regional climate of the U.S. Southwest, simulations are run (for three dry and three wet years) both with and without the irrigation scheme. Incorporation of the irrigation scheme resulted in simulated surface air temperature and humidity that were closer to observations, decreased depth of the planetary boundary layer over the CCV, and increased convective available potential energy. The result was an overall increase in precipitation over the Sierra Nevada range and the Colorado River basin during the summer. Water vapor rising from the irrigated region mainly moved northeastward and contributed to precipitation in Nevada and Idaho. Specifically, the results indicate increased precipitation on the windward side of the Sierra Nevada and over the Colorado River basin. The former is possibly linked to a sea-breeze-type circulation near the CCV, while the latter is likely associated with a wave pattern related to latent heat release over the moisture transport belt. [ABSTRACT FROM AUTHOR]

Aqueous humor flows out of the eye primarily through the conventional outflow pathway that includes the trabecular meshwork and Schlemm's canal. However, a fraction of aqueous humor passes through an alternative or ‘unconventional’ route that includes the ciliary muscle, supraciliary and suprachoroidal spaces. From there, unconventional outflow may drain through two pathways: a uveoscleral pathway where aqueous drains across the sclera to be resorbed by orbital vessels, and a uveovortex pathway where aqueous humor enters the choroid to drain through the vortex veins. We review the anatomy, physiology and pharmacology of these pathways. We also discuss methods to determine unconventional outflow rate, including direct techniques that use radioactive or fluorescent tracers recovered from tissues in the unconventional pathway and indirect methods that estimate unconventional outflow based on total outflow over a range of pressures. Indirect methods are subject to a number of assumptions and generally give poor agreement with tracer measurements. We review the variety of animal models that have been used to study conventional and unconventional outflow. The mouse appears to be a promising model because it captures several aspects of conventional and unconventional outflow dynamics common to humans, although questions remain regarding the magnitude of unconventional outflow in mice. Finally, we review future directions. There is a clear need to develop improved methods for measuring unconventional outflow in both animals and humans. [ABSTRACT FROM AUTHOR]

Protection of water resources is a major challenge today, given that territory occupation and land use are continuously increasing. In the case of karst aquifers, its dynamic complexity requires the use of specific methodologies that allow establishing local and regional flow and transport patterns. This information is particularly necessary when springs and wells harnessed for water supply are concerned. In view of the present state of the art, this work shows a new approach based on the use of a LiCl based tracer injection test through a borehole for transport characterization from a local to a regional scale. Thus a long term tracer injection test was conducted in a particularly sensitive sector of the Egino karst massif (Basque Country, Spain). The initial displacement of tracer in the vicinity of the injection was monitored in a second borehole at a radial distance of 10.24 m. This first information, assessed by a radial divergent model, allows obtaining transport characteristic parameters in this immediate vicinity during injection. At a larger (regional) scale, the tracer reaches a highly transmissive network with mean traveling velocities to the main springs being from 4.3 to 13.7 m/h. The responses obtained, particularly clear in the main spring used for water supply, and the persistence of part of the tracer in the injection zone, pose reconsidering the need for their protection. Thus, although the test allows establishing the 24-h isochrone, which is the ceiling value in present European vulnerability approaches, the results obtained advise widening the zone to protect in order to guarantee water quality in the springs. Overall, this stimulus-response test allows furthering the knowledge on the dynamics of solute transport in karst aquifers and is a particularly useful tool in studies related to source vulnerability and protection in such a complex medium. [ABSTRACT FROM AUTHOR]

The Southern Ocean is the most important area of anthropogenic carbon (C ant ) uptake in the world ocean, only rivalled in importance by the North Atlantic Ocean. Significant variability on decadal time-scales in the uptake of C ant in the Southern Ocean has been observed and modelled, likely with consequences for the interior ocean storage of C ant in the region, and implications for the global carbon budget. Here we use eight cruises between 1973 and 2012 to assess decadal variability in C ant storage rates in the southeast Atlantic sector of the Southern Ocean. For this we employed the extended multiple linear regression (eMLR) method. We relate variability in DIC (dissolved inorganic carbon) storage, which is assumed to equal anthropogenic carbon storage, to changes in ventilation as observed from repeat measurements of transient tracers. Within the Antarctic Intermediate Water (AAIW) layer, which is the dominant transport conduit for C ant into the interior ocean, moderate C ant storage rates were found without any clear temporal trend. In Subantarctic Mode Water (SAMW), a less dense water mass found north of the Subantarctic Front and above AAIW, high storage rates of C ant were observed up to about 2005 but lower rates in more recent times. The transient tracer data suggest a significant speed-up of ventilation in the summer warmed upper part of AAIW between 1998 and 2012, which is consistent with the high storage rate of C ant . A shift of more northern C ant storage to more southern storage in near surface waters was detected in the early 2000s. Beneath the AAIW the eMLR method as applied here did not detect significant storage of C ant . However, the presence of the transient tracer CFC-12 all through the water column suggests that some C ant should be present, but at concentrations not reliably quantifiable. The observed temporal variability in the interior ocean seems at a first glance to be out of phase with observed surface ocean C ant fluxes, but this can be explained by the time delay for the surface ocean signal to manifest itself in the interior of the ocean. [ABSTRACT FROM AUTHOR]

This paper reports on a first attempt of using the virtual velocity approach to assess sediment mobility and transport in two wide and complex gravel-bed rivers of northern Italy. Displacement length and virtual velocity of spray-painted tracers were measured in the field. Also, the thickness of the sediment active layer during floods was measured using scour chains and post-flood morphological changes as documented by repeated survey of channel cross-sections. The effects of eight and seven floods were studied on the Tagliamento and Brenta Rivers, where 259 and 277 spray-painted areas were surveyed, respectively. In the Tagliamento River 36% of the spray-painted areas experienced partial transport, whereas in the Brenta River this accounted for 20%. Whereas, full removal/gravel deposition was observed on 37% and 26% of these areas on the Tagliamento and Brenta Rivers, respectively. The mean displacement length of particles, the thickness of the active layer and the extent of partial transport are well correlated with the dimensionless shear stress. The virtual velocity approach allowed calculation of bed material transport over a wide range of flood magnitudes. Annual coarse sediment transport was calculated up to 150 for the Tagliamento, and 30 × 103 m3 yr−1 for the Brenta. The outcomes of this work highlight the relevance of partial transport condition, as it could represent more than 70% of the total bed material transported during low-magnitude floods, and up to 40% for near-bankfull events. Results confirm that bed material load tends to be overestimated by traditional formulas. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Water masses are the crucial factor driving the terrigenous anthropogenic organochlorine compounds (OCs) migration from the coast to open sea. Therefore, organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) were investigated in the Northern South China Sea (NSCS), where different types of water masses are generated by the East Asian summer monsoon: Pearl River estuary plume (PREP), Guangdong offshore eddy (GDEC), South China Sea warm current (SCSWC) and wind-driven upwelling current (WDUC). No discrepant distributions of OC concentrations were found in these water masses ( p > 0.05). However, compositions and diagnostic ratios of HCHs, DDTs, trans - or cis -chlordane and PCBs could reflect the discrepancies in the input, transport and transformation of OCs caused by the hydrological characteristics of water masses, therefore, this allowing them to serve as potential tracers of regional water masses. In detail, α/γ -HCH and β -HCH percentages could indicate the weathered residue in the GDEC, long-range transport in the SCSWC, rapid photodegradation in the surface WDUC and biodegradation in the deep WDUC, respectively. The predominance of o, p' -DDT and p, p' -DDT could indicate fresh input in the PREP, GDEC and WDUC. DDT/DDTs of ratios <0.5 also reflected long-range transport in the SCSWC. Different DDD/DDE ratios indicated different oxygen environments of microbial degradation in the surface and deep water of the WDUC. Trans/cis -chlordane ratios could indicate the selective degradation of trans -chlordane in different water masses. Finally, a higher proportion of penta -PCB could reflect the strong paint additive sources carried by river erosion in the PREP. [ABSTRACT FROM AUTHOR]

Non-intrusive observations are fundamental to monitor river flows and understand water processes in natural systems. Recently, the introduction of optical methods has fostered the establishment of numerous image-based techniques for characterizing the kinematics of water bodies. However, RGB image-based methods are still severely affected by illumination conditions and tracers’ visibility. In this note, the integration of particle-shaped tracers and thermal imagery is applied to characterize the surface velocity field of a natural stream. Specifically, the trajectories of a few grams of artificially deployed ice dices are reconstructed by analyzing thermal images with particle tracking velocimetry. Average surface flow velocities are in agreement with benchmark values estimated with a current meter. This proof of concept experiment demonstrates the efficacy of thermal imagery for hydrological monitoring and paves the way to the integration of thermal signals in standard water gauging systems. [ABSTRACT FROM AUTHOR]

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During the late afternoon of 18 June 2015, ozone concentrations in advance of a strong lake-breeze front arising from the Great Salt Lake in northern Utah were ~20 ppb lower than those in its wake. The lake-breeze progression and ozone concentrations in the valley were monitored by an enhanced observation network that included automated weather stations, a nearby Terminal Doppler Weather Radar, state air quality measurement sites, and mobile platforms, including a news helicopter. Southerly flow opposing the lake breeze increased convergent frontogenesis and delayed the onset of its passage through the Salt Lake valley. Ozone concentrations were exceptionally high aloft at the lake-breeze frontal boundary. The progression of this lake breeze was simulated using the Weather Research and Forecasting Model at 1-km horizontal grid spacing over northern Utah. The model was initialized using hourly analyses from the High Resolution Rapid Refresh model. Errors in the underlying surface initialization were improved by adjusting the areal extent and surface temperature of the lake to observed lake conditions. An urban canopy parameterization is also included. The opposing southerly flow was weaker in the simulation than that observed such that the simulated lake-breeze front occurred too early. Continuous passive tracers initialized within and ahead of the lake breeze highlight the dispersion and transport of pollutants arising from the lake-breeze front. Tracers within the lake breeze are confined near the surface while tracers in advance of the front are lofted over it. [ABSTRACT FROM AUTHOR]

Expanded granular sludge bed (EGSB) reactors are classified as third-generation anaerobic systems. They operate using a fluidized bed, which allows an increase in organic load, a decrease in hydraulic retention times, an increase in cell retention times, and higher treatment efficiencies compared with upflow anaerobic sludge blanket reactors. In this research, two EGSB reactors were employed and the upflow velocity, temperature, and organic load were varied. Reactors were operated with synthetic wastewater using a biodegradable substrate (dextrose). The residence time distribution of the reactor was analyzed using tracer tests. A temperature of 35°C influenced bacterial degradation kinetics, allowing an increase in the percentage of organic matter removal. At ambient temperature, a removal of 89.49% was obtained with an organic loading rate (OLR) of 3.39 kg/m3·day, while at 35°C the best removal was 93.98% with a higher OLR (4.23 kg/m3·day). Recirculation in reactors improved fluidization of the bed and mixing, favoring granulation of biomass and allowing operation of reactors under a fully mixed tank model. Biomass granulation improved settleability and made the process more efficient. It was found that an upflow velocity of 6 m/h at ambient temperature produced a high removal of chemical oxygen demand (96.83%). [ABSTRACT FROM AUTHOR]

Phytoplankton production in the Ross Sea is regulated by the availability of dissolved iron (dFe), a limiting micro-nutrient, whose sources include Circumpolar Deep Water, sea ice melt, glacial melt, and benthic sources (sediment efflux and remineralization). We employ a passive tracer dye to model the benthic dFe sources and track pathways from deep areas of the continental shelf to the surface mixed layer in simulations with and without tidal forcing, and at 5 and 1.5 km horizontal resolution. This, combined with dyes for each of the other dFe sources, provides an estimate of total dFe supply to surface waters. We find that tidal forcing increases the amount of benthic dye that covers the banks on the continental shelf. Calculations of mixed layer depth to define the surface ocean give similar average values over the shelf, but spatial patterns differ between simulations, particularly along the ice shelf front. Benthic dFe supply in simulations shows an increase with tidal forcing and a decrease with higher resolution. The changes in benthic dFe supply control the difference in total supply between simulations. Overall, the total dFe supply from simulations varies from 5.60 to 7.95 μmol m −2 year −1 , with benthic supply comprising 32–50%, comparing well with recent data and model synthesis. We suggest that including tides and using high horizontal resolution is important, especially when considering spatial variability of iron supply on the Ross Sea shelf. [ABSTRACT FROM AUTHOR]

This work measures the size distribution of the particles exiting a simple-design seeding generator. A simple model for the prediction of the droplet size mean diameter is checked against these measurements, giving good agreement. The main fields of use of these generators include tracer particles based optical measurements like Particle Image Velocimetry (PIV). This investigation provides results against which the performance of different seeding generators, liquids, etc., could be compared, at the exit of the aerosol generator. The developed generic seeding generator is thus suggested as a starting point for a basis for a future scalable standard seeding generator for other researchers investigating the production of aerosols for PIV application. The proposed generator is able to seed flows up to 0.2 kg/s with ∼10 particles/mm 3 , under normal operation conditions. Air is injected inside a PG-water (propylene glycol – water) mixture through discharging orifices bubbling in the solution. This liquid presents the advantage of being food-grade and apparently harmless to health. In addition, according to practice it seems that the characteristic time of evaporation of the droplet deposited on surfaces is small, so that there is a cleaning effect that does not exist with other fluids like oils. Droplet size distribution at the outlet of the seeding generator is performed by means of a contemporary laser diffraction analyzer Malvern Spraytech®. Measurements reveal narrow-band, single distribution droplet sizes in the order of 1.5 μm; suitable for seeding highly turbulent air flows. The use of dry air to generate particles of PG-water solution is proposed as a way of reducing the final particle diameter by means of water evaporation. Solutions with 60% mass fraction of PG reach sub-micrometric average diameters around 0.9 μm at 6 bar g feeding gauge pressure. The proposed prediction model generalizes the results in an attempt to extrapolate them to other designs or fluids. It is based on the turbulent intensity downstream the nozzle exit and indicates that the discharging orifices depth is secondary in respect to the mean droplet diameter obtained. The study also shows that the volumetric concentration of the tracer particles in the generated aerosol is not much sensitive to feeding air pressure. Once the mean droplet size has been stablished with the previously commented method, this offers the possibility of estimating the number of particles generated and, thus, establishing design rules or fluid selection criteria for seeding generators or other similar devices. For feeding pressures from 2 to 6 bar g , particle quantity generation is in the order of 10 8 particles/s per ∅ 0.5 mm nozzle. [ABSTRACT FROM AUTHOR]

We present a Newton–Krylov based solver to efficiently spin up tracers in an online ocean model. We demonstrate that the solver converges, that tracer simulations initialized with the solution from the solver have small drift, and that the solver takes orders of magnitude less computational time than the brute force spin-up approach. To demonstrate the application of the solver, we use it to efficiently spin up the tracer ideal age with respect to the circulation from different time intervals in a long physics run. We then evaluate how the spun-up ideal age tracer depends on the duration of the physics run, i.e., on how equilibrated the circulation is. [ABSTRACT FROM AUTHOR]

• Alteration of sediment properties during transport and storage in a temporary stream. • The spatial variability of soil properties was higher than the in-channel variability. • Colour properties showed the highest temporal and spatial stability. • Results are relevant for future sediment fingerprinting studies. Soil properties used as tracers in sediment fingerprinting studies are assumed to remain stable or vary in a predictable way in their transfer from sources to sinks, allowing a comparison with suspended sediment properties. Attention to the conservative behaviour of soil properties has largely focused on the differences in the particle size and organic matter content between sources and target sediments. However, in-channel biochemical alterations are also known to occur, and their magnitude is still poorly understood. An experiment to investigate the in-channel variations of soil properties during transport and storage was carried out with the most common soil properties used as tracers in sediment fingerprinting studies (i.e. colour, fallout radionuclides and geochemical elements). Twenty-eight soil samples collected from different land uses were introduced into an intermittent stream channel of a small Mediterranean catchment. Samples were recovered at different time intervals over one year. The changes in soil properties (average coefficient of variation 8.1 ± 8.8 %) were generally lower than the spatial variability of each source within the catchment (average coefficient of variation 16.3 ± 18.5 %). No significant differences were observed between samples from different land use types or when recovered at different time intervals. Soil properties that showed higher in-channel coefficients of variation were S, 137Cs, 210Pb ex , As, Mo and Na, with annual coefficients of variation > 19 %. Conversely, carbon (C) and colour properties were the most stable in time (average coefficient of variation 2.1 ± 0.4 % and 2.6 ± 2.2 %, respectively). The results presented will be informative with regard to performing future suspended sediment fingerprinting studies in Mediterranean catchments, providing a better understanding of which soil properties are more sensitive to in-channel biochemical alterations. [ABSTRACT FROM AUTHOR]

End-members mixing analysis (EMMA) was performed on in situ suspended sediment grain-size distribution (GSD) data from Haizhou Bay to estimate suspended sediment provenance and the relative contributions of different sediment sources to total seawater suspended sediment. The results show that the suspended sediment in Haizhou Bay can be expressed as a mixture of three EMs. End-member 1 represents fine-grained suspended sediment that was transported over long distances by advection; this shows a genetic connection with the old Huanghe River delta. End-member 2 represents resuspension of local sediment, while EM3 represents riverine suspended sediment. On average, advection, resuspension, and riverine input contributed 41.92%, 37.83%, and 20.25% of the total suspended sediment, respectively. Temporal changes in advection and resuspension caused considerable variability in these relative contributions. The application of EMMA herein demonstrates that it is a feasible approach to explore suspended sediment sources and their mixing processes using suspended sediment GSD data. • First study to apply end-member mixing analysis to unmixing suspended sediment. • Source apportionment of suspended sediment is proposed. • Multisource suspended sediment in situ mixing processes are investigated. [ABSTRACT FROM AUTHOR]

[Display omitted] • Geogenic solutes (Na, Sr, K, Si, and Rb) were mostly defined by clockwise hysteresis loops and dilution patterns. • Biogenic solutes influenced by soil processes (Al, Cu, DOC and TNb) resulted in anti-clockwise hysteresis behaviors and mobilization with streamflow. • Higher discharge increases water volume to dilute geogenic solutes and is related to more water passing through shallow soils leaching biogenic solutes. • The higher the discharge the more likely is a linear and non-hysteretic behaviour. Hydrometeorological characteristics can influence stream chemistry variability and the identification of their dominant drivers provides much needed insight into catchment functioning in the tropics. Particularly, the rainfall-runoff processes that determine catchment capacity to retain and deliver solutes. In this context, concentration-discharge (C-Q) relationships allow assessing solute delivery mechanisms to streams. Here, we used a high-frequency 5-minute multi-solute data set (Al, Cu, DOC, TNb, Ba, Ca, Mg, Na, Sr, K, Si, Rb) to derive hysteresis indicators (direction, magnitude and area) in relation to hydrometeorological variables for a high-elevation tropical experimental catchment. We found geogenic solutes (Na, Sr, K, Si, and Rb) were mostly defined by clockwise hysteresis loops and dilution patterns. Conversely, biogenic solutes influenced by soil processes (Al, Cu, DOC and TNb) resulted in anti-clockwise hysteresis behaviors and mobilization with streamflow. The hysteresis indicators were most strongly influenced by discharge magnitude and the solute concentration itself. As the discharge and the concentration increases (>90th of the flow duration curve) the loop area and the hysteresis index turned to cero showing a direct linear response of the solute to discharge dynamics. Additionally, increasing discharge drives greater dilution or mobilization patterns for the geogenic and biogenic solutes. Higher discharge increases water volume to dilute geogenic solutes and is related to more water passing through shallow soils leaching biogenic solutes. This study contributes to our understanding of how Páramo catchments store and release solutes for a more adequate water resource management. [ABSTRACT FROM AUTHOR]

• Comparison of multiple-models (4 to 18 calibrated parameters) with stream flow and tracer (stable isotopes, DOC) data. • Identification of the simplest model to represent a high-elevation páramo catchment. • DOC, streamflow and stable isotope dynamics originated almost exclusively from soil water fluxes. • A shallow fractured rock was necessary to simulate streamflow and tracer transport. How simple or complex catchment models need to be is still unclear particularly for tracer-aided models that go beyond hydrograph fitting. Here, we take advantage of a sub-daily hydrometric and tracer data set from a tropical montane (páramo) experimental catchment to fill this knowledge gap. We evaluated six conceptual rainfall-runoff model structures with different complexity that represent the perceptual understanding of the catchment's hydrological functioning. The models solved conservative and reactive tracer mass balances to simulate streamflow, stable isotopes, and DOC concentrations and were assessed for performance and parsimony using three calibration targets (discharge only, discharge and stable isotopes, and discharge and DOC), resulting in 18 model configurations. Although all models satisfied the discharge calibration (KGE > 0.8), differences arose when considering tracer transport. The more complex models outperformed the simpler ones in terms of goodness-of-fit and parsimony, indicating that the catchment streamflow response consisted of quick near-surface flow and tracer contributions, more mixed flow through the two main soil types (Andosols and Histosols), as well as flow from the well-mixed shallow fractured rock (up to 20 m depth). The bedrock flow pathway contributed up to ∼25% of total flow during baseflow conditions. This study provides a benchmark experiment to identify hydrological and biogeochemical behavior in tropical montane catchments using relatively parsimonious tracer-aided hydrological models. [ABSTRACT FROM AUTHOR]

Background: It is now widely recognized that health care personnel (HCP) are at risk of contamination with pathogens during personal protective equipment (PPE) doffing. Studies of this phenonemona, have utilized a variety of PPE ensembles, doffing methods, and experimental methods., Methods: A scoping review was performed, consistent with PRISMA guidance. The PubMed and sciVerse Scopus databases were searched using an a priori search strategy. Data were extracted for analysis using the matrix method, and then a narrative analysis was performed. Articles were classified based on PPE ensemble., Results: Only 19 of 151 articles were included in the final analysis. All included studies reported some post-doffing contamination, and this contamination was most frequently observed on the hands, wrist, face, and neck. Reviewed studies used a variety of tracer contaminants, PPE ensembles, doffing protocols, tracer assessment locations, and methods, making it difficult to identify patterns across studies., Discussion&concluisons: Additional research is needed to improve the study methodology related to the selection and placement of tracers to ensure sensitive detection of post-doffing contamination, compare how specific doffing procedures or pieces of PPE influence post-doffing contamination, and to understand what post-doffing contamination means for patient and HCP infection risk., (Copyright © 2022 The Authors. Published by Elsevier Inc. All rights reserved.)

The mixing of powders and the quality control of the obtained mixtures are critical operations involved in the processing of granular materials in chemical, metallurgical, food and pharmaceutical industries. Studies on mixing efficiency and the time needed for achieving homogeneity in the powder mashes production have significant importance. Depending on the characteristic of the materials, a number of methods have been used for the homogeneity tests. Very often, the degree of mixing has been determined by analyzing images of particle arrays in the sample using microscopy, photography and/or video tools. In this paper, a new PC-based method for determining the number of particles in the powder homogeneity tests has been developed. Microtracers®, red iron particles, were used as external tracer added before mixing. Iron particles in the samples of the mixtures were separated by rotary magnet and spread onto a filter paper. The filter paper was sprayed with 50% solution of ethanol for color development and the particles counted where the number of spots presented the concentration of added tracer. The number of spots was counted manually, as well as by the developed PC program. The program which analyzes scanned filter papers with spots is based on digital image analyses, where red spots were converted through few filters into a black and white, and counted. Results obtained by manual and PC counting were compared. A high correlation was established between the two counting methods.

This paper presents a revision of the history, definitions, and classification of tracers (natural and artificial, internal and external). The fundamental ideas concerning tracers are described, followed by their application illustrated by typical examples. The advantages and disadvantages of five classes among the most frequently used external tracers (fluorescent, microbial, chemical, radioactive and activable isotopes) are also described in detail. This review also presents some interesting and modern applications of tracers in the areas of diagnostics in medical practice, environmental pollution, hydrology and petroleum chemistry.

O experimento foi conduzido no município de Cascavel, Estado do Paraná, com a cultivar de soja CD 202, com o objetivo de avaliar a quantidade de calda depositada nas folhas da soja. Foram coletadas amostras, contendo 15 folhas por parcela, em cinco plantas, em diferentes extratos, sendo uma folha do extrato inferior; uma, do mediano, e uma, do superior, com a finalidade de avaliar a deposição da calda de pulverização em função da vazão e do tipo de bico. Os tratamentos foram constituídos por quatro bicos de pulverização (leque simples, duplo leque, duplo leque com injeção de ar e cone vazio) e três volumes de calda (100, 200 e 300 L ha-1). O volume de calda que apresentou maiores deposições, nos diferentes extratos das plantas de soja, foi o de 300 L ha-1; o bico de pulverização que apresentou maiores deposições, no extrato superior das plantas, foi o bico de jato plano duplo; e para os extratos mediano e inferior, o bico de jato cone vazio. As deposições ocorridas nos terços mediano e inferior das plantas de soja foram significativamente inferiores às obtidas no terço superior, independentemente do bico e da vazão utilizada; para maiores deposições, no terço superior das plantas de soja, a melhor combinação é utilizar bicos de jato plano duplo, com volumes de calda de 300 L ha-1; para maiores deposições no terço mediano e inferior das plantas de soja, a melhor combinação éutilizar bicos de jato cônico, com volumes de calda de 200 ou 300 L ha-1.The experiment was carried out in Cascavel, Paraná State, usingthe soybean cultivar CD 202, with the objective of evaluating the amount of spraying suspension deposited on soybean leaves. Samples were collected containing 15 leaves per plot in five plants in different extracts - one leaf of the lower extract, one of the mediumand one of the upper extract - with the objective of evaluating the amount of suspension deposited in function of flow and nozzle type. The treatments were constituted of four spraying nozzles (simple fan, double fan, double fan with air injection and empty cone) andthree suspension volumes (100, 200 and 300 L ha-1). The suspension volume that presented the highest depositions in the different extracts of the soybean plants was 300 L ha-1; the spraying nozzle that presented the highest depositions, in the upper plant extract was the double plane jet; for the medium and lower extracts, the jet empty cone nozzle. The depositions in middle and lower thirds of the soybean plants were significantly lower to those obtained in the upper third, regardless of the nozzle and flow used; for higherdepositions in the upper third of soybean plants, the best combination is to use double plane jet nozzles, with suspension volumes of 300 L ha-1; for higher depositions in the medium and lower third of soybean plants, the best combination is to use conical jetnozzles, with suspension volumes of 200 or 300 L ha-1.

In spite of accounting for 10-70% of the atmospheric aerosol mass, particulate-phase organic compounds are not well characterised, and many aspects of aerosol formation and evolution are still unknown. The growing awareness of the impact of particulate aerosols on climate, and the incompletely recognised but serious effects of anthropogenic constituents on air quality and human health, have conducted to several scientific studies. These investigations have provided information about the behaviour of atmospheric particulate matter and the description of the character of its carbonaceous content. The compilation of such results is important as they append to the emergent global-wide dataset of the organic composition of atmospheric aerosols. The contribution of the major emission sources to regional particulate pollution can be diagnosed by using specific molecular markers. This overview is mainly focused on results obtained with gas chromatography coupled with mass spectrometry, since it is the analytical method of choice in elucidating the solvent-extractable organic compounds in atmospheric particulate matter. A synopsis of the selection of organic tracers and the application of geochemical parameters to the analysis of organic constituents as a tool for source apportionment is shown here. Besides the assessment of current knowledge, this paper also presents the identification of further areas of concern.Apesar de constituirem 10-70% da massa do aerosol atmosférico, a caracterização dos compostos orgânicos particulados permanece ainda deficitária e vários aspectos relativos à formação e evolução do aerossol são ainda desconhecidos. A crescente preocupação com o impacto do aerosol particulado no clima e os reconhecidos efeitos dos constituintes antropogênicos na qualidade do ar e na saúde humana têm motivado a realização de numerosos estudos. Estas investigações têm fornecido informações relevantes sobre o comportamento da matéria particulada na atmosfera e sobre o seu conteúdo carbonáceo. A compilação de tais resultados reveste-se da maior importância, dado que possibilitará coligí-los numa ainda emergente base de dados global sobre a composição orgânica dos aerossóis. A contribuição das principais fontes de emissão para a poluição particulada a nível regional pode ser diagnosticada através da utilização de marcadores moleculares específicos. Esta revisão foca sobretudo os resultados obtidos por cromatografia gasosa acoplada a espectrometria de massa, dado que é o método analítico de eleição para a clarificação dos compostos orgânicos extratíveis por solventes presentes na matéria particulada atmosférica. Uma sinópse da selecção de compostos traçadores e da aplicação de parâmetros geoquímicos à análise dos constituintes orgânicos como ferramenta para estimar a contribuição das diversas fontes é aqui apresentada. Além de uma avaliação do conhecimento atual, o artigo identifica também as necessidades de investigações futuras.

The efficient use of REE as tracers of weathering processes requires further data acquisition to establish robust connections between mechanisms, mineral assemblages and REE concentration patterns. Here, results are provided corresponding to rocks from four locations in the Iberian Pyrite Belt that were altered with different intensity by sulfuric fluids. The acidic alteration was mild (pH 5–7) in Calañas and El Villar, while strong (pH below 3 to 5) in Quebrantahuesos and Tharsis. The main REE reservoir before alteration were phyllosilicates (and plagioclase/feldspar in El Villar only). Mild alteration generated mainly kaolinite while illite and some plagioclase/feldspar were preserved. Mildly altered rocks approximately preserved the relative REE concentrations of their precursors, interpreted as indicating a low fluid/rock ratio environment where binding sites in minerals outnumbered those in fluids. Strong acid alteration produced alunite, jarosite, beudantite and goethite, with partial illite preservation. Where illite and/or goethite were major minerals, this alteration generated REE patterns enriched in light REE over heavy REE or did not modify the relative REE concentrations of the original rock. However, samples where REE concentrations were controlled by alunite or jarosite had LREE > > HREE. In alunite the maximum concentration corresponded to Nd and Sm. In jarosite concentrations decreased from La to Lu, except that a positive Eu anomaly was preserved from the precursor. These REE concentration patterns are interpreted as due to crystallographic factors, controlled by the best fit of REE with charge 3+ in the 12-fold coordination site of K in jarosite and alunite. This site is larger in jarosite and fits La best, whereas the smaller site in alunite best fits Nd and Sm. Goethite REE signature is variable, perhaps due to two formation routes, (1) silicates ➔ goethite and (2) silicates ➔ jarosite ➔ goethite. Our interpretations of REE concentration in alunite, jarosite and goethite are novel and provide new routes to further develop REE as tracers of acid alteration processes. [Display omitted] • Eu anomaly was negative in altered volcanic rocks, positive in altered shales. • Kaolinite, formed at pH 5–7, inherited the REE pattern of precursor phyllosilicates. • Alunite (pH 3–5) and jarosite (pH < 3) had a modified REE pattern with LREE > > HREE. • REE signature in alunite and jarosite is controlled by the size of the K crystallographic site. • Goethite variable REE signature is caused by two formation routes, from silicates or from jarosite. [ABSTRACT FROM AUTHOR]

• Tracer-aided modelling using electrical conductivity (EC) as a surrogate of stable isotopes (18O) • EC and 18O yield similar pre-event water fractions for 37 rainstorm events in a tropical catchment. • Organic-rich soils and compact bedrock result in a quasi-conservative behavior of EC. • Use of sub-hourly EC data increases the performance of a tracer-aided hydrological model. • EC could be used in flow partitioning modelling in tropical alpine catchments. Tracer-aided hydrological models (TAHMs) are one of the most powerful tools to identify new (event) and old (pre-event) water fractions contributing to stormflow because they account both for streamflow and tracer mixing dynamics in model calibration. Nevertheless, their representativeness of hydrograph dynamics is often limited due to the unavailability of high-resolution conservative tracer data (e.g., water stable isotopes or chloride). Hence, there is a need to identify alternative tracers yielding similar flow partitioning results than "ideal" ones while requiring fewer financial resources for high-frequency monitoring (e.g., sub-hourly). Here, we compare flow partitioning results of a TAHM calibrated using high-frequency electrical conductivity (EC) and water stable isotope (18O) data collected during 37 rainfall-runoff events monitored during variable hydrometeorological conditions in the Zhurucay Ecohydrological Observatory, a tropical alpine catchment located in southern Ecuador. When the model was calibrated using the sampling resolution of stables isotopes (6-hours to 1-hour), no statistically significant differences of pre-event water fractions (PEWFs) using both tracers for model calibration were found. PEWF differences between both tracers for 89% of the events were < 20% regardless of the events' antecedent moisture and rainfall conditions. Model transfer functions were also similar suggesting that catchment internal processes inferred using both tracers are comparable. Events presenting larger differences (n = 4; up to 27% PEWF difference) had no samples collected during peak flow. Calibration of the model using EC data collected at sub-hourly intervals (every 5-minutes) showed a significant increase in model performance as compared to the frequency of collection of isotopic data. Similarity in flow partitioning results can be attributed to a quasi-conservative nature of EC due to the presence of organic-rich riparian soils (peat-type) overlying compact bedrock across the catchment. Findings also highlight the importance of capturing rapidly occurring catchment mixing processes though high-temporal frequency monitoring of tracer data. Our study encourages the value of assessing the use of alternative tracers, such as EC, to identify fast occurring rainfall-runoff processes, while lowering the costs needed to implement and sustain tracer data collection for long time periods. [ABSTRACT FROM AUTHOR]

This study is the first step of a broader project aiming to extend future research to other karst areas in the Metaliferi Mountains. Thus, the object of this scientific endeavour is represented by the karst areas located in the central-western part of the aforementioned unit. These karstic areas are characterized by a notable spatial fragmentation, taking the form of calcareous klippes in which karst systems with a certain geomorphological and hydrogeological complexity have emerged. One of the edifying aspects regarding the configuration of the karst in the analysed area is the limited karstifiable rock volume, along with its dispersion in the form of the analysed perimeters within the Metaliferi Mountains. This configuration is reflected in the differences regarding the distribution of landforms, along with the regime and characteristics of the water agent, existing between the karstic and non-karstic domains (in the case of the areas from Boiu de Sus or Deleni). On this basis, through the research carried out, the intent is to highlight the existing relations between the two previously mentioned domains, each of them being subjected to a distinct morphogenesis, which generated, in the case of the karst domain, surfaces with higher altitudes in relation to the adjacent space, thus contributing to their relative isolation. The influence of the karst environment extends beyond the surface topography, affecting the hydrographic network by reorganizing it, while concurrently inducing changes in the chemical composition of water, in the sense of increasing alkalinity following the dissolution of CaCO3. In this sense, it is highlighted how the specifics of surface drainage change as it infiltrates the karst system, by outlining the spatial distribution of the drainages, capitalizing on the tracer method. This involved the use of a saline solution at the insurgency points, followed by the collection of water samples upstream and downstream of the karst system at certain time intervals after the placement of the saline solution. These samples were analysed in the laboratory to establish the existence of links between the points of water entry into the karst and subsequent resurgences. Furthermore, the analyses highlighted how the karst environment influences the physical and chemical characteristics of the water agent. [ABSTRACT FROM AUTHOR]

Purpose: How coronary arterial 18 F-sodium fluoride ( 18 F-NaF) uptake on positron emission tomography changes over the long term and what clinical factors impact the changes remain unclear. We sought to investigate the topics in this study., Methods: We retrospectively studied 15 patients with ≥1 coronary atherosclerotic lesion/s detected on cardiac computed tomography who underwent baseline and follow-up (interval of >3 years) 18 F-NaF positron emission tomography/computed tomography scans. Focal 18 F-NaF uptake in each lesion was quantified using maximum tissue-to-background ratio (TBR max ). The temporal change in TBR max was assessed using a ratio of follow-up to baseline TBR max (R-TBR max )., Results: A total of 51 lesions were analyzed. Mean R-TBR max was 0.96 ± 0.21. CT-based lesion features (location, obstructive stenosis, plaque types, features of high-risk plaque) did not correlate with an increase in R-TBR max . In multivariate analysis, baseline TBR max significantly correlated with higher follow-up TBR max (β = 0.57, P < 0.0001), and the presence of diabetes mellitus significantly correlated with both higher follow-up TBR max (β = 0.34, P = 0.001) and elevated R-TBR max (β = 0.40, P = 0.003)., Conclusion: Higher coronary arterial 18 F-NaF uptake is likely to remain continuously high. Diabetes mellitus affects the long-term increase in coronary arterial 18 F-NaF uptake., (© 2022. The Author(s) under exclusive licence to American Society of Nuclear Cardiology.)

Ischemic heart disease is the leading cause of mortality worldwide. In this context, myocardial viability is defined as the amount of myocardium that, despite contractile dysfunction, maintains metabolic and electrical function, having the potential for functional enhancement upon revascularization. Recent advances have improved methods to detect myocardial viability. The current paper summarizes the pathophysiological basis of the current methods used to detect myocardial viability in light of the advancements in the development of new radiotracers for cardiac imaging.

Objetivou-se com este trabalho avaliar a variabilidade dos depósitos de traçadores, simulando herbicidas aplicados em pós-emergência, em populações de Brachiaria plantaginea e Commelina benghalensis infestantes da cultura da soja. Os depósitos dos traçadores foram também avaliados em plantas da cultura, utilizando-se o pulverizador de barra tratorizado, com pontas de jato plano da série 110-SF-03, aplicando o volume de 250 L ha-1 de calda preparada com 0,18% de corante Azul Brilhante e 0,18% de Amarelo Saturn Yellow. Os alvos naturais utilizados foram: plantas de soja com 150 repetições; B. plantaginea no estádio de duas a oito folhas, coletadas na linha da cultura com 141 repetições; e B. plantaginea e C. benghalensis nas entrelinhas, com 150 e 50 repetições, respectivamente. Os alvos artificiais foram constituídos por lâminas distribuídas a 0, 12,2 e 22,5 cm da linha da cultura. Após a aplicação, os alvos foram coletados individualmente e lavados com 30, 20 e 15 mL de água deionizada, para soja, lâminas e plantas daninhas, respectivamente. Estas originaram as amostras analisadas em espectrofotômetro, estimando-se o depósito de calda em µL por planta e µL cm² de área foliar. Foram ajustadas curvas de regressão entre os depósitos unitários e as freqüências acumuladas, utilizando-se o modelo de Gompertz. As relações entre os depósitos máximos e mínimos foram de 7, 4, 10 e 6 para soja, C. benghalensis e B. plantaginea na linha e na entrelinha, respectivamente. As plantas de B. plantaginea da entrelinha receberam, em média, 34% a mais de depósito do que as plantas da linha.The objective of this research was to study the variability of individual tracer deposits (simulating herbicides applied in post-emergence) on Brachiaria plantaginea and Commelina benghalensis infesting soybeans crop. The tracer deposits were evaluated also on the crop. A boom sprayer was used, equipped with 110-SF-03 nozzles and 250 L ha-1 of a solution was applied containing 0.18% of each of the following dyes: FDC-1 and Satur-Yellow; 150 soybean plants; 141 and 150 Brachiaria plantaginea plants were used as targets located in the rows and between the rows of the crop, respectively; 50 Commelina benghalensis plants located between the rows and 125 glass plates of 19.76 cm² (25 in the rows; 50 and 50 at 12.25 cm and 22.5 from the rows). The spray deposits (mL per plant or plate and mL cm-2) were individually estimated in each of the 566 targets by washing them in de-ionized water and measuring the concentration of dye FDC-1 in the solutions by spectrophotometry. The results for each target type and position were expressed in an increasing order and associated to accumulated frequencies from 0 to 100%. Regression analysis was performed according to the Gompertz model and using the individual deposits and the accumulated frequencies as independent and dependent variables, respectively. The values for ratio maximum deposit/minimum deposit were 7, 4, 10 and 6 for soybean, Commelina benghalensis and Bachiaria plantaginea in the rows and between the rows, respectively. The average deposits were 34% superior in the plants of Brachiaria plantaginea located in the rows, compared to the plants between the rows.

Com os objetivos de avaliar a deposição da calda de pulverização sobre plantas de algodão e a eficiência da pulverização com diferentes padrões de gotas sob condições adversas de temperatura e umidade, realizou-se um experimento para a determinação dos volumes de depósitos da pulverização no final de ciclo da cultura. O trabalho foi executado com pulverizador automotriz, equipado com pontas JA3 (jato cônico vazio) e jato plano com indução a ar AD-IA/D 11003 (duplo), AD-IA 11003 que, na pressão trabalhada, proporcionaram volume de aplicação de 150 L ha-1, e a ponta AD-IA 11004 que, na mesma pressão, proporcionou volume aplicado de 200 L ha-1. Para a determinação dos volumes depositados nas folhas do terço superior, médio e inferior das plantas de algodão, utilizou-se do corante alimentício azul brilhante adicionado à calda de pulverização, na concentração de 0,179%. Após a pulverização, as folhas foram lavadas, e o volume recuperado foi analisado por espectrofotometria. Os resultados obtidos foram submetidos à análise de regressão pelo modelo de Gompertz para a comparação entre os tratamentos. A ponta AD-IA 11003 proporcionou os maiores volumes de depósito nas diferentes posições da planta, e a eficiência da aplicação foi de 27,45; 35,08; 47,60 e 39,25% para as pontas JA3, AD-IA/D 11003, AD-IA 11003 e AD-IA 11004, respectivamente.The experiment was carried out to evaluate the leaf deposition and the efficiency of different drop pattern by spraying cotton plants at the end of the growing season, under adverse air temperature and humidity conditions. The sprays, applied at the same pressure, were made with a JACTO UNIPORT speed-sprayer equipped with the nozzles JA3 (hollow cone), AD-IA/D 11003 (double flat fan), and AD-IA 11003 (flat fan) for 150 L ha-1 spray volume, and the nozzle AD-IA 11004 (flat fan) for 200 L ha-1 spray volume. It was applied the FD&C Brue n.1 tracer at 0.179% in the spraying solution to determine the volume of spray deposition on leaf samples obtained from the upper, the middle, and the lower third of the plants canopy. The leaf samples were washed with 20 ml of deionized water. The recovered volumes were analyzed by spectrophotometry. The data were submitted to the Gompertz model regression analysis for treatments comparison. The nozzle AD-IA 11003 gave the highest leaf deposit in all plant parts. The application efficiency was 27.45; 35.08; 47.60 and 39.25% for the nozzles JA3, AD-IA/D 11003, AD-IA 11003, and AD-IA 11004, respectively.

For the mathematical model of conventional 3-D two-phase non-distributive and distributive tracer problems, there are unknown parameters Cww (the concentration of water component in water phase) and Coo (the concentration of oil component in oil phase) in the water and oil component functions, which would increase the computational load in the basic model to solve differences. Taking into account Cww≈1 and Coo≈1, the water and the oil component functions can be simplified through substituting Cww=1 and Coo=1. The implicit difference schemes of this simplified model are presented and solved by Gauss-Seidel iteration method. By means of rational design of the differential lattice, the obtained coefficient matrix of linear equations is strictly diagonally dominant, which can make the result unconditionally stable. Compared with the results of the non simplified model, the formation permeability error is less than 2%, and the layer thickness error is less than 5%, which indicates the operation accuracy of this simplified model can meet the requirements, and greatly reduce the calculated amount at the same time. The model has been put into practical use for the well group N2-2-P38 in southern district II in Daqing Oilfield. The amount of 10 tons ammonium thiocyanate was injected into the test area, and the amount of 14 tons normal butyl alcohol was used. The production concentration curves have been measured in three nearby production wells, and one of them is not perforation and the tracer is not detected. The time that ammonium thiocyanate concentration occur peak value is 152, 225and 42 days. The flowing velocity of injected water between the injection and the production wells is 1.65, 1.11 and 5.95 m/d. Then the average water-phase permeability of the reservoir is 0.090, 0.0731 and 0.477μm2, which are calculated and determined for production wells N2-D3-P38, N2-D2-P38 and N2-2-P138 respectively. Based on the dynamic parameters of water, production fluid, pressure and curve fitting of tracer concentration, the reservoir parameters and remaining oil saturation distribution of the 4 sediments, namely, PI1, PI2, PI3 and PI4 are obtained. [ABSTRACT FROM AUTHOR]

Accurate knowledge of ocean surface currents at high spatial and temporal resolutions is crucial for a gamut of applications. The altimeter observing system, by providing repeated global measurements of the sea surface height, has been by far the most exploited system to estimate ocean surface currents over the past 20 years. However, it neither permits the observation of currents moving away from the geostrophic balance nor is it capable of resolving the shortest spatial and temporal scales of the currents. Therefore, to overcome these limitations, in this study the ways in which the high-spatial-resolution and high-temporal-resolution information from sea surface temperature (SST) images can improve the altimeter current estimates are investigated. The method involves inverting the SST evolution equation for the velocity by prescribing the source and sink terms and employing the altimeter currents as the large-scale background flow. The method feasibility is tested using modeled data from the Mercator Ocean system. This study shows that the methodology may improve the altimeter velocities at spatial scales not resolved by the altimeter system (i.e., below 150 km) but also at larger scales, where the geostrophic equilibrium might not be the unique or dominant process of the ocean circulation. In particular, the major improvements (more than 30% on the meridional component) are obtained in the equatorial band, where the geostrophic assumption is not valid. Finally, the main issues anticipated when this method is applied using real datasets are investigated and discussed. [ABSTRACT FROM AUTHOR]