Search

The amplification effect of anthropogenic‐biogenic interactions on secondary organic aerosol (SOA) formation remains debated, particularly regarding the impact of anthropogenic emissions on biogenic SOA (BSOA) formation in forests near megacities. This study concurrently measured typical biogenic and anthropogenic SOA tracers during day and night at the summit (1,690 m a.s.l.) and foot (200 m a.s.l.) of the Nanling mountains, a large subtropical forest adjacent to the Pearl River Delta (PRD) in southern China. Results revealed unexpectedly high concentrations of BSOA tracers (149.9 ± 70.5 ng m−3 at the summit and 109.7 ± 51.2 ng m−3 at the foot), surpassing those at most other background sites worldwide. Daytime BSOA tracer levels at the foot were consistent with nighttime levels, whereas the summit showed significantly higher concentrations at night. Nighttime correlations between O₃ and BSOA tracers at the summit suggest that high O₃ levels stimulate BSOA formation. Conversely, a negative correlation between O₃ and isoprene derived SOA (SOAI) tracers at the foot indicates that other oxidants may also influence SOAI formation. BSOA tracer concentrations rose significantly with the arrival of anthropogenic pollutants (e.g., SO₂ and NO₂), indicating that anthropogenic pollution amplifies BSOA formation by enhancing aerosol acidity (pH < 3). This amplification effect could be mitigated by the reduction of aerosol acidity due to increased NH₃ and relative humidity (RH). Our findings provide valuable insights into the interactions between anthropogenic and biogenic emissions on SOA formation and vertical distribution in forests surrounding megacities. Plain Language Summary: Secondary organic aerosol (SOA) makes up a significant portion of global submicron‐sized atmospheric organic aerosols (OA), reaching up to 90% by mass. Understanding its composition and sources is essential for improving air quality and adapting climate change. However, the role of interactions between human‐made (anthropogenic) and natural (biogenic) emissions in enhancing SOA formation is still debated, especially near megacities. To investigate this, we measured biogenic and anthropogenic SOA tracers simultaneously at the summit (1,690 m a.s.l.) and foot (200 m above sea level) of the Nanling mountains, a subtropical forest near the PRD in southern China, during both day and night. Our results showed unexpectedly high concentrations of SOA tracers compared to most global sites. Isoprene‐derived SOA tracers were predominant at the summit, while monoterpene‐derived SOA tracers were more prevalent at the foot. Interactions between anthropogenic and biogenic emissions can enhance biogenic SOA formation in forested areas near megacities, although this effect can be mitigated by increase of ammonia (NH3) and RH. Also, ozone played a crucial role in nighttime biogenic SOA formation at the summit. These findings highlight the impact of anthropogenic‐biogenic interactions on SOA formation and its vertical distribution in urban‐adjacent forests. Key Points: Diurnal patterns of secondary organic aerosol (SOA) tracers were simultaneously investigated at the summit and foot of Mt. NanlingSOA tracer concentrations were found to be significantly higher than those at most other background sites worldwideInteractions between anthropogenic and biogenic emissions amplified SOA formation in forests near megacities, particularly during pollution periods [ABSTRACT FROM AUTHOR]

Recent advancements in the development of positron emission tomography (PET) tracers have significantly enhanced our ability to image neuroinflammatory processes and neurotransmitter systems, which are vital for understanding and treating neurodegenerative and psychiatric disorders. Similarly, innovative tracers in oncology provide detailed images of the metabolic and molecular characteristics of tumors, which are crucial for tailoring targeted therapies and monitoring responses, including radiotherapy. Notable advancements include programmed death ligand 1 (PD-L1)-targeting agents for lung cancer, prostate-specific membrane antigen-based tracers for prostate cancer, chemokine receptor-targeting agents for hematological malignancies, human epidermal growth factor receptor 2 (HER2)-targeting tracers for various cancers, Claudin 18 based tracers for epithelial tumors, glutamine tracers for colorectal cancer, and ascorbic acid analogs for assessing cancer metabolism and therapy efficacy. Additionally, novel tracers have been developed for non-neurological and non-oncological applications, including adrenal imaging, amyloidosis, and human immunodeficiency virus (HIV) infection. This overview focuses on the newly developed tracers, particularly those used in neurology and oncology. [ABSTRACT FROM AUTHOR]

In this study, we use field observations augmented with model simulations to examine gravel dispersion over nine years (2007–2015) in Halfmoon Creek. The observations of flow, entrainment, and dispersion were used to develop a forward model utilizing the Einstein‐Hubbell‐Sayre (EHS) compound Poisson process. The observed mean virtual velocity of the tracer population slows down with cumulative excess energy after the 2010 large event. The forward model deviates from the observations in representation of tails, overpredicts mean displacements, and shows a narrower spatial distribution. The heavy‐tailed resting times indicate prolonged immobilization of some grains, suggesting the preferential movement of other most mobile grains. As such, 34% of most mobile grains constitute 50% of the total entrainments. The consideration of preferential movement explains the longitudinal spread but still overpredicts the displacement after the 2010 event. The model was then explored to consider additional transport‐related mechanisms causing deviations, such as reduction in virtual velocity, entrainment probability, and morphological trapping of meander bends, which helps to adequately recreate the observed dispersive behavior. The available historical flow records used for simulating dispersive behavior over multiple decades reveal an abrupt increase in displacements for exceptionally large events, suggesting the exhumation of deeply buried grains back in transport. The simulation results highlight the need for tracer studies with large sample sizes and improved recovery rates for longer time frames experiencing floods of widely varying magnitudes. Such models, inspired by Einstein's stochastic theory can be valuable for various river research applications. Key Points: Simulation of tracer dispersion utilizing Einstein‐Hubbell‐Sayre model overpredicts mean displacement and fails to explain longitudinal spread of tracersGrains mobilized in previous events move preferentially in subsequent events, unlike the assumption of random movement in most transport modelsConsideration of slowdown in virtual velocity, mobility, and morphological trapping together with preferential movement explains variability [ABSTRACT FROM AUTHOR]

The Asian summer monsoon anticyclone (ASMA) plays a vital role in the transport and redistribution of the tracers in the upper troposphere and lower stratosphere during transient monsoon conditions. The ASMA can be identified using various diagnostics such as winds and divergence, potential vorticity, the Montgomery stream function or geopotential height. Its representation based on the commonly‐used existing method that takes a climatological range of the geopotential height (GPH) at a given pressure level is not robust and fails in several circumstances. In this study, we propose a new GPH method to define the ASMA for the active and break phases of the monsoon based on the GPH values at the tropical easterly jet (TEJ) and subtropical westerly jet (STJ) locations. The proposed method compares the GPH values at the locations corresponding to the wind speed maxima of TEJ and STJ at 100 hPa with the maximum GPH at 100 hPa and selects the one with the minimum difference to define the ASMA extent. The same procedures were applied to obtain the ASMA extent at 150 hPa. The ASMA extents are obtained using the method proposed here and the existing fixed GPH method for the 30 active and 27 break phases from 2005 to 2023. The fixed GPH method provides a larger ASMA extent for 24 active and 21 break phases, which appears to be an unrealistic estimation compared to the proposed method. Our proposed method identifies the ASMA extent that is larger and centred around the Iranian side during the active phases while it is smaller and centred around the Tibetan side during the break phases. Furthermore, the minimum concentration of ozone (O3), and maximum concentrations of carbon monoxide (CO) and water vapour (H2O) are also found to be centred near the Iranian side during the active phases and on the Tibetan side during the break phases. The tracer concentrations are generally higher for CO, H2O and O3 during the active phase than in the break phase. Tracer concentrations within the ASMA extent using the fixed GPH method are higher for O3 while lesser for CO and H2O when compared to the proposed method. [ABSTRACT FROM AUTHOR]

Application of hydraulic fracturing to produce “unconventional” oil and gas from shale formations and other low-permeability geological units has raised concerns about the potential environmental impacts, including potential adverse effects of fracturing fluids (FF) on groundwater. In this study, laboratory batch test experiments and new analytical methods were developed to analyze FF chemicals as potential indicators (tracers) to detect impacts of fracturing fluids on groundwater. The tests, conducted over 101–196 days, included FF with synthetic chemicals (~40,000–4,000,000 µg/L), placed in batches with groundwater and sediment at 5° and 25 °C, along with sterile controls. Using the new methods, measurable concentrations of the FF chemicals were many orders in magnitude lower (~3000 to 3,000,000 X) compared to their concentrations in synthetic fracturing fluids, indicating that these chemicals are excellent candidates as indicators of FF contamination in groundwater, if they are relatively persistent, and not prone to extensive loss by sorption during migration in the subsurface. Variable sorption and degradation of the chemicals was observed in both batch and column tests. Sorption was negligible (sorption coefficient, Kd~0.0) for some synthetic chemicals (polyethylene glycol, ethanolamines, isopropanol, and ethyl hexanol) in some tests. At the other extreme, strong sorption was observed for some of the higher molecular weight cocamido propyl betaine (max Kd = 1.17) and polyethylene glycol (max Kd = 1.12) components, and triethanolamine (max Kd = 0.47) in other tests. Apparent loss by degradation was observed for each chemical in some tests, but negligible in others. The shortest apparent half-lives were for isopropanol and ethyl hexanol at 25 °C (t½ < 11 days), and the most persistent synthetic chemicals were polyethylene glycols (t½ ≥ 182 d) and the ethanolamines (t½ ≥ 212 d). Of the potentially diagnostic FF chemicals investigated, the relatively hydrophilic and persistent lower molecular weight polyethylene glycols are some of the most promising as potential indicators of contamination of groundwater by FF.

Abstract During the July 2021 European floods approximately eight million empty dairy packaging (buttertubs) were flushed from a dairy processing facility in Belgium into the Vesdre river. Some were transported further downstream, into the Ourthe river and eventually the Meuse river. There are many unknowns when it comes to plastic transport in rivers, especially in response to floods. We therefore used this incident as an unique opportunity to study these buttertubs as a tracer for plastic transport dynamics in a riverine environment in response to an extreme flood event. Normally, it is unknown when and where individual plastic items found on riverbanks entered the environment. In this case, however, the ID stamps on the buttertups allowed for them to be traced back to the flooding of the factory. We studied the transport and deposition of these buttertubs in the Dutch Meuse over 2 years following the flood. We also collected buttertubs at different points in time to investigate their fragmentation and mass loss. Within 3 weeks of the flood, the buttertubs were transported up to 328 km from the spilling location. Overall, the majority (78%) of buttertubs we found within the first 3 weeks were deposited within less than 100 km of the point of emission. Over the following 2 years, the mean transport distance of the found buttertubs moved downstream from 100 km in July/August 2021, to 153 km in July 2023. The buttertubs average transport velocity decreased from 11.7 km/d within the first 3 weeks, to 0.2 km/d by July 2023. Based on the 89 buttertubs we collected and analyzed in detail over the 2 years, we did not find a significant mass loss. Of all 89 buttertubs found, 47 showed cracks and only 12 appeared to have pieces missing. This study shows that even during extreme flood events, the majority of spilled plastic litter is retained within a limited distance after being emitted into the river. The findings of this study can be utilized to improve plastic transport modelling, and overall better understand plastic transport in the freshwater environment.

Submesoscale flows (0.1–10 km) are often associated with large vertical velocities, which can have a significant impact on the transport of surface tracers, such as carbon. However, global models do not adequately account for these small‐scale effects, which still require a proper parameterization. In this study, we introduced a passive tracer into the surface mixed layer (ML) of a northern Atlantic Ocean simulation based on the primitive‐equation model CROCO, with a horizontal resolution of Δx = 800 m, aiming to investigate the seasonal submesoscale effects on vertical transport. Using surface vorticity and strain rate criteria, we identified regions with submesoscale fronts and quantified the associated subduction, that is the export of tracer below the ML depth. The results suggest that the tracer vertical distribution and the contribution of frontal subduction can be estimated from surface strain and vorticity. Notably, we observed significant seasonal variations. In winter, the submesoscale fronts contribute up to 40% of the total vertical advective transport of tracer below the ML, while representing only 5% of the domain. Conversely, in summer, fronts account for less than 1% of the domain and do not contribute significantly to the transport below the ML. The findings of this study contribute to a better understanding of the seasonal water subduction due to fronts in the region. Plain Language Summary: Oceanic fronts are dynamical structures characterized by enhanced gradients of variables such as temperature or density. These structures are prominent and ubiquitous at the ocean surface and can reach particularly small scales, down to a few kilometers. They are known to play an important role in the vertical exchange of carbon, nutrients or heat between the surface and the ocean interior. Due to their small scale and short lifecycle, they have not been extensively sampled and a systematic quantification of their impact is missing. In this study, we set up a numerical simulation of the ocean circulation in the North Atlantic that resolves small‐scale fronts. We release a tracer in upper layer of the ocean and analyze how it is transported at depth. Using criteria based on the flow velocity, we quantify the fraction of the ocean surface covered by fronts. We find that the average depth at which the tracer is injected depends on the prevalence of fronts, which itself shows a strong seasonality. In winter, fronts cover less than 5% of the surface area, but contribute up to 40% of the tracer vertical transport. Conversely, in summer, fronts cover less than 1% of the area and have no significant effect on tracer vertical transport. This study helps to better understand the seasonal role of fronts in vertical water transport. This paves the way for addressing questions related to how tracers such as carbon are distributed in the world's oceans. Key Points: Surface strain and vorticity criteria can be used to identify submesoscale frontsThe tracer depth injection correlates with the surface fraction of fronts, regardless of the mixed layer depth evolutionThe submesoscale fronts contribute to ∼40% of the total tracer vertical advective subduction in winter, and less than 1% in summer [ABSTRACT FROM AUTHOR]

Application of hydraulic fracturing to produce "unconventional" oil and gas from shale formations and other low-permeability geological units has raised concerns about the potential environmental impacts, including potential adverse effects of fracturing fluids (FF) on groundwater. In this study, laboratory batch test experiments and new analytical methods were developed to analyze FF chemicals as potential indicators (tracers) to detect impacts of fracturing fluids on groundwater. The tests, conducted over 101–196 days, included FF with synthetic chemicals (~40,000–4,000,000 µg/L), placed in batches with groundwater and sediment at 5° and 25 °C, along with sterile controls. Using the new methods, measurable concentrations of the FF chemicals were many orders in magnitude lower (~3000 to 3,000,000 X) compared to their concentrations in synthetic fracturing fluids, indicating that these chemicals are excellent candidates as indicators of FF contamination in groundwater, if they are relatively persistent, and not prone to extensive loss by sorption during migration in the subsurface. Variable sorption and degradation of the chemicals was observed in both batch and column tests. Sorption was negligible (sorption coefficient, Kd~0.0) for some synthetic chemicals (polyethylene glycol, ethanolamines, isopropanol, and ethyl hexanol) in some tests. At the other extreme, strong sorption was observed for some of the higher molecular weight cocamido propyl betaine (max Kd = 1.17) and polyethylene glycol (max Kd = 1.12) components, and triethanolamine (max Kd = 0.47) in other tests. Apparent loss by degradation was observed for each chemical in some tests, but negligible in others. The shortest apparent half-lives were for isopropanol and ethyl hexanol at 25 °C (t½ < 11 days), and the most persistent synthetic chemicals were polyethylene glycols (t½ ≥ 182 d) and the ethanolamines (t½ ≥ 212 d). Of the potentially diagnostic FF chemicals investigated, the relatively hydrophilic and persistent lower molecular weight polyethylene glycols are some of the most promising as potential indicators of contamination of groundwater by FF. [ABSTRACT FROM AUTHOR]

Purpose of Review: To discuss the recent advances in the diagnosis and treatment of light chain cardiac amyloidosis (AL-CM). Recent Findings: The improved recognition of AL-CM is primarily driven by improved diagnostic techniques. Cardiac MRI has emerged as a sensitive modality for the diagnosis of AL-CM. Positron emission tomography (PET) with a whole host of amyloid fibril-binding tracers has tremendous promise. On the therapeutics front, better anti-plasma cells therapies are in clinical use or under investigation, and a new front of fibril depleters are opening the doors for targeting organ recovery by promoting the resorption of amyloid fibrils. Summary: AL-CM results in significant morbidity and mortality mainly due to delayed diagnosis and lack of therapies that acutely address the underlying organ dysfunction. The combination of improved disease detection with improved therapy promises to continue transforming AL-CM into either chronic treatable or curable disease. [ABSTRACT FROM AUTHOR]

Background: To date, the benefit of image guidance during robot-assisted surgery (IGS) is an object of debate. The current study aims to address the quality of the contemporary body of literature concerning IGS in robotic surgery throughout different surgical specialties. Methods: A systematic review of all English-language articles on IGS, from January 2013 to March 2023, was conducted using PubMed, Cochrane library's Central, EMBASE, MEDLINE, and Scopus databases. Comparative studies that tested performance of IGS vs control were included for the quantitative synthesis, which addressed outcomes analyzed in at least three studies: operative time, length of stay, blood loss, surgical margins, complications, number of nodal retrievals, metastatic nodes, ischemia time, and renal function loss. Bias-corrected ratio of means (ROM) and bias-corrected odds ratio (OR) compared continuous and dichotomous variables, respectively. Subgroup analyses according to guidance type (i.e., 3D virtual reality vs ultrasound vs near-infrared fluoresce) were performed. Results: Twenty-nine studies, based on 11 surgical procedures of three specialties (general surgery, gynecology, urology), were included in the quantitative synthesis. IGS was associated with 12% reduction in length of stay (ROM 0.88; p = 0.03) and 13% reduction in blood loss (ROM 0.87; p = 0.03) but did not affect operative time (ROM 1.00; p = 0.9), or complications (OR 0.93; p = 0.4). IGS was associated with an estimated 44% increase in mean number of removed nodes (ROM 1.44; p < 0.001), and a significantly higher rate of metastatic nodal disease (OR 1.82; p < 0.001), as well as a significantly lower rate of positive surgical margins (OR 0.62; p < 0.001). In nephron sparing surgery, IGS significantly decreased renal function loss (ROM 0.37; p = 0.002). Conclusions: Robot-assisted surgery benefits from image guidance, especially in terms of pathologic outcomes, namely higher detection of metastatic nodes and lower surgical margins. Moreover, IGS enhances renal function preservation and lowers surgical blood loss. [ABSTRACT FROM AUTHOR]

Radon (Rn) and helium (He) gases from uranium decay form distinct anomalies related to buried uranium deposits. In order to trace the geochemical anomalous sources from the volcanic-related uranium deposits in deeply buried areas, systematical Rn contents and He isotope ratios were analyzed from the Daguanchang uranium deposit. The soil gas Rn concentrations above the deep uranium are ten times higher than those in barren areas, indicating that instantaneous Rn content measurements can be used to detect deeply buried uranium. The helium isotope ratios (3He/4He) of the unmineralized samples from the mineralized drill hole (ZK1) are relatively lower and uniform compared to those of the samples from no-mineral drill hole (ZK2). However, the Th and U contents of the drill core samples from ZK1 are slightly lower than those of the samples from ZK2, indicating that the lower 3He/4He ratios in ZK1 are most likely due to the addition of 4He from underlying uranium intervals. The differences in the instantaneous Rn contents are consistent with the variations in the He isotope ratios of the drill core samples. These results demonstrate that soil gas Rn and 3He/4He ratios are useful tracers and can indicate the existence of deeply buried volcanic-related hydrothermal uranium ores. [ABSTRACT FROM AUTHOR]

Background and aims: Rare earth element (REE) oxides serve as effective tracers to track aggregate dynamics. However, the impact of labeling and sieving processes on aggregate and organic matter dynamics remains uncertain. This study aimed to determine the effect of the labeling and sieving processes on soil aggregate and organic carbon dynamics. Methods: Dry and wet sieved aggregates from a Japanese typical Andisol were labeled with REE oxides. REE oxides concentrations and soil organic carbon fractions were measured during the 28-day incubation period to calculate aggregate transformation paths and soil organic carbon dynamics. Results: The findings demonstrated that REE oxides are effective tracers to track Andisol aggregate turnover. The labeling and sieving processes showed significant positive effect on aggregate turnover. During incubation, wet sieved macroaggregates displayed more transformation than dry sieved aggregates (5.26% ~ 7.24% vs. 11.03% ~ 12.81%), reflecting a higher turnover rate of macroaggregates resulting from wet sieving relative to dry sieving. Regarding organic carbon fractions, the labeling process significantly affected dissolved organic carbon (DOC), microbial biomass carbon (MBC), and free particulate organic matter (fPOM). Additionally, the degree of interference was linked to the sieving processes, with MBC and fPOM content significantly lower following wet sieving. This effect persisted during incubation, except for fPOM content, which exhibited a rapid increase accompanied by a decrease in occluded particulate organic matter (oPOM) content following the wet sieving method. Conclusion: Our results demonstrate that the effects of labeling and sieving processes should be considered when analyzing the relationship between aggregate turnover and organic carbon with REE oxides tracers. [ABSTRACT FROM AUTHOR]

Undesirable translocation of soil particles in the direction of movement of machines can occur during soil tillage. The result can be a reduction in soil fertility, especially when the cultivation is deeper. A field experiment was based on sandy-loam cambisoil, where white limestone grit was used as tracers (fraction 10–16 mm). A Kromexim blade cultivator was used for tillage, the other machine was an Akpil disc cultivator. After loosening the soil to a depth of 0.10 m, the displacement of the tracers was eva¬luated. A significant influence of the field slope and the movement direction of the machines on the displacement of the tracers was revealed. With the blade cultivator, the movement of tracers was detected up to a distance of 2.4 m when driving uphill, 3.6 m when driving in the contour direction and 4.2 m when moving down the slope. With the disc cultivator, significantly less displacement of the tracers was found – at all levels of inclination up to a distance of 1 m. The results of the field experiment can contribute to extend the knowledge of one of the negative effects on the fertility of arable soil. [ABSTRACT FROM AUTHOR]

The Citarum watershed and the Saguling reservoir are vital natural resources in Indonesia, affecting the livelihood of West Java and the DKI Jakarta population. This study aimed to assess the soil erosion in the Upper Citarum watershed and identify its source. The study used the fallout radionuclide technique, geochemical tracers, and an unmixing model to measure soil erosion and the contribution of suspended sediment sources due to erosion. Soil bulk transects and surface soil were sampled using a coring tool on the Ciwidey and Cisangkuy sub-watersheds. Riverbank and suspended sediment samples were collected from tributaries and rivers. With 137Cs, 40% of the samples had values below the minimum detectable activity, and vice versa for 210Pbex, all samples are detectable. For mitigation, bare land needs to be recovered due to its erosion (25.6 t ha−1 year−1) exceeding the tolerance erosion value (17 t ha−1 year−1). Statistically, Mg and Na were the most appropriate composite tracers for suspended sediment contribution. The unmixing model predicted the sediment contributors from bare land (58%), the riverbank (32.7%), and plantation land (9.3%). Proper land conservation could reduce sediment supply by almost 14.7% and extend the reservoir's life. This is the first study to report the feasibility of the unmixing model in Indonesia. [ABSTRACT FROM AUTHOR]

In this work, PM2.5 was sampled at Dunkerque, a medium-sized city located in northern France. The mean concentration of PM2.5 during the sampling period was 12.6 ± 9.5 μg·m−3. Samples were analyzed for elemental and organic carbon (EC/OC), water-soluble organic carbon (WSOC), humic-like substances (HULIS-C), water-soluble inorganic ions, and major and trace elements. The origin and the variations of species concentrations were examined using elemental enrichment factors, bivariate polar plot representations, and diagnostic concentration ratios. Secondary inorganic ions were the most abundant species (36% of PM2.5), followed by OC (12.5% of PM2.5). Secondary organic carbon (SOC) concentrations were estimated to account for 52% of OC. A good correlation between SOC and WSOC indicated that secondary formation processes significantly contribute to the WSOC concentrations. HULIS-C also represents almost 50% of WSOC. The determination of diagnostic ratios revealed the influence of anthropogenic emission sources such as integrated steelworks and fuel oil combustion. The clustering of 72 h air masses backward trajectories data evidenced that higher concentrations of PM2.5, OC, and secondary inorganic aerosols were recorded when air masses came from north-eastern Europe and the French continental sector, showing the considerable impact of long-range transport on the air quality in northern France. [ABSTRACT FROM AUTHOR]

This study aimed to develop and implement a nanotechnology-based alternative to traditional tracers used in the oil and gas industry for assessing interwell connectivity. A simple and rapid hydrothermal protocol for synthesizing carbon quantum dots (CQDs) using agroindustry waste was implemented. Three commercial CQDs were employed (CQDblue, CQDgreen, and CQDred); the fourth was synthesized from orange peel (CQDop). The CQDs from waste and other commercials with spherical morphology, nanometric sizes less than 11 nm in diameter, and surface roughness less than 3.1 nm were used. These tracers demonstrated high colloidal stability with a negative zeta potential, containing carbonyl-type chemical groups and unsaturations in aromatic structures that influenced their optical behavior. All materials presented high colloidal stability with negative values of charge z potential between −17.8 and −49.1. Additionally, individual quantification of these tracers is feasible even in scenarios where multiple CQDs are present in the effluent with a maximum percentage of interference of 15.5% for CQDop in the presence of the other three nanotracers. The CQDs were injected into the field once the technology was insured under laboratory conditions. Monitoring the effluents allowed the determination of connectivity for five first-line producer wells. This study enables the application of CQDs in the industry, particularly in fields where the arrangement of injector and producer wells is intricate, requiring the use of multiple tracers for a comprehensive description of the system. [ABSTRACT FROM AUTHOR]

Rivers transport elements, minerals, chemicals, and pollutants produced in their upstream basins. A sample from a river is a mixture of all of its upstream sources, making it challenging to pinpoint the contribution from each individual source. Here, we show how a nested sample design and convex optimization can be used to efficiently unmix downstream samples of a well‐mixed, conservative tracer in a steady state system into the contributions of their upstream sources. Our approach is significantly faster than previous methods. We represent the river's sub‐catchments, defined by sampling sites, using a directed acyclic graph. This graph is used to build a convex optimization problem which, thanks to its convexity, can be quickly solved to global optimality—in under a second on desktop hardware for data sets of ∼100 samples or fewer. Uncertainties in the upstream predictions can be generated using Monte Carlo resampling. We provide an open‐source implementation of this approach in Python. The inputs required are straightforward: a table containing sample locations and observed tracer concentrations, along with a D8 flow‐direction raster map. As a case study, we use this method to map the elemental geochemistry of sediment sources for rivers draining the Cairngorms mountains, UK. This method could be extended to non‐conservative and non‐steady state tracers. We also show, theoretically, how multiple tracers could be simultaneously inverted to recover upstream run‐off or erosion rates as well as source concentrations. Overall, this approach can provide valuable insights to researchers in various fields, including water quality, geochemical exploration, geochemistry, hydrology, and wastewater epidemiology. Plain Language Summary: Rivers transport solid and dissolved elements, chemicals, and pollutants from upstream to downstream. Knowing where these elements are coming from, and in what quantities, is useful in targeting environmental protection or learning about the geology and hydrology of an area. However, a single sample of a river can't provide much useful information because all of the different sources have been mixed together by the river. If multiple samples are taken upstream and downstream, we show that a computational technique called convex optimization can be used to "unmix" the river's waters or sediments revealing where the elements have come from. This approach is accurate and fast enough that we can run it thousands of times with small changes to the sampled values to get a sense of the uncertainty. Though we speak about our method in terms of rivers here, it could be useful in other contexts, such as determining where pollutants or tracers of disease outbreaks are entering sewage networks. Key Points: Unmixing sources and magnitudes of tracers from nested concentration measurements in a river basin is a convex optimisation problemWe provide new software that solves this problem very quickly given a D8 raster and some point observations of concentrationThis method can be used to apportion pollution in a river basin and in any geochemistry study that uses a nested sampling design [ABSTRACT FROM AUTHOR]

[Display omitted] • Two tracer types were used to discover the distribution of residence times (RT). • Transient was distinguished from steady-state based on lower RT and temperatures. • At steady-state 60% of the mean RT are estimated for 10% of the particles. • At transient-state the risk of insufficient hygienization increases. • Mass distribution of ball-shaped aggregates discharged from the drum was assessed. Rotary drums enable rapid composting compared to static systems. Residence times (RT) of 3–5 days are commonly applied to fulfill sanitary requirements and ensure the initial stabilization of organic matter. Practically, RT distribution (RTD) implies that a portion of the feed is discharged earlier than the mean RT, which may not guarantee safe application of the end product. This study assessed RTD and other physical–chemical and biological parameters of cattle manure and green waste composted in an EcodrumTM rotary drum (∼10 m3). Two types of tracers were used: pieces of plastic tubing and lumps of raw material in which plant seeds were buried, which were packed in nylon socks. A transient-state during which less than 50 % of the drum volume was occupied was distinguished from a steady-state stage, during which the drum operated with its optimal loading of about two-thirds of its volume. Starting temperatures inside the drum were close to ambient when the drum was mostly empty and then increased up to 60–65 °C as the occupied volume approached 50 %. The two types of tracers seemed to provide complementary measurements; under steady-state conditions, actual RTs were 60 % of the mean RT for 10 % of the feed material. The viability of plant seeds which were included in tracers was somewhat dependent on the specific RT. Under transient-state conditions, even shorter RTs (relative to the mean RT) are expected, coupled with non-thermophilic conditions, reducing the likelihood of adequate destruction of pathogens. [ABSTRACT FROM AUTHOR]

Continuing negative rainfall anomalies, coupled with climate change projections of increased drought severity and frequency, drive an urgent need to increase resilience and integration in land and water management strategies in many regions of the world. However, complex interactions between land cover change, ecohydrological partitioning and water availability are difficult to quantify, especially at different temporal and spatial scales. In conjunction with local stakeholders, we developed plausible, alternative land use scenarios (including forest diversification and agroforestry schemes) based on the existing four primary land use types (i.e., conifer and broadleaved forests, arable agriculture, and pasture) in a 66 km² drought-sensitive catchment in northern Germany. We used modelling to evaluate spatial and temporal changes in water flux partitioning, storage and ages. The spatially-distributed, traceraided ecohydrological model, EcH2O-iso, calibrated using hydrometric, ecohydrological and isotopic data at daily time steps from 2007 to 2019 was used in this assessment. The results showed that replacing conifer forests with uneven-aged mixed forests with younger broad-leaved trees had the greatest potential for reducing total evapotranspiration and increasing groundwater recharge. For coniferous forests, a 50% increase in the proportion of broad-leaved trees was projected to result in an 11% increase in groundwater recharge across the catchment. The mixed-forest management alternatives also reduced groundwater turnover times, which would support more rapid recovery of soil moisture and groundwater stores following droughts. This study demonstrates that such an ecohydrological modelling approach has the potential to contribute useful science-based evidence for policy makers allowing quantitative assessment of potential land use effects on water availability and effective communication with stakeholders. [ABSTRACT FROM AUTHOR]

Viral testing combined with hydrographic studies is considered standard good practice in determining microbiological impacts on shellfish growing areas following wastewater overflows. In this study, norovirus genogroup I and II, indicators of viral contamination (F-RNA bacteriophage genogroup II (F-RNA GII), crAssphage, pepper mild mottle virus) and Escherichia coli were monitored during periods of normal harvesting and following overflows in two commercial shellfish growing areas in Otago Harbour (Aotearoa New Zealand). Dye tracing, drogue tracking and analysis of particle tracking modelling were also undertaken to assess the dispersion, dilution and time of travel of wastewater discharged from a pump station discharge that impacts the growing areas. Norovirus was not detected in any of the 218 shellfish samples tested. PMMoV and crAssphage were more prevalent than F-RNA GII as determined by RT-qPCR. The dye study indicated long residence time of the waters (≥5 days) in the embayment impacted by the discharge. No relationships were found between the concentrations of viral indicators or E. coli and wastewater dilution, distance between the discharge and the growing areas or time since the last overflow. For the three spills studied (≤327 m3), there was little evidence of microbiological impact on the growing areas. This was likely associated with a deep shipping channel that enhances water flushing in the harbour and reduces contaminant transport to the growing areas. We recommend flexibility in the approach for closure/reopening growing areas impacted by spills, particularly for small duration/volume spills and when norovirus is not present in the community. [ABSTRACT FROM AUTHOR]

The cerebellum is involved in many motor, autonomic and cognitive functions, and new tasks that have a cerebellar contribution are discovered on a regular basis. Simultaneously, our insight into the functional compartmentalization of the cerebellum has markedly improved. Additionally, studies on cerebellar output pathways have seen a renaissance due to the development of viral tracing techniques. To create an overview of the current state of our understanding of cerebellar efferents, we undertook a systematic review of all studies on monosynaptic projections from the cerebellum to the brainstem and the diencephalon in mammals. This revealed that important projections from the cerebellum, to the motor nuclei, cerebral cortex, and basal ganglia, are predominantly di- or polysynaptic, rather than monosynaptic. Strikingly, most target areas receive cerebellar input from all three cerebellar nuclei, showing a convergence of cerebellar information at the output level. Overall, there appeared to be a large level of agreement between studies on different species as well as on the use of different types of neural tracers, making the emerging picture of the cerebellar output areas a solid one. Finally, we discuss how this cerebellar output network is affected by a range of diseases and syndromes, with also non-cerebellar diseases having impact on cerebellar output areas. [ABSTRACT FROM AUTHOR]

Understanding the nature of mixing between cloudy air and its surroundings is an important and yet, open question. In this research, we use high‐resolution (10 m) bin‐microphysics Large Eddy Simulation of a cumulus cloud, together with a Lagrangian passive tracer tracking method, to study mixing. We analyze the passive tracers as a function of their trajectories and the thermodynamic conditions they undergo inside and outside the cloud. Three main mixing regimes (core, periphery, and skin) are identified, each determining a subset of tracers with similar trajectories. These mixing regimes can be observed throughout the cloud's lifetime and they provide evidence for the presence of an undiluted core in shallow cumulus clouds. At the dissipation stage, a fourth regime is identified: cloud‐top entrainment followed by downdrafts. Plain Language Summary: The mixing of shallow clouds with their environment is a key open question in climate research and prediction. This topic is challenging due to the complexity of cloud processes and the difficulty of accurately measuring and modeling them. This study uses high‐resolution simulation and Lagrangian tracers to analyze mixing. The study identifies three different mixing regimes in cumulus clouds throughout their lifetime. Each regime is characterized by specific types of tracer trajectories. A fourth regime is identified as part of the clouds' decay. Key Points: Three mixing regimes are identified using subsets of tracers with similar trajectories in the Large Eddy Simulation of a cumulus cloudThese mixing regimes persist throughout the cloud's lifetime, providing insights into cloud mixing dynamicsThe dissipation stage of the cloud reveals cloud‐top entrainment followed by downdrafts [ABSTRACT FROM AUTHOR]

Nowadays, groundwater is the most important resource on our planet. However, due to population growth, urbanisation, and climate change, this resource is often overexploited or contaminated. In this context, carbonate aquifers provide drinking water to approximately 25% of the global population. Due to aquifers heterogeneities and anisotropic fracture systems, they can be affected by potential contamination and their optimal exploitation represents a challenge aspect. In this particular scenario, carbonate mountain aquifers encompass valuable groundwater resources due to their high recharge rates and excellent water quality; therefore, the understanding of their hydrogeological characteristics are vital for aquifers protection and water management. A valid solution to explore water movement within such aquifers and to quantify the groundwater amount can be offered using artificial tracers. At the same time, the geomechanical surveys can deep the knowledge on fracture density and orientation, providing valuable insights about fracture connection and conductivity. This study combines the advantages of six artificial tracer tests performed in four deep wells (260-500 m b.g.l.) and a geomechanical survey used, among other, to estimate hydraulic conductivity of a mountainous carbonate aquifer located in Central Italy. The results obtained by different methods highlighted the presence of multiple layers with higher conductivity values, able to sustain the groundwater flow without significant piezometric level drawdown during water pumping operations. This approach provides an effective support to the water management company operating. [ABSTRACT FROM AUTHOR]

Fibres, as abundant in agricultural by-products, exhibit a large range of physicochemical properties that can influence digestive processes such as digesta mean retention time (MRT), thereby affecting nutrient digestion kinetics. In this study, we investigated the effects of particle size of insoluble fibres, and gelation of soluble fibres on MRT of liquids, fine solids, and fibrous particles in the different segments of the gastrointestinal tract (GIT) of pigs. Twenty-four boars (51.6 ± 4.90 kg) were allocated to four diets; two diets contained 15% wheat straw, either coarsely chopped or finely ground (1-mm screen), two diets contained 27% wheat bran without or with the addition of 10% low-methylated pectin. After 14 days of adaptation to the diet, a total collection of faeces was performed to determine the total tract digestibility of nutrients. Thereafter, pigs were fed diets supplemented with tracers for at least 5 days and dissected following a frequent feeding procedure to approach steady-state passage of digesta. The MRT of liquids (Co-EDTA), fine solids (TiO2), and fibrous particles (Chromium-mordanted fibres) in the different segments of the GIT were quantified. In the stomach, particle size reduction of straw decreased the MRT of fine solids by 02:39 h, and fibrous particles by 07:21 h (P 0.10). The complete fermentation of pectin did not influence the degradation of wheat bran fibres (∼51%). In conclusion, the effects of particle size of insoluble fibres and gelling properties of soluble fibres on the passage of digesta phases were most pronounced in the stomach, but less prominent in distal segments of the GIT.

Accurately quantifying rates of soil erosion requires capturing both the volumetric nature of the visible, convergent fluvial pathways (also known as rills) and the subtle nature of the less-visible, diffuse pathways (interrill areas). The aim of this study was to use Rare Earth Oxide (REO) tracers and Structure-from-Motion (SfM) photogrammetry to elucidate retrospective information about soil erosion rates and sediment sources during different soil erosion conditions, within a controlled laboratory environment. The experimental conditions created erosion events consistent with diffuse and convergent erosion processes. REO tracers allowed the sediment transport distances of over 2 m to be described, and helped resolved the relative contribution of diffuse and convergent soil erosion; interrill areas were also identified as a significant sediment sources soil loss under convergent erosion conditions. While the potential for SfM photogrammetry to resolve sub-millimetre elevations changes was demonstrated, under some conditions non-erosional changes in surface elevation, such as compaction, exceeded volumes of soil loss via diffuse erosion. The discrepancies between SfM Photogrammetry calculations and REO tagged sediment export were beneficial, identifying that during soil erosion events sediment in both aggregate and particle form is deposited within the convergent features, even when the rill extended the full length of the soil surface. The combination of SfM photogrammetry and REO tracers has provided a novel platform for building a spatial understanding of patterns of soil loss and source apportionment between rill and interrill erosion.

Abstract Immunosuppressive cells are pivotal players in tumor progression by affecting the efficacy of conventional therapies and the prognosis of cancer patients. Visualization and real‐time evaluation of these cells are very important to achieve patient‐oriented precision oncological medicine. Noninvasive imaging techniques are excellent tools for this purpose, and various molecular imaging probes have been developed to monitor these protumoral immunosuppressive cells in the tumor microenvironment. In this review, we provide a brief update on the biology of immunosuppressive cells and outline recent progress in their visualization.

Abstract Understanding the nature of mixing between cloudy air and its surroundings is an important and yet, open question. In this research, we use high‐resolution (10 m) bin‐microphysics Large Eddy Simulation of a cumulus cloud, together with a Lagrangian passive tracer tracking method, to study mixing. We analyze the passive tracers as a function of their trajectories and the thermodynamic conditions they undergo inside and outside the cloud. Three main mixing regimes (core, periphery, and skin) are identified, each determining a subset of tracers with similar trajectories. These mixing regimes can be observed throughout the cloud's lifetime and they provide evidence for the presence of an undiluted core in shallow cumulus clouds. At the dissipation stage, a fourth regime is identified: cloud‐top entrainment followed by downdrafts.

METEX21 was an atmospheric tracer release experiment executed at the Department of Energy's Nevada National Security Site (NNSS) in the southwestern U.S to study terrain-induced wind and thermodynamic conditions that influence local-scale (<5km) plume transport under varying atmospheric forcing conditions. Meteorological observations were collected using 10-m tall meteorological towers, 2-m tall tripods with 3-d sonic anemometers, a 3-m tall eddy covariance flux tower, Doppler profiling lidars, Doppler scanning lidars, weather-balloon launched radiosondes, and a tethered balloon equipped with wind, temperature, and aerosol sensors at heights up to 800 m. A smoke tracer was released along three transects in the horizontal and vertical directions and observed with video cameras, aerosol sensors and lidars (via aerosol backscatter). The observations showed evidence of large-scale/synoptic transience as well as local-scale upslope and downslope flows, along-axis valley flows, recirculation eddies on leeward slopes, and periods of strong shear and veer aloft. The release days were classified as either synoptically-driven or locally-driven, and a single case day is presented in detail for each. Synoptically-forced days show relatively narrow smoke plumes traveling down the valley from north to south (with the predominant wind direction), with little deviation in transport direction regardless of the elevation or ground locations of the smoke releases, except near the presence of leeside recirculation eddies. Locally-forced days exhibit a wider range of plume behavior due to the combination of thermally-induced valley and slope flows, which are often flowing in different cardinal directions, and wind shear found aloft at higher altitudes and elevations. We saw evidence of smoke lofting on top of the mesas due to strong upslope flows on these days. A major finding of this experiment was the effectiveness of scanning lidars to measure 2-dimensional plume transport out to a 2-3 km distance; much farther than could be visibly observed. METEX21 was the first of three planned tracer experiments at NNSS, and future experiments will incorporate multiple tracers to improve individual plume identification so that finer resolution flow details can be attained from these measurements, as well as deploy a larger suite of meteorological instrumentation, including more temperature profiling data. [ABSTRACT FROM AUTHOR]

Copyright of Hydrogeology Journal is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Calibrating distributed hydrological models often leads to equifinality due to complex model structures, which can be further exacerbated in wetlands due to spatio‐temporal heterogeneity in ecohydrological processes. Here, step‐wise calibrations of the physically‐based distributed model EcH2O‐iso was conducted in a data‐rich wetland by minimizing a weighted average of the errors on discharge, stream isotopes, groundwater (GW) isotopes, and soil moisture. Results showed multi‐criteria calibration outperformed single‐criterion calibration as it strongly increased the overall performance, yet only marginally degraded performance of each calibration target. Isotopes were highlighted as appropriate auxiliary data as they effectively constrained the model with relatively small weights (0.1). However, those parameter sets that minimize the errors could still lead to physically implausible simulations of uncalibrated internal states or fluxes. This was further demonstrated by an approach developed to check internal fluxes based on soft data (transpiration and lateral flow), suggesting 54% of optimized models gave "right answers for the wrong reasons." By excluding those models against soft data, such an approach further constrained equifinality, and unraveled potential inconsistencies between observations and calibration. Modeling represented the wetland as a slow‐draining system mainly fed by GW, but also influenced by near‐surface flow during winter or summer convectional events. Further, heterogeneity in hydrological functioning was partly attributed to distinct evapotranspiration patterns between contrasting vegetation communities. Therefore, this study not only provided insights into wetland functioning, but also revealed potential equifinality even with abundant data for calibration, and potential solutions based on the integration of isotopes and soft data. Key Points: Multi‐criteria calibration outperforms single‐criterion calibration with improved process representationIsotopes are highlighted as appropriate auxiliary data to effectively constrain the model with relatively small weights (0.1)Checking against soft data allowed further model rejection and revealed incompatibilities between data and calibration [ABSTRACT FROM AUTHOR]

The potential interaction between metformin and exercise on glucose-lowering effects remains controversial. We studied the separated and combined effects of metformin and/or exercise on fasting and postprandial insulin sensitivity in individuals with pre-diabetes and type 2 diabetes (T2D). Eight T2D adults (60 ± 4 yr) with overweight/obesity (32 ± 4 kg·m-2) under chronic metformin treatment (9 ± 6 yr; 1281 ± 524 mg·day-1) underwent four trials; 1) taking their habitual metformin treatment (MET), 2) substituting during 96 h their metformin medication by placebo (PLAC), 3) placebo combined with 50 min bout of high-intensity interval exercise (PLAC þ EX), and 4) metformin combined with exercise (MET þ EX). Plasma glucose kinetics using stable isotopes (6,6-2H2 and [U-13C] glucose), and glucose oxidation by indirect calorimetry, were assessed at rest, during exercise, and in a subsequent oral glucose tolerance test (OGTT). Postprandial glucose and insulin concentrations were analyzed as mean and incremental area under the curve (iAUC), and insulin sensitivity was calculated (i.e., MATSUDAindex and OGISindex). During OGTT, metformin reduced glucose iAUC (i.e., MET and MET þ EX lower than PLAC and PLAC þ EX, respectively; P = 0.023). MET þ EX increased MATSUDAindex above PLAC (4.8 ± 1.4 vs. 3.3 ± 1.0, respectively; P = 0.018) and OGISindex above PLAC (358 ± 52 vs. 306 ± 46 mL·min-1·m-2, respectively; P = 0.006). Metformin decreased the plasma appearance of the ingested glucose (Ra OGTT; MET vs. PLAC, -3.5; 95% CI -0.1 to -6.8 lmol·kg-1·min-1; P = 0.043). Metformin combined with exercise potentiates insulin sensitivity during an OGTT in individuals with pre-diabetes and type 2 diabetes. Metformin's blood glucose-lowering effect seems mediated by decreased oral glucose entering the circulation (gut-liver effect) an effect partially blunted after exercise. [ABSTRACT FROM AUTHOR]

This study presents techniques based on the use of fluorescent quinine as a visual tracer for surface flows, to assess surface flow velocities in channels and streams under low luminosity conditions. Fieldwork was conducted in three open channels, with different hydraulic characteristics. A quinine solution, in both liquid and solid (ice cube) forms, was applied on the water flow surface and an Unmanned Aerial System (UAS) was used to record the movement of the fluorescent quinine. The results were compared to the velocities estimated using the thermal tracer technique and flowmeter-based velocity maps. The findings show that the quinine solution, in both liquid and solid forms, can be used to estimate open-channel surface flow velocities under low luminosity conditions. While the solid form of the quinine tracer was applied in a smaller volume than the liquid tracer, its fluorescence effect persisted longer. By comparison, the liquid tracer had the advantage of continual availability and was devoid of the constraint of melting. HIGHLIGHTS Using a UAS for surface flow velocity measurements can improve data recording in hard-to-reach survey sites.; The new quinine-based tracer allows us to observe the spatiotemporal water movement in open channels and to estimate surface flow velocities under low luminosity conditions.; Quinine tracer has high visibility under UVA light in low luminosity conditions.;

Chemical exposure via dust ingestion is of great interest to researchers and regulators because children are exposed to dust through their daily activities, and as a result, to the many chemicals contained within dust. Our goal was to develop a workflow to identify and rank organic chemicals that could be used as tracers to calculate children's dust ingestion rates. We proposed a set of criteria for a chemical to be considered a promising tracer. The best tracers must be (1) ubiquitous in dust, (2) unique to dust, (3) detectable as biomarkers in accessible biological samples, and (4) have available or obtainable ADME information for biomarker-based exposure reconstruction. To identify compounds meeting these four criteria, we developed a workflow that encompasses non-targeted analysis approaches, literature and database searching, and multimedia modeling. We then implemented an ad hoc grading system and ranked candidate chemicals based on fulfillment of our criteria (using one small, publicly available dataset to show proof of concept). Initially, five chemicals (1,3-diphenylguanidine, leucine, piperine, 6:2/8:2 fluorotelomer phosphate diester, 6:2 fluorotelomer phosphate diester) appeared to satisfy many of our criteria. However, a rigorous manual investigation raised many questions about the applicability of these chemicals as tracers. Based on the results of this initial pilot study, no individual compounds can be unequivocally considered suitable tracers for calculating dust ingestion rates. Future work must therefore consider larger datasets, generated from broader measurement studies and literature searches, as well as refinements to selection criteria, to identify robust and defensible tracer compounds.

In this work, PM2.5 was sampled at Dunkerque, a medium-sized city located in northern France. The mean concentration of PM2.5 during the sampling period was 12.6 ± 9.5 μg·m−3. Samples were analyzed for elemental and organic carbon (EC/OC), water-soluble organic carbon (WSOC), humic-like substances (HULIS-C), water-soluble inorganic ions, and major and trace elements. The origin and the variations of species concentrations were examined using elemental enrichment factors, bivariate polar plot representations, and diagnostic concentration ratios. Secondary inorganic ions were the most abundant species (36% of PM2.5), followed by OC (12.5% of PM2.5). Secondary organic carbon (SOC) concentrations were estimated to account for 52% of OC. A good correlation between SOC and WSOC indicated that secondary formation processes significantly contribute to the WSOC concentrations. HULIS-C also represents almost 50% of WSOC. The determination of diagnostic ratios revealed the influence of anthropogenic emission sources such as integrated steelworks and fuel oil combustion. The clustering of 72 h air masses backward trajectories data evidenced that higher concentrations of PM2.5, OC, and secondary inorganic aerosols were recorded when air masses came from north-eastern Europe and the French continental sector, showing the considerable impact of long-range transport on the air quality in northern France.

This study aimed to develop and implement a nanotechnology-based alternative to traditional tracers used in the oil and gas industry for assessing interwell connectivity. A simple and rapid hydrothermal protocol for synthesizing carbon quantum dots (CQDs) using agroindustry waste was implemented. Three commercial CQDs were employed (CQDblue, CQDgreen, and CQDred); the fourth was synthesized from orange peel (CQDop). The CQDs from waste and other commercials with spherical morphology, nanometric sizes less than 11 nm in diameter, and surface roughness less than 3.1 nm were used. These tracers demonstrated high colloidal stability with a negative zeta potential, containing carbonyl-type chemical groups and unsaturations in aromatic structures that influenced their optical behavior. All materials presented high colloidal stability with negative values of charge z potential between −17.8 and −49.1. Additionally, individual quantification of these tracers is feasible even in scenarios where multiple CQDs are present in the effluent with a maximum percentage of interference of 15.5% for CQDop in the presence of the other three nanotracers. The CQDs were injected into the field once the technology was insured under laboratory conditions. Monitoring the effluents allowed the determination of connectivity for five first-line producer wells. This study enables the application of CQDs in the industry, particularly in fields where the arrangement of injector and producer wells is intricate, requiring the use of multiple tracers for a comprehensive description of the system.

METEX21 was an atmospheric tracer release experiment executed at the Department of Energy’s Nevada National Security Site (NNSS) in the southwestern U.S to study terrain-induced wind and thermodynamic conditions that influence local-scale (

• Health care personnel are at risk for pathogen contamination during personal protective equipment doffing. • Variation in reviewed studies' methodology make it difficult to identify determinants or patterns of postdoffing contamination across studies. • Many doffing protocols are insufficient to prevent postdoffing contamination. • Studies where health care personnel used a specific type of personal protective equipment and followed a doffing protocol had lower postdoffing contamination rates. • Effective doffing protocol, personal protective equipment sizing, and design, and training in doffing can help reduce the risk of pathogen contamination among health care personnel. 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. 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. 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. 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. [ABSTRACT FROM AUTHOR]

Sulfur hexafluoride (SF6) is an established tracer for use in managed aquifer recharge projects. SF6 exsolves from groundwater when it encounters trapped air according to Henry's law. This results in its retardation relative to groundwater flow, which can help determine porous media saturation and flow dynamics. SF6 and the conservative, nonpartitioning tracer, bromide (Br− added as KBr), were introduced to recharge water infiltrated into stacked glacial aquifers in Thurston County, Washington, providing the opportunity to observe SF6 partitioning. Br−, which is assumed to travel at the same velocity as the groundwater, precedes SF6 at most monitoring wells (MWs). Average groundwater velocity in the unconfined aquifer in the study area ranges from 3.9 to 40 m/d, except in the southwestern corner where it is slower. SF6 in the shallow aquifer exhibits an average retardation factor of 2.5 ± 3.8, suggesting an air-to-water ratio on the order of 10−3 to 10−2 in the pore space. Notable differences in tracer arrival times at adjacent wells indicate very heterogeneous conductivity. One MW exhibits double peaks in concentrations of both tracers with different degrees of retardation for the first and second peaks. This suggests multiple flowpaths to the well with variable saturation. The confining layer between the upper two aquifers appears to allow intermittent connection between aquifers but serves as an aquitard in most areas. This study demonstrates the utility of SF6 partitioning for evaluating hydrologic conditions at prospective recharge sites.

Abstract: An inner-shelf (IS) dye plume that formed following a 3.84-h early morning surfzone (SZ) dye release off of Imperial Beach, California, is analyzed with in situ and aerial remotely sensed observations. Midmorning, 5 h after release start, the IS plume extended 800 m offshore (or ≈8Lsz, where Lsz is the surfzone width) and was surface intensified. Over the next ≈2 h, the IS plume deformed (narrowed) cross-shore with the offshore front progressing onshore at ≈5 cm s−1, deepened by up to 3 m, and elongated alongshore at ≈4.5 cm s−1 km−1 (at ≈2.5Lsz). Coincident with IS plume deformation and deepening, IS isotherms also deepened, with relatively stable IS plume joint dye and temperature statistics. Offshore tracer transport and subsequent IS plume deformation and deepening likely resulted from two phases of the diurnal internal tide (DIT). During and after deformation, the IS plume did not reenter the warm surfzone, which potentially acted as a thermal barrier. High-frequency internal waves (HF IWs) propagated through the IS plume at ≈9 cm s−1 and dissipated onshore of 4Lsz. Surface HF IW signal was elevated in the plume elongation region, suggesting a linkage between plume elongation and either the DIT or HF IW. This IS plume evolution differs from previous SZ tracer releases, highlighting the effects of release timing relative to the solar cycle or the internal tide.

Mixing models are used throughout earth and environmental science to quantify the relative contributions of sources to mixtures, based on chemical or isotopic tracers. Often, however, some end‐members are missing or their tracer distributions overlap, precluding the use of conventional mixing models. Here I show how these constraints can be overcome by exploiting the information contained in tracer time‐series fluctuations. This approach, ensemble end‐member mixing analysis (EEMMA), can potentially quantify many sources using a single tracer, even if their mean concentrations are indistinguishable. EEMMA can also quantify source contributions when some sources are unknown, and even infer the tracer time series of a missing source. Benchmark tests with synthetic data verify the reliability of this approach, thus expanding the range of mixing models that can be quantified using tracer time series. An R script is provided for the necessary calculations, including error propagation. Plain Language Summary: Chemical and isotopic tracers are widely used to partition mixtures (such as air masses, stream flows, xylem water, or biogeochemical fluxes) among potential contributing sources. These "mixing models" are widely used to improve process understanding throughout Earth and environmental science. However, because conventional mixing models are based on comparing the mean tracer concentrations in the sources and mixture, they typically require that all sources have been identified and sampled, their average tracer concentrations are distinctly different, and the number of sources does not exceed the number of independent tracers, plus one. Temporal fluctuations in tracer concentrations can provide additional information that loosens these constraints, thus expanding the range of feasible mixing models. Here I outline this approach and test its reliability using synthetic benchmark data. With this approach, in contrast to conventional mixing models, a single tracer can be used to quantify contributions from many different sources, even if their means overlap. Even when some sources are unmeasured or even unknown, this approach can estimate the remaining sources' mixing fractions, and even, given sufficiently accurate data, can estimate the mixing fraction and tracer signature of an unknown source. Thus, this approach expands the range of applications for mixing models. Key Points: Tracer fluctuations contain information that can help constrain mixing models, including those with overlapping end‐member signaturesThis approach can also constrain mixing models with many sources but only one tracer, or those in which some sources may be missingThe concepts and math behind this approach are outlined, and validated using benchmark tests; a script for the method is provided [ABSTRACT FROM AUTHOR]

This study presents techniques based on the use of fluorescent quinine as a visual tracer for surface flows, to assess surface flow velocities in channels and streams under low luminosity conditions. Fieldwork was conducted in three open channels, with different hydraulic characteristics. A quinine solution, in both liquid and solid (ice cube) forms, was applied on the water flow surface and an Unmanned Aerial System (UAS) was used to record the movement of the fluorescent quinine. The results were compared to the velocities estimated using the thermal tracer technique and flowmeter-based velocity maps. The findings show that the quinine solution, in both liquid and solid forms, can be used to estimate open-channel surface flow velocities under low luminosity conditions. While the solid form of the quinine tracer was applied in a smaller volume than the liquid tracer, its fluorescence effect persisted longer. By comparison, the liquid tracer had the advantage of continual availability and was devoid of the constraint of melting. [ABSTRACT FROM AUTHOR]

Purpose: How coronary arterial 18F-sodium fluoride (18F-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) 18F-NaF positron emission tomography/computed tomography scans. Focal 18F-NaF uptake in each lesion was quantified using maximum tissue-to-background ratio (TBRmax). The temporal change in TBRmax was assessed using a ratio of follow-up to baseline TBRmax (R-TBRmax). Results: A total of 51 lesions were analyzed. Mean R-TBRmax 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-TBRmax. In multivariate analysis, baseline TBRmax significantly correlated with higher follow-up TBRmax (β = 0.57, P < 0.0001), and the presence of diabetes mellitus significantly correlated with both higher follow-up TBRmax (β = 0.34, P = 0.001) and elevated R-TBRmax (β = 0.40, P = 0.003). Conclusion: Higher coronary arterial 18F-NaF uptake is likely to remain continuously high. Diabetes mellitus affects the long-term increase in coronary arterial 18F-NaF uptake. [ABSTRACT FROM AUTHOR]