Dye Tracer Research Articles

Solute Transport in a Multi-Channel Karst System with Immobile Zones: An Example of Downtown Salado Spring Complex, Salado, Texas

To investigate the influence of flow rate increment on the solute transport parameter of immobile zones in a karst system, a dye tracer test was conducted in the Downtown Salado Spring Complex (DSSC) comprising three springs: Big Boiling, Anderson, and Doc Benedict springs. The Multiflow two-region nonequilibrium model (2RNE) was used to simulate the breakthrough curve (BTC) of the springs, and changes in the solute transport parameters in response to flow rate increment were observed. The simulation result showed that the 2RNE model was capable of reproducing the BTC of all the DSSC springs, with an R-squared value greater than 0.9 in all flow rate increment scenarios. The research demonstrates that a positive correlation will exist between the flow rate and solute transport parameter of the immobile zones if the tracer transport to the spring is truly influenced by immobile zones. In contrast, a negative correlation will exist between the flow rate and mass transfer coefficient if the immobile zone has less influence. Overall, the research provides insights into contaminant movement in karst by documenting how tracers are retained in the immobile fluid zone.

Hydraulic, morphological, and anatomical changes over the development of cotton bolls and pedicels leading to boll opening under well-watered and water deficit conditions

The growth, development, and opening of cotton bolls largely determine the yield and quality of cotton plants. However, the hydraulic, morphological and anatomical changes of cotton bolls over this course are unclear. This study investigated the hydraulic properties, xylem structure and function of the cotton boll and the pedicel, and the boll transpiration over the developmental course of bolls under well-watered and water deficit conditions based on hydraulic measurements, dye tracing, boll water uptake, and microscopy. Results revealed that xylem structure and function of the boll and the pedicel were well maintained and bolls had a high transpiration rate during boll dehydration period under both conditions. Water deficit significantly reduced boll number, had no significant effect on the final dry matter content of bolls, and had limited effects on boll transpiration and hydraulic properties of the boll and the pedicel. This study indicates that vascular transport between the parent plant and the boll and boll transpiration were well coupled to ensure dry matter accumulation in the boll and promote boll dehydration.

Dye tracing of upward brine migration in snow

Abstract Salt is often present in the snow overlying seasonal sea ice, and has profound thermodynamic and electromagnetic effects. However, its provenance and behaviour within the snow remain uncertain. We describe two investigations tracing upward brine movement in snow: one conducted in the laboratory and one in the field. The laboratory experiments involved the addition of dyed brine to the base of terrestrial snow samples, with subsequent wicking being measured. Our field experiment involved dye being added directly (without brine) to bare sea-ice and lake ice surfaces, with snow then accumulating on top over several days. On the sea ice, the dye migrated upwards into the snow by up to 5 cm as the snow's basal layer became more salty, whereas no migration occurred in our control experiment over non-saline lake ice. This occurred in relatively dry snowpacks where brine took up $< 6\%$ of the snow's calculated pore volume, suggesting pore saturation is not required for upward salt transport. Our results highlight the potential role of microstructural parameters beyond those currently retrievable with penetrometry, and the potential value of longitudinal, process-based field studies of young snowpacks.

On-Target Deposition from Two Engine-Powered Sprayers in Medium-Foliage-Density Citrus Canopies

Spray penetration into citrus canopies is critical for adequate coverage and deposition to ensure effective pest control. However, mismatch of air assistance to target canopy characteristics can lead to unintended spraying losses through overpenetration. To evaluate the effect of air assistance on on-target deposition, two sprayers (surrogates for airflow rates) were used to apply a fluorescent tracer dye solution @ a target concentration of 300 ppm to 16 medium-foliage-density tree blocks in a commercial mandarin orchard. The complete factorial experiment in three replications, also designed for validating a model-based spray decision support tool, comprised two forward travel speeds (1.6 and 4.8 km/h), two disc-core nozzles (TeeJet® D3-25 and D6-45), and either one or two nozzle rows to obtain a wide range of application rates (496 to 9719 L/ha). Dye deposition significantly decreased with canopy depth (p =< 0.001) by nearly seven times across the 3.4 m wide canopies but was not significant over 1.2 to 2.2 m sampling height (p = 0.867). Deposition obtained with the low-airflow-rate sprayer was significantly greater (p =< 0.001) than that obtained with the high-airflow-rate sprayer over the dose range likely due to too much air pushing out spray droplets. This study underscores the importance of matching the air assistance of orchard sprayers to the target canopy.

The feasibility of targeted axillary dissection for breast cancer axillary surgery de-escalation after neoadjuvant therapy: A prospective cohort study.

Targeted axillary dissection (TAD) after neoadjuvant therapy (NAT) includes removing of marked and sentinel lymph nodes (SLNs). The aim was to investigate the optimization of TAD localization techniques after NAT among breast cancer patients. From November 2020 to 2022, we prospectively enrolled 107 lymph node-positive breast cancer patients in XX Hospital and received complete cycles of NAT. Patients were randomly divided into the following 3 groups before treatment: group A, marked node with clip (n=34); group B, marked node with 125I seed (n=32); and group C, marked node with clip and 125I seed (n=41). Dual tracers were used to search for SLNs after NAT. The main endpoint was the detection rate of marked nodes and false-negative rate (FNR). The detection rates using the TAD localization technique were 82.6% (28/34), 100% (32/32), and 100% (41/41) for groups A, B, and C, respectively (P>0.05). The FNR rates were 15.8%, 5.9%, and 5.6% among group A, B, and C, respectively (P>0.05). The FNR rates in cN1 patients were 5.1%, 2.7%, and 2.6%, among these three groups, respectively (P>0.05). The change in distance between 125I seeds and clips in axillary lymph nodes was <3mm. The FNR rates of TAD guided by dye tracer, radiolabeled tracer, and dual tracers were 5.4%, 5.2%, and 3.4%, respectively (P>0.05). The negative predictive values were 93.0%, 93.0%, and 95.2%, respectively (P>0.05). Considering inexpensive and detect rate of 125I seeds, it is recommended that placement of 125I seeds to localize metastatic nodes in neoadjuvant setting. The TAD guided by dye tracer is also feasible for axillary de-escalation surgery after NAT in countries or regions without radiolabeled colloid.

Interpretation of Soil Characteristics and Preferential Water Flow in Different Forest Covers of Karst Areas of China

Soil hydrology seriously affects the prevention of desertification in karst areas. However, water infiltration in the different soil layers of secondary forests and artificial forests in karst areas remains uncertain. This lack of clarity is also the factor that constrains local vegetation restoration. Therefore, monitoring and simulating the priority transport of soil moisture will help us understand the shallow soil moisture transport patterns after artificial vegetation restoration in the local area, providing a reference for more scientific restoration of the ecological environment and enhancement of carbon storage in karst areas. The integration of soil physical property assessments, computed tomography (CT) scanning, dye tracing studies, and HYDRUS-2D modeling was utilized to evaluate and contrast the attributes of soil macropores and the phenomenon of preferential flow across various forestland categories. This approach allowed for a comprehensive analysis of how the soil structure and water movement are influenced by different forest ecosystems and infiltration head simulations (5 mm, 15 mm, 35 mm, and 55 mm) to elucidate the dynamics of water movement across diverse soil types within karst regions, to identify the causes of water leakage due to preferential flow in secondary forests, and to understand the mechanisms of water conservation and reduction in artificial forests adopting a multifaceted approach. This study demonstrated that (1) the soil hydrological capacity of a plantation forest was 20% higher than a natural forest, which may be promoted by the clay content and distribution. (2) Afforestation-enhanced soils in karst regions demonstrate a significant capacity to mitigate the loss of clay particles during episodes of preferential flow and then improve the soil erosion resistance by about 5 times, which can effectively control desertification in karst area. (3) The uniform distribution of macropores in plantation forest soil was conducive to prevent water leakage more effectively than the secondary forest but was incapable of hindering the occurrence of preferential flow. The secondary forest had a very developed preferential flow phenomenon, and soil clay deposition occurred with an increase in depth. (4) Moreover, the results for preferential flow showed that the matrix flow depth did not increase with the increase in water quantity. Short-term and high-intensity heavy rainfall events facilitated the occurrence of preferential flow. Infiltration along the horizontal and vertical directions occurred simultaneously. These results could facilitate a further understanding of the contribution of the plantation to soil amelioration and the prevention of desertification in karst areas, and provide some suggestions for the sustainable development of forestry in karst areas where plantation restoration is an important ingredient.

A thermal infrared imaging observation system for the measurement of overland flow velocities under controlled laboratory conditions

Flow velocity is an important physical parameter in characterizing the hydraulics of water flow. The accurate measurement of overland flow velocities has great significance for understanding and modeling sediment transport and soil erosion. In this study, a Thermal Infrared Imaging Observation System (TIIOS) based on thermal infrared imaging techniques and computer vision recognition technology was established to measure overland flow velocities under controlled laboratory conditions. TIIOS has three subsystems including thermal tracer control, image acquisition and transmission, and image storage and processing. It can be used to dynamically monitor changes in shallow flow velocity by means of automatic control of thermal tracer, instantaneous image acquisition, image correction, noise removal and centroid determination. The observation precision was high with a standard deviation of 0.004 m·s−1 for flow velocity, a temporal resolution of 1/9th s, and a spatial resolution of 2 mm. The new system achieved higher accuracy compared to the traditional dye tracing and salt tracing techniques in observing the dynamic transport process of thermal tracer movement. The relative errors of the centroid velocity measured by the TIIOS ranged from −9.83 % to 6.40 %; whereas the relative errors of centroid velocity measured by salt tracer ranged from −21.36 % to 17.22 %. Measurements by the established TIIOS under different hydraulic conditions demonstrate that the relative errors of the centroid velocity are all smaller than those of the leading-edge velocity. This observational system provided a reliable way to measure shallow flow velocity for better understanding the mechanisms of water erosion processes and showed its potential to be used in field experiments under natural conditions.

Microbial life in preferential flow paths in subsurface clayey till revealed by metataxonomy and metagenomics

BackgroundSubsurface microorganisms contribute to important ecosystem services, yet little is known about how the composition of these communities is affected by small scale heterogeneity such as in preferential flow paths including biopores and fractures. This study aimed to provide a more complete characterization of microbial communities from preferential flow paths and matrix sediments of a clayey till to a depth of 400 cm by using 16S rRNA gene and fungal ITS2 amplicon sequencing of environmental DNA. Moreover, shotgun metagenomics was applied to samples from fractures located 150 cm below ground surface (bgs) to investigate the bacterial genomic adaptations resulting from fluctuating exposure to nutrients, oxygen and water.ResultsThe microbial communities changed significantly with depth. In addition, the bacterial/archaeal communities in preferential flow paths were significantly different from those in the adjacent matrix sediments, which was not the case for fungal communities. Preferential flow paths contained higher abundances of 16S rRNA and ITS gene copies than the corresponding matrix sediments and more aerobic bacterial taxa than adjacent matrix sediments at 75 and 150 cm bgs. These findings were linked to higher organic carbon and the connectivity of the flow paths to the topsoil as demonstrated by previous dye tracer experiments. Moreover, bacteria, which were differentially more abundant in the fractures than in the matrix sediment at 150 cm bgs, had higher abundances of carbohydrate active enzymes, and a greater potential for mixotrophic growth.ConclusionsOur results demonstrate that the preferential flow paths in the subsurface are unique niches that are closely connected to water flow and the fluctuating ground water table. Although no difference in fungal communities were observed between these two niches, hydraulically active flow paths contained a significantly higher abundance in fungal, archaeal and bacterial taxa. Metagenomic analysis suggests that bacteria in tectonic fractures have the genetic potential to respond to fluctuating oxygen levels and can degrade organic carbon, which should result in their increased participation in subsurface carbon cycling. This increased microbial abundance and activity needs to be considered in future research and modelling efforts of the soil subsurface.

Application of a microbial and pathogen source tracking toolbox to identify infrastructure problems in stormwater drainage networks: a case study.

Water scarcity and increasing urbanization are forcing municipalities to consider alternative water sources, such as stormwater, to fill in water supply gaps or address hydromodification of receiving urban streams. Mounting evidence suggests that stormwater is often contaminated with human feces, even in stormwater drainage systems separate from sanitary sewers. Pinpointing sources of human contamination in drainage networks is challenging given the diverse sources of fecal pollution that can impact these systems and the non-specificity of traditional fecal indicator bacteria (FIB) for identifying these host sources. As such, we used a toolbox approach that encompassed microbial source tracking (MST), FIB monitoring, and bacterial pathogen monitoring to investigate microbial contamination of stormwater in an urban municipality. We demonstrate that human sewage frequently contaminated stormwater (in >50% of routine samples), based on the presence of the human fecal marker HF183, and often exceeded microbial water quality criteria. Arcobacter butzleri, a pathogen of emerging concern, was also detected in >50% of routine samples, with 75% of these pathogen-positive samples also being positive for the human fecal marker HF183, suggesting human municipal sewage as the likely source for this pathogen. MST and FIB were used to track human fecal pollution in the drainage network to the most likely point source of contamination, for which a sewage cross-connection was identified and confirmed using tracer dyes. These results point to the ubiquitous presence of human sewage in stormwater and also provide municipalities with the tools to identify sources of anthropogenic contamination in storm drainage networks.IMPORTANCEWater scarcity, increased urbanization, and population growth are driving municipalities worldwide to consider stormwater as an alternative water source in urban environments. However, many studies suggest that stormwater is relatively poor in terms of microbial water quality, is frequently contaminated with human sewage, and therefore could represent a potential health risk depending on the type of exposure (e.g., irrigation of community gardens). Traditional monitoring of water quality based on fecal bacteria does not provide any information about the sources of fecal pollution contaminating stormwater (i.e., animals/human feces). Herein, we present a case study that uses fecal bacterial monitoring, microbial source tracking, and bacterial pathogen analysis to identify a cross-connection that contributed to human fecal intrusion into an urban stormwater network. This microbial toolbox approach can be useful for municipalities in identifying infrastructure problems in stormwater drainage networks to reduce risks associated with water reuse.

Upwelling in Cyclonic and Anticyclonic Eddies at the Middle Atlantic Bight Shelf‐Break Front

AbstractDespite the ubiquity of eddies at the Mid‐Atlantic Bight shelf‐break front, direct observations of frontal eddies at the shelf‐break front are historically sparse and their biological impact is mostly unknown. This study combines high resolution physical and biological snapshots of two frontal eddies with an idealized 3‐D regional model to investigate eddy formation, kinematics, upwelling patterns, and biological impacts. During May 2019, two eddies were observed in situ at the shelf‐break front. Each eddy showed evidence of nutrient and chlorophyll enhancement despite rotating in opposite directions and having different physical characteristics. Our results suggest that cyclonic eddies form as shelf waters are advected offshore and slope waters are advected shoreward, forming two filaments that spiral inward until sufficient water is entrained. Rising isohalines and upwelled slope water dye tracer within the model suggest that upwelling coincided with eddy formation and persisted for the duration of the eddy. In contrast, anticyclonic eddies form within troughs of the meandering shelf‐break front, with amplified frontal meanders creating recirculating flow. Upwelling of subsurface shelf water occurs in the form of detached cold pool waters during the formation of the anticyclonic eddies. The stability properties of each eddy type were estimated via the Burger number and suggest different ratios of baroclinic versus barotropic contributions to frontal eddy formation. Our observations and model results indicate that both eddy types may persist for more than a month and upwelling in both eddy types may have significant impacts on biological productivity of the shelf break.

The effects of aperture position and length in side-vented needles on root canal irrigation: A computational fluid dynamics study

IntroductionRoot canal irrigation is crucial for infection control during root canal treatment. Side-vented needles for positive pressure irrigation are commonly used in clinical practice. However, variations in needle design among manufacturers can impact the fluid dynamics of irrigation. This study aims to use computational fluid dynamics to explore the flow characteristics of different needle aperture lengths and positions, and their effects on the effectiveness and safety of irrigation, using a validated passive scalar transport numerical model. MethodsThe validation of the CFD irrigant model was achieved by comparing it with an in vitro irrigation experiment model. The CFD model used scalar concentration, while the in vitro experiment model used red dye tracing. Using a standard 30G side-vented needle as a reference, virtual needle models featuring four aperture lengths and three positions were created. These virtual irrigation needles were then placed in two root canal geometries for CFD simulation to evaluate fluid exchange capabilities and related fluid dynamic parameters. ResultsThe results of the CFD simulation, using a scalar transport model, closely matched the in vitro tracer tests for irrigation experiments across seven root canal geometries. The CFD analysis indicated that positioning the aperture lower increased the irrigant exchange distance. Notably, decreasing the aperture length to 0.25x, and positioning it at the lower end of the needle significantly increased exchange distance and shear stress, while reducing apical pressure. ConclusionsThese results indicate that the position and length of the aperture affect the exchange distance of irrigant flow, wall shear stress, and apical pressure. The CFD validation model for scalar transport, based on a steady state, can function as a valuable tool for optimizing the side-vented needle in research. Further research on the design of side-vented needles will enhance the understanding of flow characteristics beneficial for irrigation efficiency in clinical practice.

An Experimental Study of the Morphological Evolution of Rills on Slopes under Rainfall Action

Accurately monitoring the morphology and spatiotemporal evolution characteristics of the entire process of slope erosion rill development is essential to circumvent the limitations inherent in traditional methods that rely on average flow velocity for hydrodynamic parameter calculations. This study employs an environmental chamber and a self-developed slope erosion test device to perform erosion tests on slopes with varying gradients and rainfall intensities. By integrating the structure-from-motion (SfM) method, fixed grid coordinate method, and continuous camera combined with the dye tracer technique, the morphological indexes and hydrodynamic parameters of the entire rill development process are precisely computed. The main conclusions are as follows: The entire process of slope rill development can be divided into three distinct stages. The initial stage is characterized by the appearance of tiny rills with mild erosion. The middle stage involves severe transverse spreading erosion and longitudinal undercutting, resulting in diverse rill morphologies. The final stage is marked by the stabilization of morphological characteristics. The peak slope soil loss is observed during the middle stage of rill development. The most effective parameters for characterizing slope soil loss from the beginning to the end are the Reynolds number and flow shear stress, the Froude number and flow shear stress, and the Froude number during different periods. Throughout the development of rills, the flow velocity initially decreases and then gradually increases until it stabilizes. The morphological indexes, including rill density, dissected degree, inclination, and complexity, generally show an increasing trend. However, in the middle stage, the rate of increase slows down, followed by a sharp rise at certain points. The optimal hydraulic parameters for evaluating rill density across different slope gradients, which were found to be the Darcy–Weisbach drag coefficient and real-time flow velocity, for assessing rill dissected degree, complexity, and inclination, were the Reynolds number and flow power. Under varying rainfall intensities, the most effective hydraulic and kinetic parameters for evaluating rill density, dissected degree, and inclination were flow shear stress and Reynolds number; for assessing rill complexity, the Reynolds number and flow power were used. The findings of this research enhance the accuracy of hydrodynamic parameter calculations in rill erosion tests, enable precise prediction of rill development trends on slopes, and offer innovative approaches for real-time dynamic monitoring of rill morphology and characteristics. These advancements are of significant importance for soil and water conservation and sustainability.

An integrated approach for characterization of a fractured-rock carbonate aquifer in the Zagros Region of Iran

Karst aquifers typically exhibit a wide range of dissolution effects that include end-members of matrix, fractured-rock, and conduit-dominated types. This study employs an integrated approach involving geological studies, hydrogeological assessments, hydrochemical and isotopic analysis, and dye tracer tests to investigate the Sarvak limestone aquifer (SLA) in the Zagros Region, southwest Iran. Key characteristics of the SLA include numerous stratification boundaries, thin limestone layers with intercalated siliceous and marl impurities, extensive joint and fracture networks, predominant autogenic recharge, and absence of notable point recharge features (e.g., sinkholes, dolines), and the exchange flow with the Bakhtiari River (B-R) has made it a unique aquifer. Numerous pieces of evidence, such as low spatial and temporal changes in groundwater level, insignificant seasonal variations in the hydrochemical and isotopic composition of water samples, and the supersaturation state of groundwater with calcite and dolomite minerals, suggested a slow flow regime in many parts of the SLA. This regime is characterized by low velocity and long residence time of groundwater. The results reveal that despite the high solubility of carbonate rocks, extensive joint networks can limit significant karst development, leading to fluid flow behavior similar to that of fractured-rock aquifers. Therefore, SLA can be considered a fractured-rock and karst aquifer. The identified paths with fast flow in the dam area are unremarkable and cannot provide a large portion of the Pelle Khan Spring discharge.

Unsupervised Characterization of Water Composition with UAV-Based Hyperspectral Imaging and Generative Topographic Mapping

Unmanned aerial vehicles equipped with hyperspectral imagers have emerged as an essential technology for the characterization of inland water bodies. The high spectral and spatial resolutions of these systems enable the retrieval of a plethora of optically active water quality parameters via band ratio algorithms and machine learning methods. However, fitting and validating these models requires access to sufficient quantities of in situ reference data which are time-consuming and expensive to obtain. In this study, we demonstrate how Generative Topographic Mapping (GTM), a probabilistic realization of the self-organizing map, can be used to visualize high-dimensional hyperspectral imagery and extract spectral signatures corresponding to unique endmembers present in the water. Using data collected across a North Texas pond, we first apply GTM to visualize the distribution of captured reflectance spectra, revealing the small-scale spatial variability of the water composition. Next, we demonstrate how the nodes of the fitted GTM can be interpreted as unique spectral endmembers. Using extracted endmembers together with the normalized spectral similarity score, we are able to efficiently map the abundance of nearshore algae, as well as the evolution of a rhodamine tracer dye used to simulate water contamination by a localized source.

Estimation of Effective Fracture Aperture in Glacial Tills by Analysis of Dye Tracer Penetration.

This study advances a methodology to estimate effective apertures of fractures in glacial tills based on dye tracer infiltration tests and numerical simulations. The approach uses the visible penetration depth of the dye tracer along fracture flow paths as primary information to calculate effective fracture apertures. Further data used in the calculation are the dye tracer input concentration and retardation, the duration of the tracer injection, and the hydraulic gradient applied to control the infiltrating water fluxes. The method does not require measurement of hydraulic conductivity for the fractured till and enables direct observation of flow and transport patterns within the fractures (e.g., uniform flow and dye tracer distribution, channeling due to aperture variability, and presence of biogenic macropores in fractures). The approach was successfully verified by using the estimated effective fracture aperture values in Large Undisturbed Columns (LUCs) to consistently simulate both the observed LUC effluent breakthrough of a conservative bromide tracer and the water fluxes with the hydraulic gradient applied in the experiments. Sensitivity analyses revealed that estimation of small effective fracture apertures (<10 μm) required accurate determination of the dye tracer retardation factor. By contrast, in the case of larger effective apertures (>20 μm), the sensitivity of the estimated effective fracture aperture to variations in the porous material and solute transport parameters was low compared to the dominant sensitivity to the water flow through the fractures (cubic relation between flow and aperture). The proposed approach may be extended beyond laboratory applications and assist in characterizing field-scale fracture networks.

Visualizing preferential flow paths using dye tracer and species diversity theory methods to explore their correlation to soil properties with random forest algorithm

The preferential flow path development is potentially the result of spatial variations in soil properties with soil depth. However, visualizing the evolution of the preferential flow path with soil depth remains a challenge. This paper presents dye tracer and species diversity theory methods for characterizing preferential flow paths. Field dye tracer experiments were performed at three sites (tree, bush, and grass) in the Yellow River Delta wetland and dye distribution diversity indices (Simpson index (Ds), Shannon-Wiener index (H), Margalef index (Dm), and Pielou index (E)) were applied to verify their availability for preferential flow assessment. The results showed that the uniformity of the shallow-infiltrated dye at the tree site, non-uniformity of the shallow-infiltrated dye at the bush site, and deep dye infiltration at the grass site were the three typical infiltration types. The average proportion of dye-stained areas (PDA) gradually decreased with increasing soil depth. The quantitative effects of soil properties on PDA changes were profound, indicating that soil clay content at 0–10 cm depth, soil sand content at 10–20 cm depth, soil drainage capacity at 20–30 cm depth, and soil bulk density at 30–40 cm depth were the most predictive factors controlling PDA changes. Our results also showed that dye-stained patches with extremely high and high dye concentrations were the most distributed; Ds, H, Dm, and E were the highest at the tree site and E was the diversity index with the greatest importance for PDA change. The findings reveal the soil properties controlling the formation of preferential flow paths, which will improve our understanding of water resource management in the vadose zones of coastal wetlands.

Contributions of soil organic carbon-induced root- and soil properties complexity to water flow in eastern China

Water flow within the soils affects the efficiency of materials transfer mediated by water. Soil organic carbon (SOC) as an important role in active water flow events can drive the complexity of root-soil synthesis by improving root and soil properties. However, contributions of SOC-induced root- and soil properties complexity to water flow are not well understood. In this study, dye tracing experiments at the three forest stands (oak, pine, and bamboo forests) were conducted to explore water flow patterns, i.e., preferential flow paths (PFP), stream buffer zones (SBZ), and water flow zones (WFZ). X-ray microtomography (CT) scanning was performed to reconstruct the root architecture. The partial least squares path model was applied to quantitatively explore the effects of root- and soil properties on water flow. The results showed that the index of water flow connectivity (IWFC) in the PFP and WFZ patterns decreased with increasing soil depth, while IWFC in the SBZ pattern increased at first and then decreased. In the PFP pattern, soil physical properties had the larger total effects (TE = 0.624) on IWFC change compared with root properties (TE = 0.257). In the SBZ pattern, the total effects of root properties controlling IWFC change (TE = 0.510) were greater than soil physical properties (TE = −0.386). Both of them can equally affect the IWFC in the WFZ pattern. In conclusion, the influences of SOC by driving the changes of soil properties on gravity-driven convective flow process were dramatically stronger than root properties, while SOC could primarily drive the changes of root properties and thereby affect capillary-driven convective flow process. The present results can provide a scientific basis for sustainable forestry management and also a better understanding of the forestry hydrology.

DIPG-35. OVERCOMING THE BLOOD-BRAIN BARRIER CHALLENGE IN DIFFUSE MIDLINE GLIOMA

Abstract Diffuse midline gliomas (DMGs) are aggressive paediatric brainstem tumours with no known cure. The development of effective treatments is greatly impeded by the failure of most anti-tumour agents to penetrate the blood-brain barrier (BBB). Our research, along with that of others, has revealed that the BBB remains intact in DMG. We employed DMG orthotopic models to explore potential region-specific variations in response to the therapeutic agent temsirolimus as well as confocal microscopy and single-cell RNA sequencing (scRNAseq) to elucidate the impact of DMGs on brain endothelial morphology and pathways governing BBB integrity. We first assessed the effectiveness of the mTOR inhibitor temsirolimus when administered in cortex-injected DMG models compared to brainstem-injected DMG. We found significantly increased survival rates, elevated temsirolimus levels, and reduced tumour cell proliferation in the cortex versus the brainstem. Confocal imaging analysis indicated no structural differences between DMG and Matrigel-injected animals. However, scRNAseq unveiled distinct transcriptomic changes: brainstem-injected DMG exhibited downregulation of genes related to inflammatory and apoptotic pathways, whereas cortex-injected DMG showed downregulation of interferon pathways. To overcome the tightened barrier in the brainstem, we explored three MCL1 inhibitors and SNGR-TNFa (targeting CD13) as potential blood-brain barrier modulators. These inhibitors significantly reduced transendothelial electrical resistance, increased tracer dye leakage in an in vitro DMG BBB model, and decreased the protein expression of claudin-5. Moreover, in vivo, we found that administration of a single dose of either SNGR-TNFa or the MCL1 inhibitor S63845 improved penetration of Texas-Red (3KDa) in DMG-engrafted animals, indicating the effective opening of the BBB. In summary, our study revealed that DMG directly affects BBB pathways in endothelial cells, tightening the barrier and reducing treatment efficacy. MCL1 inhibitors and SNGR-TNFa show promise in modulating the BBB and have the potential to enhance therapeutic activity.

Optimizing the preparation of multi-colored dye-tracer proppants: A potential approach for quantitative localization and volume assessment of proppant flowback in multistage fractured horizontal wells

Proppant flowback is a common phenomenon after hydraulic fracturing of oil and gas wells. Especially in the large-scale sanding mode of horizontal wells, sand production after fracturing is usually serious. Proppant flowback can not only clog wellbore and wear out equipment, add additional hauling and disposal costs, but also reduce conductivity of the propped fractures, severely affecting oil and gas production. However, there is still a lack of effective means for locating sand production in horizontal wells. Traditional tracer proppants mainly use radioactive elements to monitor the shape of fractures, but they cannot tell the location and amount of sand production. In this work, dye tracer proppant of eight different colors was prepared by dyeing quartz sand proppant. The results show that all the eight kinds of dyes can dye the quartz sand proppant effectively and evenly. The optimal ratio of proppant mass to MB solution volume was determined to be 1:0.015, and the ratio of proppant mass to fixing agent volume was 1:0.0125. The dyed tracer proppant showed good dyeing stability at pH values of 6–13 and surfactant concentrations of 0–200 mg/L. The salinity and fracturing fluid did not affect its stability, and temperature had a negative effect on the stain stability. However, even in the most severe case of decolorization in the experiment, that is, after the dyed proppant was soaked for 24 h at a high temperature of 120 °C, the color of the dried dyed proppant was still clearly distinguished from that of ordinary quartz sand. In theory, using these dyed proppants can potentially tell quantitively the location and volume of sand production during horizontal large-scale fracturing flowback. Since this method has not been used in hydraulic fracturing, it only provides a new way to monitor the sand production of horizontal wells after fracturing. It can provide valuable data for adjusting subsequent fracturing process and has important implications for improving efficiency of fracturing operation of unconventional oil and gas reservoirs.

Application of Overground Rock Film Mulching (ORFM) Technology in Karst Rocky Desertification Farmland: Improving Soil Moisture Environment and Crop Root Growth

Overground rock is a prominent feature of rocky desertification landscape in karst farmland; however, people often pay attention to their adverse effects, leaving their positive effects on ecohydrological processes and plant growth as rarely studied and utilized. In this study, the effects of overground rock film mulching (ORFM) on soil water flow behavior, soil water content and temporal and spatial heterogeneity were investigated through a dye tracer test and soil moisture measurement. Moreover, the effects of this technology on the root characteristics of crops (maize and broad bean) were analyzed. The results showed that ORFM treatment significantly increased soil water content and its spatio-temporal heterogeneity by preventing preferential flow at the rock–soil interface. It suggested that this practice can provide a more favorable soil moisture environment for crop growth, which was confirmed by the differences in root characteristics of crops (maize and broad bean) under different treatments in this study. It was found that ORFM treatment reduced the root radial extent of crops but increased the root biomass and root bifurcation rate, which are widely considered to be key factors in improving the efficiency of fine root absorption. Therefore, we believe that ORFM has great potential to improve the effective use of soil water and agricultural water management in karst areas, which is essential for sustainable agricultural development in the region.