Predictive Geogenic Radon Potential (P-GRP): A novel approach for comprehensive hazard assessment and risk modeling in subsurface environment.

Geogenic radon potential (GRP) is traditionally used for mapping radon-prone areas. However, this has challenges in the accurate assessment of radon risk because of limitations such as oversimplified soil measurements and lack of geological profiles. This study presents predictive geogenic radon potential (P-GRP), integrating geological characterization and advanced modeling for the emanation and transport of radon in the subsurface environment. Seoul, South Korea, was selected as the research area for the evaluation of hazards using P-GRP, while subway station A was selected for the assessment of indoor health risks. The geology was characterized by the layers of bedrock and soil using uranium contents and porosity. The emanation of radon was modeled considering the radioactive decay chain of uranium and the pore structures. The vertical transport of radon was modeled considering the porosity variation within geological media, which was used for the calculation of P-GRP. Without loss of continuity, the P-GRP map was constructed by calculating P-GRP at a specific depth over the Seoul area. The calculation of P-GRP in the case of subway station A demonstrates that the radon concentration in the bedrock at the platform depth was expected to be 382 million Bqm-3. The indoor radon risk was calculated using the P-GRP by coupling the vapor intrusion process. This presented a high cancer risk for the employees as well as commuters. The P-GRP map of Seoul demonstrated higher hazards in granite zones compared to banded gneiss zones. These results have demonstrated that the P-GRP could be a novel and promising approach for assessing hazard and risk by geogenic radon during subsurface development.

Spin angular momentum-encoded single-photon emitters in a chiral nanoparticle-coupled WSe2 monolayer.

Spin angular momentum (SAM)-encoded single-photon emitters, also known as circularly polarized single photons, are basic building blocks for the advancement of chiral quantum optics and cryptography. Despite substantial efforts such as coupling quantum emitters to grating-like optical metasurfaces and applying intense magnetic fields, it remains challenging to generate circularly polarized single photons from a subwavelength-scale nanostructure in the absence of a magnetic field. Here, we demonstrate single-photon emitters encoded with SAM in a strained WSe2 monolayer coupled with chiral plasmonic gold nanoparticles. Single-photon emissions were observed at the nanoparticle position, exhibiting photon antibunching behavior with a g(2)(0) value of ~0.3 and circular polarization properties with a slight preference for left-circular polarization. Specifically, the measured Stokes parameters confirmed strong circular polarization characteristics, in contrast to emitters coupled with achiral gold nanocubes. Therefore, this work provides potential insights to make SAM-encoded single-photon emitters and understand the interaction of plasmonic dipoles and single photons, facilitating the development of chiral quantum optics.

Laboratory Evaluation of Storage Stability for Asphalt Binder Modified with Crumb Rubber and Styrene-Isoprene-Styrene Depending on Evaluation Factors and Blending Condition.

Modified asphalt binders are still considered important in asphalt pavement. However, the comprehensive use of various modifiers is limited due to storage stability issues. Moreover, there is a scarcity of detailed analyses regarding the degree of separation for asphalt binders among each method despite the utilization of various methods to assess the storage stability of binders. Therefore, a comprehensive analysis was conducted to assess the storage stability of asphalt binder modified with a crumb rubber modifier (CRM) and styrene-isoprene-styrene (SIS), utilizing five evaluation factors following the ASTM D7173 guidelines based on four mixing methods (A: high-shear mixing method, B: low-speed agitating method, C: high-shear mixing method + low mixing method, D: low-speed agitating method + low mixing method). To produce the modified asphalt binder, the proportions of the CRM were 5% and 10% for each binder, and 10% SIS was added to all binders. The results in this study convey that (1) the addition of the modifier led to an increase in G*/sin δ with different mixing methods, but using mixing methods (C and D) for a relatively long time resulted in a lower G*/sin δ, indicating suboptimal performance; (2) through the multiple stress creep recovery (MSCR), rheological properties of Jnr and % rec exhibited trends similar to G*/sin δ evaluation, highlighting an improved elastic recovery with a higher modifier content; (3) storage stability assessment revealed consistent trends in high-shear mixing groups (A and C), while low-speed mixing groups (B and D) exhibited an elevated separation index (SI), suggesting a sensitivity to modification conditions; (4) evaluation using the MSCR method indicated that % rec with a 3.2 kPa load is effective for the sensitive assessment of binder storage stability and Jnr showed a limited sensitivity across varying loads, advocating for % rec for precise evaluation; and (5) despite permitting various tests, achieving consistent results remains challenging. Future research should explore diverse modifiers and optimal evaluation methods to enhance knowledge of binder behavior and separation dynamics.

Hydraulic containment of TCE contaminated groundwater using pulsed pump-and-treat: Performance evaluation and vapor intrusion risk assessment.

Remedial actions for groundwater contamination such as containment, in-situ remediation, and pump-and-treat have been developed. This study investigates the hydraulic containment of Trichloroethylene (TCE) contaminated groundwater by using pulsed pump-and-treat technology. The hypothetical research site assumed the operation of pulsed pump-and-treat to manage groundwater contaminated with 0.1 mg/L of TCE. at the pump-and-treat facility. Numerical models, employing MODFLOW and MT3DMS for groundwater flow and contamination simulations, were used for case studies to evaluate the performance and risks of pump-and-treat operation strategies. Evaluation criteria included capture width, removal efficiency, and contaminant leakage. Health risks from TCE leakage were assessed using a vapor intrusion risk assessment tool in adjacent areas. In the facility-scale case study, the capture width of the pump-and-treat was controlled by pumping/injection well operations, including schedules and rates. Pumping/injection well configurations impacted facility efficiencies. Pulsed operation led to TCE leakage downstream. Site-scale case studies simulated contaminant transport through pump-and-treat considering various operation stages (continuous; pulsed), as well as various reactions of TCE in subsurface environment (non-reactive; sorption; sorption and biodegradation). Assuming non-reactive tracer, TCE in groundwater was effectively blocked during continuous operation stage but released downstream in the following pulsed operation stage. Considering chemical reactions, the influences of the pump-and-treat operation followed similar trends of the non-reactive tracer but occurred at delayed times. Groundwater contamination levels were reduced through biodegradation. Cancer and non-cancer risks could occur at points of exposure (POEs) where the contamination levels approached or fell below TCE groundwater standards.

Longevity prediction of reactive media in permeable reactive barriers considering the contamination level and groundwater velocity at the planning site, with a focus on cadmium removal by zeolite.

Zeolite is a versatile and effective reactive material used in permeable reactive barriers (PRBs) for remediating groundwater contaminated with heavy metals. In this study, we evaluated the influence of subsurface environmental conditions, namely contamination level (C0) and groundwater velocity (v), on predicting the longevity of zeolite for cadmium (Cd) removal. Batch experiments were performed to investigate the effect of C0 on Cd removal, and column experiments were performed to examine how Cd transportation through zeolite varies at different C0 and v. Breakthrough curves (BTCs) were analyzed with an advection-dispersion equation (ADE) coupled with nonequilibrium sorption rate models. The reaction parameters indicating the performance metrics of zeolite were determined using an iterative fitting approach-retardation factor (R), partitioning coefficient (ß), and mass transfer coefficient (ω). R exhibited dependence on C0, but was unrelated to v; its rapid increase at lower C0 was explained by Langmuir sorption isotherms. ß and ω, integral to sorption dynamics and mass transfer, respectively, showcased functional relationships with v. ß decreased gradually as v increased, described by the nonequilibrium sorption model, whereas ω increased steadily with v, guided by the Monod function. Using the relationship of these parameters, the fate and transport of Cd within zeolite was simulated under various subsurface environmental conditions to construct the longevity prediction function. Thus, this study introduces a method for predicting the longevity of reactive materials, which can be valuable for designing PRBs with high longevity in the future.

Facultative mycorrhization in a fern (Struthiopteris spicant L. Weiss) is bound to light intensity.

BACKGROUND: The establishment of mycorrhizal relationships between a fungus and a plant typically enhances nutrient and water uptake for the latter while securing a carbon source for the fungus. However, under a particular set of environmental conditions, such as low availability of light and abundant nutrients in the soil, the resources invested in the maintenance of the fungi surpass the benefits obtained by the host. In those cases, facultative mycorrhizal plants are capable of surviving without symbiosis. Facultative mycorrhization in ferns has been overlooked until now. The present study measured the response of Struthiopteris spicant L. Weiss, and its root-associated fungi to different levels of light and nutrient availability in terms of growth, mycorrhizal presence, and leaf nutrient content. This fern species exhibits a great tolerance to variable light, nutrient, and pH conditions, and it has been found with and without mycorrhizae. We conducted a greenhouse experiment with 80 specimens of S. spicant and three factors (Light, Phosphorus, and Nitrogen) resulting in eight treatments. RESULTS: We found a significant influence of the factor light on fungal community composition, plant biomass, and nutrient accumulation. Departing from a lack of colonization at the initial stage, plants showed a remarkable increment of more than 80% in the arbuscular mycorrhizal fungi (AMF) richness and abundance in their roots when grown under high light conditions, compared with the ones in low light. We also observed an upward trend of C:P and C:N ratios and the above- and belowground biomass production when AMF abundance increased. Furthermore, the compositional analysis of the whole fungal communities associated with S. spicant roots revealed clear differences among low-light and high-light treatments. CONCLUSIONS: This study is the first to investigate the importance of light and nutrient availability in determining fern-AMF relationships. We confirmed that Struthiopteris spicant is a facultative mycorrhizal plant. The composition and diversity of AMF found in the roots of this fern are strongly influenced by light and less by nutrient conditions. Our study shows that ferns respond very sensitively to changes in environmental factors, leading to shifts in the associated mycorrhizal communities.

Draft Genome of Nocardia canadensis sp. nov. Isolated from Petroleum-Hydrocarbon-Contaminated Soil.

The bacterial strain WB46 was isolated from the rhizosphere of willow plants (Salix purpurea L.) growing in soil contaminated with petroleum hydrocarbons. The strain was subjected to whole-genome shotgun sequencing using Illumina HiSeq. Its draft genome is 7.15 Mb, with a 69.55% GC content, containing 6387 protein-coding genes and 51 tRNA and 15 rRNA sequences. The quality and reliability of the genome were assessed using CheckM, attaining an estimated genome completeness of 98.75% and an estimated contamination of 1.68%. These results indicate a high-quality genome (>95%) and low contamination (<5%). Many of these genes are responsible for petroleum hydrocarbon degradation, such as alkane 1-monooxygenase (alkB) and naphthalene dioxygenase (ndo). 16S rRNA gene analysis, including in silico DNA-DNA hybridization (DDH) and average nucleotide identity (ANI), showed that strain WB46 belongs to the genus Nocardia, and the most closely related species is Nocardia asteroides. The strain WB46 showed a distance of 63.4% and sequence identity of 88.63%, respectively. These values fall below the threshold levels of 70% and 95%, respectively, suggesting that the strain WB46 is a new species. We propose the name of Nocardia canadensis sp. nov. for this new species. Interestingly, the sequence divergence of the 16S rRNA gene showed that the divergence only occurred in the V2 region. Therefore, the conventional V3-V4, V5-V7, or V8-V9 targeting metabarcoding, among others, would not be able to assess the diversity related to this new species.

From microbiome composition to functional engineering, one step at a time.

SUMMARYCommunities of microorganisms (microbiota) are present in all habitats on Earth and are relevant for agriculture, health, and climate. Deciphering the mechanisms that determine microbiota dynamics and functioning within the context of their respective environments or hosts (the microbiomes) is crucially important. However, the sheer taxonomic, metabolic, functional, and spatial complexity of most microbiomes poses substantial challenges to advancing our knowledge of these mechanisms. While nucleic acid sequencing technologies can chart microbiota composition with high precision, we mostly lack information about the functional roles and interactions of each strain present in a given microbiome. This limits our ability to predict microbiome function in natural habitats and, in the case of dysfunction or dysbiosis, to redirect microbiomes onto stable paths. Here, we will discuss a systematic approach (dubbed the N+1/N-1 concept) to enable step-by-step dissection of microbiome assembly and functioning, as well as intervention procedures to introduce or eliminate one particular microbial strain at a time. The N+1/N-1 concept is informed by natural invasion events and selects culturable, genetically accessible microbes with well-annotated genomes to chart their proliferation or decline within defined synthetic and/or complex natural microbiota. This approach enables harnessing classical microbiological and diversity approaches, as well as omics tools and mathematical modeling to decipher the mechanisms underlying N+1/N-1 microbiota outcomes. Application of this concept further provides stepping stones and benchmarks for microbiome structure and function analyses and more complex microbiome intervention strategies.

Performance expectation of coal waste in permeable reactive barrier for removal of cadmium considering contamination level and pore water velocity.

The effectiveness and longevity of permeable reactive barriers (PRBs) depend on the performance of the reactive materials and the subsurface environment. The relationship of the groundwater velocity on performance of coal waste for the heavy metal removal was reported in our previous study. In this study, we investigated the performance and longevity of coal waste as a PRB material for the removal of Cd considering subsurface environmental conditions such as contamination level and groundwater velocity. The artificial groundwater contaminated by Cd were prepared with various concentrations ranging from 10 to 100 mg L-1. Lab-scale column experiments were conducted using coal waste filled columns by injecting the artificial groundwater. The breakthrough curves were analyzed advection dispersion equation coupled with equilibrium sorption model to determine the retardation factor. The Cd breakthrough curves exhibited different retardation with respect to the contamination levels. The Cd transport was more retarded as the contamination level lowered. The relationship between the retardation factor and the contamination levels could be explained with empirical equations based on non-linear sorption isotherms. By adopting the velocity dependency of sorbent performance in our previous study, transport of Cd within coal waste was simulated under various subsurface environmental conditions to construct the longevity function. The function could be used for the longevity prediction of coal waste as a PRB material considering groundwater velocity and contamination level in subsurface environment.

Using enzyme activities as an indicator of soil fertility in grassland - an academic dilemma.

Grasslands play an important role in conserving natural biodiversity and providing ecosystem functions and services for societies. Soil fertility is an important property in grassland, and the monitoring of soil fertility can provide crucial information to optimize ecosystem productivity and sustainability. Testing various soil physiochemical properties related to fertility usually relies on traditional measures, such as destructive sampling, pre-test treatments, labor-intensive procedures, and costly laboratory measurements, which are often difficult to perform. However, soil enzyme activity reflecting the intensity of soil biochemical reactions is a reliable indicator of soil properties and thus enzyme assays could be an efficient alternative to evaluate soil fertility. Here, we review the latest research on the features and functions of enzymes catalyzing the biochemical processes that convert organic materials to available plant nutrients, increase soil carbon and nutrient cycling, and enhance microbial activities to improve soil fertility. We focus on the complex relationships among soil enzyme activities and functions, microbial biomass, physiochemical properties, and soil/crop management practices. We highlight the biochemistry of enzymes and the rationale for using enzyme activities to indicate soil fertility. Finally, we discuss the limits and disadvantages of the potential new molecular tool and provide suggestions to improve the reliability and feasibility of the proposed alternative.

Longevity evaluation of non-pumping reactive wells for control of groundwater contamination: Application of upscaling methods.

Non-pumping reactive wells (NPRWs) are subsurface structures used for the passive treatment of contaminated groundwater using wells containing reactive media. In the vicinity of NPRWs, a combination of hydrogeological and chemical processes makes it difficult to predict their longevity. In this study, we evaluated the longevity of NPRWs using the upscaling methods. A horizontal two-dimensional sandbox was constructed to mimic the hydrogeological and chemical processes in a single unit of NPRW (unit NPRW). The groundwater flow and solute transport were simulated numerically to validate the processes of contaminant spreading prevention in the sandbox. Dye tracing and arsenic transport tests showed different performance of NPRW due to induced flow and uneven consumption of reactivity, which is dependent on the pathway length and residence time of the coal waste. Through numerical modeling of the experiments, the fate-related processes of contamination around NPRW were described in detail in both spatial and temporal terms. The stepwise approach of the upscaling methods was used to predict the contamination-blocking performance of the entire facility based on the reactivity of the materials and the contamination removal of the unit NPRW.

Effect of Kaolinite and Cloisite Na+ on Storage Stability of Rubberized Binders.

This study aimed to evaluate the impact of a two-step modification process involving kaolinite and cloisite Na+ on the storage stability of rubberized binders. The process involved the manual combination of virgin binder PG 64-22 with crumb rubber modifier (CRM), which was heated to condition it. The preconditioned rubberized binder was then modified for two hours at a high speed of 8000 rpm using wet mixing. The second stage modification was performed in two parts, with part 1 using only crumb rubber as the modifier and part 2 involving the use of kaolinite and montmorillonite nano clays at a replacement percentage of 3% to the original weight of the binder along with the crumb rubber modifier. The Superpave and multiple shear creep recovery (MSCR) test methods were used to calculate the performance characteristics and separation index % of each modified binder. The results showed that the viscosity properties of kaolinite and montmorillonite improved the performance class of the binder, with montmorillonite demonstrating greater viscosity values than kaolinite even at high temperatures. Additionally, kaolinite with rubberized binders showed higher resistance to rutting, and the % recovery value from multiple shear creep recovery testing indicated that kaolinite with rubberized binders was more effective than montmorillonite with rubberized binders, even at higher load cycles. The use of kaolinite and montmorillonite reduced phase separation between the asphaltene phase and rubber-rich phase at higher temperatures, but the performance of the rubber binder was affected by higher temperatures. Overall, kaolinite with the rubber binder generally demonstrated greater binder performance.

A metabarcoding protocol targeting two DNA regions to analyze root-associated fungal communities in ferns and lycophytes.

Premise: Detailed studies of the fungi associated with lycophytes and ferns provide crucial insights into the early evolution of land plants. However, most investigations to date have assessed fern-fungus interactions based only on visual root inspection. In the present research, we establish and evaluate a metabarcoding protocol to analyze the fungal communities associated with fern and lycophyte roots. Methods: We used two primer pairs focused on the ITS rRNA region to screen the general fungal communities, and the 18S rRNA to target Glomeromycota fungi (i.e., arbuscular mycorrhizal fungi). To test these approaches, we collected and processed roots from 12 phylogenetically distant fern and lycophyte species. Results: We found marked compositional differences between the ITS and 18S data sets. While the ITS data set demonstrated the dominance of orders Glomerales (phylum Glomeromycota), Pleosporales, and Helotiales (both in phylum Ascomycota), the 18S data set revealed the greatest diversity of Glomeromycota. Non-metric multidimensional scaling (NMDS) ordination suggested an important geographical effect in sample similarities. Discussion: The ITS-based approach is a reliable and effective method to analyze the fungal communities associated with fern and lycophyte roots. The 18S approach is more appropriate for studies focused on the detailed screening of arbuscular mycorrhizal fungi.

Premisa: El estudio de los hongos asociados a licofitas y helechos proporciona información crucial sobre la evolución temprana de las plantas terrestres. Sin embargo, hasta el momento, la mayoría de las investigaciones ha evaluado las interacciones helecho­hongo basándose solamente en la observación directa de las raíces. En la presente investigación, establecemos y evaluamos un protocolo de metabarcoding enfocado en dos regiones de ADN para analizar las comunidades fúngicas asociadas a las raíces de helechos y licofitas. Métodos: Utilizamos dos pares de primer orientados hacia la región ITS ARNr, para la detección de las comunidades fúngicas generales, y la región 18S ARNr, para captar hongos pertenecientes al phylum Glomeromycota (i.e., hongos micorrícicos arbusculares). Para evaluar estos procedimientos, nosotros recolectamos y procesamos raíces de 12 especies de helechos y licofitas distantes desde el punto de vista filogenético. Resultados: Se observaron claras diferencias de composición entre los sets de datos ITS y 18S: mientras el primero demostró un predominio de los órdenes Glomerales (phylum Glomeromycota), Pleosporales y Helotiales (ambos en phylum Ascomycota), el set 18S reveló la mayor diversidad de hongos micorrizógenos arbusculares. Ninguno de los marcadores moleculares utilizados detectó miembros del phylum Mucoromycota en las muestras. El escalamiento multidimensional no métrico (NMDS) sugirió un papel importante de la región geográfica de origen en la determinación de las similitudes entre muestras. Discusión: El método basado en la región ITS es consistente, replicable y eficaz para analizar las comunidades fúngicas asociadas con raíces de helechos y licofitos. El enfoque 18S es más apropiado para estudios centrados en la detección de los hongos micorrizógenos arbusculares.

Effect of Blending and Curing Conditions on the Storage Stability of Rubberized Asphalt Binders.

Crumb rubber modifier (CRM) binders easily suffer from instability at high temperatures, with many suggestions being developed to evaluate their storage stability. However, much uncertainty around CRM binders still exists regarding the relationship between mixing methods and experiments in order to calculate the separation index. In this study, a laboratory investigation into how CRM binders behave regarding storage stability using different mixing methods and experiments was conducted. The CRM asphalt binder in this study was prepared through a wet mixing process with the addition of 5% and 10% crumb rubber modifier (by weight) at 200 °C. The three main modification methods were method A: high-shear mixing (8000 rpm) for 2 h, method B: low mixing (300 rpm) for 8 h, and method C: high-shear mixing (8000 rpm) for 2 h + low mixing (300 rpm) for 6 h. In addition, the effect of separation index (SI) on storage stability was assessed, measuring viscosity, G*/sin δ, and percentage recovery. In general, the results of this study revealed that method C appeared to have the most prominent effect on decreasing the difference between the values of the top and bottom parts; the results for 5% CRM using method C showed that there were no differences among the values for the top, middle, and bottom parts; from the MSCR test, method C was effective in decreasing the difference between the values of the top and bottom parts. It was observed that method C improved storage stability. However, the results for percentage recovery were relatively higher than the separation index when using rotational viscosity and G*/sin δ.

Laboratory Evaluation of Asphalt Binders Containing Styrene-Butadiene-Styrene (SBS) and Processed Oil.

The study presents an experimental evaluation to improve the resistivity of binders with "Styrene-Butadiene-Styrene" (SBS) and "Processed oil" by studying the physical properties, rheology, and cracking. For this experiment, PG 64-22 was mixed with SBS at different percentages of 5%, 10%, and 15% by weight of the original binder with two processed oil contents of 6% and 12% by weight of the binder. Laboratory tests have been conducted at various high, medium, and low temperature ranges to evaluate their properties. The processed oil polymer modified asphalt (PMA) binder is artificially aged in both the short and long-term using a Rolling Thin Film Oven (RTFO) and a Pressure Aging Vessel (PAV). The Superpave testing method was performed on modified binders using a Rotational Viscometer (RV), Dynamic Shear Rheometer (DSR), and Bending Beam Rheometer (BBR). The results of this study illustrate (1) The addition of SBS leads to higher viscosity, but the co-modification of asphalt binder with the processed oil shows a significant modulation of the viscosity value. (2) In addition, processed oil reduced the resistance to rutting, but the addition of SBS significantly improved the rutting resistance of the asphalt binder. (3) The addition of SBS and processed oil improved the value of G sin δ, notably. (4) According to BBR, it has been shown that the addition of SBS in addition to the processed oil improves the stiffness values of modified asphalt binders.

Longevity of coal waste for controlling cadmium-contaminated groundwater considering groundwater velocity.

Coal waste composed of naturally occurring minerals is applicable as a reactive medium to permeable reactive barriers due to its reactivity to heavy metals. In this study, we evaluated the longevity of coal waste as PRB media to control heavy metal-contaminated groundwater considering variable groundwater velocity. Breakthrough experiments were conducted using coal waste-filled column by injecting artificial groundwater, 10 mg/L of cadmium solution. The artificial groundwater was fed to the column at different flow rates to mimic a wide range of porewater velocities in the saturated zone. The reaction between cadmium breakthrough curves was analyzed using a two-site nonequilibrium sorption model. The cadmium breakthrough curves showed a significant retardation, which increased with decreasing porewater velocity. The greater the retardation, the longer the longevity of coal waste could be expected. The greater retardation under a slower velocity environment was due to the higher fraction of equilibrium reaction. The nonequilibrium reaction parameters could be functionalized with respect to the porewater velocity. The simulation of contaminant transport using the reaction parameters could be used as a method to evaluate the longevity of the pollution-blocking material in an underground environment.

Injection strategy for effective bacterial delivery in bioaugmentation scheme by controlling ionic strength and pore-water velocity.

For the in-situ remediation of the contaminated subsurface environment, the injection of nutrients and microorganisms changes chemical and physical conditions, which control the delivery and immobilization of microorganisms. We investigated the injection strategy for effective bacterial delivery in a bioaugmentation scheme by controlling ionic strength (IS) and pore-water velocity (v). A set of bacterial transport tests was conducted using the saturated sand column to mimic the saturated subsurface environment. The effectiveness of the injection strategies was evaluated by applying solutions with different ionic strengths into the sand column with different pore-water velocities. The deposition and delivery of bacteria through the sand column were analyzed using the first-order deposition model. The deposition and delivery of bacteria injected by various strategies were numerically simulated considering the variable deposition rate. The breakthrough curves from column experiments revealed that the bacterial deposition on the sand surface was increased by an increase in the ionic strength and by a decrease in the pore-water velocities. The rates of bacterial deposition (k1) on sand could be determined as a function of ionic strength and pore-water velocity, and it was applicable to simulate the delivery of bacteria under dynamic groundwater conditions. The numerical case study considering various injection strategies showed that the nutrient concentration controlled the bacterial delivery to the target area more significantly than the injection flow rate. Injection of bacterial solution with lower nutrient concentration could be increased the deposited bacterial concentration at the target point (Stp) by 6.2-7.1 times higher. Short pulse injection with a high injection rate decreased Stp by 67-78%. The efficiency of bacterial delivery (Ed) could be increased three times higher by lowering nutrient concentration in the injection solution. The process of evaluating the efficiency of bacterial delivery could be a prominent approach to determining the injection strategy for in-situ remediation considering variable conditions of a contaminated site.

Reciprocal recombination genomic signatures in the symbiotic arbuscular mycorrhizal fungi Rhizophagus irregularis.

Arbuscular mycorrhizal fungi (AMF) are part of the most widespread fungal-plant symbiosis. They colonize at least 80% of plant species, promote plant growth and plant diversity. These fungi are multinucleated and contain either one or two haploid nuclear genotypes (monokaryon and dikaryon) identified by the alleles at a putative mating-type locus. This taxon has been considered as an ancient asexual scandal because of the lack of observable sexual structures. Despite identification of a putative mating-type locus and functional activation of genes related to mating when two isolates co-exist, it remains unknown if the AMF life cycle involves a sexual or parasexual stage. We used publicly available genome sequences to test if Rhizophagus irregularis dikaryon genomes display signatures of sexual reproduction in the form of reciprocal recombination patterns, or if they display exclusively signatures of parasexual reproduction involving gene conversion. We used short-read and long-read sequence data to identify nucleus-specific alleles within dikaryons and then compared them to orthologous gene sequences from related monokaryon isolates displaying the same putative MAT-types as the dikaryon. We observed that the two nucleus-specific alleles of the dikaryon A5 are more related to the homolog sequences of monokaryon isolates displaying the same putative MAT-type than between each other. We also observed that these nucleus-specific alleles displayed reciprocal recombination signatures. These results confirm that dikaryon and monokaryon isolates displaying the same putative MAT-type are related in their life-cycle. These results suggest that a genetic exchange mechanism, involving reciprocal recombination in dikaryon genomes, allows AMF to generate genetic diversity.

Effect of Processed Oil on Asphalt Binder Properties.

This study investigates the effectiveness of processed oil in the modification of PG 64-22 and PG 76-22 by assessing their physical and rheological properties, and multiple comparison was conducted between the two binders. The base binders PG 64-22 and PG 76-22 were blended with processed oil at four different percentages of contents (3%, 6%, 9% and 12% by the weight of the binder) and compared with the control binder in each test. The base and modified binders were artificially short-term and long-term aged using a rolling thin film oven (RTFO) and pressure aging vessel (PAV) procedures. Superpave binder tests were performed on the modified binders by applying a rotational viscometer (RV), dynamic shear rheometer (DSR), and bending beam rheometer (BBR). The comparisons and results presented in this study indicate that (1) the processed oil has a significant effect on the binders' viscosity, which changes with respect to the increment of processed oil content. The viscosity of both modified binders decreased with the addition of 3, 6, 9 and 12% processed oil; (2) the performed DSR test showed that the addition of processed oil had a negative effect on the rutting resistance for both binders, since in PG 64-22, G*/Sin δ values decreased by 55, 65, 75 and 83% with the addition of 3, 6, 9 and 12% processed oil, respectively, while a decrement of G*/Sin δ of 24, 45, 58 and 65% with the addition of 3, 6, 9 and 12% processed oil was observed in PG 76-22; meanwhile, the fatigue cracking performance was improved and was found to be effective, while G* Sin δ in PG76-22 decreased by 9, 30, 36, and 52% and in PG 64-22 by 27, 44, 53, and 67% with the addition of 3, 6, 9 and 12% processed oil; (3) the results from the BBR test indicate significant improvement in the thermal cracking properties of the binders. The addition of 3, 6, 9 and 12% processed oil resulted in a decrease in the stiffness of both the PG 64-22 and PG 76-22 binders, with a positive effect consequently being observed on the m-values of the binders.