Logic Gates Based on 3D Vertical Junctionless Gate-All-Around Transistors with Reliable Multilevel Contact Engineering.

Vertical gate-all-around (V-GAA) represents the ultimate configuration in the forthcoming transistor industry, but it still encounters challenges in the semiconductor community. This paper introduces, for the first time, a dual-input logic gate circuit achieved using 3D vertical transistors with nanoscale sub-20-nm GAA, employing a novel technique for creating contacts and patterning metallic lines at the bottom level without the conventional lift-off process. This involves a two-step oxidation process: patterning the first field oxide to form bottom metal lines and then creating the gate oxide layer on nanowires (NWs), followed by selective removal from the top and bottom of the nanostructures. VGAA-NW transistors, fabricated using the lift-off-free approach, exhibit improved yield and reduced access resistance, leading to an enhanced drive current while maintaining good immunity against short-channel effects. Finally, elementary two-input logic gates within a single cell, using VNW transistors, demonstrate novel possibilities in advanced logic circuitry design and routing options in 3D.

Sources of the Elevating Polycyclic Aromatic Hydrocarbon Pollution in the Western South China Sea and Its Environmental Implications.

The environmental implications of polycyclic aromatic hydrocarbons (PAHs) caused by the vigorous development of offshore oil exploitation and shipping on the marine ecosystem are unclear. In this study, the PAH concentrations were systematically characterized in multiple environmental media (i.e., atmosphere, rainwater, seawater, and deep-sea sediments) in the western South China Sea (WSCS) for the first time to determine whether PAH pollution increased. The average ∑15PAHs (total concentration of 15 US EPA priority controlled PAHs excluding naphthalene) in the water of WSCS has increased and is higher than the majority of the oceans worldwide due to the synergistic influence of offshore oil extraction, shipping, and river input. The systematic model comparison confirms that the Ksoot-air model can more accurately reflect the gas-particle partitioning of PAHs in the atmosphere of the WSCS. We also found that the vertical migration of the elevating PAHs is accelerated by particulate matter, driving the migration of atmospheric PAHs to the ocean through dry and wet deposition, with 16% being contributed by the particle phase. The particulate matter sinking alters the PAH distribution in the water column and generates variation in source apportionment, while the contribution of PAHs loaded on them (>20%) to the total PAH reserves cannot be ignored as before. Hence, the ecological threat of PAHs increases by the oil drilling and shipping industry, and the driving force of particulate matter deserves continuous attention.

Interfacial States and Fano-Feshbach Resonance in Graphene-Silicon Vertical Junction.

Interfacial quantum states are drawing tremendous attention recently because of their importance in design of low-dimensional quantum heterostructures with desired charge, spin, or topological properties. Although most studies of the interfacial exchange interactions were mainly performed across the interface vertically, the lateral transport nowadays is still a major experimental method to probe these interactions indirectly. In this Letter, we fabricated a graphene and hydrogen passivated silicon interface to study the interfacial exchange processes. For the first time we found and confirmed a novel interfacial quantum state, which is specific to the 2D-3D interface. The vertically propagating electrons from silicon to graphene result in electron oscillation states at the 2D-3D interface. A harmonic oscillator model is used to explain this interfacial state. In addition, the interaction between this interfacial state (discrete energy spectrum) and the lateral band structure of graphene (continuous energy spectrum) results in Fano-Feshbach resonance. Our results show that the conventional description of the interfacial interaction in low-dimensional systems is valid only in considering the lateral band structure and its density-of-states and is incomplete for the ease of vertical transport. Our experimental observation and theoretical explanation provide more insightful understanding of various interfacial effects in low-dimensional materials, such as proximity effect, quantum tunneling, etc. More important, the Fano-Feshbach resonance may be used to realize all solid-state and scalable quantum interferometers.

Wind speed reductions by large-scale wind turbine deployments lower turbine efficiencies and set low generation limits.

Wind turbines generate electricity by removing kinetic energy from the atmosphere. Large numbers of wind turbines are likely to reduce wind speeds, which lowers estimates of electricity generation from what would be presumed from unaffected conditions. Here, we test how well wind power limits that account for this effect can be estimated without explicitly simulating atmospheric dynamics. We first use simulations with an atmospheric general circulation model (GCM) that explicitly simulates the effects of wind turbines to derive wind power limits (GCM estimate), and compare them to a simple approach derived from the climatological conditions without turbines [vertical kinetic energy (VKE) estimate]. On land, we find strong agreement between the VKE and GCM estimates with respect to electricity generation rates (0.32 and 0.37 We m-2) and wind speed reductions by 42 and 44%. Over ocean, the GCM estimate is about twice the VKE estimate (0.59 and 0.29 We m-2) and yet with comparable wind speed reductions (50 and 42%). We then show that this bias can be corrected by modifying the downward momentum flux to the surface. Thus, large-scale limits to wind power use can be derived from climatological conditions without explicitly simulating atmospheric dynamics. Consistent with the GCM simulations, the approach estimates that only comparatively few land areas are suitable to generate more than 1 We m-2 of electricity and that larger deployment scales are likely to reduce the expected electricity generation rate of each turbine. We conclude that these atmospheric effects are relevant for planning the future expansion of wind power.

Vertical versus Lateral Two-Dimensional Heterostructures: On the Topic of Atomically Abrupt p/n-Junctions.

The key appeal of two-dimensional (2D) materials such as graphene, transition metal dichalcogenides (TMDs), or phosphorene for electronic applications certainly lies in their atomically thin nature that offers opportunities for devices beyond conventional transistors. It is also this property that makes them naturally suited for a type of integration that is not possible with any three-dimensional (3D) material, that is, forming heterostructures by stacking dissimilar 2D materials together. Recently, a number of research groups have reported on the formation of atomically sharp p/n-junctions in various 2D heterostructures that show strong diode-type rectification. In this article, we will show that truly vertical heterostructures do exhibit much smaller rectification ratios and that the reported results on atomically sharp p/n-junctions can be readily understood within the framework of the gate and drain voltage response of Schottky barriers that are involved in the lateral transport.

Spatiotemporal sensitivity analysis of vertical transport of pesticides in soil.

Environmental fate and transport processes are influenced by many factors. Simulation models that mimic these processes often have complex implementations, which can lead to over-parameterization. Sensitivity analyses are subsequently used to identify critical parameters whose uncertainties can be further reduced or better described and prediction variability minimized. In this study, a variance decomposition based global sensitivity analysis technique (Sobol' method) is conducted based on estimated concentrations in vertical soil compartments using the Pesticide Root Zone Model (PRZM). Daily simulations are performed that explore the input parameter space. Estimated concentrations are compared to data collected over the course of a growing season from an experimental site in Georgia. Our results suggest that model sensitivity is conditional and should be examined at appropriate spatial and temporal resolution to avoid omitting important parameters. This approach can yield a better understanding about the interplay between sensitivity/uncertainty and model dynamics in non-monotonic, non-linear systems.

Strong upwards transport of HONO in daytime over urban area of Beijing, China.

Strong upwards transport of Nitrous acid (HONO) in daytime over urban area of Beijing was observed based on combined observations of HONO, NOx (NO and NO2), nitrate, and PM2.5 at two heights (90 m and 528 m) on the highest building of Beijing (528 m above ground). The mean HONO at the 528 m (0.26 ppb) was lower than that at the 90 m (0.54 ppb), and a clear difference in diurnal variation of HONO between the two heights was observed. HONO at the 90 m showed two peaks in the morning rush hour and mid-night, but decreased sharply in daytime (e.g., from 0.62 ppb at 08:00 to 0.34 at 14:00); while the decreasing trend of HONO in daytime significantly weakened at the 528 m (e.g., from 0.26 ppb at 08:00 to 0.27 at 14:00).With PBL development in the morning, HONO in low layer was upwards transported to the 528 m, which compensated partly HONO loss via photolysis and resulted in a relatively stable concentration at the 528 m in daytime. A positive relationship of the bulk Richardson number (Ri) in 0-500 m with the difference of HONO between the two heights during daytime (08:00-18:00) confirmed the above analyses. HONO budget analysis indicated that a strong unknown HONO source existed at the 528 m in daytime, which was negative correlated to the Ri. These results further confirmed that vertical transport of HONO from low layer was a potential HONO source at the 528 m. Moreover, the contribution of photolysis of particulate nitrate significantly increased at the 528 m. Its contribution in total HONO sources increased from 11.9 % at the 90 m to 16.0 % at the 528 m.

Investigation into the nocturnal ozone in a typical industrial city in North China Plain, China.

Ozone (O3) concentrations usually peak at midday by photochemical reactions and gradually decline after sunset due to chemical destruction and dry deposition. However, an increase in the frequency of elevated nocturnal ozone enhancement (NOE) and high nocturnal ozone value (HNOV) has been frequently observed in urban areas of eastern China, but the reasons are not well understood. In this study, taking a typical industrial city, ZiBo as a case study, we analyzed the trends, characteristics, and causes of the NOE and HNOV events in historical years by combining observations and model simulations. During the warm season (April-September) of 2017-2023, HNOV events are accompanied by low humidity, high temperature, large friction velocity, and a high boundary layer (52 days in total), whereas NOE events coincide with increases in humidity, wind speed, friction velocity, and boundary layer height (141 days in total). During the HNOV and NOE events, the nighttime average concentrations of Ox were 77 ± 7 and 12 ± 6 µg m-3 higher than the non-nocturnal O3 period, indicating enhanced atmospheric oxidizing capacity during nighttime. The modeling results indicate that both the HNOV and NOE events were mainly driven by vertical mixing and regional transport. We selected a typical period with high O3 pollution and frequent NOE and HNOV events to conduct the modeling study. Three typical nocturnal O3 events are identified: Case I was mainly driven by horizontal transport; while in the two subsequent cases, the vertical transport contribution was 80 µg m-3 h-1 (20:00 LT on June 21, 2021) and 35 µg m-3 h-1 (02:00 LT on June 26, 2021), respectively. Our study reveals that the O3 pollution in industrial cities has been extending to nighttime, primarily attributed to vertical mixing and horizontal transport within the boundary layer. This highlights the critical role of implementing regional joint control action to reduce primary emissions and eliminate residual ozone.

Modeling the settling and resuspension of microplastics in rivers: Effect of particle properties and flow conditions.

Microplastics have numerous different shapes, affecting the fate and transport of these particles in the environment. However, theoretical models generally assume microplastics to be spherical. This study aims to develop a modeling approach that incorporates the shapes of microplastics to investigate the vertical transport of microplastics in rivers and simulate the effect of particle and flow characteristics on settling and resuspension. To achieve these aims, a mechanistic model was developed utilizing the mass-balance and hydrodynamic equations. Scenario analysis was implemented assigning different values to model parameters, such as bed shear stress, shape factor and particle size to simulate the effect of flow patterns and particle properties. The model outcomes revealed that the residence time of microplastics in the water column was longest in medium bed shear stress, whilst it was shortest in low bed shear stress. This suggests that the influence of turbulence is not unidirectional; it can both increase and decrease microplastic concentrations and residence time in the water column. According to the scenario analysis, the settling flux of microplastics was the highest for near-spherical particles and increased with the size of the particles, as well as with increasing bed shear stress. However, the resuspension of particles was primarily influenced by increasing bed shear stress, but the ranking of resuspension flux values for different shaped and sized microplastics exhibited alterations with changing flow patterns. Turbulent conditions predominantly influenced the resuspension of near-spheres and large microplastics. On the contrary, the settling of fibers and small microplastics were significantly influenced by changing flow patterns, whereas near-spheres and largest particles were least affected. The model results were sensitive to changes in shape factor developed for this model, therefore this parameter should be improved in future studies.

Microplastic infiltration into mobile sediments.

This study investigates the dynamics of microplastic infiltration into non-stationary sandy sediments, a pressing environmental concern due to the rising prevalence of microplastics in aquatic ecosystems. An annular flume was used to simulate riverine bedform motion, examining the suspension and infiltration of denser-than-water microplastic particles, including polyvinyl chloride (PVC), polyamide (PA), and polylactide (PLA). The experiments focused on various particle sizes (ranging from 0.2 to 5 mm in diameter) and bedform migration speeds, known as celerities. The findings indicate that particle size is a significant factor influencing the depth of infiltration and distribution within sediment layers, whereas the impact of bedform celerities and particle densities appears less significant. This research provides novel insights into the behavior of microplastics in dynamic sedimentary environments, highlighting the intricate interaction between microplastic characteristics and sedimentary processes. The results contribute to an enhanced understanding of microplastic distribution and accumulation in riverine systems, offering crucial data for developing predictive models and formulating potential remediation strategies for microplastic pollution.

The factors influencing the vertical transport of microplastics in marine environment: A review.

There have been numerous studies that have identified the presence of low-density microplastics (MPs) in the water column and sediments. The focus of current MPs research has shifted towards the interaction of MPs with marine organisms and their potential hazards, including the uptake characteristics, biological transport and toxicological effects of MPs, but the processes involved in the deposition behavior of MPs are still poorly understood. In this review, we summarize the current state of knowledge on the vertical transport of MPs influenced by their physicochemical properties and marine organisms, and discuss their potential impact on MPs deposition. The physicochemical properties of MPs determine their initial distribution. The density, shape, and size of MPs influence their settling state in the marine environment. Marine biota play a key role in the transport of MPs to deep marine environment, mainly by changing the density and adsorption of MPs. Biofouling can alter the surface properties of MPs and increase the overall density, thus affecting the vertical flux of the plastic. Macroalgae may trap MPs particles by producing chemicals or by using electrostatic interactions. Marine swimming organisms ingest MPs and excrete them encapsulated in fecal particles, while the activity of marine benthic organisms may contribute to the transfer of MPs from surface sediments to deeper layers. In addition, MPs may be incorporated into organic particles produced by marine organisms such as marine snow or marine aggregates, increasing the vertical flux of MPs. However, due to the complexity of different sea areas and MPs properties, the deposition behavior of MPs may be the result of the interaction of multiple factors. Thus, the effects of MPs properties, marine organisms and the natural environment on MPs deposition in marine environment needs further research to fill this gap.

Vertical flux of microplastic, a case study in the Southern Ocean, South Georgia.

Estimated plastic debris floating at the ocean surface varies depending on modelling approaches, with some suggesting unaccounted sinks for marine plastic debris due to mismatches between plastic predicted to enter the ocean and that accounted for at the surface. A major knowledge gap relates to the vertical sinking of oceanic plastic. We used an array of floating sediment traps combined with optical microscopy and Raman spectroscopy to measure the microplastic flux between 50 and 150 m water depth over 24 h within a natural harbour of the sub-Antarctic island of South Georgia. This region is influenced by fishing, tourism, and research activity. We found a 69 % decrease in microplastic flux from 50 m (306 pieces/m2/day) to 150 m (94pieces/m2/day). Our study confirms the occurrence of a vertical flux of microplastic in the upper water column of the Southern Ocean, which may influence zooplankton microplastic consumption and the carbon cycle.

Influence of vertical transport on chemical evolution of dicarboxylic acids and related secondary organic aerosol from surface emission to the top of Mount Hua, Northwest China.

Dicarboxylic acids are strong hygroscopic organic compounds in the atmosphere, and thus significantly affect the cloud formation process and radiative forcing on a regional scale. So far, the evolution of dicarboxylic acids during vertical transport from the surface to the mountaintop has yet to be explicitly understood. In this study, the molecular distribution and stable carbon isotopic (δ13C) compositions of dicarboxylic acids and related organic compounds (DCRCs) in PM2.5 were measured simultaneously at the top (c. 2060 m a.s.l.) and foot (c. 400 m a.s.l.) of Mount (Mt.) Hua during the summer of 2020. Due to the strong anthropogenic emissions at ground level, the concentrations of DCRCs at foot of Mt. Hua were generally higher than those at the top. Oxalic acid (C2) was the predominant diacid in both sites, whose concentrations at foot and top of Mt. Hua were 87-852 and 40-398 ng m-3, respectively. Ratios of adipic acid to azelaic acid (C6/C9), phthalic aid to azelaic acid (pH/C9), glyoxal to methylglyoxal (Gly/mGly), and lower δ13C values (-21.0 ± 2.3 ‰ and - 21.9 ± 2.7 ‰) of C2 indicated that the contributions of anthropogenic sources to DCRCs in PM2.5 in the mountain region are more significant than biogenic sources. Aerosols from the foot of Mt. Hua could affect the atmosphere on the top of the mountain via vertical transport under the influence of daytime valley wind, even though the altitude of Mt. Hua is beyond the boundary layer most of time. The value δ13C of C2 is linearly correlated with C2/mGly, C2/pyruvic acid (Pyr), C2/glyoxylic acid (ωC2) at the top of the mountain, and C2/Gly, C2/ωC2 at the foot of the mountain, indicating that the formation pathway of C2 is mGly-Pyr-ωC2-C2 at the top of Mt. Hua and Gly-ωC2-C2 at the foot of Mt. Hua.

Effects of weathering on the properties and fate of secondary microplastics from a polystyrene single-use cup.

In this work, we probed the changes to some physicochemical properties of polystyrene microplastics generated from a disposable cup as a result of UV-weathering, using a range of spectroscopy, microscopy, and profilometry techniques. Thereafter, we aimed to understand how these physicochemical changes affect the microplastic transport potential and contaminant sorption ability in model freshwaters. Exposure to UV led to measured changes in microplastic hydrophobicity (20-23 % decrease), density (3% increase), carbonyl index (up to 746 % increase), and microscale roughness (24-86 % increase). The settling velocity of the microplastics increased by 53 % after weathering which suggests that UV aging can increase microplastic deposition to sediments. This impact of aging was greater than the effect of the water temperature. Weathered microplastics exhibited reduced sorption capacity (up to 52 % decrease) to a model hydrophobic contaminant (triclosan) compared to unaged ones. The adsorption of triclosan to both microplastics was slightly reversible with notable desorption hysteresis. These combined effects of weathering could potentially increase the transport potential while decreasing the contaminant transport abilities of microplastics. This work provides new insights on the sorption capacity and mobility of a secondary microplastic, advances our knowledge about their risks in aquatic environments, and the need to use environmentally relevant microplastics.

Developing a novel computer visualization system to simulate the uranium upward transport mechanism: Uranium pollution in arid landscapes.

Uranium (U) is a naturally occurring, radioactive, toxic trace element that poses severe risks to public and environmental health. Depleted uranium (DU) is widely used in military munitions, including penetrators. Our previous studies showed that in arid landscapes, water-soluble U released from corroded DU penetrators that were buried underground were co-transported upwards with water by evaporation-driven capillary action and eventually precipitated on the ground surface. The first objective of this study was to develop a visualization system to simulate this complex U upward transport mechanism involving cyclic capillary wetting-drying cycles. Multiple visual components such as visual elements, canvases, and animations were created using JavaScript, HTML, and CSS programming languages and coordinated to visualize this biogeochemical process in arid ecosystem landscapes. The second objective was to develop an interactive visualization exercise to allow users to study the effect of the type of capillarity solutions on the speed of the U upward transport. This study is significant in the following aspects:•Contributing a clear and comprehensible visualization of the complex U transport mechanism;•Developing a novel visualization coding framework with more advantages in simulating heavy metal upward transport mechanisms than regular software-based simulations; and•Providing educational uses such as an instructional tool in secondary and college STEM classrooms, an outreach material in promoting student interest in STEM topics and raising public awareness of U pollution, and an educational aid for understanding U mobility in order to develop effective heavy metal pollution control and remediation strategies and policies.

Extracellular polymeric substances in green alga facilitate microplastic deposition.

Microplastics (MPs) are globally ubiquitous in sediments and surface waters. Interactions between biota and MPs are complex and influence their fate and effects in the environment. Once MPs enter aquatic systems, they are colonized by biofilms that may form from the excretion of extracellular polymeric substances (EPS) from microalgae. Biofilm accumulation may change the density of the MPs, contributing to their transport to the sediments. Furthermore, benthic plantivores may consume biofilm laden MPs allowing them to enter the food web. Thus, it is crucial to understand the role algae plays in the vertical transport of MPs in the aquatic environment. In this study, Chlamydomonas was cultured with MPs at different concentrations (0-0.4 mg/mL), and temperatures ranging from 2.5 to 32.5 °C to understand the deposition dynamics and impacts of MPs on EPS production and algal density. Temperatures ranging up to 25 °C increased algal density and MPs deposition. However, at 32.5 °C, algal density and MPs deposition declined. The quantity of MPs also affected algal cell density and EPS production. MPs concentration from 0 to 0.4 mg/mL increased EPS production at all temperatures. Similarly, an increase in algal cell density and MPs deposition occurred when MPs concentration was raised to 0.3 mg/mL. Algal cultures exposed to 0.3-0.4 mg/mL of MPs had a decrease in algal cell density, with no corresponding decline in EPS production. At certain conditions, MPs can facilitate biofilm formation by stimulating EPS production, which can increase cell density thereby expediting MPs transport to the sediment.

Model analysis of vertical exchange of boundary layer ozone and its impact on surface air quality over the North China Plain.

In addition to photochemical production and horizontal regional transport, surface O3 concentration can also likely be affected by vertical transport, which is not well known so far. The process analysis was conducted by using the Regional Atmospheric Modeling System Community Multiscale Air Quality (RAMS-CMAQ) model to investigate photochemical production and the vertical transport mechanism of boundary-layer O3 during a typical O3 pollution episode in the North China Plain (NCP), and further quantify the contribution of vertical transport to surface O3. The diurnal variations of vertical budgets of O3 and NO2 in the boundary layer at multiple sites showed that there were substantial differences in the vertical distribution of O3 production and transport between urban and suburban/rural areas. In urban areas, surface O3 is consumed by titration reaction to generate NO2, which is then transported to the upper boundary layer and produces O3 by photochemical reaction. With the development of the boundary layer, the upper-layer O3 stored in the residual layer at nighttime can be transported vertically to the surface as the turbulent diffusion intensifies the next morning. While in suburban and rural areas, the vertical transport is relatively weaker because the photochemical formation of O3 occurs in the whole boundary layer, although it decreases slightly with the altitude. Model simulation showed that 20.6-27.9% of urban surface O3 changes in the morning (09:00-10:00 LST) was attributable to the downward transport from the residual layer, while it is 15.0-22.1% at suburban site. The vertical transport from above the boundary layer contributed 24.0-63.6% to daytime urban surface O3 changes, which was weak in suburban areas. Differences and similarities in O3 formation and transport mechanism in urban and suburban regions revealed here highlight the importance of earlier control and regional collaboration.

Transport and retention of polymeric and other engineered nanoparticles in porous media.

Increasing applications of nanoparticles (NPs) in agriculture have raised potential risks to soil and aquatic ecosystems. A comparative study examining the transport of commonly used NPs in porous media is of critical significance for their application and regulation in agroecosystems. In this study, laboratory column leaching experiments were conducted to investigate the transport and retention of polysuccinimide NPs (PSI-NPs) in two saturated porous media with different grain sizes, as compared with multi-walled carbon nanotubes (MWCNTs), nano-Ag and nano-TiO2. Zeta potential of the NPs was negative at pH6.3 and decreased in an order of PSI-NPs > nano-TiO2 > MWCNTs > nano-Ag. The coarse and fine sands used in this study had negative charges with similar zeta potentials. The movement of NPs was affected by grain size, with larger sizes facilitating mobility while finer sizes favoring retention of NPs in the porous matrix. The retention profile significantly varied between the two sand columns, with more NPs transported to deeper layers in the coarse sand than the fine sand. The relative percentage of NPs detected in leachate was found to be positively correlated with the zeta potential of NPs (r = 0.931). Among the NPs, nano-Ag had the most negative zeta potential, and therefore was the most mobile, followed by MWCNTs and nano-TiO2. Having the least negative zeta potential, PSI-NPs had the lowest mobility, as compared with other NPs regardless of matrix grain size. This work reveals grain size and zeta potential of NPs are major factors that influence transport of NPs along the vertical porous profile, as well as demonstrating the relative unimportance of NP composition, which could serve as important guideline in nanomaterials application, risk assessment, and waste management in agroecosystems.

Vertical migration of microplastics in porous media: Multiple controlling factors under wet-dry cycling.

Terrestrial soils are not only a large reservoir for Microplastics (MPs), but also a possible entrance to the subsurface environment, posing potential risks to the subterranean habitats and groundwater. In this study, we examined the vertical transport of MPs of four polymers, i.e., polyethylene (PE), polyethylene terephthalate (PET), polypropylene (PP) and polyamide (PA), in porous sand media driven by wet-dry cycling. The effects of polymer properties, MP size, sand particle size, wet-dry cycles, and dissolved organic matter (DOM) on their migration behavior were investigated. Surface hydrophobicity showed a strong positive correlation with MP mobility, with PA exhibiting the greatest movement potential, followed by PE, PET, and PP. The penetration depth of MP particles increased with decreasing MP particle size (dMP) and increasing sand diameter (dsand). MP particles migrated deeper in sand media when dMP/dsand < 0.11. Furthermore, frequent wet-dry cycles and the presence of DOM promoted the vertical migration of MPs in the sand. The results revealed multiple factors influencing the vertical migration of MPs in sand, which is instructive for understanding the ecological risk of MPs in potentially contaminated soil (e.g., farmland with long-term mulching) to the subsurface environment and potential negative impact to public health.

Modeling the vertical transport of antibiotic resistance genes in agricultural soils following manure application.

Antibiotic resistance genes (ARGs) may be introduced to agricultural soil through the land application of cattle manure. During a rainfall event, manure-borne ARGs may infiltrate into subsurface soil and leach into groundwater. The objective of this study was to characterize and model the vertical transport of manure-borne ARGs through soil following the land application of beef cattle manure on soil surface. In this study, soil column experiments were conducted to evaluate the influence of manure application on subsurface transport of four ARGs: erm(C), erm(F), tet(O) and tet(Q). An attachment-detachment model with the decay of ARGs in the soil was used to simulate the breakthrough of ARGs in leachates from the control column (without manure) and treatment (with manure) soil columns. Results showed that the first-order attachment coefficient (ka) was five to six orders of magnitude higher in the treatment column than in the control column. Conversely, the first-order detachment and decay coefficients (kd and µs) were not significantly changed due to manure application. These findings suggest that in areas where manure is land-applied, some manure-borne bacteria-associated ARGs will be attached to the soil, instead of leaching to groundwater in near terms.