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Resuspension of dust from carpet is an important source of human exposure to microorganisms. The microbial composition of dust can be measured using environmental DNA, such as with polymerase chain reaction (PCR) technologies. However, we need an improved understanding of collection losses and efficiencies to support accurate quantification of these exposures. The goal of this study was to characterize accuracy and precision of PCR-based analysis methods for microbial DNA in residential carpet dust. We spiked dust with known concentrations of bacterial cells Escherichia coli and Bacillus atrophaeus, as well as spores of the fungus Aspergillus fumigatus. We embedded the dust into nylon carpet of varying pile heights and recovered it by vacuuming using two different attachments. Overall reproducibility using quantitative PCR ranged from 13% to 36% coefficient of variation for this sampling procedure. Overall efficiencies associated with recovery of dust from the carpet via vacuuming and extraction of DNA from the dust ranged from 27% for A. fumigatus spores to 9% for E. coli cells. Failure to account for DNA recovery efficiencies could result in up to 11.2 times underestimation of exposure. Incorporating DNA recovery efficiencies into the analysis avoids underestimation of environmental exposures to microbes. [ABSTRACT FROM AUTHOR]

Urban air quality assessment in regard to biogenic emissions such as airborne pollen grains (PGs) is indispensable in the urban environment which significantly affects human health, climates, ecosystems, and energy production. Dispersion and deposition of PGs because of resuspension events (ReSE) are investigated using computational fluid dynamics (CFD). The mechanisms in PGs movement are achieved through the Lagrangian formulation-based discrete-phase model (DPM). The observed pollen grains distribution pattern is highly spatially dependent on heterogeneous urban obstacles as it induces modified characteristics of the wind flow field. Wind-urban structure interplays in PGs concentration variation. The simulated results identify the pollen hot-spot zones, where vortical flow features and low wind speed dominate. This approach offers a detailed understanding of the dispersion patterns of airborne PGs in urban environments because of ReSE with high resolution. [ABSTRACT FROM AUTHOR]

Moorings and axial surveys using acoustic Doppler current profilers in microtidal Masan Bay were conducted to reveal impacts of coastal seiches on sediment behaviors. The hydrodynamic circulation in the bay was dominated by sluggish tidal and residual currents, with which the coastal seiches with a 1-h period were detected. The coastal seiches velocity (useiche) accounted for approximately 30% of the total velocities, causing back-and-forth water motions along the channel. This was insufficient to resuspend bed sediments without external forcings. Nevertheless, it influenced the suspended sediment concentration (SSC) of turbidity maximum (~40 mg l-1) at the central part of bay, showing SSC anomaly of 8 mg l-1. Although the seiche-induced sediment fluxes were only 1% of the total fluxes due to offsetting effect of bidirectional flows, they reached up to 0.040x10-3 kg m-2 s-1 at each pulse of coastal seiches. Repetitive coastal seiches lifted the sediment particles to the upper layer where they would not have risen if not for seiche vertical motion. However, the distance that the coastal seiches can transport the suspended sediments was too short compared to their transportable amounts. Even if sediment particles within turbidity maximum were advected by coastal seiches, they could not leave the region. This process was intensified toward the land because the useiche slowed down the further as it moved away from the node. As long as the bed sediments were resuspended, the coastal seiches were expected to enhance the potential for water pollution by causing repetitive sediment redistribution. [ABSTRACT FROM AUTHOR]

Microalgae have rigid, complex cell walls hindering direct lipid extraction. Cell disruption techniques are used to rupture these cellular structures to increase lipid extraction. Researchers investigating the downstreamprocessing of microalgae do not always have access to microalgal cultivation systems to generate large amounts of fresh microalgal biomass. Using resuspended freeze-dried microalgal biomass as a model laboratory system for concentrated fresh biomass during cell disruption experiments offers greater flexibility in experimental planning and omits investment costs of microalgal cultivation equipment. So far, it however remains unclear whether freeze-dried resuspended biomass can be used as a model laboratory system to represent concentrated fresh biomass during cell disruption and lipid extraction experiments. This paper thus evaluated the suitability of resuspended freeze-dried Nannochloropsis as a model laboratory system for concentrated fresh Nannochloropsis during cell disruption. Ultrasound assisted cell disruption was used as example cell disruption technique and lipid extraction efficiency and free fatty acid content were investigated. Tap water and 3% sodium chloride are both suitable resuspension media for the resuspension of freeze-dried Nannochloropsis. Resuspension duration should be limited (< 120 min) to prevent the formation of free fatty acids. The condition of the biomass (concentrated fresh, or resuspended freeze-dried) prior to ultrasound assisted cell disruption did not influence the resulting lipid extraction efficiency. Resuspended freeze-dried Nannochloropsis biomass in tap water or 3% sodium chloride can thus be used as a model laboratory system for fresh microalgal biomass during research on ultrasound assisted lipid extraction. The generalization of the results to other cultivation conditions, cell disruption techniques, components of interest or microalgal species should be carefully assessed. [ABSTRACT FROM AUTHOR]

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

The pathway of dense river inflows into lakes, which affects the lake water quality, is not accurately predicted by existing models. The pathway of a dense riverine inflow in a lake with a submerged canyon is analyzed based on measurements during a 4‐month period of weakening lake stratification and weakening density excess between river and epilimnion. In line with models, the dense riverine inflow plunges upon entering the lake, continues as an underflow on the sloping lake bottom, and finally intrudes at its level of neutral buoyancy. Underflow and interflow velocities are O(0.1 m s−1). The river inflow is finally trapped in the pycnocline most of the time, even when the river's density excess and the lake's stratification are marginal. This trapping in the pycnocline is explained by the reduction of the inflow density excess due to the intense plunging mixing, which is an order of magnitude larger than that obtained in confined laboratory flumes. The pathway of the dense riverine inflow is affected by interactions of the underflow with the lake bottom and sedimentary processes. A canyon carved by the underflows confines and accelerates the underflow, which enhances its capacity to entrain and carry sediment. The entrainment of sediment that was previously deposited on the canyon bottom accelerates the underflow. Due to both effects, the underflow can temporarily break through the pycnocline and reach the hypolimnion. Existing models explain these observations qualitatively, but a quantitative prediction would require better parameterizations of the plunging mixing and the sedimentary processes. Plain Language Summary: The pathway of river inflows into lakes is not accurately predicted by existing models. We investigate the physical processes affecting the pathway of dense riverine inflow (i.e., inflow with a density higher than lake water) into a stratified lake. We investigate the conditions under which a dense riverine inflow get trapped in the pycnocline (the layer that separates warmer surface waters from cold deep waters) or break through it. Unprecedented long records of the temporal evolution of the pathway of the riverine flow into the lake during a period of weakening riverine density excess and lake stratification are conceptualized in a model, which extends existing concepts for dense riverine inflows. The entrainment of lake waters into the riverine inflow in the plunging region is larger than predicted by laboratory studies. This explains why the riverine inflow is trapped in the pycnocline most of the time. Flow confinement by a canyon carved by the riverine inflow into the lake bottom accelerates the riverine inflow and enhance sediment entrainment capacity causing short‐lived self‐accelerating turbidity currents along the lake bottom that break through the pycnocline and reach deep waters. Our results allow improved estimates of oxygen replenishment or sediment deposition from riverine water. Key Points: Plunging mixing into an unconfined ambient is an order of magnitude larger than in a confined ambientPronounced plunging mixing reduces the initial density excess explaining why the inflow is mostly trapped in the pycnoclineResuspension of lake bottom sediment can cause short‐lived self‐accelerating turbidity currents that break through the pycnocline [ABSTRACT FROM AUTHOR]

Heliozoans are ambush protists that inhabit most limnetic systems. However, ecological information about planktonic heliozoans is still limited. In this study, we investigated seasonal changes in planktonic heliozoan abundance in the deep northern and shallow southern basins of Lake Biwa at pelagic stations between August 2020 and December 2021. We compared planktonic heliozoan abundance levels between the two basins and examined the relationship between heliozoan abundance and environmental variables. In both basins, high levels of planktonic heliozoan abundance were detected in autumn, winter and spring. In the south basin, there was a significant positive correlation between planktonic heliozoan abundance and chlorophyll a concentration as well as the abundance of the diatoms Aulacoseira granulata and Aulacoseira ambigua. These results suggest that planktonic heliozoans directly or indirectly consume diatoms and that heliozoan abundance is subjected to bottom-up control. Furthermore, planktonic heliozoan abundance in the south basin was higher than that in the north basin, possibly due to the presence of waterweeds, which can serve as habitat for heliozoans, and the redistribution of planktonic heliozoans through resuspension from lake bottom sediments. [ABSTRACT FROM AUTHOR]

Clogging and resuspension of fine particles in high-turbidity rivers affect riverbed infiltration capacity and limit aquifer recharge. This study simulated these two processes on riverbeds with different particle compositions through column experiments, and assessed the riverbed infiltration rate both before and after clogging and after resuspension. Results showed that in most river sections, viscous fine particles will form internal clogging only within a depth of 30 cm, and this process will reach stability within 2 h. The riverbed infiltration rate after clogging is only 1.15%–37.50% of that before clogging. When river flow velocity exceeds 23.1–34.9 cm/s, the viscous cake layer on the riverbed will be resuspended. After resuspension, the riverbed infiltration rate can be restored to 2.13%–93.01% of that before clogging. On this basis, principal component analysis was used to screen the variables that describe particle composition, and multiple linear regression was used to construct separate quantitative relationships for the infiltration rate, its attenuation degree, and its recoverability with particle composition (represented by median particle size and curvature coefficient). The findings of this study are of great importance for further elucidating the infiltration capacity of high-turbidity rivers and provide reference value for the calculation of river leakage loss and groundwater recharge. [ABSTRACT FROM AUTHOR]

Internal solitary waves (ISWs) occur in stratified seawater and are characterized by substantial amplitudes and short periods. ISWs engender significant interactions between seawater and seafloor topography. They resuspend seabed sediments in various ways, and the submarine canyon acts as a main channel for transporting the suspended sediments from the shallow sea to the deep sea. Among the seas worldwide where ISWs are prevalent, the South China Sea exhibits the largest amplitude of ISWs, and the ISWs directly interact with the seafloor topography near the Dongsha area in the northern South China Sea. Through the analysis of the water profile and high-resolution multi-beam detection data in the vicinity of the Dongsha area, it was found that the submarine canyon exerts a great impact on the sediment resuspension and the bottom nepheloid layer formation induced by ISWs. The observation results show that the concentration of suspended particulate matter within the submarine canyon is remarkably higher than that outside the canyon. The concentration at the bottom of the canyon can reach twice that of the outside regions, forming a vast bottom nepheloid layer. In addition, with the presence of the submarine canyon, the suspended matter carried by the ISWs accumulates in the water column above the canyon, leading to a higher concentration above the canyon. ISWs not only could influence the submarine canyons, but also interacted with it. This interaction enhanced the resuspension and transport of seafloor sediments along submarine canyons and trenches. This study deepens the understanding of the effect of ISWs on sediment resuspension in submarine canyons. [ABSTRACT FROM AUTHOR]

Microalgae have rigid, complex cell walls hindering direct lipid extraction. Cell disruption techniques are used to rupture these cellular structures to increase lipid extraction. Researchers investigating the downstream processing of microalgae do not always have access to microalgal cultivation systems to generate large amounts of fresh microalgal biomass. Using resuspended freeze-dried microalgal biomass as a model laboratory system for concentrated fresh biomass during cell disruption experiments offers greater flexibility in experimental planning and omits investment costs of microalgal cultivation equipment. So far, it however remains unclear whether freeze-dried resuspended biomass can be used as a model laboratory system to represent concentrated fresh biomass during cell disruption and lipid extraction experiments. This paper thus evaluated the suitability of resuspended freeze-dried Nannochloropsis as a model laboratory system for concentrated fresh Nannochloropsis during cell disruption. Ultrasound assisted cell disruption was used as example cell disruption technique and lipid extraction efficiency and free fatty acid content were investigated. Tap water and 3% sodium chloride are both suitable resuspension media for the resuspension of freeze-dried Nannochloropsis. Resuspension duration should be limited (< 120 min) to prevent the formation of free fatty acids. The condition of the biomass (concentrated fresh, or resuspended freeze-dried) prior to ultrasound assisted cell disruption did not influence the resulting lipid extraction efficiency. Resuspended freeze-dried Nannochloropsis biomass in tap water or 3% sodium chloride can thus be used as a model laboratory system for fresh microalgal biomass during research on ultrasound assisted lipid extraction. The generalization of the results to other cultivation conditions, cell disruption techniques, components of interest or microalgal species should be carefully assessed.

In nuclear reactors, fine aerosol particles are one of the important carriers of radioactive substances. In the case of a serious accident in a nuclear reactor, the resuspension behavior of particles under the effect of transient airflow may cause a radioactive leak, which is an important content of the radioactive source term analysis. According to the deposition patterns of particles on the wall, particle resuspension can be divided into monolayer resuspension and multilayer resuspension. For the monolayer resuspension, the particle resuspension motion can be divided into lift-off motion determined by lift and adhesion, slide motion determined by drag and friction, and roll motion determined by aerodynamic torque and adhesion torque. For the multilayer resuspension, particle deposition structures affect particle resuspension and produce additional effects including cohesion, shielding effects, coverage effects, restructuration and saltation, which complicates the resuspension process. The resuspension fraction, resuspension rate, and resuspension rate constant are used to describe the resuspension process quantitatively. In terms of physical force, the resuspension process usually depends on the forces from flow including drag, lift, Brownian force, and thermophoresis force, as well as the forces from walls or other particles including cohesion, van der Waals adhesion and friction. For a nuclear reactor system, wall forces acting on particles during the resuspension are more complicated due to the potential capillary force of condensate droplets (pressurized water reactor (PWR)) and the potential sintering force under the high-temperature condition (high-temperature gas-cooled reactor (HTGR)). To predict the resuspension process, scholars proposed various prediction methods including empirical formula, mechanism model (force/torque equilibrium model and energy accumulation model), and numerical simulation method. The empirical formula is only applicable to limited working conditions, the mechanism model may lack key parameters and result in uncertain accuracy, and numerical methods including computational fluid dynamics and the Monte Carlo method can consider more realistic physical processes, but the computational cost in engineering applications is enormous. Based on above principles and methods, the particle resuspension study in the field of nuclear reactors was reviewed in this paper. For PWRs, aerosol resuspension can be induced by continuous fluid flow under convection, transient fluid flow from hydrogen explosion, and bubbling of bubbles in the liquid phase. The resuspension caused by continuous fluid flow possesses the characteristics of long duration and wide occurrence region, which accounts for the main proportion of aerosol resuspension in PWR. For HTGRs, micron-scale graphite dust is the main radioactive carrier. Available reactor experimental data are only obtained from the AVR reactor. Existing research usually uses a combination of resuspension mechanism models and modeling tests to study its resuspension fraction and evaluate dust leakage under accidents. For fusion reactors, dust is mainly generated by the fragmentation of the co-deposited layers formed by plasma and walls. The experiment is usually conducted through a simplified device of the vacuum chamber. Existing experimental research mainly focuses on the influence of geometric parameters of the breach under LOVA (loss of vacuum accidents).

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

This study aims to differentiate bio-mediated and biogenic CO3-2 precipitation or terrestrial CO3-2 input using onboard incubation techniques, to investigate the effects of resuspension in the coastal environment and to increase our understanding of predicted relationships between silicate releases and other biogeochemical variables in resuspension events. Relationships between dark silicate flux and BSi, CO3-2, OrgC, Mn (manganese) according to the seasons were examined. The silica flux is controlled by the CaCO3 coating on the diatom skeletons due to the fact that diatom skeletons act as crystallization nuclei in the calcite precipitation that is biologically affected. The reduction in flux with BSi may be due to the reduction in the surface areas of larger diatom species. The negative linear relationships observed between silica fluxes and CO3-2 is indicative of RSi fluxes constrained by bio-mediated carbonate increase. Linear relationships which are the same in their slopes but differ in their intercepts, reveal the effect of the change in diatom size on silica flux. Smaller diatoms have more surface area per unit volume, meaning an increased silica flux. On the other hand, seeing different CO3-2 values at stations with the same orgC value have increased the confidence interval (CI) 95% in the linear relationship. The presence of different silica flux values in stations with the same carbonate value may be explained both by different orgC values and by diatoms containing different group sizes. The silica flux is controlled by the CaCO3 coating on the diatom skeletons due to the fact that diatom skeletons act as crystallization nuclei in the calcite precipitation that is biologically affected. The main mechanism controlling the reactive silica flux is carbonate precipitation. The observation of different silica flux values in stations with the same carbonate values can also be explained by OrgC. [ABSTRACT FROM AUTHOR]

Julian PJ II, Schafer T, Cohen MJ, Jones P, Osborne TZ. 2023. Changes in the spatial distribution of total phosphorus in sediment and water column of a shallow subtropical lake. Lake Reserv Manage. 39:213–230. In shallow lakes, interactions between bed sediment and the water column strongly influence the availability and transport of nutrients. Lake Okeechobee, in South Florida, is a eutrophic, shallow, polymictic lake that exhibits frequent mixing of the water column and resuspension of unconsolidated sediments. The objective of this study was to evaluate the temporal and spatial patterns of water and sediment characteristics and evaluate the linkage of sediment and water column total phosphorus (TP) concentrations. Spatiotemporal generalized additive models identified key periods during which both surface water total suspended solids (TSS) and TP increased, corresponding to hurricane and tropical storm activity. Our models identified regions with persistently greater water column concentrations than the lake average, indicating potential hot spots in resuspension processes and/or internal loading. Sediment bulk density (BD) and TP were inversely correlated, indicating that light, less dense sediments have greater TP concentrations, potentially contributing to the redistribution of sediments and P. An integrated evaluation of surface water and sediment characteristics using a generalized additive model revealed that sediment TP strongly influences water column TP concentrations, potentially explaining the spatial distribution of surface water TP concentrations. The area of the lake with sediment TP concentration ≤500 mg/kg is increasing while the low bulk density sediments area is decreasing, marking a potential improvement in sediment conditions. If this trend persists, it indicates that the lake is increasingly storing P in sediments that can resist entrainment, with significant implications for assessing the trajectory of lake restoration. [ABSTRACT FROM AUTHOR]

Many respiratory viruses, including influenza and SARS-CoV-2, are transmitted via the emission and inhalation of infectious respiratory aerosols in indoor environments. Resuspended particles from indoor surfaces and clothing can be a major source of airborne microbiological contaminants in indoor environments; however, it is unknown whether resuspended viruses contribute substantially to disease transmission. In this study, we investigated the resuspension via human walking activity of influenza A virus H3N2 laboratory strain, which was generated through a nebulizer into a sealed, unventilated biosafety level 2 (BSL-2) laboratory. The mean airborne viral concentrations following the resuspension events ( 3.7 × 10 3 viral RNA copies m − 3 ) were two orders of magnitude lower than those following direct emission via the nebulizer ( 1.1 × 10 5 viral RNA copies m − 3 ). The calculated resuspension emission factor (normalized ratio of the airborne mass to mass available for resuspension on the surface) of 10 − 3 was similar to reported values for 1–2 μ m particles. Thus, depending on the infectious dose and viability of the virus, resuspension of settled respiratory viruses could lead to transmission, but the risk appears to be much lower than for direct respiratory emissions. To our knowledge, this is the first full-scale experimental study designed to quantify virus resuspension. [ABSTRACT FROM AUTHOR]

Recent research applied the United States Environmental Protection Agency's Chemical Speciation Network and Interagency Monitoring of Protected Visual Environments monitoring stations and observed that mean concentrations of atmospheric lead (Pb) in highly segregated counties are a factor of 5 higher than in well‐integrated counties and argument is made that regulation of existing airborne Pb emissions will reduce children's Pb exposure. We argue that one of the main sources of children's current Pb exposure is from resuspension of legacy Pb in soil dust and that the racial disparity of Pb exposure is associated with Pb‐contaminated community soils. Plain Language Summary: Some researchers propose that current Pb emissions explain the continuing exposure problem of metals in the air. The implication is that new regulations on current emissions of metals in the air will curtail exposure. The focus here is on soil Pb and we propose that soils became Pb‐contaminated from massive amounts of leaded gasoline and the deterioration of exterior lead‐based paints which has burdened communities with a legacy of Pb‐contamination, especially within traffic‐congested inner‐city communities. Urban soil Pb mapping provides a clear understanding of the Pb contamination burden of various communities. Because of the invisibility of Pb dust in the air and the soil, city soil Pb mapping assists with visualizing the underrecognized issue, and the environmental racial justice issues of excessive Pb contamination affecting citizens' health living within various community environments. Key Points: Legacy sources of soil metal toxicants are underrecognizedSoil lead, blood lead, and Race are inextricably associatedEnvironmental inequities impact the disparities in racial health and life expectancy [ABSTRACT FROM AUTHOR]

Under nuclear reactor severe accidents, the resuspension of radioactive aerosol may occur in the containment due to the disturbing airflow generated by hydrogen combustion, hydrogen explosion and containment depressurization resulting in the increase of radioactive source term in the containment. In this paper, for containment conditions, by considering the contact between particle and rough deposition surface, the distribution of the distance between two contact points of particle and deposition surface, rolling and lifting separation mechanism, resuspension model based on random contact with rough surface (RRCR) is established. Subsequently, the detailed torque and force analysis is carried out, which indicates that particles are more easily resuspended by rolling under low disturbing airflow velocity. The simulation result is compared with the experimental result and the prediction of different simulation methods, the RRCR model shows equivalent and better predictive ability, which can be applicable for simulation of aerosol resuspension in containment during severe accident.

Optimization of technical parameters that influence the performance of human papillomavirus (HPV) testing on self-taken samples is important. Here, the authors assessed the impact of resuspension volume on the detection of HPV using four validated HPV assays. Two self-sampling devices, FLOQSwabs® and Evalyn® Brushes, were inoculated with dilutions of HPV-16-positive cell line, then resuspended in various volumes of ThinPrep. The influence of vortexing during resuspension was also assessed. At target concentrations around the assay cutoff, larger volumes led to decreased HPV detection. Interestingly, the effect(s) of vortexing differed by the self-sampling device. Resuspension in 5 ml or less may maximize the detection of HPV sequences. Using a proxy of clinical material, the current observations underline the importance of optimizing preanalytical laboratory processes to support high-quality HPV testing of self-samples.

One of the physical parameters used as an indicator of groundwater quality is turbidity. The high level of turbidity in community groundwater is a problem in Bandung Regency. The turbidity concentration of the highest order, namely Majalaya > Rancaekek > Ciparay > Baleendah > Soreang > Pacet > Pangalengan. The highest percentage of groundwater samples exceeding the maximum permissible limit was found in Rancaekek (88%), followed by Ciparay, Majalaya, Soreang, Baleendah, Pangalengan, and Pacet (87.50%, 81.48%, 73.91%, 62.5%, 55.56%, and 50%, respectively). 24.05% samples that exceeded the maximum permissible limit were used for hygiene, sanitation and drinking purposes. Turbidity level differed significantly based on differences in topography and soil type (p 0.05). In dug wells, turbidity has a significant negative correlation with depth (p

Abstract Recent research applied the United States Environmental Protection Agency's Chemical Speciation Network and Interagency Monitoring of Protected Visual Environments monitoring stations and observed that mean concentrations of atmospheric lead (Pb) in highly segregated counties are a factor of 5 higher than in well‐integrated counties and argument is made that regulation of existing airborne Pb emissions will reduce children's Pb exposure. We argue that one of the main sources of children's current Pb exposure is from resuspension of legacy Pb in soil dust and that the racial disparity of Pb exposure is associated with Pb‐contaminated community soils.

The binational Great Lakes Water Quality Agreement (GLWQA) revised Lake Erie's phosphorus (P) loading targets, including a 40% western and central basin total P (TP) load reduction from 2008 levels. Because the Detroit and Maumee River loads are roughly equal and contribute almost 90% of the TP load to the western basin and 54% to the whole lake, they have drawn significant policy attention. The Maumee is the primary driver of western basin harmful algal blooms, and the Detroit and Maumee rivers are key drivers of central basin hypoxia and overall western and central basin eutrophication. So, accurate estimates of those loads are particularly important. While daily measurements constrain Maumee load estimates, complex flows near the Detroit River mouth, along with varying Lake Erie water levels and corresponding back flows, make measurements there a questionable representation of loading conditions. Because of this, the Detroit River load is generally estimated by adding loads from Lake Huron to those from the watersheds of the St. Clair and Detroit rivers and Lake St. Clair. However, recent research showed the load from Lake Huron has been significantly underestimated. Herein, I compare different load estimates from Lake Huron and the Detroit River, justify revised higher loads from Lake Huron with a historical reconstruction, and discuss the implications for Lake Erie models and loading targets. [ABSTRACT FROM AUTHOR]

A complete annual cycle of the dynamics of fine-grained sediment supplied by the Omo and smaller rivers is simulated for Lake Turkana, one of the world's large lakes, with the hydrodynamic, wave and sediment transport model Delft3D. The model is forced with river liquid and solid discharge and wind data in order to simulate cohesive sediment transport and resuspension. It simulates stratification due to salinity, wave generation and dissipation, and sediment advection and resuspension by waves and currents, with multiple cohesive sediment fractions. A comparison of the simulation results with remotely-sensed imagery and with available in-situ sediment deposition rates validates the model. By devising simulation scenarios in which certain processes were switched on or off, we investigated the contribution of waves, wind-induced surface and bottom currents, salinity-induced stratification and river jet, in resuspending and transporting fine sediments in the lake basin. With only the wind or river influence, most of the sediment deposition occurs in the first 10 km off the Omo River mouth and at a depth < 10 m. When waves are switched on, increased bed shear stresses resuspend most of the fine sediments, that are then deposited further and deeper in the first 30 km, in water depths > 30 m. This study sheds new light on sediment transport in Lake Turkana and in great lakes in general, favouring the view that wind-waves can be the main agent that transports sediment away from river mouths and to deeper areas, as opposed to river-plume or gravity-driven transport. [ABSTRACT FROM AUTHOR]

One of the most important sources of aerosol production in a controlled space is the human. The flow around the individual and the particles on the garment play an essential role in aerosol distribution in the environment. Such spaces are simulated from a Lagrangian or Eulerian point of view. In this research, particle resuspension from a user’s garment under horizontal and vertical unidirectional systems was studied. For this purpose, a computer program was developed and used for examination of the impacts of different particle turbulence dispersion models, such as Discrete Random Walk, in a controlled space. Moreover, the effects of flow direction, velocity, and particle density on the probability of resuspension of particles with different diameters were investigated. The results demonstrated that the vertical unidirectional system had advantages over its horizontal variant, and that increased flow velocity provided positive feedback in the vertical system but negative feedback in the horizontal one. In the horizontal system, the resuspension probability for the sizes of 5 and 0.5 microns has increased by 177 and 355 percent, respectively, compared to the vertical system. It is worth noting that the results of the isotropic and non-isotropic models for particles size below 5 microns were quite the same. For the particles size over 5 microns, the maximum percentage discrepancy of 138 in resuspension probability between the non-isotropic and isotropic models is obtained.

Using what has become a celebrated catchphrase, Philip W. Anderson once wrote that "more is different" (Science, Vol. 177, Issue 4047, pp. 393–396, 1972). First formulated in the context of condensed matter, this statement carries far beyond the sole limits of solid-state physics. It emphasizes that collective behavior can be more than the mere sum of what happens for elementary constituents or the mere collation of the evolution of each degree of freedom. Said otherwise, complex phenomena can arise out of the interplay between multiple sub-phenomena each of which can be relatively simple. The process of particle resuspension, in which discrete particles adhering on a surface are pulled off and carried away by a fluid flow, is another example involving a web of phenomena pertaining to fluid mechanics, particle dynamics and interface chemistry whose cross-effects create an intricate topic. The purpose of this review is to analyze the physics at play in particle resuspension in order to bring insights into the rich complexity of this common but challenging concern. Following the more-is-different vision, this is performed by starting from a range of practical observations and experimental data. We then work our way through the investigation of the key mechanisms which play a role in the overall process. In turn, these mechanisms reveal an array of fundamental interactions, such as particle–fluid, particle–particle and particle–surface, whose combined effects create the tapestry of current applications. At the core of this analysis are descriptions of these physical phenomena and the different ways through which they are intertwined to build up various models used to provide quantitative assessment of particle resuspension. The physics of particle resuspension implies to hold together processes occurring at extremely different space and time scales and models are key in providing a single vehicle to lead us through such multiscale journeys. This raises questions on what makes up a model and one objective of the present work is to clarify the essence of a modeling approach. In spite of its ubiquitous nature, particle resuspension is still at the early stages of developments. Many extensions need to be worked out and revisiting the art of modeling is not a moot point. The need to consider more complex objects than small and spherical particles and, moreover, to come up with unified descriptions of mono- and multilayer resuspension put the emphasis on solid model foundations if we are to go beyond current limits. This is very much modeling in the making and new ideas are proposed to stimulate interest into this everyday but challenging issue in physics. [ABSTRACT FROM AUTHOR]

Background. Green areas are thought to reduce particulate matter (PM) concentrations in urban environments. Plants are the key to PM reduction via various mechanisms, although most mechanisms do not lead to the complete removal of PM. Ultimately, PM falls into the soil via wind and rainfall. However, the fallen PM can re-entrain the atmosphere, which can affect plants capacity to reduce PM. In this study, we simulated an urban green floor and measured the resuspension of PM from the surface using a new experimental system, a wind tunnel-mounted closed chamber. Methods. The developed system is capable of quantifying the resuspension rate at the millimeter scale, which is measured by using the 1 mm node chain. This is adequate for simulating in situ green floors, including fallen branches and leaves. This addressed limitations from previous studies which focused on micrometer-scale surfaces. In this study, the surfaces consisted of three types: bare sand soil, broadleaves, and coniferous leaves. The resuspended PM was measured using a light-scattering dust detector. Results. The resuspension rate was highest of 14.45x10-4 s-1 on broad-leaved surfaces and lowest on coniferous surfaces of 5.35x10-4 s-1 (p<0:05) and was not proportional to the millimeter-scale surface roughness measured by the roller chain method. This might be due to the lower roughness density of the broad-leaved surface, which can cause more turbulence for PM resuspension. Moreover, the size distribution of the resuspended PM indicated that the particles tended to agglomerate at 2.5 mm after resuspension. Conclusion. Our findings suggest that the management of fallen leaves on the urban green floor is important in controlling PM concentrations and that the coniferous floor is more effective than the broadleaved floor in reducing PM resuspension. Future studies using the new system can be expanded to derive PM management strategies by diversifying the PM types, surfaces, and atmospheric conditions. [ABSTRACT FROM AUTHOR]

Air pollution caused by particulate matter (PM) is a current problem in many cities. With the introduction of strict emission limits and electric cars, lower particle production is expected in the future. However, there are sources of particles that cannot be easily influenced. These include resuspension, where particles deposited on surfaces re-enter the air, causing pollution multiple times. Resuspension can account for up to 18% of the total emissions in some cases. The present paper focuses on the use of the computational fluid dynamics (CFD) tools to describe the flow in a street canyon where resuspension by wind occurs. Based on the calculated flow, a resuspension model is applied to see where resuspension occurs and how far the particles can travel. The shear stresses on the surfaces and the character of the flow field in the boundary layer are evaluated. Different building configurations and flow parameters are tested using a simple 2D model. The model makes it possible to see in which parts of the street canyon resuspension can occur. It shows that the particles leave the street canyon only from the surfaces where the conditions are suitable for resuspension. These particles then enter the mainstream. However, most of the particles stay in the canyon, which can cause resuspension to pollute the air repeatedly. This effect can have a severe impact on human health. The total dispersion of particles in the urban environment is evaluated. The results may be useful for cities that clean the streets, as it is clear which areas will benefit most from the cleaning. [ABSTRACT FROM AUTHOR]

In this paper, a physics-based model for dust accumulation on the front and rear surfaces of a bifacial module is presented. The accumulation on both the surfaces is assessed considering deposition, rebound and resuspension phenomena. The lift-off phenomenon of dust particle from ground is included additionally for the rear surface. This composite model is utilized to estimate soiling on both sides, which is extended to analytically assess the energy loss of the bifacial module. Experimentation has been carried out in four phases on a 10 kWp rooftop solar PV power plant. In the first phase, result shows soiling is less on glass than on the transparent back sheet-based rear surface. In the second phase, it is observed that surface density of dust on back surface for 34 days is 0.08 g/m2, for 79 days 0.6 g/m2 and for 126 days 1.8 g/m2 which are deviated from model based calculated ones by 10%, 33.33% and 4.4% respectively. The surface density of dust accumulated on the glass-based rear surface is about (1/6)th of the front glass surface, which is validated by the model also. The measured transmittance reduction is 3.2% for the back glass substrate and 29.6% for the front glass without manual cleaning for the test period. The model leads to the interesting result that the average energy generation loss for the bifacial plant is 1.4%/day compared to 1.7%/day for the monofacial plant since the generation enhancement from the rear surface more than compensates for the soiling loss from the back surface.

In this study, a 2D segregation-dispersion model has been used to study the effect of shear induced lift on elutriation within a Reflux Classifier under continuous process conditions. The Reflux Classifier is a beneficiating technology comprising a fluidized bed with a set of parallel inclined channels above it. A 2D segregation-dispersion model of the device was utilized to study the mechanism of shear induced lift introduced as a contribution to the dispersion in the x-direction within the inclined channel. A multi-solid feed, 42 types of particle species having different densities and sizes, was simulated. It was observed that due to the shear induced lift, a phenomenon of particle resuspension occurred causing relatively higher solid volume fractions in the middle zone of the inclined channel. This happened because the coarse low-density particles experienced a higher shear induced lift and their concentration increased toward the middle zone. These coarse low-density particles and fine low-density particles moved out from the system via the overflow. Whereas, the fine dense particles experienced a low shear induced lift, hence, settled, slide backward, and discharged in the underflow. The lower Ep values ranging from 0.03 to 0.05 were obtained showing an improved separation performance. [ABSTRACT FROM AUTHOR]

Nanoparticles have proven to be effective in sensible and latent heat exchanges alike. Applications of nanoparticles in phase change processes are associated with migration and resuspension of nanoparticles upon which our existing knowledge is very limited. This work experimentally investigates the migration ratio, stability and resuspension of nanoparticles during phase change. Knowledge on migration ratio is essential to gauge the thermal and lubricative enhancements in the subsequent processes. Al2O3/Water & CuO/Water nanofluids were prepared in four mass fractions (0.05, 0.1, 0.2, 0.4) using ultrasonic agitation technique. Nanofluids with mass fraction higher than 0.5% displayed poor stability over time also, agglomeration and sedimentation were pronounced and inevitable. Nanofluid destabilises and agglomerates rapidly at temperatures closer to saturation temperature. Resuspension of agglomerated chunks were observed during nucleate boiling where the test fluid became extremely nonhomogeneous. Migration ratio was found to commensurate with volume fraction where CuO/water nanofluid exhibited 23% lesser migration ratio than Al2O3/water nanofluid. Maximum migration ratio of 17.8% was observed for Al2O3/water with 0.05 wt%. Maximum migration was found when the molecular dimensions of nanoparticles and the base fluid are of similar magnitudes. It is inadvisable to involve nanoparticles in phase change systems. [ABSTRACT FROM AUTHOR]

As the next step that occurred more than one decade after the accident at the Fukushima Dai‐ichi Nuclear Power Station (FDNPS), decontamination and demolition have been carried out in the Specified Reconstruction and Revitalization Base (SRRB) of the difficult‐to‐return zone around the FDNPS. However, the risk of internal exposure among workers due to airborne dust inhalation after building demolition operations has not been sufficiently evaluated. To evaluate the working environment and internal exposure risk due to inhalation in the SRRB of Tomioka town, Fukushima Prefecture, the cesium‐137 (137Cs) radioactivity levels in the airborne dust at building demolition sites were analyzed using gamma spectrometry. The 137Cs radioactivity levels and resuspension factors of the airborne dust at the subject building sites in the difficult‐to‐return zone remained at high levels compared with those of the control, which was located in the evacuation order‐lifted area in Tomioka town. However, the 137Cs radioactivity levels did not increase significantly, despite demolition operations that used heavy machinery. In this case, no substantial increases in accident‐derived 137Cs levels due to decontamination and demolition in the SRRB of Tomioka town, Fukushima Prefecture, were observed in the airborne dust samples, which suggests that the 137Cs radioactivity in the airborne dust is primarily associated with particles that are resuspended by localized winds accompanied by the transfer of construction vehicles as opposed to the decontamination and demolition operations. However, the internal exposure doses due to aspirating airborne dust containing 137Cs were extremely low compared with the estimated annual effective doses of decontamination workers or the limits recommended by the Japanese government. Additionally, countermeasures such as wearing protective masks could help reduce the on‐site inhalation of soil‐derived radionuclides. Integr Environ Assess Manag 2022;18:1555–1563. © 2022 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC). Key points: No substantial increase in accident‐derived 137Cs due to demolition in areas close to the Fukushima Dai‐ichi Nuclear Power Station was observed in the airborne dust.137Cs radioactivity in the airborne dust is primarily associated with particles resuspended by localized wind accompanied by transfer of construction vehicles. [ABSTRACT FROM AUTHOR]

Abstract The deposition of insoluble radiocesium-bearing microparticles (CsMPs), which were released from the Fukushima Daiichi Nuclear Power Plant (F1NPP) accident in March 2011, has resulted in the widespread contamination of eastern Japan. Obviously, these deposited insoluble CsMPs may become the secondary contamination sources by atmospheric migration or other environmental transferring process; however, the understanding of the transport mechanism remains non-elucidation, and the relevant evidence has not been directly provided. This study, for the first time, provides the direct evidence for the resuspension of these insoluble CsMPs to the atmosphere from (1) proximity of 137Cs radioactivity and resemblance of the morphology and the elemental compositions of CsMPs in the samples of soil and aerosol derived from the same sampling site, (2) the special characteristics of the resuspended CsMPs of which the ratios of Na/Si, K/Si and/or Cs/Si were smaller than those from the initially released CsMPs collected at either long distance or near F1NPP, which can be ascribed to the slowly natural corrosion of CsMPs by the loss of the small amount of soluble contents in CsMPs, and (3) high CsMPs concentration of 10 granules/g in the surface soil of our sampling site and high resuspension frequency of CsMPs in spring when predominant suspended particles were soil dust. Specifically, 15 single CsMPs were successfully isolated from the aerosol filters collected by unmanned high-volume air samplers at a severely polluted area in Fukushima Prefecture, about 25 km away from F1NPP, from January 2015 to September 2019. The mean diameter of these CsMPs was 1.8 ± 0.5 μm, and the average 137Cs radioactivity was 0.35 ± 0.23 Bq/granule. The contribution rate of the resuspended CsMPs to the atmospheric radiocesium was estimated from the ratio of 137Cs radioactivity of a single CsMP to that of the aerosol filter to be of 23.9 ± 15.3%. There has been no considerable decreasing trend in the annual CsMP resuspension frequency.

Particulate air pollution is a major environmental problem. One of the main sources of particulate matter is the circulation of vehicles on unpaved roads. On these roads, the current techniques used to limit particle flight are either expensive, environmentally harmful, or resource-intensive. Therefore, the search for inexpensive and effective methods to reduce dust emissions on unpaved roads is crucial. This study focuses on assessing the impacts of driving speed and mudflap types on particle resuspension in the wake of a passenger vehicle traveling on a dust-contaminated road. To this end, fixed and mobile measurements are taken simultaneously to assess particle dispersion after each vehicle passage. The results show that driving at 30 km/h without a mudflap is the best configuration to reduce particle resuspension, while the use of a long transverse mudflap is the worst solution. The results also show that wheels are the main source of particle emissions. • Evaluating low-cost devices for monitoring particulate emissions on unpaved roads. • Proposing inexpensive solutions to reduce particulate emissions. • Identifying the determinants of particle flight associated with vehicle dynamics. • Determining the characteristics of deposits on the road surface. • Describing the changes in emission granulometry. [ABSTRACT FROM AUTHOR]

This study investigates the role of particle shape on the aerodynamic resuspension process of irregular flat micro-particles on a substrate. We propose that these particles resuspend at higher velocities than spherical ones of the same size under the same aerodynamic forces. Two sets of data are analyzed to test the argument, the first from experiments we conducted using crushed glass particles (ranging from 80 μm to 300 μm) and the second from published data on RDX explosive residue particles (sized between 10 μm and 25 μm) published previously. We particularly analyze the shape factors of the particles used in the experiments and introduce them into a Monte Carlo (MC) simulation model. The probabilities for the time evolution of the resuspension process are calculated through a Markov chain of states. The transition probabilities entail the balance between the forces and moments involved in the mechanisms for particle detachment from the surface. The particle resuspension rate as a function of the fluid velocity is evaluated both experimental and numerically. Additionally, we assess the removal efficiency for different particle size ranges whenever possible. Both experimental and numerical results demonstrate that the resuspension fraction of irregular flat particles is significantly lower than for equally sized glass microspheres under the same conditions. Simulations corroborate previous experimental findings, indicating that smaller irregular particles exhibit higher removal efficiency. According to the MC model results, irregular particles detach by sliding rather than rolling. [Display omitted] • Experimental and numerical study on the resuspension of irregular particles. • Microspheres resuspend more easily than irregular particles under same conditions. • Effect of particle aspect ratio on removal efficiency. • Assessment of the importance of detachment mechanisms depending on particle shape. [ABSTRACT FROM AUTHOR]

This study, based on five years of monthly in situ data collected from 2018 to 2022, examines the seasonal and interannual fluctuations of suspended particulate matter (SPM) concentration in Nokoué Lagoon, Benin. Seasonally, SPM exhibits significant variations primarily influenced by changes in river discharge. During low-flow periods (December to May), SPM concentrations are relatively low (<15 mg L-1) throughout the lagoon. During this time, slight temporal variations are correlated with wind energy and likely associated with wind-induced resuspension of sediments. This is confirmed by slightly higher concentrations of SPM in the bottom layers compared to the surface. Resuspension appears to be lower in the west than in the east, likely due to the increased presence of acadjas (brush parks) in the west, reducing fetch and wind intensity, thus decreasing resuspension. At the onset of the river flood period (July–August), associated with the West African monsoon, increased river flow generates a significant turbid plume extending from the northeast of the lagoon to the Cotonou channel, connecting the lagoon to the Atlantic Ocean. SPM levels then increase considerably (>100 mg L−1), with a pronounced SPM gradient from the western to eastern regions of the lagoon. The less dense freshwater laden with sediment from the rivers flows over the denser saline water of the lagoon, leading to slightly higher SPM concentrations in the surface layers. Between September and November, SPM concentration gradually decreases as river flows reach their peak values. Thus, on a seasonal scale, the relationships between SPM and river discharge show a temporal lag, resulting in a clockwise hysteresis cycle. This is explained by the early mobilization of fine sediments during rising river flows, followed by reduced sediment availability and dilution effects as the flood peaks. On an interannual scale, SPM variations are relatively low with slight temporal shifts observed in the formation and expansion of the turbid plume and peak SPM levels. The total SPM mass in the lagoon ranges from 0.2 to 0.3 × 104 tonnes during low-flow periods to 20-30 × 104 tonnes at the onset of flooding. We also discuss uncertainties associated with SPM determination, estimated at approximately 5–15%. This study leverages a unique database in West Africa and provides valuable insights into the hydro-sedimentary dynamics of Nokoué Lagoon. • Nokoué Lagoon is characterized by strong seasonal variability in SPM. • River flows primarily drive the seasonal variability of SPM. • Wind influences SPM concentration during low-water periods. • A turbid plume of high SPM, with inorganic matter, extends in the eastern lagoon. • SPM in the western lagoon is organic matter-dominated and relatively weaker. [ABSTRACT FROM AUTHOR]

The deposition of graphite dust poses significant challenges to the helium turbines in high-temperature gas-cooled reactors. In this study, FLUENT, a Computational Fluid Dynamics (CFD) program was used with a discrete-phase model and a random-walk model to calculate the trajectories of particles (assumed spherical). Considering the interactions between particles and the wall as well as the resuspension effect of the fluid, a particle-deposition model was established and coupled to the flow-field calculations of blades with film cooling using user-defined functions. The influence of different deposition models, particle diameters, and blowing ratios on deposition were investigated. The results show rebounding and resuspending particles significantly affect the particle-deposition rate and its distribution. With increasing particle diameter, the deposition rate initially increases and then decreases. The influence of blowing ratio on deposition is complex; as the blowing ratio is increased, the deposition rate of small particles increases, while that of large particles decreases. [Display omitted] • The motion of graphite dust in helium turbines has been studied. • The deposition and resuspension of particles on the turbine wall are investigated. • The coupling effect of film cooling and graphite dust motion is considered. [ABSTRACT FROM AUTHOR]

Intertidal flats are important shallow-water habitats and buffers against coastal erosion. Strong, short-lasting meteorological events, such as storms and rainfall, are the main mechanisms of transporting (in)organic materials and sediments. Two in-situ mooring systems were installed simultaneously in the tidal channel and mudflat of Jeungdo, Korea, to understand the dynamic behaviors of suspended sediment and chlorophyll- a (chl- a) under the episodic events. During fair-weather periods with a distinct tidal cycle, the sediment in the mudflat was resuspended during the flood and then advected to the tidal channel during the ebb. The maximum suspended sediment concentration (SSC) and chl- a under storm event were approximately 9 and 2 times higher than those under fair-weather periods, respectively. Under rainfall event, the maxima were approximately 7 and 1.2 times higher than fair-weather, suggesting that sediment and microphytobenthos were highest resuspended by the meteorological events. In addition, a time lag (∼ 1.5 h) between SSC and chl- a occurred in the tidal channel during ebb tide with a rainfall event. During the post-rainfall periods, the SSC and chl- a increased, showing a positive relationship with the bed shear stress, suggesting that the rainfall event could reduce sediment stabilization. • We examined sediment and microphytobenthos dynamics during storm and rainfall events. • Episodic meteorological events influenced the redistributing sediment and chl- a. • The (de)coupling and resuspension time-lag between sediment and chl- a are evidenced. • Rainfall could reduce the stabilization of sediment and microphytobenthos. [ABSTRACT FROM AUTHOR]

The resuspension of phosphorus (P) in sediments has the most significant contribution to the overlying water. The PP release characterization during resuspension was investigated. The results indicated that the P in suspensions had more release risk compared to the sediments. The particulate P (PP) concentration (0.54 mg L−1) under high-intensity rotational speed (250 rad min−1) was about five times higher than others (0.11 mg L−1). The sorption parameters of zero equilibrium P concentration (EPC 0F) and soluble reactive P (SRP) were significantly correlated with each other (p < 0.01, r = 0.73). Suspended solids expressed stronger P source than sediments. The values of EPC 0F was highly significantly correlated with the sorption coefficient (K F) and native adsorbed P (NAP) (p < 0.01). The mean values of NAP were 0.0612 mg g−1 and 0.0604 mg g−1 in the Prophase and Metaphase, respectively, and 0.0586 mg g−1 at Anaphase. The values of P sorption index (PSI) ranged from 0.4359 to 0.6862 L g−1, with mean values of 0.5350 L g−1 (Prophase), 0.6061 L g−1 (Metaphase), and 0.4967 L g−1 (Anaphase). The degree of P saturation (DPS) decreased in the order of Anaphase (2.73%) > Prophase (2.53%) > Metaphase (2.12%). The release risk index of P (ERI) decreased in the order of Anaphase (5.47%) > Prophase (4.72%) > Metaphase (3.59%), with a range of 2.12%–8.56%. To fast and slow scale, the results of NaOH–P (V 1 <0, V 2 >0) contribution indicated that the persistent disturbance promoted the release of adsorbed dissolved PP from NaOH–P in suspended sediment to the overlying water. The contribution of HCl–P (V 2 > 0) was positive in the Anaphase of the slow scale, and HCl–P was a PP source in the frequently disturbing conditions. [Display omitted] • The effect of disturbance promotes the formation of PP. • As The disturbance continued, Calcium–Phosphorus (HCl–P) gradually dominated in the resuspension process. • The suspended solids served as a strong phosphorus "source" in the resuspension process. [ABSTRACT FROM AUTHOR]

Many respiratory viruses, including influenza and SARS-CoV-2, are transmitted via the emission and inhalation of infectious respiratory aerosols in indoor environments. Resuspended particles from indoor surfaces and clothing can be a major source of airborne microbiological contaminants in indoor environments; however, it is unknown whether resuspended viruses contribute substantially to disease transmission. In this study, we investigated the resuspension via human walking activity of influenza A virus H3N2 laboratory strain, which was generated through a nebulizer into a sealed, unventilated biosafety level 2 (BSL-2) laboratory. The mean airborne viral concentrations following the resuspension events (3.7×103 viral RNA copies m−3) were two orders of magnitude lower than those following direct emission via the nebulizer (1.1×105 viral RNA copies m−3). The calculated resuspension emission factor (normalized ratio of the airborne mass to mass available for resuspension on the surface) of 10−3 was similar to reported values for 1–2 μm particles. Thus, depending on the infectious dose and viability of the virus, resuspension of settled respiratory viruses could lead to transmission, but the risk appears to be much lower than for direct respiratory emissions. To our knowledge, this is the first full-scale experimental study designed to quantify virus resuspension.

Strong evidence suggests that clothing serves as a reservoir of chemical pollutants and particles, including bioaerosols, which may have health significance. However, little is known about the role that clothing may play as a transport vector for inhaled airborne particles. Here, we contribute toward bridging the knowledge gap by conducting experiments to investigate clothing release fraction (CRF), determined as the size-dependent ratio of released to deposited particulate matter in the diameter range 0.5-10 μm. In a fully controlled chamber with low background particle levels, we deployed a programmable robot to reproducibly quantify the size-dependent CRF as a function of motion type and intensity, dust loadings, and activity duration. On average, 0.3%-3% of deposited particles were subsequently released with fabric motion, confirming that clothing can act as a vehicle for transporting airborne particles. The CRF increased with the vigor of movement and with dust loading. Rubbing and shaking the fabric were more effective than fabric stretching in resuspending particles. We also found that most of the release happened quickly after the onset of the resuspension activity. Particle size substantially influenced the CRF, with larger particles exhibiting higher values.

Abstract Respiratory pathogens transmit primarily through particles such as droplets and aerosols. Although often overlooked, the resuspension of settled droplets is also a key facilitator of disease transmission. In this review, we discuss the three main mechanisms of aerosol generation: direct generation such as coughing and sneezing, indirect generation such as medical procedures, and resuspension of settled droplets and aerosols. The size of particles and environmental factors influence their airborne lifetime and ability to cause infection. Specifically, humidity and temperature are key factors controlling the evaporation of suspended droplets, consequently affecting the duration in which particles remain airborne. We also suggest material‐based approaches for effective prevention of disease transmission. These approaches include electrostatically charged virucidal agents and surface coatings, which have been shown to be highly effective in deactivating and reducing resuspension of pathogen‐laden aerosols.

We examined drivers of water quality during 2007–2013 in a region of Lake Ontario influenced by various anthropogenic inputs and natural influences. Nutrient concentrations generally declined from shoreline to offshore, with mean concentrations approaching background after 1 km from shore. N species were an exception to this overall pattern, often with higher concentrations coincident with a mid-nearshore Water Pollution Control Plant outfall (WPCPo). The WPCPo, however, did not appear to be a major contributor to shoreline total phosphorus (TP) or ammonia + ammonium. Shoreline TP variability increased in dry years, while E. coli and conductivity variability increased in wet years. The influence of environmental drivers on water quality differed seasonally. In summer, cross-shore winds causing resuspension appeared to be drivers of elevated nearshore TP and suspended solids (SS), while precipitation, light, and water column stability were related to E. coli. Summer biological activity was evident in higher shoreline total Kjeldhal N contributions and lower NO 3 + NO 2 and dissolved inorganic N. In fall and spring, TP, SS, and conductivity were elevated within 400 m of the shore, suggesting tributary inputs were an important P delivery mechanism to the nearshore in addition to spring resuspension events. Fall, however, represented a transitional period representing a shift from drivers dominant in summer to those in spring. The analytical approach used here reveals generalizable patterns in nearshore water quality and their drivers and may be applicable to other regions where there is a confluence of varying drivers of water quality to a nearshore region. [ABSTRACT FROM AUTHOR]

This study performed a series of experiments to study the characteristics of human-induced particle resuspension under different ventilation conditions. Four modes of supplied airspeed were evaluated: no wind, low wind (2.742 m/s), medium wind (3.849 m/s) and high wind (4.422 m/s). Results show that the steady-state particle concentration can be approximated as a linear function of the airspeed. Human walking and ventilation conditions can have a significant and coupling role in particle behaviours. In particular, human walking provides initial energy for resuspension by disturbing the local fields, and thus increases the resuspension, especially for large particles of 5–10 μm in size. The wind has two competitive effects, that is, supplying energy to keep particles suspended and pushing the particles downward, and the latter becomes dominant when the airspeed was too high. Consequently, intermediate airspeeds can intensify the effect of human walking, and introduce higher peaks of particle concentration in the human-walking stages. As for the particle number density, similar conclusions can be drawn that the effect of ventilation conditions is more pronounced on small particles less than 1 μm while that of human walking is on large particles. This work lays a foundation for revealing the particle resuspension mechanism. [ABSTRACT FROM AUTHOR]

Rich ecosystems such as estuaries and brackish lakes are vulnerable to the effects of human activities and are prone to environmental changes. In particular, the salt environment, which is the backbone of the environment, might be affected not only by direct modifications such as dredging but also in ways that were not initially envisioned. Ichkeul Lake, located in the northern part of Tunisia, is a shallow brackish lake registered as a UNESCO World Natural Heritage Site. The construction of reservoirs upstream of the inflowing river in the 1980s reduced the amount of freshwater inflow. That only had been thought to be the cause of the increase in salinity in Ishkeul Lake. On the other hand, the sedimentation in the reservoirs upstream was remarkable, and the supply of sediment from the reservoirs upstream to the Ichkeul Lake was stopped. Changes in sediment outflow may have reduced lakebed altitude and enhanced seawater intrusion. However, the environmental protection measures for the lake so far have focused only on improving the water budget and have not been quantitatively evaluated for sediment transportation. In this study, we first estimated the water budget of the lake. Then the re-suspension by wind disturbance in the lake was estimated from the correlation with the wind speed based on laboratory experiments and field measurements. The outflow of the sediment estimated with these two models was compared with the sediment volume trapped in the upstream reservoirs that would have flowed into the lake if there had been no construction of the dams. Based on this, we evaluated whether the lake is currently erosive or cumulative. As a result, the estimated annual outflow of sediment to the sea was 4300 tons/year. It was estimated that the construction of the reservoirs upstream changed the trend of lakebed height from accumulation to erosion. [ABSTRACT FROM AUTHOR]

Understanding the dynamics of radiocesium, including dissolved radiocesium with high bioavailability, in irrigation reservoirs located in nuclear disaster-affected areas is crucial. In this study, we estimated the 137Cs supply flux from an irrigation reservoir managed at low water levels by examining the inflow and outflow water quality mainly under average flow conditions. The results showed that the annual supply fluxes of total 137Cs, suspended 137Cs, and dissolved 137Cs were positive, indicating that the reservoir acted as a source of 137Cs. The source of 137Cs from the reservoir was considered to be the sediment, with suspended 137Cs due to resuspension and dissolved 137Cs due to desorption. The dissolved 137Cs activity concentration in the outflow water was positively correlated with the water temperature, suggesting that the desorption of dissolved 137Cs from the sediment can be attributed to the exchange with cations such as NH4+ generated by biological activities. The dissolved 137Cs activity concentration in the outflow water was equal to that in the inflow water in winter and exhibited seasonal variation with an increasing trend in summer. Furthermore, the carriers of suspended 137Cs in the outflow water were considered to be fine mineral soil particles including clay, along with organic matter. Therefore, the removal of bottom sediments with high 137Cs concentrations in reservoirs with low water levels would contribute to reducing the runoff of radiocesium, effectively restore freshwater resources, and allow for the resumption of agricultural water use. [ABSTRACT FROM AUTHOR]

Microplastics are increasingly recognised as posing a significant environmental threat across systems. Their pervasive presence in freshwater poses a serious concern, given the heavy reliance of both humans and biodiversity on healthy, functioning freshwater ecosystems. Acknowledgment of the potential risks led the transboundary Orange-Senqu River Commission (ORASECOM) to include sampling for microlitter (primarily microplastics) in riverine sediment, surface water, and fishes, across Southern Africa as part of the third Joint Basin Survey (JBS3) in 2021. The aim was to establish a first, basin-wide estimate of microlitter contamination across compartments, setting a baseline for further monitoring. The survey showed that the abundance of microlitter in riverine sediment (0 - 4000 particles.kg -1 dry weight (dw)) and riverine water (1.00 ± 0.71 - 69.75 ± 68.55 SD items.L -1 ) varied considerably between sample sites, with no correlation between the two. The abundance of microlitter in fishes was low (average of 0.7 ± 0.4 items.individual -1 ). Course resolution analyses suggested that microlitter concentrations in riverine sediment and riverine water at each site did not correlate with land use directly upstream, though variation in microlitter abundance did isolate some hotspots of contamination. Discharge data collected from nine gauging stations near sampling sites confirmed that low flows prevailed in the system during the study, with high flows occurring approximately 5 months prior during the summer months. There is some variation in river flow across the catchment which is a likely driver of microlitter transport. This was evident in the polymer composition for sediment and water samples. Based on the average discharge at each gauging station and microlitter concentrations measured in riverine water, the estimated microlitter load ranged from ∼889 particles.s -1 to ∼17.9 million particles.s -1 , with a substantial amount ending likely up in the mudbelt adjacent to the Orange River mouth. This assessment provides a first insight into the characterisation and distribution of microlitter in multiple compartments across the Orange-Senqu River basin. Overall, the findings highlight the need for continued monitoring across compartments at catchment scales to improve our understanding of microplastic pathways into and within riverine systems., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

To improve the understating of viral pathogens' resuspension from bed sediment and their attachment to suspended sediment, a series of flume experiments using a coliphage surrogate, PhiX174, were conducted with two sediments: sand and sandy loam. Using this data, a conceptual model was developed that quantifies the resuspension rate using a dynamic virus-sediment attachment ratio. The resuspension flux was calculated as the product of virus concentrations in bed sediment and the resuspension velocity. Two resuspension models were derived for the sediments with and without cohesive material. The resulting models correlated nondimensional bed shear stress with the virus concentration in the water. Predictions of the models satisfactorily matched the observed virus concentration. The results shed light on the underlying physics of the attachment of virus to sediment. The attachment ratio increases with bed shear stress until reaching the critical shear stress, and then decreases with a further increase of bed shear stress. Moreover, the virus reverses its attachment to sediment particles after reaching the critical condition for sediment incipient motion. The conceptual model as well as the experimental data shed light on the key processes governing the fate and transport of viral pathogens in sediment laden flow. [ABSTRACT FROM AUTHOR]

Thin‐layer capping using activated carbon has been described as a cost‐effective in situ sediment remediation method for organic contaminants. We compared the capping efficiency of powdered activated carbon (PAC) against granular activated carbon (GAC) using contaminated sediment from Oskarshamn harbor, Sweden. The effects of resuspension on contaminant retention and cap integrity were also studied. Intact sediment cores were collected from the outer harbor and brought to the laboratory. Three thin‐layer caps, consisting of PAC or GAC mixed with clay or clay only, were added to the sediment surface. Resuspension was created using a motor‐driven paddle to simulate propeller wash from ship traffic. Passive samplers were placed in the sediment and in the water column to measure the sediment‐to‐water release of polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and metals. Our results show that a thin‐layer cap with PAC reduced sediment‐to‐water fluxes of PCBs by 57% under static conditions and 91% under resuspension. Thin‐layer capping with GAC was less effective than PAC but reduced fluxes of high–molecular weight PAHs. Thin‐layer capping with activated carbon was less effective at retaining metals, except for Cd, the release of which was significantly reduced by PAC. Resuspension generally decreased water concentrations of dissolved cationic metals, perhaps because of sorption to suspended sediment particles. Sediment resuspension in treatments without capping increased fluxes of PCBs with log octanol–water partitioning coefficient (KOW) > 7 and PAHs with log KOW of 5–6, but resuspension reduced PCB and PAH fluxes through the PAC thin‐layer cap. Overall, PAC performed better than GAC, but adverse effects on the benthic community and transport of PAC to nontarget areas are drawbacks that favor the use of GAC. Environ Toxicol Chem 2022;41:1096–1110. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC. [ABSTRACT FROM AUTHOR]