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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]

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]

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]

Lanthanum modified bentonite (LMB) is typical P-inactivating agent that has been applied in over 200 lakes. Dissolved organic carbon (DOC) and high pH restrict the phosphorus (P) immobilization performance of LMB. However, the P immobilization/release behaviors of LMB-amended sediment when suspended to overlying water with high pH and DOC have not yet been studied. In the present work, batch adsorption and long-term incubation experiments were performed to study the combined effects of pH and DOC on the P control by LMB. The results showed that the coexistence of low concentration of DOC or preloading with some DOC had a negligible effect on P binding by LMB. In the presence of DOC, the P adsorption was more pronounced at pH 7.5 and was measurably less at pH 9.5. Additionally, the pH value was the key factor that decided the P removal at low DOC concentration. The increase in pH and DOC could significantly promote the release of sediment P with a higher EPC 0. Under such condition, a higher LMB dosage was needed to effectively control the P releasing from sediment. In sediment/water system with intermittent resuspension, the alkaline conditions greatly facilitated the release of sediment P and DOC, which increased from 0.087 to 0.581 mg/L, and from 11.05 to 26.56 mg/L, respectively. Under the dual effect of pH and DOC, the P-immobilization performance of LMB was weakened, and a tailor-made scheme became essential for determining the optimum dosage. The desorption experiments verified that the previously loaded phosphorus on LMB was hard to be released even under high pH and DOC conditions, with an accumulative desorption rate of less than 2%. Accordingly, to achieve the best P controlling efficiency, the application strategies depending on LMB should avoid the high DOC loading period such as the rainy season and algal blooms. [Display omitted] • PH value was the key factor that decided the P removal efficiency at low DOC concentration. • The rising in pH and DOC could significantly promote the P release from sediment. • Under the dual effect of pH and DOC, the P-immobilization performance of LMB was weakened. • The P desorption rate on P-loaded LMB was lower than 2% even in algae blooms. [ABSTRACT FROM AUTHOR]

Freshwater ecosystems are viewed as a key medium for the transport of land-based plastics into oceans. Microplastic (MP) particles in freshwater environments demonstrate high persistence and an extensive range of size and shape distributions, which make their mobility, distribution, and fate vary distinctly depending on the prevailing environmental conditions. The inherent physical properties of different plastic polymers are constantly evolving at different specific reaction rates due to the complex weathering processes in the environment. This continuously alters the underlying mechanisms governing MP dynamics and further complicates their ultimate fate in natural aquatic systems. This paper conducts a comprehensive review of the dynamic behaviour of MPs in freshwater ecosystems, focusing on investigating the settling, aggregation, retention, and suspension processes governing their transport from the source to the sink. We provide an in-depth overview of the key theoretical foundations of MP behaviour in ambient flows and the key influential factors (i.e. size, density, shape, composition). Our findings highlight intricate interplays between MP dynamic behaviours and local hydrodynamics and water chemistry, which lead to the continuous evolution of MP physicochemical properties (e.g., size, surface charge) through interactions with suspended solids, organic natural matter, and microorganisms under light and wind exposure. This dynamic poses significant challenges in predicting MP transport processes and ultimate fate. Gap analysis highlights the discrepancy between current models based on controlled laboratory conditions and complex natural environments, signifying the need for investigating MP dynamic behaviour across a wide range of environmental conditions (e.g. simulating complex flow patterns and solution chemistries of real water bodies). Further research is needed to expand field studies to correlate environment hydrodynamics with MP abundance and to conduct mesoscale experiments that accurately reflect the effects of weathering and flow hydrodynamics on MP behaviours. Integrating detailed physical experiments with numerical modelling tools is essential for a comprehensive understanding of the interactions among various MPs and their overall impact on the environment. This facilitates robust and reliable environmental risk assessment for MP control and pollution management. Key dynamic process affecting the fate of microplastics in freshwater systems. [Display omitted] [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]

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. [ABSTRACT FROM AUTHOR]

Aim: Aortic dissections emerge as severe pathologies reqiuring early diagnosis and immediate surgical intervention is mandatory in acute Type A aortic dissection, however, there are still controversies regarding the appropriate approach. The present study aims to demonstrate the effects of valve resuspension with supracoronary tube graft replacement on aortic valve insufficency in acute Type A aortic dissection. Material and Methods: The study was conducted on 108 patients who had supracoronary aortic replacement with suspension for acute Type A aortic dissection and discharged from the hospital with cure between January 1997 and January 2014. The patients were evaluated for aortic valve function by transthoracic echocardiography at the postoperative 6th and 12th months. Results: Gender distribution was 31 (29%) females and 77 (71%) males, their mean age being 53.24 ±11,3 years old. In the present study, valve function measured with preoperative and postoperative 6th and 12th months transthoracic echo revealed a significant decrease in terms of aortic valve insufficiency. After surgery, no patient required a reoperation for valve insufficency within the 1st year. Conclusion: All these have demonstrated that in the treatment of acute Type A aortic dissection, aortic insufficiency is not a restrictive factor for chosing the resuspension with supracoronary tube graft replacement method in patients without any organic disease of the aortic valve and root aneursym and in whom the rupture is not progressing proximally to affect coronary entries. By using the this method aortic dissections can treated with good results while native valve preserved. [ABSTRACT FROM AUTHOR]

The resuspension of sediment leads to an increased release of nutrients and organic substances into the overlying water column, which can have a negative effect on the oxygen budget. Especially in the warmer months with a lower oxygen saturation and higher biological activity, the oxygen content can reach critical thresholds in estuaries like the upper Elbe estuary. Many studies have dealt with the nutrient fluxes that occur during a resuspension event. However, the sediment properties that influence the oxygen consumption potential (OCP) and the different biochemical processes have not been examined in detail. To fill this gap, we investigated the biogeochemical composition, texture, and OCP of sediments at 21 locations as well as the temporal variability within one location for a period of 2 years (monthly sampling) in the upper Elbe estuary. The OCP of sediments during a seven-day resuspension event can be described by the processes of sulphate formation, nitrification, and mineralisation. Chlorophyll, total nitrogen (Ntotal), and total organic carbon showed the highest correlations with the OCP. Based on these correlations, we developed a prognosis model to calculate the OCP for the upper Elbe estuary with a single sediment parameter (Ntotal). The model is well suited to calculate the oxygen consumption of resuspended sediments in the Hamburg port area during the relevant warmer months and shows a normalised root mean squared error of < 0.11 ± 0.13. Thus, the effect of maintenance measures such as water injection dredging and ship-induced wave on the oxygen budget of the water can be calculated. [ABSTRACT FROM AUTHOR]

Continental margin sediments represent a major global sink of organic carbon (OC), and as such exert a key control on Earth’s climate. Today, OC burial in marine sediments mainly takes place under oxygen-rich water columns, where most OC is stabilized through intimate association with sediment grains and biogenic minerals. In prior episodes of Earth’s past, when large parts of the oceans were anoxic, the mode of sedimentary OC burial must have been very different, however. Present-day analogues indicate that surface sediments accumulating under low-oxygen water columns are often “soupy” in texture. Moreover, most OC occurs in large (100–2,000 μm diameter) organic and organo-mineral aggregates which, due to their low density, are prone to wave- and current-induced resuspension. Upon mobilization, these aggregates can undergo lateral transport within so-called nepheloid layers, and may be translocated hundreds of kilometres, and on timescales of thousands of years. Little is known about processes of formation, resuspension and hydrodynamic properties of these aggregates in oxygen-poor waters, or which factors control their eventual breakdown or burial. The goal of this study is to examine the drivers and biogeochemical consequences of this resuspension on OC cycling in modern, oxygen-depleted, “Semi-Liquid Ocean Bottom” (SLOB) regions. We argue that models of sediment and OM hydrodynamics and redistribution that describe sedimentation processes in oxygenated ocean waters of the modern ocean are a poor analogue for equivalent processes occurring under oxygen-deficient conditions. In the latter, we hypothesize that 1) the abundance of low-density organic-rich particles and aggregates leads to a greater propensity for sediment remobilization at low(er) shear stress, and 2) upon resuspension into low-oxygen bottom waters, remobilized OM may be subject to less degradation (less attenuation) during lateral transport, leading to efficient and widespread translocation to distal centres of deposition. We address specific aspects of the SLOB hypothesis utilizing a combination of literature and new data, focussing on the Benguela Upwelling Region as a model system.

UnlabelledBaseline information on size-resolved bacterial, fungal, and particulate matter (PM) indoor air concentrations and emission rates is presented for six school classrooms sampled in four countries. Human occupancy resulted in significantly elevated airborne bacterial (81 times on average), fungal (15 times), and PM mass (nine times) concentrations as compared to vacant conditions. Occupied indoor/outdoor (I/O) ratios consistently exceeded vacant I/O ratios. Regarding size distributions, average room-occupied bacterial, fungal, and PM geometric mean particle sizes were similar to one another while geometric means estimated for bacteria, fungi, and PM mass during vacant sampling were consistently lower than when occupied. Occupancy also resulted in elevated indoor bacterial-to-PM mass-based and number-based ratios above corresponding outdoor levels. Mean emission rates due to human occupancy were 14 million cells/person/h for bacteria, 14 million spore equivalents/person/h for fungi, and 22 mg/person/h for PM mass. Across all locations, indoor emissions contributed 83 ± 27% (bacteria), 66 ± 19% (fungi), and 83 ± 24% (PM mass) of the average indoor air concentrations during occupied times.Practical implicationsAn extensive data set of bacterial and fungal size-distributed indoor air concentrations and emission rates is presented. Analysis of these data contributes to an understanding of how indoor bacterial and fungal aerosols are influenced by human occupancy. This work extends beyond prior culture and DNA-based microbiome studies in buildings to include quantitative relationships between size-resolved bacterial and fungal concentrations in indoor air and building parameters such as occupancy, ventilation, and outdoor conditions. The work indicates that occupancy-associated emissions (e.g., via resuspension and shedding) contribute more to both bacterial and fungal indoor air concentrations than do outdoor sources for the occupied classrooms investigated in this study.

In this study, we investigated engineered nanoparticle (ENP) release associated with the contamination of personal protective clothing during the simulated motion of the human wearing the ENP-contaminated protective clothing and evaluated the relative ENP retention on the fabric. The release of airborne ENPs can contribute to inhalation exposure, which is the route of exposure of most concern to cause adverse health effects in the pulmonary system. The evaluation focuses on four popular fabric materials making the laboratory coats (cotton, polypropylene, polyester cotton blend, and Tyvek) and three types of ENPs (Al2O3, carbon black (CB), and carbon nanotube (CNT)). The magnitudes of particle contamination and resuspension were investigated by measuring the number concentration increase of airborne particles in sizes of 10 nm to 10 μm and the weight changes on fabric pieces. Collected aerosol particles and contaminated fabric surfaces were further characterized for understanding particle morphology, elements, agglomeration, and surface contamination status. The particle resuspension from the contaminated lab coat fabric was found to vary by the type of fabric material. Cotton fabric showed the highest level of particle resuspension for all three tested ENPs. Data were evaluated to determine the dominant forces responsible for ENP adhesion on the surface of the fabric. Tyvek fabric was determined as the best fabric for trapping Al2O3 and carbon black ENPs, indicating less resuspension of particles, meaning lower subsequent release, but not durable enough to wear for the long term compared with other fabrics. [ABSTRACT FROM AUTHOR]

Resuspension of dust from flooring is a major source of human exposure to microbial contaminants, but the persistence of viruses on dust and carpet and the contribution to human exposure are often unknown. The goal of this work is to determine viability of MS2 and Phi6 bacteriophages on cut carpet, looped carpet, and house dust both over time and after cleaning. Bacteriophages were nebulized onto carpet or dust in artificial saliva. Viability was measured at 0, 1, 2, 3, 4, 24, and 48 h and after cleaning by vacuum, steam, hot water extraction, and disinfection. MS2 bacteriophages showed slower viability decay rates in dust (−0.11 hr−1), cut carpet (−0.20 hr−1), and looped carpet (−0.09 hr−1) compared to Phi6 (−3.36 hr−1, −1.57 hr−1, and −0.20 hr−1, respectively). Viable viral concentrations were reduced to below the detection limit for steam and disinfection for both MS2 and Phi6 (p < 0.05), while vacuuming and hot water extraction showed no significant changes in concentration from uncleaned carpet (p > 0.05). These results demonstrate that MS2 and Phi6 bacteriophages can remain viable in carpet and dust for several hours to days, and cleaning with heat and disinfectants may be more effective than standard vacuuming. [ABSTRACT FROM AUTHOR]

This paper aims to investigate the effect of the settling behaviour of sediment particles during resuspension on the mobilisation of pollutants such as polycyclic aromatic hydrocarbons (PAHs). Sediments were collected in different areas (basin, channel, beach) of a Mediterranean harbour, located in the south of France (the Grau du Roi harbour), and then separated into different size fractions: large (80–1000 μm), intermediate (40–80 μm), and fine (< 40 μm). Total PAHs concentrations in the initial sediment ranged from 320 to 1043 μg kg-1. Study of the settling behaviour of the PAH-contaminated sediment revealed two sedimentation regimes: sedimentation by mass, which exhibits a sharp interface between the supernatant and the deposit, and sedimentation by clarification with no interface. It appears that sediment particles settle either by the clarification regime or by a combination of the two sedimentation regimes, depending on the size fraction. Particle size distribution monitoring during the settling process allowed the identification of sediment particles less than 20 μm which remain in the water column up to 20 min after resuspension and appear to be the ones that can potentially mobilise PAHs. [ABSTRACT FROM AUTHOR]

Abstract Background Despite the widely recognized importance of aquatic processes for bridging gaps in the global carbon cycle, there is still a lack of understanding of the role of riverbed processes for carbon flows and stocks in aquatic environments. Here, we added a sediment diagenesis and sediment carbon (C) resuspension module into the SWAT-C model and tested it for simulating both particulate organic C (POC) and dissolved organic C (DOC) fluxes using 4 years of monthly observations (2014–2017) in the Tuckahoe watershed (TW) in the U.S. Mid-Atlantic region. Results Sensitivity analyses show that parameters that regulate POC deposition in river networks are more sensitive than those that determine C resuspension from sediments. Further analyses indicate that allochthonous contributions to POC and DOC are about 36.6 and 46 kgC ha−1 year−1, respectively, while autochthonous contributions are less than 0.72 kgC ha−1 year−1 for both POC and DOC (less than 2% of allochthonous sources). The net deposition of POC on the riverbed (i.e., 11.4 kgC ha−1 year−1) retained ca. 31% of terrestrial inputs of POC. In addition, average annual buried C was 0.34 kgC ha−1 year−1, accounting for only 1% of terrestrial POC inputs or 3% of net POC deposition. The results indicate that about 79% of deposited organic C was converted to inorganic C (CH4 and CO2) in the sediment and eventually released into the overlying water column. Conclusion This study serves as an exploratory study on estimation of C fluxes from terrestrial to aquatic environments at the watershed scale. We demonstrated capabilities of the SWAT-C model to simulate C cycling from uplands to riverine ecosystems and estimated C sinks and sources in aquatic environments. Overall, the results highlight the importance of including carbon cycle dynamics within the riverbed in order to accurately estimate aquatic carbon fluxes and stocks. The new capabilities of SWAT-C are expected to serve as a useful tool to account for those processes in watershed C balance assessment.

The 234Th–238U disequilibrium has been widely used to quantify the sinking flux of particulate organic carbon (POC) out of the upper ocean. However, the influence of the advection on the quantification is poorly understood due to the lack of in situ measured physical parameters. Here, a Lagrangian observation was deployed for 39 h to track the variability of 234Th along with the current on the slope of the northeastern South China Sea (SCS). Contrasting to the general ocean interior, 234Th showed deficits relative to 238U in the mesopelagic waters, indicating an enhanced removal of 234Th. Concurrently, elevated total particulate matter (TPM) and POC contents were observed in the mesopelagic waters, supporting the driving force of the cross-shelf dispersion of re-suspended shelf/slope sediments for the 234Th removal. The widely used 234Th-model (ignoring physical processes) produced a much lower sinking flux of POC than the sediment trap-derived POC flux during the same observation, indicating an unneglectable influence of advection and diffusion. By considering the main horizontal advection and vertical diffusion, the 234Th–238U method gave rise to comparable results to sediment trap. 234Th-derived POC fluxes showed an increased pattern from 300 to 1,000 m, consistent with the more abundant POC where. These results indicated that advection represents an unneglectable process during the quantification of the sinking flux of 234Th over the slope of the SCS.

Inhalation exposure to the resuspended biological particles from public places can cause adverse effects on human health. In this work, carpet dust samples were first collected from twenty example conference and hotel rooms by a vacuum cleaner. A bipedal robot was then used to simulate children's walking with three different shoes (cotton socks, PVC shoes and EVA shoes) in a hotel room. The particle resuspensions were simultaneously monitored by an aerosol spectrometer. In addition, air samples were also taken using a cyclone liquid impinger operated at 400 L min−1, and further subjected to gene sequencing analysis. Our results showed that dominant bacterial genera in the carpet dusts included those containing respiratory pathogens such as Staphylococcus, Acinetobacter and Pseudomonas. The bacterial structures in carpet dusts were shown different among the samples from hotel and conference rooms (p

Foliar trichomes are specialized structures that have first contact with atmospheric particulate matter (PM), while their effects on PM accumulation are rarely investigated. In this study, epiphytic Tillandsia brachycaulos with foliar trichomes was investigated. Trichomes were removed artificially to investigate PM adsorption and resuspension. The results showed that the maximum PM (13.94±0.20 g•m-2) and natural PM content (10.65±1.10 g•m-2) on T. brachycaulos samples with foliar trichomes was significantly higher than those without foliar trichomes. After PM deposition on the leaf surface, more than 85% of PM was dispersed by wind in plants without trichomes, significantly higher than those with trichomes (30.2%). Therefore, the effects of foliar trichomes on PM were reflected not only on PM adsorption, but on PM resuspension. Foliar trichomes can decrease PM resuspension falling on the leaf surface and promote the accumulation of these particles.

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.

The aquatic vegetation patch plays a significant role on sediment net deposition in the vegetated channels. Particularly, the flow is decelerated at the leading edge of a patch that tends to induce vertical updraft, that is, a diverging flow region, in which vegetation greatly affects the pattern of sediment net deposition. This study focuses on the simulation of the sediment net deposition in the whole vegetation patch region through an innovative random displacement model, a Lagrange method, with probability‐based boundary conditions, instead of the reflection or sorption boundary at the channel bottom. The probability model of deposition and resuspension is proposed according to the flow field characteristics in the different regions of the vegetation patch. The variation of the sediment deposition and resuspension with the turbulent kinetic energy is analyzed to illustrate the effect of the turbulence induced by vegetation, represented by the dimensionless turbulent kinetic energy (ψ), on the sediment deposition and resuspension. The sediment deposition predicted by the proposed model agrees well with the experimental measurements. Results show that the effect of vegetation on the sediment deposition and resuspension motions begins to prevail when the vegetation‐induced ψ is larger than its threshold, ψ*. The threshold of ψ is predicted to be within 6.8–10 according to the simulation results in this study. As the turbulent kinetic energy increases, the deposition probability decreases continuously when ψ > ψ*. Key Points: Vegetation‐generated turbulent kinetic energy has considerable impact on the sediment deposition probability in vegetated channelsTurbulence dominates sediment deposition and resuspension motions when the dimensionless turbulent kinetic energy is larger than the thresholdRandom displacement model simulates the sediment net deposition in vegetated channel flows with the deposition and resuspension model [ABSTRACT FROM AUTHOR]

A new risk assessment scheme was developed to quantify the impact of resuspension to infection transmission indoors. Airborne and surface pathogenic particle concentration modelsincluding the effect of two major resuspension scenarios (airflow-induced particle resuspension [AIPR] and walking-induced particle resuspension [WIPR]) were derived based on two-compartment mass balance models and validated against experimental data found in theliterature. The inhalation exposure to pathogenic particles was estimated using the derived airborne concentration model, and subsequently incorporated into a dose-response model to assess the infection risk. Using the proposed risk assessment scheme, the influences of resuspension towards indoor infection transmission were examined by two hypothetical case studies. In the case of AIPR, the infection risk increased from 0 to 0.54 during 0–0.5 hours and from 0.54 to 0.57 during 0.5–4 hours. In the case of WIPR, the infection risk increasedfrom 0 to 0.87 during 0–0.5 hours and from 0.87 to 1 during 0.5–4 hours. Sensitivity analysis was conducted based on the design-of-experiments method and showed that the factors thatare related to the inspiratory rate of viable pathogens and pathogen virulence have the most significant effect on the infection probability under the occurrence of AIPR and WIPR. The risk assessment scheme could serve as an effective tool for the risk assessment of infection transmission indoors.

Humans are a prominent source of airborne biological particles in occupied indoor spaces, but few studies have quantified human bioaerosol emissions. The chamber investigation reported here employs a fluorescence-based technique to evaluate bioaerosols with high temporal and particle size resolution. In a 75-m3 chamber, occupant emission rates of coarse (2.5–10 μm) fluorescent biological aerosol particles (FBAPs) under seated, simulated office-work conditions averaged 0.9 ± 0.3 million particles per person-h. Walking was associated with a 5–6× increase in the emission rate. During both walking and sitting, 60–70% or more of emissions originated from the floor. The increase in emissions during walking (vs. while sitting) was mainly attributable to release of particles from the floor; the associated increased vigor of upper body movements also contributed. Clothing, or its frictional interaction with human skin, was demonstrated to be a source of coarse particles, and especially of the highly fluorescent fraction. Emission rates of FBAPs previously reported for lecture classes were well bounded by the experimental results obtained in this chamber study. In both settings, the size distribution of occupant FBAP emissions had a dominant mode in the 3–5 μm diameter range.

The concentrations of total suspended particles (TSPs) on four buildings near a steel plant’s bulk material storage site for iron ore, coal, limestone, and sinter were evaluated for summer and winter, where the concentrations were 58 (17–55) μg m−3 and 125 (108–155) μg m−3, respectively. A multivariate regression analysis of meteorological parameters with TSP concentrations indicates that temperature, wind speed, and frequency of rainfall are potential predictors of TSP concentrations, where the respective p values for the model are p = 0.005, p = 0.049, and p = 0.046. The strong correlation between usual co-pollutants, CO, NO2, and NOX with TSP concentrations, as indicated by the Pearson correlation values of 0.87, 0.86, and 0.77, respectively, implies substantial pollution from mobile sources. The weak correlation of SO2 with TSP concentrations rules out a significant pollution contribution from power plants. The speciation of TSPs in winter showed the percentage proportions of water-soluble ions, metal elements, and carbon content in winter as 60%, 15%, and 25%, while in summer, they were 68%, 14%, and 18%, respectively. Water-soluble ions were the most significant composition for both seasons, where the predominant species in summer and winter are SO42− and NO3−, respectively. In the TSP metal elements profile, the proportion of natural origin ones exceeded those from anthropogenic sources. The health risk assessment indicates a significant cancer risk posed by chromium, while that posed by other metal elements including Co, Ni, As, and Pb are insignificant. Additionally, all metal elements’ chronic daily occupational exposure levels were below the reference doses except for Cu and Zn. Insights from this investigation can inform decisions on the design of the TSP-capturing mechanism. Specifically, water sprays to capture the water-soluble portion would substantially reduce the amplified concentrations of TSPs, especially in winter.

The focus of this study was to determine the long-term fate of oil-residues from the 2010 Deepwater Horizon (DwH) oil spill due to remobilization, transport, and re-distribution of oil residue contaminated sediments to down-slope depocenters following initial deposition on the seafloor. We characterized hydrocarbon residues, bulk sediment organic matter, ease of resuspension, sedimentology, and accumulation rates to define distribution patterns in a 14,300 km2 area southeast of the DwH wellhead (1,500 to 2,600 m water depth). Oil-residues from the DwH were detected at low concentrations in 62% of the studied sites at specific sediment layers, denoting episodic deposition of oil-residues during 2010–2014 and 2015–2018 periods. DwH oil residues exhibited a spatial distribution pattern that did not correspond with the distribution of the surface oil slick, subsurface plume or original seafloor spatial expression. Three different regions were apparent in the overall study area and distinguished by the episodic nature of sediment accumulation, the ease of sediment resuspension, the timing of oil-residue deposition, carbon content and isotopic composition and foram fracturing extent. These data indicate that resuspension and down-slope redistribution of oil-residues occurred in the years following the DwH event and must be considered in determining the fate of the spilled oil deposited on the seafloor.

Eulerian–Lagrangian methods are common for computational fluid dynamics (CFD) modeling of particle fate. Near-wall turbulence flow profiles are frequently modeled with wall function (WF) for computational efficiency and stability. However, WF does not provide the viscous and buffer sublayers solution for Lagrangian particle tracking (LPT). This study examines Reynolds-averaged Navier-Stokes (RANS)-LPT model combinations with near-wall models (two-layer, low-Reynolds number, WF), common LPT boundary conditions (trap, reflect), near-wall grids resolution (Δy+), and LPT solver configurations. Near-wall LPT in an open channel clarifier illuminates embedded numerical errors/artifacts generated by widely-used RANS-WF-LPT model combinations as benchmarked to direct numerical simulations (DNS). Near-wall LPT can be subject to grid resolution irrespective of particle-boundary interactions and LPT boundary conditions applied. Clarifier simulations illustrate LPT solver configurations influence particulate matter (PM) separation. RANS-LPT solutions are a function of particle diameter, maximum particle integration steps, and to a lesser degree on tracked particle number. Low-Reynolds number and two-layer models improve per particle size separation predictions compared to the WF model by up to 50% for 25–100 μm particles based on physical model benchmarking. [ABSTRACT FROM AUTHOR]

Phosphorus (P) is potentially the most limiting nutrient in the Pearl River estuary, and thus, it is important to understand various sources of P. Suspended particulate matter (SPM) is usually high in the river and carries P. We hypothesize that suspended particulate reactive P (PRP) is a potential source of dissolved P and varies with estuarine hydrodynamics. To test the hypothesis, we conducted a cruise along and cross the Pearl River estuary to examine spatial variability of suspended PRP. Suspended PRP ranged at 0.01–2.65 μM, contributing 1.2–97.4% to total reactive P (TRP). Along the estuary, suspended PRP was 1.49 μM upstream and decreased downstream. Across the estuary, suspended PRP was high (1.58 μM) at low salinity and decreased eastward with increasing salinity. Tidal cycles appeared to play a significant role in regulating the variability of suspended PRP through advection and benthic resuspension of SPM. The proportion of PRP/TRP increased seaward from 1.2 to 94.8%, indicating the increasing importance of PRP in total reactive P downstream. We show that suspended particulate reactive P varied greatly and was an important part of the total phosphorus pool in the Pearl River estuary. [ABSTRACT FROM AUTHOR]

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Urban greenery is identified as a potential tool in air pollution mitigation. However, the impact is still debated. This paper introduces the innovative VIDA (Vegetation Impact Dynamic Assessment) model, specifically designed to quantify air pollution removal through deposition on vegetation. The VIDA model offers an advanced representation of vegetation that could be integrated into urban air quality dispersion models in the future. Furthermore, the model serves as a valuable tool for exploring the intricate interactions among deposition, resuspension, and wash-off processes, as well as understanding how meteorological conditions and various leaf traits influence these processes. The current version of the model focuses on particulate matter (PM) and encompasses a range of processes, including deposition on vegetation surfaces, encapsulation within the waxy cuticle, wind-driven resuspension, and wash-off. Additionally, the model takes into consideration dynamic changes in PM concentrations on the leaf surface over time, incorporating factors such as PM size fractions, meteorological conditions, and leaf characteristics. This comprehensive approach allows for the evaluation of various species or species groups based on their distinct traits. The VIDA model effectively reproduces measured data, yet continued evaluation remains crucial as new data emerges. Notably, challenges were encountered due to data scarcity and the absence of standardized methods for characterizing vegetation traits. Addressing these challenges and refining the representation of wash-off process will enhance the VIDA model's utility in predicting the dynamic relationship between vegetation and air quality. The introduction of VIDA provides a significant advancement in modelling air pollution removal by deposition to vegetation at a relevant local scale and enables inclusion of urban greenery as tool in urban planning for air pollution mitigation. • The VIDA model quantifies air pollution removal through deposition on vegetation. • VIDA models particle deposition, cuticle encapsulation, resuspension, and wash-off. • VIDA enables inclusion of urban greenery in air pollution mitigation. [ABSTRACT FROM AUTHOR]

The aim of this study was to assess the exposures received by firefighters engaged in extinguishing the large-scale wildfires in the most contaminated areas of the Ukrainian part of the Chornobyl Exclusion Zone in 2016 and 2020. The assessments are based on measurements of radionuclide airborne concentrations in the breathing zones of workers and at the aerosol sampling stations of the automated radiation monitoring system operated by SSE Ecocenter. During the wildfires, the radionuclide airborne concentrations increased by orders of magnitude compared to the background levels, reaching maximum values in the firefighting area of 1.20 ± 0.01 Bq m−3 for 90Sr, 0.18 ± 0.01 Bq m−3 for 137Cs, (1.8 ± 0.3) ∙10−4 Bq m−3 for 238Pu, (4.5 ± 0.7) ∙10−4 Bq m−3 for 239-240Pu, and (8.0 ± 1.3) ∙10−3 Bq m−3 for 241Pu. The internal effective doses to firefighters due to inhaled radionuclides did not exceed 2 μSv h−1 and were 3–5 times lower compared to the external dose of gamma radiation. Thus, the time of firefighting in the ChEZ will be limited by the external dose. [Display omitted] • Doses to firefighters during Chornobyl wildfires in 2016 and 2020 have been estimated. • Measurements of radionuclide concentrations in the breathing zone of firefighters were used to calculate doses. • Internal effective doses from inhalation of radionuclides did not exceed 2 μSv h−1 • Internal effective doses were 3–5 times lower than external doses. • In the ChEZ, the time of firefighting will be limited mainly by the external dose rate. [ABSTRACT FROM AUTHOR]

Nutrients directly control the level of primary productivity and are crucial for the stability of marine ecosystems. Focusing on the survey results in August 2020 of the Yangtze River Estuary, this study elucidated the distribution characteristics and controlling factors of three nutrients: NO 3 -N, PO 4 -P, SiO 3 -Si. The results showed that the concentrations of NO 3 -N, PO 4 -P, SiO 3 -Si in the study area were generally higher near the shore than far shore, with average concentrations of 11.40, 0.70, and 23.73 μmol/L, respectively. The ocean currents drove the distribution of nutrients, and the transport of CDW and YSCC increased the nutrient levels. The resuspension of sediment caused by factors such as terrain and weather may lead to an abnormal increase in nutrients in the bottom waters. The main controlling factors of the three nutrients were different. NO 3 -N was significantly affected by human activities, PO 4 -P and SiO 3 -Si were mainly affected by natural factors. [Display omitted] • Nutrient characteristics driven by multiple factors is explored in the Yangtze River Estuary. • The nutrient concentrations are generally higher in nearshore and bottom waters. • The ocean currents drive the distribution of the three nutrients NO 3 -N, PO 4 -P, SiO 3 -Si. • The main controlling factors of the three nutrients are quite different. [ABSTRACT FROM AUTHOR]

Microplastic (MP) contamination is a growing global concern, with lake sediments serving as a significant sink for MP due to both anthropogenic and natural activities. Given the increasing evidence of MP accumulation in sediments, it was crucial to assess their influence on sediment erosion resistance, which directly affected sediment resuspension. To fill this gap, this study focused on the effect of MP on the sediments rheological properties. After 60-day experiments, it was found that MP addition into sediments reduced sediment viscosity, yield stress, and flow point shear stress. Meanwhile, MPs also significantly altered sediment properties and extracellular polymer composition. MP addition reduced extracellular polymeric substances production and cation exchange capacity, which then worked together and led to a weak sediment structure. Seemingly, MPs changed fluid sediment characteristics and caused stronger fluidity under less shear force. Consequently, the accumulation of MP might facilitate the resuspension of sediments under smaller wind and wave disturbances. This study provided novel insights into the direct impact of MPs on sediment physical properties using rheology, thereby enhancing our understanding of the environmental behavior of MPs in lake ecosystems. [Display omitted] • The rheological properties of lake sediments were affected by microplastics. • Microplastics reduced sediment viscosity and yield stress. • Sediment rheological properties was related to extracellular polymer substances. • Cation exchange capacity in sediment changed with microplastics addition. • Microplastics might increase the potential risk of sediment re-suspension. Synopsis. The effects of MPs on the rheological properties of sediments were explored. Microplastics reduced sediment viscosity and yield stress, and might increase the potential risk of sediment re-suspension. The results revealed the sediment environmental impact of microplastics from a new perspective. [ABSTRACT FROM AUTHOR]

Ventilation duct serves as a potential target for bioterrorist attack. Understanding the dynamics ofaerosolized harmful agents in the ventilation ducts provides the fundamentals for effective control andmanagement, e.g., risk assessment. In this work, new models for predicting the concentration dynam-ics in the ventilation duct after a particle resuspension (representing the case that harmful agents aredosed when the ventilation is off and subsequently being turned on) or puff injection (representing thecase that harmful agents are dosed when the ventilation is running) event were derived based on themass balance model. The models were validated by a series of wind tunnel experiments. Indoor airborneparticle concentration models were derived by incorporating the proposed ventilation duct models forresuspension and injection cases. The effects of resuspension and injection in the duct on indoor airborneparticle concentration were examined by two hypothetical cases of Bacillus anthracis dosage using thederived models. For the same amount of BW agent dosage in the ventilation duct, the resuspension typerelease prolongs the exposure of harmful agents whereas the injection type release produces a higherpeak concentration.

Abstract This study was an attempt to understand the factors influencing the heavy metal distribution in polluted fluvial system sediments. Various biogeochemical processes and anthropogenic factors were playing an important role in altering the concentration of heavy metals in the sediments. This paper has two objectives: The first one is to investigate the effect of the variation in the physicochemical conditions on the speciation of trace elements trapped in the sediments of the Sebou River. The second one is to study the kinetics mobilization of these heavy metals. Batch resuspension experiments were conducted in order to investigate the release of heavy metals from a polluted anoxic sediment submitted to different physicochemical conditions variations. It has been revealed that in oxygenated environment, sediments were oxidized which cause the release of some heavy metals, but their concentrations, as dissolved phase, were sustained constant or were increased with time. However, in acidic and anaerobic environment, most of the metallic trace elements were released together with the iron and the manganese, but some of these elements like chromium were precipitated. However, some of other elements were maintained in solution, which represents a real human health risk.

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.

Proppant particle transport in a tortuous fracture is a common but poorly understood element of hydraulic fracturing. An experimental investigation is conducted in a narrow, tortuous slot with two 90-degree bends while flowing four particle types. These results confirm that particle transport mechanisms in a tortuous slot are more complex than a straight slot. The phenomena of particle vortices and resuspension were observed near bends. As a result of vortices, two depressions are near the bends, and a three-step, terraced profile of the bed is formed. There is a natural logarithmic correlation between the depression height and Stokes number. The fluid velocity is the primary factor affecting the proppant transport, followed by particle density and size. The hindrance effect on particle settling would be significant at low fluid velocity. This study provides fundamental insights into understanding particle-fluid mixture flow in a tortuous fracture. Unlabelled Image • Particle vortices can form around a bend in a tortuous fracture. • Particle resuspension can enhance the migration capacity of particles deeper into a tortuous fracture. • Particle settling occurs closer to the entrance due to the hindrance effect of the tortuous fracture. [ABSTRACT FROM AUTHOR]

Purpose: Numerous sites contaminated with fiber emissions from pulp and paper industries are found in coastal areas of the Baltic Sea, but there is limited knowledge about the magnitude of dispersal of persistent organic pollutants (POPs) from these anthropogenic, organic-rich sediments called fiberbanks. The aim of this study was to quantify and compare different POP dispersal pathways from such fiberbanks. Dispersal mechanisms studied included abiotic and biotic routes (dissolved in water, particle-bound, and bioaccumulation). Materials and methods: Contaminated fibrous sediments located in Ångermanälven River estuary in north-eastern Sweden were studied in sediment types representing different fiber content (i.e., fiberbanks, fiber-rich sediments, and less fiber impacted sediments). Sediment-to-water fluxes of dissolved contaminants (polychlorinated biphenyls (PCBs), hexachlorobenzene (HCB), and dichlorodiphenyltrichloroethane (DDT)) were measured in situ using benthic flux chambers. Particle resuspension was measured by sampling bottom water, before and after disturbing the sediment surface. Benthic biota was collected to determine the body burden of contaminants and to determine biota-pore water accumulation factors (BAFPW) and biota-sediment accumulation factors (BSAFs). In addition, concentrations of dissolved POPs in the water column were measured in field using passive samplers. Instrumental analysis was performed using gas chromatography coupled to a triple quadrupole mass spectrometer (GC-MS/MS). Results and discussion: The flux of dissolved Σ20PCBs was approximately two times higher from one of the investigated fiberbanks (3.4 ng m− 2 day− 1) compared to the other. The average particle burden of PCBs was also higher at this fiberbank after artificial disturbance (15 ng g−1 particle), which indicates that larger amounts of contaminants are likely to disperse via particle resuspension from this site compared to the other fiberbank (4.8 ng g− 1 particle). The difference might be associated with a layer of recently settled minerogenic material that covers one of the fiberbanks, which probably functions as a protective barrier. The lack of benthic biota implies that contaminant release by bioturbation is negligible in the studied fiberbanks. However, benthic biota from fiber-rich sediment showed bioaccumulation and biomagnification of contaminants. Conclusions: The importance of diffusive flux from fiberbanks under undisturbed conditions became apparent when the different dispersal pathways were quantified. However, no dispersal pathway could be judged as irrelevant, since even under undisturbed conditions, advective particle transport was significant. Additionally, the uptake by biota and trophic transfer can be considerable. Quantification of dispersal routes and understanding of the relative importance of various pathways is critical for proper risk assessment and management of contaminated sediments. [ABSTRACT FROM AUTHOR]

Particle dynamics play significant roles in sedimentological and geomorphological processes as well as biogeochemical cycles in estuaries. We collected a suite of water samples from the North Passage of the Changjiang (Yangtze) Estuary during different tidal conditions in summer 2009 to observe variations in the particulate 234Th, 7Be, 210Pb, and 137Cs activities as well as in particle transport, deposition, and resuspension. The mean activities of 7Be and 210Pbex in surface water during low tide were lower than those during high tide. The residence times of 7Be (1.1–3.4 d), 234Th (4.7–28 d), and 210Pb (7.9–34 d) in the North Passage increased with the increase of salinity and suspended particulate matter. The estimated results, based on a two‐dimensional model of 7Be, 234Th, and 210Pb, showed that sedimentary particles in the North Passage experienced net deposition during neap tides whereas those in more seaward areas of the North Passage exhibited net resuspension during spring tides. The 7Be/210Pbex activity ratio in seaward area of the North Passage was lower during spring tide than during neap tide but both were close to values in surface sediments beyond the estuary. Using 7Be/210Pbex and 137Cs/210Pbex activity ratios as tracers, we deduced that most of particles in the North Passage were not derived from the direct deposition of Changjiang input particles but were transported from sediment deposited offshore. These results emphasized the important contributions of offshore inputs to sediments in this channel, which should be considered when conducting channel dredging of other estuarine systems. Plain Language Summary: We investigated the tidal distribution of particulate activity of 234Thex, 7Be, 210Pbex, and 137Cs in the North Passage of the Changjiang Estuary in summer 2009. We found that the mean activities of 7Be and 210Pbex in surface water during low tide were lower than those during high tide. The residence times of 7Be (1.1–3.4 d), 234Th (4.7–28 d), and 210Pb (7.9–34 d) in the North Passage were positively correlated with salinity and suspended particulate matter. Based on a two‐dimensional model of 7Be, 234Th, and 210Pb, we estimated that sedimentary particles in the North Passage experienced net deposition during neap tides whereas those in more seaward areas of the North Passage exhibited net resuspension during spring tides. Using 7Be/210Pbex and 137Cs/210Pbex AR as tracers, we deduced that most of particles in the North Passage were not derived from the direct deposition of Changjiang input particles but were transported there from sediment deposited offshore. These results remind us to reconsider previous cognition that the source of particles in the waterway of estuary was dominated by the riverine input, especially under the background of regime shift in estuarine dynamics caused by the decline in sediment load from the upstream of river. Key Points: Particulate activity of 7Be, 234Th, 210Pb, and 137Cs varied by tidal conditionSedimentary particles in the seaward part of the waterway underwent net deposition during neap tide and net resuspension during spring tideSediments derived from the riverine supply were not the dominant source of sediments in the estuarine channel [ABSTRACT FROM AUTHOR]

The Tritium Processing Facility at the Savannah River Site releases effluent containing copper (Cu), zinc (Zn), and lead (Pb) to the H-02 constructed wetland for remediation before the final release. Sediment cores were collected in the wetland cells in both summer and winter. Concentrations of total metals in all sediment layers and acid-volatile sulfide (AVS) and simultaneously extracted metals (SEM) in surface sediments were determined. Total metal concentrations suggested most metals removed from surface water were retained by the organic-rich flocculent in the top sediment layers instead of being transported to the deeper sulfide mineral layers. The seasonal difference of AVS and SEM indicated a season-related sulfur cycle and metal removal process in the wetland cells. SEM-Zn was the major contributor to total SEM. Metals accumulating in surface sediments were mainly sequestered in AVS and SEM extractable phases including metal-sulfides and organic matter complexes. The general SEM/AVS ratio was > 1, demonstrating the metals associated with sediments were potentially mobile and/or bioavailable, which becomes a concern for the long-term sustainability of the constructed wetland. The disturbance event in the sediment triggered the release of total metals, which were mostly in particulate form and were not bioavailable. Due to the high levels of reduced ion (Fe) in the sediment, the released particulate metals were likely to form metal-scavenging particulate Fe3+ oxyhydroxides under oxic conditions. [ABSTRACT FROM AUTHOR]

UnlabelledThe role of human occupancy as a source of indoor biological aerosols is poorly understood. Size-resolved concentrations of total and biological particles in indoor air were quantified in a classroom under occupied and vacant conditions. Per-occupant emission rates were estimated through a mass-balance modeling approach, and the microbial diversity of indoor and outdoor air during occupancy was determined via rDNA gene sequence analysis. Significant increases of total particle mass and bacterial genome concentrations were observed during the occupied period compared to the vacant case. These increases varied in magnitude with the particle size and ranged from 3 to 68 times for total mass, 12-2700 times for bacterial genomes, and 1.5-5.2 times for fungal genomes. Emission rates per person-hour because of occupancy were 31 mg, 37 × 10(6) genome copies, and 7.3 × 10(6) genome copies for total particle mass, bacteria, and fungi, respectively. Of the bacterial emissions, ∼18% are from taxa that are closely associated with the human skin microbiome. This analysis provides size-resolved, per person-hour emission rates for these biological particles and illustrates the extent to which being in an occupied room results in exposure to bacteria that are associated with previous or current human occupants.Practical implicationsPresented here are the first size-resolved, per person emission rate estimates of bacterial and fungal genomes for a common occupied indoor space. The marked differences observed between total particle and bacterial size distributions suggest that size-dependent aerosol models that use total particles as a surrogate for microbial particles incorrectly assess the fate of and human exposure to airborne bacteria. The strong signal of human microbiota in airborne particulate matter in an occupied setting demonstrates that the aerosol route can be a source of exposure to microorganisms emitted from the skin, hair, nostrils, and mouths of other occupants.