Comparison of microsphere deposition in porous media versus simple shear systems

Brow, Christina N.; Li, Xiqing; Rička, J.

doi:10.1016/j.colsurfa.2004.11.005

Cited by 25 publications

(39 citation statements)

References 46 publications

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“…The porewater flow rate in subsurface environments has been shown to affect the transport of NPs and MPs. , Generally, decreased plastic deposition is observed at high porewater velocities, in agreement with studies involving other types of colloids (e.g., titanium dioxide, fullerenes). ,,, Tong and Johnson observed a decrease in retention of PS MPs in columns packed with quartz sand as flow velocity increased . This behavior was observed by others when the plastic particle and collector have the same charge (unfavorable condition). , …”

Section: Current State Of Knowledge On Micro- and Nanoplastic Aggrega...supporting

confidence: 72%

Microplastics and Nanoplastics in Aquatic Environments: Aggregation, Deposition, and Enhanced Contaminant Transport

Alimi

Budarz

Hernandez

et al. 2018

Environ. Sci. Technol.

1,842

668

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Plastic litter is widely acknowledged as a global environmental threat, and poor management and disposal lead to increasing levels in the environment. Of recent concern is the degradation of plastics from macro- to micro- and even to nanosized particles smaller than 100 nm in size. At the nanoscale, plastics are difficult to detect and can be transported in air, soil, and water compartments. While the impact of plastic debris on marine and fresh waters and organisms has been studied, the loads, transformations, transport, and fate of plastics in terrestrial and subsurface environments are largely overlooked. In this Critical Review, we first present estimated loads of plastics in different environmental compartments. We also provide a critical review of the current knowledge vis-à-vis nanoplastic (NP) and microplastic (MP) aggregation, deposition, and contaminant cotransport in the environment. Important factors that affect aggregation and deposition in natural subsurface environments are identified and critically analyzed. Factors affecting contaminant sorption onto plastic debris are discussed, and we show how polyethylene generally exhibits a greater sorption capacity than other plastic types. Finally, we highlight key knowledge gaps that need to be addressed to improve our ability to predict the risks associated with these ubiquitous contaminants in the environment by understanding their mobility, aggregation behavior and their potential to enhance the transport of other pollutants.

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Section: Current State Of Knowledge On Micro- and Nanoplastic Aggrega...supporting

confidence: 72%

Microplastics and Nanoplastics in Aquatic Environments: Aggregation, Deposition, and Enhanced Contaminant Transport

Alimi

Budarz

Hernandez

et al. 2018

Environ. Sci. Technol.

1,842

668

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“…For example, X‐ray microtomography observations by Li et al [2006a, 2006b] indicate that deposition at grain‐grain contacts is highly dependent on the solution chemistry. Deposition rates in impinging jet systems and in packed sand columns under similar hydrodynamic and chemistry conditions also demonstrate a significant role of pore structure [ Redman et al , 2004; Walker et al , 2004; Brow et al , 2005]. Hoek and Agarwal [2006] reported that colloids in small pores can experience an interaction energy that is up to five times larger than the sphere‐plate interaction energy profile.…”

Section: Evidence and Implications For Strainingmentioning

confidence: 99%

Significance of straining in colloid deposition: Evidence and implications

Bradford

Šimůnek

Bettahar

et al. 2006

Water Resources Research

243

228

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[1] Considerable research suggests that colloid deposition in porous media is frequently not consistent with filtration theory predictions under unfavorable attachment conditions. Filtration theory was developed from an analysis of colloid attachment to the solid-water interface of a single spherical grain collector and therefore does not include the potential influence of pore structure, grain-grain junctions, and surface roughness on straining deposition. This work highlights recent experimental evidence that indicates that straining can play an important role in colloid deposition under unfavorable attachment conditions and may explain many of the reported limitations of filtration theory. This conclusion is based upon pore size distribution information, size exclusion, time-and concentration-dependent deposition behavior, colloid size distribution information, hyperexponential deposition profiles, the dependence of deposition on colloid and porous medium size, batch release rates, micromodel observations, and deposition at textural interfaces. The implications of straining in unsaturated and heterogeneous systems are also discussed, as well as the potential influence of system solution chemistry and hydrodynamics. The inability of attachment theory predictions to describe experimental colloid transport data under unfavorable conditions is demonstrated. Specific tests to identify the occurrence and/or absence of straining and attachment are proposed.

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“…The most commonly used system for examining colloid deposition onto unbounded surfaces is the impinging jet system, in which the solution is directed normal to the flat surface, where upon impinging the surface it spreads radially [ Adamczyk et al , 1995; Weiss et al , 1998; Yang et al , 1998]. Colloid deposition efficiencies (ratio of colloid deposition rate in presence versus absence of an energy barrier) have been demonstrated to be much greater in porous media relative to impinging jet systems (factors of 2 to 50) under equivalent conditions [ Redman et al , 2004; Walker et al , 2004; Brow et al , 2005; Tong and Johnson , 2006], suggesting that the vast majority of colloid retention in porous media is not due to surface heterogeneity, which presumably operates in both the impinging jet and the porous media.…”

Section: New Observations Calling For New Models Of Colloid Filtrationmentioning

confidence: 99%

“…Colloids associated with secondary energy minima would be expected to translate across the grain surface owing to tangential hydrodynamic drag, unless they are retained in zones where fluid drag forces are insufficient to overcome other forces resisting their down‐gradient translation (e.g., rear stagnation points or leeward sides of protrusions) [ Johnson and Tong , 2006; Tong and Johnson , 2006]. A portion of the greater deposition efficiency in porous media relative to impinging jets (excess retention) is therefore thought to result from retention of secondary minimum‐associated colloids in loose association with the grain surfaces [ Redman et al , 2004; Walker et al , 2004; Brow et al , 2005; Tong and Johnson , 2006], whereas impinging jets (flat surfaces) lack zones to “protect” colloids from fluid drag and translation out of the system.…”

Section: New Observations Calling For New Models Of Colloid Filtrationmentioning

confidence: 99%

On colloid retention in saturated porous media in the presence of energy barriers: The failure of α, and opportunities to predict η

Tong

2007

Water Resources Research

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[1] This contribution reviews recent findings that illuminate the processes governing colloid retention in porous media under environmentally relevant conditions. In the environment, colloids act as conveyors of contaminants, or even as contaminants themselves; however, despite decades of research, we are unable to accurately predict the retention of colloids in granular aquifer media under environmental conditions, where repulsion exists between colloids and surfaces. This failure cannot be blamed solely on the complexities of the subsurface, since colloid filtration theory (CFT) works well in the absence of colloid-collector repulsion despite its idealization of porous media as consisting of spherical grains completely surrounded by fluid envelopes. Rather, the failure of CFT stems from failure to incorporate the correct mechanisms of retention when repulsion exists. Recent observations implicate wedging in grain-to-grain contacts and retention in secondary energy minima as dominant mechanisms of colloid retention in the presence of an energy barrier. Mechanistic simulations in unit cells containing grain-to-grain contacts corroborate these mechanisms of colloid retention. The resulting concept for colloid retention in the presence of an energy barrier involves translation of colloids across the collector surfaces until they become wedged within grain-to-grain contacts, or are retained via secondary energy minima (without attachment) in zones where the balance of fluid drag, diffusion, gravitational, and colloid-collector interaction forces allow retention. The above findings highlight the pore domain geometry as a dominant governor of colloid retention in so far as the geometry gives rise to grain-to-grain contacts and zones of relatively low fluid drag.Citation: Johnson, W. P., M. Tong, and X. Li (2007), On colloid retention in saturated porous media in the presence of energy barriers: The failure of a, and opportunities to predict h, Water Resour. Res., 43, W12S13,

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Comparison of microsphere deposition in porous media versus simple shear systems

Cited by 25 publications

References 46 publications

Microplastics and Nanoplastics in Aquatic Environments: Aggregation, Deposition, and Enhanced Contaminant Transport

Microplastics and Nanoplastics in Aquatic Environments: Aggregation, Deposition, and Enhanced Contaminant Transport

Significance of straining in colloid deposition: Evidence and implications

On colloid retention in saturated porous media in the presence of energy barriers: The failure of α, and opportunities to predict η

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