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Water
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Colloid and Pathogen Transport in Groundwater
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Colloid and Pathogen Transport in Groundwater

A special issue of Water (ISSN 2073-4441). This special issue belongs to the section "Hydrology".

Deadline for manuscript submissions: closed (31 May 2020) | Viewed by 14309

Special Issue Editors

Dr. Dengjun Wang

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Guest Editor
National Research Council Resident Research Associate at the United States Environmental Protection Agency
Interests: fate and transport of nanoparticles and nanohybrids; environmental applications of nanohybrids; sources and biogeochemical cycling of phosphorus in watersheds; mathematical modelling
Special Issues, Collections and Topics in MDPI journals
Dr. Verónica L. Morales

E-Mail Website
Guest Editor
Dept. Civil and Environmental Engineering, University of California at Davis, USA
Interests: physico-chemical processes, colloid fate and transport, contaminant hydrology, pore-scale processes, pore network structure, inverse modeling, stochastic groundwater modeling
Dr. Lei Wu

E-Mail Website
Guest Editor
Dept. Civil Engineering, Ohio University, USA
Interests: colloid science; in-situ microscopy and image analysis; contaminant hydrology; environmental implications of nanotechnology

Special Issue Information

Dear Colleagues,

For the past three decades, suspended colloids (of which nanomaterials are a subset) and pathogens in subsurface environments have been linked to groundwater contamination. It is known that the persistence, dispersal, long-term transport, and the fate of colloids/pathogens are dependent on regional and local geology and hydrology, electrochemical properties of the colloid/pathogen and the soil, the chemistry of the groundwater, land use and management, and the distribution of potential sources of colloids/pathogens. All these factors considered together, in turn, make it exceptionally challenging to accurately predict colloid and pathogen transport in real groundwater systems. This Special Issue calls critical attention to studies that further our understanding of this multidimensional problem. Major areas of interests include, but are not limited to, the following: (1) the characterization of the interactions of colloids/pathogens with surrounding environmental media; (2) the development of predictive tools based on the fundamental behavior of colloids/pathogens with environmental matrices to advance cost-effective solutions to colloid-related contamination problems; and (3) field and laboratory experimental observations, simulation approaches, and new theories that close the knowledge gap between theoretical findings and practical applications.

Dr. Verónica L. Morales
Dr. Lei Wu
Dr. Dengjun Wang
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Water is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • colloid and pathogen sources or removal processes
  • interactions with subsurface interfaces
  • interactions with emerging contaminants (e.g., PFAS and micro/nanoplastics)
  • transport, deposition, and mobilization
  • colloid-facilitated transport
  • homo-/hetero-aggregation
  • coupled effects from physical, chemical, and hydrodynamic factors
  • survival, growth, death/inactivation, and degradation
  • alternative model formulations
  • upscaling: interface, pore, and continuum
  • risk assessment and public health

Published Papers (4 papers)

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Research

11 pages, 11882 KiB  
Article
Precipitant Effects on Aggregates Structure of Asphaltene and Their Implications for Groundwater Remediation
by Christian B. Hammond, Dengjun Wang and Lei Wu
Water 2020, 12(8), 2116; https://doi.org/10.3390/w12082116 - 25 Jul 2020
Cited by 2 | Viewed by 2429
Abstract
Asphaltenes generally aggregate, then precipitate and deposit on the surfaces of environmental media (soil, sediment, aquifer, and aquitard). Previous studies have recognized the importance of asphaltene aggregates on the wettability of aquifer systems, which has long been regarded as a limiting factor that [...] Read more.
Asphaltenes generally aggregate, then precipitate and deposit on the surfaces of environmental media (soil, sediment, aquifer, and aquitard). Previous studies have recognized the importance of asphaltene aggregates on the wettability of aquifer systems, which has long been regarded as a limiting factor that determines the feasibility and remediation efficiency of sites contaminated by heavy oils. However, the mechanisms/factors associated with precipitant effects on asphaltene aggregates structure, and how the precipitant effects influence the wettability of surfaces remain largely unknown. Here, we observe the particle-by-particle growth of asphaltene aggregates formed at different precipitant concentrations. Our results show that aggregates for all precipitant concentrations are highly polydisperse with self-similar structures. A higher precipitant concentration leads to a more compacted aggregates structure, while precipitant concentration near to onset point results in a less compact structure. The well-known Smoluchowski model is inadequate to describe the structural evolutions of asphaltene aggregates, even for aggregation scenarios induced by a precipitant concentration at the onset point where the Smoluchowski model is expected to explain the aggregate size distribution. It is suggested that aggregates with relative high fractal dimensions observed at high precipitant concentrations can be used to explain the relatively low Stokes settling velocities observed for large asphaltene aggregates. In addition, asphaltene aggregates with high fractal dimensions are likely to have high density of nanoscale roughness which could enhance the hydrophobicity of interfaces when they deposit on the sand surface. Findings obtained from this study advance our current understandings on the fate and transport of heavy oil contaminants in the subsurface environment, which will have important implications for designing and implementing more effective and efficient remediation technologies for contaminated sites. Full article
(This article belongs to the Special Issue Colloid and Pathogen Transport in Groundwater)
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15 pages, 1092 KiB  
Article
Sedimentation and Transport of Different Soil Colloids: Effects of Goethite and Humic Acid
by Yali Chen, Jie Ma, Xiaojuan Wu, Liping Weng and Yongtao Li
Water 2020, 12(4), 980; https://doi.org/10.3390/w12040980 - 30 Mar 2020
Cited by 21 | Viewed by 3581
Abstract
Soil colloids significantly facilitate the transport of contaminants; however, little is known about the effects of highly reactive iron oxide and the most representative organic matter on the transport of soil colloids with different physicochemical properties. This study investigated the effects of goethite [...] Read more.
Soil colloids significantly facilitate the transport of contaminants; however, little is known about the effects of highly reactive iron oxide and the most representative organic matter on the transport of soil colloids with different physicochemical properties. This study investigated the effects of goethite (GT) and humic acid (HA) on the sedimentation and transport of soil colloids using settling and column experiments. The stability of soil colloids was found to be related to their properties and decreased in the following order: black soil colloids (BSc) > yellow soil colloids (YSc) > fluvo-aquic soil colloids (FSc). Organic matter increased the stability of BSc, and ionic strength (Ca2+) promoted the deposition of FSc. Colloids in individual and GT colloids (GTc) coexistence systems tended to stabilize at high pH and showed a pH-dependence whereby the stability decreased with decreasing pH. The interaction of GTc and kaolinite led to a dramatic sedimentation of YSc at pH 4.0. HA enhanced the stability of soil colloids, especially at pH 4.0, and obscured the pH-dependent sedimentation of soil colloids. The transport ability of soil colloids was the same as their stability. The addition of GT retarded the transport of soil colloids, which was quite obvious at pH 7.0. This retardation effect was attributed to the transformation of the surface charge of sand from negative to positive, which increased the electrical double-layer attraction. Although sand coated with GT–HA provided more favorable conditions for the transport of soil colloids in comparison to pure sand, the corresponding transport was relatively slow. This suggests that the filtration effect, heterogeneity, and increased surface roughness may still influence the transport of soil colloids. Full article
(This article belongs to the Special Issue Colloid and Pathogen Transport in Groundwater)
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10 pages, 1196 KiB  
Article
Cotransport of Cu with Graphene Oxide in Saturated Porous Media with Varying Degrees of Geochemical Heterogeneity
by Jianzhou He, Dengjun Wang, Tingting Fan and Dongmei Zhou
Water 2020, 12(2), 444; https://doi.org/10.3390/w12020444 - 7 Feb 2020
Cited by 6 | Viewed by 2176
Abstract
Graphene oxide (GO) is likely to encounter heavy metals due to its widespread use and inevitable release into the subsurface environment, where the ubiquitous presence of iron oxides (e.g., hematite) would affect their interaction and transport. The present study aimed to investigate the [...] Read more.
Graphene oxide (GO) is likely to encounter heavy metals due to its widespread use and inevitable release into the subsurface environment, where the ubiquitous presence of iron oxides (e.g., hematite) would affect their interaction and transport. The present study aimed to investigate the cotransport of GO (20 mg L−1) and copper (0.05 mM CuCl2) in the presence of varying degrees of geochemical heterogeneity represented by iron oxide-coated sand fractions (ω = 0‒0.45) in water-saturated columns under environmentally relevant physicochemical conditions (1 mM KCl at pH 5.0‒9.0). The Langmuir-fitted maximum adsorption capacity of Cu2+ by GO reached 137.6 mg g−1, and the presence of 0.05 mM Cu2+ decreased the colloidal stability and subsequent transport of GO in porous media. The iron oxide coating was found to significantly inhibit the transport of GO and Cu-loaded GO in sand-packed columns, which can be explained by the favorable deposition of the negatively charged GO onto patches of the positively charged iron oxide coatings at pH 5.0. Increasing the solution pH from 5.0 to 9.0 promoted the mobility of GO, with the exception of pH 7.5, in which the lowest breakthrough of GO was observed. This is possibly due to the fact that the surface charge of iron oxide approaches zero at pH 7.5, suggesting that new “favorable” sites are available for GO retention. This study deciphered the complicated interactions among engineered nanomaterials, heavy metals, and geochemical heterogeneity under environmentally relevant physicochemical conditions. Our results highlight the significant role of geochemical heterogeneity, such as iron oxide patches, in determining the fate and transport of GO and GO-heavy metal association in the subsurface environment. Full article
(This article belongs to the Special Issue Colloid and Pathogen Transport in Groundwater)
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12 pages, 996 KiB  
Article
Transport of Microplastic Particles in Saturated Porous Media
by Xianxian Chu, Tiantian Li, Zhen Li, An Yan and Chongyang Shen
Water 2019, 11(12), 2474; https://doi.org/10.3390/w11122474 - 24 Nov 2019
Cited by 44 | Viewed by 5407
Abstract
This study used polystyrene latex colloids as model microplastic particles (MPs) and systematically investigated their retention and transport in glass bead-packed columns. Different pore volumes (PVs) of MP influent suspension were first injected into the columns at different ionic strengths (ISs). The breakthrough [...] Read more.
This study used polystyrene latex colloids as model microplastic particles (MPs) and systematically investigated their retention and transport in glass bead-packed columns. Different pore volumes (PVs) of MP influent suspension were first injected into the columns at different ionic strengths (ISs). The breakthrough curves (BTCs) were obtained by measuring the MP concentrations of the effluents. Column dissection was then implemented to obtain retention profiles (RPs) of the MPs by measuring the concentration of attached MPs at different column depths. The results showed that the variation in the concentrations of retained MPs with depth changed from monotonic to non-monotonic with the increase in the PV of the injected influent suspension and solution IS. The non-monotonic retention was attributed to blocking of MPs and transfer of these colloids among collectors in the down-gradient direction. The BTCs were well simulated by the convection-diffusion equation including two types of first-order kinetic deposition (i.e., reversible and irreversible attachment). However, this model could not well simulate the non-monotonic retention profiles due to the fact that the transfer of colloids among collectors was not considered. The results in this study are critical to developing models to simulate the fate and transport of MPs in porous media such as soil. Full article
(This article belongs to the Special Issue Colloid and Pathogen Transport in Groundwater)
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