1,720,972 research outputs found
Numerical case studies on long-term effectiveness of metallic iron based permeable reactive barriers: Importance of porosity heterogeneity of the barrier
No full textThis paper presents a three-dimensional (3-D) numerical groundwater flow and transport model of a metallic iron based permeable reactive barrier (Fe0-PRB) to assess how porosity heterogeneity of the barrier medium may affect groundwater flow over time and influence the long-term effectiveness of a Fe0-PRB. A 3-D high resolution aquifer outcrop analogue was utilized to implement aquifer heterogeneity. To evaluate the treatment performance of the PRB, the contaminant plume migration and groundwater residence time were investigated. The findings demonstrate that heterogeneity of porosity reduction of the barrier medium is an important factor in estimating the long-term performance of a continuous-wall Fe0-PRB. Ignoring the porosity heterogeneity of the barrier medium leads to an underestimation of the by-passing flow by 30%-41% in ten-years simulation, and of contaminant plume spread over time. Groundwater residence time simulations shows no evident residence time reduction during the operation of the Fe0-PRB. Installation of a pea gravel equalization zone can effectively reduce the heterogeneity of the barrier medium, and minimize the by-passing flow.http://dx.doi.org/10.13039/501100002855 Ministry of Science and Technology of the People's Republic of Chin
Materials for sustainable metallic iron-based water filters: a review
No full textAbstract
Water pollution is calling for a sustainable remediation method such as the use of metallic iron (Fe
0
) to reduce and filter some pollutants, yet the reactivity and hydraulic conductivity of iron filters decline over time under field conditions. Here we review iron filters with focus on metallic corrosion in porous media, flaws in designing iron filters, next-generation filters and perspectives such as safe drinking water supply, iron for anaemia control and coping with a reactive material. We argue that assumptions sustaining the design of current Fe
0
filters are not valid because proposed solutions address the issues of declining iron reactivity and hydraulic conductivity separately. Alternatively, a recent approach suggest that each individual Fe
0
atom corroding within a filter contributes to both reactivity and permeability loss. This approach applies well to alternative iron materials such as bimetallics, composites, hybrid aggregates, e.g. Fe
0
/sand, and nano-Fe
0
. Characterizing the intrinsic reactivity of individual Fe
0
materials is a prerequisite to designing sustainable filters. Indeed, Fe
0
ratio, Fe
0
type, Fe
0
shape, initial porosity, e.g. pore size and pore size distribution, and nature and size of admixing aggregates, e.g. pumice, pyrite and sand, are interrelated parameters which all influence the generation and accumulation of iron corrosion products. Fe
0
should be characterized in long-term experiments, e.g. 12 months or longer, for Fe dissolution, H
2
generation and removal of contaminants in three media, i.e., tap water, spring water and saline water, to allow reactivity comparison and designing field-scale filters.Ministry of Science and Technology of the People's Republic of China http://dx.doi.org/10.13039/501100002855Georg-August-Universität Göttingen 50110000338
Predicting methane solubility in water and seawater by machine learning algorithms: Application to methane transport modeling
No full textA general numerical model for water level response to harmonic disturbances in aquifers considering wellbore effects
No full textThe use of feed-forward and cascade-forward neural networks to determine swelling potential of clayey soils
No full textGaussian process regression to determine water content of methane: Application to methane transport modeling
No full textInvestigation of hydraulic properties in fractured aquifers using cross-well travel-time based thermal tracer tomography: Numerical and field experiments
No full text
Tracing the Scientific History of Fe0-Based Environmental Remediation Prior to the Advent of Permeable Reactive Barriers
No full textThe technology of using metallic iron (Fe0) for in situ generation of iron oxides for water treatment is a very old one. The Fe0 remediation technology has been re-discovered in the framework of groundwater remediation using permeable reactive barriers (PRBs). Despite its simplicity, the improvement of Fe0 PRBs is fraught with difficulties regarding their operating modes. The literature dealing with Fe0 remediation contains ambiguities regarding its invention and its development. The present paper examines the sequence of contributions prior to the advent of Fe0 PRBs in order to clarify the seemingly complex picture. To achieve this, the current paper addresses the following questions: (i) What were the motivations of various authors in developing their respective innovations over the years?, (ii) what are the ancient achievements which can accelerate progress in knowledge for the development of Fe0 PRBs?, and (iii) was Fe0 really used for the removal of organic species for the first time in the 1970s? A careful examination of ancient works reveals that: (i) The wrong questions were asked during the past three decades, as Fe0 was premised as a reducing agent, (ii) credit for using Fe0 for water treatment belongs to no individual scientist, and (iii) credit for the use of Fe0 in filtration systems for safe drinking water provision belongs to scientists from the 1850s, while credit for the use of Fe0 for the removal of aqueous organic species does not belong to the pioneers of the Fe0 PRB technology. However, it was these pioneers who exploited Fe0 for groundwater remediation, thereby extending its potential. Complementing recent achievements with the chemistry of the Fe0/H2O system would facilitate the design of more sustainable Fe0-remediation systems
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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