1,721,016 research outputs found
Source apportionment of mine contamination across streamflows
Full text linkThis is the final version. Available from Elsevier via the DOI in this record.Data will be made available on request.Globally, metals released by mine waste represent a challenge for protecting water quality and ecosystems. Understanding metal dispersion in catchments is critical for developing efficient remediation strategies and reducing contamination from mining activities. Efforts to address the issue have been constrained by diffuse sources and variation of source contributions across streamflows. In the UK, metal source apportionment is typically addressed using monitoring strategies with low spatial resolution, which can underestimate the contribution of diffuse sources. In this proof-of-concept study, diffuse sources were accurately apportioned in a mining-impacted catchment in Mid-Wales (UK), using a hydrogeochemical approach with combined continuous tracer injections, gulp injections, and streambed sediment geochemistry. The continuous tracer injections identified a major Zn and Pb point source, diffuse sources due to mine waste tip runoff, and potential groundwater contributions. Variations in source contributions were estimated during high and low flow conditions, with Zn having similar sources and importance across streamflows and Pb being released mainly from overground tips during high flow conditions (22% Pb under low flow and 80% Pb under high flow). The distribution of metal-bearing sediment along the stream sheds light on metal release mechanisms across streamflow conditions. This hydrogeochemical approach for source apportionment, builds on common monitoring methods, and represents a substantial advance in accounting diffuse mine contamination sources, understanding potential metal release mechanisms, and designing remediation strategies.Liverpool John Moores Universit
Fluvial Morphology as a Driver of Lead and Zinc Geochemical Dispersion at a Catchment Scale
Full text linkMetal-mining exploitation has caused ecosystem degradation worldwide. Legacy wastes are often concentrated around former mines where monitoring and research works are mostly focused. Geochemical and physical weathering can affect metal-enriched sediment locations and their capacity to release metals at a catchment scale. This study investigated how fluvial geomorphology and soil geochemistry drive zinc and lead dispersion along the Nant Cwmnewyddion (Wales, UK). Sediments from different locations were sampled for geochemical and mineralogical investigations (portable X-ray fluorescence, scanning electron microscope, X-ray diffraction, and electron microprobe analysis). The suspended sediment fluxes in the streamwater were estimated at different streamflows to quantify the metal dispersion. Topographical and slope analysis allowed us to link sediment erosion with the exposure of primary sulphide minerals in the headwater. Zinc and lead entered the streamwater as aqueous phases or as suspended sediments. Secondary sources were localised in depositional stream areas due to topographical obstruction and a decrease in stream gradient. Sediment zinc and lead concentrations were lower in depositional areas and associated with Fe-oxide or phyllosilicates. Streamwater zinc and lead fluxes highlighted their mobility under high-flow conditions. This multi-disciplinary approach stressed the impact of the headwater mining work on the downstream catchment and provided a low-cost strategy to target sediment sampling via geomorphological observations
Iron minerals as archives of Earth's redox and biogeochemical evolution
No full textIron minerals provide sedimentary repositories of chemical information pertaining to Earth’s redox and biogeochemical evolution, from before the Great Oxidation Event some 2.5 billion years ago, to more recent events occurring up to and into the Cenozoic Era. The most powerful chemical information recorded in iron minerals comes in the form of trace-element signatures, most notably their concentrations and stable isotope compositions. Here we provide an introduction to iron mineralogy and the processes responsible for the accumulation and preservation of trace-element signatures in iron minerals, focusing on the deposition of iron minerals in three key ancient sedimentary archives: banded iron formations, ferromanganese crusts and black shales. We introduce the theory and practical use of non-traditional trace-element stable-isotope systems in redox and biogeochemical research, focusing on the recent use of iron, molybdenum and chromium stable isotopes to shed light on the redox and biogeochemical information stored in iron-rich sediments. By analysing both trace-element concentrations and stableisotope compositions recorded in iron minerals, iron-rich sedimentary archives are providing a unique window into the past, where changes in trace-element signatures shed light on major transitions in Earth’s redox and biogeochemical evolution
Removal of arsenic, nitrate, persistent organic pollutants and pathogenic microbes from water using redox-reactive minerals
No full textWater pollution is a major global problem at present, involving inorganic and organic
contaminants such as heavy metals, pesticides and pharmaceutical compounds, as well
as pathogens. Therefore, the development of water-management strategies and
appropriate water-treatment technologies has been the subject of intense research for
decades. This chapter reviews the potential use of redox-reactive minerals as reactive
media in environmental cleanup technologies especially in the removal of arsenic,
nitrate, persistent organic pollutants and pathogenic microbes. The properties and
applications of five classes of redox-reactive materials are summarized: zero-valent
metals, mixed-valence iron oxyhydroxides, Fe-bearing clays, mixed-valence manganese
oxides and titanium and zinc oxides. Examples and case studies that demonstrate the
significant role of these reactive materials in water-treatment processes are also
provided
Application of filtration and silver-ion based disinfection to purify rainwater for potable uses in rural communities of Mexico
Full text linkWith growing pressures on water supplies worldwide, rainwater harvesting (RWH) is increasingly seen as a viable option to provide drinking water to an expanding population. However, rooftop runoff is not without quality issues. Microbiological and chemical contamination have been detected in several studies, posing a health risk for consumers. This research explores the use of silver ions, combined with conventional filtration and settling mechanisms, as a safe and affordable treatment method that can be applied at a small scale. The systems were installed and tested in rural communities of San Miguel de Allende, a Mexican semi-arid region, throughout two different periods of fieldwork analyses. Lab-scale models were also implemented at UCL, in order to further refine the technology. Silver has been known for centuries to be a powerful disinfectant, with no known harmful effects to humans if applied in appropriate doses. However, implementation in small-scale rainwater harvesting systems has received little attention, possibly due to a general perception that it is complicated and/or expensive. The devices studied in this thesis are able to dose silver ions at a relatively low cost, avoiding the use of complex nano-materials. System performance is seen to be highly linked to source water conductivity and ionic strength, highlighting the importance of adapting the technology for the specific case of RWH. Total coliform elimination efficiencies of up to 99.9% are achieved in the field, with a marked exception where cross-contamination from external seepage occurs. Sites with relatively clean rooftops show an absence of total coliforms in the untreated runoff, compared with others where values as high as 1650 CFU/100 ml are recorded. Disinfection using an emerging technique for bacteriophage detection is investigated in the laboratory, indicating a capacity to inactivate viral particles. Technology adoption issues are also explored, particularly where increased contamination occurs due to insufficient stakeholder participation. Observations show that the silver ion dispensers themselves require little maintenance, while the other components of the system tend to pose more of a challenge
Introduction to redox-reactive minerals in natural systems and clean technologies
Full text linkThis is the author accepted manuscript. The final version is available from the publisher via the DOI in this recordMinerals are naturally occurring inorganic solids that make up the solid part of most solar terrestrial planets. Redox-active elements such as iron, manganese, titanium and sulfur, in these minerals allow them to engage in a wide range of electron-transfer reactions including those mediated by biota or processes involved in palaeo-weathering and biogeochemical cycling. The importance of redox-reactive minerals in many natural and industrial processes has been demonstrated by a plethora of scientific publications and industrial applications in recent decades. In this book, the influence of redox-reactive minerals on key biogeochemical processes and opportunities for their application in environmental technologies are outlined and illustrated in 14 comprehensive chapters. The book will be a key reference for Earth science students, geologists, geochemists and engineers and other researchers and practitioners in this rapidly growing interdisciplinary field
Role of redox-reactive minerals in the reuse and remediation of mine wastes
Full text linkThis is the author accepted manuscript. The final version is available from the publisher via the DOI in this recordMining, oil and gas and other extractive industries are vital and irreplaceable constituents of the modern global economy. The overall demand for the products of these industries rises inexorably with economic growth and developing prosperity. However, these industries produce vast quantities of potentially harmful waste. Many of the elemental, and hence mineralogical, components of the waste stream are redox active. This review focuses on redox-reactive minerals sourced from this waste stream in reuse and remediation schemes. Copper-, manganese- and iron-bearing mine wastes are used as pigments, in fertilizers, sorbents of toxic compounds in water treatment systems, and for the production of SO 2 and H 2 SO 4 . Some solid mine wastes can be remediated by phytostabilization, where plants are used to induce the precipitation of secondary redoxreactive minerals that sequester contaminants. Liquid wastes are remediated using a variety of abiotic and biotically-assisted schemes such as anoxic limestone drainages and permeable reactive barriers. These schemes use phases such as zero-valent iron and Feoxyhydroxides, and produce mineralogical by-products such as sulfides, green rust and oxyhydroxides. Further research is needed to optimize the reuse and remediation schemes in mine wastes and to develop new and innovative systems employing redox active minerals
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
Converting rain into drinking water: Quality issues and technological advances
No full textWith growing pressures on water supplies worldwide, rainwater harvesting is increasingly seen as a viable option to provide drinking water to an ever expanding population, particularly in developing countries. However, rooftop runoff is not without quality issues. Microbiological and chemical contamination have been detected in several studies, well above local and international guidelines, posing a health risk for consumers. Our research explores the use of silver ions, combined with conventional filtration and settling mechanisms, as a safe and affordable model for purification that can be applied on a small scale. The complete systems were installed and tested in rural communities in a Mexican semi-arid region. Efficiencies up to 99.9% were achieved in the removal of indicator microorganisms, with a marked exception where cross-contamination from external seepage occurs. Sites without overhanging branches or with relatively clean surfaces show an absence of total coliforms in the untreated runoff, compared with others where values as high as 1,650 CFU/100 ml were recorded. Thus, given adequate maintenance, the system can successfully deliver high quality drinking water, even when storage is required for long periods of time. © IWA Publishing 2011
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