Mixed Contaminants Research Articles

Mixed versus layered multi-media filter for simultaneous removal of nutrients and heavy metals from urban stormwater runoff.

Beach closings are a growing concern in coastal regions because of serious public health and economic ramifications due to the presence of pollutants in stormwater runoff. An underground permeable filter system is proposed to treat such stormwater pollution. Selection of filter media that can treat multiple contaminants in stormwater runoff has been a challenging task. This paper investigates the effectiveness of mixed or layered filter media for the removal of mixed contaminants (nutrient and heavy metal) from synthetic stormwater. Sorption experiments were used to assess the ability of the combination of various materials (calcite, zeolite, sand, and iron filings) to remove nutrients and heavy metals. Based on the results of individual removal efficiency, four sets of combinations of media mixtures were prepared: three mixed media conditions and one layered media condition. Mixed media-1, containing higher ratio of calcite, zeolite, and iron filings, was found to achieve the highest removal efficiency of nitrate (96%), Cr (~ 99%), and Cu (~ 99%). Mixed media-2 removed Zn significantly with a removal efficiency higher than 99% due to the sorption capacity of iron filings and both mixed media-2 and 3 showed efficient removal of Ni (~ 94%) in effluent. Layered media was found to be most efficient in Cd removal (~ 99%). All mixture of materials showed more than 99% removal of total phosphorus and Pb. The sorption efficiency of the different mixtures showed that a combination of traditional (sand) and alternative materials (calcite, zeolite, and iron filings) can be used as an effective medium for the treatment of nutrient and heavy metal contaminants commonly found in stormwater.

Prevalence and Prevention of Reproducibility Deficiencies in Life Sciences Research: Large-Scale Meta-Analyses.

BackgroundStudies have found that many published life sciences research results are irreproducible. Our goal was to provide comprehensive risk estimates of familiar reproducibility deficiencies to support quality improvement in research.Material/MethodsReports included were peer-reviewed, published between 1980 and 2016, and presented frequency data of basic biomedical research deficiencies. Manual and electronic literature searches were performed in seven bibliographic databases. For deficiency concepts with at least four frequency studies and with a sample size of at least 15 units in each, a meta-analysis was performed.ResultsOverall, 68 publications met our inclusion criteria. The study identified several major groups of research quality defects: study design, cell lines, statistical analysis, and reporting. In the study design group of 3 deficiencies, missing power calculation was the most frequent (82.3% [95% Confidence Interval (CI): 69.9–94.6]). Among the 6 cell line deficiencies, mixed contamination was the most frequent (22.4% [95% CI: 10.4–34.3]). Among the 3 statistical analysis deficiencies, the use of chi-square test when expected cells frequency was <5 was the most prevalent (15.7% [95% CI: −3.2–34.7]). In the reporting group of 12 deficiencies, failure to state the number of tails was the most frequent (65% [95% CI: 39.3–90.8]).ConcluisonsThe results of this study could serve as a general reference when consistently measurable sources of deficiencies need to be identified in research quality improvement.

Verification of mono- and mixed contaminations transmitting agents tick-borne infections.

In the territory of the Primorsky region, the nosoareas of causative agents of tick-borne infections often coincide and lead to mixed infection of ticks, which causes the mixed pathology in humans . We investigated ixodid ticks taken from people during the epidemic season of 2019 for the spectrum of pathogens of transmissible infections to determine the degree of their mono- and mixed infection. 651 specimens of ixodid ticks investigated. RNA/DNA pathogens was determined by the method of polymerase chain reaction (PCR), TBEV antigen by ELISA. The presence in ticks of pathogens of the following diseases was detected: Lyme borreliosis (35.3%), tick-borne replasing fever (11.3%), human granulocytic anaplasmosis (2.6%), human monocytic ehrlichiosis (2.4%), tick-borne encephalitis (1.8%), tick-borne ricketsiosis (1.0%). As agents of mono-infections, the virus of TBE, ehrlichia, anaplasma and rickettsia in ticks occurred less frequently than in combination with other pathogens. A high frequency of occurrence B. burgdorferi s.l. in mono-infection detected (58.7%). B. miyamotoi has met evenly at ticks with mono- and mixed infections. Total mixed infection of ticks was 23.1%. Borrelia have been identified in all mixed cases. Variants of double combinations (95.5 % of cases from all mixed infections) were as follows: B. burgdorferi s. l. + A. phagocytophilum, B. burgdorferi s.l. + E. chaffeensis / E. muris, B. burgdorferi s.l. + TBEV, B. burgdorferi s.l. + R. heilongjiangensis, B. burgdorferi s.l. + B. miyamotoi. The most frequent combination was B. burgdorferi s.l. + B. miyamotoi (37.8% of all mixed infections). In triple infection of B. burgdorferi s.l. + A. phagocytophilum + TBEV and B. burgdorferi s.l. + A. phagocytophilum + B. miyamotoi, the frequency of occurrence for each combination was 2.2%. Given the above, a complex laboratory diagnosis of tick-borne infections in individuals who have been bitten by a tick is necessary, including the detection of all pathogens common in focal areas.

Efficient and selective removal of SeVI and AsV mixed contaminants from aqueous media by montmorillonite-nanoscale zero valent iron nanocomposite

Nanoscale zero-valent iron (NZVI) and NZVI supported onto montmorillonite (NZVI-Mt) were synthetized and used in this study to remove SeVI and AsV from water in mono- and binary-adsorbate systems. The adsorption kinetics and isotherm data for SeVI and AsV were adequately described by the pseudo-second-order (PSO) (r2>0.94) and Freundlich (r2>0.93) equations. Results from scanning electron microscopy showed that the dimension of the NZVI immobilized on the Mt was smaller than pure NZVI. Using 0.05 g of adsorbent and an initial 200 mg L−1 AsV and SeVI concentration, the maximum adsorption capacity (qmax) and partition coefficient (PC) for AsV on NZVI-Mt in monocomponent system were 54.75 mg g-1 and 0.065 mg g-1·μM-1, which dropped respectively to 49.91 mg g-1 and 0.055 mg g-1·μM-1 under competitive system. For SeVI adsorption on NZVI-Mt in monocomponent system, qmax and PC were 28.63 mg g-1 and 0.024 mg g-1·μM-1, respectively. Values of qmax and PC were higher for NZVI-Mt than NZVI and montmorillonite, indicating that the nanocomposite contained greater adsorption sites for removing both oxyanions, but with a marked preference for AsV. Future research should evaluate the effect of different operational variables on the removal efficiency of both oxyanions by NZVI-Mt.

Multiple Optical Sensor Fusion for Mineral Mapping of Core Samples.

Geological objects are characterized by a high complexity inherent to a strong compositional variability at all scales and usually unclear class boundaries. Therefore, dedicated processing schemes are required for the analysis of such data for mineralogical mapping. On the other hand, the variety of optical sensing technology reveals different data attributes and therefore multi-sensor approaches are adapted to solve such complicated mapping problems. In this paper, we devise an adapted multi-optical sensor fusion (MOSFus) workflow which takes the geological characteristics into account. The proposed processing chain exhaustively covers all relevant stages, including data acquisition, preprocessing, feature fusion, and mineralogical mapping. The concept includes (i) a spatial feature extraction based on morphological profiles on RGB data with high spatial resolution, (ii) a specific noise reduction applied on the hyperspectral data that assumes mixed sparse and Gaussian contamination, and (iii) a subsequent dimensionality reduction using a sparse and smooth low rank analysis. The feature extraction approach allows one to fuse heterogeneous data at variable resolutions, scales, and spectral ranges and improve classification substantially. The last step of the approach, an SVM classifier, is robust to unbalanced and sparse training sets and is particularly efficient with complex imaging data. We evaluate the performance of the procedure with two different multi-optical sensor datasets. The results demonstrate the superiority of this dedicated approach over common strategies.

Strategies for mud-removal from washouts during cementing of vertical surface casing

In the context of both production and well abandonment, effective cementing of the surface casing is key in preventing leakage of formation fluids. Although there are general guidelines for the effective cementing of vertical casings, there is little known about the effects of wellbore irregularity, e.g. from formations that are badly eroded during drilling - washouts. Here we present a systematic study of the cementing of a vertical surface casing with a washout section. We study the effects of washout length, pump rate, positive density difference and viscosity ratio, all in the displacement flow of the drilling mud by a spacer. Of these parameters, flow rate increases can lead to both improved displacements and to mixing and potential contamination. A positive density difference improves the mud displacement and viscosity differences have minimal effect, at least over the ranges studied. We then propose a pumping strategy that may improve the displacement process in a targeted washout, potentially valuable as we move into the era of real-time (and while drilling) well calipers and are progressively able to include irregular borehole geometries into cementing designs.

Post-collisional potassic rocks in Western Kunlun, NW Tibet Plateau: Insights into lateral variations in the crust-mantle structure beneath the India-Asia collision zone

The collision between India and Asia created the most significant orogenic system of the Cenozoic. Although numerous collision-related igneous rocks formed, many post-collisional rocks were emplaced but have received less attention. Recently, geophysical investigations and field observations have suggested significant lateral variations in crust-mantle structure beneath the collisional zone. However, there have been few attempts so far to reveal the possible relationship between the lateral variations in crust-mantle structure and the widely distributed post-collisional rocks. To reveal the possible linkage, we investigate the Pulu volcanic rocks in Western Kunlun, NW Tibet Plateau, through a combined analysis involving whole-rock geochemistry and Sr-Nd-Pb isotopes, and mineralogy. The similar profiles (e.g., Fo and An values) of olivine, pyroxene, and plagioclase phenocrysts, along with relatively consistent whole-rock isotopic compositions argue against mixing and significant crustal contamination. The sub-continental lithospheric mantle source (SCLM) was enriched by the input of sedimentary materials as indicated by Sr-Nd-Pb isotopic compositions (87Sr/86 Sr(t) < 0.708884, 143Nd/144Nd > 0.512344, and 204Pb/207Pb < 15.6831). The Pulu volcanic rocks in Western Kunlun display high Rb/Sr ratios (> 0.05) and low Ba/Rb ratios (〈23), indicating an amphibole-free phlogopite residual source at a depth of >70 km. In addition, high LREE/HREE (LaN/YbN > 49) and Nb/Ta ratios (> 20), and olivine geothermometer confirm a garnet-bearing mantle source at >970 °C under eclogite-facies conditions. In contrast to other post-collisional rocks formed under low pressure and widely variable temperatures associated with the delamination and thinning of SCLM in the eastern and southern Tibet Plateau, post-collisional rocks in Western Kunlun formed under the high pressure and a narrow range of temperature are attributed to lithospheric fractures at great depths before delamination. Such contrasting P-T conditions of the post-collisional rocks in Western Kunlun and eastern and southern Tibet Plateau record lateral variations in crust-mantle structures beneath the India-Asia collisional zone.

Effects of Elevated Concentrations of Co-Existing Heavy Metals and PAHs in Soil on Phytoremediation

Abstract This study presents a series of laboratory experiments conducted to investigate the effects of elevated contaminant concentrations on phytoremediation of soils with mixed contaminants. A s...

Mixture of Pb, Zn and Cu on root permeability and radial oxygen loss in the mangrove Bruguiera gymnorrhiza.

A short term pot trail was employed to evaluate the exposure of mixed heavy metals (Cu, Pb and Zn) on growth, radial oxygen loss (ROL) and root anatomy in Bruguiera gymnorrhiza. The possible function of BgC4H, a cytochrome P450 gene, on root lignification was also discussed. The exposures of mixed Cu, Pb and Zn directly reduce O2 leakage at root surface. The reduced ROL inhibited by heavy metals was mainly ascribed by the changes in root anatomical features, such as decreased root porosity together with increased lignification within the exodermis. BgC4H was found to be up-regulated after 0.5-day metal exposure, and remained higher transcript levels within 3-day metal exposure when compared to control roots. Besides, the inhibited photosynthesis may also result in less oxygen can be transported to the underground roots. In summary, the mangrove B. gymnorrhiza appeared to react to external mixed metal contaminants by developing a lignified and impermeable exodermis, and such a root barrier induced by mixed Cu, Pb and Zn appeared to be an adaptive response to block metal ions enters into the roots.

Analytical methods for mixed organic chemical residues and contaminants in food.

Developing methods that can analyze multiple categories of organic chemical residues such as pesticides, veterinary drugs, mycotoxins, human drugs, and environmental contaminants in food with a single analytical procedure is a growing trend. These methods for mixed organic chemical residues and contaminants focus on the chemical properties of these analytes rather than how they are used and adulterate the food supply. This paper highlights recently published methods for mixed residue and contaminant methods in food including advances in technology (instrumental hardware, data processing programs, and sample cleanup) that allow for a larger number of compounds to be monitored simultaneously. The factors that determine the scope, or number and type of analytes in a given method, including needs for specific food commodities, complexity of the analytical procedure, and the intended purpose (qualitative vs quantitative analysis) will be examined. Although there are clear advantages to expanding the number of unwanted chemicals being monitored in the global food supply, challenges to developing and implementing mixed organic residue and contaminant methods will also be discussed. Going forward, it will be important to implement these methods to more thoroughly protect the food supply for a wide variety of targeted and non-targeted chemical residues and contaminants while also having the regulatory framework in place to effectively manage the results of these comprehensive analyses. Graphical abstract.

Remediation of inorganic contaminants in soil using electrokinetics, phytoremediation techniques

During the last decade, the expansion of urbanization and industrial activities caused serious environmental problems such as soil pollution. Currently, the vast majority of remediation projects involve disposing of contaminated soil in a landfill. With the introduction of this, cause increased landfill tax and becoming less desirable, and so robust. Novel technologies are required to remediate soil contamination with toxic contaminants, including heavy metals and organic pollutants. Electrokinetic (EK) and Phytoremediation are better techniques. Electrokinetic is an emerging remediation technology for mixed contaminants, especially in low hydraulic conductivity soils. During the electrokinetic remediation process, an electric field is applied to the specimen to remove the contaminants from soil by means of electro-osmotic (EO), electromigration (EM), and electrophoresis (EP) processes. This paper addresses the problem of contaminants in soil and has investigated the use of electrokinetic phenomena and phytoremediation as tools to bring about an increase in this factor, leading to improved degradation. Electrokinetic separation is an emerging technology that relies on the application of a low-density, the direct current through the soil to separate and extract the heavy metal. When comparing these two techniques a significant increase in the effectiveness of the remediation was noted with electrokinetics technique, with substantially faster degradation to occur.

Mycotoxicological monitoring. Part 1. Complete mixed feed for pigs and poultry (2009–2018)

Results of the ten-year annual mycotoxicological testing of complete mixed feeds for pigs and poultry submitted by holdings and processing establishments located in the Northwestern, Central, Southern, Volga and Ural Federal Districts are presented. Competitive ELISA tests showed that the occurrence of T-2 toxin, deoxynivalenol, zearalenon, fumonisines B, alternariol, ochratoxin A, citrinin, mycophenolic acid, ergoalkoloids and emodin was about 5% and quantities thereof varied within one or three orders; quantities of T-2 toxin, deoxynivalenol, zearalenon, fumonisines, and ochratoxin A might exceed maximum admissible levels for feed grains. Diacetoxyscirpenol, aflatoxin В1, sterigmatocystin and cyclopiazonic acid belonged to group of rare contaminants. Level of feed contamination with T-2 toxin and emodin was found to be consistently high during the said period; in some of the years occurrence of deoxynivalenol, fumonisines as well as ochra­toxin A, citrinin, mycophenolic acid and ergoalkoloids increased. In 2016–2018, mixed feed contamination with alternariol increased whereas contamination with fumonizin steadily decreased and level of zearalenon occurrence remained consistently low. Evidence for a wide occurrence of emodin known as “diarrheic factor” as well as for sporadic increase in mixed feed contamination with alternariol, citrinin, mycophenolic acid, mycotoxins having the highly dangerous toxic impact and long-term adverse effects, was detected for the first time. These data confirmed the need for their inclusion into the regulated group of substances significant for public health. General features of pig and poultry feed contamination as well as usefulness of regional surveys for intoxication risk prediction are described. Special attention is paid to the importance of the projects for creation of common information resources that could become a unique scientific basis for innovations in feed poisoning prevention. Original monitoring data systematized and summarized in the paper are given in electronic format in section Additional materials.

A Cd/Zn Co-hyperaccumulator and Pb accumulator, Sedum alfredii, is of high Cu tolerance

High sensitivity towards Cu toxicity is problematic when using some hyperaccumulator plants for phytoremediation of soils with mixed contamination of Cu. Sedum alfredii, a Cd/Zn co-hyperaccumulator and Pb accumulator, is widely used for remediation of Cd, Zn, and Pb co-contaminated soils in China. In this paper, the tolerance and accumulation ability of S. alfredii towards Cu stress and its potential for phytoremediation of multi-metal polluted soils have been studied. Both the hyperaccumulating ecotype (HE) and non-hyperaccumulating ecotype (NHE) of S. alfredii accumulated high Cu in the roots and translocated minimal Cu to the shoots, and Cu in the stems and leaves mostly restricted in the vascular tissues (phloem zone). The HE plants, however, exhibited high Cu resistance with stimulated lateral root growth and increased chlorophyll content under 10 μM Cu treatment. XANES analysis showed that Cu in HE roots comprised Cu2+ (46.7%), Cu-histidine (35.2%) and Cu-cell wall (18.1%). The NHE under Cu stress showed decreased biomass, reduced leaf chlorophyll content, altered root architecture, and higher Cu localized to root cell wall as compared with the HEs. Potted HE plants thrived six months in multi-metal contaminated soils including 3897 mg kg−1 available Cu. In conclusion, HE S alfredii is highly tolerant toward Cu due to metal homeostasis in root cells. Therefore, this plant has great potential to remediate Zn, Cd, and Pb contaminated soils those also contain high levels of Cu.

Simultaneous reduction of Cr(VI) and degradation of tetracycline hydrochloride by a novel iron-modified rectorite composite through heterogeneous photo-Fenton processes

• The simultaneous removal of a heavy metal and organic contaminant was achieved. • The introduction of RhB induced more iron ions into the interlayers of a rectorite. • TC increased the Cr(VI) reduction rate 46.4-fold in the Fe-R-2/H 2 O 2 /LED system. • The Fe-R-2/H 2 O 2 system exhibited a great photocatalytic activity under sunlight. • The mechanism for the simultaneous removal of TC and Cr(VI) was proposed. To develop a low-cost, efficient and environmentally benign technique for the simultaneous removal of heavy metals and organic contaminants is a great challenge in practical wastewater treatment. In this work, a novel iron-modified rectorite (Fe-R) composite was prepared via the degradation of Rhodamine B (RhB) in a Fenton-like process and used for the simultaneous degradation of tetracycline hydrochloride (TC) and reduction of Cr(VI) through heterogeneous photo-Fenton processes. The results reveal that the introduction of RhB to the rectorite could induce more iron ions into its interlayers which accelerates the decomposition of H 2 O 2 , inhibits iron leaching and enhances its electrical conductivity. The presence of TC increased the Cr(VI) reduction rate 47.4-fold in the Fe-R-2/H 2 O 2 /LED system owing to the generation of reductive intermediates which effectively reduce Cr(VI) to Cr(III), while consuming hydroxyl radicals and suppressing the reoxidation of Cr(III). The effects of various operating parameters, as well as the adaptability, reusability, stability of the catalyst and the identities of the intermediates were comprehensively investigated. This work may shed light on the design of green, efficient and recyclable heterogeneous catalysts, and advance the practical utility of heterogeneous Fenton-like process for mixed contaminants remediation.

Techno-economic assessment of an hydrometallurgical process to simultaneously remove As, Cr, Cu, PCP and PCDD/F from contaminated soil

Industrial activities lead to the contamination of large amounts of soils polluted by both inorganic and organic compounds, which are difficult to treat due to different chemical properties. The efficiency of a decontamination process developed to simultaneously remove mixed contamination of industrial soils was evaluated at the pilot-scale, as well as operating costs associated to that process to define the best remediation approach. The results showed that the treatment of the coarse fractions (>0.250 mm) of 40 kg of soil by attrition in countercurrent mode allowed the removal of 17–42% of As, 3–31% of Cr, 20–38% of Cu, and 64–75% of polychlorinated dioxins and furans (PCDD/F). Removals of 60% for As, 2.2% for Cr, 23% for Cu, and 74% for PCDD/F were obtained during the treatment of attrition sludge (<0.250 mm) by alkaline leaching process. However, the results of the techno-economic evaluation, carried out on a fixed plant with an annual treatment capacity of 7560 tons of soil treated (tst), showed that the estimated overall costs for the attrition process alone [scenario 1] (CAD$ 451/tst) were lower than the costs of the process, which additionally includes an alkaline leaching step to treat attrition sludge [scenario 2] (CAD$ 579/tst). This techno-economic evaluation also showed that the process becomes competitive with current disposal options (thermal desorption and landfilling – CAD$ 600/tst) from a certain treatment capacity, which is around of 3465 tst/yr for the scenario 1 and 6930 tst/yr for the scenario 2. On the other hand, the techno-economic evaluations are crucial to selecting feasible decontamination process for a soil remediation project, with considerations of the type of contamination, site characteristics and cost effectiveness.

Mud/Cement Displacement in Vertical Eccentric Annuli

Summary A successful cement placement can provide zonal isolation and environmental safety. Effective design of cement placement and mud removal affects all the stages of the wellbore life, from drilling ahead to production. Accurate predictions of fluid displacement in the wellbore are vital to design fluid properties and plan the cementing job. In this work, an analytical model is developed to simulate the displacement of fluids in eccentric annuli. This paper presents an analytical method for the solution of cement/mud displacement and evaluation of interfluid contamination during displacement in vertical eccentric annuli. This new approach starts by addressing the problem of single-fluid flow in eccentric annuli by analytically solving the governing transport equations for a flow inside an unwrapped annulus. The solution is then extended to a system of two fluids in a vertical annulus by adjusting the boundary conditions for displacement. The model is completed by adding the time-dependent calculation of interface between the two fluids, enabling the accurate determination of the amount of interfluid mixing and displacement efficiency. The analytical method proposed is used to simulate single- and multifluid flows and study the effect of fluid properties of cement, spacer, and drilling mud at different flow rates on displacement efficiency for both concentric and eccentric vertical annuli. Noting that the drilling fluids are non-Newtonian, the concept of apparent viscosity is used, accounting for variable apparent viscosity at different annular gaps. 3D computational-fluid-dynamics (CFD) simulations were performed and the results were compared with the analytical solution. Moreover, instability of the interface in all cases was studied, and the analysis offers an understanding of the role of fluid properties and proposes applicable optimized design to enhance the displacements. The amount of interfluid mixing and contamination that occurs during the displacement was calculated for both methods. The analytical solution and CFD produce results within a 13% difference, which sufficiently validates the analytical model. Evidence was gathered to support that the improper design of fluid properties and flow rate along with a highly eccentric annulus can lead to substantial cement contamination. This can lead to underdesigning the amount of fluids to be pumped to provide a complete mud removal and an efficient cement placement. On the other hand, learnings and models developed allow the optimization of fluid properties that can lead to the best outcomes, even for a highly eccentric annulus. The present work aims to take part in addressing the undeniable importance of a complete cement displacement by means of a semianalytical solution for the fluid displacement coupled with the interface-instability analysis, attempting to provide a realistic prediction of the amount of interfluid mixing and cement contamination, along with qualitative judgements on the quality of the cementing job. This methodology is intended to offer improvement techniques for the displacement and provide enhancements for practical industrial applications.

Feasibility of Stabilized Zn and Pb Contaminated Soils as Roadway Subgrade Materials

The authors have developed a new binder, KMP, which is made from oxalic acid‐activated phosphate rock, monopotassium phosphate (KH2PO4), and reactive magnesia (MgO). This study explores the acid neutralization capacity, strength characteristics, water‐soaking durability, resilient modulus, and pore size distribution of KMP stabilized soils with individual Zn, Pb, or coexisting Zn and Pb contaminants. For comparison purpose, Portland cement (PC) is also tested. The results show that KMP stabilized soils have a higher acid buffering capacity than PC stabilized soils, regardless of the soil contamination conditions. The water stability coefficient and resilient modulus of the KMP stabilized soils are found to be higher than PC stabilized soils. The reasons for the differences in these properties between KMP and PC stabilized soils are interpreted based on the stability and dissolubility of the main hydration products of the KMP and PC stabilized soils, the soil pore distribution, and concentration of Mg or Ca leached from the KMP and PC stabilized soils obtained from the acid neutralization capacity tests. Overall, this study demonstrates that the KMP is effective in stabilizing soils that are contaminated with Zn or Pb alone and mixed Zn and Pb contaminants, and the KMP stabilized soils are better suited as roadway subgrade material.

Investigating microbial fuel cell aided bio-remediation of mixed phenolic contaminants under oxic and anoxic environments

The work focuses on the bioelectrochemical treatment of wastewater containing phenol and trichlorophenol in microbial fuel cells (MFC) with non-coated and PANI/SnO2 modified anodes respectively. The SnO2 and PANI/SnO2 nanocomposite synthesised were characterised using XRD and FTIR techniques. The results reflected that the efficiency of the system performing oxic treatment was better than the system performing anoxic treatment. The anoxic treatment of mixed phenolic contaminant using non-coated and coated electrodes yielded the highest power densities of 375.36 and 454.81 mW/m2 respectively while the maximum power densities under oxic treatment were 464.81 and 522.77 mW/m2 respectively. The consistently higher performance of oxic MFCs in terms of power generation and treatment efficiencies infers its higher potential in treating toxic phenolic contaminants. UV/Vis spectrophotometry and cyclic voltammetry (CV) also confirm better oxic treatment. Moreover, the electrochemical impedance spectroscopy (EIS) data further justified the higher oxic performance with reduced charge transfer and ohmic resistances. The study advocates MFC as a practically feasible alternative in treating recalcitrant chemical wastes with lower energy requirements.

Multi-stage growth of the trachytic lava dome of the Puy de Dôme (Chaîne des Puys, France). Field, geomorphological and petro-geochemical evidence

Understanding lava dome eruptions is a major concern in volcanology regarding the assessment of associated hazards. This question is usually addressed through the study of active calc-alkaline domes, however, alkaline domes remaining poorly known. The Puy de Dôme is the most prominent volcano of the Chaîne des Puys Quaternary intraplate volcanic field in the French Massif Central. It is a complex trachytic lava dome ca. 11 ka old. Field investigations, geomorphological and petro-geochemical studies were performed to understand the magmatic system of this dome and reconstruct its volcanic evolution. The different lava facies were fully characterised and their relationships with the volcano building stages have been established. A new four-step evolution is proposed for the growth of this edifice. Mineralogical and geochemical variations document magmatic differentiation with self-mixing and minor crustal contamination in a zoned reservoir within the upper crust. Magma mixing and crustal contamination through fluids interactions during magma ascent and the involvement of fumarolic activity throughout the edifice building are also documented. Further, this work highlights the specific features of the Puy de Dôme compared to calc-alkaline domes: lack of lava flows and almost complete magma degassing during ascent, resulting in the lack of significant explosive activity until the last eruption step.

Assessing aquitard integrity in a complex aquifer – aquitard system contaminated by chlorinated hydrocarbons

This study investigates for the first time the integrity of multiple stacked aquitards with different degrees of contaminant degradation. Aquitard integrity was assessed in a contaminated, multi-layered, alluvial aquifer-aquitard system (Ferrara, northern Italy). The system was contaminated by mixed organic contaminants of industrial origin (mostly chlorinated ethenes) that were illegally disposed in an urban dump four to five decades ago. High spatial resolution profiles of hydraulic head, geochemistry and chlorinated hydrocarbon concentrations were determined through the multi-layered system via discrete interval sampling of continuous cores and multilevel groundwater sampling, at three locations aligned along a transect adjacent to the buried waste to a maximum depth of 53 m below the water table.The profiles revealed that the two shallow aquitards had low integrity with respect to impeding downward migration of dense non-aqueous phase liquid (DNAPL), and provided little protection to the underlying aquifers against DNAPL contamination due to preferential pathways through imperceptible fractures and/or permeable micro-beds. However, both aquitards inhibited downward DNAPL migration to some extent due to DNAPL retention along its flow paths and accumulation at lower permeability interfaces, with decreasing peak concentrations at the top of successively deeper aquitard units. Moreover, both aquitards enhanced contaminant biodegradation due to the occurrence of organic rich sub-layers, influencing the contaminant plume composition, mobility and fate in the underlying and overlying aquifers.The deepest aquitard showed evidence of DNAPL accumulation at the top and slow diffusion-dominated transport consistent with 40 years of transport, suggesting higher integrity compared to the two shallower aquitards. However, the occurrence of micro-fractures and/or discontinuities in the aquitard upgradient under the dump (source) is the most likely explanation for contamination of the deepest aquifer. Analytical 1-D simulations of the diffusion profiles in the deepest aquitard revealed that DNAPL contamination down to the top of this aquitard occurred with minimal delay after DNAPL waste disposal began.The results highlight the necessity of high-resolution vertical profiling for assessing the presence of imperceptible features relevant to DNAPL migration and integrity of individual aquitards affecting organic contaminant source zone mass and phase distributions over decades.