Physical characteristics of microplastic particles and potential for global atmospheric transport: A meta-analysis.

Recent interest in microplastic pollution of natural environments has brought forth samples which confirm the pollutant's omnipresence in a variety of ecosystems. This includes locations furthest removed from human activity. Atmospheric transport and deposition are suspected as the primary transport pathway to these remote locations. The factors most influential on participation in atmospheric transport are yet to be determined. This meta-analysis aims to identify patterns that exist between physical characteristics of microplastic particles and their potential for atmospheric transport. Our review addresses the following questions: Which characteristics of microplastic particles promote atmospheric transport and deposition into remote regions, and how significant are these factors in determining distance transported from their sources? This article analyzes commonly reported physical attributes-- shape, polymer composition and color-- from studies in urban and remote areas. The analysis of 68 studies, composed of data from 2078 samples, shows higher occurrence of microplastic particles in remote samples with fiber shapes, polyester compositions, and red, blue, and transparent colors. This meta-analysis is the first to identify patterns between physical properties of microplastic particles and extent of their participation in atmospheric transport to global remote locations.

An acute bout of high-intensity exercise affects nocturnal sleep and sleep-dependent memory consolidation.

Acute exercise has been shown to affect long-term memory and sleep. However, it is unclear whether exercise-induced changes in sleep architecture are associated with enhanced memory. Recently, it has been shown that exercise followed by a nap improved declarative memory. Whether these effects transfer to night sleep and other memory domains has not yet been studied. Here, we investigate the influence of exercise on nocturnal sleep architecture and associations with sleep-dependent procedural and declarative memory consolidation. Nineteen subjects (23.68 ± 3.97 years) were tested in a balanced cross-over design. In two evening sessions, participants either exercised (high-intensity interval training) or rested immediately after encoding two memory tasks: (1) a finger tapping task and (2) a paired-associate learning task. Subsequent nocturnal sleep was recorded by polysomnography. Retrieval was conducted the following morning. High-intensity interval training lead to an increased declarative memory retention (p = 0.047, d = 0.40) along with a decrease in REM sleep (p = 0.012, d = 0.75). Neither procedural memory nor NREM sleep were significantly affected. Exercise-induced changes in N2 showed a positive correlation with procedural memory retention which did not withstand multiple comparison correction. Exploratory analyses on sleep spindles and slow wave activity did not reveal significant effects. The present findings suggest an exercise-induced enhancement of declarative memory which aligns with changes in nocturnal sleep architecture. This gives additional support for the idea of a potential link between exercise-induced sleep modifications and memory formation which requires further investigation in larger scaled studies.

Feasibility, effectiveness and acceptability of two perturbation-based treadmill training protocols to improve reactive balance in fall-prone older adults (FEATURE): protocol for a pilot randomised controlled trial.

INTRODUCTION: Perturbation-based balance training (PBT) targets the mechanism of falls (eg, slipping, tripping) to specifically train the recovery actions needed to avoid a fall. This task-specific training has shown great promise as an effective and efficient intervention for fall prevention in older adults. However, knowledge about the dose-response relationship of PBT, as well as its feasibility and acceptability in older adults with increased risk of falling is still limited. Thus, the aim of this study is to compare the effectiveness of two different treadmill PBT protocols for improving reactive balance control in fall-prone older adults, and to evaluate the feasibility and acceptability of these protocols. METHODS AND ANALYSIS: The study is designed as a pilot randomised controlled trial with a 6-week intervention and 6-week follow-up period. Thirty-six community-dwelling, fall-prone (Timed Up and Go >12 s, habitual gait speed <1.0 m/s and/or fall history) older adults will be randomised (1:1) to receive six (weeks 1-6) or two treadmill PBT sessions (weeks 1+6) plus four conventional treadmill training sessions (weeks 2-5). Training sessions are conducted 1×/week for 30 min. Each PBT will include 40 perturbations in anterior-posterior and mediolateral directions. Reactive balance after perturbations in standing (Stepping Threshold Test (STT)) and walking (Dynamic Stepping Threshold Test (DSTT)) will be assessed as the primary outcome for effectiveness. Secondary outcomes are spatiotemporal and kinematic parameters collected during STT, DSTT and PBT, maximum perturbation magnitude for each PBT session, static and dynamic balance, physical capacity, physical activity, concerns with falling and executive functions. Feasibility will be assessed via training adherence, drop-out rate, perturbations actually performed and adverse events; and acceptability via self-designed questionnaire and focus groups. ETHICS AND DISSEMINATION: The study has been approved by the Ethics Committee of the Medical Faculty Heidelberg (S-602/2022). Findings will be disseminated through publications in peer-reviewed journals and conference presentations. TRIAL REGISTRATION NUMBER: DRKS00030805.

Risk classification of contaminated sites - Comparison of the Swedish and the German method.

To classify contaminated sites into different risk classes, many different methods exist in Europe and worldwide. However, no systematic comparison of European risk classification methods has been carried out so far to carve out the advantages and disadvantages of the methods and to homogenize them. To address this research gap, this study aims at comparing the Swedish Method for Inventories of Contaminated Sites (MIFO) with the German Individual Assessment of Contaminated Sites Method (EB) from the Hessian Agency for Nature Conservation, Environment and Geology (HLNUG) regarding the risk class categorization of 51 contaminated sites. The results revealed that with the MIFO 39% fewer contaminated sites are assigned to risk classes 1 and 2 and thus, subject to remediation compared to the EB. Moreover, in comparison to the EB, the MIFO showed a lower comparability, traceability, and a larger room for interpretation, which could be related to the lack of a quantitative approach such as a point or ranking system in the MIFO. Hence, we recommend providing the MIFO and other methods that lack a quantitative approach with a point and/or ranking system, similar to the EB, to increase their objectivity for the risk class categorization of contaminated sites.

[New approaches in exercise therapy for Parkinson's disease]. / Neue Ansätze in der Bewegungstherapie bei Morbus Parkinson.

BACKGROUND: Exercise therapy is an important component in the treatment of motor symptoms in people with Parkinson's disease (PD). In this context, goal-based task-specific training has shown to be particularly effective compared to nonspecific approaches. OBJECTIVE: In this article two novel exercise interventions for targeted improvement of motor function in PD are presented: 1) task-specific training with perturbations and 2) combined task-specific and cardiovascular training. MATERIAL AND METHODS: Summary and discussion of the current evidence for both therapeutic approaches. RESULTS: First randomized controlled trials show that perturbation training is an effective task-specific training to improve gait and balance function and potentially reduce falls. Experimental findings on combined cardiovascular exercise and task-specific training suggest that processes of neuroplasticity are enhanced, thereby improving therapy outcomes. However, the quality of evidence for both therapeutic approaches is currently low. CONCLUSION: The presented exercise approaches show promising results in first randomized controlled studies and have the potential to improve treatment outcomes in PD. Further high-quality clinical studies are needed to ensure an effective transfer into practice.

Determining effective diffusion coefficients of chlorohydrocarbons in natural clays: Unique results from highly resolved controlled release field experiments.

This study aims to precisely determine the effective diffusion coefficients of chlorohydrocarbons in low permeable units under in-situ field conditions. To this end, two controlled release field experiments using TCE and PCE as dense non-aqueous phase liquids (DNAPLs) were conducted in two natural clayey deposits. Several months to years after the controlled DNAPL release, highly resolved concentration profiles were determined for the chlorohydrocarbons that had diffused into the clayey deposits. Effective diffusion coefficients for TCE and PCE were then determined by calibrating a 3D numerical and 1D analytical model, respectively, to the measured high-resolution concentration profiles. The simulations revealed that the effective diffusion coefficients vary by as much as a factor of four within the same low permeability unit being consistent with observed small-scale heterogeneities. The determined chlorohydrocarbon effective diffusion coefficients were further used to determine the equivalent thickness of DNAPL that would completely dissolve in an idealized, parallel-plate fracture by diffusion transport into clayey deposits for the time periods of the controlled release field experiments. The equivalent TCE and PCE DNAPL film thicknesses ranged between 36 and 581 µm, respectively, comparable and exceeding fracture apertures measured in naturally fractured clay rich deposits. Hence, films of DNAPL initially contained within fractures in clay-rich deposits can completely dissolve away within a few months to a few years due to diffusion. This stored contaminant mass poses a risk to adjacent aquifers if it is re-released due to diffusion out of the matrix after source depletion or remediation.

The Effectiveness of Physical Literacy Interventions: A Systematic Review with Meta-Analysis.

BACKGROUND: The holistic concept of physical literacy assumes that individuals require adequate cognitive (knowledge and understanding), affective (motivation and confidence), and physical (physical competence) qualities to engage in lifelong physical activity behavior. In recent years, the research field has undergone rapid development and has also yielded an increasing number of interventions that aim to translate the theoretical-philosophical ideas into practical endeavors. OBJECTIVE: The goal of the present pre-registered systematic review was to (a) provide a general overview of evaluation studies on physical literacy interventions and (b) to quantitatively examine the effectiveness of physical literacy interventions. METHODS: Drawing on the 2020 Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, we searched a total of 18 databases for physical literacy interventions. Inclusion criteria were English language, publication by November 2021, and interventions using physical literacy as a theoretical underpinning or evaluation outcome. Articles that met these criteria were analyzed with respect to their basic delivery characteristics, study quality, evaluation approach, and main findings. We additionally ran meta-analyses with all non-randomized and randomized controlled trials to examine and compare the effect of these interventions on five outcome categories: (i) physical competence, (ii) motivation and confidence, (iii) knowledge and understanding, (iv) physical activity behavior, and (v) total physical literacy. Standardized mean differences (SMDs) with 95% confidence intervals (CIs) were calculated to assess the effects on the different categories. RESULTS: The screening process with two independent raters yielded 48 eligible interventions reported in 51 eligible articles. Quantitative evaluations most frequently addressed physical competence (72.2%), followed by motivation and confidence (47.2%), physical activity behavior (41.7%), and knowledge and understanding (33.3%). The controlled intervention studies (n = 24) exerted significant effects on all five physical literacy categories. Despite meaningful heterogeneity across the subgroups, the strongest effects were found for physical competence (SMD 0.90; 95% CI 0.55-1.25), followed by physical literacy aggregate scores (SMD 0.61; 95% CI 0.20-1.01), knowledge and understanding (SMD 0.54; 95% CI 0.30-0.79), physical activity behavior (SMD 0.39; 95% CI 0.23-0.55), and motivation and confidence (SMD 0.30; 95% CI 0.17-0.44). CONCLUSIONS: The present study empirically demonstrated the effectiveness of physical literacy interventions on several outcomes relevant for promoting physical activity and health. To better inform current practices, future studies are advised to identify those program characteristics that significantly influence the effectiveness of physical literacy interventions. CLINICAL TRIAL REGISTRATION: PROSPERO CRD42020188926.

Identification of chlorohydrocarbon degradation pathways in aquitards using dual element compound-specific isotope measurements in aquifers.

Compound-specific isotope analysis (CSIA) has been increasingly used to understand and quantify the (bio)degradation processes affecting chlorohydrocarbons in aquifer-aquitard systems. In this study, we aimed at investigating through reactive transport simulations if dual element (C, Cl) CSIA in aquifer samples can provide information about the occurring (bio)degradation pathways in the underlying aquitard. To that end, we modeled the continous dissolution of a 1,1,2,2-tetrachloroethane (TeCA) dense nonaqueous phase liquid (DNAPL) source in an aquifer as well as the resulting TeCA groundwater plume formation and diffusion into the underlying aquitard. The (bio)degradation of TeCA in the aquifer-aquitard system was simulated in four scenarios: TeCA biodegradation via dehydrohalogenation to trichloroethene (TCE) and TeCA dichloroelimination to dichloroethene (DCE) in the aquifer as well as in the aquitard. The simulations revealed that dual element (C, Cl) CSIA in the aquifer allows the disentanglement of whether TeCA degradation occurs in the aquifer or the aquitard and which (bio)degradation pathways occur in the aquitard. This demonstrates that chlorohydrocarbon (bio)degradation pathways in aquitards can be identified based on CSIA aquifer measurements only, which is an advantage as aquifers are easier to monitor than aquitards.

Compound-specific carbon isotope analysis of volatile organic compounds in complex soil extracts using purge and trap concentration coupled to heart-cutting two-dimensional gas chromatography-isotope ratio mass spectrometry.

Compound-specific carbon isotope analysis (CSIA) is a powerful tool to track the origin and fate of organic subsurface contaminants including petroleum and chlorinated hydrocarbons and is typically applied to water samples. However, soil can form a significant contaminant reservoir. In soil samples, it can be challenging to recover sufficient amounts of volatile organic compounds (VOC) to perform CSIA. Soil samples often contain complex contaminant mixtures and gas chromatography combustion isotope ratio mass spectrometry (GC-C-IRMS) is highly dependent on good chromatographic separation due to the conversion to a single analyte. To extend the applicability of CSIA to complex volatile organic compound mixtures in soil samples, and to recover sufficient amounts of target compounds for carbon CSIA, we compared two soil extraction solvents, tetraglyme (TGDE) and methanol, and developed a heart-cutting two-dimensional GC-GC-C-IRMS method. We used purge & trap concentration of solvent-water mixtures to increase the amount of analyte delivered to the column and thus lower method detection limits. We optimized purge & trap and chromatographic parameters for twelve target compounds, including one suffering from poor purge efficiency. By using a 30 m thick-film non-polar column in the first and a 15 m polar column in the second dimension, we achieved good chromatographic separation for the target compounds in difficult matrices and high accuracy (trueness and precision) for carbon isotopic analysis. Tetraglyme extraction was shown to offer advantages over methanol for purge & trap concentration, leading to lower target compound method detection limits for CSIA of soil samples. The applicability of the developed method was demonstrated for a case study on soil extracts from a former manufacturing facility. Our approach extends the applicability of CSIA to an important matrix that often controls the long-term fate of contaminants in the subsurface.

Sorption- and diffusion-induced isotopic fractionation in chloroethenes.

Isotopic fractionation of groundwater contaminants can occur due to degradation, diffusion and sorption. Of these, only degradation has been extensively explored, yet diffusive isotopic fractionation (DIF) and sorptive isotopic fractionation (SIF) can have significant effects on the isotopic enrichment of groundwater contaminants. Understanding how to mathematically describe and model these processes is vital to the correct interpretation of compound-specific isotope analysis (CSIA) data in the field. Here, models for these physical fractionation processes are developed and described, including the definition of a sorption enrichment factor. These models are then implemented numerically using inverse and finite-element methods to investigate two scenarios, diffusion-sorption and diffusion-sorption-advection, that have been measured in the laboratory. Concentration, δ37Cl, and δ2H data from cis-dichloroethene (cDCE) and trichloroethene (TCE) are used as inputs to the models. Unknown transport parameters including diffusive fractionation exponents are determined from an inverse modelling approach. DIF is shown to have a stronger influence on chlorine isotopologues than on hydrogen isotopologues. For both cDCE and TCE, the sorption enrichment factor of chlorine is found to be negative while that of hydrogen is positive. The presented approach and results provide novel tools and insight into DIF and SIF and underline that these processes should be taken into account when using CSIA to assess contaminant fate.

Identification of degrader bacteria and fungi enriched in rhizosphere soil from a toluene phytoremediation site using DNA stable isotope probing.

Improved knowledge of the ecology of contaminant-degrading organisms is paramount for effective assessment and remediation of aromatic hydrocarbon-impacted sites. DNA stable isotope probing was used herein to identify autochthonous degraders in rhizosphere soil from a hybrid poplar phytoremediation system incubated under semi-field-simulated conditions. High-throughput sequencing of bacterial 16S rRNA and fungal internal transcribed spacer (ITS) rRNA genes in metagenomic samples separated according to nucleic acid buoyant density was used to identify putative toluene degraders. Degrader bacteria were found mainly within the Actinobacteria and Proteobacteria phyla and classified predominantly as Cupriavidus, Rhodococcus, Luteimonas, Burkholderiaceae, Azoarcus, Cellulomonadaceae, and Pseudomonas organisms. Purpureocillium lilacinum and Mortierella alpina fungi were also found to assimilate toluene, while several strains of the fungal poplar endophyte Mortierella elongatus were indirectly implicated as potential degraders. Finally, PICRUSt2 predictive taxonomic functional modeling of 16S rRNA genes was performed to validate successful isolation of stable isotope-labeled DNA in density-resolved samples. Four unique sequences, classified within the Bdellovibrionaceae, Intrasporangiaceae, or Chitinophagaceae families, or within the Sphingobacteriales order were absent from PICRUSt2-generated models and represent potentially novel putative toluene-degrading species. This study illustrates the power of combining stable isotope amendment with advanced metagenomic and bioinformatic techniques to link biodegradation activity with unisolated microorganisms. Novelty statement: This study used emerging molecular biological techniques to identify known and new organisms implicated in aromatic hydrocarbon biodegradation from a field-scale phytoremediation system, including organisms with phyto-specific relevance and having potential for downstream applications (amendment or monitoring) in future and existing systems. Additional novelty in this study comes from the use of taxonomic functional modeling approaches for validation of stable isotope probing techniques. This study provides a basis for expanding existing reference databases of known aromatic hydrocarbon degraders from field-applicable sources and offers technological improvements for future site assessment and management purposes.

Acute exercise following skill practice promotes motor memory consolidation in Parkinson's disease.

Acute cardiovascular exercise has shown to promote neuroplastic processes supporting the consolidation of newly acquired motor skills in healthy adults. First results suggest that this concept may be transferred to populations with motor and cognitive dysfunctions. In this context, Parkinson's disease (PD) is highly relevant since patients demonstrate deficits in motor learning. Hence, in the present study we sought to explore the effect of a single post-practice exercise bout on motor memory consolidation in PD. For this purpose, 17 patients with PD (Hoehn and Yahr: 1 - 2.5, age: 60.1 ± 7.9 y) practiced a whole-body skill followed by either (i) a moderate-intense bout of cycling, or (ii) seated rest for a total of 30 min. The motor skill required the participants to balance on a tiltable platform (stabilometer) for 30 s. During skill practice, participants performed 15 trials followed by a retention test 1 day and 7 days later. We calculated time in balance (platform within ± 5° from horizontal) for each trial and within- and between-group differences in memory consolidation (i.e. offline learning = skill change from last acquisition block to retention tests) were analyzed. Groups revealed similar improvements during skill practice (F4,60 = 0.316, p = 0.866), but showed differences in offline learning, which were only evident after 7 days (F1,14 = 5.602, p = 0.033). Our results suggest that a single post-practice exercise bout is effective in enhancing long-term motor memory consolidation in a population with motor learning impairments. This may point at unique promoting effects of exercise on dopamine neurotransmission involved in memory formation. Future studies should investigate the potential role of exercise-induced effects on the dopaminergic system.

Plastic in agricultural soils - A global risk for groundwater systems and drinking water supplies? - A review.

The global plastic contamination is one of the major challenges facing mankind as plastic is ubiquitously present in all environmental compartments. In contrast to freshwater and marine environments, plastic contamination of agricultural soils was only recently subject to investigations although it represents a significant amount (14%) of the global plastic pollution. Of concern is the vertical migration of plastic particles in agricultural soils and plastic-induced enhancement of pesticide transport towards underlying groundwater systems. To assess the risk of the large plastic inventory in agricultural soils for groundwater systems and drinking water supplies, this review critically synthesizes the current knowledge of the plastic mobility and plastic-pesticide interactions in agricultural soils, identifies future research directions and evaluates associated analytical challenges. The reviewed studies provide consistent evidence for vertical migration of plastic in agricultural soils towards aquifer systems, especially for sub-micrometer sized plastic particles, analogously to the well-known migration of natural particles in the sub-micrometer range (colloids). The reviewed investigations also showed that plastic changes the sorption behavior of pesticides in agricultural soils and enhances their transport towards underlying groundwater systems. Hence, the deposited plastic in agricultural soils likely poses a major risk for underlying aquifers and drinking water supplies that rely on groundwater resources below farmlands to be contaminated by plastic and pesticides. This demonstrates that improved regulatory measures are necessary regarding the general usage of plastic in the farming process to protect aquifers and drinking water supplies from plastic and pesticide contamination and to avoid a potential human health hazard.

The importance of transects for characterizing aged organic contaminant plumes in groundwater.

A complex mixture of dissolved organic contaminants, emanating from a many decades-old, residual, dense non-aqueous phase liquid (DNAPL) source, migrates through unconfined, moderately heterogeneous, glacial-derived sediments and sedimentary rock in a residential area of Dane County, Wisconsin, USA. A portion of this contaminant plume intersects a large man-made pond, roughly 400 m downgradient of the source zone. Depth-discrete, multilevel groundwater sampling, detailed sedimentological logs, and hydraulic head profiles were used to delineate the spatial distribution of hydraulic, geologic, organic contaminant, and redox hydrochemical conditions within the established plume along two transects immediately upgradient of the pond. Twenty-one contaminants were detected and classified into four major contaminant groups: chlorinated ethenes, chlorinated ethanes, aromatics (BTEX: benzene, toluene, ethylbenzene, xylene), and aliphatic ketones. Within the glacial sediments and shallow bedrock, zones of reductive dechlorination of chlorinated ethenes and ethanes were juxtaposed with zones of BTEX and ketone degradation. Spatial heterogeneity in the concentration and distribution of contaminant groups and redox conditions was observed over lateral distances of tens of meters and vertical distances of tens of centimeters along the two transects. Although the site was situated in a complex glacial depositional environment, lithologic and hydraulic heterogeneity surprisingly only had a modest influence on the spatial distribution of plume contaminants. Depth-discrete sampling along paired, closely spaced transects (~20 m apart) was essential to assess internal plume composition/concentration evolution along flow paths with strong attenuation over short migration distances. This study shows how paired, highly resolved transects can enhance understanding of transverse and longitudinal variability in areas where contaminant-induced redox conditions control reaction zones and strong plume attenuation.

Effects of acute cardiovascular exercise on motor memory encoding and consolidation: A systematic review with meta-analysis.

Emerging evidence indicates that acute bouts of cardiovascular exercise promote motor memory formation. In this preregistered meta-analysis (CRD42018106288) we synthesize data from 22 studies published until February 2020, including a total of 862 participants. We calculated standardized mean differences (SMDs) with 95 % confidence intervals (CIs) to assess exercise effects on motor memory encoding and consolidation, respectively. The pooled data indicate that exercise mainly benefits the consolidation of memories, with exercise prior to motor practice improving early non-sleep consolidation (SMD, 0.58; 95 % CI, 0.30-0.86; p < 0.001), and post-practice exercise facilitating sleep-dependent consolidation (SMD, 0.62; 95 % CI, 0.34-0.90; p < 0.001). Strongest effects exist for high exercise intensities, and motor task nature appears to be another relevant modulator. We demonstrate that acute cardiovascular exercise particularly promotes the consolidation of acquired motor memories, and exercise timing, and intensity as well as motor task nature seem to critically modulate this relationship. These findings are discussed within currently proposed models of motor memory formation and considering molecular and systemic mechanisms of neural plasticity.

Quantification of toluene phytoextraction rates and microbial biodegradation functional profiles at a fractured bedrock phytoremediation site.

This field study evaluated the efficacy of a mature hybrid poplar phytoremediation system for the remediation of toluene in a fractured bedrock aquifer site. Phytoextraction activity of the trees and the ecology and biodegradation potential of root-colonizing bacteria that ultimately influence how much toluene is transported from the roots and phytoextracted to the aboveground point of measurement were explored. Peak-season toluene mass removal rates ranging from 313 to 743 µg/day were quantified using passive in planta contaminant sampling techniques and continuous heat dissipation transpiration measurements in tree stems. Root bacterial microbiome structure and biodegradation potential were evaluated via high-throughput sequencing and predictive metagenomic functional modelling of bacterial 16S rRNA genes in roots. Poplar roots were colonized mostly by Proteobacteria, Actinobacteria, and Bacteroidetes. Distinct, more uniform communities were observed in roots associated with trees planted in the toluene source area compared to other areas, with differences apparent at lower taxonomic levels. Significant enrichment of Streptomyces in roots was observed in the source area, implicating that genus as a potentially important poplar endophyte at toluene-impacted sites. Moreover, significantly greater aerobic toluene biodegradation capacity was predicted in these roots compared to other areas using taxonomic functional modelling. Together with passive sampling, the molecular results provided supporting evidence of biodegradation activity in the source area and contextualized the detected phytoextraction patterns. These results support the application of phytoremediation systems for aromatic hydrocarbons in environments with complex geology and demonstrate field-validated monitoring techniques to assess phytoextraction and biodegradation in these systems.

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.

Exercise Intensity Does not Modulate the Effect of Acute Exercise on Learning a Complex Whole-Body Task.

High-intensity cardiovascular exercise prior to motor skill practice is postulated to enhance motor memory consolidation (offline learning), whereas moderate-intensity bouts may benefit skill acquisition (online learning). This study aimed at investigating this suggested intensity-dependent effect of exercise in a complex whole-body task. 50 healthy young adults were randomized into one of three groups performing a bout of either (1) high-intense, (2) moderate-intense, or (3) minimal-intense cycling for a total of 17 min immediately prior to skill practice. The motor task required participants to balance on a tiltable platform (stabilometer) for 30 s. During acquisition 15 practice trials were carried out, followed by a retention test 24 h later. Time in balance was calculated for each trial and within- and between-group differences in online (skill improvement during skill acquisition) and offline learning (skill change from last acquisition block to retention) were analyzed. All participants significantly improved balance time during acquisition, with no differences observed between experimental conditions. Similarly, there were no differences in offline learning between groups. Contrary to previous reports, the present data do not support an intensity-dependent effect on motor learning, when exercise is performed prior to task practice. One reason for this might be that similar muscle groups were involved in exercise and the motor task, potentially causing fatigue or interference effects. Further, the results indicate that the memory-promoting effects of acute exercise are task-dependent and may not apply equally for motor skills of different levels of complexity.

Assessing toluene biodegradation under temporally varying redox conditions in a fractured bedrock aquifer using stable isotope methods.

In complex hydrogeological settings little is known about the extent of temporally varying redox conditions and their effect on aromatic hydrocarbon biodegradation. This study aims to assess the impact of changing redox conditions over time on aromatic hydrocarbon biodegradation in a fractured bedrock aquifer using stable isotope methods. To that end, four snapshots of highly spatio-temporally resolved contaminant and redox sensitive species concentrations, as well as stable isotope ratio profiles, were determined over a two-years time period in summer 2016, spring 2017, fall 2017 and summer 2018 in a toluene contaminated fractured bedrock aquifer. The concentration profiles of redox sensitive species and stable isotope ratio profiles for dissolved inorganic carbon (DIC) and sulfate (δ13CDIC, δ34SSO4, δ18OSO4) revealed that the aquifer alternates between oxidising (spring 2017/summer 2018) and reducing conditions (summer 2016/fall 2017). This alternation was attributed to a stronger aquifer recharge with oxygen-rich meltwater in spring 2017/summer 2018 compared to summer 2016/fall 2017. The temporally varying redox conditions coincided with various extents of toluene biodegradation revealed by the different magnitude of heavy carbon (13C) and hydrogen (2H) isotope enrichment in toluene. This indicated that the extent of toluene biodegradation and its contribution to plume attenuation was controlled by the temporally changing redox conditions. The highest toluene biodegradation was observed in summer 2016, followed by spring 2017 and fall 2017, whereby these temporal changes in biodegradation occurred throughout the whole plume. Thus, under temporally varying recharge conditions both the core and the fringe of a contaminant plume can be replenished with terminal electron acceptors causing biodegradation in the whole plume and not only at its distal end as previously suggested by the plume fringe concept. Overall, this study highlights the importance of highly temporally resolved groundwater monitoring to capture temporally varying biodegradation rates and to accurately predict biodegradation-induced contaminant attenuation in fractured bedrock aquifers.

Isotope fractionation due to aqueous phase diffusion - What do diffusion models and experiments tell? - A review.

For the interpretation of stable isotope ratio trends in saturated geochemical systems, the magnitude of aqueous phase diffusion-induced isotope fractionation needs to be known. This study reviews how five diffusion models (Fick, Maxwell-Stefan, Einstein, Langevin, Mode-Coupling Theory Analysis (MCTA) of diffusion) predict isotope fractionation due to aqueous phase diffusion and compares them with experimental results. The reviewed diffusion models were not consistent regarding the prediction of the mass (m) dependency of the aqueous phase diffusion coefficient (D). The predictions range from a square root power law (D ∝ m-0.5) to an opposite mass dependency of D (D ∝ mß). Experimental studies exhibited consistently a weak power law mass dependency of the diffusion coefficient (D ∝ m-ß with ß < 0.5) for the vast majority of dissolved species and a larger diffusion-induced isotope effect for low weight noble gases (D ∝ m-0.5). The weak power law mass dependency of D for the species other than low weight noble gases is consistent with the MCTA of diffusion. The MCTA suggests that the weak power law mass dependency of D originates from interplays between strongly mass dependent short-term and mass independent long-term solute-solvent interactions. The larger isotope fractionation for low weight noble gases could be attributed to quantum isotope effects significantly magnifying the aqueous phase diffusion-induced isotope fractionation. Our review shows, that except for low weight noble gases a weak power law mass dependency of D is likely the most adequate assumption for aqueous phase diffusion-induced isotope fractionation in geochemical systems.