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Permeable sediments, which make up almost half of the continental shelf worldwide, are potential sources of the important greenhouse gas N2O from coastal regions. Yet, the extent to which interactions between these sediments and anthropogenic pollution produce N2O is still unknown. Here we use laboratory experiments and modeling to explore the factors controlling N2O production at a eutrophic site in a temperate shallow marine embayment (Port Phillip Bay, Australia). Our results show that denitrification is the main source of N2O production within permeable sediments, but the extent to which N2O is actually released is determined by the rate of seawater exchange with the sediment bed (which governs solute residence time within the bed). In wave‐dominated coastal areas, shallower water with more intense waves (wave height > 1 m) release the most N2O, with up to 0.5% of dissolved inorganic nitrogen pumped into biologically active eutrophic sediment being released as N2O. Our results suggest rates of N2O production in coastal permeable sediments are generally low compared to other environments. Plain Language Summary: Permeable sands cover almost half of the coastal continental shelf around the world. The permeability of sand sediments, means water can flow through these sediments in complex patterns driven by waves and currents. This flow through the sediment can control nitrous oxide and methane production which are poorly understood. This is particularly important in regions impacted by nitrogen pollution where production of these greenhouse gases can be high. Here we combine experiments and modeling to explore the factors controlling N2O production at a sandy site impacted by nitrogen pollution (Port Phillip Bay, Australia). Our results show the rate of nitrous oxide release to the water column is governed by the rate of seawater exchange with the bed. Shallower water with more intense waves (wave height exceeding 1 m) releases the most N2O, with up to 0.5% of dissolved nitrogen pumped into the sediment being released as N2O. Overall, these results suggest permeable sediments have relatively low rates of nitrous oxide release most of the time. Key Points: Coastal hydrodynamics impose an important boundary condition on the production of N2O in permeable sedimentsLess than 0.5% of seawater dissolved inorganic nitrogen is converted to N2O due to forcing imposed by passing surface gravity wavesPermeable sediments are a relatively minor source of N2O emission in coastal waters of Port Phillip Bay [ABSTRACT FROM AUTHOR]

Background: Adverse effects from young people’s alcohol consumption manifest in a range of physical and psychosocial factors, including neurological issues, cognitive impairment and risk-taking behaviours. The SIPS JR-HIGH pilot trial showed alcohol screening and brief intervention (ASBI) to be acceptable to young people and schools in the north-east of England. Objectives: To conduct a two-arm, individually randomised controlled trial to evaluate the effectiveness and cost-effectiveness of ASBI for risky drinking in young people aged 14–15 years in the school setting, to monitor the fidelity of ASBI and to explore the barriers to, and facilitators of, implementation with staff, young people and parents. Design: A baseline survey with a 12-month follow-up. Interviews with 30 school staff, 21 learning mentors and nine teachers, and 33 young people and two parents. Setting: Thirty state schools in four areas of England: north-east, north-west, Kent and London. Participants: Year 10 school pupils who consented to the study (aged 14–15 years, recruited between November 2015 and June 2016), school-based staff and parents of the young people who took part in the study. Interventions: Young people who screened positively on a single alcohol screening question and consented were randomised to the intervention or control arm (blinded). The intervention was a 30-minute one-to-one structured brief intervention with a trained learning mentor and an alcohol leaflet. The control group received a healthy lifestyle leaflet (no alcohol information). Main outcome measures: The primary outcome measure was total alcohol consumed in the last 28 days. Secondary outcomes related to risky drinking, general psychological health, sexual risk-taking, energy drink consumption, age of first smoking, quality of life, quality-adjusted life-years, service utilisation and demographic information. Results: A total of 4523 young people completed the baseline survey, with 1064 screening positively (24%) and 443 being eligible to take part in the trial. Of those 443, 233 (53%) were randomised to the control arm and 210 were randomised to the intervention arm. Of the 443, 374 (84%) were successfully followed up at 12 months (intervention, n = 178; control, n = 196). The results were that the intervention showed no evidence of benefit for any alcohol-related measure when compared with the control arm. At 12 months we found a reduction from 61.9% to 43.3% using the Alcohol Use Disorders Identification Test cut-off point of 8 and cut-off point of 4 (69.0% to 60.7%). These results were not significant. A cost-effectiveness analysis showed that the average net cost saving of the brief intervention was £2865 (95% confidence interval –£11,272 to £2707) per year compared with usual practice, with the intervention showing a 76% probability of being cost saving compared with usual practice. The interview findings showed that school was an acceptable setting to carry out ASBI among staff and young people. Limitations: Recruitment of parents to take part in interviews was poor. Only 18 ASBI sessions were recorded, making it difficult to assess internal validity. Conclusions: Although the intervention was ineffective in reducing risky drinking in young people aged 14–15 years, it was well received by the young people and school staff who participated. Future work: Uniform reporting of the outcomes used for ASBI would generate more robust conclusions on the effectiveness of ASBI in the future. Pilot feasibility studies should include more than one geographical area. Future work on involving parents is needed. Trial registration: Current Controlled Trials ISRCTN45691494. Funding: This project was funded by the National Institute for Health Research (NIHR) Public Health Research programme and will be published in full in Public Health Research; Vol. 7, No. 9. See the NIHR Journals Library website for further project information.

Factors driving freshwater salinization syndrome (FSS) influence the severity of impacts and chances for recovery. We hypothesize that spread of FSS across ecosystems is a function of interactions among five state factors: human activities, geology, flowpaths, climate, and time. (1) Human activities drive pulsed or chronic inputs of salt ions and mobilization of chemical contaminants. (2) Geology drives rates of erosion, weathering, ion exchange, and acidification‐alkalinization. (3) Flowpaths drive salinization and contaminant mobilization along hydrologic cycles. (4) Climate drives rising water temperatures, salt stress, and evaporative concentration of ions and saltwater intrusion. (5) Time influences consequences, thresholds, and potentials for ecosystem recovery. We hypothesize that state factors advance FSS in distinct stages, which eventually contribute to failures in systems‐level functions (supporting drinking water, crops, biodiversity, infrastructure, etc.). We present future research directions for protecting freshwaters at risk based on five state factors and stages from diagnosis to prognosis to cure. [ABSTRACT FROM AUTHOR]

Unsteady transit time distribution (TTD) theory is a promising new approach for merging hydrologic and water quality models at the catchment scale. A major obstacle to widespread adoption of the theory, however, has been the specification of the StorAge Selection (SAS) function, which describes how the selection of water for outflow is biased by age. In this paper we hypothesize that some unsteady hydrologic systems of practical interest can be described, to first‐order, by a "shifted‐uniform" SAS that falls along a continuum between plug flow sampling (for which only the oldest water in storage is sampled for outflow) and uniform sampling (for which water in storage is sampled randomly for outflow). For this choice of SAS function, explicit formulae are derived for the evolving: (a) age distribution of water in storage; (b) age distribution of water in outflow; and (c) breakthrough concentration of a conservative solute under either continuous or impulsive addition. Model predictions conform closely to chloride and deuterium breakthrough curves measured previously in a sloping lysimeter subject to periodic wetting, although refinements of the model are needed to account for the reconfiguration of flow paths at high storage levels (the so‐called inverse storage effect). The analytical results derived in this paper should lower the barrier to applying TTD theory in practice, ease the computational demands associated with simulating solute transport through complex hydrologic systems, and provide physical insights that might not be apparent from traditional numerical solutions of the governing equations. Plain Language Summary: Many hydrologic systems, from hillslopes to water distribution systems, are intrinsically unsteady, by which we mean the flow of water and solutes varies continuously as a function of time. Historically, water quality models of such systems start by resolving the unsteady flow field first, and then "layering on" mass conservation laws in one‐, two‐ or three‐dimensions. A promising new approach, unsteady transit time distribution theory, takes an entirely different tack, by tracking the flux and age distribution of water and solute moving into and out of a control volume drawn around the system of interest. Practical implementation of the theory requires choosing a StorAge Selection (SAS) function appropriate for the system under study. In this paper we propose a SAS function, which we call a "shifted‐uniform SAS", that captures a continuum of physical behavior and thus may provide a first‐order description of many natural and engineered hydrologic systems. This choice of SAS function also leads to data‐tested formulae for predicting water quality outcomes. Key Points: Formulae are derived for age‐ranked storage in, and solute transport through, unsteady hydrologic systems under shifted‐uniform selectionThe StorAge Selection function's single parameter indicates where a system falls along a continuum between plug‐flow and uniform samplingModel predictions are concordant with published measurements of solute breakthrough in a sloping lysimeter subject to periodic wetting [ABSTRACT FROM AUTHOR]

Stormwater infrastructure substantially impacts water quality and supply. In the U.S., local agency investments rely on public support from taxes or fees. Assessing individuals' knowledge and willingness to pay helps inform potential pathways to funding and green infrastructure implementation. Using a 2018–2019 survey of 868 University of California students and staff, we analyze stormwater knowledge and willingness to pay or support public fund allocation for green infrastructure, especially natural treatment systems (NTS). Results of three separate regression models, each with a one-campus random sample and an all-campus convenience sample, show the majority of respondents supported allocating personal and campus funds for NTS. Preexisting environmental attitudes (on the New Ecological Paradigm scale) were the most common driver in nearly all models, but with inconsistent results and low explanatory power across models. Harnessing public support to increase stormwater investment may require tailored benefit messaging or other motivational frameworks, particularly in semiarid environments. [ABSTRACT FROM AUTHOR]

In this paper, we develop and validate a rigorous modeling framework, based on Duhamel's Theorem, for the unsteady one‐dimensional vertical transport of a solute across a flat sediment‐water interface (SWI) and through the benthic biolayer of a turbulent stream. The modeling framework is novel in capturing the two‐way coupling between evolving solute concentrations above and below the SWI and in allowing for a depth‐varying diffusivity. Three diffusivity profiles within the sediment (constant, exponentially decaying, and a hybrid model) are evaluated against an extensive set of previously published laboratory measurements of turbulent mass transfer across the SWI. The exponential diffusivity profile best represents experimental observations and its reference diffusivity scales with the permeability Reynolds number, a dimensionless measure of turbulence at the SWI. The depth over which turbulence‐enhanced diffusivity decays is of the order of centimeters and comparable to the thickness of the benthic biolayer. Thus, turbulent mixing across the SWI may serve as a universal transport mechanism, supplying the nutrient and energy fluxes needed to sustain microbial growth, and nutrient processing, in the benthic biolayer of stream and coastal sediments. Plain Language Summary: How far and fast pollutants travel downstream is often conditioned on what happens in a thin veneer of biologically active bottom sediments called the benthic biolayer. However, before a pollutant can be removed in the benthic biolayer, it must first be transported across the sediment‐water interface and through the interstitial fluids of these surficial sediments. In this paper we demonstrate that water column turbulence can play a key role in this process by transporting solutes into and out of the benthic biolayer of stream and coastal sediments. Key Points: A one‐dimensional diffusion model is developed and tested for dispersive mixing and turbulent diffusion in the benthic biolayerThe model reproduces measurements of solute transfer into the sediment bed when diffusivity decays exponentially with depthThe diffusivity increases with the permeability Reynolds number and decays over depths comparable to the benthic biolayer thickness [ABSTRACT FROM AUTHOR]

Many water quality and ecosystem functions performed by streams occur in the benthic biolayer, the biologically active upper (~5 cm) layer of the streambed. Solute transport through the benthic biolayer is facilitated by bedform pumping, a physical process in which dynamic and static pressure variations over the surface of stationary bedforms (e.g., ripples and dunes) drive flow across the sediment‐water interface. In this paper we derive two predictive modeling frameworks, one advective and the other diffusive, for solute transport through the benthic biolayer by bedform pumping. Both frameworks closely reproduce patterns and rates of bedform pumping previously measured in the laboratory, provided that the diffusion model's dispersion coefficient declines exponentially with depth. They are also functionally equivalent, such that parameter sets inferred from the 2D advective model can be applied to the 1D diffusive model, and vice versa. The functional equivalence and complementary strengths of these two models expand the range of questions that can be answered, for example, by adopting the 2D advective model to study the effects of geomorphic processes (such as bedform adjustments to land use change) on flow‐dependent processes and the 1D diffusive model to study problems where multiple transport mechanisms combine (such as bedform pumping and turbulent diffusion). By unifying 2D advective and 1D diffusive descriptions of bedform pumping, our analytical results provide a straightforward and computationally efficient approach for predicting, and better understanding, solute transport in the benthic biolayer of streams and coastal sediments. Plain Language Summary: How far and fast pollutants travel downstream is often conditioned on what happens in a thin veneer of biologically active bottom sediments called the benthic biolayer. However, before a pollutant can be removed in the benthic biolayer, it must first be transported across the sediment‐water interface and through the interstitial fluids of these surficial sediments. In this paper we demonstrate that one important mechanism for transporting solutes to, and through, the benthic biolayer—bedform pumping—can be interchangeably represented as either a two‐dimensional advective process or a one‐dimensional dispersion process. The complementary nature of these models expands the range of benthic biolayer processes that can be studied and predicted with the end goal of improving coastal and stream water quality. Key Points: Advective and diffusive models of solute transport through the benthic biolayer of streams by bedform pumping are derivedThe two models are functionally equivalent provided that the diffusion model's dispersion coefficient decays exponentially with depthBoth frameworks closely reproduce measured patterns and rates of bedform pumping and provide complementary predictive capabilities [ABSTRACT FROM AUTHOR]

Ultrahazardous flooding (UHF) occurs on low relief topography at the foot of mountain catchments and is characterized by rapid‐onset, high‐velocity flood flows, large fluxes of sediment and debris, and unpredictable flow paths. 20th century stormwater infrastructure seeks to contain UHF, up to a design level, using combinations of basins, reservoirs and flood control channels. However, these flood control elements may increase the risk of disasters due to: (a) increasingly frequent and intense wildfires that amplify streamflow and debris fluxes beyond infrastructure design capacity; (b) aging and underfunded infrastructure which is susceptible to clogging and failure during extreme events; and (c) expansive urban development where communities are relatively unaware and underprepared for flooding as a consequence of the "levee effect"‐‐the false sense of safety that develops in the presence of flood defenses. 20th century stormwater infrastructure for UHF has also left communities with a legacy of social and environmental challenges including poor water quality, degraded habitats, high maintenance costs, unrealized urban amenities, and altered sediment fluxes. Adopting the Los Angeles Metropolitan Region as a type‐locality for UHF, we propose a new paradigm for stormwater infrastructure based on the concept of erodible flood corridors. Our vision aims for greater sustainability and resilience to extreme events based on congruency with natural processes, conservation of resources and associated ecosystem services, minimization of flood exposure and vulnerability, and avoidance of legacy risk and energy intensive practices. This article is categorized under: Engineering Water > Sustainable Engineering of WaterEngineering Water > Planning WaterScience of Water > Water Extremes [ABSTRACT FROM AUTHOR]

Tracking of total physical activity (PA), moderate to vigorous activity (MVPA), and sedentary behavior was assessed in 42 young children (mean age at baseline 3.8 years) over a 2-year period using the Actigraph accelerometer. Tracking was analyzed using Spearman rank correlations, percentage agreements, and kappa statistics. Spearman rank correlations were r = .35 (p = .002) for total PA, r = .37 (p = .002) for MVPA, and r = .35 (p = .002) for sedentary behavior. Percentage agreements for PA, MVPA, and sedentary behavior were 38, 41, and 26 respectively. Kappa statistics for PA, MVPA, and sedentary behavior ranged from poor to fair. Results suggest low levels of tracking of total physical activity, MVPA, and sedentary behavior in young Scottish children over a 2-year period. [ABSTRACT FROM AUTHOR]

This study examined whether there was a significant seasonal variation in objectively measured habitual physical activity and sedentary behavior in young children. Participants were 209 children who attend nursery in Glasgow, Scotland, and measurements were taken using uniaxial accelerometry over 3 to 6 days. There were small but significant seasonal associations with physical activity and sedentary behavior (ANOVA: p < .001 in both cases). Total physical activity (accelerometry cpm) was significantly lower in spring than in summer, fall, and winter. We also found slight but significant seasonal variations in time spent in low-intensity activity and in moderate-to-vigorous-intensity activity. Sedentary time was significantly lower in summer vs. spring and in fall vs. spring. The present study suggests that seasonality plays only a limited role in physical activity and sedentary behavior in young children in our setting. Single measures of these variables should be adequate for research purposes in the absence of marked seasonal variability. In our sample and setting, the limited degree of seasonality precluded identification of major seasonal barriers to and opportunities for physical activity. [ABSTRACT FROM AUTHOR]

The primary aim of this study was to test the validity of two accelerometers, CSA/MTI WAM-7164 and Actiwatch(r), against direct observation of physical activity using the Children's Physical Activity Form (CPAF). CSA/MTI WAM-7164 and Actiwatch accelerometers simultaneously measured activity during structured-play classes in 3- to 4-year olds. Accelerometry output was synchronized to CPAF assessments of physical activity in 78 children. Rank order correlations between accelerometry and direct observation evaluated the ability of the accelerometers to assess total physical activity. Within-child minute-to-minute correlations were calculated between accelerometry output and direct observation. For total physical activity, CSA/MTI output was significantly correlated with CPAF (r = .72, p < .001), but output from the Actiwatch was not (r = .16, p > .05). [ABSTRACT FROM AUTHOR]