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Increasing salt production and use is shifting the natural balances of salt ions across Earth systems, causing interrelated effects across biophysical systems collectively known as freshwater salinization syndrome. In this Review, we conceptualize the natural salt cycle and synthesize increasing global trends of salt production and riverine salt concentrations and fluxes. The natural salt cycle is primarily driven by relatively slow geologic and hydrologic processes that bring different salts to the surface of the Earth. Anthropogenic activities have accelerated the processes, timescales and magnitudes of salt fluxes and altered their directionality, creating an anthropogenic salt cycle. Global salt production has increased rapidly over the past century for different salts, with approximately 300 Mt of NaCl produced per year. A salt budget for the USA suggests that salt fluxes in rivers can be within similar orders of magnitude as anthropogenic salt fluxes, and there can be substantial accumulation of salt in watersheds. Excess salt propagates along the anthropogenic salt cycle, causing freshwater salinization syndrome to extend beyond freshwater supplies and affect food and energy production, air quality, human health and infrastructure. There is a need to identify environmental limits and thresholds for salt ions and reduce salinization before planetary boundaries are exceeded, causing serious or irreversible damage across Earth systems.

Freshwater Salinization Syndrome (FSS) refers to groups of biological, physical, and chemical impacts which commonly occur together in response to salinization. FSS can be assessed by the mobilization of chemical mixtures, termed chemical cocktails, in watersheds. Currently, we do not know if salinization and mobilization of chemical cocktails along streams can be mitigated or reversed using restoration and conservation strategies. We investigated 1) the formation of chemical cocktails temporally and spatially along streams experiencing different levels of restoration and riparian forest conservation and 2) the potential for attenuation of chemical cocktails and salt ions along flowpaths through conservation and restoration areas. We monitored high-frequency temporal and longitudinal changes in streamwater chemistry in response to different pollution events (i.e., road salt, stormwater runoff, wastewater effluent, and baseflow conditions) and several types of watershed management or conservation efforts in six urban watersheds in the Chesapeake Bay watershed. Principal component analysis (PCA) indicates that chemical cocktails which formed along flowpaths (i.e., permanent reaches of a stream) varied due to pollution events. In response to winter road salt applications, the chemical cocktails were enriched in salts and metals (e.g., Na+, Mn, and Cu). During most baseflow and stormflow conditions, chemical cocktails were less enriched in salt ions and trace metals. Downstream attenuation of salt ions occurred during baseflow and stormflow conditions along flowpaths through regional parks, stream-floodplain restorations, and a national park. Conversely, chemical mixtures of salt ions and metals, which formed in response to multiple road salt applications or prolonged road salt exposure, did not show patterns of rapid attenuation downstream. Multiple linear regression was used to investigate variables that influence changes in chemical cocktails along flowpaths. Attenuation and dilution of salt ions and chemical cocktails along stream flowpaths was significantly related to riparian forest buffer width, types of salt pollution, and distance downstream. Although salt ions and chemical cocktails can be attenuated and diluted in response to conservation and restoration efforts at lower concentration ranges, there can be limitations in attenuation during road salt events, particularly if storm drains bypass riparian buffers.

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.

Freshwater salinity is rising across many regions of the United States as well as globally, a phenomenon called the freshwater salinization syndrome (FSS). The FSS mobilizes organic carbon, nutrients, heavy metals, and other contaminants sequestered in soils and freshwater sediments, alters the structures and functions of soils, streams, and riparian ecosystems, threatens drinking water supplies, and undermines progress toward many of the United Nations Sustainable Development Goals. There is an urgent need to leverage the current understanding of salinization's causes and consequences─in partnership with engineers, social scientists, policymakers, and other stakeholders─into locally tailored approaches for balancing our nation's salt budget. In this feature, we propose that the FSS can be understood as a common pool resource problem and explore Nobel Laureate Elinor Ostrom's social-ecological systems framework as an approach for identifying the conditions under which local actors may work collectively to manage the FSS in the absence of top-down regulatory controls. We adopt as a case study rising sodium concentrations in the Occoquan Reservoir, a critical water supply for up to one million residents in Northern Virginia (USA), to illustrate emerging impacts, underlying causes, possible solutions, and critical research needs.

The synergetic effects of metal(loid)s and soil characteristics on bacterial antibiotic resistance genes (ARGs) in green stormwater infrastructure (GSI) has been relatively understudied. Surface soil samples from six GSIs in Southern California over three time periods were assessed for selected ARGs, class 1 integron-integrase genes (intI1), 16S rRNA genes, and bioavailable and total concentrations of nine metal(loid)s, to investigate the relationships among ARGs, soil characteristics, and co-occurring metal(loid)s. Significant correlations existed among relative gene abundances (sul1, sul2, tetW, and intI1), total metal(loid)s (arsenic, copper, lead, vanadium, and zinc), and bioavailable metal(loid) (arsenic) (r = 0.29-0.61, padj

Stormwater capture systems have the potential to address many urban stormwater management challenges, particularly in water-scarce regions like Southern California. Here, we investigate the potential best-case limits of water supply and stormwater retention benefits delivered by a 10,000 m3 stormwater capture system equipped with real-time control (RTC) on a university campus in Southern California. Using a copula-based conditional probability analysis, two performance metrics (percent of water demand satisfied and the percent of stormwater runoff captured) are benchmarked relative to (1) precipitation seasonality (historical rainfall and a counterfactual in which the same average annual rainfall is distributed evenly over the year); (2) annual precipitation (dry, median, and wet years); and (3) three RTC algorithms (no knowledge of future rainfall or perfect knowledge of future rainfall 1 or 2 days in advance). RTC improves stormwater retention, particularly for the highly seasonal rainfall patterns in Southern California, but not water supply. Improvements to the latter will likely require implementing stormwater capture RTC in conjunction with other stormwater infrastructure innovations, such as spreading basins for groundwater recharge and widespread adoption of green stormwater infrastructure.

In urban areas, untreated stormwater runoff can pollute downstream surface waters. To intercept and treat runoff, low-impact or "green infrastructure" approaches such as using biofilters are adopted. Yet, actual biofilter pollutant removal is poorly understood; removal is often studied in laboratory columns, with variable removal of viable and culturable microbial cell numbers including pathogens. Here, to assess bacterial pollutant removal in full-scale planted biofilters, stormwater was applied, unspiked or spiked with untreated sewage, in simulated storm events under transient flow conditions, during which biofilter influents versus effluents were compared. Based on microbial biomass, sequences of bacterial community genes encoding 16S rRNA, and gene copies of the human fecal marker HF183 and of the Enterococcus spp. marker Entero1A, removal of bacterial pollutants in biofilters was limited. Dominant bacterial taxa were similar for influent versus effluent aqueous samples within each inflow treatment of either spiked or unspiked stormwater. Bacterial pollutants in soil were gradually washed out, albeit incompletely, during simulated storm flushing events. In post-storm biofilter soil cores, retained influent bacteria were concentrated in the top layers (0-10 cm), indicating that the removal of bacterial pollutants was spatially limited to surface soils. To the extent that plant-associated processes are responsible for this spatial pattern, treatment performance might be enhanced by biofilter designs that maximize influent contact with the rhizosphere.

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.

U.S. public university campuses are held directly responsible for compliance with many of the same federal- and state-level environmental regulations as cities, including stormwater management. While operating as 'cities within cities' in many respects, campuses face unique constraints in achieving stormwater regulatory compliance. To compare the abilities of campuses to comply with stormwater regulations to municipalities, we conduct mixed-methods research using primary data from five University of California (UC) campuses. Public universities constituted over 20% of California's "nontraditional" permittees under the municipal separate storm sewer system (MS4) regulation regime in 2013. We utilize semi-structured interviews with campus and regulatory officials, a survey of campus students and staff around support and willingness to pay for innovative stormwater management, and content analysis of campus stormwater management documents to examine challenges to public university stormwater compliance. We find that, despite their progressive environmental practices in other areas like energy and water conservation, even as compared to cities, stormwater management practices on the evaluated campuses are constrained by several factors: infrastructure financing limitations, lack of transparent and coordinated decision-making, a lack of campus resident involvement, and regulatory inflexibility. Our study provides new insights, both for understanding campuses as sustainable 'cities within cities' and more broadly for urban environmental compliance regimes globally.

New experimental techniques are allowing, for the first time, direct visualization of mass and momentum transport across the sediment-water interface in streams. These experimental insights are catalyzing a renaissance in our understanding of the role stream turbulence plays in a host of critical ecosystem services, including nutrient cycling. In this commentary, we briefly review the nature of stream turbulence and its role in hyporheic exchange and nutrient cycling in streams. A simple process-based model, borrowed from biochemical engineering, provides the link between empirical relationships for grain-scale turbulent mixing and nutrient processing at reach, catchment, continental, and global scales.

Constructed stormwater wetlands provide a host of ecosystem services, including potentially pathogen removal. We present results from a multi-wetland study that integrates across weather, chemical, microbiological and engineering design variables in order to identify patterns of microbial contaminant removal from inlet to outlet within wetlands and key drivers of those patterns. One or more microbial contaminants were detected at the inlet of each stormwater wetland (Escherichia coli and Enterococcus > Bacteroides HF183 > adenovirus). Bacteroides HF183 and adenovirus concentrations declined from inlet to outlet at all wetlands. However, co-removal of pathogens and fecal indicator bacteria only occurred at wetlands where microbial assemblages at the inlet (dominated by Proteobacteria and Bacteriodetes) were largely displaced by indigenous autotrophic microbial communities at the outlet (dominated by Cyanobacteria). Microbial community transitions (characterized using pyrosequencing) were well approximated by a combination of two rapid indicators: (1) fluorescent dissolved organic matter, and (2) chlorophyll a or phaeophytin a fluorescence. Within-wetland treatment of fecal markers and indicators was not strongly correlated with the catchment-to-wetland area ratio, but was diminished in older wetlands, which may point to a need for more frequent maintenance.

The discharge of excess nitrogen to streams and rivers poses an existential threat to both humans and ecosystems. A seminal study of headwater streams across the United States concluded that in-stream removal of nitrate is controlled primarily by stream chemistry and biology. Reanalysis of these data reveals that stream turbulence (in particular, turbulent mass transfer across the concentration boundary layer) imposes a previously unrecognized upper limit on the rate at which nitrate is removed from streams. The upper limit closely approximates measured nitrate removal rates in streams with low concentrations of this pollutant, a discovery that should inform stream restoration designs and efforts to assess the effects of nitrogen pollution on receiving water quality and the global nitrogen cycle.

Green infrastructure (also referred to as low impact development, or LID) has the potential to transform urban stormwater runoff from an environmental threat to a valuable water resource. In this paper we focus on the removal of fecal indicator bacteria (FIB, a pollutant responsible for runoff-associated inland and coastal beach closures) in stormwater biofilters (a common type of green infrastructure). Drawing on a combination of previously published and new laboratory studies of FIB removal in biofilters, we find that 66% of the variance in FIB removal rates can be explained by clean bed filtration theory (CBFT, 31%), antecedent dry period (14%), study effect (8%), biofilter age (7%), and the presence or absence of shrubs (6%). Our analysis suggests that, with the exception of shrubs, plants affect FIB removal indirectly by changing the infiltration rate, not directly by changing the FIB removal mechanisms or altering filtration rates in ways not already accounted for by CBFT. The analysis presented here represents a significant step forward in our understanding of how physicochemical theories (such as CBFT) can be melded with hydrology, engineering design, and ecology to improve the water quality benefits of green infrastructure.

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]

Cities in drought prone regions of the world such as South East Australia are faced with escalating water scarcity and security challenges. Here we use 72 years of urban water consumption data from Melbourne, Australia, a city that recently overcame a 12 year "Millennium Drought", to evaluate (1) the relative importance of climatic and anthropogenic drivers of urban water demand (using wavelet-based approaches) and (2) the relative contribution of various water saving strategies to demand reduction during the Millennium Drought. Our analysis points to conservation as a dominant driver of urban water savings (69%), followed by nonrevenue water reduction (e.g., reduced meter error and leaks in the potable distribution system; 29%), and potable substitution with alternative sources like rain or recycled water (3%). Per-capita consumption exhibited both climatic and anthropogenic signatures, with rainfall and temperature explaining approximately 55% of the variance. Anthropogenic controls were also strong (up to 45% variance explained). These controls were nonstationary and frequency-specific, with conservation measures like outdoor water restrictions impacting seasonal water use and technological innovation/changing social norms impacting lower frequency (baseline) use. The above-noted nonstationarity implies that wavelets, which do not assume stationarity, show promise for use in future predictive models of demand.

Catchment urbanization perturbs the water and sediment budgets of streams, degrades stream health and function, and causes a constellation of flow, water quality, and ecological symptoms collectively known as the urban stream syndrome. Low-impact development (LID) technologies address the hydrologic symptoms of the urban stream syndrome by mimicking natural flow paths and restoring a natural water balance. Over annual time scales, the volumes of stormwater that should be infiltrated and harvested can be estimated from a catchment-scale water-balance given local climate conditions and preurban land cover. For all but the wettest regions of the world, a much larger volume of stormwater runoff should be harvested than infiltrated to maintain stream hydrology in a preurban state. Efforts to prevent or reverse hydrologic symptoms associated with the urban stream syndrome will therefore require: (1) selecting the right mix of LID technologies that provide regionally tailored ratios of stormwater harvesting and infiltration; (2) integrating these LID technologies into next-generation drainage systems; (3) maximizing potential cobenefits including water supply augmentation, flood protection, improved water quality, and urban amenities; and (4) long-term hydrologic monitoring to evaluate the efficacy of LID interventions.

Bedforms are a focal point of carbon and nitrogen cycling in streams and coastal marine ecosystems. In this paper, we develop and test a mechanistic model, the "pumping and streamline segregation" or PASS model, for nitrate removal in bedforms. The PASS model dramatically reduces computational overhead associated with modeling nitrogen transformations in bedforms and reproduces (within a factor of 2 or better) previously published measurements and models of biogeochemical reaction rates, benthic fluxes, and in-sediment nutrient and oxygen concentrations. Application of the PASS model to a diverse set of marine and freshwater environments indicates that (1) physical controls on nitrate removal in a bedform include the pore water flushing rate, residence time distribution, and relative rates of respiration and transport (as represented by the Damkohler number); (2) the biogeochemical pathway for nitrate removal is an environment-specific combination of direct denitrification of stream nitrate and coupled nitrification-denitrification of stream and/or sediment ammonium; and (3) permeable sediments are almost always a net source of dissolved inorganic nitrogen. The PASS model also provides a mechanistic explanation for previously published empirical correlations showing denitrification velocity (N2 flux divided by nitrate concentration) declines as a power law of nitrate concentration in a stream (Mulholland et al. Nature, 2008, 452, 202-205).

The Millennium Drought in Southeast Australia forced greater Melbourne, a city of 4.3 million people, to find innovative ways of increasing water supply and decreasing water demand. This article explores how water managers in Melbourne reacted to the crisis and evaluates the short-and long-term impacts of their decisions. Reduced water demand occurred primarily through residential and industrial water conservation programs, restrictions, together with emergency reductions in the environmental release of water to streams. The city also experimented with using recycled water, in place of surface water, to support agriculture in the Werribee Irrigation District. Water pricing was not strengthened during the drought, and thus not regarded as a drought demand management tool, primarily because Melbourne water companies lacked independent price-setting powers. Today, five years after the end of the Millennium Drought, gains in water conservation appear to be holding steady, but recycled water for irrigation has declined for various reasons. We contend that the Millennium Drought provided Melbourne with the opportunity to develop and implement a more integrated approach to water management. Many of the innovations it forged (e.g., distributed harvesting and use of stormwater) will continue to enhance the city’s resilience to drought and reduce its vulnerability to climate variability for years to come. Nevertheless, a challenge going forward is how to sustain these achievements in light of anticipated population growth and continued climatic change. This challenge—coupled with Melbourne’s successes—hold important lessons for water-stressed cities around the world.

Enclosed beaches along urban coastlines are frequent hot spots of fecal indicator bacteria (FIB) pollution. In this paper we present field measurements and modeling studies aimed at evaluating the impact of small storm drains on FIB pollution at enclosed beaches in Newport Bay, the second largest tidal embayment in Southern California. Our results suggest that small drains have a disproportionate impact on enclosed beach water quality for five reasons: (1) dry weather surface flows (primarily from overirrigation of lawns and ornamental plants) harbor FIB at concentrations exceeding recreational water quality criteria; (2) small drains can trap dry weather runoff during high tide, and then release it in a bolus during the falling tide when drainpipe outlets are exposed; (3) nearshore turbulence is low (turbulent diffusivities approximately 10(-3) m(2) s(-1)), limiting dilution of FIB and other runoff-associated pollutants once they enter the bay; (4) once in the bay, runoff can form buoyant plumes that further limit vertical mixing and dilution; and (5) local winds can force buoyant runoff plumes back against the shoreline, where water depth is minimal and human contact likely. Outdoor water conservation and urban retrofits that minimize the volume of dry and wet weather runoff entering the local storm drain system may be the best option for improving beach water quality in Newport Bay and other urban-impacted enclosed beaches.

A simple analytical model is presented for the removal of stream-borne contaminants by hyporheic exchange across duned or rippled streambeds. The model assumes a steady-state balance between contaminant supply from the stream and first-order reaction in the sediment. Hyporheic exchange occurs by bed form pumping, in which water and contaminants flow into bed forms in high-pressure regions (downwelling zones) and out of bed forms in low-pressure regions (upwelling zones). Model-predicted contaminant concentrations are higher in downwelling zones than upwelling zones, reflecting the strong coupling that exists between transport and reaction in these systems. When flow-averaged, the concentration difference across upwelling and downwelling zones drives a net contaminant flux into the sediment bed proportional to the average downwelling velocity. The downwelling velocity is functionally equivalent to a mass transfer coefficient, and can be estimated from stream state variables including stream velocity, bed form geometry, and the hydraulic conductivity and porosity of the sediment. Increasing the mass transfer coefficient increases the fraction of streamwater cycling through the hyporheic zone (per unit length of stream) but also decreases the time contaminants undergo first-order reaction in the sediment. As a consequence, small changes in stream state variables can significantly alter the performance of hyporheic zone treatment systems.

This paper explores how the Millennium Drought changed the way Melburnians source and use their water resources and discuss what these changes may portend for other large cities in water-scarce and climate-change-vulnerable regions of the world, in particular, the Southwest region of the United States.

Humans create vast quantities of wastewater through inefficiencies and poor management of water systems. The wasting of water poses sustainability challenges, depletes energy reserves, and undermines human water security and ecosystem health. Here we review emerging approaches for reusing wastewater and minimizing its generation. These complementary options make the most of scarce freshwater resources, serve the varying water needs of both developed and developing countries, and confer a variety of environmental benefits. Their widespread adoption will require changing how freshwater is sourced, used, managed, and priced.

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.

The advent of molecular-based diagnostics has radically improved our ability to analyze the prevalence and activities of microorganisms in environmental systems. In this research. a new molecular tool (gene probe spectroscopy or GPS) was tested which may further enhance the capabilities of existing molecular techniques for carrying-out environmental analysis. With GPS, a microorganism (or a group or related microorganisms) is characterized by its hybridization to a set of non-specific oligonucleotide probes in a dot-blot format. The hybridization intensities for each probe/microorganism combination is determined experimentally and stored in a matrix database (A). Samples containing unknown mixtures of microorganisms are then hybridized with the same set of probes to obtain a set of composite hybridization intensities (b). By employing linear inverse theory, the concentration (c) of each microorganism present in the unknown sample may be computed by matrix inversion techniques: C = A -lb. With an award from the Water Resources Center, we investigated this approach using a model system consisting of four different bacteriophage (T2, M13, lambda, and 1'7) and six non-specific oligonucleotide probes each of which cross-reacts with two or more phage. In a series of tests, phage concentrations were correctly predicted by the method. illustrating its efficacy for identifying and enumerating microorganisms in fluid samples. Its application to "real" environments will require the use of DNA chip technology in which oligonucleotide probes are arrayed on glass slides. Future work will be directed toward the merging of the techniques developed in this project, namely GPS, with the DNA chip format,