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A pragmatic concern guides this perspective piece: How might researchers charged with leading convergence research better plan, design, implement, and evaluate the integrative processes and products of their research? We use a self-evaluation approach to assess the integrative processes and products of the first two years of a five-year National Science Foundation Growing Convergence Research project on addressing inland freshwater salinization. To examine the linkages between integration approaches and products, we analyzed the integrative qualities of fifteen research products and the collaborative processes used to generate these products. We found that large, heterogeneous teams with a broad mix of disciplines and professional expertise produced more interdisciplinary research products, but they relied on skilled integration by the leader, more intensive forms of collaboration, and inclusive problem framing. Teams that relied on deliberation by experts and used more consultative or cooperative mechanisms for engagement produced research that was more uni- or multi-disciplinary. We consider the efficacy of the various knowledge integration approaches used in this research and share empirically derived recommendations for designing, implementing, and evaluating convergence research. Our findings and lessons provide researchers at the helm of large-scale convergence and transdisciplinary research projects that address complex socio-environmental problems guidance on: (1) the planning and designing of projects with the explicit goal of knowledge integration; (2) the selection and implementation of appropriate knowledge integration approaches and tools; and (3) how knowledge integration can be conceptualized and evaluated for socio-environmental problems. • Convergence research (CR) initiatives can involve unidisciplinary (UD) to interdisciplinary (ID) work, depending on the phase of the project. • Large, heterogeneous teams produce more ID products with skilled integration by a leader, collaboration, and inclusive problem framing. • Teams that rely on deliberation by experts and use more consultative or cooperative mechanisms for engagement and produce UD or MD products. • Teams should pay deliberate attention to the composition of project sub-teams during the initial stages of a CR project. • Teams should build in time for small group reflective activities focused on generating integrative insights. [ABSTRACT FROM AUTHOR]

• Field-scale biofilter evaluated under realistic, transient flow conditions. • Normalization of microbial analyte removal to breakthrough of the conservative tracer bromide. • Biofilter significantly reduced 14 of 17 microbial analytes. • No significant reduction in concentration for two fecal source markers. Green stormwater infrastructure systems, such as biofilters, provide many water quality and other environmental benefits, but their ability to remove human pathogens and antibiotic resistance genes (ARGs) from stormwater runoff is not well documented. In this study, a field scale biofilter in Southern California (USA) was simultaneously evaluated for the breakthrough of a conservative tracer (bromide), conventional fecal indicators, bacterial and viral human-associated fecal source markers (HF183, crAssphage, and PMMoV), ARGs, and bacterial and viral pathogens. When challenged with a 50:50 mixture of untreated sewage and stormwater (to mimic highly contaminated storm flow) the biofilter significantly removed (p < 0.05) 14 of 17 microbial markers and ARGsin descending order of concentration reduction: erm B (2.5 log(base 10) reduction) > Salmonella (2.3) > adenovirus (1.9) > coliphage (1.5) > crAssphage (1.2) > E. coli (1.0) ∼ 16S rRNA genes (1.0) ∼ fecal coliform (1.0) ∼ intl 1 (1.0) > Enterococcus (0.9) ∼ MRSA (0.9) ∼ sul 1 (0.9) > PMMoV (0.7) > Entero1A (0.5). No significant removal was observed for GenBac3, Campylobacter , and HF183. From the bromide data, we infer that 0.5 log-units of attenuation can be attributed to the dilution of incoming stormwater with water stored in the biofilter; removal above this threshold is presumably associated with non-conservative processes, such as physicochemical filtration, die-off, and predation. Our study documents high variability (>100-fold) in the removal of different microbial contaminants and ARGs by a field-scale stormwater biofilter operated under transient flow and raises further questions about the utility of human-associated fecal source markers as surrogates for pathogen removal. [Display omitted] [ABSTRACT FROM AUTHOR]

Hydrogen peroxide concentrations [H2O2] have been measured over the last two decades in multiple studies in surface waters in coastal, estuarine and oceanic systems. Diurnal cycles consistent with a photochemical production process have frequently being observed, with [H2O2] increasing by two orders of magnitude over the course of the day, from low nM levels in the early morning to 102 nM in late afternoon. Production rates range from <10 for off-shore ocean waters to 20–60nMh−1 for near-shore coastal and estuarine environments. Slow night-time loss rates (<10nMh−1) have been attributed to biological and particle mediated processes. Diurnal cycles have also frequently been observed in fecal indicator bacteria (FIB) levels in surf zone waters monitored for microbial water quality. Measured peak peroxide concentrations in surface coastal seawaters are too low to directly cause FIB mortality based on laboratory studies, but likely contribute to oxidative stress and diurnal cycling. Peroxide levels in the surf zone may be increased by additional peroxide production mechanisms such as deposition, sediments and stressed marine biota, further enhancing impacts on FIB in marine bathing waters. [Copyright &y& Elsevier]

Sanitary sewer systems are critical urban water infrastructure that protect both human and environmental health. Their design, operation, and monitoring require novel modeling techniques that capture dominant processes while allowing for computationally efficient simulations. Open water flow in sewers and rivers are intrinsically similar processes. With this in mind, we formulated a new parsimonious model inspired by the Width Function Instantaneous Unit Hydrograph (WFIUH) approach, widely used to predict rainfall-runoff relationships in watersheds, to a sanitary sewer system consisting of nearly 10,000 sewer conduits and 120,000 residential and commercial sewage connections in Northern Virginia, U.S.A. Model predictions for the three primary components of sanitary flow, including Base Wastewater Flow (BWF), Groundwater Infiltration (GWI), and Runoff Derived Infiltration and Inflow (RDII), compare favorably with the more computationally demanding industry-standard Storm Water Management Model (SWMM). This novel application of the WFIUH modeling framework should support a number of critical water quality endpoints, including (i) sewer hydrograph separation through the quantification of BWF, GWI, and RDII outflows, (ii) evaluation of the impact of new urban developments on sewage flow dynamics, (iii) monitoring and mitigation of sanitary sewer overflows, and (iv) design and interpretation of wastewater surveillance studies. [Display omitted] • We propose, verify, and validate a novel model for flow routing in sanitary sewers. • The model infers groundwater infiltrations, assessing sewer network integrity. • The model is a reliable tool for quantifying Inflow and Infiltration in sanitary sewers. [ABSTRACT FROM AUTHOR]

Abstract Hyporheic flow and nutrient turnover in hyporheic systems are strongly influenced by in-stream bedforms. An accurate representation of topographical variations of the stream-streambed interface is therefore essential in analytical models in order to represent the couplings between hydrological and biogeochemical processes correctly. The classical Toth approach replaces the streambed surface topography by a flat surface which is identical to a truncation of the original physical flow domain into a rectangle. This simplification can lead to biased estimates of hyporheic flow and nutrient cycling within hyporheic systems. We present an alternative analytical modeling approach for solving hyporheic problems without domain truncation that explicitly accounts for topographical variations of the streambed. The presented approach is based on the application of perturbation theory. Applications of the method to hyporheic systems, ranging from the centimeter-scale of rippled bedforms to riffle structures of 10 m and larger scale, indicate a high accuracy of the approach. Highlights • Analytical modelling approach based on perturbation theory. • Representation of potential flow and biogeochemical nutrient turnover in hyporheic systems. • Accurate and flexible analytical solutions. [ABSTRACT FROM AUTHOR]

Abstract: Sewage-contaminated shallow groundwater is a potential cause of beach closures and water quality impairment in marine coastal communities. In this study we set out to evaluate the feasibility of several strategies for disinfecting sewage-contaminated shallow groundwater before it reaches the coastline. The disinfection rates of Escherichia coli (EC) and enterococci bacteria (ENT) were measured in mixtures of raw sewage and brackish shallow groundwater collected from a coastal community in southern California. Different disinfection strategies were explored, ranging from benign (aeration alone, and aeration with addition of brine) to aggressive (chemical disinfectants peracetic acid (PAA) or peroxymonosulfate (Oxone)). Aeration alone and aeration with brine did not significantly reduce the concentration of EC and ENT after 6 h of exposure, while 4–5 mg L−1 of PAA or Oxone achieved >3 log reduction after 15 min of exposure. Oxone disinfection was more rapid at higher salinities, most likely due to the formation of secondary oxidants (e.g., bromine and chlorine) that make this disinfectant inappropriate for marine applications. Using a Lagrangian modeling framework, we identify several factors that could influence the performance of in-situ disinfection with PAA, including the potential for bacterial regrowth, and the non-linear dependence of disinfection rate upon the residence time of water in the shallow groundwater. The data and analysis presented in this paper provide a framework for evaluating the feasibility of in-situ disinfection of shallow groundwater, and elucidate several topics that warrant further investigation. [Copyright &y& Elsevier]

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. [ABSTRACT FROM AUTHOR]

For many coastal regions around the world, recreational beach water quality is assessed using fecal indicator bacteria (FIB). However, the utility of FIB as indicators of recreational water illness (RWI) risk has been questioned, particularly in coastal settings with no obvious sources of human sewage. In this study we employed a source-apportionment quantitative microbial risk assessment (SA-QMRA) to assess RWI risk at a popular semi-enclosed recreational beach in Southern California (Baby Beach, City of Dana Point) with no obvious point sources of human sewage. Our SA-QMRA results suggest that, during dry weather, the median RWI risk at this beach is below the U.S. EPA recreational water quality criteria (RWQC) of 36 illness cases per 1000 bathers. During wet weather, the median RWI risk predicted by SA-QMRA depends on the assumed level of human waste associated with stormwater; the RWI risk is below the EPA RWQC illness risk benchmark 100% of the time provided that <2% of the FIB in stormwater are of human origin. However, these QMRA outcomes contrast strongly with the EPA RWQC for 30-day geometric mean of enterococci bacteria. Our results suggest that SA-QMRA is a useful framework for estimating robust RWI risk that takes into account local information about possible human and non-human sources of FIB. [ABSTRACT FROM AUTHOR]

• N export from full-scale biofilters studied for successive transient flow storms. • Soil N was mineralized, and inflow NH 4 + nitrified, during antecedent dry periods. • Low N 2 O emissions or denitrification, with high NO 3 − leaching during storms. • Denitrifying genes were abundant, but potential denitrifying enzyme activity low. • Results consistent for chemical, enzymatic, biological, and stable isotope data. Nitrogen (N) in urban runoff is often treated with green infrastructure including biofilters. However, N fates across biofilters are insufficiently understood because prior studies emphasize low N loading under laboratory conditions, or use "steady-state" flow regimes over short time scales. Here, we tested field scale biofilter N fates during simulated storms delivering realistic transient flows with high N loading. Biofilter outflow ammonium (NH 4 +-N) was 60.7 to 92.3% lower than that of the inflow. Yet the characteristic times for nitrification (days to weeks) and denitrification (days) relative to N residence times (7 to 30 h) suggested low N transformation across the biofilters. Still, across 7 successive storms, total outflow nitrate (NO 3 −-N) greatly exceeded (3100 to 3900%) inflow nitrate, a result only explainable by biofilter soil N nitrification occurring between storms. Archaeal, and bacterial amo A gene copies (2.1 × 105 to 1.2 × 106 gc g soil−1), nitrifier presence by16S rRNA gene sequencing, and outflow δ18O-NO 3 − values (-3.0 to 17.1 ‰) reinforced that nitrification was occurring. A ratio of δ18O-NO3− to δ15N-NO 3 − of 1.83 for soil eluates indicated additional processes: N assimilation, and N mineralization. Denitrification potential was suggested by enzyme activities and soil denitrifying gene copies (nir K + nir S: 3.0 × 106 to 1.8 × 107; nos Z: 5.0 × 105 to 2.2 × 106 gc g soil−1). However, nitrous oxide (N 2 O-N) emissions (13.5 to 84.3 μg N m −2 h −1) and N 2 O export (0.014 g N) were low, and soil nitrification enzyme activities (0.45 to 1.63 mg N kg soil−1day−1) exceeded those for denitrification (0.17 to 0.49 mg N kg soil−1 day−1). Taken together, chemical, bacterial, and isotopic metrics evidenced that storm inflow NH 4 +sorbs and, along with mineralized soil N, nitrifies during biofilter dry-down; little denitrification and associated N 2 O emissions ensue, and thus subsequent storms export copious NO 3 −-N. As such, pulsed pass-through biofilters require redesign to promote plant assimilation and/or denitrification of mineralized and nitrified N, to minimize NO 3 −-N generation and export. [Display omitted] [ABSTRACT FROM AUTHOR]

Research on rain gardens generally focuses on hydrology, geochemistry, and vegetation. The role of soil invertebrates has largely been overlooked, despite their well-known impacts on soil nutrient storage, removal, and processing. Surveys of three rain gardens in Melbourne, Australia, revealed a soil invertebrate community structure that differed significantly among sites but was stable across sampling dates (July 2013 and April 2014). Megadrilacea (earthworms), Enchytraeidae (potworms), and Collembola (springtails) were abundant in all sites, and together accounted for a median of 80% of total soil invertebrate abundance. Earthworms were positively correlated to soil organic matter content, but the abundances of other taxonomic groups were not strongly related to organic matter content, plant cover, or root biomass across sites. While less than 5% of total soil N was estimated to be stored in the body tissues of these three taxa, and estimated N gas emissions from earthworms (N 2 O and N 2 ) were low, ingestion and processing of soil was high (e.g., up to 417% of the upper 5 cm of soil ingested by earthworms annually in one site), suggesting that the contribution of these organisms to N cycling in rain gardens may be substantial. Thus, invertebrate communities represent an overlooked feature of rain garden design that can play an important role in the structure and function of these systems. [ABSTRACT FROM AUTHOR]

The contribution of freshwater discharge to fecal indicator bacteria (FIB) impairment of an estuarine environment can be approximated from simple, two end-member mixing models using salinity as a tracer. We conducted a yearlong time series investigation of Newport Bay, a regionally important estuarine embayment in southern California, assessing the concentrations of FIB, specifically Escherichia coli and enterococci bacteria, and salinity. In total, eight within-bay stations and one offshore control site were sampled nearly once per week and the three tributaries draining into Newport Bay were sampled approximately daily. Using salinity as a conservative tracer for water mass mixing and determining the end-member values of FIB in both the creek sites and the offshore site, we created a linear, two end-member mixing model of FIB within Newport Bay. Deviations from the mixing model suggest either an additional source of FIB to the bay (e.g. bird feces, storm drain discharge) or regrowth and/or die-off of FIB within the bay. Our results indicate that salinity mixing models can be useful in predicting changes in FIB concentrations in the estuarine environments and can help narrow the search for sources of FIB to the bay and enhance our understanding of the fate of FIB within the bay. [Copyright &y& Elsevier]